Adrenocorticoid regulation of Na+, K+-ATPase in adult rat kidney: effects on post-translational processing and mRNA abundance

The mechanisms by which adreno-corticoid hormones regulate Na⁺, K⁺-ATPase in adult kidney were studied in adrenalectomized (Adx) rats. Five days after adrenalectomy, Na⁺, K⁺-ATPase activity was significantly reduced in the renal cortex homogenate (C = 13.0±0.8 vs. Adx = 7.1±0.7 μmol Pi mg^-1 protein h^-1) and in renal microsomes (C = 30.3 ± 1.9 vs Adx = 14.6 ± 1.3 μmol Pi mg^-1 protein h^-1). Glucocorticoid replacement treatment of adrenalectomized rats with betamethasone (20 μg kg^-1 body wt twice daily for 5 days) effectively counteracted the observed reduction in Na⁺, K⁺-ATPase activity. In cortical homogenate the protein level of α1 and β1 subunits measured in immunoblots was not significantly different in Adx and control rats, indicating that 5 days after adrenalectomy the α1 and β1 subunits were present in renal cortical cells to almost normal extent but could not be assembled into a transmembrane functional unit. In support of this conclusion we found that the protein level of both the α1 and β1 subunits was significantly lower (P < 0.001 for both subunits) in microsomes from Adx than in control rats. The mRNA abundance for α1 and β1 subunits were not lower in Adx as compared to control rats 1 and 5 days after surgery. However, if Adx rats were given a single dose of betamethasone (600 μg kg^-1 body wt), a significant 2-fold increase in both α1 and β1 mRNAs was observed (P < 0.05 for both subunits). These data suggest that glucocorticoids can upregulate the mRNA of both Na⁺, K⁺-ATPase subunits but that the low renal Na⁺, K⁺-ATPase activity in adult Adx rats is mainly due to loss of glucocorticoid regulation of the post-translational processing of the enzyme.     

商陆多糖Ⅰ联合白细胞介素2对小鼠脾细胞杀瘤活性的影响

商陆多糖Ⅰ(PAP-I),0.3～3μg·ml^-1和小鼠脾细胞培养3～5d可显著增强其杀伤P815肿瘤细胞活性及IL-2(250～500IU·ml^-1)诱导的LAK细胞活性,最适浓度为1μg·ml^-1。PAP-I及IL-2和脾细胞培养的上清液对P815肿瘤细胞无细胞毒作用,但能增强脾细胞及LAK细胞杀瘤活性。PAP-I,5,10及50mg·kg-1,ip可增强脾细胞杀伤P₈₁₅和L₉₂₉细胞的活性及IL-2诱导的LAK细胞活性。     

Simplified non-enzymatic technique for isolation of epithelium and muscle from the dog prostate gland

Epithelium and muscle from the normal dog prostate were isolated with a rapid, simple, non-surgical separation (NSS) technique, involving mechanical agitation of organ cubes in a high concentration (30 microM) of EDTA for tissue dispersion, and gentle pressure filtration for recovery of epithelium and muscle. Derivation of this NSS procedure utilized the guinea pig seminal vesicle, since it can be surgically separated (SS) into pure epithelium and muscle to serve as controls for the biochemical viability of NSS prepared tissues. The NSS procedure adopted for use yielded not only pure (greater than 95%) epithelium and muscle from intact seminal vesicle, but also activities of 5 alpha-reductase and concentrations of the cytosol estrophile in each tissue, which were not significantly different from the SS counterparts. In the dog prostate gland, the concentrations of 5 alpha-reductase and the cytosol estrophile in the NSS epithelium were 1.58 and 0.43 of the NSS muscle, respectively.     

In situ binding of bouton zinc reversibly disrupts performance on a spatial memory task

Neurons with zinc in the presynaptic vesicles innervate much of the telencephalon, but the functional significance of the vesicular zinc has never been established. The present work shows that reversible binding of zinc by drug infusion into the hippocampus produces a time-locked and selective disruption of hippocampal-dependent spatial-working memory. A role for vesicular zinc in neurotransmission or neuromodulation is implied.     

Assessing dose-response relationships by cumulative exposures in epidemiological studies

BACKGROUND: If the occurrence of disease monotonically increases with the degree of exposure in an epidemiologic study, a dose-response (or exposure-response) relationship is indicated and facilitates the interpretation that the exposure has a causal role. It is not uncommon, however, that there is some effect in terms of an overall increased relative risk but no clear dose-response relationship. METHODS: Models presented here show that cumulative exposure, as involving the duration of exposure, is not an adequate parameter when more recent exposure or the intensity of the exposure plays the greater role for the disease outcome. CONCLUSIONS: In lack of a dose-response pattern by cumulative exposure, the interpretation of an overall increased risk might well be that there is no definite effect. The proper consideration should be, however, that the measure of exposure could be inadequate, suggesting a need for further analyses and evaluations of the material studied.     

