Wednesday, April 2, 2008

Philips 47" Diagonal 1080p Full HD LCD HDTV w/ Digital Tuner, 47PFL5432D/37

Experience the amazing realism of full high definition on this advanced HDTV. The tuner can receive conventional analog channels (NTSC) and the new digital channels (ATSC), including over-the-air HDTV broadcasts where available, and unscrambled digital cable channels. An exceptional contrast ratio and fast 8-ms. response time deliver excellent picture quality. Three HDMI inputs and a variety of other inputs make it simple to connect DVD players, digital cameras, camcorders, game consoles, surround-sound systems and other entertainment gear. You can even share music and photos via the built-in USB port on the side panel.

Note: You must have a source of HD programming in order to take full advantage of an HDTV. Otherwise, the picture quality of an HDTV without an HD source may not be much better than that of a standard-definition TV. Please contact your local cable or satellite TV provider for details on how to upgrade to HD programming.




Key Features & Benefits:


  • 47-inch widescreen LCD with 1080p Full HD

  • Delivers 1920 x 1080p resolution with over two million pixels for outstanding picture quality, especially from Blu-ray disc, HD DVD, PlayStation3 and Xbox360


  • Built-in ATSC digital / NTSC analog tuner

  • Receives conventional analog broadcasts and digital broadcasts including HDTV programs, where available


  • 5500:1 dynamic contrast ratio and 5-ms. response time

  • Ensure deeper blacks and brighter whites along with less blurring when there is motion onscreen


  • Pixel Plus 3 HD technology

  • Enhances each pixel by reducing noise and artifacts to produce a sharp, natural picture with vivid color and smooth motion


  • HDMI, component video, S-video, audio, USB and computer connections

  • Accommodate DVD players, camcorders, surround sound systems, computers and other gear


  • 16-watt stereo amplifier, two speakers, Virtual Dolby Digital and coaxial digital audio output

  • Furnish room-filling audio with surround sound effects and an interface for optional surround sound systems


  • Detachable stand

  • Mounts on a wall with an optional VESA-compatible 600 x 400 mm kit (sold separately)

    Specifications
    TV Technology: LCD
    TV Definition: HDTV,1080p
    HDMI: Yes
    Brightness: 500 cd/m2
    Contrast: 1100:1 (typical)
    Response Time: 5ms (typical)
    HD-Ready: Yes
    DVI: N
    Widescreen: Y
    Model No.: 47PFL5432D/37
    Shipping Weight (in pounds): 105.0
    Product in Inches (L x W x H): 4.4 x 49.2 x 27.1
    Assembled in Country of Origin: USA and/or Imported
    Origin of Components: USA and/or Imported
    Wal-Mart No.: 000568583

    http://www.walmart.com/catalog/product.do?product_id=5633686

    Sony Unveils BRAVIA LCD TV With Full HD Models & 1080p Inputs

    Sony Electronics today announced an expansion of its acclaimed BRAVIA flat-panel LCD television line, including several new models with native 1920 x 1080 full high-definition resolution panels and HDMI inputs with 1080p capability.

    The line features six new models in 40- and 46-inch screen sizes and a 32-inch set featuring 1366 x 768 (WXGA) screen resolution.

    "Our BRAVIA LCD HDTV's offer superior picture quality and unlock the power of the high-definition experience with more than five times the number of pixels compared to enhanced-definition plasma televisions. Paired with our forthcoming Blu-ray Disc player, consumers will see a level of high-definition video unmatched in the home theater," said Randy Waynick, senior vice president of the Sony Electronics' Home Products Division.

    Stunning picture quality is not the only feature that sets the BRAVIA line apart. The new XBR models feature an elegant floating glass design that is sure to inspire novice interior decorators to rethink the modern home.

    "BRAVIA TV's were designed with the critical eye in mind," Waynick added. "The art of building a television is not limited to the components inside but also the aesthetic beauty that completes the package as these new models attest."



















    BRAVIA XBR Series

    At the top of the new line is the XBR3 series including the 46-inch KDL-46XBR3 and 40-inch KDL-40XBR3. With native 1920 x 1080 panel resolution and three HDMI inputs with 1080p capability, the sets are compatible with full high-definition signal sources, such as Sony's BDP-S1 Blu-ray Disc player, which is targeted for shipment to retail late this summer.

    With the ability to display full high-definition resolution and rich colorful images, even non-1080p content -- from standard-definition to 1080i or 720p high-definition signals -- is at its best once it hits the screen. The new BRAVIA Engine Pro full digital high-definition video processor is Sony's latest and most advanced video processing system. Optimizing the video signal path, the system leverages a new version of Sony's Digital Reality Creation Multi Function Version Two Point Five (DRC-MFv2.5) with increased computing capabilities to process not only standard-definition signals, but also high-definition signals for a consistently crisp, detailed image.

    The XBR models come with Sony's Live Color Creation technology, featuring Wide Color Gamut Cold Cathode Fluorescent Lamp (WCG-CCFL) backlight. WCG-CCFL's new phosphor spectrum allow for a wider, more realistic range of colors enhancing picture.

    Framing that sharp, detailed picture is an elegant floating glass-encased, high gloss, piano black bezel with side speakers.

    Rounding out the XBR3 series feature package is a built-in ATSC tuner, PC input, two high-definition component, one S-video and three composite inputs.

    The KDL-46XBR3 and KDL-40XBR3 models will ship in September and be available for about $5,300 and $4,300, respectively.

    In addition to the piano black XBR3 models, the new XBR2 BRAVIA models feature the same 1920 x 1080 screen resolution, BRAVIA Engine Pro, HDMI inputs with 1080p capability and elegant floating glass design. However, these two models -- the 46-inch KDL-46XBR2 and 40-inch KDL-40XBR2 -- feature a silver bezel that can be replaced by one of five different colored bezels for custom integration into any decor.

    These models also feature the same audio package, built-in ATSC tuner, PC input, two high-definition component, one S-video and three composite inputs.

    The KDL-46XBR2 and KDL-40XBR2 models will also ship in September. They will be available for about $5,000 and $4,000, respectively. The optional bezels come in five colors, including red, white, blue, black and brown. They will be available at authorized dealers, Sony Style stores and direct online at www.sonystyle.com

    Rounding out the XBR2 line is the 32-inch KDL-V32XBR2 model featuring a 1366 x 768 screen resolution. It is equipped with Sony's BRAVIA Engine and Live Color Creation, which delivers a sharp and rich picture from standard definition sources as well as high-definition.

    The set's narrow, two-tone black and silver bezel incorporates invisible bottom speakers with SRS TruSurroundXT and BBE Digital Enhancement technology.

    Other features include a built-in ATSC tuner, single HDMI and PC inputs, as well as two high-definition component, two S-video and two composite inputs.

    The KDL-V32XBR2 set ships in September and will be available for about $2,500.

    BRAVIA V2500 Series

    Next in the BRAVIA line is the V2500 series, including the 46-inch KDL-46V2500 and 40-inch KDL-40V2500. These 1920 x 1080 native high-definition resolution models are equipped with two HDMI inputs with 1080p capability and the BRAVIA Engine and Live Color Creation technologies.

    The black bezel, V2500 models feature a space-saving bottom speaker design that helps the sets fit easily into existing AV cabinets.

    Other features include a digital amplifier with SRS-TruSurround XT and BBE Digital Audio Enhancement technologies for high-quality sound, a PC input, two high-definition component, two S-video and two composite inputs.

    The KDL-46V2500 and KDL-40V2500 models will ship in September for about $4,500 and $3,500, respectively.

