PubMed Health⌕ Search

Biomedical subjects

A Abrahám

Publications and source records attributed to A Abrahám.

At least 19 recordsLinked to original sources
PubMed1986

Fine structure of the neuromuscular junction in the small intestine of a teleostean fish: tench (Tinca tinca L.).

Innervation of the midgut musculature has been studied in the tench (Tinca tinca) by light and electron microscopic methods. Smooth and striated muscle layers of the tunica muscularis of the gut are innervated by the same nerve bundles. Thick nerve bundles are found in the connective tissue between the two muscle layers projecting branches into both the smooth and striated muscle layers. The nerve fibres are varicose, the varicosities contain various vesicle populations. Some of these comprise small clear vesicles (measuring 40 nm in diameter), and a few dense-core vesicles (120 nm in diameter), while in others the amount of dense-core vesicles is higher; furthermore there are varicosities containing granules of peptidergic character measuring 200 nm in diameter. Nerve fibres often form neuropil in which synapses have not been observed. Axon terminals establish parallel membrane contacts with the muscle cells without synaptic specialization in the smooth muscle layer. Innervation of the striated muscle layer seems to be poor. Motor end-plates could not be found on the muscle fibres of the midgut, while these are common in the oesophagus, where the occurrence of striated muscle fibres is dominant.

Animals↗
PubMed1983

Light- and electron-microscopic investigations into the gastro-intestinal nervous system of the vineyard snail (Helix pomatia).

In the wall of the intestinal tract, two neural plexuses run though. Both of them consist of nerve cells and nerve fibres. The cells belong to the intestinal wall. One part of the fibres is from the nervus intestinalis, the other part belongs to the process system of the parietal ganglion cells. Most of the nerve cells have a unipolar or a bipolar form, but the multipolar forms don't fall within rarities, either. In the cytoplasm, under an electron microscope, there are several endoplasmatic reticula of wide lumina and free ribosomes or those, coordinated in series. And there are but a few mitochondria. The neurosecretory granules, joined by dense-core forms and homogeneous oval granules, are characteristic. The chromatin sits closely on the nuclear membrane in the form of serrated lobes. The greatest part of the nerve fibres are full of neurosecretory granules, there are in the others elliptical granules of large format, the third is dominated by densecore forms. There are added to the nerve fibres of granule content the agranular fibres, containing no granules, as well as glia cells and glial fibrils. In the latter ones, there are plenty of glycogenous granules. Their characteristic constituents are the homogeneous and elliptical gliogranules of large size.

Animals↗
PubMed1982

Localisation and structure of the receptors in the snout skin of the European hedgehog (Erinaceus europaeus) at the level of light and electron microscopy.

Morphological investigations of the snout skin of the European hedgehog (Erinaceus europaeus) revealed many nerve bundles and nerve fibres in the corium. Under the electron microscope, fibrocytes, many Schwann cells and, close to the basal membrane, laminated corpuscles can be seen. The latter consist of laminae, laminar cells and an axon. The laminae are characterized by exocytotic vesicles and by branching. The laminar cells are narrow and long. In the axon, there are several clear vesicles and sporadic mitochondria. The axolemma and cytolemma are sharply delimited, the space between them is wide. There is no synaptic organization. In the epidermis, ascending nerve fibres run intercellularly or intracellularly; their intracellular terminals are in the upper cell layers of the stratum germinativum. Other terminations occur in the lower and median stratum corneum as well. The final portions of nerve fibres degenerate in the upper horny layer together with the corneal squamae.

Animals↗
PubMed1981

Light- and electron-microscopic investigations on human carotid bodies.

