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Biomedical subjects

L C Silva

Publications and source records attributed to L C Silva.

At least 19 recordsLinked to original sources
PubMed2005

Interleukin-6 polymorphism and Helicobacter pylori infection in Brazilian adult patients with chronic gastritis.

Helicobacter pylori is recognised as the most common cause of chronic active gastritis and this bacterium is also an important pathogenic factor in peptic ulcer disease. The biological factors that influence clinical outcome in H. pylori infection have been extensively studied. In addition to immunological factors in the host, bacterial virulence determinants in H. pylori strains are likely to play a crucial role in gastric cancer development. Singlenucleotide polymorphisms at the 5' flanking region of the interleukin (IL)-6 gene promoter (G or C at -174 base) have been identified and individuals with the G allele at position -174 have been shown to produce higher levels of IL-6 than those with the C/C genotype. The mucosal levels of IL-6 were reported to be increased in H. pylori-associated gastritis. The present study was conducted to examine any relationship between inflammatory cytokine polymorphisms and the inflammatory process in mucosa infected by H. pylori. In our study we did not find any association between the C and G alleles in adult patients with chronic gastritis and inflammatory process in gastric mucosa.

Adult↗
PubMed2001

Dimethyl sulphoxide enhances the effects of P(i) in myofibrils and inhibits the activity of rabbit skeletal muscle contractile proteins.

In the catalytic cycle of skeletal muscle, myosin alternates between strongly and weakly bound cross-bridges, with the latter contributing little to sustained tension. Here we describe the action of DMSO, an organic solvent that appears to increase the population of weakly bound cross-bridges that accumulate after the binding of ATP, but before P(i) release. DMSO (5-30%, v/v) reversibly inhibits tension and ATP hydrolysis in vertebrate skeletal muscle myofibrils, and decreases the speed of unregulated F-actin in an in vitro motility assay with heavy meromyosin. In solution, controls for enzyme activity and intrinsic tryptophan fluorescence of myosin subfragment 1 (S1) in the presence of different cations indicate that structural changes attributable to DMSO are small and reversible, and do not involve unfolding. Since DMSO depresses S1 and acto-S1 MgATPase activities in the same proportions, without altering acto-S1 affinity, the principal DMSO target apparently lies within the catalytic cycle rather than with actin-myosin binding. Inhibition by DMSO in myofibrils is the same in the presence or the absence of Ca(2+) and regulatory proteins, in contrast with the effects of ethylene glycol, and the Ca(2+) sensitivity of isometric tension is slightly decreased by DMSO. The apparent affinity for P(i) is enhanced markedly by DMSO (and to a lesser extent by ethylene glycol) in skinned fibres, suggesting that DMSO stabilizes cross-bridges that have ADP.P(i) or ATP bound to them.

Adenosine Triphosphate↗
PubMed2001

Cavernous sinus thrombosis caused by zygomycosis after unrelated bone marrow transplantation.

Invasive zygomycosis is a devastating fungal infection occurring as an opportunistic infection after bone marrow transplantation (BMT). Sinusitis can lead to fungal infection in immunosuppressed patients, and cavernous sinus thrombosis, an uncommon condition in immunocompetent patients, typically follows an infection involving the medial third of the face, nose, or paranasal sinuses. Patients undergoing unrelated-donor BMT (UD-BMT) are prone to develop life-threatening infections because of poor recovery of cellular immunity. Despite adequate clinical evaluation and treatment, the prognosis of patients with invasive fungal infections is dismal, especially when intracerebral structures are affected. We describe a case of a patient who underwent an UD-BMT and developed cavernous sinus thrombosis after sinusitis due to zygomycosis. Moreover, he also had disseminated fungal (Zygomycetes and Aspergillus) and viral (cytomegalovirus and adenovirus) infections.

Adult↗
PubMed2001

Schistosomal myeloradiculopathy due to Schistosoma mansoni: report on 23 cases.

