Friday, December 21, 2007

Are you getting all the HDTV resolution you paid for?

Not necessarily, given the results of Home Theater Mag's recent tests of 61 HDTVs. Using test patterns from a Silicon Optix HQV HD DVD, they tested deinterlacing, 3:2 detection and for the 1080p sets, bandwidth. Unfortunately, just over 54% of the HDTVs failed the deinterlacing test, 80% failed the 3:2 test, but the 1080p sets passed the bandwidth test, despite all but one (Pioneer Elite PRO-FHD1) losing some detail. If a HDTV doesn't pass these tests, then you're losing at least some visual information from a 1080i signal. Some televisions throw away half the horizontal lines, which results in a fail on the deinterlacing test, or don't perform inverse telecine on moving images appropriately, failing the 3:2 test. Of course, contrast ratio, refresh rate and black levels still contribute to overall picture quality, but you should take a look at their results to make sure you're getting every pixel you expected from your new HDTV.


Of 1080p and 1080i ...

While high definition has become a reality for many consumers, the technical jargon associated with this exiting new technology is causing much confusion. Just as we were beginning to understand the differences between Blu-ray and HD DVD along comes a new high-definition format, 1080p.

But why do we need another high-definition format anyway? Many of us have bought our HD Ready screens and were ready to sit back and enjoy this new viewing experience, but now we are all wondering if we bought the right kit in the first place.

Many of the more recent HD Ready flat screens feature a resolution of 1,366x768 pixels. This will display the commonly used 720p and 1080i formats, although 1080i/1080p signals will be downscaled to fit. To display 1080i/1080p signals in their entirety, you'll need a screen with a resolution of 1,920x1,080 pixels, coined 'Full HD' by the marketing men.

However, just because a screen has 1,920x1,080-pixels it does not necessarily mean that it will accept 1080p input - so check before you buy.

Remember, 720p, 1080i, 1080p are formats in which 'Sources' of high definition content are presented for viewing on a particular output device such as your LCD/Plasma screen. The source could originate from your TV cable provider for example, or your xbox 360. To restate the point, 1080i/1080p needs a screen resolution of 1,920x1,080-pixels to display in its entirity, but you don't have to have a screen with this resolution to display a 1080i/1080p signal - lower resolution screens downscale the signal to fit.

Taking a step back, 720p and 1080i were initially set out as the two key standards for High Definition content, with Sky HD, HD DVD and the Xbox 360 supporting these formats. Any TV that supports 720p and 1080i is classed as HD Ready. Let’s take a step back for a moment and take a quick look at the development of TV technology to see how we arrived at these standards.

In a CRT display (the TV you grew up with), a stream of electrons is generated by a gun, and is scanned across the face of the tube in scan lines, left to right and top to bottom. The face is coated in phosphors, which glow when hit by the electron stream. A method of scanning was required that would reduce the transmitted TV picture's bandwidth and work in accordance with the electricity supply frequency (50Hz in the UK and Europe and 60Hz in the US). The result was interlaced scanning.

A method of reducing bandwidth was required because early sets were not able to draw the whole picture on screen before the top of the picture began to fade, resulting in a picture of uneven brightness and intensity. To overcome this, the screen was split in half with only half the lines (each alternate line) being refreshed each cycle. Hence, the signal is interlaced to deliver a full screen refresh every second cycle. So if the interlace signal refreshes half the lines on a screen 50 times per second this results in a full screen (or frame) refresh rate of 25 times per second. The problem with interlacing is the distortion when an image moves quickly between the odd and even lines as only one set of lines is ever being refreshed.

As TV screen technologies have progressed another system called Progressive Scan has also been developed. With progressive scanning the frames are not split into two fields of odd and even lines. Instead, all of the image scan lines are drawn in one go from top to bottom. This method is sometimes referred to as 'sequential scanning' or 'non-interlaced'. The fact that frames are shown as a whole makes it similar in principle to the way film is shown at the cinema.

At this point it is worth considering what we mean by resolution in relation to TVs;

Resolution: HD-Ready TVs need to be able to display pictures at the resolution set by the new standard. Resolution can be described either in terms of "lines of resolution," or pixels. The resolution you see on your TV depends on two factors, namely the resolution of your display and the resolution of the video signal you receive. Because video images are always rectangular in shape, there is both horizontal resolution and vertical resolution to consider.

Vertical resolution: This is the number of horizontal lines that can be resolved in an image from top to bottom. The old familiar CRT TV displays 576 lines, while Digital HD television operates at a resolution of either 720 or 1080 lines. This is the most important resolution as it is most noticeable to the human eye.

Horizontal resolution: This is the number of vertical lines that can be resolved from one side of an image to the other. Horizontal resolution varies depending on the source. The number of horizontal pixels is not quite so critical as vertical resolution as it is not as obvious to the human eye during normal viewing.

An analogue TV signal in Europe, where the PAL standard is used, has 625 horizontal lines of which 576 lines are displayed and the image (or frame) is refreshed 25 times a second. This is the standard we have been used to for years.

A High Definition Digital TV signal delivers significantly more picture detail and audio quality than a standard signal, producing pictures that are significantly better, sharper and clearer;

720p: 1,280x720 pixel resolution. High-definition picture that is displayed progressively. Each line is displayed on the screen simultaneously, therefore it is smoother than an interlaced picture.

1080i: 1,920x1,080 pixel resolution. High-definition picture that is displayed interlaced. Each odd line of the picture is displayed, followed by each even line, and the resulting image is not as smooth as a progressive feed. 1080i is therefore a more detailed picture suited to documentaries and wildlife footage, but less suitable for action-oriented material such as sports and movies.

