bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pretreatment with vitamin A inhibits transforming growth factor alpha stimulation of human mammary carcinoma cells
Authors: Halter Susan A. , Winnier Angela R. , Arteaga Carlos L. 
Published: February 2005

AbstractVitamin A or retinol is an important agent in the normal differentiation and growth of cells. Retinol is an effective inhibitor of the growth of many transformed cells in vitro and in vivo but its mechanism of action is unclear. Transforming growth factor alpha (TGFα) is a known mitogen. We examined the effect of retinol treatment on TGFα stimulation of two human mammary carcinoma cell lines, one which is growth inhibited by retinol and one which is not. Pretreatment of both cell lines for 48 hours with retinol resulted in inhibition of TGFα stimulation of growth. In the T47D cell line the mechanism was not related to an effect on the cellular content of TGFα, epidermal growth factor (EGF) receptor protein, EGF receptor mRNA, or on the binding of TGFα to the EGF receptor. However, TGFα‐induced stimulation of the EGF receptor substrate, phospholipase C‐γ1, was abrogated in the T47D cell line with retinol pretreatment. In the MDA‐MB‐468 cell line, pretreatment with retinol resulted in a decrease in tyrosine phosphorylation of the EGF receptor. These results suggest that pretreatment with retinol decreases cellular proliferation seen with TGFα treatment by altering phospholipase C‐γ1 response and/or EGF receptor tyrosine kinase activity. Alteration of phospholipase C‐γ1 activity does not appear to be responsible for the inhibition of cell growth seen in the absence of TGFα stimulation. © 1993 Wiley‐Liss, Inc.
Characterization of selective glucocorticoid‐dependent responses in a glucocorticoid‐resistant smooth muscle tumor cell line
Authors: Fan Weimin , Cooper Tina M. , Norris James S. 
Published: February 2005

AbstractThe DDT1 MF2 smooth muscle cell line was derived from an estrogen/androgeninduced leiomyosarcoma arising in the hamster ductus deferens. Growth of this cell line is arrested in Go/G1 by treatment with glucocorticoids. To facilitate the study of the mechanism of glucocorticoid‐induced cell growth arrest, a glucocorticoid‐resistant variant cell line, DDT1 MF2 GR1 (GR1), was developed by genetic selection. Growth of this mutant cell line is completely resistant to the inhibitory action of glucocorticoids. However, we now demonstrate that both primary and secondary glucocorticoid‐induced events still exist in the GR1 cell line. By analyzing the expression and genetic pattern of glucocorticoid receptor, no detectable rearrangement of the glucocorticoid receptor gene was found although the expression of both mRNA and protein levels of the receptor were lower in the variant compared to wild‐type cells. In addition, we found that the expression of two growth‐associated genes, Ha‐ras and transforming growth factor β1 (TGF‐β1) are down‐regulated by glucocorticoids in wild‐type DDT1 MF2 cells but not in GR1 cells. These results indicated that the function or activity of glucocorticoid receptor in the GR1 cells is not qualitatively altered. Our data suggest that a lower glucocorticoid receptor level is not the real cause or at least not the single cause for the GR1 cell's loss of sensitivity to the inhibitory action of glucocorticoid. Instead, we postulate the existence of a defect downstream of the primary site of action of glucocorticoid receptor complexes in GR1 cells. © 1993 Wiley‐Liss, Inc.
Comparative analysis of mitogenic and morphogenic effects of HGF and EGF on rat and human hepatocytes maintained in collagen gels
Authors: Michalopoulos George K. , Bowen William , Nussler Andreas K. , Becich Michael J. , Howard Tamara A. 
Published: February 2005

AbstractHepatocytes maintained in collagen gels remain differentiated for prolonged periods of time compared to cells maintained on conventional cultures. Previous studies with other culture systems in which chemical supplements or substratum modifications enhanced hepatocyte differentiation showed that in all of these systems hepatocytes do not respond to mitogens. In this study it is shown that hepatocytes maintained between two layers of collagen gels respond to mitogens HGF (also known as scatter factor (HGF/SF)) and epidermal growth factor (EGF). Cell density did not affect the responsiveness to mitogens as in conventional cultures. In addition both mitogens (HGF more pronounced) induce characteristic morphogenic changes in which hepatocytes form processes and join in formation of cords. Hepatocytes respond to mitogens for up to 6 days in culture at which point they become refractory to further mitogenic stimulation. This occurs despite electron microscopic evidence that these cells are fully viable when they become refractory to mitogenesis. The refractory state is not modified by substitution of one growth factor for the other or by addition of growth factors at different times. Hepatocytes in the refractory state become again responsive to mitogens when the collagen gels are dispersed by collagenase and the cells are replated on conventional substrates. © 1993 Wiley‐Liss, Inc.
Contributions of K+, Na+, and Cl− to the membrane potential of intact hamster vascular endothelial cells
Authors: Miao Kai , Wondergem Robert , Hossler Fred E. , Joyner William L. 
Published: February 2005

