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M B Taubman

Publications and source records attributed to M B Taubman.

66 records · Page 4Linked to original sources
PubMed1989

Angiotensin II induces c-fos mRNA in aortic smooth muscle. Role of Ca2+ mobilization and protein kinase C activation.

Vasoconstrictors such as angiotensin II (Ang II) play an important role in the pathogenesis of hypertension. These agonists may be responsible for the abnormal vascular smooth muscle cell (VSMC) growth seen in hypertension, either indirectly as a consequence of elevating blood pressure or directly as a result of receptor-mediated effects on VSMC growth. To investigate whether Ang II might directly initiate or modulate some of the "early" genetic programs associated with growth in VSMC, the expression of the proto-oncogene c-fos was studied in cultured rat aortic VSMC. Ang II rapidly induced the accumulation of c-fos mRNA, with maximal levels occurring at approximately 30 min. Induction of c-fos mRNA by Ang II was concentration-dependent, with a maximal response at 100 nM. Ang II induction of c-fos mRNA was blocked by its competitive inhibitor, [sarcosine 1,isoleucine 8]angiotensin II. Induction of c-fos mRNA was not dependent upon Ang II-stimulated intracellular alkalinization or activation of Na+/H+ exchange, but was dependent upon mobilization of intracellular Ca2+ and protein kinase C activation. Epidermal growth factor, a VSMC mitogen, also induced c-fos mRNA in VSMC, but by a mechanism different from that of Ang II. These results demonstrate that the vasoconstrictor hormone Ang II induces in VSMC one of the earliest genes, c-fos, associated with the proliferative response.

Angiotensin II↗
PubMed1989

Molecular cloning and characterization of the ryanodine receptor/junctional channel complex cDNA from skeletal muscle sarcoplasmic reticulum.

Major progress has been made in elucidating the calcium release mechanism involved in excitation-contraction coupling. The ryanodine receptor of sarcoplasmic reticulum has been isolated and found to be morphologically identical to the foot structure, which is involved in the junctional association of terminal cisternae with the transverse tubule. The foot structure also contains the calcium release channel itself. For this reason, we refer to the foot structure as the junctional channel complex (JCC). The JCC consists of an oligomer of a single high molecular weight protein. Although progress has been made in characterizing important aspects of the structure and function of the JCC, further understanding of the JCC protein subunit awaits the molecular cloning of the JCC. We report on the isolation of cDNA clones encoding portions of the JCC from rabbit fast-twitch skeletal muscle and its tissue distribution and expression. The large size and lack of solubility of the JCC protein posed particular challenges to cloning this molecule. Among these was the necessity to develop techniques for partially digesting the JCC protein subunit with endoproteases in the presence of detergent. With this approach we obtained partial amino acid sequences from regions of the JCC and designed oligonucleotide primers and probes to synthesize and screen cDNA libraries. The rabbit skeletal muscle JCC mRNA encodes an approximately 16-kilobase mRNA present in skeletal, heart, and aortic smooth muscle, as determined by RNA blot analysis with a 700-base-pair cDNA probe. Whereas the JCC mRNA appears to be relatively abundant in adult rabbit fast-twitch skeletal muscle, it is much less abundant in heart and smooth muscle. The JCC mRNA in BC3H1 (a myoblast cell line) is reversibly regulated by growth factors in a manner similar to muscle-specific contractile protein genes.

Amino Acid Sequence↗
PubMed1989

The expression of sarcomeric muscle-specific contractile protein genes in BC3H1 cells: BC3H1 cells resemble skeletal myoblasts that are defective for commitment to terminal differentiation.

The BC3H1 cell line has been used widely as a model for studying regulation of muscle-related proteins, such as the acetylcholine receptor, myokinase, creatine kinase, and actin. These cells, derived from a nitrosourea-induced mouse brain neoplasm, have some of the morphological characteristics of smooth muscle and have been shown to express the vascular smooth muscle isoform of alpha-actin. To provide further information about the contractile protein phenotype of BC3H1 and to gain additional insights into the possible tissue of origin of these cells, we have examined the expression of a battery of contractile protein genes. During rapid growth, subconfluent BC3H1 cells express the nonmuscle isoform of alpha-tropomyosin (alpha-Tm) and the nonsarcomeric isoforms of myosin heavy and light chains (MHCs and MLCs, respectively), but do not express troponin T(TnT). However, when BC3H1 cells differentiate in response to incubation in serum-deprived medium or upon approaching confluence, they express TnT as well as sarcomeric muscle isoforms of MHC, MLC 2 and 3, alpha-Tm, and alpha-actin. These results suggest that BC3H1 is a skeletal muscle cell line of ectodermal origin that is defective for commitment to terminal differentiation.

Actins↗
PubMed1987

Cloning and characterization of mammalian myosin regulatory light chain (RLC) cDNA: the RLC gene is expressed in smooth, sarcomeric, and nonmuscle tissues.

