Biomedical subjects
Publications and source records attributed to E Massad.
A mathematical model was used to estimate malaria transmission rates based on serological data. The model is minimally stochastic and assumes an age-dependent force of infection for malaria. The transmission rates estimated were applied to a simple compartmental model in order to mimic the malaria transmission. The model has shown a good retrieving capacity for serological and parasite prevalence data.
An alternative way to estimate the endemic level of malaria amongst Brazilian indians is proposed. This is achieved by estimating the age-related 'force of infection' of malaria (the effective inoculation rate), applying a mathematical model, described elsewhere, to serological data. In addition we present a way to estimate the Basic Reproductive Rate of malaria in the same area. The results have shown a good degree of accuracy in describing the endemic pattern of malaria in the area, and also indicate some relevant aspects of its age distribution related to the design of control strategies.
This study addresses the problem of the existence of conditions for persistence or eradication of age-dependent directly transmitted infections. The usual system of differential equations describing the dynamics of the disease is transformed into integral equations. The authors show how to solve these equations and, by applying the contraction mapping theorem, give conditions for the persistence or eradication of the infection. A practical illustration of the application of the methods proposed is sketched, using data for rubella collected from a small Brazilian community.
Populations of Anopheles (Kerteszia) were sampled fortnightly over a one-year period (August 1991 to July 1992) at Ribeira Valley, S. Paulo State, Brazil. Indoor and outdoor collections were made on human bait at evening crepuscular period. The Polovodova technique for age grading was applied to 3,501 females of Anopheles cruzii and to 416 females of An. bellator. That sample represented 34.4% of the total number of mosquitoes collected. The most abundant species found was An. cruzii. However, An. bellator showed an endophagy that was almost three times greater than that of An. cruzii. The overall parous rate was 25.4% and uniparity was practically dominant one. A proportion of 26.9% of An. cruzii and 12.0% of An. bellator were found to be uniparous. Only three outdoor females of the former species (0.1%) showed biparity. Parity of An. cruzii was higher in females caught indoors than in those caught outdoors. Nevertheless, 497 nulliparous females examined (417 cruzii and 80 bellator) had ovaries that had advanced to Christophers and Mer stages III to V. These results imply that these females had already practised hematophagy. Relating these results to those from the parous females, a high statistical significance was found, leading to the conclusion that gonothophic discordance is a common pattern among these anophelines. Further, these results obtained with human bait catches strongly suggest that nearly 38.0% of these host-seeking females had already taken at least one previous blood-meal. So it is possible that enough time could thus be available for the plasmodian development in the vectors.
A relation between a rice irrigation system and mosquito breeding was established in a study undertaken at the Ribeira Valley Experimental Station, from January through December 1992. Flooding favoured Anopheles (Nyssorhynchus) and Culex (Melanoconion) species, while empty paddies condition were propitious to Aedes scapularis and Culex (Culex) species. Compared with a more primitive area of the same region, several species showed high a degree of adaptation to the anthropic environment. Among them, Anopheles albitarsis, a potential malaria vector that breeds in the irrigation system, has shown immature stage production thirteen times higher than at the natural breeding sites. In addition, Ae. scapularis, An. oswaldoi, Cx. bastagarius, and Cx. chidesteri presented high levels of synanthropy.
A study of adult Culicidae ecology was carried out from January 1992 through January 1993 at the rice irrigation system of the Ribeira Valley Experimental Station. The adaptation of Anopheles albitarsis to the anthropic environment became evident through the adult collections made at its various habitats represented by the irrigation system and the edge of the residual pond, as well as at those made within the local patchy residual woods. Other potential disease vectors were prevalent in the irrigated system too. There were Aedes scapularis, Culex nigripalpus and Cx. ribeirensis that were collected at various habitats. Remarkable differences among their prevalences were obtained such as between the natural forest and anthropic environments. In the former An. albitarsis was practically non-existent, thus suggesting that it might be considered as eusynathropic. As the populations of other species seemed to increase in the anthropic environment, they may be regarded as hemisynanthropes. Observations suggest the hypothesis that the development of irrigated land may be a factor in the emergence of An. albitarsis, and some other species, as well as the possibility of an increase in the transmission of mosquito-borne diseases such as malaria.
