Showing papers in "Basic life sciences in 1988"
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TL;DR: It is not unreasonable to expect on the basis of present data that the healthy life span can be increased by 5-10 or more years by keeping body weight down, at a level compatible with a sense of well-being, while ingesting diets adequate in essential nutrients but designed to minimize random free radical reactions in the body.
Abstract: Aging is the progressive accumulation of changes with time that are associated with or responsible for the ever-increasing susceptibility to disease and death which accompanies advancing age. These time-related changes are attributed to the aging process. The nature of the aging process has been the subject of considerable speculation. Accumulating evidence now indicates that the sum of the deleterious free radical reactions going on continuously throughout the cells and tissues constitutes the aging process or is a major contributor to it. In mammalian systems the free radical reactions are largely those involving oxygen. Dietary manipulations expected to lower the rate of production of free radical reaction damage have been shown (i) to increase the life span of mice, rats, fruit flies, nematodes, and rotifers, as well as the "life span" of neurospora; (ii) to inhibit development of some forms of cancer; (iii) to enhance humoral and cell-mediated immune responses; and (iv) to slow development of amyloidosis and the autoimmune disorders of NZB and NZB/NZW mice. In addition, studies strongly suggest that free radical reactions play a significant role in the deterioration of the cardiovascular and central nervous systems with age. The free radical theory of aging provides reasonable explanations for age-associated phenomena, including (i) the relationship of the average life spans of mammalian species to their basal metabolic rates, (ii) the clustering of degenerative diseases in the terminal part of the life span, (iii) the beneficial effect of food restriction on life span, (iv) the greater longevity of females, and (v) the increase in autoimmune manifestations with age. It is not unreasonable to expect on the basis of present data that the healthy life span can be increased by 5-10 or more years by keeping body weight down, at a level compatible with a sense of well-being, while ingesting diets adequate in essential nutrients but designed to minimize random free radical reactions in the body.
690 citations
TL;DR: It is concluded that ferryl and not HO is the main oxidant in systems containing myoglobin and haemoglobin activated by low concentrations of H2O2.
Abstract: The oxidation of 2-keto-4-thiomethyl butyric acid (KTBA) and methionine to ethylene has been used to evaluate generation of ferryl species or hydroxyl radicals by H2O2-activated haemproteins or free ferric ions. Hydrogen peroxide was generated by a glucose oxidase-glucose system at a rate of 1 microM/min. Free ferric in the presence of H2O2 oxidizes KTBA, and this was highly inhibited by hydroxyl radical scavengers, caeruloplasmin, superoxide dismutase (SOD) and EDTA. However, when metmyoglobin, methaemoglobin (MtHb) or horseradish peroxidase (HRP) were tested in the same model system, hydroxyl radical scavengers suppressed partially KTBA oxidation and caeruloplasmin, SOD and EDTA failed to inhibit the reaction. Cytochrome-c was found to be a weak promoter of KTBA oxidation in the presence of H2O2. Methionine was oxidized to ethylene by an active system which generates hydroxyl radicals, but not by H2O2-activated metmyoglobin. Ferric ions chelated to membranes or ADP in the presence of H2O2 generated enzymatically, initiated membranal lipid peroxidation only in the presence of ascorbic acid, and this was inhibited by EDTA. In contrast, metmyoglobin and methaemoglobin activated by H2O2 generated by the same system, initiated membranal lipid peroxidation and this was not inhibited by EDTA. It is concluded that ferryl and not HO. is the main oxidant in systems containing myoglobin and haemoglobin activated by low concentrations of H2O2.
93 citations
TL;DR: The thoracolumbar (TL) kyphosis is present at birth, or is noticed within the first 6 months in about 95% of newborns, and gains its maximal expression when the child becomes a sitter, between 6 and 18 months of age.
Abstract: The thoracolumbar (TL) kyphosis is present at birth, or is noticed within the first 6 months in about 95% of newborns. The curve becomes more pronounced and gains its maximal expression when the child becomes a sitter, between 6 and 18 months of age (Fig. la,b). It noticeably improves or even disappears in most children with the advent of stance and gait, simultaneously with the development of lumbosacral lordosis. Some infants, however, develop vertebral wedging of the apical vertebra that insures the permanence of a residual structural curve. Many other achondroplasts adopt a kyphotic posture while sitting throughout life even if they do not have a structural, clinically appearing kyphosis when standing.
