Application of the adverse outcome pathway (AOP) concept to structure the available in vivo and in vitro mechanistic data for allergic sensitization to food proteins

BACKGROUND

The introduction of whole new foods in a population may lead to sensitization and food allergy. This constitutes a potential public health problem and a challenge to risk assessors and managers as the existing understanding of the pathophysiological processes and the currently available biological tools for prediction of the risk for food allergy development and the severity of the reaction are not sufficient. There is a substantial body of in vivo and in vitro data describing molecular and cellular events potentially involved in food sensitization. However, these events have not been organized in a sequence of related events that is plausible to result in sensitization, and useful to challenge current hypotheses. The aim of this manuscript was to collect and structure the current mechanistic understanding of sensitization induction to food proteins by applying the concept of adverse outcome pathway (AOP).

MAIN BODY

The proposed AOP for food sensitization is based on information on molecular and cellular mechanisms and pathways evidenced to be involved in sensitization by food and food proteins and uses the AOPs for chemical skin sensitization and respiratory sensitization induction as templates. Available mechanistic data on protein respiratory sensitization were included to fill out gaps in the understanding of how proteins may affect cells, cell-cell interactions and tissue homeostasis. Analysis revealed several key events (KE) and biomarkers that may have potential use in testing and assessment of proteins for their sensitizing potential.

CONCLUSION

The application of the AOP concept to structure mechanistic in vivo and in vitro knowledge has made it possible to identify a number of methods, each addressing a specific KE, that provide information about the food allergenic potential of new proteins. When applied in the context of an integrated strategy these methods may reduce, if not replace, current animal testing approaches. The proposed AOP will be shared at the www.aopwiki.org platform to expand the mechanistic data, improve the confidence in each of the proposed KE and key event relations (KERs), and allow for the identification of new, or refinement of established KE and KERs.

Predictors of the short- and long-term survival of HIV-infected patients admitted to a Brazilian intensive care unit

The outcomes of HIV-infected patients requiring critical care have improved. However, in developing countries, information about HIV-infected patients admitted to intensive care units (ICUs) is scarce. We describe the prognosis of HIV-infected patients admitted to a Brazilian ICU and the factors predictive of short- and long-term survival. A historical cohort study, including HIV-infected patients admitted to a Brazilian ICU at an HIV/AIDS reference hospital, was conducted. Survivors were followed up for 24 months after ICU discharge. Demographic, clinical and laboratory data, disease severity scores and mortality were evaluated. Data were analysed using survival and regression models. One hundred and twenty-five patients were studied. In-ICU and in-hospital mortality rates were 46.4% and 68.0%, respectively. Multivariate analysis showed that the in-ICU mortality was significantly associated with APACHE (Acute Physiology and Chronic Health Evaluation) II scores (odds ratio [OR], 1.11; 95% confidence interval [CI], 1.03–1.11), mechanical ventilation (OR, 6.39; 95% CI, 1.29–31.76), tuberculosis treatment (OR, 2.62; 95% CI, 1.03–6.71), use of antiretroviral therapy (OR, 0.19; 95% CI, 0.05–0.77) and septic shock (OR, 4.38; 95% CI, 1.78–10.76). Septic shock was also associated with long-term survival (hazard ratio, 3.0; 95% CI, 1.31–6.90). In-hospital and in-ICU mortality were higher than those reported for developed countries. ICU admission mostly due to AIDS-related diseases may explain these differences.

Serum and cerebral spinal fluid levels of chemokines and Th2 cytokines in Schistosoma mansoni myeloradiculopathy

Schistosomal myeloradiculopathy (SMR) is the most common neurological form of Schistosoma mansoni infection. In this study we investigated the expression of chemokines and Th2 cytokines in serum and cerebral spinal fluid (CSF) of SMR patients. SMR patients presented increased serum levels of CCL11/eotaxin and CCL24/eotaxin-2 when compared to controls. SMR patients also had higher levels of IL-13 in CSF. Thus, SMR patients present enhancement of both IL-13 and CCR3 acting chemokines, both of which may facilitate the expression of a Th2 response and Th2-dependent damage to the spinal cord. As this cytokine is responsible for promoting Th2 responses, this finding is in accordance to the view that Th2 cells are important in the immunological process against the S. mansoni.

Hepatosplenic schistosomiasis in field-based studies: a combined clinical and sonographic definition

A combined clinical and sonographic classification of hepatosplenic schistosomiasis mansoni to be used in field-based studies is proposed herein. Seven hundred forty one individuals out of 892 (83%), living in an area endemic for schistosomiasis in Brazil, have been submitted to clinical and ultrasound examinations. Based on two stool examinations the overall prevalence for schistosomiasis in this area was 73%. Abdominal palpation was performed with patients in dorsal decubit, during deep breath, by two experienced physicians and a portable ultrasound was used for the evaluation of liver fibrosis, portal collaterals and spleen size. Four groups of individuals were identified using data obtained by abdominal palpation and ultrasound examination: (1) palpable spleen and intense periportal thickening in 9 individuals (1.2%); (2) spleen not palpable and intense periportal thickening in 15 (2%); (3) palpable spleen with light to moderate periportal thickening in 32 (4.3%), and (4) palpable spleen with a normal liver on ultrasound in 30 (4%). The definition of hepatosplenic schistosomiasis in field-based studies as the finding of Schistosoma mansoni eggs in the stools in an individual with splenomegaly is not acceptable anymore. Abdominal ultrasound should be combined with clinical examination to accurately identify hepatosplenics in endemic areas for schistosomiasis.

Human toxocariasis and pyogenic liver abscess: a possible association

OBJECTIVES

To study the role of human toxocariasis in the pathogenesis of pyogenic liver abscess.

METHODS

We compared the serology for toxocariasis and serum levels of IgE in 16 patients with pyogenic liver abscess to those in 32 matched (age and gender) controls to define the possible association between these two entities.

RESULTS

The serology for toxocariasis was positive in 10 of 16 patients compared with 4 of 32 controls. The relative odds and 95% confidence interval (conditional logistic regression), comparing cases and matched controls, was significant (1.4; 95% confidence interval, 1.1-1.7) for Toxocara serology. Regarding IgE serum levels, there was no difference between cases and controls.

