Gene/Protein Disease Symptom Drug Enzyme Compound
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The specific granules found in the atrial cardiac muscle cells of the normal rat were studied. The ultrastructural appearance of these granules demonstrated a fixative-dependent lability. Fixation with cacodylate buffered aldehydes yields three types of granules. However, fixation with phosphate buffered aldehydes or primary fixation with OsO4 yields granules of uniform appearance. The granules are found predominantly in the perinuclear zone; 78% of the granules are within ten linear micrometers of the center of the nucleus. Two independent methods of measurement demonstrate spherical diameters of these granules of 0.30 micron and 0.37 micron respectively. The granules are found in greater concentration at one pole of the nucleus than at the other. On the high density side there are 4.07 granules/micrometers3 which occupy 5.8% of the cytoplasmic volume. On the low density side there are 2.15 granules/micrometers3 which occupy 3.0% of the cytoplasmic volume. The granules at both poles are the same size. Atrial walls were incubated in a modified Tyrode's solution. One hour of incubation caused no change in the atrial granules. Addition of norepinephrine or L-Dopa resulted in the appearance of more granules but the size of the granules remained the same. Incubation with reserpine had no effect upon the atrial granules. Apparently the atrial myocardial cell is stimulated by exogenous catecholamine to synthesize more atrial granules which themselves do not appear to contain catecholamines.
Anat Rec 1979 Aug
PMID:Specific granules of the rat atrial muscle cell. 11 80

The previously described ability of reserpine and parachlorophenylalanine to induce the accumulation of lipid droplets in ventricular cardiac muscle cells of the bat was investigated. Lipid droplet accumulation was assessed qualitatively by light microscopy and quantitatively by morphometric analysis of electron micrographs. An hypothesis that the action of the drugs was an indirect one, mediated by the cardiac adrenergic innervation, was framed and tested. Lipid droplet accumulation occurred during a time of intense sympathetic activity, that of arousal from hibernation. The ability of the two drugs to produce the effect was antagonized by prior sympathetectomy with 6-hydroxy-dopamine. The effect was mimicked by administration of exogenous norepinephrine together with inhibitors of its catabolic enzymes, monoamine oxidase and catechol-o-methyl transferase. These observations are all consistent with the initial hypothesis and raise the possibility that endogenous norepinephrine in the cardiac sympathetic innervation might be, at least potentially, auto-toxic.
Anat Rec 1975 Feb
PMID:Lipid droplet accumulation in cardiac muscle cells of the bat: potential auto-toxicity of the cardiac sympathetic innervation. 12 30

A syndrome on four dairy farms in which calves up to two months of age died suddenly during a period of excitement usually precipitated by feeding was investigated. The description given by owners was that during, or shortly after milk feeding, the calves grunted, fell and died within one minute. Post mortem examinations revealed patchy myocardial pallor but no other lesions or evidence of infectious disease. Histopathological studies revealed peracute myocardial degeneration. Biochemical examinations have shown a selenium deficiency in in-contact calves and since this was corrected, no further cases have occurred. It is suggested that this is an additional manifestation of the selenium deficiency syndrome and that in certain circumstances, a deficiency of available selenium renders cardiac muscle vulnerable to stresses which induce severe peracute damage and leads to cardiac failure and sudden death.
Vet Rec 1978 Sep 09
PMID:Sudden death in calves associated with acute myocardial degeneration and selenium deficiency. 71 69

A new monoclonal antibody (mAb) that recognizes alpha-tropomyosin in cardiac muscle cells was used in a qualitative (polyacrylamide gel electrophoresis and indirect immunofluorescence) and quantitative (fluorescence-activated cell sorting) study of the expression of this protein during heart development. alpha-Tropomyosin expression was weak in early stages of chick embryo development (Hamburger and Hamilton stage 18), and increased steadily until Hamburger Hamilton stage 40. In early stages, the protein was found mainly in cytoplasm, whereas by the final stages, it was more abundant in the cytoskeletal compartment. The mAb cross-reacted with alpha-tropomyosin in smooth and striated muscle cells from chickens, mice, and humans, but did not cross-react with nonmuscle tropomyosin.
Anat Rec 1992 Nov
PMID:Expression of alpha-tropomyosin during cardiac development in the chick embryo. 144 59

