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Biomedical subjects

G E Novotny

Publications and source records attributed to G E Novotny.

At least 19 recordsLinked to original sources
PubMed2002

Chromaffin cell function and structure is impaired in corticotropin-releasing hormone receptor type 1-null mice.

Corticotropin-releasing hormone (CRH) is both a main regulator of the hypothalamic-pituitary-adrenocortical axis and the autonomic nervous system. CRH receptor type 1 (CRHR1)-deficient mice demonstrate alterations in behavior, impaired stress responses with adrenocortical insufficiency and aberrant neuroendocrine development, but the adrenal medulla has not been analyzed in these animals. Therefore we studied the production of adrenal catecholamines, expression of the enzyme responsible for catecholamine biosynthesis neuropeptides and the ultrastructure of chromaffin cells in CRHR1 null mice. In addition we examined whether treatment of CRHR1 null mice with adrenocorticotropic hormone (ACTH) could restore function of the adrenal medulla. CRHR1 null mice received saline or ACTH, and wild-type or heterozygous mice injected with saline served as controls. Adrenal epinephrine levels in saline-treated CRHR1 null mice were 44% those of controls (P<0.001), and the phenylethanolamine N-methyltransferase (PNMT) mRNA levels in CRHR1 null mice were only 25% of controls (P <0.001). ACTH treatment increased epinephrine and PNMT mRNA level in CRHR1 null mice but failed to restore them to normal levels. Proenkephalin mRNA in both saline- and ACTH-treated CRHR1 null mice were higher than in control animals (215.8% P <0.05, 268.9% P <0.01) whereas expression of neuropeptide Y and chromogranin B did not differ. On the ultrastructural level, chromaffin cells in saline-treated CRHR1 null mice exhibited a marked depletion in epinephrine-storing secretory granules that was not completely normalized by ACTH-treatment. In conclusion, CRHR1 is required for a normal chromaffin cell structure and function and deletion of this gene is associated with a significant impairment of epinephrine biosynthesis.

Adrenal Glands↗
PubMed2001

Regional differences in innervation of lymph nodes in the Wistar rat.

Previous light microscopic investigations have indicated that, in the rat, the innervation of mesenteric lymph nodes may be less dense than that of axillary nodes. However, nerves of the enteric system are difficult to visualise by light microscopy. Therefore we quantified the density of innervation of axillary and mesenteric lymph nodes at the ultrastructural level. The results show a highly significant difference in the density of innervation between these 2 groups of lymph nodes, but morphologically the type of the innervation does not seem to differ. In previous studies, nerves were found predominantly in regions characterised by aggregations of plasma cells. In view of this association, we suggest that the difference in innervation may reflect the migration of plasma cells out of mesenteric nodes and into the mucosa of the gut wall. By contrast, in peripherally located nodes, plasma cells tend to remain within the lymph nodes, and hence the density of innervation of these nodes is greater.

Animals↗
PubMed1998

Inactivation of baroafferents leads to loss of barosensitivity without changes in nerve morphology.

Baroreceptors are stretch-sensitive mechanoreceptors, which are silenced by preventing distension of the receptor zone. Does chronic inactivation of these peripheral afferents alter their function or morphology? Compound action potentials and morphometry of carotid sinus nerves of 10 rabbits were investigated. The baroafferents were inactivated by embedding the pressure-released carotid sinus into silicon gel. The success of this procedure was validated by the absence of spike activity of the sinus nerve during normal and elevated systemic blood pressure. The contralateral vessels of the same animals were sham-operated and also embedded into silicon, but without prevention of wall movements. After 5, 7, 14 or 28 days the nerves were functionally reinvestigated before and after release of the sinus wall. Afterwards, the morphology of the nerve cross-sections was analysed by morphometry of electron micrographs. Baroafferents did not regain spike activity during immobilisation of the sinus wall. After release of the carotid sinus wall only nerves inactivated for five days regained their pulse synchronous baroreceptor discharge. Following seven days of inactivation, baroreceptor discharge could be elicited by maximal pressure elevation in only one of three nerves. At any time later, the baroreceptor response to arterial pressure changes was lost completely. The activity of the control nerves was preserved after 28 days. No obvious differences in fibre size and myelin thickness were observed between inactivated and control nerves. Inactivation of baroafferents for more than one week leads to a loss of pressure-dependent spike activity. Since morphology did not differ between inactivated and control nerves, it is suggested that changes of baroreceptor endings are responsible for this loss of function.

Action Potentials↗
PubMed1998

A silver impregnation utilizing only reagent-grade chemicals for visualization of peripheral axons and fibroblasts.

