bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of cycloheximide and dexamethasone phosphate on hyaluronic acid synthesis and secretion in cultured human skin fibroblasts
Authors: Mapleson J. L. , Buchwald M. 
Published: February 2005

AbstractWe have studied some aspects of the regulation of hyaluronic acid synthesis in cultured human skin fibroblasts derived from normal individuals. In these cells 85% of radiolabeled glucosamine is incorporated into two types of macromolecules, hyaluronic acid and glycoproteins, characterized by district partitions between the cell and medium compartments. Treatment of cells with cycloheximide under conditions in which protein and glycoprotein synthesis is inhibited by at least 90% has no effect on hyaluronic acid synthesis. This result is consistent with the hypothesis that protein synthesis is not necessary for the synthesis of hyaluronic acid. Conversely, 5 × 10−6M dexamethasone phosphate inhibits hyaluronic acid by 60% but has no effect on protein or glycoprotein or glycoprotein synthesis. Concomitant treatment with dexamethasone phosphate and cycloheximide restores the synthesis of hyaluronic acid to normal values. The dexamethasone phosphate effect on hyaluronic acid synthesis is therefore not a primary induction response since it requires protein synthesis. The secretion of hyaluronic acid and glycoproteins from the cells into the medium is not affected by either of the two drugs. This experimental approach will be useful in the study of the regulation of glycosaminoglycan metabolism in human cells especially with respect to disorders of connective tissue.
Small nuclear rnas in cellular growth and differentiation. I: Metabolic alterations seen in friend erythroleukemic cells
Authors: Kuncio Gerald S. , Goldstein Lester 
Published: February 2005

AbstractElectrophoretic analysis of near steady‐state labeled nuclear RNA obtained from Friend virus‐transformed murine erythroleukemic cells reveals the presence of at least 15 small nuclear RNAs (snRNAs) distinct from ribosomal 5.8S or 5S. Identical qualitative distributions were obtained from logarithmically growing, stationary‐phase, and dimethyl sulfoxide‐induced, terminally differentiated cultures, indicating the constitutive synthesis of all snRNAs regardless of the proliferative or differentiated state of the cells. However, several quantitative differences in nuclear snRNA levels were observed. Progression from rapidly growing to stationary‐phase cultures was accompanied by the marked reduction in accumulation of all snRNAs except the 4.5S snRNAs. Particularly striking were the decreases in levels of U3 and the U1 group, snRNAs that are relatively abundant. Similar reductions were noted when cells were induced to differentiate, except that decreases in the levels of U2 and 4.5S were more dramatic than those seen for cells entering stationary‐phase. The data thus demonstrate that snRNA levels may be regulated both in association with changes in proliferative capacity of cells and with changes in gene expression that occur during terminal differentiation.
Adherence of murine t cells to solid substrata in the absence of serum
Authors: Barker Robert H. , O'Shea Patricia F. , Strauss Phyllis R. 
Published: February 2005

AbstractIt is generally assumed that lymphocytes do not adhere firmly to solid substrata. However, in attempting to culture murine spleen and thymus cells in RPMI 1640 without serum, we observed that some cells adhered to glass or plastic surfaces. As a minimum estimate, 10–12% of the applied spleen cells and 22% of those from thymus attached between 1 and 24 hours after plating. The cells remained attached despite extensive and vigorous washing. Viability of 70% was maintained between 4 hours and 3 days in culture. Readdition of 10% mouse or horse serum for 2 hours resulted in removal of 80% of the attached cells. The percentage of adherent cells was not affected by cell density, but was greatly reduced when cells were cultured at 4 °C. Glutaraldehyde‐fixed cells did not adhere. Adherent cells were primarily T lymphocytes. The cell‐plate distance would indicate a focal contact mode of adherence; however, the absence of filamentous material at the adherent surface and the broad, continuous surface apposition would imply a close contact mode. We conclude that attachment modes described for fibroblasts in culture are not applicable for lymphocytes.
The development of lysosomal apparatus. II. Incorporation, subcellular distribution, and intraparticulate hydrolysis of 131 I‐albumin by liver of mice at perinatal stages
Authors: Bertini Francisco , Mayorga Luis , Gonzalez Mercedes 
Published: February 2005