The 20-kD regulatory light chain (RLC) plays a central role in the regulation of smooth muscle contraction. Little is known about the structure or expression of smooth muscle myosin light chain (MLC) genes. A cDNA library was constructed in the expression vector, lambda gt-11, with mRNA derived from cultured rat aortic smooth muscle cells. Using antibody generated against tracheal smooth muscle myosin, three cDNA clones encoding a RLC were isolated, one of which, SmRLC-2, represents a full-length transcript of the RLC mRNA. The derived amino acid sequence shows 94.2% homology with the chicken gizzard RLC, and 70 and 52% homology with the rat skeletal and cardiac muscle MLC-2 proteins, respectively. Thus, the gene encoding the putative smooth muscle RLC appears to have originated by duplication of the same ancestor that gave rise to the sarcomeric MLC-2 genes. Contrary to the stringent tissue-specific expression of sarcomeric MLC-2 genes, RNA blot hybridization and S1 nuclease mapping demonstrates that the putative smooth muscle RLC gene is expressed in smooth, sarcomeric, and nonmuscle tissues at significant levels. Primer extension analysis suggests that the same promoter region is used in these different tissues. Thus the putative smooth muscle RLC gene appears to be a gene that is constitutively expressed in a large variety of cells and has a differentiated function in smooth muscle.

Animals↗
PubMed1985

The carboxyl fragment released by bacterial collagenase from human type I procollagen: antibodies to the propeptide determinants.

A protocol is offered for the isolation of the carboxyterminal propeptides of human type I procollagen and the development of an antibody specific for these propeptides. Type I procollagen was harvested from the media of cultured human fibroblasts. Digestion with bacterial collagenase released a carboxyterminal fragment that was isolated by ion-exchange chromatography. The fragment contained telopeptides joined to propeptides and could be cleaved by a carboxyl procollagen peptidase. Rabbit antibodies raised to the collagenase-generated fragment were sequentially adsorbed on affinity columns of the reference antigen and human type I collagen. The antibody obtained was shown by sensitive radioimmunoassays to recognize conformational carboxyl propeptide determinants and not to react with triple helical and telopeptide determinants of human type I collagen. Indirect immunofluorescence and indirect immunoperoxidase staining of cultured fibroblasts localized the antigen in the cytoplasm, at the cell surface, and in the extracellular matrix. A radioimmunoassay with the same antibody has reported altered concentrations of the antigen in the sera of patients with diseases affecting collagen metabolism (Taubman, et al., 1976; Savolainen et al., 1984; Carey et al., 1985).

Animals↗
PubMed1985

Epidermal growth factor, a vascular smooth muscle mitogen, induces rat aortic contraction.

Atherosclerotic arteries have enhanced reactivity to vasoconstrictors, which suggests that features of the atherosclerotic process itself may result in this abnormal responsiveness. Since vascular smooth muscle proliferation is a prominent feature of atherosclerosis, we postulated that vasoactive agonists and smooth muscle mitogens may share certain common cellular mechanisms of action which potentially contribute to this hyperreactivity. To test this hypothesis, we studied the effects of epidermal growth factor (EGF), a well-characterized mitogen, on rat aortic vascular smooth muscle, both in intact aortic strips and in culture. EGF caused contraction (EC50 = 19 nM) of rat aortic strips which maximally was equivalent to 40% of that induced by angiotensin II, a potent vasoconstrictor. EGF increased 45Ca efflux (EC50 = 3 nM) from cultured rat aortic smooth muscle cells, which was an effect shared by angiotensin II and thought to reflect increased cytosolic-free calcium concentration. EGF (7.5 nM) also stimulated growth of these cultured cells to the same extent as 10% calf serum. These results demonstrate that EGF is both a vasoconstrictor and mitogen for rat aortic smooth muscle cells. The similarities in the effects of EGF and angiotensin II suggest that certain common intracellular mechanisms of action may exist for vasoactive agonists and growth factors which may contribute to the altered vasoreactivity of atherosclerotic vessels.

Animals↗
PubMed1976

Radioimmunoassay of procollagen in serum of patients with Paget's disease of bone.

A new radioimmunoassay for human procollagen showed that the sera of 46 of 50 untreated patients with Paget's disease of bone contained increased concentrations of procollagen protein as compared to normal adults. After therapy with disodium etidronate, all the elevated serum procollagen concentrations decreased significantly, falling to normal levels in 33 of 40 patients. The procollagen levels before and after treatment were coordinate with the values for urinary total hydroxyproline and serum alkaline phosphatase activity. The data show that the radioimmunoassay for procollagen is a dependable and useful adjunct to the study of Paget's disease of bone.

Adult↗
PubMed1975

Procollagen peptidase: its mode of action on the native substrate.

Procollagen peptidase was recovered from the medium of human and mouse fibroblast cultures by precipitation with ammonium sulfate. The test substrate for the in vitro enzymatic reaction was radioactively-labeled, disulfide-linked procollagen prepared from the medium of human fibroblast cultures. The enzymatic digests were analyzed by electrophoresis in polyacrylamide gets containing sodium dodecyl sulfate and urea. The human and mouse enzymes reacted with the substrate to generate the same intermediates and final products. Procollagen peptidase acts as an endopeptidase which cleaves each of the three procollagen chains in turn. The final products of the reaction are collagen and a three-chain, disulfide-linked fragment derived from the nonhelical aminoterminal residues of procollagen.

Animals↗
PubMed1974

Radioimmunoassay for human procollagen.

Rabbit antiserums were produced against the procollagen molecule secreted into the medium of cultured human skin fibroblasts. The isolated antigenic, amino terminal portion of the procollagen molecule was purified, labeled with iodine-125, and used in a radioimmunoassay which detected nanogram quantities of the same antigen. With the assay, immunologically identical molecules were detected in the culture mediumn of different strains of human fibroblasts and in normal human serums. Serumns from human cord blood contained a 12-fold higher concentration of the antigen than serums from adults, while serums other vertebrates gave reactions to incomplete cross-reactivity or non-reactivity.

Animals↗