bluuebunny/crossref_metadata_2025_split huggingface dataset:
Contribution of response kinetics to the response pattern: Studies of responses to thyrotropin‐releasing hormone in Xenopus oocytes
Authors: Lipinsky Dafna , Gershengorn Marvin C. , Oron Yoram 
Published: February 2005

AbstractIn Xenopus oocytes injected with total rat pituitary GH3 cell RNA, thyrotropin‐releasing hormone (TRH) causes the activation of the inositol lipid transduction pathway and the induction of chloride conductance via calcium‐activated channels (Oron et al., 1987, Mol. Endocrinol., 1:918–925). This response exhibits characteristic prolonged latency (Oron et al., 1988, Proc. Natl. Acad. Sci. U.S.A., 85:3820–3824; Lipinsky et al., 1993, Pflugers Arch., 425:140–149). We examined the role of agonist diffusion in the extracellular medium in the generation of latency and the detemination of response amplitude. An increase in the viscosity of the medium markedly prolonged the latency and decreased the amplitude of the response. Moreover, an increase in the viscosity of the medium in the immediate vicinity of the oocyte had a major effect on both the latency and the amplitude of the response, which appeared to be a result of desensitization rather than restricted diffusion of chloride to the medium. Extrapolation to [TRH] ∞ yielded a diffusion‐dependent latency value of 0 and a diffusion‐independent latency value of 4 seconds. In low viscosity medium, at all TRH concentrations, diffusion contributed less than 2% to the latency of the response. This implied that events distal to ligand binding are responsible for a major part of latency. Analysis of the dependence of latency and amplitude of the response on [TRH] yielded Hill coefficients markedly smaller than unity, suggesting postreceptor negative modulation of the response. Preincubation of cells with a specific inhibitor of protein kinase C, chelerythrine, increased the Hill coefficients to unity and changed the shape of the Hill plot of response amplitudes. Our results suggest that at low agonist concentrations, even in a low viscosity medium, the prolonged latency allows negative effects on both latency and amplitude by a simultaneous activation of a protein kinase C. © 1995 Wiley‐Liss, Inc.
Effects of mild heat shock on glycogenesis and its regulation by insulin in cultured fetal hepatocytes
Authors: Zachayus J. L. , Plas C. 
Published: February 2005

AbstractThe effects of a mild heat shock were investigated using cultured 15‐day‐old fetal rat hepatocytes in which an acute glucocorticoid‐dependent glycogenic response to insulin was present. After exposure from 15 min to 2 h at 42.5°C, cell surface [125I]insulin binding progressively decreased down to 60% of the value shown in cells kept at 37°C, due to a decrease in the apparent number of insulin binding sites with little change in insulin receptor affinity. In parallel cultures, protein labeling with [35S]methionine exhibited stimulated synthesis of specific proteins, in particular, 73‐kDa Hsc (heat shock cognate) and 72‐kDa Hsp (heat shock protein). When cells were returned to 37°C after 2 h at 42.5°C, cell surface insulin binding showed a two‐third restoration within 3 h (insulin receptor half‐life = 13 h), with similar concomitant return of Hsps72,73 synthesis to preinduction levels. The rate of [14C]glucose incorporation into glycogen measured at 37°C after 1‐ to 2‐h heat treatment revealed a striking yet transient increase in basal glycogenesis (up to 5‐fold). At the same time, the glycogenesis stimulation by insulin was reduced (from 3.2 to 1.4—fold), whereas that induced by a glucose load was maintained. Induction of thermotolerance after a first heating was obtained for the heat shock‐dependent events except for the enhanced basal glycogenesis. In insulin‐unresponsive cells grown in the absence of glucocorticoids, heat shock decreased the glycogenic capacity without modifying the glucose load stimulation, supporting the hypothesis that insulin and thermal stimulation of glycogenesis share at least part of the same pathway. Inverse variations were observed between Hsps72,73 synthesis and both cell surface insulin receptor level and insulin glycogenic response in fetal hepatocytes experiencing heat stress. © 1995 Wiley‐Liss, Inc.
Suppression of tumorigenicity, but not invasion, in glioblastoma/HeLa cell hybrids
Authors: Ess Kevin , Chen Haiyan , Kier Ann , Brackenbury Robert 
Published: February 2005

