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101.
RNA polymerase II polypeptides present in [35S]methionine-labeled Chinese hamster ovary (CHO) cell extracts have been quantitatively immunoprecipitated with an anti-calf thymus RNA polymerase II serum. Analyses of the immunoprecipitates on sodium dodecyl sulfate polyacrylamide gels indicated that the immunoprecipitated polymerase II of both wild type CHO cells and the alpha-amanitin-resistant mutant Ama1 had polypeptides of molecular weight 214,000, 140,000, 34,000, 25,000, 23,000, 20,500, and 16,500. In heterozygous alpha-amanitin-resistant/alpha-amanitin-sensitive hybrid CHO cells, growth in the presence of alpha-amanitin results in the inactivation of the alpha-amanitin-sensitive RNA polymerase II activity and a compensating increase in the activity of the alpha-amanitin-resistant enzyme. Determination of the rates of synthesis and degradation of RNA polymerase II polypeptides using [35S]methionine labeling and polymerase II immunoprecipitation demonstrated that this increase in activity of alpha-amanitin-resistant polymerase II resulted from a co-ordinate increase in the rate of synthesis of at least three polypeptides of RNA polymerase II. At the same time, there was an enhanced rate of degradation of the alpha-amanitin-inactivated RNA polymerase II polypeptides.  相似文献   
102.
Administration of the immunostimulants Corynebacterium parvum, Bacillus Calmette-Guérin (BCG) or Bordetella pertussis prior to, or at the same time as, challenge with Trypanosoma congolense significantly increased survival times in mice, both of trypano-susceptible (A/J) and trypano-resistant (C57Bl) strains. The increased survival time was associated with significant alterations in parasitaemia, which included lengthening of the pre-patent period, a delay in the time taken to reach the first peak of parasitaemia and a reduction in the level of parasitaemia. Similar results were obtained when these strains of mice were challenged with Trypanosoma brucei following pre-treatment with C. parvum. Thus, by the use of immunostimulants it was possible to reduce the susceptibility of mice to trypanosomiasis and the hope is that this can also be achieved with domestic livestock.  相似文献   
103.
The display of the two distinct intermediate filament proteins, desmin and vimentin, in rat vascular smooth muscle tissue was studied by immunofluorescence microscopy on frozen sections of aorta and other blood vessels. Vascular smooth muscle cells present in these vessels always appeared rich in vimentin. However, staining of sections covering six distinct but contiguous parts of the aorta showed that the number of desmin containing cells was low distal to the truncus brachiocephalicus, but increases until in distal parts of the aorta and in the arteria iliaca communis almost all cells appear positive for desmin. Thus blood vessels show heterogeneity of intermediate filament expression not only in cross-section but can also display heterogeneity along their length. Muscular arteries such as the renal artery and the arteria femoralis, as well as arterioles and veins including the vena jugularis and the vena cava also contain desmin. Thus it may be that low numbers of desmin-positive cells are typical of elastic arteries, while muscular arteries and other blood vessels are characterized by large numbers of desmin-positive cells. We discuss whether desmin-positive and desmin-negative vascular smooth muscle cells may perform different functions and raise the possibility that desmin expression may coincide with the turn on of a specially regulated contractility program.  相似文献   
104.
Summary Isoacceptor species of certain amino acidspecific transfer ribonucleic acids (tRNAs) were fractionated by gel permeation chromatography using Sephadex G-100. The separation is attributed to the 20% ethanol-1% NaCl solvent and to the characteristics of Sephadex. Isoacceptor tRNAs specific for cysteine, arginine, phenylalanine, and histidine were recovered from commercial tRNA of yeast by this method. Highly purified cysteine-specific tRNA, obtained by a method which would not be expected to separate isoacceptor molecules when fractionated by this procedure, was shown to contain two cysteine isoacceptor tRNAs.This investigation was supported in part by Public Health Service Research Grant AM-09131 from the National Institute of Arthritis and Metabolic Diseases.  相似文献   
105.
Summary Hyperaccumulators (here defined as species containing at least 500 μg/g dryweight of either copper or cobalt in leaves), are of interest for the fields of mineral exploration and phytochemistry. Reported hyperaccumulation of copper inAeolanthus biformifolius and the presence of two other species on copper/cobalt mineralization in Shaba (Za?re) led to a survey of these elements in 49 species of the African genusAeolanthus Mart.A. biformifolius appears to be also a hyperaccumulator of Co (2520 μg/g in leaves, 4300 μg/g in corms). Cobalt levels for most species ofAeolanthus were considerably above typical values for phanerogams and indicate the favorable potential of the genus for further study.  相似文献   
106.
