摘要:

AbstractDialyzed serum albumin had considerable growth‐promoting effect on cultivated hamster cells. This effect was virtually lost on removal of the fatty acids, and it was completely restored by recombination of the fatty acid‐free albumin with the isolated and purified fatty acids.The role of albumin itself appeared to be largely that of a carrier of fatty acids, protecting the cells against toxic effects of fatty acids in free solution. This conclusion was based on two observations: Fatty acids in the absence of albumin were growth‐inhibitory except in extremely dilute solutions, and betalactoglobulin, a protein possessing, like albumin, the ability to bind and release fatty acids, could replace albumin in the presence of fatty acids with similar growth‐promoting effect.Examination of individual molecular types of fatty acids showed that all unsaturated acids tested were growth‐promoting, whereas the saturated acids were growth‐inhibiting, with the exception of stearic acid in low concentrations.Although the possibility of a mitotic triggering effect was not excluded, the fatty acids presumably stimulated growth by providing substrate for cellular metabolism, since there was a direct relationship between the degree of growth stimulation and the duration of exposure of cells to the

ISSN:0021-9541    

DOI:10.1002/jcp.1040960102

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

年代:1978

数据来源: WILEY

摘要:

AbstractTwo cell cycle‐specific temperature sensitive (ts) mutants of mammalian cell lines, AF8 and K12, are known to arrest in G1when shifted to the non‐permissive temperature. We have determined the entry into S of both AF8 and K12 cells in five different growth conditions, namely: (1) quiescent sparse cultures stimulated to proliferate by serum; (2) quiescent dense cultures stimulated by serum; (3) quiescent sparse cultures stimulated by trypsinization and replating; (4) quiescent, dense cultures stimulated by trypsinization and replating; and (5) mitotic cells collected by mitotic detachment. In addition, for each cell line and for each different growth condition, we have determined the shift‐up time, i.e., the time at which a shift‐up to the nonpermissive temperature no longer prevents the entry of cells into S. In no case did K12 or AF8 enter S at the nonpermissive temperature. At the permissive temperature, the average time of entry into S varied in different growth conditions, and so did the shift‐up time. However, in both cell lines, the distance of the average shift‐up time from the average time of entry into S was remarkably constant, regardless of the growth conditions, i.e., 1.8 hours in K12 and 8.6 h

ISSN:0021-9541    

DOI:10.1002/jcp.1040960103

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

年代:1978

数据来源: WILEY

摘要:

AbstractAdministration of radioactively labeled galactose to cultured mammalian cells brings about an accumulation of metabolic products the pattern of which seems to be governed by a variety of vectors in the intracellular milieu. By manipulation of culture conditions some of these vectors appear to be a function of glycolysis. In the non‐glycolytic culture, label from a galactose probe appears as Galactose‐1‐phosphate (Gal‐1‐P) and UDPglucuronic acid (UDPGlcUA). Conversely, glycolytic culture conditions seem not to permit the formation to UDPGlcUA since the only labeled accumulation product formed was UDPHex. A suggestion is made that the difference in metabolic activity of glucose‐fed and glucose‐starved cultures may be related to the effect of NADH on the in situ activity of UDPG dehydrogenase (UDPglucose:NAD oxidoreductase, E.C. 1.1.1.22) (abbreviation, UDPG‐DH). This prompted an investigation of the effects of NAD and NADH on the activity of partially purified UDPG‐DH. The results of these experiments strongly suggest that the activity of UDPG‐DH (in situ) is negatively controlled by increased levels of NADH; the latter condition is known to exist in glycolytically active cells (Schwartz and Johnson, 1976). Added to this is a second control mechanism which is characterized by a transient inhibition of uridylyltransferase (UDP glucose:α‐D‐galactose‐1‐phosphate uridylyltransferase, E.C. 2.7.7.12). Since it is known that there is little, if any, effect on galactokinase (ATP:D‐galactose‐1‐phosphotransferase, E.C. 2.7.1.6) activity as a result of sugar starvation (Christopher et al., 1976), the low in vivo activity of uridylyltransferase contributes not only to the increased accumulation of Gal‐1‐P but also to a drastic decrease of labeled UDPhexoses, although the pre‐existing pool of UDPhexose was found to decrease only moderately under the condition of glucose starvation (30% still persisted). The bene

