Ageing is associated with a decrease in the number of sarcolemmal ATP-sensitive K+ channels in a gender-dependent manner

The opening of sarcolemmal K(ATP) channels is considered to be an important endogenous cardioprotective mechanism. On the other hand, age-dependent changes in the myocardial susceptibility to ischemia and hypoxia have been observed in different species, including humans. Here, we have hypothesized that aging might be associated with the changes in sarcolemmal K(ATP) channels. Therefore, the main objective of the present study was to establish whether aging changes expression of cardiac sarcolemmal ATP-sensitive K+ (K(ATP)) channels. RT-PCR using primers specific for K(ATP) channel subunits, Kir6.2, Kir6.1 and SUR2A subunits was performed using total RNA from guinea-pig ventricular tissue. Whole cell electrophysiology was done on isolated guinea-pig ventricular cardiomyocytes. Western blotting using anti-Kir6.2 and anti-SUR2A antibodies was performed on cardiac membrane fraction. Tissue and cells were harvested from young and old, male and female guinea-pigs. RT-PCR analysis did not reveal significant age-related changes in levels of Kir6.1 or Kir6.2 mRNAs. However, levels of SUR2A were significantly lower in old than in young females. Such age-differences were not observed with cardiac tissue from male animals. In both old and young males, pinacidil (100 microM) induced outward currents. The difference between current density of pinacidil-sensitive component in females, but not males, was statistically significant. Western blotting analysis revealed higher levels of Kir6.2 and SUR2A proteins in cardiac membrane fraction from young than old females. The present study demonstrates that in females, but not males, aging is associated with decrease in number of cardiac K(ATP) channels which is due to decrease in levels of the SUR2A subunit.     

Toxoplasmosis--morphologic diagnosis options for the ever topical disease

It has been estimated that 60 percent of people in Croatia will be infected with Toxoplasma gondii until the age of 40. The infection is most frequently asymptomatic, or presented with an lymphadenitis, acute infection during pregnancy that can cause serious damage to the fetus in 10-30 percent, depending on the gestation phase. After acute infection Toxoplasma gondii resides in the body for life, being controlled by cellular immunity. In case of the immune system compromise, reactivation of the infection and serious inflammatory changes, mostly in the central nervous system, occur. Prenatal infection and serious clinical picture in immunocompromised patients classify toxoplasmosis among ever topical infections, thus all research toward better understanding of its pathogenesis in immunocompetent patients is of utmost importance. The aim of the study was to systematically analyze the morphology and changes in cytologic smears of lymph nodes from patients acutely infected with Toxoplasma gondii, and to morphologically visualize Toxoplasma gondii in the lymph nodes by use of specific monoclonal antibodies. For this purpose, 30 aspirates of lymph nodes of patients who had definite serologic evidence for and clinical picture of acute toxoplasma infection were analyzed by use of classic cytology and immunocytochemistry methods. Results confirmed a recognizable cytologic picture of reactive hyperplasia of follicular center cells and granulomatous inflammation, with a unique finding of Toxoplasma gondii tachyzoite in lymphatic cells.     

Sarcolemmal K(ATP) channels in ageing

This review highlights some recent research addressing sarcolemmal K(ATP) channels in ageing. These channels are abundant in cardiac myocytes where they are essential in coupling the cellular metabolic state with membrane excitability. The opening of sarcolemmal ATP-sensitive K+ (K(ATP)) channels occurs during ischaemia and protect the heart against injury. Age-dependent changes in the myocardial susceptibility to ischemia have been observed in different species, including humans. Recent research has demonstrated that ageing is associated with decrease in numbers of sarcolemmal K(ATP) in hearts from females, but not males. This phenomenon seems to be associated with age-dependent decrease in concentration of circulating estrogens. In the heart, SUR2A, a regulatory subunit of K(ATP) channels, is present in excess over Kir6.2, a pore-forming K(ATP) channel subunit. The consequence of this is that SUR2A is a subunit that controls the number of sarcolemmal K(ATP) channels. Estrogens specifically up-regulate SUR2A and, thereby, control the number of sarcolemmal K(ATP) channels. Age-dependent loss of sarcolemmal K(ATP) channels creates a cardiac phenotype more sensitive to ischaemia, which may explain, at least in part, an ageing-associated decrease of myocardial tolerance to stress that occurs in elderly women.     