1080p: 1,920x1,080 pixel resolution. High-definition picture that is displayed progressively. Each line is displayed on the screen simultaneously, therefore it is smoother than an interlaced picture. This is the ultimate high-definition standard -- the most detailed picture, displayed progressively.

There are two main formats for HDTV, namely 720p (i.e. a 720 line picture progressively scanned 50 times a second) and 1080i (1080 lines interlaced at 50 cycles per second). The picture resolution of a high definition digital TV is about 4 times greater than a typical 576 line TV picture.

The point here is that most high definition broadcast is in either 720p or 1080i, so not having a screen which is able to display 1080p may not be important to you. However, there are exceptions, and if you are a serious game player you will probably already know one of them, or to be precise two of them. The xbox360(with a little tweak) and the soon to be with us playstation 3 produce output at 1080p. Also, the new High Definition DVD format, blu-ray has also been designed for 1080p ouput. Is the difference worth the extra investment? Maybe, something you will have to judge for yourselves ...

HDTV resolution explained

Resolution is the main reason why HDTV looks so much better than standard television. On a high-def TV displaying a high-def source, a million or more pixels combine to create images that appear sharper and more realistic than TV ever has before. Resolution isn't the be-all and end-all of picture quality, however, and its numerous, well, numbers, can be incredibly intimidating at first. In this article we'll try to demystify HDTV resolution and help you cut through the hype that surrounds all of those numbers.

How important is resolution?
Not as important as you might think. According to the Imaging Science Foundation, a group that consults for home-theater maufacturers and trains professional video calibrators, the most important aspect of picture quality is contrast ratio, the second most important is color saturation, and the third is color accuracy. Resolution comes in a distant fourth, despite being easily the most-talked-about HDTV spec today.

In other words, once you get to high-definition, most people are perfectly satisfied with the sharpness of the picture. All other things being equal--namely contrast and color--HDTV looks more or less spectacular on just about any high-def television regardless of its size or the HDTV signal's resolution itself. The leap from normal TV to HDTV is so big that additional leaps in resolution--from high-def to higher-def, let's say--are tiny by comparison.

Nonetheless the HDTV landscape is littered with resolution discussions, in regard to both sources and displays, so a little knowledge of how they interact is a good thing.

Native resolution: The fix is in
For the rest of this article, we'll be talking about fixed-pixel displays. A fixed-pixel display is any HDTV or monitor that uses pixels to produce an image, including flat-panel LCD and plasma screens as well as rear-projection microdisplays and front projectors that use DLP, LCD, or LCoS technology. We'll ignore non-fixed-pixel displays; namely, direct-view and rear-projection CRTs, because they treat incoming resolutions differently than their fixed-pixel cousins do--since they don't use discrete pixels, their specs are much more difficult to pin down.

All fixed-pixel displays have a native resolution spec that tells you how many pixels the display actually has. Native resolution is the absolute limit on the amount of detail you'll see.

Fixed-pixel displays follow a few basic rules:

  • No matter the resolution of the source material, whether VHS, DVD, or HDTV, a fixed-pixel display will always convert, or scale, it to fit its native resolution.
  • If the incoming source has more pixels than the display's native resolution, you will lose some visible detail and sharpness, though often what you're left with still looks great.
  • If the incoming source has fewer pixels than the native resolution, you're not getting any extra sharpness from the television's pixels.

HDTV source resolutions
If you read those three axioms closely, you'll see that source is everything with HDTV. Or, as some unknown wag once said, "Garbage in, garbage out." There are two main HD resolutions in use today by HD broadcasters and other sources: 1080i and 720p. One is not necessarily better than the other; 1080i has more lines and pixels, but 720p is a progressive-scan format that should deliver a smoother image that stays sharper during motion. Another format is also becoming better known: 1080p, which combines the superior resolution of 1080i with the progressive-scan smoothness of 720p. True 1080p content is extremely scarce, however, and none of the major networks have announced 1080p broadcasts. The term 1080p today appears mostly in reference to the displays' native resolution, not the source.

Source resolution name Resolution in pixels HDTV? Progressive-scan? Wide-screen? Networks/sources
1080p 1,920x1,080 Yes Yes Yes Blu-ray and future HD-DVD players; PlayStation 3
1080i 1,920x1,080 Yes No Yes Includes CBS, NBC, PBS, DiscoveryHD/
Xbox 360
720p 1,280x720 Yes Yes Yes ABC, Fox, ESPNHD
480p 852x480 No Yes Yes Fox wide-screen; progressive-scan DVD players
Regular TV Up to 480 lines No No No All

Despite the obvious difference in pixel count, 720p and 1080i both look great. In fact, unless you have a very large television and excellent source material, you'll have a hard time telling the difference between any of the HDTV resolutions. It's especially difficult to tell the difference between 1080i and 1080p sources. The difference between DVD and HDTV should be visible on most HDTVs, but especially on smaller sets, it's not nearly as drastic as the difference between standard TV and HDTV.

HDTV display resolution
Now that we've considered the source, let's look at the televisions. As we mentioned above, all fixed-pixel HDTVs scale the incoming resolutions to fit the available pixels, throwing away information if they have fewer pixels and interpolating information if they have more pixels than the source.

