Biomedical subjects

K K Osen

Publications and source records attributed to K K Osen.

33 records · Page 2Linked to original sources

PubMed1984

Morphogenesis and morphology of the brain stem nuclei of Cetacea. II. The nuclei of the accessory, vagal and glossopharyngeal nerves in baleen whales.

The development and final structure of the IXth, Xth and XIth cranial nerve nuclei are studied in ironhematoxylin -, thionin - and protargol -stained serial sections of about 50 baleen whale fetuses (blue whale, Balaenoptera musculus, and fin whale, Balaenoptera physalus ) and one adult fin whale. The nucleus ambiguus is composed of three subdivisions, oral, intermediate and caudal, the last mentioned being contiguous caudally with the dorsal motor Xth nucleus. The oral division develops as three parallel cell columns which merge into a well circumscribed solitary structure with a rostrally expanded "head". It is composed of medium-sized multipolar neurons in a myelin-poor neuropil. In the fin whale a minor group of larger cells is found medial to the "head". In both species a peculiar small-celled nucleus rich in capillaries is found ventral to the "head". The intermediate division initially contains a lateral cell column and a medial region of scattered cells. The lateral column persists throughout life, while the medial field develops into three columns only one of which remains distinct in mature individuals. The cells are larger than in the oral division with the largest cells in the medial column. The two columns are surrounded by a field of scattered neurons which continues without a sharp border into the caudal division which is composed of scattered cells throughout. In its rostral half the cells are of the same multipolar type as in the intermediate division while caudally they appear flattened in the horizontal plane. The dorsal motor Xth nucleus develops as three longitudinal columns. In the fetal brain these are cytologically distinct due to different proportions of small, medium-sized and larger multipolar neurons. The spindle-shaped ventromedial column extends the entire length of the nucleus. It is composed mostly of small to medium-sized cells which caudal to the obex are elongated parallel with the neuroaxis . The dorsolateral and ventrolateral columns are restricted to the middle 1/3 of the nucleus, except in the blue whale where the former extends somewhat more rostrally. They are both characterized by the presence of large multipolar cells, the largest of which are found in the ventrolateral column. In adult specimens the cells are more equally sized and the columnar organization less distinct. The nucleus of the tractus solitarius is of about the same length as the two above mentioned nuclei. Except at the very early stages, the nucleus is ill-defined.(ABSTRACT TRUNCATED AT 400 WORDS)

Accessory Nerve↗

PubMed1980

Distribution and light microscopic features of granule cells in the cochlear nuclei of cat, rat, and mouse.

In the present study the cytology and the topography of the cochlear granule cell domain (a comprehensive term introduced here for all granule cell-containing regions of the cochlear nuclear complex) have been studied light microscopically in Nissl, Bielschowsky, and Golgi-Del Rio-Hortega material of cats, rats, and mice; in Golig rapid material of 0-14-day-old kittens; and in sections of 6-week-old kittens following HRP injections in the superficial dorsal cochlear nucleus (DCN). The domain has been parcellated in seven subdivisions which, in spite of some species' differences, are easily identifiable in all of the included animals. The cochlear granule cells are considered as a particular class of neuron, which is slightly different from, but nevertheless principally similar to the cerebellar granule cells in both shape and mode of neuronal connections. The digitiform terminals of the cochlear granule cells differentiate after the first two weeks of extrauterine life. In several respects these cells show larger variation among species than do the cerebellar granules, the similarity between the two classes of granule cells being most conspicuous in the rodent. The silver, Golgi rapid, and HRP material suggest that all, or at least the majority, of the granule cell axons project to the molecular layer of the DCN, forming parallel fibers similar to those of the cerebellar cortex. Also, the cochlear parallel fibers traverse the spiny apical dendrites of principal neurons (the pyramidal cells) and the smoother dendrites of molecular layer stellate cells.

Animals↗

PubMed1980

Fine structure of granule cells and related interneurons (termed Golgi cells) in the cochlear nuclear complex of cat, rat and mouse.

This paper describes the fine structure of granule cells and granule-associated interneurons (termed Golgi cells) in the cochlear nuclei of cat, rat and mouse. Granule cells and Golgi cells are present in defined regions of ventral and dorsal cochlear nuclei collectively termed "cochlear granule cell domain'. The granule cells are small neurons with two or three short dendrites that give rise to a few branches with terminal expansions. These participate in glomerular synaptic arrays similar to those of the cerebellar cortex. In the glomeruli the dendrites form short type 1 synapses with a large, centrally-located mossy bouton containing round synaptic vesicles and type 2 synapses with peripherally located, smaller boutons containing pleomorphic vesicles. The granule cell axons is thin and beaded and, on its way to the molecular layer of the DCN, takes a straight course, which in ventral nucleus is parallel to the pial surface. Neurons of the second category resemble cerebellar Golgi cells and occur everywhere interspersed among the granule cells. They are usually larger than the granule cells and give rise to dendrites which may branch close to and curve around the cell body. The dendrites contain numerous mitochondria and are laden with thin appendages, giving them a hairy appearance. Both the cell body and the stem dendrites participate in glomerular synaptic arrays. Golgi cell glomeruli are distinguishable from the granule cell glomeruli by unique features of the dendritic profiles and by longer, type 1 synaptic junctions with the central mossy bouton. The Golgi cell axon forms a beaded plexus close to the parent cell body. The synaptic vesicle population of the mossy boutons suggests that they are a heterogeneous group and may have multiple origins. Apparently, each of the various classes participates in both granule and Golgi cell glomeruli. The smaller peripheral boutons with pleomorphic vesicles in the two types of glomeruli may represent Golgi cell axons which make synaptic contacts with both granule and Golgi cells. The Golgi cell axons which make synaptic contacts with both granule and Golgi cells. The Golgi cell dendrites, on the other hand, are also contacted by small boutons en passant with round synaptic vesicles, which may represent granule cell axons. A tentative scheme of the circuitry in the cochlear granule cell domain is presented. The similarity with the cerebellar granule cell layer is striking.

