bluuebunny/crossref_metadata_2025_split huggingface dataset:
Long‐term exposure to chromium(VI) oxide leads to defects in sulfate transport system in chinese hamster ovary cells
Authors: Lu Yi‐Yi , Yang Jia‐Ling 
Published: May 2005

AbstractChromium(VI) resistant Chinese hamster ovary (CHO) cell lines were established in this study by exposing parental CHO‐K1 cells to sequential increases in CrO3 concentration. The final concentration of CrO3 used for selection was 7 μM for Cr7 and 16 μM for Cr16 cells. Cr16‐1 was a subclone derived from Cr16 cells. Next, these resistant cells were cultured in media without CrO3 for more than 6 months. The resistance of these cells to CrO3 was determined by colony‐forming ability following a 24‐h treatment. The LD50 of CrO3 for chromium(VI) resistant cells was at least 25‐fold higher than that of the parental cells. The cellular growth rate, chromosome number, and the hprt mutation frequency of these chromium(VI) resistant cells were quite similar to their parental cells. The glutathione level, glutathione S‐transferase, catalase activity, and metallothionine mRNA level in Cr7 and Cr16‐1 cells were not significantly different from their parental cells. Furthermore, Cr16‐1 cells were as sensitive as CHO‐K1 cells to free‐radical generating agents, including hydrogen peroxide, nickel chloride, and methanesulfonate methyl ester, and emetine, i.e., a protein synthesis inhibitor. The uptake of chromium(VI) and the remaining amount of this metal in these resistant and the parental cell lines were assayed by atomic absorption spectrophotometry. Experimental results indicated that a vastly smaller amount of CrO3 entered the resistant cell lines than their parental cells did. A comparison was made of the sulfate uptake abilities of CHO‐K1 and chromium(VI) resistant cell lines. These results revealed that the uptake of sulfate anion was substantially reduced in Cr7 and Cr16‐1 cells. Extracellular chloride reduced sulfate uptake in CHO‐K1 but not in Cr16‐1 cells. Therefore, the major causative for chromium(VI) resistance in these resistant cells could possibly be due to the defects in SO42‐/C1− transport system for uptake chromium(VI).
Unidirectional potentiation of binding between two anti‐FBP MAbs: Evaluation of involved mechanisms
Authors: Casaline Patrizia , Mezzanzanica Delia , Valota Olga , Adobati Elena , Tomassetti Antonella , Colnaghi Maria I. , Canevari Silvana 
Published: May 2005

AbstractThe monoclonal antibody MOv19 directed to a folate binding protein shows temperature‐dependent potentiation of binding of the noncompeting monoclonal antibody MOv18 to the relevant antigen, but the mechanism involved in this phinomenon had remained unclear. Use of chimeric versions of both monoclonal antibodies and the F(ab′)2 and fan fragments of MOv19 revealed an increment in MOv18 binding in all combinations irrespective of the orgin of the Fc portin of the monoclonal antibody. The potentiating effect of bivalent MOv19 fragments on 125l‐MOv18 binding was similar to that of the entire monoclonal antibody and occurred at saturating concentrations of both reagents at which monovalent binding prevails. Similarly, the monovalent fragment also induced a significant increase in MOv18 bunding. Howener, the potentiation sccurred only at very high concentrations of antibody fragment. Homologous inhibition was drastically reduced using MOv19 Fab fragment, suggesting a low binding stability of the monovalent reagent. Immunoblotting analysis and binding in the presence of exogenous purified folate binding protein indicated a cross‐linking between soluble and cell surface molecules mediated by the bivalent monoclonal antibodies. The extentof the increase in MOv18 binging at O°C with high amounts of exogenous folate binding protein was lower than that obtained at 370C in the absence of added molecule. Release of 125l‐MOv18 from the cell surface was significantly higher in the absence of MOv19 than in its presence. Affinity constant values of 125l‐MOv18 binding evaluated in the presence of MOv19 or control monoclonal antibody MINT5 were comparable, whereas the number of binding sites per cell detected by 125l‐MOv18 was significantly higher in the presence of MOv19 than MINT5. Together, the data suggest that monoclonal antibody MOv19 induces a conformational change of the molecule it binds that increases the number of antigenic sites anvailable for MOv18 binding and, in turn, the binding stability of the latter, MOv19 bivalency also contributes to the MOv18 binding increment by cross‐linking released and cell surface–anchored folate binding protein molecules. © Wiley‐Liss, Inc.
Expression of gamma‐glutamyl transpeptidase by renal epithelial cells occurs on a cell‐by‐cell basis and is inhibited by the chronic TPA treatment
Authors: Chen Jen‐Li , Amsler Kurt 
Published: May 2005

