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191.
Summary Eight transfer RNA (tRNA) genes which were previously mapped to five regions of the Pisum sativum (pea) chloroplast DNA (ctDNA) have been sequenced. They have been identified as tRNAVal(GAC), tRNAAsn(GUU), tRNAArg(ACG), tRNALeu(CAA), tRNATyr(GUA), tRNAGlu(UUC), tRNAHis(GUG), and tRNAArg(UCU) by their anticodons and by their similarity to other previously identified tRNA genes from the chloroplast DNAs of higher plants or from E. gracilis. In addition,two other tRNA genes, tRNAGly (UCC) and tRNAIle(GAU), have been partially sequenced. The tRNA genes are compared to other known chloroplast tRNA genes from higher plants and are found to be 90–100% homologous. In addition there are similarities in the overall arrangement of the individual genes between different plants. The 5 flanking regions and the internal sequences of tRNA genes have been studied for conserved regions and consensus sequences. Two unusual features have been found: there is an apparent intron in the D-loop of the tRNAGly(UCC), and the tRNAGlu(UUC) contains GATTC in its T-loop. 相似文献
192.
Chromatophores isolated from the marine phototrophic bacterium Rhodobacter sulfidophilus were found to photoreduce NAD with sulfide as the electron donor. The apparent K
m for sulfide was 370 M and the optimal pH was 7.0. The rate of NAD photoreduction in chromatophore suspensions with sulfide as the electron donor (about 7–12 M/h·mol Bchl) was approximately onetenth the rate of sulfide oxidation in whole cell suspensions. NAD photoreduction was inhibited by rotenone, carbonyl cyanide-m-chlorophenylhydrazone, and antimycin A. Sulfide reduced ubiquinone in the dark when added to anaerobic chromatophore suspensions. These results suggest that electron transport from sulfide to NAD involves an initial dark reduction of ubiquinone followed by reverse electron transport from ubiquinol to NAD mediated by NADH dehydrogenase.Abbreviations Bchl
bacteriochlorophyll
- CCCP
carbonyl cyanide-m-chlorophenylhydrazone
- MOPS
3(N-morpholino)-propane sulfonate
- Uq
ubiquinone 相似文献
193.
Théophile Bernard Jean-Alain Pocard Bertrand Perround Daniel Le Rudulier 《Archives of microbiology》1986,143(4):359-364
A total of 15 rhizobial strains representing Rhizobium meliloti, Rhizobium japonicum, Rhizobium trifolii, Rhizobium leguminosarum, Rhizobium sp. (Sesbania rostrata) and Rhizobium sp. (Hedysarum coronarium), were studied with regard to growth rate under salt stress in defined liquid media. In the presence of inhibitory concentrations of NaCl, enhancement of growth resulting from added glycine betaine was observed for R. meliloti strains and Rhizobium sp. (Hedysarum coronarium) but not for other Rhizobium species. The concentration of glycine betaine required for maximal growth stimulation was very low (1 mM) in comparison with the osmolarity of the medium. The stimulation was shown to be independent of any specific solutes. Other related compounds like proline betaine, carnitine, choline, -butyrobetaine and pipecolate betaine were also effective compounds in restoring the growth rate of cells grown in medium of elevated osmolarity. High rate of glycine betaine uptake was demonstrated in R. meliloti cells grown in media of increased osmotic strength. The intracellular concentration of this solute was found to be 308 mM in 0.3 M NaCl-grown cells and 17 times lower in minimal medium-grown cells. Glycine betaine was used for growth under conditions of low osmolarity but could not serve as sole carbon or nitrogen source in medium of increased osmotic strength. Experiments with [14C]glycine betaine showed that this molecule was not metabolized by cells subjected to osmotic stress, whereas it was rapidly converted to dimethylglycine, sarcosine and glycine in minimal medium-grown cells.Abbreviations LAS
lactate-aspartate-salts
- LGS
lactate-glutamate-salts
- LS
lactate-succinate
- MSY
mannitol-salts-yeast
- YLS
yeast-lactate-succinate 相似文献
194.