ISSN:0021-9541    

DOI:10.1002/jcp.1040960104

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

年代:1978

数据来源: WILEY

摘要:

AbstractPokeweed mitogen‐stimulated suspension cultures of mouse spleen cells produced conditioned medium able to stimulate granulocyte‐macrophage, eosinophil and megakaryocyte colony formation in agar cultures of C57BL marrow cells and granulocyte‐macrophage and erythroid colony formation in agar cultures of CBA fetal liver cells. Medium conditioned by other mouse tissues stimulated only granulocyte‐macrophage colony formation and this activity was not increased by the addition of pokeweed mitogen. Spleen cells stimulated by mixed leucocyte culture or concanavalin‐A had a weak capacity to stimulate erythroid colony formation.Production of the factors stimulating the four types of hemopoiesis was T‐lymphocyte dependent and nu/nu spleen cells were inactive. Factor production was also dependent on adherent cells but evidence from rat‐mouse combinations suggested that the T‐lymphocytes actually produced the active factors.Production of the four types of colony stimulating factors was radiosensitive (D0120–238 rads) and spleen cell populations of lighter buoyant density than 1.075 g/cm3and sedimenting at 3.5–5.0 mm/hour were able to produce active conditioned media. Fractionation experiments failed to segregate spleen populations able to produce only one of the four stimulating factors.Production of factors stimulating hemopoiesis by mitogen‐stimulated lymphoid populations could be a process contributing to the control o

ISSN:0021-9541    

DOI:10.1002/jcp.1040960105

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe effects of the antimicrotubular drugs colchicine and vinblastine on the blood platelet release reaction were studied by measuring release of14C‐5‐hydroxytryptamine (14C‐5‐HT, release I) and β‐glucuronidase (release II) from gel‐filtered human platelets. β‐glucuronidase release induced by thrombin was significantly inhibited by colchicine (0.01‐1 mM) or vinblastine (0.05–0.1 mM). Release of14C‐5‐HT, however, was unaffected at low concentrations of colchicine and only slightly inhibited at higher concentrations. Inhibition of β‐glucuronidase release depended on colchicine or vinblastine concentrations and decreased with longer time intervals (1′, 5′, 20′) after thrombin stimulation. Levels of the cytoplasmic enzyme, lactic acid dehydrogenase, in supernatants of colchicine treated platelets were not significantly different from controls. Colchicine also inhibited β‐glucuronidse release, but not14C‐5‐HT release, induced by trypsin and sodium arachidonate. Binding of14C‐colchicine by platelets was measured and it was found that platelet aggregation and release of 5‐HT induced by adenosine diphosphate, epinephrine and collagen proceeded without any alteration in colchicine binding. However, significant increases in the rate and degree of colchicine binding were observed when platelets were stimulated by thrombin, trypsin and arachidonic acid which induced aggregation, release of both 5‐HT and β‐glucuronidase. The results suggest that an alteration in platelet microtubules is correlated with the physiologic response resulting in release II and that the cellular mechanisms effecting release I and II by platelets differ qualitatively in

ISSN:0021-9541    

DOI:10.1002/jcp.1040960106

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

年代:1978

数据来源: WILEY

摘要:

AbstractLipopolysaccharide (LPS) was analyzed in order to determine which component, lipid A or polysaccharide (PS), is able to stimulate B lymphocytes from ICR lymph nodes and spleen cells from nude (nu/nu) mice into forming colonies in soft agar culture. Lipid A, obtained by acid hydrolysis of LPS and solubilized by complex‐formation with bovine serum albumin, was found to be the active moiety of LPS capable of stimulating colony growth of lymphoid cells in soft agar culture. The PS portion exhibited no significant activity at the concentrations used. Glycolipids from mutant strains ofS. minnesotawhich contain the intact lipid moiety but are deficient in PS content, were as potent asS. abortus equiLPS in stimulating B cells into colony growth. Alkaline hydrolysis of LPS which cleaves ester‐linked fatty acids, substantially decreased the number of lymphocyte colonies formed. This indicates that the intact lipid moiety is required for stimulating lymphocytes into colony formation. The synthetic glycolipid, N‐palmitoyl‐D‐glucosamine (NPG), whose structure is similar to some components of lipid A, was also able to induce B lymphocyte colony development. In summary, our data point to lipid A as the active moiety of the endotoxin which induces B lymphocytes to grow and develop into colonies in the 2‐layer soft agar cul

