Flora des Etna

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Atmospheric Pressure and Onset of Episodes of Menière’s Disease - A Repeated Measures Study

BackgroundExternal changes of air pressure are transmitted to the middle and inner ear and may be used therapeutically in Menière’s disease, one of the most common vertigo disorders. We analyzed the possible relationship of atmospheric pressure and other meteorological parameters with the onset of MD vertigo episodes in order to determine whether atmospheric pressure changes play a role in the occurrence of MD episodes.MethodsPatients of a tertiary outpatient dizziness clinic diagnosed with MD were asked to keep a daily vertigo diary to document MD episodes (2004–2009). Local air pressure, absolute temperature and dew point temperature were acquired on an hourly basis. Change in meteorological parameters was conceptualized as the maximum difference in a 24 hour time frame preceding each day. Effects were estimated using additive mixed models with a random participant effect. We included lagged air parameters, age, sex, weekday and season in the model.ResultsA total of 56 persons (59% female) with mean age 54 years were included. Mean follow-up time was 267 days. Persons experienced on average 10.3 episodes during the observation period (median 8). Age and change in air pressure were significantly associated with vertigo onset risk (Odds Ratio = 0.979 and 1.010). We could not show an effect of sex, weekday, season, air temperature, and dew point temperature.ConclusionsChange in air pressure was significantly associated with onset of MD episodes, suggesting a potential triggering mechanism in the inner ear. MD patients may possibly use air pressure changes as an early warning system for vertigo attacks in the future.     

Methylation of either cytosine in the recognition sequence CGCG inhibits ThaI cleavage of DNA.

ThaI (CGCG) sites which overlap HhaI (GCGC) sites in phi X174 and pBR322 DNA were methylated in vitro with HhaI methylase and S-adenosylmethionine to yield CGmCG, mCGCG or mCGmCG (5-methylcytosine, mC). Methylation of either cytosine in the ThaI recognition sequence rendered the DNA resistant to ThaI cleavage. Rat pituitary cell genomic DNA was digested with ThaI or 2 other known methylation-sensitive enzymes, AvaI or XhoI. After electrophoresis and ethidium bromide straining of the DNA, all 3 enzymes showed the infrequent DNA cleavage characteristic of methylation-sensitive enzymes. Comparison of pituitary growth hormone (GH) genes bearing strain-specific degrees of methylation showed the less methylated gene to be more frequently cut by either AvaI or ThaI. ThaI resistant sites in GH genes were cleaved by ThaI after exposing cells to 5-azacytidine, an inhibitor of DNA methylation. We conclude that ThaI is a useful restriction enzyme for the analysis of mC at CGCG sequences in eukaryotic DNA.     

Specific accumulation of 17 alpha-hydroxyprogesterone in microsomal membranes during the process of cytochrome P-450(C-17)-catalysed androgen biosynthesis. A dynamic study of intermediate formation and turnover.

A complete dynamic analysis of cytochrome P-450(C-17)-catalysed androgen biosynthesis from a single dose of progesterone and 17 alpha-hydroxyprogesterone in a double-label double-substrate experiment was performed in order to elucidate the controversial intermediacy of 17 alpha-hydroxyprogesterone. Label distribution within the steroid fractions as well as in the membrane and buffer compartments yields direct evidence that the endogenously formed 17 alpha-hydroxyprogesterone (which is in an 'intermediate state') accumulates to a higher degree in microsomal membranes than does the exogenously added 17 alpha-hydroxyprogesterone (which is in a 'substrate state') under certain conditions. It is also demonstrated that endogenously formed 17 alpha-hydroxyprogesterone may partly leave the membrane compartment (in terms of a 'leakage' or 'overflow' phenomenon) and is then able to equilibrate with the pool of exogenously added 17 alpha-hydroxyprogesterone. Since only the label distribution in the membrane-associated (but not always in the aqueous) 17 alpha-hydroxyprogesterone pool corresponds to the label distribution in the androgen fraction, it is concluded that only the membrane-associated 17 alpha-hydroxyprogesterone pool is directly accessible to cytochrome P-450(C-17)-catalysed conversion into androgens.