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Biomedical subjects

A C Magalhães

Publications and source records attributed to A C Magalhães.

At least 19 recordsLinked to original sources
PubMed2007

Influence of fluoride dentifrice on brushing abrasion of eroded human enamel: an in situ/ex vivo study.

This in situ/ex vivo study assessed the effect of fluoride dentifrice on eroded enamel subjected to brushing abrasion. In a crossover study performed in 2 phases, 10 volunteers wore acrylic palatal appliances, each containing 3 human enamel blocks. Dentifrice was used to brush the volunteers' teeth and the specimens subjected to abrasion. In phases A and B the dentifrices used had the same formulation, except for the absence or presence of fluoride, respectively. The blocks were subjected to erosion by immersion of the appliances in a cola drink for 5 min, 4 times a day. Then the blocks were brushed, and the appliance was replaced into the mouth. Enamel alterations were determined using profilometry and percentage change in surface microhardness (%SMHC) tests. The data were tested using the paired t test. The mean wear values (+/-SD, microm) were: group A 6.84 +/- 1.72 and group B 5.38 +/- 1.21 (p = 0.04). The mean %SMHC values (+/-SD) were: group A 54.6 +/- 16.2 and group B 45.7 +/- 6.8 (p = 0.04). Fluoride dentifrice had a protective effect on eroded enamel subjected to brushing abrasion.

Adult↗
PubMed2006

Effect of salivary stimulation on erosion of human and bovine enamel subjected or not to subsequent abrasion: an in situ/ex vivo study.

This in situ/ex vivo study evaluated whether saliva stimulated by chewing gum could prevent or reduce the wear and the percent change in microhardness (%SMH) of bovine and human enamel submitted to erosion followed by brushing abrasion immediately or after 1 h. During 2 experimental 7-day crossover phases, 9 previously selected volunteers wore intraoral palatal devices, with 12 enamel specimens (6 human and 6 bovine). In the first phase, the volunteers immersed the device for 5 min in 150 ml of cola drink, 4 times per day (at 8, 12, 16 and 20 h). Immediately after the immersions, no treatment was performed in 4 specimens, 4 other specimens were immediately brushed (0 min) using a fluoride dentifrice, and the device was replaced into the mouth. After 60 min, the remaining 4 specimens were brushed. In the second phase, the procedures were repeated, but after the immersions, the volunteers stimulated the salivary flow rate by chewing a sugar-free gum for 30 min. Changes in wear and %SMH were measured. ANOVA and Tukey's test showed statistical differences (p<0.05) for the following comparisons. The chewing gum promoted less wear and %SMH. A decreasing %SMH and an increasing enamel wear were observed in the following conditions: erosion only, 60 min and 0 min. The human enamel presented greater %SMH and less wear compared to bovine enamel. The data suggest that the salivary stimulation after an erosive or erosive/abrasive attack can reduce the dental wear and the %SMH.

Adult↗
PubMed2001

Screening of expression libraries using ELISA: identification of immunogenic proteins from Tityus bahiensis and Tityus serrulatus venom.

The present report describes the use of ELISA with cDNA expression libraries in the identification of immunogenic proteins. The methodology described was applied using libraries constructed with mRNA isolated from Tityus serrulatus and Tityus bahiensis venom glands. In addition we describe for the first time the sequence of a neurotoxin from Tityus bahiensis venom gland named TbTx5 whose amino acid sequencing showed 93% similarity with the Tityus bahiensis TbTx IV-5 neurotoxin. The methodology described can be used for the generation of an immunogenic bank in order to contribute to genome and proteome projects.

Amino Acid Sequence↗
PubMed2001

Internalization of mammalian fluorescent cellular prion protein and N-terminal deletion mutants in living cells.

