bluuebunny/crossref_metadata_2025_split huggingface dataset:
Early, anti‐immunoglobulin induced events prior to NA+‐K+ pump activation: An analysis in a monoclonal human B‐lymphoma cell population
Authors: Heikkilä Reino , Iversen Jens‐Gustav , Godal Tore 
Published: February 2005

AbstractEvents following F(ab)2 anti‐δ immunoglobulin stimulation of monoclonal (leukemic) human B cells prior to Na+‐K+ pump activation were investigated in vitro. This pump activation, measured by ouabain‐sensitive 86Rb+ uptake, appeared susceptible to the phospholipid‐interacting drugs tetracaine and quinacrine, to the antioxydant nordihydroguaiaretic acid (NDGA), and to the calmodulin antagonist trifluoperazine, while much less susceptible to the methylation inhibitor‐3‐deazaadenosine. The Ca++ ionophore A 23187 appeared to induce pump activation in a way similar to anti‐δ, as it was susceptible to the same drugs and as anti‐δ had no additional stimulating effect on A 23187‐stimulated cells. However, whereas the anti‐δ‐induced activations appeared independent of the extracellular Ca++ activity, [Ca++]e, the activation by A 23187 was potentiated by addition of the CA++ chelator ethyleneglycol‐bis (β‐aminoethyl ether) N, N'‐tetracetic acid (EGTA). Estimations by a fluorescent chelator method (quin 2) showed anti‐δ to increase the intracellular Ca++ activity, [Ca++]i both in the absence and presence of EGTA. A 23187 increased [Ca++]i strongly in Ca++ medium, but was weaker, more similar to the anti‐δ response, in EGTA medium. It is suggested that Na+‐K+ pump activation after anti‐lg stimulation in B cells may follow Ca++ mobilization from internal stores. The trifluoperazine susceptibility suggests that calmodulin regulation is involved.
Isolation and characterization of vitamin A‐sensitive chinese hamster lung cell lines
Authors: Ikezaki Kiyonobu , Akiyama Shin‐Ichi , Nakamura Mitsuo , Komiyama Sohtaro , Kuwano Michihiko 
Published: February 2005

AbstractRetinyl acetate (RA)‐sensitive variants (RAs‐2 and RAs‐3) of V79 cell line were isolated after mutagenesis with N‐methyl‐N′‐nitro‐N‐nitrosoguanidine. The variants were stable and showed a 3‐ to 4‐fold increase in sensitivity to RA compared to parental V79 cells. The RAs‐2 clone was also sensitive to retinol and retinol palmitate. The RA‐sensitivity behaves as a recessive trait in all hybrids of RAs‐2 and V79. A number of physiological parameters were indistinguishable in V79 and RAs‐2 cells, including the extent of uptake of [3H]retinol, the release of K+ from the cells induced by RA, and the levels of retinol and retinoic acid binding proteins. However, one possible correlation with the RA‐sensitive phenotype was observed: Gomori acid‐phosphatase staining of RA‐treated RAs‐2 and V79 cells indicated that lysosomal membrane of RAs‐2 cells was more labile than those of the parental V79 cells.
Phorbol ester‐stimulated murine myelopoiesis: Role of colony‐stimulating factors
Authors: Stuart Robert K. , Sensenbrenner Lyle L. , Shadduck Richard K. , Waheed Abdul , Caramatti Cecilia 
Published: February 2005

AbstractTumor promoting phorbol esters, such as 12‐0‐tetradecanoyl‐phorbol‐13‐acetate (TPA), stimulate colony formation in vitro by murine granulocyte‐macrophage progenitors (GM‐CFC) without added colony stimulating factors (CSF). To determine whether TPA induces CSF production in vitro, marrow cells were cultured for 1 to 7 days in liquid medium with or without TPA. No CSF was detected in any sample by a double antibody radioimmunoassay (sensitivity = 2 units/0.1 ml), however, colony‐stimulating activity was detected in supernatant fluid from all TPA containing cultures by bioassay. This activity appeared to result from a direct effect of TPA rather than from production of CSF, as equivalent activity was found in TPA‐containing medium incubated in the absence of marrow cells. Rabbit antiserum to purified L‐cell CSF inhibited colony formation stimulated by L‐cell CSF and WEHI‐3 CSF, but had no effect on colony formation induced by TPA. Cells from long‐term marrow cultures responded to TPA with colony formation, despite culture conditions and cell fractionation procedures that reduced the frequency of CSF‐proclucing macrophages to > 1.0%. TPA inhibited binding of radioiodinated L‐cell CSF to marrow cells, especially if the cells were first exposeed to TPA. These results do not support induction of CSF production as the major mechanism of phorbol ester stimulation of myelopoiesis. Phorbol esters may directly stimulate GM‐CFC and/or enhance their response to CSF by a mechanism involving CSF binding sites.
In vitro growth inhibition of murine leukemia cells by antibody specific for the major envelope glycoprotein (gp71) of friend leukemia virus
Authors: Genovesi Eugene V. , Collins Jeffrey J. 
Published: February 2005

