bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of the effects of human placental HGF on rat hepatocytes
Authors: Hernandez J. , Zarnegar R. , Michalopoulos G. K. 
Published: February 2005

AbstractHepatocyte growth factor (HGF) also known as hepatopoietin A (HPTA) (Michalopoulos, FASEB J., 4:176–187, 1990) is a heparin‐binding growth factor whose characterization and tissue distribution have been reported elsewhere. This growth factor was recently cloned and its amino acid sequence determined under the name of hepatocyte growth factor (HGF) (Miyazawa et al., Biochem. Biophys. Res. Commun., 163:967–973, 1989; Zarnegar et al., Biochem. Biophys. Res. Commun., 163:1370–1376, 1989; Nakamura et al., Nature, 342:440–443, 1989). Human placenta is one of the tissues that contains significant amounts of HGF. We isolated HGF from human placenta and characterized its biologic effect on rat hepatocytes. Human placenta HGF was isolated in high purity as a single chain molecule. Single chain HGF stimulated DNA synthesis in primary rat hepatocyte cultures in serum‐free medium. The maximal effect was seen at 5–10 ng/ml. The maximal response occurred at 25–48 hours after plating of the hepatocytes. Protein synthesis was also stimulated by HGF in primary rat hepatocyte cultures. There were peak responses at 19–24 and 37–42 hours after plating of the hepatocytes. TGFβ1 inhibited more than 95% of HGF‐induced DNA synthesis but only 25% of HGF‐induced protein synthesis. HGF interacted in an additive manner with EGF, a well‐known hepatocyte mitogen. There was not an additive interaction between HGF and aFGF. Regenerating liver hepatocytes obtained from rats which underwent two‐thirds partial hepatectomies (PHX) also responded to HGF in a dose‐dependent manner as the hepatocytes from normal liver.
Responsiveness of RNA degradation to amino acids in cultured rat hepatocytes: Comparison with isolated rat hepatocytes
Authors: Balavoine Sophie , Rogier Edith , Feldmann Gerard , Lardeux Bernard 
Published: February 2005

AbstractThe role of amino acids in the regulation of RNA degradation was investigated in cultured hepatocytes from fed rats previously labeled in vivo with [6‐14C]orotic acid. Rates of RNA degradation were determined between 42 and 48 h of culture from the release of radioactive cytidine in the presence of 0.5 mM unlabeled cytidine. The fractional rate was about 4.4 ± 0.4%/h in the absence of amino acids (0×). The catabolism of RNA was decreased to basal level (1.5 ± 0.3%/h) by the addition of amino acids at 10 times normal plasma concentration (10 x). The inhibition of RNA degradation, expressed as percentage of maximal deprivation‐induced response (0× minus 10×), averaged 60% at normal plasma levels of amino acids. The degree of responsiveness was greatly improved as compared to freshly isolated hepatocytes (20%) and was similar to the sensitivity previously observed with perfused livers. In cultured hepatocytes, the sensitivity of RNA degradation to amino acids was not affected by varying the volume of medium from 1 to 4 ml per dish. In freshly isolated hepatocytes, the inhibitory effect of amino acids was not modified by changing the cell density from 0.5 to 5 × 106 cells per ml. In the range of normal plasma concentration of amino acids, the low sensitivity of RNA degradation in isolated hepatocytes persisted with inhibition ranging from 10 to 20%. These findings suggest that the control of RNA degradation in both cultured and isolated hepatocytes is not affected by the total quantity of amino acids available in the medium, but their concentration is crucial. Electron microscopy observations and the inhibitory effect of 3‐methyladenine in cultured rat hepatocytes partially confirmed the role of the lysosomal system in the increase of RNA degradation and its regulation by amino acids.
Plasma membrane water permeabilities of human oocytes: The temperature dependence of water movement in individual cells
Authors: Hunter J. , Bernard A. , Fuller B. , McGrath J. , Shaw R. W. 
Published: February 2005

