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  • Cell & Developmental Biology  (41,698)
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  • 101
    ISSN: 0730-2312
    Keywords: somatostatin ; receptor isotypes ; adenylyl cyclase ; Interleukin-2 (IL-2) ; proliferation ; Jurkat cells ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The neuropeptide somatostatin (SRIF) modulates normal and leukemia T cell proliferation. However, neither molecular isotypes of receptors nor mechanisms involved in these somatostatin actions have been elucidated as yet. Here we show by using RT-PCR approach that mitogen-activated leukemia T cells (Jurkat) express mRNA for a single somatostatin receptor, sst3. This mRNA is apparently translated into protein since specific somatostatin binding sites (KI1 = 78 ± 3 pM) were detected in semipurified plasma membrane preparations by using 125I-Tyr1-SRIF14 as a radioligand. Moreover, somatostatin inhibits adenylyl cyclase activity with similar efficiency (IC50 = 23 ± 4 pM) thus strongly suggesting a functional coupling of sst3 receptor to this transduction pathway. The involvement of sst3 receptor in immuno-modulatory actions of somatostatin was assessed by analysis of neuropeptide effects on IL-2 secretion and on proliferation of mitogen-activated Jurkat cells. Our data show that in the concentrations comprised between 10 pM and 10 nM, somatostatin potentiates IL-2 secretion. This effect is correlated with somatostatin-dependent increase of Jurkat cell proliferation since the EC50 concentrations for both actions were almost identical (EC50 = 22 ± 9 pM and EC50 = 12 ± 1 pM for IL-2 secretion and proliferation, respectively). Altogether, these data strongly suggest that in mitogen-activated Jurkat cells, somatostatin increases cell proliferation through the increase of IL-2 secretion via a functional sst3 receptor negatively coupled to the adenylyl cyclase pathway. J. Cell. Biochem. 68:62-73, 1998. © 1998 Wiley-Liss, Inc.
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  • 102
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 68 (1998), S. 74-82 
    ISSN: 0730-2312
    Keywords: cell culture ; nuclei ; nuclear degradation ; endonucleases ; polycytosine degradation ; differentiation ; cornification ; stratum corneum ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Desquamin is a glycoprotein that we have isolated from the upper granular layer and the stratum corneum of human epidermis; it is not ordinarily expressed in submerged cultures, whose terminal differentiation stops short of formation of these layers. The exogenous addition of desquamin to human cultured keratinocytes extended their maturation, and hematoxylin staining indicated a loss of cell nuclei. For confirmation, cultured cells were lysed in situ, and the nuclei were incubated with desquamin for several days, then stained with hematoxylin. Damage to the nuclei was evident: the nuclear inclusions remained intact, while the surrounding basophilic nuclear matrix was degraded. Desquamin was then tested directly for nuclease activity. Ribonuclease activity was determined by incubating desquamin with human epidermal total RNA and monitoring the dose-dependent disappearance of the 28S and 18S ribosomal RNA bands in an agarose/formaldehyde gel. On RNA-containing zymogels, we confirmed the RNase activity to be specific to desquamin. Using synthetic RNA homopolymers, we found the active RNase domains to be limited to cytosine residues. On the contrary, DNA was not degraded by an analogous procedure, even after strand-separation by denaturation. J. Cell. Biochem. 68:74-82, 1998. © 1998 Wiley-Liss, Inc.
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  • 103
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 68 (1998), S. 100-109 
    ISSN: 0730-2312
    Keywords: carcinogens ; mitochondrial DNA ; nuclear DNA ; LINE ; mobile elements ; cancer ; Huntington's disease ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The nuclear DNA of normal and tumor mouse and rat tissue was examined for mitochondrial-DNA-like inserts by means of the Southern blot technique. The two probes were 32P-labeled cloned mitochondrial DNA. KpnI, which doesn't cut either mitochondrial DNA, was one of the restriction enzymes, while the enzymes that fragment mitochondrial DNA were for mouse and rat PstI and BamHI, respectively. When KpnI alone was used in the procedure a nuclear LINE family whose elements had mitochondrial-DNA-like insertions was selected. Such elements were much more abundant in tumor than in normal tissue. The results with PstI alone and BamHI alone and each combined with KpnI indicated that there were mobile LINE elements with mitochondrial-DNA-like inserts in the nuclear genome of tumor. The mouse tissues were normal liver and a transplantable lymphoid leukemic ascites cell line L1210 that had been carried for 40 years. The rat tissues were normal liver and a hepatoma freshly induced by diethylnitrosoamine in order to minimize the role of 40 years of transplantation. Our unitary hypothesis for carcinogenesis of 1971, which suggested these experiments, has been augmented to include mobile nuclear elements with inserts of mitochondrial-DNA-like sequences. Such elements have been related to diseases of genetic predisposition such as breast cancer and Huntington's disease. J. Cell. Biochem. 68:100-109, 1998. © 1998 Wiley-Liss, Inc.
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  • 104
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 68 (1998), S. 121-127 
    ISSN: 0730-2312
    Keywords: heme oxygenase ; stress protein ; overexpression ; oxidative injury ; endothelial cells ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Heme oxygenase (HO-1) is a stress protein that has been suggested to participate in defense mechanisms against agents that induce oxidative injury such as hemoglobin/heme, hypoxia-ischemia and cytokines. Overexpression of HO-1 in endothelial cells (EC) might, therefore, protect against oxidative stress produced under these pathological conditions, by generation of CO, a vasodilator, and bilirubin, which has antioxidant properties that enhance blood vessel formation to counteract hypoxia-induced injury. A plasmid containing the cytomegalovirus promoter (pCMV) neomycin human HO-1 gene complexed to cationic liposomes, lipofectin, was used to transfect rabbit coronary microvessel EC. Cells transfected with human HO-1 gene demonstrated a twofold increase in HO activity and maintained a similar phenotype as in the nontransfected cells. Cell number in transfected cells with human HO-1 gene increased by about 45%, as compared to nontransfected or those transfected with control pCMV. Transfected and nontransfected EC revealed a similar response to basic fibroblast growth factor (bFGF) in capillary formation. However, transfected cells with the human HO-1 gene exhibited a twofold increase in blood vessel formation. The angiogenic response of EC to overexpression of HO-1 gene provides direct evidence that the inductive form of HO-1 following injury represents an important tissue adaptive mechanism for moderating the severity of cell damage produced in inflammatory reaction sites of hemorrhage, thrombosis and hypoxic-ischemia. Thus, HO-1 may participate in the regulation of EC activation, proliferation and angiogenesis. J. Cell. Biochem. 68:121-127, 1998. © 1998 Wiley-Liss, Inc.
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  • 105
    ISSN: 0730-2312
    Keywords: tyrosine phosphorylation ; insulin signaling ; tyrosine kinase ; confocal microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The recently identified 53-kDa substrate of the insulin receptor family was further characterized in several retroviral-generated stable cell lines overexpressing the wild type and various mutant forms of the protein. To facilitate the study of its subcellular localization in NIH3T3 cells overexpressing insulin receptor, a myc epitope-tag was added to the carboxy terminus of the 53-kDa protein. Like the endogenous protein in Chinese hamster ovary cells, the expressed myc-tagged 53-kDa protein was found partially in the particulate fraction and was tyrosine phosphorylated in insulin-stimulated cells. Immunofluorescence studies showed for the first time that a fraction of the 53-kDa protein was localized to the plasma membrane. Confocal microscopy of cells double-labeled with antibodies to the insulin receptor and the myc epitope showed the two proteins co-localize at the plasma membrane at the level of light microscopy. Further analyses of the protein sequence of the 53-kDa substrate revealed the presence of a putative SH3 domain and two proline-rich regions, putative binding sites for SH3 and WW domains. Disruption of these three motifs by the introduction of previously characterized point mutations did not affect the membrane localization of the 53-kDa protein, its ability to serve as substrate of the insulin receptor, or its colocalization with the insulin receptor, suggesting these domains are not important in the subcellular targeting of the protein and instead may function in the interaction with subsequent signaling proteins. J. Cell. Biochem. 68:139-150, 1998. © 1998 Wiley-Liss, Inc.
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  • 106
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 68 (1998), S. 151-163 
    ISSN: 0730-2312
    Keywords: Type I procollagen ; proto-oncogenes ; steroid ; calcitriol ; osteoblast ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Changes in the synthesis of type I collagen, the major extracellular matrix component of skin and bone, are associated with normal growth, tissue repair processes, and several pathological conditions. Expression of the COL 1A1 gene is regulated by transcriptional and post-transcriptional mechanisms. However, the hormonal regulation of type I collagen synthesis in human bone has not been well characterized. We have studied the influence of calcitriol, dexamethasone, retinoic acid, and estradiol on the COL 1A1 gene expression by determining the secretion of the C-terminal propeptide (PICP) and the levels of α1(I) procollagen mRNA in cultured human MG-63 and SaOs-2 osteoblast-like osteosarcoma cells. Similar experiments were also performed with respect to expression of the nuclear proto-oncogenes, c-fos and c-jun, in MG-63 cells.In MG-63 cells, calcitriol stimulated the synthesis and secretion of PICP. The α1(I) procollagen mRNA level was elevated with no effect on message stability, indicating a transcriptional mechanism of regulation. In contrast, dexamethasone treatment was accompanied by an accelerated rate of α1(I) procollagen mRNA turnover, observed as decreased amounts of the message and the secreted PICP, implying a posttranscriptional regulation. Retinoic acid, in turn, decreased the levels of α1(I) procollagen mRNA and secreted PICP by slowing down transcription of the COL1A1 gene without any effect on message stability. The ability of these hormones to regulate the α1(I) transcripts was sensitive to puromycin treatment, suggesting an involvement of an induced mediator protein in the action of the hormones on the COL1A1 gene. Both dexamethasone and calcitriol rapidly but transiently increased the expression of the c-fos and c-jun proto-oncogenes. Neither proto-oncogene responded to retinoic acid treatment with significant changes in mRNA levels. Estradiol treatment was found to have no influence on type I procollagen synthesis.In SaOs-2 cells, which are not as well differentiated as the MG-63 cells, calcitriol and dexamethasone did not influence type I procollagen synthesis. Retinoic acid as well as estradiol reduced collagen gene expression in these cells.These findings suggest that hormonal effects on type I procollagen synthesis may depend on the maturational state of the osteoblastic cells that express different regulatory factors and receptors, resulting in, in each case, a finely adjusted rate of gene expression. J. Cell. Biochem. 68:151-163, 1998. © 1998 Wiley-Liss, Inc.
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  • 107
    ISSN: 0730-2312
    Keywords: osteoprogenitors ; marrow-stroma ; alkaline phosphatase ; bisphosphonates ; cell proliferation ; mineralization ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Bisphosphonates (BPs) are inhibitors of bone resorption and soft tissue calcification. The biological effects of the BPs in calcium-related disorders are attributed mainly to their incorporation in bone, enabling direct interaction with osteoclasts and/or osteoblasts through a variety of biochemical pathways. Structural differences account for the considerable differences in the pharmacological activity of BPs. We compared the effects of two structurally different compounds, alendronate and 2-(3′-dimethylaminopyrazinio)ethylidene-1,1-bisphosphonic acid betaine (VS-6), in an osteoprogenitor differentiation system. The BPs were examined in a bone marrow stromal-cell culture system, which normally results in osteoprogenitor differentiation. The drugs were present in the cultures from days 2 to 11 of osteogenic stimulation, a period estimated as being comparable to the end of proliferation and the matrix-maturation stages. We found that the two different BPs have opposing effects on specific alkaline phosphatase (ALP) activity, on stromal-cell proliferation, and on cell-mediated mineralization. These BPs differentially interact with cell-associated phosphohydrolysis, particularly at a concentration of 10-2 of ALP Km, in which alendronate inhibits whereas VS-6 did not inhibit phosphatase activity. VS-6 treatment resulted in similar and significantly increased mineralization at 10 and 1 μM drug concentrations, respectively. In contrast, mineralization was similar to control, and significantly decreased at 10 and 1 μM drug concentrations, respectively, under alendronate treatment. J. Cell. Biochem. 68:186-194, 1998. © 1998 Wiley-Liss, Inc.
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  • 108
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 68 (1998), S. 200-212 
    ISSN: 0730-2312
    Keywords: polyamines ; chromatin structure ; micrococcal nuclease ; cell cycle ; apoptosis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Several studies suggest that polyamines may stabilize chromatin and play a role in its structural alterations. In line with this idea, we found here by chromatin precipitation and micrococcal nuclease (MNase) digestion analyses, that spermidine and spermine stabilize or condense the nucleosomal organization of chromatin in vitro. We then investigated the possible physiological role of polyamines in the nucleosomal organization of chromatin during the cell cycle in Chinese hamster ovary (CHO) cells deficient in ornithine decarboxylase (ODC) activity. An extended polyamine deprivation (for 4 days) was found to arrest 70% of the odc- cells in S phase. MNase digestion analyses revealed that these cells have a highly loosened and destabilized nucleosomal organization. However, no marked difference in the chromatin structure was detected between the control and polyamine-depleted cells following the synchronization of the cells at the S-phase. We also show in synchronized cells that polyamine deprivation retards the traverse of the cells through the S phase already in the first cell cycle. Depletion of polyamines had no significant effect on the nucleosomal organization of chromatin in G1-early S. The polyamine-deprived cells were also capable of condensing the nucleosomal organization of chromatin in the S/G2 phase of the cell cycle. These data indicate that polyamines do not regulate the chromatin condensation state during the cell cycle, although they might have some stabilizing effect on the chromatin structure. Polyamines may, however, play an important role in the control of S-phase progression. J. Cell Biochem. 68:200-212, 1998. © 1998 Wiley-Liss, Inc.
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  • 109
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 68 (1998), S. 213-225 
    ISSN: 0730-2312
    Keywords: glutamine ; glutamate ; mitochondria ; metabolism ; HeLa cells ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The oxidative metabolism of glutamine in HeLa cells was investigated using intact cells and isolated mitochondria. The concentrations of the cytoplasmic amino acids were found to be aspartate, 8.0 mM; glutamate, 22.2 mM; glutamine, 11.3 mM; glycine, 9.8 mM; taurine, 2.3 mM; and alanine, 〈1 mM. Incubation of the cells with [14C]glutamine gave steady-state recoveries of 14C-label (estimated as exogenous glutamine) in the glutamine, glutamate, and aspartate pools, of 103%, 80%, and 25%, respectively, indicating that glutamine synthetase activity was absent and that a significant proportion of glutamate oxidation proceeded through aspartate aminotransferase. No label was detected in the alanine pool, suggesting that alanine aminotransferase activity was low in these cells. The clearance rate of [14C]glutamine through the cellular compartment was 65 nmol/min per mg protein. There was a 28 s delay after [14C]glutamine was added to the cell before 14C-label was incorporated into the cytoplasm, while the formation of glutamate commenced 10 s later.Aspartate was the major metabolite formed when the mitochondria were incubated in a medium containing either glutamine, glutamate, or glutamate plus malate. The transaminase inhibitor AOA inhibited both aspartate efflux from the mitochondria and respiration. The addition of 2-oxoglutarate failed to relieve glutamate plus malate respiration, indicating that 2-oxoglutarate is part of a well-coupled truncated cycle, of which aspartate aminotransferase has been shown to be a component [Parlo and Coleman (1984): J Biol Chem 259:9997-10003]. This was confirmed by the observation that, although it inhibited respiration, AOA did not affect the efflux of citrate from the mitochondria. Thus citrate does not appear to be a cycle component and is directly transported to the medium. Therefore, it was concluded that the truncated TCA cycle in HeLa cells is the result of both a low rate of citrate synthesis and an active citrate transporter. DNP (10 μM) induced a state III-like respiration only in the presence of succinate, which supports the evidence that NAD-linked dehydrogenases were not coupled to respiration, and suggests that these mitochondria may have a defect in complex I of the electron transport chain. Arising from the present results with HeLa cells and results extant in the literature, it has been proposed that a major regulating mechanism for the flux of glutamate carbon in tumour cells is the competitive inhibition exerted by 2-oxoglutarate on aspartate and alanine aminotransferases. This has been discussed and applied to the data. J. Cell. Biochem. 68:213-225, 1998. © 1998 Wiley-Liss, Inc.
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  • 110
    Electronic Resource
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    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 68 (1998), S. 247-258 
    ISSN: 0730-2312
    Keywords: SMCs ; bFGF ; collagen fibril structure ; mRNA ; atherosclerotic lesion ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Vascular smooth muscle cells (SMCs), the major cellular constituent of an artery, synthesize the bulk of fibrillar collagens, including type V/XI, which regulates heterotypic collagen fibril assembly. Basic fibroblast growth factor (bFGF) is a heparin-binding polypeptide growth factor that has been implicated in important events during the development of atherosclerosis, such as early intimal SMC proliferation. Here we have investigated the effects of bFGF on aortic SMC expression of type V/XI collagen. Treatment of exponentially growing or serum-deprived subconfluent cultures of bovine aortic SMCs with bFGF decreased the steady-state levels of the mRNAs for collagen type V/XI, including α1(V), α2(V), and α1(XI). The effect of bFGF was time dependent with a two- and a fourfold decrease in α2(V) mRNA observed after treatment for 24 and 48 h, respectively. This decrease resulted from a drop in the rate of α2(V) gene transcription; no change was observed in the stability of the α2(V) mRNA. Furthermore, accumulation of collagen protein decreased upon bFGF treatment. As expected, treatment with bFGF increased the rate of proliferation of serum-deprived SMCs, as judged by DNA content in the cultures, thymidine incorporation, and steady-state mRNA levels of the S-phase-expressed histone H3.2. These results suggest that bFGF plays an important role in the regulation of collagen fibril structure, with potential implications for the development and organization of an atherosclerotic lesion. J. Cell. Biochem. 68:247-258, 1998. © 1998 Wiley-Liss, Inc.