    All new BRAVIA televisions, including the previously announced S-series and U-series models, are available through sonystyle.com, at Sony Style retail stores (www.sonystyle.com/retail) and at authorized dealers nationwide.

    http://ph.hardwarezone.com/news/view.php?cid=5&id=4669

    1080p

    1080p is the shorthand name for a category of display resolutions. The number "1080" represents 1,080 lines of vertical resolution,[1] while the letter p stands for progressive scan (meaning the image is not interlaced). 1080p is considered an HDTV video mode. The term usually assumes a widescreen aspect ratio of 16:9, implying a horizontal resolution of 1920 pixels. This creates a frame resolution of 1920×1080, or 2,073,600 pixels in total. The frame rate in Hertz can be either implied by the context or specified after the letter p, such as 1080p30, meaning 30 Hz.

    1080p is sometimes referred to in marketing materials as "Full High-Definition". However, 2K/4K digital cinema technology is commercially available, and ultra-high definition video is in the research phase.

    In addition to the meaning of 1080p as a display resolution, 1080p is also used to describe video equipment capabilities. Use of 1080p and the closely related 1080i labels in consumer products may refer to a range of capabilities. For example, video equipment that upscales to 1080p takes lower resolution material and reformats it for a higher resolution display. The image that results is different from the display of original 1080p source material on a native 1080p capable display. Similarly, equipment capable of displaying both 720p and 1080i may in fact not have the capability to display 1080p or 1080i material at full resolution. It is common for this material to be downscaled to the native capability of the equipment. The term "native 1080p capable" is sometimes used to refer to equipment capable of rendering 1080p fully.

    Broadcasting standards

    The ATSC and DVB support 1080p video, but only at the frame rates of 24, 25, and 30 frames per second (1080p24, 1080p25, 1080p30) and their 1000/1001-rate slow versions (e.g., 29.97 frames per second instead of 30). Higher frame rates, such as 1080p50 and 1080p60, could only be sent with more bandwidth or if a more advanced codec (such as H.264/MPEG-4 AVC) were used. Higher frame rates such as 1080p50 and 1080p60 are foreseen as the future broadcasting standard for production.[2]

    In the United States, the ATSC is considering amending its standard to allow the incorporation of the newer codecs for optional usage like the DVB Project consortium already has done with DVB-S2.[3] However, doing so is not expected to result in widespread consumer availability of broadcast 1080p60 programming, since most of the existing digital television sets or external digital receivers in use in the United States would still only be capable of decoding the older, less-efficient MPEG-2 codec, while the bandwidth limitations do not allow for broadcasting two simultaneous streams on the same broadcast channel (e.g. both a 1080i MPEG-2 stream alongside a 1080p MPEG-4 stream).

    Production standards


    The movie industry has embraced 1080p24 as a mastering format in both native 24p form and in 24PsF form. This may be the first universal video standard which transcends continental boundaries, an area previously reserved for film.[4] Wrapping progressive video into the interlaced stream allows the video to maintain the progressive format, while minimizing bandwidth requirements using interlaced equipment.[5]

    A new high-definition progressive scan format is not available for picture creation, but is currently being developed to operate at 1080p at 50 or 60 frames per second.[2][6] This format will require a whole new range of studio equipment including cameras, storage, edit and contribution links as it has doubled the data rate of current 50 or 60 fields interlaced 1920 × 1080 from 1.485 Gbit/s to nominally 3 Gbit/s. It is unable to be broadcast in a compressed transmission to legacy MPEG-2 based HD receivers. This format will improve final pictures because of the benefits of "oversampling" and removal of interlacing artifacts.


    Availability


    Broadcasts

    It's a common misconception that HDTV broadcasts cannot be in 1080p. In the United States, the ATSC standard allows 1080p24 and 1080p30 video. In practice, all major networks use a 60 Hz format in the MPEG-2 header -- either 720p60 or 1080i30. But that only dictates the formal output of the MPEG-2 decoding process, not the actual means of encoding the frames.

    For material that originated from a 24 fps source (such as film), MPEG-2 allows the video to be coded as 1080p24, irrespective of the final output format. The progressively-coded frames are then tagged with metadata (literally, fields of the PICTURE header) instructing a decoder how to perform a 3:2 pulldown to interlace them. While the formal output of the MPEG-2 decoding process from such stations is 1080i30, the actual content is coded as 1080p24 and can be viewed as such. That is to say, twenty-four progressively-coded frames per second are present in the bitstream; it is the decoder that turns them into 60 interlaced fields per second. NBC is known to use this method with some stations.

    Even for content that has not been encoded in this fashion, it is still usually possible to extract the original 24 source frames from a 1080i30 broadcast of 24 fps material, since no information is lost even when the broadcaster (as opposed to the receiver) performs the 3:2 pulldown


    Internet content

    There has been some content released in the 1080p format on the Internet. Some notable examples include the Apple QuickTime Trailers in the QuickTime HD 720p/1080p format, and the Microsoft WMV HD Content Showcase which offers clips in both 720p and 1080p formats. Another example of 1080p content is the MacBreak 1080p podcast created by Leo Laporte and Alex Lindsay. This podcast is distributed via the BitTorrent method of distribution because of the large file sizes resulting from the high bit-rates. BitTorrent also contains many 1080p movies which have been copied from Blu-ray Disc or Broadcast sources. Often the internet is the only source for many high definition movies.[citation needed] These are frequently in MKV/WMV format and are difficult for most computers to render smoothly. All 1080p content currently (as of March 2007) distributed on the Internet has frame rate of 24, 25, or 30 frames per second.

    Consumer televisions and projectors

    There is a growing selection of consumer televisions with support for both 1080p inputs and outputs. Several televisions in 2005 offered 1080p, including sets from JVC (using a technology called D-ILA which is a variation of LCoS), Hewlett-Packard, Mitsubishi, Sony, Panasonic, etc. The 2006 Consumer Electronics Show (CES) introduced 1080p displays from most manufacturers, available in various display technologies. The manufacturers of 1080p TFT LCD screens include Sharp and a few others in Asia. Also, 3:2 pulldown reversal (reverse telecine) for film-based 1080i60 signals is beginning to appear in some newer 1080p displays, which can produce a true 1080p quality image from film-based 1080i60 programs.

    Computer monitors

    Some modern widescreen liquid crystal display (LCD) monitors can natively display 1080p content. Widescreen WUXGA monitors for example support 1920×1200 resolution, which can display a pixel for pixel reproduction of the 1080p (1920×1080) format. The resolution is rare amongst laptops, but some laptops have a 15" or a 17" display that run 1920×1200. Additionally, many 23, 24 and 27 inch widescreen LCD displays use 1920×1200 as their native resolution. Other 1080p-compatible LCDs, on the other hand, have lower than 1920×1080 native resolution and cannot display 1080p pixel for pixel. The output is resized; and although it may not be noticeable to the viewer, what is seen is a slightly degraded version of the original image.

    Cathode ray tube (CRT) computer monitors have long been capable of displaying (and exceeding) 1080p. However, since most CRT monitors have an aspect ratio of 4:3, one would either have to view the content stretched vertically or leave ¼ of the screen blank. Most CRT monitors will accept an input signal of 1920×1080 at 60 Hz, even if the specifications state that the maximum resolution is only 1024×768 at 85 Hz.[citation needed] This is because CRT circuitry only place a hard limit on the combination of vertical resolution and refresh rate, thus a lower refresh rate will allow a higher vertical resolution


    Storage format

    1080p-encoded titles have been released on HD DVD and Blu-Ray. Since the introduction of their first hardware generation, both players have been able to output 1080p video.[citation needed] Current players both allow output of film-based material in conventional interlaced 1080i30 form, and 1080p displays that are able to apply 3:2 pulldown reversal can deinterlace film-based content and achieve full 1080p image quality.