Schistosoma mansoni infection is likely to be responsible for a significant proportion of cases of myelopathy occurring in areas where schistosomiasis is endemic. The aim of this study is to describe the clinical, laboratory and therapeutic data of 23 patients with schistosomal myeloradiculopathy. The medical records of 23 patients with schistosomal myelopathy admitted to two general hospitals of Belo Horizonte (MG), in Brazil, from 1995 to 1999, were reviewed retrospectively. Seventeen patients were male (74%). The mean age for the whole group was 27 years. Lower limb weakness and associated lumbar and/or lower limb pain were reported by 20 patients (87%), and 16 (70%) were unable to walk. All individuals presented urinary retention and 19 (83%) complained of intestinal dysfunction. The treatment was based on the association of antischistosomal drugs and corticosteroids. Five patients (22%) presented a full response to treatment, 13 (57%) partial response without functional limitations and 4 (17%) partial improvement with limitations or no response. Three out of the 4 patients who stopped steroids before 45 days of treatment developed recurrence of the symptoms and signs of myelopathy. Our cases demonstrate the severe presentation of the disease and the data disclosed here suggest that treatment with steroids should be kept for months after clinical improvement.

Adolescent↗
PubMed2001

Astroglial cells derived from lateral and medial midbrain sectors differ in their synthesis and secretion of sulfated glycosaminoglycans.

Astroglial cells derived from lateral and medial midbrain sectors differ in their abilities to support neuritic growth of midbrain neurons in cocultures. These different properties of the two types of cells may be related to the composition of their extracellular matrix. We have studied the synthesis and secretion of sulfated glycosaminoglycans (GAGs) by the two cell types under control conditions and beta-D-xyloside-stimulated conditions, that stimulate the ability to synthesize and release GAGs. We have confirmed that both cell types synthesize and secrete heparan sulfate and chondroitin sulfate. Only slight differences were observed between the proportions of the two GAGs produced by the two types of cells after a 24-h labeling period. However, a marked difference was observed between the GAGs produced by the astroglial cells derived from lateral and medial midbrain sectors. The medial cells, which contain derivatives of the tectal and tegmental midline radial glia, synthesized and secreted approximately 2.3 times more chondroitin sulfate than lateral cells. The synthesis of heparan sulfate was only slightly modified by the addition of beta-D-xyloside. Overall, these results indicate that astroglial cells derived from the two midbrain sectors have marked differences in their capacity to synthesize chondroitin sulfate. Under in vivo conditions or a long period of in vitro culture, they may produce extracellular matrix at concentrations which may differentially affect neuritic growth.

Animals↗
PubMed2001

A tool for assessing the usefulness of prevalence studies done for surveillance purposes: the example of hypertension.

Every year dozens of cross-sectional studies are carried out that estimate the prevalence of risk factors for chronic noncommunicable diseases. Given that, there is potentially a large amount of information that could be extremely useful for risk factor surveillance. However, there are good reasons to question the methodological rigor and the reliability of the results coming from many of these studies. The potential benefits of the data are curtailed by the studies' shortcomings, in part often because there is no clear and explicit methodological information providing the details needed to assess the procedures that were actually used, as well as a failure to apply a uniform methodology that would allow comparisons over time or across studies. This paper is intended to be both a didactic and practical tool. It describes the construction of an instrument for assessing the usefulness of prevalence studies done within the context of surveillance activities, using the example of hypertension. The paper discusses and illustrates the most common pitfalls found with prevalence studies, and it also offers methodological standards that can guide future prevalence studies as well as stimulate future research efforts in this area.

Cross-Sectional Studies↗
PubMed2001

Prevalence estimates for hypertension in Latin America and the Caribbean: are they useful for surveillance?

OBJECTIVE: To apply a recently proposed model and assessment tool created by the authors for critically evaluating the data available on the prevalence of hypertension in LAC and assessing their usefulness for surveillance. METHODS: A bibliographic search to identify all publications that estimated the prevalence of hypertension was performed. Each of the papers located was assessed using a critical appraisal tool. RESULTS: Of the 58 studies published between 1966 and 2000, only 28 of them (48%) met the critical threshold to be considered useful for surveillance purposes. The distribution of the 28 studies in terms of their usefulness for surveillance was as follows: minimally useful, 16 studies; useful, 8 studies; and very useful, 4 studies. Several methodological shortcomings were identified, from inadequate sampling procedures and sample size to the poor quality of the primary data for planning purposes. DISCUSSION: Published studies on the prevalence of hypertension in Latin America and the Caribbean have, as a whole, limited usefulness for surveillance activities.

Caribbean Region↗
PubMed2001

[Sphenoidotomy approach to the sellar tumors: technical note].

Dissection of mucosa from the nasal septum during transphenoidal approach can lead to significant morbidity. We report our experience with sphenoidotomy approach to the sella. This procedure obviates this dissection and its complication as septal perfurations, anosmy and epistaxis. Sphenoidotomy can be done under the microscopic view, endoscopic techniques and even with headlight. This approach is a safe and effective alternative to traditional or endoscopic exposures to the sella.

