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Mitotically active, growth-arrested cells and proliferatively senescent cultures of human fetal lung fibroblasts (WI-38) were exposed to six different oxygen tensions for various lengths of time and then analyzed to determine the responses of their antioxidant defense system. Glutathione (GSH) concentration increased as a function of ambient oxygen tension in early passage cultures; the effect was larger in exponentially growing cultures than in those in a state of contact-inhibited growth arrest, but was absent in senescent cells. Conversely, the activity of glutathione disulfide reductase was greater in growth-arrested cultures than in mitotically active cells irrespective of oxygen tension. Glucose-6-phosphate dehydrogenase was lowest in log-phase cells exposed to different oxygen tensions for 24 h and in senescent cells. Both hypoxia and hyperoxia depressed selenium-dependent glutathione peroxidase activity in early passage cultures, while the activity of the enzyme progressively declined with increasing oxygen in senescent cells. The GSH S-transferase activity was unresponsive to changes in ambient oxygen tension in either young or senescent cultures. Manganese-containing superoxide dismutase (MnSOD) activity was unaffected by oxygen tension, but was elevated in young confluent cultures as compared with cultures in log-phase growth. MnSOD activity was significantly higher in senescent cultures than in early passage cultures and was also responsive to increased oxygen tension in senescent cultures. Copper–zinc-containing superoxide dismutases activity was not affected by oxygen tension or the passage of time, but it declined in senescent cultures.

Basal antioxidant defense levels are often aberrant in tumor cells; however, less attention has been given to differences in the way that normal and transformed cells respond to changes in oxidative stress. This study evaluated differences in the responses of various normal and transformed cell lines to different oxygen tensions. Exposure to hyperoxia generally failed to induce either the activity of GSH peroxidase (GPx) or the manganese-containing form of superoxide dismutase (MnSOD) after 48 h, although at 605 mm Hg oxygen, small inductions of MnSOD activity were observed in adult lung fibroblasts and amelanotic melanoma. Exposure to 605 mm Hg O2 for 48 h was inhibitory to GPx activity. MnSOD activity was strongly induced in virally transformed WI-38 cells by treatment with the herbicide paraquat or inhibition of GSH synthesis with BSO. In normal cells GSH concentration was proportional to ambient oxygen tension. Tumor cells exhibited greater GSH concentrations at low oxygen tensions than normal cells but were unable to increase GSH in response to elevation of oxygen tension. These results reveal differences in tumor and normal cell responses to changes in ambient oxygen tension and show that MnSOD activity is inducible when an appropriate stimulus is applied.

Neuropeptides are released into the extracellular space from large secretory granules. In order to reach their release sites, these granules are translocated on microtubules and thought to interact with filamentous actin as they approach the cell membrane. We have used a green fluorescent protein-tagged neuropeptide prohormone (prepro-orphanin FQ) to visualize vesicle trafficking dynamics in NS20Y cells and cultures of primary hippocampal neurons. We found that the majority of secretory granules were mobile and accumulated at both the tips of neurites as well as other apparently specialized cellular sites. We also used live-cell imaging to test the notion that peptidergic vesicle mobility was regulated by secretagogues. We show that treatment with forskolin appeared to increase vesicle rates of speed, while depolarization with high K+ had no effect, even though both treatments stimulated neuropeptide secretion. In cultured hippocampal neurons the green fluorescent protein-tagged secretory vesicles were routed to both dendrites and axons, indicating that peptidergic vesicle transport was not polarized. Basal peptidergic vesicle mobility rates in hippocampal neurons were the same as those in NS20Y cells. Taken together, these studies suggest that secretory vesicle mobility is regulated by specific classes of secretagogues and that neuropeptide containing secretory vesicles may be released from dendritic structures.

