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Biomedical subjects

K Schwartz

Publications and source records attributed to K Schwartz.

At least 271 records · Page 15Linked to original sources
PubMed1984

Different distributions of microtubules, desmin filaments and isomyosins during the onset of cardiac hypertrophy in the rat.

To elucidate the role of the cytoskeleton in the development of adult heart, microtubules and intermediate filaments of desmin were studied in young and adult rat heart myocytes during the onset of growth, after mechanical overloading induced by aortic stenosis. Such overloading is known to cause heart hypertrophy by stimulating overall protein synthesis, and to initiate a shift in myosin isozymes. For this study, we used double immunolabelling of isolated myocytes with specific antibodies raised against tubulin, desmin, and the two main isomyosins V1 and V3. Whereas desmin remained unchanged, tubulin was redistributed in arrays parallel to the long axis of the myocytes, and was densest around the nuclei. Alterations in the microtubule pattern were observed very early after aortic stenosis, during the onset of heart growth; they were transitory, and did not occur simultaneously in all myocytes. Chronological examination of myocytes labelling with both antitubulin and anti V3 myosin clearly suggested that the transitory alteration in the microtubule pattern was an early event preceding the change in the expression of the myosin gene. Results, observed in young rats, in which mitosis is stimulated by overloading, and in adult rats, exhibiting no mitosis, showed that microtubules are involved in the development of cells in which mitosis does not occur. This work provides the first evidence of a correlation in functional adult heart, between the reorganization of cytoplasmic microtubules and the onset of growth.

Animals↗
PubMed1983

Relation between sexual practices and T-cell subsets in homosexually active men.

27% of 89 young, non-ill, homosexually active men in Los Angeles had a Leu-3(OKT4)/Leu-2(OKT8) ratio less than or equal to 0 . 8. The low ratio was due to a significantly raised mean number of Leu-2 cells, whereas individuals with acquired immune deficiency syndrome had a decrease in both Leu-3 and Leu-2 cells. The term "acquired immune augmentation" may be appropriate for those with a low ratio due to raised numbers of Leu-2 cells. Those practising passive (receptive) anal intercourse had a significantly higher mean number of Leu-2 cells than did those practising only active (insertive) anal intercourse or no anal intercourse. The results of this study suggest that two distinct conditions occur in homosexually active men. Whether acquired immune augmentation is a precursor of the rarer acquired immune deficiency syndrome or is an unrelated disorder needs to be determined. In this study passive anal intercourse was associated with acquired immune augmentation.

Acquired Immunodeficiency Syndrome↗
PubMed1983

Distribution of myosin isozymes within single cardiac cells. An immunohistochemical study.

Isozymes of myosin have been localized with respect to individual cardiac myocytes in hearts from 3-week-old, adult controls, and adult hypophysectomized rats, and in cultured cardiac cells. For this purpose, affinity-purified antibodies reacting specifically with the heavy chains of each of the two major myosin isozymes of adult rat heart, V1 and V3, were used. The distribution of the two isomyosins was determined by double immuno-labeling of the same cell, V1 myosins being revealed by rhodamine and V3 myosins by fluorescein. A procedure is described which allows optimum immunological visualization of the myosin filaments of rod-shaped isolated myocytes. It was found that the response of the cardiac cells to the two antimyosins varied depending on the state of the animal. In 3-week-old rats, all cells were stained with the anti-V1, and almost none with the anti-V3 myosin. In the hypophysectomized animals, on the contrary, all cells were stained with the anti-V3 and none with the anti-V1. A mixed pattern of reactivity was observed in adult controls since 50% of the cells reacted with the anti-V1, 10% with the anti-V3, and 40% with both antibodies. In the latter case, the distributions of V1 and V3 reactivities were homogeneous throughout the cell, and absolutely superimposable. The same double reactivity and homogeneous repartition were observed in cultured cells. These findings indicate that myocytes from adult rat myocardium are heterogeneous in terms of their isomyosins content and show for the first time that two isomyosins can coexist and be equally distributed in one cardiac cell. These observations are relevant to the regulation of individual heart cell contractility.

Animals↗
PubMed1983

Myosin isoenzymes in normal and hypertrophied human ventricular myocardium.

