bluuebunny/crossref_metadata_2025_split huggingface dataset:
Carbon dioxide efflux accompanies release of fertilization acid from sea urchin eggs
Authors: Gillies R. J. , Rosenberg M. P. , Deamer D. W. 
Published: February 2005

Abstract“Fertilization acid” is released from sea urchin eggs upon fertilization and decreases the pH of the surrounding seawater. In bicarbonate‐free artificial seawater flushed with nitrogen gas, the pH shift still occurs but returns to the original value in a few minutes, suggesting that the released acid is volatile. A likely candidate for a volatile acid is carbon dioxide released from the eggs. Therefore, the total CO2 content of seawater was measured pre‐ and post‐fertilization and was found to be correlated stoichiometrically with released proton equivalents, leading to the conclusion that fertilization acid is largely carbon dioxide. Manometric analysis of cell extracts and ashed eggs suggest that the carbon dioxide may be stored in the unfertilized egg as an inorganic carbonate.
Mechanisms controlling the kinetics in proliferation and differentiation of populations of mouse myeloid leukemic cells in vitro
Authors: Hayashi Moriaki , Okabe‐Kado Junko , Hozumi Motoo 
Published: February 2005

AbstractThe kinetics of differentiation and proliferation of clone cells (B24) of mouse myeloid leukemic Ml cells in vitro were studied by quantitative determination of cellular morphology. B24 cells were induced to differentiate into only macrophagelike cells by an inducer of differentiation in conditioned medium (CM) of embryo cells. During cell differentiation, the ratio of the area of the nucleus to that of the cell (N.C.R.) decreased from about 55% to 10%. Decrease in the N.C.R. was used as an index of cell differentiation in analysis of the kinetics of differentiation of cells treated with various concentrations of CM. The results showed that the process of differentiation was promoted by increasing the concentration of CM, and that the transition of the cells from the undifferentiated state to the differentiated state occurred in a stochastic manner. Comparison of these morphometric results with those of autoradiography showed that the labeling index of the cells decreases gradually in association with decrease in the N.C.R. of the cells from 50% to 30%. A stochastic model for the kinetics of proliferation and differentiation of the cells simulated the experimental observations on the production of differentiated cells.
Epidermal growth factor initiates DNA synthesis after a time‐dependent sequence of regulatory events in Swiss 3T3 cells—interactions with hormones and growth factors
Authors: Otto Angela M. , Ulrich Marie‐Odile , de Asua Luis Jimenez 
Published: February 2005

AbstractEpidermal growth factor (EGF) stimulates the initiation of DNA synthesis in Swiss 3T3 cells after a constant prereplicative period of 14–15 hours. The final rate of initiation follows apparent first‐order kinetics and can thus be quantified by a rate constant k. The value of k can be changed by later additions during the prereplicative period: When cells stimulated by a very low concentration of EGF, alone or with insulin, which results in a relatively low value of k, receive a saturating amount of EGF at 15 hours, then k is markedly increased after 4–6 hours. Insulin alone (up to 200 ng/ml) is unable to set the lag phase, but does have a synergistic effect on the value of k given by EGF. When added at 15 hours, insulin also increases k, but after a delay of 4–6 hours. In contrast, both hydrocortisone and prostaglandin E1 (PGE1) inhibit the stimulation of DNA synthesis by EGF only during the first 8 hours of the prereplicative period of decreasing the value of k.Prostaglandin F2α (PGF2α), which stimulates DNA synthesis in a similar mode as EGF, when added with EGF has a synergistic effect on DNA synthesis. This suggests that EGF and PGF2α, nevertheless, act through different regulatory events.
Fibroblast colonies in monolayer cultures of human bone marrow
Authors: Nagao Tadami , Komatsuda Mitsumoto , Yamauchi Kunihiko , Arimori Shigeru 
Published: February 2005

AbstractIn a liquid culture of human bone marrow, the development of fibroblast colonies takes place on days 6 to 9. Twenty percent fetal calf serum is used as the stimulus for fibroblast colony growth. Human bone marrow cells are plated as 2 × 105 cells in the culture. Normal human bone marrow yields 47 ± 4 fibroblasts colonies per 2 × 105 cells plated. Bone marrow fibroblast cultures using agar or methylcellulose restrict colony formation. Marked colony suppression was observed in acute leukemia, and a discrete colony number was observed in hypoplastic anemia. This fibroblast culture method should be applied to a larger number of patients to determine whether it has a pathognomonic value and clinical significance.
Cyclic AMP‐dependent protein kinases from Balb 3T3 cells and other 3T3 derived lines
Authors: Wehner Jeanne M. , Malkinson Alvin M. , Wiser Mark F. , Sheppard J. R. 
Published: February 2005

