Ventricle Muscle Research Articles

REDISTRIBUTION OF CARDIAC OUTPUT CAUSED BY OPENING OF ARTERIOVENOUS ANASTOMOSES BY A COMBINATION OF AZAPERONE AND METOMIDATE

The effects of the butyrophenone, azaperone 5 mg kg-1 i.m. alone and after addition of the imidazole derivative metomidate 6 mg kg-1 i.v. were studied in eight conscious pigs. Fifteen minutes after administration of azaperone, systemic arterial pressure was reduced by 35% as a result of a 45% increase in systemic vascular conductance and 10% decrease in cardiac output (Q). After azaperone, 23% of the radioactive labelled microspheres (15 (SD 1) microns) injected into the left atrium were detected in the lungs as a result of opening of arteriovenous anastomoses (baseline 3%). The increase in arteriovenous anastomotic blood flow was at the expense of the nutritional (= capillary) channels. Flow to the brain was maintained, but that to the left ventricle decreased in parallel with the reduction in arterial pressure. Vascular conductance of most other organs, except the skin, increased or was maintained. The addition of metomidate had no effect on Q because an increase in stroke volume (by 30%) compensated for the decrease in heart rate. Systemic vascular conductance decreased, most noticeably in the brain, left ventricle and skeletal muscle. We conclude that azaperone alone and in combination with metomidate had only a moderate effect on Q, but caused a redistribution in favour of arteriovenous anastomoses.

Extensive Extraosseous Localization of Bone Imaging Agent in a Patient with Renal Failure and Rhabdomyolysis Accompanied by Combined Hypercalcemia and Hyperphosphatemia

Four sequential Tc-99m pyrophosphate (PYP) imaging studies were performed in a 28-year-old man with high fever and exudate pharyngitis associated with renal failure. Radiotracer localization in the left ventricle (LV), lungs, kidneys, and skeletal muscles were seen in two, initial imaging studies. In the second and third imaging studies, area of increase in activity was seen in the left-sided bowel. In studies done two months later (in the third study), the radioactivity in the skeletal muscles was no longer seen. Studies obtained nine months (in the fourth study) after the first imaging showed less radiotracer localization in the LV, lungs, and kidneys as compared to that seen in the initial study. Myocardial necrosis and microcalcification were proved by LV biopsy. The exact mechanism of extraosseous bone-imaging agent localization is unknown. However, this phenomenon may be related to renal failure, rhabdomyolysis, hypercalcemia, hyperphosphatemia, or elevated parathyroid hormone. The Tc-99m PYP imaging study is useful and sensitive in the detection of extraosseous tissue calcification and monitoring of the disease process.

Diabetic state-induced modification of Ca, Mg, Fe and Zn content of skeletal, cardiac and smooth muscles.

The metal content of diaphragm, gastrocnemius, ventricle, and bladder muscles in genetically obese diabetic KK-CAy and alloxan-diabetic ddY mice was compared with that in prediabetic KK-CAy and normal ddY mice, because the muscles of the diabetic KK-CAy mice had morphological abnormalities, such as atrophy, disappearance of Z-band, disturbed myofibrils and swollen sarcoplasmic reticulum. The amounts of calcium (Ca) in gastrocnemius, ventricle and bladder muscles from the prediabetic KK-CAy mice were significantly 7.7, 98.3, and 36.9% greater, respectively, than those in normal ddY mice. In contrast, the magnesium (Mg) content of the diaphragm, the gastrocnemius, and the ventricle in the prediabetic mice was 8.6, 7.4, and 4.3% lower, respectively, than in the ddY mice. The iron (Fe) content of the diaphragm, gastrocnemius, and ventricle muscles in the prediabetic mice was 29.2, 43.6, and 44.6% greater, respectively, than in the ddY mice. The Ca content in the gastrocnemius muscles of the diabetic KK-CAy mice and the alloxan-diabetic mice was 19.8 and 11.7% higher, respectively, than in the prediabetic and normal mice. The Ca content of the ventricle muscle was increased only in the alloxan-mice. The gastrocnemius Mg was also 9.0 and 5.5% greater in the KK-CAy and the alloxan-mice. The Fe content of the diaphragm and the gastrocnemius muscles from the KK-CAy mice was 27.3 and 23.2% greater, respectively, than in the prediabetic mice. The zinc (Zn) content of the gastrocnemius and the bladder was 16.4 and 18.0% higher, but the ventricle Zn was 13.4% lower, respectively, than in the prediabetic control. The changes in metal content induced by the diabetic state may be related to the morphological abnormalities.

