摘要:

AbstractExperiments have been carried out on the capping by lectins and antibodies of surface receptors of mouse splenic T and B lymphocytes and other cells, in which the surface distribution of the lectin or antibody, and the intracellular distribution of myosin or actin, were determined on the same cells by a double fluorescence technique. For this purpose, a general method for intracellular staining was developed which is intended to preserve sensitive antigens and fragile ultrastructural elements. The method involves mild formaldehyde fixation of the cells or tissues, infusion with concentrated sucrose, rapid freezing, and the preparation of frozen sections thinner than 2 μm thickness. The immunofluorescent or other appropriate fluorescent reagents are then applied to the thawed section. In the present experiments, intracellular actin was detected using a fluorescent staining method based on the interaction of F‐actin with heavy meromyosin, while intracellular myosin was detected by an indirect immunofluorescence procedure. Our findings were that the formation of a cap by each of the lectins or antibody reagents was always accompanied by a concentration of myosin and actin directly under the cap. These and other results suggest that capping is an active process in which actin and myosin participate directly in the formation ofallcaps. This proposal carries important new implications for the molecular mechanism of cappi

ISSN:0021-9541    

DOI:10.1002/jcp.1040950302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractThe mammary cells in virgin mice are essentially non‐proliferative, but they can be induced to undergo DNA synthesis in vitro in the presence of insulin. Time course studies on polyamine biosynthesis and DNA synthesis showed that insulin elicits sequential stimulation of the activity of the polyamine biosynthetic enzymes, ornithine decarboxylase, S‐adenosyl‐L‐methionine decarboxylase (SAMDC) and spermidine synthase, and an increase in the concentration of spermidine prior to the augmentation of DNA synthesis. At 48 to 72 hours of culture when DNA synthesis is maximal, the concentration of spermidine increased 2− to 3‐fold, whereas the level of spermine remained unchanged. Addition of methyl glyoxal bis(guanylhydrazone) (5—10 μM), a potent inhibitor of SAMDC, to the medium at the onset of culture resulted in inhibition of spermidine formation and DNA synthesis, but when added at 24 hours or 48 hours of culture, the inhibitory effect on DNA synthesis was greatly reduced. The drug, however, produced little inhibition of RNA and protein synthesis. Inhibition of DNA synthesis by the drug can be reversed by addition of spermidine or other polyamines such as putrescine, cadaverine and spermine to the culture. Spermidine is, however, the only polyamine that is effective at physiological concentrations (100∼150 pmoles/mg tissue). These results suggest a possibility that spermidine may play a key role in the regulation of mammary ce

ISSN:0021-9541    

DOI:10.1002/jcp.1040950303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractThe enzymatic activity of five acid hydrolases: acid phosphatase, arylsulfatase A, deoxyribonuclease, β‐glucuronidase, and cathepsin D, was assayed in fetal (fifteenth and eighteenth days of pregnancy) and neonatal (Days 0, 5, 10, and 15post‐partum) mouse liver. With the exception of cathepsin D, the activity increased around birth to levels varying according to the enzyme. Histochemical observations of other authors appear to justify, at least in part, the present results, which indicate that late days of fetal development and early neonatal life may constitute a transitional stage to full lysosomal enzyme functionality of the adult organThe livers of the mothers were also assayed for the same enzymes. Each activity showed a peculiar pattern which was, in turn, different from that found in the liver of the litter for the same enzyme, probably as a cause of the metabolic requirement of the glandThe hypothesis that the lysosomes are heterogeneous in their enzyme composition is suggested by the variety of enzymatic patterns found in the liver of the litters and their mot

