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Biomedical subjects

M C Pereira

Publications and source records attributed to M C Pereira.

At least 37 records · Page 2Linked to original sources
PubMed1999

Bone mineral density and androgen levels in elderly males.

To clarify the relationship of sex male hormones and bone in men, we studied in 140 healthy elderly men (aged 55-90 years) the relation between serum levels of androgens and related sex hormones, bone mineral density (BMD) at different sites, and other parameters related to bone metabolism. Our results show a slight decrease of serum-free testosterone with age, with an increase of follicle stimulating hormone (FSH) and luteinizing hormone (LH) in a third of the elderly subjects studied. BMD decreased significantly with age in all regions studied, except in the lumbar spine. We found a positive correlation between body mass index (BMI) and BMD at the lumbar spine and femoral neck (P < 0.001). No relationship was found (uni- and multivariate regression analysis) between serum androgens or sex hormone-binding globulin (SHBG) and BMD. We found a positive correlation of vitamin D binding protein (DBP) and osteocalcin with lumbar spine BMD and with BMI, DBP, IGF-1, and PTH with femoral neck BMD. In conclusion, there is a slight decline in free testosterone and BMD in the healthy elderly males. However, sex male hormones are not correlated to the decrease in hip BMD. Other age-related factors must be associated with bone loss in elderly males.

Absorptiometry, Photon↗
PubMed1999

Histological effects of iron accumulation on mice liver and spleen after administration of a metallic solution.

Special attention has been focused on the toxicity of some metallic species released from implanted materials, which accumulate in vital organs over long periods of time. A set of experiments with mice was designed to investigate the individual effects caused by iron in the liver and spleen. Histological features of these organs were evaluated and slight morphological changes were observed during the treatment time suggesting a negative correlation with the duration of the iron treatment. In addition, to associate the histological changes in the organs with iron accumulation an electrochemical method, adsorptive stripping voltammetry, was chosen to quantify the iron levels in these mentioned organs. The accuracy of the proposed method was checked by atomic absorption spectrometry. Both organs showed elevated concentrations of iron, nearly twofold, 7 days after iron administration compared to control organs.

Animals↗
PubMed1999

Mapping the gene causing hereditary primary hyperparathyroidism in a Portuguese kindred to chromosome 1q22-q31.

A Portuguese kindred with autosomal dominant isolated primary hyperparathyroidism (HPT) that was associated with parathyroid adenomas and carcinomas was investigated with the aim of determining the chromosomal location of this gene, designated HPTPort. Leukocyte DNA from 9 affected and 16 unaffected members and 7 parathyroid tumors from 4 patients was used in comparative genomic hybridization (CGH), tumor loss of heterozygosity (LOH), and family linkage studies. The CGH studies revealed abnormalities of chromosomes 1 and 13, and the results of LOH studies were consistent with the involvements of tumor suppressor genes from these regions. Family segregation studies mapped HPTPort to chromosome 1q22-q31 by establishing linkage with eight loci (D1S254, D1S222, D1S202, D1S238, D1S428, D1S2877, D1S422, and D1S412) (peak two-point LOD scores = 3. 46-5.14 at 0% recombination), and defined the location of HPT Port to a 21 cM region flanked centromerically by D1S215 and telomerically by D1S306. Thus, HPTPort has been mapped to chromosome 1q22-q31, and a characterization of this gene will help to elucidate further the mechanisms that are involved in the development of parathyroid tumors.

Adenoma↗
PubMed1999

Trypanosoma cruzi-cardiomyocytes: new contributions regarding a better understanding of this interaction.

The present paper summarizes new approaches regarding the progress done to the understanding of the interaction of Trypanosoma cruzi-cardiomyocytes. Mannose receptors localized at the surface of heart muscle cell are involved in binding and uptake of the parasite. One of the most striking events in the parasite-heart muscle cells interaction is the disruption of the actin cytoskeleton. We have investigated the regulation of the actin mRNA during the cytopathology induced in myocardial cells by the parasite. T. cruzi invasion increases calcium resting levels in cardiomyocytes. We have previously shown that Ca2+ ATPase of the sarcoplasmic reticulum (SERCA) is involved in the invasion of T. cruzi in cardiomyocytes. Treating the cells with thapsigargin, a drug that binds to all SERCA ATPases and causes depletion of intracellular calcium stores, we found a 75% inhibition in the T. cruzi-cardiomyocytes invasion.