We tested the hypothesis that hypertrophy of the human heart is associated with the redistribution of ventricular isomyosins. Human cardiac myosin was isolated from autopsy samples of left ventricular free wall of patients with cardiac hypertrophy and of fetal, young, and adult subjects without heart disease. The following parameters were studied: electrophoretic migration in denaturing and non-denaturing conditions; immunological cross-reactivities with three different types of antibodies; and early phosphate burst size and steady state ATPase activities stimulated by K+-EDTA, Ca++, Mg++, and actin. The antibodies were chosen for their ability to recognize selectively the rat V1 and V3 cardiac isomyosins. The first type was a monoclonal antibody, CCM-52, prepared against embryonic chick cardiac myosin, the second was an anti-beef atrial myosin, and the third was an anti-rat V1 myosin. CCM-52 reacted with a greater affinity with rat V3 than with rat V1, and was a probe of mammalian V3. Anti-beef atrial myosin and anti-rat V1 myosin both recognized specifically beef atrial and rat V1 myosins, and were thus considered as probes of mammalian V1. Under non-denaturing conditions, human myosins migrated as rat V3 isomyosin; under denaturing conditions, no difference was observed in any of the electrophoretic parameters between all samples tested, except for the fetal hearts which contained a fetal type of light chain. The immunological studies indicated that human myosins were composed mostly of a V3 type (HV3), but contained also some V1 isomyosin. A technique was developed to quantify the amount of human VI isomyosin which was found to range from almost 0 to 15% of total myosin, and to vary from one heart to the other, regardless of the origin of the heart. Enzymatic studies showed no significant difference between normal, hypertrophied, and fetal hearts in any of the activities tested. However, there was a significant correlation between Ca++-stimulated ATPase activities and HV1 amount (at 0.05 M KCl, n = 18, r2 equal 0.49, P less than 0.01; at 0.5 M KCl, n = 18, r 2 = 0.5, P less than 0.01). These data demonstrate the heterogeneity of human ventricular myosin, which appears to be composed, as in other mammalian species, of V1 and V3 isoforms of different ATPase activities (V1 greater than V3). However it seems that V1 to V3 shifts do not appear to be of physiological significance in the adaptation of human heart to chronic mechanical overloads.

Actins↗
PubMed1983

Adrenal pseudotumors on CT due to dilated portosystemic veins.

The adrenal and periadrenal venous systems are part of the portosystemic collateral pathways that may enlarge in portal hypertension. The cross-sectional image of the resulting enlarged venous channels may simulate an adrenal mass. Three examples of such computed tomographic (CT) scans are presented with selective venographic correlation. Patients with portal hypertension and suspected adrenal pathology may require enhanced or dynamic CT scans.

Adrenal Gland Neoplasms↗
PubMed1983

Immunological quantitation and localization of tubulin in adult rat heart isolated myocytes.

Isolated myocytes were purified from adult rat heart. Identification and localization of microtubules and quantitation of tubulin in these cells were performed by immunochemical procedures. Antibodies were raised against brain tubulin and purified by affinity chromatography. An enzyme-linked immunosorbent assay, ELISA, was developed for quantitation of tubulin. It allowed the measurement of 10 to 500 ng of tubulin. Tubulin content in adult rat cardiac myocytes was found to be approximately 10 micrograms per 100 mg of the total protein content. By means of a double immunofluorescence technique, the microtubule network, identified with antitubulin, was studied in reference to the sarcomeric A band labeled with antibodies specific to myosin heavy chains. The basis for identifying the microtubule network have included the use of specific antitubulin immunoglobulins and the sensitivity of the specific labeling of the network to antimitotic drugs and low temperature. It was found that microtubules were organized mainly around the nuclei, with important concentrations at the poles, showing extensions in the cone and in the cytoplasm as loosely organized loops. The shape of adult cardiac myocyte was not dependent upon the integrity of the microtubule network.

Alkaloids↗
PubMed1982

Comparisons of rat cardiac myosins at fetal stages in young animals and in hypothyroid adults.

Rat cardiac ventricular myosins were obtained from fetuses, from young normal animals, and from hypophysectomized adults. The purified proteins were compared by several techniques: (i) electrophoresis in non-denaturing conditions (pyrophosphate buffer), (ii) one- and two-dimensional analysis after proteolytic cleavage, (iii) immunological blotting after electrophoretic purification, and (iv) competitive enzyme-linked immunosorbent assay. Antibodies specific to each of the two major isoenzymes of adult rat heart (V1 and V3 according to the terminology of Hoh et al. (Hoh, J. F. Y., McGrath, P. A., and Hale, P. T. (1978) J. Mol. Cell. Cardiol. 10, 1053-1076) were used for the immunological studies. The heavy chains of the ventricular myosin isoenzymes of fetuses (V3F) were indistinguishable from those of the V3H isoenzyme present in hypophysectomized adults; both proteins differed from the V1 isoform of young animals. The light chains of V3F, V3H, and V1 were the same, except that V3F contained in addition a small amount of the embryonic light chain (Whalen, R. G., and Sell, S. M. (1980) Nature 286, 731-733). These results strongly suggest that adaptation of the adult rat heart to the hormonal deficiencies of hypophysectomy is mediated by the synthesis of the same myosin heavy chain form which is predominant in fetal hearts.

