The human immune system consists of many types of cells. Three primary cells are classified as the T and B lymphocytes and the macrophage. These white blood cells are the main contributors in our bodies line of defense. They become immunologically competent in different locations in our body and may later congregate in specialized areas or simply circulate throughout the body. They contact, identify (as non-self), and dispose of any and all foreign material in our bodies for a finite amount of time. Although the B, T and macrophage lymphocytes have been programmed to attack differently, they are all vital in antigen elimination. It is typical to elicit an immune response from B lymphocytes and macrophages by direct contact and usually from the T lymphocyte as a part of a cell mediated response. In either scenario, the final outcome is the disposal of foreign material.
"The lion, a dangerous and ferocious beast stealthily stalks his prey, an unsuspecting wildibeast". This is an image generally depicted to describe this seemingly fearsome creature. According to the general consensus, the lion is a savage and unforgiving predator that brings fear to the likes of all animals. This, however, cannot be. With careful studies done of this intriguing animal, scientists have shown that the lion does not live up to its reputation. The African lion is possibly one of the more communal, nurturing and social animals in its habitat. These animals demonstrate a phenomenal ability to cooperate with each other in all aspects of lion society such as rearing young, hunting, and territorial defense. Although, after careful observations of lions in their natural habitat and interacting with others of their own species, the questions still remains as to why these animals cooperate on such a level. This goes against all evolutionary theory. If fitness depends on how well an individual can reproduce, why would the lion help out individuals, other than itself, obtain food, rear young, and defend territory? The answer may be that by helping others the individual lion will indirectly benefit. By helping members of its own family reproduce and rear young, the individual will still manage to pass on a portion of it’s genes. The more genes passed on by an individual, the better their fitness. So, this may be a part of the reason behind the lion’s amazing ability to live socially and work together. In any case these creatures should be no more fearsome in the eyes of the populus than an ordinary insect.
In recent years, corals of nearly all species around the world have displayed more and more frequent bleaching events. These events have prompted scientists to look into what the specific cause might be. When a coral bleaches, it loses its zooxanthellae, or symbiotic algae, and may never regain them. If a coral does not regain the zooxanthellae it dies, and the death of even a few coral species on a given reef can have devastating consequences. Not only do fishes and other sea creatures depend on the corals for food and shelter, we depend on the coral reefs for many uses as well. Due to the ramifications of continued bleaching events, marine biologists have been frantically trying to discover the cause(s) of these episodes. A large contingent of scientists cite stresses on the corals such as heat, UV light or bacterial/viral infections, as possible explanations. Another, much smaller group, claims that these bleaching events may be a natural occurrence which enables the corals to better adapt to their changing environment. It is imperative that the cause of the bleaching events be determined so that if there is something we need to do differently, we have the chance. If we continue to allow corals to die, possibly as a result of our actions, we are watching a resource be depleted that will not replenish itself for a long time.
In the United States, the human immunodeficiency virus (HIV) that progresses to AIDS (acquired immunodeficiency syndrome) has killed over 350,000 people and has become the principal cause of death among individuals ages 24 to 44 years old. Today, advances in drug therapy have allowed HIV patients to live longer. However, investigators now have evidence on why some people with HIV progress to AIDS slowly and why some people at high risk for HIV escape infection. The knowledge and techniques of AIDS epidemiology, human molecular genetics and population genetics theory combined in finding HIV resistance alleles in humans. Through many studies, the homozygosity for the deletion mutant of CCR5 allele surfaced as protective against HIV. This finding could prove beneficial in therapeutic strategies to escape or attack HIV infection.
Salmonella is a general term applied to a group of about two thousand closely related types of bacteria, that cause food poisoning in humans. The disease caused by Salmonella bacteria is called salmonellosis. Salmonellosis can be transported into humans by way of numerous sources. One of the numerous sources are birds. Many cases of this disease arise every year. Even now in the nineteen nineties the problem continues to exist. The fact that it continues to rise in animals and humans is a cause for direct action. More than two million cases occur every year in spite of advanced food processing techniques. Although there are solutions to this problem, the problem will remain. It will continue to remain unless we as humans follow the four basic principles for preventing salmonellosis.
