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91.
Extracellular release of dissolved organic compounds by the bluegreen algal community of a brackish marsh was studied using 14C techniques. Mannitol and trehalose were identified as the most commonly released compounds. The proportions of these two extracellular compounds varied in response to light intensity and the water potential of the environment. The presence of mannitol, in particular, suggests that excretion of organic compounds in natural situations is a function of osmotic adjustment. 相似文献
92.
David T. Wong Robert C. Rathbun Frank P. Bymaster William B. Lacefield 《Life sciences》1983,33(10):917-923
A diaryltriazine, LY81067, effectively protects against pentylenetetrazole- and picrotoxin-induced convulsions in mice, with ED50 values of 5.7 and 5.8 mg/kg i.p., respectively. LY81067 enhances the binding of both 3H-GABA and 3H-flunitrazepam to specific sites in rat brain membranes. The degree of enhancement by LY81067 varies from one brain region to another and is different for the binding of 3H-GABA and 3H-flunitrazepam. In cortical membranes, LY81067 increases the affinity of 3H-GABA for both high and low affinity sites and increases the number of sites. LY81067 increases the affinity of 3H-flunitrazepam for its binding sites without greatly increasing the number of sites. Like the pyrazolopyridines, the enhancement of 3H-flunitrazepam binding by LY81067 is dependent on chloride or related anions and is reversed by picrotoxin, suggesting that LY81067 exerts its anticonvulsant effects by binding to or near picrotoxin binding sites. The differential effects of LY81067 on the enhancements of 3H-GABA and 3H-flunitrazepam binding in several brain regions suggest extensive multiplicity of GABA/benzodiazepine/picrotoxin/anioin receptor complexes. 相似文献
93.
Frank O. Brady 《Life sciences》1983,32(26):2981-2987
In a continuing study of the importance of metallothionein (MT) in the growth and development of neonates, zinc and copper metabolism in rat brain, heart, lung, spleen, and thymus has been analyzed in 5, 10, 15, 20 and 25 day old rats. Total, cytosol, and MT zinc and copper concentrations and organ contents were determined. Zinc, but very little, if any copper was associated with MT in these organs. Concentrations ranged from 0.03 to 3.3 μg Zn in MT/g; organ contents ranged from 0.003 to 2.2 μg Zn in MT/organ. Brain exhibited the highest concentrations and contents of zinc in MT, approaching the levels found in kidneys. Rank order of organ contents of zinc in MT was brain > lung > heart, spleen, thymus, during this neonatal growth period. When organ growth was rapid, a large percentage (20–95%) of the cytosolic zinc present in these organs was associated with MT, as has been previously observed with liver, kidneys, and testes. None of these organs undergoes the dramatic changes in zinc and copper metabolism previously observed in neonatal rat liver and gastrointestinal tract, and in maturing testes. They are more comparable to kidneys in their concentrations of zinc in MT. Like testes, little copper is found in these organs. 相似文献
94.
95.
Two nomograms are presented. The first enables the mean surface and body temperatures and the body heat content of a patient of given weight to be determined from measurements of skin temperature at three sites and of the core (rectal) temperature. The second enables the change in heat content of such a patient to be determined from the change in mean body temperature. 相似文献
96.
Frank B. Livingstone 《American journal of human genetics》1971,23(5):543-544
97.
98.
Glucosylation of Teichoic Acid: Solubilization and Partial Characterization of the Uridine Diphosphoglucose:Polyglycerolteichoic Acid Glucosyl Transferase from Membranes of Bacillus subtilis 总被引:4,自引:2,他引:2 下载免费PDF全文
Polyglycerolteichoic acid:glucosyl transferase (TAG transferase), one of the three enzymes involved in the pathway leading to the glucosylation of teichoic acid in Bacillus subtilis 168, was investigated. During the early stages of the growth of B. subtilis, TAG transferase is predominantly a soluble enzyme found in the cytoplasm. As growth proceeds, the amount of soluble enzyme decreases and the proportion of insoluble, membrane-bound TAG transferase increases, reaching a maximal value at the close of the logarithmic phase. Data are presented which suggest that these are two forms of the same enzyme, or have some common component. The effects of chaotropic agents, such as sodium trichloroacetate and sodium perchlorate, on the cytoplasmic membrane were also studied. These data show that such compounds can effectively remove the TAG transferase from the membrane in a water-soluble form. A study of some of the physical properties of this solubilized enzyme suggests that there is little difference between the two forms of the enzyme. Experiments are described which indicate that the glucosyl transfer by both the membrane-bound and soluble enzymes is not mediated by lipids. 相似文献
99.
Summary In contrast with the toxicities of sulfate and chloride salts added to substrates, the anions SO4 and C1 were not injurious when accumulated without leaf burning by cotton and tomato plants from atmospheres enriched with
SO2 or HC1 gases. The foregoing results are discussed in terms of cationenzyme interactions which appear to represent at least
a major cause of salt toxicity. Although anions are largely unreactive with enzymes it has long been observed that chloride
salts in soil solutions are far more toxic than sulfate salts. Five of seven species have shown nearly equal growth repressions
on substrates with 100 me/1 of C1 salts versus 200 me of SO4 salts, each added as 50 per cent Na. The ion activities of the two solutions were equal and the sum of cations in the plant
saps were similar. The osmotic differentials (average about 10 atm) between the expressed tissue fluids and these substrate
solutions were remarkably uniform within species. It is projected that the downward transport of salts via the phloem provides
for root concentrations which supply ions to the xylem and thereby control the uptake of substrate salts. 相似文献
100.
Mercuric ions, as well as organomercuric ions and cadmium ions, can inhibit deoxyribonucleic acid-mediated transformation in Bacillus subtilis 168 without decreasing the viability of the total population. Differences in the inhibition of transformation by mercuric ions are identifiable on a temporal and concentration dependence basis. Sensitivity to low concentrations (9.2 x 10(-8) M) appears early in the uptake of deoxyribonucleic acid before the transformed markers have become insensitive to deoxyribonuclease. Resistance to "low concentrations" of Hg(2+) is kinetically indistinguishable from the requirement for magnesium in the transformation process. This inactivation is not reversed by the mercury-binding compound glutathione. Sensitivity to mercuric ions at a higher concentration (5.52 x 10(-7) M) occurs after the donor deoxyribonucleic acid has become insensitive to deoxyribonuclease. These complex interactions between mercuric ions and the process of transformation are discussed. 相似文献