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...

Ddt

Effective than, the blood-brain barrier. There is an efficient DNA repair mechanism in the cells that generate sperm, but not in the sperm cells themselves. Blood lead levels in excess of 41 to 53 mg dL were associated with reduced sperm counts and infertility. Other effects include reduced testosterone levels, testicular atrophy, loss of libido, and impotence. Table 17.6 lists some toxins known to affect the male reproductive system. Toxic effects on the female reproductive system include...

Distribution And Storage

Once a toxin enters the bloodstream, it is distributed rapidly throughout the body. However, organs do not all receive equal distributions, nor do they store them with equal efficiency. Moreover, the location where most of a toxin is stored is not necessarily the primary site of toxic effect. For example, 90 of the lead in adult humans is stored in the bones, but its effects are on the kidney, nervous system, and blood cell production. Individual organs and tissues will then take toxins...

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...

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....

Other Agents

Viruses Some viruses, such as hepatitis A, rotaviruses, and Norwalk virus, can be spread by food as well as by water. In part, this is expected, since water is used in the preparation of many foods. However, unlike bacteria, viruses cannot grow or replicate in food. (Animal viruses only replicate within living animal cells.) Thus, the initial contamination must be with a sufficient quantity of viruses to constitute an infective dose, or disease will not occur. Fungi Several types of fungi can...

Eukarya

Figure 10.19 Phylogenetic tree indicating evolutionary branching and distance between groups based on on rRNA analysis. Fungi are represented by Coprinus (a mushroom), plants by Zea (corn), and animals by Homo (humans). (From Atlas, 1997 all rights reserved.) Figure 10.19 Phylogenetic tree indicating evolutionary branching and distance between groups based on on rRNA analysis. Fungi are represented by Coprinus (a mushroom), plants by Zea (corn), and animals by Homo (humans). (From Atlas, 1997...

Endocrine System And Homeostasis

The nervous system is not the only way the body controls bodily functions. It also uses chemical messengers. Some cells communicate directly with their contact neighbors through special junctions. This is usually to coordinate local activity such as ciliary movement or muscle contractions. Others release chemicals into the intercellular spaces that primarily affect cells in the same tissue. An example is the prostaglandins, a powerful fatty acid with many functions. Prostaglandins are released...

Prenatal Development

Development begins when the haploid sperm and ovum unite in the process of fertilization (or conception), to form a diploid zygote. After ovulation, a layer of cells surrounds the ovum. At least 100 sperm are needed to release an enzyme that creates gaps in this layer. Then one of the sperm may penetrate the cytoplasm of the ovum. This triggers reactions that render the ovum impermeable to additional sperm. In addition, the ovum completes meiosis II. The zygote then divides by mitotic division...

Hepatitis B

Hepatitis B, or serum hepatitis, is spread mainly through contaminated blood, often from unsterilized needles shared by drug users or used for tattoos or ear or body piercing. The virus can also be transmitted sexually. Over 100,000 people are infected yearly in the United States, but this number is decreasing due to the recent introduction of a vaccine. In addition to the initial disease, which is more severe than hepatitis A (more liver damage and fatality rate of 10 ), those infected are at...

Hydrocarbons Solvents Pahs And Similar Compounds

Here we consider other anthropogenic organic chemicals and their by-products. Solvents include many types of liquid hydrocarbons, which are used as carriers for other materials, such as pigments in paints, or for rinsing oil and grease from manufactured items. Some, such as benzene, may also be components of fuel or raw materials for synthesis of other compounds. Some of the larger molecules we consider include the polynuclear aromatic hydrocarbons (PAHs), phthalate esters, and surfactants....

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...

R

Is stabilized by the presence of the nitro groups, TNT is recalcitrant. Although it can be mineralized, biodegradation usually involves reduction of one or more of the nitro groups to an amine, which then reacts with a nitro group on an adjacent molecule (Figure 13.14). A series of such reactions leads to the disappearance of TNT through the formation of a polymer. The environmental significance of such polymers is still not thoroughly understood, as there is concern that the monomers may be...

Info

AAll are bacteria, except Plasmodium, a protozoan. A disease mainly of animals that also can be transmitted to humans (such as anthrax) is called a zoonosis (plural, zoonoses). Some infectious agents are able to survive in the environment, outside any host. This includes some species, referred to as opportunistic pathogens, which normally grow in soil or water or other environments but are capable of infecting a host that is compromised (weakened) by an injury, condition, or disease. The human...

Biological Effects Of Greenhouse Gases And Climate Change

Our industrial economy is almost entirely heterotrophic, relying on energy stored in coal and petroleum deposits. These were formed from atmospheric CO2 removed over the eons by primary production of ages past. The combustion of these resources is returning much of this to the atmosphere. The CO2 and other anthropogenic gas emissions have already resulted in more than 1 increase in the amount of energy from the sun being trapped at Earth's surface (Section 14.2.2). Now the question is What are...

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...

Water And Wastewater Disinfection Treatment

Wastewater Disinfection

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...

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...

