bluuebunny/crossref_metadata_2025_split huggingface dataset:
Suppression of tumor cell susceptibility to monocyte‐induced cell death by growth‐inhibitory signals generated during monocyte/tumor cell interaction
Authors: Horn Daniel , van der Bosch Jürgen , Rüller Stephan , Schlaak Max 
Published: May 2005

AbstractIn a recently established serum‐free in vitro system it has been demonstrated that the susceptibility of various human tumor cells to the induction of cell death by elutriated human monocytes is critically dependent on tumor cell density and growth state. In the present work it is shown by flow cytofluorometric analysis of bromodeoxyuridine incorporation rates and of expression of the proliferation‐associated nuclear antigen Ki‐67, that tumor cells forced out of the cell cycle into the quiescent state (G0), which can be accomplished by treatment with supernatant from monocyte/tumor cell interaction cultures, are no longer susceptible to the induction of cell death by monocytes. This suggests that processes essential for the lytic pathway cannot take place in quiescent cells. It is furthermore demonstrated that tumor cells are driven into G0 during interaction with monocytes and that the rate of transit from G1 to G0 increases with increasing monocyte dosage. This explains our earlier finding that maximum rates of tumor cell death are induced at rather low monocyte:tumor cell ratios of around 1:2 and that lysis is suppressed at higher monocyte dosages (van der Bosch et al.: Exp Cell Res 187:185–192, 1990). The potential significance of these findings for the supposed function of mononuclear phagocytes in tumor defense lies in the notion that tumor cells driven into G0 might escape this control and that signals involved in monocyte/tumor cell‐interaction contribute to the accumulation of tumor cells in G0.
Cellular replacement therapy for neurologic disorders: potential of genetically engineered cells
Authors: Chen Lan S. , Ray Jasodhara , Fisher Lisa J. , Kawaja Michael D. , Schinstine Malcolm , Kang Un Jung , Gage Fred H. 
Published: May 2005

AbstractNeural transplantation, a mode of cellular replacement, has been used as a therapeutic trial for Parkinson's disease. Studies indicate that tonic release of the metabolites from the graft that can be utilized by the host brain, is likely to be the major mechanism responsible for the therapeutic effect. The use of fetal tissue is complicated by ethical controversy and immunological incompatibility. Autografting adult tissue has not been successful mainly due to poor survival. Genetically engineered cells are promising alternative sources of donor cells. We have investigated the potential of primary skin fibroblasts as donor cells for intracerebral grafting. Primary skin fibroblasts survive in the brain and remain in situ. A number of genes (nerve growth factor, tyrosine hydroxylase, glutamic acid decarboxylase, and choline acetyltransferase) have been successfully introduced and expressed in the primary fibroblasts. The L‐dopasecreting primary fibroblasts exhibited a behavioral effect in a rat model of Parkinson's disease up to 8 weeks after being grafted into denervated striatum. Factors that can maximize gene transfer, transgene expression, and fibroblast survival in the brain make up the future direction of investigation.
Brain grafts and Parkinson's disease
Authors: Freed William J. , Poltorak Maciej , Takashima Hidetoshi , Lamarca Mary E. , Ginns Edward I. 
Published: May 2005

AbstractIn animal models, grafts derived from several different tissues, principally fetal substantia nigra and adrenal medulla from young adults, have been found to be effective in alleviating some of the manifestations of lesions of the substantia nigra. It has been suggested that these grafts function by diffusely secreting dopamine, by exerting trophic effects on the host brain, or by producing a new innervation of the host corpus striatum. Evidence for each of these modes of action is briefly reviewed. Several brain tissue transplantation techniques have been described. Each of these techniques has significant limitations in animal models. The significance of these limitations for human application is described, and possibilities for improving the efficacy of brain tissue transplantation in animal models and for human application are discussed.
Applications of immortalized cells in basic and clinical neurology
Authors: Geller Herbert M. , Quiñ;ones‐Jenab Vanya , Poltorak Maciej , Freed William J. 
Published: May 2005

AbstractImmortalized cell lines can serve as model systems for studies of neuronal development and restoration of function in models of neurological disease. Cell lines which result from spontaneous or experimentally‐induced tumors have been used for these purposes. More recently, the techniques of genetic engineering have resulted in the production of cell lines with specific desired characteristics. This has been accomplished by insertion of a desired gene into a pre‐existing immortal cell or by immortalizing primary cells. The production of immortal cell lines using temperature‐sensitive immortalizing genes offers an additional method of controlling gene expression, and thereby controlling cell proliferation and differentation. In the nervous system, these techniques have produced immortal cell lines with neuronal and glial properties.
Cytoplasmic proteins of porcine adipocytes: identification with monoclonal antibodies
Authors: Wright J. T. , Hausman G. J. 
Published: May 2005

