Mechanism of generation of body surface electrocardiographic P-waves in normal, middle, and lower sinus rhythms.

We used comprehensive electrophysiological/anatomical digital computer models of atrial excitation and the human torso to study the mechanisms of generation of body surface P-waves in normal sinus rhythm, and in middle and lower sinus rhythm. Simulated atrial surface isochrone maps for normal sinus rhythm support the validity of the atrial excitation model. The results suggest that the presence of specialized internodal tracts containing fast-conducting fibers is not essential to account for propagation of excitation in apparent preferential directions from the sinoatrial (SA) node to the atrioventricular node. However, in the absence of fast conducting fibers, a slowly conducting segment in the intercaval region is necessary to achieve proper excitation of the interatrial septum. P-wave notches occur in the absence of specialized fast conducting atrial tracts and anisotropies due to fiber orientation. These notches are due to the atrial geometry and the separate contributions of the right atrium, left atrium, and interatrial septum to the P-waves, and become more pronounced as the pacemaker site shifts downward in the SA node. Thus, slight changes in the origin of excitation, which result in subtle changes in the atrial excitation isochrones, produce significant and complex changes in the simulated body surface P-waves.</jats:p

Clinically-Orientated Anatomy: Five exemplars to portray the concept

It has become almost a truism that, as for many biomedical sciences courses, gross anatomy tuition for healthcare curricula (including medicine and dentistry) should be integrated with clinical components to improve vocational relevance. Nevertheless, many fundamental questions remain to be answered relating to the content to be taught, who teaches the discipline, how the students react, and whether the students are prepared to integrate the clinical and biomedical components. We additionally need evidence of how the delivery of clinical content is influenced by technical developments such as medical imaging. This article documents some examples, or case scenarios, showing how interactions between professional anatomists and clinicians can be fostered, as well as providing illustrations of different teaching styles. From a review of the literature, as well as from our own experiences, we conclude that, for many branches of medicine, it is essential to have access to human bodies for both anatomical and clinical education and training and that postgraduate anatomical teaching remains important for a variety of specialities. We therefore support the notion that a close relationship between professional anatomists and surgeons can reinforce core anatomical knowledge by deepening the understanding of its clinical importance. Paradoxically, however, there is evidence that medical students do not believe that the teachers of anatomy should necessarily be clinically qualified. Furthermore, while students appreciate the value of using clinical examples, scenarios or case histories in anatomy teaching, they remain ambivalent about their use in assessments or examinations. This article also emphasises that anatomy is important both as a scientific and a clinical, translational discipline and argues that the discipline is crucial for appreciation of the human body, not just in disease, but also in health

Methylmercury inhibits prolactin release in a cell line of pituitary origin

Heavy metals, such as methylmercury, are key environmental pollutants that easily reach human beings by bioaccumulation through the food chain. Several reports have demonstrated that endocrine organs, and especially the pituitary gland, are potential targets for mercury accumulation; however, the effects on the regulation of hormonal release are unclear. It has been suggested that serum prolactin could represent a biomarker of heavy metal exposure. The aim of this study was to evaluate the effect of methylmercury on prolactin release and the role of the nitrergic system using prolactin secretory cells (the mammosomatotroph cell line, GH3B6). Exposure to methylmercury (0-100 μM) was cytotoxic in a time- and concentration-dependent manner, with an LC50 higher than described for cells of neuronal origin, suggesting GH3B6 cells have a relative resistance. Methylmercury (at exposures as low as 1 μM for 2 h) also decreased prolactin release. Interestingly, inhibition of nitric oxide synthase by N-nitro-L-arginine completely prevented the decrease in prolactin release without acute neurotoxic effects of methylmercury. These data indicate that the decrease in prolactin production occurs via activation of the nitrergic system and is an early effect of methylmercury in cells of pituitary origin

Analisi di clorodibenzodiossine e clorodibenzofurani in matrici ambientali

Consiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7, Rome / CNR - Consiglio Nazionale delle RichercheSIGLEITItal