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J M Capasso

Publications and source records attributed to J M Capasso.

At least 91 records · Page 5Linked to original sources
PubMed1989

Alterations in collagen cross-linking impair myocardial contractility in the mouse heart.

A number of genetic disorders in humans are associated with defects in the synthesis and metabolism of collagen, which are accompanied by multiple cardiovascular disease processes. To determine whether genetically determined cross-linking abnormalities of collagen may alter cardiac function, left ventricular papillary muscles of mice with a genetic defect in the cross-linking of collagen (Movbr) were studied in vitro. With respect to controls, increases in time to peak tension, from 102 +/- 1.4 to 125 +/- 5.4 msec (p less than 0.001), and time to one-half relaxation, from 76 +/- 3.0 to 98 +/- 6.1 msec (p less than 0.05), were measured. Moreover, resting tension at the length associated with maximum developed isometric force (L) was elevated, from 11.1 +/- 1.7 to 19.3 +/- 1.1 mN/mm2 (p less than 0.001), and a similar difference was also seen throughout the physiological range of muscle lengths. In contrast, developed tension was depressed at 93-97% of L. Peak rate of tension rise and decay were diminished whereas time to peak rate of tension rise was prolonged. Isotonically, a decrease in the magnitude of peak shortening at L, from 4.0 +/- 0.5 to 2.0 +/- 0.2% (p less than 0.04), and an increase in time to peak shortening, from 100 +/- 2.3 to 129 +/- 2.8 msec (p less than 0.001), were seen. In addition, peak velocities of shortening and relengthening were diminished in the Movbr mouse heart. In conclusion, the impairment in collagen cross-linking alters cardiac mechanics by a reduction in force-generating ability and a prolongation of the timing parameters of the systolic and diastolic phases of contraction in vitro.

Animals↗
PubMed1989

Morphometric analysis of coronary capillaries during physiologic myocardial growth and induced cardiac hypertrophy: a review.

The quantitative structural properties of the ventricular myocardium with respect to its capillary concentration and distribution have been measured morphometrically during postnatal physiologic growth and later in life in the rat, and compared with those accompanying an increased load in the adult heart to determine whether induced cardiac hypertrophy is a pathologic condition or a form of accelerated myocardial growth. The following morphometric parameters of the capillary microvasculature were examined: 1. Capillary luminal volume density; 2. Capillary luminal surface density; and 3. The average diffusion distance for oxygen. The expansion of the ventricular myocardium during maturation shows a remarkable degree of well balanced compensatory response, because the capillary microvasculature and myocytes grow in proportion to the increase in cardiac mass. In older rats parenchymal cells increase more than the capillary network resulting in a reduction of the oxygenation potential of the tissue and local ischemic damage. Cardiac hypertrophy produced by pressure overload, volume overload and by a combination of both may also show alterations affecting capillary luminal volume and surface densities and the path length for oxygen molecular transport, which indicate an inadequate growth adaption of the component structures responsible for tissue oxygenation. In conclusion, myocardial enlargement that develops with age or as a result of an increased work load on the heart may lead to a conditioned state of the myocardium that can be expected to increase its vulnerability to ischemia as in pathologic cardiac hypertrophy.

Aging↗
PubMed1988

An intrinsic membrane glycoprotein of the golgi apparatus with O-linked N-acetylglucosamine facing the cytosol.

We have recently described the occurrence of integral membrane glycoproteins in rat liver smooth and rough endoplasmic reticulum with O-N-acetylglucosamine facing the cytosolic and luminal sides of the membrane (Abeijon, C., and Hirschberg, C. B. (1988) Proc. Natl. Acad. Sci. U.S.A. 85, 1010-1014). We now report that integral membrane glycoproteins with cytosolic facing O-N-acetylglucosamine also occur in membranes of rat liver Golgi apparatus. This was determined following incubation of vesicles from the Golgi apparatus, which were sealed and of the same membrane topographical orientation as in vivo, with UDP-[14C]galactose and saturating amounts of bovine milk galactosyltransferase. This enzyme does not enter the lumen of the vesicles and specifically catalyzes the addition of galactose, in a beta 1-4 linkage, to terminal N-acetylglucosamine. Under these conditions, galactose was transferred to a glycoprotein of molecular mass of 92 kDa. This protein was insoluble in sodium carbonate, pH 11.5, conditions under which integral membrane proteins remain membrane bound and was insensitive to treatment with peptide:N-glycosidase F. beta Elimination and chromatography showed that radiolabeled galactose was part of a disaccharide which was characterized as Gal beta 1-4GlcNAcitol. This glycoprotein is specific of the Golgi apparatus membrane. Intrinsic membrane glycoproteins with this unusual carbohydrate membrane orientation thus occur in the endoplasmic reticulum and Golgi apparatus of rat liver.