Plunging ranula

Saliva extravasation from the sublingual gland causes ductal lesion or obstruction and results in the formation of a ranula. It spreads through or behind the mylohyoid muscle situated on the neck. Most frequently it is located in the submandibular or submental region. The diagnosis of plunging ranula is simple if the signs of ranula are present in the intraoral cavity, whereas in case of a ranula localized on the neck definite diagnosis is made by histologic analysis of the pseudocyst that has been surgically excised in toto. Cases are presented of both types of plunging ranula treated by various surgical approaches. Plunging ranula in the submental region was treated by transoral approach, marsupialization and aspiration of the content, whereas the ranula in the submandibular region was treated by exterior cervical approach. In both cases, sublingual gland was removed. During the 3.5-year follow-up, neither recurrence of the disease in the neck area nor the occurrence of simple ranula in the intraoral region was observed.     

A point mutation in the 5' splice site of the dystrophin gene first intron responsible for X-linked dilated cardiomyopathy

X-linked dilated cardiomyopathy (XLDC) is a familial heart disease presenting in young males as a rapidly progressive congestive heart failure, without clinical signs of skeletal myopathy. This condition has recently been linked to the dystrophin gene in some families and deletions encompassing the genomic region coding for the first muscle exon have been detected. In order to identify the defect responsible for this disease at the molecular level and to understand the reasons for the selective heart involvement, a family with a severe form of XLDC was studied. In the affected members, no deletions of the dystrophin gene were observed. Analysis of the muscle promoter, first exon and intron regions revealed the presence of a single point mutation at the first exon-intron boundary, inactivating the universally conserved 5' splice site consensus sequence of the first intron. This mutation introduced a new restriction site for MseI, which cosegregates with the disease in the analyzed family. Expression of the major dystrophin mRNA isoforms (from the muscle-, brain- and Purkinje cell-promoters) was completely abolished in the myocardium, while the brain- and Purkinje cell- (but not the muscle-) isoforms were detectable in the skeletal muscle. Immunocytochemical studies with anti- dystrophin antibodies showed that the protein was reduced in quantity but normally distributed in the skeletal muscle, while it was undetectable in the cardiac muscle. These findings indicate that expression of the muscle dystrophin isoform is critical for myocardial function and suggest that selective heart involvement in dystrophin- linked dilated cardiomyopathy is related to the absence, in the heart, of a compensatory expression of dystrophin from alternative promoters.      

Comparison of signaling pathways involved in apoptosis of a thymocyte hybridoma triggered by a rat thymic medullary epithelial cell line, dexamethasone or T-cell receptor cross-linking

Using an in vitro co-culture assay we found that a rat medullary thymic epithelial cell (TEC) line (TE-R2.5) induces apoptosis of the BWRT8 thymocyte hybridoma (TH) (CD4(hi)CD8(low) alphabetaTCR(hi)). TH apoptosis induced by this TEC line was predominantly mediated by direct cell-cell contacts and was potentiated by cross-linking of the T cell receptor (TCR) by R73 monoclonal antibody (mAb). Dexamethasone (Dx) also triggered TH apoptosis but inhibited death of these cells induced by TE-R2.5 cells or immobilized R73 mAb. The TEC-induced apoptosis was independent of the LFA-1/ICAM-1 interaction but partly depended on a novel 29 kDa molecule expressed on TE-R2.5 cells. All three types of TH apoptosis were followed by the cleavage of poly-(ADP-ribose)-polymerase and were blocked by a caspase inhibitor Z-Val-Ala-Asp(OMe)-CH(2)F.PKC stimulation by phorbol myristate acetate interfered with the TH apoptosis induced by TE-R2.5 and Dx, but did not modulate the effect of R73 mAb. On the contrary, inhibition of calcineurin with cyclosporine A did not influence the apoptosis induced by TE-R2.5 and Dx, but completely prevented the R73-triggered TH cell death. The TE-R2.5-mediated BWRT8 apoptosis was suppressed by Na-orthovanadate, an inhibitor of protein tyrosine phosphatases (PTP) as well as by genistein, a protein tyrosine kinase (PTK) inhibitor, while both compounds potentiated the effect of Dx. Blocking PTP, but not PTK decreased the proapoptotic effect of R73 mAb. These results, including those using a BWRT8 subclone (BWRT8-MDP.2) which is resistant to TCR-triggered apoptosis, but sensitive to apoptosis stimulated by TE-R2.5 and Dx, indicate that TE-R2.5-induced TH apoptosis in our model is different from apoptosis in other TEC co-culture models, published so far.