AbstractAbstract Upon attaining a confluent density, populations of the renal epithelial cell line, LLC‐PK1, express progressively many properties characteristic of the renal proximal tubule cell, including gamma‐glutamyl transpeptidase activity. Expression of transpeptidase activity was inhibited reversibly by chronic treatment with the phorbol ester tumor promoter, 12‐o‐tetradecanoylphorbol‐13‐acetate(TPA). TPA treatment inhibited expression of transpeptidase activity regardless of whether added prior to or following appearance of the activity. Increased transpeptidase activity in postconfluent cell populations was due to an increased enzyme Vmax with no change in substrate Km. TPA‐treated cell populations. exhibited a low Vmax similar to subconfluent populations. Detection of transpeptidase activity at the individual cell level by enzyme histochemistry demonstrated that near‐confluent cell populations possesed few transpeptidase activity–positive cells. Progressive expression of transpeptidase activity in the cell population was due to an increasing proportion of cells in the population possessing transpeptidase activity. There was a parallel increase in the proportion of cells expressing transpeptidase protien, detected by immunofluorescence. TPA treatment inhibited apperance of both transpeptidase activity and transpeptidase protein in virtually all cells of the population. These results demonstrate that expression of transpeptidase activity in populations of LLC‐PK1 cells occurs on a cell‐by‐cell basis and reflects expression of transpeptidase protein. Chronic treatment with TPA inhibits reversibly expression of transpeptidase activity and protein, suggesting a role for protein kinase C in regulating expression of this proximal tubule–specific property. © Wiley‐Liss, Inc.
Influence of portein tyrosine phosphorylation on the experssion of the c‐myc oncogene in cancer of the large bowel
Authors: Heruth Daniel P. , Wetmore Lori A. , Leyva Albert , Rothberg Paul G. 
Published: May 2005

AbstractWe tested the potential impact of tyrosine phosphorylation on the expression of the c‐myc gene in tow colon cancer cell lines, HCT8 and SW837. We found that the protein tyrosine kinase inhibitor genistein causes a decrease in the aboundace of c‐myc RNA and an inhibition of proliferation with a similar dose response. Geldanamycin, a mechanistically different tyrosine kinase inhibitor, also causes a decrease in both the expression of cmyc RNA and proliferation. Genistein has also been found to inhibit topoisomerase II, but the topoisomerase II inhibitor novobiocin did not lower the expression of c‐myc. The most likely interpretation is that inhibition of protein tyrosine kinase activity caused a decrease in c‐myc expression in these cells. The impact of tyrosine phosphorylation on the experssion of the c‐myc gene is further supported by the finding that inhibition of phosphotyrosine phosphatase using orthovanadate causes an increase in the level of c‐myc RNA. The effect of genistein on HCT8 cells is not dependent on the synthesis of new protein and does not involve an allteration in the stability of the massage. Analysis of transcription in the cmyc gene reveals a more complicated picture with a decrease in initiation and an increase in elongation but no net change in transcription. We speculate that the genistein induced reduction in myc experssion is the result of a posttranscriptional intranuclear event(s). © Wiley‐Liss, Inc.
Bipartite structure of the proximal promoter of a human H4 histone gene
Authors: Wright Kenneth L. , Birnbaum Mark J. , van Wijnen Andre J. , Stein Gary S. , Stein Janet L. 
Published: May 2005

AbstractThe proximal promoter of the human H4 histone gene FO108 contains two regions of in vivo protein‐DNA interaction, Sites I and II. Electrophoretic mobility shift assays using a radiolabeled DNA probe revealed that several proteins present in HeLa cell nuclear extracts bound specifically to Site I (nt‐125 to nt‐86). The most prominent complex, designated HiNF‐C, and a complex of greater mobility, HiNF‐C′, were specifically compatable by an Sp1 consensus oligonucleotide. Fractionation of HiNF‐C using wheat germ agglutinin affinity chromatography suggested that, like Sp1, HiNF‐C contains N‐acetylglucosamine moieties. Two minor complexes of even greater mobility, designated HiNF‐E and F, were compatable by ATF consensus oligonucleotides. A DNA probe carrying a site‐specific mutation in the distal portion of Site I failed to bind HiNF‐E, indicating that this protein associated specifically to this region. UV cross‐linking analysis showed that several proteins of different molecular weights interact specifically with Site I. These data indicate that Site I possesses a bipartite structure and that multiple proteins present in HeLa cell nuclear extracts specifically with Site I sequences.
Transcriptional repression of the α1(I) collagen gene by ras is mediated in part by an intronic AP1 site
Authors: Slack James L. , Parker M. Iqbal , Bornstein Paul 
Published: May 2005

