bluuebunny/crossref_metadata_2025_split huggingface dataset:
Insulin receptor signaling through non‐tyrosine kinase pathways: Evidence from anti‐receptor antibodies and insulin receptor mutants
Authors: Sung Chin K. 
Published: May 2005

AbstractAlthough there is general agreement that insulin receptor tyrosine kinase activity mediates many of the actions of insulin, two types of studies suggest that non‐tyrosine kinase dependent pathways may also exist. First, both monoclonal and polyclonal antibodies to the receptor have been shown to mediate many of insulin's actions with little or no stimulation of receptor kinase. Second, insulin receptor mutants, with reduced or no tyrosine kinase activity, have been shown to mediate several actions of insulin. Non‐tyrosine kinase pathways that could signal insulin effects through the insulin receptor include non‐covalent activation of G proteins, phospholipase Cs, or docking proteins such as IRS‐1. Further studies on the chemical structures of phospholipids and their hydrolysis products involved in insulin action will be required to sort out the underlying mechanisms of insulin action via non‐tyrosine kinase dependent pathways.
Alterations in glucose transporter expression and function in diabetes: Mechanisms for insulin resistance
Authors: Kahn Barbara B. 
Published: May 2005

AbstractInsulin resistance is a major pathologic feature of human obesity and diabetes. Understanding the fundamental mechanisms underlying this insulin resistance has been advanced by the recent cloning of the genes encoding a family of facilitated diffusion glucose transporters which are expressed in characteristic patterns in mammalian tissues. Two of these transporters, GLUT1 and GLUT4, are present in muscle and adipose cells, tissues in which glucose transport is markedly stimulated by insulin. To understand the mechanisms underlying in vivo insulin resistance, regulation of these transporters is being investigated. Studies reveals divergent changes in the expression of GLUT1 and GLUT4 in a single cell type as well as tissue specific regulation. Importantly, alterations in glucose transport in rodent models of diabetes and in human obesity and diabetes cannot be entirely explained by changes in glucose transporter expression. This suggests that defects in glucose transporter function such as impaired translocation, fusion with the plasma membrane, or activation probably contribute importantly to in vivo insulin resistance.
Rate transition and regulatory coupling in endocytosis of interferon‐α and tumor necrosis factor‐α in human epithelial tumor cells
Authors: Vuk‐Pavlović Stanimir , Bajzer Željko 
Published: May 2005

AbstractThe time‐dependent concentrations of interferon‐α and tumor necrosis factor‐α associated with the membrane and internalized by cells contain information on the kinetics of endocytosis and their cellular processing. This information can be reduced quantitatively by application of the respective compartmental models. In our studies of human epithelial tumor cells interacting with human interferon‐α and human tumor necrosis factor ‐α, we accounted only for actual endocytosis and elimination of the tracer from cells by a novel method sensitive to changes in the rate of endocytosis, to the delay in tracer elimination, and to the nonlinear regulatory coupling between endocytosis and the internalized ligand. Data reduced by this method resulted in best‐fit parameter values statistically superior to values obtained by previous methods (Bajzer et al., 1989). The results indicate a change with time in the rate of endocytosis of tumor necrosis factor‐α and the inhibition of endocytosis by the endocytosed ligand‐receptor complex. We conclude that sorting and processing of interferon‐α and tumor necrosis factor ‐α are restricted by the type of both the receptor and the cell.
Vitamin D: Structure‐function analyses and the design of analogs
Authors: Okamura William H. , Palenzuela J. Antonio , Plumet Joaquin , Midland M. Mark 
Published: May 2005

AbstractThere is continuing and emerging new interest in the development of vitamin D analogs resulting from the recognition that analogs of 1α,25‐dihydroxyvitamin D3 [1α,25‐(OH)2D3] may be therapeutically useful. Side chain analogs of this steroid hormone are of particular interest because a family of lead structures have recently emerged for possible use in the treatment of certain types of cancers and skin diseases. Because of the chaotic array of side chain structures which exhibit useful therapeutic indices for these purposes, a more systematic approach towards developing intelligible structure‐function information needs development. Accordingly, a method has been devised to analyze analogs as to their side chain topology based on identifying specific occupancy volumes through conformational analysis. Dot maps have been constructed as an indication of the volume in space which the side chain of 1α,25‐(OH)2‐D3 or analogs is permitted to occupy. Volume exclusion analyses based on comparison of structural and biological data for 1α,257‐(OH)2‐D3 and analogs are anticipated to lead to a more cogent model for drug design. A cautionary note on the limitations of this approach is discussed.
Immunomodulatory role of 1,25‐dihydroxyvitamin D3
Authors: Lemire Jacques M. 
Published: May 2005