Adenoma↗
PubMed2000

Contribution of heparan sulfate to the non-permissive role of the midline glia to the growth of midbrain neurites.

Radial glial cells and astrocytes are heterogeneous with respect to morphology, cytoskeletal- and membrane-associated molecules and intercellular interactions. Astrocytes derived from lateral (L) and medial (M) midbrain sectors differ in their abilities to support neuritic growth of midbrain neurons in coculture (Garcia-Abreu et al. J Neurosci Res 40:471, 1995). There is a correlation between these abilities and the differential patterns of laminin (LN) organization that is fibrillar in growth-permissive L astrocytes and punctate in the non-permissive M astroglia (Garcia-Abreu et al. NeuroReport 6:761, 1995). There are also differences in the production of glycosaminoglycans (GAGs) by L and M midbrain astrocytes (Garcia-Abreu et al. Glia 17:339, 1996). We show that the relative amounts of the glycoproteins laminin LN, fibronectin (FN) and tenascin (TN) are virtually identical in L and M glia, thus, confirming that an abundant content of LN is not sufficient to promote neurite growth. To further analyze the role of GAGs in the properties of M and L glia, we employed enzymatic degradation of the GAGs chondroitin sulfate (CS) and heparan sulfate (HS). Treatment with chondroitinase has little effect on the non-permissive properties of M glia but reduces the growth-supporting ability of L glia. By contrast, heparitinase I produces no significant changes on L glia but leads to neurite growth promotion by M glia. Taken together, these results suggest that glial CS helps to promote neurite growth and, more importantly, they indicate that a HS proteoglycan is, at least, partially responsible for the non-permissive role of the midline glia to the growth of midbrain neurites.

Animals↗
PubMed2000

Is there a glycosaminoglycan-related heterogeneity of the thymic epithelium?

We determined the synthesis and secretion of glycosaminoglycans by three distinct preparations of mouse cultured thymic epithelial cells. These comprised primary cultures of thymic nurse cells (TNCs), which are normally located within the cortex of the thymic lobules, as well as two murine thymic epithelial cells, bearing a mixed, yet distinct, cortico-medullary phenotype. We first identified and measured the relative proportions of the various glycosaminoglycans in the three epithelial cells. Non-sulfated glycosaminoglycans are preponderantly secreted by the TNCs, while the sulfated glycans (particularly heparan sulfate) are relatively more abundant on the cell surface. The three types of epithelial cells differ markedly in their heparan sulfate composition, mainly due to different patterns of N- and O-sulfation. In addition, the cells differ in the synthesis and secretion of other glycosaminoglycans. Thus, TNCs secrete high amounts of dermatan sulfate + chondroitin sulfate to the culture medium. IT-76M1 cells secrete high proportions of heparan sulfate while 2BH4 cells show a more equilibrated proportion of dermatan sulfate/chondroitin sulfate and heparan sulfate. The three epithelial cells also differ in their capacity to produce hyaluronic acid and 2BH4 cells are distinguished by their high rate of synthesis of this glycosaminoglycan. In conclusion, our results show that distinct thymic epithelial cells can synthesize different types of glycosaminoglycans. Although it remains to be definitely determined whether these differences reflect the in vivo situation, our data provide new clues for further understanding of how glycosaminoglycan-mediated interactions behave in the thymus.

Animals↗
PubMed2000

Characterization and distribution of extracellular matrix components and receptors in GH3B6 prolactin cells.

GH3B6 cells, a rat pituitary tumor cell line, synthesize and secrete large amounts of prolactin (PRL) in vitro. In the present work, we evaluated the capacity of these cells to express extracellular matrix (ECM) components and receptors in vitro. The expression of laminin (LN), fibronectin (FN) and type IV collagen (CIV) was investigated by immunofluorescence assays. In comparison to PRL distribution, where around 50-70% of the cells contained PRL concentrated in the Golgi region, a variable immunolabeling for the three ECM components could be observed in the majority of GH3B6 cells. Importantly, this pattern was not modified when cells were cultured in the presence of 30 nM thyroliberin (TRH). The expression of the ECM receptors: alpha5beta1 (FN receptor), alpha6beta1 (LN receptor) and CD44 (hyaluronic acid receptor) could be demonstrated by cytofluorometric analysis. Using biochemical procedures, we analyzed the synthesis and secretion of glycosaminoglycans (GAGs). The cells synthesized and secreted mainly heparan sulfate (75%) with a minor amount of chondroitin sulfate/dermatan sulfate. In an attempt to evaluate the individual contribution of the ECM components to influence cell morphology and PRL distribution in vitro, GH3B6 cells were cultivated separately on LN, FN and CIV substrates. Under all conditions, it was possible to observe an increase of cell adherence to the substrate, accompanied with changes of cellular morphology, characterized by the appearance of cytoplasmatic processes. However, no changes on PRL distribution could be observed. Our results suggest that endocrine tumor cell lines are involved in synthesis of ECM components and receptors.