Norepinephrine administration causes progressive hypertrophy of the mammalian heart as measured by myocardial mass. The purpose of this study was to determine the growth response of the myocardial tissue components as well as the myocardial cell itself to norepinephrine. Young, adult cats were given low doses of norepinephrine in dextrose or dextrose alone twice daily for 15 days. On day 16, there were no changes in the animals body weight, right ventricular systolic pressure, right ventricular end-diastolic pressure, heart rate, cardiac index, or blood pressure. However, the right ventricle/body weight, the left ventricle/body weight and the total heart weight/body weight were increased significantly in the norepinephrine treated animals. The increase was on the order of 40%. The cardiac muscle cell was also significantly increased in size and both the right and left ventricular cardiac muscle cells exhibited a dramatic increase in size as measured by cross sectional area. Upon stereological examination it was found that the amount of hypertrophy as seen in the cardiac muscle cells was paralleled by the hypertrophy seen in the other tissue components of the myocardium. The volume density of the muscle cells, the interstitial components, as well as the blood vessel compartment were identical in the control and in the norepinephrine-treated groups. In conclusion, this study demonstrates that the response of the myocardium to norepinephrine is similar to that seen in response to a volume overload rather than that seen in response to pressure overload.
Anat Rec 1991 Apr
PMID:Norepinephrine-induced cardiac hypertrophy of the cat heart. 182 54

We used immunocytochemical localization of calcitonin gene-related peptide (CGRP) to trace the ontogenesis and anatomic distribution of this component of nonadrenergic noncholinergic (NANC) innervation in fetal, neonatal, and mature canine hearts and autonomic ganglia which control cardiac function. Rare varicose CGRP-immunoreactive nerve processes were present in the heart during late gestation. Abundant CGRP-immunoreactive neural tissue in the neonate suggested a burst of NANC innervation around birth. Neonatal, 1-, and 2-month-old animals all had many varicose individual nerve processes in addition to processes within bundles; however, the density of all CGRP-immunoreactive tissue appeared to decrease during this stage of development. Similarly, there were relatively more varicose stained nerve processes in the epicardial ganglia and numerous CGRP-immunoreactive cells and smooth nerve processes in the stellate ganglia of the neonate, as compared with older animals. In the mature animal CGRP-immunoreactive neural tissue in the heart was more sparse and largely confined to heterogeneous nerve bundles in the epicardium. The extramural coronary arteries were virtually the only site of innervation by individual nerve processes; CGRP-immunoreactive neural tissue was not found adjacent to working cardiac muscle fibers. At all developmental stages, the area of the sinoatrial node was the primary focus of CGRP innervation, although the atrioventricular nodal region was also preferentially innervated. In general, the atria contained more CGRP-immunoreactive tissue than the ventricles, which were only sparsely innervated. The perinatal peak in density of CGRP-immunoreactive neural tissue with subsequent decline to reach the adult pattern suggests a developmental role for NANC innervation in the dog heart.
Anat Rec 1991 Aug
PMID:Anatomic distribution of autonomic neural tissue in the developing dog heart: II. Nonadrenergic noncholinergic innervation by calcitonin gene-related peptide-immunoreactive tissue. 192 59

Using monoclonal antibodies against the M and B subunit isoforms of creatine kinase (CK) we have investigated their distribution in developing human skeletal and cardiac muscle immunohistochemically. It is demonstrated that in skeletal muscle, a switch from CK-B to CK-M takes place around the week 8 of development, whereas in the developing heart, CK-M is the predominant isoform from the earliest stage examined onward (i.e., 4 1/2 weeks of development). In all hearts examined, local differences in concentration of the CK isoforms are observed. The CK-M expression in the developing outflow tract (OFT) and conduction system is described in detail. Between the weeks 5 and 7 of development, the distal portion of the OFT is characterized by low CK-M expression, whereas around the week 8-10 of development the myocardium around the developing semilunar valves in the OFT expresses a very high level of CK-M. At all stages examined, a relatively low CK-M level is observed in those regions in which the "slow" components of the conduction system do develop (e.g., the sinoatrial junction and atrioventricular junction), whereas a relatively high concentration of CK-M is observed in those areas that are destined to become the "fast" components, i.e., the subendocardial myocardium of the ventricles. The high expression of CK-M in the developing "fast components" of the conduction system contrasts with the relatively low expression of CK-M in the force-producing myocardium of the interventricular septum and free ventricular wall.
Anat Rec 1990 Oct
PMID:Spatial distribution of "tissue-specific" antigens in the developing human heart and skeletal muscle. I. An immunohistochemical analysis of creatine kinase isoenzyme expression patterns. 224 Jun 9