66 citations
TL;DR: Methylene blue effectively inhibits superoxide and hydroxyl radical production while accelerating the conversion of xanthine to uric acid, and may have a role in reducing tissue injury associated with reperfusion.
Abstract: Superoxide and hydroxyl radical generation have been implicated in a variety of pathological conditions, including ischemic injury in myocardial, renal, and skin-flap tissue, as reperfusion of the ischemic tissue presumably leads to a burst of free radical generation 1–4,14. Tissue hypoxia during ischemia results in the conversion of xanthine dehydrogenase to xanthine oxidase and concomitant breakdown of ATP to hypoxanthine 14. Upon reperfusion the xanthine oxidase oxidizes the hypoxanthine, and large quantities of superoxide, hydrogen peroxide, and possibly hydroxyl radicals are produced. Previous attempts to inhibit oxygen radical toxicity have focused on removing the superoxide or hydroxyl radicals after their production.
65 citations
TL;DR: In vitro oxidation of lens crystallins mimics many of the post-translational modifications observed with age and in cataracts, and lends further support to earlier proposals that oxidation is a key factor inCataract formation.
Abstract: Many post-translational modifications of lens proteins occur during aging.1 Since the lens continues to grow throughout life and its cells and proteins are not turned over, these modifications accumulate in the older fiber cells.
57 citations
TL;DR: This chapter presents some of the engineering challenges in biological degradation of organic contaminants in surface soils and the subsurface environment, and the solution of these important issues presents a significant challenge to the engineering and science communities.
Abstract: Biological processes have been used well over 100 years for the treatment of organic-bearing municipal and industrial wastewaters and municipal landfills. Aerobic biological processes, such as activated sludge and trickling filters, are used in virtually every city in the United States for treating dilute municipal wastewaters. Anaerobic processes are nearly as widely used to convert the concentrated sludges resulting from dilute waste treatment into methane gas, a useful form of fuel. About 30 years ago, it was first realized that by using completely mixed treatment processes, industrial wastewaters can be readily treated even though they contain organic compounds, such as phenol, that are toxic to microorganisms at the concentrations present. This is possible because the degrading microorganisms maintain the concentration of the chemical within the reactor below the toxic threshold. Biological treatment systems for such wastewaters are now common. Thus, a wide variety of biological processes for converting many forms of hazardous chemicals to innocuous end products are well established and extensively used throughout the world.
56 citations
TL;DR: Achondroplasia is an important model for defining how to describe the natural history of a disorder, as well as how to use that information to judge various therapies and to prevent serious complications in the condition.
Abstract: Achondroplasia is an important model for defining how to describe the natural history of a disorder, as well as how to use that information to judge various therapies and to prevent serious complications in the condition.
48 citations
TL;DR: It was demonstrated that both the respiratory bursts and the autoxidation result in the production of superoxide (O2‒) and hydrogen peroxide (H2O2) in isolated beef heart mitochondrial preparations.
Abstract: Catechols and other polyphenolic compounds have been shown to autoxidize and generate reactive oxygen species. A few examples of such compounds include epinephrine, 6-hydroxydopamine,2 and pyrogallol.3 We have previously reported that members of a class of polyphenolics, the flavonoids (Figure 1), behave in a similar manner. In particular four flavonoids, myricetin (3,5,7,3’,4’,5’-hexahydroxyflavone), quercetagetin (3,5,6,7,3’,4’-hexahydroxyflavone), delphinidin chloride (3,5,7,3’,4’,5’-hexahydroxyflavylium chloride) and quercetin 3,5,7,3’4’-pentahydroxy-flavone) induce cyanide-insensitive respiration in isolated beef heart mitochondrial preparations. Additionally, these compounds autoxidize in aqueous solutions at pH 7.5, as determined by measuring oxygen consumption and oxygen-dependent spectral changes. It was demonstrated that both the respiratory bursts and the autoxidation result in the production of superoxide (O2‒) and hydrogen peroxide (H2O2).4
47 citations
TL;DR: In summary, neurological symptoms in the achondroplast are related to the anatomical spinal canal with degenerative changes and aging altering the delicate biomechanical and microvascular balance.