Animals↗
PubMed2000

Patterns of synthesis and secretion of sulfated glycosaminoglycans in primary cortical and cerebellar astrocytes in vitro.

We determined the amounts of [35S]-glycosaminoglycans (GAGs) found on the intracellular, pericellular and extracellular compartments of primary cultures of astrocytes derived from newborn rat cortex and cerebellum in vitro. Our results show that the greatest portion of newly synthesized GAGs were found in different cellular compartments, depending on the source of the astrocytes. In the cells derived from the cerebellum, the proportion of [35S]-GAGs secreted to the culture medium preponderates over the amount found in the two other compartments, whereas cells derived from the cortex accumulated higher proportions of [35S]-GAGs in the intracellular compartment than in the two other compartments. Cortical and cerebellar glial cells synthesised and secreted heparan sulfate (HS) and chondroitin 4-sulfate (C-4S). HS was predominantly accumulated on the pericellular surface, while C-4S was mostly secreted to the culture medium. Beside the difference on the distribution of total [35S]-GAGs among the three cellular compartments, no difference was observed on the relative proportions of HS and C-4S within each compartment. By defining the source of GAGs, the present study may help to complement and extend information on biosynthesis of these compounds by mammalian glial cells.

Animals↗
PubMed2000

The capacity of connective tissue stromas to sustain myelopoiesis depends both upon the growth factors and the local intercellular environment.

In adults, haemopoiesis is located in the bone marrow, where it is tightly regulated by cytokines and by a physical association of haemopoietic progenitors with the stroma. However, in pathological situations, haemopoiesis can be partly or fully dislodged to peripheral tissues. It is not clear which are the requirements for a given peripheral stroma to sustain haemopoiesis. Using the growth factor-dependent cell line FDC-P1, we have compared the myelopoietic capacities of a murine bone marrow-derived cell line S17, a liver inflammatory granuloma-derived stroma (GR) that sustains haemopoiesis, and normal skin fibroblasts (SF) that sustain neither survival nor proliferation of myeloid cells. All three stromas expressed mRNA for major haemopoietins with the exception of IL-3. Despite the incapacity of SF to sustain FDC-P1 cells, the biologically active GM-CSF could be recovered from all the studied stromas by treatment with high-salt buffers that release non-covalently bound molecules from stroma cells. Glycosaminoglycans purified from stromas had distinct effect on the GM-CSF-mediated proliferation of FDC-P1 cells: those purified from S17 and GR cells were stimulatory, whereas those obtained from SF cells were slightly stimulatory at low concentration, but inhibitory at the higher ones. We conclude that the quality of the stroma pericellular glycoconjugates is determinant for the ability of a given stroma to sustain myelopoiesis, even when biologically active haemopoietins are locally produced.

Animals↗
PubMed2000

Human gingival glycosaminoglycans in cyclosporin-induced overgrowth.

Glycosaminoglycans in normal and cyclosporin-induced gingival overgrowth were extracted by papain digestion and purified by Mono Q-FPLC chromatography. The purified glycosaminoglycans were analyzed by agarose gel electrophoresis and by the pattern of degradation products formed by chondroitin lyases on HPLC chromatography. Our results on the glycosaminoglycan composition showed presence of chondroitin 4- and 6-sulfate, dermatan sulfate, heparan sulfate and hyaluronic acid in both normal gingiva and cyclosporin-induced gingival overgrowth. The total and relative amounts of glycosaminoglycans were similar between normal and overgrown gingiva. This suggests that the glycosaminoglycan composition is not changed in cyclosporin-induced gingival overgrowth. Our present biochemical results conflict with histochemical and biosynthetic data previously reported by other groups. Those studies suggested that the affected tissues contained higher levels of glycosaminoglycans and that cyclosporin induced comparably high levels of these compounds in in vitro cultures of gingival fibroblasts. Therefore, these discrepant results suggest that a cyclosporin-induced increase on gingival glycosaminoglycans still remains an open question. The implications of these conflicting results are discussed.