AbstractThe active vitamin D metabolite 1,25‐dihydroxyvitamin D3 [1,25‐D3] is thought to promote many of its actions through interaction with a specific intracellular receptor. The discovery of such receptors in monocytes and activated lymphocytes has led investigators to evaluate the role of the hormone on the immune system. The sterol inhibits lymphocyte proliferation and immunoglobulin production in a dose‐dependent fashion. At a molecular level, 1,25‐D3 inhibits the accumulation of mRNA for IL‐2, IFN‐γ, and GM‐CSF. At a cellular level, the hormone interferes with T helper cell (Th) function, reducing Th‐induction of immunoglobulin production by B cells and inhibiting the passive transfer of cellular immunity by Th‐clones in vivo. The sterol promotes suppressor cell activity and inhibits the generation of cytotoxic and NK cells. Class II antigen expression on lymphocytes and monocytes is also affected by the hormone.When given in vivo, 1,25‐D3 has been particularly effective in the prevention of autoimmune diseases such as experimental autoimmune encephalomyelitis and murine lupus but its efficacy has been limited by its hypercalcemic effect. Synthetic vitamin D3 analogues showing excellent 1,25‐D3‐receptor binding but less pronounced hypercalcemic effects in vivo have recently enhanced the immunosuppressive properties of the hormone in autoimmunity and transplantation.
Effect of TSH in human thyroid cells: Evidence for both mitogenic and antimitogenic effects
Authors: Milazzo Giovanni , La Rosa Giacomo Lucio , Catalfamo Rosaria , Vigneri Riccardo , Belfiore Antonino 
Published: May 2005

AbstractThe well‐known mitogenic effects of TSH observed in vivo on the thyroid are not always reproducible on human thyroid cells in vitro where conflicting results have been obtained. In order to clarify this issue, we have used primary cultures of human thyroid cells obtained from normal tissue and maintained in serum‐free medium for several days. In this in vitro model we have studied the effect of TSH on growth by measuring three different parameters: [3H]‐thymidine incorporation, cell counts, and DNA measurement. Monolayer cultures were plated at both low and high cell density (2 × 104 and 8 × 104 cells/25 mm well, respectively). Although at either cell density cultures were equally able to functionally respond to TSH in terms of cAMP accumulation a significant growth response to TSH was observed only in low density cultures. In high density cultures TSH had an antimitogenic effect. Moreover, TSH potentiated the mitogenic effect of insulin only in low density cultures. In contrast to TSH, FCS induced a similar proliferative response at both high and low cell density. Following TSH stimulation, cAMP content was always increased, paralleling the effect of growth in low density but not in high density cultures. The cAMP analogues dibutyryl‐cAMP and 8‐bromo‐cAMP, as well as cholera toxin and forskolin, did not mimic the mitogenic effect of TSH but had an antiproliferative effect. In addition, these agents blunted the proliferative effect of insulin.These data suggest that in thyroid cells TSH is able to elicit both a mitogenic and an antimitogenic effect depending on the environmental conditions such as cell density. Moreover, they confirm the existence of cAMP independent pathways for thyroid cell growth. They also provide an explanation for the equivocal effects observed in vitro on human thyroid cell growth after stimulation with TSH.
Expression of cell growth and bone specific genes at single cell resolution during development of bone tissue‐like organization in primary osteoblast cultures
Authors: Pockwinse Shirwin M. , Wilming Laurens G. , Conlon Donna M. , Stein Gary S. , Lian Jane B. 
Published: May 2005

