Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Rat cardiac muscle was dissociated into single cells by a coronary perfusion technique with collagenase and hyaluronidase in a Ca-free medium. Retention of the cylindrical shape of isolated muscle cells could be achieved by regulation of [Ca2+]0 and temperature. Cells kept at 4 degrees C, and 0-01 mM CaCl2 remained cylindrical for more than a week and contracted spontaneously upon warming at 37 degrees C. At [Ca2+]0 between 0-1-2 mM and 37 degrees C, cells underwent contracture and rounded up. Scanning (SEM) and transmission electron microscopy were used to analyze the structure of cylindrical and rounded muscle cells. The extracellular aspect of the sarcolemma at lateral cell surfaces and intercalated disc regions were clearly revealed for SEM analysis. Both the distribution and number of T-tubule openings on the surfaces can be estimated and a three-dimensional description of the intercalated disc obtained. This study reveals that isolated adult heart cells are extremely sensitive to [Ca2+]0, but with careful control of this cation, this preparation should be helpful in the analysis of both sarcolemmal structure and the pathological changes which accompany myocardial injury.
 ...
PMID:Studies of isolated adult rat heart cells: the surface morphology and the influence of extracellular calcium ion concentration on cellular viability. 20 Oct 46

A new method for the study of extracellular space and cell volume of cardiac muscle is described. Canine cardiac Purkinje strands and cat papillary muscles were placed within a fluid-filled aperture connecting two sides of an experimental chamber. Direct electrical current was passed through the hole, and changes in the voltage drop across it were correlated with Purkinje strand extracellular space and cell volume. The results of experiments on 21 Purkinje strands and 4 papillary muscles yielded an extracellular space of 51 +/- 2.1% (SEM) and 23.3 +/- 2.1%, respectively. When strands were superfused with hyper- (600 mosM) and hyposmotic (150 mosM) solutions, the preparations were found to attain new steady-state volumes that were 75 +/- 3.1% and 121 +/- 9% of control, respectively. This method can be used for volumetric studies in numerous cardiac muscle preparations and should be applicable to the study of volume abnormalities associated with certain disease states.
 ...
PMID:A simple method for volumetric measurements in isolated cardiac muscle. 42 89

Myocardial relaxation is an important energy-dependent process. Hypoxia, unlike ischemia, has not been shown to impair myocardial relaxation. This difference may be because (a) the traditional index to assess isometric muscle relaxation (half time to relaxation or RT((1/2))) reflects both changes in developed tension as well as relaxation and (b) the relaxation process is highly sensitive to temperature and previous papillary muscle studies have been conducted under hypothermic conditions. The present study examines the effect of hypoxia on the relaxation process of 31 isometrically contracting kitten papillary muscles at hypothermic (29 degrees C) and euthermic (38 degrees C) conditions using RT((1/2)), the peak rate of tension fall (-dT/dt) and -dT/dt normalized for tension ([peak -dT/dt]/T and max [-dT/dt per T]). Hypoxia at 29 degrees C resulted in a fall in RT((1/2)) from 278+/-11 (SEM) to 230+/-17 ms (P < 0.01) and no change in (peak -dT/dt)/T and max (-dT/dt per T). However, at 38 degrees C, hypoxia impaired relaxation as reflected in a prolongation of RT((1/2)) from 101+/-6 to 126+/-8 ms (P < 0.01) in spite of a substantial fall in peak tension. Moreover, (peak -dT/dt)/T decreased from -15.4+/-0.7 to -11.0+/-0.8/s (P < 0.01) and max (-dT/dt per T) decreased from -25.1+/-1.8 to -13.8+/-0.9/s (P < 0.01). In conclusion, the present study demonstrates that hypoxia impairs the relaxation process of cardiac muscle.
 ...
PMID:Effect of hypoxia on myocardial relaxation in isometric cat papillary muscle. 65 89

