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101.
102.
Human blood was sheared between rotating polyethylene disks and plasma hemoglobin measured at intervals to produce kinetic
hemolysis curves (KHC), plotted as free hemoglobin concentration vs time. The KHC produced by blood samples incubated in the
presence of penicillin, streptomycin, gentamicin, and amikacin lie always below those for control samples, indicating a reduction
in hemolysis; this reduction was greater as the drug concentration was increased. Explanations in terms of alterations in
red cell structure were sought by several characterization tests of amikacin-loaded blood samples. Drug-localization studies
demonstrated that significant fractions of the total dosage were associated with the red-cell membrane. Resistive pulse spectroscopy
was used to show how amikacin affected cell size, deformability, and osmotic fragility; results were sensitive to storage
age of the blood. In all cases, the effect of shearing was to reduce cell size, deformability, and osmotic fragility. Mechanisms
for hemolytic protection by drugs are proposed. 相似文献
103.
104.
本工作研究了大鼠延髓中缝核在心血管活动调整中的作用。通过埋植套管向大鼠延髓中缝核区注射神经元兴奋剂谷氨酸钠5-μg可明显降低血压,抑制交感神经传出活动,心率无显著改变。降血压效应可被脊髓蛛网膜下腔注射5-HT受体阻断剂肉桂硫胺50μg,或腹腔注射赛庚啶15mg/kg所部分对抗;并可被皮下注射阿片受体阻断剂纳洛酮1mc/kg所削弱。结果提示:延髓中缝核-脊髓5-HT下行通路对脊髓的血管调节功能起抑制性影响,内源性阿片样物质可能参与该机制。 相似文献
105.
GEORGE STAFF ERIC N. POWELL ROBERT J. STANTON JR. HAYS CUMMINS 《Lethaia: An International Journal of Palaeontology and Stratigraphy》1985,18(3):209-232
In general, more of the biomass of the community is preserved than is its numerical abundance. Thus, the paleontologist, on the average, works with more of the community when biomass is used. Community characteristics such as taxon dominance and habitat proportions are at least as accurately derived from biomass as numerical abundance. The use of biomass is clearly more appropriate in describing energy flow and trophic proportions. Whenever possible, biomass should be used as a complement to numerical abundance in future paleoecologic reconstructions. 相似文献
106.
Pollen flow, population composition, and the adaptive significance of distyly in Linum tenuifolium L. (Linaceae) 总被引:1,自引:0,他引:1
MARC S. NICHOLLS 《Biological journal of the Linnean Society. Linnean Society of London》1985,25(3):235-242
The function of distyly as a device promoting inter-morph pollination was proposed by Darwin over a century ago, though only recently have experimental studies been undertaken to test this hypothesis. These studies are unrealistic since they assume regular spatial distribution of morphs within a population and fail to consider intra-flower pollination in assessing distyly's effects. Pollen flow in two populations of Linum tenuifolium L. was investigated using a fluorescent-dye marker technique. One population was dimorphic and self-incompatible; the other was monomorphic and self-compatible. In both populations pollen dispersal was leptokurtic with over 75% of grains detected within 5 m from the source. Intra-flower pollinations comprised a large proportion of individual stigma loads (42% for the dimorphic form; 49% for the monomorphic form). Total stigmatic loads for the dimorphic population showed equal proportions of pin and thrum pollen on both long-style and short-style stigmas, though variation in individual loads was marked. Values ranging from 34.2 to 61.5% legitimate pollen were recorded. The irregular distribution of morphs observed at the dimorphic site will reduce the efficiency of heterostyly as a device promoting intermorph pollination. The reduction in intra-flower pollination suggests adaptive significance of this floral dimorphism in increasing the efficiency of pollen dispersal to the individual. 相似文献
107.
Following a survey of a range of varieties of rye, mainly Secale cereale, for reaction to DDT, the mode of action of the pesticide in a susceptible variety was studied. Two sites of interaction of DDT with the photosynthetic electron transport chain were demonstrated. The first site of inhibition was on the oxidizing side of photosystem 2, between the sites of electron donation from diphenylcarbazide at pH 6.0 and pH 8.0 in Tris-washed chloroplasts. The second site of DDT inhibition was in the intermediate electron transport chain, and was demonstrated by using dichlorophenol-indophenol and phenyldiamines as electron donors in chloroplasts where electron flow from photosystem 2 was inhibited by 3-(3,4-dichlorophenyl)-1,1-dimethylurea. The sites are distinct from those characteristic of herbicides which affect photosynthetic electron flow. 相似文献
108.
Trypanosoma brucei: analysis of relapsing populations in sensitive and resistant breeds of cattle 总被引:1,自引:0,他引:1
G E Roelants G Duvallet W Hirsch B Kanwe M Pinder G Guidot G Libeau A Van Melick 《Experimental parasitology》1985,60(1):18-31
The clone DiTat 1.1 of Trypanosoma brucei brucei was injected into four bovids, and clones obtained from successive waves of parasitemia were used to study the expressed variant-specific surface glycoprotein repertoire. Twenty-four clones were obtained which could be classified into 12 different variable antigen types, in addition to the clone injected, using agglutination or immunofluorescence with monospecific antisera. The variable surface glycoproteins of the 25 clones were extracted using the detergent octyl-beta-D-glucopyranoside in the presence of the protease inhibitor, N-cbz-L-phenylalaninechloromethylketone. The molecular weights varied from 52,000 to 69,000 and the pI from 5.0 to 8.8. The virulence of 14 clones representing 13 variable antigen types was ascertained in mice. The mean survival time ranged from 20.5 to 43.0 days. Clones isolated from early peaks of parasitemia in the bovid were the most virulent while clones derived from later peaks were less virulent. It seems that organisms of diminishing virulence appear in bovids, leading to self-cure of the disease. All clones were sensitive to human serum in a blood infectivity inhibition test. Antibody against all virulent clones appeared in 20 cattle (10 Zebus, 10 Baoulés) which had been injected with T. brucei DiTat 1.1. There was no evidence for parasites of high or low virulence being preferentially expressed in resistant or sensitive hosts. 相似文献
109.
In 1980 a long-term study of the fishery resources of the San Francisco Bay estuary was initiated in an effort to delineate the importance of freshwater inflow to fish and invertebrate abundance and distribution in the bay. An analysis of the trawl data collected between January 1980 and December 1982 illustrates the influence of the timing and magnitude of freshwater inflows on fish fistribution and abundance in this estuary from the perspective of monthly, seasonal and annual time scales. Normally found in the delta, Suisun Bay and San Pablo Bay during periods of increased salinity, pelagic species moved downstream after the two peak flows studied, while demersal species usually found in Central San Francisco Bay moved upstream. Such upstream movements may be due in part to transport by strong density-driven currents.Timing and magnitude of monthly catches of some species varied on a seasonal cycle coincident with variations of freshwater inflow. Most species, especially the marine species, showed no consistent cycle of monthly catches. In the wet years of 1980 and 1982 the distributions of freshwater, estuarine and anadromous species were extended downstream into San Pablo, Central and South San Francisco Bays and some marine species, including the flatfish, were more abundant in the upstream areas. In the dry year of 1981 when bay salinities were higher, few marine species extended their distributions upstream into San Pablo and Suisun Bays. Jacksmelt was the only fish of the 15 most abundant species with its peak abundance in 1981. Most marine species were more abundant in the San Francisco Bay estuary in the wet years. 相似文献
110.
Neurotensin stimulates pancreatic secretion directly and by potentiating the effect of secretin. Neurotensin also inhibits gastric secretion. Secretin inhibits gastric secretion as well, but whether it also interacts with neurotensin is not known. Secretin is known to inhibit gastric mucosal blood flow (GMBF). The effect of neurotensin on GMBF is not known. Acid secretion (triple lumen perfused orogastric tube) and GMBF ([14C]aminopyrine clearance) were therefore measured in 6 subjects during neurotensin, secretin and neurotensin plus secretin infusions. Neurotensin plus secretin reduced acid secretion by a median 130 (range 34-394) mumol/min which was significantly greater than either neurotensin at 36 (7-67) mumol/min or secretin 54 (20-347) mumol/min alone (P less than 0.05). This effect appeared independent of GMBF. Neurotensin plus secretin reduced GMBF by 14 (12-27) ml/min but not significantly more than neurotensin at 11 (3-20) ml/min or secretin 18 (2-27) ml/min alone. Further, there was no correlation between changes in acid output and GMBF during infusion of the peptides. We conclude that the inhibitory effects of neurotensin and secretin on gastric secretion are at least additive and together they may function as an 'enterogastrone'. 相似文献