    Video game consoles

    Video game consoles such as Microsoft's Xbox 360 and Sony's PlayStation 3 are able to display 1080p through Component video and HDMI. Xbox 360 also supports 1080p on PC monitor or HDTV using the VGA input, the VGA HD AV cable allows the user to select specific computer resolution such as 1920x1200 and 1280x1024.

    http://en.wikipedia.org/wiki/1080p

    Philips 42PFL7432D/37 42-inch LCD HDTV

    The Philips 42PFL7432D/37 is a set that will certainly make a bold statement. It is among one of the nicest looking sets we've seen, and it comes loaded with plenty of extras. The set's gloss-black bezel and smoked-glass base with swiveling post is a design triumph. This 42-inch set features a native resolution of 1080p (1920x1080) and can handle 1,080i content with ease, while upscaling 720p accordingly. It handles standard definition TV content very well too, and has a bright and clear picture. But don't worry about the brightness hurting your eyes. Philips Ambilight will make sure you don't suffer eyestrain from prolonged viewing in the dark.

    While often considered a novelty feature by its rivals, the Ambilight system with Philips plasma and LCD HDTVs is in fact a very good feature to consider, especially as it casts a subtle light behind the set. After all, don't you remember when your mother and teachers said not to sit too close to the TV, or to watch TV in a dark room? Well, the Ambilight allows you to watch TV while further immersing you into the experience.

    For those not familiar with it, it is an exclusive feature with step-up models from Philips. Essentially it is LED-driven light bars that are the back edge of the sides of the set and this cast a light onto the wall. These can be basic white, but the company has highlighted the ability to cast colors that correspond to the onscreen action. Personally we think that a subtle white light does enough of the job, and it makes sure that your guests don't accidentally trip over the coffee table while heading to get a snack! This 42-inch LCD set also looks quite good with ambient room light as well. The screen reflects very little light, and this is a set that you can comfortably use regardless of the time of the day without the need for serious home theater black out curtains.

    Regardless of the time of the day the Philips 42PFL7432D/37 produces a very vibrant picture with good black levels and very lifelike colors. The set features multiple widescreen modes, including an auto-format feature to get the most out of your picture viewing. The 3D comb filter also ensures that aforementioned standard definition content doesn't look grainy or over saturated. The set also includes Philips Prefect Pixel HD engine, which is basically used to increase the number of lines from various content to improve the quality. We typically find this to be a rather hit or miss feature. While some of the content does look sharper, other sources just look too sharp and have the look of lower quality video. Fortunately, this is an easy enough feature to turn off. Additionally, the set's digital noise reduction helps rid excessive digital artifacts and jaggies. The multiple autopicture modes will also help ensure that you can get a good picture if you don't have the time (or patience) to manually adjust the color and contrast.

    What we found truly impressive is that this set boosts a total of three rear HDMI inputs, so the Philips 42PFL7432D/37 can easily handle your HD needs. However, we were surprised to find that the AV1 was used for composite, S-Video and one of the component inputs. Thank goodness for the second dedicated component input along with side S-Video/composite input. In truth, one S-Video input is probably all you'll need, but having to share the component seems like a poor design choice. The set does however include headphone output--a feature we always like to see--as well as USB input for viewing of JPEG photos. Additionally, the set boasts both coaxial audio input and output, so the TV can easily handle your digital audio needs.

    Speaking of audio, this is the one area where the set comes up a little short. The built-in stereo speakers are a mere 8-watts per channel. Obviously this is enough for those times when you want a few minutes of TV without powering up a surround sound system, but said system is practically required to get the full experience from this set. As this is one of the more affordable 42-inch 1080p models out this year, it is worth considering--you can spend the savings on a better surround sound system.


    Pros: Ambilight system, three HDMI inputs
    Cons: Mere 8-watt speakers, Pixel Plus can be a bit too much, component input shared with composite/S-Video

    http://products.howstuffworks.com/philips-42pfl7432d-37-42-inch-lcd-hdtv-review.htm


    Philips 32PFL9632D Review




    32in LCD
    Picture
    Sound
    Features
    Usability
    Value
    A technological feast, and possibly the best 32in LCD currently available.
    HD Ready: yes
    Resolution: 1366 x 768
    Rating: 93%


    Design

    With slightly rounded corners, the Philips 32PFL9632D introduces a subtle departure in style for the Dutch electronics manufacturers latest range of LCD TV's. Just as visually dramatic as previous LCD TV's, the slim outer grey grille-like bezel with wider inner glossy black screen frame will undoubtedly gain an instant following.

    Features

    Philips have added just a single digit to differentiate their High-End 32in LCD the 32PFL9632D from its predecessor the 32PFL9631D, but don't be fooled by this rather innocuous change. The Philips 32PFL9632D packs an extra technological punch which belies this single digit change.

    Screen: 32in 16:9
    Tuner:Digital
    Sound System: Nicam
    Resolution: 1366 x 768
    Contrast Ratio: 8,000:1
    Brightness: 550cd/m2
    Other Features: Perfect Pixel Engine, HD Natural Motion, 100Hz Clear LCD.
    Sockets: 3 HDMI, 2 SCART, Component Video, Composite Video, PC input.

    By rights, the latest incarnation of Philip's Picture Processing Engine should be Pixel Plus HD 4, but the Dutch manufacturer believes there has been enough technological development packed into this system to warrant a completely new name, 'Perfect Pixel Engine'

    Perfect Pixel Engine, like previous picture processing technology from Philips, has been designed primarily to enhance picture sharpness with both High Definition (HD) and Standard Definition (SD) sources and improve natural detail and colour performance. A main element of this system, 'HD Natural Motion circuit' improves on 'Digital Natural Motion' by employing greater amounts of processing power to improve motion fluidity.

    100Hz processing and 14-bit colour are the other main constituents of the new Perfect Pixel Engine. 100Hz processing inserts an extra picture frame into the equation to take the frame rate up from 50 fps (frames per second) to 100 fps, improving motion handling capabilities. 14-bit colour offers a much larger range of colours and potentially far more realistic and natural images.

    The 32PFL9632 introduces a new version of Philip's acclaimed 'Ambilight' system which delivers light from the sides of the LCD screen to enhance/complement the current scene. With a fully back-lit LED (replacing the previous fluorescent source) which glows through the purpose built frame surrounding the LCD panel, with light actually shinning through the frame, Philips describes the effect as "bringing light and color to life in an unparalleled, highly visual and immersive fashion, drawing the audience into the full emotional experience".

    Performance

    Don't be too concerned with the lack of Full HD (1920 x 1080 pixels) resolution on the Philips 32PFL9632D. You may have heard much recently about the benefits of the extra screen resolution, but for a 32in unit, the potential benefits are negligible. On a larger screen, Full HD comes into its own, but far more important for this size of LCD are how the in-built picture processing elements handle the incoming signal - first indications are that the 32PFL9632D handles it superbly well.

    Immediately apparent with the 32PFL9632D is that we are witnessing something special from an LCD TV with respect to motion handling capabilities. Not a huge leap forward from the likes of Panasonic and Sony, and their take on 100Hz processing, Philips's 100Hz Clear LCD is nevertheless a significant improvement, displaying a fluidity of motion not seen previously on an LCD TV.

