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Biomedical subjects

G E Novotny

Publications and source records attributed to G E Novotny.

At least 37 records · Page 2Linked to original sources
PubMed1989

Organization of collagen and other extracellular material in anterior capsular cataract.

Capsular cataract takes the form of a white-grey opacity appearing under the anterior lens capsule (anterior subcapsular cataract). The capsule is wrinkled through the action of myofibroblast-like cells developed from the anterior lenticular epithelium. The myofibroblast-like cells also produce collagen that takes on a dysplastic appearance. Collagenous microfibrils accumulate to form fibre-like aggregations. These aggregations represent an abnormal collagen density (collagen condensation or attraction) in comparison to normal collagenous fibrils and fibres. Within the anterior capsular cataract 4 topological regions may be distinguished: Cell regions (1), stratification regions (2), aggregation regions (3), and intermediate regions (4). It is postulated that these regions represent different stages in the maturation and degradation of collagen, in the absence of phagocytic elements.

Cataract↗
PubMed1988

Intraepidermal nerves in human digital skin.

Intraepidermal nerve fibers of human glabrous digital skin were investigated using a new silver impregnation method. Nerves were observed to enter the epidermis without regional preference, and to extend into the stratum granulosum. They are non-varicose (smooth) or varicose and range from less than 0.2 micron to approximately 2 micron in diameter, with varicosities up to 3 micron in diameter. Some axons branch profusely within the epithelium, giving off fine branches of differing diameters, while others appear to remain unbranched. At least some intraepidermal axons are fine branches of larger axons taking a horizontal course below the epithelial layer. Others are, at least topically, closely associated with Meissner's corpuscles. At 57 nerves per mm2 surface area, the density of intraepidermal nerves found in this investigation is much greater than that reported in recent publications, and agrees closely with values given in several older studies.

Axons↗
PubMed1988

Ultrastructural analysis of lymph node innervation in the rat.

The morphological analysis of nerves in axillary lymph nodes of the rat revealed the presence of two types of axon possessing either a more or a less electron-lucent matrix. The more electron-lucent axons enter the node finely myelinated, do not contain synaptic vesicles and quickly divide to form branches approaching the basement membranes of blood vessels, as well as cellular elements. They may be interpreted as sensory axons. The less electron-lucent axons are unmyelinated, and contain three distinct populations of synaptic vesicles. These may all be present in one axonal varicosity, so that the existence of cotransmitters is highly probable.

Animals↗
PubMed1988

Silver impregnation of peripheral and central axons.

A silver impregnation method suitable for peripheral and central nervous system axons is described. Essential features are the use of reagent grade chemicals only, a pretreatment solution to ensure optimal impregnation of different organs from different animals and species, and an unvarying procedure. The results are compared to those obtainable with a number of current impregnation methods and with modern immunocytochemical reactions.

Animals↗
PubMed1987

Experimental carotenoid retinopathy. I. Functional and morphological alterations of the rabbit retina after 11 months dietary carotenoid application.

beta-Carotene, canthaxanthin, and beta-carotene plus canthaxanthin were administered to "chinchilla bastard" pigmented rabbits in their rabbit diet (approximately 200 ppm carotenoid per group). The effect of the carotenoids on retinal function and morphology was tested against a control group in the course of 11 months. Electroretinography showed that in contrast to the control animals, beta-carotene-treated rabbits produced increasing peak latencies of the scotopic b-waves. In the canthaxanthin-treated rabbits, a- and b-waves showed hypernormal amplitudes at low cumulative dosages (approximately 0.5-2 g) and reduced amplitudes at higher dosages (about 5 g). The peak latencies of the scotopic a- and b-waves increased remarkably. This effect was still stronger in the carotenoid combination. Histology and electron microscopy indicated that in contrast to the control animals, canthaxanthin-treated rabbits showed a reduction in retinal thickness in some samples. In particular, they exhibited alterations in the granular layers and a marked diminuation of the photoreceptor outer segments and morphological alterations of the photoreceptor inner segments with massive deposition of electron-dense material. In all animals treated with carotenoids, lipid droplets of the retinal pigment epithelium were enlarged in size and number.

Animals↗
PubMed1986

The lenticular capsule and cellular migration in anterior capsular cataract.

