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.     

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.     

Strain differences in peritoneal macrophage activity and susceptibility to experimental allergic encephalomyelitis induction in rats

The objective of the present study was to investigate the relevance of peripheral macrophage activity for the susceptibility to the induction of experimental allergic encephalomyelitis (EAE). Rats of EAE-susceptible Dark Agouti and EAEresistant Albino Oxford strain were immunized with guinea pig spinal cord homogenate (DA_GPSC and AO_GPSC), while non-immunized rats served as controls (DA_NIM, AO_NIM). On day 15 after immunization rats were sacrificed and their peritoneal macrophages tested for adherence capacity, zymosan phagocytosis and respiratory burst. Macrophages from AONIM rats exhibited lower adherence capacity and higher phagocytosis and H₂O₂ production when compared to macrophages from DANIM rats. Immunization with GPSC decreased adherence and phagocytosis and increased H₂O₂ production in macrophages from AO rats, but did not influence these activities in macrophages from DA rats. The results from the present study suggest that inflammatory activities of macrophages from AO rats could be considered as regulatory mechanisms connected with the resistance to EAE induction.     

Horizontal vestibular nystagmus. I. Identification of medial vestibular neurones

1. The properities of inputs from the horizontal semi-circular canal to neurones of the medial vestibular nucleus have been studied intracellularly in the unanaesthetized encéphale isolé cat. 2. Secondary neurones of the bestibulo-abducens reflex arc were identified by their orthodromic response to labyrinthine stimulation and by antidromic excitation from the contralateral abducens nucleus. 3. The responses of medial vestibular cells receiving only labyrinthine in puts are also described. These were seen to be predominantly excitatory though IPSPs were observed in a few cases. 4. Identified vestibular neurones were intracellularly injected with procion yellow and showed different morphological characteristics correlated with function.     

Low levels of immunoglobulin A in children with intrinsic asthma: a possible protection against atopy

Immunoglobulin A and G (IgA, IgG) serum concentrations were detected in children with nonallergic/intrinsic (36 children) or allergic/extrinsic asthma (43 children) and in age-matching control children (40 children). Asthmatic children with allergic asthma had lower IgA (1.36+/-0.54 g/L) and higher IgG (10.48+/-2.77 g/L) levels than the age-matching control children group (1.63+/-0.69 vs. 9.01+/-2.32 g/L). Children with nonallergic/intrinsic asthma had lower IgA (1.03+/-0.41 g/L) ( p = 0.004) and IgG (8.38+/-1.93 g/L) (p = 0.001) levels than the allergic/extrinsic asthma group (1.36+/-0.54 vs. 10.48+/-2.77 g/L). Low IgA levels were found in children with nonallergic/intrinsic asthma and high IgG levels were found in those children with allergic/extrinsic childhood asthma. The hypothesis is that the increased incidence of asthma in the population may be caused by a decrease in childhood infections (hygiene hypothesis). Frequent infections in early life boost the immune system, stimulating Th1-type response in young children and reducing the risk of atopic diseases. Our hypothesis is that low IgA (and/or IgG) levels in our patients might be responsible for infection development among those children with nonallergic/intrinsic asthma. These infections stimulate the normal development of immune system in young children, reducing risk of atopy, so that those children do not get allergic/extrinsic childhood asthma. Intrinsic childhood asthma=nonallergic (nonatopic) childhood asthma. Extrinsic childhood asthma=allergic (atopic) childhood asthma.     

Determination of mandelic acid enantiomers in urine by gas chromatography and electron-capture or flame ionisation detection

A sensitive and stereospecific GC method was developed for the analysis of R- and S-enantiomers of mandelic acid (MA) in urine, using a chiral CP Chirasil-Dex-CB column. The enantiomers of MA were derivatised with isopropanol into their corresponding isopropyl esters and determined either directly with flame ionisation detection (FID) or after subsequent derivatisation of a hydroxy group with pentafluoropropionic anhydride with electron-capture detection (ECD). Both derivatisation steps proceeded with negligible inversion of enantiomers (<1%). The limit of detection of the FID determination was 8 and 5 mg/l for R-MA and S-MA, respectively and of the ECD determination 1 mg/l for both enantiomers. Repeatability (within-day precision) and reproducibility (day-to-day precision) was for both enantiomers below 7.5% for the FID and below 5.8% for the ECD analysis. The method was applied to urine of volunteers exposed to 105 and 420 mg styrene/m3 air. In the urine of the exposed volunteers, the S-enantiomer showed higher excretion compared to that of the R-enantiomer, with marked interindividual differences in excretion of both enantiomers.