Immunity And The Lymphatic System

The immune system consists of defenses against foreign matter that gains entry to the body. It consists of the lymphatic system plus components of numerous other systems of the body. Many toxic pollutants either stimulate or suppress the immune system. The lymphatic system consists of lymph, lymphatic vessels, lymphocytes, and lymphoid tissues and organs. Lymph is a fluid similar to plasma. Lymphatic vessels are similar in structure to veins. They conduct lymph from peripheral tissues to the...

Abnormal Microbial Infection

Although the vast majority of microbes pose no threat whatsoever to human health, there are many forms that are outright hazards. The importance of the infectious diseases they cause is demonstrated by the rates of mortality (death) to which they can be linked. Even today, infectious disease is the world's leading cause of death, with fatalities exceeding 15 million per year (Figure 12.1). Rates of overall morbidity (illness, both fatal and nonfatal) are of course much higher and have a...

Meningococcal Meningitis

Neisseria meningitidis is part of the normal biota of the nasal cavity and throat in a fourth or more of the population, but these carriers show no symptoms of disease. For reasons not yet fully understood, these bacteria may invade the bloodstream and subsequently invade and colonize the meninges (the membranes that surround the spinal cord and brain). Early symptoms may include headache, fever, and vomiting, and death can quickly follow, due to the endotoxin produced (a toxin associated with...

Genetic Disease

Many diseases are caused by genetic defects. The corresponding alleles may be dominant or recessive and may be found on autosomes or on sex chromosomes. Some genetic diseases are associated with extra chromosomes or missing pieces. An example of a dominant autosomal genetic disease is Huntington's disease. It results in neurological degradation leading to death. Because the symptoms do not appear until a person is about 40 years old, the victim may already have produced a family, potentially...

Major Wetland Types

Here we highlight several of the most extensive wetlands types, of the many that exist. Our interest is in those most likely to be affected by development activities. Tidal Salt Marshes Salt marshes tend to form in protected areas such as in the shelter of spits, bars, or islands, in bays, and in estuaries. Marshes may grow with sedimentation supplied by rivers or tidal action and influenced by sediment-trapping effects of the biota. In some places, sea-level rise results in an increase in the...

Individual Variability

Even when given the same exposure to a toxin, individuals vary in their responses. The causes of variation include genetic, nutritional, age and sex, metabolic activity level, life stage, or exposure history leading to lesions, sensitization, or enzyme induction. Several examples in humans will show that individuals of the same species can have large genetic differences in responses to toxins. Many Orientals are genetically predisposed to a more rapid metabolism of ethanol to acetalydehyde....

Synaptic Transmission

At the end of the axon, the neuron must transmit the signal to another neuron or to an effector. This is done through the synapse. Most synapses involve the use of a chemical, called a neurotransmitter, to communicate the signal across a gap from one cell to another. One of the most widespread neurotransmitters is acetylcholine (ACh). This neurotransmitter is a target of many insecticides, in particular the organophosphorus and carbamate pesticides. The axon ends in a synaptic knob (Figure...

Oxidation of Fats and Amino Acids

Obviously, glucose is not the only fuel used by living things. Our foods contain other sugars, such as lactose in milk and fructose in the disaccharide sucrose (table sugar). The success of dieters hinges on the body's ability to use fat as fuel of course, this is why the body stores fat in the first place. Under starvation conditions, the body obtains its energy for basic cell function by cannibalizing itself, by oxidizing its proteins. The sugars are converted fairly easily into either...

Reproduction And Development

The reproductive system is the only system that is not essential to a person's survival. It is, however, essential to the survival of the species. Because cells replicate continually, they are subject to errors of replication, either due to the inborn rate of error or because of environmental agents such as chemical pollutants or radiation. This makes the reproductive organs susceptible to diseases associated with genetic damage. These range from cancer, which affects the individual, to birth...

