bluuebunny/crossref_metadata_2025_split huggingface dataset:
Potassium transport and content during G1 and S phase following serum stimulation of 3T3 cells
Authors: Tupper Joseph T. , Zorgniotti Flavia , Mills Barry 
Published: February 2005

AbstractThe effect of serum stimulation on unidirectional and net K flux and their relationship to the initiation of DNA synthesis has been investigated in mouse 3T3 fibroblasts. Stimulation of quiescent 3T3 cells with 20% serum results in the initiation of S phase approximately ten hours after serum addition. During transition from G1 to S phase distinct changes in K transport and cellular K content occur. Total unidirectional K influx undergoes an immediate 2‐fold increase upon serum addition, an observation in qualitative agreement with previous results (Rozengurt and Heppel, 1975). This total increase in unidirectional K influx represents a proportional increase in the active, ouabain sensitive component and the K‐K exchange component. The initial increase in total flux is followed by a gradual decline over a 16‐hour period to levels approaching those of quiescent cells. Following the initial increase in unidirectional K influx is an approximately 75% increase in cell K on a per milligram protein basis or a 40% increase on a per volume basis. This increase peaks at four to five hours and then declines to initial levels at 10 to 14 hours. Populations of quiescent cells given 20% serum plus 0.5 mM ouabain simultaneously are totally blocked from entering S phase, as determined by the appearance of 3H‐thymidine labeled nuclei. However, if the ouabain is removed after six hours these cells then undergo the same changes in unidirectional K influx and content as serum stimulated cells with entrance into S phase retarded by five to six hours. If ouabain is added to serum stimulated cells at six hours, after the increase in K transport and K content have occurred, entrance into S phase is not entirely blocked. In cells stimulated with serum and 0.5 mM dBcAMP plus 1 mM theophylline simultaneously, entrance into S phase is greatly reduced as compared to serum stimulation only. However, the early and late changes in K flux and K content are not substantially altered. This indicates that the K transport events associated with G1 and early S phase are not directly regulated by changes in cAMP levels which follow serum stimulation.
The activity of the pneumococcal autolytic system and the fate of the bacterium during ingestion by rabbit polymorphonuclear leukocytes
Authors: Tomasz Alexander , Beckerdite Susan , McDonnell Maureen , Elsbach Peter 
Published: February 2005

AbstractThe extent to which autolytic microbial enzymes are involved in the fate of microorganisms ingested by phagocytes has not been determined. It is known, however, that activation of degradative enzymes occurs during certain microbicidal events.We examined the possible role of the pneumococcal autolytic enzyme (an N‐acetylmuramyl‐L‐alanine amidase) in the loss of viability and degradation of pneumococci during phagocytosis by rabbit polymorphonuclear leukocytes. Three bacterial systems were compared: (a) wild type pneumococci with an active autolytic system; (b) wild type bacteria grown under conditions that block the endogenous autolytic activity and (c) a mutant strain defective in the major autolytic enzyme of this bacterium. No differences could be detected between the autolysis‐positive and negative bacteria in the rate of killing and in the fate of macromolecular cell constitutents during ingestion by rabbit peritoneal polymorphonuclear leukocytes.
3‐O‐methylglucose transport by rat thymocyte subpopulations
Authors: Reeves John P. 
Published: February 2005

AbstractRat thymocytes can be separated into two subpopulations by centrifugation for 20 minutes at 1,600 g in an 18/26/36% (w/v) discontinuous gradient of bovine serum albumin. Approximately 13% of the cells band at the 18/26% interface (light cells) while the remaining cells band at the 26/36% interface (heavy cells). In vitro and in vivo studies of 3H‐thymidine incorporation indicate that the light cells are 2‐ to 3‐fold enriched in the rapidly dividing lymphoblast subpopulation of thymocytes as compared to heavy cells. Light cells transport the non‐metabolizable glucose analogue 3‐O‐methylglucose (3‐MeGlc) approximately four times faster than heavy cells. The time course of 3‐MeGlc uptake is biphasic for light, heavy and unfractionated thymocytes. While the half‐times of the rapid (1 minute) and slow (20–45 minute) phases of uptake are similar for all three types of cells, the contributions of the rapid phase to total uptake are 50% for light cells, 20% for unfractionated thymocytes and 10% for heavy cells. The results show that 3‐MeGlc transport activity differs markedly within certain thymocyte subpopulations. The correlation between the contributions of the rapid phase of uptake and the proportion of lymphoblasts in the thymocyte fractions suggests that the lymphoblast and small lymphocyte subpopulations might be responsible for the rapid and slow phase of 3‐MeGlc uptake, respectively.
Hexose uptake and control of fibroblast proliferation
Authors: Naiditch William P. , Cunningham Dennis D. 
Published: February 2005

AbstractThe role of glucose uptake in control of cell growth was studied by experimentally varying the rate of glucose uptake and examining the subsequent effect on initiation and cessation of cell proliferation. The rate of glucose uptake was varied by adjusting the concentration of glucose in the culture medium. This permitted analysis of two changes in rate of glucose uptake which are closely related to the regulation of cell growth: (1) the rapid increase in glucose uptake that can be detected within several minutes after mitogenic stimulation of quiescent fibroblasts and (2) the decrease in glucose uptake which accompanies growth to a quiescent state.Quiescent cultures of mouse 3T3, human diploid foreskin and secondary chick embryo cells were switched to fresh serum‐containing medium with either the normal amount of glucose or a reduced level that lowered the rate of glucose uptake below the rate characteristic of quiescent control cells. The subsequent increases in cell number were equal in both media, demonstrating that the increase in glucose uptake, commonly observed after mitogenic stimulation, was not necessary for initiation of cell division. Measurements of intracellular D‐glucose pools after serum stimulation of quiescent cells revealed that the increase in glucose uptake was not accompanied by a detectable change in the intracellular concentration of glucose.Nonconfluent growing cultures of mouse 3T3, human diploid foreskin and secondary chick embryo cells were switched to low glucose media, lowering the rate of glucose uptake below levels observed for quiescent cells. This did not affect rates of DNA synthesis or cell division over a several‐day period. Thus, the decrease in glucose uptake, which usually occurs at about the same time as the decrease in DNA synthesis as cells grow to quiescence, does not cause the decline in cell proliferation. Experiments indicated that there was no set temporal relationship between the decline in glucose uptake and DNA synthesis as cells grew to quiescence. The sequence was variable and probably depended on the cell type as well as culture conditions. Measurements of intracellular D‐glucose pools in secondary chick embryo cells demonstrated that the internal concentration of glucose in these cells did not significantly vary during growth to quiescence. Taken together, our results show that these fluctuations in the rate of glucose uptake do not lead to detectable changes in the intracellular concentration of glucose and that they do not control cell proliferation rates under usual culture conditions.
Methionine metabolism in BHK cells: The regulation of methionine adenosyltransferase
Authors: Caboche Michel 
Published: February 2005

AbstractThe regulation of methionine adenosyltransferase (MAT), an enzyme involved in SAM Abbreviations: DEAE cellulose, diethylaminoethyl cellulose; Hydroxo‐B1,2, (5.6‐dimethylbenzimidazolyl) hydroxo‐cobamide; MAMP, methioninol AMP; MAT, ATP: L‐methionine S‐adenosyltransferase; MTS, methionly tRNA synthetase; SAM, S‐adenosyl L‐methionine; tRNAmet, L‐methionine acceptor transfer RNA.
biosynthesis was studied in baby hamster kidney cells. A 4‐fold increase of the specific activity of MAT gradually occurred when cells were transferred to a medium containing low amounts of methionine. In a methionine rich medium the MAT specific activity of previously induced cells slowly decreased (half inactivation time: 30 hours). Actinomycin D and cycloheximide blocked the induction of the enzyme. The analysis of the mechanism of repression of MAT biosynthesis by methionine strongly suggested that a post‐transcriptional process of regulation was involved. The induction of MAT was not affected by the growth phase of cells.No evidence of a direct correlation between the intracellular amounts of aminoacylated tRNAmet and MAT repression was shown. A clone showing a reduced MTS activity was isolated by a (3H‐methyl) methionine suicide technique. The regulation of MAT remained unaffected in this clone. Cycloleucine, an inhibitor of in vivo SAM biosynthesis, induced the biosynthesis of MAT in a methionine rich medium. These results suggest that MAT is regulated by SAM, or a derivative of SAM, in hamster cells.A Cycloleucine resistant clone was isolated. This clone showed increased intracellular SAM pool and MAT activity. No evidence for a structural modification of the enzyme was shown. A regulatory mutation might be involved in this clone.
Human fibroblast conditioned media contains growth‐promoting activities for low density cells
Authors: Millis Albert J. T. , Hoyle Marian , Field Brenda 
Published: February 2005

AbstractNormal diploid human fibroblasts, cultured at high density (1–2 × 105 cells per cm2) release two growth promoting activities into the culture medium. The fibroblast proliferation activity‐conditioned medium facilitates the attachment of low density cells to the substrate. That activity resides in a non‐dialyzable material that is sensitive to proteolytic inactivation. A second activity is dialyzable and can be recovered in the dialysate. In the presence of serum it stimulates cell growth. After 168 hours of incubation conditioned medium cultures contain five times more cells than are present in comparable cultures without conditioned medium. A reproducible biological assay for each activity is described.
Polyamine biosynthesis and accumulation during the G1 to S phase transition
Authors: Fuller David J. M. , Gerner Eugene W. , Russell Diane Haddock 
Published: February 2005

AbstractOrnithine decarboxylase, an important enzyme in growth regulation, is increased in CHO cells in G1 phase of the cell cycle and decreases as the cells progress into S phase. S‐adenosyl‐L‐methionine decarboxylase activity, which is dependent on either the presence of putrescine or spermidine for the synthesis of spermidine and spermine respectively, shows a maximal increase in late G1/early S phase which corresponds very closely with the cell cycle phase specific accumulation of spermidine and spermine during S phase. Total culture evaluation of spermidine and spermine, which included extracellular as well as intracellular concentrations, indicated that extracellular accumulations of these polyamines occurred only in G1 and that entry into S phase was concomitant with intracellular accumulation patterns. Hyperthermia (43°C for 1 hour) in mid‐G1 phase of the cell cycle resulted in rapid decreases in the activities of ornithine decarboxylase and S‐adenosyl‐L‐methionine decarboxylase. In these cells, DNA replication was also not detectable until nine hours after mitosis, a time at which there had been recovery of ornithine decarboxylase and S‐adenosyl‐L‐methionine decarboxylase activities. Previous data have further indicated a requirement for polyamine reaccumulation before control DNA replication rates are resumed. We therefore suggest that polyamine biosynthesis and intracellular accumulation are both temporal and quantitative prerequisites for transition through S phase.
The characterization of SV40‐transformed cell lines derived from mouse teratocarcinoma: Growth properties and differentiated characteristics
Authors: Topp W. , Hall J. D. , Rifkin D. , Levine A. J. , Pollack R. 
Published: February 2005

AbstractMouse teratocarcinoma cells derived from embryoid bodies of 129SVsl mice were cultured in vitro to permit their differentiation. These cells were then infected with simiam virus 40 (SV40) and 31 cloned cell lines (SVTER) were derived from these cultures. All 31 SVTER cell lines contained the SV40 tumor (T) antigen and grew as permanent lines in culture. Mock‐infected embryoid body cultures did not give rise to permanent cell lines. The morphology of each SVTER cell line was distinct and did not change during successive subclonings.The growth properties and tumorigenic potential of all 31 SVTER cell lines were investigated. None of these lines produced tumors in 129SVsl mice. Each cell line was tested for its ability to (1) grow in medium containing 1% serum, (2) plate on a cell monolayer, and (3) form clones in methocel suspension. Only three of the SVTER cell lines were transformed with respect to all three of these criteria. Most of these cell lines were minimal transformation.The SVTER cell lines were tested for creatine phosphokinase (CPK), an enzyme activity characteristic of mouse brain and muscle tissue, and the protease, plasminogen activator (PA) which is found in embryoid bodies and several differentiated cell types. Some of the SVTER cell lines contained high levels of CPK, while others had high levels of PA and a third group of cells contained neither enzyme activity. No SVTER cell line was found with high levels of both these enzyme activities. This result suggests that mutually exclusive sets of genes are expressed in these cells as might be expected from the distinct tissue distribution of the two enzyme activities studied. These SVTER cell lines may be useful in reconstructing developmental pathways of differentiating teratomas in vitro.
Decreased membrane potassium permeability and transport in human chronic leukemic and tonsillar lymphocytes
Authors: Segel George B. , Lichtman Marshall A. 
Published: February 2005

AbstractHuman blood T‐lymphocytes increase their potassium (K+) permeability and active K+ transport following lectin or antigen stimulation. We have studied the permeability and active transport of K+ by lymphocytes in chronic lymphocytic leukemia (CLL) to determine if their membrane K+ transport was similar to resting or lectin‐stimulated normal blood lymphocytes. K+ transport was assessed both by the rate of isotopic 42K+ uptake and by the rate of change in cell K+ concentration after inhibition of the K+ transport system with ouabain.CLL lymphocytes had a marked decrease in membrane K+ permeability and active transport of K+ when compared to blood T lymphocytes. K+ transport in five subjects with CLL (10 mmol. 1 cell water−1. h−1) was half that in normal blood T‐lymphocytes (20 mmol. 1 cell water−1 h−1). Phytohemagglutinin (PHA) treatment of CLL lymphocytes did not increase significantly their active K+ transport, whereas K+ transport by normal T‐lymphocytes increased by 100%.Since there were 73% T‐lymphocytes in normal blood and 14% in CLL blood, the difference in membrane K+ turnover could be related either to neoplasia or to the proposed B‐lymphocyte origin of CLL. We studied human tonsillar lymphocytes which contained a mean of 34% T‐cells. In five studies of tonsils, K+ transport was 14 mmol. 1 cell water−1. h−1 and treatment with PHA increased K+ transport only 30%. The intermediate values for basal K+ transport and K+ transport in response to PHA in tonsillar lymphocytes were consistent with the proportion of T‐lymphocytes present. These data suggest that B‐lymphocytes have reduced membrane permeability and active transport of K+. Thus the marked decrease in CLL lymphocyte membrane K+ permeability and transport may be a reflection of its presumed B‐cell origin, rather than a membrane alteration related to malignant transformation.
Effect of the growth state on protein turnover in two lines of cultured BHK cells
Authors: Tanaka Keiji , Ichihara Akira 
Published: February 2005

AbstractTwo BHK cell lines (21 and 21/13) showed different rates of protein synthesis and degradation during growth in monolayer culture. During cell growth the rate of protein synthesis decreased progressively in BHK 21 cells, whereas in BHK 21/13 cells it remained constant. Furthermore, use of cell free systems showed that polysomes of BHK 21 were disaggregated markedly in the stationary phase, whereas those of BHK 21/13 were not. The rates of translation for protein synthesis in the two cell lines were similar, and were not affected by the growth state. The translation rates were measured as the times of ribosome transit and of peptide chain completion. This suggests that the decreased rate of protein synthesis in BHK 21 in the stationary phase may be due to a decreased rate of chain initiation.The curves for decay of proteins labeled with 3H‐leucine in 30 minutes were identical in the two cell lines in the growing state, showing a biphasic pattern due to rapidly degraded components (T1/2 = 16 h) and slowly degraded components (T1/2 = 65 h). However, in the stationary phase the half‐life of the rapidly degraded components of BHK 21/13 became 5 hours, while that of BHK 21 remained 16 hours. The half‐lives of slowly degraded proteins in the two cell lines were similar. It was also shown by the method of approach to equilibrium that the proteins of BHK 21/13 cells were degraded about twice as fast as those of BHK 21 cells in the stationary phase.Since there is no difference in the protein contents of the two cell lines at any stage of cell growth, it seems that during cell culture protein turnove of BHK 21 cells is controlled mainly by the rate of protein degradation.
Preparation of colony stimulating activity from large batches of human urine and production of antisera against it
Authors: Laukel H. , Gassel W.‐D. , Dosch H.‐M. , Schmidt W. , Havemann K. 
Published: February 2005

AbstractIn vitro induction of myelopoetic colonies from mouse bone marrow has been used for measurement of leucopoetic colony stimulating activity (CSA) isolated from large batches of human urine. After high flow dialysis in artificial kidneys and immediate adsorption to DEAE‐Cellulose, followed by purification on Con A‐Sepharose, treatment with insoluble Papain and gelfiltration on Sephadex G 100, enrichment of CSA was about 6,000‐fold. An important step of the enrichment procedure was the separation from a CSA‐inhibiting protein, probably combining with CSA.Specific activity was further increased by preparative polyacrylamide gel electrophoresis to 5.3 × 106 units per mg protein. The total enrichment exceeded 25,000‐fold.The final purification product consisted of a group of closely related proteins with high specific activity.Antisera raised with one of the electrophoretic fractions suppressed bioactivity in each of the different purification steps including the final CSA fractions differing in electrophoretic mobility. The antisera furthermore inhibited CSA in human lung and monocyte conditioned media but had only very little effect on partially purified CSA from stimulated human lymphocytes as well as CSA derived from mouse lung conditioned medium.
Antibody‐mediated suppression of bone marrow colony formation in vitro
Authors: Meyer‐Hamme Sabine , Bluestein Harry G. 
Published: February 2005