    The impressive motion handling capabilities of the 32PFL9632D contribute to increased level of performance in other areas. High Definition (HD) looks superb, with a level of sharpness and detail that places the 32PFL9632D firmly in an elite leading pack of 32in LCD TV's.

    Black levels are again at least a match for for the best 32in LCD TV's, and provide a platform for an incredibly rich and vibrant colour palette. 14-bit colour provides an exceptional range of colours which translate into highly realistic and wholly natural images even with tricky skin tones.

    Before we get too carried away, we have to point out that black levels are still behind the best that plasma technology can offer, and motion handling capabilities, although impressive, will not appeal to everyone. Many of you out there prefer the more natural motion handling capabilities of plasma, while LCD can appear over processed and just too vivid.

    Conclusion

    The 32PFL9632D is not perfect, but is arguably good enough to be at the head of an elite leading pack of 32in LCD TV's.

    http://www.hdtvorg.co.uk/reviews/lcd/Philips_32PFL9632D.htm

    Philips feminizes the LCD TV

    With its 'Design Collection' of LCD TV's the Dutch electronics giant is cottoning on to the fact that style sells. It is actually focusing some of its design efforts around market research that suggests that for 98% of female consumers style is an important factor in the buying process.

    Andrea Ragnetti, Philips' consumer lifestyle guru is at the forefront of a growing trend within large consumer focused organisations who have recognized the increasing importance of female buying power.

    Three new LCD TV series' the 7000, 5000 and 3000 certainly lean towards a more 'femmine' style without being overtly directed towards the fairer sex. The new panels however have substance to back up the style with

    The top of the range 1080p 7000 series comes equipped with 120Hz processing, an extremely rapid 2 millisecond response time along with an impressive 4 HDMI (v1.3) inputs.

    The new panels will feature Philips' proprietary HD Digital Natural Motion technology (HD DNM) which has been designed to reduce on-screen juddering, while Motion Estimation Motion Compensation (MEMC) acts to further smooth motion by inserting compensating frames within faster scenes.

    With a growing reputation for producing some of the most technologically advanced LCD TV's around, Philips' like other manufacturers have begun to realize the importance of psychological aspects and how they affect their bottom line

    http://hdtvorg.co.uk/news/articles/2008013002.htm

    Sony Bravia KDL-40D3500 40in LCD TV

    So how come the 40D3500 only earns a 7 for picture quality? Because it suffers more than it really should from that old LCD bugbear of motion blur. And so while static images look superb, whenever anything moves around the screen at any sort of speed - especially if you're watching standard definition - the picture starts to look smeared and indistinct. And no matter what we did with the image's various settings, there wasn't a single thing we could do about it. Grrr.


    Moving on to the 40D3500's audio, there's enough raw, distortion-free power to give at least a modicum of satisfaction when watching even a pretty intense action movie. Voices remain clear no matter how loud everything else in the mix is, though as with many LCD TVs, bass feels a little ‘poppy', lacking the sheer depth to really make a good, meaty explosion sound convincing.

    Verdict

    In some ways - black levels and colours, at any rate - the 40D3500 continues Sony's forward progression with LCD. But it needs to get its head around this motion-handling business too if it's really to start challenging the very top LCD dogs.

    http://www.trustedreviews.com/tvs/review/2008/02/24/Sony-Bravia-KDL-40D3500-40in-LCD-TV/p3

    Sony Bravia KDL-40D3500

    Product properties
    Built-In Digital TV Tuner / Freeview Yes A digital TV tuner built into a HD Ready TV is not necessarily able to transmit HD signals. The tuner itself needs to be HDTV labeled. To be certain, contact the retailer or manufacturer.
    Screen
    Screen Size 40.0 inches Picture size is measured in inches.
    An inch is 2.54 cm. The size of the screen is measured diagonally from corner to corner.
    Type LCD What technology is the TV based on?
    Tube- The most common technology. Today there are several types of picture tubes, among others flat tubes that give a very sharp and flicker free picture ...
    More info
    Digital TV
    HDTV Compatible Yes HDTV-compatible means that the TV can receive a HD-signal(720p/1080i) and display it, but not with the highest HD-quality. This might be because the TV:s resolution is too low or the TV might be missing the digital inputs required (DVI and/or HDMI with HDCP support).
    HD-Ready Yes High Definition TV (HDTV) means that a TV can broadcast signals of at least 720p or 1080i via any of the TVs inputs, usually the component-input. “HD-ready” is a license that can be executed by EICTA ...
    More info
    Picture
    1080p24 Support Yes
    Screen Format Widescreen The picture format of the TV.

    4:3 - The standard picture format is 4:3 - which is the relation between the width and height of the TV screen. This is the almost square picture format that ha ...
    More info

    Full HD (1920x1080) Yes (1920x1080) Filtering on 1080p will show all HD-Ready TVs with a minimum resolution of 1920x1080. This means that the TV can not only receive but also show the content of the highest consumer HDTV resolution.
    ...
    More info
    Progressive Scan Yes A television with progressive scanning can generate a picture in a single pass, in a similar way to a computer screen. A standard television uses an interlacing format, alternating lines 50 times a se ...
    More info
    Supported Picture Formats 80i/p, 576i/p, 720p, 1080i/p
    NTSC Playback Yes
    PiP (Picture in Picture) Yes
    Frequency/Hertz N/A The scanning frequency.
    50 Hz - The picture is updated 50 times per second.
    100 Hz - The picture is updated 100 times per second, giving a sharper picture with less obvious "flicker".
    Zoom Yes
    Image Enhancement Engine Sony Bravia Engine
    Sound
    Speakers Stereo Type of sound
    Mono - the sound comes through a single channel, even if the TV has two speakers.
    Stereo - The sound comes through two channels and creates a more realistic, richer ...
    More info
    Speaker output 20 W Indicates the sound effect.
    For example, 2x10W means that the model has two sound channels with a power of 10 Watts each. Watt - in short, the measure of the amplifier's power.
    LCD/Plasma/DLP
    Resolution 1920x1080
    Contrast Ratio 1800:1 The contrast ratio is interpreted in a wide variety of ways. Some retailers and/or manufacturers states the dynamic contrast while others choose to show the static contrast ratio. These ...
    More info
    Brightness 450 cd/m2
    Pixel response time 8.0 ms
    Viewing angle H/V 178/178 degrees
    Connections
    Component Inputs 1 The three-jack (RCA/Phono) component video connection splits the video signal into three parts (one brightness and two color signals). Component video has increased bandwidth for color information, re ...
    More info
    HDMI Input 2 High Definition Media Interface. A type of connection for connecting Digital Video and Audio.
    Scart Connections 2 A SCART connector is a physical and electrical interconnection between two pieces of audio-visual equipment, such as a television set and a video cassette recorder (VCR). Each device has a female 21-p ...
    More info
    VGA (HD-15) Inputs 1 A connector for a computer cable in which the plug and socket are D-shaped so they only fit together one way. DB connectors are often used for serial ports. DB-9 connectors have 9 pins and are used to ...
    More info
    S-Video Input Yes Short for Super-Video, a technology for transmitting video signals over a cable by dividing the video information into two separate signals: one for color (chrominance), and the other for brightness ( ...
    More info
    Phono output Yes
    Features
    Built-In DVD / HDD / VCR No
    Additional Stand/Cabinet included No Shows if a Stand/Cabinet is included with the TV. This specification can be different from country to country. So please check with retailer to be sure.
    Measures
    Dimensions HxWxD 64.3x98.1x11 cm
    Weight 20.5 kg
    Related
    Manufacturer Sony
    Miscellaneous Miscellaneous

    http://www.pricerunner.co.uk/pi/2-1009391/TVs/Sony-Bravia-KDL-40D3500-Product-Info

    Sony KDL-40D3500 Review



    Sony KDL-40D3000


    Design

    The KDL-40D3500 is the embodiment of Sony's design philosophy with a chic matte black understated presence that simply oozes class. Build quality is back to its very best with the Sony looking like it could have been sculpted from a solid block of metal.