Adult↗
PubMed2000

A sulfated polysaccharide from the sarcoplasmic reticulum of sea cucumber smooth muscle is an endogenous inhibitor of the Ca(2+)-ATPase.

Vesicles derived from the endoplasmic reticulum of sea cucumber smooth muscle retain a membrane bound Ca(2+)-ATPase that is able to transport Ca(2+) into the vesicles at the expense of ATP hydrolysis. In contrast with vesicles obtained from rabbit muscles, the activity of the Ca(2+)-dependent ATPase from sea cucumber is dependent on monovalent cations (K(+)>Na(+)>Li(+)). With the addition of highly sulfated polysaccharide to vesicle preparations from rabbit muscle, Ca(2+) uptake decreases sharply and becomes highly sensitive to monovalent cations, as observed with vesicles from sea cucumber muscle. These results led us to investigate the possible occurrence of a highly sulfated polysaccharide on vesicles from the endoplasmic reticulum of sea cucumber smooth muscle, acting as an "endogenous" Ca(2+)-ATPase inhibitor. In fact, vesicles derived from the invertebrate, but not from rabbit muscle, contain a highly sulfated polysaccharide. This compound inhibits Ca(2+) uptake in vesicles obtained from rabbit muscle and the inhibition is antagonized by monovalent cation. In addition, sea cucumber muscles contain high concentrations of another polysaccharide, which surrounds the muscle fibers, and was characterized as a fucosylated chondroitin sulfate. Possibly the occurrence of sulfated polysaccharides in the sea cucumber muscles is related with unique properties of the invertebrate body wall, which can rapidly and reversibly alter its mechanical properties, with change in length by more than 200%.

Animals↗
PubMed1999

Thymic epithelial cells synthesize a heparan sulfate with a highly sulfated region.

Epithelial cells are important components of the thymus microenvironment and are involved in thymocyte differentiation. The production and secretion of sulfated glycosaminoglycans by these cells grown in culture were investigated using labeling with radioactive 35S-Na2SO4 and 3H-glucosamine. The major glycosaminoglycans synthesized by these cells are heparan sulfate and hyaluronic acid. The structure of the heparan sulfate was investigated by the pattern of degradation products formed by deaminative cleavage with nitrous acid. The ratio 35S-sulfate/ H-glucosamine is high in the segments of the heparan sulfate released during the deaminative cleavage with nitrous acid but low in the resistant portion of the molecule. Thus, the heparan sulfate synthesized by the thymic epithelial cells contains a highly sulfated region. Digestion with heparitinase reveals that this highly sulfated region is a heparin-like segment of the molecule. The heparan sulfate is rapidly incorporated into the cell surface but its secretion to the extracellular medium requires a longer incubation period. Finally, heparin was used to mimic the possible effect of this heparan sulfate with a highly sulfated region, as ascertained by its ability to modulate thymocyte adhesion to thymic epithelial cells. Since heparin actually enhanced thymocyte adhesion, it is suggested that the heparan sulfate described herein, secreted by the thymic epithelium, may play a role upon intrathymic heterotypic cellular interactions.

Animals↗
PubMed1999

Comparative bioavailability of two different diclofenac formulations in healthy volunteers.

The aim of the study was to assess the bioequivalence of two different diclofenac (CAS 15307-86-5) formulations (diclofenac free acid suspension as test formulation and diclofenac resinate suspension, Cataflam, as reference formulation) in 24 healthy volunteers. After an overnight fast, the volunteers received a single oral dose (50 mg) of each formulation, following an open, randomized, two-period crossover design, with a fourteen-day washout interval between doses. Serum samples were obtained over a 24-h interval post-dosing, and were analysed for their diclofenac content by HPLC-UV. No adverse effect was reported for any of the formulations administered. Geometric mean test/reference individual ratios were: 92.8% for AUC(0-24 h), 93.2% for AUC(0-infinity), 117.2% for Cmax, 131.0% for Ke and 76.2% for T1/2. The variability of Cmax parameter expressed as CV was greater than 25%. Since the 90% CI for AUC(0-24 h) mean ratio were within the 80-125% interval proposed by the Food and Drug Administration, it can be concluded that diclofenac free acid formulation is bioequivalent to diclofenac resinate formulation for the extent of absorption. Since the European Community Agency accepts a 90% CI for Cmax of 70-143%, it can be concluded that diclofenac free acid formulation is bioequivalent to diclofenac resinate formulation for both the rate and the extent of absorption after single dose administration.

Administration, Oral↗