AbstractWe have previously shown that transformation of fibroblasts by ras results in transcriptional inhibition of the α1(I) gene. An α1(I)‐hGH chimeric plasmid containing 3.7 kb of 5′ flanking and 4.4 kb of α1(I) transcribed sequence was regulated appropriately by ras in a transient transfection assay. In contrast, a similar plasmid containing α1(I) DNA from −220 to + 500 was virtually unresponsive to ras. The regions from −3700 to −220 and + 500 to + 4400 contributed equally to the ras‐mediated inhibition of the parental plasmid. Deletion analysis indicated that a short fragment, between +500 and +890 in the first intron of the α1(I) gene, was recognized differently in ras‐transformed and wild‐type cells. A previously described AP1 site in this fragment stimulated α1(I) transcription in Rat1 fibroblasts but was inactive in ras‐ transformed cells. Mobility shift assays using nuclear extracts from the two cell types demonstrated differences in binding to the α1(I) AP1 site. We conclude that ras transformation suppresses the function of a cell‐specific enhancer in the first intron of the α1(I) collagen gene.
Bone morphogenetic proteins inhibit adipocyte differentiation by bone marrow stromal cells
Authors: Gimble J. M. , Morgan C. , Kelly K. , Wu X. , Dandapani V. , Wang C.‐S. , Rosen V. 
Published: May 2005

AbstractThe bone morphogenetic proteins were originally identified based on their ability to induce ectopic bone formation in vivo and have since been identified as members of the transforming growth factor‐β gene superfamily. It has been well established that the bone morphogenetic cytokines enhance osteogenic activity in bone marrow stromal cells in vitro. Recent reports have described how bone morphogenetic proteins inhibited myogenic differentiation of bone marrow stromal cells in vitro. In vivo, bone marrow stromal cells differentiate along the related adipogenic pathway with advancing age. The current work reports the inhibitory effects of the bone morphorphogenetic proteins on adipogenesis in a multipotent murine bone marrow stromal cell line, BMS2. When exposed to bone morphogenetic protein‐2, the pre‐adipocyte BMS2 cells exhibited the expected induction of the osteogenic‐related enzyme, alkaline phosphatase. Following induction of the BMS2 cells with adipogenic agonists, adipocyte differentiation was assessed by morphologic, enzymatic, and mRNA markers. Flow cytometric analysis combined with staining by the lipophilic fluorescent dye, Nile red, was used to quantitate the extent of lipid accumulation within the BMS2 cells. By this morphologic criteria, the bone morphogenetic proteins inhibited adipogenesis at concentrations of 50 to 500 ng/ml. This correlated with decreased levels of adipocyte specific enzymes and mRNAs. The BMS2 pre‐adipocytes constitutively expressed mRNA encoding bone morphogenetic protein‐4 and this was inhibited by adipogenic agonists. Together, these findings demonstrate that bone morphogenetic proteins act as adipogenic antagonists. This supports the hypothesis that adipogenesis and osteogenesis in the bone marrow microenvironment are reciprocally regulated.
β3‐Adrenergic activation of adenylyl cyclase in mouse white adipocytes: modulation by GTP and effect of obesity
Authors: Bégin‐Heick Nicole 
Published: May 2005

AbstractLipolysis and adenylyl cyclase (AC) activation in response to β‐adrenergic agents are abnormally low in white epididymal adipose tissue (WAT) of the ob/ob mouse. The abundance of G‐proteins (Gsα and Giα) linked to AC is also abnormally low. By contrast, β‐adrenergic receptor (β‐AR) levels were previously found to be normal in WAT and elevated in liver. The relative importance of various forms of the β‐AR in mouse WAT was reassessed in view of the discovery of the β3‐AR. The results show that (1) the β3‐AR is mainly responsible for AC activation in lean‐mouse WAT; (2) the β3‐AR is only partly responsible for AC activation in obese mouse WAT; and (3) GTP modulates β3—‐but not β1—‐or β2‐AR activation of AC in a biphasic manner. Therefore, the β3‐AR appears responsible for the well‐known bimodal effect of GTP on β‐adrenergic receptor‐mediated AC activity in WAT.
Overexpression of cellular activity and protein level of protein kinase FA/GSK‐3α correlates with human thyroid tumor cell dedifferentiation
Authors: Lee Tsong‐Tze , Ho Yat‐Sen , Yu Jau‐Song , Yang Shiaw‐Der 
Published: May 2005