AbstractPrimary cultures of calvarial derived normal diploid osteoblasts undergo a developmental expression of genes reflecting growth, extracellular matrix maturation, and mineralization during development of multilayered nodules having a bone tissue‐like organization. Scanning electron microscopy of the developing cultures indicates the transition from the uniform distribution of cuboidal osteoblasts to multilayered nodules of smaller cells with a pronounced orientation of perinodular cells towards the apex of the nodule. Ultrastructural analysis of the nodule by transmission electron microscopy indicates that the deposition of mineral is confined to the extracellular matrix where cells appear more osteocytic. The cell body contains rough endoplasmic reticulum and golgi, while these intracellular organelles are not present in the developing cellular processes. To understand the regulation of temporally expressed genes requires an understanding of which genes are selectively expressed on a single cell basis as the bone tissue‐like organization develops. In situ hybridization analysis using 35S labelled histone gene probes, together with 3H‐thymidine labelling and autoradiography, indicate that greater than 98% of the pre‐confluent osteoblasts are proliferating. By two weeks, both the foci of multilayered cells and internodular cell regions have down‐regulated cell growth associated genes. Post‐proliferatively, but not earlier, initial expression of both osteocalcin and osteopontin are restricted to the multilayered nodules where all cells exhibit expression. While total mRNA levels for osteopontin and osteocalcin are coordinately upregulated with an increase in mineral deposition, in situ hybridization has revealed that expression of osteocalcin and osteopontin occurs predominantly in cells associated with the developing nodules. In contrast, proliferating rat osteosarcoma cells (ROS 17/2.8) concomitantly express histone H4, along with osteopontin and osteocalcin. These in situ analyses of gene expression during osteoblast growth and differentiation at the single cell level establish that a population of proliferating calvarial‐derived cells subsequently expresses osteopontin and osteocalcin in cells developing into multilayered nodules with a tissue‐like organization.
Reversible hyperphosphorylation and reorganization of vimentin intermediate filaments by okadaic acid in 9L rat brain tumor cells
Authors: Lee Wen‐Chuan , Yu Jou‐Song , Yang Shiaw‐Der , Lai Yiu‐Kay 
Published: May 2005

AbstractOkadaic acid (OA), a protein phosphatase inhibitor, was found to induce hyperphosphorylation and reorganization of vimentin intermediate filaments in 9L rat brain tumor cells. The process was dose dependent. Vimentin phosphorylation was initially enhanced by 400 nM OA in 30 min and reached maximal level (about 26‐fold) when cells were treated with 400 nM OA for 90 min. Upon removal of OA, dephosphorylation of the hyperphosphory‐lated vimentin was observed and the levels of phosphorylation returned to that of the controls after the cells recovered under normal growing conditions for 11 h. The phosphorylation and dephosphorylation of vimentin induced by OA concomitantly resulted in reversible reorganization of vimentin filaments and alteration of cell morphology. Cells rounded up as they were entering mitosis in the presence of OA and returned to normal appearance after 11 h of recovery. Immuno‐staining with anti‐vimentin antibody revealed that vimentin filaments were disassembled and clustered around the nucleus when the cells were treated with OA but subsequently returned to the filamentous states when OA was removed. Two‐dimensional electrophoresis analysis further revealed that hyperphosphorylation of vimentin generated at least seven isoforms having different isoelectric points. Furthermore, the enhanced vimentin phosphorylation was accompanied by changes in the detergent‐solubility of the protein. In untreated cells, the detergent‐soluble and ‐insoluble vimentins were of equal amounts but the solubility could be increased when vimentins were hyperphosphorylated in the presence of OA. Taken together, the results indicated that OA could be involved in reversible hyperphosphorylation and reorganization of vimentin intermediate filaments, which may play an important role in the structure‐function regulation of cytoskeleton in the cell.
Stable expression of a cDNA encoding a human β1 → 3galactosyltransferase responsible for lacto‐series type 1 core chain synthesis in non‐expressing cells: Variation in the nature of cell surface antigens expressed
Authors: Sherwood Anne L. , Greene Thomas G. , Holmes Eric H. 
Published: May 2005