AbstractMembrane water permeability values were measured in individual fresh human pre‐ovulatory oocytes using real time microscopy in a microscope diffusion chamber. The cells were exposed to anisosmotic conditions, their volume responses measured, and from these data the Lp values were computed employing the Kedem‐Katchalsky analyses of irreversible thermodynamics. Lp values were measured at four temperatures for each oocyte between 37°C and 10°C, and the temperature‐related Arrhenius activation energy (Ea) calculated. It was apparent that individual oocytes exhibited a wide range of Lp values; at 37°C Lp values ranged between 0.33 and 1.80 μm/atm/min. However, each oocyte exhibited the expected inverse linear correlation between Lp and temperature, with high linear correlations (R2 values between 0.73 and 0.96). A mean value for Ea of 8.61 ± 5.11 Kcal/mol was computed. It is apparent that pre‐ovulatory human oocytes express a range of biological diversity in terms of membrane water transport, and this fact needs to be considered when attempting to formulate cryopreservation protocols for storage of these oocytes.
Entactin promotes adhesion and long‐term maintenance of cultured regenerated skeletal myotubes
Authors: Funanage Vicky L. , Smith Susan M. , Minnich Michelle A. 
Published: February 2005

AbstractThe basal lamina protein, laminin, has been shown to promote migration and proliferation of cultured skeletal myoblasts, resulting in increased myotube formation. However, skeletal myotubes adhere poorly to a laminin substrate, and long‐term cultures of skeletal myotubes on laminin have not been achieved. We have found that cultured satellite cells from bupivacaine‐damaged rat skeletal muscle actively proliferate and differentiate on a diluted Matrigel substrate composed of laminin, type IV collagen, heparan sulfate proteoglycan, and entactin. Myotubes cultured on diluted Matrigel are contractile and have never been observed to detach from the culture dish; rather, myotubes generally atrophy after 2–3 weeks in culture. Antibodies directed against the various protein components of Matrigel were used to determine the role of each component in enhancing muscle differentiation. Anti‐laminin impaired satellite cell adhesion, whereas antibodies against either type IV collagen or heparan sulfate proteoglycan had no effect. Anti‐entactin did not inhibit attachment, proliferation, or fusion of cultured satellite cells; however, myotubes exposed to anti‐entactin failed to adhere to the culture dish after spontaneous myotube contractions began. We conclude that entactin is responsible for long‐term maintenance and maturation of contractile skeletal myotubes on a diluted Matrigel substrate. This is the first study to assign a biological function for entactin in myogenesis.
Urokinase‐type plasminogen activator mediates basic fibroblast growth factor‐induced bovine endothelial cell migration independent of its proteolytic activity
Authors: Odekon Lale E. , Sato Yasufumi , Rifkin Daniel B. 
Published: February 2005

AbstractThe dependence of urokinase‐type plasminogen activator (uPA) induction on endogenous basic fibroblast growth factor (bFGF) activity during endothelial cell migration was investigated utilizing a combination of wounded endothelial cell monolayers and substrate overlay techniques. Purified polyclonal rabbit immunoglobulin G (IgG) against bFGF blocked the appearance of uPA‐dependent lytic activity normally observed at the edge of a wounded bovine aortic endothelial (BAE) cell monolayer. Additionally, the migration of cells into the denuded area was inhibited 30–50% by antibodies either to bFGF or to bovine uPA. Incubation of wounded monolayers with either purified bovine uPA or agents able to induce PA activity, such as phorbol myristate acetate (PMA), vanadate, or bFGF, resulted in enhanced migration of cells (28–50%). Anti‐bovine uPA IgG blocked a significant fraction (25%) of BAE cell migration induced by exposure to exogenous bFGF. The role of uPA in migration of wounded BAE cells was not dependent on plasmin generation. Furthermore, the amino terminal fragment (ATF) of human recombinant (hr) uPA, which is enzymatically inactive, stimulated BAE cell movement (36%) as well as intact uPA. ATF of hr uPA also stimulated endothelial cell movement in the presence of anti‐bFGF IgG. These results suggest that BAE cell migration from the edge of a wounded monolayer is dependent upon local increases of uPA mediated by endogenous bFGF. Moreover, the data support the conclusion that migration is stimulated via a signalling mechanism dependent upon occupancy of the uPA receptor but independent of uPA‐mediated proteolysis.
TGF‐β–induced G2/M delay in proliferating rabbit articular chondrocytes is associated with an enhancement of replication rate and a cAMP decrease: Possible involvement of pertussis toxin‐sensitive pathway
Authors: Vivien Denis , Galéra Philippe , Lebrun Emmanuel , Daireaux Michelle , Loyau Gérard , Pujol Jean‐Pierre 
Published: February 2005

