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991.
Amino acids, salts, and vitamins were combined with dextrose to test their effect on growth and sporulation of Entomophthora virulenta in liquid shake culture. The addition of a vitamin solution to the tested media did not enhance growth or sporulation. MgSO4·7H2O was the only salt individually tested that allowed for good growth and sporulation. MgSO4·7H2O concentrations exceeding 250 mg/liter in media lacking other salts inhibited sporulation. A simple medium of l-arginine, l-leucine, glycine, and mineral salts allowed high growth and sporulation. 相似文献
992.
M Shoyab 《Chemico-biological interactions》1979,28(1):47-59
The binding of labeled carcinogen [3H]DMBA to murine epidermal cells (MEC) DNA in culture has been studied. The influence of unlabeled noncarcinogenic and carcinogenic polycyclic aromatic hydrocarbons (PAH), several PAH metablites, and various directly and indirectly acting non-PAH carcinogens on the binding of [3H]DMBA to MEC DNA has been examined. All the carcinogenic PAH and some of non-carcinogenic PAH effectively inhibit the binding of [3H]DMBA to MEC DNA. The non-PAH chemical carcinogens requiring metabolic activation also reduce the binding of labeled DMBA to MEC DNA; however, a higher concentration of these compounds is required for 50% inhibition of binding than the concentrations of PAH for the same degree of inhibition of binding of [3H]DMBA to MEC DNA. The directly acting carcinogens do not significantly inhibit the binding of [3H]DMBA to DNA. The relationship between structures of PAH and their ability to inhibit the binding of [3H]DMBA to MEC DNA is also discussed. Thus, it appears that the binding of DMBA to cellular DNA is primarily controlled at a level of metabolism and to some extent at the level of binding of reactive metabolites to DNA. 相似文献
993.
Demonstration of growth in porcine thyroid cell culture 总被引:2,自引:0,他引:2
Eagle's minimum essential medium supplemented with 20 per cent newborn calf serum (N.C.S.) allows porcine thyroid cell survival but not cell growth in vitro. In NCTC 109 medium supplemented with 20 per cent N.C.S. these cells actively grow and may be serially propagated. Cell population doubling time expressed as DNA doubling value is 3.5 days at 37 degrees C in 95 per cent air-5 per cent CO2. Thyrotropin does not affect porcine thyroid cell multiplication in vitro but stimulates the plating efficiency in primary cultures to about 130 per cent of controls. Cell selection was obtained by replacing media with Earle's balanced salt solution. This operation provoked death of nearly all cells by day 18 but subsequent addition of growth medium resulted in proliferation of epithelial cell clones. From generation 2 to generation 8, cells produce thyroglobulin but they do not actively trap iodide nor form follicles when thyrotropin is added to the media. Cell selection, demonstration of growth, as well as freeze-storage techniques described in this paper permit selection and storage of porcine thyroid cells and the potential constitution of cell collections. 相似文献
994.
A chemolithoautotrophic type of metabolism, which was hitherto unknown for purple nonsulfur bacteria, was demonstrated by growth experiments using Rhodopseudomonas capsulata Kb1 and Rhodopseudomonas acidophila 10050. These strains were able to grow in a mineral medium in the dark at the expense of H2, O2, and CO2. A minimum doubling time of 9 h was obtained for R. capsulata under an atmosphere containing less than 15% oxygen; higher oxygen concentrations suppressed autotrophic but not chemoorganotrophic growth. Oxygen sensitivity of chemoautotrophically growing cells of R. acidophila was even more pronounced, whereas cells growing chemotrophically on methanol almost tolerated the oxygen concentration of air. Highest oxygen sensitivity of growth of R. acidophila was observed with formate as substrate. The growth yield of cultures grown semiaerobically in the dark on methanol was 0.23 g dry cell material per g methanol consumed. 相似文献
995.
Repair of a vascular wound is mediated by migration and subsequent replication of the endothelial cells that form the inner lining of blood vessels. We have measured the growth response of human umbilical vein endothelial cells (HuE) to two polypeptides that are transiently produced in high concentrations at the site of a wound; the platelet-derived growth factor (PDGF) and the protease thrombin. When 104 HuE cells are seeded as a dense island (2-mm diameter) in the center of a 16-mm tissue culture well in medium containing 20% human serum derived from platelet-poor plasma (PDS), no increase in cell number or colony size is observed. With the addition of 0.5 ng/ml partially purified PDGF, colony size increases and the number of cells after 8 days is 4.8 × 104. When human thrombin (1 μg/ml) is added along with the PDGF, the cell number rises to 9.2 × 104. Thrombin alone stimulates no increase in cell number. Although partially purified PDGF stimulates endothelial cells maintained in PDS as well as those maintained in whole blood serum (WBS), pure PDGF is active only when assayed in medium that contains WBS and is supplemented with thrombin. These results suggest the existence of a second class of platelet-derived factors that enable HuE cells to respond to the mitogenic activity of the purified platelet mitogen and thrombin. 相似文献
996.
