bluuebunny/crossref_metadata_2025_split huggingface dataset:
Defensins are mitogenic for epithelial cells and fibroblasts
Authors: Murphy Christopher J. , Foster Bradley A. , Mannis Mark J. , Selsted Michael E. , Reid Ted W. 
Published: February 2005

AbstractDefensins are a family of structurally homologous peptides contained within phagocytic cells. Although these peptides are best known for their broad spectrum antimicrobial properties, they also inhibit ACTH (corticotropin) stimulated corticosterone production, chemoattract monocytes, and lyse mammalian cells. We now report that these peptides are potent mitogens in vitro in the same concentration range that they display potent antimicrobial activity in vitro. These concentrations are in the same range as those expected to be present in vivo during the wound healing process. All defensins tested were stimulatory for epithelial cells and fibroblasts and acted synergistically with insulin. These are the first data to disclose the strong growth‐promoting effects of this unique family of peptides and point to another basic mechanism whereby the macrophage and neutrophil may participate in a variety of trophic, physiologic, and pathologic processes.
Poliovirus‐induced intracellular alkalinization involves a proton ATPase and protein phosphorylation
Authors: Holsey Charles , Nair C. N. 
Published: February 2005

AbstractWe reported previously that poliovirus infection induces alkalinization in HeLa cells and that an alkaline intracellular pH (pHi) promoted viral replication. Additional experiments were carried out to understand the underlying mechanism. Virus‐infected or control monolayer cultures were incubated with nominally bicarbonate‐free Eagle's minimal essential medium (MEM) buffered with N‐2‐hydroxyethylpiperazine‐N‐3‐ethanesulfonic acid (HEPES), and immediately following preincubations, changes in pHi were monitored via benzoic acid uptake around 2 h postinfection. The absence of pH increase in cells infected with ultraviolet light‐inactivated virus (UV‐virus) indicated that viral gene expression was required for this effect. On the other hand, lack of effect of 3 mM guanidine, an inhibitor of poliovirus‐specific RNA but not protein synthesis, suggested that translation of input viral genome RNA is sufficient for the pH increase. Activation of Na+/H+ exchange, Cl−HCO−3 exchange, or H+‐ATPase was considered as possible mechanisms by which alkalinization occurs in virus‐infected cells. Na+/H+ exchange was excluded because the pH effect occurred in a Na+/H+ exchange deficient HeLa cell mutant. Similarly, Cl−/HCO−3 exchange was excluded because virus‐specific alkalinization was evident in the presence of Cl− or bicarbonate deficient medium and was not associated with an increase in HCO−3 uptake or a decrease in Cl− uptake. Lack of dependence on Na+, abrogation by 10 μM 7‐chloro‐4‐nitrobenz‐2‐oxa‐1,3‐diazole (NBD‐Cl), and resistance to 1 mM vandate suggested that this effect was due to the activation of a vacuolar‐type (V) proton ATPase. Studies using protein kinase inhibitors indicated that activation of the ATPase in virus‐infected cells probably involved protein kinase C‐mediated phosphorylation. © 1993 Wiley‐Liss, Inc.
Cobalamin metabolism in cultured human chorionic villus cells
Authors: Begley James A. , Colligan Pamela D. , Chu Richard C. , Hall Charles A. 
Published: February 2005

