bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of cortisol, 17β‐estradiol and thyroliberin on prolactin and growth hormone production, cell grwoth and cell cycle distribution in cultured rat pituitary tumour cells
Authors: Clausen O. P. F. , Gautvik K. M. , Haug E. 
Published: February 2005

AbstractProlactin and growth hormone production were measured in a rat pituitary tumour cell strain (GH3) after treatment with cortisol (5 × 10−6 M), thyroliberin (2.5 × 10−6 M) and 17β‐estradiol (10−6 M). The changes in hormone production were related to alterations in cell growth rate and cell cycle distribution. Cortisol inhibited prolactin production, stimulated growth hormone production and reduced the cellular growth rate measured two days after start of treatment (maximum about 40% inhibition). Flow‐micro fluorometric analysis of DNA distributions showed that cortisol treatment reduced the relative number of cells in S phase (maximum effect about 50%) with a compensatory increase of the proportion of cells in G1 phase. The lack of inhibition of prolactin production after three days of cortisol treatment may partly be related to the increased number of cells in G1 phase. Thyroliberin and 17β‐estradiol did not significantly affect cell growth after six days of treatment, although the fraction of cells in S phase was reduced by approximately 40% with a corresponding increase of cells in G1 phase. For thyroliberin and 17β‐estradiol, the stimulatory effect on prolactin production and the inhibitory effect on growth hormone production witin a period of treatment of six days cannot be explained by a shift in cell cycle distributions. None of the three hormones influenced the growth fraction which was equal to unity.In conclusion, thyroliberin and 17β‐etradiol are able to change prolactin and growth hormone production without altering the cell cycle distribution. However, the effects of cortisol on prolactin and growth hormone production may partly be due to an alteration in cell cycle traverse resulting in an increased number of cells in the G1 phase.
Nature of cells forming erythroid colonies in agar after stimulation by spleen conditioned medium
Authors: Johnson G. R. , Metcalf D. 
Published: February 2005

AbstractErythroid colony formation in agar cultures of CBA cells was stimulated by the addition of pokeweed mitogen‐stimulated C57BL spleen conditioned medium. Both 48‐hour colonies (“48‐hour benzidine‐positive aggregates”) and day 7 large burst or unicentric erythroid colonies (“erythroid colonies”) developed, together with many neutrophil and/or macrophage colonies.In CBA mice, the cells forming erythroid colonies occurred with maximum frequency (650/105 cells) in 10‐ to 11‐day‐old yolk sac and fetal liver but were present also in fetal blood, spleen and bone marrow. The frequency of these cells fell sharply with increasing age and only occasional cells (2/105 cells) were present in adult marrow. A marked strain variation was noted, CBA mice having the highest levels of erythroid colony‐forming cells.The erythroid colony‐forming cells in 12‐day CBA fetal liver were radiosensitive (Do 110–125 rads), mainly in cycle and were non‐adherent, light density, cells sedimenting with a peak velocity of 6–9 mm/hr. These properties are similar to those of other hemopoietic progenitor cells in fetal tissues. The relationship of these apparently erythropoietin‐independent erythroid colony‐forming cells to those forming similar colonies after stimulation by erythropoietin remains to be determined.
The role of adenosine 3′, 5′‐cyclic monophosphate in the density‐dependent regulation of growth and tyrosinase activity of b‐16 melanoma cells
Authors: Wade David R. , Burkart Mary E. 
Published: February 2005

AbstractIncubation of cultured B‐16 melanoma cells with 1‐methyl‐3‐isobutyl xanthine (MIX) produced a sustained rise in intracellular adenosine 3′,5′‐cyclic monophosphate (cAMP) which preceded an increase in the specific activity of tyrosinase (EC 1.10.3.1). Cultures of two clones of melanoma cells, one having a mean population doubling time twice that of the other, showed density‐dependent inhibition of growth. The tyrosinase activity of each line increased progressively during logarithmic growth, reaching maximal values shortly after the cultures achieved confluence. Intracellular cAMP levels fell during logarithmic growth, being minimal in confluent cultures. The stimulatory effects of MIX and confluence on tyrosinase activity were additive. Cells plated at high density had a lower tyrosinase activity than cells allowed to achieve a similar density by successive division from sparsely planted cultures although the intracellular cAMP levels of such cultures were not different. We support the observations of other investigators that agents which increase intracellular cAMP concentrations can both inhibit cell division and stimulate tyrosinase activity. There are, however, mechanisms for increasing tyrosinase activity and inhibiting cell division which are expressed as B‐16 melanoma cells approach confluence and which are not mediated by an increase in intracellular cAMP concentrations.
Epithelioid and fibroblastic rat kidney cell clones: Epidermal growth factor (EGF) receptors and the effect of mouse sarcoma virus transformation
Authors: De Larco Joseph E. , Todaro George J. 
Published: February 2005