AbstractThis study was undertaken to gain more insight into the mechanism whereby TGF‐β influences the cell cycle progression of cultured rabbit articular chondrocytes. Using proliferating chondrocytes in fetal calf serum‐containing medium, we have previously shown that TGF‐β induced a recruitment of cells at the end of the S phase (G2/M) observed 24 h after addition. The delayed cells may then be released, producing a proliferative effect at 48 h, provided a substantial amount of FCS (10%) is present in the medium. Otherwise, in low level of serum (2% FCS, for example), only inhibition of cell proliferation is observed. In chondrocytes synchronized in S phase by a thymidine block, we investigated here the time‐course incorporation of [3H]‐thymidine into DNA, the cell cycle traverse by flow cytofluorometric study of DNA content, the expression of PCNA (Proliferating Cell Nuclear Antigen), and cAMP levels. The data demonstrate that TGF‐β provoked a decrease of cAMP content (0.5–1 h) followed by an enhancement of the DNA synthesis rate (4 h) which was detectable through cytofluorometric analysis and [3H]‐thymidine labeling and correlated with the PCNA expression. In contrast, addition of cAMP analogues to the cultures resulted in an inhibition of replication rate. We also showed that pertussis toxin produced a decrease of the DNA synthesis rate, in a transient manner and only in the presence of TGF‐β. All these results suggest that TGF‐β may accelerate the replication process of cyclized chondrocytes, making then accumulate at the G2/M boundary, via a mechanism that could involve the adenylate cyclase activity and a Gi‐protein. The factor might be responsible for producing a pool of cells having already replicated their DNA and therefore capable of re‐entering the cell cycle without delay. This cell population could serve as a tissue reserve able to induce a mitosis wave when necessary—for example, in the repair of tissue damage.
Enhanced wound healing in animal models by interferon and an interferon inducer
Authors: Bhartiya Deepa , Sklarsh Jerold W. , Maheshwari Radha K. 
Published: February 2005

AbstractHealing of wounds is a significant biological process that involves the interactions of different cell types, growth factors, cytokines, and extracellular matrix molecules. Mice and rats were treated in vivo with interferon (IFN) α/β or polyinosinic‐polycytidylic acid (Poly I:C), a ds‐RNA, a potent inducer of IFN. We observed faster and enhanced closure of wounds as compared to untreated controls on day 7 (wound area measured on Macintosh II CX using NIH image 1.30u program), increased migration of dermal fibroblasts in the wound bed, complete re‐epithelialization evidenced by routine histology and scanning electron microscopic procedures, and increased collagen synthesis, which correlates to greater tensile strength. In addition, classical immunofluorecence procedures using frozen sections showed that dermal fibroblasts synthesized much more laminin following Poly I:C treatment, whereas no effect was observed on fibronectin synthesis. These results suggest that Poly I:C and IFN treatment result in a faster restoration of tissue integrity in both full skin punch biopsy and skin incision models.
Inhibition of heme synthesis decreases transferrin receptor expression in mouse erythroleukemia cells
Authors: Hradilek A. , Fuchs O. , Neuwirt J. 
Published: February 2005

AbstractThe coordination of transferrin receptor (TfR) expression and heme synthesis was investigated in mouse erythroleukemia (MEL) cells of line 707 treated with heme synthesis inhibitors or in a variant line Fw genetically deficient in heme synthesis. Cells of line 707 were induced for differentiation by 5 mM hexamethylene bisacetamide (HMBA). TfR expression increased in the course of induction, as judged by increased TfR mRNA synthesis, increased cytoplasmic TfR mRNA level, and by the increased number of cellular 125I‐Tf binding sites, Addition of 0.1 mM succinylacetone (SA) decreased cellular TfR to the level comparable with the uninduced cells. The decrease was reverted by the iron chelator desferrioxamine (DFO) but not by exogenous hemin. In short‐term (1–2 hours) incubation, SA inhibited 59Fe incorporation from transferrin into heme, whereas total cellular 59Fe uptake was increased. A decrease in TfR mRNA synthesis was apparent after 2 hours of SA treatment. Conversely, glutathione peroxidase mRNA synthesis, previously shown to be inducible by iron, was increased by SA treatment. Cells of heme deficient line Fw did not increase the number of Tf binding sites after the induction of differentiation by 5 mM sodium butyrate. SA had no effect on TfR expression in Fw cells. The results suggest that the depletion of cellular non‐heme iron due to the increase in heme synthesis maintains a high level of transferrin receptor expression in differentiating erythroid cells even after the cessation of cell division.
Induction of proliferating cell nuclear antigen (PCNA) complex formation in quiescent fibroblasts from a xeroderma pigmentosum patient
Authors: Miura Masahiko , Domon Masaharu , Sasaki Takehito , Takasaki Yoshinari 
Published: February 2005

