共查询到20条相似文献，搜索用时 31 毫秒
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One hour after administration of L-dopa (50 to 300 milligrams per kilogram), there is a marked disaggregation of brain polysomes in immature rats. Adult animals show a similar response, but require larger doses of the amino acid (500 milligrams per kilogram). Single doses of L-dopa significantly elevate amounts of tryptophan in the brain; hence their effect on polysomes does not result from the unavailability of this amino acid. 相似文献
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Radiation doses from airborne effluents of model coal-fired and nuclear power plants (1000 megawatts electric) are compared. Assuming a 1 percent ash release to the atmosphere (Environmental Protection Agency regulation) and 1 part per million of uranium and 2 parts per million of thorium in the coal (approximately the U.S. average), population doses from the coal plant are typically higher than those from pressurized-water or boiling-water reactors that meet government regulations. Higher radionuclide contents and ash releases are common and would result in increased doses from the coal plant. The study does not assess the impact of non-radiological pollutants or the total radiological impacts of a coal versus a nuclear economy. 相似文献
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A representative psychotogen, lysergic acid diethylamide (LSD-25), in doses small enough to be devoid of gross effects, increases response latency in rats to a tone indicating the availability of water reward; this effect is greatly reduced by prophylactic administration of a representative phenothiazine tranquilizer, chlorpromazine (CPZ), in doses that per se do not affect performance. The nature of the chlorpromazine action and its competition with lysergic acid diethylamide is revealed by the effects of chlorpromazine in larger doses. 相似文献
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Cholecystokinin inhibits tail pinch-induced eating in rats 总被引：3，自引：0，他引：3
C B Nemeroff A J Osbahr G Bissette G Jahnke M A Lipton A J Prange 《Science (New York, N.Y.)》1978,200(4343):793-794
Peripheral administration of the COOH-terminal octapeptide of cholecystokinin in doses from 1 to 100 micrograms per kilogram of body weight (0.25 to 25.0 micrograms per rat) significantly antagonized tail pinch-induced eating in rats, an animal model for stress-induced human hyperphagia. Centrally administered cholecystokinin was effective only in high doses (3 micrograms into the cerebral ventricle). The finding that the minimal effective dose of cholecystokinin in suppressing stress-induced appetitive behavior is smaller after peripheral than central administration suggests that the peptide is acting on peripheral, as opposed to central nervous system, substrates. 相似文献
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Persistent increase in brain serotonin turnover after chronic administration of LSD in the rat 总被引：1，自引：0，他引：1
Lysergic acid diethylamide at doses of 20 micrograms per kilogram per day was administered orally to rats for I month. Eighteen hours after the final dose a 25 to 30 percent increase in the synthesis and turnover of serotonin was noted, as well as a moderate but significant increase in the concentration of tryptophan (18 percent) and serotonin (13 percent) in the brain. 相似文献
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研究了60Co-γ射线处理蚕豆干种子的诱变效果,结果表明,不同照射剂量对M1生育期、生物学性状、光合生理有明显的影响,随着剂量的增加生育进程逐渐延迟,生育期延长;株高、分枝数、单株荚数、单株粒数、百粒重等呈递减趋势,且变异系数逐渐增大;诱变处理后,叶片叶绿素含量及光合速率变化规律基本相同,即在结荚期前各处理比对照高,结荚期后,各处理比对照低。 相似文献
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25-Hydroxycholecalciferol stimulates release of previously incorporated calcium-45 from fetal rat bones in doses of 0.9 to 27 units per milliliter. This effect cannot be produced by much larger doses of vitamin D(3). Comparison of stimulation of bone resorption by 25-hydroxycholecalciferol and parathyroid hormone reveals similarities with respect to time course, dose-response slope, and inhibition by calcitonin. 相似文献
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Phenobarbital: effects of long-term administration on behavior and brain of artificially reared rats
Two doses of phenobarbital were given daily for 2 weeks to infant rats fed by intragastric cannulas. The larger dose (60 milligrams per kilogram of body weight) resulted in decreased spontaneous activity and increased responses to novel stimuli. The smaller dose (15 milligrams per kilogram) resulted in increased spontaneous activity and also an increase of responses to novel stimuli. The larger dose produced a 12 percent reduction in brain growth, while the smaller dose was associated with a 3 percent reduction in brain growth. 相似文献
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D S Grosch 《Science (New York, N.Y.)》1967,155(762):592-593
Brine shrimp die within 5 days after being given doses of above 10(-5) parts of DDT per million. At this and lower doses, shrimp deposited broods at a normal frequency, and cysts predominated. The number of cysts that emerged and the survival of larvae to adulthood from broods of treated parents exceeded those from controls. Therefore lethality based on induced dominant or sex-linked recessive gene mutation was not evident. Decreased fecundity is due to maternal debility. 相似文献