AbstractIn the present study, monoclonal antibodies were produced using porcine adipocyte extracts as the immunogen. Two of the monoclonal antibodies, designated CB6 and IB4, exhibited reactivity toward only cells containing lipid in stromal‐vascular cell cultures. The antigens recognized by the CB6 and IB4 monoclonal antibodies were 50 kD and 55 kD proteins, respectively. In vivo, IB4 immunoreactivity was detected only in lipid‐containing cells, whereas immunofluorescence using CB6 was also detectable around muscle fiber bundles underlying the subcutaneous mesenchyme. In fetal subcutaneous mesenchyme, CB6 and IB4 immunoreactivities toward lipid‐containing cells increased with developmental age, but each was not detectable in cells containing the smallest lipid droplets. In stromal‐vascular cultures containing adipocytes, 48 hour treatment with the anti‐lipogenic agent, growth hormone, only slightly altered CB6 immunoreactivity, whereas IB4 immunoreactivity was reduced by more than sixfold. The exact identity of the CB6 and IB4 antigens was not determined, but each may be useful as markers for studying regulation of adipocyte metabolism.
Isolation of heparan sulfate proteoglycan from beneath the monolayers of rat hepatocytes and its binding to type IV collagen
Authors: Babu P. B. Santhosh , Sudhakaran P. R. 
Published: May 2005

AbstractPrimary cultures of rat hepatocytes maintained as monolayer in a serum‐free medium synthesise and secrete sulphated proteoglycans. Nearly 5% of the total 35(S)‐sulphated material was obtained in a soluble form from beneath the cell layer. A shift in gel filtration pattern on β‐elimination with alkali suggested that it is a sulphated proteoglycan. On ion exchange chromatography over Dowex AG 1×2, the major fraction was eluted with 1.25 M NaCl. Further, nearly 80% of the 35(S)‐labeled material was susceptible to nitrous acid degradation and more than 90% of the material was resistant to chondroitinase ABC digestion suggesting that it is predominantly a heparan sulphate proteoglycan (HSPG). Since HSPG is a major component of basement membrane, its binding with collagen was studied by a solid phase binding assay. About 75% of the 35(S) HSPG bound to wells coated with type IV collagen whereas only about 20% bound to type I collagen at physiological pH. Binding to collagen IV was reduced by about 50% when free GAG chains were used indicating that the protein core is also involved in interaction with the collagen. These results indicate the possible role of this basal extracellular heparan sulphate proteoglycan in the basal lamina formation.
Tumor necrosis factor stimulates ornithine decarboxylase activity in human fibroblasts and tumor target cells
Authors: Donato Nicholas J. , Rotbein Judy , Rosenblum Michael G. 
Published: May 2005

AbstractThe activity of the polyamine biosynthetic enzyme, ornithine decarboxylase (ODC), has been shown to be rapidly modulated by a variety of growth regulatory molecules. In this report the effect of the growth modulatory peptide, tumor necrosis factor, on ODC activity was examined on two cell lines which express equivalent TNF binding properties, but differ in their growth response when exposed to this factor. TNF treatment of WI‐38 fibroblasts stimulated both their growth and induced ODC activity 5–10‐fold when measured 6–24 h after TNF incubation. TNF induced cytotoxicity in ME‐180 cervical carcinoma cells and, interestingly, stimulated both ODC activity (3–6‐fold) and putrescine accumulation when measured prior to the onset of cytotoxicity. Induction of ODC was TNF concentration‐dependent and paralleled the concentration‐dependency for cytotoxicity. Based upon studies with cycloheximide, de novo protein biosynthesis was required for TNF‐mediated ODC induction in ME‐180 cells.The effects of other growth inhibitory peptides and growth factors were analyzed for their combined effect on ODC activity in TNF‐treated or untreated ME‐180 cells. Interferon gamma treatment had no significant effect on basal ODC activity but inhibited TNF‐mediated ODC induction by ∼50%. EGF treatment resulted in a potent stimulation of ODC activity which was not effected by TNF pre‐treatment or coadministration on ME‐180 cells. These results suggest that TNF has properties which are similar to those of a growth factor and distinct from those of other growth inhibitory peptides. The early growth factor‐like actions of TNF occur on both normal fibroblasts and some tumor cells and evidence suggests that these effects are antagonistic to the antiproliferative effects of TNF.
Laminin carbohydrates are implicated in cell signaling
Authors: Chandrasekaran S. , Dean John W. , Giniger Martin S. , Tanzer Marvin L. 
Published: May 2005