Aging↗
PubMed1982

Denervation of newborn rat muscle does not block the appearance of adult fast myosin heavy chain.

Several observations, both in vivo and in vitro, have indicated that the development and maturation of mammalian skeletal muscle fibres is influenced by nerve-muscle interactions. Morphological maturation of newly regenerated adult mouse muscle fibers in an organotypic nerve-muscle culture system depends on the presence of spinal cord neurones. Sciatic nerve transection in newborn rats has been shown to modify the development of the histochemical and contractile properties of the denervated muscles. In addition, neural influences are important for the appearance of certain of the myosin small subunits. It has been proposed that the nerve also controls the changes in myosin heavy chain isozymes appearing during development. One such transition occurs in rat muscle where the neonatal form of myosin heavy chain is replaced by the adult form during the second post-natal week. Here we demonstrate that innervation of the rat gastrocnemius muscle (a fast-contracting muscle in the adult) is not required for the appearance of the adult form of myosin heavy chain.

Animals↗
PubMed1981

Myosin isoenzyme changes in several models of rat cardiac hypertrophy.

We studied the effect of chronic mechanical overloading on the isoenzyme composition of rat cardiac myosin in several experimental models: aortic stenosis (AS), aortic incompetence (AI), aortocaval fistula (ACF), overload of the non-infarcted area after left coronary ligation (INF), and overload of the spontaneously hypertensive rats (SHR). Samples of the left and right ventricles were isolated from these hearts, and myosins were analyzed by electrophoresis in non-dissociating conditions. The myosin isoenzymes were called V1, V2, and V3 in order of decreasing mobility, according to the nomenclature of Hoh et al. Controls of the Wistar and Wistar Kyoto (WKY) strains were almost exclusively V1, A slow age-dependent shift toward V3 was observed in the left ventricles of adult Wistar rats, which at 30 weeks of age (body weight 600 g) contained approximately 15% of this form. In all models of cardiac hypertrophy, an isoenzymic redistribution was observed with a significant increase in V3. The level of V3 was statistically correlated with the degree of hypertrophy in the AS, (n = 11, r - 0.6, P less than 0.05), the AI (n = 14, 4 = 0.88, P less than 0.001), and the AS + AI(n = 14, 4 = 0.69, P less than 0.01) but not in the ACF (n = 16, r = 0.46). The isoenzymic changes could account for the decreases in both myosin ATPase activity and cardiac contractility described previously in our laboratory and by others. They also demonstrate that changes in myosin isoenzymes represent a general response of the rat heart, to chronic mechanical overloading.

Animals↗
PubMed1980

Use of antibodies against dodecylsulfate-denatured heavy meromyosins to probe structural differences between muscular myosin isoenzymes.

Heavy meromyosin, a tryptic myosin fragment, was purified from rabbit fast twitch muscles and rat cardiac ventricles. Both types of heavy meromyosin were denatured by sodium dodecylsulfate and used to immunize guinea-pigs after chromatography on Sephadex G-10 to remove excess dodecylsulfate. Micro-complement fixation analysis showed that the antisera were specific to a denatured configuration of heavy meromyosin and myosin, and hardly recognized the native proteins. Cross-reactions performed with both rabbit skeletal and rat cardiac antisera indicated that the antigenic structures of denatured myosins varied according both to species (man, rabbit, rat or mouse), and to muscle-type (red skeletal slow twitch, while skeletal fast twitch, cardiac atria or cardiac ventricles). Denatured heavy meromyosin chromatography on Sephadex G-200 in the presence of 0.1% sodium dodecylsulfate enabled separation of several polypeptides groups. Of these, a polypeptide of Mr 29000 was the most reactive and exhibited the same immunological specificities as the whole myosin molecule. The use of antibodies against denatured heavy meromyosin in conjunction with micro-complement fixation therefore provides a discriminant means, not only for estimating the structural relationship between several myosin isoenzymes, but also for localizing constant and variable regions in the heavy chains of these isoenzymes.

Animals↗