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81.
Prostatic steroid-binding protein, whose expression is stimulated by androgens, consists of two subunits, one containing the polypeptides C1 and C3 and the other containing the polypeptides C2 and C3. We have isolated and sequenced cDNA clones specific for C3 mRNA and used them to isolate and characterize genomic clones for two C3 genes. Both genes are 3.2 kilobases with identical exon/intron arrangements, which is similar to the organization of the C1 and C2 genes, suggesting that they may have arisen by duplications of an ancestral gene. Finally, homologous human genes have not been detected. 相似文献
82.
A recently introduced approach far estimating the photosynthetic quantum efficiency (φ) of a freshwater or marine phytoplankton community has been applied for the first time to high latitude polar ecosystems, namely four lakes of southern Victoria Land, Antarctica. Values for φ at various depths ranged from 0.0022–0.1560 when calculated using a recommended mean extinction coefficient for phytoplankton (i.e. k?c= 0.016). By contrast, φ ranged from 0.0037–0.0760 when calculated using an empirically estimated value for k?c of 0.0328. If the recommended k?c= 0.016 more closely approaches an accurate estimate, then the φ valves indicate that the phytoplankton convert light to organic carbon more efficiently than elsewhere. However, if the empirically derived k?c= 0.0328 more closely approaches an accurate estimate, then the φ values indicate the phytoplankton trap light more efficiently than elsewhere. Although we have not resolved whether light conversion (φ) or light trapping are more efficient, the results show that the phytoplankton of these Antarctic lakes are well adapted to performing photosynthesis under extremely low light conditions. 相似文献
83.
This study further defines the craniofacial malformations induced by triamcinolone acetonide in the rhesus monkey. Ten timed-mated pregnant rhesus monkeys (Macaca mulatta) received intramuscular injections of 10 mg/kg TAC on days 23, 25, 27, 29, and 31 of gestation. Results of previous experiments with rhesus and bonnet monkeys and baboons indicated that specific craniofacial and brain malformations could be induced with TAC during this period of pregnancy (Hendrickx et al., '80). Stage-matched TAC-treated and control embryos (stages 17-18 and 22) and age-matched TAC-treated and control fetuses (50, 60, and 70 days gestation) were removed by hysterotomy. Stage 17-18 TAC embryos appeared grossly normal but histologic evaluation revealed a shortened anlage of the posterior cranial base. Stage 22 TAC embryos and all TAC fetuses exhibited craniofacial dysmorphia and encephalocele. The developing sphenoid was the earliest affected and most severely malformed bone. Its defects included reduced anterioposterior and transverse dimensions, reduced orbitosphenoid and alisphenoid, abnormal pituitary fossa, and reduced dorsum and tuberculum sellae. In addition, shortening of the posterior cranial base and decreased cranial base angle was a consistent finding in the treated embryos and fetuses. Decreased ossification and remodeling in the facial bones and abnormal position due to the malformed sphenoid occurred. 相似文献
84.
85.
Jerry L. Phillips Stephanie Waddingham Deborah A. Spiva 《Biological trace element research》1983,5(1):47-53
Lymphocytes were obtained from two patients with paroxysmal nocturnal hemoglobinuria as well as from apparently healthy controls and from patients with acute lymphoblastic leukemia and chronic lymphocytic leukemia. Subsequently, several aspects of zinc metabolism were studied in vitro in short-term cultures of these lymphocytes in order to assess lymphocyte functional capacity. The results of mitogen stimulation and zinc uptake studies for lymphocytes from donors with paroxysmal nocturnal hemoglobinuria were similar to those obtained for leukemic lymphocytes. The results of studies to determine the inducibility of the low molecular weight zinc-binding protein, metallothionein, by zinc were complicated by the decrease in overall protein synthesis in lymphocytes from donors in the paroxysmal nocturnal hemoglobinuria. It is proposed that paroxysmal nocturnal hemoglobinuria is indeed a clonal disorder and the relationship between lymphocytes in this disorder and leukemic lymphocytes is discussed. 相似文献
86.
The optimum conditions for sodium periodate induced lymphocyte transformation occur at low concentrations of NaIO4, low temperature, pH between 6 and 7.5, and with short periods of exposure to the NaIO4. Exposures for prolonged times at elevated temperatures or to NaIO4 at pH above 7.5 result in diminished responses. The finding of maximum lymphocyte response under these conditions is compatible with the proposal that the triggering event in NaIO4 transformation of lymphocytes is the oxidation and cleavage of the two terminal carbon atoms of sialic acid. Exposure of lymphocytes to NaIO4 under conditions of higher temperature, higher pH or longer exposure times does not significantly reduce their ability to respond to phytohemagglutinin (PHA) or pokeweed mitogen (PWM). This finding suggests that these mitogens have different target sites from that of NaIO4 or that they are acting on different populations of lymphocytes. 相似文献
87.
A Structure determination of the naturally occuring marine algal polysaccharide poly-β-D -mannuronic acid is described. The structure consists of 1e → 4e linked D -mannuronic acid chains with the monosaccharide units in the C1 chair conformation. The X-ray fiber diffraction photograph obtained from bundles of fibers prepared from Fucus vesiculosus has been indexed to an orthorhombic unit cell in which a =7.6 Å, b (fiber axis) = 10.4 Å, c = 8.6 Å, the unit cell containing two disaccharide chain segments with space group P212121. A sheet-like structure involving one intra-chain, one intra-sheet, and one inter-sheet hydrogen bond per monosaccharide is proposed. Features of the chain-packing arrangement are compared with mannan. 相似文献
88.
89.
Summary Negative staining showed the presence of microcrystals in various polysaccharides. Cellulose microcrystals from Valoniopsis, Vaucheria, and an unidentified tunicate had widths of 20, 27, and 30 Å, respectively. Mannan microcrystals from Acetabularia were 10x25 Å and were oriented in linear arrays with their long axis perpendicular to the array axis. dichotomosiphon and Caulerpa xylans had respective microcrystal widths of 22 and 24 Å. All microcrystals appeared as component part of microfibrils. 相似文献
90.
Mutants of yeast with altered oxidative energy metabolism: selection and genetic characterization 总被引:2,自引:1,他引:1
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Isolation of a series of mutants, characterized by decreased ability to utilize nonfermentable carbon sources for growth and presence of all cytochromes, is reported. A total of 161 mutants, showing deficient growth on glycerol but able to reduce 2,3,5-triphenyltetrazolium chloride, were isolated, purified, and characterized by ability to grow on various carbon sources. Mutants showing decreased growth were examined by low-temperature spectroscopy, and the 35 strains shown to possess all cytochromes were retained for further studies. These strains were characterized by growth on various nonfermentable carbon sources, relative yield on glucose medium, and respiration (Q(O2)) of glucose and ethyl alcohol. Genetic studies revealed that at least 19 of the 35 mutants are the result of mutation in single nuclear genes. Furthermore, at least 11 complementation groups are represented among these 19 mutants. Mutants within two complementation groups were shown to be very similar in various properties. These studies demonstrate that a large number of nuclear genes control oxidative energy metabolism and that the characteristics of mutants of the general class are extremely diverse. 相似文献