bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of the effects of class 1 and class 2 heparin‐binding growth factors on protein synthesis and actin mRNA expression in BALB/c‐3T3 cells
Authors: Rybak Susanna M. , Lobb Roy R. , Fett James W. 
Published: February 2005

AbstractBiological effects of class 1 or class 2 heparin‐binding growth factors (HBGFs) were compared in BALB/c‐3T3 cells. Changes in protein synthesis, as monitored by two‐dimensional gel electrophoresis, reveal that while both HBGFs induce the same changes in the synthesis of intracellular proteins, class 2 HBGF selectively increases the synthesis of a 43‐kD extracellular protein. Heparin, which potentiates the mitogenic activity of class 1 but not class 2 HBGF, does not potenitate the changes in protein synthesis elicited by HBGF‐1. Since each HBGF increases actin synthesis, regulation of actin mRNA expression was examined. Actin mRNA levels increase rapidly and transiently in response to either HBGF, and similar superinduction responses are observed in the presence of HBGF and cycloheximide. Although the maximum increase in actin mRNA stimulated by either HBGF is similar, the levels of mRNA induced by class 2 HBGF remain elevated up to 48 hours compared to the level induced by class 1 HBGF. These results imply that in the same cell type class 1 and class 2 HBGFs may modulate some biological effects differently.
Effect of ultraviolet light on the expression of genes for human U1 RNA
Authors: Thirunavukkarasu Chellaiah , Choudhury Kanakendu , Ninichuck Andrew J. , Choudhury Indrani , Eliceiri George L. 
Published: February 2005

AbstractTwo types of UV‐light‐induced inhibitions of the synthesis of small nuclear RNA species U1, U2, U3, U4, and U5 were described previously: an immediate inhibition and a separate, delayed suppression that requires 1‐2 hr of postirradiation cell incubation and UV doses that are about tenfold lower. In the present report, U1 RNA transcription in isolated nuclei from HeLa cells, assayed by RNAase T1 protection, reproduced the delayed inhibition. The sizes of the protected RNA fragments suggest that it is the initiation of U1 RNA transcription that is blocked during this inhibition. Transient expression of a marked human U1 RNA gene that contains 425 and 92 nucleotides of the 5′ and 3′ flanking sequences, respectively, showed delayed, but not immediate inhibition (while the endogenous U1 RNA genes exhibited immediate suppression). This indicates that continuity of the U1 gene flanking sequences beyond those segments and/or chromosomal integration of the U1 gene are not needed for the delayed inhibition, but may be required for the immediate inhibition. Irradiation of a U1 RNA gene, followed by its injection into Xenopus laevis oocyte nuclei, did not reproduce the immediate or delayed inhibitions. This suggests that direct UV radiation damage to DNA in the U1 RNA gene region is not the critical lesion in either the immediate or delayed UV‐light‐induced inhibitions of U1 RNA synthesis. In addition, the RNAase T1 protection pattern of transcripts synthesized in isolated nuclei from nonirradiated HeLa cells suggests that these cells may produce small amounts of U1 RNA molecules with variant nucleotide sequences in the mature region of the transcript.
Effects of 5‐azacytidine, sodium butyrate, and phorbol esters on amino acid transport system A in a kidney epithelial cell line, MDCK: Evidence for multiple mechanisms of regulation
Authors: Boerner Paula , Saier Milton H. 
Published: February 2005

AbstractNeutral amino acid transport by system A was investigated in the epithelial cell lines MDCK and MDCK‐T1. The latter line is a chemically induced, oncogenically transformed line derived from MDCK. Inducers of differentiation, sodiuum butyrate and 5‐azacytidine, and a tumor promotor, TPA, were used as probes to delineate pathways of regulation involved in system A response to a variety of physiological conditions and agents. Azacytidine, an inhibitor of DNA methylation, and butyrate, an enhancer of histone acetylation, inhibited expression of system A, had little effect on system ASC, and slightly stimulated system L. Inhibition of system A expression by butyrate and azacytidine occurred under different conditions. Increases in system A activity due to amino acid starvation or transformation were inhibited by butyrate but not by azacytidine. Repressed system A activity, normally observed in the presence of high levels of amino acids, was more sensitive to azacytidine than to butyrate. The tumor promotor, TPA, stimulated system A activity in MDCK cells under normal growth conditions but did not stimulate activity in amino acid‐starved MDCK cells or in MDCK‐T1 cells. Stimulation of system A activity by TPA was prevented by prior exposure to butyrate but not to azacytidine. These results suggest (1) that system A expression observed in growing amino‐acid‐repressed MDCK cells is modulated by an azacytidine‐sensitive mechanism and (2) that the elevated expression of system A activity induced by amino acid starvation, by chemical transformation to MDCK‐T1, and by TPA is modulated by a butyrate‐sensitive mechanism.
Requirement for mevalonate in cycling cells: Quantitative and temporal aspects
Authors: Doyle James W. , Kandutsch Andrew A. 
Published: February 2005