AbstractSomatic cell hybrids between SNB‐19 human glioblastoma cells and human D98OR HeLa parental cells were produced and analyzed for their ability to form tumors in nude mice and to invade reconstituted extracellular matrix (Matrigel). Whereas both the SNB‐19 and D98OR HeLa parental cells form tumors, four of six hybrid lines did not form tumors, even after periods up to six months, suggesting that each cell type can complement the tumorigenicity of the other. SNB‐19 cells showed high rates of Matrigel invasion at all cell densities examined, whereas D98OR HeLa cells showed lower rates of invasion that were further reduced at high cell density. All six hybrid cell lines displayed a combination of these properties: at low cell density, the hybrids showed high rates of invasion, similar to the SNB‐19 cells, but the invasion rate diminished at higher cell densities, similar to the D98OR HeLa cells. Taken together, these results provide new experimental evidence that several distinct genetic changes are involved in generating the tumorigenic and invasive phenotype of glioblastoma cells. © 1995 Wiley‐Liss, Inc.
Transcriptional and posttranscriptional regulation of urokinase‐type plasminogen activator expression in endothelial cells by basic fibroblast growth factor
Authors: Gualandris Anna , Presta Marco 
Published: February 2005

AbstractThe mechanism of induction of urokinase‐type plasminogen activator (uPA) by basic fibroblast growth factor (bFGF) was explored in fetal bovine aortic endothelial GM 7373 cells. A three‐ to four‐fold increase in the steady‐state levels of uPA mRNA was observed after 6 h of incubation of the cell cultures with bFGF. Accordingly, nuclear run‐on experiments showed a 2–2.4‐fold increase in the rate of uPA gene transcription during the first 4 h of treatment with the growth factor. bFGF did not affect uPA mRNA stability, as evaluated by chase experiments with the mRNA synthesis inhibitor actinomycin D. Upregulation of uPA mRNA was followed by a delayed increase in uPA protein synthesis paralleled by an increase in secreted and cell‐associated uPA activity. Twelve h were required before accumulated uPA mRNA was translated into the corresponding protein. During this time interval, the continuous presence of biologically active bFGF in the extracellular environment represented an absolute requirement for uPA mRNA translation. Substitution of residues Lys‐27, Lys‐30, and Arg‐31 to glutamine residues in the bFGF molecule resulted in a mutant (M1Q‐bFGF) that caused uPA mRNA accumulation in the absence of a significant increase in cell‐associated uPA activity. M1Q‐bFGF also induced an increase in cell‐associated uPA activity only when added to the cell cultures in the presence of soluble heparin. These results provide evidence that bFGF can affect uPA expression in endothelial GM 7373 cells both at transcriptional and posttranscriptional/translational levels. They also show the possibility to dissociate upregulation of uPA mRNA from upregulation of uPA activity by mutagenesis of the bFGF molecule. © 1995 Wiley‐Liss, Inc.
Impaired alveolar macrophage function in smoke inhalation injury
Authors: Herlihy J. P. , Vermeulen M. W. , Joseph P. M. , Hales C. A. 
Published: February 2005

AbstractThe high incidence of both bacterial pneumonia and the adult respiratory distress syndrome (ARDS) associated with smoke inhalation injury (SII) may result, at least in part, from smoke‐induced injury to the alveolar macrophage (AM). Specifically, we hypothesized that AM antimicrobial function, ability to phagocytose apoptotic PMNs, and capacity to prevent apoptosis in PMNs are impaired by smoke. To test these hypotheses, AMs were harvested by bronchoalveolar lavage from sheep before and after the animal was exposed to cotton smoke. The two populations of AMs were incubated with Pseudomonas aeruginosa (PSA) in vitro. Normal AMs (NAMs) phagocytosed a mean of 99 ± 11% of the PSA placed in their wells, whereas smoke‐exposed AMs (SAMs) ingested only 60 ± 8%. NAMs killed 80 ± 8% of PSA ingested, whereas SAMs killed only 56 ± 16% (P < 0.05). When sheep PMNs, allowed to undergo apoptosis, were incubated with the two AM populations, 66 ± 3% of the NAMs and 40 ± 6% of the SAMs demonstrated phagocytosis of these apoptotic PMNs (P < 0.05). Fresh sheep PMNs were incubated in unconditioned media, NAM and SAM‐conditioned media, and followed over 48 hr for the development of apoptosis and maintenance of viability. The NAM‐conditioned media markedly prevented apoptosis and augmented PMN survival relative to the unconditioned and SAM‐conditioned media (P < 0.05). The poor antimicrobial function known to be characteristic of apoptotic PMNs, together with the directly impaired antimicrobial function of AMs, may contribute to the infectious complications of Sll. If the PMNs recruited to the lung in Sll are not properly supported by the AMs following smoke injury, large numbers may undergo apoptosis. If not properly disposed of by these SAMs, the apoptotic PMNs could eventually lyse, releasing tissue toxins, resulting in escalation of lung injury and leading to ARDS. © 1995 Wiley‐Liss, Inc.
Three patterns of cytokine expression potentially involved in epithelial‐fibroblast interactions of human ocular surface
Authors: Li De‐Quan , Tseng Scheffer C. G. 
Published: February 2005