Animals↗

PubMed1980

Scanning electron microscopy and x-ray microanalysis of mineral deposits in lungs of a patient with pleural mesothelioma.

Scanning electron microscopy of lung tissue, ashed at low temperature, and obtained from an insulation worker who had died of pleural mesothelioma, showed the presence of numerous inorganic particles and fibres. A regional variation in fibre concentration in different tissue samples was found, and the size distribution of naked fibres and asbestos bodies was determined. By energy dispersive x-ray microanalysis the fibres were identified mainly as amphibole asbestos. This method also showed the presence of particles containing titanium and of fragments of diatom shells. Despite a mean concentration of 33 x 10(6) fibres per gram of dry tissue no significant lung fibrosis was found.

Adult↗

PubMed1979

The cochlear nuclei in man.

The human cochlear nuclei are composed of a ventral and a dorsal nucleus which are similar, though not identical, in their cytoarchitecture to those of other mammals. The ventral cochlear nucleus (VCN) consists of a rostral area of spherical cells, a central area of multipolar and globular cells, a posterior area of octopus cells, and laterodorsal cap of small neurons. The interareal boundaries are less distinct in man than in the cat. The central region of multipolar cells and the cap area of small cells constitute the bulk of the human VCN. The spherical, globular, and octopus cells appear relatively less numerous in man than in other mammals. The dorsal cochlear nucleus (DCN) in man is relatively large, but lacks the typical stratification seen in other mammals, with only vestiges of the granular and molecular layers remaining. Virtually the entire DCN consists of an area of cochlear fiber neuropil containing pyramidal cells, small neurons, and occasional giant cells. The pyramidal cells have lost their typical radial orientation and lie scattered within the cochlear neuropil. Thus the entire human DCN may be equivalent to layers 2 and 3 of this nucleus in other mammals. In spite of the relatively large DCN, the acoustic striae appear small. This is in contrast to the large trapezoid body leaving the VCN. Intrinsic and descending fiber pathways to the cochlear nuclei are not clearly defined and may be less prominent in man than in the cat.

Acetylcholinesterase↗

PubMed1978

The cochlear nerve in the cat: topography, cochleotopy, and fiber spectrum.

The topographical and cytological features of the cochlear nerve in normal adult cats were studied by microdissection, light microscopy, transmission and scanning electron microscopy. The 2-mm long cochlear nerve trunk is situated within the internal acoustic meatus. The nerve is wrapped like a roll with the more basal fibers situated peripheral to the more apical ones. The fibers are fasciculated according to their target in the cochlea and follow a helical course with the sharpest spiralling in the distal portion of the fiber. Apical and basal coil fibers are of approximately the same length measured from the spiral lamina to the rostral border of the anteroventral cochlear nucleus. The nerve contains about 90% thick, myelinated fibers, about 10% unmyelinated axons, and a few thin, but heavily myelinated axons. The first group shows a unimodal distribution of axonal diameters, with a gradual increase in average diameter from basal to apical coil fibers. The number of axonal microtubules and neurofilaments have a high linear correlation to axonal circumference without principal cochleotopic differences. The myelin sheaths are thicker and the internodal segments shorter than expected from similarly sized peripheral fibers in rodents. The possible nature and origin of the three fiber categories are discussed.

Animals↗

PubMed1978

Temporal and spatial sequence of anterograde degeneration in the cochlear nerve fibers of the cat. A light microscopic study.

This study deals with anterograde degeneration in the cochlear nerve fibers following cochlear lesions. The observations are based on 2-mum thick sections of material embedded in resin according to procedures used in electron microscopy and stained with toluidine blue. Among the various operative approaches used in this study, sparing of the modiolus afforded the least local reaction and furnished the material best suited for anterograde degneration studies in this nerve only 2 mm long. The anterograde degeneration of the cochlear nerve is characterized by segmental swelling of myelinated nerve fibers followed by shrinkage of the axoplasm and collapse of the distended myelin sheaths. The swelling, which begins at the nodal-paranodal region of the axon, is preceded by accumulation in the cytoplasm of granular organelles, presumably mitochondria and lysosomes. The portions of the cochlear fibers situated in the nerve root, i.e., within the cochlear nuclei and including the axon terminals, follow essentially the same pattern of degeneration as those in the peripheral portion of the nerve. Both peripherally and centrally degenerative changes occur first in the basal, high frequency fibers and centrally degenerative changes occur first in the basal, high frequency fibers and progress to the apical, low frequency fibers. The difference between the two extremes in the onset of degeneration is, approximately, 24 hours. Once initiated, however, the pace of degeneration is the same along the whole fiber spectrum.

Animals↗

PubMed1977