Native resolution ¹ Commonly called ² Meets definition of high-def? ³ Frequency Typical TV types
1,920x1,080 1080p Yes Rare but getting more common especially in larger TVs Flat-panel LCD; DLP, LCD, and LCoS projection; very high-end plasma
1,366x768 768p Yes Very common in all screen sizes Flat-panel LCD; 50-inch plasma
1,280x720 720p Yes Common in rear-projection but not flat-panels DLP, LCD, and LCoS projection
1,024x768 HDTV plasma Yes The most common plasma resolution 37- and 42-inch plasma
852x480 EDTV plasma No Increasingly rare 37- and 42-inch plasma
640x480 VGA No Increasingly rare Small LCD TVs

Technically speaking, all of these numbers are accurate and useful, but don't put too much stock in them. In the real world, it's difficult to tell the difference between native resolutions once you get into high-def. For example, despite the fact that a 37-inch LCD with "only" 1,366x768 pixels has to throw away a good deal of information to display a 1080i football game on CBS, you'd be hard-pressed to see more detail on a similar 37-inch LCD with 1,920x1,080 resolution.

The truth about 1080p
In the last couple of years, there has been a big influx of HDTVs with 1080p native resolution, which typically cost a good deal more than their lower-resolution counterparts. But as we've been saying all along, once you get to high-def, the difference between resolutions becomes much more difficult to appreciate. We've done side-by-side tests between two 46-inch LCD HDTVs, one with 1366x768 resolution and the other with 1080p resolution, using the same 1080i source material, and it was extremely difficult for us to see any difference. It becomes even more difficult at smaller screen sizes or farther seating distances--say, more than 1.5 times the diagonal measurement of the screen. We've reviewed a 37-inch 1080p LCD, for example, where it was impossible to see the separation between horizontal lines at farther than 45 inches away.

Here are a few reviews where we compared 1080p displays directly to lower-resolution models:
We're not telling you to ignore 1080p HDTVs. They technically do deliver more detail, which can enhance the viewing experience for more eagle-eyed viewers. Also, many manufacturers build other picture-quality benefits, such as better contrast and/or color, into their 1080p HDTVs simply because those sets are the high-end models. And given the continuing march of technology, we expect more and more 1080p models to become available at lower and lower prices. Today, however, the premium for 1080p is still pretty steep, and unless you're getting a very large set, say 50 inches or more, we don't recommend basing a buying decision on whether or not the television has 1080p native resolution.
¹ This is the number of physical pixels the television uses to produce a picture. You may notice that few of the resolutions in the table match the HDTV source resolutions exactly. That's mainly because TV makers find it more cost efficient to make panels with the pixel resolutions in the table and then scale the incoming sources to fit the screen. It's true that ideally you'd like to exactly match the incoming source with the display's native resolution, but it's much less important in HDTV than in, say, computer monitors. That's because scalers in HDTVs generally do a good job of converting the signals, and because most HDTV is in motion and seen from a distance, as opposed to static text seen up close.

² All fixed-pixel displays are natively progressive-scan, meaning that even if the source is interlaced, they'll convert it to progressive-scan for display. That's why, for example, you'll hear about a "1080p LCD" but never a "1080i LCD."

³ According to the CEA's DTV definitions, which, for obscure marketing reasons, actually include televisions that have fewer pixels than HDTV source resolutions in the section above.

Understanding HDTV Resolution - Video source resolution

The two most common high-def video source resolutions are 720p and 1080i. All HDTV broadcasts, including local over-the-air broadcasts, satellite and cable signals, use one of these formats. 1080i is the most common resolution, but both formats have their benefits and limitations:

  • 1080i has more lines and pixels to show more detail, so it's great for slow-moving programs with lots of close-ups — think Law and Order or nature documentaries on The Discovery Channel. But the "i" tells you that it's an interlaced format, which means fewer video frames per second, so it doesn't handle fast-moving video as well as 720p.
  • The "p" in 720p tells you it's a progressive-scan format, which means it presents fast-moving action much more cleanly. It's ideal for things like sports and action-packed video games.
What about 1080p?

These days, the most talked-about HD format is 1080p, which combines the superior resolution of 1080i with the progressive-scan smoothness of 720p. True 1080p content is still scarce, however; it's mainly available from HD DVD and Blu-ray high-definition disc players and video game consoles such as the Xbox 360™ and PS3. When you hear 1080p mentioned, it's usually referring to a TV's screen resolution rather than a source.

One more thing

Another key thing to understand about video source resolution is that it can also limit how good your HDTV's picture looks. If you give your TV a lower-resolution source, like a fuzzy analog cable channel, that's what you'll see — a high-def TV can't transform a poor picture into a great-looking picture. If you want to see true high-definition images on your HDTV, you'll need to feed it a high-def source — 720p, 1080i, or (in a few cases) 1080p.

What "i" and "p" mean, and how they can affect the level of picture detail

As we mentioned before, "i" stands for interlaced-scan and "p" stands for progressive-scan. These terms originated when all TVs used picture tubes, and images were "scanned" — painted across the screen line by line. Interlaced-scan images required two passes to create a complete video frame, while progressive-scan displayed the entire frame with just one pass (see illustration below). The frame rate for interlaced video is 30 frames per second while progressive-scan video is 60 frames per second.

Interlaced scan splits each video frame into two "fields," displaying all the even horizontal scan lines (2,4,6…) in 1/60th of a second, followed by the odd scan lines (1,3,5…) during the next 1/60th of a second. That means you'll see a complete video frame every 1/30th of a second.

Progressive scan, on the other hand, displays all the lines in a single sweep (1,2,3,4…). You'll see a complete frame every 1/60th of a second.

The bottom line

Today's digital TV displays are nearly all effectively progressive-scan, so interlaced and progressive are mostly relevant when describing video source signals sent to the TV. The main thing to remember is that a progressive signal has twice as much picture information as an equivalent interlaced signal, and generally looks a little more solid and stable, with on-screen motion that's more fluid.

