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Biomedical subjects

L M Vieira

Publications and source records attributed to L M Vieira.

At least 19 recordsLinked to original sources
PubMed2004

Morphology and viability analysis of Streptomyces clavuligerus in industrial cultivation systems.

The effects of varying inoculum age and production scale upon the morphology and viability of Streptomyces clavuligerus were studied by analyzing visible and fluorescent light images acquired throughout pilot-plant and pre-industrial scale fermentations. Changes in production scale reveal that in 5 m(3) fermentors, the maximum hyphal area obtained is double the value obtained in 0.5 m(3) fermentors. It is probably due to the higher shear stresses acting upon hyphae in the 0.5 m(3) fermentor caused by higher tip speeds observed in these. The morphological quantification based on elongation and branching rates allowed fermentations to be pattern classified into distinct physiological time zones namely elongation, branching, fragmentation, etc. The general pattern observed for fermentations inoculated with late exponential phase inocula was similar to the pattern of fermentations run with stationary phase inocula except that both the elongation and branching periods started earlier in the former case. Using the available staining technique and image acquisition system, the viability seemed to be generally high and constant throughout the time course of all the studied fermentations.

Bioreactors↗
PubMed2002

Evaluation of the blood coagulation mechanism and platelet aggregation in individuals with mechanical or biological heart prostheses.

Oral anticoagulants have been widely employed to decrease thrombotic risk by reducing the levels of vitamin K-dependent clotting factors. Paradoxically, the use of oral anticoagulants also decreases the levels of natural anticoagulants (protein C and protein S), which favors the hypercoagulability state. Increased platelet activation has been reported in patients undergoing warfarin treatment. These findings have raised questions about the antagonistic effect of oral anticoagulants and their implications for hemostatic balance. The aim of this study is to determine the relationship between warfarin dosage and prothrombin time [International Normalized Ratio (INR)], platelet aggregation, vitamin K-dependent clotting factors, and protein C and protein S. Blood samples from 27 patients were analyzed, seven with mechanical prostheses and 20 with biological prostheses, and 27 controls. Multiple regression analysis showed that factor II most significantly determines the INR. Results showed that the INR, clotting factors, and protein C and protein S activity did not correlate with warfarin dosage, highlighting the need for accurate laboratory monitoring of those undergoing anticoagulant therapy.

Adolescent↗
PubMed2001

Real time monitoring biomass concentration in Streptomyces clavuligerus cultivations with industrial media using a capacitance probe.

On-line monitoring biomass concentration in mycelial fed-batch cultivations of Streptomyces clavuligerus grown with soluble and partially insoluble complex media, was investigated with an in-situ capacitance probe fitted to an industrial pilot-plant tank. Standard off-line and on-line biomass determinations, including cell dry weight, packed mycelial volume, viscosity, DNA concentration and total CO(2) evolution in the exhaust gases, were performed throughout the experiments and compared to on-line capacitance measurements. Linear relations between capacitance and all other measurements were developed for both media that hold only in defined process phases, depending on the biomass state and the amount of insoluble matter present. For the industrial complex culture media good linear relations were obtained in the fast growth phase between capacitance and DNA concentration and total CO(2) evolution, while in the subsequent transition and stationary phases only with apparent viscosity was a reasonable correlation found. The capacitance probe was shown to be a valuable tool for real-time monitoring biomass concentration in industrial-like cultivation of mycelial streptomycetes.

Bioreactors↗
PubMed2001

Effects of preculture variability on clavulanic acid fermentation.

The production profile of clavulanic acid by Streptomyces clavuligerus was shown to be strongly dependent on inoculum activity. Two sets of fermentations (A and B) were investigated at industrial pilot-plant scale using complex media. Type A fermentations were inoculated using late exponential growth phase mycelia. Type B fermentations were inoculated using mycelia harvested at stationary phase. Productivities throughout type A fermentations were consistently higher than type B, reaching a maximum at about 70 h and then decaying to the same final productivities at 140 h of type B runs. Several scheduling alternatives, based on combinations of the two inocula types and different fermentation lengths, were compared in terms of the overall process economics (fermentation and downstream). An increase of ca. 22% on the overall process profit is predicted using late exponential growth phase inocula and a fermentation duration of only 96 h. A new operating strategy was thus proposed for inoculum production based on the control of preculture activity using off-gas analysis. This method ensures higher productivity and better batch-to-batch reproducibility of clavulanic acid fermentations than traditional methods based on constant age inocula.

Anti-Bacterial Agents↗
PubMed2000

Pathogenesis of nerve damage in leprosy: genetic polymorphism regulates the production of TNF alpha.