AbstractTransient expression of a human colonic adenocarcinoma Colo 205 cell derived cDNA in cell lines which ordinarily express only neolacto‐series glycolipids has resulted in the expression of a β1 → 3galactosyltransferase gene responsible for synthesis of glycolipids based upon the lacto‐series type 1 core chain. Calcium phosphate transfected cells were panned on anti‐lgM coated plates after initial treatment with a combination of monoclonal antibodies specific for type 1 chain terminal structures (TE‐3) and a very broadly specific antibody reactive with multiple type 1 chain derivatives (TE‐2). Adherent cells after panning were capable of efficiently transferring Gal in β1 → 3‐linkage to the acceptor glycolipid Lc3. Using these reagents, clones of stably transfected human colonic adenocarcinoma HCT‐15 cells were produced and isolated. Parental HCT‐15 cells do not express type 1 chain based antigens. The nature of the type 1 chain based antigens produced in each of these clones was analyzed by solid phase antibody binding assays. Three types of behavior were observed. Formation of type 1 terminal structures that were either exclusively sialylated or fucosylated, or a mixture of sialylated and fucosylated determinants occurred. In contrast, no difference in type 2 antigen expression between any clone and the parental cells was observed. These data suggest that coordination of subsequent reactions capable of modifying type 1 chain structures is not the same in all clones. The relationship of these results to aspects of cellular regulation of carbohydrate biosynthesis is discussed. © 1992 Wiley‐Liss, Inc.
Use of microgravity bioreactors for development of an in vitro rat salivary gland cell culture model
Authors: Lewis Marian L. , Moriarity Debra M. , Campbell P. Samuel 
Published: May 2005

AbstractDuring development, salivary gland (SG) cells both secrete factors which modulate cellular behavior and express specific hormone receptors. Whether SG cell growth is modulated by an autocrine epidermal growth factor (EGF) receptor‐mediated signal transduction pathway is not clearly understood. SG tissue is the synthesis site for functionally distinct products including growth factors, digestive enzymes, and homeostasis maintaining factors. Historically, SG cells have proven difficult to grow and may be only maintained as limited three‐dimensional ductal‐type structures in collagen gels or on reconstituted basement membrane gels. A novel approach to establishing primary rat SG cultures is use of microgravity bioreactors originally designed by NASA as low‐shear culture systems for predicting cell growth and differentiation in the microgravity environment of space. These completely fluid‐filled bioreactors, which are oriented horizontally and rotate, have proven advantageous for Earth‐based culture of three‐dimensional cell assemblies, tissue‐like aggregates, and glandular structures. Use of microgravity bioreactors for establishing in vitro models to investigate steroid‐mediated secretion of EGF by normal SG cells may also prove useful for the investigation of cancer and other salivary gland disorders. These microgravity bioreactors promise challenging opportunities for future applications in basic and applied cell research. © 1993 Wiley‐Liss, Inc.
Binding of tissue‐type plasminogen activator to human melanoma cells
Authors: Bizik Jozef , Stephens Ross W. , Grofova Marta , Vaheri Antti 
Published: May 2005

AbstractWe have shown (Bizik et al., Cell Regul 1:895–905, 1990) that tPA can activate plasminogen on the surface of human melanoma cells in the presence of α2‐macroglobulin (α2M) secretion. In the present study, we investigated the binding of tPA on the surface of Bowes melanoma cells, selected since they lacked production of PAI‐1 and α2M. Elution of tPA from the cell layers indicated that polylysine (5 μg/ml) and tranexamic acid (10 mM), an analog of lysine, were the most efficient agents for disrupting the interaction between tPA and cell surface component(s). Using a panel of monoclonal antibodies against individual domains of tPA revealed that an antibody directed to the kringle‐2 domain of tPA interfered most significantly with cell‐surface plasmin generation. As tPA is a glycoprotein, interactions between the tPA sugar moieties and cell surface were also tested by the use of a series of monosaccharides. N‐acetyl‐D‐glucosamine (100 mM) was the most potent sugar to release tPA from melanoma cells, but the results indicated that the oligosaccharides of tPA play only a supportive role in the binding of tPA to the cell surface. Quantitative comparison of the cell surface localized tPA, which was eluted by tranexamic acid, with the total cellular tPA showed that cell surface bound tPA could represent up to 10%. We conclude that tPA interacts with the melanoma cell surface in a similar manner as has been described for binding of tPA to fibrin and to the putative endothelial cell surface receptor. © 1993 Wiley‐Liss, Inc.
Role of transverse tubules in insulin stimulated muscle glucose transport
Authors: Dohm G. Lynis , Dolan Patricia L. , Frisell Wilhelm R. , Dudek Ronald W. 
Published: May 2005