AbstractCobalamin (Cbl, vitamin B12) metabolism was analyzed in cultures of human chorionic villus (CV) cells obtained at 9–10 weeks of gestation. CV cells were shown to synthesize transcobalamin II (TCII) and to possess a high affinity receptor for that molecule. The cells bound and internalized radioactive cyanocobalamin (CN[57Co]Cbl) complexed to TCII. This internalized CN[57Co]Cbl was found to be converted to both methylCbl and adenosylCbl, the two intracellular coenzyme forms of Cbl, and bound to the two known intracellular Cbl requiring enzymes, methionine synthase (MS) and methylmalonyl‐CoA mutase. Both enzyme systems were found to be functional in the intact cell by demonstrating the incorporation of the radioactive label from both [14C]CH3‐tetrahydrofolate and [14C]propionate into acid insoluble products. MS activity was also detected in lysed cell material. CV cells were shown not to be auxotrophic for methionine since they were able to utilize homocysteine in place of methionine for cell division. Since CV cells are capable of performing many of the complex events associated with Cbl metabolism, it may be possible to use these cells to diagnose genetic defects of Cbl metabolism. © 1993 Wiley‐Liss, Inc.
Apoptosis of human erythroid colony‐forming cells is decreased by stem cell factor and insulin‐like growth factor I as well as erythropoietin
Authors: Muta Koichiro , Krantz Sanford B. 
Published: February 2005

AbstractTo clarify the manner by which erythropoietin (EP), stem cell factor (SCF), or insulin‐like growth factor I (IGF‐I) regulate erythropoiesis, apoptosis of human erythroid progenitor cells was investigated. Human burst‐forming units‐erythroid (BFU‐E) partially purified from peripheral blood were cultured for 6 days to generate erythroid colony‐forming cells (ECFC), which consist mainly of colony‐forming units‐erythroid (CFU‐E). The cells were labeled with [3H]thymidine, incubated in serum‐free liquid media, at 37°C, for 16 h, and the pattern of DNA breakdown was analyzed by agarose gel electrophoresis. When these cells were incubated without EP, 70% of the total cellular DNA was broken down into DNA fragments of less than 5 kilobases and nuclear condensation and fragmentation, characteristic of apoptosis, were evident. While EP greatly reduced the amount of DNA breakdown to 23%, SCF and IGF‐I each reduced the amount of DNA breakdown to 38–46% and, when added together, to 24%. Dose‐response experiments with SCF and IGF‐I showed a dose‐dependent reduction in DNA fragmentation at concentrations that stimulate colony formation in serum‐free semisolid cultures. Finally, assays of ECFC performed by the plasma clot method, after serum‐free liquid culture, at 37°C, for 16 h, demonstrated marked protection of erythroid colony‐forming capacity by SCF or IGF‐I in the absence of EP, as well as by EP itself. These data indicate that human erythroid progenitor cells undergo apoptosis which is reduced by SCF and IGF‐I as well as EP and suggest that the control of apoptosis by each of these factors has a prominent role in the regulation of erythropoiesis. © 1993 Wiley‐Liss, Inc.
Histamine and cis‐urocanic acid augment tumor necrosis factor‐alpha mediated induction of keratinocyte intercellular adhesion molecule‐1 expression
Authors: Mitra Raj S. , Shimizu Yoji , Nickoloff Brian J. 
Published: February 2005

AbstractEarly cellular and molecular events in inflamed skin include the active participation of epidermal keratinocytes (KCs) and dermal mast cells which can produce diffusible mediators such as tumor necrosis factor‐alpha (TNF‐α), histamine, and urocanic acid (UCA). Rapid induction of adhesion molecules such as intercellular adhesion molecule‐1 (ICAM‐1) by KCs is observed following a highly diverse array of stimuli which can provoke both irritant, inflammatory, as well as allergic and immune reactions. To determine if the aforementioned mediators could interact in either an additive or synergistic fashion with each other, cultured KCs were exposed to these mediators alone and in combination, and the degree of ICAM‐1 mRNA and protein quantitated. Whereas histamine or cis‐UCA alone only weakly induced KC ICAM‐1, when they were combined with TNF‐α, significant augmentation was observed by Northern blot hybridization studies, immunostaining, and FACS analysis. Other histamine derivatives such as L‐histidine, 1‐methylhistidine, 3‐methylhistidine, or all‐trans‐UCA had no effect. Histamine pretreatment did not affect cell surface high affinity TNF‐α receptors, as determined by ligand binding and immunodetection, and did not induce KC TNF‐α production. The KC histamine receptor was also characterized and found not to be influenced by TNF‐α, cis‐UCA, all‐trans‐UCA, or diphenyhydramine (an H1 antagonist), but it was inhibited by cimetidine (an H2 antagonist). These results demonstrate that 1) KCs can be induced to express ICAM‐1 by exposure to histamine and cis‐UCA, 2) histamine and cis‐UCA can also augment TNF‐α inducible ICAM‐1 mRNA and cell surface protein expression, 3) this augmentation does not directly involve changes in KC TNF‐α receptor number, affinity, or TNF‐α production and, 4) KCs possess a type 2 histamine receptor which is not the photoreceptor for UCA. These findings highlight the potential for cross‐talk between molecules produced by resident cutaneous cell types above (i.e., KCs) and below (i.e., mast cells) the epidermal basement membrane zone. These cells and their mediators can cooperate to respond to either exogenous or endogenous stimuli leading to rapid and strong KC ICAM‐1 expression. Such induction of this important adhesion molecule by KCs ensures the retention of T lymphocytes necessary to participate in the maintenance of cutaneous immunohomeostasis. © 1993 Wiley‐Liss, Inc.
Activation of protein kinase C inhibits human keratinocyte migration
Authors: Ando Yoshihiro , Lazarus Gerald S. , Jensen Pamela J. 
Published: February 2005

