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J Moravec

Publications and source records attributed to J Moravec.

At least 37 records · Page 2Linked to original sources
PubMed1985

Terminal nervous plexus of the atrioventricular junction of the rat. Microanatomical aspects and regional specialization.

The paraformaldehyde-fixed hearts of adult rats were embedded in paraffin. Serial sections throughout the interatrial septum and the atrioventricular junction were examined in the optical microscope after having been silver stained. The density and the distribution of different nervous elements in the perinodal nerve plexus were studied and the results compared with the electron-microscopic data. These data confirm that at the level of the atrioventricular junction, a dense terminal network can be seen. It is composed of both terminal nerve fibers and ganglionic cells forming a small ganglion adjacent to the lower edge of the bundle of His and a thin ganglionic lamina in the interatrial septum. Apart from small neurons, previously described as cholinergic, large neurosecretory cells could also be demonstrated in some of the serial thin sections through the Hissian ganglion. The neuromuscular junctions between the terminal nerve fibers and specialized cells exhibit regional specialization. While the distal portion of the atrioventricular node and the bundle of His receive essentially efferent fibers, afferent coiled endings prevail in the reticular portion of the atrioventricular node and in the adjacent interatrial septum. Similar structures, larger in diameter, can also be seen around the muscular fibers and around the capillaries of the interventricular septum. The functional significance of the aforedescribed regional specialization of the terminal innervation of the atrioventricular junction is briefly discussed.

Animals↗
PubMed1984

Intrinsic innervation of the atrioventricular junction of the rat heart.

Alternate serial semithin and thin sections of the glutaraldehyde-fixed interatrial septum and atrioventricular junction of adult rat were examined in light and electron microscopes. The animals were pretreated with a false precursor of catecholamines, i.e., with 5-OH-dopamine, in order to differentiate the adrenergic component of the intrinsic nervous system. According to the light microscope data, two kinds of ganglia can be distinguished at the level of the interatrial septum. Those of the first kind are composed of large pale cells with voluminous nuclei. Those of the other kind resemble acinuslike clusters of small osmiophilic cells. Another small ganglion is invariably associated with the distal edge of the bundle of His. At the electron-microscope level, two types of ganglionic cells are found in the meshes of the peri- and intranodal plexus: 1) small neurons (10 microns) with richly developed neuropiles, and 2) large 5-OH-dopamine contrasted neurosecretory cells (up to 25 microns) containing electron-dense vesicles typical of sympathetic neurons. Numerous glomeruli with dendrodendritic and axodendritic connections are also found in the vicinity of the specialized tissue; and, in the nodal interstitium, several clusters of small chromaffin cells (5 microns) and a network of multipolar satellite cells similar to the interstitial cells of Cajal can be distinguished. Our data suggest that the microanatomical and cytological organization of the terminal innervation of the node of Aschoff-Tawara and of the bundle to His resembles that of the myenteric plexus. The physiological significance of these ultrastructural data for the local control of electrophysiological properties of the atrioventricular junction is briefly considered.

Animals↗
PubMed1984

Lipid intermediates in chronically volume-overloaded rat hearts. Effect of diffuse ischemia.

Tissue contents of intermediates of fatty acid metabolism were determined in isolated volume-overloaded rat hearts, 3 months after creation of an aorto-caval fistula. In the absence of any modification of blood carnitine, tissue levels of total carnitine were reduced by 33% in overloaded hearts compared to normal hearts. Total tissue CoA was unchanged. Fifteen minutes of whole-heart ischemia (i.e. a 50% reduction in coronary flow) did not increase levels of long-chain acyl esters of CoA and carnitine of the overloaded myocardium, in the presence of glucose as the only exogenous substrate. This was associated with lower than normal levels of long-chain acyl carnitine under normoxic conditions. The addition of exogenous palmitate (1.5 mM) resulted in an ischemia-induced accumulation of long-chain acyl-CoA and acyl carnitine in the overloaded heart although to a smaller extent than in the normal heart under similar perfusion conditions.