AbstractSignals transmitted from mesenchyme to epithelia or vice versa constitute the basis of reciprocal epithelial‐mesenchymal interactions. As a first step toward understanding epithelial‐mesenchymal interactions on the ocular surface where the transit amplifying cell‐containing corneal epithelium is anatomically separated from the stem cell‐containing limbal epithelium, we sought to characterize the expression patterns of cytokines and their receptors by primary epithelial and early‐passaged fibroblast cultures of human cornea and limbus. Northern hybridization with oligonucleotide and cDNA probes to a total of 25 cytokines and 12 of their receptors revealed that the positively expressed cytokines could be divided into the following four patterns. Type I: TGF‐α, IL‐β, and PDGF‐B were expressed exclusively by epithelial cells but their respective receptors EGFR and IL‐1R were predominantly and PDGFR‐β was exclusively expressed by fibroblasts. Type II: IGF‐I, TGF‐β1, β2, LIF, and bFGR, and their receptors were expressed by both epithelial cells and fibroblasts. FGFR‐1 (flg) and FGFR‐2 (bek) were expressed more by fibroblasts and bFGF was expressed more by corneal than limbal epithelial cells. Type III: keratinocyte growth factor (KGF) and hepatocyte growth factor (HGF) were expressed exclusively by fibroblasts and their respective receptors, KGFR and c‐met, were predominantly expressed by epithelial cells. Combined with RT‐PCR, the quantity of KGF and KGFR transcripts was highest in limbal fibroblasts and epithelial cells, respectively. In contrast, the quantity of HGF and HGFR (c‐met) transcripts was highest in corneal fibroblasts and epithelial cells, respectively. Type IV: M‐CSF and IL‐8 were expressed by fibroblasts and/or epithelial cells but their receptors were not expressed by epithelial cells nor fibroblasts, but by immune or inflammatory cells. In addition to these potential paracrine actions, autocrine actions mediated by TGF‐α/EGFR, IL‐β/IL1‐R, and bFGF/FGFR‐1 were more expressed by corneal than limbal epithelial cells. Immunofluorescence staining on human corneoscleral cryosections confirmed that EGFR and bFGF were not expressed by the limbal basal epithelium, but expressed strongly by the corneal epithelium, a pattern consistent with Northern hybridization. These results indicate that ocular surface epithelial cells and fibroblasts can express a myriad of cytokines, among which the first three patterns constitute the network of potential epithelial‐mesenchymal cytokine dialogues. The difference of certain cytokine expression between corneal and limbal regions suggests that this network participates in normal epithelial growth and differentiation, and plays an important role in wound healing. © 1995 Wiley‐Liss, Inc.
Bafilomycin A1 inhibits lysosomal, phagosomal, and plasma membrane H+‐ATPase and induces lysosomal enzyme secretion in macrophages
Authors: Tapper Hans , Sundler Roger 
Published: February 2005

AbstractBafilomycin A1, a specific inhibitor of H+‐ATPases of the vacuolar type, was in the present study shown, at similar concentrations, to induce secretion of lysosomal enzyme and to elevate lysosomal pH in mouse macrophages. These results lend support to the previous suggestion of a triggering role for an increase in lysosomal pH and a permissive role for cytosolic pH in the exocytosis of macrophage lysosomal enzyme. Vacuolar H+‐ATPases are present in the macrophage plasma membrane as well as in intracellular membranes, for example, those of the lysosomal and phagosomal compartments. Phagosomal acidification was shown to be achieved in part by a mechanism with a similar sensitivity to bafilomycin A1 as lysosomal H+ transport and in part by an early, bafilomycin A1‐insensitive mechanism. We found a lesser sensitivity towards bafilomycin A1 of the lysosomal and phagosomal H+‐ATPase than that localized in the plasma membrane, indicating differences among H+‐ATPases at the subcellular level. Also, by attempts to mobilize lysosomal H+‐ATPase to the plasma membrane, support was obtained for the notion that subcellular H+‐ATPase populations differ and thus possibly could be differentially regulated. © 1995 Wiley‐Liss, Inc.
Na+ transport processes in isolated guinea pig nasal gland acinar cells
Authors: Ikeda Katsuhisa , Ishigaki Motoaki , Wu Dazheng , Sunose Hiroshi , Takasaka Tomonori 
Published: February 2005

