bluuebunny/crossref_metadata_2025_split huggingface dataset:
Insulin stimulates GDP release from G proteins in the rat and human liver plasma membranes
Authors: Ravindra R. , Caro J. F. 
Published: May 2005

AbstractPlasma membranes (1–2 mg protein) prepared from the livers of adult male rats and human organ donors were incubated with 0.6 μM [α‐32P] guanosine triphosphate (GTP) in an adenosine triphosphate (ATP)‐regenerating buffer at 37°C for 1 h; during this incubation, the [32P]GTP is hydrolyzed and the nucleotide that is predominantly bound to the membranes is [32P] guanosine diphosphate (GDP). [32P]GDP release from the liver membranes was proportional to the protein concentration and increased as a function of time. At 5 mM, Ca2+, Mg2+, Mn2+, and Zn2+ maximally inhibited GDP release by 80–90%, whereas, 5 mM Cu2+ maximally stimulated the reaction by 100%. Therefore, cations were not included in the buffer used in the GDP release step. One μM Gpp(NH)p (5′‐guanylylimidodiphosphate), a nonhydrolyzable analog of GTP, maximally stimulated [32P]GDP release in the liver membranes by up to 30%. Although 10 nM Gpp(NH)p had no effect on GDP release, it appeared to stabilize the hormonal effect by blocking further GDP/GTP exchange.In the rat membranes, 1–100 nM glucagon (used as a positive control) stimulated [32P]GDP release by about 17% (P < .05); similarly, 0.1–100 nM insulin stimulated [32P]GDP release by 10–13% (P < .05). In the human membranes, 10 pM to 100 nM insulin stimulated [32P]GDP release by 7–10%. In the rat membranes, 10 nM insulin stimulated [32P]GDP release by 17 and 24% at 2 and 4 min, respectively (P < .05); in the human membranes, 10 nM insulin stimulated [32P]GDP release by about 9% at 2 and 4 min. Normal rabbit IgG (used as a control for insulin receptor antibody) by itself stimulated the GDP release by rat and human membranes. However, the stimulation of the GDP release by insulin receptor antibody was consistently higher than that observed with normal rabbit IgG. Four to 15 μg of insulin receptor antibody stimulated [32P]GDP release by 12–22% (P < .05) and 7–14% in rat and human membranes, respectively. These results indicate that ligand binding to the insulin receptor results in a functional interaction of the receptor with a guanine nucleotide‐binding transducer protein (G protein) and activation of GTP/GDP exchange.
Identification and characterization of two proximal elements in the rat osteocalcin gene promoter that may confer species‐specific regulation
Authors: Heinrichs A. A. J. , Banerjee C. , Bortell R. , Owen T. A. , Stein J. L. , Stein G. S. , Lian J. B. 
Published: May 2005

AbstractThe rat osteocalcin gene encodes a 6‐kD osteoblast‐specific protein that is expressed postproliferatively. The developmental and steroid hormone responsive expression of the osteocalcin gene is transcriptionally regulated by a promoter with multiple basal and enhancer elements that exhibit activity controlled by a series of physiological mediators (e.g., 1,25(OH)2D3, glucocorticoids). In this study, we established the contribution of the rat osteocalcin (OC) box domain ( −99 to −76), a proximal basal element with a CCAAT motif as a central core, to transcriptional activity of the rat osteocalcin gene with in vivo co‐transfection assays. By this same assay, however, the highly homologous (22 of 24 nt) human OC box element was unable to compete for transcription factor binding with the rat OC promoter. In vitro protein/DNA interaction studies confirm the presence of two protein binding sites in the OC box region, one of which overlaps the CCAAT motif and, at least in part, accounts for species‐specific expression. Competition analysis established that the single nucleotide substitution of adenine for thymine, which converts the core motif of the rat OC box (CCAAT) to the core motif of the human OC box (CCAAA), accounts for observed species differences in transcription factor interactions. The CCAAT‐specific protein/DNA interactions are heat stable and insensitive to phosphatase treatment. A second protein/DNA interaction located upstream of the CCAAT motif includes two steroid‐like half‐elements. These interactions are heat labile and sensitive to phosphatase treatment in contrast to the CCAAT‐specific interactions. The human OC promoter contains only a single steroid‐like half‐element, while two steroid half‐elements with an 11 nucleotide spacer are present in the rat OC promoter. These observed variations in sequence organization and transactivation factor binding in analogous proximal basal regulatory regions of the OC gene promoter may provide a basis for species‐restricted variations in responsiveness to physiological mediators of OC gene expression at the transcriptional level.
Differential distribution of vesicular carriers during differentiation and synapse formation
Authors: Bursztajn Sherry , Jong Yei J. , Berman S. A. 
Published: May 2005

