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151.
152.
I Dormehl F Redelinghuys N Hugo D Oliver W Pilloy 《Journal of medical primatology》1992,21(5):270-274
Single photon emission computed tomography of the brain can be useful in animal experimentation directed toward cerebral conditions. A well established and understood baboon model, necessarily under anesthesia, could be especially valuable in such investigations. Six normal baboons were studied under various anesthetic agents and their combinations: ketamine, thiopentone, pentobarbitone, and halothane. Cerebral blood flow (CBF) studies were performed with 99mTc-HMPAO. CBF effects from various anesthesia were detected, requiring careful choice of the anesthesia for cerebral investigations. 相似文献
153.
The effect of varying the solute species on the crystallization of the Ca2(+)-ATPase from rabbit muscle reticulum (SR) is reported. We have found that substitution of KCl with salts of organic acids in the crystallization protocol reported by Pikula et al. has a profound effect on the size of two-dimensional crystalline arrays. Crystalline arrays of up to 3 microns diameter have been obtained by incubating purified calcium ATPase in standard crystallization medium but with 0.8 M sodium propionate substituted for KCl. These two-dimensional (2-D) arrays display a reduced tendency to stack in addition to having larger planar dimensions. Increasing the KCl concentration does not have the same effect on stacking or crystal growth that sodium propionate has. The production of 2-D sheets has some dependence on the hydrocarbon chain length of the salt because crystals formed in propionate were larger and less stacked than those formed in acetate or formate. There seems to be no dependence on cation. These observations suggest that in addition to reducing the forces that lead to stacking of the sheets, propionate may facilitate incorporation of the detergent-solubilized protein into the 2-D sheet. 相似文献
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156.
J M Oliver R D Berlin 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》1982,299(1095):215-235
The long-range movements of membrane ligand-receptor complexes into surface caps and into the pseudopods of cells performing phagocytosis, the uropods of motile cells and the cleavage furrows of dividing cells appear to be analogous processes. A common mechanism to explain these movements must take into account several recent observations. First, laser photobleaching studies have indicated that Concanavalin A-receptor movement occurs unidirectionally; and analyses of Con A redistribution by quantitative video intensification microscopy (QUAVIM) have shown that movement may exceed the maximum rates measured for protein diffusion in membranes. These are the results predicted for a process of directed migration but not for a process of diffusion with entrapment. In addition it has been found that membrane receptors may segregate out of as well as into cap, pseudopod, uropod and cleavage furrow regions and that topographical heterogeneity on asymmetric cells is not restricted to membrane molecular determinants but extends to a range of endocytic functions and to a macromolecular complex, the coated pit. All dynamic surface events are arrested during mitosis. A new model for the regulation of plasma membrane topography has been developed from these diverse quantitative, functional and morphological data. Its essence is the entrainment of selected membrane determinants on membrane waves directed towards regions such as caps, pseudopods, uropods and cleavage furrows. The waves are initiated by tension due to asymmetric microfilament-membrane interaction. 相似文献
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158.
The long range movements of membrane-bound ligands into surface caps and into the pseudopods of phagocytizing cells, the uropods of motile cells and the cleavage furrow of dividing cells appear to be analogous processes. A common mechanism to explain these movements must take into account several new and central observations: ligand-receptor complexes can migrate to regions of existing microfilament accumulation; laser photobleaching studies with fluorescent Con A indicate that ligand-receptor movement occurs unidirectionally; video computer analyses of Con A redistribution show that movement may exceed the maximum rates measured for protein diffusion in membranes. These observations are not consistent with models in which ligand-receptor movement occurs by diffusion or by direct interaction with contractile microfilaments. However, they can be satisfied by a new model that proposes the entrainment of selected membrane determinants on membrane waves directed towards regions such as caps, pseudopodia, uropods or cleavage furrow. These oriented waves are initiated by tension due to asymmetric microfilamentmembrane interaction. 相似文献
159.
Uptake of Exogenous Glutamate and Aspartate by Circumventricular Organs but Not Other Regions of Brain 总被引:1,自引:1,他引:0
Madelon T. Price John W. Olney Oliver H. Lowry Susan Buchsbaum 《Journal of neurochemistry》1981,36(5):1774-1780
Abstract: Glutamate (Glu) and aspartate (Asp) concentrations in blood and selected regions of brain were measured at sequential intervals over a 3-h period following subcutaneous administration of Glu, Asp, or Glu plus Asp (2 mg/g body wt) to 4-day-old mouse or rat pups. Marked serum elevations of the administered amino acids (peak values exceeding 200 times control levels) were detected within 1 h. In circumventricular organ (CVO) regions of brain, which are thought to have no blood-brain barriers, a sharp and steady increase in tissue concentrations of the administered amino acids (peak values 4–10 times higher than control levels) occurred during a 15–120 min interval, whereas no appreciable increases were detected in other brain regions. When 2 mg/g Glu plus 2 mg/g Asp were administered, CVO tissue concentrations of each amino acid rose to approximately the same level obtained when the individual amino acids were given. It is concluded that blood-brain barriers preventing net entry of Glu or Asp into brain proper are relatively well established by the 4th postnatal day in rodents, but that CVO brain regions lack such barriers; selective access of blood-borne Glu or Asp to CVO neurons explains why these neurons are selectively destroyed by systemic administration of these neurotoxic amino acids. 相似文献
160.
Complete accounts of the natural products chemistry of Bonnemaisonia nootkana, B. asparagoides, B. hamifera and Trailliella intricata are described. In contrast to the chemistry of the closely related alga Asparagopsis, Bonnemaisonia spp. do not produce halomethanes, but instead an array of C7-C9 halogen-containing ketones, alcohols and carboxylic acids. Biomimetic syntheses of these compounds suggest they are precursors and products of in vivo Favorsky rearrangements. 相似文献