The cellular prion protein (PrP(c)) is a glycosylphosphatidylinositol (GPI)-anchored plasma membrane protein whose conformational altered forms (PrP(sc)) are known to cause neurodegenerative diseases in mammals. In order to investigate the intracellular traffic of mammalian PrP(c) in living cells, we have generated a green fluorescent protein (GFP) tagged version of PrP(c). The recombinant protein was properly anchored at the cell surface and its distribution pattern was similar to that of the endogenous PrP(c), with labeling at the plasma membrane and in an intracellular perinuclear compartment. Comparison of the steady-state distribution of GFP-PrP(c) and two N-terminal deletion mutants (Delta32-121 and Delta32-134), that cause neurological symptoms when expressed in PrP knockout mice, was carried out. The mutant proteins accumulated in the plasma membrane at the expense of decreased labeling in the perinuclear region when compared with GFP-PrP(c). In addition, GFP-PrP(c), but not the two mutants, internalized from the plasma membrane in response to Cu2+ treatment and accumulated at a perinuclear region in SN56 cells. Our data suggest that GFP-PrP(c) can be used to follow constitutive and induced PrP(c) traffic in living cells.

Animals↗
PubMed1997

Chilling stress leads to increased cell membrane rigidity in roots of coffee (Coffea arabica L.) seedlings.

Tropical and sub-tropical higher plant species show marked growth inhibition when exposed to chilling temperatures. In root tip segments of coffee seedlings which were subjected for 6 days to temperatures of 10, 15, 20 and 25 degrees C, in darkness, we have detected an increased amount of malondialdehyde formed in the 10 degrees C treatment, accompanied by higher electrolyte leakage. The electron paramagnetic resonance (EPR) technique and the fatty acid spin probes 5-, 12- and 16-doxylstearic acid were used to assess cellular membrane fluidity. At the depth of the 5th and 16th carbon atom of the alkyl chains the nitroxide radical detected more rigid membranes in seedlings subjected to 10 degrees C compared with 15 and 25 degrees C. At the C-12 position of the chains the probe showed very restricted motion and was insensitive to chilling induced membrane alterations. EPR parameters for intact tissues and microsome preparations from root tips showed that the fluidity was essentially the same when evaluated at C-5 and C-16 positions of the chains, and was considerably more fluid for microsomal membranes in the region of the C-12 position of the bilayers. The rotational motion of the nitroxide at C-16 position of the chains experienced a phase transition at about 15 degrees C. The calculated energy barriers for reorientational motion of the probe 16-doxylstearic acid were higher at temperatures of 5-15 degrees C than in the interval of 15-25 degrees C, suggesting that below the phase transition the membrane lipids assume a more ordered and compacted array. Membrane rigidity induced by chilling was interpreted as due to lipid peroxidation that could have been facilitated by higher density of peroxidizable chains below the membrane phase transition.

Coffee↗
PubMed1997

MR imaging of intramedullary and intradural-extramedullary spinal cysticercosis.

OBJECTIVE: The purpose of our study was to retrospectively review the MR imaging findings in a group of patients with clinically proven cysticercosis involving the spinal cord, the spinal subarachnoid space, or both. MATERIALS AND METHODS: We retrospectively reviewed images of 16 patients with clinically diagnosed spinal cysticercosis to summarize the imaging characteristics. All patients underwent T1- and T2-weighted sagittal, axial, or both sagittal and axial MR imaging before i.v. administration of paramagnetic contrast media. Thirteen patients also underwent sagittal, axial, or both sagittal and axial T1-weighted MR imaging after i.v. gadolinium administration. In addition, all patients underwent cranial CT, MR imaging, or both to reveal possible evidence of cranial cysticercosis. RESULTS: MR imaging revealed isolated intradural-extramedullary involvement (n = 9), isolated intramedullary involvement (n = 3), combined intradural-extramedullary and intramedullary involvement (n = 3), and/or syringomyelia caused by infection and associated with chronic spinal arachnoiditis (n = 2). Evidence of intradural-extramedullary disease included cystic structures within the subarachnoid space or homogeneous sheetlike enhancement within the subarachnoid space over the surface of the spinal cord. Evidence of intramedullary disease included focal cystic lesions or syringomyelic cavitation of the spinal cord. All patients had evidence of simultaneous intracranial cysticercosis as shown on cranial CT, MR imaging, or both. CONCLUSION: In the absence of scolex visualization, cysticercotic involvement of the spinal cord or spinal subarachnoid space has a nonspecific appearance on MR imaging. On the basis of the findings in this group of patients, we believe that spinal cysticercosis is most often accompanied by intracranial disease.