AbstractIn order to investigate a requirement for isoprenoid compounds in the cell cycle, DNA synthesis was examined in cultured Chinese hamster ovary cells in which mevalonate biosynthesis was blocked with mevinolin, a competitive inhibitor of 3‐hydroxy‐3‐methylglutaryl coenzyme A (HMG‐CoA) reductase. Treatment of exponentially‐growing cultures with mevinolin led to a decline in DNA synthesis and cell cycle arrest in G1. Synchronous DNA synthesis and cell division could be restored in the arrested cultures, in the absence of exogenous mevalonate, by removing the inhibitor from the culture thereby allowing expression of an induced level of HMG‐CoA reductase. In order to quantitate the mevalonate requirement for entry into S phase, recovery of DNA synthesis was made dependent upon added mevalonate by preventing the induction of the enzyme using 25‐hydroxycholesterol, a specific repressor of HMG‐CoA reductase synthesis. When cultures were treated with both inhibitors, optimal recovery of DNA synthesis was obtained with 200 μg/ml mevalonate following an 8 h lag, whereas a progressively longer lag‐time was found with lower concentrations of mevalonate. Exogenous dolichol, ubiquinone, or isopentenyladenine had no effect on the arrest or recovery of DNA synthesis. Cholesterol was required during the arrest incubation for cell viability, but was not sufficient for recovery in the absence of mevalonate. The recovery of DNA synthesis by 200 μg/ml mevalonate, which was maximal 14–16 h after the addition of mevalonate, only required that the mevalonate be present for the first 4 h, whereas more than an 8‐h incubation was required for maximal recovery with 25 μg/ml mevalonate. Maximal recovery at either concentration of mevalonate was achieved after approximately 400 fmol mevalonate/μg protein was incorporated into non‐saponifiable lipids. This quantity represents approximately 0.1% of the mevalonate required for the synthesis of total cellular isoprenoid compounds. The results indicate that production of a quantitatively minor product(s) of mevalonate metabolism is required during the first 4 h following release of the block before other cellular events necessary for entry into S phase can occur.
Differentiation in culture of cells from an avian holocrine secretory gland: Preparation of isolated cells and conditions which induce accumulation of malic enzyme
Authors: Carpenter William R. , Goodridge Alan G. 
Published: February 2005

AbstractMammalian sebaceous glands contain cells which are constantly going through a process of cell division, differentiation, and destruction. Birds have an analogous holocrine secretory gland, the uropygial gland, which is an excellent model for mammalian sebaceous glands and for analysis of the differentiation. Isolated uropygial cells were purified in good yield, and with high viability, after enzymatic digestion of the duck uropygial gland. Almost exclusively progenitor (basal) cells are recovered after separation of isolated cells on a Percoll density gradient; mature uropygial cells are destroyed during preparation of isolated cells. In primary culture, uropygial gland cells grow to confluence and partially duplicate the in vivo differentiation pathway. Malic enzyme activity increases 30‐fold during 4 wks in culture, but there is little, if any, accumulation of fatty acid synthase and only a modest deposition of fat droplets. Medium conditioned by chick embryo fibroblasts inhibits the accumulation of malic enzyme without affecting cell growth. The basement membrane components, collagen, laminin, and Matrigel™, which stimulate differentiation in other cell systems, were without effect on uropygial gland cultures. Triiodothyronine, cyclic AMP, and dexamethasone together with isobutylmethylxanthine had no effect on cell growth or malic enzyme activity. Epidermal growth factor, which stimulates cell division, increased cell number with no increase in malic enzyme accumulation. Factors which would stimulate further differentiation are missing from our culture system, but may include components of the basal lamina and/or factors secreted by mesenchymal cells.
Lateral diffusion of the secretory component (SC) in the basolateral membrane of the human colon carcinoma cell line HT29 assessed with fluorescence recovery after photobleaching
Authors: Gustafsson Mikael , Sundqvist Tommy , Magnusson Karl‐Eric 
Published: February 2005