Graph comparing 1080p, 1080i and 720p

This graph shows the total amount of picture information displayed at each resolution, per second. 1080p's combination of high screen resolution and progressive-scan frame rate allow it to deliver twice as much picture information as the other options — which means a clearer, smoother picture. Hopefully, we'll see more 1080p content soon.

What happens if your TV and video source have different resolutions?

This scenario actually happens all the time, and fortunately with today's HDTVs, you don't really need to worry about it. Whether the resolution of your video source material is low (VHS), medium (DVD), or high (HDTV), a fixed-pixel TV will always automatically convert or scale the video signal to fit the screen's native resolution. Scaling lower-quality signals to fit a TV's higher-resolution screen is often called upconversion. Upconversion works great with a good source like DVD, but it can't make snowy analog antenna reception or a noisy cable picture look flawlessly crisp and clear.

Similarly, if the incoming source has more pixels than the screen's native resolution, the video signal has to be "downconverted." It's like trying to pour 10 pounds of sugar into a 5-pound bag: You have to throw away some detail to fit the image on the screen. That's one of the reasons 1080p TVs are so popular — they can display every pixel of every available high-def resolution, so they never have to throw any detail out. But if you don't get a 1080p TV, don't worry — downconverted video can still look great. The best example is 1080i HD broadcasts that are downconverted to be viewed on 768p TVs.

Is 1080p for you?

Despite the fact that there aren't many 1080p sources, a 1080p HDTV may still be the way to go. For one thing, you'll never have to "throw away" any detail from any of your high-def sources. And as we mentioned earlier, a 1080p TV actually has twice the resolution of a 768p TV. So if you want to ensure that you'll see every exquisite detail, a 1080p set is an excellent choice. But there are some other factors to consider. To figure out where resolution fits on your priority list, ask yourself these questions:

  • How large a screen do you want, and how far from your TV will you be sitting? Chances are you won't be able to see much difference between 1080p and non-1080p HDTVs unless their screens are relatively large (46" or bigger). Even then, if you sit at the farther end of our recommended viewing distance range, you might be just as happy with a 768p or 720p TV. But if you plan to get a larger screen and sit closer, you'll appreciate the extra detail 1080p sets can offer.
  • Is 1080p something you're willing to pay extra for? If you want the sharpest picture around, and you don't mind spending another few hundred dollars or so to get it, then the answer is yes. Plus, you usually find 1080p resolution in upper-range models that also offer superior video processing, additional inputs, and more advanced features and conveniences. But you may decide you'd rather put that money toward a larger screen, or a wall-mountable flat-panel TV instead of a less-pricey rear-projection model.

Understanding HDTV Resolution

What the numbers mean, and what really matters

If you're shopping for an HDTV, you've probably seen terms like "720p" and "1080p", or "1366 x 768 pixels" used to describe a television's resolution. But what exactly do those numbers mean, and what do they say about a TV's performance? In this article, we'll walk you through the basics of resolution, and give you some practical tips to help you decide how high a resolution you need for your new HDTV.

What is resolution?

The main reason high-definition TV pictures look so much sharper and clearer than regular TV is HDTV's higher resolution. In today's world of digital TVs, resolution is measured in pixels, with more pixels providing higher resolution. Old-fashioned TVs had the equivalent of around 300,000 pixels, while today's HDTVs offer one to two million — up to six times more. All those additional pixels mean a huge jump in picture quality.

Side-by-side comparison of two versions of the same image, with different resolutions

The image on the left simulates the picture resolution of an old-fashioned TV, while the image on the right simulates high-definition TV. Notice the soft edges and jagged lines in the non-HD image.

When we talk about picture resolution, we're actually talking about two things: the resolution of your TV's screen and the resolution of the video source (your DVD player, cable box, etc.). Both are important, and each can affect the other in determining the quality of the picture you see. Let's take a closer look at each so you know how they relate, and how to get a good high-resolution picture.

TV screen resolution

Nearly all of today's HDTVs are "fixed-pixel displays," meaning their screens use a fixed number of pixels to produce a picture. That includes flat-panel LCD and plasma TVs, as well as front- and rear-projection types that use DLP, LCD, or LCoS technology.

All of these fixed-pixel displays have a native resolution that tells you the maximum level of image detail a TV can produce. Two of the most common resolutions are 768p and 1080p, though you may also see 720p.

You may see these same resolutions listed as "1366 x 768 pixels" or "1920 x 1080 pixels." That tells you precisely how many pixels the screen actually has: the first number is the horizontal resolution and the second number is the vertical resolution. Multiplying these two numbers gives you a screen's total pixel count. As an example, 1920 x 1080 = 2,073,600 pixels, which is usually simplified to "2 million." By comparison, 1366 x 768 = 1,049,088 pixels — slightly over one million.

Comparison of three common screen resolutions

These grids simulate the different-sized pixels of common TV screen resolutions, from 480i (the resolution of old-fashioned TVs) to high-definition 720p and 1080p. As resolution increases, the pixels get smaller, allowing much finer picture detail to be accurately displayed.

Now, let's move on to video source resolution. Then, we'll explain what "i" and "p" mean when you see one of those letters next to a resolution number.

Stem cell controversy - Objection

Value of life

An embryo is actually a human; it should be valued as highly as a human life.

The reasoning can be summed up by the fact that, once an egg is fertilized, unless inhibited, it will develop into a fully-developed adult. This opinion is often related to religious doctrines which assert that conception marks the beginning of human life or the presence of a soul. Based upon this reasoning, the subsequent argument against embryonic stem cell research is that human life is inherently valuable and cannot be involuntarily destroyed to save another life.