Myosin light chains of guinea-pig striated muscles. Similarities and differences with rat myosin light chains

1. 1. Myosin light chains of guinea-pig striated muscles have been screened by two-dimensional gel electrophoresis and compared to rat myosin light chains. 2. 2. The fast type light chains 1F and 3F, slow type light chains 1S and 2S, and embryonic type light chain 1E are shown to differ in the two rodents; only the fast type light chains 2F co-electrophorese on the gel. 3. 3. In guinea-pig, as in rat, ventricle muscle light chains appear the same as the 1S and 2S light chains and atrial light chain type 1 the same as the 1E light chain. We show that this embryonic light chain of guinea-pig myosin is difficult to identify and may be confused with the adult 1F light chain.

The effects of atriopeptin and angiotensin on the rat right ventricle

1. 1. Atriopeptin had no effect, whereas angiotensin increased the force of the electrically stimulated ventricle muscle. 2. 2. Atriopeptin and angiotensin had no effect on the combined response to muscle stimulation and isoprenaline. 3. 3. Following incubation of the ventricle with [ 3H]noradrenaline, atriopeptin and angiotensin had no effect on the spontaneous or nerve-evoked outflow of radioactivity.

Permeability to various cations of the voltage-dependent sodium channel of isolated rat hippocampal pyramidal neurons

The permeability to various cations of the voltage-dependent sodium channel of isolated rat hippocampal pyramidal neurons was investigated under the voltage-clamp condition. The neurons were dispersed enzymatically and mechanically and perfused internally using a suction pipette technique. The permeability sequence, estimated from the reveral potential of the inward current was Li + > Na + > hydrazine + > formamidine + > guanidine + > methylguanidine + > monomethylamine +. Thus the ionic selectivity of the voltage-dependent sodium channel of rat central nervous system neurons is similar to that in the squid axon, myelinated frog nerve fiber and rat ventricle muscle.

Effect of hypophysectomy on tissue glycogen concentrations in the fetal pig.

The glycogen content was estimated in the liver, lung, cardiac ventricle and skeletal muscle of fetal pigs which had been hypophysectomized between 69-84 days of gestation, decapitated between 35-42 days of gestation or left intact. Comparisons made preterm (103-108 days) or at term (112-114 days) indicated that both liver and skeletal muscle glycogen content were significantly lower in the absence of the fetal pituitary, whereas concentrations in the fetal lungs were significantly higher. There were no significant differences in cardiac glycogen content between hypophysectomized and intact fetuses. Plasma glucose concentrations in both umbilical artery and vein were similar, but plasma arterial fructose concentrations were significantly higher in the hypophysectomized fetuses.

A Potassium-Selective Channel in Isolated Lymnaea Stagnalis Heart Muscle Cells

ABSTRACT Lymnaea stagnalis heart ventricle muscle cells, isolated by enzymatic dispersion, are suitable for patch clamp recording. A channel has been identified which is primarily selective for potassium, although it also appears to conduct sodium. This channel is not blocked by 4-aminopyridine or tetraethylammonium but is sensitive to quinidine. The relationship between the membrane potential, the external potassium concentration and the channel currents, when compared with results obtained from whole cell recording, suggests that this channel could mediate a large part of the cell’s resting conductance. The probability of this channel being open is increased by stretching the patched cell membrane. This has led to speculations about further possible functional roles for this channel.

Thermoregulatory and acute-phase responses to endotoxin of full- term-pregnant rabbits.