Resting adults Culicidae were collected from January 1992 through January 1993 in several habitats of the Ribeira Valley region. The diversity of species found among them suggested that the vegetation remaining within human settlements favored the survival and the population increase of some mosquitoes. Among there are: Ae. scapularis, Ae. serratus, Cx. (Culex), Cx. nigripalpus and Cx. (Melanoconion) such as Cx. ribeirensis. That preservation role may be attributed to the rearing of livestock and the consequent increase in the number of blood sources. These species may be classified as hemisynanthropes and Cx. oedipus apparently evolving to the eusynanthropic status. On the other hand, An. cruzii showed an asynanthropic behaviour, with a low degree of survival in the modified human environment. Epidemiological implications of the data are mentioned.
The search of scientific answers to problems due to procedures involving professional actions is a permanent challenge to the nurses committed with the improving of nursing care. In face of the intensive muscle soreness provoked by penicillin G benzatin shots, an experimental evaluation of this procedure was carried out in order to observe the influences of concentration and volumes used. This evaluation could give some insights to improve the nursing care, particularly those linked to the manipulation of the penicillin injection. The study was performed in the Faculty of Medicine of the University of São Paulo, in 27 Male Wistar rats. After the injection of the drug or saline solution in the right and left limb, respectively, the animals were sacrificed and the muscles in which the solution were injected were histologically examined. The use of penicillin provoked intensive inflammatory reaction, the peak intensity being attained after 48 hours. A remaining effect lasted about thirty days. The inflammatory reaction was similar for the three concentrations of penicillin. Nevertheless, the present research does not bring data that should modify the current injection procedures.
Rats were used as biological indicators of air quality in two heavily polluted Brazilian towns: São Paulo and Cubatão. They were exposed for 6 months to ambient air in areas where the pollution was known to be severe. The following parameters were studied and compared to those of control animals: respiratory mechanics, mucociliary transport, morphometry of respiratory epithelium and distal air spaces, and general morphological alterations. The results showed lesions of the distal and upper airways in rats exposed in Cubatão, whereas the animals from São Paulo showed only alterations of the upper airways but of greater intensity than those observed in the Cubatão group. There are both qualitative and quantitative differences in the pollutants of these places: in São Paulo automobile exhaust gases dominate and in Cubatão the pollution is due mainly to particulates of industrial sources. The correlation of the pathological findings with the pollutants is discussed and it is concluded that biological indicators are useful to monitor air pollutions which reached dangerous levels in São Paulo and Cubatão.
A model originally designed to fit population growth data was investigated to determine whether it could fit spirometric traces as a function of time in normal and ill humans and in normal rats, obtained, respectively, by spirometer and whole-body plethysmography. The model showed great accuracy when applied to a simple spirometer coupled with an analog-to-digital converter interfaced with a personal computer. It also proved to be a good alternative for the more expensive and less accurate electronic devices, as derivative systems, and may be an attractive method for research and/or diagnostic centers.
1. The resistance of Klebsiella pneumoniae to amikacin and gentamicin was studied by a mathematical model to predict the rate of sensitivity decrease. The results accurately matched experimental data, showing that the model is a reliable predicting tool. 2. The observations were carried out over six years and included 2677 cultures that were positive for K. pneumoniae. At the beginning of the observation period, 85.7% of the cultures were sensitive to amikacin and 40.8% were sensitive to gentamicin. Sensitivity to amikacin showed a surprisingly rapid decrease; at the end of the experimental period, amikacin and gentamicin sensitivities were 33.3% and 27.8%, respectively. 3. We conclude that patterns of resistance of other bacteria could be investigated using this method.
A comparative chronic inhalation exposure study was performed to investigate the potential health effects of gasoline and ethanol engine exhaust fumes. Test atmospheres of gasoline and ethanol exhaust were given to Wistar rats and Balb C mice housed in inhalation chambers for a period of 5 weeks. Gas concentration and physical parameters were continually monitored during the exposure period. Several biological parameters were assessed after the exposure including pulmonary function, mutagenicity, and hematological, biochemical, and morphological examinations. The results demonstrated that the chronic toxicity of the gasoline-fueled engine is significantly higher than that of the ethanol engine.
