Search PubMed⌕ Search

Biomedical subjects

A Oksche

Publications and source records attributed to A Oksche.

At least 73 records · Page 4Linked to original sources
PubMed1982

Intrinsic neurons and neural connections of the pineal organ of the house sparrow, Passer domesticus, as revealed by anterograde and retrograde transport of horseradish peroxidase.

In Passer domesticus, intrapineal nerve cells were labeled by uptake of microiontophoretically administered horseradish peroxidase (HRP). Unipolar nerve cells with a dichotomously branching stem process are the main source of the dominant pinelaofugal component of the pineal tract, whereas multipolar and bipolar neurons appear to represent interneurons. HRP-Labeled nerve fibers are observed in the distal division (end-piece) of the pineal organ; they can be regarded either as processes of intrapineal neurons or projections of pinealopetal axons originating from central neurons. Furthermore, scattered labeled nerve fibers occur in different portions of the pineal stalk. Nerve fibers containing HRP were also demonstrated in the medial and lateral divisions of the habenular complex and in the periventricular layer of the hypothalamus; these axons apparently represent anterogradely labeled pinealofugal elements. On the other hand, retrogradely labeled neurons were found in the medial habenular complex and in the periventricular hypothalamic gray near the paraventricular nucleus, indicating that the pineal organ receives a pinealopetal innervation arising from the central nervous system. Ultrastructurally, the neuropil of the pineal organ of P. domesticus displays single basal processes of pinealocytes containing synaptic ribbons in association with clear synaptic vesicles. Occasionally, conventional synapses were observed the presynaptic terminals of which exhibit granular inclusions. The pineal tract consisting of four to six spatially separated fiber bundles comprises mainly unmyelinated elements accompanied by only few myelinated axons. The functional role of the neural apparatus revealed in the present study is discussed in context with the humoral (hormonal) control of circadian functions; the latter type of activity has been shown to exist in the pineal organ of P. domesticus (Zimmerman 1976).

Animals↗
PubMed1978

The sites of encephalic photoreception in phosoperiodic induction of the growth of the testes in the white-crowned sparrow, Zonotrichia leucophrys gambelii.

In bilaterally enucleated White-crowned Sparrows, Zonotrichia leucophrys gambelii, testicular growth and development at rates similar to those of intact birds subjected to long days, can be induced by illumination of sites within and near the ventromedial hypothalamus from the tips of single, chronically implanted, light-conducting fibers. Essentially identical results are obtained with the same mode of encephalic illumination of birds with intact eyes held on short days that are otherwise nonstimulatory. Examination of the distribution of the sites of the fibers from which weak illumination induced testicular growth, increase in plasma level of luteinizing hormone or increase in plasma level of testosterone suggests that most of the photoreceptors must lie either within the ventromedial hypothalamus or in sites ventral thereto, such as the tuberal complex. For the time being, at least, we find it necessary to assume that some photosensitive elements of the system occur outside of the ventral hypothalamus.

Activity Cycles↗
PubMed1977

Immunocytochemical investigation of the hypothalamo-neurohypophysial system in birds.

The results of an immunohistochemical investigation of the hypothalamo-neurohypophysial system in several species of birds have shown that: (1) mesotocin and vasotocin are synthesized in separate neurons; (2) in all species investigated the distribution of mesotocinergic and vasotocinergic perikarya follows a common pattern; (3) the external zone of the avian anterior median eminence contains exclusively vasotocinergic nerve fibers, originating in supraoptic and ventral paraventricular regions; (4) the distribution of immunoreactive elements in the neural lobe shows a definite species-dependent pattern.

Animals↗
PubMed1976

The fine structure of the hypothalamic secretory neurons of the white-crowned sparrow, Zonotrichia leucophrys gambelii (Passeriformes: Fringillidae). II. Magnocellular and parvocellular nuclei of the rostral hypothalamus.

The fine structures of the neurons and neuropils of the magnocellular supraoptic nucleus and the parvocellular nuclei of the rostral hypothalamus, including the suprachiasmatic and medial, lateral and periventricular preoptic nuclei, and the neuronal apparatus of the organum vasculosum laminae terminalis, have been examined in the male White-crowned Sparrow, Zonotrichia leucophrys gambelii, by correlated light and electron microscopy. The magnocellular supraoptic nucleus is characterized by large neurosecretory perikarya which contain a well developed Golgi complex and dense-cored granules 1,500-2,200 A in diameter. The neuropil displays axons, dendrites and glial fibers. Some axonal profiles contain dense-cored vesicles 800-1,000 A in diameter and clear vesicles 500 A in diameter. Axo-somatic and axo-dendritic synapses are conspicuous in this nuclear region. The suprachiasmatic nucleus is characterized by an accumulation of small neurons with moderately developed cellular organelles and some dense-cored granules, approximately 1,000 A in diameter. The profiles of axons within the neuropil contain dense-cored granules 800-1,000 A in diameter and clear vesicles 500 A in diameter. The neurons of the medial preoptic nucleus are relatively large and exhibit well developed cellular organelles and dense-cored granules 1,300 to 1,500 A in diameter. Granular materials are formed within the Golgi complex. The medial preoptic nucleus is rich in secretory perikarya. Occasionally, neurons with granules 1,500-2,200 A in diameter are encountered in the lateral preoptic and periventricular preoptic nuclei. They may be considered as scattered elements of the magnocellular (supraoptic and paraventricular) system. The organum vasculosum laminae terminalis consists of three layers, i.e., ependymal, internal and external zones, and exhibits a vascular arrangement similar to that of the median eminence. The perikarya of the parvocellular neurons and their axons in the internal zone contain numerous secretory granules ranging from 1,300 to 1,500 A in diameter.

Animals↗
PubMed1975

The fine structure of the hypothalamic secretory neurons of the white-crowned sparrow, Zonotrichia leucophrys gambelii (Passeriformes: Fringillidae). I. Parvocellular tuberal nuclei.

The fine structure of the parvocellular tuberal nuclei and that of the ependyma bordering the third ventricle in the basal hypothalamus of the White-crowned Sparrow, Zonotrichia leucophrys gambelii, have been investigated. Photoperiodically stimulated birds have been compared with birds held on short days. The perikarya of the neurons of the basal infundibular (tuberal) nucleus, and in part, of the more dorsal layers, contain dense-cored granules (1000-1500 A). The granules in the anterior part of the nucleus are somewhat larger than those of the posterior part. The synapses and the synaptic relationships of these cells are described. The single-layered ependyma of the third ventricle in the basal hypothalamus may be divided into the dorsal typical ependyma, the ventrolateral "glandular" ependyma, and the ventral "glandular" ependyma. Cells of the ventral ependyma lack apical cilia but bear a few microvillous processes. They have well-developed Golgi apparatus, conspicuous polysomes, and frequently dense, irregularly-shaped granules. Basal cytoplasmic processes extend ventrally to the outer surface of the median eminence. Photoperiodic stimulation appears to increase the numbers of apical protrusions of the cells in the ventral glandular ependyma and to cause an increase in size of the nerve cells of the basal infundibular nucleus.

Animals↗