Just noticed it is a very old book. Published in 90s so some information are out dated.
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If there were no compensating disadvantage in having the human body operate at 40° C. (103° F.), it ought to stay at that temperature all the time, so as to prevent infections from ever getting started. But even this moderate fever has costs; it depletes nutrient reserves 20 percent faster and causes temporary male sterility. Still higher fevers can cause delirium and perhaps seizures and lasting tissue damage. It should also be realized that no regulation mechanism can perfectly anticipate all situations.
If there were no compensating disadvantage in having the human body operate at 40° C. (103° F.), it ought to stay at that temperature all the time, so as to prevent infections from ever getting started. But even this moderate fever has costs; it depletes nutrient reserves 20 percent faster and causes temporary male sterility. Still higher fevers can cause delirium and perhaps seizures and lasting tissue damage.
Egg white protein is 12 percent conalbumin, a molecule whose structure tightly binds iron and thereby withholds it from any bacteria that might get in. The protein in human milk is 20 percent lactoferrin, another molecule designed to bind iron. Cow’s milk has only about 2 percent lactoferrin, and breast-fed babies consequently have fewer infections than those fed from bottles.
Transferrin, another protein that binds iron tightly. Transferrin releases iron only to cells that carry special recognition markers. Bacteria lack the needed code and can’t get the iron. People suffering from protein deprivation may have levels of transferrin less than 10 percent of normal. If they receive iron supplements before the body has time to rebuild its supply of transferrin, free iron in the blood makes fatal infections likely—as has been a tragic outcome of some attempts to relieve victims of famine.
Iron is a crucial and scarce resource for bacteria, and their hosts have evolved a wide variety of mechanisms to keep them from getting it. In the presence of infection, the body releases a chemical called leukocyte endogenous mediator (LEM), which both raises body temperature and greatly decreases the availability of iron in the blood.
Iron is a crucial and scarce resource for bacteria, and their hosts have evolved a wide variety of mechanisms to keep them from getting it. In the presence of infection, the body releases a chemical called leukocyte endogenous mediator (LEM), which both raises body temperature and greatly decreases the availability of iron in the blood. Iron absorption by the gut is also decreased during infection. Even our food preferences change.
When absorbed toxins enter the circulation, they pass by a special group of cells in the brain, the only brain cells directly exposed to the blood. When these cells detect toxins, they stimulate the brain’s chemoreceptor trigger zone to respond first with nausea and then with vomiting.
The distress of nausea discourages us from eating more of the noxious substance, and its memory discourages future sampling of whatever food seemed to cause it.
Unusually small for human cells, sperm are still large compared to bacteria. Potential pathogens can stick to sperm cells and be transported from the outside to deep within a woman’s reproductive system.
Unusually small for human cells, sperm are still large compared to bacteria. Potential pathogens can stick to sperm cells and be transported from the outside to deep within a woman’s reproductive system. Only recently has the threat of sperm-borne pathogens been recognized.
many aspects of menstruation seem designed as an effective defense against uterine infection.
This is supported by evidence that menstrual blood differs from circulating blood in ways that make it more effective in destroying pathogens while minimizing losses of nutrients.
How does the body recognize cells as its own? Each cell has a molecular pattern on its surface, called the major histocompatibility complex (MHC), which is like a photo ID card. When cells are infected, they transport protein from the invader to the MHC, where it is bound. Like individuals with obviously fake ID cards, such cells are priority targets for the killer cells of the immune system.
It makes a protein that blocks the ability of the cell to move foreign proteins to the MHC.
when cells are infected, they transport protein from the invader to the MHC, where it is bound. Like individuals with obviously fake ID cards, such cells are priority targets for the killer cells of the immune system. The adenovirus, makes a protein that blocks the ability of the cell to move foreign proteins to the MHC.
Invaders may accomplish this just as door-to-door peddlers do, by appearing to offer something else. The rabies virus binds to acetylcholine receptors as if it were a useful neurotransmitter; the cowpox virus to epidermal growth-factor receptors as if it were a hormone; and the Epstein-Barr virus (which causes mononucleosis) to a C4 receptor. Rhinovirus, a common cause of colds, binds to the intercellular adhesion molecule (ICAM) on the surface of the lymphocytes that line the respiratory tract.