Abstract: Kyphosis is fairly common in achondroplasia; 30 percent of the early thoracolumbar kyphoses persist. A third of these or approximately 10 percent of achondroplasts have a progressive kyphosis. Some control of the kyphosis early is possible orthotically using an underarm orthosis or TLSO (thoraco-lumbo-sacral-orthosis). This improves the clinical appearance and may have some impact on the lumbosacral hyperlordosis. There are no long term longitudinal studies as yet to document stabilization of the spine in the corrected position. The important question is whether there is a decrease in the 30 percent residual kyphoses or 10 percent progressive kyphoses in adulthood in treated patients. Of additional concern is the respiratory effects of some of these restrictive devices on the pulmonary function in children with small thoraces and thus pre-existing potential respiratory dysfunction.
47 citations
TL;DR: The question of what to do when environmental oil contamination occurs is asked in order to minimize its persistence and thus its long-term effects and treatment methods should enhance rather than inhibit the natural rates of oil biodegradation.
Abstract: Although most oil pollutants enter the environment as a result of chronic inputs associated with the extraction, production, transport, utilization, and disposal of this fossil fuel resource, most public concern occurs when there are large accidental oil spills, particularly if these pollute water supplies or recreational areas. Great public attention has been given to oil pollution of the seas, where several major tanker and offshore oil well accidents have released large amounts of oil into the marine environment, visibly contaminating beaches and seabirds. The absence of a “major” spillage in the past few years that could have contaminated recreational beaches, and the scientifically accepted recognition that oiled ecosystems recover as a result of natural processes that remove oil pollutants, have led to diminished public and scientific interest in the environmental fate of oil pollutants. Chronic sources of petroleum pollution, spillages that contaminate groundwater, and land disposal of oily sludges remain problems that may be mitigated by bioremediation and deserve continued study.
46 citations
TL;DR: Longitudinal studies are called for, because they control for cohort effects and, of course, allow within-subject comparisons, and age-comparative work is often flawed.
Abstract: There is a vast literature on the course of psychometric intelligence over the adult life span that has made us familiar with the finding that most abilities tend to peak in early midlife, plateau until the late fifties or early sixties, and then show decline, initially at slow pace, but accelerating as the late seventies are reached (Botwinick, 1977; Cunningham, in press; Labouvie-Vief, 1985; Schaie, 1980a). There remains some controversy on the specific ages at which certain abilities peak and on the ages at which significant decline can first be detected (Botwinick, 1977; Willis, 1985). Data from cross-sectional studies usually draw relatively pessimistic conclusions for those variables where positive cohort trends have been observed, and unduly optimistic conclusions for those variables where cohort trends have been negative. Age-comparative work is often flawed, moreover, because of the fact that it is difficult or impossible to match samples differing widely in age with respect to other variables that might critically effect the dependent variable of interest. Longitudinal studies are consequently called for, because they control for cohort effects and, of course, allow within-subject comparisons.
TL;DR: The maintenance of macromolecular integrity and function, particularly in DNA, appears to be a major determinant of the longevity and functional capacity of biological systems and the need for specific biomarkers to elucidate the biochemical nature of DNA lesions and their repair is suggested.
Abstract: The maintenance of macromolecular integrity and function, particularly in DNA, appears to be a major determinant of the longevity and functional capacity of biological systems.1 DNA damage induced by active oxygen species therefore may be of primary importance in cancer and aging2–4. This suggests the need for specific biomarkers (a) to elucidate the biochemical nature of DNA lesions and their repair and (b) to monitor noninvasively the generation and removal of DNA damage in biological systems. Several types of damage are known to result from the interactions of free radicals with chromatin, including single- and double-strand breaks, base and sugar alterations, and DNA-protein crosslinks.5 Each of these types of damage seems to be amenable to chemical analysis by the techniques of high performance liquid chromatography (HPLC), gas chromatography/mass spectrometry (GC/MS), alkaline and neutral elution, and other chromatographic and filter techniques. Of particular interest have been the measurements of specific products of oxidative damage to DNA and proteins, such as thymine glycol, thymidine glycol, base-amino acid crosslinks, and altered amino acids. Recently, the measurement of thymine glycol (TG), thymidine glycol (dR-TG), and 5-hydroxymethyluracil (HMU) in urine has been suggested to be a suitable approach for the in situ assessment of oxidative DNA damage caused by every day metabolic processes.References
TL;DR: The free radical theory of aging proposed by Harman provides a molecular basis for the possible mechanisms for such ubiquitous phenomena as age-related deterioration and cell death.
