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1.
Summary The paper describes a hexagonal array of nuclear pores in a non-redundant region of the nuclear envelope underlying the basal surface of the rat spermatozoon head. It is concluded that intranuclear material protruding through these pores is the cause of the characteristic rows of circular bumps found in surface replicas of this region. 相似文献
2.
Summary Recent evidence has revived the idea that translocation of macromolecules between nucleus and cytoplasm may be regulated via expansion and contraction of the entire diameter of the nuclear pore complex. The present investigation does not support this hypothesis.Acknowledgments. We are indebted to Dr J.H.M. Willison for discussion of his and Dr Rajaraman's results before their publication. We also wish to thank Dr C. Thurston, Dr D.H. Williamson and Dr K. Lambert for providing some of the specimens used in this investigation. N.J. Severs acknowledges the support of the Science Research Council and the Cancer Research Campaign. 相似文献
3.
The prokaryotic pore-forming proteins are synthesized in the cytoplasm, and are assembled in their functional form in the outer membrane. They begin to traverse the cytoplasmic membrane via the SecY/SecA export pathway, which is shared also by periplasmic proteins. The sorting signals that direct these proteins to the outer membrane could be present in the three-dimensional conformations of the proteins, but some results suggest that they may be present in short, contiguous sequences. Outer membrane proteins share a rather hydrophilic amino acid composition, and appear to be rich in beta-sheets (with the exception of lipoproteins). This observation as well as the demonstration of periplasmic export intermediates favor the secretion pathway through the periplasm, as opposed to export through fusion sites between the inner and the outer membrane, but such intermediates have not yet been observed with the wild type proteins under physiological conditions. 相似文献
4.
Résumé Chez le bouc, le mouton et le buffle, la gouttelette cytoplasmique du spermatozoïde précoce contient des inclusions cytoplasmiques de différents genres: (1) des bâtonnets et granules sudanophiles constitués pars des phospholipides et des protéides, (2) un ou deux corps sudanophobes constitués par de l'acide ribonucléique et des protéides, et (3) des granules mitochondriés constitués par des lipoprotéides. 相似文献
5.
C A Mannella 《Experientia》1990,46(2):137-145
Structural information about the channel in the mitochondrial outer membrane, derived from sequence analysis and electron microscopy of two-dimensional crystals, is summarized. A model for the channel is presented, consisting of a cylindrical beta-barrel that is formed by one or two 30-kDa polypeptides, with an alpha-carbon backbone diameter of 3.8 nm. The radial distributions of basic amino acids and lipid-contact regions on the projected cylinder are mapped relative to interchannel bonding sites inferred from channel packing in the arrays. Speculation on the kinds of conformational changes that the channel might undergo is also presented. 相似文献
6.
Autoradiographic studies with 3H aldosterone demonstrate nuclear concentration of hormone in neurons of the hippocampus, septum, allocortical regions and brain stem reticular formation and motor nuclei of cranial nerves and in the meninges. The results suggest that mineralocorticoids have wide ranging effects on different parts of the central nervous system. 相似文献
7.
W. W. Franke J. Kartenbeck Barbara Deumling 《Cellular and molecular life sciences : CMLS》1971,27(4):372-373
Zusammenfassung Aus den Fliessgleichgewichts-Werten (mittlere Kernporenzahl und RNA-Synthesegeschwindigkeiten) der ausdifferenzierten Rattenleberzelle wurde die Kernporen-Durchflussrate (NPFR) für ribosomale und transfer RNA berechnet. Diese Hepatocytenwerte werden mit den entsprechenden RNA-Transportleistungen der Kernporenkomplexe anderer Zelltypen verglichen. 相似文献
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9.
Marion K. Birmingham W. E. Stumpf M. Sar 《Cellular and molecular life sciences : CMLS》1979,35(9):1240-1241
Summary Autoradiographic studies with3H aldosterone demonstrate nuclear concentration of hormone in neurons of the hippocampus, septum, allocortical regionss and brain stem reticular formation and motor nuclei of cranial nerves and in the meninges. The results suggest that mineralocorticoids have wide ranging effects on different parts of the central nervous system.This work was supported by the Medical Research Council of Canada and by PHS grant NS09914. We thank Ms Brenda McClain for technical assistance. 相似文献
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11.
