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1.
Quinacrine: mechanisms of antimalarial action 总被引：1，自引：0，他引：1
Two new interesting modes of action of quinacrine have been discovered. The first concerns a dose-related inhibition of uptake of [8-(3)H] adenosine into host cells of parasitized blood. Second, the drug inhibits the incorporation of tritiated adenosine triphosphate primarily into RNA but also into DNA of the erythrocyte-free malarial parasite Plasmodium berghei. 相似文献
2.
[(3)H]RNA with a high specific activity was prepared from larvae of Drosophila melanogaster grown 4 days in contact with [(3)H]uridine. Purified tritiated 5S RNA was annealed to the DNA of polytene chromosomes, which had been denatured in formamide. The 5S RNA genes are placed within the region 56E-F of the right arm of chromosome 2. This localization was determined from autoradiographs, where the radioactivity from hybrids of [(3)H]RNA and DNA was confined to the 56E-F segment. 相似文献
3.
Azam F Beers JR Campbell L Carlucci AF Holm-Hansen O Reid FM Karl DM 《Science (New York, N.Y.)》1979,203(4379):451-453
Seawater samples below the Ross Ice Shelf were collected through an access hole at J9, approximately 400 kilometers from the Ross Sea, Antarctica. The 237-meter water column had sparse populations of bacteria (8.7 x 10(6) to 1.2 x 10(7) per liter), microplankters (10(2) to 10(3) per cubic meter), and zooplankters (10 to 20 per cubic meter) at the depths studied. Microbial biomass estimates from cellular adenosine 5'-triphosphate measurements were very low (10 to 150 nanograms of carbon per liter), comparable with values for the abyssal ocean. Microbial populations assimilated tritiated D-glucose, thymidine, uridine, and adenosine triphosphate at extremely low rates, comparable with deep-sea heterotrophic populations. Sediment samples had 10(7) to 10(8) bacteria per gram (dry weight), which were metabolically active as shown by respiration of uniformly labeled D-[(14)C]glucose. From this study it cannot be determined whether these organisms in the water column and sediments constitute a functioning food web. 相似文献
4.
Metabolic dependence of fast axoplasmic transport in nerve 总被引：4，自引：0，他引：4
Fast axoplasmic transport, shown in cat sciatic nerves by a crest of labeled activity after injection of the L7 ganglion with [(3)H]-leucine or [ (3)H]-lysine, was stopped within 15 minutes after death of the animals by bleeding. If the sciatic nerves were removed from the animals and placed in a chamber supplied with oxygen at 38 degrees centigrade, fast transport was sustained. Transport was rapidly blocked in similar in vitro preparations when the nerves were kept in a nitrogen environment. Fast axoplasmic transport is closely dependent upon oxibdative metabolism. 相似文献
5.
Tritiated digoxin binding to (Na+ + K+)-activated adenosine triphosphatase: possible allosteric site 总被引：9，自引：0，他引：9
Tritiated H(3)-digoxin specifically binds to a cardiac (Na(+) + K(+))-activated adenosine triphosphatase. In the presence of adenosine triphosphate and other nucleoside di- and triphosphates, binding is stimulated by sodium ion, the apparent rate constant being similar to that reported for phosphorus-32 incorporation from adenosine triphosphate and for the adenosine triphosphatase activity. In the presence of magnesium, manganese, inorganic phosphate, or other ions, sodium ion inhibits binding. The data support an allosteric type of sodium-potassium ion pump. 相似文献
6.
Alkaline hydrolyzates of RNA made in vivo by Escherichia coli contain ribonucleoside-3'-monophosphate-5'-triphosphates. These probably arise by hydrolysis of the initial nucleoside triphosphate from the 5' terminus of the nascent RNA chains. Logarithmically growing cultures, labeled for 45 seconds with (32)P-labeled phosphate, yield about 2000 molecules of labeled tetraphosphate per cell, this yield increasing only slightly with continued labeling. Only the tetraphosphates of adenosine and guanosine have been found in Escherichia coli, and these two are present in approximately equal amounts. 相似文献
7.