CONCLUSIONS

Human toxocariasis can be one of the predisposing causes of pyogenic liver abscess, especially in tropical countries in which this parasitic disease is common. Treatment of human toxocariasis may prevent morbid complications like hepatic abscess and should be considered in patients with clinical and/or serological evidence of Toxocara infection.

Nested case-control study in a serological survey to evaluate the effectiveness of a Chagas disease control programme in Brazil

OBJECTIVE

To identify risk factors associated with Trypanosoma cruzi infections in areas under surveillance in the State of Minas Gerais, Brazil.

METHODS

A model using a nested case-control design incorporated within a serological survey of schoolchildren which was employed to evaluate the effectiveness of the Chagas disease control programme.

FINDINGS

In a sample of 40,374 schoolchildren (aged 7-14 years) surveyed, 16 children tested positive for T. cruzi antibody (by indirect immunofluorescence and indirect haemagglutination). In the case-control study, each case was randomly matched to three seronegative controls (classroom and age +/- 1 year). Compared to controls, T. cruzi-seropositive children were more likely to have a seropositive mother (odds ratio (OR) = 6.8; 95% confidence interval (CI) = 0.71-63.9) or a seropositive family member (OR = 8.6; 95% CI = 1.0-75.5).

CONCLUSION

Use of the nested case-control model in a sero-epidemiological survey to evaluate risk factors for T. cruzi transmission was adequate for assessing the effectiveness of a Chagas disease control programme.

Differential patterns of glucose-induced electrical activity and intracellular calcium responses in single mouse and rat pancreatic islets

Although isolated rat islets are widely used to study in vitro insulin secretion and the underlying metabolic and ionic processes, knowledge on the properties of glucose-induced electrical activity (GIEA), a key step in glucose-response coupling, has been gathered almost exclusively from microdissected mouse islets. Using a modified intracellular recording technique, we have now compared the patterns of GIEA in collagenase-isolated rat and mouse islets. Resting membrane potentials of rat and mouse beta-cells were approximately -50 and -60 mV, respectively. Both rat and mouse beta-cells displayed prompt membrane depolarizations in response to glucose. However, whereas the latter exhibited a bursting pattern consisting of alternating hyperpolarized and depolarized active phases, rat beta-cells fired action potentials from a nonoscillating membrane potential at all glucose concentrations (8.4-22.0 mmol/l). This was mirrored by changes in the intracellular Ca2+ concentration ([Ca2+]i), which was oscillatory in mouse and nonoscillatory in rat islets. Stimulated rat beta-cells were strongly hyperpolarized by diazoxide, an activator of ATP-dependent K+ channels. Glucose evoked dose-dependent depolarizations and [Ca2+]i increases in both rat (EC50 5.9-6.9 mmol/l) and mouse islets (EC50 8.3-9.5 mmol/l), although it did not affect the burst plateau potential in the latter case. We conclude that there are important differences between beta-cells from both species with respect to early steps in the stimulus-secretion coupling cascade based on the following findings: 1) mouse beta-cells have a larger resting K+ conductance in 2 mmol/l glucose, 2) rat beta-cells lack the compensatory mechanism responsible for generating membrane potential oscillations and holding the depolarized plateau potential in mouse beta-cells, and 3) the electrical and [Ca2+]i dose-response curves in rat beta-cells are shifted toward lower glucose concentrations. Exploring the molecular basis of these differences may clarify several a priori assumptions on the electrophysiological properties of rat beta-cells, which could foster the development of new working models of pancreatic beta-cell function.

[Bancroftian filariasis in urban areas of Alagoas State, Northeast Brazil: study in the general population]

In order to assess the present status of lymphatic filariasis in Alagoas State, Brazil, hemoscopic surveys were carried out in the human population of the three different physiographic regions of the State. Blood samples were collected by thick smear technique taken after 10:00 p.m. From a total of 101 cities of the State, 10 were randomly selected, Bancroftian filariasis was only found in Maceió, the capital of Alagoas State. In a cross-sectional survey conducted among the general population of 4 neighborhoods in the city, 10,973 individuals were examined, 226 were microfilaraemic with prevalence in the city neighborhoods ranging from 0 to 5.4%. Prevalence rates and microfilariae density were significantly higher in males. Among the examined inhabitants born out of Maceió, microfilariae carriers had lived a significantly longer time in endemic areas than the amicrofilaraemic subjects. Based on the data obtained in the present study, measures to avoid expansion of bancroftian filariasis in the region were established.

Sexually transmitted diseases in homosexual and bisexual males from a cohort of human immunodeficiency virus negative volunteers (Project Horizonte), Belo Horizonte, Brazil

Sexually transmitted diseases (STD) are very frequent in the whole world. Males who do not use a condom during their sexual relations are at great risk. We report cases of STD during six months of observation, among homosexual/bisexual males who participate in the Project Horizonte. There were 16 cases of genital warts, 6 cases of human immunodeficiency virus infection, 24 cases of unspecific urethritis, 28 cases of herpes simplex virus infection, 30 cases of syphilis, 58 cases of gonorrhea and 84 cases of pediculosis. We concluded that a condom must be used in all sexual relations and new counseling techniques are needed, to avoid this situation.

Schistosoma mansoni: assessment of morbidity before and after control

The literature on the assessment of morbidity due to Schistosoma mansoni infection is updated. Imaging techniques such as ultrasonography, echodoppler cardiography, computerized tomography (CT scan) and magnetic resonance imaging (MRI) introduced a new perspective, and expanded our knowledge on morbidity. Three well-defined syndromes caused by schistosomiasis mansoni have been described: the stage of invasion, acute schistosomiasis (Katayama fever), and chronic schistosomiasis. Complications of the acute and chronic syndromes have also been reported: pulmonary hypertension, neuroschistosomiasis, association with Salmonella, association with Staphylococci, viral hepatitis B, glomerulonephritis. In most individuals with hepatosplenic schistosomiasis the spleen is increased in size. Hepatosplenic schistosomiasis can, however, occur without splenomegaly. The definition of hepatosplenic schistosomiasis in endemic areas as the finding of S. mansoni eggs in the stools in an individual with hepatosplenomegaly is not satisfactory anymore. Many aspects of morbidity are expected to change after schistosomiasis control. Some are expected to change quickly (worm burden, Salmonella bacteremia, hepatosplenic schistosomiasis in children) whereas others shall remain for years (pulmonary hypertension, glomerulonephritis, neuroschistosomiasis). Intestinal schistosomiasis in individuals with low worm burdens is very difficult to diagnose and therefore laborious to control.