The hypothalamic-pituitary-adrenal (HPA) axis is regulated by stress-related excitatory inputs, and various inhibitory and negative-feedback controls by glucocorticoids and opioids, including pro-opiomelanocortin (POMC)-derived peptides. The role of POMC-derived peptides of pituitary origin in the modulation of brain POMC mRNA expression and opioid receptor binding was investigated using a line of transgenic mice that express a fusion gene composed of the pituitary expression-specific promoter region of the POMC gene driving the herpes simplex viral-1 thymidine kinase (TK). Male adult mice were treated with the antiherpes agent ganciclovir that selectively ablates cells expressing TK. Following treatment, POMC mRNA levels, measured by quantitative solution hybridization/RNase protection assays, were decreased by 48% in the pituitary of the TK+/+ mice, reflecting an expected loss of the pituitary corticotrope POMC cells. This treatment also significantly lowered pituitary beta-endorphin immunoreactivity content and plasma concentrations of corticosterone. In contrast, POMC mRNA levels were increased by 79% in the hypothalamus of the TK+/+ mice with pituitary POMC cell ablation. Binding of [(3)H]DAMGO to mu opioid receptors, as measured by quantitative autoradiography, was significantly reduced in several brain regions including the central grey, median raphe and superficial grey layer of the superior colliculus. These regions are innervated by hypothalamic POMC neurones. No significant differences in binding to either kappa or delta opioid receptors were found in the brain regions studied. These results suggest that POMC-derived peptides of pituitary origin may exert a tonic negative-feedback effect on hypothalamic POMC neurones. In turn, the downregulation of central mu opioid receptors in this model may be mediated through a mechanism related to hypothalamic POMC overexpression.

Mechanical overloading of cartilage has been implicated in the initiation and progression of osteoarthrosis. Our objectives were to identify threshold levels of strain rate and peak stress at which sub-impact loads could induce cartilage matrix damage and chondrocyte injury in bovine osteochondral explants and to explore relationships between matrix damage, spatial patterns of cell injury, and applied loads. Single sub-impact loads characterized by a constant strain rate between 3×10−5 and 0.7 s −1 to a peak stress between 3.5 and 14 MPa were applied, after which explants were maintained in culture for four days. At the higher strain rates, matrix mechanical failure (tissue cracks) and cell deactivation were most severe near the cartilage superficial zone and were associated with sustained increased release of proteoglycan from explants. In contrast, low strain rate loading was associated with cell deactivation in the absence of visible matrix damage. Furthermore, cell activity and proteoglycan synthesis were suppressed throughout the cartilage depth, but in a radially dependent manner with the most severe effects at the center of cylindrical explants. Results highlight spatial patterns of matrix damage and cell injury which depend upon the nature of injurious loading applied. These patterns of injury may also differ in terms of their long-term implications for progression of degradative disease and possibilities for cartilage repair.

Evapotranspiration coefficients and aerodynamic roughness and bulk stomatal resistance parameters were developed for predicting evapotranspiration (Et) from narrow, isolated stands of cattail and bulrush (hydrophytes) using measurements from drainage lysimeters. Peak ratios of Et from vegetation in the center of 6 m wide stands of hydrophytes to Et from alfalfa averaged 1.6 for cattails and 1.8 for bulrushes. A ratio of momentum roughness height to vegetative height of 0.3 for use in the Penman-Monteith equation best fit experimental data. Errors between prediction equations and lysimeter measurements were minimized using linear, segmented evapotranspiration coefficient curves as compared to using a fitted Penman-Monteith approach.

Diethylstilbestrol induces proliferation of Syrian hamster renal proximal tubular cells. By counting the number of cells in culture, we showed that liposomes containing superoxide dismutase or catalase suppressed diethylstilbestrol-induced proliferation, whereas empty liposomes or liposomes containing inactivated superoxide dismutase did not. Liposomes containing antioxidant enzymes did not suppress proliferation of cells in control media or of cells treated with ethinyl estradiol. In the absence of liposomes, exogenous superoxide dismutase did not suppress diethylstilbestrol-induced proliferation. The decrease in cell number when diethylstilbestrol-treated cells were treated with antioxidant enzyme-containing liposomes was not due to decreased cell viability. Results were confirmed by measuring a correlate of cell proliferation immunohistochemically, using an antibody to proliferating cell nuclear antigen. A larger proportion of diethylstilbestrol-treated cells than of control cell showed nuclear immunostaining with this antibody. The number of cells immunostained in diethylstilbestrol-treated cultures was sharply decreased by the addition of superoxide dismutase- or catalase-containing liposomes. Our studies suggest a role for active oxygen species in diethylstilbestrol-induced proliferation of cultured proximal tubular cells.

