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P Tóth

Publications and source records attributed to P Tóth.

At least 55 records · Page 3Linked to original sources
PubMed1987

Retinal projections in gymnotid fishes.

Retinal projections were studied in four species of gymnotid fishes, Gymnotus carapo, Hypopomus artedi, Eigenmannia virescens and Sternopygus sp. with the aid of cobalt or HRP labelling and autoradiographic techniques. The optic tract gives off a small branch, the axial optic tract and then, after crossing in the midline, splits into a dorsomedial, dorsal and ventral fascicle. E. virescens and Sternopygus sp. display in addition an accessory optic tract. In all four species retinal projections are bilateral; ipsilateral projections, however, are extremely sparse. In all four species, the retinal fibres terminate bilaterally in the suprachiasmatic nucleus, dorsolateral optic nucleus of the thalamus and the optic nucleus of the posterior commissure; a bilateral retinotectal projection was only found in E. virescens and G. carapo. Retinal projections are only contralateral to the ventromedial nucleus of the thalamus, the central pretectal nucleus and the accessory optic nucleus. The contralateral retinotectal fibres terminate in the stratum fibrosum and griseum superficiale, and in the stratum album centrale and stratum periventriculare. A small accessory optic tract and nucleus were detected in E. virescens and Sternopygus sp. but not in G. carapo and H. artedi. The results indicate that the visual system of gymnotid fish is as simple as that of mormyrids. The poor visibility in the environment where these animals live and the additional sensory system which these animals possess may explain the poor development of the visual system.

Animals↗
PubMed1986

Simultaneous labelling of two different central nervous system pathways with horseradish peroxidase and cobalt in Gnathonemus petersii and Rana esculenta.

A new and simple simultaneous labelling procedure is described that gives the possibility of studying interneuronal connections and territorial overlap of different pathways. This method uses horseradish peroxidase (HRP) labelling in combination with the cobalt-filling technique. The blue colour of the HRP reaction end-product formed from 0-tolidine (Neuroscience, 4 (1979) 1805-1852) and the dark brown of cobalt-filled neurons and their processes allow easy distinction of the two different labels. Since both markers can be transported anterogradely and retrogradely by axons, this combination of the two techniques seems to be a very useful tool for neuroanatomical research. We have tested this method in a weakly electric fish, Gnathonemus petersii, and in frog, Rana esculenta.

Animals↗
PubMed1986

Ultrastructural, lectin histochemical and immunohistological observations on Merkel cell tumors.

The clinicopathological and ultrastructural findings of 10 cases of Merkel cell tumor (MCT) are presented. Three patients died rapidly due to tumor dissemination. The tumor cells in eight out of the 10 cases were positive for neuron-specific enolase, however, all were negative for the ten polypeptide hormones examined, as well as for the argentaffin and argyrophil reactions. One of the patients had suffered from chronic lymphocytic leukaemia. Particularly in this case, but also in the others, the differentiation of MCT from a malignant lymphoma necessitated immuno-histological, lectin histochemical and ultrastructural studies. The focal peanut agglutinin positivity of the tumor cells in 6 out of the 10 MCTs seems to be a characteristic feature of these cells.

Aged↗
PubMed1986

[Comparative evaluation of carticaine and bupivacaine in epidural anesthesia in cesarean section].

Lumbar epidural anaesthesia with Carticain (Ultracain) has been applied in 25 Caesarean Sections. The resulting data (waiting period, effective length and quality of the analgesia, blood pressure drop, postoperative phase, newborn state, side effects) have been compared with those of Bupivacain (Marcain) used for the same purpose. Carticain is fitted for purposes of obstetrical anaesthesia, even more than Bupivacain, owing to its slighter blood-pressure diminishing effect, and shorter waiting period.

Adult↗
PubMed1986

Lymphonodal response to sensitization with 2,4-dinitrochlorobenzene (DNCB) in laboratory rats.

The authors investigated the lymphonodal response to peripherally administered 2,4-dinitrochlorobenzene (DNCB). DNCB is known as a strong irritant binding to membrane proteins of the Langerhans cells of the skin. The conjugate is a potent neoantigen able to induce local tumor-destruction and raise cellular immune defence. White laboratory rats were used for the experiments. Their popliteal lymph nodes were investigated after sensitization with DNCB and i.c. injection of H3-thymidine and Patent Blue Violet at several intervals following the challenge with the hapten DNCB. Changes of weight of lymph nodes further uptake of H3-thymidine by the cells were investigated by autoradiography, while the content of H3-DNA indicating an increased DNA-metabolism due to blastic transformation of the small lymphocytes, was determined quantitatively by a liquid scintillation method. The data obtained speak for the usefulness of DNCB as an immunostimulant, comparable to BCG but of less toxicity.

Animals↗
PubMed1985

Presynaptic autoinhibition during rest and sodium-pump inhibition in isolated rat portal vein preparation.