Kinetic and Physical Studies of Cell Death Induced By Chemotherapeutic Agents Or Hyperthermia 总被引:3,自引:0,他引:3
J. E. D. Dyson† Deena M. Simmons Jill Daniel J. M. McLaughlin P. Quirke‡ C. C. Bird‡ 《Cell proliferation》1986,19(3):311-324
The kinetics of three physical parameters: cell density, relative cytoplasmic viscosity and DNA stability to denaturation have been measured during the period preceding cell death induced by hyperthermia, methylprednisolone and a series of cancer chemotherapeutic agents. This series of measurements employed cultured human lymphoblastoid cells as an experimental system to establish the changes that can be observed in the early stages of cell death, prior to applying such measurements to tissue biopsies from solid human tumours. Cell death, induced by hyperthermia up to 43°C, methylprednisolone, vincristine, 5-fluorouracil, BCNU and melphalan, showed essentially identical and reproducible changes corresponding to those which characterize programmed cell death (apoptosis). Such changes could also be observed following hyperthermia above 43°C, but reproducibility was poor and increasing damage to the cell membranes was evident. In cells treated with adriamycin or methotrexate, cell sub-populations showing an increase in cell density were not detected. Measurements of DNA stability were readily performed by flow cytofluorometry thus allowing rapid quantitation of the fraction of cells in the early stages of cell death. Modified flow cytometric instrumentation would further allow measurement of cytoplastic viscosity as an additional parameter to indicate entry into programmed cell death. This suggests that these measurements could readily be applied to cell suspensions derived from tumour tissue biopsies for a more accurate assessment of tumour growth rate, and to allow monitoring of response to therapy in sequential tumour biopsies. 相似文献
195.
Genetic Analysis of Murine Arylsulfatase C and Steroid Sulfatase 总被引:2,自引:1,他引:1
SWR/J mice possess two- to threefold higher 4-methylumbelliferyl sulfate (4MUS), dehydroepiandrosterone sulfate (DHEAS) and estrone sulfate (E1S) sulfatase activities in liver and kidney extracts than do A/J mice. These interstrain activity differences are maintained throughout the 6- to 45-day postnatal period. Characteristics of the hepatic activities of SWR/J mice suggest that all three activities reside in the same enzyme. Biochemical properties of the SWR/J and A/J enzyme were not significantly different. Expression of hepatic enzyme activity is subject to regulation by an autosomal locus possessing two alleles with additive effects. Postnuclear E1S- and DHEAS-sulfatase activities are primarily microsomal. Although postnuclear hepatic 4MUS-sulfatase activity is predominantly microsomal, renal activity is primarily nonmicrosomal. Only that portion of 4MUS-sulfatase occurring in cell membranes appears capable of hydrolyzing E1S and DHEAS. The hepatic- and renal-specific subcellular distributions of 4MUS-sulfatase activity may reflect tissue differences in enzyme processing. Renal 4MUS-sulfatase activity is also controlled by an autosomal gene with two alleles having additive effects. Positive correlation between hepatic and renal 4MUS-sulfatase activities indicates that both activities are most likely influenced by the same gene. 相似文献
196.
Susceptibilities of Algae and Legionella pneumophila to Cooling Tower Biocides 总被引:3,自引:2,他引:1 下载免费PDF全文
Reginald J. Soracco Helen K. Gill Carl B. Fliermans Daniel H. Pope 《Applied microbiology》1983,45(4):1254-1260
Nine algal strains and nine Legionella pneumophila strains were tested in laboratory culture for their susceptibility to inhibition by a variety of commercially available microbiocides. The responses ranged from ineffective to effective at 1/100 the manufacturers' recommended pulse doses. Tests were also performed to determine whether the action of the microbiocide was bacteriostatic or bacteriocidal. 相似文献
197.