Oxygen toxicity is believed to arise from changes in the rates at which cells generate reactive oxygen species (ROS). Sensitivity to hyperoxia has been postulated to depend on levels of antioxidant defense. Human cells obtained from fetal tissues have lower antioxidant defenses than those obtained from adult tissue. The present study was performed to determine whether the differences in fetal and adult antioxidant defense levels modulated their responses to changes in the ambient oxygen concentration. Our results demonstrate that oxygen modulates the proliferation of human fetal and adult skin fibroblasts in a similar fashion. In general, skin fibroblasts grew better at approximately 31 mm Hg, regardless of donor age. Manganese superoxide dismutase, catalase, and glutathione peroxidase activities were lower in fetal cells than in adult fibroblasts. Copper/zinc superoxide dismutase and glucose-6-phosphate dehydrogenase were similar in fetal and postnatal tissues and were unaltered appreciably by hyperoxic exposure. Glutathione concentration increased at higher oxygen tensions; however, the increase was much greater in fetal cells than in cultures derived from adult skin. These observations demonstrate that the capacity of fetal and adult cells to cope with oxidative stress, while similar, result from distinct mechanisms.

We have determined the activities, protein, and mRNA abundances as well as the level of transcriptional activation of two intracellular forms of the free radical metabolizing enzyme superoxide dismutase in 29 human skin fibroblast lines established from donors of different ages. SOD-1 (a copper and zinc containing form of SOD) and SOD-2 (a manganese containing form of the enzyme) activities were both observed to be significantly lower in cell lines derived from fetal skin than in lines established from postnatal skin (ages 17-94 years). The percent of total activity contributed by SOD-1 decreased in an age-associated manner from approximately 50% in the fetal lines to less than 20% in lines established from old tissue donors. All of the cell lines were screened to exclude the possibility that they contained a polymorphism known to influence SOD-2 activity. Northern blot analysis revealed three SOD-1 mRNA transcripts that were 0.5, 0.7, and 1.9 kb in length. Although SOD-1 protein abundance was lower in fetal lines than in lines derived from postnatal donors, SOD-1 mRNA abundance did not differ between fetal cells and cell lines derived from young donors. SOD-2 protein abundance and mRNA abundance were both significantly lower in fetal lines than in postnatal lines. No postnatal age-dependent differences were observed in any of the SOD-2 parameters examined. Nuclear run-on analysis revealed that fetal cell lines exhibited a lower level of transcriptional initiation for SOD-1 than postnatal lines. The transcription of SOD-2 was readily detected in postnatal lines, but undetectable in fetal lines. These results are consistent with multiple levels of control for SOD-1 expression and with a strong transcriptional influence on SOD-2 expression.