Adult↗
PubMed1995

[Significance of the nuclear magnetic resonance in the detection of coronary artery patency after thrombolysis].

PURPOSE: To determine the value of magnetic resonance imaging (MRI) in the noninvasive detection of infarct related coronary artery patency after thrombolysis. METHODS: We studied 26 patients with acute myocardial infarction submitted to thrombolysis underwent MRI studies before and after 0.1mmol/kg gadolinium-DTPA injection within the first 48 h of MI. Signal intensity was assessed by circumferential profile analysis techniques. RESULTS: The average ratio of signal intensity of infarcted tissue over normal myocardium (I/N) was significantly higher in patients with patent arteries (1.3 +/- 0.13 vs 1.12 +/- 0.07, p < 0.02). Compared to coronariography MRI, sensitivity of 81% and specificity of 100% for the diagnosis of coronary patency. CONCLUSION: Gadolinium infusion increased infarcted and normal myocardium differentiation. The study of gadolinium kinetics at MRI is a promising technique for noninvasive diagnosis of coronary patency.

Aged↗
PubMed1995

[Magnetic resonance imaging in chronic Chagas cardiopathy. Correlation with endomyocardial biopsy findings].

PURPOSE: To study the correlation between magnetic resonance imaging of the heart and right ventricle endomyocardial biopsy results in chronic Chagas' heart disease. METHODS: Ten patients with Chagas' disease, mean age 47 +/- 7 years, all males, in congestive heart failure with New York Heart Association class II (2 patients), III (6) and IV (2) were studied. Mean left ventricular ejection fraction was at echocardiogram 36 +/- 6%. The patients were submitted to right ventricular endomyocardial biopsy and magnetic resonance imaging of the heart. The results of this group were compared with a control group of patients with idiopathic dilated cardiomyopathy, with mean age of 46 +/- 10 years and left ventricular ejection fraction of 30 +/- 4%, in heart failure with functional class II (1 patient), III (5) and IV (1). RESULTS: All patients with Chagas' heart disease presented an increase in magnetic ressonance imaging signal of the heart after gadolinium use. The septal signal intensity changed from 0.87 +/- 0.06 to 1.54 +/- 0.16 (p < 0.001). In the control group the mean septal signal intensity was 0.93 +/- 0.07 before and 0.89 +/- 0.06 after the gadolinium (p = ns). Eight patients of the Chagas' disease group had biopsy proven myocarditis and two had borderline myocarditis. However, only one patient of the control group had diagnosis of borderline myocarditis. CONCLUSION: Myocarditis is frequently found in Chagas' heart disease patients and who unlike controls present a significant increase in myocardial signal intensity after gadolinium infusion. The magnetic resonance imaging of the heart seems a promising alternative method for the diagnosis of an inflammatory process in Chagas' heart disease.

Adult↗
PubMed1976

Influence of Temperature on Nitrate Metabolism and Leaf Expansion in Soybean (Glycine max L. Merr.) Seedlings.

The effect of various day temperatures on NADH-nitrate reductase, NADH- and NADPH-glutamate dehydrogenases, nitrate, protein and leaf area, measured at intervals during the ontogeny of the first trifoliolate soybean leaf, was determined. At 32.5 C and 25 C, nitrate concentration, nitrate reductase, and NADPH-glutamate dehydrogenase activities increased concurrently with leaf development and then decreased as leaf maturation progressed. At 40 C, these three components showed no initial increase and the concentration or activities decreased throughout the development of the leaf. The effects of temperature on NADH-glutamate dehydrogenase were the reverse. Rates of protein accumulation were higher at 40 C during the first 2 days of leaf development while higher rates were measured the first 5 days of leaf growth at 32.5 C. At 25 C, protein accumulation was low during the first 3 days of leaf growth, increased in the period of 3 to 5 days, and then declined up to 8 days of leaf development. Leaf expansion progressed at faster rates at 32.5 C and 25 C and at a much slower rate at 40 C. Leaf growth was essentially complete after the fifth day regardless of temperature.In crude leaf homogenates, apparent irreversible inactivation temperatures were 36 C for nitrate reductase and 65 C for NADPH-glutamate dehydrogenase. In vivo studies indicated a lower inactivation temperature for NADPH-glutamate dehydrogenase; however, it was still more heat-tolerant than nitrate reductase.We envisaged that reduced nitrogen supplied by NO(3) (-) assimilation is a factor in leaf expansion.