AbstractMouse fetuses at 15th and 18th day of gestation, and newborns aging 0, 5, 10, and 15 days were injected i.p. with 131 I‐albumin (RISA). The degree of incorporation by liver and the intraparticulate hydrolysis of RISA in 27,000g × 10 min. particles increased after birth. By this time, changes in subcellular distribution of RISA and marker enzymes were also observed. Following an i.p. injection of India ink, numerous hepatic cells stained with carbon particles were observed at the light microscope from day 5 of life. The results suggest that the lysosomal apparatus acquires full capacity to incorporate colloidal particles and to degrade foreign macromolecules in the first week of life.
Growth of C6 glioma cells in serum‐containing medium decreases β‐adrenergic receptor number
Authors: Dibner Mark D. , Insel Paul A. 
Published: February 2005

AbstractRat C6 glioma cells were grown in 5% fetal bovine serum‐containing medium and under serum‐free, defined conditions. In order to ask whether cells grown in serum‐free medium are phenotypically identical to cells grown in serum, we examined effects of cell growth under both conditions on the β‐adrenergic receptor, a cell surface marker that activates adenylate cyclase and thereby regulates these cells. β‐Adrenergic receptors were qualitatively similar in cells grown in serum‐containing and serum‐free media, but the number of receptors was 30‐50% less in cells grown with serum. This effect required several days to occur or to be reversed. The decreased number of receptors appeared to be caused by an inhibitory effect of serum on receptor number and not by a stimulatory action of the constituents of the serum‐free medium. Growth medium with 5% fetal bovine serum maximally inhibited β‐adrenergic receptor numbers with 1% serum causing a half‐maximal inhibition. The ability of serum to inhibit the expression of β‐adrenergic receptors could be blocked by dialyzing but not by boiling fetal bovine serum. β‐Adrenergic receptor‐stimulated cyclic AMP accumulation was also decreased by growth in medium containing serum. These studies demonstrate that compared to growth of cells in serum‐free medium, growth in serum‐containing medium can inhibit expression of cell surface β‐adrenergic receptors. These results imply that the presence of serum in medium in which cells are grown alters properties in the plasma membrane and may alter hormonal responses in such cells.
Megakaryocytopoiesis in the mouse: Response to varying platelet demand
Authors: Burstein Samuel A. , Adamson John W. , Erb Susan K. , Harker Laurence A. 
Published: February 2005

AbstractThe response of murine megakaryocytopoiesis was studied under conditions of varying platelet demand. Twenty‐four hours after mice were given a single injection of rabbit anti‐platelet serum, megakaryocyte number and volume were increased, becoming maximal at 65 and 40 hr, respectively. Total body megakaryocytic colony‐forming unit (CFU‐M) numbers did not change until 90 hr, when a 35% increase in the experimental group was noted. The percentage of CFU‐M in DNA synthesis in the experimental group was 38 ± 2% at 24 hr, 49 ± 1% at 40 hr, and returned to normal (11 ± 3%) at 90 hr. When mice were made thrombocytotic by platelet transfusions, both megakaryocyte number and volume were decreased compared to controls, while no difference was noted in the number and percentage of CFU‐M in DNA synthesis. Finally, experiments were performed to examine the effect of platelet transfusions on regenerating marrow. Experimental mice were given platelet transfusions while control animals received platelet buffer solution. At sacrifice the number and volume of megakaryocytes in the experimental group (platelet count 2.568 × 106/μl) were less than controls (platelet count 0.363 × 106/μl), while the number and percentage of CFU‐M in DNA synthesis were similar in both groups. These results demonstrate that CFU‐M are not immediately responsive to acute changes in platelet demand. The data suggest that megakaryo‐cytopoiesis is structured on at least two levels which are independently regulated.
The relationship between tumor promoter binding and epstein‐barr virus induction in human lymphoblastoid cell lines
Authors: Yamamoto Naoki , Bauer Georg 
Published: February 2005