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  • 111
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 68 (1998), S. 281-285 
    ISSN: 0730-2312
    Keywords: QM ; large P-antigen ; 60S ribosomal subunit ; colocalization ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: QM is a human cDNA originally isolated as a transcript elevated in a nontumorigenic Wilms' tumor microcell hybrid, relative to the tumorigenic parental cell line. The QM gene encodes a 24 kDa basic protein that peripherally associates with the ribosomes. Recently, the gene for this protein has also been shown in Saccharomyces cerevisiaeto encode an essential 60S ribosomal subunit protein that is required for the joining of the 40S and 60S subunits. Since the association of QM with ribosomes can be disrupted with 1M NaCl, which has no effect on the association of core ribosomal proteins, indirect immunofluorescent cell staining was performed to colocalize the QM protein with the human large P-antigen, a core ribosomal protein of the 60S subunit, and to determine whether the assembly of the QM protein onto the 60S ribosomal subunit occurs in the nucleolus or in the cytoplasm. Our results reveal that QM co-localizes with the large P-antigen only to the cytoplasm where the rough endoplasmic reticulum is found and not to the nucleolus where ribosome assembly occurs. This finding suggests that the QM protein is most likely involved in a late step of the 60S subunit assembly and is added to the 60S ribosomal subunit in the cytoplasm and not in the nucleolus. J. Cell. Biochem. 68:281-285, 1998. © 1998 Wiley-Liss, Inc.
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  • 112
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 68 (1998), S. 287-297 
    ISSN: 0730-2312
    Keywords: aorta ; mineralization ; calcification ; hydroxyapatite ; inhibitors ; arteriosclerosis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Mineralization of aorta is known to occur late in life and appears to be a pathological phenomenon. In vitro studies revealed that the matrix prepared from the thoracic aorta pieces after their extraction with 3% Na2HPO4 and 0.1 mM CaCl2 were mineralized under physiological conditions of temperature, pH, and ionic strength of the media to form matrix-bound mineral phase resembling hydroxyapatite in nature. However, the matrix identically prepared from the unextracted rabbits aortae failed to mineralize under identical assay conditions. The addition of the aorta extract in the assay system inhibited the above mineralization process. Standard biochemical techniques, e.g., dialysis, ion exchange, and molecular sieve chromatography, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and amino acid analysis by high-performance liquid chromatography were employed to isolate, purify, and characterize the potent inhibitory biomolecules from the aorta extract. The inhibitory activity of the aorta extract was found to be primarily due to the presence of three biomolecules having molecular weights of 66, 45, and 27-29 kDa. The above inhibitory biomolecules loosely associated with aorta may be involved in the control of calcification associated with arteriosclerosis. J. Cell. Biochem. 68:287-297, 1998. © 1998 Wiley-Liss, Inc.
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  • 113
    ISSN: 0730-2312
    Keywords: mechanical loading ; gene expression ; osteopontin ; myeloperoxidase ; rats ; differential display ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The skeleton has the ability to alter its mass, geometry, and strength in response to mechanical stress. In order to elucidate the molecular mechanisms underlying this phenomenon, differential display reverse transcriptase-polymerase chain reaction (DDRT-PCR) was used to analyze gene expression in endocortical bone of mature female rats. Female Sprague-Dawley rats, approximately 8 months old, received either a sham or bending load using a four-point loading apparatus on the right tibia. RNA was collected at 1 h and 24 h after load was applied, reverse-transcribed into cDNA, and used in DDRT-PCR. Parallel display of samples from sham and loaded bones on a sequencing gel showed several regulated bands. Further analysis of seven of these bands allowed us to isolate two genes that are regulated in response to a loading stimulus. Nucleotide analysis showed that one of the differentially expressed bands shares 99% sequence identity with rat osteopontin (OPN), a noncollagenous bone matrix protein. Northern blot analysis confirms that OPN mRNA expression is increased by nearly 4-fold, at 6 h and 24 h after loading. The second band shares 90% homology with mouse myeloperoxidase (MPO), a bactericidal enzyme found primarily in neutrophils and monocytes. Semiquantitative PCR confirms that MPO expression is decreased 4- to 10-fold, at 1 h and 24 h after loading. Tissue distribution analysis confirmed MPO expression in bone but not in other tissues examined. In vitro analysis showed that MPO expression was not detectable in total RNA from UMR 106 osteoblastic cells or in confluent primary cultures of osteoblasts derived from either rat primary spongiosa or diaphyseal marrow. Database analysis suggests that MPO is expressed by osteocytes. These findings reinforce the association of OPN expression to bone turnover and describes for the first time, decreased expression of MPO during load-induced bone formation. These results suggest a role for both OPN and MPO expression in bone cell function. J. Cell. Biochem. 68:355-365, 1998. © 1998 Wiley-Liss, Inc.
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  • 114
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    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 68 (1998), S. 378-388 
    ISSN: 0730-2312
    Keywords: apoptosis ; growth suppression ; retinoic acid receptors ; ovarian cancer ; AHPN ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: We have used conformationally restricted retinoids to investigate the role of individual RAR subtypes and RXR in mediating the growth response of ovarian tumor cells to retinoids. Our results show that treatment of all-trans-RA-sensitive CAOV-3 cells with retinoids that bind and activate a single RAR or RXR led to a partial inhibition of growth. Treatment of all-trans-RA- resistant SKOV-3 cells did not alter growth. Maximum inhibition of growth, comparable to that observed following treatment with natural retinoids such as all-trans-RA and 9-cis-RA, was obtained only following treatment with a combination of an RAR-selective compound and an RXR-selective one. These results suggest that activation of both RAR and RXR classes is required in order to obtain maximum inhibition of ovarian tumor cell growth by retinoids. In addition, one compound, AHPN, was found to inhibit both RA-sensitive CAOV-3 and RA-resistant SKOV-3 cells. Further study of the effects of this retinoid showed that AHPN acts through an apoptotic pathway. Taken together, our results suggest that retinoids may serve as effective anti-proliferative agents in the treatment of ovarian cancer. J. Cell. Biochem. 68:378-388, 1998. © 1998 Wiley-Liss, Inc.
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  • 115
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    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 68 (1998), S. 436-445 
    ISSN: 0730-2312
    Keywords: mouse ; PDI family proteins ; retinoic acid ; dibutyryl cAMP ; differentiation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: We investigated the expression of protein disulfide isomerase family proteins (PDI, ERp61, and ERp72) in mouse F9 teratocarcinoma cells during differentiation induced by treatment with retinoic acid and dibutyryl cAMP. Each member of this family was expressed at a constitutive level in undifferentiated F9 cells. During differentiation of F9 cells to parietal or visceral endodermal cells the protein level of all these enzymes increased, although the extent of this increase in both protein and mRNA levels varied among the enzymes. Certain proteins were found to be co-immunoprecipitated with PDI, ERp61, and ERp72 in the presence of a chemical crosslinker. Type IV collagen was significantly coprecipitated with PDI whereas laminin was equally coprecipitated with the three proteins. Furthermore, 210 kDa protein characteristically coprecipitated with ERp72. Thus, the induction of PDI family proteins during the differentiation of F9 cells and their association with different proteins may implicate specific functions of each member of this family despite the common redox activity capable of catalyzing the disulfide bond formation. J. Cell. Biochem. 68:436-445, 1998. © 1998 Wiley-Liss, Inc.
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  • 116
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    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 68 (1998), S. 427-435 
    ISSN: 0730-2312
    Keywords: α2-macroglobulin ; albumin ; placenta ; zinc ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: We have investigated the binding and internalization of α2-macroglobulin and serum albumin by human placental syncytiotrophoblast cells in vitro. The time course (obtained at 4°C) of α2-macroglobulin binding indicated that an equilibrium was reached after 4 h. The binding of 125I-labelled α2-macroglobulin to syncytiotrophoblast cells was competitively reduced in the presence of excess unlabelled α2-macroglobulin. When the concentration-dependence of binding was examined over a wide concentration range, non-linear regression analysis yielded a Kd of 6.4 nM. In the case of albumin, binding was weak and ligand dissociated from the cell surface during aqueous washing making it impractical to analyze the binding reaction. In other experiments, syncytiotrophoblast cells were incubated with 125I-labelled α2-macroglobulin at 37°C. Under these conditions, trypsin-resistant cell-associated radioactivity increased with time consistent with ligand internalization. 125I-Labelled-ligand was internalized with a t1/2 of about 5 min. After a lag period some radioactivity was released back into the incubation medium. When measured at times up to 210 min, this was found to consist of mostly TCA-precipitable material that had been lost from the cell surface. However, when the incubation was extended to 24 h, almost 15% of the initial cell-associated radioactivity was released to the extracellular medium as TCA-soluble material, consistent with a slow rate of ligand degradation. The specific binding of 65Zn-labelled α2M was similar to that of the 125I-labelled ligand and trypsin-resistance measurements provided evidence of α2M-mediated 65Zn uptake. These results support a role for syncytiotrophoblast in the metabolism of α2-macroglobulin during pregnancy and are also consistent with a role for α2-macroglobulin in the maternal-fetal transport of zinc. J. Cell. Biochem. 68:427-435, 1998. © 1998 Wiley-Liss, Inc.
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  • 117
    ISSN: 0730-2312
    Keywords: small heat shock proteins ; TNFα ; phosphorylation mutant ; SB203580 ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The role of murine Hsp25 phosphorylation in the protection mediated by this protein against TNFα- or H2O2-mediated cytotoxicity was investigated in L929 cell lines expressing wild type (wt-) or nonphosphorylatable (mt-) Hsp25. We show that mt-Hsp25, in which the phosphorylation sites, serines 15 and 86, were replaced by alanines, is still efficient in decreasing intracellular reactive oxygen species levels and in raising glutathione cellular content, leading the protective activity of mt-Hsp25 against oxidative stress to be identical to that of wt-Hsp25. To independently investigate the role of Hsp25 phosphorylation, we blocked TNFα-induced phosphorylation of wt-Hsp25 using SB203580, a specific inhibitor of the P38 MAP kinase. This treatment did not abolish the protective activity of Hsp25 against TNFα. The pattern of Hsp25 oligomerization was also analyzed, showing mt-Hsp25 to constitutively display large native sizes, as does wt-Hsp25 after TNFα treatment in the presence of SB203580. Our results, therefore, are consistent with the possibility that the hyperaggregated form of Hsp25 is responsible for the protective activity against oxidative stress and that the phosphorylation of serines 15 and/or 86 by interfering with this structural reorganization, may lead to the inactivation of Hsp25 protective activity. J. Cell. Biochem. 69:436-452, 1998. © 1998 Wiley-Liss, Inc.
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  • 118
    ISSN: 0730-2312
    Keywords: taxol ; microtubules ; vimentin ; intermediate filaments ; protein phosphorylation ; protein kinases ; inhibitors ; cytoskeleton ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Taxol, a microtubule stabilizing agent, has been extensively investigated for its antitumor activity. The cytotoxic effect of taxol is generally attributed to its antimicrotubule activity and is believed to be cell cycle dependent. Herein, we report that taxol induces hyperphosphorylation and reorganization of the vimentin intermediate filament in 9L rat brain tumor cells, in concentration- and time-dependent manner. Phosphorylation of vimentin was maximum at 10-6 M of taxol treatment for 8 h and diminished at higher (10-5 M) concentration. Enhanced phosphorylation of vimentin was detectable at 2 h treatment with 10-6 M taxol and was maximum after 12 h of treatment. Taxol-induced phosphorylation of vimentin was largely abolished in cells pretreated with staurosporine and bisindolymaleimide but was unaffected by H-89, KT-5926, SB203580, genistein, and olomoucine. Thus, protein kinase C may be involved in this process. Hyperphosphorylation of vimentin was accompanied by rounding up of cells as revealed by scanning electron microscopy. Moreover, there was a concomitant reorganization of the vimentin intermediate filament in the taxol-treated cells, whereas the microtubules and the actin microfilaments were less affected. Taken together, our data demonstrate that taxol induces hyperphosphorylation of vimentin with concomitant reorganization of the vimentin intermediate filament and that this process may be mediated via a protein kinase C signaling pathway. J. Cell Biochem. 68:472-483, 1998. © 1998 Wiley-Liss, Inc.
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  • 119
    ISSN: 0730-2312
    Keywords: transcription factor ; nuclear matrix ; YY1 ; amino acids ; functional regulation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The multifunctional transcription factor YY1 is associated with the nuclear matrix. In osteoblasts, the interaction of several nuclear matrix-associated transcription factors with the bone specific osteocalcin gene contributes to tissue-specific and steroid hormone-mediated transcription. A canonical nuclear matrix targeting signal (NMTS) is present in all members of the AML/CBFβ transcription factor family, but not in other transcription factors. Therefore, we defined sequences that direct YY1 (414 amino acids) to the nuclear matrix. A series of epitope tagged deletion constructs were expressed in HeLa S3 and in human Saos-2 osteosarcoma cells. Subcellular distribution was determined in whole cells and nuclear matrices in situ by immunofluorescence. We demonstrated that amino acids 257-341 in the C-terminal domain of YY1 are necessary for nuclear matrix association. We also observed that sequences within the N-terminal domain of YY1 permit weak nuclear matrix binding. Our data further suggest that the Gal4 epitope tag contains sequences that affect subcellular localization, but not targeting to the nuclear matrix. The targeted association of YY1 with the nuclear matrix provides an additional level of functional regulation for this transcription factor that can exhibit positive and negative control. J. Cell. Biochem. 68:500-510, 1998. © 1998 Wiley-Liss, Inc.
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  • 120
    ISSN: 0730-2312
    Keywords: nuclear matrix ; replication origin ; topoisomerase II-mediated DNA loop excision ; DNA loop anchorage sites ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The recently developed procedure of topoisomerase II-mediated DNA loop excision has been used to analyze the topological organization of a human genome fragment containing the gene encoding lamin B2 and the ppv1 gene. A 3.5 kb long DNA loop anchorage/topoisomerase II cleavage region was found within the area under study. This region includes the end of the lamin B2 coding unit and an intergenic region where an origin of DNA replication was previously found. These observations further corroborate the hypothesis that DNA replication origins are located at or close to DNA loop anchorage regions. J. Cell. Biochem. 69:13-18, 1998. © 1998 Wiley-Liss, Inc.
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  • 121
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    Journal of Cellular Biochemistry 69 (1998), S. 30-43 
    ISSN: 0730-2312
    Keywords: hyperthermia ; calreticulin ; chaperone complexes ; prompt glycosylation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Acute heat stress leads to the glycosylation of a “prompt” stress glycoprotein, P-SG67/64, identified as calreticulin. In the present study, we used immunoprecipitation to investigate the interactions of P-SG/calreticulin with other proteins during cellular recovery from heat stress. In heat-stressed CHO and M21 cells, both glycosylated and unglycosylated P-SGs interact with HSP90, GRP94, GRP78, and the other prompt stress glycoprotein, P-SG50, in an ATP-independent manner. Specificity of HSP-P-SG interactions was determined by chemical cross-linking with the homo-bifunctional agent DSP (3,3′-dithiobis[succinimidyl propionate]). Characterization of the cross-linked complexes involving calreticulin and heat shock proteins (HSPs) showed an average mass of 400-600 kDa by gel filtration chromatography. Overall, the consistent association of glycosylated and unglycosylated calreticulin with P-SG50 and unglycosylated HSPs suggests that P-SG/calreticulin is an active member of the cast of glycone/aglycone chaperones that cooperate to achieve cellular recovery from acute heat stress. J. Cell. Biochem. 69:30-43, 1998. © 1998 Wiley-Liss, Inc.
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  • 122
    ISSN: 0730-2312
    Keywords: angiotensin II ; G proteins ; Src tyrosine kinases ; c-Fos ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Angiotensin II stimulates a biphasic activation of Raf-1, MEK, and ERK in WB liver epithelial cells. The first peak of activity is rapid and transient and is followed by a sustained phase. Angiotensin II also causes a rapid activation of p21ras in these cells. Moreover, two Src family kinases (Fyn and Yes) were activated by angiotensin II in a time- and concentration-dependent manner. Microinjection of antibodies against Fyn and Yes blocked angiotensin II-induced DNA synthesis and c-Fos expression in WB cells, indicating an obligatory involvement of these tyrosine kinases in the activation of the ERK cascade by angiotensin II. Finally, substantial reduction of the angiotensin II-stimulated activation of Fyn, Raf-1, ERK, and expression of c-Fos by pertussis toxin pretreatment argues that G proteins of the Gi family as well as the Gq family are involved in angiotensin II-mediated mitogenic pathways in WB cells. J. Cell. Biochem. 69:63-71, 1998. © 1998 Wiley-Liss, Inc.