Fever, a fall in the plasma level of iron (Fe), and rises in the levels of certain plasma glycoproteins (indexed by protein-bound-N-acetylneuraminic acid [NANA]) normally occur during infection; they are thought to be mutually enhancing in host defense. It has been reported that fever is suppressed at full term of pregnancy; however, it is not known whether the blood chemical changes are similarly affected. Also, the mechanism for the suppression of fever is controversial. Since uteroplacental blood flow is at its maximum near term, competition between the demands of the fetoplacental unit and of thermoregulatory effectors might result in underperfusion of thermogenic tissues and therefore provide a basis for the lack of fever. To examine these questions, the changes in colonic temperature (Tco) and regional blood flow induced by Salmonella enteritidis endotoxin (LPS, 2 micrograms/kg iv) were compared in conscious nonpregnant and 30-day-pregnant rabbits 35 min after injection, using 15-microgram radiolabeled microspheres. In different rabbits, the effects of LPS on Tco and plasma Fe and NANA levels were measured before mating and at term. LPS induced fevers similar in heights and courses in both nonpregnant and full-term pregnant rabbits It caused decreases in the blood flows to brain, tongue, mammary gland, small intestine, and ear and increases in the blood flows to masseter muscle, bone, liver (hepatic artery), and left ventricle; blood flows to the kidneys, spleen, right ventricle, ovaries, and myometrium did not change. There were no significant differences in these vascular responses between nonpregnant and 30-day-pregnant rabbits, except a 28% reduction in the blood flow to the placentas.

X-ray analysis of Lymnaea stagnalis muscle fibres does not suggest that the sarcolemma is permeable to lanthanum ions.

The cross-striated muscle from the heart ventricle and the smooth penis retractor muscle of the freshwater snail Lymnaea stagnalis have been investigated by X-ray microanalysis to establish whether lanthanum can cross the plasma membrane, as has been reported by other investigators. Tissues were incubated in 1 mM ionic lanthanum before fixation in phosphate- or cacodylate-buffered fixative. X-ray mapping for emissions in the lanthanum energy range indicates a concentration of emissions that coincided only with the network of sub-surface transverse tubules formed by the invagination of the plasma membrane and with the plasma membrane/extracellular space interface. X-ray energy spectra were collected from various cell compartments; peak-to-background ratios were obtained and analysed statistically. Cacodylate buffer is less effective than phosphate buffer in precipitating lanthanum, but no evidence to suggest the redistribution of lanthanum in cacodylate-buffered preparations was found. Lanthanum is precipitated only in the sub-surface transverse tubules and at the plasma membrane/extracellular space interface in both heart ventricle muscle and penis retractor muscle, fixed in either phosphate or cacodylate buffer. There was no evidence of lanthanum precipitation in the background cytoplasm or on any cytoplasmic organelle. These results confirm our hypothesis that lanthanum does not cross the plasma membranes in these molluscan tissues.

Effects of 5-hydroxytryptamine on membrane potential, contractility, accumulation of cyclic AMP, and Ca2+ movements in anterior aorta and ventricle of Aplysia

Effects of 5-hydroxytryptamine (serotonin; 5-HT) on the anterior aorta and ventricle muscle of the marine gastropod Aplysia are characterized. Bath-applied 5-HT depolarizes muscle fibers and causes tension increases in both the anterior aorta and ventricle above ca. 10(-9) M. Iontophoretically applied 5-HT caused localized depolarizations of anterior aorta muscle fibers. 5-HT increases the levels of adenosine-3',5'-cyclic monophosphate (cAMP) markedly in the anterior aorta of A. kurodai and A. californica and in the ventricle of A. kurodai. Effects of 5-HT on the contractility of and cAMP synthesis in the anterior aorta and ventricle are both blocked by methysergide. 5-HT and cAMP analogs stimulate 45Ca2+ efflux from the ventricle, implying that the effects of cAMP on contractility involve intracellular Ca2+ movements.