The structure and quantitative contribution of membrane systems (transverse-axial tubular system [TATS] and sarcoplasmic reticulum [SR]) have been investigated in the heart of the adult guinea pig. Although previous quantitative studies have been made of guinea pig myocardium, this is the first such study that has utilized tissue in which membrane system elements were clearly identified by selective staining (in this case by the osmium-ferrocyanide [OsFeCN] postfixation method). Both membrane systems are highly developed in ventricular cells, but a TATS is essentially absent from atrial myocytes. The ventricular TATS consists principally of large-bore elements which may be oriented transversely, axially, or obliquely, making numerous anastomoses with one another to form a highly interconnected system of extracellular spaces that penetrate to all myoplasmic depths of the ventricular cell. The cell coat that lines the lumina of these tubules is structured, containing fibrillar structures that run along the length of the tubule. The volume fraction (VV) of the ventricular TATS is low (2.5-3.2%), in consideration of the qualitative prominence of the TATS in these cells. The relative total population of sarcoplasmic reticulum is higher in the atria (VV of 10-11%) than in the ventricles (VV of ca. 8%). In all guinea pig myocytes, several major structural divisions of SR can be discerned, which include network SR, junctional SR, corbular SR, and cisternal SR. Junctional SR (J-SR) in the atrial cells is limited almost exclusively to peripheral saccules of junctional SR (PJSR), whereas both interior J-SR and PJSR are present in the ventricle. Two distinct morphological types of PJSR appear in atrial cells, including both flattened and distended saccules, the latter resembling PJSR of lower vertebrate heart. Spheroidal bodies of SR with opaque contents (corbular SR) are prominent at or near Z-line levels of the sarcomeres of atrial and ventricular cells. Cisternal SR is likely a subset of network SR, but some examples appear related to rough endoplasmic reticulum. An overall impression obtained from this study is that guinea pig atria are composed of structurally primitive cells, whereas the ventricular cardiac muscle cells are more highly developed entities.
Anat Rec 1988 Dec
PMID:Membrane systems of guinea pig myocardium: ultrastructure and morphometric studies. 246 4

The distributions of desmin and vimentin were examined in frozen sections of cardiac muscle from embryonic, newborn, and adult Syrian hamster by using immunofluorescent methods. Frozen sections of newborn and adult skeletal muscle were used for comparison. Cardiac myocytes from day 9 in utero embryos already show a clear association of desmin with the sarcomeric myofibrils. In newborn hearts, desmin is localized in the myofibrillar Z-line areas as well as in the peripheral cytoplasm of the cell. Three days after birth, desmin is associated with the intercalated discs. Thus, in adult cardiac muscle, desmin is present in both Z-bands and intercalated discs. Skeletal muscle of newborn and adult hamster also contains desmin associated with the Z-lines of myofibrils. Vimentin is associated with the myofibrils of day 9 in utero cardiac muscle cells. The protein remains associated with the myofibrillar Z-lines in the newborns and adults. No detectable staining for vimentin was observed in newborn or adult hamster skeletal muscle. The existence of vimentin as well as desmin in differentiated cardiac muscle may be a consequence of the somewhat more epithelial-like nature of cardiac cells as compared to skeletal muscle syncitia.
Anat Rec 1989 Apr
PMID:Immunofluorescent localization of desmin and vimentin in developing cardiac muscle of Syrian hamster. 265 8

Light and electron microscopy were used to study the structure and distribution of thin collagenous septa (sheets) in dog and rabbit cardiac muscle to determine whether they, like thick collagenous septa, could affect electrical impulse propagation. Generally, thin septa (0.2-0.5 micron) ensheathed myocytes or groups of myocytes for short distances and thicker septa partially or completely ensheathed groups of myocytes for long distances (up to several mm); together, thin, and thick septa divided the myocardial mass into myocyte cords (funicles) of 10-30 micron diameter. Septal architecture varied not only between regions and within regions at different ages but also within single bundles, precluding the assumption that the architecture found in one bundle can be applied to another. Electron microscopy demonstrated that thick septa consisted of many tightly packed collagen fibrils, often with distinct layers running at different angles; thin septa consisting largely of circumferential collagen fibrils. Thin septa in dog ventricular papillary muscle generally contained few and widely spaced collagen fibrils, whereas thin septa in dog atrial Bachmann's bundle contained tightly packed collagen fibrils. In either site, thin septa were rarely breached by nexuses and thus marked sites where lateral intercellular electrical coupling was unlikely. Serial 7 micron cross sections of dog Bachmann's bundle stained by a modification of the picrosirius red technique showed that thin septa sometimes persisted uninterrupted over several myocyte lengths. The results provide evidence that thin septa comprised of tightly packed collagen fibrils may significantly modify impulse propagation transverse to the longitudinal axis of the myocytes.
Anat Rec 1987 May
PMID:Thin collagenous septa in cardiac muscle. 360 60


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