AbstractIn the dispersed acinar cells of the submucosal nasal gland in the guinea pig, intracellular Na+ concentration ([Na+]i) was measured with a microfluorimetric imaging method and the cytosolic indicator dye, sodium‐binding benzofuran isophthalate, under HCO3−‐free conditions. In the unstimulated condition, the [Na+]i was averaged to 12.8 ± 5.2 mM. Addition of 100 μM ouabain or removal of external K+ caused an increase in [Na+]i. Replacement of external Cl− with NO3− or addition of 0.5 mM furosemide reversibly decreased the [Na+]i. The recovery process from the reduced [Na+]i was inhibited by removal of either K+ or Cl− in the bath solution. These findings indicate the presence of a continuous influx of Na+ coupled with K+ and Cl− movement. Application of acetylcholine (ACh, 1 μM) caused an increase in [Na+]i by about 15–20 mM, which was completely inhibited by addition of 10 μM atropine. Increased cytosolic Na+ induced by ACh was extruded by the Na+‐K+ pump. Removal of external Cl− and addition of 50 μM dimethylamiloride inhibited ACh‐induced increase in [Na+]i by about 66% and 19%, respectively. In both unstimulated and stimulated state, Na+‐K+ pump, Na‐K‐Cl cotransport, and Na+‐H+ exchange play a critical role in maintaining intracellular electrolyte environment and in controlling a continuous secretion of nasal fluids. © 1995 Wiley‐Liss, Inc.
Biphasic effect of 1,25‐dihydroxyvitamin D3 on primary mouse epidermal keratinocyte proliferation
Authors: Bollag Wendy B. , Ducote Janet , Harmon Charles S. 
Published: February 2005

Abstract1,25‐Dihydroxyvitamin D3 [1,25(OH)2D3] has been proposed as a physiologic regulator of keratinocyte growth and differentiation. Utilizing a proliferative serum‐free culture system, we have found that at physiologic (picomolar) concentrations this hormone stimulated proliferation of primary mouse epidermal keratinocytes; at higher (nanomolar to micromolar) doses, growth was inhibited by 1,25(OH)2D3. We investigated the nature of the signal transduction mechanism underlying the response to 1,25(OH)2D3 and observed little or no effect of either low or high concentrations of the hormone on cytosolic calcium levels or Fos expression. Furthermore, the protein kinase C inhibitor, Ro 31‐7549, had very little effect on the growth inhibition induced by a high dose (1 μM) of 1,25(OH)2D3. This lack of rapid signal transduction events was consistent with the inability of a short (4‐hour) exposure to 1,25(OH)2D3 to initiate a complete growth‐inhibitory response as measured using [3H]thymidine incorporation. Our results indicate that physiologic concentrations of 1,25(OH)2D3 are required for optimal keratinocyte growth. Furthermore, we found no evidence of rapid effects of 1,25(OH)2D3 and suggest that in mouse epidermal keratinocytes, the response to this hormone is mediated by a slow transduction pathway, such as that activated by the intracellular 1,25(OH)2D3 receptor (VDR). © 1995 Wiley‐Liss, Inc.
Hematopoietic‐promoting activity of the murine stromal cell line MS‐5 is not related to the expression of the major hematopoietic cytokines
Authors: Kobari Ladan , Dubart Anne , Le Pesteur Françoise , Vainchenker William , Sainteny Françoise 
Published: February 2005