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  • 123
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    Journal of Cellular Biochemistry 69 (1998), S. 87-93 
    ISSN: 0730-2312
    Keywords: MAP kinase pathways ; JNK ; human osteoblasts ; interleukin-1β ; UMR-106 cells ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: We recently demonstrated the activation of extracellular signal- regulated protein kinase 1 and 2 (ERK1 and ERK2) by IGF-1, FGF-2, and PDGF-BB in normal human osteoblastic (HOB) cells as well as in rat and mouse osteoblastic cells. In this report, we have examined whether c-Jun NH2-Terminal Kinase (JNK) pathway is activated by growth factors and interleukin-1β (IL-1β) in normal HOB and rat UMR-106 cells using immune-complex kinase assay and anti-active JNK antibody, which recognizes activated forms of both JNK1 and JNK2. Results have demonstrated the presence of JNK1 and JNK2 proteins in normal HOB and UMR-106 cells. Both JNK1 and JNK2 were activated by IL-1β. IL-1β preferentially activated JNK pathway in a dose- and time-dependent manner and had little effect on ERK pathway. On the other hand, FGF-2 did not activate JNK but most strongly activated ERK pathway. The activation of JNK was maximal at 20 min whereas maximal activation of ERK1 and ERK2 was observed within 10 min. Results have clearly demonstrated that IL-1β preferentially activates JNK pathway whereas FGF-2 activates ERK pathway in normal human and rat UMR-106 osteoblastic cells. J. Cell. Biochem. 69:87-93, 1998. © 1998 Wiley-Liss, Inc.
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  • 124
    ISSN: 0730-2312
    Keywords: haemochromatosis gene ; histone gene cluster ; YACs ; cosmid contig ; sequences ; species comparison ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The HFE (HLA-H) gene is a strong candidate gene for hereditary haemochromatosis and was localized on the short arm of chromosome 6 to 6p21.3-p22. In addition, the sequence of the homologous mouse and rat cDNA and a partial sequence from the mouse gene have been reported recently. In this report, we describe the location of the human and the mouse HFE (HLA-H) gene within the histone gene clusters on the human chromosome 6 and the mouse chromosome 13. Both the human and the murine gene were located on syntenic regions within the histone gene clusters in the vicinity of the histone H1t gene. The genomic sequence of the human HFE (HLA-H) gene and the 3′ portion of the homologous mouse gene were determined. Comparison of the genomic sequences from man and mouse and the cDNA sequence from rat shows significant similarities, also beyond the transcribed region of the mouse gene. J. Cell. Biochem. 69:117-126, 1998. © 1998 Wiley-Liss, Inc.
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  • 125
    ISSN: 0730-2312
    Keywords: transcription ; mRNA stability ; dexamethasone ; gene regulation ; glucocorticoid receptor ; rat calvarial osteoblasts ; osteopontin ; vitamin D receptor ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: We have examined the contribution of transcriptional mechanisms to the pleiotropic effects of glucocorticoids on basal and vitamin D stimulated expression of the developmentally regulated bone-specific osteocalcin (OC) gene. OC expression was systematically investigated at the level of protein, mRNA, and newly synthesized transcripts during maturation of the bone cell phenotype in cultures of fetal rat calvarial-derived osteoblasts. Our results indicate that transcriptional control of basal and hormone-regulated OC expression predominates in immature osteoblasts prior to matrix mineralization. However, in mature osteoblasts OC expression is controlled primarily by posttranscriptional mechanisms reflected by elevated mRNA levels with a decline in transcription. Vitamin D, alone or in combination with Dex, is a significant factor contributing to mRNA stabilization in mature osteoblasts with a mineralized extracellular matrix. Transcriptional modifications in response to Dex are reflected by quantitative differences between proliferating and mature osteoblasts in the formation of glucocorticoid receptor binding complexes at the proximal OC glucocorticoid response element. Vitamin D and glucocorticoid receptor mRNA levels are significantly higher in mature osteoblasts than in early stage bone cells. However, receptor complexes do not appear to be rate limiting in proliferating osteoblasts when the OC gene is not transcribed. Our results indicate (1) developmental stage-specific effects of steroid hormone on transcriptional regulation of bone expressed genes, and (2) inverse relationships between levels of transcription and cellular representation of mRNA with OC message stabilized in mature osteoblasts. J. Cell. Biochem. 69:154-168, 1998. © 1998 Wiley-Liss, Inc.
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  • 126
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    Journal of Cellular Biochemistry 69 (1998), S. 181-188 
    ISSN: 0730-2312
    Keywords: magnetic fields ; HSP70 gene expression ; human HSP70 promoter ; c-myc protein binding sites ; cellular stress ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: We investigated c-myc protein-binding sites on the HSP70 promoter as modulators of the induction of HSP70 gene expression in response to magnetic field stimulation (8μT at 60Hz) and whether the presence of c-myc protein potentiates transactivation of HSP70 expression. A 320 base pair region in the HSP70 promoter (+1 to -320) was analyzed. This region contains two c-myc-protein binding sites with consensus sequences located at -230 and -160 nucleotide positions (relative to the transcription initiation site) and overlapping with the region reported for the regulation of HSP70 gene expression by c-myc protein. This promoter region is upstream of other regulatory sequences, including the heat shock element (HSE), AP-2, and serum response element (SRE). Transfectants containing both c-myc protein-binding sites, HSP-MYC A and HSP-MYC B, and exposed to magnetic fields showed a 3.0-fold increase in expression of CAT activity as compared with sham-exposed control transfectants. Transfectants containing one c-myc binding site, HSP-MYC A, and exposed to magnetic fields showed a 2.3-fold increase in CAT expression. Transfectants in which both HSP-MYC A and HSP-MYC B binding sites were deleted showed no magnetic field sensitivity; values were virtually identical with sham-exposed controls. If the c-myc expression vector was not co-transfected with the constructs containing myc-binding sites, there was no difference in the expression of CAT activity between magnetically stimulated and sham-exposed controls, although both responded to heat shock. These data suggest that endogenous elevated levels of myc protein contribute to the induction of HSP70 in response to magnetic field stimulation. J. Cell. Biochem. 69:181-188, 1998. © 1998 Wiley-Liss, Inc.
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  • 127
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    Journal of Cellular Biochemistry 69 (1998), S. 211-220 
    ISSN: 0730-2312
    Keywords: nuclear matrix ; protein kinase CK2 ; disulfide bonds ; sodium tetrathionate ; iodoacetamide ; sulfhydryl crosslinking ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Nuclear matrix (NM) appears to be an intranuclear locale for significant and dynamic association of the ubiquitous multifunctional messenger-independent serine/threonine protein kinase CK2 that has been implicated in growth control [Tawfic et al. (1996): J Cell Biochem 61:165-171]. We have examined the nature of the association of CK2 with the NM. Nuclei prepared in the presence of a sulfhydryl-blocking reagent such as iodoacetamide demonstrate a reduction in the amount of CK2 associated with the NM to less than 5% of the control. On the other hand, when nuclei are treated with the sulfhydryl crosslinking reagent sodium tetrathionate, NM-associated CK2 increases severalfold. Treatment of nuclei with sodium tetrathionate followed by 2-mercaptoethanol blocks this increase. Nuclei isolated from rat liver and prostate behaved similarly, suggesting an identical mode of association of CK2 with the NM regardless of the organ. These results indicate a role of sulfhydryl interactions such that NM anchoring of CK2 occurs via its β subunit, which contains several vicinal cysteine residues. Further, various sulfhydryl-blocking reagents inhibited CK2 activity in a concentration-dependent manner, and the inhibitory effect was reversed by agents such as dithiothreitol, implying that cysteine residues in the CK2 play a role in its catalytic activity. J. Cell. Biochem. 69:211-220, 1998. Published 1998 Wiley-Liss, Inc.
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  • 128
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    Journal of Cellular Biochemistry 69 (1998), S. 201-210 
    ISSN: 0730-2312
    Keywords: sodium butyrate ; alkaline phosphatase ; A5 cells ; A5-DAP cells ; A5-BAG cells ; β-galactosidase ; retroviral vectors ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: We have studied the effects of sodium butyrate (NaBu) on the expression of genes transduced by retroviral vectors and stably expressed in two salivary gland-derived cell lines, A5-DAP and A5-BAG, established earlier. These cell lines were obtained by infecting A5 cells with the retroviral vectors DAP and BAG, respectively, and by selecting neomycin-resistant transduced cells. A5-DAP cells express human placental alkaline phosphatase (PLAP) and A5-BAG cells bacterial β-galactosidase, both under the control of the viral long terminal repeat (LTR) enhancer-promoter. NaBu in the concentration of 2-8 mM inhibited the growth of A5-DAP cells, and induced the expression of heat-stable PLAP. These effects of NaBu were dose-dependent. Induction of PLAP in clones of A5-DAP cells that express different basal levels of the enzyme was not correlated with the relative inducibilty by NaBu. Exposure to 4 mM NaBu for 48 h increased the PLAP mRNA level by 31%. A5-DAP cells released, in a time-dependent manner, PLAP into the culture medium. Cells treated with NaBu released more PLAP than untreated cells in proportion to their elevated level of the enzyme. The parent A5 cells also express a low level of tissue non-specific type alkaline phosphatase, which was also induced by NaBu. NaBu inhibited the growth of A5-BAG cells also, and increased the β-galactosidase level. These data indicate the genes transduced by retroviral vectors can be induced by NaBu, which most likely interacts with the viral LTR. J. Cell. Biochem. 69:201-210, 1998. © 1998 Wiley-Liss, Inc.
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  • 129
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    Journal of Cellular Biochemistry 69 (1998), S. 221-231 
    ISSN: 0730-2312
    Keywords: sodium fluoride ; stress response ; stress proteins ; heat shock proteins ; rat brain tumor 9L cells ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: We herein demonstrate that sodium fluoride (NaF) acts as a stress response inducer on HeLa and 9L rat brain tumor cells. NaF is only slightly cytotoxic, and inhibitory to Ser/Thr-phosphatases but not to Tyr-phosphatases in both cell lines. After treatment with 5 mM NaF for 2 h, the phosphorylation levels of vimentin and an alkali-resistant 65-kDa phosphoprotein were enhanced, a common phenomenon detected in cells under a variety of stress conditions. Under an identical treatment protocol, in which the cells were treated with 5 mM NaF for 2 h and then allowed to recover under normal growing conditions for up to 12 h, NaF differentially induced the cytoplasmic/nuclear heat-shock protein70s (including both the inducible and the constitutively expressed members of this protein family) in HeLa cells and the endoplasmic reticulum residing heat-shock protein70 (the glucose-regulated protein with an apparent molecular weight of 78 kDa) in 9L cells. Electrophoretic mobility shift assays (EMSA) using probes containing well-characterized regulatory elements revealed the activation of the heat-shock factor in HeLa but not in 9L cells; this is in good agreement with the stress protein induction pattern. Additional differential induction of binding activities toward EMSA probes individually containing NF-κB, AP-2, and CRE-like elements were detected in NaF-treated cells. The possible involvement of these binding sites as well as the corresponding factors in the stress response are discussed. J. Cell. Biochem. 69:221-231, 1998. © 1998 Wiley-Liss, Inc.
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  • 130
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    Journal of Cellular Biochemistry 70 (1998), S. 213-221 
    ISSN: 0730-2312
    Keywords: transcription ; nucleus ; cell architecture ; nuclear matrix ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: After many years of reductionistic approaches to characterize molecular mechanisms involved in transcription, the number of factors recognized to take part in this process has increased remarkably and continues to grow. When considering posttranslational modifications in conjunction with the large number of factors involved in modulating the activity of transcription complex components, the overall intricacy becomes staggering. After two decades of intensive molecular investigations, there has been a concerted effort to integrate these findings with cellular approaches to understand transcription on a more global level. This sort of reasoning actually revisits studies of approximately 20 years ago that considered the functional consequences of steroid receptor association with nuclear structure. With an abundance of new molecular probes and increasingly powerful instruments to detect them in fixed and, more recently, live cells, the issue of functional subnuclear organization is receiving increased attention. In this report, we focus on advances in characterizing the functional significance of transcription factor association with the nucleoskeleton. In particular, we consider recent biochemical and “molecular morphology” data that point to the importance of dynamic spatial and solubility partitioning of gene regulators with nuclear architecture. J. Cell. Biochem. 70:213-221, 1998. © 1998 Wiley-Liss, Inc.
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  • 131
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    Journal of Cellular Biochemistry 70 (1998), S. 222-230 
    ISSN: 0730-2312
    Keywords: functional organization of the nucleus ; nucleolus ; speckled compartment ; targeting sequence ; DNA replication ; RNA splicing ; nuclear matrix ; cell cycle ; DNA methyltransferase ; DNA ligase I ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Though there are no separating membranes within the nucleus, different factors are often concentrated at sites where their respective function is required, a phenomenum referred to as functional organization of the nucleus. How is then this organization achieved and how are the different metabolic processes integrated in the nucleus? One emerging principle was revealed by the identification of protein domains that, though not involved in catalysis, regulate enzyme activity at a higher order level by targeting enzymes to the right place at the right time. These targeting sequences constitute an assembly code for nuclear ‘protein factories,’ which ensure the extremely high efficiency and accuracy needed in a complex and competitive environment as the living mammalian cell. J. Cell. Biochem. 70:222- 230, 1998. © 1998 Wiley-Liss, Inc.
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  • 132
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    Journal of Cellular Biochemistry 70 (1998), S. 231-239 
    ISSN: 0730-2312
    Keywords: nuclear pore complexes ; nuclear localization signals ; nuclear export signals ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Transport of proteins into and out of the nucleus occurs through nuclear pore complexes (NPCs) and is mediated by the interaction of transport factors with nucleoporins at the NPC. Nuclear import of proteins containing classical nuclear localization signals (NLSs) is mediated by a heterodimeric protein complex, composed of karyopherin α and β1, that docks via β1 the NLS-protein to the NPC. The GTPase Ran; the RanGDP binding protein, p10; and the RanGTP binding protein, RanBP1 are involved in translocation of the docked NLS-protein into the nucleus. Recently, new distinct nuclear import and export pathways that are mediated by members of the karyopherin β family have been discovered. Karyopherin β2 mediates import of mRNA binding proteins, whereas karyopherin β3 and β4 mediate import of a set of ribosomal proteins. Two other β karyopherin family members, CRM1 and CAS, mediate export of proteins containing leucine-rich nuclear export signals (NES) and reexport of karyopherin α, respectively. This growing family contains new members that constitute potential transport factors for cargoes yet to be identified in the future. The common features of the members of karyopherin β family are the ability to bind RanGTP and the ability to interact directly with nucleoporins at the NPC. The challenge for the future will be to identify the distinct or, perhaps, overlapping cargo(es) for each member of the karyopherin β superfamily and to characterize the molecular mechanisms of translocation of karyopherins together with their cargoes through the NPC. J. Cell. Biochem. 70:231-239, 1998.© 1998 Wiley-Liss, Inc.
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  • 133
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    Journal of Cellular Biochemistry 70 (1998), S. 240-251 
    ISSN: 0730-2312
    Keywords: actin ; actin-like proteins ; lamin ; nuclear matrix ; perinuclear actin shells ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Perinuclear actin shells have been reported in a variety of organisms. The shells have been identified by staining perinuclear material with fluorescently-labelled phalloidin, but have not been localized to a specific subcellular compartment at the ultrastructural level. We show here that the shells of 3T3 cells lie in the peripheral nuclear matrix. Nuclear shells and matrix actin in other parts of the nucleus are not usually detected by immunohistochemical staining because they are inaccessible to antibodies or to phalloidin. Immunohistochemical detection of nuclear actin is only possible during its deposition at the end of mitosis, or in interphase nuclei that have been extracted with detergent, digested with nucleases and washed with high salt buffers. J. Cell. Biochem. 70:240-251, 1998. © 1998 Wiley-Liss, Inc.
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  • 134
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    Journal of Cellular Biochemistry 70 (1998), S. 281-287 
    ISSN: 0730-2312
    Keywords: retinoblastoma protein ; TATA-binding protein ; repressor ; TSA ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The retinoblastoma (RB) tumour suppressor protein negatively regulates cell proliferation by modulating transcription of growth-regulatory genes. Recruitment of Rb to promoters, by association with E2F complex or by fusion with heterologous DNA-binding domains, demonstrated that Rb represses directly transcription. Recent studies also suggest that the RB protein is able to repress gene transcription mediated by the RNA polymerase I and III. Since the TATA-binding protein (TBP) is an important component for transcription mediated by all three RNA polymerases, we have analysed the functional interaction between Rb and TBP in vivo in the context of RNA pol II-driven transcription. We demonstrated that in mammalian cells Rb tethered to promoter represses TBP-mediated activation in vivo, and Rb-mediated repression is reversed in the presence of the inhibition of histone deacetylase activity by trichostatin A (TSA). J. Cell. Biochem. 70:281-287, 1998. © 1998 Wiley-Liss, Inc.