Risk factors for tuberculosis among human immunodeficiency virus-infected persons. A case-control study in Belo Horizonte, Minas Gerais, Brazil (1985-1996)

The objective of this study was to identify tuberculosis risk factors and possible surrogate markers among human immunodeficiency virus (HIV)-infected persons. A retrospective case-control study was carried out at the HIV outpatient clinic of the Universidade Federal de Minas Gerais in Belo Horizonte. We reviewed the demographic, social-economical and medical data of 477 HIV-infected individuals evaluated from 1985 to 1996. The variables were submitted to an univariate and stratified analysis. Aids related complex (ARC), past history of pneumonia, past history of hospitalization, CD4 count and no antiretroviral use were identified as possible effect modifiers and confounding variables, and were submitted to logistic regression analysis by the stepwise method. ARC had an odds ratio (OR) of 3.5 (CI 95% - 1.2-10.8) for tuberculosis development. Past history of pneumonia (OR 1.7 - CI 95% 0.6-5.2) and the CD4 count (OR 0.4 - CI 0. 2-1.2) had no statistical significance. These results show that ARC is an important clinical surrogate for tuberculosis in HIV-infected patients. Despite the need of confirmation in future studies, these results suggest that the ideal moment for tuberculosis chemoprophylaxis could be previous to the introduction of antiretroviral treatment or even just after the diagnosis of HIV infection.

The microfilarial periodicity of Wuchereria bancrofti in north-eastern Brazil

The periodicity of Wuchereria bancrofti microfilariae (mff) in peripheral blood was analysed in 42 microfilaraemics living in Maceió, in Alagoas state, north-eastern Brazil. Nine blood samples were collected from each subject, over a 24-h period, and two quantitative (60-microliter) thick smears were prepared from each sample. Although all the subjects had detectable microfilaraemias from 23.00 hours to 06.00 hours, no mff could be detected in most (71.4%) of the smears prepared from samples collected at 15.00 hours. Samples collected during the day, at 15.00 hours, contained 170 times fewer mff/microliter than those collected at 01.00 hours, when microfilaraemias were generally most intense. For diagnosis of bancroftian filariasis in Maceió, blood samples should be collected between 22.00 and 03.00 hours, when microfilarial counts will be at least 90% of the peak counts. The circadian variation observed was independent of the subject's gender and microfilarial density. Mathematical analysis, using a simple harmonic-wave model, indicated a periodicity index of 127.6 and that maximum microfilarial densities occurred at 00.51 hours, confirming the nocturnal pattern of microfilaraemia in the study area.

Schistosomiasis and associated infections

In hospital-based series viral hepatitis B has been frequently described in association with schistosomiasis whilst in field-based studies the association has not been confirmed. The association between schistosomiasis and Salmonella bacteraemia has been well documented. More recently, acute schistosomiasis has been shown to be a facilitating factor in the genesis of pyogenic liver abscesses caused by Staphylococcus aureus. New evidences indicate an interaction between the acquired immunodeficiency syndrome (AIDS) and schistosomiasis. In this paper, data on the association of schistosomiasis with other infections are updated.

Chronic carriers of hepatitis B surface antigen in an endemic area for schistosomiasis mansoni in Brazil

Data on the association of schistosomiasis and hepatitis B in field-based studies are scarce. Two areas have been selected for this study: i) Queixadinha, endemic for schistosomiasis, with a population of 693 individuals, and ii) Capão, a control non-endemic area, with 515 inhabitants. Sera of all individuals in both areas were tested for hepatitis B infection, yearly, from 1994 to 1997. In the first area hepatitis B was found in 32.1% of children up to one year old and reached a peak of 68.7% in the age range of 15 to 19 years. In the control area the prevalence of hepatitis B was under 5% up to 19 years of age and the highest prevalence was observed in adults over 45. HBsAg was detected in 9.4% of the individuals living in the endemic area for schistosomiasis and in 1.4% of the controls (OR = 4.98; 95% CI = 3.7-6.7). The index of chronicity of HBsAg was not statistically different in the studied areas (8.1% x 7.3%; OR = 1.09; 95% CI = 0.42-3.03), nor was it different for people with and without schistosomiasis in Queixadinha (8.7% x 7.0%). We conclude that the Schistosoma mansoni infection has not altered the course of hepatitis B in the studied area.

Lymphatic filariasis in Brazilian urban area (Maceió, Alagoas)

A cross-sectional survey conducted among evening students was used to determine the prevalence of Wuchereria bancrofti infection in Maceió, capital of the State of Alagoas, northeast Brazil. A single thick-blood smear was used, being collected between 10 p.m. and 12 a.m. From a total of 29,551 students enrolled at evening elementary schools in the 33 city sectors, 16,569 (56.4%) were random selected for inclusion in the study. From those, 10,857 (65.5%) were interviewed and examined and 73 (0.7%) were found to have microfilaraemia. Autochthonous W. bancrofti carriers live in 10 of the 33 city sectors, suggesting a focal distribution. Moreover, 84% of infections were diagnosed among 29% of all students examined, inhabiting three contiguous sectors at the city central area, presenting infection rates up to 5.3%. Students living in city sectors with prevalence of microfilariae carriers greater than 1% were found to have a higher risk for infection when compared to students from the rest of the town [Relative Odds (RO) 12.8, 95% CI 6.7-25.1]. Eleven positive individuals from non endemic areas were living in Maceió for more than 10 years; time of residence in the area was a major risk factor for infection among students not born in the region (p < 0.01). Regarding sex, male students presented a higher proportion of positive (RO 1.7, 95% CI 1.1-2.9).