Mutations of conserved arginines in the membrane domain of erythroid band 3 lead to a decrease in membrane-associated band 3 and to the phenotype of hereditary spherocytosis

To elucidate the molecular basis of band 3 deficiency in a recently defined subset of patients with autosomal dominant hereditary spherocytosis (HS), we screened band 3 cDNA for single-strand conformation polymorphism (SSCP). In 5 of 17 (29%) unrelated HS subjects with band 3 deficiency, we detected substitutions R760W, R760Q, R808C, and R870W that were all coinherited with the HS phenotype. The involved arginines are highly conserved throughout evolution. To examine whether or not the product of the mutant allele is inserted into the membrane, we studied one HS subject who was doubly heterozygous for the R760Q mutation and the K56E (band 3sMEMPHIS) polymorphism that results in altered electrophoretic mobility of the band 3 Memphis proteolytic fragments. We detected only the band 3MEMPHIS in the erythrocyte membrane indicating that the protein product of the mutant, R760Q, band 3 allele is absent from the red blood cell membrane. These findings suggest that the R760Q substitution, and probably the other arginine subsitutions, produce band 3 deficiency either by precluding incorporation of the mutant protein into the red blood cell membrane or by leading to loss of mutant protein from differentiating erythroid precursors.     

Polymorphonuclear leukocyte heterogeneity in neonates and adults

We have used a mouse monoclonal antibody (31D8) to determine whether differences in neutrophil (PMN) subpopulations might help explain decreased PMN chemotaxis in neonates compared with that of adults. 31D8 has been shown to bind heterogeneously to adult PMNs. Approximately 80% of the PMNs that strongly bind 31D8 (31D8 "bright") are the same cells that depolarize and migrate chemotactically when stimulated with the chemoattractant N-formyl-methionylleucylphenylalanine, while the 20% that weakly bind 31D8 fail to similarly respond. All neonatal PMNs bound 31D8 heterogeneously. There was a smaller population of 31D8 "bright" cells in neonates at birth (76% +/- 6%, n = 45) compared with that of neonates at three to 15 days of age (82% +/- 5%, n = 10, P less than 0.002) and both were smaller than that of adults (88% +/- 4%, n = 45, P less than 0.001 and P less than 0.001). Neonatal cord PMNs, which traversed a micropore filter in a modified Boyden chemotaxis chamber in the presence of a chemoattractant, had an increased percentage of 31D8 "bright" cells (89% +/- 7%) than did PMNs which remained above the filter (82% +/- 7%, n = 10, P = 0.034). PMN chemotaxis was less in neonates at birth (32.7 +/- 4.5 micron) than at three to six days of age (36.8 +/- 11.3 micron) and both were decreased compared with that of adults (69.1 +/- 12.4 micron, P less than 0.001 and P less than 0.001). These findings indicate that decreased PMN chemotaxis in neonates may be due in part to a smaller PMN subpopulation of highly motile cells.     

Spatial arrangements of microfibrils in myocardial scars: application of antibody to fibrillin

Acute myocardial infarction kills myocytes; viable and necrotic myocytes disconnect and the ends of the viable cells become anchored to collagen fibers during reparative scar tissue formation. These anchorages have not been examined in detail, although previous studies have shown that microfibrils (MFs) concentrate at the edges of scars and at the tips of normal papillary muscles. We examined the spatial arrangements of MFs at these two sites in human hearts. Light and electron microscopic observations were made on tissue samples oriented in the long axis of myocytes and stained with monoclonal antibodies to fibrillin, a glycoprotein component of human microfibrils. MFs had identical arrangements at both sites, where they formed fibrous connections between myofibers and collagen fibers. These connections were oriented in the long axis of the muscle cells. At the myocyte ends, MFs appeared to intertwine with MFs in the normal endomysium; in the main body of the connections, MFs formed compact, 200 to 500 nm thick, fibrillin-positive fibers; and at the collagen ends, MFs splayed out among collagen fibrils. These observations indicate that MFs form myofiber-collagen fiber linkages at sites where the power of myocardial contraction is being transmitted to the extracellular connective tissue framework. Formation of such linkages seems to be an important step in the successful repair of necrotic myocardial lesions.