Showing papers by "Universidade Federal de Minas Gerais published in 1992"

U-Pb Geochronology of Archean magmatism and Proterozoic metamorphism in the Quadrilátero Ferrífero, southern São Francisco craton, Brazil

Abstract: The Quadrilatero Ferrifero is a metallogenic district (Au, Fe, Mn) located in the southernmost Sao Francisco craton in eastern Brazil. It is composed of Archean granitoids, gneisses, and a greenstone belt sequence (Rio das Velhas Supergroup), overlain by a Proterozoic clastic-chemical sedimentary sequence hosting a thick Lake Superior-type banded iron formation (Minas Supergroup). A U-Pb study of the main units leads to the following conclusions: granitoid emplacement was dated at 2776 +7/-6 Ma and 2721 ± 3 Ma; two felsic volcanic rocks from the Rio das Velhas Supergroup yielded ages of 2776 +23/-10 Ma and 2772 ± 6 Ma. These data indicate that greenstone-belt volcanism was coeval with granitoid emplacement, a common feature of greenstone-belt terrains, but so far undocumented in the southern Sao Francisco shield. The younger granitoid intrusion marks the stabilization of the shield in Late Archean time. Zircon cores older than 2776 Ma, together with other data, indicate the presence of continental crust 2.88-3.1 Ga old in the Quadrilatero Ferrifero. A detrital zircon from the uppermost formation in the Minas Supergroup (Sabara Formation) is concordant at 2125 ± 4 Ma and provides the first age constraint on the deposition of the Supergroup. Monazite from two pegmatites and titanite from an amphibolite enclave in gneisses from the Bacao Complex, in central Quadrilatero Ferrifero, yielded ages between 2060 Ma and 2030 Ma. These data may constrain the minimum age for the deposition of the Minas Supergroup. In addition, they indicate that the Early Proterozoic Transamazomian orogeny is represented by amphibolite-facies metamorphism and partial melting of Archean crust.

Differential baroreceptor reflex modulation by centrally infused angiotensin peptides

Abstract: The present study was designed to investigate the effect of intracerebroventricular (icv) and intravenous (iv) infusion of angiotensin (ANG)-(1-7), ANG III, and ANG II on the baroreceptor control of heart rate (BHR) in conscious rats. Reflex changes in HR were elicited by bolus iv injection of either phenylephrine or sodium nitroprusside before and within 1 and 3 h of icv infusion of ANG II (n = 10), ANG III (n = 9), ANG-(1-7) (n = 9), or saline (n = 9) at a rate of 3 nmol.7.5 microliter-1.h-1. In another group of animals (n = 23), iv infusion of the same amount of ANG peptides was carried out at a rate of 0.7 ml/h. The average ratio of changes in HR in beats per minute and changes in mean arterial pressure (MAP, mmHg) was used as an index of BHR sensitivity. ANG II and ANG III produced a significant increase in the basal levels of MAP, but only during the first hour of infusion (iv or icv). No significant changes in baseline HR were observed. ANG-(1-7) and saline infusion did not change basal levels of HR or MAP (iv or icv). ANG II (iv and icv) and ANG III (icv) caused a significant decrease in the BHR sensitivity for reflex bradycardia. In contrast, icv infusion of ANG-(1-7) induced a significant increase in BHR sensitivity for reflex bradycardia (-3.0 +/- 0.3, 1 h, and -2.8 +/- 0.1 beats.min-1.mmHg-1, 3 h vs. -2.1 +/- 0.2 beats.min-1.mmHg-1, before infusion).(ABSTRACT TRUNCATED AT 250 WORDS)