AbstractThe lateral diffusion of the secretory component (SC), acting as a receptor for dimeric IgA in the basolateral side of intestinal epithelial cells, was studied in the human colonic carcinoma cell line HT29. The HT29 cells were grown in Dulbecco's modified Eagle's medium in which galactose had been substituted for glucose to promote development of small intestine‐like cells, with a distinct separation of the basolateral side from the apical surface. The SC was stained with rhodamine‐labeled polyclonal anti‐human SC rabbit antibodies (Ig) or Fab fragments, and the lateral mobility was assessed with the fluorescence recovery after photobleaching technique. The average lateral diffusion was consistent with a diffusion constant of 7.7 ± 2.0 (mean value ± SD; n = 29) and 7.1 ± 2.3 (n = 30) × 10−10 cm2s−1 for Ig‐and Fab‐labeled receptors, respectively, which is slower than lipid diffusion but is similar to that found for other membrane receptors. The corresponding values for the fraction of mobile receptors were 66 ± 13% and 71 ± 12%, respectively. Cells were labeled from the top of the culture plate, and cells adjacent to a mechanically made rift or a natural opening in the cell monolayer were labeled more strongly, confirming the microscope‐based impression that the basolateral surface primarily harboured the SC receptor.
Tissue distribution of murine hemopoietic growth factor mRNA production
Authors: Troutt Anthony B. , Lee Frank 
Published: February 2005

AbstractWe have studied the tissue distribution of interleukin (IL) and hemopoietic colony‐stimulating factor (CSF) transcripts in mice by S1‐nuclease protection analysis. Accumulation of several of these mRNAs in response to intravenous injection of lipopolysaccharide (IPS) appears to occur in a tissue‐specific fashion. IL‐1α transcripts accumulate in spleen and lung; IL‐6 transcripts accumulate in kidney, heart, and spleen; granulocyte‐macrophage‐CSF transcripts accumulate in lung and heart; and granulocyte‐CSF transcripts accumulate in heart. Three distinct patterns of in vivo mRNA accumulation were detected: (1) silent—interleukins 2–5 showed no transcripts in either LPS‐treated or untreated animals; (2) induced—IL‐1α, IL‐6, granulocyte‐macrophage (GM)‐CSF, and G‐CSF transcripts were increased in abundance in LPS‐injected mice; and (3) constitutive—M‐CSF transcripts were found in similar amounts in both untreated and treated mice and were present in all tissues examined.
Altered formation of DNA replication intermediates in cells growing in different culture conditions
Authors: lönn Ulf , Lönn Sigrid , Nylen Urban , Winblad Gerard 
Published: February 2005

AbstractIn human melanoma cells one can detect two discrete DNA replication intermediates, 10‐kb DNA intermediates and Okakzaki fragments. Both intermediates are seen when cells are rapidly growing in medium supplemented with fetal calf serum. When the medium is supplemented with newborn calf serum, one can detect Okakzaki fragments but not 10‐kb DNA intermediates. In contrast we do not detect changes in the replicon sizes in the two media.
Induction of interleukin‐1 receptors on chondrocytes by fibroblast growth factor: A possible mechanism for modulation of interleukin‐1 activity
Authors: Chandrasekhar Srinivasan , Harvey Anita K. 
Published: February 2005

AbstractInterleukin‐1 is a polypeptide factor with profound effects on several cell types, such as chondrocytes, fibroblasts, and T‐cells. The ability of interleukin‐1 to induce the synthesis of matrix‐degradative enzymes, as well as prostangladin E2, suggests a pivotal role for this mediator in chronic inflammation. Previous studies have shown that the effect of human monocyte interleukin‐1 on the synthesis of collagenase and neutral proteases by chondrocytes was enhanced by basic fibroblast growth factor. Using recombinant human interleukin‐1 B, we have examined whether the potentiation of interleukin‐1 effects by fibroblast growth factor is related to changes in the number or affinity of interleukin‐1 receptors. Our studies confirm that rabbit articular chondrocytes in culture contain a single class of high‐affinity receptors for interleukin‐1 with a Ka of 0.9–1.1 × 10– 13M–1While the untreated chondrocytes contain approximately 1,620 receptors per cell, fibroblast growth factor‐treated cells exhibit a higher number of receptors (approximately 2,960 per cell) with no apparent change in the affinity. The increase in receptor number can be abolished by inhibitors of lysosomal function, indicating a requirement for intracellular processing of the fibroblast growth factor. Our results suggest that the potentiation of interleukin‐1 catabolic effects by fibroblast growth factor may be related to its ability to induce additional interleukin‐1 receptors on the chondrocyte cell surface.
Expression of von Willebrand factor in porcine vessels: Heterogeneity at the level of von Willebrand factor mRNA
Authors: Bahnak Bruce R. , Wu Qing‐Yu , Coulombel Laure , Assouline Zahra , Kerbiriou‐Nabias Daniele , Piétu Genevieve , Drouet Ludovic , Caen Jacques P. , Meyer Dominique 
Published: February 2005

