Text c. Obesity

Exercise 9. Discuss the questions:

1. What is overweight and obesity?

2. How do overweight and obesity affect human health?

3. What factors account for the wide spread of obesity in the modern society?

slumber – сон, дрема plump – упитанный, толстый nocturnal – ночной diurnal - дневной dim – тусклый, неяркий twilight – сумерки

Exercise 10. Listen to the text (Script 48) to check some of your answers in exercise 9. What factor has been revealed to affect the raising rates of obesity?

Exercise 11. Listen to the text again. What do the following figures refer to in the text:

3 16 8 8 weeks

50% 55% 10%

Exercise 12. Using information from the text prove the statements:

1. Light regulates the body's biological clock.

2. Persistent exposure to nocturnal light leads to increases in weight, body fat and glucose intolerance.

3. Changing an animal’s natural cycle of day and night affects its weight.

4. The spread of electric lighting might affect the rate of obesity in humans.

Text d. The epigenetics of fat

Exercise 13. Discuss the questions:

1. What effects does physical exercise produce on the human body? What mechanisms provide for these effects?

2. What is adipose tissue responsible for in the human body?

3. What is epigenetics? How does it work? What is it responsible for in the body? What epigenetic markers do you know?

treadmill – беговая дорожка senility – старческая немощь, дряхлость workout – тренировка surplus – избыток

Exercise 14. Listen to the text (Script 49) to check some of your answers in exercise 13. How does physical exercise alter the way genes work in the tissue that stores fat?

Exercise 15. Listen to the text again. What do the following figures refer to in the text:

6 23 30s and 40s 3 1.8

18,000 7,663 18 21

Exercise 16. Using information from the text answer the questions:

1. What experiment was conducted to investigate the effects of physical exercise?

2. What results did the experiment demonstrate?

3. What did the follow-up experiment reveal?

Scripts Unit 1. Human body

Script 1. Blood transfusion

Painted out

How to disguise red blood cells so that their blood group is invisible.

There are 29 possible combinations of human blood groups, and for a patient to be given a safe transfusion the right one needs to be available. Besides the familiar ABO and rhesus systems, science has (after a sticky start) uncovered the MNS system, the Kell system, the Lewis system and the D+ and D- group. Choose wrong or settle for a less than perfect match because no other is to hand - and antibodies produced by the recipient's immune system may attack the foreign cells. That can lead to serious consequences. In the worst cases a patient's organs may fail and he may die.

Several attempts have been made to create artificial blood from chemicals that readily dissolve and transport oxygen, or to process the natural stuff in ways that eliminate the antigenic proteins which provoke this immune response. None, so far, has succeeded. But that has not stopped people trying. The latest effort, reported in Biomacromolecules by Maryam Tabrizian of McGill University in Montreal and her colleagues, follows the second approach, but with a twist. Instead of purging the antigenic proteins from red blood cells, Dr Tabrizian covers them up.

In essence, what she is doing is painting the cells. And, like all good decorators, she uses two coats. The first - the undercoat - is a material that sticks both to the fatty surface membrane of the red cells and to the mixture Dr Tabrizian chose as the outer coat. Crucially, this second mixture is of no interest whatsoever to the immune system. Nor is anything buried beneath it. Like blemishes on a bathroom wall, the antigenic proteins become invisible when painted over.

In practice, as is often the case when decorating a house, more than two coats may be needed to cover things up. But the layers can be alternated to any thickness desired, and inconvenient antigens thus hidden from view.

And it seems to work. When Dr Tabrizian exposed the newly coated blood cells to antibodies that would normally have been expected to stick to them and cause them to gather in useless clumps, nothing happened. Nor does the coating appear to harm the cells. That is mainly because red blood cells do very little other than absorbing and releasing oxygen and carbon dioxide as appropriate. They have no nuclei and no metabolism worth speaking of, so there is little to go wrong. Both types of paint are, though, permeable by oxygen and carbon dioxide, and that permeability means the red blood cells can still do their job. Initial tests monitoring the flow of oxygen in and out of the cells show that they are able to transfer the gas just as efficiently as cells that have not been tampered with.

What Dr Tabrizian and her colleagues have not yet done is put their new creation back in an animal. That is the next test. But if the cells do work in vivo as well as in vitro, the team will have taken a big step on the road to the much-desired goal of blood transfusion that no longer has to worry about matching blood groups. (From The Economist, March 19, 2011)

Script 2. Medical technology

A not-so-hard graft

Transplantable blood vessels can now be grown as desired.

Another advance in the emerging technology of regenerative medicine has just been announced. It should soon be possible to make blood vessels that can be stored and used "off the shelf" for surgery that requires arteries or veins to be bypassed. The vessels, prototypes of which are described this week in a paper in Science Translational Medicine, are made by Humacyte, a small firm based in Durham, North Carolina, that was founded by Shannon Dahl, the paper's principal author, and two colleagues.

The recipe Dr Dahl and her colleagues concocted begins with smooth-muscle cells. Smooth muscle is different from the familiar sort that cloaks bones and enables bodily movement. It is a component of organs such as the gut and the blood vessels that sometimes need to change shape while they are functioning.

To make artificial blood vessels the team took smooth-muscle cells from fresh corpses and cultured them on tubular scaffolds made of a material called polyglycolic acid. Grown this way, smooth muscle secretes collagen, a structural protein that is, among several other things in the body, an important component of the walls of blood vessels. The polyglycolic acid degrades spontaneously over the course of a few weeks with the consequence that it is, in effect, replaced by the collagen. The result is a tube of the length and diameter of the original scaffold, that is composed of collagen and smooth-muscle cells - a structure similar to a natural blood vessel.

Transplanting that into a patient, however, would risk provoking an immune reaction, since the muscle cells are "foreign" tissue. To get around this, Dr Dahl and her colleagues wash the muscle cells away with a detergent, leaving just the collagen. Though the end product is a nonliving simulacrum of a blood vessel rather than an artificial version of the real, biologically active thing, experiments on animals suggest that it works well enough to substitute for a diseased natural vessel (for example, a clogged coronary artery that might otherwise cause a heart attack). It can also act as a "tap" from which the blood of people whose kidneys have failed might be drawn for dialysis.

At the moment, the options for either of these things are limited. The best approach is to use a length of vessel taken from elsewhere in the patient's body (commonly, his leg). But that requires such transplants to be healthy themselves - and each length of transplanted vessel can be used only once. Synthetic vessels made of Teflon exist, but they are prone to infection and blockage by blood clots, and tend to work for only a few months.

The animal experiments suggest the new, all-collagen vessels are capable of lasting at least a year without noticeable deterioration. They are also, once implanted, able to remodel themselves in ways that improve their function - changing shape in response to blood flow, being colonized by cells from the patient's body, and showing signs of incorporating elastin, another structural protein found in natural vessels.

Also, if kept in a suitable saline buffer at 4"C, they can be transplanted a year after they were made without a perceptible degradation of their properties. So, if human trials confirm these results, the surgical-repairer's toolkit will have acquired a useful additional instrument - and the age of the cyborg will be just that little bit nearer. (From The Economist, February 5, 2011)