AbstractFibroblastic and epithelioid clones have been isolated from the normal rat kidney line, NRK. These clones were studied for their ability to bind epidermal growth factor (EGF), susceptibility to transformation by mouse sarcoma virus (MSV), and alteration in EGF binding upon sarcoma virus transformation. The epithelioid clones bound much more EGF than the fibroblastic clones; Scatchard plots on two of these clones, one epithelioid and one fibroblastic, showed that the higher EGF binding (1.3 × 105 molecules per cell for the epithelioid clone and 1.3 × 104 molecules per cell for the fibroblastic clone) was due to a greater number of receptors on the epithelioid cells rather than to a difference in the apparent affinity constant. When the clones were transformed by Moloney murine sarcoma virus the EGF binding decreased, the effect being greater with the fibroblastic clones. In 20 out of 20 independently isolated sarcoma virus transformed fibroblastic clones, the level of EGF binding was either greatly reduced or completely eliminated. In contrast to EGF, another growth factor, multiplication stimulating activity (MSA), bound to a greater extent to the fibroblastic clones than the epithelioid clones, and its binding was not decreased by sarcoma virus transformation. The results show that loss of EGF binding ability correlates with expression of the murine sarcoma virus transformation.
Serum‐stimulated changes in calcium transport and distribution in mouse 3T3 cells and their modification by dibutyryl cyclic AMP
Authors: Tupper Joseph T. , Rosso Mario Del , Hazelton Bonnie , Zorgniotti Flavia 
Published: February 2005

AbstractSerum stimulation of quiescent 3T3 cells returns the cells to a proliferative state. Changes in Ca content, transport and distribution during the transition through G1 and S phase have been investigated following serum stimulation of these cells. 45Ca exchange data indicate at least two kinetically defined cellular compartments for Ca; a rapidly exchanging component presumably representing surface Ca which is removable by EGTA and a slowly exchanging component presumably representing cytoplasmically located Ca. Previous studies (Tupper and Zorgniotti, 1977) indicate that the approach to quiescence in the 3T3 cells is characterized by a large increase in the surface Ca component. The present data demonstrate that this component is rapidly lost following serum stimulation. Furthermore, the serum induces an 8‐fold increase in Ca influx into the cytoplasmic compartment and a reduction in the unidirectional efflux rate coefficient for Ca. The increased Ca uptake peaks at approximately six hours (mid G1) and is accompanied by a parallel increase in cellular Ca. Prior to entrance of the cells into S phase (10—12 hours), Ca uptake declines. This is followed by a slower decline in cytoplasmic Ca levels. Simultaneous addition of fresh serum plus 0.5 mM dibutyryl cAMP inhibits the entrance of the cells into S phase. Under these conditions the loss of surface Ca is not blocked. However, the presence of 0.5 mM dibutyryl cAMP inhibits the increase in Ca uptake and, in turn, diminishes the increase in cellular Ca following serum stimulation. In contrast, a low level of dibutyryl cAMP (0.1 mM) enhances progression through G1 phase but also reduces both Ca uptake and Ca content of the cells. The data suggest that the serum induced changes in Ca content and transport are linked to intracellular cyclic nucleotide levels and progression through G1 phase and that extracellular cAMP elevating agents may enhance or inhibit these interactions in a concentration dependent manner.
The effect of tobacco smoke on the metabolism and function of rat alveolar macrophages
Authors: Drath David B. , Harper Annabel , Gharibian Jane , Karnovsky Manfred L. , Huber Gary L. 
Published: February 2005