Estrogen formation by the isolated perfused rhesus monkey brain 总被引：3，自引：0，他引：3
Perfusion of two isolated brains from immature male rhesus monkeys with [(3)H]androstenedione resulted in the identification of free and conjugated [(3)H]estrone and free [(3)H]estradiol from the perfusates. In the dissected cerebral tissues, estrogens were recovered only from the hypothalamus and limbic system. The production of estrogens from androstenedione during the 40-minute perfusions in these two experiments totaled 1.58 and 2.83 nanograms. 相似文献
8.
Puffing and histone acetylation in polytene chromosomes 总被引：1，自引：0，他引：1
Fixation with picric acid or formaldehyde retains incorporated [(3)H]acetate which is lost after fixation with ethanol and acetic acid. Unlike [(3)H]uridine, [(3)H]acetate is diffusely incorporated into polytene chromosomes, and not preferentially into existing or newly induced puffs. It is suggested that puff formation does not include an acetylation of histones. 相似文献
9.
Vitamin D-deficient rats produce [(3)H]1,25-dihydroxyvitamin D(3) from [(3)H]25-hydroxyvitamin D(3) regardless of dietary content of calcium or phosphate. A daily dose of 130 picomoles of 1,25-dihydroxyvitamin D(3) for a period of 5 days reduces production of [(3)H]1,25-dihydroxyvitamin D(3) to essentially zero and stimulates production of [(3)H]24,25-dihydroxyvitamin D(3). A daily dose of 325 picomoles of 25-hydroxyvitamin D(3) has a similar but less dramatic effect. On the other hand, 650 picomoles daily of 24,25-dihydroxyvitamin D(3) given to vitamin D-deficient rats had no effect. Thus it appears that 1,25-dihydroxyvitamin D(3) is an important factor in the regulation of kidney metabolism of 25-hydroxyvitamin D(3). 相似文献
10.
Dopaminergic terminals in the rat cortex 总被引：15，自引：0，他引：15
The destruction of ascending noradreniergic pathways by bilateral microinjections of 6-hydroxydopamnine made laterally to the pedunculus cerebellaris superior completely abolished the in vitro synthesis of [(3)H]norepinephrine from L-[(3)H]tyrosine in slices and in synaptosomes of the rat cortex. However, normal [(3)H]dopamine synthesis could still be observed in both cortical preparations from animals with lesions. These results provide the first biochemical support for the existence of dopaminergic terminals independent of noradrenergic terminals in the rat cortex. 相似文献
11.
The influx of K+ into swollen mitochondria in the presence of valinomycin results in the synthesis of adenosine triphosphate in which approximately one H+ disappears per adenosine triphosphate synthesized. The synthesis is blocked by atractyloside but is insensitive to oligomycin and relatively insensitive to uncouplers. 相似文献
12.
13.
( 3 H)lysergic acid diethylamide: cellular autoradiographic localization in rat brain 总被引：2，自引：0，他引：2
Intravenous administration of [(3)H]lysergic acid diethylamide(LSD) to rats resulted in accumulation of the drug in the brain within 15 minutes. Autoradiographic methods were used to differentiate free and bound [(3)H]LSD in brain tissue.Free [(3)H]LSD was generally distributed in the pituitary and pineal glands, cerebellum, hippocampus,and choroid plexus.Bound [(3)H]LSD was localized in neurons of the cortex, caudate nucleus, midbrain, and medulla,as well as in choroid plexus epithelium. 相似文献
14.
The rate of disappearance of intracisternally administered [(3)H]norepinephrine from rat brain gradually declines as a multiphasic exponential function of time. Conversion to [(3)H]normetanephrine accounts for a larger fraction of the [(3)H]norepinephrine released in the brain shortly after its intracisternal injection than that released at later times. Pools of norepinephrine in the brain thus appear to differ in their turnover rates and pathways of metabolism. The pool of norepinephrine with a rapid rate of turnover and an appreciable conversion to normetanephrine, identified by the techniques reported here, may correspond to a pool of newly synthesized norepinephrine in the brain. 相似文献
15.
Dopamine: release from the brain in vivo by amantadine 总被引：4，自引：0，他引：4
After dopamine stores in the caudate nucleus of cats were labeled with [(3)H]dopamine, the ventricular system was perfused with artificial cerebrospinal fluid. The addition of amantadine to the perfusing fluid caused a doserelated increase in the concentrations of [(3)H]dopamine appearing in the perfusion effluent. Subthreshold concentrations of amantadine also enhanced the efflux of [(3)H]dopamine induced by electrical stimulation of the caudate nucleus. 相似文献
16.