AbstractThe tumor promoter TPA (12‐0‐tetradecanoyl‐phorbol‐13‐acetate) efficiently induces the synthesis of Epstein‐Barr virus (EBV) antigens in EBV‐genome‐harboring human lymphoblastoid cells. We attempted to obtain information on the binding of TPA to cells and on the relationship between TPA‐binding and EBV induction by the use of tritiated TPA (3H‐TPA). Our data show: (1) In the absence of cells TPA can bind to serum completely within 60 minutes. (2) Cells can compete for a proportion of serum‐bound TPA. (3) Binding of TPA to cells reaches equilibrium within 60 minutes and is higher at 37° than 0°C. In the absence of serum, the rate of binding is about twice as high as in the presence of serum. (4) Dissociation of TPA from cells also seems to be rapid. When the cells are incubated with cold TPA after prior treatment with 3H‐TPA, followed by washing, a much higher rate of release of labeled TPA is observed than in cultures to which fresh medium is added exclusively. Dissociation is higher in the presence of serum than in the absence of it. If radiolabeled cells are analyzed after serial washing, the rate of cell‐associated/noncell‐associated radioactivity indicates that the proportion of molecules required for EBV induction is dissociated rapidly.
The role of protein accumulation in the cell cycle control of human NHIK 3025 cells
Authors: Rønning Ø. W. , Lindmo T. , Pettersen E. O. , Seglen P. O. 
Published: February 2005

AbstractThe cell cycle kinetics of NHIK 3025 cells, synchronized by mitotic selection, was studied in the presence of cycloheximide at concentrations (0.125‐1.25 μM) which inhibited protein synthesis partially and slowed down the rate of cell cycle traverse.The median cell cycle duration was equal to the protein doubling time in both the control cells and in the cycloheximide‐treated cultures at all drug concentrations. This conclusion was valid whether protein synthesis was continuously depressed by cycloheximide throughout the entire cell cycle, or temporarily inhibited during shorter periods at various stages of the cell cycle. These results may indicate that cell division does not take place before the cell has reached a critical size, or has completed a protein accumulation‐dependent sequence of events.When present throughout the cell cycle, cycloheximide increased the median G1 duration proportionally to the total cell cycle prolongation. However, the entry of cells into S, once initiated, proceeded at an almost unaffected rate even at cycloheximide concentrations which reduced the rate of protein synthesis 50%.The onset of DNA synthesis seemed to take place in the cycloheximide‐treated cells at a time when the protein content was lower than in the control cells. This might suggest that DNA synthesis in NHIK 3025 cells is not initiated at a critical cell mass.
Mechanism of glucocorticoid‐mediated inhibition of murine erythroid colony formation in vitro
Authors: Gidari Anthony S. 
Published: February 2005

AbstractThe mechanism by which glucocorticoids influence erythroid colony formation by murine bone marrow cells was studied in a plasma clot culture system. All glucocorticoids tested, including 9α‐fluorocortisol (> 10−8M), cortisol (≥ 10−8M), dexamethasone (> 10−7M), and corticosterone (≥ 10−7M), inhibited erythroid colony formation; none enhanced colony formation. Inhibition by a prototypic glucocorticoid, dexamethasone, was evident at all concentrations of erythropoietin (25–200 mU) in the clots. The percent dexamethasone‐sensitive cells killed by high specific activity [3H]‐TdR (∼ 78%) was the same as the percent erythroid colony‐forming cells killed by this treatment, and the inhibition appears to represent a direct effect on the erythroid colony‐forming cell since: (1) Cells exposed (1 hour) to dexamethasone, washed, and cultured in steroid‐free medium formed a reduced number of colonies (67% of control); (2) dexamethasone decreased colony formation by marrow depleted of adherent cells or obtained from either nude or neonatally thymectomized mice; and (3) co‐cultivation studies of normal marrow with that obtained from glucocorticoid‐treated mice, which forms a reduced number of colonies in vitro, indicated that this inhibition was not the result of enhanced suppressor cell or reduced stimulatory cell activity.The proliferative rate of colony‐forming cells obtained from dexamethasone‐treated mice, as determined with high specific activity [3H]‐TdR, was reduced ( ∼ 38% of control), suggesting that a reduction in the proliferative rate of the colony‐forming cell is the major mechanism of the glucocorticoid‐mediated inhibition of erythroid colony formation. In addition, dexamethasone, added 24 hours after the initiation of the cultures, inhibited the growth of developing erythroid colonies, indicating a potential inhibitory action on the proliferation of the progeny of the colony‐forming cell.
Differential conjugation of polyamines to calf nuclear and nucleolar proteins
Authors: Haddox Mari K. , Russell Diane Haddock 
Published: February 2005