AbstractThe transmembrane potential (Vm) of vascular endothelial cells (EC) is an important property that may be involved in intra‐ and intercellular signal transduction for various vascular functions. In this study, Vm of intact aortic and vena caval EC from hamsters were measured using conventional microelectrodes. Vascular strips with the luminal surface upwards were suffused in a tissue chamber with krebs solution in physiological conditions. The resting Vm of aortic and vena caval EC was found to be −40± 1 mV (n = 55) and −43± 1 mV (n = 15), respectively. The Vm recordings were confirmed to have originated from EC by scanning and transmission electron microscopy combined with the comparison of electrical recordings between normal and endothelium‐denuded aortic strips. The input resistance varied from 10–240 MΩ, which implied the presence of electrical coupling between vascular EC. Elevating the K+ level in the suffusate from 4.7 mM to 50 and 100 mM depolarized aortic EC by 19% and 29% and vena caval EC by 18% and 29%, respectively. These low percentages indicated a relatively small contribution of [K+] to the resting Vm of vascular EC. A positive correlation (r> 0.69) between the resting Vm and the magnitude of depolarization by the high [K+]0 may be related to the involvement of voltage‐dependent K+ channels. The hyperpolarization caused by lowering both [Na+]0 and [CI−]0 suggested the disengagement of some electrogenic transport systems in the membrane, such as a Na+ ‐K+ ‐CI− cotransporter. The transference number (tion), as an index of membrane conductance for specific ions, was calculated for K+ (15‐20%), Na+ (16%), and Cl− (9‐15%), demonstrating that both Na+ and Cl− as well as K+ contribute to the overall resting Vm. Our study documented some basic electrophysiology of the vascular EC when both structural and functional properties of the cell were maintained, thus furthering the understanding of the essential role of endothelial cells in mediating vascular functions. © 1993 Wiley‐Liss, Inc.
An N‐cadherin–like protein contributes to solute barrier maintenance in cultured endothelium
Authors: Alexander J. S. , Blaschuk O. W. , Haselton F. R. 
Published: February 2005

AbstractWe investigated the role of cadherins in the solute barrier maintained by endothelial cells in vitro. Cell‐column chromatographic measurement of endothelial barrier showed that reducing normal extracellular calcium from 1.2 to 0.12 mM increased endothelial permeability to 250% of baseline after 20 min. Restoring normal calcium restored the barrier within 15 min which remained stable for at least 60 min. We used sulfo‐NHS‐biotin and anti‐cadherin antibodies to characterize endothelial proteins with possible roles in the maintenance of endothelial barrier. The non‐specific probe sulfo‐NHS‐biotin identified at least ten endothelial cell surface proteins, with greatest labelling occurring at molecular weights of 125 and 145 kD. Six proteins, including the 125 and 145 kD proteins, associated with the cytoskeleton. Western blotting for the presence of classical cadherins containing the conserved cytoplasmic sequence CDPTAPPYDSLLVFDYEG detected two bands at 145 and 125 kD which associated with the cytoskeleton. Western blotting with an antibody, which recognizes FHLRAHAVDINGNQV, an extracellular homotypic binding region of N‐cadherin, detects three bands. Of these three, one protein had a molecular weight of 125 kD and was associated with the cytoskeleton. Immunofluorescence with both N‐cadherin and anti‐peptide 1 antibodies found staining at endothelial cell borders. The utility of a newly developed cell‐column calcium switch assay was tested by verifying the functional role of the previously described epithelial cadherin, uvomorulin, in epithelial barrier. We then applied this method to endothelial cell columns and found the N‐cadherin antibody interfered with the reforming of interendothelial junctions. These results suggest that, as in epithelial cells, cadherins in bovine endothelial cells have a functional role in forming the calcium sensitive endothelial junction and may play an important role in the formation of normal barrier. © 1993 Wiley‐Liss, Inc.
Leukocyte‐deactivating factor from macrophages: Partial purification and biochemical characterization. A novel cytokine
Authors: Camarero Valéria C. P. C. , Colepicolo Pio , Ribeiro José M. C. , Karnovsky Manfred L. 
Published: February 2005