Journal Article↗
PubMedDate not supplied

[Lumbar disc hernia: indications for percutaneous discectomy].

The treatment of herniated lumbar disc by non-surgical procedures, through automated percutaneous discectomy, was introduced in Brazil by the authors in 1988. In this preliminary report the results obtained with this method in three patients are presented. Existing literature mentions a rate of 80% successful results in selected cases submitted to this treatment.

Adult↗
PubMedDate not supplied

Wilson's disease: magnetic resonance imaging (MRI) with clinical correlations in 16 cases.

The purpose of this study was to evaluate MRI findings in a group of patients with Wilson's disease, trying to establish possible correlations between clinical and image data. Sixteen patients (8 males and 8 females), with ages ranging from 11 to 50 years, and duration of illness ranging from 5 months to 32 years, were submitted to MRI in a 1.5T System. Four patients were asymptomatic, 4 had mild neurological findings, 2 were moderately affected and the remaining 6 had a severe form of the disease. All patients were receiving D-penicillamine by the time of the study. The most symptomatic patients presented five or more sites of abnormalities on MRI. The putamen was affected in all symptomatic individuals and one asymptomatic and 11 of them presented dystonia on neurological examination. A striking feature was the peripheral localization of putaminal hyperintense lesions on T2 weighted images. In eight cases, striatum or "substantia nigra" lesions explained parkinsonism observed on neurological examination. MRI seems to be an efficient method to study neurological involvement of Wilson's disease allowing some interesting anatomo-clinical correlations.

Adolescent↗
PubMedDate not supplied

[Paracoccidioidomycosis of the central nervous system: study of 5 cases by magnetic resonance].

Paracoccidioidomycosis is a systemic mycosis, endemic in South and Central America, that affects the central nervous system in almost 10% of the cases. Neurological involvement includes to different clinical forms: meningeal and granulomatous form, also known as pseudotummoral form. Five patients with intracranial paracoccidioidomycosis were submitted to MR examination in a 1.5T system. All patients presented multiple round or lobulated lesions, hyperintense in T1-weighted images and predominantly hypointese in T2-weighted images. The lesions were distributed diffusely, with a slight predominance in the supratentorial compartment, although infratentorial lesions were also observed, mainly in the cerebellum. All lesions had ring or nodular contrast enhancement. Three patients were reexamined for treatment control, with disappearance of the lesions in two, with persistence of hypointense area in T2-weighted images. MR imaging proves to be a good method to evaluate the neurological involvement in paracoccidioidomycosis, mainly due to its high sensitivity for posterior fossa lesions. Further studies are needed to correlate the MR findings and the changes found in MR examination after treatment.

Adult↗
PubMedDate not supplied

[INRAD 2000].

Explore the source record for details and available documents.

Brazil↗
PubMedDate not supplied

MRI of congenital pituitary insufficiency.

We compared 1.5 T magnetic resonance (MR) image findings in 193 patients with congenital pituitary insufficiency. One hundred and thirty nine of the MR studies were obtained in patients who had isolated growth hormone deficiency (GHD). Other fifty-four patients had multiple pituitary hormone deficiency (MPHD). On MR images, normal anterior and posterior lobes of the pituitary gland can be clearly differentiated because the posterior lobe has a characteristic high intensity on T1-weighted images. In fifty-four patients, the high-intensity of the posterior lobe was not seen, but a similar high signal intensity was observed at the proximal stump in fifty-one patients. This high-intensity area is the newly formed ectopic posterior lobe, which also secrets anti-diuretic hormone just as the posterior lobe would. MR imaging can demonstrate the transection of the pituitary stalk and the formation of the ectopic lobe, revealing to be a usefull diagnostic tool in the definition of the type of alteration in growth defects of endocrine origin.

Adolescent↗