Immunity and Vaccination

Immunity (the ability to resist infection based on mobilization of the immune system) to many diseases can result from a prior infection of the same agent. Getting the measles, for example, protects the host from being infected again later. Thus, a person can contract many diseases only once. Colds and influenza, on the other hand, stem from viruses that continue to produce new strains that avoid the body's predeveloped defenses, so that they may be contracted repeatedly. Prior exposure also...

Bacillus Circulans

Bacillus Circulans

Order Bifidobacteriales Bifidobacterium Order Bifidobacteriales Bifidobacterium a All classes are listed, but not all orders. Only some representative, important, and interesting genera are included. as resistant. The endospore develops within the vegetative cell (Figure 10.27) and is then released through cell lysis. Under suitable conditions, the endospore can later germinate to produce a new vegetative cell. This ability is of obvious survival value in the soil, where conditions suitable for...

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,...

Excretory System

Excretion is the elimination of waste products from the body. We excrete substances mostly in the urine or the feces, but also by sweat, milk, other body fluids, and even in our hair. Excretion is important from an environmental viewpoint for two reasons (1) It is a means by which the body eliminates toxic substances and (2) excretory organs may themselves be susceptible to the action of toxic substances, damaging their ability to maintain homeostasis. In this section we focus on urinary...

Nitrogen Cycle Reservoirs

Nitrogen Cycle Ammonification

Eventually, the oxygen concentration dropped from the normal 21 to a dangerous 14 , and the total volume of the atmosphere decreased. (Huge, flexible lungs connected to the system gradually collapsed to maintain atmospheric pressure within.) It was suspected that the oxygen was being lost to respiration, but mysteriously, the increase in CO2 from 330 ppmv to 4000 ppmv could not account for this. The high CO2 levels lowered the pH of the crew's blood, which decreased the ability...

Substrate Utilization

In many cases, to the environmental engineer and scientist it might actually be the substrate that is of greater direct concern than the microorganisms. For example, in biological wastewater treatment, the substrates are the constituents of the waste that are to be removed. Similarly, in polluted aquifers or streams, the contaminants may be the substrates. In such cases, the growth of the microorganisms themselves may be of only secondary interest. Microorganisms may utilize substrates as a...

Respiratory System

Lower Respiratory System Inferior Lobe

The respiratory system has the primary function of exchanging the gases O2 and CO2 between the blood and the atmosphere. Along with the integument and the digestive tract, it is a major area of contact between the body and the environment. In fact, it is the major area of exposure, in terms of the volume of environmental material contacted. Besides infectious illness, the respiratory system is susceptible to gaseous and particulate pollutants, ranging from irritants to carcinogens. The upper...

Carbohydrates

Carbohydrates include sugars, starches, and structural materials such as cellulose. All have the empirical chemical formula CH2O n. For example, glucose is C6H12O6, so n is 6. Glyceraldehyde is one of the simplest carbohydrates, with an n of 3. The large number of hydroxide groups on carbohydrates renders them hydrophilic. Carbohydrates are classified into several groups Monosaccharides are the simplest and are building blocks for the others. They have relatively low molar masses, and n in the...

Synaptic Transmission

Synaptic Knobs

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 9.3 ,...

Aerobic Respiration

Bartha Biometer Flasks

A generalized overall reaction for aerobic respiration of organic material can be expressed as organic matter O2 CO2 H2O new biomass energy Analogous reactions can be developed for inorganic substrates such as ammonia and hydrogen sulfide, which are used by lithotrophic organisms. The rate of change of each of the six quantities in this equation in theory could be used to measure the rate of aerobic microbial activity. This is typically done by making repetitive measurements of disappearance or...

Counts Of Microorganism Numbers

Direct Counts Microorganisms

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 chamber...

Arthropods

Arthropods Crabs Respiratory System

Arthropods jointed legs include the spiders, centipedes, millipedes, insects, and crustaceans. They represent an evolutionary advance that allowed them to form the greatest diversity and number of species of all the phyla, about 1 million species known. The advance was the development of a jointed exoskeleton made of chitin, a nitrogenous poly-saccharide, bound with protein. In crustaceans the exoskeleton also contains calcium salts for added strength. Other innovations with this phylum are...

Genetic Engineering and Society

Along with the benefits of genetic engineering described above come numerous actual and potential dangers in its application. Experience with introduction of natural nonnative species into an ecosystem has shown the potential for disaster. Often introduced deliberately, they have often been found to occupy unexpected niches in the ecosystem, displacing other organisms. Many examples exist. The kudzu vine was introduced to the southern United States to control erosion, but proliferated beyond...

Cloning and Recombinant DNA

A clone is a genetically identical copy of a DNA molecule, a cell, or an organism. Clones of DNA are produced in order to obtain sufficient genetic material for applications, such as DNA analysis or for producing recombinant DNA. Recombinant DNA is DNA formed by joining segments of DNA from different organisms. Recall that recombination occurs naturally between chromosomes in the same cell during meiosis and results in segments of DNA from one chromosome being included in another. Recombinant...