Kees Kersting 《Hydrobiologia》1978,59(2):113-120
Some results of studies with Daphnia magna are presented. These results can be used as background information for toxicologists, but the techniques referred to might well be used for toxicity tests. Daphnia magna is a filter-feeder. With the Coulter Counter it was shown that the feeding mechanism is aselective for size of the food particles. It was also shown that algal cells can pass the gut of Daphnia magna several times before being completely digested. The uptake of food is proportional to the food concentration up to a critical concentration. Above this concentration the food uptake is constant. Respiration is also dependent on the food concentration, and has a maximum value at food concentrations near the critical concentration of the feeding process. Growth efficiency is independent of the food concentration. The effect of temperature on the feeding process is different for low and high food concentrations. Growth efficiency is maximal at 10°C and above 22°C growth efficiency was negative, which means that the population cannot survive under the experimental conditions used, at temperatures above 22°C. 相似文献
997.
Analysis of Dioscorea deltoidea tissue cultures grown in the presence of 2,4-D, indole-3-butyric acid, isopentenyladenine, benzyladenine and GA singly and in combination showed that the medium with 2,4-D most consistently favored diosgenin production. GA and high benzyladenine concentrations were toxic. 相似文献
998.
Effect of sodium butyrate on mammalian cells in culture: A review 总被引:10,自引:0,他引:10
Kedar N. Prasad Pramod K. Sinha 《In vitro cellular & developmental biology. Plant》1976,12(2):125-132
Summary Sodium butyrate produces reversible changes in morphology, growth rate, and enzyme activities of several mammalian cell types
in culture. Some of these changes are similar to those produced by agents which increase the intracellular level of adenosine
3′,5′-cyclic monophosphate (cAMP) or by analogs of cAMP. Sodium butyrate increases the intracellular level of cAMP by about
two fold in neuroblastoma cells; therefore, some of the effects of sodium butyrate on these cells may in part be mediated
by cAMP. Sodium butyrate appears to have properties of a good chemotherapeutic agent for neuroblastoma tumors because the
treatment of neuroblastoma cells in culture causes cell death and “differentiation”; however, it is either innocuous or produces
reversible morphological and biochemical alterations in other cell types. 相似文献
999.
Some methods for measuring the uptake of sugars by yeasts were investigated critically. A study was made of the effects of starvation of Pichia pinus, Candida utilis, Saccharomyces cerevisiae and Rhodosporidium toruloides on their uptake of d-glucose and 2-deoxy-d-glucose. Marked changes in the rates of uptake of these sugars occurred during 10 h of starvation, including (a) an immediate increase of up to 75% above that for growing cells and (b) a continuous decline to as little as 4%. Each yeast behaved differently. The rates did not remain constant during the periods of starvation often used for studies on the transport of sugars into yeasts. For Pichia pinus, there were striking differences, associated with starvation, between the transport of 2-deoxy-d-glucose and d-glucose, despite evidence that the two sugars enter this yeast by means of the same carrier. Some physiological explanations for these findings are discussed. 相似文献
1000.
The uptake of various amino acids into Streptomyces hydrogenans grown in chemostatically and turbidostatically controlled steady state cultures has been investigated. A close correlation between transport capacity and the growth rates of the cells was found. As shown by kinetic analysis, the increased transport is due to elevated maximum uptake rates, the apparent Michaelis constants remaining unchanged. Analysis of the unidirectional fluxes of cycloleucine revealed that not only the influx is raised as the growth rate is increased but also the efflux. Hence, the conclusion is drawn that the growth-rate dependent modulation of transport capacity is, at least, partially due to the variation of the concentration of active transport components. Since the cells were grown in the absence of external amino acids the results suggest that amino acid transport into S. hydrogenans is under the control of endogenous effectors.List of Abbreviations AIB
2-aminoisobutyric acid
- Cycloleucine
1-aminocyclopentane-1-carboxylic acid 相似文献