Analysis of Morphological and Morphometric Changes in a Parenchymal Tissue after the Radiofrequency Ablation Procedure.

Background and Objectives: Prostate cancer is on the rise in the European Union, and radiofrequency ablation (RFA) is one of the minimally invasive treatment options used for its treatment. Therefore, the aim of this study was to investigate and analyze the effects of RFA on prostate tissues. Materials and Methods: A standard prostate RFA procedure was performed on 13 non-purebred dogs in three sessions: no cooling (NC), cooling with a 0.1% NaCl solution (C.01), and cooling using a 0.9% NaCl solution (C.09). Microtome-cut 2-3 µm sections of prostate samples were stained with hematoxylin and eosin and further examined. Results: A histopathologic evaluation identified four zones of exposure: direct, application, necrosis, and transitional, as the damage on tissues decreased going further from the ablation site. The areas and perimeters of these zones were calculated, and geometric shapes of ablative lesions were evaluated using the quotient formula. Areas and perimeters of prostate tissue lesions in the NC and C.09 sessions were of similar size, whereas those found in C.01 were statistically significantly smaller. Lesions observed in session C.01 were of the most regular geometric shape, while the most irregular ones were found in session C.09. The shapes of lesions closest to the ablation electrode were the most irregular, becoming more regular the further away from the electrode they were. Conclusions: Prostate RFA leads to tissue damage with distinct morphological zones. Notably, the prostate lesions were the smallest and the most regular in shape after RFA procedures using the 0.1% NaCl cooling solution. It can be argued that smaller ablation sites may result in smaller scars, thus allowing for faster tissue healing if the blood flow and innervation at the ablation site are not compromised.

Nicotinic potentiation of frog retinotectal transmission in tectum layer F by α3ß2, α4ß2, α2ß4, α6ß2, or α7 acetylcholine receptor subtypes.

OBJECTIVE: The aim of the study was to explore the effect of semi-specific antagonists and agonists of the nicotinic acetylcholine receptors on the paired-pulse facilitation and nicotinic tonic and phasic potentiation of the frog retinotectal synaptic transmission. MATERIALS AND METHODS: The experiments were performed in vivo on adult frogs, Rana temporaria. An individual retina ganglion cell (or its retinotectal fiber) was stimulated by current pulses delivered through multichannel stimulating electrode positioned on the retina. Responses to a discharge of a single retinal ganglion cell were recorded in the tectum by an extracellular carbon-fiber microelectrode positioned in the terminal arborization of the retinotectal fiber in the tectum layer F. The effect of the antagonists and agonists of the nicotinic acetylcholine receptors on the tectal responses has been tested. RESULTS: We found that the antagonists, MLA and DHßE, and agonists, RJR-2403 and choline, of the nicotinic acetylcholine receptors of the α3ß2, α4ß2, α2ß4, α6ß2 or α7 subtypes have had no effect on the phasic and tonic potentiation of the retinotectal transmission. The paired-pulse facilitation of the retinotectal transmission was not appreciably affected by the antagonists, but the choline, agonist of the α7 subtype receptor, has significantly decreased the paired-pulse facilitation. CONCLUSIONS: The tonic and phasic potentiation of the retinotectal transmission in the tectum layer F were not mediated by the receptors of α3ß2, α4ß2, α2ß4, α6ß2 or α7 subtype. The results suggest that presynaptic nicotinic acetylcholine receptors of the frog optic fibers are different from those of the mammalian optic fibers.

The scientific heritage of Professor Aron Gutman (Commemorating the 10th anniversary of Aron Gutman's death).

Aron Gutman started his scientific research when he was a student of the Department of Physics and Mathematics, Vilnius University. At that time, he developed the theory of nonhomogenous vector relations between magnetic moments of electrons in an atom and applied it for explanation of energy spectrum of real atoms. Since 1960, he worked in Kaunas Medical Institute, and his main field of scientific interests was theoretical biophysics and electrophysiology of living tissues and cells. The earlier biophysical works of A. Gutman dealt with problems of the bioelectrical fields that underlie electroencephalogram, electrocorticogram, and electrocardiogram. The most important achievement was a theory of individual potential or postsynaptic field potential of synapses from individual axon (EEG quantum) and its role in shaping of electroencephalogram. In the later works (from 1971), he looked into properties and function of the individual nerve cells. He had created and developed the theory of nonlinear (bistable) dendrites and analyzed functional implications of such dendrites. In the last works, A. Gutman tried to relate the functioning of the nervous system at the cellular and system levels. He made efforts to find connection between the properties of individual neurones and principles (laws) of functioning of the nervous system. He had managed to relate dendritic bistability of neurones and Gelfand-Tsetlin principle of the functioning of the central nervous system (also known as the principle of minimal afferentiation). He explained some regularities in motor control by the dendritic bistability of motoneurones.