Another trick is to evade the immune system. The trypanosome that causes African sleeping sickness does this by rapidly changing its disguises. It takes the body about ten days to make enough antibodies to control the trypanosome, but on about the ninth day, the trypanosome changes its disguise by exposing an entirely new surface layer of proteins, thus escaping attack by the antibodies. The trypanosome has genes for more than a thousand different antigenic coats and so can live on for years in the human host, always one step ahead of the immune system.
Malarial parasites have special surface proteins that allow them to bind to the walls of blood vessels so that they are not swept to the spleen, where they would be filtered out and killed. The genes that code for these binding proteins in malarial parasites mutate at a rate of 2 percent per generation, just enough so that the immune system cannot lock in on the organism.
The pneumococcal bacteria that cause pneumonia use a different trick to circumvent the immune system. They have “slippery” polysaccharides on their surface that white blood cells can’t get a grip on.
The external chemistry of some bacteria and some worms is so similar to that of human cells that the host may have difficulty in recognizing them as foreign. (Thus antibodies sometimes attack both invader and host cells.) The streptococcus bacterium, a longtime associate of humans, is especially adept at this trick. The antibodies to some strains cause rheumatic fever, in which a person’s antibodies attack his or her own joints and heart. Similar antibody attack on nerve cells in the basal ganglia of the brain can cause Sydenham’s chorea, with its characteristic uncontrollable muscle twitches. Interestingly, many patients who have obsessive-compulsive
The external chemistry of some bacteria and some worms is so similar to that of human cells that the host may have difficulty in recognizing them as foreign. (Thus antibodies sometimes attack both invader and host cells.)
Why doesn’t the complement system attack our own cells? In part because our cells have a layer of sialic acid, a chemical that protects them from attack by the complement system.
Shock is caused by chemical lipopolysaccharide (LPS) formed by the bacteria.
LPS is a necessary component of the cell wall of this whole group of bacteria. Hosts recognize this reliable cue to the presence of dangerous infection and react strongly—sometimes too strongly. Here is an example of a defensive weapon that can turn on its bearer. The human immunodeficiency virus (HIV), the virus that causes AIDS, hides in the helper T cells that bring antigens to the attention of the immune system.
toxins produced by fungi could kill the bacteria that cause human disease.
Antibiotics are chemical warfare agents that evolved in fungi and bacteria to protect them from pathogens and competitors.
They are themselves infected by tiny rings of DNA called plasmids, which occasionally leave a part of their DNA behind as a new part of the bacterial genome. In 1976, it was discovered that the bacteria that cause gonorrhea had gotten the genes that code for penicillin-destroying enzymes via plasmids from Escherichia coli,
Gene mutations can be transmitted by plasmid infection or other processes to different species of bacteria.
An important recent example is zidovudine (AZT), used to delay the onset of AIDS in HIV-infected individuals. Unfortunately, AZT, like antibiotics, is not as reliable as it once was because some HIV strains are now (no surprise) resistant to AZT.
HIV is a retrovirus, a really minimal sort of organism with special limitations and special strengths. It has no DNA of its own. Its minute RNA code acts by slowly subverting the DNA-replicating machinery of the host to make copies of itself.
within-host selection favors increased virulence, while between-host selection acts to decrease it.
This evolutionary perspective suggests that diseases spread by personal contact should generally be less virulent than those conveyed by insects or other vectors.
The history of medicine shows repeatedly that the best place to acquire a fatal disease is not a brothel or a crowded sweatshop but a hospital.
If a burn destroys the cells that replace the epidermis, special mechanisms are required to protect the site from infection, clear away the dead tissue, and infuse the region with new skin cells that can grow and gradually resurface the site of the burn.
People who are outdoors for hours every day adapt to their amount of usual exposure and are unlikely to get sunburnt. The risk of melanoma is related more closely to the number of sunburns than to the total amount of time spent in the sun.
Toxin manufacture requires materials and energy, and the toxins may be dangerous to the plant that produces them. In general, a plant can have high toxin levels or rapid growth, but not both.
A plant has no nervous system, but it does have electrical signaling and a hormone system that can keep all its parts informed about what takes place in a small region.
boiling corn with alkali balances the amino acid composition and frees the vitamin niacin, which prevents pellagra,
Nausea and food aversions during pregnancy evolved, she argues, to impose dietary restrictions on the mother and thereby minimize fetal exposure to toxins.