AbstractAbstract Computer analysis of protein phosphorylation sites sequence revealed that transcriptional factors and viral oncoproteins are prime targets for regulation of proline‐directed protein phosphorylation, suggesting an association of the proline‐directed protein kinase (PDPK) family with neoplastic transformation and tumorigenesis. In this report, an immunoprecipitate activity assay of protein kinase FA/glycogen synthase kinase‐3α (kinase FA/GSK‐3α) (a member of the PDPK family) has been optimized for human thyroid tissue and used to demonstrate for the first time significantly increased (P < 0.001) activity in thyroid carcinoma (24.2 ± 2.8 units/mg of protein) (n = 7), thyroid adenoma (14.5 ± 2.2 units/mg of protein) (n = 6), and thyroid hyperplasia (8.0 ± 2.4 units/mg of protein) (n = 5) when compared to five normal controls (4.1 ± 1.8 units/mg of protein). Immunoblotting analysis further revealed that increased activity of kinase FA/GSK‐3α in thyroid tumor cells is due to overexpression of protein level and cellular activity of kinase FA/GSK‐3α is involved in human thyroid tumor cell dedifferentiation, supporting an association of PDPK with neoplastic transformation and tumorigenesis. Since kinase FA/GSK‐3α may function as a possible regulator of transcription factors/protooncogenes, kinase FA/GSK‐3α may therefore play an important role in thyroid cell carcinogenesis, especially in its differentiation.
Light and electron microscopic immunocytochemical localization of two major proteins in garlic bulb
Authors: Wen G. Y. , Mato A. , Wisniewski H. M. , Malik M. N. , Jenkins E. C. , Sheikh A. M. , Kim K. S. 
Published: May 2005

AbstractGarlic is known as a potent spice and a medicine with broad therapeutic properties ranging from antibacterial to anticancer, antidiabetic, and anticoagulant. Two major proteins of 40 KD and 14 KD constituting approximately 96% of total garlic proteins have been recently purified at our Institute. This immunocytochemical and ultrastructural study revealed that the 40 KD protein was localized in the parenchyma sheath cells (PSC) of garlic bulbs, whereas the 14 KD protein was present in the cortical cells (CC). Immunogold electron microscopy study indicated that the 40 KD protein was specifically localized in the globular granules of the cytoplasmic area of PSC. Each globular granule was amorphous and homogenous with membrane limiting its outermost layer. The yellowish color of PSC in freshly cut slices of garlic bulb suggested that PSC may have sulfur‐containing compounds such as allicin, the primary contributor of the pungency and medicinal properties of garlic. Ellman's reagent test quantitatively revealed that there were 17.8 n moles sulfhydryl (SH)/ml of 40 KD garlic protein. Microtubule tubulin in mitotic figures from PHA‐stimulated human short‐term whole blood cultures reacted strongly with antitubulin antibody but reacted negatively with anti‐40 KD garlic protein antibodies and therefore was not related to the 40 KD garlic protein immunocytochemically.
Molecular mechanisms of bone resorption
Authors: Teitelbaum Steven L. , Abu‐Amer Yousef , Ross F. Patrick 
Published: May 2005

AbstractThis review focuses on osteoclast ontogeny and function, emphasizing three aspects. We describe how a combination of laboratory models available to study the cell plus examination of the osteopetroses, a family of sclerotic diseases of the skeleton, have yielded major insights into osteoclast ontogeny and function. We proceed to describe the cell and molecular machinery enabling osteoclasts to resorb bone. The final, and most speculative, aspect of the review addresses possible mechanisms by which the osteoclast assumes its characteristic morphology, that of a polarized cell on bone. Since little direct information has been forthcoming as to how the osteoclast polarizes, we draw on other polarized cells. In particular, we examine the role of microtubules and members of the small GTPase family, the latter mediating polarized targeting of intracellular vesicles. In the case of the osteoclast, such vesicles probably represent the origin of the highly convoluted ruffled membrane, the cell's characteristic bone resorptive organ. © 1995 Wiley‐Liss, Inc.
Possible role for protein kinase C in the pathogenesis of inborn errors of metabolism
Authors: Boneh Avihu 
Published: May 2005