AbstractAntisera to mouse brain reacts with hematopoietic stem cells in the mouse bone marrow. We have examined the effect of anti‐mouse brain serum (AMBS) on the development of in vitro colonies from mouse bone marrow cells. The addition of 5% AMBS to the cultures markedly decreased the numbers of colonies formed to an average of 10% of the number obtained with normal rabbit serum. AMBS suppressed formation induced by colony stimulating factors (CSF) derived from three different sources; serum from endotoxin treated mice, mouse L‐cell conditioned media, and human peripheral blood mononuclear cell conditioned media. The suppressive activity was quantitatively recovered in the IgG fraction of AMBS. Divalent F (ab′)AHBS, rabbit anti‐human brain serum; AMBS, rabbit anti‐mouse brain serum; BM, bone marrow; CFU‐C, colony forming unit in vitro; CFU‐S, spleen colony forming unit; CSF, colony stimulating factor; FCS, fetal calf serum; MEM, minimal essential medium; NRS, normal rabbit serum; PBS, 0.01 M sodium phosphate, 0.15 M sodium chloride, pH 7.4.
fragments were as effective as the intact IgG in decreasing colony formation. Fab fragments were not suppressive. These results suggest that colony formation is induced via a dynamic interaction between CSF and the progenitor cell membrane, and that antibody directed at cell membrane antigen(s) interferes with the generation of the induction signal.
A hypotetraploid human T lymphoid cell line established by cell fusion
Authors: Ishii Kazuhiro , Yodoi Junji , Hanaoka Masao , Furuyama Jun‐Ichi 
Published: February 2005

AbstractA human T lymphoid cell line was established by cell hybridization technique from peripheral blood leucocytes of a patient with Sezary syndrome. The cells beared the surface antigens of human T lymphocyte specificity as demonstrated by immune cytolysis tests, but did not form E rosettes with sheep red blood cells. Isozyme patterns of enzymes in this line such as lactate dehydrogenase, glucose 6‐phosphate dehydrogenase and esterase were of human type. The line had 79 chromosomes in modal number. This case supports the proposal that the production of tetraploids is favourable for establishment of cell lines.
Control of normal differentiation of myeloid leukemic cells. XII. Inducibility for some stages of differentiation by dimethylsulfoxide and its disassociation from inducibility by MGI
Authors: Maeda Sakan , Sachs Leo 
Published: February 2005

AbstractThere are clones of myeloid leukemic cells that can be induced to differentiate by the normal differentiation‐inducing protein MGI to form Fc and C3 rosettes, mature macrophages and granulocytes. One of these clones (MGI+DMSO+) was also inducible by dimethylsulfoxide (DMSO) for C3 but not Fc rosettes, and for mature macrophages but not for mature granulocytes. Other clones (MGI+DMSO−) were inducible by MGI but not DMSO and a third type of clone (MGI−DMSO−) was not inducible by either compound. Clones that differed in their inducibility by DMSO showed a similar inhibition of cell multiplication by DMSO. The results indicate, that some stages of differentiation can be induced by DMSO in an appropriate clone of myeloid leukemic cells and that there are different cellular sites for induction by DMSO and MGI.
Effects of an acridine half‐mustard (ICR 191) on growth and ploidy of frog cells in culture
Authors: Viceps‐Madore Dace 
Published: February 2005

AbstractThe effects of an acridine half‐mustard, ICR 191, on the growth rate and ploidy of four haploid and two diploid lines of Rana pipiens cells in culture were studied. Growth curves indicate that the haploid and diploid cell lines were equally resistant to a 4‐hour exposure of this drug (0.1 μM to 10 μM). ICR 191 treatment induced the haploid cell cultures to become diploid. The proportion of diploid cells increased progressively with respect to time after the 4‐hour exposure period. The greater the concentration of ICR 191 applied, the more rapid the rate of conversion. Autoradiographic determinations of percent labelled nuclei indicate that DNA synthesis was not inhibited in haploid or in diploid cells. Therefore, the increased proportion of diploid cells did not originate from the small percentage of diploid cells in the initial population. Instead, the haploid cells were converted to diploid cells. Time lapse cinematography indicated that the conversion mechanism was other than cell fusion. Conversion to higher ploidy did not occur when diploid cell cultures were exposed to ICR 191.