Archive for July, 2009


Causes of Asthma and Pneumonia

Asthma and pneumonia are among the most common breathing diseases. There are a number of factors that cause them.

Attacks of asthma can be caused by a temporary narrowing of the air passages. This may be due to swelling of the walls, or to the production of too much mucus. It may also be caused by the contraction of muscles in the walls of the air passages. Breathing becomes more difficult as in bronchitis. Asthmatic attacks occur in people who are especially sensitive to certain things, such as pollen carried in the air by wind currents. Some asthmatic people are sensitive to other things. Dusts, feathers, the fur of certain animals, some cosmetics or certain foods can all cause asthma. Excitement or worry can also bring on an attack of asthma in some people. Many asthmatic people feel wheezy and short of breath in a smoky atmosphere.

In case of pneumonia the lungs become inflamed. It is usually caused by certain bacteria, or by other microbes called viruses. These get into the lungs and multiply so that the walls of the alveoli become swollen and inflamed. The alveoli become filled with fluid and blood cells. Movement of oxygen into the blood therefore slows down. In a healthy person there are few microbes which can cause pneumonia. However in someone with, for example, chronic bronchitis, some of the bacteria which normally live harmlessly in the upper air passages, can get into the lungs and cause pneumonia. It is pneumonia which often finally kills those who suffer from bronchitis.

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Endotherms and Biochemical Reactions

Birds, mammals, and representatives from some other groups of organisms are thermoregulators called “endotherms.” Endotherms have the capability of internally generating sufficient amounts of heat to raise their body temperature considerably above the environmental temperature. Endotherms have been freed, to some extent, from the effects of environmental temperature. They can remain active, maintaining optimal conditions for their biochemical reactions, over a wide range oi environmental temperatures. Subtle changes in environmental temperature which would markedly affect the biochemical reactions of nonthermoregulators do not affect endotherms.

There is another group of thermoregulators which, unlike the endotherms, lack the metabolic machinery to generate internally large quantities of heat—the ectotherms. Reptiles, fishes, and representatives from many other groups of animals are ectotherms. An ectotherm relies primarily on behavioral adjustments to maintain a fairly constant body temperature. A lizard such as the desert iguana, for example, regulates its body temperature at 39°C ±10°C by moving into the sunlight when its body temperature falls below 38°C and into the shade when its body temperature rises above 40°C. This form of thermoregulation, which is energetically cheaper than generating the heat internally, nonetheless provides the advantages of biochemical stability found in the endotherms. However, the ectotherm can only regulate its body temperature in environments which have the appropriate thermal profile. At night, on overcast days, or during the winter, the ectotherm “slows down” as its body temperature falls toward the environmental temperature.

The regulation of body temperature, therefore, allows an organism to maintain a thermodynamically stable internal environment in which increases or decreases in the rates of millions of individual biochemical reactions can be changed by the organism (by changing the concentrations of enzymes or substrates) without the need to compensate for changes in environmental temperature.

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On the Subject of Scientific Method

As I browse through the great libraries of the world, the Widener Library at Harvard, the Library of Congress, the Library of the British Museum, I am again and again impressed by the fact that science is made chiefly not by advance in content, but by advance in method. Newton could not have solved introductory problems of celestial mechanics until he had invented the method of the calculus. Helmholtz could not discover the nature of tone qualities without inventing metal resonators, and showing how they were to be used. Max Planck could not give us quantum theory except by investigating the dynamics of black-body radiation. Pavlov could not give us the behavior world of classical conditioning without the conditioned response method. Freud could not give us the theory of the unconscious without working through the psychoanalytic method.

Indeed the predetermination of concepts by methods is one of the general, almost universal, realities of modern science. You will find in the Widener Library, for example, a vast graveyard of psychological ideas, stimulating and challenging in their era, but without a method which could give them life; while even rather meager and humble experimentalists have proved capable of building a structure of experimental psychology—a house in which personalities like Wertheimer or Hull or Tolman can look out of the windows upon an exciting and vast domain.

The glory and the bane of modern life is the scientific method. The nurse, the social worker, no less than the physician and the engineer, the critic of literature, indeed, even the critic of music and the fine arts, lives or dies by his method, and his method becomes more and more like the method of science. Dip for a moment, for example, into the fascinating world of cultural anthropology and prehistory, and the challenging and maddening world of the analysis of historical artifacts, records, and documents, and see what is happening to them all by methods of dating through carbon 14. You will find that science has descended upon the earlier, cruder methods as the lava of Vesuvius descended upon Pompeii.