Diagnostic electrocardiography in epidemiological studies of Chagas' disease: multicenter evaluation of a standardized method

An electrocardiographic recording method with an associated reading guide, designed for epidemiological studies on Chagas' disease, was tested to assess its diagnostic reproducibility. Six cardiologists from five countries each read 100 electrocardiographic (ECG) tracings, including 30 from chronic chagasic patients, then reread them after an interval of 6 months. The readings were blind, with the tracings numbered randomly for the first reading and renumbered randomly for the second reading. The physicians, all experienced in interpreting ECGs from chagasic patients, followed printed instructions for reading the tracings. Reproducibility of the readings was evaluated using the kappa (kappa) index for concordance. The results showed a high degree of interobserver concordance with respect to the diagnosis of normal vs. abnormal tracings (kappa = 0.66; SE 0.02). While the interpretations of some categories of ECG abnormalities were highly reproducible, others, especially those having a low prevalence, showed lower levels of concordance. Intraobserver concordance was uniformly higher than interobserver concordance. The findings of this study justify the use by specialists of the recording of readings method proposed for epidemiological studies on Chagas' disease, but warrant caution in the interpretation of some categories of electrocardiographic alterations.

Dacryocystographic examination does not identify early seventh nerve failure in leprosy patients

Dacryocystographic examination was performed in two groups of patients: patients having leprosy and those not having leprosy, in order to look for early failure of the facial nerve. The results of this study show that this kind of examination does not improve diagnosis of leprosy.

Chagas Disease Control Programme in Brazil: a study of the effectiveness of 13 years of intervention

Reported is an evaluation of 13 years of intervention by the Chagas Disease Control Programme in an endemic area (Montalvania) in the State of Minas Gerais, Brazil. The design used was an epidemiological panel study. The reduction of Trypanosoma cruzi infection rates was estimated from data collected on three separate occasions: a serological survey in 1975-80, a quasi-experimental study in 1987, and the present investigation. A random sample of 156 households was selected and blood samples were collected from 653 inhabitants. The data routinely collected by the control programme were analysed to correlate the results with the incidence of T. cruzi. The overall prevalence of infection was 2.3%; however, no participant under 14 years of age was found to have a positive serological test. The total reduction in T. cruzi infection rates in this area from the start of the programme's activities was estimated to be 83.5%. Cross-sectional comparisons for the age groups 2-6 years and 7-14 years indicated a 100% reduction in T. cruzi incidence rates; but cohort comparisons showed that 100% reduction was achieved only for the 2-6-years age group.

Epidemiological and clinical aspects of snakebite in Belo Horizonte, southeast Brazil

Epidemiologic and clinical aspects of 310 hospitalized snakebite patients and 310 matched controls were described, over a seven years period, from an emergency hospital in Belo Horizontal, Southeast Brazil. The diagnosis was based upon clinical picture or actual snake identification. Fifty six percent of victims were bitten by the snakes of genus Bothrops, 32.0% by Crotalus, 1.0% by Lachesis and 10.0% undetermined. During the study period, stable number of cases and marked seasonal variation were noted. In comparing cases of snakebite and controls, those from a rural area or who were involved in agricultural labor activity were identified as a high risk group, with an odds ratio (OR) of 14.7 and 6.7, respectively, in favor of being bitten. Upon treatment, snakebite patients were 13.5 times more likely to have had early anaphylactic reactions than their controls, with a higher association in the age group > or = 20 years (OR = 30.3). Increased risks were also detected for pyrexia (OR = 11.7), with a marked association in the group under 19 years old (OR = 16.6). Severe cases of snakebite are an important treatable cause of morbidity in Brazil but therapy may be potentially life threatening. The higher case-fatality ratio encountered, compared to national statistics may be due the representativeness of the more severe cases who sought hospitalization. Preventing snakebite and early referral of those who are bitten is proposed.

Latex particle agglutination test in the diagnosis of Haemophilus influenzae type B, Streptococcus pneumoniae and Neisseria meningitidis A and C meningitis in infants and children

The knowledge of purulent meningitis etiology is essential in deciding the immediate therapy; in developing countries, however, the etiological agent identification does not reach 60% of the cases. A comparative study using the latex particle agglutination test (LPAT) in cerebrospinal fluid (CSF) for the diagnosis of meningitis due to Haemophilus influenzae type b, Streptococcus pneumoniae or Neisseria meningitidis A and C was carried out in Belo Horizonte MG, Brazil. CSF culture was used as a gold-standard. Two hundred and ninety-nine children, ranging from 3 months to 14 years of age, were included in the investigation. One hundred and forty-four presented a positive CSF culture for the above mentioned bacteria; the remaining presented meningitis due to other organisms (other bacteria or viral) or a normal CSF. The sensitivity and the specificity of LPAT was 95.7 and 100.0% for N. meningitidis C, 95.2 and 100.0% for H. influenzae type b and 86.5 and 100.0% for S. pneumoniae, respectively. When all three organisms were considered simultaneously, the sensitivity and the specificity was 93.0 and 100.0%, respectively. Taking into consideration a realistic estimate of disease prevalence in the community where the diagnostic test is being used, the positive predictive value and the posttest probability were estimated as 36.7 and 47.1% for children < 5 years and as 21.3 and 35.1% for children < 14 years of age, respectively. LPAT is a useful diagnostic test for meningitis due to the studied pathogens, especially in developing countries where laboratory facilities are limited.

[Epidemiology of Toxoplasma gondii infection in the municipality of Ribeirâo das Neves, MG. I. Importance of domestic animals as sources of T. gondii infection in humans]

During a six month period (June 1983 to January 1984), a case-control study was carried out to determine if the variables associated with domestic animals contact would be correlated with the prevalence of Toxoplasma gondii infection. A randomized sample of 500 subjects from the population of Ribeirão das Neves, Minas Gerais, Brazil was studied. A statistically significant correlation was found with cat, chicken and pig contact but none with consumption of meat, milk and eggs.

