I. Rojik

Biochemical and morphological changes in carp (Cyprinus carpio L.) liver following exposure to copper sulfate and tannic acid

As a consequence of human activity various toxicants reach the aquatic ecosystems; humics may interact with them and may change their toxicity. Many fish are exposed to a considerable concentration of humics and pollutants. Because of paucity of data on the biochemical action of tannins in the presence of the fungicide CuSO4 a comparative study was undertaken. The alterations of redox-parameters in carp liver were monitored and tissue necrosis was followed by measuring the plasma transaminase activities and by electron microscopy. Tannic acid, a representative phenolic/humic compound, exerted prooxidant effects in carp, which may be partially due to formation of prooxidant intermediates/end-products via its biotransformation. Alternatively, tannic acid may partially inhibit the antioxidant enzymes of fish. The response to CuSO4 was more severe. Although tannic acid alone acted as a prooxidant in fish, electron micrographs demonstrated that it reduced the necrotizing effect of copper, which may be due to the complexing activity of tannic acid with the biomolecules of the hepatocytes and to the H2O2-degrading activity of tannin-CuSO4 combination. Our results indicate that the heavy metal-detoxifying capacity of tannin may be significant; however, tannin-exposure alone or combined with metals may be toxic for fish due to enzyme inhibition and oxidative stress induction.

Neonatal monocular enucleation-induced cross-modal effects observed in the cortex of adult rat

The cortices of neonatally enucleated rats were explored for somatosensory responses with special reference to an extension into the occipital cortex. Monocular enucleation was performed on rats at birth. The animals were raised and from the age of three months the activity evoked by either electric stimulation of the vibrissa pad or bending of the vibrissae was tested in the contralateral cortex by electric recording and autoradiography. It was found that early enucleation caused an expansion of the somatosensory responses, among others into the visual area. Neurons responsive to visual and somatosensory stimuli were demonstrated in the anterior part of the primary and secondary visual areas, contralateral to the enucleation. Electrophysiological and autoradiographic studies unambiguously proved that early enucleation exerted a significant cross-modal effect on the somatosensory responsive area.

Comparative study of the neuronal plasticity along the neuraxis of the vibrissal sensory system of adult rat following unilateral infraorbital nerve damage and subsequent regeneration

Abstract The aim of the present study was to examine the physiological consequences of a unilateral infraorbital nerve lesion and its regeneration at different levels of the somatosensory neuraxis. In animals whose right infraorbital nerve had been crushed, a large unresponsive area was found in the main brainstem trigeminal nucleus (Pr5). Responses evoked by ipsilateral vibrissal deflection in the middle of Pr5 reappeared only on days 22–35 after the nerve had been transected, whereas recovery from the nerve crush took only 7–9 days. However, no sign of short-term neuronal plasticity was observed in Pr5 after peripheral nerve injury. An enlargement of the receptive fields in two-thirds of the units and a lengthening in the delay of the evoked responses were observed as long-term plastic changes in Pr5 neurons after peripheral-nerve regeneration. In the ventral posteromedial nucleus of the thalamus (VPM) of partly denervated animals, however, only minutes or hours after the nerve crush, certain units were found to respond in some cases not only to the vibrissae, but also to mechanical stimulation of the face over the eye (two units), the nose (one unit), and the midline (one unit). Apart from the experiments involving incomplete denervation, the vibrissal representation areas of the VPM were unresponsive to stimulation of both the vibrissae and other parts of the face until nerve regeneration had occurred. In the somatosensory cortex, an infraorbital nerve crush immediately resulted in a large cortical area being unresponsive to vibrissal deflection. It was noteworthy, however, that shortly after the nerve crush, this large unresponsive whisker representation cortical area was invaded from the rostromedial direction by responses evoked by stimulation of the forepaw digits. In spite of the reappearance of vibrissa-evoked responses 7–10 days after the nerve crush, an expanded digital representation could still be observed 3 weeks after the nerve crush, resulting in an overlapping area of digital and vibrissal representations. The withdrawal of the expanded representation of forepaw digits was completed by 60 days after the nerve crush. The results obtained in Pr5, the VPM, and the cortex strongly suggest that the higher the station in the neuraxis, the greater the degree of plasticity after infraorbital nerve injury.

Inhibitory effect of vasopressin receptor antagonist OPC-31260 on experimental brain oedema induced by global cerebral ischaemia

SummaryThe effects of the non-peptide vasopressin V2 receptor antagonist 5-dimethylamino-1-[4-(2-methylbenzoylamino)benzoyl]-2,3,4,5-tetrahydro-1H-benzazepine hydrochloride (OPC-31260) on the cerebral oedema induced by general cerebral hypoxia were studied in rats. The general cerebral hypoxia was produced by bilateral common carotid ligation in Sprague-Dawley rats of the CFY strain. By 6 h after the ligation, half of the rats had died, but the survival rate was significantly higher following OPC-31260 administration. Electron microscopic examinations revealed typical ischaemic changes after the carotid ligation. The carotid ligation increased the brain contents of water and Na+ and enhanced the plasma vasopressin level. The increased brain water and Na+ accumulation was prevented by OPC-31260 administration, but the plasma vasopressin level was further enhanced by OPC-31260. These results demonstrate the important role of vasopressin in the development of the disturbances in brain water and electrolyte balance in response to general cerebral hypoxia. The carotid ligation-induced cerebral oedema was significantly reduced following oral OPC-31260 administration. The protective mechanism exerted by OPC-31260 stems from its influence on the renal vasopressin V2 receptors. These observations might suggest an effective approach to the treatment of global hypoxia-induced cerebral oedema in humans.