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Pentylenetetrazol enhances memory function 总被引：3，自引：0，他引：3
Pentylenetetrazol, in oral doses of 1 to 30 milligrams per kilogram of body weight, significantly facilitated one-trial learning and memory retention in CF1 mice, whether administered before or immediately after the initial trial. The effects appeared significantly greater than those observed in earlier studies with oral administration of strychnine or picrotoxin at 0.2 to 0.8 and 2.4 milligrams per kilogram, respectively. 相似文献
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Bladder tumors in rats fed cyclohexylamine or high doses of a mixture of cyclamate and saccharin 总被引：8，自引：0，他引：8
J M Price C G Biava B L Oser E E Vogin J Steinfeld H L Ley 《Science (New York, N.Y.)》1970,167(921):1131-1132
Papillary transitional cell tumors were found in the urinary bladders in 8 rats out of 80 that received 2600 milligrams per kilogram of body weight per day of a mixture of sodium cyclamate and sodium saccharin (10:1) for up to 105 weeks. From week 79 on, several of these rats received cyclohexylamine hydrochloride (125 milligrams per kilogram per day, the molecular equivalent of the conversion of about 10 percent of the cyclamate dosage to cyclohexylamine) in addition to the sodium cyclamate and sodium saccharin. In another study in which 50 rats were fed daily 15 milligrams of cyclohexylamine sulfate per kilogram of body weight for 2 years, eight males and nine females survived. One of the eight males had a tumor of the urinary bladder. In neither study were bladder tumors found in the control rats or in rats treated with lower doses of the compounds. 相似文献
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试验采用四因素三水平正交设计的方法,研究了影响玉米高产的品种、密度、施氮量、施磷量之间的关系,得到了陕北沟谷地春玉米7 650 kg.hm-2的最佳农艺措施组合方案。在本试验条件下,四项农艺措施对产量的影响顺序为密度>品种>施氮量>施磷量,最佳农艺措施组合为密度6.00万株.hm-2,纯氮330 kg,纯磷138kg,品种3 819。生育期指标试验结果表明,四因素中品种对生育期影响达到显著水平。研究结果可作为类似地区春玉米高产栽培的参考。 相似文献
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Substance P: does it produce analgesia or hyperalgesia? 总被引：2，自引：0，他引：2
In the hot plate test, substance P given intravenously at doses of 5 x 10-5 and 5 x 10-4 gram per kilogram caused analgesia, while lower doses caused hyperalgesia. The influence of substance P on nociception depended on the individual mouse's sensitivity to pain (control response latency). Analgesia was produced by substance P administered to mice with high sensitivity to thermic stimulation, whereas hyperalgesia occurred in mice whose control latencies were longer than normal. This result is interpreted as an indication that substance P is capable of normalizing responsiveness to pain and could be classified as a regulatory peptide. 相似文献
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Alcohol self-administration disrupts reproductive function in female macaque monkeys 总被引：2，自引：0，他引：2
N K Mello M P Bree J H Mendelson J Ellingboe N W King P Sehgal 《Science (New York, N.Y.)》1983,221(4611):677-679
Female macaque monkeys self-administered high doses of alcohol (2.9 to 4.4 grams per kilogram per day) for 3 to 6 1/2 months. Amenorrhea, atrophy of the uterus, decreased ovarian mass, and significant depression of luteinizing hormone levels were associated with chronic alcohol intoxication. Reproductive system failure in female primates following self-induced dependence on alcohol parallels the results of clinical studies of alcoholic women. 相似文献
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Five chimpanzees were given Delta(9)-tetrahydrocannabinol (Delta(9)THC): 1.0 milligram per kilogram of body weight for 21 days and 4.0 milligrams per kilogram of body weight for 42 days. Although accuracy and speed of performance on a delayed matching-to-sample task were significantly affected by both doses, tolerance to Delta(9)THC did not develop. No long-term behavioral effects of Delta(9)THC were observed after termination of the drug regimens. 相似文献
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不同剂量稀土对金雨金合欢幼苗生长的影响 总被引：2，自引：0，他引：2
为明确稀土对金雨金合欢幼苗生长的影响,采用8种不同剂量的稀土对金雨金合幼苗进行根施。结果表明:1)金雨金合欢幼苗施入稀土后,7～10d起幼苗形态出现不同的变化,比对照出现相同反应提早5～6d;2)90d的各项测定生长指标分析表明,每株施入0.05～1.00g剂量稀土,对幼苗生长具有较好的促进作用,其幼苗高、地径净增长,全苗鲜、干重量,叶片总面积,根系总长度、根系表面积和根尖数量总体上呈有规律的增长趋势,均显著高于对照(P<0.05),以施入剂量0.25g·株-1处理表现最好,其苗木出圃率达到100%,与对照相比,苗高、地径净增长了204.0%和102.0%,叶片总面积、根系总长度、根系表面积和根尖数量分别增长了976%、339%、405%和187%,全苗鲜、干重量,提高了61.5%和133.3%;3)当施入剂量超过2.00g·株-1时,苗木生长开始受抑,出现"毒害"反应,其各项生长指标下降,部分苗木死亡,并随剂量增大,生长受抑程度加剧,生长指标下降速度增大,幼苗死亡数量增多。表明低浓度的稀土溶液根施,对金雨金合欢幼苗生长具有促进作用,高浓度则抑制了其生长,甚至会导致死亡。 相似文献
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关中奶山羊超数排卵的研究 总被引：2，自引：0，他引：2
用FSH恒量法、FSH减量法、FSH和LH混合法及PMSG法处理获得头均可用胚数分别为5.5,5.8,4.0和3.2枚;从情期的6～8,9～11,12～15和16～18d开始超排获得的头均可用胚数分别为3.4,5.7,5.5和4.1枚;对2,3,4,5和6岁以上供体超排获得的头均可用胚数分别为3.2,4.7,5.1,5.7和2.9枚;在9,10,11,12月和次年1月超排获得的头均可用胚数分别为2.8,4.7,5.8,5.3和3.2枚。结果证明,在10～12月,从情期的9～15d开始,采用FSH恒量法或FSH减量法对3～5岁的关中奶山羊进行超排可获得更好效果。 相似文献
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Various meliorants are shown to reduce the degree of lead and cadmium mobility in polluted agrozem by 20–60% on average. Sodium sulfide and superphosphate at doses of 120 kg of active ingredient per/ha (a.i./ha) and phosphorite meal at a dose of 1.5 t/ha somewhat stand apart in the effectiveness of this action. 相似文献