摘要:

AbstractThe relative toxicity of numerous cardiotonic steroids (viz. ouabain, digitoxin, digoxin, convallatoxin, SC4453, bufalin, gitaloxin, digoxigenin, actodigin, oleandrin, digitoxigenin, gitoxin, strophanthidin, gitoxigenin, lanatosides A, B and C, α‐ and β‐acetyl digoxin, α‐ and β‐methyl digoxin) and related compounds towards a number of independent cell lines established from human, monkey, mouse, Syrian hamster, and Chinese hamster have been determined. All cardiac glycosides and their genins, as well as the cardiotonic alkaloid cassaine, exhibited>100‐fold higher toxicity towards cultured human and monkey cells in comparison to the cell lines of mouse, Syrian hamster, and Chinese hamster origins. These differences are species‐related as all cell lines (both normal as well as transformed) from any one species, as well as cells from the closely related species (e.g., man and monkey or mouse, Chinese hamster, and Syrian hamster), showed similar sensitivity towards these drugs. The failure to see any significant differences in cellular toxicity for a larger number of other compounds which either bear limited structural resemblance to cardiac glycosides (viz. estradiol 17‐β‐acetate, testosterone propionate, 21‐acetoxy pregnenolone, β‐estradiol, digitonin, tigogenin, and tomatine) or interact with the Na+/K+ATPase in a different manner (viz. veratridine, sanguinarine nitrate, penicillic acid, vanadium pentoxide, harmaline‐HCI, 5,5′‐diphenyl hydantoin, quindonium bromide, and methyl quinolizinum bromide) provides strong evidence that the observed species‐related differences are highly specific for cardiotonic steroids. Studies on the binding of [3H]ouabain show that, in comparison to human and monkey cell lines, no significant binding of the drug is observed in cells derived from the resistant species (i.e., mouse and Chinese hamster). The Na+/K+ATPase from cells of the resistant species is inhibited at much higher concentrations of ouabain and digitoxin in comparison to the enzyme from human cells, and a good correlation is observed between these concentrations and those reported for inhibition of the enzyme from isolated heart muscles of the same species. These results provide strong evidence that the species‐related differences in sensitivity to digitalis have a cellular basis and that the cultured cells from various mammalian species provide a useful model system for investigating the mechan

ISSN:0021-9541    

DOI:10.1002/jcp.1041270202

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

年代:1986

数据来源: WILEY

摘要:

AbstractIn order to study the signal transduction mechanism of human endothelial cells (EC), the regulation of superoxide anion (O2−) release in EC has been investigated using the calcium ionophore A23187 and phorbol myristate acetate (PMA), a potential activator of the Ca2+activated, phospholipid‐dependent protein kinase, designated “protein kinase C.” PMA enhanced O2−release from EC, and this enhancement occurred regardless of the presence or absence of extracellular Ca2+. A similar increase was produced by A23187; omission of extracellular Ca2+prevented this increase. Simultaneous stimulation with PMA and A23187 produced a large increase in O2−release at submaximal concentrations of these agents, which, when added separately, caused minimal effects. These findings indicate that the activation of protein kinase C and mobilization of Ca2+evoked by PMA and A23187 respectively are synergistically effective for eliciting a full physiological response of EC in the generation and rel

ISSN:0021-9541    

DOI:10.1002/jcp.1041270203

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

年代:1986

数据来源: WILEY

摘要:

AbstractAs has been observed with many types of cultured cells, chicken embryo fibroblasts (CEF) when exposed to the tumor promoter 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA) develop a 3‐ to 4‐fold increase in hexose transport activity in 4 h. This increase in transport activity occurred despite a modest decline of 20% in [3H]leucine incorporation into acid insoluble fractions. Cycloheximide largely, but not completely, blocked the increase in transport activity during TPA exposure. The effects of TPA were somewhat similar to those of glucose starvation induced enhancement of hexose transport activity. Furthermore, with TPA there was no additive effect to that produced by glucose starvation. Plasma membrane enriched fractions were prepared from CEF treated with or without TPA. Membranes prepared from TPA exposed cells had a two‐fold enhancement of stereospecific D‐glucose transport activity as well as D‐glucose inhibitable [3H]cytochalasin B binding as compared to the membranes from control CEF. There was no effect on transport when membranes were exposed to TPA in vitro. These results provide strong evidence that TPA exposure leads to an increase in the number of functioning transporters, an effect largely requiring

ISSN:0021-9541    

DOI:10.1002/jcp.1041270204

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

年代:1986

数据来源: WILEY

摘要:

AbstractStudies were conducted to explore the effects of mevinolin, a competitive inhibitor of HMG CoA reductase, on the growth and morphology of normal and transformed murine fibroblasts. Mevinolin is known to block DNA synthesis and cell growth in a number of kinds of non‐transformed cells. Eight cell lines were studied, including two normal fibroblast cell lines (C3H 10T 1/2 and NIH 3T3) and derivatives of these cell lines transformed by chemical carcinogens, X‐irradiation or the H‐ras oncogene. All of the eight cell lines displayed appreciable growth inhibition by 5 μM mevinolin and marked inhibition by 30 μM mevinolin. Mevinolin also induced a marked rounding in the morphology of all of the cell lines. These effects of mevinolin on cell growth and morphology were blocked or reversed by the addition of mevalonic acid. Thus, both normal and transformed cells require mevalonate, or an as yet unidentified metabolite of mevalonate for their growth, even though some transformed cells have become relatively autonomous of other growth factors. Whereas mevinolin acted primarily as a cytostatic agent for most of the cell lines studied, with the transformed cell line MCA/10T 1/2, which ordinarily grows to a very high cell density, prolonged exposure to mevinolin caused marked cytotoxicity. Thus mevinolin might be useful as an anti‐tumor agent for specif

ISSN:0021-9541    

DOI:10.1002/jcp.1041270205

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

年代:1986

数据来源: WILEY

摘要:

AbstractAll‐trans‐retinal stimulated the release of superoxide by human and guinea pig neutrophils 63 ± 14 SD and 53 ± 5 SD nmol of O2−/min/107cells, respectively. Superoxide release by unstimulated cells was negligible. All‐trans‐retinal also induced morphological changes (i.e., evaginations) in these cells. Other retinoids were effective in instigating these phenomena. The similarities of these effects to those instigated by cis‐unsaturated fatty acids (Badwey, J.A., et al., 1984, J. Biol. Chem.,259:7870–7877) are discussed in light of poss

ISSN:0021-9541    

DOI:10.1002/jcp.1041270206

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

年代:1986

数据来源: WILEY

摘要:

AbstractFour T‐cell and two B‐cell lines from patients with lymphoblastic leukemia were examined with a panel of monoclonal antibodies for a variety of lineage and differentiation stage‐associated antigens during growth in liquid suspension. In five of the lines, markers normally associated with the granulopoietic lineage were found and the level of expression of these markers varied during culture. The sixth line, MOLT‐3, was examined in more detail. Using clonal selection it was found that phenotypic heterogeneity could readily be obtained and that subclones could be acquired that expressed a wide range of markers, typically in reproducible kinetic patterns, that were not detected on the parent clone. Previous results were confirmed showing that treatment with the drug 5‐azacytidine (5‐aza) prior to selection promoted the expression of the granulopoietic lineage associated antigen 80H.5 on MOLT‐3 subclones; however, treatment with 5‐aza appeared to inhibit substantially the expression of other novel markers by subclones following a second selection compared to untreated controls. It appears that the expression of markers normally associated with other lineages on leukemic lymphoblasts (lineage infidelity) may be characteristic of such lines and that phenotypically variant subclones expressing lineage infidelity can readily be obtained by c

ISSN:0021-9541    

DOI:10.1002/jcp.1041270207

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe role of cyclic AMP on endothelial cell proliferation was investigated, since these cells can be exposed to high concentrations of physiological and pharmacological agents that alter cyclic AMP metabolism. Cloned bovine aortic endothelial cells were plated at 25,000 cells/35mm dish and grown for 5 days in the presence of phosphodiesterase (PDE) inhibitors, forskolin, or cyclic AMP analogs. The PDE inhibitors dipyridamole, ZK 62 711, isobutylmethylxanthine (IBMX) and theophylline inhibited cell growth in a concentration‐dependent manner. Dipyridamole produced a 30% and a 50% inhibition at 5μM and 12.5μM, while higher concentrations were cytotoxic. At its therapeutic plasma concentration range (50‐100μM) theophylline inhibited cell proliferation by 15–25%, while IBMX and the highly specific cyclic AMP phosphodiesterase inhibitor, ZK 62 711 inhibited growth by 60–80% and 40–50%, respectively. Forskolin (5μM) increased cyclic AMP levels and cyclic AMP‐kinase activity ratios by 2.5‐fold and 2‐fold. In the absence of PDE inhibitors forskolin produced a 20% growth inhibition at 0.5μM and a 60% inhibition at 10μM. The forskolin dose‐response curve was not altered by theophylline, but was shifted to the left by approximately 10‐fold with dipyridamole and ZK 62 711 and 5‐fold with IBMX. Forskolin (5μM), by itself produced a 1.8‐fold increase in cyclic AMP. In the presence of 5μM theophylline, dipyridamole, IBMX, and ZK 62 711, cyclic AMP was increased by forskolin 2.0, 2.6, 3.5, and 6.6‐fold, respectively. 8‐Bromo cyclic AMP and dibutyryl cyclic AMP produced a 55% and 60% growth inhibition at 100μM. The cyclic GMP analogs were less effective inhibitors of growth (15–30%). Our results demonstrate that cyclic AMP analogs and pharmacological agents that elevate intracellular cyclic AMP levels inhibit cell growth and suggest that cyclic AMP may be an important endogenous regul

