Pathophysiological Mechanisms Underlying Vasovagal Syncope in Young Subjects

The occurrence of vasovagal fainting is common in young subjects, but the origin of the precipitating hemodynamic mechanisms involved remain a subject of considerable speculation. Vasovagal fainting is not a sudden onset phenomenon, early failure of vascular resistance responses occurs in faint-prone young subjects. The variability of hemodynamic responses during the actual faint is large, but the main mechanism operative during, is withdrawal of sympathetic outflow to blood vessels in skeletal muscle with impairment of ability to maintain vasomotor tone.     

Fetal and Neonatal Effects of Maternal Cocaine Use

Marijuana was the drug of the 1960s and heroin the drug of the 1970s. Cocaine was the popular drug of the 1980s, and cocaine's popularity appears to have continued into the 1990s. Cocaine use increased dramatically between 1974 and 1985. This article reviews the trends of cocaine use, fetal and maternal pharmacodynamics of cocaine, intrauterine effects of cocaine on the fetus, and the neonatal manifestations of cocaine exposure.     

Liver stem cells: when the going gets tough they get going

The ability of the liver to regenerate is widely acknowledged, and this is usually accomplished by the entry of normally proliferatively quiescent hepatocytes into the cell cycle. However, when hepatocyte regeneration is impaired, small bile ducts proliferate and invade into the adjacent hepatocyte parenchyma. In humans and experimental animals these ductal cells are referred to as oval cells, and their association with defective regeneration has led to the belief that they are the progeny of facultative stem cells. Oval cells are of great biological interest since they may represent a target population for hepatic carcinogens, and they may also be useful vehicles for ex vivo gene therapy for the correction of inborn errors of metabolism.
The ability of oval cells to differentiate into hepatocytes has been demonstrated unequivocally. However, this process only occurs when the regenerative capacity of hepatocytes is overwhelmed, and thus, unlike the intestinal epithelium, the liver is not behaving as a classical continually renewing stem cell-fed lineage.     

A method for simultaneous determination of plasma and erythrocyte antioxidant status. Evaluation of the antioxidant activity of vitamin E in healthy volunteers

1Since oxygen free radicals are directly involved in a variety of pathologies such as atherosclerosis, diabetes mellitus, inflammation and/or when a deficit of defences of the organism against radicals occurs, we developed a suitable and simple method to determine both the erythrocyte sensitivity to an oxidative stress and plasma antioxidant protective capacity. 2This test is based on the introduction at 37° C of a radical initiator, 2,2′-azobis (2-amidinopropane) dihydrochloride (AAPH), within an erythrocyte suspension leading to a membrane alteration and ultimately to haemolysis. The latter can be quantified by determining the lacticodeshydrogenase activity released in the medium. The erythrocyte sensitivity to haemolysis and the volume of plasma inhibiting 50% of the haemolysis were determined. 3Intra-assay CVs were 1.9 % for erythrocyte sensitivity to oxidative stress and 3.4% for inhibitory 50% plasma volume. Inter-assay CVs for both erythrocyte sensitivity and inhibitory 50% plasma volume were 4%. 4The reliability of this method was assessed and applied to test the protective effect of vitamin E, a well known antioxidant agent, in six healthy volunteers. Two weeks after daily administration of 500 mg of vitamin E, the mean plasma vitamin E concentration increased by 41% from 10.7±2.0 mg l⁻¹ before treatment (P<0.05). As the vitamin E concentration increased, the mean inhibitory 50% plasma volume and the percentage of haemolysed erythrocytes decreased respectively by 29% from 3.35±0.5 μl (P<0.05) and 18% from 71.5±3.8% (P<0.05). No significative variation of these parameters was observed in six adult men without vitamin E supplementation. 5Thus, this global and simple test permits an antioxidant status evaluation of a patient. It can be applied to various pathologies and allows the potency of new antioxidant molecules to be evaluated.     

Epidermolysis bullosa acquisita with pulmonary tuberculosis: a case report

Our case is that of a 67-year-old man who presented with a blistering, scarring eruption at sites of trauma. Histologically the blistering was subepidermal. IgG and C₃ were present at the basement membrane zone. Electronmicroscopy demonstrated bulla formation to be beneath the basal lamina and that it contained amorphous electron-dense material. These clinical and investigational findings are consistent with a diagnosis of epidermolysis bullosa acquisita (EBA). The patient also had pulmonary tuberculosis which again highlights the association between EBA and diseases in which the immune system is compromised.     

Effectiveness of two direct-mail strategies to encourage women to have cervical (Pap) smears

The aim of this study was to assess the acceptability, utilisazionand differential effectiveness of two direct-mail strategiesfor increasing community Papanicolaou (Pap) smear rates. Thetwo strategies were: a personally addressed letter containingsimple information about Pap smears and a personally addressedletter combined with a series of targeted behavioural promptsdesigned to address a number of aspects of screening which previousresearch had shown to be associated with poor screening rates.The two strategies were assessed in two geo graphically separatedpostal regions in Australia. Each region represented approximately10 women aged 18–70 wars. Outcome data on the change inregional Pap smear rates were obtained from government healthinsurance claims for cervical screening and from pathology servicerecords. Both interventions resulted in statistically significantincreases in attendances for screening over the post-interventionperiod. 42.2% in the region receiving the simple prompt and39.6% in the region receiving the multi-faceted approach Therewas no sigrujicant difference between the two intervention regions.The results indicate that direct-mail strategies can be effectivein prompting attendance for cervical cancer screening. Further,nore, it would appear that a simple informational strategy canbe at least as effective as a more elaborate package. Both interventionsresulted in similar increases in attendances of around 40%.     

Mercuric chloride induced autoimmune disease in Brown-Norway rats: sequential search for anti-basement membrane antibodies and circulating immune complexes

Mercuric chloride induces in the Brown-Norway rat a biphasic autoimmune disease characterized initially by linear IgG deposits along the glomerular basement membrane followed later by granular IgG deposition. In the present study, anti-glomerular basement membrane antibodies and immune complex-like material were sequentially assessed in serial serum samples. Both were transiently found at the same period. Glomerular linear IgG deposits were present on day 11 but circulating anti-glomerular basement membrane antibodies were only found later on day 16. Circulating immune complexes were first detectable on day 8 before the earliest granular IgG deposits were first observed in the spleen vessels on day 16. The disappearance of circulating anti-glomerular basement membrane antibodies and of circulating immune complexes, although HgCl2 injections were pursued, is in agreement with the self-limited character of mercuric chloride induced autoimmune disease and suggests the induction of immunosuppressive mechanisms.