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  • 135
    ISSN: 0730-2312
    Keywords: lymphocyte ; monocyte ; cell line ; cell culture ; microgravity ; experiment development ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The results of experiments performed in recent years on board facilities such as the Space Shuttle/Spacelab have demonstrated that many cell systems, ranging from simple bacteria to mammalian cells, are sensitive to the microgravity environment, suggesting gravity affects fundamental cellular processes. However, performing well-controlled experiments aboard spacecraft offers unique challenges to the cell biologist. Although systems such as the European ‘Biorack’ provide generic experiment facilities including an incubator, on-board 1-g reference centrifuge, and contained area for manipulations, the experimenter must still establish a system for performing cell culture experiments that is compatible with the constraints of spaceflight. Two different cell culture kits developed by the French Space Agency, CNES, were recently used to perform a series of experiments during four flights of the ‘Biorack’ facility aboard the Space Shuttle. The first unit, Generic Cell Activation Kit 1 (GCAK-1), contains six separate culture units per cassette, each consisting of a culture chamber, activator chamber, filtration system (permitting separation of cells from supernatent in-flight), injection port, and supernatent collection chamber. The second unit (GCAK-2) also contains six separate culture units, including a culture, activator, and fixation chambers. Both hardware units permit relatively complex cell culture manipulations without extensive use of spacecraft resources (crew time, volume, mass, power), or the need for excessive safety measures. Possible operations include stimulation of cultures with activators, separation of cells from supernatent, fixation/lysis, manipulation of radiolabelled reagents, and medium exchange. Investigations performed aboard the Space Shuttle in six different experiments used Jurkat, purified T-cells or U937 cells, the results of which are reported separately. We report here the behaviour of Jurkat and U937 cells in the GCAK hardware in ground- based investigations simulating the conditions expected in the flight experiment. Several parameters including cell concentration, time between cell loading and activation, and storage temperature on cell survival were examined to characterise cell response and optimise the experiments to be flown aboard the Space Shuttle. Results indicate that the objectives of the experiments could be met with delays up to 5 days between cell loading into the hardware and initial in flight experiment activation, without the need for medium exchange. Experiment hardware of this kind, which is adaptable to a wide range of cell types and can be easily interfaced to different spacecraft facilities, offers the possibility for a wide range of experimenters successfully and easily to utilise future flight opportunities. J. Cell. Biochem. 70:252-267, 1998. © 1998 Wiley-Liss, Inc.
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  • 136
    ISSN: 0730-2312
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: No abstract.
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  • 137
    ISSN: 0730-2312
    Keywords: insulin ; insulin receptor ; breast cancer cells ; insulin receptor substrate 1 ; phosphatidylinositol-3-kinase ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: In many human breast cancers and cultured cell lines, insulin receptor expression is elevated, and insulin, via its own insulin receptor, can stimulate cell growth. It has recently been demonstrated that the enzyme phosphatidylinositol-3-kinase (PI3-K) mediates various aspects of insulin receptor signaling including cell growth. In order to understand the mechanisms for insulin-stimulated cell growth in human breast cancer, we measured insulin-stimulable PI3-K activity in a non-transformed breast epithelial cell line, MCF-10A, and in two malignantly transformed cell lines, ZR-75-1 and MDA-MB157. All three cell lines express comparable amounts of insulin receptors whose tyrosine autophosphorylation is increased by insulin, and in these cell lines insulin stimulates growth. In MDA-MB157 and MCF-10A cells, insulin stimulated PI3-K activity three- to fourfold. In ZR-75-1 cells, however, insulin did not stimulate PI3-K activity. In ZR-75-1 cells PI3-K protein was present, and its activity was stimulated by epidermal growth factor, suggesting that there might be a defect in insulin receptor signaling upstream of PI3-K and downstream of the insulin receptor. Next, we studied insulin receptor substrate-1 (IRS-1), a major endogenous substrate for the insulin receptor which, when tyrosine is phosphorylated by the insulin receptor, interacts with and activates PI3-K. In ZR-75-1 cells, there were reduced levels of protein for IRS-1. In these cells, both Shc tyrosine phosphorylation and mitogen-activated protein kinase (MAP-K) activity were increased by the insulin receptor (indicating that the p21ras pathway may account for insulin-stimulated cell growth in ZR-75-1 cells).The PI3-K inhibitor LY294002 (50 μM) reduced insulin-stimulated growth in MCF-10A and MDA-MB157 cell lines, whereas it did not modify insulin effect on ZR-75-1 cell growth. The MAP-K/Erk (MEK) inhibitor PD98059 (50 μM) consistently reduced insulin-dependent growth in all three cell lines.Taken together, these data suggest that in breast cancer cells insulin may stimulate cell growth via PI3-K-dependent or-independent pathways. J. Cell. Biochem. 70:268-280, 1998. © 1998 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
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  • 138
    ISSN: 0730-2312
    Keywords: analog ; bone ; growth inhibition ; differentiation ; vitamin D ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: 1,25-Dihydroxyvitamin D3 (1,25D) is involved in the regulation of proliferation and differentiation of a variety of cell types including cancer cells. In recent years, numerous new vitamin D3 analogs have been developed in order to obtain favorable therapeutic properties. The effects of a new 20-epi analog, CB1093 (20-epi-22-ethoxy-23-yne-24a,26a,27a-trihomo-1α,25(OH)2D3), on the proliferation and differentiation of human MG-63 osteosarcoma cell line were compared here with those of the parent compound 1,25D. Proliferation of the MG-63 cells was inhibited similarly by 22%, 50% and 59% after treatment with 0.1 μM 1,25D or CB1093 for 48 h, 96 h, and 144 h, respectively. In transfection experiments, the compounds were equipotent in stimulating reporter gene activity under the control of human osteocalcin gene promoter. In cell culture experiments, however, CB1093 was more potent than 1,25D at low concentrations and more effective for a longer period of time in activating the osteocalcin gene expression at mRNA and protein levels. Also, a 6-h pretreatment and subsequent culture for up to 120 h without 1,25D or CB1093 yielded higher osteocalcin mRNA and protein levels with analog-treated cells than with 1,25D-treated cells. The electrophoretic mobility shift assay (EMSA) revealed stronger VDR-VDRE binding with analog-treated MG-63 cells than with 1,25D-treated cells. The differences in the DNA binding of 1,25D-bound vs. analog-bound VDR, however, largely disappeared when the binding reactions were performed with recombinant hVDR and hRXRβ proteins. These results demonstrate that the new analog CB1093 was equally or even more effective than 1,25D in regulating all human osteosarcoma cell functions ranging from growth inhibition to marker gene expression and that the differences in effectivity most probably resulted from interactions of the hVDR:hRXRβ-complex with additional nuclear proteins. J. Cell. Biochem. 70:414-424, 1998. © 1998 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
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  • 139
    Electronic Resource
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    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 70 (1998), S. 346-353 
    ISSN: 0730-2312
    Keywords: MHC class II ; T-helper cells ; phosphotyrosine kinase ; phospholipase C-γ1 ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Major histocompatibility complex (MHC) class II are expressed on most activated human lymphocytes. They direct antigen presentation events in dendritic cells and B cells (collectively called antigen presenting cells), but the role for MHC class II in human T cells is not well understood. To understand the role of surface MHC class II and to identify the molecules involved in signaling, we have defined the early activation sequence in T cells when MHC class II are engaged by a specific antibody. Specifically, we have characterized the involvement of phosphotyrosine kinases, phospholipase C (PLC), and Ca2+ mobilization. With the engagement by either whole anti-class II antibody or its Fab fragments, the enzymatic activity of p56lck and ZAP-70 increased, but there was no increase in p59fyn activity. In addition, the intracellular free Ca2+ increased, which was due to enhanced influx and not to the mobilization of intracytoplasmic Ca2+. These events did not require cross-linking because they were not significantly augmented by the addition of antispecies antibody. The coimmunoprecipitation of tyrosine phosphorylated PLC-γ1 with surface MHC class II suggested that PLC-γ1 could be recruited to MHC class II after engagement. These results show the complexities of the early signals transduced by the engagement of surface MHC class II on T cells. J. Cell. Biochem. 70:346-353, 1998. © 1998 Wiley-Liss, Inc.
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  • 140
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    Journal of Cellular Biochemistry 70 (1998), S. 354-365 
    ISSN: 0730-2312
    Keywords: human fetal colon ; apolipoprotein A-I, A-IV, B-48, B-100 ; hydrocortisone ; insulin ; epidermal growth factor ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The present investigation aimed at defining the localization of apolipoproteins (apo) A-I, A-IV, B-48, and B-100 along the crypt-villus axis of the human fetal colon, their biogenesis during gestation, and their hormonal regulation. Using immunofluoresence, the distribution of apo A-I and A-IV appeared as a gradient, increasing from the developing crypt to the tip of the villus. On the other hand, apo B-100 staining was found in the crypt and the lower mid-villus region with varying intensities in the upper villus cells, while the 2D8 antibody which recognizes both apo B-100 and B-48, revealed uniform staining along the crypt-villus axis. Apolipoprotein synthesis, determined by [35S] methionine labeling, immunoprecipitation, and SDS-PAGE showed a predominance of apo A-IV (53%), followed by apo A-I (23.9%), apo B-48 (13.4%), and apo B-100 (9.7%). The synthesis of each apolipoprotein was significantly modulated by hydrocortisone, insulin and epidermal growth factor (EGF). Apart from a decrease in apo B-100 exerted by EGF and a reduction in apo A-I resulting from the addition of insulin, the other apolipoproteins were all enhanced. Our data confirm that the fetal colon has the capacity to synthesize apolipoprotein A-I, A-IV, B-48, and B-100 and establish that their synthesis are modulated by hormonal and growth factors known to be involved in the regulatory mechanism of the functional development of human jejunum. J. Cell. Biochem. 70:354-365, 1998. © 1998 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
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  • 141
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    Journal of Cellular Biochemistry 70 (1998), S. 366-375 
    ISSN: 0730-2312
    Keywords: transcription ; myogenesis ; MADS domain ; DNA binding ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Previous investigations have demonstrated synergistic interactions in vivo between CCAC and A/T-rich nucleotide sequence motifs as functional components of muscle-specific transcriptional enhancers. Using CCAC and A/T-rich elements from the myoglobin and muscle creatine kinase (MCK) gene enhancers, Sp1 and myocyte-specific enhancer factor-2 (MEF-2) were identified as cognate binding proteins that recognize these sites. Physical interactions between Sp1 and MEF-2 were demonstrated by immunological detection of both proteins in DNA binding complexes formed in vitro by nuclear extracts in the presence of only the A/T sequence motif, by coprecipitation of recombinant MEF-2 in the presence of a glutathione-S-transferase-Sp1 fusion protein bound to glutathione beads, and by a two-hybrid assay in Saccharomyces cerevisiae. The interaction with Sp1 in vitro and in vivo is specific for MEF-2 and was not observed with serum response factor, a related MADS domain protein. Forced expression of Sp1 and MEF-2 in insect cells otherwise lacking these factors promotes synergistic transcriptional activation of a promoter containing binding sites for both proteins. These data expand the repertoire of functional and physical interactions between lineage-restricted (MEF-2) and ubiquitous (Sp1) transcription factors that may be important for myogenic differentiation. J. Cell. Biochem. 70:366-375, 1998. © 1998 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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  • 142
    ISSN: 0730-2312
    Keywords: anabolic ; bone ; MMP-9 ; osteoblast ; parathyroid hormone ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Intermittent doses of parathyroid hormone (PTH) stimulate bone formation in animals and humans, but the molecular mechanisms underlying this phenomenon are not understood. Bone formation culminates with the expression of type I collagen, osteocalcin, and alkaline phosphatase, but genes that initiate and support the anabolic response are not known. To identify novel PTH-regulated genes in bone during the anabolic response, we used differential display-polymerase chain reaction (DDRT-PCR) to analyze RNA from young male rats injected with either human PTH (1-34) or vehicle control, once daily for 5 days. Total RNA was isolated from the distal femur metaphysis at 1, 6, and 48 h after the final injection and subjected to DDRT-PCR. We identified three PTH-responsive transcripts as matrix metalloproteinase-9 (MMP-9), creatine kinase, and the α1(I) polypeptide chain (COL1A1) of type I collagen. The concomitant upregulation of MMP-9 and COL1A1 during bone formation was particularly intriguing. Further characterization of MMP-9 expression revealed that it was localized to osteoblasts, osteocytes, megakaryocytes, and cells of the bone marrow in the rat distal femur metaphysis. Northern analysis for MMP-9 expression in other tissues indicated that this transcript was present in the kidney and brain. In vitro, PTH regulated the protein synthesis of MMP-9 by osteoblasts of the primary spongiosa. We propose that PTH may promote bone formation by mediating the subtle variation in MMP activities, thus preparing the extracellular matrix for the subsequent bone cell migration and deposition of new osteoid. J. Cell. Biochem. 70:391-401, 1998. © 1998 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
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  • 143
    ISSN: 0730-2312
    Keywords: osteopontin ; integrins ; mechano-transduction ; tyrosine kinase ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Osteopontin is a predominant integrin binding protein of bone and its expression has been shown to be induced by mechanical stimuli within osteoblasts (Toma et al. [1997] J. Bone Miner. Res. 12:1626-1636). The present studies examined if the cell adhesion would mimic the mechano-transduction that stimulated opn mRNA expression and whether integrin receptors were involved in these processes. Osteopontin mRNA expression was induced three- to four-fold, 24 hours after embryonic chicken calvaria osteoblast attachment to fibronectin (FN), however no induction was observed if the cells were plated on tissue culture plastic alone. Osteopontin mRNA induction in response to cell attachment on FN was dependent on new protein synthesis and the activation of a tyrosine protein kinase(s) but unlike mechano-induction was independent of the maintenance of the cell's microfilament structure. Integrin receptor(s) were shown to be involved in mediating the signal transduction processes of both cell attachment and mechanical stimulation since incubation of osteoblasts with the integrin binding peptide RGDS partially blocked the induction of opn expression in response to both stimuli. Interestingly, incubation of the osteoblasts that were adherent on tissue culture plastic alone with the RGDS peptide lead to an induction in opn expression suggesting that integrin occupancy by itself was sufficient to initiate the signal transduction process that induced opn expression. In order to assess the role of integrin occupancy vs. focal adhesion complex formation that accompanies cell attachment, in the signal transduction process that induces opn expression, receptor clustering was stimulated pharmacologically with bombesin or lysophasphatidic acid in osteoblasts attached to tissue culture plastic. Neither compound in the absence of occupancy of the integrin receptors was capable of stimulating opn expression in attached cells, however if the cells were placed in suspension pharmacological mediation of receptor clustering and integrin occupancy were additive in their effect of inducing opn expression. These data demonstrate that induction of opn expression by mechanical stimuli and cell attachment are commonly mediated through integrin receptor(s). However, when cells are attached receptor clustering alone which accompanies focal adhesion formation was incapable of mediating signal transduction suggesting that receptor occupancy was a prerequisite to the signal transduction process that leads to the induction of opn mRNA expression. J. Cell. Biochem. 70:376-390. © 1998 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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  • 144
    ISSN: 0730-2312
    Keywords: genome ; calmodulin ; smooth muscle ; immunohistochemistry ; heart ; development ; protein kinase ; tissue selective ; calcium ; signal transduction ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: We report that the genetic locus that encodes vertebrate smooth muscle and nonmuscle myosin light chain kinase (MLCK) and kinase-related protein (KRP) has a complex arrangement and a complex pattern of expression. Three proteins are encoded by 31 exons that have only one variation, that of the first exon of KRP, and the genomic locus spans approximately 100 kb of DNA. The three proteins can differ in their relative abundance and localization among tissues and with development. MLCK is a calmodulin (CaM) regulated protein kinase that phosphorylates the light chain of myosin II. The chicken has two MLCK isoforms encoded by the MLCK/KRP locus. KRP does not bind CaM and is not a protein kinase. However, KRP binds to and regulates the structure of myosin II. Thus, KRP and MLCK have the same subcellular target, the myosin II molecular motor system. We examined the tissue and cellular localization of KRP and MLCK in the chicken embryo and in adult chicken tissues. We report on the selective localization of KRP and MLCK among and within tissues and on a differential distribution of the proteins between embryonic and adult tissues. The results fill a void in our knowledge about the organization of the MLCK/KRP genetic locus, which appears to be a late evolving regulatory paradigm, and suggest an independent and complex regulation of expression of the gene products from the MLCK/KRP genetic locus that may reflect a basic principle found in other eukaryotic gene clusters that encode functionally linked proteins. J. Cell. Biochem. 70:402-413, 1998. © 1998 Wiley-Liss, Inc.
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  • 145
    ISSN: 0730-2312
    Keywords: opioids ; cathepsin D ; pS2 ; estrogen ; cancer ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: In many cancer cell lines, including breast, prostate, lung, brain, head and neck, retina, and the gastrointestinal tract, opioids decrease cell proliferation in a dose-dependent and reversible manner. Opioid and/ or other neuropeptide receptors mediate this decrease. We report that only the steroid-hormone-sensitive cell lines MCF7 and T47D respond to opioid growth inhibition in a dose-dependent manner. Therefore, an interaction of the opioid and steroid receptor system might exist, as is the case with insulin. To investigate this interaction, we have assayed two estrogen-inducible proteins (pS2 and the lysosomal enzyme cathepsin D) in MCF7 and T47D cells. When cells were grown in the presence of FBS (in which case a minimal quantity of estrogens and/ or opioids is provided by the serum), we observed either no effect of etorphine or ethylketocyclazocine (EKC) or an increase of secretion and/ or production of pS2 and cathepsin D. However, when cells were cultured in charcoal-stripped serum and in the absence of phenol red, the effect of the two opioids is different: EKC decreased the production and/ or secretion of pS2 and cathepsin D, whereas etorphine increased their synthesis and/ or secretion. The differential effect of the two general opioids was attributed to their different receptor selectivity. Furthermore, the variations of the ratio of secreted/ produced protein and the use of cycloheximide indicate that opioids selectively modify the regulatory pathway of each protein discretely. In conclusion, through the interaction with opioid and perhaps other membrane-receptor sites, opioid agonists modify in a dose-dependent manner the production and the secretion of two estrogen-regulated proteins. Opioids may therefore disturb hormonal signals mediated by the estrogen receptors. Hence, these chemicals may have potential endocrine disrupting activities. J. Cell. Biochem. 71:416-428, 1998. © 1998 Wiley-Liss, Inc.