AbstractWe have examined how laminin carbohydrates participate in cellular responses and have focused upon cell spreading and neurite outgrowth. Our earlier studies showed that unglycosylated laminin fully supported cell adhesion but did not promote subsequent spreading of mouse melanoma cells or neurite outgrowth of rat pheochromocytoma cells (Dean et al. (1990): J Biol Chem 265:12553–12562). In the present experiments, we determined whether those cellular responses could be restored to adherent cells. When a mixture of unglycosylated and glycosylated laminins was used as a substratum for mouse melanoma cells, some cells began to spread when 30% glycosylated laminin was present. At least 65% glycosylated laminin was required to elicit a maximal spreading response by the majority of the cells. In separate experiments, we found that cell spreading was fully restored by a pronase digest of glycosylated laminin; a similar digest of unglycosylated laminin had no effect. These results indicate that laminin carbohydrates, rather than polypeptide sequences, were responsible for cell spreading. We also conclude that substrate attachment of the carbohydrate moieties was not essential. In other experiments, laminins containing immature oligosaccharides were produced using two glycosylation pathway inhibitors, swainsonine or castanospermine. When such laminins were used to study cell spreading or neurite outgrowth, laminin containing immature oligosaccharides was as effective as laminin which contains fully processed oligosaccharides. In contrast, laminin with partially processed oligosaccharides had incomplete activity. These composite reconstitution experiments show that laminin carbohydrates provide essential information to responsive cells, enabling them to progress from an adherent state to a spread form or to extend neurite processes.
Transformation effector and suppressor genes
Authors: Boylan Michael Owen , Zarbl Helmut 
Published: May 2005

AbstractMuch has been learned about the molecular basis of cancer from the study of the dominantly acting viral and cellular oncogenes and their normal progenitors, the proto‐oncogenes. More recent studies have resulted in the isolation and characterization of several genes prototypic of a second class of cancer genes. Whereas oncogenes act to promote the growth of cells, members of this latter class of genes act to inhibit cellular growth and are believed to contribute to the tumorigenic phenotype only when their activities are absent. This new class of cancer genes is referred to by a number of different names including; anti‐oncogenes, recessive oncogenes, growth suppressor genes, tumor suppressor genes and emerogenes. Although only a few of these cancer genes have been identified, to date, it is likely that many additional genes of this class await identification. A third class of genes, necessary for the development of the cancer phenotype, is comprised of the transformation effector genes. These are normal cellular genes that encode proteins that cooperate with or activate oncogene functions and thereby induce the development of the neoplastic phenotype. The inactivation of transformation effector functions would therefore inhibit the ability of certain dominantly acting oncogenes to transform cells. The approaches outlined here describe functional assays for the isolation and molecular characterization of transformation effector and suppressor genes.
Triggering of the proteinase dipeptidyl peptidase IV (CD26) amplifies human T lymphocyte proliferation
Authors: Bednarczyk John L. , Carroll Susan M. , Marin Carmen , McIntyre Bradley W. 
Published: May 2005

AbstractCD26 (Ta1, dipeptidyl peptidase IV) is a Mr 105,000 protein expressed at high levels on activated T lymphocytes and is a potential marker of memory T cells. Reciprocal immunodepletion and solid phase double determinant binding studies showed that mAb AC7 and the CD26‐specific mAb anti‐Ta1 reacted with spatially distinct sites on the same molecule. The proteinase dipeptidyl peptidase IV (DPP IV) was immunoprecipitated with mAb AC7 and its enzymatic activity directly assayed using an enzyme overlay membrane system. High levels of DPP IV activity were detected on the T cell tumor line CCRF‐HSB‐2 and on PBMC stimulated by a variety of methods. By itself, soluble mAb AC7 was not mitogenic for T cells but enhanced T cell proliferation that resulted from treatment with phorbol myristic acetate (PMA) in the presence of accessory cells. T cell proliferation was also induced by co‐immobilized mAb AC7 and mAb OKT3 (anti‐CD3). Cultures of T cells growing in the presence of IL‐2 responded with accelerated growth when exposed to a combination of immobilized mAb AC7 and soluble mAb OKT3, a result not seen with freshly isolated T cells.
Developmental expression and hormonal regulation of the rat matrix GLA protein (MGP) gene in chondrogenesis and osteogenesis
Authors: Barone Leesa M. , Owen Thomas A. , Tassinari Melissa S. , Bortell Rita , Stein Gary S. , Lian Jane B. 
Published: May 2005