A silver impregnation procedure is described that enables the representation of numerous tissue components. It especially visualizes nerves and fibroblasts, which may be clearly distinguished from other tissue elements. Since it can be performed on thick sections, three-dimensional analysis of nerve terminations and fibroblasts in the tissues can be performed. The results are illustrated with the innervation of the rat snout and human labial sweat glands for nerves, and with bovine and pathological human material for fibroblasts. Axons are visualized as thin, sinuous black structures, sometimes, as in the case of autonomic efferents, with varicosities. Fibroblasts are revealed in their total extent by the darker staining of their nuclei and cytoplasm compared with that of the surrounding collagen. Cell processes can thus be followed for long distances, and may be seen to approach other cells. Previously published methods for the visualization of nerves and fibroblasts depended upon the use of commercial formalin, which is subject to the manufacturers' modifications. The method presented here uses exclusively analytical-grade reagents and distilled water. It is also less dependent than other methods on the fixation protocol.

Animals↗
PubMed1994

Plasticity of innervation of the medulla of axillary lymph nodes in the rat after antigenic stimulation.

The purpose of this investigation was to test the hypothesis that activation of the immune system in rats will lead to changes in the density of innervation in lymph nodes. In order to reduce the variability between animals, the rats were reared under sterile conditions and immunostimulation was effected by subcutaneous application of bovine albumin in a region draining to the axillary lymph nodes of both sides. Control animals received an equivalent application of sterile physiological saline. The animals were sacrificed 10 days and 27 days and 4 months after immunostimulation. The nerves in the axillary lymph nodes were quantified by light microscopy in silver impregnated sections and at the ultrastructural level on ultrathin sections. The survival times were chosen so that the first group was in the ascending phase of antibody production, the second group at the peak, and the third group in the declining phase. Both at the light and ultrastructural levels, there were statistically significant differences in the density of innervation of medulla between the groups, with a particularly pronounced increase in the group 4 months after immunostimulation. At the ultrastructural level, there was also an increase in the density of incompletely ensheathed axonal profiles in the parenchyma of the medulla, while the nerves associated with blood vessels were not increased. We conclude that immunostimulation leads to morphological changes in the innervation of the medulla of axillary lymph nodes, that are consistent with the concept of functional activation of the autonomic nervous system through the immune system.

Animals↗
PubMed1993

Effects of 6-hydroxydopamine on pre- and post-junctional 5-HT1-like receptor-mediated responses in dog saphenous vein.

To investigate whether 5-HT1-like receptor-mediated inhibition of adenosine 3':5'-cyclic monophosphate (cyclic AMP) accumulation occurs in nerves or smooth muscle of saphenous vein, infusions of 6-hydroxydopamine (6-OHDA) were administered to dogs with the aim of inducing sympathetic nerve damage. The effects of 6-OHDA on other 5-HT1-like receptor-mediated responses at the pre- and post-junctional level were investigated for comparison by studying 5-hydroxytryptamine (5-HT)-induced inhibition of 3H-noradrenaline release and contraction of smooth muscle respectively. Disruption of nerve function by 6-OHDA was revealed by the lack of catecholaminergic fluorescence and neurogenic contractile responses in saphenous veins from dogs treated with 6-OHDA. In addition, severe impairment of neuronal uptake mechanisms were apparent since basal efflux of 3H-noradrenaline, electrically-evoked release of 3H-noradrenaline and remaining 3H-noradrenaline content were considerably reduced. Some 3H-noradrenaline was taken up and released in 6-OHDA-treated tissues which is consistent with the existence of nerve varicosities resistant to the present dosing regime of 6-OHDA, an observation substantiated by electron microscopy studies showing inconsistent lesions of nerve terminals. 6-OHDA pre-treatment potentiated the smooth muscle contractile responses mediated by 5-HT1-like receptors as well as potentiating 5-HT-evoked inhibition of prostaglandin E2-stimulated cyclic AMP accumulation. It did not, however, affect 5-HT-induced inhibition of 3H-noradrenaline release. The present results suggest that inhibition of cyclic AMP accumulation by 5-HT occurs predominantly in smooth muscle.

Animals↗
PubMed1993

In vivo determination of concentration-effect curves of local anaesthetics in man.

In clinical use, the concentrations of local anaesthetics at the site of action are unknown. With the method described here, concentrations of local anaesthetics can be predetermined and kept constant at the site of action. In six volunteers, a blister was raised on the ventral surface of the forearm. After removal of the epithelium, the blister base was rinsed continuously with carbogenated Tyrode's solution with and without increasing concentrations of bupivacaine (Carbostesin) for 15 min each. The effects of bupivacaine were determined by changes in the perception (tactile sensation) of drops falling on the blister base from increasing heights. The minimal height at which the drops were just perceived characterized the threshold of perception. With increasing bupivacaine concentrations, threshold increased until the drops were no longer perceived, at a median concentration of 2.48 mmol litre-1 (range 1.24-3.10 mmol litre-1). After the blister base was rinsed with Tyrode's solution, threshold of perception reached baseline values, which was in accordance with an intact blister base.

Adult↗
PubMed1993

The effect of immunostimulation on thymic innervation in the rat.