Experimental Chagas' disease in dogs

Abstract: This paper describes the development of experimental Chagas' disease in 64 out-bred young dogs. Twenty-nine animals were inoculated with the Be-62 and 35 with Be-78 Trypanosoma cruzi strains. Twenty-six were infected with blood trypomastigotes by different inoculation routes and 38 with metacyclic trypomastigotes from the vector via the conjunctival route. Twenty of the 26 dogs infected with blood trypomastigotes were autopsied during the acute phase. Eleven died spontaneously and nine were sacrificed. Six remained alive until they died suddenly (two) or were autopsied (four). Twelve of the 38 dogs infected with metacyclic trypomastigotes evolved naturally to the chronic phase and remained alive for 24-48 months. The parasitemia, clinical aspects and serology (IgM and IgG) as well as electrocardiogram, hemogram and heart anatomo-histopathologic patterns of acute and chronic cardiac forms of Chagas' disease as seen in human infections, were reproduced. The most important finding is the reproductibility of diffuse fibrosing chronic chagasic cardiopathy in all dogs infected with Be-78 T. cruzi strain autopsied between the 90th and 864th days of infection. Thus, the dog can be considered as a suitable experimental model to study Chagas' disease according to the requisites of the World Health Organization (1984). Futhermore the animal is easily obtained and easy to handle and maintain in experimental laboratory conditions.

Analysis of switching frequency reduction methods applied to sliding mode controlled DC-DC converters

Abstract: The operation of sliding mode controlled DC-DC power converters operating at finite switching frequency is studied. Several methods currently used for reduction of power electronic converter switching frequency are considered. The finite switching frequency behavior of the control system that arises from the use of those switching frequency reduction methods is analyzed from the viewpoint of dynamic and steady-state errors. Simulation and experimental results are presented. Hardware details for the implementation of the switching frequency reduction methods that lead to the best results are also given. >

Duodenal ulcer and eradication of Helicobacter pylori in a developing country. An 18-month follow-up study.

Abstract: Forty-eight patients with endoscopically proven duodenal ulcer (DU) and Helicobacter pylori infection detected by 14C-urea breath test (BT) were assigned to 5 days of treatment with furazolidone, metronidazole, and amoxicillin in addition to eventual classical anti-ulcer agents if necessary. Clinical evaluation and BT were repeated at 2, 6, and 18 months after therapy to determine H. pylori eradication or reinfection. Endoscopy was also repeated at 6 and 18 months after treatment to detect DU relapse. In 29 (60%) patients H. pylori had been eradicated at 2 months after therapy, and in 19 (40%) infection persisted. After successful eradication, 6 of 29 (20.7%) were reinfected. All 24 patients who were negative at the 18-month evaluation were asymptomatic, free of anti-ulcer drugs, and with healed ulcers, whereas among the 19 positive patients followed up, 11 (57%) continued to be symptomatic and still using anti-ulcer agents (p < 0.010), and 10 (53%) showed active ulcers at endoscopy (p < 0.010). H. pylori...

Effect of dietary chitin on cholesterol absorption and metabolism in rats.

Abstract: The effect of chitin at the level of 5% in the diet on cholesterol absorption and metabolism was studied in Wistar rats fed on diet containing beef tallow (7%) and cholesterol (1%). When compared with pair-fed controls, rats fed on diet containing chitin had: (1) similar weight gain and feed efficiency, (2) lower apparent protein digestibility, (3) equivalent liver steatosis, (4) reduced levels of liver triglycerides and cholesterol, (5) similar levels of serum and fecal cholesterol, (6) higher excretion of triglycerides in feces.

Host specificity and seed dispersal of Psittacanthus robustus (Loranthaceae) in south-east Brazil

Abstract: Psittacanthus robustus (Loranthaceae) is a Neotropical mistletoe which grows mainly on species of Vochysiaceae in Brazilian ‘cerrado’ regions. Its parasitizing pattern involves: (a) the height and the aspect of the crown of the host-plants; (b) the presence of sticky substance in the fruits of the parasite; and (c) the feeding behaviour and habitat selection of the dispersal agent, the swallowtanager Tersina viridis viridis. The feeding behaviour of this bird on fruits of P. robustus facilitates seed release and seedling establishment; its foraging habit and habitat selection account for high concentrations of the parasites on their preferred host-plants.

The L short-scar mammaplasty: a new approach.

Abstract: An improved L mammaplasty technique was employed in 178 patients aged 13 to 55 years, with reductions of up to 1280 gm per breast, with small, well-positioned, and undistorted scars. I have obtained a satisfactory final shape of the breast with no major complications over a 3-year follow-up period. The markings are based on chest width and on the quantity of skin that will remain. The technique allows the surgeon to remove more skin, and it is indicated for minor, moderate, and large hypertrophies, as well as for ptotic and asymmetrical breasts. The resection comprises skin and mammary tissue from the inferior and middle portions of the breast, preserving the main lactiferous ducts. In case of hypertrophic breasts, the base is removed, preserving the branches of the lateral cutaneous nerves, which derive from the third, fourth, and fifth intercostal nerves.

