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971.
P J Cook A Huggett R Graham-Pole I T Savage I M James 《BMJ (Clinical research ed.)》1983,286(6359):100-102
The hypnotic and residual sedative effects of the first and seventh of seven regular night-time doses of nitrazepam 5 mg, temazepam 20 mg, and placebo were studied in 58 elderly inpatients. Plasma temazepam and nitrazepam concentrations rose by about 50% and 113% respectively between the mornings of day 1 and day 7. Patients reported sleeping well more often after the first dose of either hypnotic (p less than 0.05), but there was no difference after the seventh dose. Reaction time was unchanged on the morning after the first dose but was significantly prolonged after the seventh dose of both hypnotics (p less than 0.01). The time taken to eliminate the letter E from a page of prose tended to be prolonged after the first dose of both drugs (temazepam v placebo, p less than 0.05; nitrazepam v placebo, not significant) and was further prolonged on the morning after the seventh dose of nitrazepam (nitrazepam v placebo, p less than 0.05). Thus plasma accumulation of the drug was associated with a deterioration in daytime performance. This change in performance did not correlate with age, cerebral blood flow, or plasma concentration, but patients of low intelligence tended to be more severely affected. 相似文献
972.
James W. Carpenter 《Zoo biology》1983,2(3):165-178
This keynote address was presented at the Conference on the Conservation of Endangered Species in Zoological Parks and Aquariums on April 18, 1982 at the National Aquarium in Baltimore. It outlines 1) future trends in the world's environment, resources, and population; 2) factors affecting species decline; 3) reasons for preserving life forms; and 4) techniques, with emphasis on captive propagation, used to assist in species recovery. 相似文献
973.
James W. Wallace Kenneth R. Markham David E. Giannasi John T. Mickel Don L. Yopp Luis D. Gomez J. Dan Pittillo Robert Soeder 《American journal of botany》1982,69(3):356-362
A survey for 1,3,6,7-tetrahydroxy-C-glycosylxanthones of representative species within the primitive vascular plants, emphasizing the leptosporangiate ferns, has indicated a limited distribution of these compounds within three leptosporangiate families: Hymenophyllaceae, Aspleniaceae and Marsileaceae. In the Hymenophyllaceae the distribution of these compounds appears to be a useful criterion for segregating species of Mecodium from other species of Hymenophyllum (sensu lato) and suggests that the tubulate vs. the valvate indusial condition may not be an ideal character for separating all species of Hymenophyllum (s.l.) from those of Trichomanes (s.l.). These compounds appear useful for delimiting several species of Elaphoglossum section Pachyglossa and support a relationship among the Aspleniaceae, Athyriaceae, and Elaphoglossaceae. Their presence in Marsilea also raises questions as to the origin of this group of plants. 相似文献
974.
Kinetics of Formate Metabolism in Methanobacterium formicicum and Methanospirillum hungatei 总被引:7,自引:6,他引:1 下载免费PDF全文
The kinetics of formate metabolism in Methanobacterium formicicum and Methanospirillum hungatei were studied with log-phase formate-grown cultures. The progress of formate degradation was followed by the formyltetrahydrofolate synthetase assay for formate and fitted to the integrated form of the Michaelis-Menten equation. The Km and Vmax values for Methanobacterium formicicum were 0.58 mM formate and 0.037 mol of formate h−1 g−1 (dry weight), respectively. The lowest concentration of formate metabolized by Methanobacterium formicicum was 26 μM. The Km and Vmax values for Methanospirillum hungatei were 0.22 mM and 0.044 mol of formate h−1 g−1 (dry weight), respectively. The lowest concentration of formate metabolized by Methanospirillum hungatei was 15 μM. The apparent Km for formate by formate dehydrogenase in cell-free extracts of Methanospirillum hungatei was 0.11 mM. The Km for H2 uptake by cultures of Methanobacterium formicicum was 6 μM dissolved H2. Formate and H2 were equivalent electron donors for methanogenesis when both substrates were above saturation; however, H2 uptake was severely depressed when formate was above saturation and the dissolved H2 was below 6 μM. Formate-grown cultures of Methanobacterium formicicum that were substrate limited for 57 h showed an immediate increase in growth and methanogenesis when formate was added to above saturation. 相似文献
975.