We have produced and characterized lines of transgenic mice expressing a fusion gene composed of the pituitary expression-specific promoter region of the POMC gene, driving the herpes simplex viral-1 thymidine kinase. Adult mice were treated with the antiherpes agent ganciclovir at 70 mg/kg body weight (ip, twice daily for 10-12 days). Approximately 98% of the pituitary intermediate lobe melanotropes and anterior lobe corticotropes were ablated as determined by immunocytochemistry and RIA specific for the POMC-derived peptides, ACTH, beta-endorphin, and alpha-MSH. The number of lactotropes, somatotropes, thyrotropes, and gonadotropes was not altered compared with controls, indicating that in the adult pituitary, POMC products are not required to maintain the distribution of cell types. As expected, plasma corticosterone levels were substantially decreased after POMC cell ablation. In situ hybridization studies showed that the mouse ACTH receptor was expressed uniformly throughout the adrenal cortex, and RNase protection assays revealed that the ACTH receptor mRNA decreased after pituitary POMC cell ablation. Additionally, RNase protection assays showed that pituitary POMC cell ablation resulted in the decrease of adrenal p450c11 beta transcripts while p450c11AS (aldosterone synthase) mRNA levels remained constant. These data demonstrate differential regulation of steroid pathway-specific enzymes by POMC products. Our results also suggest that the thymidine kinase cell obliteration technique may not be dependent on cell division as a prerequisite for cytotoxicity, thus supporting the idea that targeted molecular ablation using cell- and tissue-specific promoter sequences to drive viral thymidine kinase expression can be refined further to study other nonmitotic cells.

Targeted tumorigenesis, using the POMC gene promoter ligated to the simian virus 40 large T antigen, generated transgenic mice with massive tumors of the intermediate lobe (IL) of the pituitary. Inoculation of nude mice with the IL tumor cells resulted in very large secondary tumors. As the IL from several species produces a potent PRL-releasing factor (PRF), it was of interest to determine whether IL tumors from these mice also contain PRF. The objectives were to 1) measure serum PRL levels in mice with IL tumors, 2) determine whether these tumors contain PRF and examine its chromatographic properties, and 3) analyze whether this PRF is related to POMC, its derivatives, or other PRL secretagogues. Serum PRL levels were 5- to 6-fold higher in transgenic than in control mice. Primary and secondary IL tumors were acid extracted and successively fractionated using Sephadex G-100 gel filtration and reverse phase and gel permeation HPLC. PRF activity was determined using short term incubation of tissue extracts or column fractions with GH3 cells. Crude tumor extracts exhibited a strong and dose-dependent PRF activity. Upon chromatography, the PRF activity from either primary or secondary tumors resolved into two classes of compounds: a big PRF with an estimated mol wt of 70-80 kilodaltons and two small, very hydrophobic peptides. The elution profiles of the three PRFs differed from those of beta-endorphin, alpha MSH, beta MSH, ACTH, TRH, oxytocin, angiotensin II, vasoactive intestinal polypeptide, or corticotropin-like intermediate peptide. In summary, we have identified an animal model with IL tumors that has hyperprolactinemia and overproduces PRF. Two classes of PRFs, big and small, were resolved which differ from POMC derivatives and known regulators of PRL release. These data suggest that PRF is produced by melanotrophs, but is not a product of the POMC gene. The IL tumors should provide an excellent source for the purification and structural elucidation of PRFs.

Astrocytes have previously been shown to respond to cytokines such as interleukin-1 beta, tumor necrosis factor-alpha, and gamma-interferon from multiple sources including microglia and astrocytes. Recently, astrocytes have also been shown to express the opioid precursor gene proenkephalin and proenkephalin-derived peptides. The objectives of the current study were to determine if immune cytokines regulate proenkephalin gene expression in primary cultures of neonatal rat cerebral astrocytes. Northern analysis of RNA from primary cultures of neonatal rat cerebral astrocytes indicated that proenkephalin transcript levels were decreased by approximately 50% with gamma-interferon treatment and increased approximately 100% by treatment with both tumor necrosis factor-alpha and interleukin-1 beta relative to untreated controls. Tumor necrosis factor-alpha treatment was unable to reverse the inhibitory effect of gamma-interferon pretreatment on proenkephalin messenger RNA levels in the astrocytes. In contrast, expression of the constitutively expressed glutamine synthetase gene was not altered by either tumor necrosis factor-alpha or gamma-interferon treatment. These cytokines also regulate the secretion of proenkephalin-derived peptides from astrocytes. The levels of immunoreactive Met-enkephalin-Arg6-Phe7 were increased by approximately 50% with tumor necrosis factor-alpha and decreased by approximately 40% with gamma-interferon relative to untreated controls. Tumor necrosis factor-alpha was again unable to reverse the inhibitory effect of gamma-interferon pretreatment on the secretion of proenkephalin-derived peptides. These results provide additional support for the hypothesis that rapidly proliferating astrocytes may serve an important and pivotal role in mediating the bi-directional neuroimmune interactions during central nervous system disease, infection, or trauma.