AbstractThe expression of the von Willebrand factor (vWF) gene by cultured endothelial cells from the porcine pulmonary artery, aorta, and lung was compared at the levels of messenger (m)RNA and antigen. Steady‐state levels of vWF mRNA were determined by dot‐blot analysis using a partial human vWF cDNA as the hybridization probe; vWF mRNA from cultured aortic endothelial cells, and vWF antigen secreted into the culture supernatants were barely detectable. In contrast, vWF mRNA and antigen from the pulmonary artery endothelial cells were approximately eight to nine times that demonstrated by aortic cells. Levels of vWF mRNA and antigen in cultured lung cells were intermediate of those found in the pulmonary artery and aorta and correlated with the estimated number of cells demonstrated to be of endothelial origin in the mixed cell populations grown from the lung. Differences between the levels of vWF mRNA found in cultured cells from the pulmonary artery and those found in the aorta were maintained in cells processed directly from these vessels. Correlation between the levels of vWF mRNA and antigen in endothelial cells from different vessels of the pig suggests that the differential control of vWF synthesis is at the level of transcription. Furthermore, maintenance in cultured cells of the difference in transcription rates that were observed in vivo suggests that vWF gene expression is not exclusively regulated through environmental factors.
Regulation of skeletal muscle satellite cell proliferation and differentiation by transforming growth factor‐beta, insulin‐like growth factor I, and fibroblast growth factor
Authors: Allen Ronald E. , Boxhorn Linda K. 
Published: February 2005

AbstractSkeletal muscle satellite cells were cultured from mature rats and were treated in vitro with various combinations of transforming growth factor (TGF)‐beta, fibroblast growth factor (FGF), and insulin‐like growth factor I (IGF‐I). In serum‐free defined medium the following observations were made: TGF‐beta depressed proliferation and inhibited differentiation; FGF stimulated proliferation and depressed differentiation; IGF‐I stimulated proliferation to a small degree but demonstrated a more pronounced stimulation of differentiation. In evaluating combinations of these three factors, the differentiation inhibiting effect of TGF‐beta could not be counteracted by any combination of IGF‐I or FGF. The proliferation‐depressing activity of TGF‐beta, however, could not inhibit the mitogenic activity of FGF. Maximum stimulation of proliferation was observed in the presence of both FGF and IGF‐I. The highest percentage fusion was also observed under these conditions, but differentiation with minimal proliferation resulted from treatment with IGF‐I, alone. By altering the concentrations of TGF‐beta, FGF, and IGF‐I, satellite cells can be induced to proliferate, differentiate, or to remain quiescent.
Tumor promoter 12‐0‐tetradecanoyl‐phorbol‐13‐acetate (TPA) can reduce the Ca‐transporting ability of Ca‐lonophores in T lymphocytes: The involvement of intracellular heavy metal lons
Authors: Csermely Péter , Somogyi János 
Published: February 2005

Abstract12‐0‐tetradecanoyl‐phorbol‐13‐acetate (TPA) can significantly reduce the Caionophore‐induced rise in the intracellular calcium concentration (Cai) of T lymphocytes measured by quin2 or fura‐2 fluorescence. This counteraction of TPA is maximal at a preincubation of 90 min at TPA concentrations higher than 20 nM. 45Ca uptake and efflux measurements directly indicate that TPA does not activate the calcium extrusion systems in thymocytes but impairs the Ca‐transporting ability of Ca‐ionophores. TPA causes no immobilization of the Ca‐ionophores as it is demonstrated by the lack of significant changes in fluorescence and fluorescence polarisation of A23187 during TPA incubation. Similarly the energy transfer between the Tyr, Try groups of membrane proteins and A23187 shows no significant difference in control and TPA treated thymocytes. This indicates that A23187 is not in a membrane proteinbound form after TPA preincubation. The intracellular heavy metal chelator, N,N,N′,N′‐tetrakis(2‐pyridylmethyl)ethylenediamine (TPEN) restores the ionophoretic ability of Ca‐ionophores in TPA pretreated cells to the control level. Diacyl‐glycerols also impair the Ca‐transporting ability of Ca‐ionophores. TPEN prevents this effect as well. These findings suggest that TPA and diacylglycerols may cause an increase in the availability of intracellular heavy metal ions. Our results may reflect a new, physiologically important mechanism of the action of diacyl‐glycerols and phorbol esters.
Smooth muscle gelsolin and a Ca2+‐sensitive contractile cell model
Authors: Kanno Kimiyoshi , Sasaki Yasuharu 
Published: February 2005

