Hexachlorophene-induced degeneration of adrenergic nerves: application of quantitative image analysis to Falck-Hillarp fluorescence histochemistry

Expression of eight neuropeptides in intraocular spinal cord grafts: organotypical and disturbed patterns as evidenced by immunohistochemistry

The present study examines the distribution of several neuropeptides, as revealed by immunohistochemistry in the isolated cord. Fetal rat spinal cord was grafted to the anterior chamber of the adult Sprague-Dawley albino rats. After intraocular maturation for 2-3 months, the amount and distribution of somatostatin, neuropeptide Y, substance P, enkephalin, vasoactive intestinal peptide, peptide histidine-isoleucine, calcitonin gene-related peptide and cholecystokinin immunoreactive terminals and cell bodies were analysed using indirect fluorescence immunohistochemistry. The visualization of immunoreactive cell bodies in the grafts was enhanced using a novel intraocular colchicine treatment. In the graft a rich network of somatostatin-positive terminals was found with a high density in well-demarcated areas reminiscent of substantia gelatinosa of the dorsal horn of normal spinal cord. A large number of small- to medium-sized somatostatin neurons was found throughout the grafts without colchicine treatment. This is in contrast to normal spinal cord, where positive neurons were difficult to visualize without colchicine and were mainly confined to the dorsal horn. Neuropeptide Y had a distribution in the grafts similar to that of somatostatin and neuropeptide Y cells were found throughout the grafts without colchicine treatment. In normal spinal cord, neuropeptide Y-positive fibers were found mainly in substantia gelatinosa with a sparse network in the ventral horn. Enkephalin-positive fibers were found throughout the grafts. The distribution of fibers resembled that of somatostatin and neuropeptide Y with distinct zones of high fiber density in well-demarcated areas, whereas the density of nerve fibers in the rest of the graft neuropil was moderate to low. The distribution of substance P was similar to that of enkephalin. After colchicine treatment, both enkephalin- and substance P-positive cell bodies were visualized. In the intact spinal cord both peptides were seen in the entire gray matter with the highest concentrations in the superficial laminae of the dorsal horn. Antisera against calcitonin gene related-peptide, revealed a sparse terminal network and many large cells, which might represent motoneurons. A sparse network of varicose cholecystokinin-immunoreactive fibers was found evenly distributed in the grafts. In normal spinal cord a dense cholecystokinin-positive network of primary sensory afferent origin was found in the dorsal horn. In the grafts cholecystokinin cell bodies were seen after colchicine treatment.(ABSTRACT TRUNCATED AT 400 WORDS)

Spinal cord interneuron degenerative atrophy caused by peripheral nerve lesions is prevented by serotonin depletion

Peripheral nerve section causes a degenerative atrophy of substance P sensory input and of met-enkephalin interneurons in the dorsal horn of the spinal cord. Radioimmunoassay of both peptides indicates that the decrease in peptide levels ranges from 30 to 50%, that it occurs several days after lesioning, and that it is simultaneous for the two peptides. Quantitative immunocytochemistry performed by computer-assisted analysis of met-enkephalin-positive boutons shows that following sciatic nerve lesions there is a decreased density of immunoreactive boutons per unit area in the substantia gelatinosa of the dorsal horn in the lumbar cord ipsilateral to the lesion. Within 24 h of nerve injury there is a significant and transient enhancement of serotonin turnover, as indicated by the increased levels of 5-hydroxyindolacetic acid in the lumbar cord, without any change in serotonin concentrations. The restoration of normal serotonin metabolism at d 10 postlesioning coincides with the peptidergic loss. However, if, prior to nerve resection, serotonin stores are depleted by p-chlorophenylalanine treatment, the damage to met-enkephalin interneurons is fully prevented, while substance P loss does still occur. These results suggest that signals caused by the section of a peripheral nerve are directly responsible for substance P loss in the spinal cord and are, presumably, rapidly transported into the CNS, causing an activation of the serotoninergic raphe neurons projecting to spinal cord. The activation of this system is likely responsible for the degenerative atrophy of the met-enkephalin interneurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitation of noradrenaline nerve density in mouse iris by computer-assisted image analysis

The density of noradrenaline (NA)-containing nerve fibres in mouse iris was measured with computer-assisted image analysis techniques both under normal conditions and during regeneration. Noradrenaline nerves were visualized by Falck-Hillarp formaldehyde condensation technique in whole-mount spread preparations of mouse irides. The samples were analysed in a fluorescence microscope connected to a commercially available image analysis system (IBAS/Kontron). A software program was developed for specific detection of fluorescence and the nerve density was determined by calculating the area covered by fluorescence in percentage of total measuring field. The method showed good reproducibility as observed both when repeated measurements were performed in the same measuring field or when consecutive measurements on the same set of irides were performed. Also the inter-assay variation between control values in the different experiments was low. Loading of the adrenergic nerves by incubation in alpha-methyl-NA or conditions leading to partial diffusion of the fluorophore had minor effects on the nerve density values. The regeneration of the NA nerve fibres after a selective toxic sympathectomy with 6-hydroxydopamine was also studied. The nerve fibre density values measured by image analysis correlated well with the uptake of [3H]NA; the endogenous NA levels recovered much more slowly, however. It thus seems that endogenous transmitter levels might be a somewhat insensitive index of nerve terminal regrowth, at least in early stages of regeneration. The results indicate that image analysis is a powerful tool to quantitate a transmitter-identified nerve terminal network in a histological preparation.

