bluuebunny/crossref_metadata_2025_split huggingface dataset:
Growth of normal human keratinocytes and fibroblasts in serum‐free medium is stimulated by acidic and basic fibroblast growth factor
Authors: Shipley Gary D. , Keeble Winifred W. , Hendrickson Jill E. , Coffey Robert J. , Pittelkow Mark R. 
Published: February 2005

AbstractKeratinocytes and fibroblasts isolated from human neonatal foreskin can be plated and grown through multiple rounds of division in vitro under defined serum‐free conditions. We utilized these growth conditions to examine the mitogenic potential of acidic and basic fibroblast growth factor (aFGF and bFGF) on these cells. Our results demonstrate that both aFGF and bFGF can stimulate the proliferation of keratinocytes and fibroblasts. aFGF is a more potent mitogen than bFGF for keratinocytes. In contrast, bFGF appears to be more potent than aFGF in stimulating the growth of fibroblast cultures. Heparin sulfate (10 μg/ml) dramatically inhibited the ability of bFGF to stimulate the proliferation of keratinocytes. In comparison, heparin slightly inhibited the stimulatory effect of aFGF and had no effect on epidermal growth factor (EGF) stimulation in keratinocyte cultures. In fibroblast cultures the addition of heparin enhanced the mitogenic effect of aFGF, had a minimal stimulatory effect on the mitogenic activity of bFGF, and had no effect on EGF‐stimulated growth. Our results demonstrate that the proliferation in vitro of two normal cell types found in the skin can be influenced by aFGF and bFGF and demonstrate cell‐type specific differences in the responsiveness of fibroblasts and keratinocytes to these growth factors and heparin.
Nonterminally differentiated cells express decreased growth factor responsiveness
Authors: Hoerl Bryan J. , Scott Robert E. 
Published: February 2005

AbstractIn 3T3 T mesenchymal stem cells, at least four types of biological states exist that can mediate the control of cell differentiation and/or proliferation. These include the predifferentiation growth arrest state, the nonterminal differentiation state, the terminal differentiation state, and a growth arrest state induced by growth factor/serum deficiency. The current studies were performed to investigate the relative mitogenic responsiveness of cells at these four states and specifically to determine if nonterminally differentiated cells show decreased responsiveness to specific mitogens. Twenty‐five different serum, plasma, and growth factor combinations were evaluated. The results show that undifferentiated, growth‐arrested cells are highly responsive to numerous mitogens and that by definition terminally differentiated cells are not responsive to any mitogens. In contrast, nonterminally differentiated cells demonstrate a unique pattern of mitogenic responsiveness. Whereas nonterminally differentiated cells can be stimulated to proliferate by high concentrations of serum or plasma supplemented with growth factors, they cannot be stimulated to proliferate by combinations of multiple purified growth factors. These results suggest that the process of nonterminal differentiation is associated with a significant change in factors/cofactors required to stimulate cell proliferation and that these factors/cofactors are present in plasma.
Effects of n‐alcohols on junctional coupling and amylase secretion of pancreatic acinar cells
Authors: Chanson Marc , Bruzzone Roberto , Bosco Domenico , Meda Paolo 
Published: February 2005

AbstractWe have tested the effects of alcohols differing by their alkyl chain length on the membrane channels and amylase secretion of rat pancreatic acinar cells. In intact acini, alcohols with a chain of seven, eight, or nine carbons (C‐7, C‐8, and C‐9) induced dye uncoupling and increased basal amylase release. These effects were readily reversible after alcohol removal. By contrast, an alcohol with a chain of 15 carbons (C‐15) and several alcohols with chains of fewer than six carbons (C‐2, C‐4, and C‐6) did not uncouple acinar cells and had no effects on amylase secretion. Neither did alkanes and oxidized derivatives of C‐7 and C‐8 alcohols did not affect dye coupling. Double patch‐clamp experiments on pairs of acinar cells, under conditions of strong cytosolic Ca2+ and pH buffering, showed that C‐7, C‐8, and C‐9 alcohols blocked completely and reversibly the electrical conductance of junctional channels. Furthermore, studies of single voltage‐clamped acinar cells revealed that the uncoupling alcohols did not affect the resting nonjunctional membrane conductances. Thus the alcohols that did not affect acinar cell coupling did not affect amylase secretion, whereas the alcohols that caused uncoupling increased secretion. The latter effect was not mediated by changes in the conductance of nonjunctional membrane, cytosolic Ca2+, and pH and, as revealed by an immunological hemolytic plaque assay for amylase, had a time course consistent with the rapid (within 1 min) inhibition of coupling. These data provide new support for the view that the regulation of cell‐to‐cell communications is correlated with that of digestive enzyme secretion.
Differential effects of follicle‐stimulating hormone, insulin, and insulin‐like growth factor I on hexose uptake and lactate production by rat Sertoli cells
Authors: Oonk Ria B. , Jansen Ruud , Grootegoed J. Anton 
Published: February 2005