AbstractA deactivating factor (MDF) is released from granuloma‐like lesions of mice (giant and epithelioid macrophages) to the surrounding medium. Test cells incubated in the presence of MDF display dramatic inhibition of superoxide anion (O2−) release when stimulated. This failure to manifest O2 release is observed whether PMA, all‐transretinal, or fMet‐Leu‐Phe is the stimulating agent. MDF acts on different cell types from different species; mouse macrophages as well as guinea pig, human, and mouse neutrophils. Such results suggest that it is a universal regulatory cytokine with high affinity for phagocytic lineages. The factor was subjected to various purification methods: ultrafiltration, gel chromatography, and reversed phase HPLC. A crude preparation that resulted from conditioning of medium by old macrophages (MCM) shows two peaks of activity when subjected to gel filtration. These correspond to molecular weights for the active principle of 3 and 11 kD. When the factor was obtained by extraction of the same cells after washing and sonication. Only the former peak was seen. Fractions corresponding to a MW of 3 kD from several preparations were combined and subjected to HPLC. MDF activity then appeared in a single fraction. MDF is thus putatively a modulator of the cidal activity of phagocytic cells that utilize release of reactive oxygen species for cytocidal activity. © 1993 Wiley‐Liss, Inc.
Effects of ultraviolet irradiation on human skin‐derived epidermal cells in vitro
Authors: Dissanayake N. S. , Greenoak G. E. , Mason R. S. 
Published: February 2005

AbstractThe effects of UVA, mixed UVA + B, and solar‐simulated irradiation were examined in human keratinocytes and melanocytes cultured in vitro. Irradiation with UVA, UVA + 3, or the solar simulator caused a dose‐dependent decrease in keratinocyte cell numbers and thymidine incorporation at 24 hours, with recovery after 48 and 72 hours. Divided dose regimens reduced the inhibitory effect of ultraviolet (UV) irradiation on cell numbers measured 24 hours after the last irradiation. Exposure to both UVA and UVA + B increased formation of cornified envelopes. Similar irradiance doses of UVA 80 minutes (1.12 J/cm2) and UVA + B 40 minutes (1.04 J/cm2) caused 2.4‐ and 3.3‐fold increases in cornified envelope formation, respectively. With solar‐simulated irradiation, the cornified envelope formation was increased by 3.5‐fold after exposure of 8 minutes (2.6 J/cm2). Irradiation of melanocytes with UVA, UVA + B, or solar‐simulated irradiation resulted in a dose‐dependent decrease in melanocyte numbers after 24 hours compared with sham‐irradiated controls. As a result of UV irradiation, tyrosinase activity of melanocytes measured at 24 hours was stimulated. UVA + B irradiation (1.04 J/cm2) increased tyrosinase activity approximately twofold, while UVA alone (1.1 J/cm2) increased tyrosinase four to sixfold and solar‐simulated irradiation (1.3 J/cm2) increased tyrosinase approximately twofold compared to the control cells. Melanin content increased in cells after both UVA and mixed UVA + B irradiation. These results indicate that both UVA and mixed UVA + B irradiation had qualitatively similar effects on the proliferative and functional activity of skin‐derived cells but that the type of irradiation and the dosage regimen affect the dose‐response relationship. © 1993 Wiley‐Liss, Inc.
Insulin induces rapid accumulation of insulin receptors and increases tyrosine kinase activity in the nucleus of cultured adipocytes
Authors: Kim Sung‐Jin , Kahn C. Ronald 
Published: February 2005

AbstractTo better understand the mechanism by which insulin exerts effects on events at the cell nucleus, we have studied insulin receptors and tyrosine kinase activity in nuclei isolated by sucrose density gradient centrifugation following insulin treatment of differentiated 3T3‐F442A cells. Insulin stimulated nuclear accumulation of insulin receptors by approximately threefold at 5 min. The half‐maximal effect was observed with 1–10 nM insulin. Following insulin treatment, phosphotyrosine content associated with the nuclear insulin receptor was also increased by twofold at 5 min with a similar insulin concentration dependency. These nuclear insulin receptors differ from the membrane‐associated insulin receptors in that they were not efficiently solubilized with 1% Triton X–100. During the same period of time, insulin stimulaced nuclear tyrosine kinase activity toward the exogenous substrate poly Glu4: Tyr1 tenfold in a time‐dependent manner reaching a maximum at 30 min. The insulin receptor substrate protein 1 (IRS‐1) could not be detected in the nucleus by immunoblotting. However, a nuclear protein with Mr ≈ 220 kDa was tyrosine phosphorylated, and insulin further stimulated this process threefold >30 mins. Surface labeling was performed to determine if the nuclear insulin receptors would emerge from the plasma membrane fraction. Using 1251‐BPA‐insulin with intact cells, the intensity of nuclear insulin receptor labeling was negligible and not increased throughout 30 min incubation at 37°C. In contrast, there was an increase in labeled receptors in the microsomal fraction following insulin treatment. Taken together, these results indicate that insulin rapidly increases nuclear insulin receptor appearance and activates nuclear tyrosine kinase activity. The insulin‐induced accumulation of nuclear insulin receptors cannot be accounted for by internalization of surface membrane receptors. These effects of insulin may play an important role in action of the hormone at the nuclear level. © 1993 Wiley‐Liss, Inc.
In vitro expression of osteoblastic markers in cells isolated from normal fetal and postnatal human bone and from bone of patients with osteogenesis imperfecta
Authors: Morike M. , Schulz M. , Brenner R. E. , Bushart G. B. , Teller W. M. , Vetter U. 
Published: February 2005