As an extension of this, it is argued that the tendency by some supporters of embryonic stem cell researchers to dismiss the ethical significance of embryo destruction may act to devalue human life.[citation needed] Moreover, it has been argued that "the line at which an embryo becomes a human life remains as arbitrary as ever".[17]

Viability is another standard under which embryos and fetuses have been regarded as human lives. In the United States, the 1973 Supreme Court case of Roe v. Wade concluded that viability determined the permissibility of abortions performed for reasons other than the protection of the woman's health, defining viability as the point at which a fetus is "potentially able to live outside the mother's womb, albeit with artificial aid."[18] The point of viability was 24 to 28 weeks when the case was decided and has since moved to about 22 weeks due to advancement in medical technology. If further technological advances allow a sperm and egg to be combined and fully developed completely outside of the womb, an embryo will be viable as soon as it is conceived, and under the viability standard, life will begin at conception.

Better alternatives

Embryonic stem cells should be abandoned in favor of alternatives, such as those involving adult stem cells.

This argument is used by opponents of embryonic destruction as well as researchers specializing in adult stem cell research.

It is often claimed by pro-life supporters that the use of adult stem cells from sources such as umbilical cord blood has consistently produced more promising results than the use of embryonic stem cells.[19] Furthermore, adult stem cell research may be able to make greater advances if less money and resources were channeled into embryonic stem cell research.[20]

Adult stem cells have already produced therapies, while embryonic stem cells have not.[21][22] Moreover, there have been many advances in adult stem cell research, including a recent study where pluripotent adult stem cells were manufactured from differentiated fibroblast by the addition of specific transcription factors. [23] Newly created stem cells were developed into an embryo and were integrated into newborn mouse tissues, analogous to the properties of embryonic stem cells.

This argument remains hotly debated on both sides. Those critical of embryonic stem cell research point to a current lack of practical treatments, while supporters argue that advances will come with more time and that breakthroughs cannot be predicted.

Scientific flaws

The use of embryonic stem cell in therapies may be fundamentally flawed.

For instance, one study suggests that autologous embryonic stem cells generated for therapeutic cloning may still suffer from immune rejection.[24] The researchers note that: "Our results raise the provocative possibility that even genetically matched cells derived by therapeutic cloning may still face barriers to effective transplantation for some disorders." In other words, therapeutic cloning may not always produce matched tissues. In contrast, there are reports of adult stem cells being successfully reintegrated into an autogenic animal.

Another concern with embryonic stem cell treatments is a tendency of stem cells from embryos to create tumors. [21][25] However, the tumorigenic potential of embryonic stem cells remains poorly described.

Overstatement of research potential

Scientists have long promised spectacular results from embryonic stem cell research, and this has not yet occurred[17][26][27]

Conspicuously, such criticism has even come from researchers themselves. For example, in November 2004, Princeton University president and geneticist Shirley Tilghman said, "Some of the public pronouncements in the field of stem-cell research come close to overpromising at best and delusional fantasizing at worst."[28] Similarly, fertility expert and former president of the British Association for the Advancement of Science, Lord Winston has warned of a public backlash against stem cell research if it fails to deliver on some of the "hype" surrounding potential treatments.[29]

Stem cell controversy - Viewpoints

The status of the human embryo and human embryonic stem cell research is a controversial issue as, with the present state of technology, the creation of a human embryonic stem cell line requires the destruction of a human embryo. Stem cell debates have motivated and reinvigorated the pro-life movement, whose members are concerned with the rights and status of the embryo as an early-aged human life. They believe that embryonic stem cell research instrumentalizes and violates the sanctity of life and constitutes murder.[10] The fundamental assertion of those who oppose embryonic stem cell research is the belief that human life is inviolable, combined with the opinion that human life begins when a sperm cell fertilizes an egg cell to form a single cell.

A portion of stem cell researchers use embryos that were created but not used in in vitro fertility treatments to derive new stem cell lines. Most of these embryos are to be destroyed, or stored for long periods of time, long past their viable storage life. In the United States alone, there have been estimates of at least 400,000 such embryos.[11] This has led some opponents of abortion, such as Senator Orrin Hatch, to support human embryonic stem cell research.[12]

Medical researchers widely submit that stem cell research has the potential to dramatically alter approaches to understanding and treating diseases, and to alleviate suffering. In the future, most medical researchers anticipate being able to use technologies derived from stem cell research to treat a variety of diseases and impairments. Spinal cord injuries and Parkinson's disease are two examples that have been championed by high-profile media personalities (for instance, Christopher Reeve and Michael J. Fox). The anticipated medical benefits of stem cell research add urgency to the debates, which has been appealed to by proponents of embryonic stem cell research.

Recently, researchers at Advanced Cell Technology of Worcester, Mass., succeeded in obtaining stem cells from mouse embryos without killing the embryos. [1] If this technique and its reliability are improved, it would alleviate some of the ethical problems related to embryonic stem cell research.

Another technique announced in 2007 may also defuse the longstanding debate and controversy. Research teams in the United States and Japan have developed a simple and cost effective method of reprogramming human skin cells to function much like embryonic stem cells by introducing artificial viruses. While extracting and cloning stem cells is complex and extremely expensive, the newly discovered method of reprogramming cells is much cheaper. However, the technique may disrupt the DNA in the new stem cells, resulting in damaged and cancerous tissue. More research will be required before non-cancerous stem cells can be created.[2][3][4][5]



The benefits of stem cell research outweigh the cost in terms of embryonic "life"

  • Embryonic stem cells have the capacity to grow indefinitely in a laboratory environment and can differentiate into almost all types of bodily tissue. This makes embryonic stem cells an attractive prospect for cellular therapies to treat a wide range of diseases.[13]
  • The social, economic and personal costs of the diseases that embryonic stem cells have the potential to treat are far greater than the costs associated with the destruction of embryos.

