摘要:

AbstractWe have examined the effects of colchicine on concanavalin A (Con A)‐ and phytohemagglutinin (PHA)‐stimulated human peripheral blood lymphocytes and from the time course of proliferation have extracted the relative size of the responding cell population, the rate of entry of this population into S‐phase, and the length of the lag period. Additions of colchicine at any time did not appear to influence the size of the responding population nor did it greatly affect the duration of the lag period. Only the rate at which the cell population enters initial S‐phase is a function of the time of previous exposure to colchicine. Colchicine does not appear to inhibit the commitment of stimulated lymphocytes to enter the cell cycle. Rather, it merely serves to decrease the biochemical processes responsible for fixing a maximal rate of entry into

ISSN:0021-9541    

DOI:10.1002/jcp.1041120202

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe isolation and characterization of variant embryonal carcinoma (EC) cells possessing altered cell‐surface structures is described. The lectin peanut agglutinin (PNA), which binds to EC cells but not their differentiated derivatives, was used to select the variants. Clones resistant to the cytotoxic effect of PNA were isolated at a frequency of 4 × 10–5following mutagenesis. The resistant phenotype was stable in the absence of selection in all eight clones tested. The increased frequency of resistant clones following mutagenesis and the stability of the phenotype suggests a mutational origin. Somatic cell hybrids constructed between wild‐type cells and two different PNA‐resistant cell lines were sensitive to PNA; this suggests that the resistant phenotype is recessive. Binding assays demonstrated that resistant cells exhibited a twofold to fourfold reduction in the total amount of PNA bound. Together with the recessive behavior of the phenotype, this suggests that resistant cells are deficient for PNA receptors. The PNA‐resistant cells also showed reduced binding of monoclonal antibody against stage‐specific embryonic antigen 1 (SSEA–1) in indirect cytotoxicity tests. All eight PNA‐resistant lines isolated were tumorigenic in syngeneic mice and gave rise to well‐differentiated teratocarcinomas. The PNA‐resistant cells behaved like their wild‐type parents in a cell recognition assay; when incubated in suspension with endodermal cells, they sorted out to form simple embryoid bodies (a core of EC cells surrounded by an endodermal rind). Thus, EC cells can form tumors, differentiate, and recognize differentiated cells in a sorting assay despite a reduction in expression of the embryo‐specific cell surface structures (s) that bind PNA

ISSN:0021-9541    

DOI:10.1002/jcp.1041120203

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

年代:1982

数据来源: WILEY

摘要:

AbstractHuman platelet‐derived growth factor (PDGF) stimulates release of arachidonic acid from cellular phospholipids, synthesis and release of prostaglandins from the cell, and initiation of DNA synthesis in cultures of 3T3 Swiss mouse fibroblasts at similar concentrations with four independent preparations representing a million‐fold range of purification. Stimulation of archidonic acid and prostaglandin release is an early event (beginning within minutes) in the response to PDGF treatment. Incubating cells with PDGF at 4°C followed by washing leads to activation of archidonic acid release on warming the cells to 37°C, consistent with binding of the factor to the cell surface. PDGF‐stimulated arachidonic acid release, prostaglandin release, and initiation of DNA synthesis are all inhibited by phenylglyoxal at similar concentrations. These results suggest that activation of arachidonic acid release from phospholipids plays an essential role in the mechanism by which PDGF stimulates the initiation of DNA synthesis in 3T3 cells. The stimulation of initiation of DNA synthesis by PDGF does not appear to be mediated by the synthesis of prostaglandins or other known arachidonic acid metabolites because neither indomethacin (a fatty acid cyclooxygenase inhibitor) nor phenidone (a lipoxygenase inhibitor) inhibit initiation of DNA synthesis at concentrations which inhibit arachidonic acid metabolism. Although the activation of arachidonic acid release by PDGF is a calcium‐dependent process, a simple calcium flux appears unimportant to the mechanism of activation. Evidence was also obtained against an involvement of sodium fluxes or proteolytic activity in the mechanism of stimulating arachidonic acid release by PDGF

ISSN:0021-9541    

DOI:10.1002/jcp.1041120204

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

年代:1982

数据来源: WILEY

摘要:

AbstractTwo transport systems for neutral amino acids have been characterised in LLC‐PK1cells. The first, which transport alanine in a sodium‐dependent manner, also mediates alanine exchange and is preferentially inhibited by serine, cysteine, and α‐amino‐n‐butyric acid. This system resembles the ASC system in Ehrlich ascites and some other cell types. There is only a small contribution of other systems to alanine uptake. The second, which transports leucine with no requirement for sodium and mediates leucine exchange, is blocked by 2‐aminonorbornane‐2‐carboxylic acid and hydrophobic amino acids. This system is similar to the L system described in other cell types. LLC‐PK1cells retain several other features implying renal proximal tubule origin; our results thus suggest that these transport systems may be involved in the reabsorption of neutral amino acids by t

