摘要:

AbstractProliferation of smooth muscle cells from the pulmonary arteries and aortas of fetal calves is inhibited by heparin in vitro. This effect is reversible and dose dependent. Comparisons with effects of other polysaccharides indicate that only extensively sulfated polysaccharides inhibit proliferation of smooth muscle cells but that specific structural features of heparin are required to achieve maximum effect. Heparin‐Sepharose chromatography of medium containing fetal calf serum reduces the ability of that medium to promote growth of smooth muscle cells from fetal pulmonary arteries, suggesting that heparin may remove soluble growth factors in serum. However, inhibition of fetal pulmonary artery smooth muscle cell proliferation by heparin is identical in media supplemented either with serum prepared from fetal calf plasma, in which platelet‐derived growth factor (PDGF) is not detectable, or with fetal calf serum, which contains relatively abundant PDGF (114 pg/ml). Thus, inhibition of fetal pulmonary artery smooth muscle cell proliferation by heparin is not mediated solely by decreased availability or activity of exogenous PDGF. These studies suggest that morphogenesis of the smooth muscle investment of the pulmonary arteries could be regulated by local production of heparinlike inhibitors of smooth muscle cell gro

ISSN:0021-9541    

DOI:10.1002/jcp.1041270102

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

年代:1986

数据来源: WILEY

摘要:

AbstractSheep reticulocytes from phlebotomized animals have a total transferrin binding potential that may exceed by an order of magnitude the surface binding capacity. Steady state uptake of transferrin at 37°C is generally less than 50% of the total transferrin binding capacity. During long‐term incubation of the reticulocytes, all transferrin binding ability is lost, the ability to internalize being lost most rapidly. The loss in ability to bind transferrin during long‐term incubation is independent of the number of surface transferrin binding sites, since removal of surface receptors with pronase does not affect the rate of loss of the internal pool of receptors during long‐term incubation. Moreover, after removing surface receptors with pronase, only a fraction of the original number of receptors is restored to the surface, despite the presence of a large pool of internal receptors. These data suggest that only a fraction of the internal pool of receptors is capable of recycling to the cell surface in sheep reticul

ISSN:0021-9541    

DOI:10.1002/jcp.1041270103

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe plasmamembrane potential (ΔΨp) of murine erythroleukemia (MEL) cells has been determined by measuring the distribution of the lipophilic cation tetraphenylphosphonium (TPP+) across the plasmamembrane. TPP+accumulation within the cells (experimental accumulation ratio, ARexp) was measured by adding 2 μM TPP+directly to the culture flasks, avoiding any other perturbation of the experimental system. The mitochondrial contribution to ARexp, evaluated by adding carbonyl cyanide p‐trifluoromethoxyphenylhydrazone (FCCP) or 2,4‐dinitrophenol (DNP), was apparently negligible in standard cultures, ARexpbeing substantially the same in either the absence or presence of these uncouplers. However, the addition of oligomycin produced a strong ARexpenhancement, which was abolished by FCCP, suggesting that MEL cell mitochondria are in state 3. The aspecific TPP+binding was estimated by a new mathematical approach worked out to fit ARexpvalues measured in the presence of valinomycin at various extracellular K+concentrations and plotted against the ratio of intracellular to extracellular K+concentration ([K+]i/[K+]e). This binding was found to be close to zero in MEL cells. By applying the Nernst equation directly to ARexpvalues, ΔΨpof these cells was then measured; this potential varying from −65 mV to −16 mV (inside negative) is inversely related to the cell density on the culture surface on which the cells sediment (cells/cm2; CD). The dependence of ΔΨpon CD is practically eliminated by valinomycin and appears to be related to a cell interaction with the culture surface of the flasks, suggesting that in the immediate environment of MEL cells one or more factors are produced that modulate the K+plasma membrane per

ISSN:0021-9541    

DOI:10.1002/jcp.1041270104

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

年代:1986

数据来源: WILEY

摘要:

AbstractAlterations in receptor‐independent activation of adenylate cyclase during proliferation and differentiation of L6E9 myoblasts were studied using Mn2+, forskolin, and Gpp(NH)p. Analyses were performed 3,6, and 10 days following subculture, corresponding to onset of proliferation, end of proliferation with start of differentiation, and completion of differentiation, respectively. The apparent activation constant for Mn2+decreases with the age of the culture; the apparent activation constant for Mg2+does not. Bimodal activation by Mn2+, i.e., at concentrations greater than 10 mM, results in total adenylate cyclase activity less than the Vmax and occurs exclusively in differentiated cultures. Independent of the presence of Mg2+, forskolin activation occurs with low‐ and high‐affinity constants in differentiated cultures and with a low affinity constant in youngest cultures; intermediate cultures (day 6) demonstrate low‐ and high‐affinity activation only in the presence of high Mg2+. In contrast, the Vmax for forskolin increases with increasing Mg2+in all culture ages. Although Gpp(NH)p‐dependent adenylate cyclase activation occurs with an apparent activation constant independent of culture age and Mg2+, low Mg2+fosters bimodal activation by Gpp(NH)p, i.e., above 100 μM nucleotide, total adenylate cyclase activity is less than the Vmax. The loss of stimulatory capacity by high Gpp(NH)p is greatest in differentiated cultures. Additional experiments are presented to substantiate that bimodal activation by Gpp(NH)p is specific. Cholera‐ and pertussis toxin‐dependent ADP ribosylation patterns demonstrate a marked decrease in both Ns and Ni in differentiated cultures. The data suggest that alterations in postreceptor activation of adenylate cyclase during the course of differentiation and proliferation are mediated by guanine nucleotide binding proteins as well as by allosteric cation

ISSN:0021-9541    

DOI:10.1002/jcp.1041270105

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

年代:1986

数据来源: WILEY

摘要:

AbstractNorepinephrine (NE) produced a dose‐dependent inhibition of125I‐epidermal growth factor (EGF) binding to adult rat hepatocytes in primary culture. This effect was maximal after 1 hr of incubation with NE and could be blocked by the presence of an α1‐specific adrenergic receptor antagonist. The inhibition of binding correlates with the ability of NE to enhance hepatocyte DNA synthesis in the presence of EGF and appears to be mediated by a reduction in EGF receptor number, without a significant change in receptor af

ISSN:0021-9541    

DOI:10.1002/jcp.1041270106

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe maintenance of hemopoietic precursors in long‐term liquid bone marrow cultures (LTBMC) is associated with the presence of an adherent stromal layer composed of heterogeneous cell populations. We have used a culture assay to promote the growth of one of its cellular components and characterize its properties. Freshly obtained bone marrow cells and cells derived from the adherent layer of LTBMC were grown in methylcellulose‐clotted plasma in the presence of phytohemagglutinin‐stimulated leukocyte‐conditioned medium (PHA‐LCM), hydrocortisone (HC), and citrated normal human plasma. Both sources contained cells (CFU‐RF) that gave rise to colonies of cells with a reticulofibroblastoid appearance. In the presence of HC, most colonies contained lipid‐laden cells. Colonies could be further propagated as adherent layers when transferred into liquid cultures. These cells produced laminin, fibronectin, and collagen types I, III, IV, and V. They were negative for Von Willebrand factor VIII. The ability to synthesize laminin and collagen type IV distinguished these cells from a population of previously described bone marrow fibroblasts (CFU‐F). The relationship of CFU‐RF to hemopoietic precursors was investigated using patients with chronic myeloid leukemia and bone marrow transplant recipients. Cells within CFU‐RF‐derived colonies were uniformly negative for the Philadelphia chromosome, thus making it unlikely that they belonged to the malignant hemopoietic clone. CFU‐RF‐derived colonies in bone marrow transplant recipients were found to be exclusively of host origin. Both observations support the view that CFU‐RF is not part of the repertoir

ISSN:0021-9541    

DOI:10.1002/jcp.1041270107

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe study of growth of endometrial cells is of importance in reproductive biology. Several factors and hormones are thought to play important roles in the control of growth. Prostaglandin F2α(PGF2α) causes an increase in both tritiated thymidine ([3H]Tdr) incorporation into DNA and in the cell number of primary cultures of rabbit endometrial cells cultured in a serum‐free, chemically defined media. Prostaglandins F1α, E1, E2, A2, and B2and arachidonic acid (all tested at 10−7M) do not affect [3H]Tdr incorporation as compared to control cultures. The increase in [3H]Tdr incorporation into DNA in response to PGF2αstimulation is concentration‐dependent (optimal ∼3 × 10−7M) and is seen starting ∼9 hr poststimulation. Both prostaglandin E1(PGE1) and prostaglandin E2(PGE2), but not PGs F1α, I2, A2, B2, their parent molecules, or related molecules, antagonize and can completely block the PGF2α‐induced increase in [3H]Tdr incorporation into DNA. This antagonism is seen both when the cells are pretreated with PGE1prior to the PGF2αstimulation and when the cells are exposed to both PGE1and PGF2αsimultaneously. Exogenously added 8‐Br‐cAMP mimics the PGE1antagonism of PGF2α. The PGF2α‐induced increase in [3H]Tdr incorporation is not synergistic, antagonistic, or additive with the [3H]Tdr incorporation increase in response to either estradiol‐17β or epidermal growth factor. The specific effect of PGF2αon primary culture endometrial cell growth and its antagonism by PGE1, PG

ISSN:0021-9541    

DOI:10.1002/jcp.1041270108

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

年代:1986

数据来源: WILEY

摘要:

AbstractSeveral factors and hormones are thought to play a role in the growth control of endometrial cells. We have shown that prostaglandin F2α(PGF2α) is a growth factor for primary cultures of rabbit endometrial cells grown in serum‐free, chemically defined medium and that prostaglandin E1(PGE1) antagonizes the PGF2αinduction of growth (Orlicky et al., 1986). [3H]PGF2αbinds to whole cells in a time (optimal ∼30 min)‐ and temperature‐dependent (optimal 37°C), disassociable (90% disassociable within 30 min), saturable (Kd1= 4.9 × 10−8M, n1= 1.2 × 105molecules/cell; Kd2= 2.6 × 10−7M, n2= 3.0 × 105molecules/cell), and specific manner. [3H]PGE1binds in a time‐dependent (optimal 25 min), disassociable (90% disassociable within 10 min), saturable (Kd = 6.4 × 10−8M, n = 1.2 × 105molecules/cell), and specific manner. This specific binding of [3H]PGF2αand [3H]PGE1is down‐regulatable by prior treatment of the cultures with unlabeled ligand, and up‐regulatable by prior treatment of the cultures with indomethacin to inhibit endogenous PG synthesis. Proteolytic enzyme treatment for 2 min reduces the specific binding of PGF2αby 75%. PGE1stimulates intracellular cAMP synthesis and accumulation in a time (optimal 10 min)‐ and concentration (half‐maximal stimulation at 10−6M)‐dependent manner but has no effect on intracellular cGMP. PGF2αhas no effect on either intracellular cAMP or cGMP in this system. We describe here for the first time the analysis at a biochemical level of the interaction between two prostaglandins, antagonistic to

ISSN:0021-9541    

DOI:10.1002/jcp.1041270109

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

年代:1986

数据来源: WILEY

摘要:

AbstractRespiratory tract epithelia are one type of tissue targeted by vitamin A. In this study the effects of vitamin A and its analogs (retinoids) on human bronchial epithelial (HBE) cells have been investigated in a serum‐free hormone‐supplemented medium. This serum‐free medium, which was developed for the longterm cultivation of protease‐dissociated HBE cells, consists of Ham's F12 nutrient medium supplemented with insulin, transferrin, epidermal growth factor, hydrocortisone, cholera toxin, and bovine hypothalamus extract. Under these in vitro conditions, retinoids specifically stimulate the synthesis and secretion of hyaluronate (HA) and alter the pattern of synthesis of keratin proteins. In regard to HA, the degree of stimulation ranges from two‐fold to ten‐fold and is concentration dependent. In regard to keratin proteins, the most prominent effects of retinoids are inhibition of synthesis of the 48 kd and 50 kd keratin proteins (corresponding to cytokeratins 16 and 14, respectively, in the catalog of human cytokeratins; Moll et al., 1982) and stimulation of synthesis of the 40 kd and 52–54 kd proteins. The data indicate that retinoid effects on HA and keratin protein synthesis occur at different levels. The stimulation of HA synthesis occurs immediately after the addition of retinoid and cannot be prevented by pretreatment with actinomycin D, whereas the alterations in the pattern of keratin protein synthesis appear later and are inhibited by treatment with actinomycin D at or before the administration of retinoid. This study demonstrates that HBE cultures maintained in the serum‐free condition can serve as an in vitro model to elucidate the mechanisms of r

ISSN:0021-9541    

DOI:10.1002/jcp.1041270110

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

年代:1986

数据来源: WILEY

摘要:

AbstractStimulation of quiescent cultures of AKR‐2B cells with transforming growth factor type β (TGFβ) resulted in a transitory increase in actin cytoplasmic poly(A) + RNA. Levels of actin mRNA peaked approximately 4–8 hours subsequent to TGFβ addition and approached basal levels by 24 hours. The accumulation of actin transcripts was dose dependent and insensitive to inhibitors of protein synthesis; 1–3 ng/ml TGFβ induced maximal actin gene expression. Actin isotype‐specific probes demonstrated that both β‐ and γ‐cytoplasmic actins ar

ISSN:0021-9541    

DOI:10.1002/jcp.1041270111

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

年代:1986

数据来源: WILEY