Human potential and humanity

The value of an embryo should not be placed on par with the value of a child or adult

This argument often goes hand-in-hand with the utilitarian argument, and can be presented in several forms:

  • Embryos, while of value, are not equivalent to human life while they are still incapable of existing outside the womb (i.e. they only have the potential for life).
  • Approximately 18% of zygotes do not implant after conception. [6] Thus far more embryos are lost due to chance than are proposed to be used for embryonic stem cell research or treatments.
  • Blastocysts are a cluster of human cells that have not differentiated into distinct organ tissue; making cells of the inner cell mass no more "human" than a skin cell .[13]
  • Some parties contend that embryos are not humans, believing that the life of Homo sapiens only begins when the heartbeat develops, which is during the 5th week of pregnancy,[14] or when the brain begins developing activity, which has been detected at 54 days after conception.[15]


The ends (i.e. new treatments and cures) justify the means (i.e. the destruction of embryos)

This can be seen as a more extreme view of the utilitarianism argument.


If an embryo is going to be destroyed anyway, isn't it more efficient to make practical use of it?

  • In vitro fertilization (IVF) generates large numbers of unused embryos (e.g. 70,000 in Australia alone).[13] Many of these thousands of IVF embryos are slated for destruction. Using them for scientific research utilizes a resource that would otherwise be wasted.[13]
  • While the destruction of human embryos is required to establish a stem cell line, no new embryos have to be destroyed to work with existing stem cell lines. It would be wasteful not to continue to make use of these cell lines as a resource.[13]
  • Abortions are legal in many countries and jurisdictions. A logical argument follows that if these embryos are being destroyed anyway, why not use them for stem cell research or treatments?


Embryonic stem cells can be considered far more useful therapeutically than adult stem cells

This is usually presented as a counter-argument to using adult stem cells as an alternative that doesn't involve embryonic destruction.

  • Embryonic stem cells make up a significant proportion of a developing embryo, while adult stem cells exist as minor populations within a mature individual (e.g. in every 10,000 cells of the bone marrow, only 10 will be usable stem cells). Thus, embryonic stem cells are likely to be easier to isolate and grow ex vivo than adult stem cells.[13]
  • Embryonic stem cells divide more rapidly than adult stem cells, potentially making it easier to generate large numbers of cells for therapeutic means. In contrast, adult stem cell might not divide fast enough to offer immediate treatment.[13]
  • Embryonic stem cells have greater plasticity, allowing them to treat a wider range of diseases.[13]
  • Adult stem cells from the patient's own body might not be effective in treatment of genetic disorders. Allogeneic embryonic stem cell transplantation (i.e. from a healthy donor) may be more practical in these cases than gene therapy of a patient's own cell.[13]
  • DNA abnormalities found in adult stem cells that are caused by toxins and sunlight may make them poorly suited for treatment.[13]
  • Embryonic stem cells have been shown to be effective in treating heart damage in mice.[13]

Beginning of life

  • Clones can be produced without fertilization taking place, and the clones are alive.
  • Before the primitive streak is formed when the embryo attaches to the uterus at approximately 14 days after fertilization, a single fertilized egg can split in two to form identical twins. Also, rarely, two separately fertilized eggs can, instead of resulting in fraternal twins, fuse together and develop into a single human individual (a tetragametic chimera).[16]
  • Therefore before the primitive streak is formed, an individual human life does not exist at fertilization, as it can go on to split into two separate individuals. Therefore, an individual human life begins when the primitive streak is formed — beyond which the cell group cannot split to make twins — and not before. Therefore the blastocysts destroyed for embryonic stem cells do not have human life, and it is ethical to use them. [16]

Stem cell controversy

Stem cell controversy is the ethical debate centered around research involving the creation, usage and destruction of human embryonic stem cells. Some opponents of the research argue that this practice is a slippery slope to reproductive cloning and fundamentally devalues the worth of a human being. Contrarily, medical researchers in the field argue that it is necessary to pursue embryonic stem cell research because the resultant technologies could have significant medical potential, and that excess embryos created for in vitro fertilisation could be donated with consent and used for the research. This in turn, conflicts with opponents in the pro-life movement, who advocate for the protection of human embryos. The ensuing debate has prompted authorities around the world to seek regulatory frameworks and highlighted the fact that embryonic stem cell research represents a social and ethical challenge.

Stem cell use in animals


Stem cell treatment has begun on horses, or mainly to treat injuries to the tendons, ligaments, and joints of sport horses or racehorses. Fat is harvested from the tail head and processed, and an animal may receive treatment within three days after the sample is taken. Injuries that may be treated include Degenerative Joint Disease, soft-tissue injuries, Osteochondrosis, fractures, and sub-chonral bone cysts. Currently, research is also being performed on stem cell application in laminitis and COPD.[18]


There is currently research being performed on the usefulness of stem cells (mesoangioblasts) in canine muscular dystrophy. This work, which has been successfully translated from mice to dogs could provide a means of treating muscular dystrophy in humans

Stem cell treatments

Medical researchers believe that stem cell treatments have the potential to change the face of human disease and alleviate suffering. A number of stem cell treatments already exist, although most are still experimental and/or costly, with the notable exception of bone marrow transplantation. In the future, medical researchers anticipate being able to use technologies derived from adult and embryonic stem cell research to treat cancer, Type 1 diabetes mellitus, spinal cord injuries, and muscle damage, amongst a number of other diseases and impairments.