Studies carried out over the last decade have strongly suggested that TNF alpha both overtly participates in the cell-mediated immune response against Mycobacterium leprae, and is overproduced during reaction. In addition, reactions are intimately related to the onset of nerve damage. Finally, TNF alpha has been implicated in the pathogenesis of many human and experimental autoimmune peripheral neuropathies that, as in leprosy, result in demyelination and axonal lesions. Because of recent findings associating human TNF alpha mutant alleles at the -308 position with increased production of TNF alpha in many immunological and infectious diseases, an investigation of the role of TNF2 in predisposing leprosy patients to reaction has been undertaken. Analysis of 300 patients with leprosy--210 multibacillary and 90 paucibacillary--has shown that the percentage of reactional patients was similar among both carriers and non-carriers of the TNF2 allele. However, a separate analysis of 57 carriers of TNF2 found that reactions occurred much more frequently among heterozygous than among homozygous patients. Moreover, the frequency of neuritis was somewhat greater among the heterozygous patients than among the non-carriers. Enhanced serum levels of TNF alpha have been noted in both TNF-1 and TNF-2 mutant patients in the course of leprosy reaction. Our observations to date suggest that other factors not related to the presence of the mutant gene may lead to the TNF alpha hyper-responsiveness observed during reaction.

Alleles↗
PubMed2000

Use of ML dipstick as a tool to classify leprosy patients.

Leprosy control services face the problem of leprosy patients being misclassified by the lack of or the poor quality of skinsmear examination services. Misclassification increases the risk of relapse due to insufficient treatment if a multibacillary (MB) patient is classified as paucibacillary (PB), thereby also prolonging the time that the patient is infectious. The World Health Organization (WHO) recommends at present an alternative classification based on the number of skin lesions. Its reliability, however, has been questioned. Our investigation sought to determine the usefulness of the ML Dipstick, a simple field assay to detect IgM antibodies to phenolic glycolipid-I of Mycobacterium leprae, for the classification of leprosy patients in addition to lesion count. In this study, 264 leprosy patients were investigated. Of 130 patients with a positive bacterial index (BI), 19 (14.6%) had less than 6 lesions and would have been classified as PB. Out of 134 patients with a negative BI, 26 (19.4%) had 6 or more lesions and would have been classified as MB patients if the lesion counting system would apply. Thus, the classification based on the number of lesions only was found to be 85% sensitive and 81% specific (using the BI as the gold standard) at detecting MB cases among the studied population. Sensitivity would have increased if patients would have been classified according to a combination of the number of lesions and the dipstick result. In that case patients are classified as MB when they are either dipstick positive (N = 16), have more than 6 lesions (N = 43), or both (N = 94). Patients negative for both dipstick and number of lesions would have been classified as PB (N = 111). The classification based on the number of lesions alone left 19 BI-positive cases classified as PB, while the combination method of the ML Dipstick and number of lesions left only 8 BI-positive cases classified as PB (5 borderline, 2 borderline lepromatous and 1 tuberculoid), thus preventing undertreatment. The combination method of the ML Dipstick and lesion counting was found to be 94% sensitive and 77% specific, which is an improvement of 9% (chi-squared test, p = 0.025) in sensitivity compared to lesion counting only. The results of this study indicate that testing all patients initially classified by lesion counting as PB (48% in our study population) with the dipstick can significantly contribute to improved classification of leprosy patients for treatment purposes.

Antibodies, Bacterial↗
PubMed1995

Four new mutations in the NADH-cytochrome b5 reductase gene from patients with recessive congenital methemoglobinemia type II.

Recessive congenital methemoglobinemia (RCM) due to NADH-cytochrome b5 reductase (cytb5r) deficiency leads to two different types of diseases. In the type I form, cyanosis is the only symptom, and the soluble enzyme is defective in red blood cells. In the type II form, cyanosis is associated with severe mental retardation and neurologic impairment; the enzymatic defect is systemic, involving both soluble and membrane-bound isoforms. We characterized mutations responsible for cytb5r deficiency in three unrelated patients with severe RCM type II. The first patient presented a homozygous exon 5 skipping. The only mutation detected was a homozygous G to C transversion at position +8, downstream from the 5' splice site of exon 5. We suggest that this unusual mutation might be responsible for the abnormal splicing of the primary transcripts, resulting in frameshift with premature STOP codon. The second mutation found corresponds to a homozygous C to T transition changing the Arg-218 codon to a premature STOP codon in exon 8. The third case was a compound heterozygote, carrying two different mutant alleles in the cyb5r gene. One allele presented a missense mutation with replacement of Cys-203 (TGC) by Arg (CGC) in exon 7. The second allele carried a 3-bp deletion (TGA) of nucleotides 815 to 817, modifying two contiguous codons in exon 9 of the cDNA with loss of Met-272. These results confirm the genetic polymorphism of cytb5r gene mutations identified in RCM type II, as observed for the mutations described in the RCM type I, and shed light on the molecular bases of the two different diseases associated with cytb5r deficiency.