    Features

    A change in model number from 3000 to 3500 would suggest that the KDL-40D3500 represented a relatively minor upgrade from its predecessor the KDL-40D3000. However, the changes in specification are more wide ranging than you would imagine.

    To begin with, the 40D3500 gains a Full HD (1920 x 1080) resolution which can potentially give a marked improvement in the display of sources such as Sky Tv (1080i). The 1080 lines of resolution match the resolution of the screen negating the need for any picture scaling to fit. If you have a device which outputs pictures in the superior 1080p (e.g. Sony's PlayStation 3) the 3500 can accept those pictures in their full glory.

    http://www.hdtvorg.co.uk/reviews/lcd/sony_kdl-40d3500.htm

    Sony Bravia KDL-40D3500 40in LCD TV

    Considering that it's surprisingly affordable for a full HD, 40in LCD TV from a premium brand, the 40D3500 is passably well stocked with features. The single most significant of these is Sony's Bravia Engine image processing system, designed to boost colours, contrast, motion clarity, detailing and noise suppression. Even though the 40D3500 only gets the most basic version of the Bravia Engine (as opposed to the EX and Pro versions found higher up the Sony tree), that should still be enough to produce likeable results based on past experience.

    Live Colour Creation, meanwhile, uses a mixture of processing and a wide colour gamut backlight system to produce a claimed 30 per cent more colour range than conventional LCD technology. Plus there's a Photo TV HD process claimed to reproduce digital still photographs in their optimal quality, Sony's ‘S-Force' pseudo surround sound mode, picture-and-picture facilities, and both MPEG and standard noise reduction facilities.


    In many ways the 40D3500 puts its various picture aids to good use. Colours, for instance, are something of a triumph, boasting a combination of terrific vibrancy (a more expressive range than we're used to seeing with LCD) and best of all, the most natural tones we've yet seen from a Sony LCD TV. In fact, precious few flat TVs from any rival brand deliver colours so subtle and credible, especially where skin tones are concerned. The full HD resolution helps colour blends look finer, too.

    The 40D3500 also impresses with its contrast. Bright whites look crisp and devoid of the yellowish tone that can trouble many LCD TVs, while dark scenes benefit from some impressively deep black levels besmirched by pleasingly little of the clouding or blue undertone that affects many LCDs - including this Sony's own predecessors.


    The black level response is not, it has to be said, anything to rival that of Pioneer's KURO sets. But then to be honest this is no more than we would have expected.

    Relatively static HD images, meanwhile, highlight another benefit of the 40D3500: its exceptional sharpness. Fine details are rendered with total, noiseless precision, giving the image exactly the sort of ‘snap' we love to see with our HD stuff. Plus the image tends to look more three-dimensional thanks to all the background detail that's resolved.

    The Bravia Engine system is additionally to be congratulated for removing noise of pretty much all types from pictures of both HD and SD flavours.

    http://www.trustedreviews.com/tvs/review/2008/02/24/Sony-Bravia-KDL-40D3500-40in-LCD-TV/p2

    SONY KDL40D3500 40 INCH LCD TV

    SONY KDL40D3500 40 INCH LCD TV features stunning 6.2 mega pixel 1080p resolution, BRAVIA Engine picture enhancement technology, 24p True Cinema to create a realistic cinema experience at home and 2 HDMI inputs for easy connectivity to High Definition sources such as Blu-Ray

    Product Specifications

    Resolution
    Full HD 1920 x 1080
    Colour
    Black
    Contrast Ratio
    1,600:1
    Response Time
    8 ms
    Tuner
    Analogue/Digital Freeview
    Speakers
    Yes
    HD Ready
    Full HD (1080)
    Dimensions
    98 x 65 x 11 cms
    Weight
    24 Kgs
    Warranty
    1 year manufacturer
    Connections
    2 x HDMI
    S Video

    Component

    2 x Scart

    Composite

    PC Input

    Included Accessories
    Remote Control
    Table Top Stand
    Optional Accessories
    Wall Bracket
    Floor Stand

    http://www.1staudiovisual.co.uk/catalog/sony-kdl40d3500-inch-p-2991.html?tduid=7e0d4c1119fb445e1c8988d3d97bd030&ref=208

    SONY KDL40D3500 -- 40" HD READY LCD WIDESCREEN TELEVISION

    Video Signal
    576i
    480p
    576p
    1080i
    720p
    1080p
    24p input

    Timer

    Clock
    Sleep Timer
    On/Off Timer (with Clock setting)

    Accessories

    AC Cable
    Coax Cable
    Operating Instructions
    VESA Mounting Holes
    Table-Top Stand - Supplied
    Remote Commander - RM-ED009
    Table Stand Supplied
    Wall-Mount Bracket - SU-WL500 (optional)
    TV Stand - SU-FL300M (optional)

    Audio

    Digital Amplifier
    S-Force Front Surround
    Power Output (W) - 10W + 10W (Total 20W)
    Sound Mode - Dynamic/Standard/Custom
    Steady Sound
    Auto Volume Adjustment
    Speaker Off

    Colour System

    NTSC 3.58/4.43 (Video In)
    PAL
    Secam

    Connectors

    PC Input (15pin D-Sub) + Audio In
    Component
    HDMI
    HDMI 2
    4 Pin (Y/C) In
    MiniJack (Head/Earphone) (mm) - 3.5
    PCMCIA Card Slot
    RCA Audio Out
    RCA AV Input
    RF In
    Scart 1 - YES (RGB)
    Scart 2 - YES (RGB)
    Bravia Theatre Sync

    Dimensions

    With Table Stand (W x H x D, cm) - 98.1 x 69.2 x 26.5
    Without Table Stand (W x H x D, cm) - 98.1 x 64.3 x 11.0

    General Data

    Colour - Black
    Power Consumption (Standby) (W) - 0.3
    Power Consumption (W) - 193
    Weight Inc. Stand (kg) - 24
    Weight Without Stand (Kg) - 20.5

    Menu

    On Timer
    OSD Menu
    Parental Lock
    Sleep Timer

    Menu Languages

    Bulgarian Menu
    Czech Menu
    Danish Menu
    Dutch Menu
    English Menu
    Finnish Menu
    French Menu
    German Menu
    Greek Menu
    Hungarian MenU
    Italian Menu
    Norwegian Menu
    Polish Menu
    Portuguese Menu
    Romanian Menu
    Russian Menu
    Slovakian Menu
    Spanish Menu
    Swedish Menu
    Turkish Menu

    Picture

    On Screen Contrast - 1800:1
    Dynamic Contrast - 16000:1
    Brightness - 450 cd/m2
    Response Time - 8 mseC
    Viewing Angle - 178 °
    Backlight - WCG-CCFL
    BRAVIA ENGINE
    Input Skip
    Live Colour Creation
    Picture Mode - Vivid/Standard/Cinema
    Theatre Mode
    Photo TV HD
    Power Saving + Picture Off
    14:9 Mode
    16:9 Mode
    4:3 Mode
    AFD (Auto Format Detect)
    Auto 16:9 (line 23)
    Auto Noise Reduction
    Digital Comb Filter
    Display Resolution (Pixels) - 6.2 Mega Pixels
    Display Technology - LCD
    Picture In Picture
    Picture & Picture
    Screen Aspect Ratio - 16:9
    Screen Size (inch) - 40
    Screen Size (cm)
    Smart Mode
    Wide
    Zoom