AbstractAccumulated evidence indicates that proliferating cell nuclear antigen (PCNA) is an auxiliary protein of DNA polymerase δ and forms tight association with DNA replication sites during DNA replication or DNA repair synthesis. In this study, such PCNA complex formation was investigated by the indirect immunofluorescence method, using both normal human fibroblasts and those derived from a xeroderma pigmentosum group A (XP‐A) patient. XP‐A fibroblasts in both proliferating and quiescent states did not show any differences from normal fibroblasts in the properties of PCNA‐staining in the untreated conditions. The PCNA complex formation was induced in quiescent normal fibroblasts by both ultraviolet light (UV)‐ and X‐irradiation, whereas in XP‐A fibroblasts it was induced by X‐irradiation, but not by UV‐irradiation. However, PCNA complex was induced in quiescent XP‐A fibroblasts by UV‐irradiation when the cells had previously incorporated 5‐bromodeoxyuridine (BrdU). These observations indicate a close correlation of PCNA complex formation and unscheduled DNA synthesis (UDS). Thus, it was concluded that PCNA complex formation was commonly induced in at least three conditions to produce UDS in spite of different types of DNA damages and DNA repair mechanisms.
Acquisition of thermotolerance induced by heat and arsenite in HeLa S3 cells: Multiple pathways to induce tolerance?
Authors: Kampinga H. H. , Brunsting J. F. , Konings A. W. T. 
Published: February 2005

AbstractRecent data indicate that cells may acquire thermotolerance via more than one route. In this study, we observed differences in thermotolerance development in HeLa S3 cells induced by prior heating (15 minutes at 44°C) or pretreatment with sodium‐arsenite (1 hour at 37°C, 100 μM). Inhibition of overall protein and heat shock protein (HSP) synthesis (>95%) by cycloheximide (25 μg/ml) during tolerance development nearly completely abolished thermotolerance induced by arsenite, while significant levels of heat‐induced thermotolerance were still apparent. The same dependence of protein synthesis was found for resistance against sodium‐arsenite toxicity. Toxic heat, but not toxic arsenite treatments caused heat damage in the cell nucleus, measured as an increase in the protein mass of nuclei isolated from treated cells (intranuclear protein aggregation). Recovery from this intranuclear protein aggregation was observed during post‐heat incubations of the cells at 37°C. The rate of recovery was faster in heat‐induced tolerant cells than in nontolerant cells. Arsenite‐induced tolerant cells did not show an enhanced rate of recovery from the heat‐induced intranuclear protein aggregation. In parallel, hyperthermic inhibition of RNA synthesis was the same in tolerant and nontolerant cells, whereas post‐heat recovery was enhanced in heat‐induced, but not arsenite‐induced thermotolerant cells. The more rapid recovery from heat damage in the nucleus (protein aggregation and RNA synthesis) in cells made tolerant by a prior heat treatment seemed related to the ability of heat (but not arsenite) to induce HSP translocations to the nucleus.
Serotonin increases the cAMP concentration and the phosphoenolpyruvate carboxykinase mRNA in rat kidney, small intestine, and liver
Authors: Zabala Marta T. , Lorenzo Paloma , Alvarez Luis , Berlanga Juan J. , García‐ruíz Josefa P. 
Published: February 2005

AbstractWithin 60 min of the administration of serotonin to fasted‐refed rats, there was a 5‐, 16‐, and 20‐fold stimulation of the mRNA coding for the cytosolic form of P‐enolpyruvate carboxykinase in the kidney, small intestine and liver, respectively. This stimulation was 5‐, 1.3‐, and 2‐fold higher than noted in the same tissue after 24 h of starvation. Dose‐ and time‐response curves to serotonin in the three tissues were similar. The level of PEPCK mRNA in the liver was significantly elevated within 30 min of serotonin administration, whereas 60 min was required in the small intestine and the kidney. The direct effect of serotonin on PEPCK mRNA was also assessed in hepatocytes maintained in primary culture. Serotonin (10−8M to 10−4M) caused a dose‐dependent increase in the level of PEPCK mRNA and a transient increase in cAMP concentration. Within the first min of serotonin (10−6M) addition to cells, cAMP concentration increased 4‐fold and returned after 10 min to basal level. Therefore, these results provide functional evidence of serotonin action in the rat peripheric tissues and suggest that cAMP is involved in its intracellular signalling.
“HepG2/erythroid/brain” type glucose transporter (GLUT1) is highly expressed in human epidermis: Keratinocyte differentiation affects glut1 levels in reconstituted epidermis
Authors: Gherzi Roberto , Melioli Giovanni , de Luca Michele , D'Agostino Antonella , Distefano Gianfranco , Guastella Marina , D'Anna Fiorella , Franzi Adriano T. , Cancedda Ranieri 
Published: February 2005

