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121.
Substructure of the glomerular slit diaphragm in freeze-fractured normal rat kidney 总被引:4,自引:3,他引:1 下载免费PDF全文
In the renal glomerulus, the narrow slits between adjacent epithelial podocytes are bridged by a diaphragm (2, 8, 11). In rat and mouse kidneys fixed by perfusion with tannic acid and glutaraldehyde (TAG), it has recently been discovered that this diaphragm has a highly ordered, isoporous substructure (9). It consists of a regular array of alternating cross bridges extending from the podocyte plasma membranes to a centrally running filament. This zipperlike pattern results in two rows of rectangular pores, approximately 40 X 140 A in cross section, dimensions consistent with the proposed role of the diaphragm as an important filtration barrier to plasma proteins (6). In the present study, we found in freeze-cleaved and in freeze-etched normal rat glomeruli that the surface of the slit diaphragm has an appearance conforming to the pattern found in sectioned material. 相似文献
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Inhibition of phosphatidylinositol synthesis and the inactivation of calcium entry after prolonged exposure of the blowfly salivary gland to 5-hydroxytryptamine. 下载免费PDF全文
The incorporation of [32P]Pi into all salivary-gland phospholipids except phosphatidic acid was inhibited by 5-hydroxytryptamine. The accumulation of [32P]Pi into phosphatidic acid was actually enhanced by 5-hydroxytryptamine. There was an inhibition of labelled inositol incorporation into phosphatidylinositol by 5-hydroxytryptamine, which seems to be mediated by calcium because it was mimicked by the ionophore A23187, but was prevented if glands were stimulated with 5-hydroxytryptamine in the absence of external calcium. Inhibition of synthesis together with stimulation of breakdown will decrease the concentration of phosphatidylinositol, which could account for the inactivation of calcium transport observed at high 5-hydroxytryptamine concentrations. When salivary glands were stimulated with 1 micrometer-5-hydroxytryptamine, there was a rapid increase in the transfer of 45Ca2+ from the medium into the saliva, but with time this transport declined to a low value. If the glands were washed free of 5-hydroxytryptamine and incubated in the presence of 2mM-inositol for 1 h, the increase in calcium transport caused by 5-hydroxytryptamine was restored. There was little recovery in the absence of inositol. If glands were stimulated with 5-hydroxytryptamine in the absence of external calcium, a condition which prevents the inhibition of phosphatidylinositol synthesis, calcium transport in response to 5-hydroxytryptamine was greater than in glands preincubated with 5-hydroxytryptamine in the presence of calcium. The inactivation of calcium transport may result from a decrease in phosphatidylinositol concentration. These results support the hypothesis that the hydrolysis of phosphatidylinositol plays some role in either the opening or closing of calcium 'gates'. 相似文献
125.
Changes in cyclic AMP and cyclic GMP concentrations during the action of 5-hydroxytryptamine on an insect salivary gland. 总被引:4,自引:2,他引:2 下载免费PDF全文
Salivary glands from adult blowflies (Calliphora erythrocephala Meigen) were studied in vitro. The time course of changes in cyclic AMP content of the glands was followed at different concentration of 5-hydroxytryptamine. There was an immediate biphasic rise and fall in cyclic AMP content, following by a slower rise and subsequent gradual decline. The initial rise preceded the onset of fluid secretion by the glands. Rises in cyclic AMP content were inhibited by compound RMI 12330 A (an adenylate cyclase inhibitor) and were halted after about 15-20s if the glands were deprived of Ca2+. Theophylline (a phosphodiesterase inhibitor) abolished the decline phase of the fast response, Losses of cyclic AMP from the glands either to the bathing medium or to the saliva were small and could not account for the rapid fall found. Evidence is presented that cyclic GMP is not involved in the process of initiating secretion in the blowfly salivary gland. 相似文献
126.