Effect of carboxylate group modification on enzymatic and cardiotoxic properties of snake venom phospholipases A 2

By treating Naja nigricollis and Naja naja atra phospholipase A 2 with carbodiimide and semicarbazide, we obtained derivatives having varied numbers of modified carboxylate groups. When tested on artificial and natural substrates, derivatives of both enzymes with a modified carboxylate group at the active site (Asp-49) retained little enzymatic activity ( 1 4 1 to 10%). However, the derivatives of N. nigricollis also lost most of their lethal potency (5% of native), while those of N. n. atra retained considerable lethality (29%). Caboxyl modification with protection of Asp-49 in N. n. atra enzyme resulted in a derivative with lethal potency equal to or greater than the native enzyme and enzymatic activity which was low on all substrates (12 – 17% of native). Similar protection of Asp-49 at the active site in N. nigricollis enzyme produced a derivative with decreased enzymatic activity on artificial substrate (22% of native) and decreased lethality (17 – 33% of native), but with full enzymatic activity on natural substrates. When tested on electrical and mechanical properties of the isolated perfused heart and the isolated ventricle muscle wall, the derivatives of both enzymes retained considerably more of the cardiotoxic activity than would have been expected based on their residual enzymatic activity. The one exception occurred with the least modified N. nigricollis derivative which had an unaltered Asp-49, this enzyme retained both cardiotoxic activity and full enzymatic activity on natural substrates. The extent of phospholipid hydrolysis following treatment was measured in the isolated heart preparation and in hearts removed from mice following i.v. injection of the phospholipases. Very low levels of phospholipid hydrolysis were observed and no correlation could be made between the extent of hydrolysis and the pharmacological potencies of these enzymes. Modification of the enzymatic active site, whether of Asp-49 in this study of His-48 in prior studies, leads to a large decrease in both enzymatic activity and lethal potency. Asp and Gluresidues outside of the enzymatic site contribute significantly to the lethal potency of the N. nigricollis enzyme and to the enzymatic activity of the N. n. atra enzyme. Based on these and previous data we conclude that changes in isoelectric points are not responsible for altered lethal potencies following chemical modification and that some pharmacological effects of snake venom phospholipases A 2 are due to a non-enzymatic action, suggesting two distinct but perhaps overlapping active sites.

The Ionic Basis of the Resting Potential in a Cross-Striated Muscle of the Aquatic Snail Lymnaea Stagnalis

ABSTRACT The mean resting potential in the heart ventricle muscle cells of the freshwater snail Lymnaea stagnalis was found to be – 61·2±3·5(..)mV (ranging from –56mV to –68mV). The average intracellular potassium concentration was estimated to be 51·5 ± 14·6 (..) m (ranging from 27·8 m to 77·3 m). The membrane of the heart ventricle muscle cells appears to be permeable to both potassium and chloride, as changes in the extracellular concentration of either of these ions resulted in a change in the membrane potential. A ten-fold change in the extracellular potassium concentration was associated with a 50·4 ± 3·8 (..) mV slope when the potassium concentration was above about 6 m. Deviations from the straight-line relation predicted for a potassium electrode could be accounted for by introducing a term for sodium permeability. The ionic basis of the membrane potential in these cells can be described by a modified form of the Goldman-Hodgkin-Katz equation.

The effect of the molluscicide Frescon on smooth and cross-striated muscles of Lymnaea stagnalis and Helix aspersa

The molluscicide Frescon ( N-(triphenylmethyl)morpholine) induces prolonged, irreversible contractions (contractures) in the isolated heart ventricle, penis retractor, and foot muscles of the aquatic snail Lymnaea stagnalis. It also causes contracture of the penis retractor muscle, but not the heart ventricle, of the terrestrial snail Helix aspersa. Since Frescon-induced contracture is not accompanied by a depolarization of the sarcolemma of Lymnaea heart ventricle muscle cells, it is suggested that the action of this molluscicide is associated with a membrane potential-independent activation of the contractile machinery. The rapid response of Lymnaea musculature to Frescon suggests that the direct contracture-inducing action of this molluscicide could explain its toxicity to the whole animal.

Myocardial healing and repair after experimental infarction in the rabbit.