Actins↗
PubMed1999

Control of equine piroplasmosis in Brazil.

The importance of equine piroplasmosis control in endemic countries has increased in recent years and plays an important role to maintain the international market open to the horse industry. The purpose of this study was to demonstrate the occurrence of equine piroplasmosis (Babesia equi or Theileria equi and Babesia caballi) in Brazil--a country where the disease occurs endemically--in different climatic conditions, and to evaluate the results of a strategy for tick control in order to decrease infection rates. Blood samples were taken from 720 horses on 28 farms from different regions and subjected for complement fixation testing. The strategy was based on the control of the tick population by spraying the horses with acaricides, treating positive horses and preventing cattle and horses from grazing together. A significant association was found in the prevalence of antibody titres in tropical and subtropical areas. A significantly lower prevalence rate occurred on those farms where measures to control tick population were established. Farms in endemic countries may significantly reduce the prevalence of equine piroplasmosis by establishing measures to control the tick population and treating chronic carrier horses. Additional measures for controlling ticks in tropical areas are also discussed.

Animals↗
PubMed1998

Evaluation of nickel toxicity on liver, spleen, and kidney of mice after administration of high-dose metal ion.

The toxic effects caused by nickel (Ni) per si were explored by performing in vivo studies on mice following subcutaneous administration of a metallic solution of nickel at 1, 2, 3, and 4 weeks to evaluate the side effects of this metal ion when released from stainless steel implants. Other groups were similarly injected with HBSS and used as controls. Accumulation of Ni ions on liver, spleen, and kidney was assessed by an electrochemical method, adsorptive stripping voltammetry (AdSV) using microelectrodes, and atomic absorption spectrometry (AAS). Alterations of those organs induced by Ni ions were studied, showing that several histological changes had been induced. Chemical analysis and histological features indicate that Ni is partially accumulated in the study organs.

Animals↗
PubMed1998

Adsorptive stripping measurements of iron accumulation in mice kidney using microelectrodes and histological features.

The toxic effects caused by iron in kidney was performed on experimental studies with mice following administration of a metallic solution of this species to simulate the iron corrosion products of a metallic implant. To quantify the total levels of iron present in this organ, an electrochemical method was chosen based on the application of square wave voltammetry using adsorptive collection of iron-catechol on a mercury film microelectrode (MFM). The optimal working conditions to produce a very stable and reproducible iron peak in the digested kidney samples were found to be pH = 7.2 provided by 8.0 mmol/L PIPES buffer, catechol concentration of 3.0 x 10(-4) mol/L, deposition potential -1.80 V and deposition time 20 s. These results were compared with those obtained by atomic absorption spectrometry (AAS) indicating a good performance of the electrochemical method used. The analytical results show an increase of iron concentration with treatment time, which indicates that this metal ion is partially accumulated in the kidney. This accumulation induces with time some morphological alterations as evidenced by the histological analysis.

Animals↗
PubMed1998

[Cutaneous reconstruction at the leg and foot level. Experience in 277 clinical cases].

The authors present their clinical experience of leg and foot reconstruction with 227 clinical cases. Based on these cases the authors analyse the use of 18 musculocutaneous, 53 axial, 72 septocutaneous and 84 free flaps, totalling 29 different kinds of flaps performed. Although no definitive conclusions can be drawn about which are the best flaps for foot and leg reconstruction, the preferential options are pointed out.

Adolescent↗
PubMed1997

Heart muscle cells share common neutral glycosphingolipids with Trypanosoma cruzi.

