Francisco Cumsille

Search for primary infection by Pneumocystis carinii in a cohort of normal, healthy infants.

To determine whether Pneumocystis carinii is associated with clinical illness in the competent host, 107 normal, healthy infants were enrolled in a 2-year prospective cohort study in Chile. P. carinii was identified by specific stains and nested--deoxyribonucleic acid (DNA) amplification of the large subunit mitochondrial ribosomal ribonucleic acid gene of P. carinii f. sp. hominis, and seroconversion was assessed by enzyme-linked immunosorbent assay of serum samples drawn every 2 months. P. carinii DNA was identified in nasopharyngeal aspirates obtained during episodes of mild respiratory infection in 24 (32%) of 74 infants from whom specimens were available for testing. Three (12.5%) of those 24 infants versus 0 of 50 infants who tested negative for P. carinii had apnea episodes. Seroconversion developed in 67 (85%) of 79 infants who remained in the study by 20 months of age and occurred in the absence of any symptoms of disease in 14 (20.8%). The study indicates that P. carinii DNA can be frequently detected in healthy infants, and it raises the hypothesis that they may be an infectious reservoir of P. carinii in the community. Further investigation is needed to identify whether P. carinii causes overt respiratory disease in infants.

Long-term treatment with cisapride and antibiotics in liver cirrhosis: effect on small intestinal motility, bacterial overgrowth, and liver function

OBJECTIVES:Altered small-bowel motility, lengthening of the orocecal transit time, and small-intestinal bacterial overgrowth have been described in patients with liver cirrhosis. These changes might be related to the progressive course and poor prognosis of the disease. We investigated the effect of a long-term treatment with cisapride and an antibiotic regimen on small-intestinal motor activity, orocecal transit time, bacterial overgrowth, and some parameters of liver function.METHODS:Thirty-four patients with liver cirrhosis of different etiology entered in the study. They were randomly allocated to receive cisapride (12), an alternating regimen of norfloxacin and neomycin (12), or placebo (10) during a period of 6 months. At entry and at 3 and 6 months, a stationary small-intestinal manometry was performed, and orocecal transit time and small-intestinal bacterial overgrowth were also investigated using the H2 breath test. Liver function was estimated with clinical and laboratory measurements (Child-Pugh score).RESULTS:After 6 months, both cisapride and antibiotics significantly improved fasting cyclic activity, reduced the duration of orocecal transit time, and decreased small-intestinal bacterial overgrowth. Cisapride administration was followed also by an increase in the amplitude of contractions. No statistically significant variations in these parameters were observed with placebo. An improvement of liver function was observed at 3 and 6 months with both cisapride and antibiotics.CONCLUSIONS:Long-term treatment with cisapride or antibiotics reversed altered small-intestinal motility and bacterial overgrowth in patients with liver cirrhosis. These findings suggest a possible role for prokinetics and antibiotics as a modality of treatment in selected cases of decompensated cirrhosis.

Altered Small Bowel Motility in Patients with Liver Cirrhosis Depends on Severity of Liver Disease

Abnormal small bowel motility has been describedin patients with liver cirrhosis but the mechanismsinvolved are unknown. The aim was to investigate apossible relationship between the severity of liver failure and the intensity of small intestinalabnormalities. Motility was studied during fasting, bymeans of perfused catheters and external transducers, on33 cirrhotics with different etiologies; 8 were at Child-Pugh stage A, 12 stage B, and 13 stageC. Both abnormalities of MMC and increased clusteredactivity were recorded. Absence of cycling activity wasmost frequently observed in Child-Pugh stage C patients compared to Child-Pugh stage Acirrhotics. A significant increase in clusteredcontractions from 4.7 ± 0.4/hr in stage Apatients to 11.3 ± 1.1 in stage C was recorded.The frequency and amplitude of contractions was also increased fromChild-Pugh stage A to stage C. Our findings might berelated to a delayed transit time observed in thesepatients and a higher prevalence of bacterial overgrowth in cirrhotics with more advanced liverdisease.