AbstractCyclic AMP‐dependent protein kinase and 3H‐cAMP‐binding activities were determined in normal Balb 3T3 cells and compared with the same preparations from SV40, chemical, and spontaneous transformants of 3T3 cells. The cytosolic protein kinase activities and protein kinase activity ratios were similar in all cell lines, although when the normal 3T3 cytosol was prepared by homogenization it contained less 3H‐cAMP binding activity than the transformed 3T3 cytosols. The Triton X‐100 treated particulate fractions from the normal and transformed 3T3 cells contained similar protein kinase and binding activities.The isozymic profile of cAMP‐dependent protein kinases was examined by DEAE‐chromatography. The 3T3 cells contained only type II isozyme in either cytosolic or membrane fractions. All transformants of the 3T3 cells contained both type I and type II isozymes. Other cell cultures, including chicken embryo fibroblasts, rat kidney cells, and human or calf endothelial cells contained type I and type II isozymes.Binding of the photoaffinity analogue of cAMP, 8‐N3 cAMP, to the regulatory subunits of protein kinases in sonicates obtained from Balb 3T3 and SV 3T3 cells followed by separation on SDS polyacrylamide electrophoresis showed that the amount of RII subunit was approximately equal in the two cell lines. RI in Balb 3T3 cells was detectable but in a much lower quantity than in SV 3T3 cells.The cyclic AMP dependent‐protein kinases from Balb 3T3 cells appear to be different from SV 3T3 cells by three criteria: 3H‐cAMP binding in homogenates, DEAE chromatographic separation of isozymes, and 8‐N3 cAMP binding.
Effect of aminonucleoside on transcription, methylation, and maturation of ribosomal RNA in SV40‐transformed human lung fibroblasts
Authors: Tunkel Allan R. , Studzinski George P. 
Published: February 2005

AbstractThe effects of puromycin aminonucleoside (AMS) have been studied in the nucleoli of SV40‐transformed human lung fibroblasts with attention to the relationships between transcription, methylation, and maturation of ribosomal RNA (rRNA). Inhibition of the transcription of pre‐rRNA became evident between 1 and 2 hr of exposure to AMS, and the degree of inhibition remained approximately constant throughout the remainder of the 18‐hr period of study. Methylation of the ribose units of pre‐rRNA was inhibited by AMS approximately as much as RNA transcription, but later, suggesting that the inhibition of methylation is a consequence of the lowered rate of RNA transcription. It was also noted that ribose methylation of nucleolar RNA occurs in the absence of concurrent RNA transcription, indicating that rRNA may be methylated post‐transcriptionally. Exposure of the fibroblasts to fresh serum had the capacity to increase the rate of nucleolar RNA transcription if the fibroblasts were treated with AMS for periods of less than 2 hr but was ineffective thereafter, confirming that the inhibitory effect of AMS on pre‐rRNA transcription is established in approximately 2 hr. On the other hand, processing of the primary transcript (45 S RNA) to the mature rRNA species (28 and 18 S) was inhibited more gradually, with a complete inhibition of rRNA maturation being noted after 18 hr of AMS treatment. These data are consistent with the view that the primary effect of AMS is on the rate of rRNA transcription, with a later effect on its maturation, while RNA methylation is reduced only because of the diminished availability of the RNA substrate.
Evaluation of Mg2+ as an intracellular regulator of uridine uptake
Authors: Vidair C. , Rubin H. 
Published: February 2005