Angiotensin-(1-7) is a potent antidiuretic peptide in rats.

Abstract: We have shown previously that angiotensin-(1-7) (Asp-Arg-Val-Tyr-Ile-His-Pro) is a biologically active endogenous angiotensin which is a major product of angiotensin I processing by an angiotensin converting enzyme (ACE)-independent pathway. Intense staining for angiotensin-(1-7) immunoreactivity was demonstrable in brain areas related to the maintenance of hydromineral balance, suggesting the involvement of this peptide in this process. In the present study we investigated the antidiuretic effect of angiotensin-(1-7) by determining its effect on the water diuresis produced by an ip water load (5 ml/100 g) in male Wistar rats. The peptide had a pronounced antidiuretic effect when administered peripherally in doses ranging from 5.5 to 22 pmol/100 g. In contrast, angiotensin II presented only a small effect with the highest dose used (20 pmol/100 g). Comparison of the potency of angiotensin-(1-7) and vasopressin (AVP) showed that both peptides act in the same molar range although AVP was slightly more potent than angiotensin-(1-7). Urine volumes for 22 pmol/100 g angiotensin-(1-7) were 0.85 +/- 0.26 and 3.47 +/- 0.36 ml for hours 1 and 2, respectively, whereas they were 0.54 +/- 0.40 and 2.38 +/- 0.64 ml for 10 pmol/100 g AVP. There was apparent additivity of effect when 10 pmol of each peptide were administered simultaneously (0.0 and 1.72 +/- 0.45 ml vs 2.58 +/- 0.45 and 3.85 +/- 0.35 ml for control for hours 1 and 2, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Immune responses during human schistosomiasis mansoni. XVIII. Immunologic status of pregnant women and their neonates.

Abstract: The immune status of peripheral blood mononuclear cells (PBMC) and sera of pregnant women infected with the helminth Schistosoma mansoni was studied during pregnancy and the cord blood mononuclear cells (CBMC) and sera from their offspring were studied at parturition. PBMC pokeweed mitogen-induced responses were maintained in gravid women, but the responses to both schistosome and non-schistosome antigenic preparations declined progressively during pregnancy. Schistosomal antigens stimulated proliferative responses by the CBMC of many neonates born of infected mothers, but not those of uninfected mothers. These specific responses by CBMC of only neonates born of infected mothers are indicative of in utero, cell-mediated sensitization of the neonates, which could be due either to circulating schistosomal antigens or to anti-idiotypic antibodies which cross the placenta during gestation. Sera from infected mothers and the cord blood sera from their babies showed the same levels of specific IgG anti-schistosomal activity. Anti-schistosomal IgM levels were maintained during pregnancy to some antigens and not to others, while such antibodies were rarely found in cord blood sera, and then only at very low levels.

Analysis of anti-keyhole limpet haemocyanin antibody in Brazilians supports its use for the diagnosis of acute schistosomiasis mansoni

Abstract: Antibody (immunoglobulin (Ig) G) to the haemocyanin of the keyhole limpet (KLH) (Megathura crenulata), which shares a well defined carbohydrate epitope with the surface of schistosomula of Schistosoma mansoni, was determined by enzyme-linked immunosorbent assay (ELISA) in the sera of Brazilians with acute schistosomiasis. Of 53 such individuals tested, 51 had a level of KLH reactivity in excess of the mean +2 standard deviations of that exhibited by chronically infected individuals. This difference in reactivity allowed the acute cases to be readily identified by visual inspection of ELISA plates. The levels of IgG in patients with hepatointestinal and hepatosplenic schistosomiasis, as well as in non-infected, seropositive residents of endemic areas and infected children from endemic areas, were not statistically different from those of intestinal patients. Significant levels of anti-KLH IgG were not detected in patients with leishmaniasis, Chagas disease, ancylostomiasis or ascariasis. The results support the use of KLH as a means of rapidly and easily identifying individuals with acute schistosomiasis.