With the death of the old comes a new life. The world is suddenly caught, disciplined, and forced into order by the very nature of the message of science. There is a great deal of “playing dead” and a great deal of “playing deaf,” particularly among some students of personality who are more at home in the generous tradition of an impressionistic type of literary and artistic criticism. They were content because it was their life to say that a painting must or must not have been painted by Rembrandt because of its atmosphere, or because of the personality which was breathed into it. Unfortunately, they set up arguments like this against the simple realities of analysis of paint and of canvas, and if the kind of paint used is simply incompatible with the given interpretation, the scientific method must—however grudgingly—be accepted. It will be my thesis that intuition will gain rather than lose, will become richer rather than poorer by this acknowledgement of the role of science. My primary point is that the method of science sweeps like a homogeneous glacier-like process down over the whole of the world, and that it does certain things to the people who study personality in their social settings which can never be undone by any alternative, never reversed by another method, however suggestive and however valuable.

I have said that method predetermines the subject matter of the special disciplines. But what would really be better would be to say that there is a mutual predetermination of concept by method, and of method by concept. The concepts which belong to Western European culture serve, in large degree, to shape the mind of the person who invents a method. The method leads back into the structure of the science he is creating. It is, in general, a time-space system of ideas—strictly a time-space-mass-energy system of ideas, still essentially Newtonian—that underlies the structure of physical science, and the modern physical science working through the theory of the nucleus, the theory of energy, quantum theory, the theory of new and challenging aspects of time and of space, has been forced upon the modern thinker. The new concepts, frightfully abstract as they are, have worked their way back to guide and limit the invention of new methods which will confirm or modify them.

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Body Temperature Regulation

The energy expended by “warm-blooded” organisms, such as ourselves, to regulate our body temperature is enormous: temperature regulation is costly. For example, at low environmental temperatures, people might have to expend 1800 kcal/day, or more, solely to generate the heat necessary to maintain a body temperature of 37°C and perhaps 10% more at febrile temperatures. This expenditure of energy often amounts to over 90% of the total energy used in any given day for performing external work. The energy, of course, comes from the food we eat, and as a result, we must eat an equivalent amount of kcal of food each day just to regulate body temperature. On days when our food intake falls below our daily energy expenditure, we rely on our stores of fat for this source of energy, resulting in a loss of weight. One can calculate, approximately, the amount of energy saved by a resting human-sized organism which does not regulate its body temperature, and therefore remains at a constant environmental temperature, say 20°C. This organism would have a metabolic rate (energy expenditure) roughly equivalent to that of the American alligator, or about 60 kcal/day. In other words, regulating can cost about thirty times more than not regulating body temperature f 1800 kcal/day vs. 60 kcal/day). Expending and therefore procuring such large amounts of energy have led to numerous adaptations in birds, mammals, and other “warm-blooded” organisms. These adaptations have increased the efficiency of these organisms to obtain, digest, and utilize large volumes of food. Based on the enormous energy cost of regulating body temperature, it is often speculated that there must be some adaptive value in maintaining body temperature at a high and fairly constant level rather than allowing body temperature to fluctuate with the environmental temperature. The adaptive value of regulating body temperature is thought to be related to the effect of temperature on biochemical reactions.

The physiology of any organism can ultimately be reduced to a series of chemical reactions. Most of these reactions are strongly influenced by temperature. The effect of increasing temperature on the rate of increase in biochemical reactions is often greater than can be explained simply by the thermally induced increase in the average kinetic energy of the reacting molecules. For example, many biochemical reactions increase their reaction rate two to threefold over a 10°C rise in temperature. Based on simple molecular kinetics, a 10°C rise in temperature should have increased the reaction rate only a few percent. In the late 1800s, the Swedish physical chemist Arrhenius proposed that the often logarithmic increase in the reaction rates of biochemical reactions is related to their activation energy. Arrhenius mathematically characterized the effects of temperature on biochemical reactions, pointing out that most biochemical reactions tend to increase logarithmically with increasing temperature to a point of maximization. Above this optimal temperature, the reactions decrease. Examples of this profound effect temperature has on biological systems can be seen in its effect on the growth rates of various organisms.

Organisms which regulate their body temperature maintain a degree of biochemical stability not found in the non-thermoregulators. Not only have their biochemical reactions evolved to function optimally at or near the regulated body temperature, but, perhaps more importantly, these reactions can now occur in comparative independence of the environmental temperature. A normal reduction in the environmental temperature does not slow the metabolic processes of a thermoregulator like a bird or mammal.