Abstract: The biological aging processes are time-dependent deteriorative changes occurring in all living cells. Several investigators have postulated that these age-related changes are due primarily to alterations in cellular membrane structure and function.1,2 The free radical theory of aging proposed by Harman provides a molecular basis for the possible mechanisms for such ubiquitous phenomena.3
TL;DR: The accumulation of xenobiotic compounds in the environment has had a profound effect on the physical, social, economic, and political well-being and there has been a growing demand for their safe disposal or destruction.
Abstract: The accumulation of xenobiotic compounds in our environment has had a profound effect on our physical, social, economic, and political well-being Some of these substances have been found to be harmful to humans, while others, including polychlorinated biphenyls (PCBs), have only been implicated as such In either case, there has been a growing demand for their safe disposal or, preferably, destruction
TL;DR: Improvements in detection limits, sample volumes and analysis time are offered in the determination of 8-hydroxydeoxyguanosine in human urine based on reversed-phase HPLC combined with electrochemical detection.
Abstract: A sensitive analytical method has been developed for the determination of 8-hydroxydeoxyguanosine (h8dG) in human urine, based on reversed-phase HPLC combined with electrochemical detection. Previous attempts to use urine as a means to monitor DNA oxidative damage have centered around the detection of thymine glycol, thymidine glycol, and 5-hydroxymethyluracil.1–3 The present assay offers improvements in detection limits, sample volumes and analysis time.
TL;DR: The inhabited islands of Hawaii encompass a land mass of 6,422 square miles and an ethnically heterogeneous population and the incidence rates for cancer well illustrate this variability, as shown in Table 1.
Abstract: The inhabited islands of Hawaii encompass a land mass of 6,422 square miles1 and an ethnically heterogeneous population. Five ethnic groups in particular have resided in the islands for many decades and comprise the majority of the present population. These include Caucasians, Japanese, Chinese, Filipinos, and native Polynesians or Hawaiians. Although these ethnic groups are generally intermixed throughout the islands, their risks for disease are markedly different2. The incidence rates for cancer well illustrate this variability3, as shown in Table 1.
TL;DR: It is evident from the results summarized here that a variety of MFO systems catalyze the oxidation inactivation of enzymes, and the possibility that protein oxidation is implicated in various diseases, viz, arthritis, pulmonary dysfunction, and carcinogenesis deserves consideration.
Abstract: A number of enzymatic and nonenzymatic mixed-function oxidation (MFO) systems catalyze the oxidation of enzymes1–6 With oxidation, the enzymes are converted to catalytically inactive or less active forms that are more sensitive to heat denaturat ion7 and to proteolytic degradation8–11 Enzyme oxidation is likely the basis of some normal biological functions, eg, in the killing of bacteria by neutrophils, in limitation of the inflammatory response, in controlling the switch from anaerobic to aerobic metabolism, and in the regulation of the turnover of some enzymes Enzyme oxidation also might be implicated in a variety of pathological disorders, including arthritis, aging, carcinogenesis, broncho-pulmonary dysplasia and adult respiratory distress syndrome, retinopathy of prematurity, and reperfusion-mediated ischemic damage
TL;DR: Through a decade of research, peroxidation has been implicated in human retinal degenerations and Senile macular degeneration is yet another candidate for peroxidated-induced degeneration.
Abstract: Through a decade of research, peroxidation has been implicated in human retinal degenerations Ocular siderosis, or iron in the eye, has long been known to result in retinal degeneration Certain retinotoxic drugs, such as adriamycin, are believed to act by peroxidative mechanisms The retina can also be damaged by excess light, presumably through photo-oxidative processes Senile macular degeneration is yet another candidate for peroxidation-induced degeneration Finally, retinopathy of prematurity occurs only in premature infants housed in elevated levels of atmospheric oxygen Although the agent in each of these insults may be different, cell destruction and death apparently proceed through pathways common to lipid or protein oxidation
TL;DR: Catalases, together with superoxide dismutases and peroxidases, provide aerobic cells with a defense system for removal of superoxide radical and of hydroperoxides and are of considerable interest in the production of hydroxyl radical by the reduction of H2O2.
Abstract: Catalases (H2O2:H2O2 oxidoreductase; EC 1.11.1.6) are metalloenzymes that catalyze the elimination of H2O2 according to the equation:
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Catalases, together with superoxide dismutases and peroxidases, provide aerobic cells with a defense system for removal of superoxide radical and of hydroperoxides. H2O2 is a cellular toxicant in its own right. Considerable interest in the production of hydroxyl radical by the reduction of H2O2 (equation 2)
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mediated by transition metals or other cellular reductants has arisen.