AbstractWe studied the expression of osteoblastic markers in cultured cells isolated from the bone of 15 patients with different clinical forms of osteogenesis imperfecta (OI) and of seven fetal and postnatal controls. Cultured bone cells of ten OI patients produced abnormal collagen type I. Similar to controls, OI bone cells produced predominantly collagen type I with traces of collagen types III and V. The 1,25(OH)2 vitamin D3‐stimulated synthesis of osteocalcin, a specific osteoblastic marker protein, was similar in OI bone cells and age‐matched controls. Bone cells from fetal controls and from patients with the perinatal lethal OI type II produced less osteocalcin than bone cells from postnatal controls and surviving OI patients. OI bone cells responded to parath.yroid hormone (PTH) by increased production of cAMP similar to controls. Bone cells from fetal controls and from OI type II donors showed a decreased response to PTH. Activity of the bone‐liver‐kidney isoenzyme alkaline phosphatase (AP) was detected in all control and OI bone cells. The expression of all osteoblastic markers was similar in bone cells producing abnormal collagen type I. These observations show that OI bone cells in vitro express a pattern of osteoblastic markers similar to age‐matched control bone cells indicating that osteoblastic differentiation is not altered by the underlying defects of collagen type I metabolism in OI bone cells. © 1993 Wiley‐Liss, Inc.
Activation of the 92 kDa type IV collagenase by tissue kallikrein
Authors: Desriviéres Sylvane , Lu He , Peyri Nicole , Soria Claudine , Legrand Yves , Ménashi Suzanne 
Published: February 2005

AbstractType IV collagenases are secreted as latent 92 and 72 kDa proenzymes which are then activated extracellularly. The mechanisms by which they are activated in vivo are not clear. We have studied the activation of porcine endothelial cell type IV collagenases by tissue and plasma kallikrein, and found that tissue kallikrein was a very efficient activator of the 92 kDa type IV collagenase. Enzyme cleavage was observed at concentrations of tissue kallikrein as low as 0.1 μg/ml. Plasma kallikrein had no effect. By comparison, plasmin, which has been proposed to be the physiological activator of interstitial collagenase and stromelysin, and elastase were much less effective, and high concentrations (plasmin at 100–200 μg/ml and elastase at 20 μg/ml) were required to cause only a limited cleavage which was not associated with an increase in activity, as observed by the gelatin‐gel lysis assay. In addition tissue kallikrein was found by immunohistochemistry to be present in the extracellular matrix of the intima of porcine aortic vessel wall. These findings suggest that tissue kallikrein can be a potential activator of the 92 kDa type IV collagenase in vivo. © 1993 Wiley‐Liss, Inc.
Morphological and proliferative responses of endothelial cells to hydrostatic pressure: Role of fibroblast growth factor
Authors: Acevedo Arlene D. , Bowser Samuel S. , Gerritsen Mary E. , Bizios Rena 
Published: February 2005