AbstractThe rate of uptake of the nucleoside uridine increases within minutes after adding a growth stimulus to quiescent 3T3 cells. We have previously shown this uptake rate to be highly sensitive to changes in the intracellular concentration of Mg2+. In the present paper, the alteration of uptake by Mg2+ is shown to occur at the phosphorylation step — the same point at which serum acts to modulate uridine uptake. The serum stimulation of uridine uptake can be mimicked by Mg2+ alone or blocked by partially depleting cells of their Mg2+. Work with cell‐free extracts shows that the uridine kinase enzyme responds to Mg2+ in a manner similar to that exhibited by whole cells whose concentrations of Mg2+ have been raised. In addition, the enzyme's inhibition by ATP is relieved by raising the Mg2+ concentration. Thymidine uptake, a reaction which does not respond quickly to mitogenic stimulation, is unaffected by alterations in Mg2+ concentration. These results are discussed in terms of a possible role for Mg2+ as an intracellular regulator of uridine uptake and other reactions of the coordinate response of cells to external effectors.
Procaine inhibits the erythroid differentiation of MEL cells by blocking commitment: Possible involvement of calcium metabolism
Authors: Tsiftsoglou Asterios S. , Mitrani Alberto A. , Housman David E. 
Published: February 2005

AbstractThe action of procaine on the terminal erythroid differentiation of murine erythroleukemia (MEL) cells has been investigated at the level of individual cells. At concentrations (7 × 10−4 M) which had no inhibitory effect on cell growth, pretreatment of these cells with procaine for 12–24 hr caused a pronounced inhibition (> 90%) of commitment to terminal erythroid differentiation of dimethyl sulfoxide (DMSO)‐treated cells. Simultaneous treatment of MEL cells with DMSO and procaine, however, resulted to only slight inhibition (< 20%) of commitment. Blockade of commitment by procaine pretreatment appears to be general since it was observed in cells treated with other inducers (6‐thioguanine, dimethylformamide). Procaine pretreatment did not abolish the ability of MEL cells to complete the “latent period” and commit upon the removal of the block. Reversal of procaine inhibition of commitment was obtained by the addition of either CaCl2 (1.0 mM), calcium ionophore A23817 (1 μg/ml), but not of MgCl2 (1.0 mM). From these data we conclude that procaine inhibits the terminal erythroid differentiation of MEL cells by blocking an event or process required for commitment which occurs prior to commitment itself. Our results suggest that this process involves calcium metabolism.
Mechanism of synergistic induction of DNA synthesis by epidermal growth factor and tumor promoters
Authors: Matrisian Lynn M. , Bowden George T. , Magun Bruce E. 
Published: February 2005

AbstractEvidence is presented to support our previously proposed hypothesis that the hyperplastic effect of tumor promoters is related to their ability to alter existing physiological levels of growth factors in target tissues. Epidermal growth factor and phorbol ester tumor promoters acted synergistically at low (0.001–0.05 ng/ml) but not high (> 0.1 ng/ml) EGF concentrations to induce DNA synthesis in cultured Rat‐1 fibroblast cells. The degree of synergism correlated with the tumor‐promoting ability of the compound. The tumor promoters decreased 125I‐EGF binding to cellular receptors in a dose‐dependent manner that also correlated with the tumor‐promoting ability of the compound. The inhibition of EGF binding by phorbolester compounds resulted in a decrease in the amount of EGF degraded as compared to control cultures. At limiting EGF concentrations, the sparing of EGF degradation resulted in an increase in the amount of EGF remaining in the culture medium after 12 h of incubation and a concomitant increase in the amount of EGF bound to phorbol ester‐treated cells at this time as compared to control cultures. The ability of a phorbol ester compound to alter EGF degradation and to stimulate DNA synthesis synergistically with EGF correlated with the tumor‐promoting ability of the compound and occurred only at low EGF concentrations.
Protection of heat induced cytoxicity by glycerol
Authors: Lin P.‐S. , Kwock L. , Hefter K. 
Published: February 2005

AbstractGlycerol, at concentrations of 2–10% is a potent hyperthermic (43°–45°C) protector of cultured Chinese hamster cells, V79. Furthermore, the sensitization effect of low pH on heat death is also drastically reduced by the addition of glycerol into the culture medium. Together with the known cellular effects of heat and the role of glycerol in various cellular structures and functions, the data suggest that microtubules and membranes may be involved in the expression of heat‐induced cell death.
Growth, biochemistry, and morphology of isolated rabbit aortic smooth muscle cells maintained in the presence or absence of serum
Authors: Yau‐Young Annie O. , Shio Helen , Fowler Stanley 
Published: February 2005