A light and electron-microscopical study was performed on six lenses harboring anterior capsular cataract. The cataracts are typically divided by numerous sheets of basement membranes that merge with the lenticular capsule at the edge of the cataract. Basally, the cataract may or may not be bounded by a basement membrane. Myofibroblastlike cells may be observed, apparently traversing the basal border of the capsular cataract. Within the substance of the lens, isolated aggregations of collagenous material are present. Degenerating cells or collagenous aggregations are situated within the lenticular capsule. It is suggested that this configuration arises through the merging of basement membrane systems, surrounding the cells within the cataract, with the lenticular capsule.

Adult↗
PubMed1986

Innervation of lymph nodes: a combined silver impregnation and electron-microscopic study.

Using silver impregnation and electron-microscopic techniques, nerves have been demonstrated in rat axillary, cervical and inguinal lymph nodes, and their distribution was investigated. With the electron microscope, vesicle-containing varicosities or terminals are demonstrated in close proximity to reticulum cells, lymphocytes, plasmablasts and mature plasma cells. Nerves supplying the blood vessels possibly differ from those supplying stromal or lymphocytic elements.

Animals↗
PubMed1985

Ultrastructural investigations on anterior capsular cataract. Cellular elements and their relationship to basement membrane and collagen synthesis.

A reinvestigation of the cellular elements in anterior capsular cataract of six lenses was performed at the light and ultrastructural levels. In addition to the fibroblastic characteristics described by previous authors, the cells were found to contain sublemmal filaments classifiable as myofilaments, as typically present in myofibroblasts. Cell shape varies in a manner consistent with contractility. Apparently contracted cells predominate within capsular folds. The number of cells was found to decrease with increasing maturity of the cataract. In old cataracts, only degenerating cells are to be found. The significance of these observations is discussed, and it is concluded that the anterior capsular cataract is a process bearing considerable similarity to wound healing.

Adult↗
PubMed1985

Ultrastructural investigation of extracellular structures in subcapsular white corrugated cataract (anterior capsular cataract).

Electron microscopic investigations were performed on six extracted lenses from patients undergoing operative treatment of subcapsular white corrugated cataract. The lens capsule itself was unaltered. There was a pronounced extracellular space under the capsule. In this area collagenous aggregations equivalent in size to collagenous fibres and fibrils could be seen. Collagenous microfibrils and delicate microfilaments were also present. The latter could be observed with and without cross-striations. The fibrous structures are distinguished by considerable variations in shape and diameter. The precursor stages of these fibrous materials are produced by myofibroblast-like cells, probably derived from the lenticular epithelium.

Cataract↗
PubMed1984

Myofibroblast-like cells in human anterior capsular cataract.

In six cases of anterior capsular cataract, cells present in the subcapsular zone were investigated. In addition to organelles previously described, the cells were found to contain 7 nm and 15 nm filaments, suggestive of actin and myosin. The cells varied in shape from elongated or flat to rounded. Maculae adhaerentes, gap junctions and basement membranes were present. It is concluded that these cells closely resemble myofibroblasts, by virtue of their cytology and behaviour. The significance of this observation, concerning hypotheses on the genesis of anterior capsular cataract is discussed.

Adult↗
PubMed1984

Formation of cytoplasm-containing vesicles from double-walled coated invaginations containing oligodendrocytic cytoplasm at the axon-myelin sheath interface in adult mammalian central nervous system.

Double-walled coated invaginations ( DWCIs ) of the axolemma, containing oligodendroglial cytoplasm and presumably giving rise to double-walled coated vesicles ( DWCVs ), are observed in the central nervous system (CNS) of adult monkey and mouse. By means of serial sections, DWCIs are clearly distinguishable from the also observable adaxonal invaginations of oligodendroglial cytoplasm. DWCIs range in diameter from 60 to 190 nm with a circular or oval cross section. Their incidence in different regions of the CNS has been determined and evidence is adduced that DWCIs occur randomly along the axolemma.

Animals↗
PubMed1982

On the distribution of retinal afferents to the primate lateral geniculate nucleus.

A quantitative study has been carried out on the number of synaptic ring images, visible after neurofibrillar silver impregnation, in laminae 5 and 6 of the primate lateral geniculate nucleus in normal animals and after enucleation of the contralateral eye. In a statistical experiment the number of rings was found to be significantly increased between 6 and 11 d after unilateral enucleation in both lamina 6 and lamina 5 of the contralateral geniculate nucleus. Analysis of the time course of ring proliferation suggests the presence of 2 separate generative processes in lamina 6 at different times after enucleation. Only the second of these processes appears to exist in lamina 5. It is proposed that these observations are compatible with the hypothesis that there is a diffuse, sparse projection of collaterals of retinal Y axons from one eye to more than one lamina of the lateral geniculate nucleus.