Acetylglucosamine↗
PubMed1987

Morphology, composition, and function of struts between cardiac myocytes of rat and hamster.

The morphology, composition, and function of struts that interconnect the lateral surfaces of cardiomyocytes were examined in the hearts of rats and hamsters. Methods included brightfield and fluorescent light microscopy, secondary and backscatter scanning electron microscopy, and transmission electron microscopy in conjunction with silver stain, cationic dye, and antibody to type-I collagen. These studies reveal a twisted, beaded appearance and a complex substructure of collagen fibrils embedded in a ground substance that has a positive reaction with cationic dye. A hierarchy of patterns of branching and attachment was seen among intercellular struts ranging in diameter from 0.1 micron to several micron. The hypothesis that struts tether not only the surfaces but the contractile lattices of laterally adjacent myocytes is supported by the following: (a) the attachments of struts to the collagen weave of the sarcolemma, often lateral to the level of Z bands, (b) the presence of collagen type I in a composite material arrangement, (c) the relative dispositions and configurational changes of struts and myocyte surfaces in various physiological states and induced, non-physiological perturbations of cardiac muscle, (d) the corrugated sarcolemmas with infoldings near Z bands, and (e) the continuity of intracellular filaments from Z bands to the inner aspect of the sarcolemma in relaxed and contracted myocytes. Implications of struts acting as tethers and sites for storage of energy in the motions of myocytes during the cardiac cycle are discussed.

Animals↗
PubMed1986

3'-O-(4-benzoyl)benzoylcytidine 5'-triphosphate. A substrate and photoaffinity label for CMP-N-acetylneuraminic acid synthetase.

A photoreactive, radiolabeled pyrimidine nucleotide, 3'-O-(4-benzoyl)benzoylcytidine 5'-triphosphate was synthesized from benzoylbenzoic acid and radiolabeled CTP. Benzoylbenzoyl-[5-3H]CTP could substitute for CTP, in an enzymatic reaction with N-acetylneuraminic acid catalyzed by Escherichia coli or rat liver CMP-NeuAc synthetase, to yield radiolabeled benzoyl-benzoyl-CMP-NeuAc. E. coli CMP-NeuAc synthetase could be specifically radiolabeled using benzoylbenzoyl-[alpha-32P]CTP as a photoaffinity label. This specific covalent binding occurred using enzyme preparations of different degrees of purity. These results suggest that benzoylbenzoic acid derivatives of pyrimidines should be of general use in the identification and active site mapping of pyrimidine-requiring proteins and enzymes. These include glycosyltransferases, sugar nucleotide synthetases, and transporters, and enzymes participating in the conjugation of bile acids and biosynthesis of nucleic acids and choline nucleotides.

Affinity Labels↗
PubMed1986

Excitation-contraction coupling in rat myocardium: alterations with long term ethanol consumption.

The mechanical and electrical effects of chronic ethanol consumption were studied in rats maintained on 40% ethanol and water solution (40% of caloric intake) for a 30 week period and in controls. Left ventricular papillary muscles from male Wistar rats were studied by myography at 30 degrees C, 0.1 Hz stimulation, and external calcium concentration of 2.4 mmol X litre-1. No significant difference was found between alcoholic and control rats with regard to resting tension. Developed tension, time to peak tension, time to one half relaxation, and time to peak shortening were, however, significantly decreased in preparations from the study animals. Velocity of shortening and relengthening at all relative loads studied were depressed in alcoholic preparations. No significant difference was found in action potential between the two groups with regard to resting membrane potential, action potential amplitude, overshoot, or maximum rate of rise of the upstroke. In contrast, the duration at 50% (APD50) and 75% (APD75) of total repolarisation was significantly shorter for action potential in the alcoholic group than in the controls. Thus chronic ethanol ingestion results in an inability to develop normal levels of force, depressed force-velocity relation, and shortening of action potential duration.

Action Potentials↗
PubMed1986

Effects of hypothyroidism and hypoparathyroidism on rat myocardium: mechanical and electrical alterations.