TL;DR: Results from genomic DNA blotting experiments indicate that the dSpm-13 element had excised from the locus in each stable derivative analyzed, and the role of RNA splicing in this phenomenon and the recent finding of an acceptor splice site within the terminal inverted repeat are discussed.
Abstract: The bz-m13 allele of maize contains a defective Suppressor-mutator (dSpm) transposable element and gives rise to a variety of stable and unstable derivatives in the presence of an autonomous Suppressor-mutator (Spm) element. The dSpm-13 element of bz-m13 consists of 2,241 base pairs (bp) and is located within the second exon of the bronze-1 (bz) gene. A number of the stable derivatives, both functional and nonfunctional, derived from bz-m13 were characterized molecularly. Resu ts from genomic DNA blotting experiments indicate that the dSpm-13 element had excised from the locus in each stable derivative analyzed. The unstable derivatives bz-m13CS9 and bz-m13CS6 contain dSpm elements in the same position and orientation as the dSpm-13 element, but they differ in the length of the element. The dSpm-13CS9 element is 902 bp and arose via a deletion between two 5-bp direct repeats within the dSpm-13 element. The dSpm-13CS6 element is 2,239 bp and only differs from dSpm-13 by a 2-bp deletion at the end of one of the 13-bp terminal inverted repeats. The effect of these deletions on the frequency and timing of Spm-induced excision is discussed herein. In the absence of Spm, each of the bz-m13 alleles conditions a nonmutant phenotype despite the presence of the insertions in the second exon. The role of RNA splicing in this phenomenon and the recent finding of an acceptor splice site within the terminal inverted repeat are also discussed.
TL;DR: Based on work from the laboratory and studies by others, the following hypothesis is proposed to explain the interaction among xanthine oxidase, PMNs, and tissue injury in the postischemic small intestine.
Abstract: It is now well recognized that ischemia/reperfusion-induced tissue injury is a major factor in the pathogenesis of certain life threatening diseases such as stroke and coronary artery disease. Studies indicate that this injury occurs at the time of reperfusion rather than during the period of ischemia. There is now a large body of experimental data which suggests that oxy radicals mediate the microvascular and parenchymal cell damage observed during reperfusion of ischemic tissues. Reactive oxygen metabolites have been implicated in ischemia/reperfusion injury in the small intestine, heart, liver, pancreas, and brain.
TL;DR: The goal of the human genome project is to decipher the human genetic information (i.e. determine the sequence of the DNA bases) for the benefit of mankind.
Abstract: The goal of the human genome project is to decipher the human genetic information (i.e. determine the sequence of the DNA bases) for the benefit of mankind. Questions about this project center on emphasis and approach, not on the scientific value. One important question focuses on the need to sequence the entire genome rather than subsets of the genome, since it is thought that more than 80 percent of the human genome may not contain useful genetic information.
TL;DR: This presentation reports the experience at the Johns Hopkins Hospital with the surgical management of thoracolumbar kyphosis in achondroplasia in patients who had had no childhood brace treatment for their kYphosis or had persisted in having a significant kyPHosis despite bracing.
Abstract: This presentation reports my experience at the Johns Hopkins Hospital with the surgical management of thoracolumbar kyphosis in achondroplasia. These patients had had no childhood brace treatment for their kyphosis or had persisted in having a significant kyphosis despite bracing. Two major types of thoracolumbar kyphosis were seen: one group with severe wedging at the apical vertebrae and the other group with several adjacent vertebrae having mild to moderate wedging.
TL;DR: The largest fraction of dioxygen in mammalian systems is associated with hemoglobin, and it has been demonstrated that autoxidation coincides with the formation of superoxide.
Abstract: The largest fraction of dioxygen in mammalian systems is associated with hemoglobin. The primary function of hemoglobin is the transport of oxygen from the lungs to the tissues, which requires reversible oxygen binding. Nevertheless, a slow rate of autoxidation does take place. It has furthermore been demonstrated that autoxidation coincides with the formation of superoxide.1,2
TL;DR: There are several important questions to address on the subject of genetic versus environmental contributions to individual risk of cancer and toxicity, how large is the genetic contribution and howLarge is the environmental contribution.
Abstract: There are several important questions to address on the subject of genetic versus environmental contributions to individual risk of cancer and toxicity, (i) How large is the genetic contribution and how large is the environmental contribution? (ii) How great is the genetic variability between individuals? (iii) How can these differences be explained on a molecular basis? (iv) Is it possible to detect these differences in a routine assay? (v) Is it financially feasible to screen populations to determine risk? (vi) Who will want to know such information and why?