Neutral glycosphingolipids were isolated from mouse heart muscle cells and their structures were analyzed. The molecular compositions of these glycosphingolipids were examined using column chromatography, HPTLC, GC-MS and fast atom bombardment-mass spectrometry (FAB-MS). Monohexosylceramides are a mixture of glucosyl- and galactosylceramides in a ratio of 1:1, sphingosine as the long chain base and as fatty acyl groups mainly C16, C18 saturated and C22 and C24 hydroxy fatty acids. Dihexosylceramide, identified as lactosylceramide contains C18 sphingosine and C18, C20 and C22 were the major fatty acids. No evidence for the occurrence of hydroxylated fatty acids in this glycolipid could be obtained from the GC-MS data. Our results clearly demonstrated that Trypanosoma cruzi and heart muscle cells have similar glycosphingolipid structures. In addition, heart muscle cells neutral glycosphingolipids have been shown to be immunoreactive. Antibodies reactive with each of the immunogenic glycolipids from heart cells or T. cruzi epimastigotes were present in the sera of human patients with Chagas disease as detected by ELISA. These cross-reactive antigens could be involved in the Chagasic autoimmunity.

Animals↗
PubMed1997

Therapy of post-renal transplantation hyperlipidaemia: comparative study with simvastatin and fish oil.

BACKGROUND: Recipients of renal transplantation (RT) exhibit disturbances of serum lipids and apoproteins that may contribute to their cardiovascular morbidity and mortality. In our renal transplant department the hypercholesterolaemia prevalence at the first and fifth year of RT is 70.0% and 81.2%, respectively. Lipid-lowering therapy has been utilized in many Transplant Units. The aim of our study was to evaluate post-RT hyperlipidaemia control with simvastatin or fish oil. METHODS: Forty-three RT patients (26 men and 17 women) with persistent hypercholesterolaemia and stable graft function which were resistant to a lipid-lowering diet (American Heart Association Step Two) were randomized into two groups and treated for 3 months with simvastatin (S) (10mg/day; n = 25) and fish oil (F) (6 g/day; n = 18). Total cholesterol (TC), LDL-cholesterol (LDL-C), HDL-cholesterol (HDL-C), lipoprotein a (Lp(a)), apolipoprotein A1 (Apo A1), and apolipoprotein B (Apo B) were monitored and at the study baseline they were similar between the two groups. RESULTS: No side effects were detected after 3 months of therapy. In group S, the concentrations of TC (271 +/- 46 mg% vs 228 +/- 49 mg%; P < 0.001), TG (180 +/- 78 vs 134 +/- 45; P < 0.01), LDL-C (177 +/- 40 vs 144 +/- 43; P < 0.01) and Apo B (96 +/- 18 vs 82 +/- 16; P < 0.001) were significantly reduced, and Apo A1 concentration had increased (135 +/- 24 vs 149 +/- 30; P < 0.01). In group F, the concentrations of TC (266 +/- 25 vs 240 +/- 31; P < 0.001), TG (203 +/- 105 vs 156 +/- 72; P = 0.02) and HDL-C (63 +/- 15 vs 53 +/- 12; P < 0.01) were significantly reduced. CONCLUSIONS: We concluded that low-dose simvastatin and fish oil are both effective and safe in correcting post-RT hyperlipidaemia. Further prospective studies with larger follow-up are needed to clarify whether this therapy has an impact on cardiovascular morbidity and mortality in RT patients.

Adult↗
PubMed1994

Calcitonin-producing insulinoma: clinical, immunocytochemical and cytogenetical study.

The case of a patient with a large goitre associated with hypercalcitoninaemia and fasting hypoglycaemia is reported. Pentagastrin (PG) test was negative. Repeated measurements of fasting glycaemia, insulin and C peptide established the diagnosis of insulinoma. After localization by endoscopic ultrasonography, a distal pancreatectomy was performed and a small insulinoma was recovered. Glycaemia and calcitonin (CT) became normal. The tumour cells displayed a strong immunoreactivity for insulin and CT. Cytogenetical evaluation of the tumour revealed a translocation t(1;9) (p13;p22).

Aged↗
PubMed1993

Heart muscle cells acutely infected with Trypanosoma cruzi: characterization of electrophysiology and neurotransmitter responses.