However, there still exists a great deal of social and scientific uncertainty surrounding embryonic stem cell research, which will only be overcome through years of intensive research and by gaining the acceptance of the public.

Furthermore, very promising treatments of serious diseases with adult stem cells have already been attempted. The advantage of adult stem cells over embryonic stem cells is that there are no rejection issues, because the stem cells are from the same body.

Current treatments

For over 30 years, bone marrow and more recently umbilical cord blood stem cells have been used to treat cancer patients with conditions such as leukemia and lymphoma. During chemotherapy, most growing cells are killed by the cytotoxic agents. These agents not only kill the leukemia or neoplastic cells, but also those which release the stem cells from the bone marrow. It is this unfortunate side effect of the chemotherapy that the Stem Cell Transplant attempts to reverse; by introducing a Donor's healthy Stem Cells the damaged or destroyed Blood Producing Cells of the patient are replaced. In all current Stem Cell treatments obtaining Stem Cells from a matched Donor is preferable to using the patients own. If (always as a last resort and usually because no matched Donor can be found) it is deemed necessary for the patients own stem cells to be used and the patient has not stored their own collection of stem cells (umbilical cord blood), bone marrow samples must therefore be removed before chemotherapy, and are re-injected afterwards.[citation needed]

Potential treatments

Brain damage

Stroke and traumatic brain injury lead to cell death characterized by a loss of neurons and oligodendrocytes within the brain. Healthy adult brains contain neural stem cells that divide, and act to maintain stem cells numbers or become progenitor cells. In healthy adult animals, progenitor cells migrate within the brain and function primarily to maintain neuron populations for olfaction (the sense of smell). Interestingly, in pregnancy and after injury this system appears to be regulated by growth factors and can increase the rate at which new brain matter is formed. In the case of brain injury, although the reparative process appears to initiate, substantial recovery is rarely observed in adults suggesting a lack of robustness. Recently, results from research conducted in rats subjected to stroke suggested that administration of drugs to increase the stem cell division rate and direct the survival and differentiation of newly formed cells could be successful. In the study referenced below, biological drugs were administered after stroke to activate two key steps in the reparative process. Findings from this study seem to support a new strategy for the treatment of stroke using a simple elegant approach aimed at directing recovery from stroke by potentially protecting and/or regenerating new tissue. The authors found that, within weeks, recovery of brain structure is accompanied by recovery of lost limb function suggesting the potential for development of a new class of stroke therapy or brain injury therapy in humans.[citation needed]


Research injecting neural (adult) stem cells into the brains of dogs can be very successful in treating cancerous tumors. With traditional techniques brain cancer is almost impossible to treat because it spreads so rapidly. Researchers at the Harvard Medical School caused intracranial tumours in rodents. Then, they injected human neural stem cells. Within days the cells had migrated into the cancerous area and produced cytosine deaminase, an enzyme that converts a non-toxic pro-drug into a chemotheraputic agent. As a result, the injected substance was able to reduce tumor mass by 80 percent. The stem cells neither differentiated nor turned tumorigenic.[1]

Spinal cord injury

A team of Korean researchers reported on November 25, 2004, that they had transplanted multipotent adult stem cells from umbilical cord blood to a patient suffering from a spinal cord injury and she can now walk on her own, without difficulty. The patient had not been able stand up for the last 19 years. The team was co-headed by researchers at Chosun University, Seoul National University and the Seoul Cord Blood Bank (SCB). For the unprecedented clinical test, the scientists isolated adult stem cells from umbilical cord blood and then injected them into the damaged part of the spinal cord.[2][3][4][5]

The Korean researchers have followed up on their original work. The original treatment was conducted in November 2004. On April 18, 2005, the researchers announced that they will be conducting a second treatment on the woman.[6] The researchers have followed up with a case study write-up on their work. It is located in the journal Cytotherapy.[7]

According to the October 7, 2005 issue of The Week, University of California researchers injected human embryonic stem cells into paralyzed mice, which resulted in the mice regaining the ability to move and walk four months later. The researchers discovered upon dissecting the mice that the stem cells regenerated not only the neurons, but also the cells of the myelin sheath, a layer of cells which insulates neural impulses and speeds them up, facilitating communication with the brain (damage to which is often the cause of neurological injury in humans).[8].

In January 2005, researchers at the University of Wisconsin-Madison differentiated human blastocyst stem cells into neural stem cells, then into the beginnings of motor neurons, and finally into spinal motor neuron cells, the cell type that, in the human body, transmits messages from the brain to the spinal cord. The newly generated motor neurons exhibited electrical activity, the signature action of neurons. Lead researcher Su-Chun Zhang described the process as "you need to teach the blastocyst stem cells to change step by step, where each step has different conditions and a strict window of time."

Transforming blastocyst stem cells into motor neurons had eluded researchers for decades. The next step will be to test if the newly generated neurons can communicate with other cells when transplanted into a living animal; the first test will be in chicken embryos. Su-Chun said their trial-and-error study helped them learn how motor neuron cells, which are key to the nervous system, develop in the first place. The new cells could be used to treat diseases like Lou Gehrig's disease, muscular dystrophy, and spinal cord injuries.