AbstractNuclei and nucleoli isolated from calf liver contain acid‐precipitable putrescine, spermidine and spermine conjugates. The polyamines are released upon peptide bond hydrolysis. All of the nuclear putrescine conjugate and a major portion of the polyamine conjugates are localized within the nucleolus. Nuclei and nucleoli also contain, in proportions consistent with the nucleolar/nuclear protein ratio, the putative conjugating enzyme, transglutaminase, as well as amine acceptor substrates to which radiolabeled putrescine can be conjugated by endogenous enzyme. Extraction of the isolated organelles with saline solutions of increasing ionic strength showed a differential distribution of the polyamine derivatives: all the covalently linked putrescine was associated with the less soluble components of the chromatin residue, while the spermidine and spermine conjugates were associated with several salt‐extractable protein fractions as well as tightly bound to the chromatin pellet. Mono‐γ‐glutamyl putrescine was detected after proteolytic digestion of the 600 mM NaCl fraction, further suggesting the enzymatic action of transglutaminase(s) in the conjugation process.
SV40‐transformed human cells fail to grow in zinc concentrations which permit normal human fibroblast proliferation
Authors: Epstein J. 
Published: February 2005

AbstractZinc is a metal known to be required for normal growth of both cells and organisms. When normal and SV40‐transformed human tumor cells are plated and grown in medium containg zinc sulfate, a significant fraction of the transformed cells fail to grow at zinc concentrations which are relatively nontoxic to the normal fibroblasts. Although cultured cells respond to certain metallic ions by incresing their metallothionein content, no difference in the ability of normal and transformed cells to produce metallothionein in response to zinc exposure could be detected, thus ruling out this mechanism as a basic for the differing abilities of the cells to grwo in zinc in vitro. These results suggest that zinc may be capable of differntially regulating the growth of normal and SV40− transformed human fibroblasts.
A biochemical investigation of the adenovirus‐induced G1 to S phase progression: Thymidine kinase, ornithine decarboxylase, and inhibitors of polyamine biosynthesis
Authors: Cheetham Brian F. , Bellett Alan J. D. 
Published: February 2005

AbstractBiochemical events were investigated in the G1 to S phase progression induced in quiescent rodent cells by human adenovirus type 5 (Ad5) and by serum. Thymidine kinase activity increased after infection of cells with Ad5 or addition of 10% serum. These stimulations were additive. An early viral gene was respnsible for induction by Ad5, but the early mutants ts36, ts37, and ts125 induced thymidine kinase at the permissive and nonpermissive temperatures. Several differences were found between cells stimulated by serum compared with Ad5. Induction of thymidine kinase was delayed in Ad5‐ infected cells, insensitive to 0.01 μ/ml actinomycin D and relatively resistant to reduced Ca2+ compared with induction by serum. Ornithine decarboxylase was induced by serum, but not by Ad5. α‐Methylornithine had little effect on the induction of thymidine kinase by Ad5, but reduced the induction of thymidine kinase by serum, suggesting that Ad5‐induced entry into S phase is uncoupled from polyamine biosynthesis. Methylglyoxal bis(guanylhydrazone), however, prevented the induction of thymidine kinase by both serum and Ad5. Adenovirus infection appears to induce cellular DNA synthesis and thymidine kinase in G1‐arrested cells by a mechanism different from serum, and by passes events in the normal G1 to S phase progression.
Intracellular localization of certain membrane glycoproteins in mouse T‐lymphoma cells using immunoferrtin staining of ultrathin frozen sections
Authors: Bourguignon Lilly Y. W. , Butman Bryan T. 
Published: February 2005

AbstractComparative studies on the cellular morphology of cultured mouse T‐lymphoma cells (with particular emphasis on organelles and membrane‐associated materials) were conducted using both frozen thin sections and epon thin sections. Due to the fact that the frozen thin sectioning technique allows antigenicity to be retained and also permits good accessbility of the external macromolecular reagents to the interior of the cell, we have been able to explore the intracellular localization of some membrane glycoproteins such as Con A‐binding sites and viral membrane glycoprotein, gp 69/71. Our data indicate that most of the membranous cellular structures (e.g., rough endoplamic reticulum, vesicles, Golgi and nuclear envelope) contain the Con A‐specific sugars, mannose, and glucose. In addition, we have found that intracellular gp 69/71 molecules exist in an aggregated form at the terminal region of cisternae of rough endoplasmic reticulum and in vesicles of two size ranges (0.1 to 0.15 μ and 0.3 to 0.4μm) as wells as in the cytoplasm close to the plasma membrane. These findings have not only confirmed close some of the previous biochemical data but have also provided new information concening the biochemical nature of intracellular membrane components and the possible biosynthetic fate of membrane precursor molecules.
Effect of growth stage on histone H1 metabolism in human diploid fibroblasts
Authors: Sakagami Hiroshi , Mitsui Youji , Murota Sei‐Itsu , Yamada Masa‐Atsu 
Published: February 2005