AbstractAlveolar macrophages harvested by bronchopulmonary lavage from rats exposed to tobacco smoke for 30 days (“smokers”) showed alterations in oxidative metabolism, lactate production and phagocytosis of inert starch particles when compared with control macrophages. Phagocytosis of viable Staphylococcus aureus was unaffected by tobacco smoke. Glucose oxidation measured by conversion of glucose‐1‐14C to 14CO2 was moderately affected while oxidation of glucose‐6‐14C to 14CO2 was not. Smokers routinely yielded fewer cells than controls, though these cells contained approximately 17% more protein than did controls. Opsonization of particles was not necessary for macrophages from either smoker or control animals to manifest a respiratory burst and increased superoxide and hydrogen peroxide release during phagocytosis. The glycolytic inhibitors, sodium fluoride and iodoacetamide, while effectively blocking glycolysis, did not inhibit phagocytosis by macrophages from either group. The results reported clearly distinguish alveolar macrophages from other phagocytic cells (peritoneal macrophages and polymorphonuclear leukocytes) and suggest a state of non‐specific activation caused by exposure to tobacco smoke.
Retention of transformant specific type III collagen in dibutyryl cAMP treated Kirsten sarcoma virus transformed BALB 3T3 cells and in a flat revertant
Authors: Hata Ryu‐Ichiro , Peterkofsky Beverly 
Published: February 2005

AbstractWe previously reported that Kirsten sarcoma virus transformed BALB 3T3 (Ki‐3T3) cell cultures contained mainly type I collagen and about 30% of another type designated by us as Y and which appears to be type III collagen, [α1 (III)]3. Clones of BALB 3T3 which exhibited contact‐inhibition were found to contain mainly type I collagen [α1(I)]2α2, and about 25% of another type (X) which was composed of three α1 chains differing from those of type III (Hata, R. and B. Peterkofsky, 1977 Proc. Nat. Acad. Sci. (U.S.A.), 74: 2933—2937). Since dibutyryl 3′:5′ cyclic adenosine monophosphate (dbcAMP) increases collagen synthesis and alters other transformation specific properties of Ki‐3T3 cells, we determined whether treatment of Ki‐3T3 cells with this compound restored the normal collagen phenotype. We also analyzed the collagen of a revertant of Ki‐3T3 which exhibits properties similar to those of the dbcAMP treated transformant. Procollagen labeled with radioactive proline was isolated from the medium or cells of cultures and was converted to collagen with pepsin; the collagen was analyzed by carboxymethyl cellulose (CMC) chromatography or gel electrophoresis under denaturing conditions. Ki‐3T3 cells treated with 0.5 mM dbcAMP continued to accumulate type III collagen but there was an increase in the number of α1 chains eluting from CMC columns in the same position as α1 (I) suggesting increased accumulation of type X collagen. Although the revertant was similar to dbcAMP treated cells in that it exhibited a flattened morphology and a high relative rate of collagen synthesis, the collagen profile was similar to that of the transformant, consisting mainly of types I and III. These results indicate that accumulation of type III collagen is unaffected by dbcAMP but suggest that cAMP may be involved in the regulation of type X collagen. The failure of dbcAMP or reversion to affect the occurrence of type III collagen supports the mechanism of cell selection as a means of explaining the specific occurrence of type III collagen in sarcoma virus transformed 3T3 cells.
The effect of protein degradation on cellular growth characteristics
Authors: Baxter G. C. , Stanners C. P. 
Published: February 2005

AbstractThe role of protein degradation in cellular proliferation was investigated by measurements of the rates of degradation of labile and stable proteins for a number of cell types under various growth conditions. The rate of protein degradation was found to be a relatively invariant parameter in that it did not change after strong inhibition of protein synthesis with cycloheximide or histidinol, it was the same in both exponential and stationary phase, and it did not correlate with the presence or absence of malignant tranformation.Using three different cell types with widely differing division rates, the rate of cell division and DNA synthesis (in %/hr) was found to be precisely equal to the rate of protein accumulation (in %/hr), i.e., to the rate of protein synthesis minus the rate of protein degradation. Division rates between the different cell types appeared to be determined chiefly by the rate of protein synthesis though, especially at low division rates, the rate of protein degradation could represent a large component of the protein accumulation rate.
Localization of pyruvate kinase isozymes in bovine kidney and comparison of these patterns with those of lactate dehydrogenases and aldolases
Authors: Cardenas Janet M. , Richards Thomas C. , Gabourel Linda 
Published: February 2005

