The slow-twitch soleus muscle (SOL) exhibits decreased twitch tension (cold depression) in response to a decreased temperature, whereas the fast-twitch extensor digitorum longus (EDL) muscle shows enhanced twitch tension (cold potentiation). On the other hand, the slow-twitch SOL muscle is more sensitive to twitch potentiation and contractures evoked by caffeine than the fast-twitch EDL muscle. In order to reveal the effects of these counteracting conditions
(temperature and caffeine), we have studied the combined effects of temperature changes on the potentiation effects of caffeine in modulating muscle contractions and contractures in both muscles. Isolated muscles, bathed in a Tyrode solution containing 0.1-60 mM caffeine, were stimulated directly and isometric single twitches, fused tetanic
contractions and contractures were recorded at 35 °C and 20 °C. Our results showed that twitches and tetani of both SOL and EDL were potentiated and prolonged in the presence of 0.3-10 mM caffeine. Despite the cold depression, the extent of potentiation of the twitch tension by caffeine in the SOL muscle at 20 °C was by 10-15 % higher than that at 35 °C, while no significant difference was noted in the EDL muscle between both temperatures. Since the increase of twitch tension was significantly higher than potentiation of tetani in both muscles, the twitch-tetanus ratio was enhanced. Higher concentrations of caffeine induced contractures in both muscles; the contracture threshold was, however, lower in the SOL than in the EDL muscle at both temperatures. Furthermore, the maximal tension was achieved at lower caffeine concentrations in the SOL muscle at both 35 °C and 20 °C compared to the EDL muscle. These effects of caffeine were rapidly and completely reversed in both muscles when the test solution was replaced by the Tyrode solution. The results have indicated that the potentiation effect of caffeine is both time- and temperature-dependent process that is more pronounced in the slow-twitch SOL than in the fast-twitch EDL muscles.
The dental pulp represents an easily acces-sible source of adult dental pulp stem cells (DPSCs). The preferred approach to DPSC isolation is enzymatic digestion. However, the duration of the enzymatic activity is crucial. The purpose of this study was to isolate the DPSC populations using this method, characterize their biological properties and proliferation capacity, and to determine their ability to differentiate into mature cells. Before enzymatic
digestion using 0.05% trypsin, we used the homogenization method in order to obtain a fine homogenate from the solid pulp tissue. The stem cells were cultivated in modified cultivation medium for mesenchymal adult progenitor cells containing 2% foetal bovine serum, growth factors and insulin-transferrin-
selenium supplement. We were successfully able to isolate 10 populations of DPSCs. The vitality of DPSCs did not drop below
90 %. However, the DPSCs showed a significant decrease in the relative telomere length number with increasing passaging (P < 0.05). Isolated DPSCs highly expressed the CD markers: CD29, CD44, CD90, CD13, CD73 and CD166. In contrast, CD markers CD31, CD106, CD34 and CD45 were negative or low positive. We confirmed the high osteogenic and chondrogenic potential of the isolated stem cells. Isolated DPSCs did not show signs of cell degeneration or spontaneous differentiation during the entire cultivation. In addition, we were able to shorten the enzyme activity duration, and we were the first to demonstrate trypsin as the enzyme used for the enzymatic digestion method with the viability over 90 % of isolated DPSCs using this method. and Corresponding author: Nela Pilbauerová
Muscle phenotype is determined by combined effects of intrinsic genetic and extrinsic factors like innervation, hormonal levels and mechanical factors or muscle activity. We have been studying the effect of altered thyroid hormone levels on the expression of myosin heavy chain (MyHC) isoforms in control and regenerating soleus and extensor
digitorum longus muscles of euthyroid, hypothyroid or hyperthyroid female inbred Lewis rats. The fiber type composition has been determined according to the mATPase activity and immunocytochemical staining of MyHC isoforms, the content of MyHC isoforms has been determined by SDS-PAGE, the mRNA levels have been measured by RT-PCR and the ultrastructural transformation has been analyzed by electron-microscopy. Our results indicate that although the innervation plays a decisive role in the determination of muscle phenotype, levels of thyroid hormones contribute to the extent of muscle phenotype transformation.