AbstractMatrix Gla protein (MGP), a vitamin K dependent protein, has recently been identified in many tissues. However, it is accumulated only in bone and cartilage suggesting that the expression of MGP may be related to the development and/or maintance of the phenotypic properties of these tissues. We systematically evaluated MGP mRNA expression as a function of bone and cartilage development and also as regulated by vitamin D during growth and cellular differentiation. Three experimental models of cartilage and bone development were employed:colon; an in vivo model for endochondral bone formation, as well as in primary cells of normal diploid rat chondrocyte and osteoblast cultures. MGP was expressed at the highest level during cartilage formation and calcification in vivo during endochondral bone formation. In chondrocyte cultures, MGP mRNA was present throughout the culture period but increased only after 3 weeks concomitantly with type I collagen mRNA. In osteoblast cultures, MGP mRNA was expressed during the proliferative period and exhibited increased expression during the period of matrix development. In contrast to osteocalcin (bone Gla protein), this increase was not dependent on mineralization but was related to the extent of differentiation associated with and potentially induced by extracellular matrix formation. During the proliferative period, type I collagen mRNA peaked and thereafter declined, while type I collagen protein steadily accumulated in the extracellular matrix. Constant MGP levels were maintained in the mineralization period of osteoblast differentiation in vitro which is consistent with the constant levels found during the osteogenic period of the in vivo system. MGP mRNA levels in both osteoblasts and chondrocytes in culture were significantly elevated by 1,25‐(OH)2D3 (10−8 M, 48 h) throughout the time course of cellular growth and differentiation. Interestingly, when MGP mRNA transcripts from vitamin D treated and untreated chondrocytes and osteoblasts were analyzed by high resolution Northern blot analysis, we observed two distinct species of MGP mRNA in the vitamin D treated chondrocyte cultures while all other cultures examined exhibited only a single MGP mRNA transcript. Primer extension analysis indicated a single transcription start site in both osteoblasts and chondrocytes with or without vitamin D treatment, suggesting that the lower molecular weight MGP message in vitamin D treated chondrocytes may be related to a modification in post‐transcriptional processing. In conclusion, these results show that the selective accumulation of MGP in bone and cartilage tissues in vitro may be related to the development and/or maintance of a collagenous matrix as reflected by increases in MGP mRNA during these periods. Moreover, our data suggest that cartilage and bone MGP mRNA may in part be selectively regulated by 1,25‐(OH)2D3 at the post‐transcriptional level.
Probing nucleosome core secondary structure before and after α‐chymotrypsin treatment by raman spectroscopy and thermal denaturation
Authors: Rosenberg‐Nicolson Nancy Lynn 
Published: May 2005

AbstractNucleosome cores were digested with α‐chymotrypsin until histone H3 was degraded to a partial histone, CP1. As we reported previously, cleavage occurred at leucine 20 to H3 and resulted in an increase in circular dichroism between 265 to 285 nm. Some modest core unfolding was also observed as determined by a small decrease in the sedimentation coefficient. Studies reported here deal with the analysis of core secondary structure and subsequent perturbation caused by treatment with α‐chymotrypsin. Raman spectroscopy indicated that chymotryptic treatment promoted a change in the conformational environment of a population of core histone tyrosines. In addition, a shift from B‐form to an intermediate B‐ or A‐form was observed for core DNA. High‐resolution thermal denaturation was used to determine alterations in the stabilization of core DNA related to perturbation of the core histones. Brief chymotryptic treatment indicated changes in both pre‐melt and irreversible transitions.
Platelet factor 4 selectively inhibits binding of TGF‐β1 to the type I TGF‐β1 receptor
Authors: Whitson Robert H. , Wong Wee Ling , Itakura Keiichi 
Published: May 2005