Two groups of 12 male Wistar rats received either 243 ppm of acetaldehyde or 5.7 ppm of formaldehyde for 8 h a day, 5 days a week during 5 weeks. These levels represent three times the threshold limit values (TLV) for these substances in Brazilian legislation. The animals were evaluated by pulmonary function tests before and after exposure to the pollutants. The data obtained from these rats were compared with those of 12 controls, housed in identical conditions for the same length of time but breathing normal air. The results showed an increase of the functional residual capacity, residual volume, total lung capacity and respiratory frequency in the rats exposed to acetaldehyde atmosphere. The animals exposed to formaldehyde did not present pulmonary function alterations when compared with the controls. The damage caused by acetaldehyde to the peripheral regions of the lung parenchyma, affecting small airways or altering pulmonary elastic properties, is discussed. It is suggested that the Brazilian TLV for acetaldehyde (78 ppm) is not as safe as that for formaldehyde (1.6 ppm).
A comparative inhalation exposure study was performed to investigate the potential health effect of gasoline and ethanol engine exhaust fumes. Wistar rats housed in inhalation chambers were exposed to test atmospheres of various concentrations of carbon monoxide (CO) and gasoline and ethanol exhaust fumes diluted with air. CO level, temperature, relative humidity and flow rate were monitored continually to control the gas concentration and the environment. The dilution method gave a concentration within 1.0% of the target. The LC50s for 3-h exposures were determined for the 3 test atmospheres. The results demonstrated that the acute toxicity, in terms of LC50, of the gasoline-fuelled engine was significantly higher than that of the ethanol-fuelled engine.
This paper describes the effects of repeated exposure to gasoline and ethanol exhaust fumes on the pulmonary mechanics of rats assessed by whole-body plethysmography. Two groups of 12 male Wistar albino rats each were tested before and after exposure to diluted gasoline or ethanol exhaust gases for 5 weeks, 8 h per day and 5 days per week. An additional group of 12 rats were exposed to clean air under the same experimental conditions. The variations of the functional parameters observed in the three groups before and after exposure were compared. Peak Expiratory Flow and Forced Expiratory Mean Flows in the ranges 0-25%, 25-50% and 50-75% of Forced Vital Capacity were significantly reduced in animals exposed to gasoline exhaust fumes, whereas the group exposed to ethanol exhaust fumes did not differ from the control group. This respiratory impairment is probably due to the presence of SO2 and the quality of the hydrocarbons in gasoline exhaust gases.
A simple technic for studying the pulmonary mechanics of rats by whole body plethysmography is presented. The parameters measured were: Tidal Volume (TV); Respiratory Frequency (RF); Transpulmonary Basal Pressure (TBP); Dynamic Compliance (Cdyn); Functional Residual Capacity (FRC); Transpulmonary Pressure/Volume curve (TP/V); Forced Expiratory Volume of 1/4 second (FEV 1/4); Expiratory Reserve Volume (ERV); Inspiratory Capacity (IC); Inspiratory Reserve Volume (IRV); Forced Vital Capacity (FVC); Residual Volume (RV); Forced Expiratory Mean Flow between 100-50% (FEMF 100-50), 50-25% (FEMF 50-25) and 25-0% (FEMF 25-0) of the FVC, and Total Lung Capacity (TLC). In order to verify the accuracy of the technic, common male adult Wistar rats, in which pulmonary obstructive disease is normally expected, were first submitted to these functional tests and then to pathological examination. According to the intensity of the morphological pulmonary lesion, the rats were divided in two groups: with and without suppurative pneumopathy. The analysis of the pulmonary function data showed significant decrease of the FEV 1/4 and FEMF 50-25 and increase of the FRC and RV in the groups with pulmonary suppuration. Thus, a discriminant function could be established to characterize the two groups with 100% efficiency. It was concluded that these pulmonary function tests are a valuable and reliable tool to detect lung diseases in rats.
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