The mechanical and electrical effects of hypoparathyroidism (Px), hypothyroidism (Tx), and hypothyroidism combined with hypoparathyroidism (TPx) were investigated by comparing simultaneously recorded transmembrane action potentials and isometric and isotonic contractions recorded from the myocardium. Left ventricular papillary muscles from male Wistar rats were studied electrically and mechanically in a muscle bath at 30 degree C, stimulated at 0.1 Hz and external calcium = 2.4 mM. No significant difference was found between control (C), Px, Tx, and TPx preparations with regard to resting tension and developed tension. However, time to peak tension, time to one half relaxation and time to peak shortening were significantly increased in preparations from animals that were Px, Tx, and TPx as compared with age-matched controls. Maximum velocities of shortening (Vs) and relengthening (Vr) at all relative loads studied were significantly depressed in Px preparations when compared with those of C muscles. A greater depression was found in the Tx muscle and still greater depression of these indices was noted in TPx muscles. No significant difference was found between C, Px, Tx, and TPx action potential with regard to resting membrane potential (RMP), action potential amplitude (AMP), overshoot (OS), or maximum rate of rise of the upstroke (Vmax).(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1986

Myocardial biochemical, contractile, and electrical performance after imposition of hypertension in young and old rats.

The effects of renovascular hypertension on the biochemical, contractile, and electrical performance of myocardial tissue from rats of various ages has been examined. Male Fischer rats, 2, 7, 12, and 17 months old, were made hypertensive by constriction of the left renal artery. Ten weeks after the onset of hypertension, left ventricular papillary muscles were isolated from those four groups when 5, 10, 15, and 20 months old, respectively. Mechanical performance and transmembrane electrical events were recorded simultaneously. Contractile protein enzyme activity was determined in the same hearts from which papillary muscles were used for acquisition of mechanical and electrical information. There was a slight increase in blood pressure in control groups as a function of age while blood pressure maintained a range of approximately 179-188 mm Hg for all hypertensive groups. Heart weight of control animals increased significantly from 5 months to 20 months of age from 539 +/- 26 to 1088 +/- 56 mg, representing an increase of 101%. In hypertensive animals, heart weight increased 50% in 5-month-, 15% in 10-month-, 50% in 15-month-, and 11.7% in 20-month-old animals. Although control groups revealed alterations in mechanical, electrical, and biochemical parameters that increased as a function of age, the magnitude of the biochemical, contractile, and electrical response to hypertension varied monotonically with the extent of myocardial hypertrophy, rather than age per se. Adaptation to the stress of hypertension was observed in each age group, and was revealed as prolongation of mechanical and electrical timing parameters, depression of the load-velocity relation, and contractile protein enzyme activity. Thus, the stress of hypertension, which was tolerated by the 10- and 20-month-old animals with lesser relative hypertrophy and lesser changes in measured parameters, may represent a differential adaptation to the stress of hypertension.

Action Potentials↗
PubMed1985

Phosphoproteins and protein kinases of the Golgi apparatus membrane.

Incubation of a highly purified fraction derived from rat liver Golgi apparatus with [gamma-32P]ATP results in phosphorylation of several endogenous phosphoproteins. One phosphoprotein with an apparent Mr of 48,300 is radiolabeled to an apparent extent at least 5-fold higher than any other phosphoprotein as part of either the Golgi apparatus or highly purified rat liver fractions derived from the rough endoplasmic reticulum, mitochondria, plasma membrane, coated vesicles, cytosol, and total homogenate. Approximately 70% of the 48.3-kDa phosphoprotein appears to be a specific extrinsic Golgi membrane protein with the phosphorylated amino acid being threonine. The protein kinase which phosphorylates the 48.3-kDa protein is an intrinsic Golgi membrane protein and is dependent on Mg2+, independent of Ca2+, calmodulin, and cAMP, and is inhibited by N-ethylmaleimide. Preliminary evidence suggests that there are also intrinsic membrane protein kinases in the Golgi apparatus which are dependent on Ca2+ and cAMP. The physiological role of the above phosphoproteins and protein kinases is not known.

Adenosine Triphosphate↗
PubMed1985

Microvascular spasm as a cause of cardiomyopathies and the calcium-blocking agent verapamil as potential primary therapy.