AbstractSmooth muscle gelsolin, termed smooth muscle 90‐kDa protein in our previous paper (Kanno et al. FEBS Lett. 1985; 184:202–206), was purified from bovine aorta. Antibody prepared against smooth muscle gelsolin was used to detect the presence of gelsolin in human lung fibroblast MRC‐5 cells permeabilized with Triton X‐100 (MRC‐5 cell models). These cells contracted in the presence of MgATP and Ca2+ in doses over 1 μM. Immunofluorescence microscopy using phalloidin and antigelsolin antibody showed that gelsolin was distributed along the stress fibers, except for a marginal bundle of cells, when MRC‐5 cells were growth‐arrested in serum‐depleted medium. Making use of immunoblotting and indirect immunofluorescence techniques, we demonstrated that gelsolin is not retained in the MRC‐5 cell models. We used purified smooth muscle gelsolin as a specific agent to sever the actin filaments. Preincubation of MRC‐5 cell models with gelsolin led to a destruction of stress fibers, in a dose‐ and Ca2+‐dependent manner. The contractility was also lost, in the same manner described above, thereby indicating that a continuous distribution of actin filaments within the stress fibers is required for cell contraction. Treatment of MRC‐5 cells with the Ca2+ ionophore A23187 induced an extracellular Ca2+‐dependent contraction but not a massive destruction of stress fibers, thereby indicating that most of the endogenous gelsolin was inactive under these conditions. Our interpretation of these results is that increases in cytoplasmic Ca2+ concentrations are sufficient for the contraction but may be too transient to activate endogenous gelsolin and thereby disrupt the stress fibers. Indeed, the inhibition of contraction of the MRC‐5 cell, as induced by smooth muscle gelsolin, required preincubation in the presence of Ca2+, before the addition of MgATP. These results suggest that destruction of the stress fibers by endogenous gelsolin, which leads to inhibition of cell contraction, may occur if the cytoplasmic Ca2+ is maintained at high concentrations for a few minutes.
Effects of heat and other inducers of the stress response on protein degradation in Chinese hamster and Drosophila cells
Authors: Westwood J. Tim , Steinhardt Richard A. 
Published: February 2005

AbstractMany recent studies have suggested that heat and other inducers of the heat shock (stress) response in eukaryotic cells might result in the generation of abnormal proteins which would result in the overloading of protein degradation systems and the stabilization of proteins involved in positively regulating heat shock (hs) gene expression. In this study we have examined the effects different heat treatments and other hs inducers have on protein degradation in Chinese hamster ovary (CHO) and Drosophila Kc and Schneider cells. We have found that intermediate temperatures which induced the hs response (42°C in CHO and 34°C in Kc cells) did increase protein degradation rates whereas, higher temperatures which also induced the hs response (45°C in CHO and 37°C in Kc cells) initially increased but then decreased protein degradation rates. While these results are consistent with a model in which the protein degradation system is being overloaded and/or components of it are being depleted, we have found several conditions which induce hs proteins which rule out this mechanism. Exposure of either cell type to amino acid analogs (5mM canavanine or 5 mM S‐aminoethyl cysteine) resulted in the rapid degradation of those proteins which had incorporated the analogs in both CHO and Drosophila cells. However, the addition of analogs had little or no effect on the degradation of preexisting proteins, indicating that the introduction of abnormal proteins probably didn't overload the protein degradation system(s). The addition of 100 (μ)M cadmium sulfate or 100 (μ)M sodium arsenite had little or no effect on protein degradation rates in CHO cells even though both were good inducers of the hs proteins. Thus, exposure to inducers of the hs response does not universally increase protein degradation rates nor does it stabilize preexisting proteins. Therefore, the degradation of abnormal proteins is probably not involved in inducing the hs genes.