ISSN:0021-9541    

DOI:10.1002/jcp.1040960107

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe C3H/10T 1/2 embryo cell line, which is nontumorigenic when inoculated subcutaneously in saline suspension, produces tumors when implanted subcutaneously attached to 1 × 5 × 10 mm plastic plates. Under these in vivo conditions there is direct selection for “spontaneous” transformants that have undergone the specific cellular alterations required for neoplastic behavior. This is in contrast to the conventional situation where transformants are obtained in vitro and are only secondarily tested in vivo for neoplastic behavior. Early passages of cell lines from four different C3H/10T 1/2 tumors explanted back in culture were quantitatively examined for tumorigenicity and for alteration in the properties of density inhibition, anchorage dependence, serum requirement, and plasminogen activator production. A fairly consistent quantitative relationship was found between the degree of growth aggressiveness in vivo and the degree of expression of these phenotypic markers of the transformed state in vitro during early passages of the cell lines after tumor explant

ISSN:0021-9541    

DOI:10.1002/jcp.1040960108

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

年代:1978

数据来源: WILEY

摘要:

AbstractW/Wvmice were injected with antiplatelet serum to produce thrombocytopenia or with platelet transfusions to induce thrombocytosis. The responses of their platelets and megakaryocytes were followed to determine if proliferative abnormalities of the megakaryocytic system would be detected.W/Wvmice responded normally to the stimulation from thrombocytopenia with rebound thrombocytosis, macromegakaryocytosis, and macrothrombocytosis. The megakaryocytes of these mice became smaller than normal in response to post‐thrombocytopenic rebound thrombocytosis but not to transfusion‐induced thrombocytosis. Thus, endogenous thrombocytosis appeared to be a more potent suppressor of megakaryocyte growth than exogenous.These results failed to reveal an effective abnormality of the thrombocytopoietic regulatory system of W/Wvmice in spite of their intrinsically reduced numbers of megakaryocytes and the well known defect of stem cell proliferation. Thrombocytopoietic regulation appeared, therefore, to occur mainly at the committed, rather then pluripotential, stem cell level, and normal responses of the platelet system were observed in spite of severe abnormalities at the pluri‐potential stem cell

ISSN:0021-9541    

DOI:10.1002/jcp.1040960109

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe mutation rate to thioguanine resistance was 3.11 × 10−6in a near diploid V79 hamster cell line and 7.58 × 10−8in a near tetraploid derivative produced with colchicine. The specific activities of glucose‐6‐phosphate dehydrogenase and phosphoglycerate kinase of the tetraploid line were greater than that of the diploid which suggests that twice the number of active X chromosomes were present in the tetraploid. These results are compatible with the hypothesis that spontaneous variants resistant to thioguanine arise through mutation and chromosomal segregation, as has been suggested for induced mutations in tetraploid hams

ISSN:0021-9541    

DOI:10.1002/jcp.1040960110

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

年代:1978

数据来源: WILEY

摘要:

AbstractExogenous ATP has been shown earlier to activate a permeability change in transformed 3T3 cultures leading to massive efflux of the acidsoluble pools. This leads to reduction of the basal rate of glycolysis to a very low level so that glycolysis becomes almost totally dependent on the addition to the medium of glucose, inorganic phosphate and ADP in order to restore the rate to that of untreated cells. No such depression of glycolysis is observed in untreated transformed cells or in ATP‐treated normal 3T3 cells. In such permeabilized cultures, phosphorylated intermediates such as glucose‐6‐phosphate and fructose‐1,6‐diphosphate can serve as effective substrates for lactic acid formation. ATP treatment of cultured cells also allows molecules as big as NADP to enter the cells and participate in the pentose phosphate shunt pathway. This ability to temporarily and differentially render transformed cells permeable allows a review of several aspects of cellular metabolism and biosynthesis in the intact cell where the cellular organization is maintained. Furthermore, it deserves serious consideration as a means to achieve differential cytotoxicity of transformed cells by chemotherapeutic agents which, on their own, are indiscriminate in the

ISSN:0021-9541    

DOI:10.1002/jcp.1040960111

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

年代:1978

数据来源: WILEY