Úvod: Poškození kognitivních funkcí je jedním z neuropsychiatrických projevů systémového lupus erythematodes (SLE), podle literárních dat bývá asociováno se sekundárním antifosfolipidovým syndromem. Etiologie není zcela známa. Pacienti a metody: Pomocí dotazníku ?mini-mental state examination? (MMSE) jsme porovnali kognitivní status pacientů se SLE starších 45 let, u kterých jsme zjišťovali přítomnost antifosfolipidových protilátek. Výsledky: Pacienti s antifosfolipidovými protilátkami v porovnání s pacienty bez těchto protilátek vykazovali statisticky významně nižší bodové skóre v testu MMSE. Zároveň však nebyl rozdíl mezi skupinou pacientů, kteří splnili kritéria pro sekundární antifosfolipidový syndrom (APS), a těmi, u kterých byly detekovatelné pouze antifosfolipidové protilátky. Diskuse a závěr: Na možnost zhoršování kognitivních funkcí u pacientů se SLE a antifosfolipidovými protilátkami (nejen s APS) by mělo být pamatováno a cíleně po něm pátráno pomocí MMSE, které je schopno snížení kognitivních funkcí zachytit., Ľubica Cibičková, T. Soukup, E. Čermáková, and Lit. 26
Skeletal muscles of small rodents contain four main fiber types, namely type 1, 2A, 2X/D and 2B fibers containing myosin heavy chain (MyHC) 1, 2a, 2x/d and 2b isoforms. Each of these MyHC isoforms is the product of a distinct gene and their expression is believed to be primarily transcriptionally controlled. In most rat muscles, messenger RNA (mRNA) transcripts for MyHC1, 2a, 2x/d and 2b and their corresponding protein products were found with the exception of the soleus muscle, where typically only MyHC1 and 2a transcripts and protein isoforms were demonstrated under normal conditions. Here we show the expression of all four MyHC1, 2a, 2x/d and 2b mRNA transcripts in the soleus muscle under normal conditions in euthyroid, as well as in experimental hypothyroid and hyperthyroid (with the exception of 2b MyHC transcript) 7-month-old female inbred Lewis rats. This is not matched, however, by the appearance of corresponding four isoforms, as we have found that 2x/d and 2b protein isoforms are not present at levels detectable by SDS-PAGE. We also show that the chronic hypothyroid and hyperthyroid status affects the expression of MyHC isoforms both at the mRNA and protein levels.
Cardiac gap junctions have been implicated in maintaining intercellular electrical and metabolic couplings. The abnormalities in connexin-43 (Cx43) lead to conduction defects and contractile dysfunction. We have evaluated the expression and phoshorylation status of Cx43 in the left ventricular myocardium of male and female 16-month-old rats submitted to 14-week L-thyroxine (T4) treatment. Western blot analysis revealed the presence of fully or intermediately phosphorylated and unphosphorylated forms of Cx43. We have found no significant differences in Cx43 expression and phosphorylation between T4-treated and control untreated animals. However, expression of Cx43 was significantly higher in female compared to male rats. We conclude that T4 administration has no effect on Cx43 expression, but there are sex-dependent differences in Cx43 expression in the left ventricles between aging male and female rats.
To reveal the effect of foreign innervation and altered thyroid status on fiber type composition and the myosin heavy chain (MyHC) isoform expression in the rat slow soleus (SOL) and fast extensor digitorum longus (EDL) muscles, a method of heterochronous isotransplantation was developed. In this experimental procedure, the SOL or EDL muscles of young inbred Lewis rats are grafted either into the host EDL or SOL muscles of adult rats of the same strain with normal or experimentally altered thyroid status. To estimate the extent of fiber type transitions in the transplanted muscles, the SOL and EDL muscle from the unoperated leg and unoperated muscles from the operated leg could be legitimately used as controls, but only when the experimental procedure itself does not affect these muscles. To verify this assumption, we have compared the fiber type composition and the MyHC isoform content of unoperated contralateral SOL and EDL muscles and ipsilateral unoperated SOL muscle of experimental rats after unilateral isotransplantation into the host EDL muscle with corresponding muscles of the naive rats of the same age and strain. We provide compelling evidence that the unilateral heterochronous isotransplantation has no significant effect on the fiber type composition and the MyHC isoform content of unoperated muscles of experimental animals. Hence, these muscles can be used as controls in our grafting experiments.