    Sound System
    B/G
    D/K
    I
    L
    NICAM

    Teletext

    Digital Text
    EPG (NexTView/Digital EPG)
    Text Page Memory - 700

    Tuning
    Analogue Terrestrial Tuner
    Digital Terrestrial Tuner (MPEG 2)
    Digital TV Cable Tuner (with supported operators)
    Favourite Channels
    Channel Coverage CATV - S1-S20
    Channel Coverage HYPER - S21-S41
    Channel Coverage UHF - E21-E69
    Channel Coverage VHF - E2-E12
    Channel Skip
    No. of Tuners - 1
    Station Labelling

    http://www.beyondtelevision.co.uk/thisProduct.asp?ID=1289

    A Little Telomerase Isn’t Enough

    Chromosome ends, or telomeres, are repetitive stretches of DNA that protect chromosomes in much the same way as plastic tips on shoelaces prevent the fabric from fraying. Each time a cell divides, its chromosome ends get a little shorter, and eventually the cell can no longer divide because its critical genetic information is exposed. In stem cells, however, a protein called telomerase normally maintains the telomeres’ length, allowing the cells to divide indefinitely.

    Now, the Hopkins researchers report that mice engineered to have just half the normal amount of telomerase can’t maintain their stem cells’ chromosome ends, showing that a little telomerase isn’t enough. In these “half-telomerase” mice, their telomeres shortened over time, bringing an early demise to stem cells that replenish the blood supply, immune system and intestine, the researchers report. Moreover, offspring of these mice bred to have normal levels of telomerase still exhibited early loss of stem cells, the researchers report in the Dec. 16 issue of Cell.

    “These offspring have what we have called ‘occult’ genetic disease — their genetic make-up is perfectly normal, but they still have the physical problems of their parents,” says Carol Greider, Ph.D., director and professor of molecular biology and genetics in the Johns Hopkins Institute of Basic Biomedical Sciences. “This phenomenon could complicate the hunt for disease genes.”

    Scientists generally figure that inherited disease accompanies an inherited mutation in one or more genes. In the case of the genetically normal offspring of two half-telomerase parents, however, the disease is still present. The problem in these animals turns out to be the animal’s inherited telomere length, not the status of the telomerase gene, says Greider.

    “If you were to search for the genetic mutation behind this mouse’s disease, you wouldn’t find it — there isn’t one,” says Greider. “These mice develop disease only because their telomeres are short, and having telomerase doesn’t lengthen them right away.”

    http://biosingularity.wordpress.com/2005/12/24/a-little-telomerase-isnt-enough-study-links-length-of-chromosome-ends-to-a-rare-disease-of-stem-cells/

    Telomeres

    Telomeres, together with the enzyme Telomerase are mentioned a lot lately in association with both aging and with cancer. It seems that their gradual shortening during the lifetime of a cell eventually results in damage to DNA and thus the genes of which they are a part. This has led to a great deal of research into Telomeres and Telomerase, some of which will be outlined in this section of the site. First of all however, let us get some of the basic definitions out of the way.

    Definition of a Telomere

    A telomere is a region of highly repetitive DNA at the end of a linear chromosome that functions as a disposable buffer. Every time linear eukaryotic chromosomes are replicated during late S-phase the DNA polymerase complex is incapable of replicating all the way to the end of the chromosome; if it were not for telomeres, this would quickly result in the loss of useful genetic information, which is needed to sustain a cell’s activities. http://en.wikipedia.org/wiki/Telomere

    Definition of Telomerase

    Telomerase is the reverse transcriptase responsible for the extension of telomeric repeat sequences in most species studied. If telomerase activity is diminished or absent, telomeres will shorten. Shortened telomeres appear to lead to cell senescence. Eventually telomeric sequences can shorten to the point where they are not long enough to support the telomere-protein complex protecting the ends and the chromosomes become unstable. These shortened ends become 'sticky' and promote chromosome rearrangements. Some rearrangements may contribute to the development of cancers. http://www.genlink.wustl.edu/teldb/tel.html

    Role, Function and Compesition of Telomeres

    In the majority of Prokaryotes, the chromosomes are circular. This means that they do not have ends that are prone to damage or ‘premature replication termination.’ Note that a small number of bacteria, Borrelia and Streptomyces for example, do possess linear chromosomes (together with circular plasmids). These chromosomes are very different however, from those which are found in Eukaryotic cells (such as those in humans.

    A telomere consists of repeating base sequences (in humans this is a repeating string of TTAGGG bases between 3 to 20 kilobases in length). In addition to the telomere itself, there is a 100-300 kilobase sequence associated with the telomere, which is located between the telomere and the rest of the chromosome.

    As replication of DNA occurs during the lifetime of an organism, the telomeres gradually shorten. This shortening eventually results in damage to the chromosomes themselves and to the genes that they contain. The results of this are either a reduction in the cells ability to express its genes and a descent into cellular senescence (cellular dormancy) or in some cases the over or under-expression of specific genes. When this chromosomal damage leads to either an over or under-expression of certain genes, then cellular functionality can be compromised. In some cases the organisms survival can also be compromised as cellular replication can become unchecked. These cells thus become cancerous and can lead to the death of the organism.

    Role, Function and Compesition of Telomeres

    During DNA replication, The DNA unzips and a complimentary strand is formed against the unzipped sections. Telomeres shorten during this process due to the ‘lagging strand’ phenomenon.

    Basically DNA replication does not begin at the end of the DNA, but in the centre. DNA Helicase unzips the DNA forming Replication bubbles. An RNA Primer or Primase then attaches to each DNA strand and replication begins in the 3-5 direction, thus forming a new strand in the 5 -3 direction.

    DNA polymerases move and replicate the DNA in the 3 to the 5 direction (thus making a replica strand in the 5 to 3 direction). Note that 3 refers to the 3 OH group of the sugar and the 5 refers to the 5 phosphate group of the nucleotide.

    The leading strand of DNA is the strand that is oriented in the 3-5 direction. The primer of complementary molecules that binds to the first few of the exposed bases ends with a 3 sugar group. The phosphate of a new nucleotide can be attached here by DNA polymerase. DNA polymerase then continues along the strand, synthesising a new strand as it goes. An animation of this process can be seen below, provided by the Nobel e-museum.

    http://www.nobel.se/medicine/educational/dna/a/replication/replication_ani.html.

    The lagging strand however, faces more problems when it comes to replication. Because DNA polymerase can only attach to the 3 sugar group and thus move in the 3 to the 5 direction, it needs therefore to move in small jumps (in the opposite direction to overall replication) to replicate the lagging strand. See below animation. This is again provided by the Nobel e-museum.

    http://www.nobel.se/medicine/educational/dna/a/replication/lagging_ani.html

    Note that the small segments of DNA and primers which are produced on the lagging strand are called Okazaki fragments. Another DNA polymerase enzyme is then recruited to remove the primers and to replace them with DNA. Finally DNA Ligase seals the gaps between the Okazaki fragments.


    DNA Replication


    DNA Replication

    The problem with Telomere shortening occurs because, in order to change the RNA primers into DNA, there must be another DNA segment in front of the primer. There is a DNA segment ahead of the primer at every section of the strand, except where the last primer attaches (the end of the telomere). This means that this final primer cannot be replaced with DNA. It does get removed by various enzymes however, but in the process, the telomere shortens.