AbstractThe involvement of protein kinase C (PKC) in epidermal growth factor (EGF)‐induced human keratinocyte migration was studied with the phagokinetic assay. It was concluded that PKC activation does not mediate, but rather inhibits, EGF‐induced keratinocyte migration. The following experimental observations support these conclusions: 1) The PKC inhibitor H‐7 did not inhibit EGF‐induced migration but instead led to a modest enhancement. 2) PKC activators such as phorbol‐12‐myristate‐13‐acetate (PMA), phorbol‐12,13‐dibutyrate (PDBu), and 1,2‐dioctanoly‐sn‐glycerol inhibited migration, but biologically inactive 4α‐PMA had no effect. 3) PMA did not inhibit keratinocyte attachment and spreading but blocked migration almost immediately after addition. 4) Migration of PKC‐depleted cells, which were produced by prolonged treatment with PDBu, was enhanced similarly to normal cells by EGF. 5) PKC‐depleted cells were not susceptible to the inhibitory effects of phorbol esters on migration. Additional experiments, in which cells were preactivated with EGF, suggested that PKC inhibits the EGF effect at a post‐receptor level. The inhibitory effect of PKC on keratinocyte migration was not restricted to EGF‐induced migration; PKC activation also inhibited keratinocyte migration induced by bovine pituitary extract, insulin, insulin‐like growth factor‐1, and keratinocyte growth factor. © 1993 Wiley‐Liss, Inc.
Constitutive expression of c‐myc does not relieve cAMP‐mediated growth arrest in human lymphoid reh cells
Authors: Andersson Kristin Brevik , Deggerdal Arne , Skjønsberg Cecilia , Smeland Erlend B. , Blomhoff Heidi Kiil 
Published: February 2005

AbstractThe Reh cell system is suitable for evaluating events important for control of proliferation independently of mechanisms involved in differentiation, as Reh cells are unable to differentiate. In the human pre‐B cell line Reh, activation of adenylate cyclase by forskolin induces a five to tenfold rapid, transient downregulation of steady‐state c‐myc RNA within 4 hours. Concurrently, the cells are strongly growth arrested in the G1 phase of the cell cycle. To clarify if the observed growth arrest could be relieved by constitutive expression of c‐myc, an exogenous c‐myc gene under constitutive promoter control was introduced into Reh cells by electroporation. The c‐myc‐expressing construct pDMmycHyg contained human c‐myc exons 2 and 3 driven by the Mo‐MLV LTR and conferred hygromycin resistance. Exogenous c‐myc RNA transcripts and protein were constitutively expressed in the transfected clones at levels roughly twice as high as the level in nontransfected cells. Total c‐myc protein levels were unchanged upon treatment of transfected clones with forskolin. Yet, the transfected cells were not released from growth arrest. Furthermore, the transfected Reh cells did not differentiate upon forskolin treatment. Constitutive overexpression of c‐myc is therefore not sufficient for relieving forskolin‐mediated effects on growth arrest in Reh cells. © 1993 Wiley‐Liss, Inc.
Transcriptional and posttranscriptional regulation of hepatic β2‐adrenergic receptor gene expression during development
Authors: Baeyens Dennis A. , Cornett Lawrence E. 
Published: February 2005