AbstractMetabolism of histone H1 at different stages of cell growth was investigated in order to get a better understanding of the role of histone H1 in the cell growth of human diploid fibroblasts. Histone H1 content exhibited some fluctuation during the culture stage of cell growth. When cells entered confluent phase, the ratio of histone H1 to total histones decreased significantly. Histone H1 had a tunover half‐life of 80 hours whereas nucleosomal histones did not significantly turn‐over regardless of the growth stage. DNA synthesis was drastically diminished with increase cell density whereas histone synthesis was less sensitive to contact inhibition. The gradual decline of histone H1 content with increased cell density suggest that its degradation is slightly superior to its residual synthesis. When the confluent cells were seeded at low density, cell proliferation resumed and histone H1 was synthesized and deposited to chromatin in a greater amoun than nucleosomal histones, thus resulting in an abrupt increase of histone H1 content. The possible role of histone H1 metabolism in normal cell is discussed.
The effect of metabolic inhibition on lon contents and sodium exchange in human lymphocytes
Authors: Negendank William , Shaller Calvin 
Published: February 2005

AbstractLymphocytes depleted of ATP by incubation in iodoacetate (IAA) and nitrogen (N2) lost K and gained Na. Isotopic Na exchange showed a fast fraction and a slower exponential fraction, the latter conventionally assumed to reflect surface membrane properties. The gain of cell Na was not accounted for by a decrease in 22Na efflux in either the slow or the fast fraction. After 3–5 hours, Na efflux increased. These results led us to question the concept that normal cell ion levels are maintained by an ATPase pump and could not be explained by exchange diffusion, cotransport, countertransport, or other inherently dissipative mechanisms. The data are, on the other hand, consistent with the concept that cell ion contents are determined by their relative exclusion from cell water coupled with selective adsorption onto fixed macromolecular anionic sites within the cell. In this view, the IAA, N2‐induced rise in cell Na is due to the occupancy of adsorption sites losing K, while the increased isotopic exchange is due to a decreased activation energy for ion‐site interaction.
Hormonal and nutritional factors influencing glycogen deposition in primary cultures of rat liver parenchymal cells
Authors: Weber Charles A. , Kletzien Rolf F. 
Published: February 2005

AbstractThe effect of the glucocorticoids, insulin, and glucose concentration on glycogen deposition in adult rat liver parenchymal cells maintained in a chemically defined, serum‐free medium has been studied. Increasing the medium concentration of glucose from 5.6 mM to 30.6mM in the absence of hormones increased cellular glycogen content from 6.5 to 51 μg of glycogen per mg of cell protein. Treatment of the cells with insulin increased the glycogen content by 15 to 30% at medium glucose concentrations above 10.6 mM. The addition of the synthetic glucocorticoid, dexamethasone, to the culture medium resulted in 40 to 105% increases in glycogen content at glucose concentrations greater than 5.6 mM. The addition of dexamethasone and insulin together in the culture medium resulted in an increase in glycogen content that was greater than the additive effect of each hormone alone. This established that glucose concentrations above 10.6 mM stimulate glycogen deposition in the absence of any hormonal stimulus. In addition, glucocorticoids directly stimulate glycogen deposition at glucose concentrations which are greater than physiological (5.6 mM).
Effects of pyruvate on the growth of normal and transformed hamster embryo fibroblasts
Authors: Sens Donald A. , Hochstadt Bruce , Amos Harold 
Published: February 2005

AbstractThe growth of NIL and NILpy hamster embryo fibroblasts was determined in the presence and absence of pyruvate as a component of the growth medium. It was demonstrated that NIL cells respond to the presence of pyruvate by decreasing cell doubling time, glucose utilization, glutamine utilization, and increasing lactate production with the effects being more pronounced at low inoculum densities. Polyoma‐virus transformed NIL cells (NILpy) demonstrate none of the above effects upon pyruvate addition regardless of initial cell inoculum density.