    In human blood cells, the range of lengths of the telomeres varies between 8000 base pairs at birth, to 1,500 base pairs in the elderly. During cellular division, an average of 30 to 200 base pairs are removed from the ends of the telomeres.

    In normal cases, the cells of a human can divide between 50 to 70 times, with the telomeres shortening with each division, until the cells either commit suicide through a process known as Apoptosis, become Senescent (dormant) or transform to cancerous cells due to genetic damage.

    The process of Cellular senescence due to Telomere Shortening

    Cellular Senescence

    As a cells telomeres shorten during multiple cellular divisions, DNA damage occurs and the cell, recognising this damage shuts itself down. Below is a simplified diagram of how this occurs.


    Telomere shortening and aging

    DNA damage results in an activation of the p53 gene. p53 then activates p21, which blocks the actions of a number of CDK’s (Cycline Dependent Kinases). Note that CDK’s are involved in the regulation of the cell cycle, transcription and mRNA processing. The blocking of certain CDK’s prevents the phosphorylation of pRb. This lack of hyperphosphorylated pRb results in a failure of expression of several critical genes, which are involved in cellular division. Cellular division then stops.

    Telomerase and Telomere extension

    A study was conducted (as so many aging studies are) using the nematode Caenorhabditis elegans (Joeng KS, Song EJ, Lee KJ, Lee J (2004). "Long lifespan in worms with long telomeric DNA". Nature Genetics 36 (6): 607-11.). This study indicates that by lengthening the Telomere, longevity can be increased.

    Two distinct groups of Nematodes were engineered. The only difference between the two groups, was the length of the Telomere. The group with the longer telomere’s lived approximately 20 percent longer than the group with the shorter telomeres. Also, it was observed that the Nematode’s with the longer telomeres possessed a greater resistance to the effects of heat exposure.

    Telomerase is the natural enzyme which promotes telomere repair. It is however not active in most cells. It certainly is active though in stem cells, germ cells, hair follicles and (worryingly) in 90 percent of cancer cells. Telomerase functions by adding bases to the ends of the telomeres. As a result of this telomerase activity, these cells seem to possess a kind of immortality.

    In 1990 a team at Geron Corp in Menlo Park, California led by Serge Lichtsteiner and Andrea Bodnar,in association with the University of texas Southwestern Medical center, managed to activate the production of telomerase in cells that do not usually produce this enzyme. The results were that the telomeres started to lengthen. By the time that they released the results of their study, their cells had divided 20 or more times than would normally be expected before senescence would set in. These cells also seemed to retain their normal gene expression and showed no signs of becoming cancerous.

    I will now try to explain in more detail the details and results of the teams study.

    Basically, telomerase is present in all cell types, however the human gene for the catalytic protein telomerase transcriptase (hTRT) is present only in immortal cells (such as stem cells or cancerous cells). Scientists from the teams observed that lengthening of telomeres in retinal pigment epithelial cells, foreskin fibroblasts and vascular endothelial cells by introducing the hTRT gene into these cells, results in a resumption of telomerase activity. This resumption resulted in the extended longevity of the cultured cells, as discussed previously.

    Varying Telomere decline

    One interesting study by Peter Lansdorp of the Terry Fox Laboratory, Canada, observed in human fibroblasts that the rate of telomere shortening as cells divide varies between different telomeres. This variation is between 50 to 150 base pairs per cell division. It is worth noting that the telomeres that are shorter initially. For example in humans the 17p telomere, are not necessarily the ones to be destroyed first! It does seem that it is the shortening of specific telomeres that are linked to a cells decline into senescence, apoptosis or its transformation into a cancer. Martens et al, 1998, observed that the shortening of telomeres 1p, 5p and 22p, but not that of 17p, showed a statistical correlation with the descent into cellular senescence.

    Despite all of the above outlined observations, it is a statement of fact that the mean telomere length of a species does not always relate to the longevity of that species. For example Katuo et al, 1999, noted that of all studied primates, humans seem to have both the shortest telomeres and the longest lifespan! Bassham et al, 1998, also observed that the long lived frog Xenopus Laevis displayed a great variation in telomere length and that telomere length could even diminish between parent and offspring, with no detectable consequences.

    To summarise, it seems that it has not yet been determined whether the instability of a chromosome and its eventual deterioration is a result of general telomere shortening or the shortening of specific telomeres. It has however been found that by artificially lengthening the telomeres of cells, which do not normally have a mechanism to lengthen their own telomeres, the cells longevity and ability to function normally for longer, does increase. More research therefore needs to be conducted in order to determine the exact significance of telomere length in the aging of an organism and the exact consequences of artificially stimulating telomere repair.

    http://www.whyweage.com/node/11


    Chromosomes

    Eukaryotic DNA is arranged into chromosomes. It has long been assumed that each chromosome contains a single very long, linear DNA molecule though this has been demonstrated in only a few species. For example in yeast pulsed field gel electrophoresis (which is a technique for separating very long pieces of DNA) shows that the number of individual DNA molecules in the nucleus is approximately the same as the number of chromosomes.

    These chromosomes have three functions:

    1. they replicate once per cell cycle - during the S phase of interphase

    2. they segregate to daughter cells at mitosis

    3. they package DNA into managable units

    Chromosomes possess within their DNA, specialised nucleotide sequences which are necessary for these functions.

    Replication Sequences

    Origins of replication

    These are the sites where replication begins and there are usually a large number of these on each eukaryotic chromosome.

    The DNA sequences which comprise origins of replication have been isolated from yeast. These have been called autonomously replicating sequences or ARSs. An ARS is defined as a region of DNA which is necessary and sufficient to ensure replication of a circular piece of DNA once per S phase.

    ARS sequences were identified by cloning random fragments of yeast chromosomal DNA into a plasmid vector and then introducing them into yeast cells. If this plasmid contains a drug resistance marker and the yeast cells are plated on a medium containing the drug - only those cells containing a replicating plasmid will be able to form a colony. About a dozen different ARSs have been isolated in this way and it has been calculated that there are approximately 400 ARSs spread over the 17 chromosomes of yeast.

    ARS.gif (34837 bytes)

    Mutational analysis has identified a region of about 50 bp that is required for proper ARS function. When the nucleotide sequence of different ARSs was compared it was found that there is an 11 bp sequence found in all of them - this suggests that this sequence is important, and indeed mutations in this region (region A) abolish ARS activity. However, the 11 bp sequence on its own cannot act as an ARS. Additional DNA sequences (B1-B3) are necessary for its function - this DNA shows no similarity between different ARSs but it often contains imperfect matches to the consensus sequence.

    A complex of 6 proteins, called the origin recognition complex or ORC, binds to the ARS. The function of these proteins has yet to be determined. One important function must be the initial unwinding of the two strands of the DNA helix. It may be significant that the conserved core sequence is AT rich - AT base pairs are weaker than GC base pairs and so are more easily broken.

    http://bssv01.lancs.ac.uk/ADS/BIOS336/336L5.html

    Does the fountain of youth spring from our chromosomes?

    The search for immortality has long been a quest of the human spirit. Whether it manifests as a belief in some sort of spiritual afterlife or in prolonging our mortal lives, humanity seems to find the ending of consciousness a horrid thought. Naturally, the mechanisms for why people grow old and die would gain a huge amount of attention by both researchers and the non-scientific community. Many scientists believe the key to mortality has already been found, and it is located at the ends of our chromosomes. Research has discovered that regions of repetitive DNA stretches called telomeres found on the ends of our DNA strands are cut shorter every time they are copied. Eventually the telomeres are worn away and genes near the end of the chromosomes are lost which contain protein instructions the body desperately needs to survive. Some believe that it is this slow yet eventual erosion of the ends of our chromosomes that leads to aging. The discoveries in this area will have a huge impact on more than just showing the way to a possible fountain of youth. Cancer research and cloning may also hinge on developments in the field of telomere research.