AbstractAs an approach for characterizing the molecules involved in the proliferation and differentiation of hematopoietic stem cells we have compared the ability of four murine stromal cell lines, MS‐5, MS‐K, both derived from Dexter cultures, BMS1 and BMS2 both derived from Whitlock‐Witte cultures, to sustain murine long term hematopoiesis and to express the major hematopoietic cytokine genes. As opposed to the three other cell lines, MS‐5 supports the maintenance of stem cells for up to 4–5 weeks. However, reconstituting stem cell output was reduced while clonogenic cell (day 12 and day 8 spleen colony‐forming units, granulo‐macrophagic, and erythroid progenitor cells) output was markedly increased. This hematopoietic‐promoting activity is at least in part mediated by soluble molecules since medium conditioned with MS‐5 cells was able to partially complement the nonsupportive cell line BMS1. The comparative study of the cytokine gene expression in MS‐5 and in the nonsupportive cell lines included Northern blot and reverse transcriptase‐polymerase chain reaction analysis of messenger RNA for interleukin‐1, ‐3, ‐6, granulo‐macrophagic‐colony‐stimulating factor (GM‐CSF), granulocyte‐CSF, macrophage‐CSF, stem cell factor, transforming growth factor‐beta, tumor necrosis factor‐alpha, macrophage inflammatory protein‐1 alpha, and leukemia inhibitory factor. None of these molecules or their association were found to clearly confer to the MS‐5 cell line its hematopoietic‐promoting activity raising the possibility that uncharacterized molecule(s) would be involved in the proliferation and differentiation of stem cells. © 1995 Wiley‐Liss, Inc.
Regulation of myelin basic protein gene transcription: Identification of a distal cis‐acting regulatory element
Authors: Haque Nasreen S. , Haas Susan , Knobler Robert L. , Khalili Kamel 
Published: February 2005

AbstractThe myelin basic protein (MBP) gene contains sequences located upstream of its transcription start site which play a key role in glial‐specific transcription of the MBP promoter. Earlier analysis of the 320 bp upstream regulatory sequence of MBP has revealed multiple cis‐acting regulatory motifs which differentially regulate transcription of a heterologous promoter fused to a reporter gene in glial and nonglial cells. In the present study, we have focused on a region designated MB3, which is located between −93 to −130 nucleotides with respect to the RNA start site, and contains a binding site for the NF1/CTF family of transcription activators. Results from DNase I footprint protection analysis of nuclear proteins prepared from mouse brain revealed a major region within the MB3 regulatory element that specifically interacts with the proteins derived from mouse brain at various stages of brain development. Using synthetic oligonucleotides spanning the protected region, we show that the double‐stranded MB3 sequence interacts with nuclear proteins from mouse brain and forms specific major C1 and a minor C2 complex. Methylation interference experiments have allowed the identification of the G‐residues within nucleotides −100 to −108, named MB3a, which are distinct from the NF1/CTF of MB3 that contact with nuclear proteins to form the major C1 complex. Results from band shift studies revealed assembly of the C1 complex upon incubation of MB3 DNA with the nuclear proteins from various cells of glial origin. Site‐directed mutagenesis experiments revealed that the identified G‐residues for DNA‐protein interaction are important to confer transcriptional activity to this domain in transiently transfected glial cells. © 1995 Wiley‐Liss, Inc.
Carboxyl‐terminal truncation of leucine76 converts heparin‐binding EGF‐like growth factor from a heparin‐enhancible to a heparin‐suppressible growth factor
Authors: Cook Paul W. , Damm Deborah , Garrick Brett L. , Wood Kathleen M. , Karkaria Cyrus E. , Higashiyama Shigeki , Klagsbrun Michael , Abraham Judith A. 
Published: February 2005

AbstractPrevious studies have indicated that heparin differentially regulates heparin‐binding EGF‐like growth factor (HB‐EGF) and amphiregulin (AR) mitogenic activity. To further explore this phenomenon, these mitogens were compared under identical cell culture conditions in two different assays. The results of our present investigation demonstrated that AR‐mediated mitogenic activity in the murine AKR‐2B fibroblast‐like cell line was inhibited by heparin, while HB‐EGF activity was enhanced. However, the absolute effect of heparin appeared to be cell type specific since HB‐EGF mitogenic activity was not dramatically affected by coincubation with heparin when tested on human dermal fibroblasts. Several studies have indicated that mutation of a conserved leucine in the carboxyl‐terminal region of both EGF and transforming growth factor‐α results in decreased affinity for EGF receptors. Since this leucine is present in the analogous position of HB‐EGF, but absent in AR, we examined the effect of deleting this residue by carboxyl‐terminal truncation of HB‐EGF. Analysis of recombinant forms of HB‐EGF demonstrated that HB‐EGF can be converted to a heparin‐inhibited growth factor if the putative mature form of the protein is truncated by two residues (leucine76 and proline77) at the carboxyl terminus. Further analysis demonstrated that only leucine76 appears to be required for heparin‐dependent enhancement of HB‐EGF‐mediated mitogenic activity, indicating that this amino acid may play a pivotal role in controlling the response of HB‐EGF to heparin or related glycosaminoglycan sulfates. Our results also suggest that expression of different HB‐EGF forms in vivo could result in the production of HB‐EGFs with divergent responses to sulfated glycosaminoglycans and proteoglycans. © 1995 Wiley‐Liss, Inc.