AbstractHepatic responsiveness to β2‐adrenergic stimulation is dynamically regulated during early development as well as following hepatic injury and disease. In the present study, the molecular mechanisms that underlie the decline in the steady‐state levels of hepatic β2‐adrenergic receptor mRNA that occurs during development in the male rat were investigated. As determined by nuclear run‐on assays, an age‐associated reduction in β2‐adrenergic receptor gene transcription was observed. The transcription rate of the β2‐adrenergic receptor gene in postnatal day 18 liver was approximately 50% lower than that of fetal liver. Stability of β2‐adrenergic receptor gene transcripts was highest (t1/2 ≈ 6 h) in hepatocytes isolated from fetal rats and was lowest (t1/2 ≈ 1 h) in hepatocytes isolated from postnatal day 14 rats. In fetal hepatocytes, but not postnatal day 2 hepatocytes, cycloheximide appeared to stabilize β2‐adrenergic receptor gene transcripts in the presence of actinomycin D. These findings establish the molecular basis of reduced steady‐state levels of β2‐adrenergic receptor mRNA in liver during early postnatal development and suggest multilevel regulatory control of hepatic β2‐adrenergic receptor gene expression. © 1993 Wiley‐Liss, Inc.
“Macrophage” nitric oxide synthase is a glucocorticoid‐inhibitable primary response gene in 3T3 cells
Authors: Gilbert Rebecca S. , Herschman Harvey R. 
Published: February 2005

AbstractBoth nitric oxide and prostaglandins are potent paracrine mediators of intercellular communication. An endotoxin‐lipopolysaccharide (LPS) inducible form of nitric oxide synthase (mac‐NOS) has recently been cloned from murine macrophages. An inducible prostaglandin synthase (TIS1O/PGS‐2), cloned from 3T3 cells, is also induced in LPS‐activated macrophage. Because of the wide range of ligands that induce primary response genes in 3T3 cells, the ease of studying chimeric promoter constructs in 3T3 cells, and the importance of both nitric oxide and prostaglandins as paracrine mediators, we examined expression of mac‐NOS in 3T3 cells. Tetradecanoyl phorbol‐13 acetate (TPA), forskolin, platelet‐derived growth factor, fibroblast growth factor, and serum all induce mac‐NOS expression in Swiss 3T3 cells. Thus the mac‐NOS gene can respond to a far wider range of inducers than previously suspected. mac‐NOS is a primary response gene; cycloheximide does not block induction. TPA‐induced mac‐NOS and TIS10/PGS‐2 mRNA accumulation patterns are similar. LPS is a potent inducer of mac‐NOS in Swiss 3T3 cells but cannot induce TIS10/PGS‐2. In contrast, v‐src expression induces TIS10/PGS‐2 message, but not iNOS message in a BALB/c 3T3 cell line containing a temperature‐sensitive v‐src gene. Dexamethasone (DEX) prevents induction of TIS10/PGS‐2, but not most other primary response genes. DEX also blocks mac‐NOS induction in Swiss 3T3 cells. The inducible TIS10/PGS‐2 and mac‐NOS genes, responsible for the production of two distinct paracrine agents, appear to share many regulatory features in 3T3 cells. © 1993 Wiley‐Liss, Inc.
Evidence that a neutral cholesteryl ester hydrolase is responsible for the extralysosomal hydrolysis of high‐density lipoprotein cholesteryl ester in rat hepatoma cells (Fu5AH)
Authors: Delamatre John G. , Carter Robert M. , Hornick Conrad A. 
Published: February 2005