The metabolic fate of 9-fluoro-11β,16α,17,21-tetrahydroxy-l, 4-pregnadiene-3,20-dione cyclic 16,17-acetal with 2-14C-acetone, triaacinolone acetonide (TA) was studied in rabbits, dogs, monkeys and rats and found to be qualitatively similar in all species. In the dog, rat and monkey the major excretory route was the feces irrespective of the mode of administration. In the rabbit the excreted radioactivity was equally distributed between urine and feces. The metabolites were isolated by preparative thin layer chroma tography, located by autoradiography, eluted and analyzed by MS, IR, UV and NMR. The major metabolites of triamcinolone acetonide (TA) were identified as the C-21 carboxylic acids of TA and of the 6β hydroxy-TA,(6β-OH-TA) and the previously identified (1,2) 6β-OH-TA. In addition MS and UV data indicate the presence of 9-fluoro-11β,16α, 17-trihydroxy-3,20-dioxo-1,4,6-pregnatrien-21-oic acid cyclic 16,17 acetal with 2-14C-acetone.  相似文献   
107.
Between 1969 and 1975 in California, 1,953 cases of meningococcal disease were reported. For cases reported in 1973, 1974 and 1975, detailed information about chemoprophylaxis of cases and contacts was obtained in addition to demographic and laboratory data. A review of data for the seven years showed a reduction in the case rate from 2.6 to 0.6 per 100,000 population, but this drop was due primarily to a very substantial decline in the military rate from 35.7 to 1.8 per 100,000 population. No reduction was apparent in the case fatality rate. Five groups of associated meningococcal disease cases were identified for a total of nine secondary or coprimary cases among 862 household contacts. Associated cases occurred in 10.4 per 1,000 household contacts—a rate several hundred times greater than that for the general population.The study findings indicate that many physicians are unaware of the following: (1) nonhousehold contacts are at little or no risk of contracting meningococcal disease; (2) prophylaxis should be offered only to household or intimate contacts immediately upon identification of an index case without waiting for test results for meningococcal carriage; (3) valid medical and epidemiologic indications exist for administering prophylaxis to household contacts who are culture negative as well as those who are culture positive; (4) the current drug of choice for prophylaxis is rifampin, but since no drug is completely effective, close medical observation remains the most important factor in the management of household or intimate contacts to meningococcal disease.  相似文献   
108.
Multiple biochemical assays of microbial mass and activities were applied to the estuarine detrital microbiota colonizing morphologically similar polyvinyl chloride needles and needles from slash pine (Pinus elliottii). Biodegradable pine needles consistently showed 2- to 10-fold higher values of extractable adenosine 5'-triphosphate, rates of oxygen utilization, activities of alkaline phosphatase and phosphodiesterase, and the mucopeptide cell wall component muramic acid than did the polyvinyl chloride needles, during a 14-week incubation in a semitropical estuary. The higher activities by the microbiota of the biodegradable substrate correlated with estimates of the microbial density from scanning electron microscopy. The microbial community associated with the nondegradable substrate showed minimal activity of beta-d-galactosidase, beta-d-glucosidase, and alpha-d-mannosidase in contrast to the biota of the degradable substrate, which showed 10- to 100-fold higher activities of these glycoesterases. These enzymes logically could be involved in catabolism of the carbohydrate polymers of the detritus. Assuming equivalent rates of predation, a surface that is also a utilizable substrate supports a three- to fivefold more active microbial population.  相似文献   
109.
The behavior of a microdialysis probe in vivo is mathematically described. A diffusion-reaction model is developed that not only accounts for transport of substances through tissues and probe membranes but also accounts for transport across the microvasculature and metabolism. Time-dependent equations are presented both for the effluent microdialysate concentration and for concentration profiles about the probe. The analysis applies either to measuring the tissue pharmacokinetics of drugs administered systemically, or for sampling of endogenously produced substances from tissue. In addition, an expression is developed for the transient concentration about the probe when it is used as an infusion device. All mathematical expressions are found to be a sum of an algebraic and an integral term. Theoretical prediction of time-dependent probe behavior in brain has been compared with experimental data for acetaminophen administered at 15 mg/kg to rats by intravenous bolus. Plasma and whole striatal tissue samples were used to describe plasma kinetics and to estimate a capillary permeability-area product of 0.07 min-1. Theoretical prediction of transient effluent dialysate concentrations exhibited close agreement with experimental data over 60 min. Terminal decline of the dialysate effluent concentration was slightly overestimated but theoretical concentrations still lay within the 95% confidence interval of the experimental data at 112 min. Microvasculature transport and metabolism play major roles in determining microdialysate transient responses. Extraction fraction (recovery) has been shown to be a declining function in time for five probe operating conditions. High rates of metabolism and/or capillary transport affect the time required to approach steady-state extraction, shortening the time as the rates increase. Conversely, for substances characterized by low permeabilities and negligible metabolism, experimental situations exist that are predicted to have very slow approaches to microdialysis steady state.  相似文献   
110.
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