Biomedical subjects
D C Nelson
Publications and source records attributed to D C Nelson.
Use of reduced sulfur compounds by Beggiatoa sp.
A strain of Beggiatoa cf. leptomitiformis (OH-75-B, clone 2a) was isolated which is unique among reported strains in its ability to deposit internal sulfur granules from thiosulfate. It also deposited these characteristic granules (as all BEggiatoa species do) from sulfide. In cultures where growth was limited by exhaustion of organic substrates, these granules generally comprised about 20% of the total cell weight. With medium containing acetate and thiosulfate, no measurable utilization of thiosulfate or deposition of elemental sulfur (S0) took place until after the exponential growth phase. Neither sulfide nor thiosulfate added an increment to heterotrophic growth yield except for the weight of the deposited S0. The deposition of S0 from thiosulfate was probably a disproportionation in which S0 and sulfate were produced in a 1:1 ratio. Some of the S0 was further oxidized to sulfate. No autotrophic or mixotrophic growth was demonstrated for this strain. When inoculated in small, well-dispersed quantities into yeast extract medium, this strain grew only after long lags. Addition of the enzyme catalase eliminated initial lags and increased growth rates slightly. In contrast, catalase had no influence on growth rate when added to mineral medium containing acetate. In yeast extract medium, the inhibition of growth rate was presumably because of peroxides. Addition of thiosulfate was almost as effective as catalase in eliminating this inhibition. The S0 granules which, in this case, were deposited during the exponential growth phase, appeared to be partly responsible for this relief. This strain of Beggiatoa sp. remained active for at least 5 days under strictly anaerobic conditions, and under those conditions, it increased its dry weight by about 2.5-fold. Anaerobic "growth" and maintenance required the presence of an energy source, such as acetate. When cells containing much internal S0 were transferred to an organic anaerobic medium, a substantial portion of the internal S0 was eventually converted to sulfide.
Organic nutrition of Beggiatoa sp.
Culture OH-75-B of Beggiatoa sp. differed significantly from any described previously in its utilization of organic carbon and reduced sulfur compounds. It deposited internal sulfur granules characteristic of Beggiatoa sp. with either sulfide or thiosulfate in the medium. This strain (OH-75-B, clone 2a) could be grown in agitated liquid cultures on mineral medium with acetate as the only source of organic carbon. The resultant growth yields and rates were comparable to those for typical heterotrophs. Of the other simple organic compounds tested, only pyruvate, lactate, or ethanol could singly support the growth of this strain. Single sugars or amino acids neither supported growth nor enhanced it when added to acetate-containing medium. In contrast, compounds of the tricarboxylic acid cycle enhanced growth yields when tested in concert with acetate. These and fluoroacetate inhibition results indicate that Beggiatoa sp. possesses a functional tricarboxylic acid cycle. Poor yields characterized the growth of this strain on dilute yeast extract medium, and higher concentrations of yeast extract proved inhibitory. The enzyme catalase, contrary to the findings of others, had no synergistic influence on growth yields when added to medium containing yeast extract or acetate or both.
Renal vein thrombosis associated with nephrotic syndrome and gold therapy in rheumatoid arthritis.
In this case of renal vein thrombosis secondary to a nephrotic syndrome, we postulate renal disease resulted from gold therapy. We know of no previous report relating gold toxicity and renal vein thrombosis. It should be emphasized that with increasing use of gold, proteinuria and nephrotic syndrome may be more common than once suspected and, when present, predispose to the development of renal vein thrombosis.
A device for recording flow and volume data in population surveys.
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Apparent distinctiveness of the actions of gibberellic acid in aleurone layers.
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Cardiovascular effects of atropine and neostigmine in man.
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The effect of cimetidine on hepatic drug elimination in cirrhosis.
Both cimetidine therapy and cirrhosis individually interfere with normal elimination of various drugs. Cimetidine is often prescribed in patients with cirrhosis but there is incomplete data on its effect on drug elimination in cirrhotics. The purpose of this study was to address this issue. Eight stable cirrhotics were studied prior to and following 7 days of cimetidine administration, (300 mg orally q.i.d.). Chlordiazepoxide (Librium), which is eliminated by the liver after demethylation, and indocyanine green, which is removed by the liver without biotransformation, were used as probes. Consistent with the concept that cimetidine interferes with drug metabolism by inhibiting microsomal oxidation, chlordiazepoxide clearance in the cirrhotics was inhibited by cimetidine (p less than 0.05), but indocyanine green clearance was unaffected. As shown by us previously (Roberts, R. K. et al., Gastroenterology 1978; 75:479-485), untreated cirrhotics had substantially lower chlordiazepoxide clearance than did controls. The inhibitory effect of cimetidine on chlordiazepoxide clearance was less in cirrhotics than in controls (p less than 0.05). In all subjects, there was excellent correlation between initial clearance and magnitude of depression in clearance after cimetidine, i.e., the larger the initial clearance, the larger the change (r = 0.97, p less than 0.0001). Forty-eight hours after stopping cimetidine, chlordiazepoxide clearance returned to baseline in cirrhotics and controls. Our data demonstrate that cimetidine and cirrhosis may act additively to impair drug metabolism. This effect of cimetidine on chlordiazepoxide clearance is smaller in cirrhotics than in controls, but, because of impaired initial drug elimination in cirrhosis, it may result in adverse clinical effects.
The effect of open-back vehicles on casualty rates: the case of Papua New Guinea.
Vehicle characteristics and vehicle use are frequently cited in the literature as potentially important factors contributing to the high motor-vehicle-related fatality rates reported by developing countries. Vehicles in developing countries are frequently overloaded, and improper vehicles are used to transport passengers. This paper seeks to estimate the importance of occupancy and vehicle type on the high motor-vehicle-related fatality rates in developing nations, using data for Papua New Guinea, a small South Pacific developing nation. This is achieved by establishing patterns of crash involvement and morbidity rates for vehicle types and ownership. Relative risk of crash involvement and relative risk of casualty for drivers and passengers are examined for open and closed vehicles. Finally, an estimate of the importance of vehicle type on the fatality rate is developed. The results demonstrate the need to disaggregate factors contributing to severity and occurrence in the study of road safety in developing countries.
Outcomes measurement and management with a large Medicaid population: a public/private collaboration.
Recipients, consumer advocates and purchasers expect managed care companies, in partnership with their provider networks, to measure and to continuously improve quality of care. This task is especially challenging when the beneficiaries of that care are covered by a publicly funded program. Yet this will be an increasingly common occurrence as more states contract with managed care companies for the care management of their Medicaid populations. In this article, the authors describe the outcomes measurement and management program of the first statewide managed Medicaid behavioral health carve-out program. Much of the foundation of that program has been built through collaborative efforts between the Massachusetts Division of Medical Assistance as purchaser, MHMA as managed care vendor, recipients, providers and other stakeholders. The authors report on the FMH/MHMA experience and what they learned. The principles derived from this outcomes program may be helpful to other states and to managed care companies undertaking similar public/private partnerships.