ISSN:0021-9541    

DOI:10.1002/jcp.1040950304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractThe relationship between plasminogen activator levels and the expression of the transformed phenotype was studied in a 5‐bromodeoxyuridine (BrdUrd) dependent mutant of Syrian hamster melanoma cells. In terms of cell morphology and cellular interactions, the BrdUrd dependent cells resemble transformed cells when grown in the presence of BrdUrd but resemble untransformed cells when grown in the absence of BrdUrd. It was found that the BrdUrd dependent cells release significant levels of plasminogen activator only when cultured in the absence of BrdUrd. In the presence of BrdUrd, the release of plasminogen activator by the dependent cells is suppressed, and the decreased level of plasminogen activator released in the presence of BrdUrd seems to be due to decreased production of active enzyme. Growth tests revealed that the BrdUrd dependent cells, when attached to a substrate, required BrdUrd in order to attain high densities. Furthermore, the cells are able to grow well in soft agar only in the presence of BrdUrd. These results suggest that the production and release of high levels of plasminogen activator are not related (either as cause or effect) to the expression of the transformed phenotype in the BrdUrd dependent cellsThe effect of dog serum (as a plasminogen source) on the BrdUrd dependent cells also was tested. It was found that cells cultured in medium containing dog serum exhibit a morphological alteration, but only in the absence of BrdUrd. The morphological response of the cells to dog serum resembles that previously observed with virus‐transformed cells. In the BrdUrd dependent cells, the morphological response to dog serum appears correlated with the release of plasminogen activator but separated from other transformed characterist

ISSN:0021-9541    

DOI:10.1002/jcp.1040950305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractThe potent tumor promoter tetradecanoyl phorbol acetate (TPA) induces early changes in ion movements analogous to those induced by prostaglandins E1and F2α. Among the earliest changes induced by TPA is a significant increase in32Piincorporation within 15 minutes incubation of TPA (10−8−10−6M) with post‐confluent Swiss 3T3 mouse embryonic fibroblasts. Similarly, the active phorbol ester homolog 4‐;β‐;OH phorbol didecanoate but not the inactive stereoisomeric 4‐β‐OH phorbol didecanoate stimulated32Piincorporation. Also, TPA at the above concentrations stimulated86Rb+influx shortly after administration. Both fluxes were ouabain‐sensitive in accord with the idea that an early effect of TPA is to alter (Na++ K+)−ATPase activity. Further, prostaglandin E1(10−7−10−6M) and prostaglandin F2α(3 × 10−9−10−7M) caused a similar stimulation of86Rb+and32Piuptake. The finding that water‐soluble prostaglandin F2αalso exhibited stimulatory effects indicated that those hormone‐induced responses are not mediated by solvent interactions. The similar responses of phorbol esters and prostaglandin derivatives suggests that phorbol esters and prostaglandin derivatives may act at common membrane sitesThe finding that stimulatory effects were observed at discrete times in the logarithmic phase of growth suggests that the activation of membr

ISSN:0021-9541    

DOI:10.1002/jcp.1040950306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractTemperature‐sensitive Chinese hamster cells (K12) have been shown to be defective for the initiation of new rounds of DNA replication when incubated at the restrictive temperature (40.5°). By temperature shift experiments with synchronous cultures, we have marked out the step at which the mutation is expressed as the four hours preceding the initiation of DNa synthesis. The block imposed by the mutation has been shown to be irreversible. In order to approach the biochemical characterization of the temperature‐sensitive function in K12 cells, we have analyzed the cellular proteins synthesized under permissive (35°) and restrictive temperatures. The synthesis of three polypeptides is markedly enhanced when K12 cells are incubated at 40.5°. One of them (band B) has turned out to be a useful biochemical marker of the expression of K12 mutation since its synthesis is not affected in otherts‐mutants or in hybrids in which K12 mutation is complemented. In addition, the alteration in band B synthesis is irreversible and occurs during the same stage of the cell cycle at which the mutated function is e

ISSN:0021-9541    

DOI:10.1002/jcp.1040950307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractTreatment of Friend leukemia cells with BrdU, the thymidine analog which interferes with DMSO induced differentiation in these cells as well as the expression of differentiated character in many other cell systems, is capable of inducing erythroid differentiation. Globin mRNA, as assayed by hybridization to globin cDNA, increases 2.5− to 30−fold after appropriate treatment with BrdU. This effect was observed with several different subclones of three independent Friend tumor cell lines. After BrdU treatment, globin mRNA content may reach up to 10—20% of the levels in DMSO induced cultures. The induction of erythroid differentiation is also apparent when accumulated heme content or the appearance of benzidine positive cells is monitoredOne Friend cell line (745) we examined was not induced by BrdU although it incorporated an amount of BrdU into its DNA comparable to that incorporated by the other cell lines. In addition, BrdUdidinterfere with DMSO induction in this cell lineThese results suggest that two different mechanisms may be operative in regulating erythroid differentiation in Friend leukemia cells. While BrdU interferes with the mechanism activated by DMSO treatment, this analog could independently activate an alternative mech

ISSN:0021-9541    

DOI:10.1002/jcp.1040950308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractRed blood cells of rat exhibit an enhanced hypertonic calcium uptake after incubation with diazenedicarboxylic acids bis (N,N‐dimethylamide) (diamide). Over the ranges reported in this paper the amount of membrane alteration is strongly and linearly dependent on the diamide concentration and on the osmolarity of the incubation medium. Treatment with 2,3‐dihydroxy‐1,4‐dithiolbutane (dithioerythritol or DTE), after diamide removal, restores red blood cells calcium intake to values similar to those of the control. The results indicate that the sinergic action of diamide and hypertonicity can oxidize some thiol groups essential for the cation barrier main

ISSN:0021-9541    

DOI:10.1002/jcp.1040950309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractThe changes in rate of protein synthesis and cell division and the distribution of polyribosomes and globin mRNA on the polyribosomes of Friend erythroleukemia (FL) cells exposed to 2% DMSO and maintained at low cell density, were examined at different times after exposure to DMSO. The rate of protein synthesis and the capacity of cells to divide declined in concert to 50% of the level found in untreated cell cultures at 24 hours after exposure. Thereafter these rates recovered to 70% of the rate found in untreated control cultures until 96 hours post‐exposure and then irreversibly declined as the cells lost the capacity to divide. The proportion of ribosomes present as polyribosomes in cells exposed to DMSO paralleled the capacity of these cells to synthesize protein. The distribution of polyribosomes analyzed by sedimentation in sucrose gradients demonstrated that a discrete, abundant class of polyribosomes composed of pentamers to heptamers appeared as early as 48 hours after exposure to DMSO. The appearance of an abundant class of polyribosomes was correlated with globin synthesis be demonstrating that a discrete class of polyribosomes arises in cells treated with the inducers hexamethylene bisacetamide and hemi

ISSN:0021-9541    

DOI:10.1002/jcp.1040950310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractThe object of this study was to develop a map of G1 phase on the basis of the progressive changes taking place in the morphology of the prematurely condensed chromosomes as the cells traverse through G1 and then use this technique to determine the cell cycle location of normal and transformed cell populations in plateau phase. The morphology of the prematurely condensed chromosomes (PCC) of G1 cells in random populations was found to be highly variable. For a better understanding of the relationship between the morphology of the G1‐PCC and their position within G1 phase, synchronized populations of Chinese hamster ovary (CHO) cells in early, mid‐, and late G1 phase were fused with mitotic cells. Early G1 cells resulted in highly condensed G1‐PCC, while late G1 cells gave very extended G1‐PCC. Mid‐G1 cells resulted in PCC of intermediate condensation. To test the validity of these criteria for mapping the position of a cell in the cell cycle, synchronous G1 cell populations were treated with a variety of metabolic inhibitors. Cycloheximide and actinomycin D were shown to block cell in early G1 phase, while excess thymidine and hydroxyurea blocked cells in early S phase. The results presented here indicate that, upon reaching plateau phase, normal cell populations (BALB‐C mouse 3T3, human PA‐2, and WI 38) stop in early G1, while most cells in transformed cell lines (CHO, HeLa, and mouse SV‐3T3) accumu

ISSN:0021-9541    

DOI:10.1002/jcp.1040950311

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY