bluuebunny/crossref_metadata_2025_split huggingface dataset:
Release of a factor during early stages of contact between hamster sperm and eggs in vitro
Authors: Hartmann John F. , Hutchinson Cameron F. 
Published: February 2005

AbstractA sensitive bioassay was devised which detected the release of a factor resulting from contact between the surfaces of sperm and zona pellucida of the golden hamster in vitro. This assay is based upon the ability of the factor to induce premature binding between the gametes. Release of the factor occurred in a dose‐dependent manner as a function of increasing concentration of sperm, but only after they were capacitated, i.e., subjecting sperm to those conditions which endow them with the ability to penetrate the egg. The factor was released, in what appeared to be pulses of activity, throughout the 40‐minutes prepenetration period, and this release culminated in a large pulse which was rapidly terminated soon after penetration began. The factor was also detected following contact with homologous zonae pellucidae from which the vitellus had been mechanically removed. Thus, factor release and cessation of its release occurred independently of the vitellus. When hamster eggs or isolated zonae were replaced by those of the mouse, the factor was not detected even though hamster sperm attached to them; nor was it recovered when isolated zonae or eggs of the hamster were treated with trypsin before exposure to sperm. Factor release and penetration of eggs were inhibited in a similar manner as a function of increasing concentrations of trypsin. This finding and the observation that the factor was not detected when the sperm were not capacitated, and therefore incapable of penetration, suggests that a relationship may exist between factor release and penetration.
Relationship of heat labile glucose‐6‐phosphate dehydrogenase and multiple molecular forms of the enzyme in senescent human fibroblasts
Authors: Duncan Michael R. , Dell'Orco Robert T. , Guthrie Patrick L. 
Published: February 2005

AbstractHuman fibroblasts derived from newborn foreskin and designated CF‐3 were assayed for heat labile glucose‐6‐phosphate dehydrogenase (G6PD) when they had grown to confluency, as well as when they were arrested in an essentially nonmitotic state. Under both culture conditions there was an increase in heat labile G6PD (up to 25% of the total activity) as cells progressed through their in vitro lifespan; however, arrested cells exhibited less heat labile G6PD than did comparable growth controls (5–10% decrease). Acrylamide gel electrophoresis of crude G6PD preparations revealed three distinct bands of enzymatic activity. One of the bands was tentatively identified as the dimeric form of the enzyme and another as the tetrameric form. The tetrameric form was more heat sensitive, and the percent to the total activity of this form increased as the cells became senescent. The percent of total activity of the tetrameric form was comparable to the percent heat liable enzyme assayed at a given population doubling level. These results indicated that the observed increase in heat lability of G6PD with age may be due to a shift in equilibrium to the tetrameric form of the enzyme rather than the synthesis of aberrant enzyme molecules.
Membrane transport by guinea pig peritoneal exudate leukocytes: Effect of phagocytosis on hexose and amino acid transport
Authors: Straus David C. , Imhoff John G. , Bonventre Peter F. 
Published: February 2005

AbstractShort term, carrier mediated transport of D‐glucose, L‐leucine and L‐lysine by guinea pig peritoneal macrophages was characterized. Analysis of the amino acid transport demonstrated two‐limbed double reciprocal plots suggesting two transport systems for each amino acid. The low concentration limb of the curves established a Km of 0.1 mM for L‐leucine and 0.05 mM for L‐lysine; Vmax values were 2.0 and 2.85 nmole/mg protein/90 seconds, respectively. Leucine and lysine were shown to be competitive inhibitors of each other. Further competition studies revealed that other amino acids also had affinity for these carriers. Amino acid transport was found to be sensitive to sulfhydryl active compounds. Colchicine treatment of peritoneal macrophages did not inhibit the transport of the amino acids tested. Preloading macrophages with latex beads or heat‐killed staphylocci by phagocytosis stimulated 2‐deoxy‐D‐glucose (2‐dOG) uptake markedly, but had no measurable effect on amino acid transport. Although total transport of 2‐dOG increased in post‐phagocytic macrophages, the kinetics of the system were not altered significantly. The Km for both pre‐ and post‐phagocytic transport of 2‐dOG was shown to be 1.2 mM and the Vmax was shown to increase from a pre‐phagocytic value of 20 nmoles/mg protein/90 seconds to a post‐phagocytic 27 nmoles/mg protein/90 seconds. Phagocytosis of heat‐killed staphylococci by guinea pig polymorphonuclear leukocytes (PMNs), however, did not cause an augmentation in hexose transport in the cells. The presence of colchicine during phagocytosis did not alter subsequent uptake of amino acids by the macrophages.
Transformed BHK cells exhibiting normal or subnormal sugar uptake
Authors: Moolten F. L. , Moolten D. N. , Capparell N. J. 
Published: February 2005

AbstractThe uptake of deoxyglucose was compared in BHK cells and in DMN4B cells, a conditionally transformed line of BHK cells which exhibits transformed behavior at 38.5° but not at 32°. At 32°, DMN4B cells took up deoxyglucose more slowly than BHK cells, reflecting a higher Km for uptake of this sugar. When both cell lines were grown at 38.5°, the Km for DMN4B cells was reduced to a level only slightly greater than for BHK cells, and deoxyglucose uptake became similar in the two cell lines. Growth in glucose‐free medium for 22 hours stimulated deoxyglucose uptake in both BHK and DMN4B cells; under these conditions, uptake was equal in the two cells lines, both at 32° and 38.5°. Glycolysis, as measured by lactic acid production, was slower in DMN4B than BHK cells, but in contrast to deoxyglucose uptake, this difference was observed at 38.5° rather than 32°. The observation that the subnormal deoxyglucose uptake of DMN4B cells in the untransformed state (32°) can be normalized by growth at 38.5°, a temperature permissive for transformation, suggests that membrane changes facilitating sugar uptake, which have been found in other transformed cells, are associated with transformation in DMN4B cells as well. However, the failure of uptake to exceed normal in these cells indicates that their transformed behavior is not attributable to excessive sugar uptake per se.
Differences in surface membrane ecto‐ATPase and ecto‐AMPase in normal and malignant cells I. Decrease in ecto‐ATPase in myeloid leukemic cells and the independent regulation of ecto‐ATPase and ecto‐AMPase
Authors: Weiss Benny , Sachs Leo 
Published: February 2005

AbstractThe hydrolysis of ATP and AMP by enzymes located on the external side of the plasma membrane (ecto‐ATPase and ecto‐AMPase) was studied in mouse myeloid leukemic cells, normal early myeloid cells, and normal mature granulocytes and macrophages. Nine clones of myeloid leukemic cells were used belonging to three groups that differ in their ability to be induced to differentiate by the differentiation‐inducing protein MGI. These three groups consisted of MGI+D+ that can be induced to undergo complete differentiation, MGI+D+ that can be induced to partially differentiate and MGI−D− with no induction of differentiation. The ecto‐ATPase activity of normal early myeloid cells was similar to that of normal mature granulocytes and macrophages and higher than that of any of the leukemic cells. Among the leukemic cells, the MGI−D− cells had the highest level of ecto‐ATPase activity.The behaviour of ecto‐AMPase differed from that of ecto‐ATPase. Some MGI−D− clones had a higher ecto‐AMPase activity than normal cells and MGI+D− and MGI+D+ cells showed no detectable activity. Neither the ecto‐ATPase nor ecto‐AMPase activities changed after induction of differentiation in normal early myeloid or MGI+D+ leukemic cells. The results indicate that the myeloid leukemic cells had a decreased ability to hydrolyse external ATP, that there can be an independent regulation of ecto‐ATPase and ecto‐AMPase and that neither of these enzyme activities changed during differentiation.
Identification of a chromosome that controls malignancy in chinese hamster cells
Authors: Bloch‐Shtacher Navah , Sachs Leo 
Published: February 2005

AbstractA chromosome that controls malignancy in Chinese hamster cells has been identified by analysis of the Giemsa banding pattern of a malignant cell line transformed by simian virus 40 (SV40), non‐malignant revertants from this line, segregants from the revertants that were again malignant and a cell line transformed by methylcholanthrene. The malignant cell line transformed by SV40 was near diploid and had gained additional material of chromosome 3. Revertants with a suppression of malignancy and malignant segregants from these revertants were near triploid. The malignant segregants also showed a gain of material of chromosome 3 compared to the non‐malignant revertants from which they were derived. Malignancy of these cells was associated with the ability to form colonies in agar. Cells of a line transformed by methylcholanthrene were malignant, formed almost no colonies in agar and the only chromosome change from the normal diploid chromosome banding complement was the addition of a long arm of chromosome 3. The results indicate that chromosome 3 carries gene(s) that control malignancy in Chinese hamster cells in cell lines transformed by a viral or a chemical carcinogen and that malignancy was induced in both cell types by an increase of these genes.
Variation in potassium transport properties of mouse 3T3 cells as a result of subcultivation
Authors: Tupper Joseph T. 
Published: February 2005

AbstractUnidirectional potassium influx and the fraction of this influx sensitive to ouabain, an inhibitor of the (Na + K) activated ATPase, have been evaluated as a function of subcultivation of the 3T3 and SV40 transformed 3T3 cell. Total and ouabain‐sensitive K influx change little over approximately 50 passages of the transformed 3T3 cell. In contrast, these components of K influx increase nearly 5‐fold over a similar number of passages of the 3T3 cell. During early passages total and ouabain‐sensitive K influx of the 3T3 cell are below that of the SV40 3T3 cell on a per cell volume basis. At later passages the magnitude of these components of K transport exceed those found in the SV40 3T3 cell. Previous studies have reported the ouabain‐sensitive uptake of K and the levels of (Na + K) activated ATPase as being higher, lower or equivalent in the 3T3 versus transformed 3T3 cell. The present data suggest these differences may result from the degree to which the cells were passaged at the time of the experiments. Evaluation of previous studies substantiates this conclusion.
Altered biochemical properties of mitochondria in mouse mammary epithelial cells during primary culture
Authors: White Michael T. , Nandi S. 
Published: February 2005

AbstractVarious biochemical properties of mitochondria isolated from primary monolayer cultures of mammary epithelial cells from mid‐pregnant or hormonally stimulated mice were examined daily for seven or eight days. When compared with mitochondria from mammary glands of mid‐pregnant animals, the specific activities of several mitochondrial enzymes were greatly reduced in cells after seven days in culture. There was a 5‐ to 6‐fold reduction in the specific activities of cytochrome oxidase, succinate dehydrogenase and α glycerophosphate oxidase while malate dehydrogenase and adenylate kinase activities were 2‐ to 3‐fold lower. The reduction in mitochondrial enzyme activities was gradual and related to the length of time the cells were in culture. Progressive changes were also seen in the electrophoresis profiles of mitochondrial proteins in SDS‐urea polyacrylamide gels. Mitochondria isolated from 1‐, 2‐, 3‐ and 8‐day cell cultures showed a continuous reduction in the relative amounts of several mitochondrial polypeptides in the gel profiles. Addition of 35S‐methionine to cell cultures for short and long periods indicated that mitochondrial protein synthesis continued throughout the 8‐day culture period. However, the synthesis of several particular polypeptides was reduced progressively during the culture period. These studies indicate that mouse mammary epithelial cells have a lowered capacity for respiratory metabolism as a result of specific mitochondrial alterations which might be associated with the general loss of differentiated morphology by those cells during monolayer culture.
Embryonic diapause in the marsupial Macropus eugenii. Stimulation of nuclear RNA polymerase activity in the blastocyst during resumption of development
Authors: Moore G. P. M. 
Published: February 2005

AbstractDuring the breeding season from January to June, female wallabies which are suckling a young animal in the pouch may carry a dormant embryo (lactational quiescence). Removal of the pouch young during this period results in a resumption of embryo development. In the latter half of the year, the embryo will not reactivate after removing the suckling young (seasonal quiescence). In this situation, development resumes spontaneously in late December or may be induced prematurely by progesterone treatment. The response of the genome of quiescent macropod blastocysts was studied during the early period of growth. Changes in the transcriptional activity of the embryo cells were measured by assay for endogenous RNA polymerases. Embryos actively synthesized RNA during both lactational and seasonal quiescence. Termination of seasonal quiescence resulted in increases in RNA polymerase activities within the nucleolus and nucleoplasm of the cell. This occurred on the day following the summer solstice, December 22, 1974, in animals captured in the wild, or within 48 hours of administration of progesterone. Embryos which were induced to resume development during the breeding season also showed increases in nucleolar and nucleo‐plasmic polymerase activities within five days of removal of suckling young from the pouch. In all situations, the response of the nucleolar enzymes was greater than that of the nucleoplasmic enzymes. This is in agreement with other observations of the regulation of gene activity in growth‐stimulated cells.
ATP, trehalose, glucose and ammonium ion localization in the two cell types of Dictyostelium discoideum
Authors: Wilson Jeanne B. , Rutherford Charles L. 
Published: February 2005

AbstractUltra‐microfluorometric techniques were adapted to follow several compounds related to energy metabolism through the developmental cycle of Dictyostelium discoideum. Each compound (ATP, trehalose, glucose, and ammonium ion) was found to be present in stalk and/or spore cells. The accumulation of NH4+ was interpreted as an indication of protein degradation, a source of energy in this organism. During the early stages of differentiation NH4+ was localized only in prestalk cells. However, it accumulated in spore cells during culmination such that levels were comparable in the two cells types by the end of development. Trehalose, an energy source for germinating spores, was found in both cell types but was preferentially degraded in stalk cells late in development. Glucose, the degradation product of trehalose, was localized in prestalk cells and varied inversely with trehalose levels. ATP was not localized in a specific cell type during development. However, ATP declined in stalk cells at an earlier stage of development.
The role of butyrate in the reverse transformation reaction in mammalian cells
Authors: Storrie Brian , Puck Theodore T. , Wenger Leonor 
Published: February 2005

AbstractThe reverse transformation reaction of Chinese hamster ovary cells from compact, epithelial‐like, randomly growing, heavily knobbed, lectin reactive cells into stretched, tighly adherent, smooth‐surfaced, lectin resistant, fibroblast‐like cells normally elicited by dibutyryl cAMP can be produced to its complete extent by N6‐monobutyryl cAMP or 8‐bromo‐cAMP. O2‐monobutyryl cAMP is ineffective as is cAMP itself in the absence of an inhibitor of phosphodiesterase activity. In the presence of a phosphodiesterase inhibitor, cAMP is fully effective. These results indicate that the role of the butyryl groups of dibutyryl cAMP and, especially, the N6‐butyryl, in the reverse transformation raction is protection of the cAMP analogue from degradation.Butyrate at concentrations of about 1 mM does produce a response which to some extent mimics that of cAMP analogues. The cells, however, fail to assume a fibroblastic‐like shape, but rather become flattened. The butyrate effect is much slower and less readily reversible than that evoked by cAMP analogues. Butyrate produces an approximately 2‐fold increase in intracellular cAMP levels. These results are consistent with the hypothesis that butyrate effects, in part, are mediated by cAMP.
Inhibition of spermidine and spermine synthesis leads to growth arrest of rat embryo fibroblasts in G1
Authors: Rupniak H. T. , Paul D. 
Published: February 2005

AbstractFollowing growth stimulation of rat embryo fibroblast (REF) cells previously arrested in G1 by serum deprivation, there occurs a large increase in the synthesis of the polyamines putrescine, spermidine and spermine. Methylglyoxal bis(guanylhydrazone) (MGBG), a potent inhibitor of S‐adenosylmethionine decarboxylase can block the accumulation of both spermidine and spermine over a period of several days. Under such conditions REF cells treated with MGBG will approximately double in number and then become growth‐arrested again predominantly in the G1 phase of the cell cycle. REF cells therefore appear to contain sufficient spermidine and spermine to progress through one cell cycle before the intracellular levels of these polyamines is reduced sufficiently to arrest growth in the absence of continued polyamine synthesis. Limitation of intracellular polyamine levels is therefore not the mechanism by which deprivation of serum growth factors arrests cell growth. While continued growth is nevertheless dependent on polyamine synthesis, this cell type is capable of limited proliferation in its absence. Addition of spermidine or spermine to MGBG‐arrested REF cells results in a rapid resumption of proliferation demonstrating that either polyamine can fulfill the role played by these polyamines in the growth process. Low levels of spermidine and spermine therefore arrest this cell type at a resriction point in G1 at which it is decided whether the intracellular level of these polyamines is sufficiently high to enable a cell to enter into and complete a new cell cycle. This polyamine‐sensitive restriction point is considered to be analogous to the restriction point(s) in G1 at which serum and nutrient limitation act.
Isolation of high‐rate DNA synthetic cells by Con A chromatography
Authors: Wallenbrock Mark A. , Killion Jerald J. 
Published: February 2005