The origin of cardiomyopathies, a major cause of cardiac disability and death, has been largely unexplained. Pathologic features, common to all cardiomyopathies independent of origin, include ventricular hypertrophy and diffuse scarring with variable amounts of ventricular dilatation. This problem was studied experimentally in 2 models of congestive cardiomyopathy: the hereditary cardiomyopathic Syrian hamster and the hypertensive-diabetic rat. In both the genetic and the acquired disease models, there is focal myocytolytic necrosis followed by healing with focal scars, ventricular wall hypertrophy, ventricular dilatation with congestive heart failure and, ultimately, death. In view of the heterogeneous pathologic features of both diseases, silicone rubber perfusions have been used to study the microcirculation of the heart in these animals; microvascular spasm has been demonstrated early in the disease associated with small areas of myocytolytic necrosis that undergo subsequent fibrosis. Reactive hypertrophy then ensues as a compensatory response to this myocellular necrosis; it is the combination of cell loss and slowly decreasing contractility resulting from the reactive hypertrophy, which culminates in a cardiomyopathy. Administration of verapamil or prazosin to the cardiomyopathic Syrian hamster prevents microvascular spasm and development of cardiomyopathic changes in the myocardium. In view of these and other findings related to the anatomy and hyperreactivity of microcirculation, it is concluded that hypertrophic congestive cardiomyopathies may be caused by focal cell loss due to microvascular spasm and reperfusion injury, with the subsequent development of focal fibrosis and reactive hypertrophy in response to the myocardial necrosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Extracellular structures in heart muscle.

The extracellular matrix of heart muscle contains a considerable variety of structures. We have systematically studied the morphology of these structures using several methods of fixation and microscopy. Endomysial connections between cells are comprised of struts of collagen [1] as well as combinations of elastin fibers, collagen fibers, and microfibrils. The rest of the extracellular matrix is filled with a polyanionic lattice of unit collagen fibrils, microthreads, and granules. In the course of these investigations, we have observed regions of structural continuity across the sarcolemma, from endomysial collagen struts to Z-bands. We have also correlated the mechanical resistance to stretch with orientation of epimysial collagen fibers and sarcomere lengths in living as well as fixed rat papillary muscles. Our observations suggest that the extracellular skeletal framework plays an important role in normal cardiac function.

Animals↗
PubMed1985

Calcium induced reversible alterations in excitation-contraction coupling in verapamil treated rat myocardium.

We studied the effects of a calcium channel blocking agent, verapamil (V) (2 to 10 micrograms/ml), in the presence of increasing external calcium on simultaneously recorded transmembrane electrophysiological properties and mechanical function of rat myocardium. Left ventricular papillary muscles from male Fischer 344 rats were studied electrically, by standard microelectrode techniques, and mechanically in an isolated tissue bath at 30 degrees C. Control (0 micrograms/ml V + 2.4 mM Ca2+) = C, action potential duration at 50% and 75% repolarization (D50ap and D75ap) recorded from papillary muscles were short (14.1 +/- 0.75 ms; 33.3 +/- 2.7 ms) compared with recordings from papillary muscles subjected to increasing doses of verapamil (2, 4, 6, 8, or 10 micrograms/ml) + 2.4 mM Ca2+ = V, (17.3 +/- 0.77 ms; 121.4 +/- 8.9 ms: 10 micrograms/ml) (P less than 0.001). Upon augmentation of external calcium [10 micrograms/ml Verapamil + augmented Ca2+ (4.8, 7.2, or 9.6 mM] = VCa, D50ap and D75ap decreased but still remained significantly longer than control D50ap and D75ap (15.1 +/- 0.77 ms; 110.1 +/- 7.9 ms). Developed tension (Td), time to peak developed tension (TPT), time to one-half relaxation (T1/2R) and resting tension (Tr) decreased as a function of verapamil concentration. Although TPT and T1/2R returned toward C values when external calcium was increased, Tr continued to decrease while Td increased above control levels. A significant correlation was found between measured parameters of contraction and transmembrane action potential for C and VCa muscles. However, in V muscles no significant correlation was observed between these same mechanical and electrical parameters.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Size and shape of enzymatically isolated ventricular myocytes from rats and cardiomyopathic hamsters.

Rod-shaped and branched ventricular myocytes from rats and cardiomyopathic hamsters (strain 53.58) were isolated enzymatically, and their widths and lengths were measured in physiological salt solutions containing normal levels of calcium (2.5 mmol). In rats of approximately 200 g body weight, the average myocyte width and length are 25 micron and 115 micron. The isolated cells are also classified according to shape with nearly 50% branched or otherwise irregular. Myocytes of the hearts of the 53.58 strain of cardiomyopathic hamsters at 7 months of age are significantly larger than control hamsters of the same age, indicating that cellular hypertrophy has occurred. Estimates of the number of cells in the ventricles indicate that there is a cell loss of nearly 13% in the myopathic heart. A consideration of the significance of wider and longer myocytes with undiminished myofibrillar mass lead to the conclusion that the decreased contractility displayed by the cardiomyopathic hamster heart must be due, at least in part, to functional defects in the myofibrillar apparatus, in the system of activation, or in cellular integration.

