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951.
Ulf Ljungberg Christer Jansson Bertil Andersson Hans-Erik Åkerlund 《Biochemical and biophysical research communications》1983,113(3):738-744
Photosystem II thylakoid particles possessing high rates of oxygen evolution, were shown to have a very simple polypeptide composition. Upon washing of these particles with 250 mM NaCl the oxygen evolution was inhibited up to 80% concomitant with a release of two polypeptides of 23 and 16 kDa. Readdition of the pure 23 kDa protein to the depleted thylakoids under low ionic strength reconstituted more than half of the lost activity. No stimulation was obtained with the 16 kDa protein alone or in combination with glycerol. The results give further strong evidence that the 23 kDa protein is an essential component in the oxygen evolving complex. The possible involvement of other proteins in this complex is discussed in light of the demonstrated simple polypeptide pattern of the photosystem II particles. 相似文献
952.
Saccharomyces cerevisiae was transformed with the Escherichia coli ompA gene coding for an outer membrane protein. Yeast transformants containing the pYTLJ101 plasmid, consisting of the ompA gene cloned in pSC101 and the HindIII-3 fragment of 2-μm DNA, express the foreign membrane protein. The protein synthesized in yeast has an Mr value very similar if not identical to that of the mature E. coli protein. The expressed protein is present in yeast mitochondrial and plasma membrane fractions. The yeast cell can tolerate about 250 molecules of the foreign membrane protein per cell, although the transformants show altered growth kinetics. 相似文献
953.
Ammonium Production by Dissimilatory Nitrate Reducers Isolated from Baltic Sea Water, as Indicated by 15N Study
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Bacteria able to perform dissimilatory nitrate reduction to ammonium were isolated from low-oxygen masses in the Baltic Sea. In liquid media enriched with 15NO3− and incubated anaerobically, the NH4+-producing isolates transformed 25 to 72% of the 15NO3− to 15NH4+. 相似文献
954.
Richard H. Schmidt Martin Ingvar Olle Lindvall Ulf Stenevi ers Björklund 《Journal of neurochemistry》1982,38(3):737-748
Dopaminergic innervation of the caudate nucleus in adult rats can be partially restored by the grafting of embryonic substantia nigra into the overlying parietal cortex with concomitant compensation of certain behavioral abnormalities. In this study the function of such grafts was investigated neurochemically by quantification of transmitter metabolism and glucose utilization in the reinnervated target. Rats with unilateral 6-hydroxydopamine lesions of the nigrostriatal bundle received a single graft to the dorsal caudate-putamen and were screened for rotational behavior following 5 mg/kg methamphetamine. The grafts restored dopamine concentrations in the caudate-putamen from initially less than 0.5% to an average of 13.6% of normal in rats with behavioral compensation. The ratio of 3,4-dihydroxyphenylacetic acid to dopamine, which is a measure of the rate of transmitter turnover, were equivalent in transplanted and normal control rats. Moreover, measurements of DOPA accumulation for a 30-min period after DOPA decarboxylase inhibition indicated similar fractional dopamine turnover rates in normal and transplant-reinnervated tissues. Correlations between rotational behavior and dopamine concentrations showed that reinnervation to only 3% of normal was sufficient to counterbalance the motor asymmetry. Measurements of glucose utilization by [14C]deoxyglucose autoradiography indicated equivalent metabolic rates for the grafted tissue and the intact substantia nigra. 6-Hydroxydopamine denervation of the caudate-putamen had no significant effect on neuronal metabolism in that region, nor did subsequent reinnervation from a graft. Grafts, however, were associated with a 16% reduction of glucose uptake in the ipsilateral globus pallidus, indicating a significant transsynaptic influence of the nigral transplants on neuronal metabolism in the host brain. Overall the results indicate that behaviorally functional neuronal grafts spontaneously metabolize dopamine and utilize glucose at rates characteristic of the intact nigrostriatal system. This provides further evidence that ectopic intracortical nigral transplants can reinstate dopaminergic neurotransmission in regions of the host brain initially denervated by the 6-hydroxydopamine lesion. 相似文献
955.
Summary Three single cell clones of the obligate methylotrophic bacterium Methylomonas clara originating from one fermentor culture were assayed for their DNA content. Apart from chromosomal DNA which showed no difference in the three strains, only two strains were found to carry plasmids with identical buoyant density and GC content but differing in contour length (12.4 m and 4.9 m respectively). According to their restriction pattern they are derived from each other. Both plasmids are not involved in methanol metabolism, since the third strain was found to be devoid of plasmids. The possibility of using these plasmids to establish vectors for gene cloning is evident, since during prolonged vegetative growth the specific plasmid content remains constant. 相似文献
956.
Mouse macrophages in vitro secrete an esterase capable of hydrolysing the chromogenic peptide substrate S-2222. The enzyme activity is inhibited by antithrombin and heparin. Also, the cells produce other hydrolytic activity, mainly associated with the cells capable of decomposing S-2160 and resistant to antithrombin and heparin. 相似文献
957.