The functionally first of all considerable components of the carotid bodies are glomus cells and nerve fibres. The glomus cells form two groups. The chemoreceptor cells belong in one of these, the capsular cells in the other. The chemoreceptor cells are polygonal bodies. in their cytoplasm, organella are expressed. The cell nucleus is round, chromatin is homogeneous. Cells are characterized by the osmiophilic bodies. The capsular cells are long-shaped bodies with processes, they are associated with the chemoreceptor cells and sometimes lap over these, like veils. A number of the nerve fibres take place in Schwann's cells wrapped in a mesaxon membrane. The larger part, surrounds the round cell-nests consisting of chemoreceptor cells with a close-meshed network. From the network some fibres draw to the chemoreceptor cells and terminate on these in the form of boutons. Nerve endings form synapses with the chemoreceptor cells. Three forms of these have been found. One of these is the conventional synapsis, the other the saccular synapsis and the third one the parallel contact. Conventional synapses contain all the components identified in the neurons of the central nervous system. Saccular synapses are the magnified pictures of boutons. They consist of axolemma, axoplasm, synaptic vesicles, and mitochondria. In the parallel contacts, the axolemma and cytolemma touch each other. In the axoplasm, there are synaptic vesicles and mitochondria. Conventional synapses conduct peripherally, saccular synapses and parallel contacts centrally. On chemoreceptor cells, there are no neuronal marks, consequently, they are no interneurons. For reciprocal synapses the morphological bases are missing. The chemoreceptor cells are sensory cells.

Carotid Body↗
PubMed1978

[Ultrastructural studies of the duck cere with special reference to Grandry and Herbst bodies].

The results of the investigations into the cere of the domestic duck (Anas boscas domestica) and the mallard (Anas platyrhyncha) may be summarized as follows. The parts of ceroma are the epidermis and the corium. The epidermis is a laminated epithelium and the corium consists of fibrous connective tissues. The later one frequently contains mastocytes and pigment cells. There are many blood vessels, Schwann's cells, nerve fibres, Grandry's and Herbst's bodies. The sensory cells of Grandry's bodies are bodies with processes. They are characterized by the round nucleus, dense core vesicles, the small Golgi's complexes, the narrow endoplasmatic ducts and the cytoplasmatic fascicles. In the nerve fibre running between the sensory cells there are plenty of mitochondria but few clear vesicles and neurofilaments. The axolemma, cytolemma, and the empty space lying between these are sharply obvious. In Grandry's bodies with more than one sensory cells the nerve fibre ramifies. In the branches there are no mitochondria. These are replaced by clear vesicles. In Grandry's bodies with one sensory cell the axon ends in a disc growing narrow at its termination. Both of them are full of mitochondria. The terminal disc is characterized by the elliptical bodies and the thickenings of the membrane. Herbst's body consists of three parts. One of these is the inner knob, the other is the inner cavity, the third is the external capsule. The inner knob consists of two series of cells. The number of cells is ten in both rows each. From the cells, 20 to 50 lamina-like processes are originating. The laminar system of every cell is connected with the system of the cell before and behind it, as well as with the laminar system of the other side. In the nerve fibre running between the rows of cells mainly in its terminal part, some groups are formed by mitochondria, the dense-core vesicles, and the elliptical bodies. The inner cavity consists of laminae of different breadths, limited by cavities full of some meshwork. The laminae vary in form and extent. There are among them some ramifying ones, some forms terminating in a point and some of blunt ends. They are characterized by dense and long ribosomeseries, arranged close to one another. The external capsule consists of several parallel laminae, separated from one another by collagenous fibrin fascicles. The laminae are mostly narrow, their cytoplasm is spongoid, they are characterized by egg-shaped cysterns. There is no synaptic organization either in Grandry's or in Herbst's body. The junction between the membrane is to be regarded as a parallel contact in both places.

Animals↗
PubMed1976

Structure of synapes in the supraoesophageal ganglion of the water beetle (Dytiscus marginalis).

1. Light- and electron microscopic investigations prove that synapses, without any exception, are confined to the neuropil. 2. Under the light-microscope, synapses display the shape of terminal boutons at the ends of the nerve fibres; in some cases they appear as smaller or larger plates. Electron microscopic investigations suggest that also varicosities of nerve fibres can be regarded as synapses, though these might have possible arisen from axoplasmatic peristalsis. 3. Electron microscopically the overwhelming majority of the synapses are axodendritic contacts; axo-axonic contacts occur less often. 4. The generally accepted characteristics of synapses are defective. Membrane thickenings and intersynaptic spaces are missing. Accordingly, synapses in the supraoesophageal ganglion of the water beetle differ markedly from those described in Vertebrates. 5. Synaptic vesicles sometimes fill the axoplasm of the nerve fibre completely. In other cases, clusters of synaptic vesicles can be seen, on both sides of the contact. 6. Synaptic vesicles are mixed with neurosecretory granules. Synaptic vesicles may appear also in the dendrites.

Animals↗