Wednesday, October 10, 2012

Nutrition - Nova (Dying to be Thin)

Why do we eat? How do our bodies use the foods we eat? What organ or system in your body may not be getting enough of what it needs? This interactive feature from NOVA "Dying to Be Thin" Web site will fill you in. Just click on a body part or on the name of a nutrient to find out what you need to eat to stay healthy.
NOVA Body Needs
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  • Media Type: Interactive
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  • Level: Grades 3-8

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Source: NOVA: "Dying to Be Thin" Web site
This resource can be found on the NOVA: "Dying to Be Thin" Web site.

Background

Standards of beauty have changed over the years. In the late 1800s, advertisers regularly used models who would be considered overweight by today's standards. Times have changed dramatically. Most Americans are exposed to thousands of media messages every day -- in magazines and newspapers, on television, on outdoor billboards, and over the Internet. These messages promote bodies that are thin and, in some cases, unrealistically proportioned, and they are creating a culture of young people who are obsessed with losing weight.

As a result of this obsession, many people have sworn off fat. They avoid eating fat in any form and, instead, obtain most of their calories from carbohydrates, like bread and pasta. For decades, doctors and health experts supported this fat-free nutritional strategy. Fat was the enemy, they said; it was the cause of obesity and heart disease. Carbohydrates were your friends and could be consumed, many thought, in mass quantities with few concerns about health consequences. Recent studies, however, have begun to reveal the flaws in this thinking.

A nutritional plan that shuns fat ignores this food's important role in the body. While fat's main purpose is to store energy, it serves many other functions as well. Either in its whole form or broken down into small molecules, fat does the following: provides insulation, builds membranes, aids digestion, promotes proper nervous system function, regulates hormones, keeps the skin healthy, and aids the chemical communication between cells. And these are just a few of the important things that fat does for us. Still, many people continue on a fat-free path.

Somewhat surprisingly, fat-free diets often result in the accumulation of excess body fat. Carbohydrates, including sugars and starchy foods, provide the body's most efficient form of energy. They are broken down quickly into glucose, the sugar that cells need in order to function. This is why energy bars used by athletes are made up primarily of carbohydrates: They are quickly broken down in the stomach, and the resulting sugars are easily transported throughout the body via the bloodstream.

When the body is active at high intensity for long periods of time, carbohydrates must be eaten regularly to provide the cells with the energy they need. Carbohydrates that are consumed when the body is at rest, however, are stored. Relatively small amounts of carbohydrates can be stored in the muscles and the liver as a complex sugar called glycogen. When glycogen stores are full, however, and there is no further demand for sugar, carbohydrates are stored as fat.

Although most doctors and nutritionists still recommend that people get the majority of their calories from carbohydrates, they also suggest that many people would benefit from increasing their fat intake. According to most nutritionists, the ratio of carbohydrate, fat, and protein calories should, in fact, be much closer to equal -- at 40, 30, and 30 percent respectively. They stress that exercising and eating moderately from all of the food groups is the proper path to better health.

Questions for Discussion

  • Could you stay healthy eating three or fewer of the foods shown here? Explain your answer, using information from the site.
  • Why do you think 75 percent of the U.S. population doesn't meet daily recommended dietary needs? What ideas do you have about changing the nutritional habits of people in this country?
SOURCE: http://www.pbs.org/wgbh/nova/education/body/body-needs.html?elq=0937217e29c949998c57be7bcd65db11&elqCampaignId=431

DNA - Nova

NOVA
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DNA. It's what makes you unique. Unless you have an identical twin, your DNA is different from that of every other person in the world. And that’s what makes DNA fingerprinting possible. Experts can use DNA fingerprints for everything from determining a biological mother or father to identifying the suspect of a crime. What, then, is a DNA fingerprint and how is it made? Here, you'll find out by solving a mystery—a crime of sorts. First, you’ll create a DNA fingerprint (we'll supply the lab and all necessary materials). Then you’ll compare this DNA fingerprint to those of all seven suspects to nab the perpetrator. Ready? Let's get to work!