TL;DR: The group came into this area of free radical injury to heart muscle subsequent to the early studies of Drs.
Abstract: Recently, with the advent of thrombolytic therapy and emergency angioplasty for acute infarction interest in reperfusion injury has intensified. The question is whether all myocardial necrosis is reflective of the duration and severity of ischemia or whether there are cells which are alive at the end of the period of ischemia and undergo necrosis as a result of events that occur during or after reperfusion. These comments are entirely limited to three specific issues free-radical- induced reperfusion injury. Our group came into this area of free radical injury to heart muscle subsequent to the early studies of Drs. McCord1, Luchessi2 and Hearse3 and their colleagues. Therefore, we had the opportunity to focus our attention to three specific issues that we viewed as pivotal: (1) Are mechanisms that have been proposed to produce free radicals at the moment of reperfusion supported by direct measured oxygen based free radicals? (2) Does superoxide dismutase (SOD) administered as a therapeutic agent into the perfusate have any directly measurable effect on the presumed burst of oxygen free radicals on reperfusion. There has been considerable doubt as to whether SOD in the perfusate can reduce injurious, possibly intracellularly generated radicals?
TL;DR: The majority of achondroplastic children are fit and able throughout their early childhood, but a small minority are disabled by cervico-medullary compression at the foramen magnum or by chronic recurrent otitis media.
Abstract: The majority of achondroplastic children are fit and able throughout their early childhood. A small minority are disabled by cervico-medullary compression at the foramen magnum or by chronic recurrent otitis media. The first complaints in neurologically intact children are of leg pain due to progressive deformity at about 6 years of age.
TL;DR: Atheroma or atherosclerosis is a disease affecting major arteries, wherein the intimai layer of the artery is engorged with both intracellular and extracellular lipids, mostly cholesterol esters.
Abstract: Atheroma or atherosclerosis is a disease affecting major arteries, wherein the intimai layer of the artery is engorged with both intracellular and extracellular lipids, mostly cholesterol esters. Cholesterol, particularly that associated with low density lipoproteins (LDL), has been identified as a major risk factor. The precise mechanism(s) by which LDL cholesterol becomes atherogenic has not been well understood.
TL;DR: This work has used the transposable element Spm to tag and clone maize regulatory loci and shows that if a mutable allele can be shown to be under Spm control, one can be reasonably confident of successfully cloning that allele.
Abstract: Transposon tagging has become the method of choice for isolating genes whose products are in low abundance. We have recently used the transposable element Spm to tag and clone maize regulatory loci. Our choice of Spm was dictated by several factors: The frequency of transposition of Spm is high enough to obtain detectable transposition events, into loci affecting kernel traits, in populations of <106 seed. Although the copy number of Spm is high in the maize genome, insertions into the gene of interest can be distinguished from other Spm copies by digesting DNAs from segregating populations with methyl-sensitive restriction enzymes, and hybridizing with Spm-specific probes. Since all members of the Spm family thus far examined share DNA homology, hybridization with appropriate probes allows detection of insertions of both autonomous and defective elements. Thus, if a mutable allele can be shown to be under Spm control, one can be reasonably confident of successfully cloning that allele.
TL;DR: The mechanisms used by anaerobic bacterial communities to degrade organic molecules are of interest not only to increase the understanding of biogeochemical cycling, but also to explore the potential of microorganisms to degrade xenobiotic molecules in an aerobic environments.
Abstract: The mechanisms used by anaerobic bacterial communities to degrade organic molecules are of interest not only to increase our understanding of biogeochemical cycling, but also to explore the potential of microorganisms to degrade xenobiotic molecules in anaerobic environments (12). This has been of increasing concern in recent years, as many man-made chemicals are found to be toxic or mutagenic. New methods must be found to dispose of these compounds when they are no longer of use and to clean up contaminated areas. Digestion by anaerobic bacteria is an attractive possibility for disposal of synthetic chemicals, because it can require less energy than other methods of waste disposal; construction costs for anaerobic treatment facilities are lower; and anaerobic digestion offers the possibility of recovering useful products, such as intermediary metabolites or methane gas (30). Studying these processes also aids in predicting the fate of xenobiotics that have been introduced into natural anaerobic envi-ronments.