R Benz 《Experientia》1990,46(2):131-137
The matrix space of mitochondria is surrounded by two membranes. The mitochondrial inner membrane contains the respiration chain and a large number of highly specific carriers for the mostly anionic substrates of mitochondrial metabolism. In contrast to this the permeability properties of the mitochondrial outer membrane are by far less specific. It acts as a molecular sieve for hydrophilic molecules with a defined exclusion limit around 3000 Da. Responsible for the extremely high permeability of the mitochondrial outer membrane is the presence of a pore-forming protein termed mitochondrial porin. Mitochondrial porins have been isolated from a variety of eukaryotic cells. They are basic proteins with molecular masses between 30 and 35 kDa. Reconstitution experiments define their function as pore-forming components with a single-channel conductance of about 0.40 nS (nano Siemens) in 0.1 M KCl at low voltages. In the open state mitochondrial porin behaves as a general diffusion pore with an effective diameter of 1.7 nm. Eukaryotic porins are slightly anion-selective in the open state but become cation-selective after voltage-dependent closure. 相似文献
12.
Zusammenfassung Gruppen von 2–4 somatischen Kernen haploiderTriturus-Embryonen wurden in diploide, ungefurchte Eier injiziert, 11 haplo-diploide Mosaik-Larven entwickelten sich bis zum frühen Neurula-Stadium. Nachkommen von Kernen aus dem neuralen Ektoderm oder Chorda-Mesoderm von Spendern im Neurula-Stadium fanden sich in allen drei Keimblättern der Wirtslarve. 相似文献
13.
It could be demonstrated that intraportal infusion of prostaglandin A1 (1 mug/min/100 g body wt.) in Wistar rats significantly increases bile flow. An analysis of the relationship between bile salt excretion and bile flow revealed that this choleresis is due to an increase in the bile salt independent fraction of bile. 相似文献
14.
The rat neonatal cerebellar cortex has been studied using the freeze fracture technique. In the dendritic postsynaptic membrane, intramembrane particles containing an electron-dense central area have been detected. This type of area could be a platinum aggregate within a channel which, crossing the particle, may connect the postsynaptic cytoplasm with the synaptic cleft. 相似文献
15.
Summary Large nuclear blebs have been observed in oocytes of the fish,Clarias batrachus. The bleb, which contains nucleoplasm, is finally extruded from the nucleus. The extruded body is DNase-sensitive, and it implies that some amount of DNA is extruded from the nucleus of these oocytes.Acknowledgments. We are thankful to Dr. R.K. Sharan, Department of Zoology, Patna University, for providing laboratory facilities, and to Dr V.G. Jhingran and Dr P.V. Dehadrai of ICAR for their keen interest in the work. 相似文献
16.
In rats the bile flow and the estimated bile acid independant flow (BAIF) were significantly lower at 17.00 h than at 08.00 and 24.00 h. The decrease in BAIF paralleled the decrease in liver weight. Bile acid excretion was not different. 相似文献
17.
This study suggests that replacement of intracellular potassium by rubidium ions might lower the resting membrane potential. Thus rubidium-treated rats were more responsive to depolarizing influences and generated more cyclic AMP in the brainstem and consequently the behavioral changes. 相似文献
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Under the postulated existence of a mechanism regulating the NREM sleep- REM sleep sequence and a reset of this mechanism by long awakenings, the variability of sleep cycle in the rat was studied. Awakenings of various durations were included in the definition of sleep cycle boundaries. Results show that an intervening awakening of 1 min is close to the limit under which the same cycle seems to be resumed after the awakening and above which the previous cycle is abortive and a new cycle will start after the next sleep onset. 相似文献
20.
Riassunto É stata condotta una indagine sul numero delle protrusioni nucleari del tipo drumstick nei leucociti polimorfonucleati di diversi esemplari di Antropomorfe (Gorilla, Pan, Pongo). Queste protrusioni sono state ris contrate in entrambi i sessi, talvolta anche più di una (fino a 6) per nucleo ed in proporzione diversa nelle diverse speci.
Supported in part by a grant from the Italian Consiglio Nazionale delle Ricerche, Grant No. 7854/H. 相似文献
Supported in part by a grant from the Italian Consiglio Nazionale delle Ricerche, Grant No. 7854/H. 相似文献