AbstractThe separation of L1210 cells with columns of Con A‐derivatized nylon was investigated. Most of the cells bound to the column irreversibly. The binding was lectin‐specific. Cells were pulse labeled with 3H‐thymidine and applied to Con A columns. Those cells not binding the columns were enriched in incorporated thymidine compared to the unseparated population. Data is presented which suggests that a small, synchronized fraction of cells synthesizing DNA at a high rate is reduced in Con A‐nylon affinity. It is proposed that L1210 cell DNA synthesis is not uniform in rate and that changes in this rate are related to changes in the ability of cells to bind Con A‐nylon.
Stimulation of DNA synthesis in human fibroblasts by thrombin
Authors: Pohjanpelto Pirkko 
Published: February 2005

AbstractEarlier work showed that thrombin stimulates proliferation of human fibroblasts in serumfree medium. This work demonstrates (1) that thrombin has to be present during most or all of the G1 period to ensure maximal DNA synthesis, (2) that DNA synthesis increases about three hours later after thrombin than after serum treatment, (3) that both thrombin and serum activate transport of uridine, D‐2‐deoxy‐glucose and putrescine, (4) that thrombin is able to increase 3H‐thymidine incorporation also in SV40 transformed human fibroblasts, in HeLa cells and in two continuous monkey cell lines.
Epidermal growth factor induced membrane changes in 3T3 cells
Authors: Aharonov Aharon , Vlodavsky Israel , Pruss Rebecca M. , Fox C. Fred , Herschman Harvey R. 
Published: February 2005

AbstractEpidermal growth factor (EGF) is a mitogen for Swiss 3T3 cells. Short incubation periods with physiological concentrations of EGF induced increased binding of Swiss 3T3 cells to Con A‐coated nylon fibers. This effect was not induced in an EGF non‐responsive 3T3 variant, in the transformed murine XC cells or in Swiss SV3T3 cells. The increase in Con A fiber‐binding seems to be specific for EGF, since it was not observed in response to insulin, prostaglandin F2α or a higher serum concentration, which also initiate cell division of confluent quiescent 3T3 cells.EGF also reduced Con A‐mediated hemadsorption to 3T3, but had no effect on hemadsorption by the EGF non‐responsive 3T3 variant. There was no change in the number of Con A‐receptors on 3T3 cells after EGF treatment. Binding to WGA‐coated fibers and WGA‐mediated hemadsorption were not effected by preincubation with EGF.
Effect of low dose rate irradiation on the division potential of cells in vitro. IV. Embryonic and adult human lung fibroblast‐like cells
Authors: Macieira‐Coelho A. , Diatloff C. , Billard M. , Fertil B. , Malaise E. , Fries D. 
Published: February 2005

AbstractEarly and late passage human embryonic lung fibroblasts were compared with early passage adult lung fibroblasts with regards to their survival (number of population doublings), after low dose rate ionizing radiation. It was found that early passage embryonic cells are quite resistant to this type of radiation. Late passage embryonic and early passage adult fibroblasts are more sensitive to ionizing radiations. The results suggest that cell aging is accompanied by an increased sensitivity to low dose rate ionizing radiation and favor the idea that aging in vitro, expressed as a function of the fibroblast division potential, is correlated with aging in vivo.
The capping of lymphocytes and other cells, studied by an improved method for immunofluorescence staining of frozen sections
Authors: Bourguignon Lilly Y. W. , Tokuyasu K. T. , Singer S. J. 
Published: February 2005

AbstractExperiments have been carried out on the capping by lectins and antibodies of surface receptors of mouse splenic T and B lymphocytes and other cells, in which the surface distribution of the lectin or antibody, and the intracellular distribution of myosin or actin, were determined on the same cells by a double fluorescence technique. For this purpose, a general method for intracellular staining was developed which is intended to preserve sensitive antigens and fragile ultrastructural elements. The method involves mild formaldehyde fixation of the cells or tissues, infusion with concentrated sucrose, rapid freezing, and the preparation of frozen sections thinner than 2 μm thickness. The immunofluorescent or other appropriate fluorescent reagents are then applied to the thawed section. In the present experiments, intracellular actin was detected using a fluorescent staining method based on the interaction of F‐actin with heavy meromyosin, while intracellular myosin was detected by an indirect immunofluorescence procedure. Our findings were that the formation of a cap by each of the lectins or antibody reagents was always accompanied by a concentration of myosin and actin directly under the cap. These and other results suggest that capping is an active process in which actin and myosin participate directly in the formation of all caps. This proposal carries important new implications for the molecular mechanism of capping.