Metabolic gradients are known to influence cellular differentiation at critical junctures of development. The existence of these gradients will stimulate variations in the rate of generation of active oxygen metabolites by metabolic pathways. Recent evidence suggests that cellular oxidation can induce changes in gene expression during normal development. Conversely, antioxidants such as ascorbate, alpha-tocopherol and beta-carotene are inhibitory to differentiation in many types of cells. One basis of oxidative influence on gene expression stems from changes in cellular calcium distribution.

The activities of superoxide dismutase (SOD), catalase, glutathione peroxidase, glutathione S-transferases, GSSG reductase, thiol transferases, gamma glutamyl-cysteine synthetase, and glucose-6-phosphate dehydrogenase, and the concentrations of H2O2 and reduced and oxidized glutathione were determined in the various developmental stages of houseflies. Housefly development was correlated with a progressive increase of cellular oxidizing equivalents and a loss of cellular reducing capacity. The loss of reducing equivalents appeared to result from a decrease in the activity of enzymes involved in glutathione and NADPH synthesis and a concomitant increase in glutathione-oxidizing enzymes. Relatively little change was observed in SOD activity during housefly development; however, the electrophoretic pattern of MnSOD varied in a manner specific to developmental stage. A striking increase in H2O2 concentration occurred prior to pupation possibly due to changes in substrate catabolism. These results support the hypothesis that the cellular environment becomes progressively more oxidizing during development.

Metabolic gradients are established during early phases of development and their existence influences subsequent developmental events. Variations in oxygen supply and oxygen metabolism associated with the gradation of metabolic rate in embryos appear to form one basis for the influence of metabolic gradients on development. The rate of oxygen metabolism affects the rate of oxidant generation by various cellular biochemical pathways. Cells contain antioxidant defenses that respond to variations in cellular oxidant production. Large changes in the activity of the antioxidant enzyme superoxide dismutase and changes in cellular redox state occur during the differentiation of many types of cells. These changes correspond to an increased rate of oxidant production; the cellular environment becomes more prooxidizing during differentiation. Evidence is presented that implicates oxidants as a factor that can stimulate alterations in gene expression. Possible mechanisms by which oxidants influence gene expression are also discussed.

We have previously reported that calcium is required for the starvation-induced differentiation of the slime mold, Physarum polycephalum. With the exception of calcium, each component of the complex starvation medium may be withheld and the organism will still differentiate into spherules. The results of the present study reveal that spherulation will proceed normally when the microplasmoidal cells are transferred from nutrient medium to a citrate buffer containing only 8 mM Ca CI2. Electron microscopy and X-ray microprobe analysis reveal that there is an initial increase in the population of calcium-containing mitochondrial granules when the microplasmodia are induced to differentiate. However, as differentiation proceeds, these granules decrease in number and are virtually absent from the mitochondria of mature spherules. The accumulation and depletion of calcium-containing granules is not observed in a nondifferentiating strain of Physarum cultured under standard conditions, but is observed when this strain is first treated with a calcium-enriched nutrient medium that conditions it for spherulation. Changes in the cellular concentrations of NADH and lipid peroxides, and in the activity of superoxide dismutase, correspond temporally to the pattern of increase and depletion of the calcium-containing inclusions. The oxidative stress associated with starvation-induced spherulation may be a consequence of the active accumulation of calcium; the mobilization of this calcium may then be the event that initiates differentiation.