Age Factors↗
PubMed1984

Effect of nucleotides on translocation of sugar nucleotides and adenosine 3'-phosphate 5'-phosphosulfate into Golgi apparatus vesicles.

Recent studies from this laboratory have suggested that rat-liver Golgi apparatus derived membranes contain different proteins which can translocate in vitro CMP-N-acetylneuraminic acid, GDP-fucose and adenosine 3'-phosphate 5'-phosphosulfate from an external compartment into a lumenal one. The aim of this study was to define the role of the nucleotide, sugar and sulfate moieties of sugar nucleotides and adenosine 3'-phosphate 5'-phosphosulfate in translocation of these latter compounds across Golgi vesicle membranes. Indirect evidence was obtained suggesting that the nucleotide (but not sugar or sulfate) is a necessary recognition feature for binding to the Golgi membrane (measured as inhibition of translocation) but is not sufficient for overall translocation; this latter event also depends on the type of sugar. Important recognition features for inhibition of translocation of the above sugar nucleotides and adenosine 3'-phosphate 5'-phosphosulfate were found to be the type of nucleotide base (purine or pyrimidine) and the position of the phosphate group in the ribose. Thus, UMP and CMP were found to be competitive inhibitors of translocation of CMP-N-acetylneuraminic acid, while AMP did not inhibit. Structural features of the nucleotides which were less important in inhibition of translocation (and thus presumably in binding) of the above sugar nucleotides and adenosine 3'-phosphate 5'-phosphosulfate were the number of phosphate groups in the nucleotide (CDP and CMP inhibited to a similar extent), the presence of ribose or deoxyribose in the nucleotide, a replacement of hydrogen in positions 5 of pyrimidines or 8 in purines by halogens or an azido group. The sugar or sulfate did not inhibit translocation of the above sugar nucleotides and adenosine 3'-phosphate 5'-phosphosulfate into Golgi vesicles and therefore appear not to be involved in their binding to the Golgi membrane.

Adenine Nucleotides↗
PubMed1984

U1 small nuclear RNA-like sequences in human high molecular weight RNA.

Human U1 small nuclear RNA synthesis was shown earlier to be very sensitive to UV radiation. This led us to test for the possible presence of U1 RNA-like sequences in large RNAs. Human RNA was analyzed in gel blots hybridized with U1 DNA probes. A high molecular weight, heterodisperse RNA population was detected, which hybridizes both to a U1 RNA-coding region single-stranded DNA probe, and to a U1 gene fragment that contains only 6 nucleotides of flanking sequence. These large RNAs can be hybrid selected using immobilized U1 DNA, and have an average size of several kilobases. Additional observations support the claims that the high molecular weight RNA hybridization signal is not an aggregation artifact and that it is sequence specific.

Carcinoma↗
PubMed1984

Effect of atractylosides, palmitoyl coenzyme A, and anion transport inhibitors on translocation of nucleotide sugars and nucleotide sulfate into Golgi vesicles.

The effect of palmitoyl coenzyme A, atractylosides, and anion transport inhibitors on translocation into rat liver Golgi vesicles of adenosine 3'-phosphate 5'-phosphosulfate (PAPS), CMP-N-acetylneuraminic acid, and GDP-fucose was studied. Translocation of the above three nucleotide derivatives was inhibited by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS; 50% inhibition required 10-20 microM DIDS). The inhibition of translocation of PAPS by DIDS was used to demonstrate that sulfation of macromolecules within Golgi vesicles is preceded by translocation of PAPS into the vesicles. Palmitoyl coenzyme A, at concentrations below its critical micellar concentration, specifically inhibited translocation into Golgi vesicles of PAPS but not CMP-NeuAc and GDP-fucose. Inhibition of PAPS translocation by 50% required 9 microM palmitoyl coenzyme A. Translocation of PAPS but not of CMP-NeuAc or GDP-fucose was also inhibited by atractyloside or carboxyatractyloside with 50% inhibition requiring 15 microM either glycoside. This pattern of inhibition suggests structural similarities between the putative translocator of PAPS in Golgi membranes and the ATP/ADP translocator of mitochondria.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