AbstractThe stimulatory effects of follicle‐stimulating hormone (FSH), insulin, and insulin‐like growth factor I (IGF‐I) on lactate production and hexose uptake by Sertoli cells from immature rats were studied. The time‐courses and the maximal stimulatory effects of FSH, insulin, and IGF‐I on lactate production were virtually identical. When Sertoli cells were incubated in the presence of FSH in combination with insulin or IGF‐I (submaximal doses), additive but no pronounced synergistic effects were observed. The stimulatory effects of FSH and insulin were not dependent on the presence of extracellular calcium. 2‐Deoxy‐D‐glucose (2‐DOG), an analogue of D‐glucose, was used to investigate the hexose transport system of Sertoli cells. Uptake of 2‐DOG was linear in time and virtually all of the intracellular 2‐DOG was phosphorylated up to 30 min of incubation; 2‐DOG uptake was inhibited by c ytochalasin B, but not by cytochalasin E. D‐glucose, but not D‐galactose, appeared to be an effective competitor of 2‐DOG uptake. The Km of 2‐DOG uptake was not influenced by FSH, insulin, and IGF‐I. FSH had no effect on the Vmax of 2‐DOG uptake, whereas insulin and IGF‐I caused a 30% stimulation of the Vmax. It is concluded that FSH, insulin, and IGF‐I stimulate lactate production by cultured Sertoli cells, but that only insulin and IGF‐I stimulate hexose transport. The insulin‐like effect of FSH or Sertoli cells may principally involve stimulation of glycolytic enzyme activities.
Specific interactions of histone H1 and a 45 kilodalton nuclear protein with a putative matrix attachment site in the distal promoter region of a cell cycle‐regulated human histone gene
Authors: Pauli U. , Chiu J. F. , Ditullio P. , Kroeger P. , Shalhoub V. , Rowe T. , Stein G. , Stein J. 
Published: February 2005

AbstractProtein‐DNA interactions within the promoter of a cell cycle‐regulated human H4 histone gene were examined by binding of 5′‐end‐labeled DNA segments to Western blots of nuclear protein fractions. Specific protein interactions were observed with DNA segments located between −500 bp and −1,070 bp upstream of the ATG initiation codon and included a histone H1 binding segment flanked on both sides by binding sites for a 45 kD nuclear protein. This region of the gene contains a DNase I‐sensitive site in the center (−720 to −820 bp), and sequence analysis revealed the presence of scaffold attachment sequences in the two flanking segments. Topoisomerase II consensus sequences and in vitro topoisomerase II cleavage sites were also detected in the two flanking segments. Our results suggest that the 45 kd nuclear protein may preferentially interact with these two segments of the H4 histone gene to mediate association with the nuclear matrix. The presence of negative regulatory elements in this putative matrix attachment region provides a basis for the speculation that such nuclear proteins are associated with alterations in gene‐matrix interaction that are functionally related to gene expression.
Epidermal growth factor binding, stimulation of phosphorylation, and inhibition of gluconeogenesis in rat proximal tubule
Authors: Harris Raymond C. , Daniel Thomas O. 
Published: February 2005