AbstractArterial smooth muscle cells undergo marked biochemical and morphological changes upon culturing. We have studied the time course of these changes in smooth muscle cells isolated from normal rabbit aortas by enzymic digestion and then maintained in Dulbecco's modified Eagle's medium with or without 10% rabbit serum. Subcultured smooth muscle cells were also examined. Isolated cells cultured in the presence of serum multiply rapidly and by 9 days exhibit features typical of subcultured cells including multilayered growth, elevated marker enzyme activities of subcellular organelles, and proliferation of organelles. In contrast, isolated cells cultured in the absence of serum remain quiescent, as indicated by the low level (<10%) of 3H‐thymidine incorporation into nuclei and constant DNA content of the cultures. These cells spread slowly to form a monolayer of randomly oriented cells and they retain differentiated morphological features. Their enzyme activities remain at the levels of those of freshly isolated cells initially, but by 5 days some enzyme activities increase, in particular those of the acid hydrolases and catalase. Rates of pinocytosis and protein synthesis in these cells are comparable to those of cells maintained in serum‐supplemented medium for the same period, but are significantly less than those measured in subcultured cells. Within 5 days, morphological alterations in the serum‐deprived cells occur including the presence of increased numbers of lysosomes. Quiescent cultures of enzymically isolated cells may be a useful tool for short‐term biochemical and physiological studies of differentiated arterial smooth muscle cells.
Effects of prior sterol depletion on neurite outgrowth in neuroblastoma cells
Authors: Maltese William A. , Reitz Beverly A. , Volpe Joseph J. 
Published: February 2005

AbstractThe effect of decreasing cellular sterol content on neurite outgrowth in C1300 (Neuro 2A) neuroblastoma cells in serum‐free medium has been studied. Sterol‐depleted, undifferentiated neuroblastoma cells were obtained by growing cells for 24 h in medium containing lipoprotein‐poor serum and 25‐hydroxy‐cholesterol (25‐OHC). Under these conditions the activity of 3‐hydroxy‐3‐methyl‐glutaryl‐CoA reductase and the incorporation of [14C] acetate into sterols were almost completely suppressed, and the sterol/phospholipid ratio of the cells declined to 60% of that in cultures grown without 25‐OHC. The sterol‐depleted cells were viable and exhibited rates of DNA, RNA, protein and fatty acid synthesis comparable to those measured in control cultures.Sterol depletion had no detectable effect on the number of cells that were able to undergo morphological differentiation within 3 h after removal of serum from the medium. However, by 24 h most of the sterol‐depleted cells had retracted their neurites. The observation that addition of low‐density lipoprotein was able to restore neurite outgrowth in cultures treated with 25‐OHC indicates that the inability of sterol‐depleted cells to maintain their neurites is related specifically to the decline in the sterol content rather than to a general cytotoxic effect of 25‐OHC. Our findings suggest that incorporation of cholesterol into the cell membrane is important for long‐term maintenance and elongation of neuroblastoma neurites, but that the initial morphological change (i.e., within 3 h after removal of serum) is apparently a separate and distinct event, not dependent on the availability of cholesterol.
Regulation of granulopoiesis and distribution of granulocytes in early phase of bacterial infection
Authors: Hartmann D. W. , Entringer M. A. , Robinson W. A. , Vasil M. L. , Drebing C. J. , Morton N. J. , Ture L. 
Published: February 2005

AbstractStudies have been carried out to determine the effect of bacterial infection on CSF production, CFU‐C activation, and bacterial clearance by mature granulocytes in mice infected with Escherichia coli. These studies have shown that immediately after bacterial infection (5 minutes), serum colony‐stimulating factor (CSF) levels and bone marrow colony‐forming units in culture (CFU‐C) levels are elevated. This is followed by oscillator rises in both of these parameters and the appearance of granulocytes in the infected site. With clearance of bacteria, CSF and CFU‐C levels return to normal. These studies have indicated further that bacterial infection is a major stimulus for granulocyte production through the CSF‐CFU‐C system and that clearance of bacteria by mature granulocytes may serve as a negative feedback regulatory arm.
Regulation of murine B lymphocyte plasma membrane protein turnover and shedding
Authors: Emerson Stephen G. , Cone Robert E. 
Published: February 2005

