bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inhibition of sulfate transport in ehrlich ascites tumor cells by 4‐acetamido‐4′‐isothiocyano‐stilbene‐2,2′‐disulfonic acid (SITS)
Authors: Villereal Mitchel L. , Levinson Charles 
Published: February 2005

AbstractThe effects of the nonpenetrating amino reactive reagent 4‐acetamido‐4′‐isothiocyano‐stilbene‐2‐2′‐dilsulfonic acid (SITS) on anion transport (sulfate, chloride, and inorganic phosphate) were investigated in Ehrlich ascites tumor cells. Short time exposure to SITS produces a reversible inhibition (92%) of sulfate transport. The kinetics of interaction suggest that reversibly bound SITS competitively inhibits sulfate transport, Ki = 3 × 10−6 M. Incubation of tumor cells with SITS (1 × 10−4 M) for longer periods of time results in a time dependent irreversible inhibition of sulfate transport which obeys first order kinetics. The rate coefficient for the inactivation process is 0.040 min−1. The kinetics of irreversible inhibition is best explained by the irreversible binding of SITS to the sulfate transport site, and therefore makes SITS a potentially useful probe for the quantitation of these sites in the tumor cell. The lack of effect of irreversibly bound SITS on either chloride or inorganic phosphate transport points to a specificity in the interaction of SITS with the tumor cell membrane, as well as indicating that an alternate pathway exists for the movement of these anions across the membrane.
Endosymbiosis in amoebae: Recently established endosymbionts have become required cytoplasmic components
Authors: Jeon K. W. , Jeon M. S. 
Published: February 2005

AbstractA strain of large, free‐living amoeba that became dependent on bacterial endosymbionts which had infected the amoebae initially as intracellular parasites, was studied by micrurgy and electron microscopy. The results show that the infected host cells require the presence of live endosymbionts for their survival. Thus, the nucleus of an infected amoeba can form a viable cell with the cytoplasm of a noninfected amoeba only when live endosymbionts are present. The endosymbiotic bacteria are not digested by the host amoebae and are not themselves used as nutritional supplement. While the host amoebae are dependent specifically on the endosymbionts, the latter can live inside amoebae of different strains, indicating that their dependence on the host cells is not yet strain specific.
α‐Aminoisobutyric Acid Transport into Human Glia and Glioma Cells in Culture
Authors: Ronquist G. , Ågren G. , Ponten J. , Westermark B. 
Published: February 2005

AbstractThe AIB transport into human glia and glioma cells in culture has been studied. Because of the high affinity of AIB to the plastic culture dishes, a special washing technique had to be developed. With this technique, it was possible to perform transport experiments in a single plate containing about one million cells. The cells were viable, intact and adhered to the supporting medium throughout the experiment.The AIB transport into both types of cells was Na+‐dependent and showed saturation kinetics when the small component of the transport due to diffusion had been subtracted.The AIB transport capacity of neoplastic glioma cells was 3.6 times higher than that of glia cells. This difference was related to the Vmax‐values for the two types of cells. The apparent Km‐values were the same.Inhibition experiments with other amino acids support the view that AIB is transported via System A in both glia and glioma cells.Sulfhydryl reagents (ethacrynic acid and NEM) and cytochalasin B clearly inhibited the AIB transport into glia cells whereas the effect on glioma cells was minimal.
Different recovery patterns of mouse haemopoietic stem cells in response to cytotoxic agents
Authors: Blackett N. M. , Millard R. E. 
Published: February 2005

AbstractThe response and subsequent recovery of mouse haemopoietic progenitor cells (spleen colony forming cells and agar colony forming cells) has been studied following two cytotoxic agents. Busulphan was administered to normal mice and vinblastine to mice where the progenitor cell proliferation rate had been increased by a period of continuous γ‐irradiation. With both these agents there is a difference between the response of the spleen colony forming cells and the agar colony forming cells during the first five days. They then recover together, but much more slowly after busulphan than after vinblastine even though their proliferation rate is increased.The rate of progenitor cell recovery after busulphan is increased if the progenitor cells are depleted further by vinblastine. However, methotrexate, which severely depletes the peripheral blood count and bone marrow cellularity but not the progenitor cells, has no effect on the recovery following busulphan.These results suggest that following cytotoxic agents the agar colony forming cells (“committed” stem cells) are not self‐maintaining but are dependent on a supply of cells from the pluripotential spleen colony forming cells. In addition it appears that the depletion of the progenitor cells of the bone marrow and not the depletion of the maturing cells, provides a stimulus for stem cell recovery.
The H+/site ratio of mitochondrial electron transport
Authors: Brand Martin D. , Reynafarje Baltazar , Lehninger Albert L. 
Published: February 2005