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  • 146
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    Journal of Cellular Biochemistry 70 (1998), S. 157-158 
    ISSN: 0730-2312
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: No abstract.
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  • 147
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    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 70 (1998), S. 141-155 
    ISSN: 0730-2312
    Keywords: endothelial cell ; tyrosine phosphatase ; vanadate ; permeability ; MLCK ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The involvement of tyrosine protein phosphorylation in the regulation of endothelial cell (EC) contraction and barrier function is poorly understood. We have previously shown that myosin light chain (MLC) phosphorylation catalyzed by a novel 214 kDa EC myosin light chain kinase (MLCK) isoform is a key event in EC contraction and barrier dysfunction [Garcia et al. (1995): J Cell Physiol 163:510-522; Garcia et al. (1997): Am J Respir Cell Mol Biol 16:487-491]. In this study, we tested the hypothesis that tyrosine phosphatases participate in the regulation of EC contraction and barrier function via modulation of MLCK activity. The tyrosine phosphatase inhibitor, sodium orthovanadate (vanadate), significantly decreased electrical resistance across bovine EC monolayers and increased albumin permeability consistent with EC barrier impairment. Vanadate significantly increased EC MLC phosphorylation in a time-dependent manner (maximal increase observed at 10 min) and augmented both the MLC phosphorylation and permeability responses produced by thrombin, an agonist which rapidly increases tyrosine kinase activities. The vanadate-mediated increase in MLC phosphorylation was not associated with alterations in either phosphorylase A Ser/Thr phosphatase activities or in cytosolic [Ca2+] but was strongly associated with significant increases in EC MLCK phosphotyrosine content. These data suggest that tyrosine phosphatase activities may participate in EC contractile and barrier responses via the regulation of the tyrosine phosphorylation status of EC MLCK. J. Cell. Biochem. 70:141-155, 1998. © 1998 Wiley-Liss, Inc.
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  • 148
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    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 70 (1998), S. 172-180 
    ISSN: 0730-2312
    Keywords: nuclear matrix ; nuclear structure ; cancer ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Cancer is diagnosed by examining the architectural alterations to cells and tissues. Changes in nuclear structure are among the most universal of these and include increases in nuclear size, deformities in nuclear shape, and changes in the internal organization of the nucleus. These may all reflect changes in the nuclear matrix, a non-chromatin nuclear scaffolding determining nuclear form, higher order chromatin folding, and the spatial organization of nucleic acid metabolism. Malignancy-induced changes in this structure may have profound effects on chromatin folding, on the fidelity of genome replication, and on gene expression. Elucidating the mechanisms and the biological consequences of nuclear changes will require the identification of the major structural molecules of the internal nuclear matrix and an understanding of their assembly into structural elements. If biochemical correlates to malignant alterations in nuclear structure can be identified then nuclear matrix proteins and, perhaps nuclear matrix-associated structural RNAs, may be an attractive set of diagnostic markers and therapeutic targets. J. Cell. Biochem. 70:172-180, 1998. © 1998 Wiley-Liss, Inc.
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  • 149
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    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 70 (1998), S. 193-199 
    ISSN: 0730-2312
    Keywords: parathyroid hormone-related peptide ; nucleus ; nucleolus ; intracrine actions ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: It is becoming increasingly apparent that parathyroid hormone-related peptide (PTHrP) modulates cellular function in a dual mode of action: first, by binding and activating its cognate cell surface G-protein-coupled receptor and, second, by direct intracellular effects following translocation to the nucleus and/or nucleolus of the target cell. Little is presently known about the mechanisms and events that determine the timing and degree of PTHrP nuclear translocation or the role it may serve in normal or dysregulated cellular function. Clarifying the nuclear actions of PTHrP would add significantly to our present understanding of this protein as a signaling molecule during embryonic development and as an oncoprotein whose expression in many tumors correlates with increased tumor aggressiveness and propensity for metastasis. J. Cell. Biochem. 70:193-199, 1998. © 1998 Wiley-Liss, Inc.
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  • 150
    ISSN: 0730-2312
    Keywords: gene expression ; AML/CBF transcription factors ; nuclear matrix ; cancer ; nuclear domains ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Functional interrelationships between components of nuclear architecture and control of gene expression are becoming increasingly evident. In this article we focus on the concept that association of genes and cognate transcription factors with the nuclear matrix may support the formation and/or activities of nuclear domains that facilitate transcriptional regulation. Several lines of evidence are consistent with the concept that association of transcription factors with the nuclear matrix may be obligatory for fidelity of gene expression and maximal transcriptional activity. The identification of specific regions of transcription factors that are responsible for intranuclear trafficking to nuclear matrix-associated sites that support transcription, reinforces the linkage of nuclear structure to regulation of genes. CBFA2/AML-1 and CBFA1/AML-3 provide paradigms for directing gene regulatory factors to RNA polymerase II containing foci within the nucleus. The implications of modifications in the intranuclear trafficking of transcription factors for developmental and tissue-specific control, as well as for aberrations in gene expression that are associated with cancer and neurological disorders, are addressed. J. Cell. Biochem. 70:200-212, 1998. © 1998 Wiley-Liss, Inc.
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  • 151
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    Journal of Cellular Biochemistry 71 (1998), S. 264-276 
    ISSN: 0730-2312
    Keywords: HGF/SF ; MSH ; c-met ; tyrosinase ; B16 melanoma ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Reiterated selection in vivo of B16 murine melanoma cells for enhanced liver metastatic ability yielded a cell line (B16-LS9) dramatically overexpressing a constitutively active hepatocyte growth factor/scatter factor (HGF/SF) receptor, the product of the c-met proto-oncogene. Most likely because of their overexpressing c-met, B16-LS9 cells appear to be more responsive than parental B16-F1 cells to HGF stimulation, in terms of motility, invasion, and growth. They are also more pigmented, and express higher levels of tyrosinase as compared to parental B16-F1 cells. Therefore, we set out to explore whether HGF/SF and the liver might influence the differentiation state of B16 cells. We found that HGF/SF and MSH, two factors which reportedly have a strong influence on the phenotype and the malignant behavior of melanoma cells, may act at different levels, and with opposite results, on the regulation of gene expression. In fact, while MSH induces, at the transcriptional level, an increase in the production of both c-met and tyrosinase, HGF/SF, in contrast, promotes a decrease in the expression of both c-met and tyrosinase, however at a posttranscriptional level. These two opposite effects can counter-balance each other, when the cells are treated with both factors at the same time, apparently through a mechanism involving MAP kinase activation. The effects were, however, additive when morphological changes were considered. Most intriguingly, we also describe a very strong downregulatory activity, limited to tyrosinase expression, by hepatocytes in coculture with B16 cells. This activity, also at the posttranscriptional level, is much stronger than that exerted by HGF/SF, and appears to be due to a labile soluble factor produced by the hepatocytes. J. Cell. Biochem. 71:264-276, 1998. © 1998 Wiley-Liss, Inc.
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  • 152
    ISSN: 0730-2312
    Keywords: lysyl oxidase ; cyclooxygenase-1 ; type I collagen α1 ; prostaglandin E2 ; prostaglandin E2 receptors ; cyclic AMP ; interleukin-1β ; transforming growth factor-β ; forskolin ; 11-deoxy PGE1 ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: In a recent communication, we demonstrated that prostaglandin E2 (PGE2) lowers basal while it ablates interleukin-1β( (IL-1β) and transforming growth factor-β (TGFβ) upregulated lysyl oxidase (LO) mRNA levels. Correspondingly, PGE2 increases cyclooxygenase-1 (COX1) mRNA in diploid, human embryo lung fibroblasts (IMR90) [Roy et al., 1996]. We now report that these actions by PGE2 are routed through cAMP via the PGE2, EP2 receptor. Among the PGE2 receptor types, the IMR90 predominantly express the EP2 mRNA. These cells also express EP3 and EP4 mRNA at comparatively low levels. Northern blot analyses show that 11-deoxy PGE1, an EP2/EP4 agonist, emulates the action of PGE2. In a similar manner to PGE2, 11-deoxy PGE1 decreases basal and TGF-β induced type I collagen α1 (COL) mRNA, basal and IL-1β induced LO mRNA while it increases COX1 mRNA. Sulprostone, an EP3/EP1 agonist, has no effect on the expression of these three genes. Forskolin, an adenylate cyclase activator, acts in a very similar manner to PGE2or 11-deoxy PGE1. It suppresses both basal and TGF-β induced COL mRNA levels. Both PGE2 and 11-deoxy PGE1 increase cAMP to a level comparable with forskolin. The role of the EP2 receptor in controlling collagen production is further underscored in the immortalized Rat-1 fibroblasts, derived from Fischer rat embryos, which do not express detectable EP2 mRNA. In these cells, PGE2 has little effect on COL mRNA level, whereas forskolin increases it. Furthermore, forskolin increases cAMP level in Rat-1 cells, whereas PGE2 does not. Overall, these results illustrate that much of the PGE2 action on the expression of COL, LO, and COX1 genes is mediated through the EP2 receptor and a subsequent increase in intracellular cAMP. J. Cell. Biochem. 71:254-263, 1998. © 1998 Wiley-Liss, Inc.
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  • 153
    ISSN: 0730-2312
    Keywords: Id ; cytokines ; hematopoiesis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Hematopoietic development is regulated by a complex mixture of cytokine growth factors that guide growth and differentiation of progenitor cell populations at different stages in their development. The genetic programs that drive this process are controlled at the molecular level by the type and number of transcriptional regulators coexpressed in the cell. Both positive- and negative-acting helix-loop-helix transcription factors are expressed during hematopoietic development, with the Id-type transdominant negative regulators controlling the net helix-loop-helix activation potential in the cell at any given time. It has been demonstrated that some of these Id factors are involved in the checkpoint at which undifferentiated progenitor cells make the commitment to terminal maturation. Therefore, we sought to determine whether these Id family factors are selectively induced or extinguished by cytokines that act at different points during hematopoiesis. NFS-60, a myeloid progenitor line that proliferates in response to multiple cytokines, was stimulated by treatment with SCF, IL-3, IL-6, G-CSF, and erythropoietin. Id-1 expression correlated tightly with cellular proliferation: it declined when growth factor stimulation was withdrawn and was quickly induced whenever the cell began to proliferate. The regulation of Id-2 was more complex: its expression was slightly upregulated in factor-deprived cells but only strongly reinduced after extended exposure to cytokines that drive granulocytic differentiation (IL-6, G-CSF, and TGFβ1). These data support a cell-cycle regulatory role for Id-1 in multipotent myeloid progenitor cells and a role for Id-2 during terminal granulocytic differentiation. J. Cell. Biochem. 71:277-285, 1998. © 1998 Wiley-Liss, Inc.
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  • 154
    ISSN: 0730-2312
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Srebrow A, Friedmann Y, Ravanpay A, Daniel CW, Bissell MJ (1998): Expression of Hoxa-1 and Hoxb-7 is regulated by extracellular matrix-dependent signals in mammary epithelial cells. J Cell Biochem 69:377-391.In Figure 3 on pages 384 and Figure 4 on page 385, two labels were misprinted. The top label on the right side of Figure 3B should have been Hoxb-7 instead of Hoxb-1, and the center label of Figure 4B should have been Hoxb-7 instead of Hoxa-7. The corrected figures are reprinted on the following pages.The Publisher apologizes for the error.
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  • 155
    ISSN: 0730-2312
    Keywords: IGFBP ; cAMP ; PKA ; prostaglandin ; bone ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Insulin-like growth factor (IGF)-I and IGF-II are expressed at biologically effective levels by bone cells. Their stability and activity are modulated by coexpression of IGF binding proteins (IGFBPs). Secreted IGFBPs may partition to soluble, cell-associated, and matrix-bound compartments. Extracellular localization may sequester, store, or present IGFs to appropriate receptors. Of the six IGFBPs known, rat osteoblasts synthesize all but IGFBP-1. Of these, IGFBP-3, -4, and -5 mRNAs are induced by an increase in cAMP. Little is known about extracellular IGFBP localization in bone and nothing about IGFBP expression by nonosteoblastic periosteal bone cells. We compared basal IGFBP expression in periosteal and osteoblast bone cell cultures and assessed the effects of changes in cAMP-dependent protein kinase A or protein kinase C. Basal IGFBP gene expression differed principally in that more IGFBP-2 and -5 occurred in osteoblast cultures, and more IGFBP-3 and -6 occurred in periosteal cultures. An increase in cAMP enhanced IGFBP-3, -4, and -5 mRNA and accordingly increased soluble IGFBP-3, -4, and -5 and matrix-bound IGFBP-3 and -5 in both bone cell populations. In contrast, protein kinase C activators suppressed IGFBP-5 mRNA, and its basal protein levels remained very low. We also detected low Mr bands reactive with antisera to IGFBP-2, -3, and -5, suggesting proteolytic processing or degradation. Our studies reveal that various bone cell populations secrete and bind IGFBPs in selective ways. Importantly, inhibitory IGFBP-4 does not significantly accumulate in cell-associated compartments, even though its secretion is enhanced by cAMP. Because IGFBPs bind IGFs less tightly in cell-bound compartments, they may prolong anabolic effects by agents that increase bone cell cAMP. J. Cell. Biochem. 71:351-362, 1998. © 1998 Wiley-Liss, Inc.
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  • 156
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    Journal of Cellular Biochemistry 71 (1998), S. 382-391 
    ISSN: 0730-2312
    Keywords: dexamethasone ; bone marrow cell cultures ; IGF-I ; vertebrae ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Osteoblast-like cell cultures have been established from the marrow of adult rat vertebrae. We have simultaneously examined the response to dexamethasone (dex) treatment in cultures of young adult female vertebral and femoral marrow cells. Alkaline phosphatase (AP) activity was analyzed as well as the expression of mRNAs for osteocalcin (OC) and insulin-like growth factor I (IGF-I). The vertebral and femoral marrow cells were maintained for 7 days in primary culture with or without 10-8 M dex and then 6 days in secondary culture without dex or with 10-8 M or 10-7 M dex. All cells were examined on day 6 of secondary culture. Vertebral and femoral cultures each expressed the highest AP enzyme levels when grown with dex in primary culture (10-8 M) and secondary culture (10-7 M). Under all experimental conditions, vertebral cultures had lower AP enzyme activity than femoral cultures. When dex was omitted from secondary culture, OC gene expression was not detected in either vertebral or femoral passaged cells even if dex was present in primary culture. For dex conditions where OC was expressed, vertebral cultures had higher OC mRNA steady-state levels than femoral cultures. IGF-I gene expression was detected by Northern analysis in both vertebral and femoral secondary cultures. However, vertebral marrow cultures had much higher IGF-I mRNA levels compared to femoral cultures whether or not dex was present in primary culture. These findings demonstrate that dex supports the differentiation of both vertebral and femoral adult marrow osteogenic cells into osteoblasts. Our results support the hypothesis that osteoblastic marrow cultures differ depending upon which location in the skeleton they are from and that there are skeletal site-dependent differences in the insulin-like growth factor system components. J. Cell. Biochem. 71:382-391, 1998. © 1998 Wiley-Liss, Inc.
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  • 157
    ISSN: 0730-2312
    Keywords: Ishikawa cells ; endometrium ; biotin ; multinucleated cells ; predomes ; domes ; pinopods ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Human Ishikawa endometrial cells form domes when confluent monolayers are stimulated with fresh fetal bovine serum. Extensive structural and biochemical changes have been detected during the approximately 30 h differentiation period. The earliest detectable change involves the formation of multinucleated structures and the appearance of “granules” that stain for biotin within those structures. Nuclei become associated with each other and are ultimately enclosed within a biotin-containing membrane. Aggregated membrane-sheathed nuclei and the cells containing them begin to elevate from the dish as biotin staining becomes apparent in apical membranes. The elevated structures are called predomes and consist of one or more very large cells containing the sheathed nuclei. Apical membranes of these unusual cells extend far out into the medium in structures that resemble endometrial pinopods. A lumen under the elevated cells fills with transcytosed fluid. As differentiation proceeds, highly concentrated chromatin material that was flattened against apical and lateral membranes of the predome cells begins to disperse. Small mononuclear cells evolve from larger predome cells. Apical membranes of predome and dome cells continue to stain for biotin. Gel electrophoresis of SDS-solubilized biotin-containing membranes, followed by Western blot analysis using avidin-linked peroxidase, resulted in three stained bands with molecular weights similar to those of the mitochondrial carboxylases: propionyl carboxylase, methylmalonyl carboxylase, and pyruvate carboxylase. J. Cell. Biochem. 71:400-415, 1998. © 1998 Wiley-Liss, Inc.