AbstractAlthough the strongest evidence for recruitment of glucose transporters in response to insulin comes from studies with adipocytes, studies in muscle seem in general to confirm that glucose transporters are also translocated to the cell membrane in muscle in response to insulin. However, the observation that transverse tubule (T‐tubule) membranes contain approximately five times more glucose transporter than sarcolemma raised a question as to where glucose transport occurs in muscle. The T‐tubule membrane system is continuous with the surface sarcolemma and is a tubule system in which extracellular fluid is in proximity with the interior of the muscle fiber. The purpose of this Prospects article is to evaluate the possibility that the T‐tubule membrane may represent a major site of glucose transport in skeletal muscle.Using immunocytochemical techniques we have located GLUT4 glucose transporters on the T‐tubule membrane and in vesicles near T‐tubules. Since T‐tubules form channels into the interior of the muscle fiber, glucose could diffuse or be moved by some peristaltic‐like pumping action into the transverse tubules and then be transported across the membrane deep into the interior of the muscle fiber. This mode of transport directly into the interior of the cell would be advantageous over transport across the sarcolemma and subsequent diffusion around the myofibrils to reach the interior of the muscle. Thus, in addition to the role of the T‐tubule in ion fluxes and contraction, this unique membrane system can also provide a pathway for the delivery of substrates into the center of the muscle cell where many glycolytic enzymes and glycogen deposits are located.
Spatial organization of the synthesis of cytoskeletal proteins
Authors: Fulton A. B. 
Published: May 2005

AbstractThe cytoskeleton of most cells is complex and spatially diverse. The mRNAs for some cytoskeletal proteins are localized, suggesting that synthesis of these proteins may occur at sites appropriate for function or assembly. mRNA concentrations were first observed for several oocyte and embryonic mRNAs. Some insight has been gained into the mechanisms that help to position these mRNAs. More surprising to some, many cytoskeletal mRNAs are also localized. Among them are mRNAs for actin, tubulin, intermediate filaments, and a variety of associated proteins. Different mRNAs in the same cell can be located in different places; the same mRNA can be located in different places; the same mRNA can be located differently at different times of development. For example, we observed vimentin mRNA in developing chicken muscle cultures by fluorescent in situ hybridization. We found that vimentin mRNA takes on a variety of positions during myogenesis, ending up located with its cognate protein at costameres. This last pattern is significant because it is too finely structured to have a function in the soluble phase and probably reflects contranslational assembly of this particular protein. Analogies can be made between oocyte or embryonic positions (animal/vegetal poles, oocyte cortex, and interior) and somatic cell positions (anterior/posterior and cell cortex/cell center). These analogies may point to conserved mechanisms for moving and retaining mRNA. Localization of cytoskeletal synthesis, through the mRNA or by other means, may prove as important for assembling and maintaining differentiated cytoskeletal structures and somatic cells as mRNA location is for organizing the embryo. Mechanisms that permit mRNA localization are likely to be conserved.
Expression of insulin‐like growth factor binding proteins in human breast cancer correlates with estrogen receptor status
Authors: Figueroa Jose A. , Jackson James G. , McGuire William L. , Krywicki Robert F. , Yee Douglas 
Published: May 2005

AbstractThe insulin‐like growth factors (IGFs) have been implicated in the growth regulation of human breast cancer. Since the IGFs are associated with specific binding proteins (IGFBPs) which may modulate receptor/ligand interactions, production of IGFBPs by breast cancer cells could alter their IGF‐dependent growth. This study examined the expression of IGFBPs 4, 5, and 6 in eight breast cancer cell lines (BCCLs) using ribonuclease (RNase) protection assays. IGFBP‐4 mRNA was detected in all BCCLs studied. IGFBP‐5 expression was higher in estrogen receptor (ER) positive cells, while IGFBP‐6 mRNA was detected in only two ER negative BCCLs. We also found that E2 treatment enhanced the expression of IGFBPs 2, 4, and 5 in T47‐D cells. We next studied IGFBP mRNA expression in 40 primary breast tumors. All tumors expressed mRNA for IGFBPs 2–6 but none expressed IGFBP‐1 message. IGFBP‐3 expression was higher in ER negative tumors, while that of IGFBP‐4 and ‐5 was higher in ER positive specimens. These differences were statistically significant (P < .05). Ligand blot analysis of tumor extracts confirmed the presence of IGFBPs in breast cancer tissues. Thus, differential IGFBP expression in ER positive and negative tumors suggests an important role for this protein in breast cancer biology.