Validity of serology for American trypanosomiasis with eluates from filter paper

This study evaluates whether blood collected on filter paper kept at 4 degrees C and tested at different intervals of time (1, 7, 15, 30 and 60 days after collection) would present similar results when compared to the serum samples and whether the type of filter paper influences the results. Eluates from filter paper samples were tested for Trypanosoma cruzi antibodies using indirect immunofluorescence antibody test (IFAT), indirect haemagglutination (IHA) and enzyme-linked immunosorbent assay (ELISA) as reference, the antibody titer in sera. Analysis of data showed that results obtained with IFAT, IHA (cut off point = 1:40) and ELISA in sera had similar sensitivity and good concordance among reactions. The use of a multiple linear regression model indicated that titer fall in eluates occurs up to the 7th day after the collection, and it is more marked for samples with lower antibodies titers. However, no significant differences were observed by IFAT, IHA (cut off point = 1:20) and ELISA in the proportion of positive reactions between sera and eluates. The results also showed that Melitta, Klabin or Whatman (reference) filter papers could be indicated for surveys, since they have shown similar capacity of maintenance of anti-T. cruzi immunoglobulins.

Sonographic features of portal hypertension in schistosomiasis mansoni

The diagnostic value of real-time sonography in the study of portal hypertension was assessed in 66 patients with hepatosplenic schistosomiasis mansoni, all with Symmers's fibrosis and esophageal varices. Seventy-one individuals without schistosomiasis were selected as controls. The inner diameters of the portal vessels were measured by sonography in all patients and controls: splenoportography was also performed in the schistosomal group. Intra-splenic pressure was over 30 cm of water in 44 of 60 patients with schistosomiasis. The upper limit of normality for portal vessel diameters was set through receiver operating characteristic curve at 12 mm for portal vein, 9 mm for splenic vein at splenic hilus, and 9 mm for superior mesenteric vein. The best discriminative vein for the diagnosis of portal hypertension was the splenic vein followed by the portal vein. A direct correlation was observed between the diameter of the splenic vein, measured by sonography, and the intra-splenic pressure. Except for the paraumbilical and mesenteric veins, more frequently identified by sonography, there was no statistical difference in the frequency of visualization of splanchnic vessels by sonography or splenoportography.

[Hemotherapy and transfusional Chagas' disease in Brazil]

With the increased presence of Chagas' disease in urban areas and the rising importance of transfusional transmission of Trypanosoma cruzi, a proper and realistic approach to hemotherapeutic treatment has become crucial in Brazil. Bringing together data from various institutions, this study analyzed hemotherapy and the problem of transfusional Chagas' disease in 850 Brazilian municipalities from 1988 to 1989. It was found that some type of hemotherapy was practiced in 68.8% of these municipalities at the time, this practice being qualitatively and quantitatively proportional to the population size of the municipality. The official blood bank system supplied the blood used in 13% of these services. In relation to prevention of the main diseases transmissible by transfusion, prior screening of donors was carried out by 75.2% of the services for syphilis, 65.4% for hepatitis, 53.8% for AIDS, and 66.9% for Chagas' disease. These percentages vary by region and by size of the municipality. The majority of donors are classified as voluntary, with only 2% categorized as paid donors. In the case of Chagas' disease, most services used only one serologic technique to screen donors, most commonly hemagglutination or immunofluorescence, while only 10.3% of services had previous experience with chemoprophylaxis using gentian violet. The proportion of potential donors with positive serology for anti-Trypanosoma cruzi antibodies was around 1%. These data were confirmed by information from blood banks and Brazilian hemotherapy professionals.

Social networks and daily activities of street youth in Belo Horizonte, Brazil. Street Youth Study Group

Social networks and daily activities of children and adolescents living and/or working on the streets of a large Brazilian city were examined. Drawing on data collected through structured surveys, in-depth interviews, focus group discussions, and field observations, we described street youths' family situation, social resources, institutional experiences, survival activities, and problem behaviors and investigated differences attributable to age, gender, and living situation (at home or on the street). Youngsters who lived at home and worked on the street appeared to be experiencing orderly development despite their impoverished circumstances. Youngsters who lived on the street showed hallmarks of psychological and physical risk, including parental loss, diminished social support, substance abuse, and early onset of sexual activity. Possible implications of these contextual differences for development are discussed, and directions for future research are suggested.

HIV risk behavior and medical status of underprivileged youths in Belo Horizonte, Brazil

METHODS

From June 1989 to April 1991, 394 adolescents aged 10-18 years randomly selected upon admission at a state shelter in Belo Horizonte, Brazil underwent health history interview, physical examination, serology for HIV, hepatitis B, and syphilis, and stool examination. Participants were classified as street-based youths (n = 195) or home-based youths (n = 199). The age distribution was similar in both groups, although males were overrepresented among street-based youths (79.5% versus 62.3%).

RESULTS

Compared with home-based youths, street-based youths reported earlier onset (p = 0.009) and higher rates of sexual activity (odds ratio [OR], 2.1; 95% confidence interval [CI], 1.4-3.3), sexual abuse (OR, 3.7; 95% CI, 1.2-10.1), and sexually transmitted diseases (OR, 2.9; 95% CI, 1.3-6.6). Overall condom use was low in both groups. Street-based youths were 7.8 times more likely to use drugs than home-based youths (95% CI, 4.9-12.7). Inhalants and marijuana were the more commonly used drugs. Intravenous drug use was low.

CONCLUSIONS

Although chronic malnutrition and multiple parasitosis were common findings in both groups, street-based youths were more likely to present disorders related to trauma and poor hygienic conditions. Antibodies to HIV were detected in four (2%) street-based youths and in none of the home-based youths. This study confirms that street youths are at higher risk for HIV infection than their home-based peers and indicates a need for HIV prevention programs targeting this population.

A quasi-experimental epidemiological model for evaluating public health programmes: efficacy of a Chagas disease control programme in Brazil

Reported is the assessment of a model to evaluate the efficacy of public health programmes, using the example of the Chagas Disease Control Programme in the State of Minas Gerais, Brazil. The reduction in Trypanosoma cruzi infection rates in areas where interventions had been carried out for 5 years and 10 years, respectively, were compared with those where there had been no intervention (controls). A random sample of 470 households was selected and blood samples were collected from the 2354 inhabitants, 854 (36.3%) of whom were born after the start of the control programme. The data routinely collected by the control programme were also analysed to correlate the results with the incidence of T. cruzi infection. The programme efficacy was estimated by comparing the infection rates found in the study with those published by the Chagas Disease Serological Study (1975-80). Cross-sectional comparison of the data for the age group 2-6 years indicated that there had been a reduction in T. cruzi infection incidences of 94.7%, 63.2%, and 65%, respectively, in areas where interventions had been carried out for 10 years, 5 years, and in the control areas. Cohort comparison indicated, however, that the reduction (52.6%) occurred only in the intervention-10 area.