Studies on the mechanism for entry of vesicular stomatitis virus glycoprotein g mRNA into membrane-bound polyribosome complexes 下载免费PDF全文
Glycoprotein mRNA (G mRNA) of vesicular stomatitis virus is synthesized in the cytosol fraction of infected HeLa cells. Shortly after synthesis, this mRNA associates with 40S ribosomal subunits and subsequently forms 80S monosomes in the cytosol fraction. The bulk of labeled G mRNA is then found in polysomes associated with the membrane, without first appearing in the subunit or monomer pool of the membrane-bound fraction. Inhibition of the initiation of protein synthesis by pactamycin or muconomycin A blocks entry of newly synthesized G m RNA into membrane-bound polysomes. Under these circumstances, labeled G mRNA accumulates into the cytosol. Inhibition of the elongation of protein synthesis by cucloheximide, however, allows entry of 60 percent of newly synthesized G mRNA into membrane-bound polysomes. Furthermore, prelabeled G mRNA associated with membrane-bound polysomes is released from the membrane fraction in vivo by pactamycin or mucomycon A and in vitro by 1mM puromycin - 0.5 M KCI. This release is not due to nonspecific effects of the drugs. These results demonstrate that association of G mRNA with membrane-bound polysomes is dependent upon polysome formation and initiation of protein synthesis. Therefore, direct association of the 3' end of G mRNA with the membrane does not appear to be the initial event in the formation of membrane-bound polysomes. 相似文献
127.
H?Bukulmez AL?Matthews CM?Sullivan C?Chen MJ?Kraay RC?Elston RW?Moskowitz VM?Goldberg ML?WarmanEmail author 《Arthritis research & therapy》2005,8(1):R25
In order to determine whether there is a genetic component to hip or knee joint failure due to idiopathic osteoarthritis (OA),
we invited patients (probands) undergoing hip or knee arthroplasty for management of idiopathic OA to provide detailed family
histories regarding the prevalence of idiopathic OA requiring joint replacement in their siblings. We also invited their spouses
to provide detailed family histories about their siblings to serve as a control group. In the probands, we confirmed the diagnosis
of idiopathic OA using American College of Rheumatology criteria. The cohorts included the siblings of 635 probands undergoing
total hip replacement, the siblings of 486 probands undergoing total knee replacement, and the siblings of 787 spouses. We
compared the prevalence of arthroplasty for idiopathic OA among the siblings of the probands with that among the siblings
of the spouses, and we used logistic regression to identify independent risk factors for hip and knee arthroplasty in the
siblings. Familial aggregation for hip arthroplasty, but not for knee arthroplasty, was observed after controlling for age
and sex, suggesting a genetic contribution to end-stage hip OA but not to end-stage knee OA. We conclude that attempts to
identify genes that predispose to idiopathic OA resulting in joint failure are more likely to be successful in patients with
hip OA than in those with knee OA. 相似文献
128.
The hypocretins modulate arousal via actions across multiple terminal fields. Thus, alterations in hypocretin neurotransmission may contribute to altered sleep patterns observed during lactation. This study examined whether lactation is associated with alterations in the number of hypocretin neurons and in diurnal Fos-immunoreactivity within hypocretin neurons in female mice. Alterations in Fos-immunoreactivity were also examined within two hypocretin terminal regions; the medial preoptic area and the locus coeruleus. Fos-immunoreactivity was increased within hypocretin neurons and the medial preoptic area in lactating females. No differences were observed in the number of hypocretin neurons or in Fos-immunoreactivity within the locus coeruleus. 相似文献
129.
应用免疫组织化学SP法对4例饲喂黄曲霉毒素B1的Wistar大鼠肝组织中AFB1-DNA加合物的染色及常规HE染色发现,4例肝细胞核均出现异型性,但未见肝细胞坏死、增生灶及肝细胞癌;免疫组化揭示部分肝细胞核出现棕黄色、不均质状的AFB1-DNA加合物,阳性细胞数占10~85%。结果提示免疫组织化学方法可作为一种AFB1的定位方法,AFB1在动物致癌过程中AFB1-DNA加合物可能具有启动作用 相似文献
130.