AbstractElectrophoretic and immunofluorescence analysis were used to study the distribution of pyruvate kinase isozymes in the bovine kidney. Electrophoretic analysis demonstrated the presence of large amounts of K4 plus small amounts of K‐M hybrids in cortical, medullary, and papillary sections cut from the kidney. Nearly all of the K‐L hybrids seen in whole kidney extracts were found in cortical sections. Immunofluorescence of frozen sections revealed the presence of type L subunits in the tubules but the complete absence of this subunit type in glomeruli. Glomeruli do contain large quantities of pyruvate kinase isozymes, probably K4 and K‐M hybrids, that cross‐react with antibodies produced against type M pyruvate kinase.Type L‐containing forms of pyruvate kinase and aldolase type B both appear to be found in cell types thought to be capable of catalyzing gluconeogenesis, while type K pyruvate kinase and type A aldolase are found in predominantly glycolytic cell types of the kidney. Lactate dehydrogenase isozymic patterns appear to be less closely correlated with glycolytic versus gluconeogenic functions of the kidney but may be determined more directly by other metabolic functions.
Intracellular plasminogen activator activity in growing and quiescent cells
Authors: Loskutoff David J. , Paul Dieter 
Published: February 2005

AbstractIntracellular plasminogen activator (PA) was examined in 3T3 and transformed 3T3 cells under various growth conditions to determine whether expression of this activity changes with the growth state. During exponential growth, SV40 and benzpyrene (BP) transformed 3T3 cells exhibited 3‐ to 5‐fold more intracellular PA activity than untransformed 3T3 cells. This relationship changed as the cells exhausted serum factors and arrested in G1. The specific activity of intracellular PA in cells that have retained a serum‐sensitive restriction point in G1 (G0) (3T3 and BP 3T3) increased 200‐ and 20‐fold, respectively, at this time, while the level in cells that have lost most growth control mechanisms (SV3T3) remained constant. At confluency, 3T3 cells had considerably more PA than either of their transformed counterparts. Sparse cultures of 3T3 and BP3T3 cells arrest at G1 following serum depravation, and also accumulate high intracellular PA activity. The addition of serum or purified epidermal growth factor to these cultures initiated cell proliferation and resulted in a rapid, actinomycin D‐sensitive loss of this activity. Less than 50% of the original activity remained 30 minutes after growth stimulation. This loss of intracellular PA activity did not appear to result from the presence of serum or cellular inhibitors. Intracellular PA activity remained low following growth stimulation. It increased again as the cells traversed through G1. These findings indicate that intracellular PA activity fluctuates with the growth state of cells, and may be related to the cell cycle. Culture conditions which place cells, whether normal or transformed, in G1 arrest lead to increased intracellular PA, while factors that initiate growth again result in a rapid loss of this activity. This behavior is lacking in cells not subject to density‐dependent inhibition of growth. Like many other correlates of transformation, comparison of intracellular PA in normal and transformed cells must be defined in terms of the growth state of the cells in question.
Insulin binding sites on rat liver nuclear membranes: Biochemical and immunofluorescent studies
Authors: Horvat Agnes 
Published: February 2005

AbstractPreliminary investigations (Horvat et al., '75) indicated the nucleus of rat liver as a site for specific binding of insulin. In this report these observations are confirmed. Nuclei from rat liver were isolated in a highly purified state as verified by interference contrast and electron microscopy and by chemical analysis. Extensive scanning of the preparations did not reveal the presence of structures resembling plasma membranes. The nuclear envelope was isolated by a modification of the method of Kay et al. ('72). Electron micrographs showed the presence of nuclear “ghosts” and few other recognizable nuclear elements, but no plasma membranes (60–80 Å thick) were detected. The preparation was found to contain specific insulin binding activity. Specificity of the binding sites for insulin was demonstrated in competition studies with other polypeptide hormones and a synthetic insulin analog. Scatchard analysis of the binding data indicates the presence of a single class of high affinity receptors. In contrast to findings with plasma membranes the hormone‐receptor complex is very stable and the kinetics of the dissociation of bound [125I]‐insulin do not indicate negative cooperativity of the binding sites. Immunofluorescent labeling of intact, unfixed nuclei showed a specific fluorescent halo only around those nuclei that have been preincubated with insulin. All other controls were negative.
Methionine metabolism in BHK cells: Preliminary characterization of the physiological effects of cycloleucine, an inhibitor of S‐adenosylmethionine biosynthesis
Authors: Caboche Michel , Hatzfeld Jacques 
Published: February 2005

