A Relationship Between Fluctuations in Heart Rate and The Duration of Subsequent Episodes of Atrial Fibrillation

A relationship between autonomic tone and the onset of paroxysmal atrial fibrillation in some patients is recognised Episodes of PAF may vary enormously in duration, however, from a few beats to many hours. Whether autonomic tone influences the duration of ihe episodes has been less well investigated.
From a database of Holter recording taken from patients with symptomatic PAF, we identified all episodes of at least 30 seconds duration which were preceded by noise free sinus rhythm. This study examined the heart rate prior to AF onset, the change in heart rate over the final minute of sinus rhythm and the time of AF onset, and compared the data from those episodes of AF of more than 5 minutes duration to the shorter ones. Heart rate was slower before long episodes of AF, but this was found to predominantly represent data from separate recordings. A highly significant rise in heart rate was detected prior to long AF episodes compared to shorter ones. Daytime AF episodes were slightly longer than nocturnal ones.
The most important finding was that longer AF episodes were typified by a heart rate acceleration. This suggests that, regardless of underlying aetiology, and increase in sympathetic tone may be important in the sustenance of episodes of PAF.     

Caveolin-3 in muscular dystrophy

The dystrophin-glycoprotein complex (DGC) serves as a link between cytoplasmic actin, the membrane and the extracellular matrix of striated muscle. Genetic defects in genes encoding a subset of DGC proteins result in muscular dystrophy and a secondary decrease in other DGC proteins. Caveolae are dynamic structures that have been implicated in a number of functions including endocytosis, potocytosis and signal transduction. Caveolin (VIP-21) is thought to play a structural role in the formation of non-clathrin-coated vesicles in a number of different cell types. Caveolin-3, or M-caveolin, was identified as a muscle- specific form of the caveolin family. We show that caveolin-3 co- purifies with dystrophin, and that a fraction of caveolin-3 is a dystrophin-associated protein. We isolated the gene for human caveolin- 3 and mapped it to chromosome 3p25. We determined the genomic organization of human caveolin-3 and devised a screening strategy to look for mutations in caveolin-3 in patients with muscular dystrophy. Of 82 patients screened, two nucleotide changes were found that resulted in amino acid substitutions (G55S and C71W); these changes were not seen in a control population. The amino acid changes map to a functionally important domain in caveolin-3, suggesting that these are not benign polymorphisms and instead are disease-causing mutations.      

Is there a relationship between antipsychotic blood levels and their clinical efficacy? An analysis of studies design and methodology

Summary— There are now more than 50 studies concerning neuroleptic blood levels and clinical outcome relationships. Haloperidol, the most studied, is the only antipsychotic permitting some conclusions. A number of authors suggest that the striking lack of agreement between different studies results from heterogeneity of their quality. Here, we have used a scoring system for assessing the quality of those studies. According to this system, none (0/14) of the studies having a score <0.60 was able to show a therapeutic window, as compared to 53% (10/19) of those having a score ≥0.60 (p = 0.002, Fisher exact test). Also, the studies able to identify the presence of a therapeutic window during haloperidol treatment were those having sample sizes >20 ( p = 0.06) and those whose patients were treated with fixed doses ( p = 0.02). The diagnosis of schizophrenia in the studies seems not to be an exclusive condition, as compared with those also including schizophreniform and schizoaffective disorders (p = 0.12). Our qualitative analysis of haloperidol blood level publications seem to indicate that an upper limit may exist for haloperidol efficacy; values above this limit seem not to provide any supplementary clinical improvement and may even reduce therapeutic effect.     

Thresholds for detection of a target against a background grating suggest visual dysfunction in migraine with aura but not migraine without aura

Square-wave gratings with particular spatial characteristics in visual illusions. Patients with migraine are particularly susceptible to these illusions and report disc. it. Their discomfort tends to be greater when the gratings are illuminated by red light, a tendency 1 known by controls. Gratings that induce illusions have been found to impair the recognition of opt superimposed targets in headache-free control subjects. We measured the impairment of target detection under illuminants of various chromaticities in migraineurs with and without aura and in mat controls. Migraineurs with aura had significantly higher thresholds for target detection than either migraineurs without aura or controls; in addition, the effect of chromaticity was slightly more pronounced in both migraine groups than in the control group. These findings are consistent with a recent suggestion that migraine with aura might give rise to subclinical damage to the primary visual cortex.