Influence of vertical dimension on masseter muscle electromyographic activity in patients with mandibular dysfunction

Occlusal splints were adjusted to different vertical heights and used to single out the influence of vertical dimension of occlusion in increments on BT-EMG activity of the masseter muscle in patients with mandibular dysfunction. The vertical dimension of least EMG activity was determined for each of 60 patients, who were randomly divided into three groups according to the vertical dimension at which the occlusal splint was adjusted: group No. 1, 1 mm from occlusal vertical dimension; group No. 2, mean vertical dimension, 4.25 mm; group No. 3, mean vertical dimension, 8.25 mm. Results showed a significant reduction of masseter BT-EMG activity (series A and B) at the end of the 3-week treatment period for patients in group Nos. 2 and 3 in comparison with group No. 1. Furthermore, the short-term use of occlusal splints with a vertical height that exceeded the so-called physiologic interocclusal distance did not result in an increase in masseter BT-EMG activity. This study suggests that an increase of vertical dimension of occlusion to or near the vertical dimension of least EMG activity by means of occlusal splints can be an effective way to obtain a reduction in masseteric muscle activity.

Consumption of licit and illicit drugs in Chile: results of the 1998 study and comparison with the 1994 and 1996 studies

The principal results are presented here from the Third National Study of the Consumption of Drugs, which was carried out in Chile by the National Board for Narcotics Control between 1 September 1998 and 15 January 1999. The 1998 study used the same methodological design as the first and second studies, which were done in 1994 and 1996. The 1998 study expanded the sample to 31,665 individuals, who were representative of a population of 6,940,727 people from 12 to 64 years old, both sexes, and five socioeconomic levels and who were residents of urban areas in 62 commune administrative divisions of the 13 regions of the country. Results from the 1998 study are compared with those from 1996 and 1994. The 1998 study shows that 17.5% of Chileans have at some time in their life used one of the three illicit drugs most popular in the country: marijuana (16.8%), coca paste (2.3%), and cocaine hydrochloride (4.0%). The prevalence of use of any of the three drugs, mainly marijuana, during the preceding year was 5.3% and during the preceding month 2.2%. With respect to licit drugs, 28.4% of Chileans have at some time in their lives used antianxiety drugs, 84.4% of them have consumed alcohol, and 71.9% have used tobacco. Most of the people who once used illegal drugs have stopped doing so: 71.6% in the case of marijuana, 64.1% with coca paste, and 66.8% with cocaine hydrochloride. For legal drugs, the percentages were lower: 55.5% for anxiolytics, 16.0% for alcohol, and 34.5% for tobacco. The consumption of licit and illicit drugs was several times greater among men than among women, except for anxiolytics, whose use was three times greater among women. Drug use was more frequent among persons between 19 and 25 years old. Consumption of illegal drugs was more frequent at higher socioeconomic levels, and use of licit drugs was more common in the lower socioeconomic levels. The 50th percentile of the age of initiating drug use was 17 years for alcohol, 15 for tobacco, 30 for antianxiety agents, 17 for marijuana, 20 for coca paste, and 21 for cocaine hydrochloride. Comparing the results of the three studies shows that, after an increase in the use of licit drugs between 1994 and 1996, there was a stabilization in 1998. With illegal drugs there was a modest increase in consumption between 1996 and 1998, following a small reduction between 1994 and 1996.

Effect of dichotomizinlg a continuous variable on the model structure in multiple linear regression models

This mansscript studies analytically the consequences of changing the scale of measurement of a continuous independent variable in a multiple linear regression setting. Assuming the continuous outcome variable, a continuous exposure variable, and a continuous control variable follow a trivariate Gaussian distribution, we examine the effect upon the structure of the modei of dichotomizing the continuous control variable. It is shown that, after dichotomizaiion, the condirionai expected vaiiie of the response is a quotient of two non-hear functions and hence is no longer linear in the exposure variable. Thus, when an underlying continuous independent variable is dichotomized in multiple linear regression, and one fits a linear model using the dichotomous variable, this models linear structure is misspecified. The estimates obtained from this model are incorrect and potentially misleading.