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  • Media Type: Interactive
  • Size: 283.0 KB
  • Level: Grades 6-12
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Source: NOVA: "The Killer's Trail" Web site
This feature originally appeared, in a different design, on the site for the NOVA program .

Background

In the last 15 years, DNA has played an increasingly important role in our legal system. Tissue evidence is now routinely collected during criminal investigations in hopes that it will provide genetic clues linking suspected criminals to crimes.

DNA profiles help forensic investigators determine whether two tissue samples -- one from the crime scene and one from a suspect -- came from the same individual. Fortunately, the genetic comparison doesn't require that investigators look at all of the DNA found in the tissue samples. That would take months or even years. Instead, by marking a small number of segments of DNA in one sample and then checking for the presence or absence of those segments in the other sample, investigators can say with some assurance whether the samples are from the same person.

How do they do it? Investigators use chemicals to cut the long strands of DNA into much smaller segments. Each segment has a specific length, but all of them share the same repeating sequence of bases (or nucleotides). The chemicals cut the segments at the beginning and at the end of the repeating string of nucleotides, so one segment might be ATCATCATCATCATC, for example, while another might be ATCATC. (The DNA segments used in forensic investigations are, of course, much longer than this.)

Investigators use a process called gel electrophoresis to separate these repeating segments according to length. Next, they introduce a small set of radioactive "markers" to the sample. These markers are segments of DNA of known length, with bases that complement the code of, and bind to, sample segments of the same length. The sample segment above (ATCATCATCATCATC), for example, would be tagged by a marker with the complementary code TAGTAGTAGTAGTAG.

Markers that do not bind to sample segments are then rinsed away, leaving in place only those markers that bound to complementary sample segments. Photographic film, which darkens when exposed to the radioactive markers, identifies the location of all marked sample segments. This film, then, becomes the DNA "fingerprint" that forensic investigators analyze.

The final step is a relatively simple matter of lining up the sample profiles side by side and comparing them for the presence or absence of segments with particular lengths. The more segments the two samples have in common, the more likely it is that the samples came from the same person.

Questions for Discussion

  • Describe the process of DNA fingerprinting.
  • In what ways is it like actual fingerprinting and in what ways is it different?
  • How conclusive is the evidence of DNA fingerprinting?
  • Where is there possibility for error?

SOURCE: http://www.pbs.org/wgbh/nova/education/body/create-dna-fingerprint.html?elq=0937217e29c949998c57be7bcd65db11&elqCampaignId=431

Thursday, October 4, 2012

BPA Timeline

source: http://www.jsonline.com/watchdog/watchdogreports/34532374.html 
Nov 15, 2008

Watchdog Reports      The history of BPA     TIMELINE


1891: Bisphenol A, or BPA, is developed.

1930s: The chemical is used as a synthetic estrogen.

1960s: Food manufacturers begin to use BPA to make hard, clear plastic for items such as baby bottles and the lining of metal food cans, including liquid baby formula.

1998: Patricia Hunt, a geneticist at Washington State University, notices that control mice had many more defective eggs when stored in polycarbonate cages.

2000-present: More than 1,000 studies are published showing harm to lab animals from BPA, including cancer, obesity, diabetes, reproductive failures and neurological disorders.

2008: Annual sales of BPA exceed $6 billion.
April 2008: Canadian health officials begin steps to declare BPA a toxin and to have it banned from use in baby bottles and tableware for children. Several manufacturers - including Nalgene, Wal-Mart, Toys "R" Us and CVS pharmacies - announce plans to phase out use of the chemical in children's products.

August 2008: The Food and Drug Administration declares BPA to be safe.

September 2008: The National Toxicology Program, an advisory board to the FDA and Environmental Protection Agency, releases its report expressing some concern for how BPA affects the prostate and neural development of fetuses, infants and children. It also expressed concern about the chemical's effect on breast tissue and early puberty.

A study published in the Journal of the American Medical Association in September tied BPA to heart disease in humans. Lawmakers start to call for a ban of the chemical in children's products.

October 2008: The FDA's Science Board finds that the FDA ignored hundreds of studies on BPA and advises the agency to reopen its investigation of the chemical. A study finds that even low levels of BPA can interfere with chemotherapy for breast cancer patients.