AbstractCoated and noncoated vesicles participate in cellular protein transport. Both acetylcholine receptors (AChR) and acetylcholinesterase (AChE) are transported via coated vesicles, some of which accumulate beneath the neuromuscular synapse where AChRs cluster. To investigate the mechanisms by which these proteins are transported during postsynaptic remodeling, we purified coated vesicles from the bovine brain via column chromatography (Sephacryl S‐1000) and raised monoclonal antibodies to epitopes of the vesicular membranes enriched in AChE. We assayed for AChE (coated vesicle enriched), hexosaminidase (lysosomal contaminants), NADH cytochrome C reductase (mitochondrial containing), and protein and demonstrated electron microscopically using negative staining that the vesicular fraction contained 95% pure coated vesicles. We then injected coated vesicle fractions and the fractions from which the coat was removed intraperitoneally into mice and obtained three monoclonal antibodies: C‐33, C‐172, and F‐22. On immunoblots of purified vesicles and cultured skeletal muscle, mAb C‐33 stained a 180 Kd band and mAb C‐172 stained a 100 kd band. MAb F‐22 stained 50 kd and 55 kd bands and was not characterized further. Immunofluorescent microscopy with C‐33 and C‐172 revealed punctate fluorescence whose distribution depends upon the stage of myotube development. Four days after plating, myotubes showed punctate fluorescence throughout the myotube, whereas those stained 8 days after plating showed a punctate perinuclear distribution. Myotubes innervated by ciliary neurons show punctate fluorescence limited to the nuclear periphery and most concentrated around nuclei which line up beneath neuronal processes. This differential vesicular distribution, observed during myotube differentiation and innervation, suggests that these vesicles participate in vesicular membrane traffic.
Cytokine regulation of metalloproteinase gene expression
Authors: Mauviel Alain 
Published: May 2005

AbstractMatrix metalloproteinases belong to a family of zinc‐dependent enzymes capable of degrading extracellular matrix and basement membrane components. Their expression is greatly modulated by cytokines and growth factors and involves the gene products of the Fos and Jun families of oncogenes. After extra(peri)cellular activation, their activity can be further controlled by specific tissue inhibitors of metalloproteinases. A correct balance between these regulatory mechanisms is necessary to ensure matrix remodeling in normal physiological processes such as embryonic development, but the overexpression of these enzymes may initiate or contribute to pathological situations such as cartilage degradation in rheumatoid arthritis or to tumor progression and metastasis. Delineation of the mechanisms of metalloproteinase and metalloproteinase inhibitors gene expression, understanding of their mode of interactions, and characterization of their patterns of expression in various tissues in normal and pathological states will lead to new therapeutic strategies to counteract the deleterious effects of matrix metalloproteinases in human disease.
Role of cytokines in bone resorption
Authors: Mundy Gregory R. 
Published: May 2005

AbstractOsteoclastic bone resorption is modulated in humans by powerful osteotropic factors which are generated in the immediate vicinity of bone resorbing surfaces. These factors are released from marrow mononuclear cells and from some bone cells, and some are actually incorporated into the noncollagenous bone matrix from where they are released when bone is resorbed. They are likely important not only in the control of normal bone remodeling, but also in a number of disease states associated with disordered remodeling. In this review, current concepts of the effects of these factors on cells in the osteoclast lineage will be discussed.
Cytokine cross‐talk between phagocytic cells and lymphocytes: Relevance for differentiation/activation of phagocytic cells and regulation of adaptive immunity
Authors: Trinchieri Giorgio , Kubin Marek , Bellone Graziella , Cassatella Marco A. 
Published: May 2005