GM1 ganglioside counteracts selective neurotoxin-induced lesion of developing serotonin neurons in rat spinal cord

The effect of exogenous monosialoganglioside GM1 on neurotoxin-induced lesioning of bulbo-spinal serotonergic neurons of newborn rats was studied by means of biochemical and immunocytochemical techniques. 5,7-dihydroxytryptamine (5,7-HT, a selective serotonin neurotoxin) treatment of newborn rats caused a pronounced reduction of 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) levels in the thoracic and lumbar spinal cord, while an increase of 5-HT and 5-HIAA was found in the pons medulla. These biochemical alterations were regionally correlated with similar changes in 5-HT nerve terminal density analyzed by image analysis. GM1 administration (30 mg/kg for 4 consecutive days) antagonized the reduction of 5-HT and 5-HIAA levels induced by 5,7-HT treatment in the lumbar spinal cord of 2-month-old rats, as well as the decrease of 5-HT nerve terminal density in both thoracic and lumbar spinal cord of 1- and 2-month-old rats. A minor counteracting effect of GM1 was found in the pons medulla where the neurotoxin induced an increase of 5-HT and 5-HIAA levels. These data support the hypothesis that GM1 may have a preventing action on retrograde degenerative processes following chemical lesion and/or a growth-stimulating effect on injured 5-HT neurons.

Image analysis of the histochemical demonstration of glucose-6-phosphatase activity in rat liver

Activities of histochemically demonstrated glucose-6-phosphatase were quantified by computerized densitometry using image analysis in livers of female adult Wistar rats fed ad libitum and fasted 22 h before sacrifice. Mean optical densities along the path between small portal tracts and efferent hepatic venous branches and enzyme activities obtained from biochemical assays exhibited a strong positive correlation. The gradients of high periportal to lower perivenous glucose-6-phosphatase activities were analysed by profiles of optical density along these distances. Mapping optical densities in an image of equidensity range provided information on the distribution pattern of hepatic glucose-6-phosphatase over an extended two-dimensional area. This visualisation of histochemical enzyme reaction based on quantitative data supports the approach of sampling across the entire protal----hepatic venous distance disregarding parenchymal zonation. Utilities provided by computer assisted image analysis will have some bearing for further adequate quantitative description of liver function and structural make up.

Effect of GM1 ganglioside on neonatally neurotoxin induced degeneration of serotonin neurons in the rat brain

The effect of exogenous GM1 ganglioside on the 5,7-dihydroxytryptamine (5,7-HT; a selective serotonin neurotoxin) induced alteration of the postnatal development of central 5-hydroxytryptamine (5-HT; serotonin) neurons has been investigated using neuro-chemical and immunocytochemical techniques. Neonatal 5,7-HT (50 mg/kg s.c.) treatment is known to lead to a marked and a permanent degeneration of distant 5-HT nerve terminal projections (e.g. in cerebral cortex, hippocampus and spinal cord), while projections close to the 5-HT perikarya in the mesencephalon and pons-medulla increase their nerve density. These regional alterations are reflected by decreases and increases, respectively, of endogenous 5-HT, [3H]5-HT uptake in vitro and number of 5-HT nerve terminals demonstrated by immunocytochemistry. Treatment of newborn rats with GM1 (4 X 30 mg/kg s.c.; 24 h interval) had no significant effect on the postnatal development of 5-HT neurons. GM1 administration had furthermore no effect on the 5,7-HT induced alteration of the regional 5-HT levels and [3H]5-HT uptake in the cerebral cortex acutely, indicating that GM1 did not significantly interfere with the primary neurodegenerative actions of 5,7-HT. At the age of 1 month a clear counteracting effect of GM1 was observed, in particular of the 5,7-HT induced 5-HT denervations. The 5-HT levels in the frontal and occipital cortex were reduced to 25 and 20% of control after 5,7-HT alone, while these values were 70 and 40%, respectively, after 5,7-HT and GM1 treatment. A similar antagonizing effect of GM1 was found in the frontal cortex when measuring [3H]5-HT uptake. GM1 treatment also caused a minor reduction of the 5,7-HT induced increase of the 5-HT levels in striatum and mesencephalon. Quantitation of 5-HT nerve terminal density in sections processed for 5-HT immunocytochemistry using an automatic image analysis system showed markedly more nerve terminals in the frontal and occipital cortex after 5,7-HT + GM1 compared to 5,7-HT treatment alone. Minor counteracting effects of GM1 were noted in the hippocampus and spinal cord (thoracic-lumbar) as evaluated by chemical 5-HT assay, although substantial counteracting effects were observed locally in these areas by quantitative immunocytochemistry.(ABSTRACT TRUNCATED AT 400 WORDS)

Chlorhexidine-induced degeneration of adrenergic nerves

Possible toxic effects of chlorhexidine (CHX) on the sympathetic adrenergic ground plexus were studied in whole mounts of albino rat irides using Falck-Hillarp fluorescence histochemistry. CHX dissolved in an isotone , buffered sodium-acetate solution or in 70% alcohol was injected into the anterior chamber of eye. CHX caused a marked and dose-dependent degeneration of adrenergic nerves. Two days after the lowest dose, 0,25 micrograms (5 microliters of a 0.05% CHX solution), approximately 30% of the nerves had disappeared. Almost complete degeneration was observed after the same time with higher doses (2.5 micrograms, 5.0 micrograms, and 7.5 micrograms corresponding to 0.5, 1.0, and 1.5% CHX respectively). Two weeks after the lowest dose, the nerves had regenerated almost completely. With the highest dose used, only some 40% of the normal adrenergic nerve plexus had reformed after 51 days. Alcohol as a solvent did not have an additive effect on the neurotoxic action caused by CHX. The results demonstrate yet another aspect of chlorhexidine neurotoxicity, degeneration of peripheral adrenergic nerve terminals. This suggests that neurotoxic actions on thin unmyelinated fiber systems should be looked for also in the central nervous system (CNS).