Primary cell cultures of mouse ventricular myocardium were infected with Trypanosoma cruzi, to study the consequences of T. cruzi-muscle cell interaction on the rate of spontaneous contractions, on the responses to norepinephrine, and on action potential parameters. Single cells or small cell groups of infected cultures were subjected to pharmacological and electrophysiological experiments. In concentrations ranging from 1 nM to 100 microM, norepinephrine exerted positive or negative chronotropic effects mediated by alpha-adrenergic receptors. A significant number of infected cells (25%) did not respond to the agonist. Two days after infection the cultures exhibited a higher frequency of spontaneous contractions (20%), paralleled by an increase in firing rate and a decrease in the action potential duration without significant changes in maximum diastolic potential and action potential amplitude. A decrease in alpha-adrenergic receptor-mediated positive chronotropic response to norepinephrine was also observed in 2-day infected cells. Cells made to phagocyte ferritin particles showed an increase in the rate of spontaneous contractions, but no changes in the positive chronotropic responses to norepinephrine. In conclusion, these observations show that during acute infection with T. cruzi, there are alterations in automaticity and in the chronotropic responses to norepinephrine, whose mechanisms are related to the process of parasite endocytosis by the cardiac cells.

Animals↗
PubMed1993

Myofibrillar breakdown and cytoskeletal alterations in heart muscle cells during invasion by Trypanosoma cruzi: immunological and ultrastructural study.

The cytoskeletal organization of normal and Trypanosoma cruzi-infected mouse embryo heart muscle cells (HMC) in primary culture was investigated using immunofluorescence and transmission electron microscopy. Fluorescent probes revealed that in the early stages of infection, up to 24 h, the HMC cytoskeleton appeared to accommodate the intracellular parasites perinuclearly, with only a few cells displaying a slight disturbance in the distribution of filaments. However, as the infection progressed (48 to 72 h), microtubules and desmin filaments were disrupted. Breakdown of myofibrils occurred in regions where the parasites were present, followed by formation of actin polygons. Using Triton X-100 treated whole cell mount, we obtained a striking preservation of the three-dimensional architecture of the cytoskeleton. Combining electron spectroscopic imaging (ESI) with contrast tuning, we detected a highly interconnected cytoskeletal network in normal cells, and a loose network in infected cells. Bundles of filaments running under and over the parasites were also observed. Our results demonstrate that T. cruzi infection induces myofibrillar breakdown and destruction of several cytoskeleton filaments in heart muscle cells.

Animals↗
PubMed1992

A kindred with multiple endocrine neoplasia type 2A associated with pruritic skin lesions.

BACKGROUND: A kindred affected by multiple endocrine neoplasia type 2A (MEN 2A), associated with symmetric, bilateral, scapular pruritic skin lesions (PSL), is reported. METHODS: There were 21 members, including the propositus, in four generations. Screening of 10 family members showed a palpable thyroid tumor in 1 and positive results for a pentagastrin test in 7 others. Two of these patients had surgically confirmed pheochromocytoma. Two others had a biochemical diagnosis of pheochromocytoma but did not have surgery. RESULTS: Medullary thyroid carcinoma was confirmed in five patients and nodular C-cell hyperplasia in another. In five affected adults, PSL were observed in the interscapular region, crossing the midline in some. These lesions were characterized by hyperkeratosis and hyperpigmentation. In all the patients, the pruritus had been present long before the clinical or biochemical diagnosis. Skin biopsies were performed in two of these patients. No amyloid deposits were found (Congo red stain and electron microscopic examination were used). Two children (14 and 6 years old) in the fourth generation complained of scapular pruritus, although skin lesions were not apparent. CONCLUSIONS: Localized PSL must be sought when screening for MEN 2A.

Adolescent↗
PubMed1992

Glycolipid and protein profiles of normal and Trypanosoma cruzi infected heart muscle cells.

Using Triton X-114, glycolipids and proteins were extracted from heart muscle cells (HMC) infected with Trypanosoma cruzi clone Dm28c and from uninfected HMC, and analysed by SDS-PAGE and high-performance thin-layer chromatography (HPTLC). Two major differences were observed: (a) two proteins with a molecular mass of 92 kDa and 69 kDa were present in the uninfected cells but absent from the infected cells and (b) a 70-90 kDa protein band was detected only in parasitized cells. These differences would seem to constitute alterations taking place during the process of cell recognition and/or parasite interiorization. No differences were observed in the respective glycolipid compositions, of control and infected cells analysed by HPTLC. A glycolipid with the same mobility as the neutral glycolipid isolated from epimastigotes of T. cruzi was detected in the uninfected cells. This finding may lend support to the previously described hypothesis that molecular mimicry is implicated in the cardioneuropathology of Chagas' disease.

Animals↗