Physiological changes in, and phosphate uptake by potato plants during development of, and recovery from phosphate deficiency 总被引:6,自引:0,他引:6
The development of phosphate deficiency (P-stress) was observed in rooted sprouts of Solanum tuberosum L. cv. Desiree growing in solutions without phosphate. Shoot growth was inhibited by P-stress within 3 to 5 days of terminating the phosphate supply, while significant effects on root growth were not recorded until 7 to 9 days. Thus, the shoot:root dry weight ratio decreased from 4.3 to 2.6 over a 10-day period. Growth in the absence of an exogenous phosphate supply progressively diluted the phosphorus in the plant. The proportional decrease in concentration was similar in roots and shoots over a 7-day period, even though the former were growing more quickly. The potential for phosphate uptake per unit weight of root increased rapidly during the first 3 days of P-stress. When the plants were provided subsequently with a labelled, 1 mol m?3 phosphate solution, the absorption rate was 3 to 4-fold greater than that of control plants which had received a continuous phosphate supply. The increased rate of uptake by P-stressed plants was accounted for by an increase (3-fold) in the Vmax of system 1 for phosphate transport and by a marked increase in the affinity of the system for phosphate (decrease in Km). In the early stages of P-stress, before marked changes in growth were measured, the proportion of labelled phosphate translocated to the shoots increased slightly relative to the controls when a phosphate supply was restored. In the later stages of stress a greater proportion was retained in the root system of P-stressed plants than in that of controls. In plants with roots divided between solutions containing or lacking a phosphate supply, the increased absorption rate was determined by the general demand for phosphate in the plant and not by the P-status of the particular root where uptake was measured. By contrast, the poportion translocated was strongly dependent on the P-status of the root. The restoration of a phosphate supply to P-stressed plants was marked by a rapid increase in the P concentration in snoots and roots which returned to levels similar to unstressed controls within 24 h. The enhanced uptake rate persisted for at least 5 days, resulting in supra-normal concentrations of P in both shoots and roots, and in the formation of extensive necrotic areas between the veins of mature leaves. Autoradiographs showed accumulations of 32P in these lesions and at the points where guttation droplets formed on leaves. 相似文献
198.
Daniel S. Levine 《Bulletin of mathematical biology》1983,45(6):901-915
A system of mixed integrodifferential and partial differential equations for an agestructured predator-prey system is studied here. The predator eats all ages of prey, but more of the very young and very old than of the intermediate ages. The existence of periodic solutions corresponding to stable coexistence is proved for a suitable range of parameters by bifurcation theory. 相似文献
199.
Recovery from a viral respiratory tract infection. IV. Specificity of protection by cytotoxic T lymphocytes 总被引:3,自引:0,他引:3
M A Wells S Daniel J Y Djeu S C Kiley F A Ennis 《Journal of immunology (Baltimore, Md. : 1950)》1983,130(6):2908-2914
Immune spleen cells enhanced for influenza-specific cytotoxic activity after exposure to virus-infected stimulator cells in vitro effect recovery when transferred to nude and immunocompetent mice with influenza pneumonia (5). This protective effect correlated with the virus-specific cytotoxic activity of the transferred lymphocytes and is removed by treatment with anti-0 serum and complement. The experiments presented here indicate that spleen cells taken directly from mice undergoing a primary or secondary infection are less protective than immune spleen cells that are restimulated in vitro before transfer. This decreased ability to clear pulmonary virus and effect survival correlated with their relatively lower levels of influenza-specific cytotoxicity. Protection did not correlate with the level of natural killer cell activity of transferred cells. The results also indicate the immune spleen cells that are protective are influenza A subtype cross-reactive and are H-2-restricted; H-2d immune spleen cells effected recovery of H-2d but not H-2k challenged mice. 相似文献
200.
Daniel G. Doughtie Philip J. Conklin K.Ranga Rao 《Journal of invertebrate pathology》1983,42(2):249-258
Adult grass shrimp were exposed to four concentrations (0.5, 1.0, 2.0 and 4.0 ppm) of hexavalent chromium for 28 days. At the end of the exposure period, over 50% of the surviving shrimp possessed cuticular lesions that had many of the gross characteristics of “shell disease.” These lesions were usually associated with articulations of the appendages and abdomen. Furthermore, it was found that at increasing levels of chromium exposure, there was a proportionate increase in the loss of limbs such that nearly 50% of the limbs were lost in grass shrimp exposed to the highest test concentration of chromium. Histological and ultrastructural examination of numerous lesions demonstrated a range of degenerative features within the subcuticular epithelium that included cytoplasmic vacuolization, mitochondrial swelling, chromatin emargination, and the presence of unusual nuclear inclusions that appear to indicate direct chromium toxicity. Additionally, a marked retardation in new epicuticle and exocuticle formation was observed in viable tissues associated with lesions in late premolt shrimp. It is proposed that chromium interferes with the normal functions of subcuticular epithelium, particularly cuticle formation, and subsequently causes structural weaknesses or perforations to develop in the cuticle of newly moted shrimp. Because of these chromium-induced exoskeletal deficiencies, a viaduct for pathogenic organisms (e.g., bacteria) and direct chromium influx is formed that perpetuates lesion development. 相似文献