Categorización de variables en el análisis estadístico de datos: consecuencias sobre la interpretación de resultados

Frequently during the process of data analysis in epidemiological studies, the scale of one or more continuous variables is changed. The objective of this paper was to assess the consequences of categorizing variables during data analysis. We studied three situations with different scenarios for statistical analysis with regression models. The results show that dichotomizing continuous variables can substantially modify the relationships between dependent and independent variables. Thus, for example, in epidemiological studies trying to evaluate the effect of an exposure on a response, the magnitude and/or the direction of this effect can be biased by dichotomizing a variable. We therefore recommend avoiding, as much as possible, the categorization of variables when doing analyses.

Prevalence of Marijuana Use among University Students in Bolivia, Colombia, Ecuador, and Peru

Young adults 18 to 25 years old show the highest prevalence of marijuana use in Latin America. This study analyzes the changes in prevalence of marijuana use among university students in the Andean Community (Bolivia, Colombia, Ecuador, and Peru) from two studies carried out in 2009 and in 2012. Data were collected through representative two-stage samples of universities and students in the Andean Community. An online survey was administered using a standardized questionnaire. Prevalence was calculated for lifetime, past year, and past month. Marijuana was the most widely used illicit substance consumed among university students, in 2009 and in 2012. Past month prevalence among university students in 2009 in Colombia was 5.27%, in Peru 1.00%, in Ecuador 1.68%, and in Bolivia 0.76%. Past month prevalence in 2012 in Colombia was 7.14%, in Ecuador 3.67%, in Peru 1.62%, and in Bolivia 1.45% in 2012. Among university students in the Andean Community, past month prevalence increased among both males and females between 2009 and 2012 in most countries. Marijuana continues to be the most commonly used illicit drug in Latin American countries. Increases in prevalence among young adults could have important implications for national drug policy.

Small-intestine absorption during continuous intraduodenal infusion of nutrients in dogs

Motility and exocrine and endocrine secretions of the gastrointestinal tract are modified during postprandial periods. Experimental evidence suggests that nutrients stimulate small-intestine absorption, but the mechanisms involved are uncertain. Further, the effects of mixing nutrients with different physicochemical compositions on absorption and motility are not completely elucidated. With the use of a canine model, we investigated the effects of a mixture of different lipids and proteins on small-intestine motility and absorption. Two cannulae, one in the proximal duodenum and one in the distal ileum, were implanted in the dogs. Absorption of a continuous duodenal infusion of eight test mixtures consisting of long- and medium-chain fatty-acid triacylglycerols, soy protein and its hydrolysate, casein and its hydrolysate, and variable amounts of glucose, and glucose polymer were analyzed by measuring the volume, concentration, and total amount of triacylglycerols, nitrogen, and glucose recovered from the ileal cannula. Significant differences in absorption were observed across test mixtures. Significantly lower absorption of H(2)O and nutrients was observed with test mixtures prepared with medium-chain fatty-acid triacylglycerols and soy protein compared with test mixtures prepared with corn oil, casein, and hydrolysates of both proteins. We concluded that the physicochemical characteristics of nutrients in elemental diets continuously infused into the duodenum are important for determining small-intestine absorption.

Relationship between small intestinal fasting motility and vomiting in dogs

Preceding vomiting, several changes in small intestinal motility have been described. They consist mainly of high-amplitude retrograde contractions and inhibition of motility before and after these contractions. The recordings of 94 episodes of emesis occurring spontaneously, during manometric studies of intestinal motility by means of infused catheters in dogs with gastric and duodenal cannulae, showed that 95.7% of all episodes developed during phase II of the migratory motor complex. In order to establish whether different phases of the fasting cyclic activity are associated with a different sensitivity to emetic stimulus, two agents, apomorphine, a centrally acting drug and copper sulfate, a peripherally acting agent, were administered at the beginning of phases I and II of the migratory motor complex. Coincident with spontaneously occurring vomiting, a statistically significative greater number of responses to both emetic agents was observed during phase II as compared to phase I. This finding suggests that cyclic changes of the small bowel motility are related to changes in the threshold of the vomiting center.