AbstractCytokines represent one of the most important elements in the communication among different cell types. They play an increasingly better understood role in the communication among hematopoietic cells and in particular in the reciprocal regulation of effector cell types of innate or natural resistance (phagocytic cells and Natural Killer (NK) cells) and those of adaptive immunity (T and B lymphocytes). Lymphocytes produce several cytokines with either stimulatory (e.g., colony stimulatory factor) or suppressive (e.g., tumor necrosis factors and interferons) effects on proliferation of early hematopoietic cells. Many of these cytokines, alone or acting in synergistic combinations, also have a differentiation‐inducing ability on immature myeloid cells and act as powerful potentiators of the cellular functions of terminally differentiated phagocytic cells. The communication between lymphocytes and phagocytic cells is not unidirectional, as phagocytic cells produce factors that regulate lymphocyte activation. In addition to their role as antigen presenting cells expressing costimulatory accessory molecules and secreting cytokines (e.g., IL‐1, IL‐6, TNF), phagocytic cells have been recently shown to produce Natural Killer cell Stimulatory Factor (NKSF/IL‐12). IL‐12 is a heterodimeric cytokine with important modulatory functions on cytotoxicity of NK and T cells, lymphocyte proliferation, lymphokine production, and development of T helper cell subsets. These communications between phagocytic cells and lymphocytes are further regulated by negative and positive feedback mechanisms that contribute to maintain the homeostasis of the system in physiologic conditions and to govern the changes in this equilibrium needed for the response to infectious or other foreign agents.
TGF‐β1 is an organizer of responses to neurodgeneration
Authors: Finch Caleb E. , Laping Nicholas J. , Morgan Todd E. , Nichols Nancy R. , Pasinetti Giulio M. 
Published: May 2005

AbstractTGF‐β1 mRNA and protein were recently found to increase in animal brains after experimental lesions that cause local deafferentation or neuron death. Elevations of TGF‐β1 mRNA after lesions are prominent in microglia but are also observed in neurons and astrocytes. Moreover, TGF‐β1 mRNA autoinduces its own mRNA in the brain. These responses provide models for studying the increases of TGF‐β1 protein observed in βA/amyloid‐containing extracellular plaques of Alzheimer's disease (AD) and Down's syndrome (DS) and in brain cells of AIDS victims. Involvement of TGF‐β1 in these human brain disorders is discussed in relation to the potent effects of TGF‐β1 on wound healing and inflammatory responses in peripheral tissues.We hypothesize that TGF‐β1 and possibly other TGF‐β peptides have organizing roles in responses to neurodegeneration and brain injury that are similar to those observed in non‐neural tissues. Work from many laboratories has shown that activities of TGF‐β peptides on brain cells include chemotaxis, modification of extracellular matrix, and regulation of cytoskeletal gene expression and of neurotrophins. Similar activities of the TGF‐β's are well established in other tissues.
Immunohistochemical localization of the avian progesterone receptor and its candidate receptor binding factor (RBF‐1)
Authors: Zhuang Y.‐H. , Landers J. P. , Schuchard M. D. , Syvälä H. , Gosse B. , Ruesink T. , Spelsberg T. C. , Tuohimaa P. 
Published: May 2005

AbstractAn avian oviduct nuclear matrix protein in the 6–10 kDa size range has been implicated to function in the cell‐free nuclear binding of the avian oviduct progesterone receptor (PR). This protein, termed the receptor binding factor‐1 (RBF‐1), has been purified and partially characterized [Schuchard et al.: Biochemistry 30:4535–4542, 1991]. This paper describes the immunohistochemical co‐localization of the RBF‐1 and PR in the avian oviduct cell nuclei and rat reproductive cell nuclei using antibodies directed specifically against the RBF‐1 and activated PR. In the undifferentiated oviduct, the immunoreactivities for both PR and RBF‐1 were co‐localized in the nuclei of only epithelial cells, but not the stromal cells or smooth muscle cells. In the partially differentiated oviduct of estrogen treated chicks, the immunoreactivity co‐localized in the nuclei of not only epithelial but also glandular and stromal cells. Staining for the PR, but not RBF‐1, was detected in the smooth muscle cells. The intensity of the PR but not the RBF‐1 staining was markedly down‐regulated in these cells at 2 and 6 h after treatment of the animals with progesterone (P). However, the band patterns for RBF‐1 in the Western blots did show qualitative changes which may reflect P‐induced post‐translational modifications which alter the epitope on the RBF‐1. Interestingly, immunohistochemical analysis of several reproductive tissues of the rat showed that certain cell types in the uterus, ovary, and prostate displayed strong positive nuclear staining for an RBF‐1–like antigen(s). Western blot analyses of the rat reproductive tissues showed that the immunoreactive component was a 15 kDa antigenically related RBF‐1 which was only present in the uterus.
Phorbol ester‐induced transcription of an immediate‐early response gene by human T cells is inhibited by co‐treatment with calcium ionophore
Authors: Scott Judith L. , Dunn Stephanie M. , Zeng Tao , Baker Elizabeth , Sutherland Grant R. , Burns Gordon F. 
Published: May 2005