The mechanical properties of cardiac muscle during ultrasonic irradiation have been studied in vitro. Left anterior papillary muscle from normal rats was suspended in buffered lactated Ringers solution equilibrated with 95% O2, and 5% CO2 and maintained at 20 degrees C. The muscles were stimulated to contract isometrically three times per minute at the length which produced maximum tension. Each muscle was irradiated with a MHz ultrasound at an average power of 2.4 Wcm-2 for a period of 10 min with a 10 min recovery period. Irradiation caused an average increase in temperature of the muscle of 1.7 +/- 0.2 degrees C (mean +/- SEM). Irradiation caused the resting tension (1.46 +/- 0.13g) to decrease by 17.8 +/- 4.7% and the developed tension (3.33 +/- 0.61g) to decrease by 4.1 +/- 0.9%. Since changes in contractile properties have been reported with temperature the bath temperature was raised and changes in contraction observed. When compensated for effects of temperature, the changes in resting tension became - 13.3 +/- 4.1% while the change in developed tension became + 1.6 +/- 2.3%. The change in resting tension is highly significant (p less than 0.05 paired t-test) while the change in developed tension is not. Thus 1 MHz ultrasound at an intensity of 2.4 Wcm-2 appears to affect resting tension of cardiac muscle without affecting the active tension. Since changes in cardiac mechanics of this type have not been described previously the effects of ultrasound appears to be unique.
 ...
PMID:The effects of ultrasound on the mechanical properties of rat cardiac muscle. 67 75

Aggregations of isolated embryonic and adult heart cells were studied so as to examine in detail the formation of cell contacts, the assembly of cells into multicellular systems, and cell co-operation in forming organized and differentiating tissues. At selected intervals after initiating rotation cultures, aggregates were examined microscopically for evidence of contractility, and subsequently processed for scanning and transmission electron microscopy (TEM, SEM). By continuous accretion of single cells, and the joining of small clusters, the aggregates increased in size. Cells within the aggregates exhibited rhythmic and synchronous contractility by 3--12 h of culture, suggesting the formation of low-resistance inter-cellular junctions between apposed cells. Two populations of cells could be recognized by 9--12 h with SEM. One was spherical in surface view and the other was flattened. Spherical cells possessed myofibrils, and were classified as cardiac myocytes which occupied the core of the aggregate. The flattened cells were devoid of myofibrils and non-muscle in nature. They covered the surface in a multilayered epithelium. At 12h the aggregates were round to oval, covered by flattened cells, but individual round cells could still be recognized. Intercalated discs were frequently observed in 12 h aggregates. The junctional complexes observed in 12--72 h aggregates include desmosomes, fascia adherens and gap junctions. Most of the aggregation was completed by 24 h, and at later time periods, i.e. 48--72 h, the external surface of the aggregates was smoothed out with epithelial investment. In these aggregates myofibrils and intercellular junctions became reconstructed in less than 24 h. Unlike embryonic myocardial cells, adult cells did not form aggregates of numerous cells. Instead, they formed irregular clusters of 2--5 cells during 3--48 h of culture. Intercellular contacts and suggestive desmosomal materials were observed between adherent cardiac muscle cells. When culture continued for 48--72 h, the cells underwent supercontraction and became non-viable, suggesting that the terminally differentiated adult myocardial cells are incapable of regenerating constituents obligatory for histogenetic reconstruction.
 ...
PMID:Reconstruction of mammalian heart tissue from embryonic heart cell suspension with reference to the aggregation of adult heart cells. 75 14

The goal of this study was to develop, on a rational basis, an index of the intrinsic diastolic elastic properties of the left ventricle. A relatively simple analytic model employing a thin-walled spherical geometry coupled with an approximate formulation of a two-dimensional constitutive relation, was used to examine the primary determinants of the pressure-volume relationship of the intact heart. The results permit comparison with other indices of compliance or wall stiffness. The slope of the dP/dV vs P curve was found to be sensitive to the non-linear elastic constant K, but is also sensitive to variations in cardiac muscle volume. VdP/dV was found to be sensitive to pressure. m = d(log P)/d(log V) = (V/P)(dP/dV) is proposed as an index sensitive to K and relatively insensitive to both pressure and initial cardiac geometry. The index is compared with published studies. Using the data of Fester and Samet, mean values of the asymptotic log-log P-V slope, m, evaluated at end-diastole for normal, idiopathic hypertrophy, mild, moderate and severe coronary artery disease were 3.95 +/- 0.60 (SEM), 5.05 +/- 1.60, 5.24 +/- 0.96, 8.35 +/- 2.06, and 15.13 +/- 3.0, respectively. At values of LVEDP less than 7 mm Hg the concept of simple distension is questioned. The advantages and limitations of this approximate index are discussed. This index seems to afford a practical measure of the elastic properties of the wall over a rather wide range of pressure, volume, wall mass and wall thickness.
 ...
PMID:Asymptotic slope of log pressure vs log volume as an approximate index of the diastolic elastic properties of the myocardium in man. 124 75

