摘要:

AbstractLong‐term exposure to hypertonic (HT) culture media has been found to perturb the cell cycle and change gene expression in various animal cell types. A lower growth rate, with exit of cells from the cycling compartment has been observed previously in human transformed EUE. cells. The aim of this study was to investigate if the kinetic changes after long‐term HT stress, were typical of transformed cells or could be also found in primary cultures of normal cells. Human transformed cells from normal and neoplastic tissues, and normal human cells of epithelial and connective origin have been studied. After the incorporation of bromodeoxyuridine (BrdUrd), the frequency of S‐phase cells was estimated by dual‐parameter flow cytometry of DNA content versus BrdUrd immuno‐labelling; the total growth fraction was also estimated, after immunolabelling with an anti‐PCNA antibody. We also investigated, by polyacrylamide gel electrophoresis, changes in the amount of a 35 kDa protien band, which increased in EUE cells grown in an HT medium, and which may be directly involved in cell resistance to hypertonicity. Lower BrdUrd labelling indices and higher frequencies of cells in the G0/1range of DNA content were common features of all the cells in HT media, irrespective of their tissue of origin; other cycle phases may also be involved, depending on the cell type considered. The mechanisms by which cells cope with the HT environment could however, differ, since only some cell types showed an increase of the 35 kDa stress protein found originally in H

ISSN:0263-6484    

DOI:10.1002/cbf.290130103

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractAlthough vanadium is found abundantly in animal and plant kingdoms its biological effects are not clear. Vanadate compounds have been shown to normalize blood glucose levels in streptozotocin treated rats, enhance glucose oxidation and improve the sensitivity to insulin by enhanced receptor binding in rat adipocytes. The aim of the present study was to investigate the effect of vanadate, at high (0–8 mmol l−1) and low (0–1·0 mmol l−1) physiological concentrations, on [125I]‐insulin binding in the placenta of three groups of pateints, namely from normal (N) controls, gestational diabetics (GDM) and women with risk factors in their medical history for developing diabetes mellitus (RF). Vanadate at low concentrations (0·2–0·6 mmol l−1) enhanced the maximal binding 2‐fold in GDM placenta but only increased (up to 1·2‐fold) the binding slightly at high cncentrations (5 mmol l−1). However with placenta from normal or women at risk, vanadate increased the [125I]‐insulin binding up to 1·2‐fold both at low and high concentrations. Thus it appears that vanadate augements insulin binding in the placenta from women with g

ISSN:0263-6484    

DOI:10.1002/cbf.290130104

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractSome synthetic peptides increased the luminol‐dependent chemiluminescence of mouse blood during phagocytosis. It is suggested that the levels of antimicrobial activity of the neutrophil peroxidase system can be raised very quickly (within some dozen of seconds) by these peptides. This raises the possibility of finding a new approach to the therapy for infectious disease

ISSN:0263-6484    

DOI:10.1002/cbf.290130105

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractSoluble phospholipase A2activity was characterized in two human monocytic cell lines, U937 and Mono Mac 6. The enzyme showed an absolute requirement for Ca++, an alkaline pH optimum and Michaelis‐Menten kinetics in both cell lines. Differentiation of U937 and Mono Mac 6 cells with 1,25 (OH)2vitamin D3(10 nM, 72 h) enhanced PLA2activity by 82 per cent and 56 per cent, respectively. Furthermore, kinetic experiments revealed that enzyme activity increased within 3 h when cells were brought from the nonproliferative phase of growth to the start of a new cycle of cell proliferation. This initial activation of PLA2could be inhibited by cycloheximide and actinomycin D, indicating the requirement of gene transcription. Taken together, these results suggest a role of cytosolic, Ca++‐dependent PLA2in differentiation and growth of monocytic ce

ISSN:0263-6484    

DOI:10.1002/cbf.290130106

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractGuinea pig peritoneal macrophages have on their surface two receptors, one (Fcγ1/γ2R) binding both guinea pig IgG1 and IgG2 and the second (Fcγ2R) binding only IgG2 immunoglobulins. We have previously shown that treatment of macrophages with neuraminidase or glycosylation inhibitors affects, in a different way, the binding of guinea pig IgG1, IgG2, and rabbit IgG. In the present study we have shown that pretreatment of guinea pig macrophages with lectins (Con A, WGA, and PNA) also has a different effect on the interaction of the cells with IgG. The lectins increased the binding of guinea pig IgG1, whereas rabbit IgG and guinea pig IgG2 were bound with a lower efficiency than in the case of control cells. Since sialic acid residues seem to modulate the activity of receptors and WGA interacts with sialylated oligosaccharides, we determined the IgG‐binding characteristics for WGA‐pretreated macrophages. We found that the increase in IgG1‐binding ability was caused by an increase in the value ofKapp, but the number of IgG‐binding sites was lower than in the control cells. In the case of rabbit IgG and guinea pig IgG2 we observed a decrease of both the value ofKappand the number of IgG‐binding sites. WGA did not interact directly with the Fcγ receptor. The results of our former papers and the different effects of lectins of various specificities described in this paper suggest different positions of Fcγ1/γ2and Fcγ2R in the plane of the plane of the macrophage membrane in respect to various membrane glycoconjugates. Interaction of IgG with macrophage Fcγ receptors depends in a different way on glycoconjugates on the surface of the macrophage. Our results suggest that changes in glycosylation of macrophage surface glycoconjugates may be used by the cell for regulating the binding activities of the macroph

