摘要:

AbstractWe have found that cation transport in red cells from chick embryos is stimulated by the hormone epinephrine and that this response develops as the embryonic definitive cells mature. Sodium efflux and potassium influx are significantly stimulated (50%) by epinephrine in red cells from embryos incubated ten days or longer, whereas cation fluxes in erythroid cells from 8‐ or 9‐day embryos are stimulated little or not at all.The effect of epinephrine may be mediated by cyclic AMP as adenylate cyclase activity in membranes isolated from embryonic red cells is only slightly stimulated at nine days, but the response increases as the cells mature to a maximum of about 180%. Also the stimulation of cation transport by epinephrine is blocked by propranolol, but not by phentolamine. Although the younger cells respond poorly to epinephrine, cyclic AMP significantly stimulates transport.The enhancement of cation fluxes by epinephrine or cyclic AMP occurs even in the presence of ouabain. Since both K influx and Na efflux are enhanced by these agents, their action is most likely on some form of the “Na‐K” pump which is not ouabain sensitive resulting in a significant increase in the maximum velocity of the pump. We suggest the hypothesis that there are two classes of “Na‐K” pump in these embryonic cells. One pump is similar to that found in many erythrocytes including mammalian cells in that it selectively pumps potassium in and sodium out, is ouabain‐sensitive, and is primarily involved in maintaining intracellular cation concentrations. The second pump is enhanced by epinephrineviacyclic AMP, is not inhibited by ouabain, and may have lower ion selectivity. This hormone sensitive pump activity is lost as the cells mature, a process which is completed when the animal is fully grown and no longer has significant numbers of embryonic cells i

ISSN:0021-9541    

DOI:10.1002/jcp.1040940102

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe rates of3H‐thymidine incorporation and of cell proliferation in chick embryo fibroblast cultures are reduced coordinately when the [Mg2+] of the external medium is reduced below the physiological concentration of about 0.8 mM. These effects of moderately reduced [Mg2+] and the accompanying change in appearance of the cells, resemble the effects produced by lowering the [serum]of the medium. Cells subjected to severe Mg2+deprivation, especially at low [Ca2+], die and detach from the culture dish. Cells kept at a reduced rate of proliferation for three days by moderate Mg2+deprivation are quickly restored to rapid proliferation upon restoration of the normal [Mg2+] of the medium. The rate of proliferation of the chick embryo cells is reduced markedly by lowering [Ca2+] about 100‐fold, but unlike the case of Mg2+‐deprivation this can occur without significant effect on the rate of3H‐thymidine incorporation. More severe Ca2+deprivation, which does lower the rate of3H‐thymidine incorporation, produces retraction of cells from one another and from the dish, and results in a distinctly abnormal, rounded appearance. The results lend weight to the thesis that free [Mg2+] plays a central role within the cell in the coordinate control of metabolism and growth. They also suggest that the effects produced by varying [Ca2+] in the medium are caused by changes at the external surface of

ISSN:0021-9541    

DOI:10.1002/jcp.1040940103

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

年代:1978

数据来源: WILEY

摘要:

AbstractIn vitro induction of myelopoetic colonies from mouse bone marrow has been used for measurement of leucopoetic colony stimulating activity (CSA) isolated from large batches of human urine. After high flow dialysis in artificial kidneys and immediate adsorption to DEAE‐Cellulose, followed by purification on Con A‐Sepharose, treatment with insoluble Papain and gelfiltration on Sephadex G 100, enrichment of CSA was about 6,000‐fold. An important step of the enrichment procedure was the separation from a CSA‐inhibiting protein, probably combining with CSA.Specific activity was further increased by preparative polyacrylamide gel electrophoresis to 5.3 × 106units per mg protein. The total enrichment exceeded 25,000‐fold.The final purification product consisted of a group of closely related proteins with high specific activity.Antisera raised with one of the electrophoretic fractions suppressed bioactivity in each of the different purification steps including the final CSA fractions differing in electrophoretic mobility. The antisera furthermore inhibited CSA in human lung and monocyte conditioned media but had only very little effect on partially purified CSA from stimulated human lymphocytes as well as CSA derived from mouse lung conditio

ISSN:0021-9541    

DOI:10.1002/jcp.1040940104

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

年代:1978

数据来源: WILEY

摘要:

AbstractDuring the breeding season from January to June, female wallabies which are suckling a young animal in the pouch may carry a dormant embryo (lactational quiescence). Removal of the pouch young during this period results in a resumption of embryo development. In the latter half of the year, the embryo will not reactivate after removing the suckling young (seasonal quiescence). In this situation, development resumes spontaneously in late December or may be induced prematurely by progesterone treatment. The response of the genome of quiescent macropod blastocysts was studied during the early period of growth. Changes in the transcriptional activity of the embryo cells were measured by assay for endogenous RNA polymerases. Embryos actively synthesized RNA during both lactational and seasonal quiescence. Termination of seasonal quiescence resulted in increases in RNA polymerase activities within the nucleolus and nucleoplasm of the cell. This occurred on the day following the summer solstice, December 22, 1974, in animals captured in the wild, or within 48 hours of administration of progesterone. Embryos which were induced to resume development during the breeding season also showed increases in nucleolar and nucleo‐plasmic polymerase activities within five days of removal of suckling young from the pouch. In all situations, the response of the nucleolar enzymes was greater than that of the nucleoplasmic enzymes. This is in agreement with other observations of the regulation of gene activity in growth‐stimulated ce

ISSN:0021-9541    

DOI:10.1002/jcp.1040940105

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

年代:1978

数据来源: WILEY

摘要:

AbstractUltra‐microfluorometric techniques were adapted to follow several compounds related to energy metabolism through the developmental cycle ofDictyostelium discoideum. Each compound (ATP, trehalose, glucose, and ammonium ion) was found to be present in stalk and/or spore cells. The accumulation of NH4+ was interpreted as an indication of protein degradation, a source of energy in this organism. During the early stages of differentiation NH4+was localized only in prestalk cells. However, it accumulated in spore cells during culmination such that levels were comparable in the two cells types by the end of development. Trehalose, an energy source for germinating spores, was found in both cell types but was preferentially degraded in stalk cells late in development. Glucose, the degradation product of trehalose, was localized in prestalk cells and varied inversely with trehalose levels. ATP was not localized in a specific cell type during development. However, ATP declined in stalk cells at an earlier stage of developmen

ISSN:0021-9541    

DOI:10.1002/jcp.1040940106

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

年代:1978

数据来源: WILEY

摘要:

AbstractAntisera to mouse brain reacts with hematopoietic stem cells in the mouse bone marrow. We have examined the effect of anti‐mouse brain serum (AMBS) on the development of in vitro colonies from mouse bone marrow cells. The addition of 5% AMBS to the cultures markedly decreased the numbers of colonies formed to an average of 10% of the number obtained with normal rabbit serum. AMBS suppressed formation induced by colony stimulating factors (CSF) derived from three different sources; serum from endotoxin treated mice, mouse L‐cell conditioned media, and human peripheral blood mononuclear cell conditioned media. The suppressive activity was quantitatively recovered in the IgG fraction of AMBS. Divalent F (ab′)AHBS, rabbit anti‐human brain serum; AMBS, rabbit anti‐mouse brain serum; BM, bone marrow; CFU‐C, colony forming unit in vitro; CFU‐S, spleen colony forming unit; CSF, colony stimulating factor; FCS, fetal calf serum; MEM, minimal essential medium; NRS, normal rabbit serum; PBS, 0.01 M sodium phosphate, 0.15 M sodium chloride, pH 7.4.fragments were as effective as the intact IgG in decreasing colony formation. Fab fragments were not suppressive. These results suggest that colony formation is induced via a dynamic interaction between CSF and the progenitor cell membrane, and that antibody directed at cell membrane antigen(s) interferes with the generation of the ind

ISSN:0021-9541    

DOI:10.1002/jcp.1040940107

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

年代:1978

数据来源: WILEY

摘要:

AbstractElevated concentrations of cyclic AMP elicit only minor reductions in growth rate and saturation density in undifferentiated Friend erythroleukemic cells. During the course of dimethylsulfoxide (DMSO)‐induced differentiation, Friend cells convert from a cyclic AMP‐tolerant state to a phenotype characterized by a high degree of sensitivity to cyclic AMP‐mediated growth arrest.Conversion to cyclic AMP sensitivity is detectable after 30 hours growth in medium containing 2% DMSO, and either 0.5 mM 8‐Br‐cyclic AMP or 5 nM cholera toxin. Cultures of differentiating Friend cells achieved a stationary phase density that was approximately 8‐fold higher than the cell density observed in parallel, differentiating cultures treated with 0.5 mM 8‐Br‐cyclic AMP. Temporally, the appearance of cyclic AMP‐sensitivity corresponds to the early expression of in vitro erythroid differentiation (Ross et al., ′74), but growth arrest does not alter the subsequent accumulation of hemoglobin in non‐dividing DMSO‐induced cells. Since growth arrest is preceded by a round of cell division, these observations are consistent with the concept that DMSO must be present during DNA replication for the subsequent expression of hemoglobin synthesis (McClintock and Papaconstantinou, ′74; Levy et

ISSN:0021-9541    

DOI:10.1002/jcp.1040940108

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe reverse transformation reaction of Chinese hamster ovary cells from compact, epithelial‐like, randomly growing, heavily knobbed, lectin reactive cells into stretched, tighly adherent, smooth‐surfaced, lectin resistant, fibroblast‐like cells normally elicited by dibutyryl cAMP can be produced to its complete extent by N6‐monobutyryl cAMP or 8‐bromo‐cAMP. O2‐monobutyryl cAMP is ineffective as is cAMP itself in the absence of an inhibitor of phosphodiesterase activity. In the presence of a phosphodiesterase inhibitor, cAMP is fully effective. These results indicate that the role of the butyryl groups of dibutyryl cAMP and, especially, the N6‐butyryl, in the reverse transformation raction is protection of the cAMP analogue from degradation.Butyrate at concentrations of about 1 mM does produce a response which to some extent mimics that of cAMP analogues. The cells, however, fail to assume a fibroblastic‐like shape, but rather become flattened. The butyrate effect is much slower and less readily reversible than that evoked by cAMP analogues. Butyrate produces an approximately 2‐fold increase in intracellular cAMP levels. These results are consistent with the hypothesis that butyrate effects, in part, a

ISSN:0021-9541    

DOI:10.1002/jcp.1040940109

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

年代:1978

数据来源: WILEY

摘要:

AbstractRat embryo fibroblasts, grown in Eagle's MEM with 10% serum, showed a rapid increase in autophagic vacuoles when placed in MEM with 0–1% serum. Concurrent with this response, degradation of cellular proteins showed a 2‐fold increase. We did not find any increases in cathepsin D, β‐glucuronidase, β‐galactosidase, and β‐glucosidase, or proteolytic activity of cell homogenates at pH 3.7 towards endogenous substrates. Homogenates prepared in 250 mM sucrose at pH 7.0 showed a 40% increase in protein breakdown. These data support the hypothesis that the induced increase in proteolysis, characteristic of cells placed in a nutritionally deficient medium, is effected by an activated vacuolar apparatus (lysosomes and autophagic vacuoles). We suggest, however, that this mechanism is distinct from normal protein turnover in the cell, but can be rapidly induced by appropriate alterations in the cellular environment. Finally, this induced proteolytic mechanism is not dependent upon an increase in lysosomal enzymes, but rather a structural alteration within the cell which effects a transfer of cellular proteins into the vacuol

ISSN:0021-9541    

DOI:10.1002/jcp.1040940110

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

年代:1978

数据来源: WILEY

摘要:

AbstractThere is a marked increase in the concentration of putrescine during the first ten hours following partial hepatectomy in rats. The concentration of spermidine also increases but to a smaller degree. Putrescine levels return to normal between 10 and 24 hours after the operation, whereas the increased spermidine level is maintained. The production of putrescine and spermidine appears to be initiated by the induction of ornithine decarboxylase which shows a single peak of activity at four hours after hepatectomy. The activity of S‐adenosylmethionine decarboxylase shows little change following hepatectomy. The changes in polyamine levels and the activities of the enzymes of polyamine metabolism are not affected by thyroparathyroidectomy 72 hours prior to hepatectomy. Thus although these hypocalcemic conditions considerably reduce and delay DNA synthesis and mitosis, the prereplicative changes in polyamine metabolism still occur. These data suggest that the hepatocytes in hypocalcemic animals have become activated and moved to an advanced stage of prereplicative development before being blocke

ISSN:0021-9541    

DOI:10.1002/jcp.1040940111

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

年代:1978

数据来源: WILEY