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81.
Steinar Solberg Tor Larsen Leif Jørgensen 《In vitro cellular & developmental biology. Plant》1985,21(11):612-616
Summary This study examined whether nonconfluent endothelial cell cultures reacted differently than confluent ones toward thrombin-stimulated
platelets or a heparinized salt solution. The adherence to the endothelial cell cultures of51Cr-labeled human platelets stimulated at different thrombin concentrations was studied. There was significantly higher adherence
of stimulated platelets to nonconfluent cultures compared with confluent ones. This was confirmed by scanning electron microscopy,
which also revealed a tendency for the platelets to adhere at the cell periphery. Electron microscopy also showed that thrombin-stimulated
platelets induced endothelial cell contraction. Part of the peripheral endothelial cell surface toward the bottom of the culture
dish was inverted, facing the lumen of the dish. This phenomenon was particularly seen in nonconfluent cultures. When51Cr-labeled endothelial cultures were incubated with a mildly injurious fluid as heparinized sodium acetate and 20% serum,
at 20° C for 30 min, the nonconfluent cultures showed significantly more cell detachment and release of51Cr than the confluent ones. We conclude that under the conditions of the present experiments there are differences in the
reactivity of confluent and nonconfluent endothelial cell cultures. These differences probably reflect biological dissimilarities.
In experiments where properties of cultured endothelium are studied, care should be taken that the degree of confluency is
standardized. 相似文献
82.
Quantitative samples were used to investigate density, biomass and annual production of the benthic invertebrate fauna in a small Danish stream. Forty-eight taxa were found and the total invertebrate densities varied from 3 810 m?2 in July to 20 040 m?2 in December. The total mean annual biomass of the invertebrate fauna was 6.1 g ash-free dry wt m?2. The annual production of the invertebrates was estimated from their mean annual biomass and their annual P/B ratio. Production of the primary consumers (herbivores and detritivores) was 21.4 g ash-free dry wt m?2 y?1 and of secondary consumers (carnivores) 1.1 g m?2 y?1. The amount of invertebrate production available to the trout population and the importance of the species as food for trout are discussed. 相似文献
83.
Abstract: D, L(±)-4-Hydroxy-3-methoxyphenylglycol (HMPG) labelled with three deuterium atoms was used to study turnover of plasma free HMPG following an intravenous injection. Ten healthy men were given a pulse dose of either 4.3 μmol or 2.2 μmol of labelled HMPG ([2H3]HMPG piperazine salt). Plasma and urine levels of both endogenous and labelled HMPG were subsequently followed by gas chromatography-mass spectrometry with selected ion detection. Kinetic calculations based upon a single-compartment model were consistent with a monoexponential elimination of plasma free HMPG. The half-life of HMPG was 0.46 and 0.78 h (mean values in the two dose groups). The HMPG production rate was 2.01 and 2.35 μmol/hour, and the urinary excretion rate of HMPG (free and conjugated) was 0.48 and 0.47 μmol/h. The endogenous plasma level of free HMPG was 25 and 33 nmol/L. The results show that HMPG turns over rapidly and that HMPG is further metabolized extensively. About one-fourth of the HMPG produced is excreted in urine as free and conjugated HMPG. 相似文献
84.
The kinetics of haemolysis of rabbit erythrocytes byCroton tiglium lectin was studied as a function of concentration of the lectin and erythrocytes. The length of the prelytic period decreased with increasing lectin concentrations, indicating that the secondary events at the membrane which follow the binding of the lectin to cell surface carbohydrate receptors are accelerated at higher surface concentrations of the lectin. The rate or extent of haemolysis was not affected by the inclusion of ions like K+, Ca2+ and Mg2+ in the medium or by the substitution of ionic medium by a non-ionic medium. The inhibition of haemagglutination and haemolysis of rabbit red cells byCroton tiglium lectin by antilectin rabbit serum was observed. A possible mechanism of haemolysis by the lectin is discussed. 相似文献
85.
N-Acetyl-D-galactosamine in β-linkage being ubiquitous in cell surface glycoproteins, their interaction with lectins specific for this sugar moiety may be a significant event in cell adhesion phenomena. This article discusses the common β-N-acetyl galactosamine-specific lectins, with particular stress on the lectin from winged beans (Psophocarpus tetragonolobus). 相似文献
86.
Demonstration of an “Excitation-Contraction Recoupling” Mechanism in Mammalian Ventricular Myocardium 总被引:1,自引:0,他引:1
A PROCESS called “excitation-contraction coupling” has been generally accepted to take place only in the direction of excitation to contraction. Through this mechanism a propagated action potential initiates an active state in skeletal or cardiac muscle and the muscle contracts. We propose that, in the mammalian ventricular myocardium at least, the process is not unidirectional and an important reverse coupling between the contractile system and the excitable plasma membrane has been overlooked. Through this feedback interaction the mode of contraction (that is, isotonic or isometric) not only determines the instantaneous electrical state of the plasma membrane, but also influences the mechanical events of the subsequent beats. Thus when Kaufmann et al.1 recorded intracellular action potentials from cat papillary muscle, the time course of the repolarization was altered depending on the mode of contraction. Some kind of contraction-excitation feedback has also been suggested by Stauch2 and Lab3,4. They showed a difference in the shape of the monophasic action potential, as recorded by a suction electrode, when comparing isotonic and isovolumic contraction of the intact ventricle. But their experimental conditions did not allow satisfactory analysis of the phenomenon. 相似文献
87.
Role of the Galactose Binding Protein in Chemotaxis of <Emphasis Type="Italic">Escherichia coli</Emphasis> toward Galactose 总被引:51,自引:0,他引:51
The galactose binding protein is the part of the galactose chemoreceptor which recognizes the attractants galactose, glucose and a number of structurally related chemicals. 相似文献
88.
Ribosomes,G-factor and Siomycin 总被引:13,自引:0,他引:13
G-factor interacts with the 50S ribo-somal subunit at a site which is distinct from the peptidyl transferase centre and which is inactivated by siomycin. 相似文献
89.
RICHARD L. SIMMONS MARTIN L. LIPSCHULTZ ANGELYN RIOS PRASANTA K. RAY 《Nature: New biology》1971,231(21):111-112
DURING outbred pregnancy the mother is exposed to genetically foreign tissue because the offspring inherits transplantation antigens from the father. The survival of the foetus is ensured by the intervention of the trophoblast which does not express transplantation antigens between mother and foetus: mouse trophoblast is not rejected even when transplanted into immune recipients1,3. The mechanism of this failure to express histocompatibility antigens is not understood1–4, but Kirby et al. have suggested that the extracellular fibrinoid surrounding trophoblast cells is involved5,6. Currie has suggested that the thick sialomucinous glycocalyx of the trophoblast cell might “mask” the histocompatibility antigens on the trophoblast7,8 and has demonstrated that neuraminidase unmasked these antigens8. Our experiments, however, show that trophoblast incubated with neuraminidase cannot sensitize allogeneic mice to donor histocompatibility antigens. Furthermore, pretreatment of trophoblastic implants with neuraminidase did not interfere with their proliferation and growth in highly immune allogeneic recipients. 相似文献
90.
Binding of Radioactively Labelled Concanavalin A and Wheat Germ Agglutinin to Normal and Virus-transformed Cells 总被引:32,自引:0,他引:32
VARIOUS substances isolated from plants cause animal cells to clump. Several of these lectins1 preferentially agglutinate cells which have been transformed spontaneously or by chemicals or viruses2–7. The best known lectins of this class are concanavalin A (Con A) isolated from jack beans8 and wheat germ agglutinin4, which seem to bind to carbohydrate groups on the cell surface. The determinants recognized by the lectins seem to be N-acetyl-D-glucosamine for WGA4 and probably α-methyl-D-glucopyranoside for Con A6. 相似文献