Info

AFW, freshwater S, saline B, benthic or attached P, planktonic. Source Horne and Goldman (1994). aFW, freshwater S, saline B, benthic or attached P, planktonic. Source Horne and Goldman (1994). TABLE 15.7 Characteristics of Some Common Insect Larvae Damselflies (Odonata) Dragonflies (Odonata) Water bugs (Hemiptera) Caddisfly (Trichoptera) Water beetles (Coleoptera) Order Diptera (and family) Mosquitoes Blackflies True midges (chironomids) Horseflies Slow and stagnant Slow and stagnant All...

Effects on Particular Organs or Organ Systems

The discussion in this section concerns effects in organs or organ systems of vertebrate animals. Within that group the emphasis is, of course, on humans. As mentioned above, particular toxins will tend to target particular organs or organ systems. The liver and the kidney are common targets of toxic activity because of their role in detoxification and their large blood flow. The skin and eyes, lungs, and digestive tract are vulnerable to the more reactive toxicants, as they are the sites of...

Testing for Carcinogenicity and Teratogenicity

Carcinogenic potential can be detected by three types of tests long-term carcinogenicity studies, rapid screening tests, and biomarkers. Long-term tests are the most definitive. These generally use mice or rats and last the lifetime of the animals (18 and 24 months, respectively). Two or three dose levels are usually used, the highest being the maximum tolerated dose'' (MTD). The MTD is estimated from 90-day studies and is chosen so as not to produce severe noncarcinogenic toxicological effects...

Eukaryotic Cell Structure And Function

Membranes, penetrated by numerous protein pores. (In prokaryotes, the DNA is not isolated from the cytoplasm by a membrane, and the structure is called a nuclear region rather than a nucleus.) Each of the DNA molecules in the nucleus is contained in a chromosome. A chromosome is a complex of a DNA molecule and associated proteins. Chromosomal DNA forms a template for protein synthesis. Protein synthesis takes place outside the nucleus in the cytoplasm. The nucleus synthesizes RNA molecules,...

Chordates Including the Vertebrates

Finally, we come to the phylum that includes ourselves. The chordates incorporated evolutionary innovations that made it possible for them to grow to great size, forming the largest animals on land (dinosaurs and elephants) and in the water (whales). The four unique characteristics of the phylum Chordata are 1. They have the presence of a notocord at some point in their development. The notocord is a flexible skeletal rod that runs the length of the organism. It remains in adult lampreys and...

Nervous System Organization

The nervous system may be the best example of the whole is more than the sum of its parts.'' Even accounting for the fact that the behavior of individual neurons is much more complex than described above, it is difficult to explain our higher behaviors, such as language, abstract reasoning, and self-consciousness, in terms of them. That is a far greater task than explaining the functioning of a computer in terms of the action of individual transistors. Those higher behaviors depend on neuronal...

Counts Of Microorganism Numbers

Counts of microorganisms may be made by direct microscopic techniques or through indirect methods such as culturing. Figure 11.9 Petroff-Hauser counting cell. Figure 11.9 Petroff-Hauser counting cell. In some samples, microorganisms can simply be counted under the microscope. Counting chambers specialized microscope slides with wells holding a fixed volume are available for this purpose. Some, such as the Petroff-Hauser cell (Figure 11.9), also have a grid marked on them. An example of a...

Water And Wastewater Disinfection Treatment

One of the most significant public health advances over the past century was that of developing, and then routinely applying, suitable engineering methods for disinfecting potable waters that could retard, and ideally obviate, the transmission of waterborne disease. Rudimental disinfection measures based on water filtration used by the ancient Egyptians and heat treatment have long been practiced, but the advent of commercially available chlorine during the late nineteenth and early twentieth...

Ebola

The index first noted case for the Ebola virus took place in Zaire in 1976, with more than 300 victims of this severe hemorrhagic bleeding fever. A second outbreak in Sudan killed another 150 people, and other, usually smaller outbreaks have since been reported, mainly in east, central, and southern areas of Africa. Ebola virus spreads through the body, with rapid necrosis death of cells in the infected organs, particularly those of the liver, lymph system, kidneys, ovaries, and testes....