Nitrous Oxide Production by Organisms Other than Nitrifiers or Denitrifiers 总被引:17,自引:12,他引:5 下载免费PDF全文
Heterotrophic bacteria, yeasts, fungi, plants, and animal breath were investigated as possible sources of N2O. Microbes found to produce N2O from NO3− but not consume it were: (i) all of the nitrate-respiring bacteria examined, including strains of Escherichia, Serratia, Klebsiella, Enterobacter, Erwinia, and Bacillus; (ii) one of the assimilatory nitrate-reducing bacteria examined, Azotobacter vinelandii, but not Azotobacter macrocytogenes or Acinetobacter sp.; and (iii) some but not all of the assimilatory nitrate-reducing yeasts and fungi, including strains of Hansenula, Rhodotorula, Aspergillus, Alternaria, and Fusarium. The NO3−-reducing obligate anaerobe Clostridium KDHS2 did not produce N2O. Production of N2O occurred only in stationary phase. The nitrate-respiring bacteria produced much more N2O than the other organisms, with yields of N2O ranging from 3 to 36% of 3.5 mM NO3−. Production of N2O was apparently not regulated by ammonium and was not restricted to aerobic or anaerobic conditions. Plants do not appear to produce N2O, although N2O was found to arise from some damaged plant tops, probably due to microbial growth. Concentrations of N2O above the ambient level in the atmosphere were found in human breath and appeared to increase after a meal of high-nitrate food. 相似文献
976.
Kinetics of Hydrogen Consumption by Rumen Fluid, Anaerobic Digestor Sludge, and Sediment 总被引:16,自引:16,他引:0 下载免费PDF全文
Michaelis-Menten kinetic parameters for H2 consumption by three methanogenic habitats were determined from progress curve and initial velocity experiments. The influences of mass transfer resistance, endogenous H2 production, and growth on apparent parameter estimates were also investigated. Kinetic parameters could not be determined for undiluted rumen fluid and some digestor sludge from gas-phase measurements of H2, since mass transfer of H2 across the gas-liquid interface was rate limiting. However, accurate values were obtained once the samples were diluted. H2 consumption by digestor sludge with a long retention time and by hypereutrophic lake sediment was not phase transfer limited. The Km values for H2 uptake by these habitats were similar, with means of 5.8, 6.0, and 7.1 μM for rumen fluid, digestor sludge, and sediment, respectively. Vmax estimates suggested a ratio of activity of approximately 100 (rumen fluid):10 (sludge):1 (sediment); their ranges were as follows: rumen fluid, 14 to 28 mM h−1; Holt sludge, 0.7 to 4.3 mM h−1; and Wintergreen sediment, 0.13 to 0.49 mM h−1. The principles of phase transfer limitation, studied here for H2, are the same for all gaseous substrates and products. The limitations and errors associated with gas phase determination of kinetic parameters were evaluated with a mathematical model that combined mass transport and Michaelis-Menten kinetics. Three criteria are described which can be used to evaluate the possibility that a phase transfer limitation exists. If it does not exist, (i) substrate consumption curves are Michaelis-Menten and not first order, (ii) the Km is independent of initial substrate concentration, and (iii) the Km is independent of biomass (Vmax) and remains constant with dilution of sample. Errors in the Michaelis-Menten kinetic parameters are caused by endogenously produced H2, but they were <15% for rumen fluid and 10% for lake sediment and digestor sludge. Increases in Vmax during the course of progress curve experiments were not great enough to produce systematic deviations from Michaelis-Menten kinetics. 相似文献
977.