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  • 158
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    Journal of Cellular Biochemistry 72 (1998), S. 73-82 
    ISSN: 0730-2312
    Keywords: osteoblast ; bone ; stem cells ; osteoprogenitor ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Osteoblasts are the skeletal cells responsible for synthesis, deposition, and mineralization of the extracellular matrix of bone. By mechanisms that are only beginning to be understood, stem and primitive osteoprogenitors and related mesenchymal precursors arise in the embryo and at least some appear to persist in the adult organism, where they contribute to replacement of osteoblasts in bone turnover and in fracture healing. In this paper, the nature of these cells, whether they constitute a stem cell pool or a committed progenitor pool, and aspects of their apparent plasticity are discussed. Current understanding of differential expression of osteoblast-associated genes during osteoprogenitor proliferation and differentiation to mature matrix synthesizing osteoblasts is summarized. Finally, evidence is discussed that supports the hypothesis that the mature osteoblast phenotype is heterogeneous with subpopulations of osteoblasts expressing only subsets of the known osteoblast markers, raising also the possibility of multiple parallel differentiation pathways and perhaps even different progenitor pools. J. Cell. Biochem. Suppls. 30/31:73-82, 1998. © 1998 Wiley-Liss, Inc.
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  • 159
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1-9 
    ISSN: 0887-6266
    Keywords: small-angle neutron scattering ; SANS ; polystyrene ; polyvinylmethylether ; radius of gyration ; Zimm analysis ; random phase approximation ; phase diagram ; polymer blends ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Small-angle neutron scattering was used to measure the radius of gyration and thermodynamics of blends of poly(vinylmethylether) (PVME) at dilute concentration in deuterated polystyrene (PSD). The data were analyzed using the Zimm equation and the random phase approximation theory. For PVME with a weight-average molecular weight of 38,400 the value of the radius of gyration, Rg, was found to be 47 Å in the limit of the concentration of PVME extrapolated to zero. Analysis of the temperature dependence of the Flory interaction parameter, χ/v0, indicates that phase separation should occur at approximately 300°C for a sample with φPVME ≅ 9%. No significant temperature dependence of Rg was found over the experimental range studied. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1-9, 1998
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  • 160
    ISSN: 0887-6266
    Keywords: liquid crystal ; block copolymer ; polyester block ; polymethacrylate block ; magnetic field ; X-ray diffraction ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The phase and orientational behaviors of a series of liquid crystalline (LC) AB-type diblock copolymers comprising thermotropic main-chain (MC) polyester and side-group (SG) polymethacrylate blocks were investigated by X-ray diffraction. The MC and SG blocks were phase separated and gave rise to their individual mesophases that coexisted at equilibrium. The samples were oriented by using either a magnetic field or a mechanical field. In magnetically aligned samples both the MC and SG microphases were oriented with their smectic planes orthogonal to the magnetic field direction, independent of the copolymer composition. Mechanically aligned, fiber samples showed different orientations of the MC and SG smectic planes for different sample compositions. In this case the disposition of the smectic planes of the MC and SG blocks was driven by the relative length of the two blocks. Some features of the X-ray patterns of the copolymers were compared to those of the MC and SG homopolymers. In addition, the MC smectic domains crystallized on annealing without affecting the orientation that had been achieved by applying a magnetic field. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 21-29, 1998
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  • 161
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 49-54 
    ISSN: 0887-6266
    Keywords: substituted poly(paraphenylene) ; phase transitions ; synchrotron radiation ; mesophases ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The thermal behavior of poly(para-2,5-didecyl-p-phenylene) has been investigated by differential scanning calorimetry and real time X-ray diffraction. Poly(para-2,5-didecyl-p-phenylene) is a semicrystalline material that crystallizes in a layered structure. The system exhibits two thermal transitions in the investigated temperature range. The first one, occurring at lower temperatures, provokes a reduction of the layered spacing accompanied by an appreciable disordering of the lateral side chains. Above the first transition the material is shearable, highly viscous, and birefringent. Thus, we have associated this transition to the formation of a layered mesophase. The higher temperature transition exhibits a twofold endothermic DSC peak and is characterized by the disappearance of X-ray diffracted intensity. At temperatures above the second transition the system presents the characteristics of an isotropic melt. Consequently, we have associated this transition with the complete disordering of the polymeric backbones. By following an appropriate thermal treatment it has been shown that the twofold shape of the endotherm characterizing the higher temperature transition can be changed into a single endotherm. This effect has been interpreted as being due to the kinetics of main-chain ordering. This ordering seems to proceed by the initial growth of domains with a high level of order followed by the subsequent increase of these domains through the inclusion of less ordered material. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 49-54, 1998
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  • 162
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 85-93 
    ISSN: 0887-6266
    Keywords: polybutadiene ; poly(methyl methacrylate) ; poly(butadiene-block-methyl methacrylate) ; compatibilization ; micelle ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Compatibilization of blends of polybutadiene and poly(methyl methacrylate) with butadiene-methyl methacrylate diblock copolymers has been investigated by transmission electron microscopy. When the diblock copolymers are added to the blends, the size of PB particles decreases and their size distribution gets narrower. In PB/PMMA7.6K blends with P(B-b-MMA)25.2K as a compatibilizer, most of micelles exist in the PMMA phase. However, using P(B-b-MMA)38K as a compatibilizer, the micellar aggregation exists in PB particles besides that existing in the PMMA phase. The core of a micelle in the PMMA phase is about 10 nm. In this article the influences of temperature and homo-PMMA molecular weight on compatibilization were also examined. At a high temperature PB particles in blends tend to agglomerate into bigger particles. When the molecular weight of PMMA is close to that of the corresponding block of the copolymer, the best compatibilization result would be achieved. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 85-93, 1998
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  • 163
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 113-126 
    ISSN: 0887-6266
    Keywords: enthalpy relaxation ; physical aging ; DSC ; glassy state ; thermoplastic polymers ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The enthalpy relaxation of a series of linear amorphous polyesters (poly(propylene isophthalate) (PPIP), poly(propylene terephthalate) (PPTP), poly(ethylene terephthalate) (PETP), and poly(dipropylene terephthalate) (PDPT)) has been investigated by differential scanning calorimetry (DSC). These polyesters have been annealed at equal undercooling below their respective glass transition temperatures, Tg, (Tg - 27°C, Tg - 15°C, and Tg - 9°C) for periods of time from 15 min to 480 h. The key parameters of structural relaxation, namely the apparent activation energy (Δh*), the nonlinearity parameter (x) and the nonexponentiality parameter (β), have been determined for each polyester and related to an effective relaxation rate (1/τeff) and to the chemical structure. We observe that the variation of the structural relaxation parameters shows a trend that is common to other polymeric systems, whereby an increase of x and β corresponds a decrease in Δh*. The comparison of these parameters in PETP and in PPTP gives information about the effect of the introduction of a methyl group pendant from the main chain; the x parameter increases (i.e., a reduced contribution of the structure to the relaxation times), β increases (i.e., a narrow distribution of relaxation times), and Δh* decreases. Additionally, enthalpy relaxation experiments show that a decrease of Δh* correlates with an increase of 1/τeff, when they are measured at a fixed value of the excess enthalpy, δH. The introduction of an isopropyl ether group in PDPT with respect to PPTP decreases both x and β, but increases Δh*, which the rate of relaxation decreases. The ring substitution in PPTP and PPIP originates less significant changes in the structural parameters. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 113-126, 1998
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  • 164
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 163-169 
    ISSN: 0887-6266
    Keywords: acetone ; poly(ethylene terephthalate) ; mass transport ; solvent-induced crystallites ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The acetone transport in poly(ethylene terephthalate) (PET) and related phenomena was investigated. Based on Harmon's model for Case I, Case II, and the anomalous transport, we analyzed the data of mass uptake. The diffusivity for Case I and the velocity for Case II satisfied the Arrhenius plot. It was found that the solvent moves from outer surfaces to the center according to Case I kinetics, and there is movement in the opposite direction according to Case II kinetics during the mass uptake. This result indicated that pure Case II behavior did not appear in the PET-acetone system. The saturated amount of acetone in PET satisfied the van't Hoff plot. X-ray diffraction pattern and DSC curve showed solvent-induced crystallites and thermal crystallites. The results of density measurement explained the difference of the sorption kinetics between the acetone-treated PET crystallites and thermally treated PET. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 163-169, 1998
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  • 165
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 617-627 
    ISSN: 0887-6266
    Keywords: isotactic polypropylene foams ; supercritical propane solutions ; high surface areas ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Crystallization of isotactic polypropylene (iPP) from homogeneous solution in supercritical propane yields open-cell foams of high surface area (120-150 m2/g). Their morphology usually consists of microspheres with a dense core and a porous periphery of radiating fibrils. Pore radii covering the mesopore range (2-50 nm), making their largest contribution at 10-20 nm, were calculated from nitrogen adsorption isotherms. Surface areas of the correct order of magnitude are obtained by assuming that gas adsorption takes place on the surfaces of lamellar crystals. Crystallization of iPP from n-butane and n-heptane generates foams of lower mesoporosity and smaller surface area. These more “liquid-like” solvents do not allow the formation of an open network of mesopores or they promote its collapse upon their removal. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 617-627, 1998
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  • 166
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 693-703 
    ISSN: 0887-6266
    Keywords: phase separation ; NMR spectroscopy ; block copolymers ; reaction injection molding ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The microphase separation (MPS) in polyureas based on methylene diphenyl diisocyanate (MDI) hard segment, diethyltoluenediamine chain extender, and amino-terminated polypropylene glycol soft segment prepared by reaction injection molding (RIM) was studied by advanced solid-state NMR spectroscopy. Incomplete microphase separation leads to the presence of mobilized hard segments dispersed in the soft segment domains as well as immobilized soft segments residing in the hard domains. This is detected by 1H-NMR spectra recorded under spinning at the magic angle (MAS) as well as two-dimensional wide-line separation (WISE) NMR spectra. The sizes of the various domains as well as the interfaces between them are quantified by spin diffusion measurements. In this way the impact of annealing, method of polymerization, and hard segment content on MPS is studied. Whereas annealing at temperatures up to 170°C results in improving the MPS, major changes are observed after annealing at higher temperatures (190°C), where the system changes from “soft-in-hard” to “hard-in-soft” behavior. The MPS decreases with increasing hard segment content. The highest MPS is observed for solution polymerized samples. The various NMR experiments clearly reveal the nonequilibrium nature of RIM systems. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 693-703, 1998
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  • 167
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 743-753 
    ISSN: 0887-6266
    Keywords: polyacrylamides ; specific viscosity ; polyelectrolyte solutions ; light scattering ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dependences of the specific viscosity of several polyelectrolytes on polyelectrolyte concentration, salt concentration or solution ionic strength, solution pH value, solvent quality, and solution temperature were systematically investigated. We found that the specific viscosity obeys a more general relation: ηsp = Acp2/(cp + 2cs)3/2 + B, where ηsp is the polyelectrolyte specific viscosity, cp and cs are polymer and salt concentrations, respectively. The prefactor A depends critically on chain size, solvent quality, and temperature in qualitative agreement with the theory proposed by Rabin et al. The intercept B is nonzero or less than zero in polyelectrolyte solutions with low ionic strength. When a sufficient amount of salt has been added, B is reduced to zero and we recover the Rabin et al.'s relation. The physical interpretation for the intercept B is that it represents the inverse of the strength of electrostatic interaction between a polyion and counterions, in quantitative agreement with the well-known emperical Fuoss's relation. Furthermore, the existence of nonzero B allows us to calculate the condition for the maximum in the reduced viscosity-polymer concentration curve in a polyelectrolyte solution system without salt. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 743-753, 1998
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  • 168
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 789-795 
    ISSN: 0887-6266
    Keywords: in situ polymerization ; nanocomposite ; toughness ; nylon 6 ; silica ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A novel method, in situ polymerization, was used for the preparation of nylon 6/silica nanocomposites, and the mechanical properties of the nanocomposites were examined. The results showed that the tensile strength, elongation at break, and impact strength of silica-modified nanocomposites exhibited a tendency of up and down with the silica content increasing, while those of silica-unmodified nanocomposites decreased gradually. It also exhibited that the mechanical properties of silica-modified nanocomposites have maximum values only when 5% silica particles were filled. Based on the relationship between impact strength of the nanocomposites and the matrix ligament thickness τ, a new criterion was proposed to explain the unique mechanical properties of nylon 6/silica nanocomposites. The nylon 6/silica nanocomposites can be toughened only when the matrix ligament thickness is less than τc and greater than τa, where τa is the matrix ligament thickness when silica particles begin to aggregate, and τc is the critical matrix ligament thickness when silica particles begin to toughen the nylon 6 matrix. The matrix ligament thickness, τ, is not independent, which related with the volume fraction of the inorganic component because the diameter of inorganic particles remains constant during processing. According to the observation of Electron Scanning Microscope (SEM), the process of dispersion to aggregation of silica particles in the nylon 6 matrix with increasing of the silica content was observed, and this result strongly supported our proposal. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 789-795, 1998
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  • 169
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 827-840 
    ISSN: 0887-6266
    Keywords: polyimides ; imidization ; perylenetetracarboxydiimide ; electron transfer ; fluorescence quenching ; polyimide blends ; miscibility ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Perylenetetracarboxydiimide (PEDI) molecularly dispersed in polyamic acid (PAA) and polyimide (PI) films has unique fluorescence properties. An originally strong fluorescence of PEDI is efficiently quenched in the PAA films. The systematic variation of the chain structure of the PAA matrices revealed that the aromatic amide groups in the PAA chains function as a quencher. When a PAA derived from 3,4,3′4′-biphenyltetracarboxylic dianhydride (BPDA) and p-phenylenediamine (PDA), BPDA/PDA, was used as a matrix polymer, the fluorescence of the dye dispersed in the film increased abruptly as imidization of the matrix proceeds. But annealing at temperatures higher than 320°C in the step-heating process caused a gradual decrease in the fluorescence intensity. The decreased intensity results from the dye-PDA units interactions intensified by the denser molecular packing of the matrix polymer chains. PEDI shows significant dependence of the fluorescence intensity on the chain structure of the PI matrices. In the various PI films containing a fixed diamine component, the dye fluorescence intensity reduces linearly with an increase in the intramolecular charge transfer ability of the PI matrices. From the result, we propose a fluorescence quenching mechanism through multistep electron transfer processes. The BPDA/PDA polyimide matrix leads to a strong PEDI fluorescence whereas the pyromellitic dianhydride (PMDA)-based PI matrices do not. For the blends composed of these PIs, the fluorescence of PEDI bound into the main chains provides a valuable indicator of the miscibility on the molecular level. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 827-840, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1275-1281 
    ISSN: 0887-6266
    Keywords: chitosan ; polyethylene glycol polyblend ; intermolecular interaction ; viscometry ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The molecular structures of polyethylene glycol (PEG) and chitosan (CS) are illustrated as follows: 1CS2PEG\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm HO} \hbox{--} {\rm CH}_2 {\rm CH}_2 \rlap{--} ({\rm O} \hbox{--} {\rm CH}_2 {\rm CH}_2 \rlap{--} {\rm O} \hbox{--} {\rm CH}_2 {\rm CH}_2 \hbox{--} {\rm OH} $$\end{document} The intermolecular interactions between these two polymers were studied by viscometry with a thermodynamic parameter α, which was first proposed by Sun et al. The weight additive rule of the intrinsic viscosity of polyblend relating to the values of each polymeric constituent was attested to with PEG/CS polyblend. The calculation formula of Huggins coefficient for polyblend, km, was theoretically deduced, and a very simple expression of α was obtained. First, the values of α for PEG/CS blends with different PEG molecular weight were estimated from the experimental viscosity data of the polyblends with different mixed ratio. According to these values of α, it can be predicted that an attractive interaction exists between the molecule of PEG and that of CS. Second, the viscosity of CS was measured in pseudo-solvents (PEG dissolved in 0.01N sodium chloride aqueous solution) with different PEG concentrations. From these viscosity data, the values of cross Huggins coefficient are calculated to be all larger than the values of the Huggins coefficient both for CS and for PEG. On the revised α criterion, the dissimilar molecular interaction in PEG/CS polyblend is demonstrated to be attractive too. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1275-1281, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1313-1320 
    ISSN: 0887-6266
    Keywords: swelling ; polyacrylamide gels ; swelling in polymer solutions ; polymer-polymer interaction parameter ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Swelling behavior of polyacrylamide (PAAm) and polyacrylamide-co-polyacrylic acid (PAAm-co-PAAc) gels was investigated in aqueous solutions of monodisperse PAAms with molecular weights (Mw) ranging from 1.5 × 103 to 5 × 106 g/mol. The volume of the gels decreases as the PAAm concentration in the external solution increases. This decrease becomes more pronounced as the molecular weight of PAAm increases. The classical Flory-Huggins (FH) theory correctly predicts the swelling behavior of nonionic PAAm gels in PAAm solutions. The polymer-polymer interaction parameter χ23 was found to decrease as the molecular weight of PAAm increases. The swelling behavior of PAAm-co-PAAc gels in PAAm solutions deviates from the predictions of the FH theory. This is probably due to the change of the ionization degree of AAc units depending on the polymer concentration in the external solution. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1313-1320, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1349-1359 
    ISSN: 0887-6266
    Keywords: reaction-induced phase separation ; polysulfone-epoxy blends ; epoxy-anhydride networks ; polysulfone-modified epoxies ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The reaction-induced phase separation in a blend of a commercial polysulfone (PSu) with diepoxide-cyclic anhydride monomers, was studied. The diepoxide was based on diglycidylether of bisphenol A (DGEBA) and the hardener was methyl tetrahydrophthalic anhydride (MTHPA), used in stoichiometric proportion. Benzyldimethylamine (BDMA) was used as initiator. PSu had no influence on the polymerization kinetics, the gel conversion, and the overall heat of reaction per epoxy equivalent. A kinetic model including initiation, propagation, and termination steps was used to estimate the distribution of linear and branched species in the first stages of the chain-wise copolymerization. This distribution, together with the PSu distribution, were taken into account in a thermodynamic model of the blend. The interaction parameter was fitted from experimental determinations of conversions at the start of phase separation, obtained under different conditions. The thermodynamic model was used to explain the complex morphologies developed in materials containing different PSu concentrations as well as their dynamic mechanical response. The shift in glass transition temperatures was explained by the fractionation of different species during the phase separation process. Phase inversion produced a significant decrease of the elastic modulus in the glassy state and a thermoplastic-like behavior of the material in the rubbery region. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1349-1359, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1371-1382 
    ISSN: 0887-6266