AbstractDiethylumbelliferyl phosphate (UBP) has been shown to inhibit the neutral cholesteryl ester hydrolase activity responsible for hydrolysis of cellular lipid droplet cholesteryl ester (Harrison et al., 1990). The potential for (UBP) to inhibit uptake and hydrolysis of high density lipoprotein (HDL) cholestryl ester was studied in Fu5AH hepatoma cells, a model for HDL cholesterol delivery. Coincubation of 3H‐cholesteryl ester labeled HDL with UBP resulted in a 72% decrease in the cellular free cholesterol/cholesterl ester (FC/CE) isotope ratio, indicating an inhibition in the conversion of cholesteryl ester to free cholesterol. Total cellular 3H‐CE uptake was modestly (27%) but significantly decreased by UBP. Pulsechase experiments (15 min. pulse and 7 min. chase) were used to study the hydrolysis of HDL 3H‐CE in subcellular fractions separated by percoll gradients. The conversion of 3H‐CE to 3H‐FC could be demonstrated in fractions that comigrated with the plasma membrane/endosome fractions but were well separated from lysosomes. Neutral cholesteryl ester hydrolase activity was detected in those same fractions. These results suggest that an extralysosomal pathway is operating in the metabolism of HDL cholesterol and its delivery to hepatoma cells. © 1993 Wiley‐Liss, Inc.
Comparative studies of the granulopoietic enhancing effects of biosynthetic human insulin‐like growth factors I and II
Authors: Merchav Shoshana , Lake Mats , Skottner Anna 
Published: February 2005

AbstractThe effect of biosynthetic human insulin‐like growth factor I (IGF‐I) and IGF‐II on the in vitro growth of human marrow myeloid progenitors in the presence of recombinant human granulocyte colony stimulating factor (rhG‐CSF), granulocyte‐macrophage CSF (rhGM‐CSF), or interleukin‐3 (rhIL‐3), was investigated. IGF‐I and IGF‐II similarly enhanced the growth of myeloid progenitors in cultures stimulated with any of the above hemopoietic regulators. Analysis of colony composition showed an increase in the numbers of granulocyte colonies, but no alteration in the numbers of macrophage or granulocyte/macrophage colonies. IGF‐I induced an increase of 62 ± 16%, 84 ± 13%, and 107 ± 18% in granulocyte colony numbers in the presence of G‐CSF, GM‐CSF, or IL‐3, respectively. The values for IGF‐II were 66 ± 13%, 96 ± 12%, and 91 ± 12%. Similar enhancement of myeloid colony formation by both peptides was also detected in G‐CSF and GM‐CSF‐stimulated cultures of marrow cells that had been depleted of accessory cells, while neither peptide exerted any effect in the presence of IL‐3 in such cultures. The growth‐promoting effects of IGF‐I and IGF‐II were completely abrogated by monoclonal antibodies directed against the IGF‐I (Type I) membrane receptor. IGF‐I and IGF‐II thus appear to exert their effects on human marrow myeloid progenitors via a direct mechanism involving the Type I receptor. © 1993 Wiley‐Liss, Inc.
Regulation of integrin‐mediated adhesion at focal contacts by cyclic AMP
Authors: Class William F. , Kreisberg Jeffrey I. 
Published: February 2005

