Boundary lipids in the nicotinic acetylcholine receptor microenvironment.

The structural and functional properties of the nicotinic acetylcholine receptor (AChR), the archetype molecule in the superfamily of Cys-looped ligand-gated ion channels, are strongly dependent on the lipids in the vicinal microenvironment. The influence on receptor properties is mainly exerted by the AChR-vicinal ("shell" or "annular") lipids, which occur in the liquid-ordered phase as opposed to the more disordered and "fluid" bulk membrane lipids. Fluorescence studies from our laboratory have identified discrete sites for fatty acids, phospholipids, and cholesterol on the AChR protein, and electron-spin resonance spectroscopy has enabled the establishment of the stoichiometry and selectivity of the shell lipid for the AChR and the disclosure of lipid sites in the AChR transmembrane region. Experimental evidence supports the notion that the interface between the protein moiety and the adjacent lipid shell is the locus of a variety of pharmacologically relevant processes, including the action of steroids and other lipids. I surmise that the outermost ring of M4 helices constitutes the boundary interface, most suitable to convey the signals from the lipid microenvironment to the rest of the transmembrane region, and to the channel inner ring in particular.

Evaluación de un programa de intervención breve motivacional para fumadores: resultados de un estudio piloto / Evaluation of a brief motivational intervention program for smokers: results of a pilot study

Tobacco consumption is a world-wide public health problem that has been associated with different types of cancer, cardiovascular and respiratory diseases, alterations in the reproductive system, dental problems and some eye diseases. In Mexico the National Survey of Addictions (2002) reported that 26.4% of the urban population between 12 and 65 years and 14.3% of the rural population are smokers. The Secretary of Health indicated that more than 53000 people died from diseases related to tobacco consumption. The consumption of tobacco stands among the ten first causes of morbidity and mortality in Mexico. In this sense, smoking is considered as one of the main public health problems in Mexico. Several organisms and institutions have undertaken actions in an attempt to solve it, such as the development of educative programs directed to the general population and programs to help smokers to quit this habit. Some of the main strategies to reduce cigarette consumption include nicotine replacement therapy, therapy not based on nicotine (antidepressants, some opiate antagonists and anxiolytic drugs), psychological programs, and the combination of some of them. Regarding psychological treatments, behavioral and cognitive behavioral techniques for smoking cessation hold empirical evidence about their efficacy for reducing the abuse of substances. In Mexico, psychological, nicotinic and non-nicotinic treatments to stop smoking are used. Nevertheless, the methodological and theoretical grounds of the psychological interventions are not well-established and there are no specific data about the changes in the consumption pattern after the application of the interventions and whether the effects of the treatment stay through the time. Specifically, the information about the efficacy of the brief interventions on smokers in the Mexican population is scarce. Although different studies have demonstrated that the brief motivational interventions are more effective to reduce the abuse of different substances than intensive interventions or no interventions at all, the techniques are not widely used in the treatment of tobacco consumption in Mexican population. With this evidence, the National Autonomous University of Mexico (UNAM) developed the Brief Motivational Intervention Program to treat smokers. The Brief Motivational Intervention is based in the Social Cognitive Theory, the Prevention of Relapses Model, in techniques of motivational interview and self-control techniques. Therefore, the goal of the present research is to evaluate a brief motivational intervention program for smokers. In order to achieve this aim, 10 individuals between 19 and 55 years old participated in the program; five individuals showed low nicotine dependence and five severe nicotine dependence according to the Questionnaire of Fagerström Tolerance. There was a public invitation and the participants consent to participate voluntarily in the <

Prebiotic ingestion does not improve gastrointestinal barrier function in burn patients.

Prebiotics increase intestinal levels of health-promoting bacteria implicated in decreasing pathogen colonization, stimulating immune functions and stabilizing gut barrier functions, parameters which are altered in burn patients. We propose that regular intake of a prebiotic, oligofructose (OF), might help to improve the altered gastrointestinal (GI) permeability observed in burn patients. A randomized, double-blind, controlled clinical trial was carried out in 41 burn patients (mean burn surface area=17.1+/-8.2%) who ingested daily 6 g of oligofructose (OF group) or sucrose as placebo (Control group) during 15 days. Gastrointestinal permeability to sucrose and lactulose/mannitol (L/M) was evaluated on days 1 (before treatment) 3, 7, 14 and 21. A permeability test was also performed in 18 healthy subjects as controls. Thirty-one patients completed the protocol (dropout rate=24.4%). Healthy subjects had a basal sucrose excretion of 21.3 mg (14.0-32.5 mg) and a basal L/M ratio of 0.017% (0.009-0.022%). Sucrose excretion increased 5-fold and L/M ratio 4.4-fold in burn patients on day 1 and these high levels of marker excretion decreased significantly throughout the study (p=0.016 and 0.000001, respectively). No differences between the OF and Control groups were observed for sucrose excretion or L/M ratio. In conclusion, the normalization of gastrointestinal permeability is not accelerated by prebiotic intake.