Snake bite and antivenom complications in Belo Horizonte, Brazil

Factors associated with clinical complications of snake bite and antivenom therapy were studied in 310 hospital patients admitted with snake bite over 6 years to a tertiary referral hospital in Belo Horizonte, southeast Brazil. Overall, 17.4% had early clinical complications including tissue loss associated with abscess and necrosis, acute renal failure, shock, acute lung oedema and intracranial haemorrhage. 3% had permanent sequelae, caused by muscle contractures and amputations, chronic renal failure, or death. Early complications were associated with the following: age under 9 years (P = 0.04), residence in a rural area (P = 0.04), and a delay of more than 8 h in seeking clinical care (P < 0.01). Antivenom was administered to 98.1% of patients; 13.8% presented with anaphylaxis and 11.8% with pyrexia. Individuals from a rural area had a higher occurrence of anaphylactic reactions (P = 0.03). Neither anaphylaxis nor pyrexia was linked with antivenom type and dosage. This study suggested that antivenom might be associated with a reduced risk of serious injuries related to snake bite, especially when administered within the first 8 h. Complications appeared to be a far greater risk than adverse reactions to the antivenom.

[Present status of bancroftian filariasis in Maceió, State of Alagoas, Brazil]

Epidemiological and entomological surveys were carried out in the human and mosquito populations in Maceió, Alagoas, in order to assess the present status of bancroftian lymphatic filariasis. Examination of thick blood smears of 10,450 students from different areas of the city revealed 0.66% Wuchereria bancrofti microfilaria carriers. The distribution of filariasis is focal in the city, 80% of the individuals with patent infection living in two neighboring areas with 1.24% and 5.25% prevalence. Parallel studies performed with samples of all age groups in the human population showed similar microfilaria prevalence rates observed previously in the student survey. However, thick blood smears taken from members of families with at least one subject with patent infection gave a prevalence six times greater suggesting, increased transmission in households. The percentage of carriers was higher in the youngest age group (< 20 years). Culex quinquefasciatus mosquitos caught at the locations where the autochthonous cases were found presented natural infection rates ranging from 0.28% to 4.62%. The combination of all these findings indicates occurrence of active transmission of W. bancrofti in the urban area of Maceió, Alagoas State. Based on these data, measures for the potential control of filariasis were planned.

[Evaluation of the efficacy of the Chagas' Disease Control Program: methodological aspects]

The efficacy of the Chagas' Disease Control Program was estimated in Minas Gerais State. Areas with different intervention times (10 and 5 years) and without intervention (control) were compared in order to verify a possible reduction in Trypanosoma cruzi infection incidence rates among those born after the Control Program. The Program efficacy was estimated comparing this study's infection rates with rates published by the Chagas' Disease Serological Survey, conducted between 1975-1980. The cross-sectional comparison for the 2-6-year age group showed a reduction of 94.7%, 63.2%, and 65.2% respectively, in areas where interventions had been carried for 10 years, 5 years, and in control areas. Cohort comparison, however indicated that reduction (52.6) occurred only in the area with 10 years of intervention. The data routinely collected by the Control Program were also analyzed and correlated with the incidence of T. cruzi infection. The results showed association between the Control Program and reduction in T. cruzi infection, measured by serological tests.

Sexual practices and attitudes of street youth in Belo Horizonte, Brazil. Street Youth Study Group

Street youth are at risk of HIV infection worldwide. To develop effective prevention strategies, information about the meanings and functions of sexual activity for street youth is needed. In this paper, data from structured questionnaires, focus group discussions, in-depth interviews and field observations are used to build up a picture of the sexual culture of 9-to-18-year-olds living and/or working on the streets of a large Brazilian city. The findings reveal that these children and adolescents engage in sexual behavior that puts them at risk of sexually transmitted diseases, including HIV/AIDS, and reinforce that sex is a multi-determined and entrenched behavior in this population. Interventions must take into account the fact that for street youth, sex is used as a means of ensuring survival, seeking comfort, finding pleasure, and dealing with psychological issues that arise during adolescence.

Bursting electrical activity in pancreatic beta-cells: evidence that the channel underlying the burst is sensitive to Ca2+ influx through L-type Ca2+ channels

In glucose-stimulated pancreatic beta-cells, the membrane potential alternates between a hyperpolarized silent phase and a depolarized phase with Ca2+ action potentials. The molecular and ionic mechanisms underlying these bursts of electrical activity remain unknown. We have observed that 10.2-12.8 mM Ca2+, 1 microM Bay K 8644 and 2 mM tetraethylammonium (TEA) trigger bursts of electrical activity and oscillations of intracellular free Ca2+ concentration ([Ca2+]i) in the presence of 100 microM tolbutamide. The [Ca2+]i was monitored from single islets of Langerhans using fura-2 microfluorescence techniques. Both the high-Ca(2+)- and Bay-K-8644-evoked [Ca2+]i oscillations overshot the [Ca2+]i recorded in tolbutamide. Nifedipine (10-20 microM) caused an immediate membrane hyperpolarization, which was followed by a slow depolarization to a level close to the burst active phase potential. The latter depolarization was accompanied by suppression of spiking activity. Exposure to high Ca2+ in the presence of nifedipine caused a steady depolarization of approximately 8 mV. Ionomycin (10 microM) caused membrane hyperpolarization in the presence of 7.7 mM Ca2+, which was not abolished by nifedipine. Charybdotoxin (CTX, 40-80 nM), TEA (2 mM) and quinine (200 microM) did not suppress the high-Ca(2+)-evoked bursts. It is concluded that: (1) the channel underlying the burst is sensitive to [Ca2+]i rises mediated by Ca2+ influx through L-type Ca2+ channels, (2) both the ATP-dependent K+ channel and the CTX- and TEA-sensitive Ca(2+)-dependent K+ channel are highly unlikely to provide the pacemaker current underlying the burst.(ABSTRACT TRUNCATED AT 250 WORDS)