AbstractCyclic AMP (cAMP) elevation causes diverse types of cultured cells to round partially and develop arborized cell processes. Renal glomerular mesangial cells are smooth, muscle‐like cells and in culture contain abundant actin microfilament cables that insert into substratum focal contacts. cAMP elevation causes adhesion loss, microfilament cable fragmentation, and shape change in cultured mesangial cells. We investigated the roles of the classical vitronectin (αVβ3 integrin) and fibronectin (α5β1 integrin) receptors in these changes. Mesangial cells on vitronectin‐rich substrata contained microfilament cables that terminated in focal contacts that stained with antibodies to vitronectin receptor. cAMP elevation caused loss of focal contact and associated vitronectin receptor. Both fibronectin and its receptor stained in a fibrillary pattern at the cell surface under control conditions but appeared aggregated along the cell processes after cAMP elevation. This suggested that cAMP elevation caused loss of adhesion mediated by vitronectin receptor but not by fibronectin receptor. We plated cells onto fibronectin‐coated slides to test the effect of ligand immobilization on the cellular response to cAMP. On fibronectin‐coated slides fibronectin receptor was observed in peripheral focal contacts where actin filaments terminated, as seen with vitronectin receptor on vitronectin‐coated substrata, and in abundant linear arrays distributed along microfilaments as well. Substratum contacts mediated by fibronectin receptor along the length of actin filaments have been termed fibronexus contacts. After cAMP elevation, microfilaments fragmented and fibronectin receptor disappeared from peripheral focal contacts, but the more central contacts along residual microfilament fragments appeared intact. Also, substratum adhesion was maintained after cAMP elevation on fibronectin—but not on vitronectincoated surfaces. Although other types of extracellular matrix receptors may also be involved, our observations suggest that cAMP regulates adhesion at focal contacts but not at fibronexus‐type extracellular matrix contacts. © 1993 Wiley‐Liss, Inc.
MSH receptors in immortalized human epidermal keratinocytes: A potential mechanism for coordinate regulation of the epidermal‐melanin unit
Authors: Chakraborty Ashok , Pawelek John 
Published: February 2005

AbstractReceptors for melanotropin (MSH) were found to be expressed by immortalized primary human epidermal keratinocytes (RHEK‐1). Using 125I‐βMSH as a probe, the MSH receptors from mouse melanoma cells and human keratinocytes were found to be remarkably similar. In each cell line, there were high and low affinity receptors, with the high affinity classes showing positive cooperativity. Competition of 125l‐βMSH for binding with non‐radioactive MSH revealed similar profiles. Cross‐linking studies, followed by gel electrophoresis and autoradiography, showed almost identical gel migration patterns. Both cell types expressed internal as well as plasma membrane binding sites. MSH receptors on both cell types were up‐regulated by ultraviolet light and by MSH itself. Although the function of MSH receptors expressed by the immortalized keratinocytes is unknown, the results are consistent with recent reports that proliferation of epidermal keratinocytes is stimulated by MSH and that proopiomelanocortin genes are expresed in the epidermis. These results support a model in which keratinocytes and melanocytes, interacting in an “epidermal‐melanin unit,” each respond to UV light signals with increased MSH receptor activity. © 1993 Wiley‐Liss, Inc.
Adenovirus and protein kinase C have distinct molecular requirements for regulating epidermal growth factor receptor trafficking
Authors: Hoffman Brian L. , Takishima Kunio , Rosner Marsha Rich , Carlin Cathleen 
Published: February 2005

AbstractThe ligand‐activated tyrosine kinase receptor for epidermal growth factor (EGF) is down‐regulated by an integral membrane protein coded for by the E3 early transcription unit of group C adenoviruses. The E3 protein appears to block recycling of constitutively internalized receptors, causing them instead to traffic to lysosomes where they are degraded. Expression of functional EGF receptors is also regulated by protein kinase C (PKC), which directly phosphorylates the EGF receptor at Thr‐654. The goal of this study was to determine potential interactions between PKC and the E3 protein, since membrane‐bound PKC activity is elevated by the adenovirus E1A protein. Our results show that although tumor promoters which activate PKC cause a coordinate induction of E3 protein synthesis and EGF receptor degradation, the E3 protein‐induced pathway for receptor down‐regulation functions independently of PKC and other kinases that are inhibited by staurosporine. This suggests that in contrast to other mechanisms that modulate receptor expression (i.e., ligand and PKC), the E3 protein is not regulated by phosphorylation but is constitutively active. We also report that adenovirusmediated degradation is the preferred pathway in infected cells stimulated with 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA) to induce receptor recycling. © 1993 Wiley‐Liss, Inc.