不同磷源对海洋卡盾藻生长和碱性磷酸酶活性的影响 总被引：1，自引：1，他引：0
[目的]研究不同磷源对海洋卡盾藻（Chattonella marina）生长和藻细胞碱性磷酸酶活性（APA）的影响。[方法]磷源分别为无机磷（NaH2PO4.2H2O）及有机磷源葡萄糖-6-磷酸（G-6-P）、甘油磷酸钠（G-P）、三磷酸腺苷（ATP）和卵磷脂（LEC）。[结果]海洋卡盾藻可以有效利用NaH2PO4.2H2O,对G-6-P、G-P、ATP也有一定的利用能力,但不能有效利用LEC。以NaH2PO4.2H2O、G-6-P、G-P和ATP为磷源培养的海洋卡盾藻的APA分别从起始的5.86 pmol/（cell.h）下降至第6天的1.25、1.12、1.58和1.72 pmol/（cell.h）,而后分别迅速上升至7.35、4.14、3.55和6.25 pmol/（cell.h）。[结论]该研究可为深入研究海洋卡盾的藻营养生理提供指导。 相似文献
17.
Dinitrogen (N2) was reduced to ammonia at room temperature and 1 atmosphere with molybdenum catalysts that contain tetradentate [HIPTN3N]3- triamidoamine ligands (such as [HIPTN3N]Mo(N2), where [HIPTN3N]3- is [(3,5-(2,4,6-i-Pr3C6H2)2C6H3NCH2CH2)3N]3-) in heptane. Slow addition of the proton source [(2,6-lutidinium)(BAr'4), where Ar' is 3,5-(CF3)2C6H3]and reductant (decamethyl chromocene) was critical for achieving high efficiency ( approximately 66% in four turnovers). Numerous x-ray studies, along with isolation and characterization of six proposed intermediates in the catalytic reaction under noncatalytic conditions, suggest that N2 was reduced at a sterically protected, single molybdenum center that cycled from Mo(III) through Mo(VI) states. 相似文献
18.
Protein-tyrosine kinase activity in Saccharomyces cerevisiae 总被引：14，自引：0，他引：14
Saccharomyces cerevisiae was examined for tyrosine kinase activity in vitro because this organism offers molecular and genetic approaches for analyzing the role of tyrosine phosphorylation in cellular growth control that are unavailable in higher eukaryotes. Yeast extracts phosphorylated a random copolymer (glutamic acid:tyrosine, 80:20) at tyrosine in a reaction that was linear with respect to time and protein concentration. In the absence of added copolymer, phosphotyrosine was 0.1 percent of the total phosphoamino acids labeled with [gamma-32P]adenosine triphosphate in endogenous yeast proteins. However, specific activities of these reactions were low (approximately 1 percent of those in extracts of chick embryo fibroblasts). Lack of significant incorporation of label from [alpha-32P]adenosine triphosphate into the copolymer or endogenous yeast proteins demonstrated that nucleotide interconversion, adenylylation, and subsequent hydrolysis could not account for the generation of phosphotyrosine observed. 相似文献
19.
Adenosine 3',5'-monophosphate: regional differences in chick embryos at the head process stage 总被引：1，自引：0，他引：1
The concentrations of adenosine 3',5'-monophosphate and adenosine triphosphate and the activity of phosphodiesterase were determined in different regions of chick embryos at the head process stage. Adenosine 3',5'-monophosphate, adenosine triphosphate, and phosphodiesterase were estimated to be higher in the mesoderm-forming portions of the hypoblast than in portions that form neural structures from Hensen's node or the epiblast. 相似文献
20.
In organ cultures of intact rat pineal glands, N(6)O(2')-dibutyryl adenosine 3', 5'-monophosphate stimulates the conversion of tritiated trytophan to tritiated melatonin, as does L-norepinephrine. Potential sites of stimulation of melatonin production by dibutyryl cyclic adenosine monophosphate are discussed, based on observations that the dibutyryl analog also stimulates the conversion of serotonin labeled with carbon-14 to carbon-14-labeled melatonin without altering hydroxyin-dole-O-methyl transferase activity or intracellular accumulation of serotonin labeled with carbon-14. 相似文献