The effect of enalapril and angiotensin II on junctional conductance (gj) of isolated rat heart cell pairs was investigated. It was found that enalapril (1 micrograms/ml) increases gj by 106 +/- 3.1% (SEM) (n = 20) within 4 min. The effect of enalapril on gj was not suppressed by propranolol (10(-6) M) or by a cAMP-dependent protein kinase inhibitor. Angiotensin II (1 micrograms/ml) reduced gj by 55%. These observations might indicate that an intrinsic renin-angiotensin system in heart is involved in the control of gj in cardiac muscle.
 ...
PMID:Enalapril, an inhibitor of angiotensin converting enzyme, increases the junctional conductance in isolated heart cell pairs. 172 43

We have investigated the response to endothelin of isolated atrial and ventricular trabeculae from failing human hearts obtained at transplant. Results indicate that endothelin exerts a significant positive inotropic effect on human atrial and ventricular tissue, with increases in developed tension of 74.6 +/- 14.1% (+/- SEM) and 9.9 +/- 4.0%, respectively. Further studies on rat cardiac muscle demonstrate that the greater inotropic effect on atrial than ventricular muscle is also exhibited by the rat heart in vitro, with 39.9 +/- 10.7% and 17.1 +/- 5.9% increases in developed tension for atria and papillary muscle, respectively. Studies in rat atria also provide no evidence for an effect of endothelin on the frequency of spontaneous contractions. These results suggest that the potential exists for regulation of cardiac function in humans and rats by endothelial-derived factors such as endothelin, possibly via augmentation of atrial systole.
 ...
PMID:Endothelin is a positive inotropic agent in human and rat heart in vitro. 264 79

1. The effects of jaundice on renal and circulatory function were investigated in chronic bile duct ligated (CBDL) rats 6 days after surgery. Sham operated (SO) animals served as controls. 2. Body weight was significantly reduced, whereas blood pressure remained unaltered, 6 days after bile duct ligation when serum bilirubin had risen to 169 +/- 18 (SEM) as compared with 2.8 +/- 0.3 mumol/l in SO rats. When compared with control values before surgery, urinary volume had significantly increased and absolute excretion of sodium, potassium, chloride and phosphate had decreased on day 6 after CBDL. Endogenous creatinine clearance was markedly depressed when compared with SO rats. Whereas fractional excretion of potassium remained unaltered, fractional excretion of sodium and of phosphate was significantly increased. 3. Except for a significant increase in urinary thromboxane B2 (TXB2) excretion in CBDL rats, no significant changes were observed in urinary excretion of prostaglandin (PG) E2, in the synthesis of PGE2, 6-keto-PGF1 alpha and TXB2 by isolated aortic tissue in vitro, nor in renal and cardiac adenosine triphosphatase activities or renal cortical mitochondrial function. 4. The adenosine triphosphate content of kidney cortex and cardiac mitochondrial function were significantly depressed in CBDL rats. 5. The results demonstrate that jaundice in CBDL rats is associated with functional and metabolic disturbances of the kidney and cardiac muscle, which may contribute to the renal and haemodynamic characteristics observed in jaundiced animals and humans.
 ...
PMID:The kidney and cardiovascular system in obstructive jaundice: functional and metabolic studies in conscious rats. 282 70

The number of putative calcium channels in cardiac muscle from young adult hamsters (60 days old) was compared in normal (F1B) hamsters and two different mutant strains (CHF 146 and Bio 14.6) which express cardiomyopathy and muscular dystrophy. Equilibrium binding assays of high affinity sites for [3H]-nitrendipine in ventricular homogenate preparations showed that the maximum number of [3H]-nitrendipine binding sites (Bmax), which corresponds to the number of putative calcium channels, was not significantly different in normal and cardiomyopathic hearts: 79(SEM 9), 64(14) and 69(10) fmol.mg-1 protein in 4-6 hearts from F1B, Bio 14.6 and CHF 146 hamster strains, respectively. Similar results were obtained with binding data after partial purification of the preparation. These data are in agreement with earlier studies comparing two normal strains (CHF 148 and random bred Syrian hamsters) with cardiomyopathic (CHF 146) hamsters, and conflict with other studies comparing normal and cardiomyopathic hamsters. Comparisons with the conflicting data suggest (a) that change in the number of high affinity [3H]-nitrendipine binding sites is not responsible for calcium overload and cell necrosis in cardiomyopathy, and (b) that increased numbers of low affinity [3H]-nitrendipine binding sites may emerge in cardiomyopathic hearts.
 ...
PMID:[3H]-nitrendipine binding sites in normal and cardiomyopathic hamsters: absence of a selective increase in putative calcium channels in cardiomyopathic hearts. 285 22


1 2 3 4 Next >>