Nausea and food aversions during pregnancy evolved, she argues, to impose dietary restrictions on the mother and thereby minimize fetal exposure to toxins. The fetus is a minor nutritional burden on the mother in the early weeks of pregnancy, and a healthy, well-nourished woman can often afford to eat less.
as many as eight out of ten conceptions end in early abortion or later miscarriage. The majority are never noticed because they occur before or just after implantation of the embryo. If a gene were to decrease the chances of miscarriage even slightly, it could be selected for even if it also increased the risk of developing a disease.
whenever a blurred image falls onto the retina, the brain sends back a message, in the form of a growth factor, that induces expansion of the eyeball. The clincher: when only one part of the visual field is blurry, only that part of the eye grows.
the whole immune system is age biased. It releases damaging chemicals that protect us from infection, but these same chemicals inevitably damage tissues and may ultimately lead to senescence and cancer.
Free radicals, for instance, are reactive molecules that damage whatever tissue they contact. Our bodies have developed a number of defenses, especially a compound called Superoxide dismutase (SOD), that neutralizes free radicals before they can cause much damage.
Urate is a very efficient scavenger of highly reactive and harmful oxygen species—namely hydroxyl radical, Superoxide anión, singlet oxygen, and oxygenated heme intermediates in high Fe valence states (+4 and +5). Indeed urate is about as effective as ascorbate as an antioxidant.
our mouth is below and in front of our nose, but our food-conveying esophagus is behind the air-conveying trachea in our chest, so the tubes must cross in the throat. If food blocks this intersection, air cannot reach our lungs.
When a foreign substance enters the body, it is taken into cells called macrophages (macro means “big” and phage means “to eat”), which process the proteins from the substance and then pass them on to white blood cells called helper T cells, which take the proteins to another kind of white cell called B cells. If the B cell happens to make antibodies to that foreign protein, it is stimulated by the T cell to divide and make those antibodies. Most often that antibody is the familiar immunoglobulin G (IgG), but, for certain substances, the B cell is instead induced to make IgE antibody, the substances that mediate allergic reactions.
The IgE antibody circulates in the blood, where about one out of one hundred to one out of four thousand molecules attaches to the membranes of still other cells called basophils (if they are in the circulation) or mast cells (if they are localized).
These mast cells are primed, like mines floating in a harbor, waiting for reexposure to the allergen. When it does return and is bound by two or more IgE molecules on the surface of the mast cell, the cell pours out a cocktail of at least ten chemicals in the space of eight minutes.
The most widely accepted view is that the IgE system is there to fight parasitic worms.
Profet proposes that the IgE system evolved as a backup defense against toxins.
the backup defense, allergy, which gets toxins out of you in a hurry. Shedding tears gets them out of the eyes. Mucous secretions and sneezing and coughing get them out of the respiratory tract. Vomiting gets them out of the stomach. Diarrhea gets them out of parts of the digestive system beyond the stomach.
Still another possible function of the IgE system may be to defend against ectoparasites such as ticks, chiggers, scabies, lice, fleas, and bedbugs.
The eternal line of germ cells gives rise to individual bodies with a limited life span.
a virus is not very different from a single gene in a human cell and can sometimes settle into a niche on a chromosome as if it belonged there. From such a position it can readily subvert the normal machinery of the cell.
Like bacteria and larger parasites, viruses can also produce toxins that weaken cellular-control mechanisms.
The undeniable observation is that the more menstrual cycles a woman has, the more likely she is to get a reproductive-system cancer.
An individual who is genetically identical to many others is vulnerable to any pathogen that discovers the key to exploiting this bonanza of susceptible individuals.
Therapists have long known that many depressions go away only after a person finally gives up some long-sought goal and turns his or her energies in another direction.
They have argued that depression often results when a person is unable to win a hierarchy battle and yet refuses to yield to the more powerful person. They suggest that depression is an involuntary signal of submissiveness that decreases the likelihood of attacks by dominants.
They have argued that depression often results when a person is unable to win a hierarchy battle and yet refuses to yield to the more powerful person. They suggest that depression is an involuntary signal of submissiveness that decreases the likelihood of attacks by dominants. In case studies they describe how submitting voluntarily can end depression.