AbstractEpidermal growth factor and insulin share many biological activities, including stimulation of cell proliferation, ion flux, glycolysis, fatty acid and glycogen synthesis, and activation of receptor‐linked tyrosine kinase activity. In the kidney, insulin has been shown to regulate transport processes and inhibit gluconeogenesis in the proximal tubule. Since the kidney represents a major source of EGF, the present studies investigated whether proximal tubule contained EGF receptors, whether EGF receptors were localized to apical or basolateral membranes, and whether EGF receptor activation participated in the regulation of an important proximal tubule function, gluconeogenesis.Specific EGF receptors were demonstrated in the basolateral membrane of proximal tubule. Following incubation with 125l EGF, basolateral membranes demonstrated equilibrium binding at 4°C and 23°C. There was 78 ± 2% specific binding (n = 13). The dissociation constant (Kd) was 1.5 × 1 0−9 M and maximal binding was 44 fmol/mg protein. There was ninefold more specific binding to proximal tubule basolateral membrane than to brush border membrane. In basolateral, but not brush border membranes, EGF induced phosphorylation of the tyrosine residues of intrinsic membrane proteins, including a 170 kDa protein, corresponding to the EGF receptor.In the presence of the gluconeogenic substrates, alanine, lactate, and succinate, proximal tubule suspensions synthesized glucose. EGF inhibited glucose production in a concentration‐dependent manner over a concentration range of 3 × 10−11 to 3 × 10−9 M. In addition, EGF inhibited angiotensin ll‐stimulated glucose production in the proximal tubule suspensions. EGF did not significantly increase net glucose metabolism nor decrease cellular ATP concentrations.Therefore, these studies demonstrated that rat proximal tubule contained specific receptors for EGF that were localized to the basolateral membrane and linked to tyrosine kinase activity. EGF significantly inhibited proximal tubule glucose production without significantly increasing net glucose consumption.
Second messenger function of phosphatidic acid in platelet activation
Authors: Kroll Michael H. , Zavoico George B. , Schafer Andrew I. 
Published: February 2005

AbstractPhosphatidic acid (PA) is synthesized as the result of the receptor‐mediated response of platelets to physiologic agonists. The role of PA in platelet signal transduction, however, is largely unknown. We have examined the responses of platelets to 1‐stearoyl‐2‐arachidonoyl phosphatidic acid (SAPA), the predominant molecular species of human platelet PA. SAPA alone causes platelet aggregation, and pretreatment of platelets with SAPA markedly enhances thrombin‐induced aggregation and secretion. Addition of SAPA to intact human platelets causes rapid breakdown of phosphatidylinositol‐4,5‐bisphosphate (PIP2) and the generation of diacylglycerol and endogenous PA. These reactions are associated with mobilization of intracellular calcium and activation of protein kinase C. SAPA also stimulates the release of endogenous arachidonic acid and its conversion to thromboxane A2. Furthermore, platelet activation by SAPA is blocked by indomethacin, indicating that the actions of SAPA are mediated by cyclooxygenase products. These findings suggest that SAPA may play an important role as an endogenous positive feedback signal to amplify receptor‐mediated activation of PIP2‐specific phospholipase C in human platelets.
Pulmonary alveolar macrophages express a polyamine transport system
Authors: Saunders Nicholas A. , Ilett Kenneth F. , Minchin Rodney F. 
Published: February 2005

AbstractPolyamine transport is an important mechanism by which cells regulate their intracellular polyamine content. It is well established that the lung has a high capacity for polyamine transport, and recently the polyamine putrescine has been shown to be selectively accumulated into the type II pneumocyte of rabbit lung slices (Saunders et al.:Lab. Invest., 95:380–386, 1988). In addition, it has been suggested that there may be more than one polyamine transport system in lung tissue (Byers et al.:Am. J. Physiol., 252:C663‐C669, 1987). In the present study, we have examined whether there are differences in the distribution of putrescine and spermidine uptake activities in isolated rabbit lung cells. We report that pulmonary alveolar macrophages have a greater rate of uptake of both putrescine and spermidine than the total lung cell population. Kinetic analysis of the polyamine uptake system present in macrophages showed putrescine uptake consisted of a saturable (Km = 2.1 μM) and nonsaturable component whilst spermidine uptake consisted of both a high‐ and a low‐capacity saturable component (Km = 0.16 μM and 1.97 μM, respectively). The rate of polyamine transport was similar to those reported for many proliferative or tumor cell‐lines and appeans to be greater than any other major lung cell type. Inhibition studies of the transport of polyamines into pulmonary alveolar macrophages suggested that the uptake of both putrescine and spermidine was mediated by the same system, which could not be described by simple Michaelis‐Menten kinetics. The transport appears to be reversible due to significant efflux. This is the first study to describe the presence of multiple polyamine transport systems in pulmonary alveolar macrophages.
Fura 2 analysis of cytosolic calcium regulation in elutriated rat gastric parietal cells
Authors: Black E. W. , Cornwell T. L. , Lincoln T. M. , Strada S. J. , Thompson W. J. 
Published: February 2005