The effects of total inhibition of catalase, induced by 3-amino-1,2,4-triazole, on the adult housefly (Musca domestica) were examined. The lack of catalase activity had no effect on the longevity of the houseflies. Inorganic-peroxide concentration was elevated at younger ages, but declined in older flies. The rate of oxygen consumption by the flies was greatly decreased and the levels of oxidized as well as reduced glutathione were augmented. Superoxide dismutase activity showed a slight increase. This study suggests that loss of catalase activity does not affect survival of houseflies due to adaptive responses.

Confluent cultures of human skin fibroblast lines established from fetal and postnatal donors were exposed to a broad range of oxygen tensions (10-600 mmHg) for 1 wk; superoxide dismutase (SOD) activity was subsequently determined. Hyperoxia increased SOD activity slightly in postnatal lines but not in fetal lines. The magnitude of the increase in postnatal lines was not significant. Fetal lines exhibit only about one-fifth the SOD activity observed in postnatal lines. The results indicate that, while development-associated changes in SOD do occur in human cells, these alterations do not result from variations in ambient oxygen tension.

Glycerol starvation of an Escherichia coli glycerol auxotroph results in a specific inhibition of membrane phospholipid synthesis. Mindich ((1972) J. Bacteriol. 110, 96-102) observed only a trace accumulation of free fatty acid following glycerol deprivation. We have repeated these experiments using glycerol auxotrophs which also possess a lesion in beta oxidation. This defect was introduced in order to control fatty acid degradation. In contrast to the previous results, we find free fatty acid does accumulate during glycerol starvation. Similar results were found using beta oxidation-defective (fadE-) derivatives of both gpsA and plsB glycerol auxotrophs. Upon glycerol starvation of a plsB- fadE- strain, phospholipid synthesis is 90 percent inhibited. Following a lag of 20 to 40 min, free fatty acid synthesis begins and proceeds at a rate that steadily increases until the rate of fatty acid synthesis is equal to that found in glycerol-supplemented cultures. The accumulation of free fatty acid is the result of de novo synthesis. The average chain length of the fatty acid in the unesterified fraction is abnormally long. Two 20-carbon fatty acids, cis-13-eicosenoic acid and arachidic acid, are found in this frction. Furthermore, a greatly increased level of stearic acid and a small amount of a C-22 (behenic) acid are found in the free fatty acid fraction. These data indicate that acyl transfer into phospholipid is a major determinant of phospholipid acyl moiety chain length. Other experiments have shown that the free fatty acid fraction in glycerol-starved cells is metabolically active. This fraction turns over despite the defective beta oxidation system. Restoration of glycerol to starved cells allows the incorporation of the unesterified fatty acids into phospholipid.

Microplasmodia of Physarum polycephalum differentiate into spherules when the CaCI2 concentration of their nutrient medium is increased to 54mM (high- calcium). The salts starvation medium routinely used to induce differentiation contains 8mM CaCI2. This medium will not induce spherulation in the ab- sence of a calcium salt; no other metal is essential. High-calcium also induces the spherulation of a strain of Physarum that had not been previously ob- served to spherulate. The striking increase in superoxide dismutase activity (SOD) and the decrease in glutathione concentration (GSH) that are charac- teristic of salts-induced spherulation do not occur in salts media containing high-calcium. In the absence of calcium, no significant change in SOD is observed and very little change in GSH occurs. The immediate effect of the oxidative stress associated with spherulation may be the release of calcium stores into the cytosol. The parameters modulating this stress are, in turn, sensitive to exogenous calcium concentrations. Cellular differentiation is ultimately due to qualita- tive and quantitative alterations in gene expression. At present the nature of the mechanisms governing devel- opmental changes in gene expression remains obscure. Cytoplasmic fields, gradients, and morphogenetic deter- minants are widely believed to modulate the transition of embryonic tissues into differentiated cell types (Na- menwirth, 1974; Summerbell, 1979; Summerbell et al., 1973; Wolpert, 1978). Among the factors which appear to play a role in development are the metabolic and chemical gradients observed in developing organisms; these arise from regional variations in surfaceholume ratio and from differential vascularization of the embry- onic tissues (Boveri, 1901; Browder, 1980; Caplan and Ordahl, 1978; Child, 1915). The effects of metabolic gra- dients on development may be partly due to differential nutrient supply; however, there is also evidence that variations in molecular oxygen concentration play a role in the regulation of developmental processes (Jargiello and Caplan, 1983; Caplan and Koutroupas, 1973). The mechanism by which oxygen and its metabolites affect gene expression is presently unknown.