AbstractLactoperoxidase‐catalyzed cell surface radioiodination was employed to radiolabel murine splenic B‐cell membrane immunoglobulins (IgM and IgD) and alloantigens encoded by the Major Histocompatibility Complex (I‐Ak, I‐Ek, H‐2Kk, H‐2Dk). The fate of the radiolabeled proteins was monitored by in vitro culture of labeled cells and isolation of labeled antigens from detergent lysates of the cells or culture fluids obtained at different times during culture. The effects of temperature, antimetabolites, colchicine, and cytochalasins on membrane protein catabolism demonstrated heterogeneity in rate, energy dependence, and cytoskeletal control of turnover suggesting that functional domains of turnover control exist in the B lymphocyte membrane.
Stimulation of DNA synthesis by transient exposure of cell cultures to TPA or polypeptide mitogens: Induction of competence or incomplete removal?
Authors: Dicker Phillip , Rozengurt Enrique 
Published: February 2005

AbstractA transient exposure of cell cultures to 12‐0‐tetradecanoyl‐phorbol‐13‐acetate (TPA) is sufficient to stimulate DNA synthesis during a subsequent incubation TPA‐free medium. We show that (1) a substantial fraction of TPA remains bound to cultures following a transient exposure to TPA and thorough washing, (2) the ability of TPA to induce DNA synthesis is a function of the amount of TPA bound to cell cultures irrespective of whether it is incubated continuously with cultures or transiently exposed to cultures under various conditions, and that (3) a transient exposure of cultures to phorbol 12‐13‐dibuytrate (PDB), a mitogenic phorbol ester which binds reversibly to cell cultures, does not stimulate DNA synthesis during a subsequent incubation in PDB‐free medium. Therefore the persisting effects of TPA are due to it binding to cultures in a manner resistant to washing and not due to the induction of a stable cellular change prerequisite for mitogenesis. Further, we show that certain combinations of polypeptide growth factors induce DNA synthesis in the absence of any such stable cellular change. Evidence is also presented that the persisting effects on DNA synthesis following transient exposure of cultures to other polypeptide growth factors (e.g., platelet‐derived growth factor) reflect tenacious binding rather than induction of a lasting biological event.
Induction of human malignant T‐lymphoblastic cell lines MOLT‐3 and jurkat by 12‐O‐tetradecanoylphorbol‐13‐acetate: Biochemical, physical, and morphological characterization
Authors: Nagasawa Kohei , Howatson Allan , Mak Tak W. 
Published: February 2005

AbstractThe process of induction of human malignant T‐lymphoblastic cell line MOLT‐3 by the phorbol ester 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA) was examined. It was found that the induction process by TPA, which included increase in cells with receptors to sheep red blood cells (E‐rosette positive‐E+) and decrease in the levels of the marker enzyme terminal deoxynucleotidyl transferase (TdT) was not affected by the presence of DNA synthesis inhibitor arabinofuranosylcytosine (Ara‐C). The exposure time to TPA required to elicit these changes was found to be short, in the order of 1 hour or less. The kinetics of the increase in E+ cells, decrease in the levels of TdT in these cells, or decrease in the ability to proliferate as measured by colony formation were similar with exposure to TPA for 1, 6, 24, or 96 hours. We have examined the effect of antitumor promoter compounds on their ability to block induction of MOLT‐3 cells by TPA. Results indicated that none of these compounds, dexamethasone, antipain, retinoic acid, and L‐1‐tosylamide‐2‐phenylethylchloromethyl ketone (TPCK), was effective in reducing the number of E+ cells induced by TPA.Examination of three other leukemic T‐cell lines indicated that, in addition to MOLT‐3, the leukemic T‐cell line Jurkat also responded to TPA, whereas two other leukemic T‐cells lines CCRF‐CEM and CCRF‐HSB‐2 did not. Certain physical and morphological changes were also observed after stimulation of MOLT‐3 cells and Jurkat cells by TPA. We found that, following the addition of TPA, the cell volumes of MOLT‐3 cells decreased from an average of 1150 μm3 to about 500 μm3, whereas those of Jurkat were reduced to about 700 μm3 from 1100 μm3. Electron microscopic studies of these lymphoblasts also revealed that after treatment with TPA the induced cells were generally smaller in size with increase in the density of the nuclear materials and condensation of the chromatin structures.