Biomedical subjects
Publications and source records attributed to J Linhart.
The regular position of spindle poles in bi- and multipolar cell divisions is interpreted as the result of expanding caps on the surface of cell nuclei first proposed by Mazia in 1986. In a computer model it is shown that expanding caps position their centers with the maximal distance between them, which is in complete accordance with findings in experimentally influenced cell divisions in which multiple poles are formed.
Procaine-treated eggs can be penetrated by more than one spermatozoon. Supernumerary male pronuclei can fuse with the female one giving raise to multipolar spindles or remain isolated within the egg's cytoplasm forming their own spindle. In all types of multiple mitotic figures (asters and spindles) the distribution of asters is equidistant either uniplanar or at maximum distance like at the apices of a polyhedron. Astral rays are not different from spindle fibers: they can attach to and attract chromosomes of "foreign" mitotic figures. When several mitotic figures are present in one egg, the partner asters are always of the same size, and microtubules of one aster never interdigitate with those of others. The hypothesis that positioning of centrosomes is brought about by spreading of a centrosome organizer in the form of an expanding calotte on the surface of the nucleus (Mazia, D., Int. Rev. Cytol. 100, 49-92 (1987)) is supported by a computer model.
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The changes in blood flow through selected brain structures and the changes in the total RNA content of cells of these structures were examined after a single administration of yeast RNA to 6-month-old male rats. The total content of ribosomal RNA in cells of the limbic system (septum, hippocampus, hypothalamus) increased 48 hrs after the administration of 100 mg i.p. yeast RNA , dropped after 7 days (in hypothalamus), 21 and 30 days (in hippocampus), 30 days (in septum). In cells of the limbic system as a whole there is a higher total RNA content in experimental rats. No changes were observed in the cells of parietal brain cortex. Blood flow increased in limbic structures 21 and 30 days after RNA administration and in septum and in hippocampus also 90 days after application. No changes were observed in parietal brain cortex, bulbi olfactorii, cerebellum and brain stem. Histochemical changes correlated positively with blood flow changes in the limbic system 14, 21, 30 and 90 days after RNA application. The body weight of experimental rats did not differ from that of control animals. The changes in haemodynamic parameters were transient and were demonstrated as fluctuations in heart rate, cardiac output, and peripheral resistance. Blood pressure experienced no changes.
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The study was aimed at evaluating the effect of pyridinolcarbamate in patients with atherosclerosis obliterans of the lower limbs. A single intravenous administration of the drug did not induce changes in resting blood flow, but elicited a significant decline in capillary filtration rate. In a double-blind cross-over trial patients reported a significant prolongation of walking distance after 6 months of pyridinolcarbamate treatment. Sensation of cold in the lower limbs was not affected. Pyridinolcarbamate did not influence peak values of blood flow through the calf but they appeared significantly earlier. No significant changes were seen at the evaluation of the elevation and dependency test and performance using tiptoeing test. Likewise the findings of systolic pressure in the lower limbs, pulse wave morphology, and claudication distance on treadmill did not confirm a therapeutic effect of pyridinolcarbamate.
Three weeks of ischemia of the right hind limb in rat produced by ligature and severing of the right common iliac artery, resulted in changes in FFA transport and blood flow in the regenerating tibialis muscle. FFA transport was measured using i.v. administered palmitate-1-14C bound to albumin. Uptake of palmitate-1-14C or 86Rb 90 s after i.v. administration was decreased in ischemic tibialis muscle, whereas no apparent effect of ischemia on the contralateral muscle was seen. Plasma FFA outflow rate measured according Beker and Rostami was not affected by the presence of an ischemic extremity in comparison with control animals. The plasma FFA inflow rate into the ischemic muscle was markedly decreased to values of 6.5 mmumoles FFA/min/g whereas in control animals values were 18.8 mmumoles FFA/min/g wet tissue. Decreased FFA inflow rate to the ischemic tibialis muscle was due to the decreased radioactivity of palmitate-1-14C in the muscle under the conditions of a constant plasma FFA pool. Differences in the uptake of palmitate-1-14C in tibialis muscle were dependent upon the muscle blood flow, which was markedly decreased in the ischemic muscle on indirect measurement with 86Rb or with the 133Xe clearance.
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The effect of the anabolic hormone 19-nortestosterone propionate (Superanabolon Spofa) on the metabolism of chronically ischaemic striated muscle (anterior tibial m.) was studied in a described model in the rat. Metabolic changes were estimated in terms of the activities of a number of enzymes in muscle fibres. Enzyme activities (AcP, ATPase, CE, LDH, MDH) were determined both biochemically and histochemically excepting SDH, which was determined only by the histochemical way. Morphological changes were investigated by routine histology. Administration of 19-nortestosterone propionate prevented enzymatic changes which are typical for chronic ischaemia, primarily the decrease in the activities of dehydrogenases of Krebs' cycle tricarboxylic acides (MDH, SDH). In addition, the ratio of red to white muscle fibres increased. Administration of anabolic hormone has a similar favourable action on ischaemic muscle as training, studied previously.