Although many morphological and functional similarities exist between early birds and dinosaurs, there is still a lot of controversy surrounding where the dinosaur lineage ended and where the bird lineage began. Some dinosaurs, like birds, were believed to be endothermic, bipedal, flying, toothless and feathered. Archaeopteryx seems to be the perfect "missing link", in that it combines the characteristics of birds and dinosaurs in one organism. The controversy arrises when one tries to determine whether Archaeopteryx and/or Mononykus are birds or dinosaurs. There is also considerable controversy over the lifestyles of these two organisms, ie determining the purpose of the feathers, determining the function of bipedalism, deciding whether they were arboreal or cursorial and establishing their ability to fly. In order to resolve these conflicts, two groups of scientists, Chiappe at al. and Zhou et al. have looked at varying morphological and osteological characteristics and have tried to interpret them in different ways. In the end, they've come up with entirely different conclusions. It is my goal to address both views, at least in part, and to give a general overview of dinosaur bird evolution as an explanation for the origin of these controversies.
HIV (human immunodeficiency virus) causes AIDS (acquired immunodeficiency syndrome) by gaining a foothold in macrophages. Macrophages are important immune cells that rid the body of unwanted molecules (antigens). In order to enter macrophages, HIV must bind to two receptor proteins displayed on the macrophage. These receptors are CCR5 and CD4. A small percentage of the population has a mutation of the CCR5 producing gene. As a result, these individuals in the population have a genetic immunity to HIV proliferation in their macrophages (M-Tropic infection). Amazingly, these individuals show no adverse immune effects due to lacking the proper CCR5 receptor protein. By centering on this mutation, researchers are searching for a way to create a vaccine of sorts for use in the general population. Their focus has been on creating a way to block the CCR5 receptor in wild type individuals.
Leptin, a hormone, secreted by adipose tissue in proportion to body adiposity is thought to be involved in the central nervous system regulation of food intake and body weight. There are at least six different forms of leptin receptors. One of them is expressed in high levels in hypothalamus. Leptin is found to have weight reducing effect in mice. Therfore high levels of leptin lead to low percentage of fat in the body. In the obese people, however, there is a normal level of leptin produced but the sensitivity to the action of leptin is reduced.
Respiratory Distress Syndrome (RDS) is the most common & harmful problem affecting premature infants today. RDS occurs because premature infants cannot produce a key fluid called surfactant. Surfactant is a fluid composed primarily of proteins and fatty acids. The primary role of surfactant is to reduce surface tension in the lungs in order to prevent the alveoli from collapsing. Additional properties have recently been discovered. Development of synthetic surfactant treatments appear to be the most promising. Continued studies aim to improve the stability of synthetic surfactant to produce a monolayer on the surface of the alveoli in premature infants.
Nitrogen is essential for life and the biological processes in both plants and animals. Most of the nitrogen on earth is located in our atmosphere as an unreactive gas. In order for plants to use this atmospheric nitrogen they have to "fix" it by splitting apart the tightly bound N2 molecules and joining them with other atoms (such as oxygen). But taking the nitrogen from the atmosphere and fixing it takes time. To deal with this problem, along with the problem of over-population, scientists invented inorganic fertilizers to speed up this process by adding usuable nitrogen directly to the soil. This succeeded in quickly and efficiently growing crops, but not without consequences. Studies have shown that overuse of nitrogen fertilizers causes deaths of lakes and streams, soil acidification, erosion, local health problems, and even atmospheric pollution. It does not look like we will cut the use of these fertilizers in the near future, so the question we have to ask is: Is their use more beneficial or detrimental to us?