AbstractHuman T cells require two discrete signals to initiate their proliferation. In Jurkat T cells the first signal can be provided by the phorbol ester TPA and the second by the calcium ionophore A23187. We have isolated a cDNA from Jurkat T cells representing mRNA induced by TPA but inhibited by simultaneous treatment of the cells with antibody, lectin, or A23187. Sequencing revealed identity of the Jurkat clone to a cDNA, termed ETR101, recently isolated from HL60 promyelocytic leukaemia cells and shown to be an immediate early gene expressed upon TPA stimulation of these cells [Shimizu et al.: J Biol Chem 266:12157, 1991]. The gene is also induced very rapidly upon TPA treatment of Jurkat cells and is superinduced by co‐treatment with cycloheximide. The predicted amino acid sequence encoded by ETR101 has weak homology to JunB and JunD, therefore it is of some interest that these three genes share the chromosomal localization, 19p13.2. The divergent effects of TPA treatment upon cell proliferation and differentiation in different circumstances allow some speculation about a possible role for the ETR101 gene product upon cellular differentiation.
Expression of PNA‐binding sites on specific glycoproteins by human melanoma cells is associated with a high metastatic potential
Authors: Zebda Noureddine , Bailly Maryse , Brown Spencer , Doré Jean‐François , Berthier‐Vergnes Odile 
Published: May 2005

AbstractLectin‐binding patterns of seven human melanoma clones and variants selected from the same parental cell line and differing in their spontaneous metastatic potential in an animal model were compared by flow cytometry and Scatchard analysis. Human melanoma clones and variants with high and low metastatic potential could be distinguished by their peanut agglutinin (PNA)–binding patterns, but not by their wheat germ agglutinin (WGA)–, Ulex europaeus agglutinin I (UEA I)–, and soybean agglutinin (SBA)–binding patterns. Low metastatatic clones and variants proved to be made up of a single poorly peanut agglutinin–binding cell population (2.20–3.52 × 106 sites/cell, Ka = 2.48–2.75 × 106 M−1). By contrast, highly metastatic variants were found to be constituted by two cellular subpopulations, exhibiting respectively a moderate (2.62–3.72 × 106 sites/cell) and a high peanut agglutinin staining (17.68–18.76 × 106 sites/cell). One highly metastatic clone was found to be homogeneously constituted by a single population of cells strongly binding this lectin (18.86 × 106 sites/cell) with an association constant of 4.06 × 106 M−1. Using an EPICS V cytometer, these two subpopulations were sorted from a highly metastatic variant and tested for their metastatic abilities: cells with high PNA binding generated a higher frequency of metastases than did moderately PNA‐binding cells. Following treatment with Vibrio cholerae neuraminidase, all cells from all variants and clones were brightly labeled by PNA, collecting in a single peak with similar fluorescence intensities. Electrophoresis of total cellular proteins and subsequent detection with labeled PNA on Western blots show two major PNA‐reactive glycoproteins with apparent molecular weights of 140 and 110 kDa (MAGP1 and MAGP2), expressed only in highly metastatic cells, but which can be strongly labeled by PNA in slightly metastatic cells following a treatment with neuraminidase. These results provide evidence that the expression of terminal galactose (β1–3)N‐acetyl galactosamine structures, positioned on MAGP1 and MAGP2 glycoproteins, is associated with the metastatic potential of human melanoma cells.
Expression of estrogen receptors in estrogen receptor–negative human breast carcinoma cells: Modulation of epidermal growth factor‐receptor (EGF‐R) and transforming growth factor α (TGFα) gene expression
Authors: Sheikh M. Saeed , Shao Zhi‐Ming , Chen Jian‐Chyi , Li Xiao‐Su , Hussain Arif , Fontana Joseph A. 
Published: May 2005