Neonatal tetanus mortality in Veracruz, Mexico, 1989.

This article describes a survey conducted in the State of Veracruz, Mexico, to estimate neonatal tetanus (NNT) mortality. The survey, which entailed visits to 72,720 households, collected data on 8,401 live births and 209 infant deaths occurring between April 1988 and May 1989. Twenty-six of the 209 fatalities conformed to a WHO standard case definition of death from neonatal tetanus. The estimated neonatal tetanus mortality was thus 3.1 deaths per 1,000 live births (95% confidence limits = 1.7, 4.5). Comparison of this rate to reported figures suggests that for every NNT death recorded in Veracruz during the study period, as many as 50 others went unreported. A case-control study nested within the survey was conducted to assess preventable NNT risk factors. Limited information on 13 NNT deaths and 217 controls showed an increased risk for neonates who were delivered at home and whose parents' ethnic background was Mexican Indian. Five of the 13 fatalities had their umbilical cords cut with a domestic or traditional cutting tool such as a reed cane, as compared to none of the 217 controls. The observed vaccine efficacy of 2+ doses of tetanus toxoid was 70% (95% confidence limits = 52, 100). Both the mothers of neonates who died of NNT and their controls missed an average of five opportunities to receive tetanus toxoid. These findings underscore the need to launch a perinatal health program serving Mexico's high-risk populations.

[The social impact of the vaccination against measles in Mexico. Comments during the course of the epidemics of 1988-1990]. / El impacto social de la vacunación contra el sarampión en México. Comentarios durante el curso de la epidemia de 1988-1990.

A number of issues have arisen concerning the current measles epidemic. In this paper we review: 1) the causes of this cyclic rise; 2) the benefit of a vaccination program sustained during more than 15 years; 3) the vaccine efficacy, as well as 4) the vaccination coverage goal for controlling measles. Immediate causes of the epidemic recurrence are: 1) low vaccination coverage, and 2) an increasing absolute number of newborns enlarges the pool of susceptibles. A strategy to identify now-vaccinated children in a systematic fashion is suggested. As long as measles transmission occurs even if measles vaccination coverage increases, the proportion of vaccinated cases will not decrease. Within optimal values of vaccine efficacy this proportion will increase as the coverage increases. The universal goal for measles vaccination is stressed.

[Estimate of the cost/benefit ratio of measles vaccination]. / Estimación de la razón beneficio/costo de la vacunación contra el sarampión.

Among primary health care programs, one of those that has the highest benefit/cost ratio is measles immunization. An estimate of cases, complicated cases and deaths that could have occurred if such immunization program would not have been run, and costs of medical care (hospitalization, physician's visits, medical treatment and rehabilitation), were calculated. Since population at risk has a steady-state given by those who enter -births- and releave it -when they are 15 years old-, if the program did not exist more than 2 million cases and at least 60,000 deaths from measles would have occurred annually. This hypothetical situation is compared with the actual situation of measles in Mexico during the 80's; 1) no more than 100,000 cases could have been estimated to occur in the very extreme case of notifying only one out of 10 cases. 2) The proportions of vaccinated and immune children under five reach 70 percent; this situation has produced 3) a fade out of epidemicity and has increased the critical size of community population for epidemics and doubled the interepidemic interval with the corollary of 4) increasing the average age of infection. The average cost of vaccinating a child was estimated near 1.25 dollars (US). Estimated costs of disease are related to individual losses. Taking into account these factors, benefit/cost ratio of measles immunization in Mexico is, at least, 100:1. Measles transmission patterns in Mexico are discussed since they lead to increase the benefit/cost ratio as compared to countries where the age of infection was put up before the immunization era. To expand investments on measles immunization is recommended.

[Tuberculosis surveys in Guerrero and new estimates of the magnitude of tuberculosis infection in Mexico]. / Encuestas tuberculínicas en Guerrero y nuevas estimaciones de la magnitud de la infección tuberculosa en México.

Tuberculosis infection surveys are carried out by tuberculin skin test (Mantoux) which is a simple, cheap, valid and reliable procedure for the estimation of prevalence and incidence rates. In 1987 a survey was undertaken in children of 6-7 years old who attended the elementary school and who were not vaccinated (BCG) in the region of Iguala, México. Out of 6,095 children of such age group, just 531 were not vaccinated, thus the prevalence figure was 2.5% (CL05 = 0.1%, 5.3%). On the basis of the findings by Izaguirre et al, 26 years ago, who reported that about 10% of the children of this age group were infected, it can be estimated that the annual risk of infection is about three newly infected each year per 1,000 population. It is necessary to provide better estimates of the whole tuberculosis incidence rate.