Acyl Coenzyme A↗
PubMed1981

[Cardiomegaly due to iron deficiency in the rat (author's transl)].

The effects of chronic iron deficiency were studied in new born rats. Hemoglobin concentrations were significantly depressed throughout the experimental period when compared with those of control animals. At third postnatal month, there was a 56% increase of absolute heart weight and a 230% increase of relative heart weight. Heart weight increased much more than myocytes dimensions. This finding may be interpreted as characteristic of a double process of hypertrophy and hyperplasia. Both cell hypertrophy and multiplication were responsible for the observed hypertrophy of the heart. Number of capillaries/mm2 was unchanged, but both mean capillary diameter and total surface of capillary wall increased progressively during the period of anemia. The adaptation to myocardial hypoxia may be, in this experiment situation, localized at the capillary level rather than at the mitochondria. At cell level, we did not note any particular modification of the ultrastructure and particularly no degenerative change. No mitochondrial lesions were found even in severe anemics (blood hemoglobin below 3.2 g/100 ml).

Anemia, Hypochromic↗
PubMed1981

Some morphological aspects of the atrioventricular junction in the rat heart.

The interrelationships of different components of atrioventricular junction of the rat heart were examined on serial sections. The results are the following: 1) The atrioventricular node of the rat is situated at the level of membraneous septum separating left ventricular cavity from the right atrium. This particular localization may be of functional significance since at this level both the state of systemic arterial circulation and venous return, can be integrated. 2) Apart from the node of Aschoff-Tawara adjacent to the upper edge of muscular septum, an accessory atrioventricular node is regularly present close to the aortic root. 3) In the proximity of both atrioventricular nodes we found vascular lacunae containing abundant mastocytes and chromaffin cells. These pictures seem to suggest the existence of local chemoregulation and transmitter liberation. 4) His bundle is apposed to subendocardial fibrous lamina running from mitral valve to the cartilaginous ring of the aortic root. This association of specialized cells with their connective environment reminds the organization of different mechanoreceptors described in literature.

Animals↗
PubMed1979

[Contribution of ultrastructural analysis to the knowledge of the neuromuscular relationships in the nodal and conduction tissue].

The ultrastructure of the atrio-ventricular junction in the rat heart fixed in situ was studied on serial fine sections. The relationships between the specialized tissue and the nervous system were studied after labelling adrenergic endings with 5-OH-dopamine. Among the various types of nerve endings a distinction may be made between: 1) adrenergic or cholinergic free endings; 2) large "cluster" endings of the cholinergic types, seen mainly in the equatorial regions of nodal cells; 3) small diameter cholinergic before the development of heart failure or significant card synaptic images; 4) afferent neurons, whose endings, rich in glycogen and mitochondria supply the conduction tissue fibres, getting into or through the muscle fibre. The intermembrane space is then 20 nm. The analogy between the images observed and the ultrastructural aspects of intrafusorial fibres in skeletal muscle is discussed.

Adrenergic Fibers↗
PubMed1979

[The left ventricle at different stages of a two steps mechanical overloading. Electron microscopic study in the rat (author's transl)].

The left ventricle myocardium of rats subjected to a two steps mechanical overloading (abdominal aorta constriction + aortic insufficiency) was examined in the light and electron microscopes at several stages of the load, and particularly after 3 to 6 months when the animals exhibited congestive heart failure. In these conditions, the heart weight exceeded the control by more than 100 %. In the later stages, the absence of parallelism between heart weight and cell diameter was compatible with a process of hyperplasia. Cellular lesions looking like recent were found more and more frequently with time. Within apparently normal cells proliferation of small mitochondria, nucleoli and Golgi apparatus are compatible with some deficit in energy balance, which is usually encountered only in early stages of the load.

Animals↗