Evaluation of the routine use of the nasogastric tube in digestive operation by a prospective controlled study.

Abstract: This prospective, randomized controlled trial was undertaken to evaluate the effect of tube decompression of the stomach after surgical procedure on the digestive tract. One hundred and nine patients were randomly allocated to postoperative treatment with (57 patients) or without (52 patients) nasogastric tubes. No significant differences were found between the two groups in the duration of hospitalization, time to begin peroral fluid intake, occurrence of hiccups, vomiting, nausea, parotiditis, nasal septum necrosis, anastomotic leak and wound dehiscence. Moreover, abdominal distension, pyrosis, otalgia, dysphagia, odynophagia and atelectasis occurred more often in intubated patients as shown by chi-square analysis of the data with Yates correction, with the level of significance at p = less than 0.05. Tube decompression of the stomach does not relieve intestinal paralysis after digestive operations. These data seem to indicate that the routine prophylactic use of a nasogastric tube is unnecessary in gastrointestinal operations.

Estimating the Total Number of Distinct Species Using Presence and Absence Data

Abstract: SUMMARY Consider the problem of estimating the total number of distinct species in some specified region under investigation. Suppose the region is divided into N disjoint subregions or quadrats of equal area. A sample of size n quadrats is chosen, n 1. The other is to place at random n quadrats of equal area and fixed shape in the region of investigation. In both cases the n quadrats in the sample are assumed to be disjoint and are totally observed. So in fact when quadrat sampling is used, a random sample of space is taken instead of a random sample of individuals. It has been observed that species are often present with some natural clumping, which creates dependence between quadrats and within quadrats. Heltshe and Forrester (1983) and Smith and van Belle (1984) introduced some estimators for S when quadrat sampling is used; see also Burnham and Overton (1979). The estimators they proposed are nonparametric and were developed by using jackknife and bootstrap arguments. For a particular example, Palmer (1990) compared several estimators and showed that the first-order jackknife estimator is preferred within this group. In this paper we introduce some empirical Bayes estimators for S when quadrat sampling is used by imposing a grid on the region. The probabilistic model used to derive these estimators is basically a version of the Efron and Thisted (1976) model adapted to the case of quadrat

Spiral bacterium associated with gastric, ileal and caecal mucosa of mice.

Abstract: Summary A spiral shaped bacterium was seen in smears and histological sections (stained by carbolfuchsin) of gastric, ileal and caecal mucosa as well as in stool smears from mice. A significant correlation between the presence of the spiral bacterium and the occurrence of gastritis was observed but the ileal and caecal mucosa seemed unaffected. The bacterium was Gram negative and grew on BHM and Skirrow's medium, under microaerophilic conditions, at 37°C. Its major biochemical characteristics included positive catalase and oxidase reactions and a rapidly positive urease test. There were 2 or 3 spiral turns per cell and a tuft of up to 12 sheathed flagella on each pointed end. Entwined, braided periplasmic fibrils covered the surface of the cell. This spiral bacterium seemed to be part of the normal intestinal flora but was associated with gastritis.

Is multiple sclerosis in Brazil and Asia alike

Abstract: The clinical picture of 67 consecutive patients with definite multiple sclerosis in Belo Horizonte, Brazil, was analysed. There were 20 patients with the predominant optic-spinal form of the disease and eight with Devic's disease. Visual loss occurred in 43% of the cases as the presenting symptom and in 84% in the course of the illness. Symptoms related to spinal cord and cerebellar involvement were observed in 64% and 52% respectively. The high prevalence of visual and spinal abnormalities at onset and during the course of the illness, the lesser common involvement of the cerebellum and the relative frequency of Devic's disease make multiple sclerosis in Brazil similar to that observed in Eastern countries in distinction to the clinical pattern seen in the United States and Europe.

Lossy transmission line transient analysis by the finite element method

Abstract: A time-domain finite-element (TDFE) method applied to the analysis of electrical transients on lossy transmission lines is presented. The general telegraph equations are solved numerically at discrete time steps. Examples of voltage waveform on lossy single-phase lines are shown. Preliminary results indicate that the TDFE method works well for single-phase lossy transmission line transient analysis. >