The syncytial slime mold Physarum polycephalum has been widely employed as a model for the study of a variety of cellular events; however, the overwhelming emphasis in modern Physarum research has been on those areas directly related to growth and differentiation (22). Mitosis is synchronous following an interphase period of 8–10 h and mitotic synchrony implies metabolic synchrony (13). All events involved in the regulation of differentiation are therefore presumed to be amplified since they should occur simultaneously. This hypothesis has been the basis for intensive efforts to identify the role of specific enzymes (15), nucleic acids (2,8), and nuclear proteins (17) in the developmental processes of eucaryotes. A considerable volume of literature concerning developmental processes in Physarum has accumulated since Rusch (22) first introduced the organism as a model system for probing the events that govern the life cycle of cells. At this time little conclusive information has resulted; endogenous events and factors which induce specific cell state transitions have not been identified. A perennial problem has been to distinguish between the events that are causative and the events which are the consequence of differentiation. For example, when Physarum differentiates into groups of dormant spherules (sclerotia) dramatic changes occur in the electrophoretic profile of the nonhistone chromosomal proteins; however, it has not been possible to determine whether these changes induce differentiation or are a parallel response to the inductive treatment (17).

Metabolic gradients exist in developing organisms and are believed to influence development. It has been postulated that the effects of these gradients on development result from differential oxygen supplies to tissues. Oxygen has been found to influence the course of development. Cells and tissues in various stages of differentiation exhibit discrete changes in their antioxidant defenses and in parameters of oxidation. Metabolically generated oxidants have been implicated as one factor that directs the initiation of certain developmental events. Also implicated as factors that modulate developmental processes are the cellular distribution of ions and the cytoskeleton both of which can be influenced by oxidants. The interaction of oxidants with ion balance and cytoskeleton is discussed.

This study from Frankfurt, although similar to other reports with respect to clinical findings, presents further evidence of a varied etiology for hand, foot and mouth disease (HFMD). Of the 6 patients with HFMD, 5 had virologic evidence of coxsackievirus B5 infection, and 1 had definite evidence of coxsackievirus B2 infection. Our data suggest an etiologic association of coxsackievirus group B with HFMD.

Evidence is presented that supports a role for the enzyme superoxide dismutase (SOD) in the differentiation of the slime mold, Physarum polycephalum. SOD activity increases 46-fold during differentiation. A strain of Physarum that does not differentiate exhibits no change in SOD activity. Addition of SOD, via liposomes, to the nondifferentiating strain induces differentiation; this effect is enhanced by an inhibitor of glutathione synthesis. Other antioxidants selected for study failed to induce differentiation. Conversely, oxidative treatments including introduction of d -amino acid oxidase, via liposomes, induced differentiation. Cellular oxidation is the probable cause of the SOD effect.

There is presently no single, widely accepted, unifying theory of aging that is applicable to a wide spectrum of organisms. This fact has led many gerontologists to believe that mechanisms of aging may differ in various phylogenetic groups, albeit no compelling evidence or a priori reason has been forwarded to support this view. Given the basic similarity of molecular and cellular processes in living systems, it is indeed more probable that the contrary may be true, and that the underlying causal mechanisms of aging are essentially similar in all organisms. Conceptually, theories of aging can be assigned to two fundamentally different schools. One view regards aging as a continuation of the process of differentiation involving a programmed “shutdown” of genomic activity or a sequential activation of specific genes whose products have deleterious effects on cellular functions. Alternatively, aging is postulated to be a direct or indirect product of metabolic damage arising from the inadequacy of protective and reparative mechanisms.