The hemoglobin binding sites on the inner surface of the erythrocyte membrane were identified by measuring the fraction of hemoglobin released following selective proteolytic or lipolytic enzyme digestion. In addition, binding stoichiometry to and fractional hemoglobin release from inside-out vesicle preparations of human and rabbit membranes were compared since rabbit membranes differ significantly from human membranes only in that they lack glycophorin. Our results show that rabbit inside-out vesicles bind about 65% less human or rabbit hemoglobin under conditions of optimal and stoichiometric binding, despite being otherwise similar in composition. We suggest that this difference is either directly or indirectly due to the absence of glycophorin in rabbit membranes. Further supportive evidence includes demonstrating (a) that neuraminidase treatment of human membranes did not affect hemoglobin binding and (b) that reconstitution of isolated glycophorin into phospholipid vesicles increased the hemoglobin binding capacity in a manner proportional to the fraction of glycophorin molecules oriented with their cytoplasmic sides exposed to the exterior of the vesicle. Proteolysis of human inside-out vesicles either before or after addition of hemoglobin reduced the binding capacity by about 25%. This is consistent with the known proportion of total hemoglobin binding sites involving band 3 protein and the selective lability of the cytoplasmic aspect of band 3 protein to proteolysis. Phospholipid involvement in hemoglobin binding was determined using various phospholipase C preparations which differ in their reactivity profiles. Approximately 38% of the bound hemoglobin was released upon cleavage of phospholipid headgroups. These results suggest that the predominant sites of binding for hemoglobin on the inner surface of the red cell membrane are the two major integral membrane glycoproteins. 相似文献
978.
Polygena T. Tuazon James T. Stull Jolinda A. Traugh 《Biochemical and biophysical research communications》1982,108(2):910-917
Protease activated kinase I from rabbit reticulocytes has been shown to phosphorylate the P-light chain of myosin light chains isolated from rabbit skeletal muscle. The enzyme is not activated by Ca2+ and calmodulin or phospholipids. Protease activated kinase I is not inhibited by trifluoperazine at concentrations up to 200 μM or by the antibody to the Ca2+, calmodulin-dependent myosin light chain kinase from rabbit skeletal muscle. Two-dimensional peptide mapping of chymotryptic digests of myosin P-light chain show the site phosphorylated by the protease activated kinase is different from that phosphorylated by the Ca2+, calmodulin-dependent myosin light chain kinase. 相似文献
979.
James R. Wilson Milton M. Weiser Boris Albini Jay R. Schenck Harry G. Rittenhouse A.A. Hirata Eric G. Berger 《Biochemical and biophysical research communications》1982,105(2):737-744
Preparations of human malignant effusion galactosyltransferase activity purified according to previously published techniques using enzyme-specific affinity chromatography consistently produced antibodies directed toward immunoglobulins with no detectable antigalactosyltransferase. Double immunodiffusion analysis of the antigen showed the presence of both IgG and IgA. Affinity chromatography with anti-human IgG-Sepharose and anti-human serum-Sepharose resulted in a 48,000-fold purification of galactosyltransferase activity with no detectable IgG by radioimmunoassay. Immunization of rabbits with this preparation produced antibodies directed against galactosyltransferase activity and minimal anti-Ig. The persistence of immunoglobulins during the purification of soluble galactosyltransferase activity through two enzyme-specific affinity chromatographic steps suggests an association of immunoglobulins with galactosyltransferase activity. 相似文献
980.
James R. White Heather N. Yeowell 《Biochemical and biophysical research communications》1982,106(2):407-411
The lethal action of streptonigrin on strains of is greatly enhanced by citrate (10?2 M). Desferrioxamine (2×10?4 M), when added with streptonigrin and citrate, eliminates the citrate enhancement. These observations point to a role for iron in the bactericidal mechanism of streptonigrin. Extracellular citrate is known to promote the acquisition of iron by by delivering it as a ferric citrate complex to a specific transport apparatus on the cell envelope. Therefore, it may promote action of streptonigrin by increasing the intracellular concentration of available iron. Desferrioxamine, which forms a much stronger complex with ferric ion than does citrate, would be expected to suppress the ferric citrate effect, and this was observed. 相似文献