AbstractAn in vitro complement (C′)‐independent growth cytostasis model is described in which the replication of Friend leukemia virus (FLV)‐induced erythroleukemia cells (of the FLC‐745 cell line) is inhibited by goat serum directed against the major FLV envelope glycoprotein, gp71. The cytostatic effect is reversible, with the degree of this reversibility dependent on both the concentration and duration of exposure to immune serum. The inhibitory factor in heat‐activated goat anti‐FLV gp71 (δGαFLV gp71) serum has been identified as virus‐specific IgG antibody, and F(ab')2 fragments of this antibody are highly effective in suppressing FLC‐745 cell growth. Studies with various murine leukemia and lymphoma cell lines, as well as with a panel of antisera directed against various murine oncornaviruses or viral proteins, have demonstrated that antibodies reactive with the group or type determinants of FLV gp71 are capable of mediating cytostasis. Under conditions of antibody‐mediated growth inhibition of FLC‐745 cells, specific modulation of gp71 expression is followed by nonspecific modulation of H‐2d antigen expression. In addition, considerable cell death occurs in cytostatic cultures which is accompanied by continued division (as measured by DNA synthesis) of a portion of the cell population. Cytofluorimetric analysis of nuclei from growth‐inhibited FLC‐745 cells demonstrates a diminution in the frequency of cells in the G2/M phase of the cell cycle. It is suggested that antibody‐mediate FLC‐745 cell growth inhibition operates via a blockade of the cell cycle which prevents most cells in the population from traversing G2/M. While these blocked cells appear to be subject to slow cytolysis by a C′‐independent mechanism, a portion of the cells escape this blockade and continue to replicate, thus offsetting the death of the former cells to yield a relatively constant density of viable cells for at least 72–96 h of growth inhibition. The possible relevance of this in vitro phenomenon to in vivo passive therapy against FLV‐induced disease with GαFLV gp71 and similar antisera is briefly considered.
Immunocytochemical localization of chick DNA polymerases α and β+
Authors: Matsukage Akio , Yamamoto Susumu , Yamaguchi Masamitsu , Kusakabe Moriaki , Takahashi Taijo 
Published: February 2005

AbstractAn immunofluorescent method using specific antibodies was employed to detect DNA polymerases α and β in chick cells. With monoclonal antibodies produced by four independent hybridoma clones, most of the DNA polymerase α was shown to be present in nuclei of cultured chick embryonic cells. With a polyclonal, but highly specific, antibody against DNA polymerase β, this enzyme was also shown to be present in nuclei. DNA polymerase α was detected in proliferating cells before cell contact and in lesser amount in resting cells after cell contact, indicating that its content is closely correlated with cell proliferation. On the other hand, similar amounts of DNA polymerase β were detected in proliferating and resting cells. Furthermore, DNA polymerase β was detected in nuclei of most cells, while DNA polymerase α was detected only in large round nuclei in seminiferous tubules of chick testis. DNA polymerase α is presumably present in cells that are capable of DNA replication, and during the cell cycle it seems to remain in the nuclei during the G1, S, and G2 phases, but to leave from condensed chromatin for the cytoplasm during the mitotic phase.
Characterization of the early and late stages of myelomonocytic leukemia induced by friend helper‐independent virus F‐MuLV: Isolation and induction of friend myelomonocytic leukemic cell lines
Authors: Shibuya Tsunefumi , Mak Tak W. 
Published: February 2005

AbstractWith the use of cloned helper‐independent Friend leukemia virus (F‐MuLV), we have induced a high incidence (∼︁ 70%) of myelomonocytic leukemia in mice resistant (Fv‐6rr or Fv‐6rs) to erythroleukemia induction by this virus. The spleen cells from these mice (DBA/2 or BALB/c × DBA/2) were found to contain a high level of progenitor cells capable of forming granulocytic and macrophage colonies (CFU‐GM). These CFU‐GM, however, were different from those in the speens of uninfected mice, as they were either very sensitive to or independent of conditioned medium. No erythroid progenitor bursts (BFU‐E) or precursor (CFU‐E) cells were detected in the speens of these diseased animals. If these mice with myelomonocytic leukemia were kept alive by transfusion of red blood cells from uninfected mice, tumorigenic cell lines, capable of being transplanted, into adult mice can be isolated. Three such cell lines TTA‐1, TTA‐3, and TTA‐9 have been established, and they retain their morphology of monocytes and macrophages as well as being positive for the monocyte‐specific stain α‐naphtyl‐acetate esterase. These myelomonocytic leukemia cell lines can also be induced in culture by speen cell‐conditioned medium to differentiate into macrophages. Other conditioned media such as L‐cell‐conditioned medium, phytophemmaglutinin‐stimulated leukocyte‐conditioned medium, and WEHI‐3 conditioned medium were less effective in their abilities to stimulate differentiation in these myelomonocytic leukemia cell lines.
Concanavalin A increases spontaneous beat rate of embryonic chick heart cell aggregates
Authors: Myrdal Sigrid E. , Dehaan Robert L. 
Published: February 2005

AbstractThe plant lectin concanavalin A (Con A), at concentrations of 5–200 μg/ml, induced a twofold to fivefold increase in spontaneous beat rate of cultured aggregates of ventricular cells from seven‐day chick embryos. This response was time, dose, and temperature dependent and was accompanied by a decrease in transmembrane potential. It could be blocked or reversed by α‐methyl‐D‐mannoside but was not reversed by dilution alone. Binding of the lectin occurred in the cold, but a temperature‐dependent process was also necessary to produce the response. Divalent (succinyl) Con A did not cause a beat rate increase. Whole heart aggregates responded similarly but less intensely than ventricular aggregates. Atrial aggregates, and whole heart aggregates treated with 5 μg/ml of Con A, produced a biphasic chronotropic response, first decreasing then increasing their beat rates. These results suggest that saccharide‐bearing macromolecules on the heart cell surface play a role in regulating spontaneous beat rate.
A reevaluation of the response of human umbilical vein endothelial cells to certain growth factors
Authors: Knauer Daniel J. , Cunningham Dennis D. 
Published: February 2005

AbstractHuman umbilical vein endothelial cells (HUV‐EC) were isolated and maintained in pure culture on a fibronectin matrix with hypothalamic derived endothelial cell growth factor included in the culture medium. HUV‐EC maintained under these conditons displayed only slight alterations in morphological appearance and continued to produce Factor VIII antigen. The cells showed an unaltered growth response to serum and added growth factors up to passage 16 (>30 population doublings). We found that epidermal growth factor (EGF) was potently mitogenic for HUV‐EC, but only in the presence of endothelial cell growth factor. Also in contrast to a previous report, we were unable to demonstrate a potentiation of this response by human α‐thrombin. Because of these discrepancies, we performed studies to determine if they might be explained by a difference in the interaction of our HUV‐EC with EGF. In studies utilizing 125I‐EGF as tracer probe, we determined that our HUV‐EC have an EGF receptor number of 13,000 sites/cell with an apparent Kd∼︁4.0 × 10−9 M. In addition, receptor‐bound 125I‐EGF was rapidly internalized and degraded presumably by a lysosomally mediated pathway since degradation was complete to the amino acid level. These results are in agreement with those previously published and thus do not provide a basis on which to resolve discrepancies regarding the growth response of HUV‐EC to various growth factors.
Constancy of cell buoyant density for cultured murine cells
Authors: Loken M. R. , Kubitschek H. E. 
Published: February 2005