ISSN:0021-9541    

DOI:10.1002/jcp.1041120205

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe mechanism of volume regulation in hypotonic media was analysed in human peripheral blood mononuclear (PBM) cells. Electronic cell sizing showed that hypotonic swelling is followed by a regulatory volume decrease (RVD) phase. This was confirmed by both electron microscopy and by cellular water determinations. The rate of regulatory shrinking was proportional to the degree of hypotonicity in the 0.5–0.9 X isotonic range. Cell viability was only marginally affected in this range. The content of cellular K+decreased during RVD, while Na+content remained unchanged. Similarly, the efflux of86Rb (used as a K+analog) increased upon dilution, whereas22Na efflux was not altered.86Rb uptake was enhanced by hypotonic stress and both ouabain‐sensitive and ‐insensitive components were affected. A ouabain‐sensitive stimulation was also seen in Na+‐ free media. Ouabain partially inhibited RVD only if added to the cells hours before hypotonic challenge. A normal shrinking response was observed in K+‐free media, and also in Na+‐free media when Li+, choline+, or Tris+were the substitutes. In high K+or Rb+hypotonic media shrinking was absent and a second swelling phase was observed. Cs+displayed an intermediate behavior, with shrinking observed at lower dilutions and secondary swelling at higher ones. The direction and magnitude of the response also changed when the external K+concentration was varied and, with 50 mM K+, no regulatory volume change occurred following hypotonic stress. These findings suggest that RVD occurs largely by a passive loss of cellular K+, resulting from a selective increase in permeability to this ion. In addition, the (Na‐K) pump appears to be activated upon cell swelling by a mechanism other than Na+entry into the cell, but this activation is not es

ISSN:0021-9541    

DOI:10.1002/jcp.1041120206

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

年代:1982

数据来源: WILEY

摘要:

AbstractUsing a serum‐free system, we have investigated the influence of human fibronectin (HFN) and selected growth factors (GF) on the attachment and growth of normal human keratinocytes in vitro. Single‐cell suspensions of keratinocytes from near‐confluent primary plates, plated on 5–10 μg/cm2HFN, showed approximately 30–40% attachment after 2–24 hours of incubation at 37°C, compared with 4–6% attachment on uncoated platic plates. Percentage of attached cells was independent of seed density, tissue donor age, in vitro culture age, or medium composition, while subsequent cellular proliferation was strongly dependent on these factors. Keratinocytes grown on an adequate HFN matrix in a previously described hormone‐supplemented medium (Maciag et al., 1981a) achieved four to eight population doublings over 7–12 days at densities ≥ 104cell/cm2. Removal of most GF individually from the medium had little or no effect on growth, while removal of epidermal growth factor (EGF) alone reduced growth by 30–35% and removal of bovine brain extract (BE) alone reduced growth by approximately 90%. Conversely, EGF alone in basal medium supported approximately 10% control growth, BE alone supported 30–40% control growth, and the combination of EGF and BE approximately 70%. In addition to its major effect on proliferation in this system, BE was necessary to preserve normal keratinocyte morphology and protein production. These findings expand earlier observations that HFN facilitates keratinocyte attachment in vitro and that a brain‐derived extract can exert a major positive influenc

ISSN:0021-9541    

DOI:10.1002/jcp.1041120207

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

年代:1982

数据来源: WILEY

摘要:

AbstractAC1 cells, a bovine adrenocortical cell clone, are rapidly arrested and killed by 2 mM aminooxyacetate, an inhibitor of transmination reactions. Toxicity of aminooxyacetate to cultured bovine adrenocortical cells was previously linked to a high ratio of capacity for oxidation of glutamine relative to pyruvate and was reversible by adding excess glutamine. The toxic effects of aminooxyacetate were shown in the present study to be completely prevented by the simultaneous addition of low concentrations (<100 nM) ofd‐α‐tocopherol (vitamin E) or selenious acid or higher concentration of other tocopherols, antioxidants, and ubiquinones (coenzymes Q6and Q10). When antioxidant analogs were tested, it was found that structural features of the molecules that increase antioxidant potency increased potency for prevention of aminooxyacetate toxicity. α‐Tocopherol‐supplemented AC1 cells were found to be significantly less sensitive than nonsupplemented cells to growth inhibition by rotenone but not by fluorocitrate or dinitrophenol. Dinitrophenol (100 m̈M) stimulated substrate oxidation fivefold but had relatively slight effects on growth, either with or without α‐tocopherol, indicating that limitation of the maximal activity of the tricarboxylic acid cycle and respiratory chain is probably not responsible for the sensitivity to aminooxyacetate and rotenone in cells not supplemented with α‐tocopherol. Sensitivity to growth inhibition by rotenone and the prevention by ubiquinones of aminooxyacetate toxicity suggest a restriction of electron flow at the NADH‐ubiquinone step. The resultant higher NADH/NAD+ratio would result in a lowered capacity for metabolism of pyruvate with consequent dependence for tricarboxylic acid cycle function and energy production on 2‐oxoglutarate from glutamine by the transmination pathway. Vitamin E and other antioxidants may restore efficient function of ubiquinone by preventing side reactions involving lipid peroxidation. Selenium may have a similar effect as cofactor for glutathione peroxidase. A high ratio of capacity for oxidation of glutamine relative to pyruvate and accompanying sensitivity to aminooxyacetate may reflect a deficiency of vitamin E and selenium in adrenocorti

ISSN:0021-9541    

DOI:10.1002/jcp.1041120208

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe recently established human promyelocytic cell line HL‐60 was induced to differentiate in the present of DMSO. During this process, physiochemical, and functional changes were detected simultaneously. After exposure to DMSO for more than 1 day, the cell volume decreased and the tendency for hydrophobic interaction increased. Using a hydrophobic two‐phase system in counter current distribution fashion, it was then possible to separate more mature metamyelocytes and segmented granulocytes from immature myeloblasts and promyelocytes. Increased functional maturity was reflected by increased chemiluminescence (CL) response and phagocytic activity. Using yeast particles opsonized with IgG as stimulating agent, the CL response increased already after 1 day in DMSO, in parallel with increased phagocytosis of these particles. In contrast, C3b‐opsonized yeast and phorbol 12‐myristate 13‐acetate (PMA) did not enhance the CL response conspiquously until days 3–4. These data suggest that Fc receptor function linked to phagocytosis and the activation of oxidative metabolism develop earlier than that of C3b and PMA. The dissociation between Fc‐ and PMA‐dependent stimulation of the oxidative metabolism may reflect different mechanism

ISSN:0021-9541    

DOI:10.1002/jcp.1041120209

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe effect of cyclophosphamide (CY) on megakaryocytopoiesis in mice was examined with assays of megakaryocyte colony‐forming cells (Meg‐CFC) in bone marrow and spleen and simultaneous determinations of peripheral blood counts, after a single intraperitoneal dose (200 mg/kg) of CY. Significant rebound thrombocytosis (170% of normal) occurred at day 11 after injection with CY, although only modest preceding thrombocytopenia (70% of normal) was observed. After an initial 3–5‐day period of suppression, total megakaryocyte colony‐forming cells (Meg‐CFC) in both bone marrow and spleen of CY‐treated mice demonstrated rebound increases at 5 and 7 days, respectively, after administration of the drug. Granulocyte‐macrophage colony‐forming cells (GM‐CFC) exhibited alterations which were similar to those of Meg‐CFC, suggesting similar sensitivities of Meg‐CFC and GM‐CFC to CY. The increase in Meg‐CFC in both bone marrow and spleen preceded development of thrombocytosis by 4–6 days. This suggests that increased platelet counts in CY‐treated mice are attributable, at least in part, to alterations in feedback mechanisms which control megakaryocytopoiesis, with resultant stimulation of the megak

ISSN:0021-9541    

DOI:10.1002/jcp.1041120210

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe regulation of amino acid transport in L6 muscle cells by amino acid deprivation was investigated. Proline uptake was Na+‐dependent, saturable and concentrative, and was predominantly through system A. Proline uptake was inhibited by alanine, α‐amino isobutyric acid (AIB), and by α‐methylamino isobutyric acid, but not by lysine or valine. At 25°C, Km of proline uptake was 0.5 mM. Amino acid‐deprivation resulted in a progressive increase in the rate of proline uptake, reaching up to 6‐fold stimulation after 6 hours. The basal and stimulated transport were equally Na+‐dependent, and both were inhibited by competition with the same amino acids. Kinetic analysis showed that Km decreased by a factor of 2.4 and Vmax increased 1.9‐fold in deprived cells. Amino acid‐deprivation did not stimulate amino acid uptake through systems other than system A. This suggests that the higher Km in proline‐supplemented cells is not due to release of intracellular amino acids into unstirred layers surrounding the cells. The presence of amino acids which are substrates of system A (including AIB) during proline‐deprivation,preventedstimulation of proline uptake, whereas those transported by systems Ly+or L exclusively were ineffective. The stimulation of the transport‐rate in deprived cells could bereversedby subsequent exposure to proline or other substrates of system A. L6 cells, deprived of proline for 6 hours, retained the stimulation of transport after detachment from the monolayers with trypsin. Uptake rates were comparable in suspended and attached cells in monolayer culture. Thus, amino acid‐depreivation of L6 cells results in an adaptive increase in proline uptake, which is not due to unstirred layers but appears to be mediated by other mechanisms of sele

ISSN:0021-9541    

DOI:10.1002/jcp.1041120211

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

年代:1982

数据来源: WILEY