AbstractA low molecular weight inhibitor of TGF‐β1 binding was detected in partially purified human platelet extracts by using Hep 3B hepatoma cells in the binding assays. The inhibitory protein was purified to homogeneity and was identified as platelet factor 4 on the basis of its amino acid sequence. TGF‐β1 binding to Hep 3B cells was almost completely inhibited by 100 nM concentrations of platelet factor 4, but TGF‐β1 binding to NRK 49F fibroblasts was inhibited only slightly. Affinity cross‐linking experiments revealed that these differences in the inhibition of TGF‐β1 binding by platelet factor 4 were due to differences in the complements of TGF‐β1 binding proteins present on these two cell types. In Hep 3B cells the majority of bound TGF‐β1 was cross‐linked to a complex which had an apparent molecular weight of 70 kDa. TGF‐β1 binding to this protein was the most sensitive to inhibition by platelet factor 4. Based on its size and TGF‐β1 binding properties, we believe this protein is the type I TGF‐β1 receptor. Hep 3B cells also had a high‐affinity TGF‐β1 binding protein which appeared as an 80 kDa complex, and which we believe to be the type II TGF‐β1 receptor. TGF‐β1 binding to this protein was not inhibited by platelet factor 4. TGF‐β1 was also cross‐linked to complexes of higher molecular weights in Hep 3B cells, but it was not clear whether any of them represented the type III TGF‐β1 receptor. In NRK 49F cells, the majority of bound TGF‐β1 was cross‐linked to a high molecular weight complex which probably represented the type III TGF‐β1 receptor. NRK 49F cells also had type I TGF‐β1 receptors and platelet factor 4 inhibited binding to these receptors in the NRK cells. Since the type I receptor contributed only a small percentage of total TGF‐β1 binding, however, the overall effects of platelet factor 4 on TGF‐β1 binding to NRK 49F cells were negligible. We were unable to demonstrate specific or saturable binding of platelet factor 4 to Hep 3B cells using either direct binding or affinity cross‐linking assays. Thus, it is not clear whether platelet factor 4 inhibits TGF‐β1 binding by competition for binding to the type I receptor.Modest concentrations of TGF‐β1 reduced the adherence of Hep 3B cells to tissue culture dishes. Platelet factor 4 did not mimic this effect of TGF‐β1, nor did it inhibit the effect, even at concentrations which were sufficient to completely inhibit binding to the type I TGF‐β1 binding protein/receptor. This suggests that the type I binding protein does not mediate the effect of TGF‐β1 on Hep 3B cell adhesion.
Regulation of the transmodulated epidermal growth factor receptor by cholera toxin and the protein phosphatase inhibitor okadaic acid
Authors: Winston Jeffrey T. , Olashaw Nancy E. , Pledger W. J. 
Published: May 2005

AbstractAddition of tumor promoting phorbol esters, such as phorbol 12‐myristate 13‐acetate (PMA), to many cell lines results in a decrease of 125I‐epidermal growth factor (EGF) binding and increased serine/threonine phosphorylation of the EGF receptor in a process termed transmodulation. It is, however, unclear whether or not receptor phosphorylation is causally related to the inhibition of high affinity EGF binding. We have investigated the significance of phosphorylation/dephosphorylation events in the mechanism of PMA‐induced transmodulation using the adenylate cyclase activator cholera toxin and the serine/threonine protein phosphatase inhibitor okadaic acid. In Rat‐1 fibroblasts treated at 37°C, PMA induced a rapid decrease in EGF binding which persisted for 3 hours. In contrast, cells exposed to PMA in the presence of cholera toxin exhibited a marked recovery of binding within 60 minutes. The PMA‐stimulated decrease in binding correlated with a rapid increase in the phosphorylation state of the EGF receptor. While phosphorylation of the receptor was sustained at an elevated level for at least three hours in cells receiving PMA alone, EGF receptor phosphorylation decreased between 1 and 3 hours in cells treated with PMA and cholera toxin. Furthermore, the cholera toxin‐stimulated return of EGF binding was inhibited by treatment with the phosphatase inhibitor okadaic acid. These results suggest that a cholera toxin‐activated phosphatase can increase binding capacity of the transmodulated EGF receptor in Rat‐1 cells. Cholera toxin treatment elicited a qualitatively similar response in cells transmodulated by platelet‐derived growth factor (PDGF). Okadaic acid antagonized the natural return of binding observed in cells stimulated with PDGF alone, indicating that a dephosphorylation event may be required for the recovery of normal EGF binding after receptor transmodulation.