Ulf Molau 《Nordic Journal of Botany》1981,1(5):595-615
Sect. Calceolaria (= Aposecos) of Calceolaria (Scrophulariaceae) in NW South America is revised, and the other species of the section are briefly discussed. The section comprises annual herbs with somewhat succulent stems and leaf–blades that are usually pinnately dissected (pinnatifid). Four species are recognized in the investigated area, viz. C. mexicana, C. tenuis, C. tripartita , and C. chelidonioides , and their chromosome numbers are reported (2n = 32, 60, 64, and 60 respectively). The basic number in sect. Calceolaria is x = 8. Two new combinations are made, viz. C. mexicana ssp. prostrata (Kränzlin) Molau and C. mexicana ssp. perijensis (Pennell) Molau. The species of sect. Calceolaria are intersterile and facultatively autogamous, and each species comprises numerous pure lines, some of which may be morphologically discernible.
In the appendices, chromosome numbers are listed and the occurrence of elaiophores in all NW South American species of Calceolaria is indicated. The chromosome numbers of C. crenata ssp. australis, C. adenanthera, C. gossypina, C. semiconnata, C. stricta, C. sericea , and C. comosa (all 2n = 36) have not previously been reported. A revised key to the sections of Calceolaria in NW South America is also provided. 相似文献
In the appendices, chromosome numbers are listed and the occurrence of elaiophores in all NW South American species of Calceolaria is indicated. The chromosome numbers of C. crenata ssp. australis, C. adenanthera, C. gossypina, C. semiconnata, C. stricta, C. sericea , and C. comosa (all 2n = 36) have not previously been reported. A revised key to the sections of Calceolaria in NW South America is also provided. 相似文献
958.
959.
Summary The characteristic localization of the silver-negative A2 cells in the central part of the pancreatic islets in the horse offers a good opportunity to study the ultrastructure and histochemistry of this type of islet cell. Electron microscopical analyses revealed that the A2 cells contained dense spherical granules varying considerably in size. Light and dark A2 cells were identified. The presence of numerous secretory granules of very low density was the most conspicous feature of the B cells. These cells also showed considerable differences in density. A second type of peripheral islet cell was characterized by a very high content of mitochondria and ribosomes. These small islet cells contained tiny granules and are probably identical with the A1 cells.Negative reactions for alkaline and acid phosphatases were obtained throughout the islet tissue, while a strong glucose-6-phosphatase activity was displayed by the peripheral cells. The diphosphopyridine and triphosphopyridine nucleotide diaphorase activities were high in the peripheral cells, considerably weaker reactions being noted in the A2 cells. On the whole there was a low succinic dehydrogenase activity in the islet tissue with a somewhat weaker enzyme staining in the A2 than in the peripheral cells. The reactions for glucose-6-phosphate dehydrogenase and lactic dehydrogenase were also less pronounced in the A2 cells than in the intensely reacting peripheral cells.The following abbreviations are used DPN
Diphosphopyridine nucleotide
- DPND
Diphosphopyridine nucleotide diaphorase
- DPNH
Diphosphopyridine nucleotide, reduced form
- G-6-PD
Glucose-6-phosphate dehydrogenase
- LD
Lactic dehydrogenase
- MTT
3,5-diphenyl-2-(4,5-dimethylthiazol-2-yl)-tetrazolium bromide
- Nitro-BT
2,2-di-p-nitrophenyl-5,5-diphenyl-3,3-(3,3-dimethoxy-4,4-biphenylene)-ditetrazolium chloride
- SD
Succinic dehydrogenase
- TPN
Triphosphopyridine nucleotide
- TPND
Triphosphopyridine nucleotide diaphorase
- TPNH
Triphosphopyridine nucleotide, reduced form
Supported by the Swedish Medical Research Council and the research grant A-5759 from the National Institute of Arthritis and Metabolic Diseases, United States Public Health Service. 相似文献
960.
Östen Ljunggren Hans Johansson Ulf H. Lerner Erik Lindh Sverker Ljunghall 《Bioscience reports》1992,12(3):207-214
The effects of parathyroid hormone (PTH) on cytoplasmic free CA2+ (Ca
i
2+
) and cAMP-formation were investigated in the rat osteosarcoma cell line UMR 106-01.In fura-2 loaded adherent single cells bPTH 1-34 (10 nM–1M) induced a rapid transient increase in Ca
i
2+
in 11% of the studied cells. In fura-2 tracings from UMR 106-01 cells in suspension, bPTH 1-34 (0.1 M) induced a transient increase in Ca
i
2+
in 20% of the experiments. The transient increase in Ca
i
2+
seen in suspensions of cells was not abolished by addition of EGTA (2.5 mM) prior to challenge with PTH, suggesting that the increase in Ca
i
2+
was derived from intracellular stores.A marked rapid increase in cAMP-formation was observed in all experiments with cells in suspension, also in the experiments where PTH did not affect Ca
i
2+
.These data show that PTH causes a release of Ca2+ from intracellular stores in a small percentage of osteosarcoma UMR 106-01 cells, and that PTH is capable of inducing an increase in cAMP-formation without affecting Ca
i
2+
in osteoblasts. 相似文献