Adequacy of healing after acute myocardial infarction may determine the incidence of postmyocardial infarction rupture and ventricular aneurysm. Accordingly, in 36 rabbits, from 1 to 8 days after coronary ligation, and in 18 shams, we measured collagen formation and mechanical resistance of the infarcted left ventricle to stretch and rupture. Prolyl hydroxylase, an intracellular enzyme of collagen synthesis, increased from control activity of 3970 +/- 431 to 9224 +/- 643 counts/min per mg (cpm/mg) extractable protein (P less than 0.01) at 48 hours and was nearly maximal at 3 days postmyocardial infarction (14,518 +/- 2,030 cpm/mg, P less than 0.01). Lysyl oxidase, an extracellular collagen cross-linkage enzyme, increased from control activity of 29.6 +/- 4.8 to 74.7 +/- 18.8 cpm/mg extractable protein (P less than 0.01) at 72 hours and peaked at 121.5 +/- 7.3 (P less than 0.01) 4-6 days postmyocardial infarction. Hydroxyproline, a measure of collagen content, increased from control of 2.8 +/- 0.2 to 5.3 +/- 0.6 mg/g dry weight (P less than 0.05) at 72 hours and continued to increase at 8 days postmyocardial infarction (14.5 +/- 1.7 mg/g dry weight; P less than 0.01). When enzyme activities and hydroxyproline content were expressed relative to other reference bases, including DNA, tissue protein, dry weight, and total left ventricle, similar results were obtained. The mechanical properties of the infarcted left ventricle were determined by filling a balloon in the excised left ventricle until rupture. The rupture threshold in the normal left ventricle, [664 +/- 43 mm Hg (n = 16)], was not significantly different from that of the infarcted left ventricle on days 1-8 postmyocardial infarction. However, left ventricular rupture occurred more often through the myocardial infarction on days 1-4 postmyocardial infarction (59%) than on days 6 and 8 (18%; P = 0.03) when collagen content had significantly increased. Wall stress at the point of rupture in left ventricles from shams and normals was 30 +/- 2 g/mm2; tensile strength in isolated left ventricle muscle strips was 25 +/- 4 g/mm2 and in isolated scar strips at 7 days postmyocardial infarction was 59 +/- 7 g/mm2. The passive stiffness of the infarcted left ventricle increased from control of 61 +/- 5 to 94 +/- 6 mm Hg/100 microliters (P less than 0.05) at 4 days and 100 +/- 7 mm Hg/100 microliters (P less than 0.01) at 6 days postmyocardial infarction. Stiffness correlated with hydroxyproline content over the 8 days postmyocardial infarction (r = 0.599; P less than 0.001). Thus, the acutely infarcted ventricle was highly resistant to rupture during the initial 48 hours postmyocardial infarction, before any increase in collagen occurred. This result suggests that the preinfarction collagen content has an important role in preventing rupture. After 72 hours postmyocardial infarction, collagen synthesis appeared to be a determinant of infarct stiffness and resistance of the infarcted ventricle to rupture.

Comparison of cyclic amp-dependent phosphorylation of sarcolemma and sarcoplasmic reticulum from rat cardiac ventricle muscle

1. 1. The phosphorylation by cAMP and protein kinase I of rat cardiac sarcolemma (SL) and sarcoplasmic reticulum (SR) isolated from the same homogenate, was compared. 2. 2. In both fractions, the phosphate incorporation is strongly dependent on the ATP and the membrane protein concentration. 3. 3. SDS-gel electrophoresis reveals that in the SL preparation a protein of M r = 24,500 and a glycoprotein of M r = 17,500 are mainly phosphorylated, while in the SR fraction the main phosphate incorporation is found in a protein having a M r = 37,000. 4. 4. Isoprenaline stimulates the phosphorylation of SL but not of SR. Propranolol abolished that stimulatory action of isoprenaline completely, suggesting that the β-adrenoceptor is involved.