In the presence of cocaine and corticosterone low-frequency (2 Hz) nerve stimulation evoked release of [3H]noradrenaline measured from isolated rat portal vein preparation. In normal Krebs solution exogenously applied l-noradrenaline (3 X 10(-8)-10(-6) M) significantly reduced the nerve-evoked [3H]noradrenaline release. The IC50 value of L-noradrenaline proved to be 1.8 X 10(-7) M. Yohimbine (3 X 10(-7) M) maximally blocked the alpha 2-adrenoceptors and enhanced nerve-evoked [3H]noradrenaline release. In the presence of 5.9 mM external K+, ouabain up to 10(-4) M did not affect either the resting or the stimulation-evoked release of radioactivity from tissues. In the absence of external K+ both the resting and the nerve-evoked release of [3H]noradrenaline increased markedly. When K+ was readmitted to preparations which had been kept in K+-free solution both the resting and the stimulation-evoked [3H]noradrenaline release were greatly reduced temporarily. In K+-free solution L-noradrenaline (10(-6) M) and yohimbine (3 X 10(-7) M) failed to significantly alter the nerve-evoked release. However, 3 X 10(-6) M yohimbine in K+-free solution significantly increased the stimulation-evoked release of [3H]noradrenaline. It is concluded that presynaptic alpha 2-adrenoceptor-mediated "negative feed-back" is present in rat portal vein preparations which can be inhibited by the preferential alpha 2-adrenoceptor blocker, yohimbine. However, if the Na+-pump is inhibited (which by itself enhanced the transmitter release), presynaptic autoinhibition is more pronounced, since a high concentration of yohimbine is required to block it.

Animals↗
PubMed1985

Behavioural elements of the paradise fish (Macropodus opercularis). II. A functional analysis.

The effects of various environmental influences, such as presence of a living predator, dominant conspecific or frightening artificial stimulus, on particular behavioural elements of the paradise fish (Macropodus opercularis) were studied. It has been found that certain sets of the elements are manifested as organizational complexes which characterize a certain mood or form of defensive behaviour. The compound elements of these complexes seemed to be partly interchangeable, partly under environmental control. The main behavioural complexes of the paradise fish were the Territorial complex characterizing the peaceful, home-living animal, Emotionality complex appearing in case of immediate and past danger, Active and Passive defense complexes which represent alternatives in defense, depending on particular stimulus settings. Some supporting evidence for these behavioural complexes are presented and discussed.

Animals↗
PubMed1985

Behavioural elements of the paradise fish (Macropodus opercularis). I. Regularities of defensive behaviour.

Elements of behaviour were described for the paradise fish on the basis of the topography, location and orientation of the animal observed in various seminatural and laboratory environments. Correlations and repeatability of the parameters of observation were analyzed. Environmental influences, such as periods of the day, housing, feeding, raising conditions, presence of various frightening stimuli and species, and strain differences, were studied. Several functional connections were found among the behavioural elements.

Animals↗
PubMed1985

Ethological analysis of social and environmental effects on the distribution of the behavioural elements of the paradise fish (Macropodus opercularis L.).

The behaviour of the paradise fish in a new environment was examined. The influence of space, the number of conspecifics, the number of each sex in the various groups and the time allowed for habituation on the distribution of various behavioural elements were revealed. By means of principal component analysis five biologically meaningful factors were extracted. Using the scores of the various factors as indices of settlement, fear passive behaviours and exploration, special effects of the environment were assessed. In small tanks the fish are in an emotionally low but stable continuously trying to escape. Being prevented from escaping they develop various passive behaviour forms which alternate with escape. In a large tank the main occupation of a female fish on its own is exploration at the start; this is accompanied by a fearful state. In groups of four the activity of exploration is less and the fearful state is not so pronounced. The presence of males seems to secure the most stable state in a new environment though after about two days the males start breeding activities and this involves a new spectrum of activities.

Animals↗
PubMed1985

[The sublingual bar].

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Dental Occlusion, Balanced↗
PubMed1985

Morphology of the cells of origin of descending pathways to the spinal cord in Rana esculenta. A tracing study using cobaltic-lysine complex.

The localization and morphological characteristics of neurons projecting to the spinal cord were studied with cobalt-filling technique. Cobaltic-lysine complex was iontophorized into descending pathways in the lumbar and cervical intumescence of the spinal cord and in some parts of the rhombencephalon. Well-filled cells located mainly in the rhombencephalon and telencephalon could be characterised as fusiform, triangular, multipolar and irregular neurons. Piriform and pyramidal cells predominated among projection neurons in the mesencephalon. Bilateral descending spinal pathways originate from the reticular nuclei of the rhombencephalon, nucleus vestibularis lateralis, nucl. anterodorsalis- and anteroventralis mesencephali, nucl. posterior thalami, nucl. ventralis hypothalami, area preoptica anterior and the striatum ventrale. Crossed pathways descend from the nucl. vestibularis descendens, nucl. tractus solitarii, nucl. cerebelli and the nucleus ruber. Uncrossed fibres originate from the nucl. tractus spinalis nervi trigemini, nucl. posteroventralis tegmenti, nucl. profundus mesencephali, nucl. fasciculi longitudinalis medialis and the nucleus ventrolateralis thalami. The organization of the frog's descending pathways is very similar to those in reptiles and in many ways to those in mammals. The possible synaptic connections of projection neurons have been discussed.

Animals↗