Heart damage

Several clinical trials targeting heart disease have shown that adult stem cell therapy is safe and effective. Adult stem cell therapy for heart disease is commercially available on at least five continents at last count (2007). The most well known of these companies is Theravitae, a private company located in Bangkok, Thailand. More than 250 heart patients have traveled to Thailand to receive Theravitae’s adult stem cell therapy called Vescell to treat their heart disease. Theravitae reports that 75% of their heart patients have an improved quality of life after receiving their adult stem cell treatment. The worldwide results (over 2000 treated) are similar despite many different types of adult stem cells being implanted into very sick heart patients by doctors in over two dozen countries. The plethora of more recent USA FDA-approved clinical trials are showing much the same results as Theravitae’s 75% success rate.

Using the patient's own bone marrow derived stem cells, Dr. Amit Patel at the University of Pittsburgh, McGowan Institute of Regenerative Medicine has shown a dramatic increase in ejection fraction for patients with congestive heart failure. He has worked with many other countries such as Argentina, Uruguay, Ecuador, Greece, Japan, and Thailand where he has taught minimally invasive techniques to companies like Theravitae for the treatment of non-ischemic (idiopathic) and ischemic heart failure.

A Brazilian stem cell bank, has performed sample manipulation in more than 30 cell therapy procedures in cardiac patients.

Haematopoiesis (blood cell formation)

In December 2004, a team of researchers led by Dr. Luc Douay at the University of Paris developed a method to produce large numbers of red blood cells. The Nature Biotechnology paper, entitled Ex vivo generation of fully mature human red blood cells, describes the process: precursor red blood cells, called hematopoietic stem cells, are grown together with stromal cells, creating an environment that mimics the conditions of bone marrow, the natural site of red blood cell growth. Erythropoietin, a growth factor, is added, coaxing the stem cells to complete terminal differentiation into red blood cells.

Further research into this technique will have potential benefits to gene therapy, blood transfusion, and topical medicine.


Hair follicles also contain stem cells, and some researchers predict research on these follicle stem cells may lead to successes in treating baldness through "hair multiplication", also known as "hair cloning", as early as 2007. This treatment is expected to work through taking stem cells from existing follicles, multiplying them in cultures, and implanting the new follicles into the scalp. Later treatments may be able to simply signal follicle stem cells to give off chemical signals to nearby follicle cells which have shrunk during the aging process, which in turn respond to these signals by regenerating and once again making healthy hair. Hair Cloning Nears Reality as Baldness Cure (WebMD November 2004)

Missing teeth

In 2004, scientists at King's College London discovered a way to cultivate a complete tooth in mice[9] and were able to grow them stand-alone in the laboratory. Researchers are confident that this technology can be used to grow live teeth in human patients.

In theory, stem cells taken from the patient could be coaxed in the lab into turning into a tooth bud which, when implanted in the gums, will give rise to a new tooth, which would be expected to take two months to grow.[10] It will fuse with the jawbone and release chemicals that encourage nerves and blood vessels to connect with it. The process is similar to what happens when humans grow their original adult teeth.

It's estimated that it may take until 2009 before the technology is widely available to the general public, but the genetic research scientist behind the technique, Professor Paul Sharpe of King's College, estimates the method could be ready to test on patients by 2007.[11] His startup company, Odontis, fully expects to offer tooth replacement therapy by the end of the decade.

In 2005, Cryopraxis a stem cell bank in Brazil, collected baby tooth stem cells and harvested different types of differentiated cell types including neurons. This technology may one day make baby teeth a good source of stem cells.

In the next three years, Paul Sharpe hopes to identify more-accessible stem cells that may be able to form not only teeth, but also--and more importantly--roots.[12]


There has been success in regrowing cochlea hair cells with the use of stem cells.[13]

Blindness and vision impairment

Since 2003, researchers have successfully transplanted retinal stem cells into damaged eyes to restore vision. Using embryonic stem cells, scientists are able to grow a thin sheet of totipotent stem cells in the laboratory. When these sheets are transplanted over the damaged retina, the stem cells stimulate renewed repair, eventually restoring vision.[14] The latest such development was in June 2005, when researchers at the Queen Victoria Hospital of Sussex, England were able to restore the sight of forty patients using the same technique. The group, led by Dr. Sheraz Daya, was able to successfully use adult stem cells obtained from the patient, a relative, or even a cadaver. Further rounds of trials are ongoing.[15]

In April 2005, doctors in the UK transplanted corneal stem cells from an organ donor to the cornea of Deborah Catlyn, a woman who was blinded in one eye when an acid was thrown in her eye at a nightclub. The cornea, which is the transparent window of the eye, is a particularly suitable site for transplants. In fact, the first successful human transplant was carried out in 1905 on a cornea by Dr. Eduard Zirm. The recipient was Alois Gloger, a labourer who had been blinded in an accident. The cornea has the remarkable property that it does not contain any blood vessels, making it relatively easy to transplant. The majority of corneal transplants carried out today are due to a degenerative disease called keratoconus which causes vision impairment and has no known cure even after corneal transplant. It is hoped that stem cell research will one day provide a cure to such debilitating corneal disorders.

As more research yields increasingly precise techniques, stem cell transplantation to restore vision may become viable on a large scale.[citation needed] The University Hospital of New Jersey claims a success rate growing the new cells from transplanted stem cells varies from 25 percent to 70 percent.[16]

ALS (Lou Gehrig's Disease)

In the April 4, 2001 edition of JAMA (Vol. 285, 1691-1693),[17] Drs. Gearhart and Kerr of Johns Hopkins University used stem cells to cure rats of an ALS-like disease. The rats were injected with a virus to kill the spinal cord motor nerves related to leg movement. Dr. Gearhart and Dr. Kerr then injected the spinal cords of the rats with stem cells. These migrated to the sites of injury where they were able to regenerate the dead nerve cells restoring the rats which were once again able to walk.