Toxoplasmosis and mental retardation--report of a case-control study

A case-control study evaluating the association between mental retardation and toxoplasmosis was conducted among 845 school children in Belo Horizonte, MG, Brazil. Cases (450) were mentally retarded children attending a public school for special education. Controls (395) were children from the regular public school system. Clinical and anthropometric examinations and interviews were carried out to determine risk factors for toxoplasmosis and mental retardation. Diagnosis of Toxoplasma gondii infection was based upon an indirect immunofluorescent test (IFA); 55% of cases and 29% of controls were positive. The Relative Odds of mental retardation in children with positive serology was 3.0 (95% CI 2.2-4.0). Maternal exposure to cats and contact with soil were associated with an increased risk of mental retardation. Retinochoroiditis was fourfold more prevalent among cases than controls and was only diagnosed in T. gondii IFA positive participants. Congenital toxoplasmosis, in its subclinical form, appears to be an important component in the etiology of mental retardation, especially in high risk (lower socio-economic) groups. The population attributable risk was estimated as 6.0-9.0%, suggesting the amount of mental retardation associated with this infection.

High external Ca2+ levels trigger membrane potential oscillations in mouse pancreatic beta-cells during blockade of K(ATP) channels

Glucose depolarizes the pancreatic beta-cell and induces membrane potential oscillations, but the nature of the underlying oscillatory conductance remains unknown. We have now investigated the effects of the Ca2+ ionophore ionomycin and high external Ca2+ concentration ([Ca2+]o) on glucose-induced electrical activity and whole islet intracellular free Ca2+ concentration ([Ca2+]i), under conditions where the K(ATP) channel was blocked (100 microM tolbutamide or 4 microM glibenclamide). Raising [Ca2+]o to 10.2 or 12.8 mM, but not to 5.1 or 7.7 mM, turned continuous electrical activity into bursting activity. High [Ca2+]o (12.8 mM) regenerated a pattern of fast [Ca2+]i oscillations overshooting the levels recorded in tolbutamide. Ionomycin (10 microM) raised the [Ca2+]i and synergized with 5.1 mM Ca2+ to hyperpolarize the beta-cell membrane. The data indicate that a [Ca2+]i-sensitive and sulphonylurea-insensitive oscillatory conductance underlies the beta-cell bursting activity.

Epidemiology of Schistosoma mansoni infection in a low-endemic area in Brazil: clinical and nutritional characteristics

A cross-sectional case-control study designed to evaluate the role of malnutrition in the association between the intensity of Schistosoma mansoni infection and clinical schistosomiasis, was conducted in an area with both low frequency of infection and low morbidity of schistosomiasis in Brazil. Cases (256) were patients with a positive stool examination for S. mansoni; their geometrical mean number of eggs/gram of feces was 90. Controls (256) were a random sample of the negative participants paired to the cases by age, sex and length of residence in the area. The clinical signs and symptoms found to be associated with S. mansoni infection, comparing cases and controls, were blood in stools and presence of a palpable liver. A linear trend in the relative odds of these signs and symptoms with increasing levels of infection was detected. Adjusting by the level of egg excretion, the existence of an interaction between palpable liver and ethnic group (white) was suggested. No differences in the nutritional status of infected and non-infected participants were found.

Exposure to acellular blood products and risk of HIV infection in hemophiliacs from Belo Horizonte, Brazil

Results of a HIV prevalence study conducted in hemophiliacs from Belo Horizonte, Brazil are presented. History of exposure to acellular blood components was determined for the five year period prior to entry in the study, which occurred during 1986 and 1987. Patients with coagulations disorders (hemophilia A = 132, hemophilia B = 16 and coagulation disorders other than hemophilia = 16) were transfused with liquid cryoprecipitate, locally produced, lyophilized cryoprecipitate, imported from São Paulo (Brazil) and factor VIII and IX, imported from Rio de Janeiro (Brazil), Europe, and United States. Thirty six (22%) tested HIV seropositive. The univariate and multivariate analysis (logistic model) demonstrated that the risk of HIV infection during the study period was associated with the total units of acellular blood components transfused. In addition, the proportional contribution of the individual components to the total acellular units transfused, namely a increase in factor VIII/IX and lyophilized cryoprecipitate proportions, were found to be associated with HIV seropositivity. This analysis suggest that not only the total amount of units was an important determinant of HIV infection, but that the risk was also associated with the specific component of blood transfused.

Comparison on the performance of Leishmania major-like and Leishmania braziliensis braziliensis as antigen for New World leishmaniasis IgG-immunofluorescence test

The performance of an antigen of L. major-like promastigotes for the serological diagnosis of mucocutaneous leishmaniasis in the IgG-immunofluorescent test was compared to that of an antigen of L.braziliensis braziliensis. Each antigen was used to test two hundred and twenty-four sera of etiologies such as mucocutaneous leishmaniasis, deep mycoses, toxoplasmosis, malaria. Chagas' disease, visceral leishmaniasis, anti-nuclear factor, schistosomiasis, rheumatoid factor and normal controls. Agreement between responses to each antigen was high: 77.2% of leishmaniases sera agreed on a positive or a negative result to both antigens and 91.1% of control sera. Cross reactivity was restricted to Chagas' disease sera, visceral leishmaniasis, anti-nuclear factor and paracoccidioidomycosis. The quantitative response of leishmaniasis and Chagas' disease sera to both antigens was evaluated by a linear regression; although the y-intercept and the slope were different for each antigen, neither was better than the other in the disclosure of anti-Leishmania antibodies. In the case of Chagas' disease sera the L.major-like antigen was better than L.b.braziliensis' to disclose cross-reacting antibodies.