AbstractProtein kinase C (PKC) is a ubiquitous enzyme family implicated in the regulation of a large number of short‐ and long‐term intracellular processes. It is hypothesized that modulation of PKC activity may represent, at least in part, a functional link between mutations (genotype) that lead to the pathological accumulation of naturally occurring compounds that affect PKC activity and perturbation of PKC‐mediated substrate phosphorylation and cellular function in the corresponding diseases (phenotype). This model provides a unifying putative mechanism by which the phenotypic expression of some inborn errors of metabolism may be explained.Recent studies in a cell‐free system of human skin fibroblasts support the hypothesis that alteration of PKC activity may represent the functional link between accumulation of sphingolipids and fatty acyl‐CoA esters, and perturbation of cell function in sphingolipidoses and fatty acid oxidation defects, respectively. Further studies will elucidate the effects of these alterations on PKC‐mediated short‐ and long‐term cellular functions in these diseases, as well as the possible role of PKC in the pathogensis of other diseases. © 1995 Wiley‐Liss, Inc.
Synthesis of stromal glycosaminoglycans in response to injury
Authors: Brown C. T. , Applebaum E. , Banwatt R. , Trinkaus‐Randall V. 
Published: May 2005

AbstractOur goal is to examine the synthesis and deposition of corneal glycosaminoglycans (GAGs) in response to a wound created by the insertion of porous discs into stromal interlamellar pockets. The disc and the surrounding stromal tissue were assayed and compared to contralateral control stroma and to sham operated corneas at 14,42, and 84 days. The tissue and/or discs were removed and labeled with 35S‐sulfate for 18 h; GAGs were extracted with 4 M guanidine–HCl. Extracts were chromatographed on Q‐Sepharose columns, bound proteoglycans were eluted with a linear salt gradient, and radioactive fractions were analyzed. Total GAG content was determined colorimetrically, using dimethylmethylene blue. Specific GAGs were determined using enzymatic digestion with selective polysaccharide lyases and protein cores were examined using SDS–PAGE. The nonbound fractions from the chromatography were assayed for TGF‐β using Western blot analysis and for hyaluronic acid using an 125I‐radiometric assay. Specific GAGs were localized 42 days after the disc had been implanted in the stroma. The placement of the discs into the stroma resulted in a decrease in the total amount of GAG. However, the ratio of dermatan‐chondroitin sulfate and heparan sulfate to keratan sulfate increased in the surrounding tissue and disc. Hyaluronic acid was elevated at day 14 in the surrounding tissue, and not until day 84 in the disc. Western blot analysis of surrounding tissue extracts revealed forms of TGF‐β that migrated with an apparent molecular mass of 63 and 43 kDa. The results indicate that the insertion of discs into interlamellar pockets causes changes in the sulfation and proportion of the glycosaminoglycans in the surrounding tissue and the disc. These changes are coincident with the appearance of TGF‐β. After 84 days, the population of glycosaminoglycans in the disc begins to resemble the surrounding stroma. This model will allow us to examine further the synthesis and deposition of proteins following an extensive wound in which cells must migrate to the wound site and then undergo extensive remodeling. © 1995 Wiley‐Liss, Inc.
Purification and stability characterization of a cell regulatory sialoglgycopeptide inhibitor
Authors: Moos Philip J. , Fattaey Heideh K. , Johnson Terry C. 
Published: May 2005

AbstractPrevious attempts to physically separate the cell cycle inhibitory and protease in activities in preparations of a purified cell regulatory sialoglycopeptide (CeReS) inhibitor were largely unsuccessful. Gradient elution of the inhibitor preparation from a DEAE HPLC column separated the cell growth inhibitor from the protease, and the two activities have been shown to be distinct and non‐overlapping. The additional purification increased the specific biological activity of the CeReS preparation by approximately two‐fold. The major inhibitory fraction that eluted from the DEAE column was further analyzed by tricine‐SDS‐PAGE and microbore reverse phase HPLC and shown to be homogeneous in nature. Two other fractions separated by DEAE HPLC, also devoid of protease activity, were shown to be inhibitory to cell proliferation and most likely represented modified relatives of the CeReS inhibitor. The highly purified CeReS was chemically characterized for amino acid and carbohydrate composition and the role of the carbohydrate in cell proliferation inhibition, stability, and protease resistance was assessed. © 1995 Wiley‐Liss, Inc.