Animals↗
PubMed1982

A relative volumetric analysis of the lateral geniculate nucleus after enucleation.

The relative volumes occupied by nerve cell somata, axons, myelin, the remaining neuropil, glial cell nuclei, blood vessels and degenerating terminals have been determined in the foveal and parafoveal portions of laminae 5 and 6 of the monkey (Macaca fascicularis) lateral geniculate nucleus, in control animals and at varying times after unilateral enucleation. The proportions occupied by these tissue components are very similar within the same lamina of all control animals, but differ significantly between lamina 5 and 6. After enucleation there are alterations, not only in the denervated lamina 6, but also in lamina 5.

Animals↗
PubMed1980

Observations on the lateral geniculate nucleus of the monkey (Macaca fasicularis) after eye removal: a light and electron microscopic study. II. Axonal and dendritic degeneration.

Morphological parameters of the axons and dendrites in the lateral geniculate nucleus have been studied in the normal monkey and after varying periods of enucleation, at the light and electron microscopic levels. Gross aspects of the alterations evident at the ultrastructural level can be correlated with changes visible in the light microscope. Signs of axonal fragmentation were never observed following enucleation; retinal afferent fibres seem to gradually thin out and disappear, taking on an osmiophilic appearance in the electron microscope during this process. Changes in the surface structure of axons are considered to be due to an altered reaction of myelin in the degenerating nucleus. Myelin is not removed to any great extent. The dendritic responses to enucleation (including those of synaptic profiles containing flat vesicles) are believed to result from an unspecific compensatory reaction to increased hydration and are not considered to be primarily degenerative. Since pale terminal degeneration seems to be of the same nature it is concluded that such early signs of presumed terminal death are unreliable. Dark degeneration of dendrites was not observed in the lateral geniculate nucleus of the enucleated monkey.

Animals↗
PubMed1980

Observations on the lateral geniculate nucleus of the monkey (Macaca fascicularis) after eye removal: a light and electron microscopic study. III. Glial reactions.

The light and electron microscopic morphology of non-neuronal elements within the lateral geniculate nucleus has been studied in normal monkeys and after enucleation. In the normal lateral geniculate nucleus it is possible to find light and dark astrocytes; light, medium and dark oligodendrocytes; microglia, and the so-called "third" glial element of VAUGHN and PETERS (1968). Two types of perivascular elements are also present. After enucleation, the first overt response is an oedematous reaction in the denervated regions, without concomitant disruption of the capillary endothelium. The oedema seems to be connected with swelling and disruption of astroglia. After the first days of enucleation, the microglia disappear and are replaced by phagocytic glia (WONG-RILEY, 1972). From the presence of intermediate stages at characteristic sites within the nucleus, it is concluded that phagocytic glia develop from the same precursor as the "third" glial elements and that they are both immature forms of microglial cells.

Animals↗
PubMed1979

Synaptic ring images after silver impregnation.

In view of the contradictory results obtained from a number of studies on the nature of ring images found after neurofibrillar silver impregnation, this question was reinvestigated at the ultrastructural level in the lateral geniculate nucleus of the monkey. The ring images found here are produced by silver deposits on ring-shaped accumulations of neurofilaments in the afferent synapses of retinal origin. Tubular impregnation of axons was not found to be a factor in the genesis of ring images.

Cytoskeleton↗
PubMed1979

Observations on the lateral geniculate nucleus of the monkey (Macaca fascicularis) after eye removal: a light and electron microscopic study. I. Classification and degeneration of optic fibre terminals.

The morphological signs of terminal degeneration are compared at the light and electron microscopic levels in the lateral geniculate nucleus of Macaca fascicularis, from 29 hours to 10 days after eye removal. A close correlation can be found between the appearance of degenerating RLP-terminals (i.e. large terminals containing round vesicles and pale mitochondria), which display marked, unorganized neurofilamentous hyperplasia, and the club-shaped structures revealed by neurofibrillary staning. The ring-shaped entities present in silver-impregnated material closely resemble annular bundles of neurofilaments located in smaller retinal terminals within the neuropil. Various non-filamentous degenerative forms of particularly small terminals are also described. It is concluded that the clubs and rings visualized by neurofibrillary stains in the lateral geniculate nucleus of the monkey do, indeed, represent synaptic structures. The implications of this conclusion are discussed, as are possible reasons that contrary conclusions have been drawn by other investigators. It is further suggested that club and ring formation of degenerating retinal afferents may be related to Y and X axons in the optic tract, respectively.

Animals↗