AbstractSubconfluent bovine pulmonary artery endothelial cells on rigid substrates were exposed to 1.5–15 cm H2O sustained hydrostatic pressure for up to 7 days and exhibited elongation, cytoskeletal rearrangement, increased cell proliferation, and bilayering. The role of basic fibroblast growth factor (bFGF) in the mechanism(s) of these endothelial cell responses to sustained hydrostatic pressure was investigated. Evidence that bFGF was released from endothelial cells exposed to sustained hydrostatic pressure or compression was provided by the following experimental results: (1) Cells exposed to control (3 mm H2O) pressure displayed intense nuclear and cytoplasmic bFGF staining by immunocytochemical techniques; this staining was absent in cells exposed to 10 cm H2O for 7 days. (2) Conditioned medium from endothelial cells exposed to 10 cm H2O for 7 days contained at ansferable, growth‐promoting activity exhibiting heparin‐Sepharose affinity, lability to both heat and freeze/thawing, and neutralization by anti‐bovine bFGF. (3) Suramin (0.1 mM), a growth‐factor receptor inhibitor, abrogated the proliferative and morphological responses of endothelial cells exposed to sustained hydrostatic pressure. Endothelial cells exposed to elevated hydrostatic pressure demonstrated no detectable decrement in cell viability as assessed by Trypan blue exclusion. The results of the present study indicate that hydrostatic pressure or compression can induce bFGF release from endothelial cells independent of cell injury or death; bFGF is subsequently responsible for the morphological, proliferative, and bilayering responses of endothelial cells to hydrostatic pressure. © 1993 Wiley‐Liss, Inc.
Isoproterenol‐ and insulin‐induced hyperpolarization in rat skeletal muscle
Authors: Li Kai‐Xun , Sperelakis Nicholas 
Published: February 2005

AbstractUsing conventional microelectrode techniques, we investigated the combined effects of isoproterenol (Iso) and insulin (Ins) on the resting membrane potential (RMP) of isolated rat skeletal muscles. In soleus muscle, Iso (1 μM) and Ins (4 units/L) separately induced a hyperpolarization of 9.2 mV and 4.8 mV, respectively. Combined administration of Iso and Ins induced a hyperpolarization of 12.4 mV, larger than either one separately. A similar observation was made in Na+‐loaded rewarming experiments. 8‐Br‐cAMP (1 mM and 3 mM) and forskolin (10 μM, an adenylate cyclase activator) induced a hyperpolarization of 5.3 mV, 8 mV, and 6.0 mV, respectively. This hyperpolarizing action was blocked by ouabain indicating that the Na‐K pump was involved in the hyperpolarization. 8‐BrcGMP (3 mM) had no effect on RMP; however, it blocked or reversed the hyperpolarization caused by 8‐Br‐cAMP (1 mM). In addition, 8‐Br‐cGMP partially inhibited the hyperpolarizing effect of Iso (1 μM) by 40% and completely prevented the effect of Ins. The phorbol ester, PMA, (1 μM, a PKC activator) induced a ouabain‐inhibitable hyperpolarization. These results suggest that cAMP and PKC are involved in the Iso‐ and Ins‐induced hyperpolarization and that Iso and Ins influence the RMP presumably through regulation of the electrogenic Na‐K pump via different mechanisms. © 1993 Wiley‐Liss, Inc.
Regulation of amino acid transport and protein metabolism in myotubes derived from chicken muscle satellite cells by insulin‐like growth factor‐I
Authors: Duclos M. J. , Chevalier B. , Goddard C. , Simon J. 
Published: February 2005

AbstractThe effects of insulin and insulin‐like growth factor‐I (IGF‐I) on amino acid transport and protein metabolism were compared in myotubes derived from chicken breast muscle satellite cells. Protein synthesis was assessed by continuous labelling with [3H]‐tyrosine. Protein degradation was estimated by the release of trichloroacetic acid (TCA) soluble radioactivity by cells which had been previously labelled with [3H]‐tyrosine for 3 days. Amino acid transport was measured in myotubes incubated in Dulbecco's modified Eagle's medium (DMEM) 0.5% bovine serum albumin (BSA) with or without insulin or IGF‐I. Subsequent [3H]‐aminoisobutyric acid (AIB) uptake was then measured in amino acid‐free medium. IGF‐I was more efficient than insulin at equimolar concentration (3.2 nmol/l) in stimulating protein synthesis (127 and 113% of basal, respectively) and inhibiting protein degradation (32% and 13% inhibition of protein degradation following 4 h incubation). Half maximal effective concentrations for stimulation of AIB uptake were 0.27 ± 0.03 nmol/l and 34.8 ± 3.1 nmol/l for IGF‐I and insulin respectively, with maximal stimulation of about 340% of basal. Cycloheximide (3.6 μmol/l) diminished IGF‐I‐stimulated AIB uptake by 55%. Chicken growth hormone had no effect on basal AIB uptake in these cells and neither glucagon nor dexamethasone had an effect on basal or IGF‐I‐stimulated AIB uptake. This study demonstrates an anabolic effect for IGF‐I in myotubes derived from primary chicken satellite cells which is mediated by the type I IGF receptor, since the cation‐independent mannose 6‐phosphate receptor does not bind IGF‐II in chicken cells. © 1993 Wiley‐Liss, Inc.