    Telomeres exist as the body’s way of solving a problem with DNA replication. DNA is replicated by the use of an enzyme called DNA polymerase. DNA polymerase functions to copy our chromosomal DNA, using an existing DNA "parental" strand as a template. The polymerase performs this feat by attaching nucleotides to polymerize a new "daughter" DNA strand in complement to the parental strand. Adenine (A) is added to the new strand complementary to thymine (T) while guanine (G) is added complementary to cytosine (C), and visa versa. There are two main problems with the capabilities of the DNA polymerase. The first is that it can’t start from scratch. There must be a segment of the new strand from which the polymerase can begin attaching new nucleotides. The use of primers easily solves this problem. These primers are RNA fragments that bind by random assortment complementary to sites on the parent strand of DNA, and must be in place before the DNA polymerase can begin copying the parent strand.


    The second problem caused by DNA polymerase during replication is much more difficult for cells to surpass. DNA polymerase can only work in a 5’ to 3’ direction. The terms 5’ and 3’ refer to the sugar molecule in the sugar/phosphate DNA backbone. The numbers relate to the carbon in that ring of sugar. 5’ is the fifth carbon in that ring. 3’ is the third. In order for the polymerase to attach a new complementary nucleotide, an alcohol (-OH) group must be available on the 3’ carbon of the sugar molecule. That is the site where the polymerase attaches the phosphate group of the next nucleotide. This phosphate group is subsequently attached to the 5’ carbon of the new nucleotide’s sugar group. The polymerase can therefore only work from the direction of the previously attached 5’ carbon to the 3’ carbon, which has the –OH group available for the attachment of the next nucleotide. The problem with this unidirectional movement lies with the primers, for they can’t stay in the new strand because they are RNA, and not DNA. Removal of these RNA primers is really not a problem when they are located in the middle of the new daughter strand. There will be a 5’ carbon available for a DNA polymerase to fill in the gap that remained after primer removal. However, the problem lies at the beginning each chromosome. A primer was necessary to provide a 5’ carbon for the beginning of synthesis, yet once it is removed, an upstream 5’ carbon is not available from which a polymerase can attach nucleotides and fill in the gap. Therefore, because the nucleotides are are not replaced after removal of the first primer at the beginning of every chromosome, every time the chromosome replicates the daughter strand will be shorter than the parental strand. Studies have shown that the length of a chromosome shortens by about 50 nucleotides every time it replicates. The damage isn’t huge compared to the overall length of a chromosome, but it does mean the chromosome is mortal in that it is slowly being eaten away at the ends with every cell division. If any of these 50 nucleotides contains the instruction to begin the transcription of a gene, that gene and the protein it encodes will never be usable by the body again.


    Replication shortens the chromosome


    The body’s natural cure to this dilemma is the production of expendable nucleotides at the 3’ end of every chromosome. These "cannon fodder" nucleotides are called telomeres. Telomeres are repetitive hexameric (6 base pair) sequences of DNA. In humans this repeated G-rich sequence is AGGGTT. These sequences are 1000-1700 base pairs long at the beginning of a mammalian life. Cells seldom survive past about 50 divisions in vitro, which most researchers ascribe to the deletion of too many genes in the process of replication.

    Oddly, these telomeres are not encoded in the initial DNA resulting from egg fertilization. What this means is that the telomeres must be added later in development. In 1985 Elizabeth Blackburn and Carol Greider discovered a new DNA polymerase which can add telomeres to DNA. This polymerase, called telomerase, is a ribonucleoprotein present in the very early stages of development. Telomerase activity stops in later development, as it is only required to put the telomeres in place once. Ribonucleoproteins contain RNA, which telomerase uses as a template to synthesize the hexameric DNA telomeres. Because telomerase is a polymerase that copies an RNA template (its own) into DNA, it is a reverse transcriptase. A reverse transcriptase is so named because it is capable of writing codes of DNA from an RNA template which is the reverse of transcription. Reverse transcriptases have gained a lot of fame because they are used by retroviruses, notably HIV, for viral replication.

    Telomerase binds to the 3’ end of a chromosome and lines its own RNA template so that a few of its RNA base pairs are complementary to that of the strand. Another segment of the ribozyme hangs over the edge providing a template for the synthesis of the telomeres (CCUAAC). Telomerase synthesizes the hexomeric sequence and then translocates to a new 3’ recognition site, which is within the hexanucleotide it just produced, and repeats the procedure. A normal DNA polymerase and primer can then complete the complementary strand’s 5’ end with all of the new hexomeric repeats--all except the last bit of course. The exact details of telomerase function are currently under research, but its currently understood mechanism as a DNA polymerase that carries its own template appears quite unique and phenomenal.

    Could the "Fountain of Youth," simply be a shot of telomerase? Some research hints that this might be a good start to combat aging. For example, recent studies have shown that mice deficient in the gene for encoding telomerase RNA (mTR) developed liver cirrhosis sooner and regenerated much slower than normal mice. These same mice also showed improved liver function upon receiving gene delivery of telomerase. In the future, it may be possible to induce telomerase to reset aging cells back to their chromosomal state during a person’s young and vibrant 20’s. However, in most cases the addition of telomerase into somatic cells late in development would be a death sentence. Cell death (apoptosis) is often a good thing in the body. If some cells didn’t die, some tissues would never stop growing. Apoptosis is a crucial tool used by the body to maintain proper development. Certain cells must die at certain times or else the entire organism will perish.

    Another aging-related subject that telomere research might prove helpful to is cloning research. Cloning researchers have found that unfortunately the telomeres of cloned animals (such as the famed cloned sheep named "Dolly") are much shorter than a counterpart of the same developmental "age". Even though cloning technology has attained successful birth rates as high as 80%, most of these clones die before even reaching adulthood. Shortened telomeres appear to be the most likely cause of these deaths. Research seeks to uncover a means of safely extending the telomeres of the clones. Some may hope that the solution to the clone problem will eventually bring about a magic youth potion to humanity.


    Telomerases might be cancer's Achilles heel


    Besides the prevention of age-related health problems, another motivating drive for telomerase research is to develop effective cancer treatments. Scientists are attempting to destroy the telomeres by eradicating telomerase activity in cancer cells. The purpose is to limit the number of divisions possible in these cells. Normal somatic cells have no telomerase present in them because the expression of the telomerase gene is shut down early in life. Because these cells live a long time in the body, the telomeres created early in life are long enough to serve them for the number of divisions they need to make during the lifetime of the organism. However, cancer cells are defined by unbridled cell division, and therefore it is the telomerase which allows cancer cells to continue their unhindered proliferation and subsequent immortality. One of the mutations that leads to a cell becoming cancerous is one that disrupts the cells ability to shut down telomerase expression. Cancer researchers have become very interested in designing drugs that target and inactivate telomerase, for if telomerase could be inactivated this would lead to cancer cells becoming mortal again and stop them in their tracks.

    Although using telomere research for finding a treatment for cancer is a popular concept that everyone supports, the idea of significantly extending life is much more controversial. With the population of Earth bulging proudly over 6 billion souls one has to ponder if human immortality would be a blessing at this point in time. Endless life could be to society what cell immortality is to the body.

    http://www3.interscience.wiley.com:8100/legacy/college/boyer/0471661791/cutting_edge/telomeres/telomeres.htm