AbstractCycloleucine is in vitro a competitive inhibitor of methionine adenosyltransferase, an enzyme involved in S‐adenosylmethionine biosynthesis. The physiological effects of this drug on baby hamster kidney cells have been studied. When cells are grown in a medium containing 10 μM methionine, cycloleucine is an inhibitor of cell proliferation; high concentrations of methionine are able to withdraw this inhibition suggesting that cycloleucine toxicity is related to methionine metabolism. The drug does not primarily affect methionine uptake and its subsequent use for protein biosynthesis. Cycloleucine toxicity is correlated with a block of SAM biosynthesis and nucleic acids methylations. The actions of cycloleucine on progression in the cell cycle and DNA, RNA and protein biosynthesis are studied. The implications of these results are discussed.
Transforming viruses directly reduce the cellular growth requirement for a platelet derived growth factor
Authors: Scher Charles D. , Pledger W. J. , Martin Paul , Antoniades Harry , Stiles Charles D. 
Published: February 2005

AbstractEarly passage mouse embryo fibroblasts, mouse 3T3 cell lines, and early passage diploid human fibroblasts grew to higher cell densities in tissue culture medium supplemented with serum than in medium supplemented with defibrinogenated platelet‐poor plasma (PPP). Unlike the mouse cells, the human fibroblasts displayed this differential growth response only in the presence of hypophysiologic concentrations of calcium. The addition of heat‐treated extracts of human platelets to PPP‐supplemented medium stimulated the replication of both the normal mouse cells and early passage human embryo fibroblasts.Human or mouse fibroblasts transformed by either retroviruses or by SV40, including SV40 infected “serum revertants” and “flat transformants,” grew to equal cell densities in medium supplemented with either serum or PPP. Infection of Balb/c‐3T3 cells with SV40 rapidly induced them to grow in PPP‐supplemented medium demonstrating that the ability of SV40‐transformed cell lines to proliferate in PPP‐supplemented medium does not arise from the cell culture selection procedures usually employed to obtain stable virus‐transformed cell lines. 3T3 cells infected but not transformed by retroviruses do not replicate in PPP‐supplemented medium demonstrating that reduction of the growth requirement for the platelet growth factor(s) by retroviruses is a transformation‐specific response. Cell cultures that did not proliferate well in PPP‐supplemented medium did not form tumors when inoculated into athymic nude mice. Many, although not all, of the lines which grew well in PPP medium were tumorigenic in nude mice. Together, these findings indicate that: (1) normal fibroblast‐like cells display a growth requirement for factor(s) present in serum but not found in PPP; (2) this serum specific growth factor is derived from platelets; (3) a primary response to viral transforming genes is a reduction in the growth requirement for these platelet‐derived factors; and (4) cells that have a reduced requirement for the platelet‐derived growth factor are often tumorigenic.
Plasminogen activator synthesis by cultured human embryonic lung cells: Characterization of the suppressive effect of corticosteroids
Authors: Rifkin Daniel B. 
Published: February 2005

AbstractThe synthesis of plasminogen activator (PA) by cultured human embryonic lung (HuEL) cells has been examined. The production of PA by these cells was found to be reversibly inhibited by physiological levels of glucocorticoids. The suppression of PA synthesis in HuEL cells was not accompanied by an inhibition of cell growth. Moreover, the glucocorticoid induced deinduction of plasminogen activator synthesis occurred in both growing and non‐growing cells. The inhibition of PA production by corticosteroids appeared to have a requirement for DNA‐dependent RNA synthesis since the inhibition of DNA‐dependent RNA synthesis at the time of exposure of cells to corticosteroids prevented the deinduction of PA.