AbstractThe relationship between cell cycle and cell density was determined for three different lines of mouse cells by equilbrium centrifugation of suspension cultures. The mean cell densities of the three lines differed significantly, with values of 1.0622, 1.0678, 1.0540 gm/ml for 70Z/3, S 107, and ABE 8, respectively. However, the density distributions within each of the three lines were indistinguishable, with an average coefficient of variation about 5% of the mean reduced density (i.e., density minus one). Quantitative DNA analysis of the cells separated by density showed that the proportion of cells in G1, S, and G2 + M phase of the cell cycle changed very little or not at all with cell density. In addition, cells separated by size (and therefore by phase of the cell cycle) using velocity sedimentation had the same means and distributions of densities. These results indicate that there is little or no change in cell density as the cells traverse the life cycle and that buoyant density appears to be a constant property of a cell type.
Evidence for differences in the mechanism of cell cycle arrest between senescent and serum‐deprived human fibroblasts: Heterokaryon and metabolic inhibitor studies
Authors: Burmer Glenna C. , Rabinovitch Peter S. , Norwood Thomas H. 
Published: February 2005

AbstractIt has previously been shown that serum‐deprived, early passage quiescent human diploid fibroblastlike (HDFL) cells are able to inhibit cycling cells from entry into DNA synthesis upon cell fusion. We have found that the degree of inhibition of DNA synthesis in the heterokaryon correlates with the duration of serum deprivation, which is consistent with the suggestion that serum‐deprived cells may enter progressively deeper stages of G0 as they increase their time in quiescence. In contrast to fusions with senescent cells, in heterokaryons between serum‐deprived early passage and cycling young cells transient inhibition of protein synthesis with cycloheximide or inhibition of RNA synthesis with 5–6‐dichloro‐1‐β‐D‐ribofuranosyl benzimidazole (DRB) did not stimulate nuclear [3H]‐thymidine incorporation. These results suggest that differences may exist in the mechanisms responsible for inhibiting cell cycle progression in senescent vs early passage quiescent HDFL cells.
In vitro hemopoiesis within a microenvironment created by MC3T3‐G2/PA6 preadipocytes
Authors: Kodama Hiro‐Aki , Sudo Hiroko , Koyama Hideki , Kasai Shiro , Yamamoto Shigehisa 
Published: February 2005

AbstractThe clonal preadipose cell line, MC3T3‐G2/PA6, has the capacity to differentiate into adipocytes in response to glucocorticoids and to support in vitro growth of hemopoietic stem cells (CFU‐S). To study the relationship between these capacities, we precultured the MC3T3‐G2/PA6 cells for varying days in the presence or absence of dexamethasone and then cocultured them with mouse bone marrow cells. Logarithmically growing cultures contained no detectable adipocytes and showed the highest growth‐supporting activity for CFU‐S, whereas cultures containing the largest number of adipocytes showed the lowest activity. When bone marrow cells were seeded onto 3‐day‐old MC3T3‐G2/PA6 preadipocyte layers at 1 × 105 cells/35‐mm dish, day 12 CFU‐S grew with a population doubling time of about 37 hr, and at least 75% of them were associated with the cell layer between days 2 and 7. In the absence of the preadipocytes, CFU‐S were not detected in the adherent cell fraction and decreased with a half‐life of about 18 hr. More than 80% of CFU‐C were also found to be associated with the preadipocyte layer, and they increased about 24‐fold in number during 7 days in culture. Morphologically, hemopoietic cells developing into mature granulocytes and macrophages were distributed between the layers of preadipocytes. Dendritic processes of preadipocytes were frequently in close alignment with the hemopoietic cells. However, adipocytes failed to show such an intimate association with hemopoietic cells. These results indicate that MC3T3‐G2/PA6 cells in the preadipocyte stage, but not in the adipocyte stage, have the capacity to support CFU‐S growth, and that hemopoiesis in our cocultivation system proceed within the microenvironmental milieu provided by MC3T3‐G2/PA6 preadipocytes.
Growth factors that stimulate human granulocyte—macrophage colony formation produced by the cell line CM‐S
Authors: Bertolini Luisa , Butler Richard H. , Revoltella Roberto P. 
Published: February 2005