    Keywords: epoxy resins ; thermosets ; glass transition ; yield behavior ; fracture toughness ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effects of crosslink functionality (fc), molecular weight between crosslinks (Mc), and chain stiffness display on the thermal and mechanical behavior of epoxy networks are determined. Both fc and Mc are controlled by blending different functionality amines with a difunctional epoxy resin. Chain stiffness is controlled by changing the chemical structure of the various amines. In agreement with rubber elasticity theory, the rubbery moduli are dependent on fc and Mc, but independent of chain stiffness. The glassy moduli and secondary relaxations of these networks are relatively independent of fc, Mc, and chain stiffness. However, the glass transition temperatures (Tg) of these networks are dependent on all three structural variables. This trend is consistent with free volume theory and entropic theories of Tg. fc, Mc, and chain stiffness control the yield strength of these networks in a manner similar to that of Tg and is the result that both properties involve flow or relaxation processes. Fracture toughness, as measured by the critical stress intensity factor (KIc), revealed that fc and Mc are both critical parameters. The fracture behavior is the result of the fracture toughness being controlled by the ability of the network to yield in front of the crack tip. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1371-1382, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1805-1819 
    ISSN: 0887-6266
    Keywords: polymer blend ; PA6 ; PPE ; epoxy ; reactive compatibilizer ; coupling agent ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A tetrafunctional epoxy monomer, N,N,N′-N′-tetraglycidyl-4,4′-diaminodiphenyl methane (TGDDM), has demonstrated to be a highly efficient reactive compatibilizer in compatibilizing the immiscible and incompatible polymer blends of polyamide-6 (PA6) and poly(2,6-dimethyl-1,4-phenylene ether) (PPE). This epoxy coupler can react with both PA6 and PPE to form various PA6-co-TGDDM-co-PPE mixed copolymers. These interfacially formed PA6-co-TGDDM-co-PPE copolymers tend to anchor along the interface to reduce the interfacial tension and result in finer phase domains and enhanced interfacial adhesion. A simple one-step melt blending has demonstrated to be more efficient in producing a better compatibilized PA6/PPE blend than a two-step sequential blending. The mechanical property improvement of the compatibilized blend over the uncompatibilized counterpart is very drastic, by considering the addition of a very small amount, a few fractions of 1%, of this epoxy coupling agent. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1805-1819, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1847-1856 
    ISSN: 0887-6266
    Keywords: electrical transport ; dielectric properties ; barium titanate ; carbon black ; epoxy resin ; relaxation processes ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Conductivity and dielectric constant of a three-component 0-3 composite of epoxy resin-barium titanate-carbon black (0-3 composites are systems in which the filler is in the form of 0-dimensional (point-like, disperse) particles in a three-dimensional polymeric matrix1) have been investigated both at DC and the frequency range of 20-106 c/s. The effect of barium titanate concentration on percolation threshold, critical indices and the mechanism of conduction has been examined. An attempt was made to describe the electrical properties of composites with models originally developed for two-component systems' dielectric-conductor. With increasing barium titanate concentration the agreement of experimentally found frequency dependencies of conductivity and dielectric constant with models based on Debye's equation was found to degrade. An adequate description of electrical properties of composites' dielectric-ferroelectric-conductor should be based on the Havriliak-Negami equation. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1847-1856, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1889-1899 
    ISSN: 0887-6266
    Keywords: polymer ; blend ; cocontinuity ; phase inversion ; interface ; morphology ; elasticity ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In this work the level of continuity and cocontinuity for blends of HDPE/PS prepared on a twin-screw extruder have been studied by both morphology and dissolution studies. Addition of SEBS as an interfacial modifier results in a shift of the percolation threshold for dispersed PS to higher concentrations. The region of phase inversion, however, is maintained at 70% PS. The shift in the percolation threshold to higher values is related to reduced elongation of the PS dispersed phase after interfacial compatibilization. These results indicate that an interfacial modifier significantly influences percolation phenomena without shifting the region of phase inversion. Models based on viscosity ratio have failed to predict the region of phase inversion in this study. Elastic effects are shown to be able to describe the basic tendencies. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1889-1899, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1927-1934 
    ISSN: 0887-6266
    Keywords: side chain liquid crystal polymers ; β-relaxation ; rotation of mesogenic units ; compensation law ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A strong dependence of the rotational dynamics of the mesogenic units (β-relaxation) on the order of the mesophase was found in sidechain liquid crystal polymers. The preexponential frequency factor, \documentclass{article}\pagestyle{empty}\begin{document}$ f_{\beta \infty }^* $\end{document} and the activation energy \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm E}_{\alpha \beta }^{\rm *} $\end{document} of the β-relaxation rate both increase significantly (i.e., obeying a compensation law) with increasing order of the mesophase which is accompanied by a decrease of the mean lateral mesogenic distance. In this work, we show how these experimental results can be interpreted in a quantitative manner by using the general results of the coupling model for cooperative motions. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1927-1934, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2005-2013 
    ISSN: 0887-6266
    Keywords: sphere doublets ; light scattering ; suspension ; flow ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The polarized or depolarized light scattering by well-defined monodispersed sphere doublets is investigated. Two configurations of doublets are studied. In the first (at rest) the doublets are randomly oriented in a plane, in the second the doublets are oriented in a preferred direction. This is achieved by submitting a suspension of doublets to a shear flow. The scattering patterns are compared to two theoretical predictions based on simplified geometries. In the first approach, the doublet is approximated by two interpenetrating spheres scattering independently, whereas in the second, an ellipsoid geometry is used. A good qualitative comparison is obtained. However, the HV and VH patterns of a randomly dispersed suspension are not similar. The observation of the flow of a doublet suspension in shear shows that the doublets are spiraling around the vorticity axis. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2005-2013, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2461-2470 
    ISSN: 0887-6266
    Keywords: dielectric relaxation spectroscopy ; thermosets ; interpenetrating polymer networks ; curing reaction ; temperature-modulated differential scanning calorimetry ; glass transition ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Dielectric relaxation spectroscopy (3 kHz ≤ ƒ ≤ 3 MHz), differential scanning calorimetry, and temperature-modulated calorimetry have been performed during isothermal curing of an epoxy network (diglycidylether of bisphenol A crosslinked with diaminodiphenyl methane), and of two thermoplast modified epoxy resins (semi-interpenetrating polymer networks) consisting of the epoxy network component and different amounts (10 and 20 wt %) of a linear high Tg polymer (polysulfone or polyethersulfone). During reaction, the homogeneous-mixtures phase separate into an epoxy-rich and a linear polymer-rich phase with different mobilities of the electrical dipoles. The complex dielectric permittivity is composed of a contribution from the ionic dc-conductivity and a contribution from relaxations of the permanent electrical dipoles in the two phases. The decrease of the dc-conductivity in the initial stage of cure is related to the time for gelation or vitrification. The contribution of the dipole relaxations to the dielectric permittivity reflects an increase of the relaxation times with curing time for both phases. The time-dependent changes in the complex dielectric permittivity are described by a simple two-phase model based on two Havriliak-Negami functions combined with Vogel-Fulcher equations for the description of the curing-time dependence of the relaxation times. The increase of the relaxation times in the phases during isothermal curing is incorporated by time-dependent Vogel temperatures. The latter are related to the time evolution of the glass-transition temperatures in the two phases measured independently by calorimetry. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2461-2470, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2483-2492 
    ISSN: 0887-6266
    Keywords: low-density polyethylene ; surface modification of polymers ; scanning force microscopy ; self-assembled monolayer of thiols ; chemical force microscopy ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In this article, we present the results of a study on the surface properties of chromic acid-oxidized low-density polyethylene (LDPE) by scanning force microscopy (SFM) and contact angle measurements. LDPE films were surface modified by a chromic acid treatment with subsequent annealing in argon and reconstruction in boiling water as described by Rasmussen, Stedronsky, and Whitesides [J. Am. Chem. Soc., 99, 4736 (1977)]. The LDPE oxidation in chromic acid was monitored in situ by contact mode SFM. Initially stacks of lamellae became exposed, and at later stages a granular morphology was observed. By tapping mode SFM, the sample roughness was shown to increase during the first 10 min of oxidation from initially ca. 20 nm to ca. 50 nm. Gold-coated SFM probes (tips) functionalized with self-assembled monolayers were used to determine the pull-off force characteristics in ethanol. Variations in the contact area between SFM tips and polymer surfaces that exposed sharp crystalline features were shown to obscure the results of pull-off force measurements. However, on annealed and subsequently reconstructed samples with lower roughness, the results of force measurements correlated well with the measured contact angles. Over the range of surface energies studied, the normalized pull-off force between carboxylic acid-modified tips and these smooth samples was shown to depend approximately linearly on the cosine of the contact angle. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2483-2492, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 31-38 
    ISSN: 0887-6266
    Keywords: liquid crystals ; thermosets ; smectic epoxy ; nematic ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Deformation experiments were carried out for densely crosslinked smectic-like networks obtained from diepoxy monomers with twin mesogen architecture. For the initially unoriented smectic networks, the network could be aligned up to an orientation parameter of 0.35 by applying 8 MPa of external stress in the rubbery regime. X-ray diffraction measurements revealed that the deformed smectic network possesses both smectic-A like and smectic-C like structure. It is thought that after extension domains initially oriented parallel to the external stress displayed a smectic-A-like structure, whereas domains initially tilted with respect to the tensile direction showed a stress-induced smectic-C like structure. A smectic network oriented under a.c. electric fields with an orientation parameter of 0.4 had a smectic-A like structure and possessed linear elasticity in the rubbery regime. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 31-38, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 439-445 
    ISSN: 0887-6266
    Keywords: cholesteric order ; electron microscopy ; periodical lamellar structure ; macromolecules ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The macromolecular cholesteric structure in the ethyl-cyanoethyl cellulose [(E-CE)C]/acrylic acid [AA] cholesteric liquid crystalline solutions is studied by directly observing the morphology and structure of the ethyl-cyanoethyl cellulose [(E-CE)C]/polyacrylic acid [PAA] using electron microscopy. A periodical lamellar structure is observed in ultrathin slices of the composites with cholesteric order by both transmission electron microscopy (TEM) and low-voltage scanning electron microscopy (LVSEM). It is suggested that the periodical lamellar structure is induced by the twist of the molecular orientation in the cholesteric phase and reflects the structural features of the macromolecular cholesteric phase. The macromolecular cholesteric phase exhibits the twisted ring morphology in the initial stage of the formation of the liquid crystalline phase. The swelling of the ultrathin slices with cholesteric order in water is heterogeneous, which suggests the tight packing of the (E-CE)C chains in the direction of the helix axis in the macromolecular cholesteric phase. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 439-445, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 495-517 
    ISSN: 0887-6266
    Keywords: crystallization ; DSC ; multiple melting ; nascent morphology ; polyethylene ; synchrotron ; UHMW PE ; WAXS ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The nascent morphology of UHMW PE exhibits high melting point, high crystallinity, and increased WAXS line breadth relative to samples formed by melt crystallization. Different empirical relationships between crystal size and melting point are observed for nascent and molded samples. This differentiation is removed following nitric acid treatment of the nascent flake. Solid-state annealing behavior is differentiated by several regimes. Regime I is characterized by increasing crystallite dimensions and crystallinity at low annealing temperatures. Regime II[a] and II[b] is identified by double melting in DSC scans of moldings and nascent flake, respectively. The double melting is due to partial melting with incomplete recrystallization. Regime II[a] of moldings is differentiated from Regime II[b] of flake by an increase in melting point of the higher melting endotherm. Within Regime II[b], the partial melting of the nascent structure is sensitive to the distribution of morphological stability. Regime III is initiated at annealing temperatures approaching the zero heating rate melting point, and shows melting kinetics by DSC or time-resolved WAXS using synchrotron x-ray radiation. The superheat, partially associated with Regime III behavior, is sensitive to morphological heterogeneity and annealing history. Morphological models are discussed which highlight the role of noncrystalline regions and melting kinetics on the melting behavior of nascent form crystallinity. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 495-517, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 567-572 
    ISSN: 0887-6266
    Keywords: surface ; interfaces ; diffusion ; polystyrene ; polyphenylene oxide ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Symmetric polydisperse (Mw = 23 × 104, Mw/Mn = 2.84) and monodisperse (Mw = 21 × 104, Mw/Mn 〈 1.05) polystyrene (PS), and asymmetric polydisperse PS/poly(2,6-dimethyl 1,4-phenylene oxide) (PPO) interfaces have been bonded in the vicinity of the glass transition temperature (Tg) of PS. In a lap-shear joint geometry, strength develops in all cases with time to the fourth power, which indicates that it is diffusion controlled. Strength developing at short times at the polydisperse PS/PS interface, at 90°C, is higher than that at the monodisperse interface, at 92°C (at Tg - 13°C in both cases), presumably due to the contribution of the low molecular weight species. The decrease of strength at the PS/PPO interface when the bonding temperature decreases from 113 to 70°C, i.e., from Tg + 10°C to Tg - 33°C of the bulk PS, indicates a high molecular mobility at the surface as compared to that in the bulk, and can be expressed by a classical diffusion equation, which is valid above Tg (of the surface layer). © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 567-572, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 629-640 
    ISSN: 0887-6266
    Keywords: poly(acrylonitrile) ; two-stage draw ; morphology and tensile properties ; effect of molecular weight ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Ultradrawing of atactic poly(acrylonitrile) (PAN) was investigated for a Mv series, ranging 8.0 × 104-2.3 × 106. Samples for the draw were prepared from 0.5-30 wt % solutions of PAN in N,N′-dimethylformamide. The solutions were converted to a gel by quenching from 100 to 0°C. The dried gel films were initially drawn uniaxially by solid-state coextrusion (first-stage draw) to an extrusion draw ratio (EDR) of 16, followed by further tensile draw at 100-250°C (second-stage draw). The maximum total draw ratio (DRt,max) and tensile properties achieved by two-stage draw increased remarkably with sample Mv. Other factors affecting ductility were the solution concentration from which gel was made and the second-stage draw temperature. The effects of these variables became more prominent with increasing Mv. The temperature for optimum second-stage draw increased with sample Mv. Both the initial gel and the drawn products showed no small-angle X-ray long period scattering maximum, suggesting the absence of a chain-folded lamellae structure, which had been found in our previous study on the drawing of nascent PAN powder. The chain orientation function (fc) and sample density (ρs) increased rapidly with DRt in the lower range (DRt 〈 30) and approached constant values of fc = 0.980-0.996 and ρs = 1.177-1.181 g/cm3, respectively, at higher DRt 〉 30-100. The tensile modulus also showed a similar increase with DRt. The tensile strength increased linearly with DRt, reaching a maximum, and decreased slightly at yet higher DRt. The highest modulus of 28.5 GPa and strength of 1.6 GPa were achieved with the highest Mv of 2.3 × 106. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 629-640, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 681-692 
    ISSN: 0887-6266
    Keywords: high-density polyethylene ; nonisothermal crystallization kinetics ; plateau temperature ; regime transition ; crystallinity ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The quiescent nonisothermal bulk crystallization kinetics of two high-density polyethylene resins were investigated by a modified light-depolarizing microscopy (LDM) technique. The technique allows studies at average cooling rates up to 2500°C/min. The polymer was found to crystallize at a pseudo-isothermal temperature even at these very high cooling rates. The overall bulk crystallization rate increased rapidly as the cooling rate and supercooling increased. Crystallization kinetics was analyzed by Avrami analysis. Avrami exponents near 3 suggested spherical growth geometry and instantaneous nucleation at predetermined sites. Observation of spherulites by optical microscopy together with a number density of spherulites that changed little with increase in cooling rate or supercooling supported this model of crystallization behavior. Analysis of the half-time of crystallization based on the Lauritzen and Hoffman secondary nucleation theory indicated that the regime II-III transition was found to occur at a degree of supercooling of approximately 22°C. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 681-692, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 727-741 
    ISSN: 0887-6266
    Keywords: liquid crystal polymer ; aromatic polyester ; molecular modeling ; Monte Carlo ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The condensed phase of the alternating copolyester of p-hydroxybenzoic acid (HBA) and 2-hydroxy-6-naphthoic acid (HNA) is investigated by studying the room temperature packing arrangement of the copolymer chains. A molecular modeling methodology is employed with a Monte Carlo sampling of the configurational phase space. Realistic poly(HBA-alt-HNA) polymer chains are represented by an explicit atom representation of the HBA/HNA dimers. States are sampled from the NVT ensemble using a sampling scheme consisting of (1) valence and torsional variations, (2) rigid body rotations of the chain about the chain axis, and (3) rigid body translations of the chain. The effect of chain packing on the conformation of chains, as well as the relative intra- and intermolecular orientations of aromatic rings, is investigated. Correlation of chain positioning along the chain axis is dominated by aromatic rings maintaining a center-to-center plane of registry. These layers of aromatic units pack with a preference for edge-to-face orientations in a herringbone-type pattern and have an intermolecular ring angle between the pairs of aromatic rings in the unit cell that is ca. 68°. The aromatic rings, on average, are rotated 38° out from the b-c plane. The phenylene rings of these copolyesters are less restricted in their relative orientation in comparison to the naphthalene rings. Intramolecular orientational probability density distributions indicate a preference for staggering the successive aromatic rings along the chain, with a staggering angle of ca. 66°. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 727-741, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 797-803 
    ISSN: 0887-6266
    Keywords: polynorbornene ; gas separation ; membrane ; free volume ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A study of gas transport properties of novel polynorbornenes with increasing length of an aliphatic pendant group R (CH3—, CH3(CH2)3—, CH3(CH2)5—, CH3(CH2)9—) has been performed. These polymers were synthesized using novel organometallic complex catalysts via an addition polymerization route. This reaction route maintained the bridged norbornene ring structure in the final polymer backbone. Gas permeability and glass transition temperature were found to be higher than those for polynorbornenes prepared by ring-opening metathesis and reported in the literature. It was shown that for noncondensable gases such as H2 and He the selectivity over N2 decreased when the length of the pendant group increased, but remained relatively stable for the more condensable gases (O2 and CO2). The permeability coefficient is correlated well to the inverse of the fractional free volume of the polymers. The more condensable gases showed a deviation from this correlation for the longest pendant group, probably due to an increase of the solubility effect. This polymer series demonstrated a simultaneous increase in permeability and selectivity, uncommon for polymers. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 797-803, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1219-1225 
    ISSN: 0887-6266
    Keywords: poly(ethylene terephthalate) ; oligomer ; poly(ethylene glycol) ; epoxy resin ; concentrated solution ; crystallinity ; thermoreversible gel ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Poly(ethylene terephthalate) (PET) was rapidly crystallized through thermoreversible gelation in a liquid ethylene glycol oligomer or in epoxy resin. The solutions formed gel rapidly on cooling. Polarized light microscopy and small-angle light scattering showed that these gels contain large, regular PET spherulites. The gels may be formed by two consecutive processes: the phase separation and crystallization, and gelation by formation of a three-dimensional PET network in the oligomer solvents, where the nodes of the network are PET spherulites. The crystallinity of PET recovered from polymer/oligomer gels is near 72% measured by wide-angle X-ray diffraction method, which is about 20% higher than PET samples crystallized by solution crystallization in small molecule solvent, high temperature annealing, and stretching techniques. It takes only a few minutes to form the highly crystalline phase PET in the PET/oligomer system, and the crystallinity of the dried gel is independent of the concentration of the original solution. Excimer-fluoresence and Raman spectroscopic studies indicated that PET recovered from the gels are in an ordered state with few chain entanglements. The entanglement density of the recovered PET recovered from a 20 wt % solution in ethylene glycol oligomer is as low as that of freeze-extracted PET from a 0.5 wt % solution in phenol. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1219-1225, 1998
    Additional Material: 7 Ill.