Tissue specific isozymes of alanopine dehydrogenase in the channeled whelk Busycotypus canaliculatum

The tissues of the channeled whelk Busycotypus canaliculatum displayed activities of three glycolytic dehydrogenases, alanopine dehydrogenase (ADH), octopine dehydrogenase (ODH), and lactate dehydrogenase (LDH). ADH and ODH were present in all seven tissues (hepatopancreas, gill, kidney, and mantle, ventricle, foot, and proboscis muscles) tested. ADH was the major cytosolic dehydrogenase activity in all tissues except proboscis, while ODH was present in high activities only in the four muscular tissues. Significant LDH activity occurred only in the two muscles which perform sustained work, ventricle, and proboscis.Tissue specific isozymes of ADH were identified. Three forms, specific for hepatopancreas, gill–kidney, and muscle tissues, were separable by isoelectrofocusing (pI's 5.69, 5.58, and 5.93, respectively), chromatofocusing, and polyacrylamide gel electrophoresis. The three isozymes differed kinetically showing significant differences in apparent Km's for L-alanine (e.g., 8.84 ± 0.03, 10.64 ± 0.40, and 13.12 ± 0.65 mM for hepatopancreas, ventricle, and gill, respectively) and even greater differences in apparent Km's for glycine (619 ± 55, 1412 ± 115, and 2542 ± 230 mM for the above three tissues, respectively). The ratios Km(gly)/Km(ala) averaged 70, 192, and 132 for the three isozymes, hepatopancreas, gill–kidney and muscle, respectively.The physiological functions of ADH isozymes in the whelk may be similar to those of the M and H isozymes of LDH in vertebrates or the muscle and brain specific isozymes of ODH in cephalopod molluscs.

Ouabain potentiation and Ca release from sarcoplasmic reticulum in cardiac and skeletal muscle cells.

In this article, we describe a possible mechanism of ouabain potentiation in heart based on the following findings in cardiac and skeletal muscles of various species. (1) In heart ventricle muscles of frog and guinea pig, the ouabain potentiation is produced without an effect on Ca influx. In both frog and cat heart ventricle muscles, ouabain potentiates the rapid cooling contracture with or without caffeine in a Ca-deprived medium. It follows, therefore, that the ouabain potentiation is produced by an "intracellular" mechanism. (2) In crab single muscle fibers, contractile responses such as twitch, potassium-induced contracture, caffeine-induced contracture, and water-induced contracture are remarkably potentiated if ouabain is present within the fibers by microinjection, whereas the situation is reversed if the drug is given extracellularly. (3) The ouabain potentiated the Ca release from fragmented sarcoplasmic reticulum (FSR) isolated from cat, guinea pig, and frog heart and from skeletal muscles as a result of the procedures used, such as changing the ionic environment. (4) In frog, cat, and guinea pig heart ventricle muscles, a reduction of contractility as a result of pretreatment with urea--Ringer's was completely cancelled by ouabain almost without influencing the membrane depolarization. Based on these findings and others, the deduction was made that the positive inotropic effect of cardiac glycosides on the heart is brought about by potentiation of contraction - Ca release from the intracellular store sites, namely the sarcoplasmic reticulum.

Purification and characterization of cardiac sarcolemma and sarcoplasmic reticulum from rat ventricle muscle

Cardiac sarcolemma and sarcoplasmic reticulum membrane preparations from rat ven tricle muscle were isolated and purified by a differential centrifugation procedure, based on the Harigaya and Schwartz and Suko and Hasselbach procedures. The sarcolemma fraction is enriched in ouabain-sensitive (Na +-K +) ATPase, hormone-sensitive adenylate cyclase, and specific dihydroalprenolol binding. The sarcoplasmic reticulum fraction is enriched in NADPH-cytochrome c reductase, while hormone-sensitive adenylate cyclase and dihydroalprenolol binding is negligible. Further characterization by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed significant differences in protein profiles between the two preparations. Electron microscopic analysis of the two preparations revealed the presence of sealed vesicles. By means of freeze-fracturing electron microscopy the membrane orientation of the vesicles in both preparations was determined.

174 - Effects of ouabain and X-537A on contractility and Ca- influx in cardiac ventricle muscles.

174 - Effects of ouabain and X-537A on contractility and Ca- influx in cardiac ventricle muscles.