AbstractA number of studies suggest that an inverse correlation exists between the epidermal growth factor–receptor and the estrogen receptor expression in primary human breast carcinoma as well as in established human breast carcinoma cell lines. Recent studies suggest that the epidermal growth factor–receptor does not regulate the estrogen receptor gene expression. Whether the estrogen receptor regulates the epidermal growth factor–receptor gene expression is not known. We addressed this question by stably transfecting the estrogen receptor cDNA into the estrogen receptor–negative human breast carcinoma cell line MDA‐MB‐231. Constitutive expression of functional estrogen receptors in the transfactants resulted in increased mRNA levels of both epidermal growth factor–receptor and transforming growth factor α. Estradiol treatment of transfected cells, although enhancing transforming growth factor α mRNA levels, did not modulate epidermal growth factor–receptor mRNA levels. The estrogen receptor–transfected cells grown in estrogenic regular medium, however, exhibited lower constitutive levels of epidermal growth factor–receptor mRNA than in steroid‐stripped medium, suggesting that estrogens coupled with some factors normally present in the regular medium may indeed downmodulate epidermal growth factor–receptor mRNA. Sodium butyrate treatment enhanced epidermal growth factor–receptor mRNA levels in nontransfected cells grown in regular estrogenic as well as in steroid stripped medium. Sodium butyrate enhancement of epidermal growth factor–receptor mRNA levels was completely abolished in estrogen receptor–transfected cells grown in regular estrogenic medium and blunted in steroid stripped medium. Using various epidermal growth factor–receptor gene promoter‐CAT constructs in transient transfection assays, we further demonstrate that sodium butyrate enhanced transcription of the epidermal growth factor–receptor gene. The putative sodium butyrate responsive element(s) appears to localize within the proximal 384 bp of the epidermal growth factor–receptor gene promoter region. Although the interactions between estrogen receptor and epidermal growth factor–receptor are rather complex, taken together, our data suggest that estrogen receptor can indeed modulate the epidermal growth factor–receptor mRNA expression.
Apolipoprotein E: A potent inhibitor of endothelial and tumor cell proliferation
Authors: Vogel Tikva , Guo Neng‐Hua , Guy Rachel , Drezlich Nina , Krutzsch Henry C. , Blake Diane A. , Panet Amos , Roberts David D. 
Published: May 2005

AbstractRecombinant human apolipoprotein E3 (apoE), purified from E. coli, inhibited the proliferation of several cell types, including endothelial cells and tumor cells in a dose‐ and time‐dependent manner. ApoE inhibited both de novo DNA synthesis and proliferation as assessed by an increase in cell number. Maximal inhibition of cell growth by apoE was achieved under conditions where proliferation was dependent on heparin‐binding growth factors. Thus, at low serum concentrations (0–2.5%) basic fibroblast growth factor (bFGF) stimulated the proliferation of bovine aortic endothelial (BAE) cells severalfold. The bFGF‐dependent proliferation was dramatically inhibited by apoE with an IC50 ≈ 50 nM. Under conditions where cell proliferation was mainly serum‐dependent, apoE also suppressed growth but required higher concentrations to be effective (IC50 ≈ 500 nM). ApoE also inhibited growth of bovine corneal endothelial cells, human melanoma cells, and human breast carcinoma cells. The IC50 values obtained with these cells were generally 3–5 times higher than with BAE cells. Inhibition of cell proliferation by apoE was reversible and dependent on the time of apoE addition to the culture. In addition, apoE inhibited the chemotactic response of endothelial cells that were induced to migrate by a gradient of soluble bFGF. Inhibition of cell proliferation by apoE may be mediated both by competition for growth factor binding to proteoglycans and by an antiadhesive activity of apoE. The present results demonstrate that apoE is a potent inhibitor of proliferation of several cell types and suggest that apoE may be effective in modulating angiogenesis, tumor cell growth, and metastasis.