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101.
Summary Exudate can be obtained from incisions made in the bark of the stem of actively growing Ricinus plants. 14C-labelled assimilates from a fed leaf are rapidly detected in the exudate. This movement was both acropetal and basipetal from the fed leaf, at rates of over 100 cm h-1. Estimated rates within intact plants were 80–84 cm h-1.In contrast with xylem sap obtained from the same plant, the exudate obtained had an alkaline pH (8.2), a high dry matter content (10–12.5%), high sugar content (8–10%) which was predominantly sucrose; high potassium content (60–80 mM) and low calcium content (0.5–1.0 mM).It is concluded, on the basis of the present evidence, that the exudate is a true sample of the sieve tube sap undergoing translocation. 相似文献
102.
The rates of intracellular DNA synthesis at various temperatures between 39 ° and 31 °C were determined in hamster fibroblasts and HeLa cells by measuring average amounts of 3H-thymidine incorporated per cell in S phase per unit of time. The energy of activation and Q10 for intracellular DNA synthesis were calculated from the slopes of the relative rates of DNA synthesis in HeLa cells and hamster fibroblasts vs. time, plotted on Arrhenius coordinates. In both cell types the incorporation of thymidine into DNA is characterized by an energy of activation of 21 000 calories/mole and a Q10 of 2.94. The absolute rates of DNA synthesis were determined in hamster cells at various temperatures, with values ranging from 1.44 to 0.60 × 10?14 g DNA/ min/cell at 39 ° to 31 °C, respectively. The length of the S phase of the hamster cell was calculated over a 39 ° to 31 °C range, and found to be 5.0 to 11.9 h, respectively. It is concluded that the S phase length is partly determined by the rate of temperature-dependent DNA synthesis. 相似文献
103.
Grey seals on the West Hoyle Bank feed on a variety of fish and have a high incidence of dermal lesions, often associated with emaciation and nematode parasite infection. Corynebacterium phocae has been isolated from an active lesion. The significance of large numbers of seals in the Dee Estuary bearing lesions is discussed and the occurrence of seals with lesions elsewhere in British waters is reviewed. No evidence was found to associate the dermal lesions with any environmental factor and it is probable that lesions develop as a result of infection of minor wounds. 相似文献
104.
Isolation of ouabain-resistant human diploid fibroblasts 总被引:17,自引:0,他引:17
Seventeen clones resistant to the cytotoxic action of ouabain were isolated in culture by direct selection from 5 independent strains of diploid human fibroblasts. Resistant clones were recovered at frequencies on the order of 10?7 per wild type cell selected from populations treated with the mutagen EMS, but no resistant cells were detected among 108 unmutagenized cells. Most selected clones remained ouabain-resistant following further propagation in the absence of drug. The growth of wild type cells was inhibited by 50% at ouabain concentrations of 2–5 × 10?8 M, while resistant clones required 15–180 fold higher drug concentrations to cause equivalent inhibition. Ouabain-resistant clones showed increased resistance of K+ transport function to ouabain inhibition that paralleled their increased resistance to growth inhibition. Initial experiments suggest that under selective conditions the resistant diploid fibroblasts differ significantly from wild type in binding of 3H-ouabain per unit surface area. The ouabain-resistant cells were similar to wild type in transport properties unrelated to ouabain inhibition. Resistant cells had normal karyotypes and senesced with a lifespan similar to control clones. The ouabain-resistant phenotypes of these diploid human fibroblast isolates apparently reflect point mutations that specifically affect the Na+/K+ transport ATPase with respect to ouabain-binding and/or response to bound ouabain. 相似文献
105.
106.
On the number of sodium pumping sites in cell membranes 总被引:7,自引:0,他引:7
107.
The use of computers to study rates of lipid metabolism 总被引:6,自引:0,他引:6
N Baker 《Journal of lipid research》1969,10(1):1-24
Many complex problems of lipid metabolism are especially suited for multicompartmental analysis with computers. Examples are presented. The use of a model as a means of communicating one's working hypothesis and the model as it relates to experimental design are discussed. A number of principles relating to experimental design and to the interpretation and presentation of data are illustrated by 12 studies selected from the literature. These include evaluations of turnover and transport rates of liver and plasma triglycerides, triglyceride synthesis, phospholipid synthesis, and lipid oxidation to CO2. A discussion of computer-oriented vs. noncomputer-oriented techniques is included. Some of the practical problems involved in computer analysis are also considered. Among these are the choice of computer, computer applications, stepwise vs. multicompartmental analysis, validity of single-injection type experiments, avoidance of multicompartmental analysis, nonsteady state systems, and nomenclature. 相似文献
108.
109.
A man presented with the sudden onset of pernicious anaemia at the age of 21. He had been treated for hypothyroidism since the age of 6. His father and only paternal aunt were also found to have pernicious anaemia. Gastric and thyroid antibody studies showed one or more antibodies to be present in all three subjects, as well as in the patient''s mother. 相似文献
110.
Use of Erythrocytes Sensitized with Purified Pneumococcal Polysaccharides for the Assay of Antibody and Antibody-producing Cells 总被引:53,自引:2,他引:51 下载免费PDF全文
A method was described for the sensitization of erythrocytes with purified type-specific pneumococcal polysaccharide antigens using chromium chloride as a coupling agent. Erythrocytes so sensitized can be used in routine passive hemagglutination and hemolysis tests as well as in the technique of localized hemolysis-in-gel for the detection of specific antibody and specific antibody-producing cells, respectively. 相似文献