AbstractThe number of H+ ejected during passage of 2e− through each energy‐conserving site of the mitochondrial respiratory chain (the H+/site ratio) was measured in three ways. In each case transmembrane movements of endogenous phosphate were minimized. (1) Measurement of the uptake of weak acids during loading of mitochondria with Ca2+ demonstrated that 2.0 weak acid anions were accumulated per Ca2+ ion. Since 1.7 to 2.0 Ca2+ ions were taken up per site, these data correspond to an H+/site ratio of 3.5 to 4.0. (2) More direct measurement of H+ ejection using the oxygen pulse technique demonstrated that the H+/site ratio was 3.0. In these experiments phosphate movements were prevented by addition of N‐ethylmaleimide to inhibit phosphate‐hydroxide antiport, by washing the mitochondria to remove endogenous phosphate, or by working at 5°C to reduce the rate of phosphate transport. When phosphate movements were allowed, H+/site ratios of 2.0 were observed. (3) Measurement of the initial steady rates of oxygen consumption and H+ ejection following addition of substrate to aerobic, substrate‐limited mitochondria yielded H+/site ratios of 2.0, which were elevated to 4.0 when phosphate transport was prevented as described above.Previous determinations of the H+/site ratio were thus underestimates due to the unrecognized movements of endogenous phosphate; our results show that the H+/site ratio is at least 3.0 and may be as high as 4.0.
Is glucose transport enhanced in virus‐transformed mammalian cells? A dissenting view
Authors: Romano Antonio H. 
Published: February 2005

AbstractMuch of the literature on the uptake of glucose by untransformed and transformed animal cells is based on experiments carried out with 2‐deoxy‐D‐glucose (2‐DOG). Results obtained with this analog can be ambiguous, since 2‐DOG can be phosphorylated by hexokinases of animal cells. An intracellular trapping mechanism is thus provided. Therefore, the total flux of 2‐DOG into the cell is a resultant of both transport and hexokinase action, and the measurement of total 2‐DOG incorporation is a valid measurement of transport only if 2‐DOG is phosphorylated as rapidly as it enters the cell. Evidence is presented here that this is not necessarily the case; significant levels of free intracellular 2‐DOG approaching external concentrations were found in untransformed and transformed mouse 3T3 cells even at early times during uptake. Differences in total intracellular 2‐DOG between untransformed and transformed cells were accounted for entirely by 2‐deoxyglucose phosphate. Thus, it appears the apparent increase of 2‐DOG uptake accompanying transformation in these cell lines is not due to an effect on the transport process, but on enhanced phosphorylation, which is a reflection of an alteration in the regulation of glycolysis. The ambiguity introduced by phosphorylation can be obviated by the use of an analog that cannot be phosphorylated, such as 3‐O‐methyl‐D‐glucose. The rate of transport and efflux of this sugar was not found to be different in untransformed versus transformed 3T3 cells. Moreover, deficiencies of this analog as a substrate for the glucose transport system are pointed out.
High‐affinity cytochalasin b binding to normal and transformed BALB/3T3 cells
Authors: Atlas Susan J. , Lin Shin 
Published: February 2005

AbstractTo study the molecular basis of changes in sugar uptake rate in cultured mouse fibroblasts with different physiological states, we have measured the high affinity binding of [3H] cytochalasin B, a potent sugar transport inhibitor, to actively growing and contact inhibited Balb/3T3 cells as well as to 3T12 and SV3T3 cells. Binding was the same whether the cells were detached from dishes with EDTA or trypsin. The amount of drug bound to intact cells measured with a centrifugation assay was essentially the same as that bound to cell sonicates measured with equilibrium dialysis. Cytochalasin B binding to intact cells was extremely rapid and reversible over a wide range of drug concentrations, and was not affected by 0.1 M D‐glucose or L‐glucose in the assay medium. Actively growing and contact inhibited 3T3 cells had a similar number of high affinity cytochalasin B binding sites per cell, while 3T12 and SV3T3 cells had one third to one fourth the number of sites per cell. However, the number of sites per μg cellular protein appeared to be similar for cells in all of the physiological states examined.
Neoplastic potentials and regulation of uptake of nutrients. I. A glutamine independent variant of polyoma bhk with a very high neoplastic potential
Authors: Gammon Maureen T. , Isselbacher Kurt J. 
Published: February 2005

AbstractA variant of polyoma BHK cells is described which is capable of growing in a glutamine‐free medium. These glutamine‐independent variant cells (GIV) have a size and morphologic appearance intermediate between the nontransformed (BHK) and polyoma transformed (Py6) cell line. In contrast to Py6, the GIV cells grow more slowly, produce less lactic acid and do not grow in suspension. However, their adherence to substrate and release of galactosyl‐transferase into the medium is comparable to that seen with the parent PyBHK. Most striking is the finding that GIV cells are more readily agglutinated by Concanavalin A and when inoculated into hamsters are much more tumorigenic than the parent Py6 cells.
Differences in neutral amino acid and glucose transport between brush border and basolateral plasma membrane of intestinal epithelial cells
Authors: Hopfer Ulrich , Sigrist‐Nelson Kristine , Ammann Elvira , Murer Heini 
Published: February 2005

AbstractA comparison of L‐valine and D‐glucose transport was carried out with vesicles of plasma membrane isolated either from the luminal (brush border) or from the contra‐luminal (basolateral) region of small intestinal epithelial cells. The existence of transport systems for both non‐electrolytes was demonstrated by stereospecificity and saturability of uptake, as well as tracer coupling. Transport of L‐valine and D‐glucose differs markedly in the two types of plasma membrane with respect to stimulation by Na+. The presence of Na+ stimulated initial L‐valine and D‐glucose uptake in brush border, but not in basolateral membrane. Moreover, an electro‐chemical Na+ gradient, oriented with the lower potential on the inside, supported accumulation of the non‐electrolytes above medium concentration only in the brush border membrane. L‐Valine and D‐glucose transport also were saturated at lower concentrations in brush border (10‐20 mM) than in basolateral plasma membranes (30‐50 mM). A third difference between the two membranes was found in the effectiveness of known inhibitors of D‐glucose transport. In brush border membranes phlorizin was more potent than phloretin and 2′,3′,4′‐trihydroxy‐4‐methoxy chalcone and cytochalasin B did not inhibit at all. In contrast, with the basolateral plasma membranes the order of potency was changed to phloretin = 2′,3′,4′‐trihydroxy‐4‐methoxy chalcone > cytochalasin B > phlorizin.These results indicate the presence of different types of transport systems for monosaccharides and neutral amino acids in the luminal and contra‐luminal region of the plasma membrane. Active transepithelial transport can be explained on the basis of the different properties of the non‐electrolyte transport systems in the two cellular regions and an electro‐chemical Na+ gradient that is dependent on cellular metabolism.
Heparan sulfates of mouse cells. Analysis of parent and transformed 3T3 cell lines
Authors: Underhill Charles B. , Keller John M. 
Published: February 2005

AbstractHeparan sulfate from the surface of a variety of mouse cells at different cell densities was examined by ion‐exchange chromatography. The results of this analysis show that:

The heparan sulfate from new isolates of Swiss 3T3 cells transformed SV40 virus (a DNA tumor virus) elutes from DEAE‐cellulose at a lower ionic strength than that from the parent cell type. This finding confirms our earlier observation with an established SV40‐transformed cell line (Underhill and Keller, 1975) and eliminates the possibility that this change is caused by extended passage in culture.
For both parent and transformed 3T3 cells, the heparan sulfates from low and high density cultures were the same as judged by chromatography on DEAE‐cellulose. This result demonstrates that the transformation‐dependent change which we have observed is independent of cell density.
The heparan sulfate from Balb/c 3T3 cells transformed with Kirsten murine sarcoma virus (an RNA tumor virus) elutes from DEAE‐cellulose prior to that from parent Balb/c 3T3 cells. This result extends the transformation dependent change in heparan sulfate to the Balb/c 3T3 cell line and to cells transformed with an RNA virus.
Differential effects of ACTH or 8‐Br‐cAMP on growth and replication in a functional adrenal tumor cell line
Authors: Weidman E. Russell , Gill Gordon N. 
Published: February 2005

AbstractThe effects of ACTH and 8‐Br‐cAMP on growth and replication of a functional mouse adrenal tumor cell line (Y‐1) were investigated. ACTH and 8‐Br‐cAMP both inhibited DNA synthesis and replication when added to randomly growing cell cultures. ACTH addition and serum deprivation each arrested cells in G1; an additional point of arrest in G2 occurred with 8‐Br‐cAMP. Cells whose growth was arrested in G1 by ACTH had a significantly larger volume and protein and RNA content compared to cells arrested in G1 by serum deprivation. When ACTH or 8‐Br‐cAMP was added with serum to cells arrested by serum deprivation, the wave of DNA synthesis and cell division seen with serum was abolished. ACTH and 8‐Br‐cAMP had no effect on the serum‐induced increases in protein and RNA content, rates of leucine incorporation into protein and uridine incorporation into RNA, and RNA polymerase I activity observed in cells during the pre‐replicative period. Partial inhibition of the serum‐induced increase in uridine transport occurred. ACTH and cAMP do not appear to inhibit replication by generalized negative pleiotypic effects but rather to inhibit the initiation of DNA synthesis more specifically. The ACTH‐arrested Y‐1 cell resembles an in vivo hypertrophied adrenal cortical cell.
Organ interactions in the regulation of hematopoiesis: In vitro interactions of bone, thymus, and spleen with bone marrow stem cells in normal, Sl/Sld and W/Wv mice
Authors: Cline Martin J. , Le Fevre Carol , Golde David W. 
Published: February 2005

AbstractHematopoietic cell differentiation is influenced by organ‐dependent microenvironmental factors as well as humoral regulators. A technique is described for examining certain aspects of the hemopoietic inductive microenvironment in vitro.Suspension and agar cultures of mouse bone marrow were used to study the effects of organ stromal factors on cellular proliferation and differentiation. Bone, spleen, and thymus fragments from irradiated mice were placed in direct contact with or separated by a Nuclepore membrane from syngeneic marrow cells growing in suspension cultures. Normal adult mouse bone and spleen influenced granulocytic differentiation as well as cell proliferation.In this system, bone marrow and organ fragments from W/Wv and Sl/Sld mice behaved like those of their non‐anemic littermates. The most prominent difference between W/Wv and Sl/Sla mice and their normal counterparts was observed in the induction of CFU‐C from splenic precursors under the influence of CSA. In both types of anemic mice, in vitro generation of CFU‐C from spleen was abnormal in young animals but was corrected by four months of age.
Messenger RNA regulation in human diploid fibroblasts
Authors: Meedel Thomas H. , Levine Elliot M. 
Published: February 2005

AbstractIn resting, non‐growing human diploid fibroblasts the amount of rRNA is reduced 1.8‐fold, cytoplasmic polysomes are disaggregated, and the level of poly‐A RNA (mRNA) is reduced 1.8‐fold in relation to growing cells. The distribution of poly‐A RNA is altered in resting, non‐growing cells so that an average of 64% of the total cytoplasmic poly‐A RNA sediments along with particles lighter than 80S (prepolysomal) in sucrose density gradients. By comparison, in growing cells only 30% of the cytoplasmic poly‐A RNA sediments in the prepolysomal region. In SDS sucrose gradients, the sedimentation profile of the prepolysomal poly‐A RNA from resting cells resembles that of polysomal poly‐A RNA from those cells. In contrast, the average size of prepolysomal poly‐A RNA from growing cells is much smaller than that of the polysomal poly‐A RNA from those cells. These data are compatible with the possibility that resting cell prepolysomal poly‐A is untranslated mRNA. Also consistent with this interpretation are experiments which demonstrate that one‐quarter to one‐third of the prepolysomal poly‐A RNA of resting cells is recruited into polysomes in the presence of cycloheximide.
Differential effects of inhibitors of cell division upon the growth stimulating activities of insulin and serum in nutritionally depleted human and mouse cells
Authors: Kamely Daphne 
Published: February 2005

AbstractCultured mouse and human cells were arrested in their growth by artificially depriving them of phosphate. The quiescent cells could be stimulated to synthesize DNA and to divide by addition to the growth medium of insulin, dialyzed serum and/or the full concentration of phosphate. In order to gain insight into mechanisms by which insulin and serum stimulate growth, the inhibitory effects of antimitotic agents were examined. Of the inhibitors tested, vinblastine and cytocalasin B abolished the growth promoting activity of insulin, while colchicine inhibited the activity of both serum and insulin. The present results suggest that insulin‐stimulated growth is mediated by a different pathway than serum‐stimulated growth and is sensitive to mechanisms that occur at various times prior to insulin addition.
The effects of erythropoietin in vitro on spleen colony‐forming cells
Authors: Van Zant Gary , Goldwasser Eugene , Pech Nancy 
Published: February 2005

AbstractErythropoietin (epo) added to liquid cultures of mouse bone marrow cells affected both the numbers of spleen colony‐forming cells (CFU) in the cultures and the types of spleen colonies formed from these cells in irradiated hosts. Epo caused an increase in the numbers of CFU detected in cultures on the second day; this effect persisted through day 10, with the maximal increase occurring on the seventh day. The magnitude of the rise on day 7 was proportional to the amount of epo added. The increase in spleen colonies found with cells cultured in the presence of epo was due solely to erythroid colonies. After seven days in culture without epo, there was a peak of cells that formed non‐erythroid colonies. This peak did not appear when the cells were cultured in the presence of epo.
The effects of biotin and fatty acids on SV3T3 cell growth in the presence of normal calf serum
Authors: Messmer Trudy O. , Young Delano V. 
Published: February 2005

AbstractThe growth of SV3T3 cells in medium containing a low concentration (0.20% v/v) of normal calf serum is enhanced by the addition of biotin or certain unsaturated fatty acids. The biotin effect on the final viable cell density is 5‐ to 10‐fold over the control and is extremely potent, exerting a saturating response at a concentration of approximately 200 pg/ml. The optimal growth response observed with fatty acids is 5‐fold over the control and requires the combination of nervonic acid, palmitoleic acid, and arachidonic acid. The fatty acids are probably not replacing the function of biotin since these two substances are additive in their growth effects.
Secondary activities of diverse inhibitors potentiate the response of hamster embryo cultures to a mitotic stimulus
Authors: Mironescu Stefan , Ellem Kay A. O. 
Published: February 2005

AbstractThe reversal of the density dependent inhibition of replication (DDIR) of Syrian hamster embryo cultures by fresh medium containing 30–50% fetal bovine serum was poorly synchronized. There were two waves of DNA synthesis eight to nine hours apart, which by examination of autoradiograms of cultures pulse‐labeled with 3H‐thymidine, were found to involve 55% and 45% of the cell population. The second wave was found to be due to a subpopulation of epithelioid cells set in the predominantly fibroblastic cell cultures.Pretreatment of the DDIR cultures with hydroxyurea (HU) or arabinosyl cytosine (ara‐C), followed by serum stimulation in the absence of the drugs, led to an enhancement of the synchrony. The effect increased with lengthening of the contact with antimetabolites, to a maximum after 20 hours' pre‐exposure, and was in part due to the shortening of the G1 phase of the epithelioid elements, and in part to increasing the synchrony of the fibroblastic cells. The resulting synchrony involved some 95% of the cells in simultaneous DNA synthesis after a median G1 period of 12 hours. The effect had no relationship to the role of HU and ara‐C as specific inhibitors of DNA synthesis since the cultures were mitotically quiescent, and a similar enhanced response could be induced in DDIR cultures by prestimulation exposure lasting only two hours to cycloheximide (cyx), an inhibitor of protein synthesis. Pre‐exposure of DDIR cultures to actinomycin D did not potentiate the cell response. A survey of the known secondary inhibitions caused by these three antimetabolites suggests that they all may cause deficiencies in the glycolipid or glycoprotein moieties of the cell surface. These observations provide a useful, simple means of improving synchrony in these systems and may prove to be a useful probe for investigating the role of the cell surface in regulating cell replication.
Replication kinetics of three DNA sequence families in synchronized mouse cells
Authors: Dooley Douglas C. , Ozer Harvey L. 
Published: February 2005

AbstractBalb/C 3T3 cells entered the quiescent G0 state following serum deprivation. On addition of fresh serum, more than 95% of the culture resumed growth, but with asynchronous kinetics. If hydroxyurea were added just before the first cells reached S phase, at least 90% of the cells accumulated at the Gl/S border over the next ten hours. When the block was removed, the culture moved synchronously into S phase. As the cells traversed S, the replication kinetics of three classes of rapidly renaturing DNA were analyzed. Main band highly repeated DNA and foldback DNA replicated continuously. In contrast, satellite DNA replication did not commence until three hours into S, whereupon its rate of synthesis increased very rapidly, reaching a maximum within the next two hours. These results are discussed in the light of earlier work utilizing other methods of cell synchronization.