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91.
The presence of testosterone-estradiol binding globulin (TeBG) in a variety of higher vertebrate species has been investigated by an ammonium sulphate precipitation technique. TeBG has been demonstrated in significant amounts in primates, carnivora, marsupiala, and some artiodactyla, even in circumstances where previously electrophoretic studies failed to identify it. For the first time it has also been shown in trace amounts in certain rodents and birds. TeBG in the kangaroo substantiates the primitiveness of the protein in the mammal line and its absence in certain orders and species of eutherian mammals must represent a secondary loss.  相似文献   
92.
Direct microscopic measurements of biomass in soil require conversion factors for calculation of the mass of microorganisms from the measured volumes. These factors were determined for two bacteria, five fungi, and a yeast isolated from soil. Moisture stress conditions occurring in nature were simulated by growth in two media using shake cultures, on agar plates, and on membranes held at 34, 330, and 1,390 kPa of suction. The observed conversion factors, i.e., the ratio between dry weight and wet volume, generally increased with increasing moisture stress. The ratios for fungi ranged from 0.11 to 0.41 g/cm3 with an average of 0.33 g/cm3. Correction of earlier data assuming 80% water and a wet-weight specific gravity of 1.1 would require a conversion factor of 1.44. The dry-weight specific gravity of bacteria and yeasts ranged from 0.38 to 1.4 g/cm3 with an average of 0.8 g/cm3. These high values can only occur at 10% ash if no more than 50% of the cell is water, and a specific conversion factor to correct past data for bacterial biomass has not yet been suggested. The high conversion factors for bacteria and yeast could not be explained by shrinkage of cells due to heat fixing, but shrinkage during preparation could not be completely discounted. Moisture stress affected the C, N, and P content of the various organisms, with the ash contents increasing with increasing moisture stress. Although further work is necessary to obtain accurate conversion factors between biovolume and biomass, especially for bacteria, this study clearly indicates that existing data on the specific gravity and the water and nutrient content of microorganisms grown in shake cultures cannot be applied when quantifying the soil microbial biomass.  相似文献   
93.
Summary Under selective growth conditions a revertant of mouse cells, defective in hypoxanthine phosphoribosyltransferase activity (HPRT, EC-No. 2.4.2.8), was isolated, which contained an electrophoretically abnormal form of HPRT activity. The specific HPRT activity in crude extracts of the revertant cells is about 30% of the level determined in normal wild type cells. The variant HPRT reacts with antiserum against normal mouse HPRT but the rate of heat inactivation of the variant activity is different from the wild type form. By isozyme and karyotype analyses of somatic cell hybrids between the revertant mouse cells and Chinese hamster cells we found that the abnormal HPRT activity is coded for by the mouse X-chromosome as expected for a mutation in the structural HPRT gene.DNA has been purified from the abnormal HPRT revertant cells and incubated with mouse A9 cells (HPRT-). After growth in selective medium one clone was isolated which expressed the electrophoretically abnormal form of HPRT. Six clones showed the normal form of HPRT due to reversion of the defective HRRT locus in A9 cells. This result indicates DNA-mediated transfer of the mouse HPRT gene at a frequency of about 0.5×10-7. A similar frequency has been found for transfer of the variant HPRT locus via isolated metaphase chromosomes to A9 recipient cells. When placed in non-selective media the DNA-mediated transferent cells gradually lost their ability to express the HPRT transgenome at a rate of about 6% per average cell generation.  相似文献   
94.
A new phototrophic bacterium was isolated from Jordanian and Kenyan alkaline salt lakes. Cells are rod shaped, 1.5 m wide and 2–4 m long, and motile by polar flagella. They divide by binary fission, and possess photosynthetic membranes as lamellar stacks similar to those in the other species of the genus Ectothiorhodospira and the brown colored Rhodospirillum species. The presence of bacteriochlorophyll a and carotenoids of the normal spirilloxanthin series is indicated by the absorption spectra of living cells. Under certain growth conditions the cells form gas vacuoles, may become immotile and float to the top of the culture medium. Sulfide and thiosulfate are used as photosynthetic electron donors. During the oxidation of sulfide to sulfate, elemental sulfur is formed, which is accumulated outside the cells. The organisms are strictly anaerobic, do not require vitamins, are moderately halophilic and need alkaline pH-values for growth. The new species Ectothiorhodospira vacuolata is proposed.  相似文献   
95.
Rhodopseudomonas globiformis is able to grow on sulfate as sole source of sulfur, but only at concentrations below 1 mM. Good growth was observed with thiosulfate, cysteine or methionine as sulfur sources. Tetrathionate supported slow growth. Sulfide and sulfite were growth inhibitory. Growth inhibition by higher sulfate concentrations was overcome by the addition of O-acetylserine, which is known as derepressor of sulfate-assimilating enzymes, and by reduced glutathione. All enzymes of the sulfate assimilation pathway. ATP-sulfurylase, adenylylphosphate-sulfotransferase, thiosulfonate reductase and O-acetylserine sulfhydrylase are present in R. globiformis. Sulfate was taken up by the cells and the sulfur incorporated into the amino acids cysteine, methionine and homocysteine. It is concluded, that the failure of R. globiformis to grow on higher concentrations of sulfate is caused by disregulation of the sulfate assimilation pathway. Some preliminary evidence for this view is given in comparing the activities of some of the involved enzymes after growth on different sulfur sources and by examining the effect of O-acetylserine on these activities.Abbreviations DTE dl-dithioerythritol - APS adenosine 5-phosphosulfate, adenylyl sulfate - PAPS 3-phosphoadenosine 5-phosphosulfate, 3-phosphoadenylylsulfate  相似文献   
96.
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98.
Summary A case of Meckel or Gruber syndrome is reported, together with a survey of the relevant literature of recent years (1971–1977), in reference to a probably autosomal recessive inheritance of this malformation.  相似文献   
99.
The separation of the enantiomers of lactic and glyceric acids can be achieved by capillary gas chromatography on SP-1000 using the corresponding O-acetylated menthyl esters. The structures of the derivatives were proved by proton magnetic resonance spectroscopy and mass spectrometry. The method has been used for the determination of the absolute configurations of lactic and glyceric acids isolated from serum and urine from different patients.  相似文献   
100.
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