Two different polysensory systems in the suprasylvian gyrus of the cat. An electrophysiological and autoradiographic study

Abstract The suprasylvian gyrus of cats was systematically mapped by recording acoustic and somatosensory-evoked potentials under pentobarbital and chloralose anaesthesia. In this way two polysensory systems could be differentiated. One of them operates only under chloralose anaesthesia and proved to be identical with the long latency association fields: the anterior middle suprasylvian association area and the posterior middle suprasylvian association area, discovered by Thompson , Johnson & Hopes (1963). The other one is localized to the anterior suprasylvian gyrus and exhibits short latency-evoked potentials and is also active under pentobarbital anaesthesia. The incorporation of [ 3 H]-glycine, as demonstrated by autoradiography, showed good correspondence with the electrophysiological findings and so provides a morphological way of localising the two polysensory systems.

Prevention of hypoxic brain oedema by the administration of vasopressin receptor antagonist OPC-31260

The numerous situations which can result in cerebral hypoxic damage occur in newborn infants and in the elderly. In research aimed at more effective therapeutic intervention in ischaemic disorders of the brain, the animal model used and the principles of the causal therapy should be better outlined. The effects of the non-peptide AVPR (V2) antagonist 5-dimethylamino-1-[4-(2-methylbenzoylamino) benzoyl]-2,3,4,5-tetrahydro-1H-benzazepine hydrochloride (OPC-31260) on the cerebral oedema induced by general cerebral hypoxia were studied in rats. The general cerebral hypoxia was produced by bilateral common carotid ligation in Sprague-Dawley rats of the CFY strain. By 6h after the ligation, half of the rats had died, but the survival rate was significantly higher following OPC-31260 administration. Electron microscopic examinations revealed typical ischaemic changes after the carotid ligation, and OPC-31260 treatment did not significantly reduce the hypoxic signs in the brain cortex; only a certain decrease in the pericapillary oedema was observed. The carotid ligation increased the brain contents of water and Na(+) and enhanced the plasma AVP level. The increased brain water and Na(+) accumulation was prevented by OPC-31260 administration, but the plasma AVP level was further enhanced by OPC-31260. These results demonstrate the important role of AVP in the development of the disturbances in brain water and electrolyte balance in response to general cerebral hypoxia. The carotid ligation-induced cerebral oedema was significantly reduced following oral OPC-31260 administration. The protective mechanism exerted by OPC-31260 stems from its influence on the renal AVPR (V2). These observations might suggest an effective approach to the treatment of global hypoxia-induced cerebral oedema in humans.

Modification induced in visual cortical activity of rat by neonatal monocular enucleation

MONOCULAR enucieation was performed on rats at birth. The animals were raised and from the age of 3 months the evoked activity was tested in the contralateral visual cortex both by mapping of evoked potentials and by autoradiography. It was found that monocular enucleation changed the distribution of the evoked activity characteristically. The focus of activity shifted laterally and was restricted to the binocular part of the primary visual cortex, while hardly any evoked activity or labelled neurons were found in its medial part.

Afferent fibers to the anterior suprasylvian gyrus from the medial geniculate body of cat

Afferents to the anterior suprasylvian gyrus (ASG) from the medial geniculate body of cat were demonstrated by means of autoradiography. [3H]Glycine was injected stereotactically into the medial division of the medial geniculate body (mMGB). After a 3-day survival period, the auditory cortices and the ASG were excised. Labelled terminals were found in the ASG, in the anterior auditory field (AAF) and in the acoustic cortex (AI). The density of labelling was highest in the ASG and lower in the AAF and AI. The afferents from the mMGB made synaptic contacts in the 3rd layer of the cortices examined.

The functional projections of the anterior ventralis nucleus, as revealed by autoradiography

The effect of stimulation of ventral anterior nuclei of the thalamus (VA) was studied in different areas of cat cortex (sensory, motor and association) with [3H]glycine autoradiography. One-hour VA stimulation resulted in the most intensive [3H]glycine incorporation in the second, third and fifth layers of the anterior suprasylvian gyrus and of the motor cortex. The labelling was less intensive in the sensory (auditory) and association (posterior middle suprasylvian association area) cortices, but the effect of VA stimulation reached these regions as well. The VA stimulation resulted in evoked potentials over the whole area examined, with highest amplitude and shortest latency in the anterior suprasylvian gyrus. It is suggested that the [3H]glycine autoradiography is suitable to study the functional projection of non-specific thalamocortical systems.

Effect of Epileptogenic Agents on the Incorporation of 3H-Glycine into Proteins in the Cat's Cerebral Cortex

Summary: Filter paper strips soaked in 3H‐glycine solution were applied to acoustic cortex of cats, anaesthetized with Nembutal and pretreated with epileptogenic agents (Metrazol. G‐penicillin, and 3‐amino‐pyridine) and cy‐cloheximide. The untreated contralateral hemisphere served as control. After I h incubation, both cortical samples were excised simultaneously and fixed in Bouin solution for autoradiography. Incorporation was blocked by cyclo‐heximide. There was no glycine incorporation on the penicillin‐treated side, while pyramidal cells were intensively labelled in layers II‐V of the mirror focus. 3‐Aminopyridine produced the same result. Metrazol as convulsant proved to be far weaker than the previous two. The intensity of incorporation was significantly more intensive in the mirror focus than in the primary one. Penicillin and 3‐aminopyridine, while provoking cortical seizures, seem to inhibit glycine incorporation into a neuron‐specific, function‐dependent protein contained by the labelled cells in the autoradiogram.