Vaccination of humans against cutaneous leishmaniasis: cellular and humoral immune responses

Brazilian army conscripts were vaccinated against American cutaneous leishmaniasis by using nonliving polyvalent promastigote Leish vaccine 5 or Leish vaccine 6 (vaccines with five or six Leishmania stocks) with or without Corynebacterium parvum. No statistically significant differences in lymphocyte stimulation indices were found between vaccinated groups with or without C. parvum, but lymphocyte stimulation indices of all vaccinees were significantly higher (P less than 0.001) than those of the placebo group. A correlation of 90% was found between positive skin test results and positive lymphocyte stimulation indices. Eight major antigens with estimated molecular masses of 13.5, 25, 40, 63, 73, 85, 97, and 160 kilodaltons were recognized by Leish vaccine 5 sera. Our finding also demonstrated the predominance of immunoglobulin M antibody in sera of vaccinated subjects and that a component of Leish vaccine 5, gp63, was immunogenic in humans both at the T-cell level and at the antibody level.

Factors associated with AIDS and AIDS-like syndrome among homosexual and bisexual men in Minas Gerais, Brazil

A case-control study to determine factors associated with AIDS and AIDS-like syndrome among homosexual/bisexual men was conducted in the State of Minas Gerais (Brazil). Eighty-three per cent (45 patients) of all AIDS/AIDS-like syndrome cases in homosexual/bisexual men reported in Minas Gerais between February, 1986 and June, 1987 were compared to 133 seronegative controls seen at the same clinic. Blood samples were tested by ELISA and confirmed by Western blot. Sex with men from the USA, sex with someone who developed AIDS, number of male partners (greater than or equal to 100 lifetime), age (greater than or equal to 30 years old) and ethnicity (white) were independently associated with AIDS/AIDS-like syndrome (Odds Ratios = 5.5, 4.3, 3.9, 3.5 and 2.7, respectively). Thirty-nine per cent of cases and 44% of controls reported bisexual activity during the previous two years. From these, a high proportion reported anal intercourse with women in the same period (53% of bisexual cases and 33% of bisexual controls). Bisexual men had more male partners than female partners in the previous two years (median male partners = 20 for cases and five for controls; median female partners = three for both cases and controls). This explains in part why the epidemic has increased more rapidly among men then among women in Minas Gerais, despite the large proportion of bisexuals with the disease.

Sensitivity, specificity and positive predictive value of selected clinical signs and symptoms associated with schistosomiasis mansoni

The signs and symptoms classically associated with Schistosoma mansoni infection were analysed in relation to their sensitivity, specificity and positive predictive value in identifying S. mansoni patients as well as more severe forms of the disease under field conditions. Data was collected in a survey conducted in a small urban area in the south east of Brazil (14.3% infection in the studied sample with a geometrical mean excretion of 95.5 S. mansoni eggs/gram of faeces). 'Blood in the stool' and a 'palpable and hardened liver' showed the highest positive predictive value; their presence, even in relatively low prevalence areas may be used by the health field workers as an indication of the existence of more advanced clinical forms of the disease.

Risk assessment for acquiring meningitis tuberculosis among children not vaccinated with BCG: a case-control study

This case-control study was conducted to assess the risk, among children aged 0-12 years, of developing meningitis tuberculosis (MT) associated with a lack of intradermal BCG vaccination. Cases (45) of MT admitted for treatment at the Fundacao Benjamin Guimaraes Hospital (Belo Horizonte, MG, Brazil), from 1975 to 1981, were matched for age at hospitalization, date of hospitalization and nutritional status, with two types of controls--patients with acute diarrhoea (AD) and patients with acute non-tuberculous bacterial pneumonias (BP)--admitted to the same hospital. Vaccination status was ascertained from the patients' medical records. Results showed a risk for MT, estimated by the odds ratio, between BCG non-vaccinated and BCG vaccinated patients, of 6.7 (95% Cl 2.3-19.0) comparing cases and AD controls, of 4.0 (95% Cl 1.5-11.0) comparing cases and BP controls and 5.7 (95% Cl 2.3-14.0) comparing cases with both controls. When adjustments were made for place of residence (Metropolitan Region of Belo Horizonte and other regions of Minas Gerais State), the risks decreased to 5.2 (95% Cl 1.9-14.0) and 2.9 (95% Cl 1.2-7.3) comparing cases with AD and BP controls, respectively.

Water-contact patterns and socioeconomic variables in the epidemiology of schistosomiasis mansoni in an endemic area in Brazil

A study was carried out in Comercinho in south-east Brazil where information relating to socioeconomic factors and water contacts was obtained from 290 (99% of the total) households and 1208 (82% of the total) inhabitants, respectively. Stool examinations and physical examinations were performed on 90% and 82% of the population, respectively. The rates of Schistosoma mansoni infection and splenomegaly were higher in families whose heads were manual workers, in individuals living in houses without piped water and of poor construction, and in those who were born in Comercinho. A total of 1017 (84%) individuals reported water contact; 75% of these contacts were for household activities or bathing and 21% for leisure. The faecal egg counts decreased in persons over 15 years of age, while the degree (intensity) of water contact did not. The mean degree of water contact was higher in individuals without than with piped water in the household (96.8+/-0.6 v. 25.7+/-0.6). The main risk factors for splenomegaly weer no piped water, intense water contact, bathing in streams, and daily contact (odds ratio=7.3, 5.1, 4.5 and 3.6, respectively). These results indicate that the extension of piped water to houses should decrease the incidence of splenomegaly in this endemic area.

Controlled field trials of a vaccine against New World cutaneous leishmaniasis

Two controlled, double blind field trials of a non-living promastigote vaccine against New World Cutaneous Leishmaniasis (NWCL) were conducted in 1981 and 1983 in Brazil. Brazilian Army conscripts were randomly assigned to the vaccine or placebo groups and tested during their training in the Amazon jungle, a high risk area for NWCL. The results obtained showed: no significant differences between the vaccine and the placebo groups with respect to a number of characteristics (age, race, previous contact with the jungle, etc.); no significant differences between the participants who got and who did not get NWCL during the trial, with respect to length of exposure, contact with the jungle, etc. and a reduction of 67.3 and 85.7% in the annual incidence rate of NWCL, in 1981 and 1983 respectively (although the difference between incidence rates of the disease in vaccinated and control groups in the 1983 trial was not statistically significant), among those vaccinated who had converted to a positive leishmanin skin test as compared with the placebo groups.