AbstractCM‐S is an autonomous cell line of human hemopoietic precursor cells inducible to monocyte‐macrophage differentiation in response to appropriate inducing agents. CM‐S cells produce factors that stimulate their own growth and proliferation, and are also capable of stimulating clonal proliferation of human, but not mouse, monocytic and granulocytic bone marrow progenitor cells in viscous medium. Preliminary purification steps have demonstrated at least two species, one of which (MW 30,000–50,000) retains both these activities, while the other (MW ≤ 10,000) apparently retains only the autostimulatory activity. CM‐S cells could thus be a useful source for the purification of human colony stimulating factors (CSFs). CM‐S cells also respond to factors present in human placenta conditioned medium, known to contain human CSF. This suggests that CM‐S cells could provide a homogeneous target cell population for testing CSFs from other human sources.
The role of the G1 period in the life cycle of eukaryotic cells
Authors: Rao Potu N. , Satya‐Prakash K. L. , Wang Yong Chao 
Published: February 2005

AbstractThe objective of this study was to test the concept that the G1 period lacks any specific function in the life cycle of mammalian cells and hence could be drastically reduced without any effect on the generation time. HeLa cells were grown in medium containing an optimum dose (60 μM) of hydroxyurea at which the duration of S period was prolonged with little or no increase in generation time. At this concentration of hydroxyurea, we observed a maximum of 3 h (or 28.5%) reduction in the G1 period. We also studied the effects of synchronization in S phase by single and double thymidine blocks on cell size and its relationship to the duration of G1 in the subsequent cycle. By these treatments, we could reduce the G1 period by not more than 2 to 3 h. The reduction in G1 period was not directly proportional to the size (volume) of the G1 cells. These results suggest that G1 period has certain specific functions and cannot be eliminated by alterations in culture conditions.
Sequence of cell life phases in a finitely proliferative population of cultured rat cells: A genealogical study
Authors: Matsumura Toshiharu 
Published: February 2005

AbstractFamily trees of rat liver epitheliallike cells (RLECs), which proliferate finitely in primary culture, were obtained by time‐lapse cinemicrography (TLC). In family trees, RLECs were classified into those terminated with division (class D cells), those terminated with incomplete division (class I cells), i.e., division followed by fusion of two daughter cells, and the combined population (class N cells) of those terminated with death and those surviving for 120 hr or more with their termination not detected by TLC. The interphase period, but not the intersibling period, of class D cells became distributed more broadly with time on the family tree. These results for class D cells fit best to a transition probability model with two indeterminate states (Brooks et al., Cell, 19:493–504, 1980) when the model is modified in such a way that the transition probability for one of the two indeterminate states decreases with time. During proliferation of RLECs, some of the class D cells reproduce, while others showed transition, in part by way of class I cells, to class N cells. The frequency of transition from class D to class N increased with time in the family tree. Two sibling cells of a parent mitotic cell were simultaneously either class D or class N at a significantly high frequency, suggesting that the transition had been determined in the preceding cells. The present observations confirm previously described observations on human diploid cells, and in addition, reveal some new details of the finitely proliferative nature of somatic diploid cells.
Effect of ouabain and furosemide on pepsinogen secretion by gastric glands in vitro
Authors: Gibert Anne J. , Hersey Stephen J. 
Published: February 2005

AbstractGastric glands were isolated from rabbit stomach and pepsinogen secretion was measured after stimulation with isoproterenol, forskolin, 8‐bromo cyclic adenosine monophosphate (8‐bromo cAMP), cholecystokinin octapeptide (CCK‐OP), carbachol, and hyperosmolar medium. The responses to these stimuli in medium containing 143 mM Na+ and 5.4 mM K+ (normal medium) were compared with responses to the same stimuli in media containing either 0 Na+ and 5.4 mM K+, or 143 mM Na+ and O K+. In addition, the effects of ouabain and furosemide on secretion elicited by these stimuli were determined. Medium containing 0 Na+ inhibited all stimuli. Medium containing 0 K+ inhibited the action of 8‐bromo cAMP and stimuli postulated to be mediated by cAMP. Ouabain inhibited the same stimuli as O K+ medium, and, in addition, inhibitied the response to hyperosmolar medium. However, ouabain enhanced the response to CCK‐OP. Furosemide inhibited the response to hyperosmolar medium but had no effect on the action of any secretagogue employed. Intraglandular [Na+] increased and [K+] decreased after exposure to K+‐free medium or ouabain. cAMP content of the glands was assayed after stimulation with both isoproterenol and hyperosmolar medium. Isoproterenol and hyperosmolar medium significantly increased cAMP levels. The results are discussed in relation to possible involvement of ion transport or intracellular ion concentration in the secretory process.