ISSN:0021-9541    

DOI:10.1002/jcp.1041270208

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

年代:1986

数据来源: WILEY

摘要:

AbstractGrowth factors, mitogens, and malignant transformation can alter the rate of amino acid uptake in mammalian cells. It has been suggested that the effects of these stimuli on proliferation are mediated by activation of Na+/H+exchange. In lymphocytes, Na+/H+exchange can also be activated by phorbol esters and by hypertonic media. To determine the relationship between the cation antiport and amino acid transport, we tested the effects of these agents on the uptake of α‐aminoisobutyric acid (AIB), methyl‐AlB, proline, and leucine in rat thymocytes. Both 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA) and hypertonicity stimulated amino acid uptake through system A (AIB, proline, and methyl‐AlB). In addition, TPA, but not hypertonicity, also elevated leucine uptake. The stimulation of the Na+‐dependent system A was not due to an increased inward electrochemical Na+gradient. The effects of TPA and hypertonic treatment were not identical: Stimulation of AIB uptake by TPA was observed within minutes, whereas at least 1 hr was required for the effect of hypertonicity to become noticeable. Moreover, stimulation by hypertonicity but not that by TPA, was partially inhibited by cycloheximide, suggesting a role of protein synthesis. That stimulation of Na+/H+exchange does not mediate the effects on amino acid transport is suggested by two findings: (1) the stimulation of AIB uptake was not prevented by concentrations of amiloride or of 5‐(N,N‐disubstituted) amiloride analogs that completely inhibit the Na+/H+antiport and (2) conditions that mimic the effect of the antiport, namely, increasing [Na+]ior raising pHifailed to stimulate amino acid uptake. Thus, in lymphocytes, activation of Na+/H+exchange and stimulation of amino acid transport are

ISSN:0021-9541    

DOI:10.1002/jcp.1041270209

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

年代:1986

数据来源: WILEY

摘要:

AbstractDevelopment of resistance to colchicine in the mouse macrophage‐like cell line J774.2 coincides with the expression of a variety of phenotypic traits. A cloned subline (J7/CLC‐20), maintained in 20 μM colchicine, exhibits reduced steady‐state association with drug, increased presence of a 140,000–145,000 dalton (140–145 kD) phosphoglycoprotein associated with the plasma membrane, double minute chromosomes and cross‐resistance to other drugs. While similar phenotypic traits are observed in J774.2 cells resistant to taxol and vinblastine, differences in the electrophoretic mobilities of the resistance‐specific glycoproteins in each of the three sublines suggest that multi‐drug resistant sublines exhibit specificity for individual drugs. In an attempt to elucidate the relationships between the phenotypic traits associated with colchicine resistance, the degree of colchicine resistance in J7/CLC‐20 cells was modulated and the levels of expression of the phenotypic traits were quantitated. In the absence of colchicine in the growth medium, J7/CLC‐20 cells reverted to drug sensitivity within 35 days. A decrease in the level of resistance coincided with coordinate changes in both the quantity of the resistance‐specific glycoprotein and the average number of double minute chromosomes. We propose that the emergence and disappearance of the resistance‐specific glycoprotein and double minute chromosomes may be closely linked. However, J7/CLC‐20 cells which had regained their drug sensitivity after growth in drug‐free medium maintained a reduced level of steady‐state drug association. The persistence of reduced drug association in cells that have reverted to a drug‐sensitive state suggests that this phenomenon, although related to colchicine resistance, need not be the primary or o

ISSN:0021-9541    

DOI:10.1002/jcp.1041270210

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe role of glucose metabolism in sperm cell motility was examined in purified human spermatozoa from the perspective of elucidating its possible significance in spontaneous and experimental diabetes. After a 4‐h incubation in the absence of D‐glucose, the mean progressive velocity of human spermatozoa was 40% lower than that of control cells kept in the presence of D‐glucose. The decline was rapidly overcome by the addition of D‐glucose or D‐fructose, the amplitude of this stimulatory effect being independent of the ambient hexose concentration. Between 1.4 and 16.7 mM glucose, spermatozoal glucose oxidation also proceeded independently of the extracellular glucose levels, whereas both insulin (100nM) and glucagon (100nM) failed to significantly affect the rate of glucose metabolism or cellular motility. It is speculated from these results that an alteration in seminal hexose concentrations or pancreatic hormone levels may be an unlikely cause for the reduced sperm motility that is characteristically observed in diabetic patients. Human spermatozoa rapidly incorporated D‐glucose and 3‐0‐methyl‐D‐glucose but excluded the glucose‐analogue alloxan, which may explain their resistance against the toxic effects of this diabetogenic drug, in spite of their intrinsic sensitivity to organic peroxides such aster

ISSN:0021-9541    

DOI:10.1002/jcp.1041270211

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

年代:1986

数据来源: WILEY