ISSN:0263-6484    

DOI:10.1002/cbf.290130107

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractGranules containing acid hydrolases have been detected in human platelets but have not been thoroughly characterized.We have studied the activity and characteristics of glycohydrolases present in normal human platelets, evaluated their release upon stimulation with thrombin, and assessed the contribution of platelet ‐ released lysosomal contents to the glycohydrolase activity present in normal serum. Platelets contained a remarkable glycohydrolase activity with a prevalence of β ‐N‐acetylhexosaminidase. All glycohydrolases were released to some extent upon stimulation with thrombin and contributed to the glycohydrolase activity found in human serum. α‐Mannosidase and α‐galactosidase were partially inactivated after release by a mechanism as yet undefined. In addition, thrombin stimulation affects the intraplatelet isoenzyme pattern of β‐N‐acetylhexosaminidase by producing the appeara

ISSN:0263-6484    

DOI:10.1002/cbf.290130108

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractSeveral studies indicate that the cytoskeleton may be involved in modulating the cellular response to environmental signals. We have studied the role of the cytoskeleton in regulating glycosaminoglycan (GAG) synthesis and secretion, hyaluronate (HA) endocytosis, the activities of hexoglycosidases, protein synthesis and secretion. Fibroblasts were treated with colchicine (1–8 μM) and nocodazole (1 or 4 μM) to alter microtubules or cytochalasin B (0·5–4 μM) to alter microfilaments. Colchicine inhibited GAG synthesis and secretion in a concentration‐dependent manner. It reduced protein and sulphated GAG secretion, while HA secretion was not affected. Concentration‐dependent disruption of microtubules from the periphery toward the cellular centre with nocodazole inhibited only the secretion of GAG. Centrosomal microtubles appeared to be required to promote GAG synthesis; intact microtubules promoted the transport of secretory products, intercompatmental transport of lysosomal enzymes and lysosome maturation, but not protein synthesis and HA secretion. Cytochalasin B treatment inhibited, in a concentration‐dependent manner, the synthesis and secretion of GAGs and proteins, and the endocytosis of HA. Intact microfilament mesh‐works appeared to be required to promote synthesis and secretion of proteins and proteoglycans and to contribute to the transmembrane control of receptor‐mediated endocytosis. Drug treatment of concanvalin A (Con A)‐stimulated fibroblasts inhibited the stimulation of GAG synthesis. It is probable that this effect may result, in part, from drug‐induced effects on Con A

ISSN:0263-6484    

DOI:10.1002/cbf.290130109

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe effect of citrinin on Ca2+transport was studied in isolated kidney cortex and liver mitochondria, and baby hamster kidney cultured cells. The mycotoxin significantly inhibited the activity of 2‐oxoglutarate and pyruvate dehydrogenases in both kidney cortex and liver mitochondria. Citrinin promoted a decrease in the velocity and in the total capacity of Ca2+uptake, in both mitochondria. Apparently, citrinin acts by a mechanism similar to ruthenium red. In intact cultured cells, citrinin also had a preferential effect on mitochondrial Ca2+fluxes. Citrinin promoted a marked decrease in the Ca2+level in the mitochondrial matrix, whereas that of the extramitochondiral fraction became less affected. All the observed effects were dependent on the citrinin concentratio

ISSN:0263-6484    

DOI:10.1002/cbf.290130110

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractLower concentrations of choline chloride and ethanolamine (10−3M; 10−5M) increased phosphatidyl inositol (PI), phosphatidyl inositol monophosphate (PIP) and phosphatidyl inositol bisphosphate (PIP2) level ofTetrahymena, while higher concentrations (10−2M) decreased them. These two substances also influenced, however in a less obvious way, the transformation of inositol phospholipids. The experiments draw attention to the sensitivity of the precursors of the second messenger system at a phylogenetically low

ISSN:0263-6484    

DOI:10.1002/cbf.290130111

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe mechanism by which all‐trans retinoic acid (RA) stimulates gap junctional intercellular communication (GJIC) in the rat liver epithelial cell line. IAR203, was investigated. When RA, at 0·1 μMfor 24–48 h, enhanced the dye transfer in IAR203 cells (× 1·4), it increased the amount of connexin43 (Cx43) in the cell–cell contact regions of the plasma membrane, as evidenced by analysis by Western blot and by immunofluorescence. It had no effect on the level of Cx43 mRNA. Freeze‐fracture analysis of the size of gap junctions revealed an increase of the proportion of small gap junctions in RA‐treated cells. We conclude that, in IAR203 cells, RA stimulates GJIC by acting at the post‐tran‐scriptional level of Cx43 regulation. The possibility that RA acts indirectly on the regulation of Cx43 expression, and increases the helf‐life of Cx43 by inducing adhesion mol

ISSN:0263-6484    

DOI:10.1002/cbf.290130112

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY