Acta biologica Academiae Scientiarum Hungaricae最新文献

The neurotoxic action of the fungicide Tinestan 60 WP (containing 60% triphenyltin acetate) was examined in male rats. Due to daily doses as small doses as 6 and 0.6 mg/kg daily administered over six weeks the exploratory activity in maze was diminished, the animals made significantly more errors. There was no difference between the poisoned and the control groups in the speed of acquisition of the conditioned avoidance responses, however the extinction was significantly slower, as a sign of slower development of active inhibition. Tested in stress situation the behaviour of poisoned animals altered, as a sign of decreased habituation. It is concluded that Tinestan crosses the blood-brain barrier, and induces diminished plasticity of the CNS.

Goal-directed movements, such as punching and pointing, need preprogramming of postural support and visual control. These processes are recorded in man by EEG, EMG, oculogram, and a platform. The earliest cerebral correlate of voluntary action is the Bereitschaftspotential (readiness potential) or, after a trigger signal, the expectancy wave (CNV). These bilateral negative potential shifts increase to a Zielbewegungspotential (aiming potential) when a goal-directed movement is made, and end with a positive shift, when the goal is reached. During these cerebral potentials an attentive eye saccade is directed towards the target and an ordered sequence of bilateral muscle activations follows. This coordinated motor activity in trunk and leg muscles corresponds to a readiness innervation that prepares body posture and balance. It precedes the final aimed movement of the arm towards the target and postural adjustments such as the compensation of body and head rotation by the vestibular-ocular reflex. The temporal order of the cerebral, oculomotor and muscular events is schematized for punching and pointing movements in a figure. The limits of conscious control and the necessity of automatized learning for voluntary skilled movement under visual control are discussed. Some speculations are made about a possible origin of slow potential shifts by surface negative dipoles in columnar modules of the parasagittal cortex during the programming and monitoring of aimed motion.

The effect of the salts NaCl, KCl, CsCl, NH4Cl, NaBr, CH3COONa, NaNO3 and Na2CO3 on the alpha-amylase activity of dialysed and nondialysed human granulocyte extracts was measured. The optimum activity was found at the 0.02 M salt concentrations. The highest enzyme activity was found with NaCl, CsCl, NH4Cl and KCl. The apoamylase was successfully reactivated with the cations Ca2+, Ba2+, Mn2+, while reactivations with Co2+, Ni2+, Mg2+ are below the limits of significance.

Double retrograde tracer experiments (HRP, 3H-apo-HRP) were performed to investigate the organization of thalamic neurons projecting to visual cortical areas. The distribution of labelled cells was in agreement with previous findings, showing a topographical and overlapping pattern of these thalamocortical projections. If a restricted thalamic region in the lateralis posterior-pulvinar complex projected into more than one cortical area, the projection neurons to each individual area were intermingled. However, each neuron projected only into one area and there was no anatomical evidence for the presence of neurons projecting to more than one cortical area.

Marr-Albus model of the cerebellum is based on the assumption that parallel fiber-Purkinje cell synapses are plastically modifiable under influences of conjunctive activation of a climbing fiber and a mossy fiber on the same Purkinje cell. This article introduces a positive support for this assumption derived from the recent experiment by Ito. Sakurai and Tongroach on rabbit flocculus. Possible reasons why the experimental verification of Marr-Albus' assumption has been so difficult are considered, and applicability of Marr-Albus model of the cerebellum to problems of motor learning is discussed.

Luteinizing hormone releasing hormone (LHRH) and somatostatin content of the two halves of the median eminence of the rat hypothalamus were determined by radioimmunoassay three weeks after following deafferentations: (1) unilateral knife cut in front of, laterally and above the preoptic area (preoptic deafferentation); (2) unilateral arched cut at the midlevel of the suprachiasmatic region (suprachiasmatic deafferentation); (3) unilateral arched cut behind the optic chiasm (retrochiasmatic deafferentation); (4) cutting around the medial basal hypothalamus on one side starting with the cut at the posterior level of the optic chiasm (complete deafferentation). Preoptic deafferentation caused a more than 50% decrease in the LHRH content of the ipsilateral half of the median eminence. The reduction in LHRH was even greater (about 70%) in rats with suprachiasmatic deafferentation and only about 15% of the neurohormone was found in the ipsilateral half of the median eminence after unilateral retrochiasmatic or complete deafferentation. The median eminence somatostatin showed practically no change after unilateral preoptic deafferentation, while it was reduced by about 50, 60 and 80% in the ipsilateral half median eminence after a unilateral suprachiasmatic, retrochiasmatic and complete deafferentation, respectively. The results are consistent with the assumption that the majority of the LHRH perikarya projecting to the median eminence are located partly in the preoptic-anterior hypothalamic area and partly in brain regions in front of or above this area. Most of the somatostatin perikarya with terminals in the median eminence are in the preoptic-anterior hypothalamic region.

Light and electron microscopic studies were made on the receptor cells in the sole of the snail Helix pomatia. The cell bodies of the primary receptor cells, which can frequently be found in columnar or ganglion-like groups are situated at different depths below the basal lamina. The perikarya of the sensory cells usually measure 12 micrometers by 8 micrometers. Their nuclei are usually invaginated and contain large amounts of marginal heterochromatic substance. The nucleus usually measures 8 micrometers by 6 micrometers. The cytoplasm contains a well-developed Golgi apparatus consisting of several stacked lamellae surrounded by clear and dense-core vesicle. There are differences between cells in the amount of smooth and rough endoplasmic reticulum, in the free ribosomes and in other cytoplasmic elements. The axonal processes of the sensory cells are generally thin and connected to the subepithelial plexus. There are axonic swellings containing a mixed vesicle population, some of them near the muscle cell processes. We failed to find typical axo-axonic synaptic connections in the subepithelial nerve plexus as well as in motor connections within the muscle cell processes. On the basis of the ultrastructural features of the vesicles and other organelles we failed to classify different types of sensory cells. The ultrastructural difference between sensory cell bodies may be explained with a presumptive differentiation process.

Beta-adrenergic antagonist L-alprenolol was labelled for radioactivity and UV fluorescence, and the binding to intact cultured chicken brain cells under equilibrium conditions, as the model of the experiments in vivo, was probed. The application of fluorescent label did not explore any cell type or cell particle with enhanced binding. The analysis of the radiolabelled alprenolol-binding revealed a non-specific accumulation on the surface of these cells, which was inhibited by unlabelled alprenolol excess, however, this is the peculiarity of the specific binding. Our results emphasize that for the characterization of membrane receptors of intact cells, the accurate separation of specific and non-specific binding is required. The application of a ligand concentration as low as possible and a very effective washing procedure for the removal of the unbound (and the bulk of the nonspecifically bound) label is recommended.

The toxicity and mutagenicity of 1,2,4,5-tetrachlorobenzene (TCB), 1,4,5-trichloro-2,6-nitrobenzene (TCNB), pentachloronitrobenzene (PCNB), methyl-l-(butyl-carbamoyl)-2-benzimidazole carbamate (BENOMYL) fungicides and dimethy-2,3,5,6-tetrachloro-terephthalate (DCPA) herbicide were studied. The test compounds were administered by larval feeding. Benomyl was found to be the most toxic compound, its LC50 value was 0.24 mM. DCPA had no toxic effect in the 0.1--10 mM concentration range. The sex-linked recessive lethal was used for detection of genetic end point. No significant increase in mutation frequency was observed after the larvae had been fed on media containing pesticides under the LC50 concentration.