AbstractThe calcium probe, Fura 2, is used to establish and partially characterize histamine‐, carbachol‐ and forskolin‐induced calcium transients in enriched parietal cell populations prepared by centrifugal elutriation of dispersed rat fundic mucosa cell isolates. The magnitude of the maximal carbachol response, which is blocked by atropine but not cimetidine, is nearly five times that of histamine or forskolin. Time to peak responses for carbachol, forskolin, and histamine are approximately 7, 17, and 28 sec, respectively. Carbachol‐, histamine‐, and forskolin‐induced increases in Fura 2 fluorescence appear dependent upon extracellular calcium, since these responses are attentuated in low calcium media and blocked by EGTA in low‐calcium media or by lanthanum in high‐ or low‐calcium medium. Trifluoperazine and fenoctimine, at concentrations that inhibit secretion, have no effect on either carbachol‐ or histamine‐induced increases in cytosolic calcium. Seven major calcium/EGTA‐sensitive phosphopro‐teins are identified by SDS‐PAGE electrophoresis of ATP 32P‐labeled cell sonicates. We conclude that cytosolic calcium in enriched rat gastric parietal cell populations is regulated by secretagogue receptor‐controlled calcium channels. We postulate that these channels may be controlled by cyclic AMP‐dependent phosphorylation, since neither changes in cyclic AMP nor calcium alone mediate the effects of secretagogues entirely, but the interplay between these two second‐messenger systems potentiates the actions of these agents. The role of cytosolic calcium as a second messenger in secretagogue action appears similar to that of cyclic AMP in that a specific cellular concentration must be reached to initiate acid secretion.
Stochastic model for multipotent hemopoietic progenitor differentiation
Authors: Tsuji Kohichiro , Nakahata Tatsutoshi 
Published: February 2005

AbstractIn this study, the authors propose a stochastic model for multipotent hemopoietic progenitor differentiation, which assumes that there is a fixed probability (P) that a progenitor with a potential for differentiation along a particular lineage maintains the potential in each cell division in each daughter cell, and this differentiation process of each lineage proceeds independently. To examine the applicability of this model, a sequential micromanipulation of paired progenitors was carried out and followed by cytological examination of the cells contained in the colonies derived from these progenitors; then calculation was made of the ratio of the number of paired colonies containing cell(s) with a particular lineage to the number of paired colonies in which only one colony contained cell(s) with the lineage at the first and second cell division. The ratios were similar at the first and second cell division within each lineage. Furthermore, the frequences of each lineage in multilineage hemopoietic colonies were calculated using the P values obtained from these micromanipulation experiments. The expected frequencies were similar to those in the actual experiments. These results suggested that the stochastic model was applicable to multipotent hemopoietic progenitor differentiation.
Novel action of carnitine: Inhibition of aggregation of dispersed cells elicited by clusterin in vitro
Authors: Fritz Irving B. , Burdzy Krystyna 
Published: February 2005

AbstractA novel effect of carnitine and O‐acylcarnitine derivatives has been described. The presence of these compounds has been shown to inhibit the aggregation of erythrocytes otherwise elicited by the addition of clusterin or fetuin. The specificity of carnitine action has been investigated by comparing influences of chemically related compounds. The concentrations required for inhibition by approximately 50% of aggregation of erythrocytes by clusterin under in vitro conditions defined were determined to be 1.5 mM for L(‐) or D(+) enantiomers of carnitine; 0.5 mM for decanoyl(−)‐ or (+)‐carnitine; 0.13 mM for lauroyl(−) ‐or (+)‐carnitine, and 0.05 mM for myristoyl(−)‐ or (+)‐carnitine. In contrast, concentrations up to 12.5 mM of dimethylcarnitine, deoxycarnitine, acetylcho‐line, acetyl‐β‐methylcholine, or inositol had no detectable inhibitory effect on aggregation elicited by clusterin. Clusterin addition also resulted in the aggregation of three other cell types examined (guinea pig spermatozoa, a cell line derived from testes of neonatal mice called TM4 cells, and Sertoli cells from testes of 20 day‐old rats). As in the case with erythrocytes, the presence of carnitine inhibited aggregation of spermatozoa, TM4 cells, and Sertoli cells in suspension. We consider possible mechanisms by which carnitine inhibits aggregation of erythrocytes and other populations of dispersed cells incubated in the presence of clusterin.
Rapidly reversible enzyme inhibition in a temperature‐sensitive mammalian cell mutant lacks thermotolerance
Authors: Vidair Charles A. , Dewey William C. 
Published: February 2005