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 373-381 
    ISSN: 0887-6266
    Keywords: pressure-sensitive adhesive ; PSA ; tackifier ; tack adhesion ; polyisoprene ; poly(ethylene-propylene) ; pulsed gradient spin echo-nuclear magnetic resonance ; PGSE-NMR ; diffusion ; n-butyl ester of abietic acid ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A detailed study of the mobility of a tackifying resin in a pressure-sensitive adhesive (PSA) has been done for the first time. The objective of this work is to relate changes in adhesive performance with tackifier loading to tackifier mobility. Tackifiers are low-molecular weight resins that improve the overall performance of PSAs. They increase the adhesive tack or the ability to form a bond of measurable strength after brief contact under slight applied pressure. In this study the diffusion of n-butyl ester of abietic acid (n-BEAA) in either polyisoprene (PI) (Mw = 195,000 Mw/Mn ∼ 1.05) or poly(ethylene-propylene) (PEP) (Mw = 40,000 Mw/Mn ∼ 2.30) was measured by Pulsed Gradient Spin Echo-Nuclear Magnetic Resonance (PGSE-NMR) as a function of both tackifier concentration and temperature. The concentration dependence of the tackifier's diffusion coefficient was weak for both systems. The weak variation in mobility with composition for the PI/n-BEAA system was consistent with that system's weak variation in tack with composition. On the other hand, blends of PEP/n-BEAA showed only modest variation in mobility, even though these adhesive systems showed appreciable enhancement of tack at intermediate compositions. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 373-381, 1998
    Additional Material: 6 Ill.
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  • 191
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1321-1334 
    ISSN: 0887-6266
    Keywords: gloss ; rough surface ; specular reflectance ; correlation length ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A general expression for gloss within the scalar Kirchhoff's theory is derived in terms of the detector collecting angle, and two statistical parameters that characterize the surface roughness. Analytical expressions for gloss are derived for an exponential and a Gaussian correlation function, and numerical results for these and other quasi-exponential correlation functions are presented. It is shown that the incoherent contribution to gloss is significant in common polymeric surfaces. The latter implies that surface height correlations cannot be neglected in the evaluation of gloss. It is also shown that for a correlation function with a single characteristic length, gloss scales with the correlation length Lc in the same way as with the detector collecting angle. This fact can be used to determine Lc with a glossmeter, and an experimental method to achieve this is proposed. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1321-1334, 1998
    Additional Material: 12 Ill.
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  • 192
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1361-1370 
    ISSN: 0887-6266
    Keywords: transcrystallinity ; PTFE fiber/PP composites ; heterogeneous nucleation ; crystal growth rate ; orientation ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect of shear rates on the transcrystallization of polypropylene (PP) on the polytetrafluoroethylene (PTFE) fibers has been quantitatively investigated using a polarized optical microscope equipped with a hot stage and a tensile testing machine. The PTFE fibers were pulled at different rates, from 0.17 to 8.33 μm/s, to induce a range of shear rates, about 0.02 to 1.16 1/s, in the PP melt adjacent to the fiber. The induction time, nucleation rate, and saturated nucleation density at the fiber surface were determined at various crystallization temperatures. It was found that both the nucleation rate and the saturated nucleation density increase with increasing shear rates. However, the induction time is significantly reduced. Based on the theory of heterogeneous nucleation, the interfacial free energy difference functions Δσ;TCL of PP on PTFE fibers at different levels of shear rates were determined and compared with that obtained from crystallization under quiescent conditions. Results showed that the magnitude of ΔσTCL decreased to be about one-third of that for the quiescent crystallization, when a shear rate of 1.16 1/s was applied. The application of a shear stress to the supercooled PP melt by fiber pulling leads to enhance the development of transcrystallinity. Moreover, both the thickness and the crystal growth rate of transcrystalline layers were found to increase with the increasing rate of fiber pulling, especially at low crystallization temperatures where regime III prevails (see text). Surface morphology of PTFE fibers was revealed using a scanning electron microscope and an atomic force microscope. It is argued that the presence of fibrillar-type features at the fiber surface is the main factor responsible for the development of transcrystallinity. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1361-1370, 1998
    Additional Material: 14 Ill.
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 483-494 
    ISSN: 0887-6266
    Keywords: small penetrants ; sorption isotherms ; site distribution ; elastic distortion ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Pressure-composition isotherms were determined at 20°C for CO2 in Kapton and various substituted polycarbonates and for H2O, Ar, N2, CH4, and acetone in bisphenol-A-polycarbonate. The isotherms are described by two parameters an average free energy of sorption and a width of a Gaussian distribution of free sorption energies. Within the framework of a recent model these parameters can be calculated assuming an elastic distortion of the polymer caused by the incorporation of solute atoms in preexisting holes. By comparing experimental values with predictions of the model the experimental width of the free energy distribution is only 30% smaller than the theoretical one. Functional relationships are obeyed between the sorption parameters on the one hand and glass transition temperature, average hole volume, and molecular volume of the solute on the other hand. Deviations occur for larger molecules like acetone and ethylene which are attributed to a viscoelastic distortion of the polymer. Comparing free energies of solution for the rubbery and glassy state of the polymer reveals more negative values for the glassy polymers despite their extra elastic distortion energy. This discrepancy is overcome by taking into account that the occupied volume has to be re-formed in the case of the rubbery or liquid polymer. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 483-494, 1998
    Additional Material: 12 Ill.
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1451-1463 
    ISSN: 0887-6266
    Keywords: bulk modulus ; heat capacity ; high-pressure ; poly(vinyl acetate) ; thermal conductivity ; transient hot-wire method ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The thermal conductivity λ and heat capacity per unit volume of poly(vinyl acetate) (260 kg mol-1 in weight average molecular weight) have been measured in the temperature range 150-450 K at pressures up to 1 GPa using the transient hot-wire method, which yielded λ = 0.19 W m-1 K-1 at atmospheric pressure and room temperature. The bulk modulus K has been measured in the temperature range 150-353 K up to 1 GPa. At atmospheric pressure and room temperature, K = 4.0 GPa and (∂K/∂p)T = 8.3. The volume data were used to calculate the volume dependence of λ, \documentclass{article}\pagestyle{empty}\begin{document}$g = - \left( {\frac{{\partial \lambda /\lambda }}{{\partial V/V}}} \right)_T .$\end{document} The values for g of the liquid and glassy states were 3.0 and 2.7, respectively, and g of the latter was almost independent of volume and temperature. Theoretical models can predict the value for g of the glassy state to within 25%. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1451-1463, 1998
    Additional Material: 8 Ill.
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1483-1500 
    ISSN: 0887-6266
    Keywords: dilute polystyrene solution ; flow birefringence ; transient elongational flow ; local orientation angle ; polymer molecular weight ; affine deformation model ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Transient elongational flow, created by forcing a polymer solution across a narrow contraction, is characterized by a high strain rate of limited duration. Due to an inherent short residence time, this type of flow generally is considered as being less efficient in extending isolated flexible molecular coils than “stagnation” point elongational flow. Rheo-optical measurements revealed, nevertheless, a readily detectable birefringence zone above a critical strain rate in the immediate orifice entrance. Birefringence was studied for dilute PS solutions (100-400 ppm) in decalin as a function of fluid strain rate (\documentclass{article}\pagestyle{empty}\begin{document}$\dot \varepsilon $\end{document} = 1000-38,000 s-1) and polymer molecular weight (M = 1.93-10.2·106). Transient elongational flow is complicated by the presence of local orientation distribution along the different streamlines. To account for this effect, a numerical technique has been devised to compute local birefringence (Δn) from experimental retardation (δ). Results show a uniform birefringence distribution across the capillary entrance and a steep decrease with the axial distance. Molecular extension ratio calculated with the Kuhn-Grün theory suggests that polymers may uncoil up to one third of the chain contour length at the approach of capillary entrance. Although extension ratio determined at the inlet could be fitted with an affine deformation model, notable departure from this simple representation is observed when molecular strain is calculated along the streamline. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1483-1500, 1998
    Additional Material: 16 Ill.
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1547-1556 
    ISSN: 0887-6266
    Keywords: gas permeation ; plasticization ; semiinterpenetrating polymer network ; polyimide ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: CO2-induced plasticization may significantly spoil the membrane performance in high-pressure CO2/CH4 separations. The polymer matrix swells upon sorption of CO2, which accelerates the permeation of CH4. The polymer membrane looses its selectivity. To make membranes attractive for, for example, natural gas upgrading, plasticization should be minimized. In this article we study a polymer membrane stabilization by a semiinterpenetrating polymer network (s-ipn) formation. For this purpose, the polyimide Matrimid 5218 is blended with the oligomer Thermid FA-700 and subsequently heat treated at 265°C. Homogeneous films are prepared with different Matrimid/Thermid ratios and different curing times. The stability of the modified membrane is tested with permeation experiments with pure CO2 as well as CO2/CH4 gas mixtures. The original membrane shows a minimum in its permeability vs. pressure curves, but the modified membranes do not indicating suppressed plasticization. Membrane performances for CO2/CH4 gas mixtures showed that the plasticizing effect indeed accelerates the permeation of methane. The modified membrane clearly shows suppression of the undesired methane acceleration. It was also found that just blending Matrimid and Thermid was not sufficient to suppress plasticization. The subsequent heat treatment that results in the s-ipn was necessary to obtain a stabilized permeability. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1547-1556, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1579-1590 
    ISSN: 0887-6266
    Keywords: infrared spectroscopy ; polymer blends ; poly(vinyl cinnamate) ; UV curing ; hydrogen bonds ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The results of an infrared spectroscopic characterization of poly(vinyl cinnamate) (PVCIN) and its blends with poly(4-vinyl phenol) (PVPh) are reported before and after photo-crosslinking the PVCIN by exposure to UV radiation. The purpose of this article is to demonstrate methodology, and it is shown that quantitative analysis of the fraction of unsaturated (—C=C—) double bonds, “free” (non-hydrogen bonded) and hydrogen bonded unsaturated (—CO—C=C—) and saturated (—CO—C—C—) acetoxy carbonyl groups is feasible in these blends as a function of UV exposure time. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1579-1590, 1998
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1617-1624 
    ISSN: 0887-6266
    Keywords: hydrogen-bonded living polymers ; supramolecular ; liquid crystalline polymers ; X-ray scattering ; Fourier transform infrared (FTIR) ; structure ; association chain polymers ; self-assembly ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A main chain hydrogen-bonded liquid crystalline polymer was formed by melt mixing two complementary components, A and B, which in their individual states do not exhibit liquid crystallinity. The structure of the polymer and the thermal stability of its mesophase were studied using synchrotron radiation SAXS/WAXS/DSC at Daresbury (UK) and by variable temperature Fourier transform infrared. The chain extension, or “polymerization” process, was accelerated at the point when the polymer formed a liquid crystalline phase upon cooling from the isotropic melt. The polymer has an aabb chain structure and forms a smectic layer with a length of the A-B repeating unit. The hydrogen-bonded main chain polymer studied here is a monotropic liquid crystal. Above 150°C, it exhibits kinetic stabilization of its monotropic smectic phase. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1617-1624, 1998
    Additional Material: 11 Ill.
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1703-1711 
    ISSN: 0887-6266
    Keywords: complex shear modulus ; ultrasonic measurements ; dynamic-mechanical measurements ; acrylic-type copolymers ; film formation ; glass-rubber relaxation ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An ultrasonic shear wave reflection method was applied to study film formation and temperature dependence of the complex shear modulus (G*=G′ + iG″) in different amorphous films made of aqueous dispersions of acrylic-type copolymers. The data are compared with dynamic-mechanical measurements in the low frequency range. It is shown that the temperature dependence of the storage (G′) and the loss modulus (G″) for both methods can be fitted by the same set of parameters using the Havriliak-Negami function incorporating the Vogel-Fulcher-Tamman-Hesse equation for the temperature dependence of relaxation times. The temperature dependence of the relaxation times obtained from the fits to the ultrasonic shear modulus is compared to the shift factors of the dynamic-mechanical measurements. The agreement between both methods is good. This suggests an almost thermorheological simplicity of the samples for the main glass-rubber relaxation and demonstrates the capacity of the ultrasonic rheometer. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1703-1711, 1998
    Additional Material: 7 Ill.
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    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1679-1694 
    ISSN: 0887-6266
    Keywords: crystallization kinetics ; thermotropic liquid crystalline polymers ; polyimide ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We have studied the nonisothermal and isothermal crystallization kinetics of an aromatic thermotropic liquid crystalline polyimide synthesized from 1,2,4,5-benzenetetracarboxylic dianhydride (PMDA) and 1,3-bis[4-(4′-aminophenoxy) cumyl] benzene (BACB) by means of differential scanning calorimetry (DSC). Polarized light microscopy (PLM) and wide-angle X-ray diffraction (WAXD) results confirm that this polyimide exhibits a smectic texture. Nonisothermal crystallization showed two strong and one weak exothermic peaks during cooling. The phase transition from isotropic melt to liquid crystalline state is extremely fast which completes in several seconds. The mesophase transition has a small Avrami parameter, n, of approximate 1. The isothermal crystallization of 253-258°C has been examined. The average value n is about 2.6 and the temperature-dependent rate constant k changes about two orders of magnitude in the crystallization temperature range of 6°C. The slope of ln k versus 1/(TcΔT) is calculated to be -2.4 × 105, which suggests nucleation control, via primary and/or secondary nucleation for the crystallization process. During the annealing process, a new phase (slow transition) is induced, which grows gradually with annealing time. At lower annealing temperatures (220-230°C), the slow transition process seems not to be influenced by the crystals formed during cooling process and its Avrami parameter n is ca. 0.3-0.4. However, the slow transition was hindered by the crystals formed during cooling process when annealed at higher temperature (230-240°C). © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1679-1694, 1998
    Additional Material: 15 Ill.
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