AbstractIn mature animals, the “HepG2/erythroid/brain” glucose transporter isoform (GLUT1) appears to be expressed at the highest levels at blood tissue barriers; however, these levels may still be lower than the levels of expression seen in fetal tissues. Also, glucose transporters might serve as water channels. Therefore, we decided to investigate GLUT1 expression in human epidermis, a very active tissue, in terms of metabolism, even if not directly vascularized. We found GLUT1 transcripts in human skin and demonstrated, by immunohistochemistry, that GLUT1 protein is highly expressed in the basal layer and, to a lower extent, in the immediately suprabasal layer of the epidermis. This distribution pattern suggested that GLUT1 expression is affected by keratinocyte differentiation. To investigate this possibility, we used human epidermis reconstituted in culture. Our culture system allows the reconstruction of a stratified squamous epithelium which has been successfully grafted onto patients presenting large skin defects. Human keratinocytes have been cultured under conditions which allow a modulation of cellular differentiation and stratification. We observed that (i) GLUT1 expression is 4–6‐fold higher in “stem‐like” basal cells than in large, differentiated keratinocytes; (ii) culture conditions causing cell differentiation reduce GLUT1 expression, while conditions which minimize either differentiation or stratification of keratinocytes enhance GLUT1 expression. Finally, we found that IGF‐1 and insulin, probably acting through the IGF‐1 receptor, increase GLUT1 expression and stimulate glucose transport activity in epidermis reconstituted in culture. In conclusion, our data demonstrate that GLUT1 is highly expressed in the basal layers of human epidermis and that its expression is modulated by keratinocyte differentiation.
Periods of oscillatory growth in developing ocular lens correspond with cell cycle times
Authors: Brewitt Barbara , Teller David C. , Clark John I. 
Published: February 2005

AbstractLens growth rates oscillated throughout neonatal rat lens development. Changes in weight, soluble protein content, and cell division were quantitatively analyzed between birth and 26 days of age. Fourier analysis of daily changes in total weight and soluble protein content identified reproducible periodicities of 50–57 hours. Shorter periodicities of 14–18 hours and 18–21 hours were found by analyzing changes in lens dry weight/6 hours and cell division/7 hours. Changes in dry weight and cell division also contained a second periodicity of 36 hours and 30–43 hours, respectively. The periods of observed oscillations corresponded to the length of stages of the lens epithelial cell cycle. Oscillating growth rates during development emphasize the importance of oscillatory patterns during lens epithelial cell proliferation, differentiation, and tissue development.
Heat‐resistant variants of the Chinese hamster ovary cell: Alteration of cellular structure and expression of vimentin
Authors: Lee Yong J. , Hou Zi‐Zheng , Curetty Lindali , Armour Elwood P. , Al‐Saadi Abdul , Bernstein Jay , Corry Peter M. 
Published: February 2005

AbstractThree heat‐resistant mutant cell lines (78‐1, 78‐2, 78‐3) were previously selected from Chinese hamster ovary cells. In this study, we investigated whether the differences in intrinsic thermal sensitivity result from alteration of stress protein levels or cellular structural changes. Although there was no significant difference in the levels of stress proteins, i.e., constitutive HSP70 in wild type and three heat‐resistant mutant strains, there were marked differences in the amounts of vimentin among the cell lines. Two‐dimensional gel electrophoresis and Western blot showed a 2.3–2.9‐fold increase in the level of vimentin in the mutant cells under normal growth conditions. Northern blot also revealed higher amounts of vimentin mRNA in the mutant cells. Electron microscopy and immunofluorescence suggest that increased amounts of the vimentin‐containing intermediate filaments are correlated with the heat‐resistant phenotypes. © 1992 Wiley‐Liss, Inc.