AbstractThe temperature‐sensitive (ts) Chinese hamster ovary (CHO) cell mutant tsH1 contains a thermolabile leucyl‐tRNA synthetase. Upon incubation at the nonpermissive temperature of 39.5°C, the enzyme became reversibly inhibited over a period of minutes, and the cells lost viability over a period of many hours. However, killing of tsH1 by acute heating at 45°C was identical to that of wild‐type (SC) cells. In addition, the heat‐induced inhibition of protein synthesis was similar for both cell types, as measured after acute heating at 45°C. Furthermore, both killing and inhibition of protein synthesis showed thermotolerance in both cell types. In contrast to the effects at 45°C, at 39.5°C, neither the inhibition of leucyltRNA synthetase activity nor the killing of tsH1 expressed thermotolerance. Also, treatment of tsH1 at 39.5°C did not induce thermotolerance to killing at 45°C. The inhibition of leucyl‐tRNA synthetase activity in tsH1 at 39.5°C was further distinguished from the 45°C‐induced inhibition of protein synthesis in SC cells by a much more rapid reversal of the inhibition of leucyl‐tRNA synthetase activity. Also, the rate of reversal of the inhibition of protein synthesis by 45°C in SC cells was decreased by increased heat dose. Such was not true for the 39.5°C inhibition of leucyl‐tRNA synthetase activity in tsH1. The data indicate that there exist two distinct types of thermal inhibition‐one slowly reversible type which was observed during and after heating at 45°C and both induced and expressed thermotolerance, and a second, rapidly reversible type, which was evident only during heating of tsH1 at 39.5°C and neither induced nor expressed thermotolerance.
Cell enlargement: One possible mechanism underlying cellular senescence
Authors: Angello John C. , Pendergrass William R. , Norwood Thomas H. , Prothero John 
Published: February 2005

AbstractWe previously demonstrated an inverse relationship between the G1 volume of human diploid fibroblast‐like (HDFL) cells obtained from foreskin tissue and clonal replicative potential. On the basis of these results, we suggested that one process underlying in vitro senescence is a progressive increase in the mean cell volume of successive progeny within clonal lineages. We now report that the size of HDFL cells, as well as of chick embryo fibroblasts, can be increased in the virtual absence of cell division by culturing at low density and at low serum concentration (0.1‐1.0%). Consequent to an increase in cell size, the replicative potential of the cells is reduced to the level of later‐passage cells of similar size. By clonal analysis, the populations of enlarged cells contain up to three times as many nondividing cells as do controls. In the enlarged populations, the proportion of cells producing attenuated clones (four or fewer progeny) increases by about 30%, whereas the proportion of cells yielding >32 cells declines by a similar percentage. These observations lead us to propose that replicative potential may be limited by cell size, which in turn may be regulated by a kinetic relationship between cellular growth and cell division cycles.
Heparin stimulates the synthesis and modifies the sulfation pattern of heparan sulfate proteoglycan from endothelial cells
Authors: Nader Helena B. , Buonassisi Vincenzo , Colburn Patricia , Dietrich Carl P. 
Published: February 2005

AbstractHeparin stimulates 2‐3‐fold, in a concentration‐dependent manner, the synthesis of heparan sulfate secreted by cultured endothelial cells. The increase in synthetic rate takes place immediately after exposure of the cells to heparin, affects only heparan sulfate, and is specific for the endothelial cell. No stimulation by other glycosaminoglycans was observed. Analysis of the disaccharide products formed by the action of heparitinases reveals a higher degree of sulfation of the uronic acid residues in the heparan sulfate of cells exposed to heparin.