In order to test whether the thymic innervation shows morphological plasticity in response to thymic functional changes, the density of thymic innervation was determined in sterile control animals and three groups of antigenically stimulated sterile rats. Thymic function was defined from the numbers of mitotic cells present in the thymic cortex, and these were reduced by antigenic stimulation. The innervation was determined separately for the various compartments of the thymus. Nerves were present in the capsule and the septa, but could not be found in either cortex or medulla of the thymic parenchyma. A statistically significant increase in the density of innervation after antigenic stimulation was found for the vessel and the non-vessel innervation of the septa. No significant changes were found in the innervation of the capsule.

Animals↗
PubMed1993

A light and electron microscopic quantitative analysis of the innervation of axillary lymph nodes in juvenile and old rats.

The innervation of axillary lymph nodes from 20 juvenile rats (aged < 6 wk) was compared with that of 20 old rats (aged > 2 y). One half of each group was investigated by light microscopy on silver-impregnated paraffin sections, the other half by electron microscopy. The lymph nodes of the old animals were larger than those of juvenile animals, as derived from the volumes analysed by light microscopy. By both light and electron microscopy, the nerves were found to be confined almost exclusively to the medulla and were frequently associated with groups of plasma cells. Nerves identified as cortical in location were consistently found only in cortical areas adjacent to the medulla. In the old animals the nerves were thicker and more prominent in the light microscopic preparations. No such differences were noted at the ultrastructural level. Myelinated nerves were found in all lymph nodes, except in a single old animal. Quantitative analysis of the nerves revealed a significant increase in the density of innervation of the medulla in the old animals both by light and electron microscopy. By light microscopy there also appeared to be a significant increase in the innervation density of the cortex, but these nerves were considered to be mislocalized because of difficulty in precise localisation at this level of magnification. On light microscopy, a significant increase in the incidence of nerve branching was found in the nodes of the old animals.

Aging↗
PubMed1992

Quantification of thymic innervation in juvenile and aged rats.

Thymic innervation has been quantified using silver impregnation and light microscopy on 5 juvenile and 5 aged rats. There is an increase in innervation density of the thymus with age, exceeding the reduction of thymic volume due to involution. The density of innervation correlates inversely with thymic volume. From previous studies, we conclude that thymic innervation is confined to the extraparenchymal compartment. Ultrastructural morphometry shows this compartment to maintain its volume during involution of the remaining thymic tissue. Related only to the extraparenchymal compartment, the innervation increases by a factor two with age.

Age Factors↗
PubMed1990

Thymic innervation in the rat: a light and electron microscopical study.

The innervation of the rat thymus was studied by light and electron microscopy in juvenile and aged rats. By light microscopy numerous fine nerves were found in the connective tissue septa penetrating between the thymic lobules. These septa were clearly delineated in the juvenile animals, but indistinct in the aged rats, thus creating the spurious impression that thymic parenchyma contains nerves. In the aged animals the nerves are thicker, tortuous, and more branched than in juvenile animals. Electron microscopy confirms the light microscopic observations: no nerves were found within the thymic parenchyma. The thymic capsule and larger connective tissue septa contain bundles of myelinated and unmyelinated axons, surrounded by a perineural sheath. Within the extraparenchymal compartment, which is greatly enlarged in aged animals, efferent and sensory nerves, devoid of perineurium, were found to contact mainly reticular cells, and in rare instances plasma cells and lymphocytes. The majority of axonal varicosities are not closely related to cellular elements, and, in general, vesicles are relatively infrequent. The possible functional significance of these observations is discussed.

Aging↗
PubMed1990

A simple procedure for demonstrating the overall morphology of fibroblasts in routine histological preparations of adult tissues, using silver impregnation.

A silver impregnation procedure for the total visualization of fibroblasts, with all their processes, is described. The method is applicable to routine formalin-fixed paraffin sections, or to formalin-fixed or native cryostat sections. The results are illustrated with examples from loose and dense connective tissue. Fibroblasts are visualized as cells with long, branching dendritic processes. The fibroblasts maintain contact with each other via these processes, thus forming a reticulum of cells, even in adult connective tissue.

Adolescent↗
PubMed1989

Lesion and regeneration of the anterior and posterior lens capsule and cortex in rabbits Nd:YAG laser.

With a mode-locked Nd:YAG laser set at various energy levels, anterior and posterior capsular and cortical lesions were produced in the lens of rabbits. Biomicroscopic and Scheimpflug examinations showed the anterior lesion to be healing in a whitish scar that was restricted to the area of the original lesion. Histology and transmission electron microscopy (TEM) demonstrated the proliferation of epithelial cells that produced a new, continuous, basement membrane-like capsule. In the area of the lesion collagenous material, myofibroblast-like cells and macrophages were found. Laser-induced lesions in the posterior lens capsule and lens protein resulted in damage to the capsule and grey opacity of the lenticular proteins, which remained unchanged for 6 weeks. Neither inflammatory nor epithelial cells appeared within the locally damaged lens. Macrophages migrated from the vitreous into the lesion; they were observed either in intercellular clefts or within a lens fibre, almost completely taking up their cross section.

Animals↗