Amino Acid Sequence↗
PubMed1995

Cellular immune response to Mycobacterium leprae infection in human immunodeficiency virus-infected individuals.

The immune responses to Mycobacterium leprae and other mycobacterial antigens were studied in 11 leprosy patients with concurrent human immunodeficiency virus type 1 (HIV-1) infection. Three patients manifested borderline lepromatous leprosy, and eight patients had borderline tuberculoid (BT) leprosy. Despite the low CD4+ T-cell count in the peripheral blood, no histologic or phenotypic change in the cellular infiltrate in either the lepromatous or tuberculoid lesions was observed when compared with HIV-1-negative patients. Lepromatous lesions contained heavily parasitized macrophages and few CD8+ T cells. Lesions from the patients with BT leprosy showed extensive CD4+ T-cell infiltration despite a significant reduction in CD4+ T-cell counts in the peripheral blood. No acid-fast bacilli were detected in the tuberculoid lesions. HIV-1 infection did not alter the lack of response in lepromatous leprosy to M. leprae antigens either in vitro or in vivo. In contrast, the skin test response to M. leprae antigens as well as the in vitro lymphoproliferative responses to mycobacterial antigens that are usually seen in patients with tuberculoid leprosy were abrogated in the BT HIV-1+ patients. However, production of gamma interferon in response to the same stimuli was preserved in most of the patients. Analysis of cytokine gene expression showed activation of additional cytokine genes in the unstimulated peripheral blood cells of patients with both leprosy and HIV-1 infections as compared with cells from patients with leprosy alone. These results suggest that granuloma formation in leprosy can be independent of the impaired CD4+ T-cell response of the HIV-1 infection. Furthermore, in HIV-1+ individuals with M. leprae infection, activation of cytokine genes is observed even when the circulating CD4+ T-cell count is significantly reduced.

Antigens, Bacterial↗
PubMed1995

Effect of high-salt intake on blood pressure and vascular reactivity of diabetic rats.

The etiopathogenesis of diabetes mellitus (DM)-associated hypertension is not known. Sodium and an increased vascular reactivity to vasopressor agents have been implicated in the pathogenesis of this disease in humans. The aim of the present study was to experimentally evaluate the possible role of salt intake and changes in vascular reactivity in the pathogenesis of DM-associated hypertension. Male Wistar rats, weighing 180 to 200 g, rendered diabetic by streptozotocin (65 mg/kg) and maintained moderately hyperglycemic with insulin were submitted to high-salt intake (tap water replaced with 1.0% NaCl) for 8 weeks (D+salt rats, N = 8). Mean arterial pressure and reactivity of the isolated aorta to norepinephrine and angiotensin II were then determined. Diabetic rats on normal-salt intake (group D+nl, N = 6) or normal-salt intake (group non-D+nl, N = 8) were used as controls. Mean blood pressure was significantly higher in D+salt rats (123 +/- 3 mmHg) compared with the D+nl (113 +/- 3 mmHg), non-D+salt (111 +/- 2 mmHg) and non-D+nl (105 +/- 2 mmHg) groups. Mean blood pressure was also significantly higher in diabetic rats on normal-salt intake compared with control rats on normal-salt intake. Vascular reactivity of the aorta to norepinephrine was increased only in diabetic rats on high-salt intake. No modification in reactivity was detected with regard to the reactivity to angiotensin II. We conclude that high-salt intake increases blood pressure in diabetic rats and that increased aorta vascular reactivity to norepinephrine might be involved in the blood pressure alteration.

Analysis of Variance↗
PubMed1991

Prevalence of autoantibodies in simplex and multiplex families of Brazilian insulin-dependent diabetic patients.

1. Forty-one simplex and 6 multiplex families of Brazilian IDDM patients were studied by the indirect immunofluorescence technique to determine the prevalence of the following autoantibodies: islet cells (ICA), islet cells which fix complement (ICA-CF), thyroid microsomes (TMA), thyroglobulin (TGA), and gastric-parietal cells (PCA). A total of 54 IDDM patients belonging to two family groups were analyzed. 2. A significantly higher frequency of ICA-CF and TMA was detected among the siblings from multiplex families than among those from simplex families (18.7% vs 1.7%). 3. A prospective study of 5 ICA-positive siblings was undertaken, and 2 who later became diabetic were found to be positive to both ICA and ICA-CF. 4. The prevalence of islet-cell antibodies in these 54 Brazilian IDDM patients and their unaffected first-degree relatives from genetically mixed groups suggests that the humoral autoimmune mechanisms of the disease are probably identical to those observed in other populations of different ethnic backgrounds.

Adolescent↗
PubMed1991

Serum levels of tumour necrosis factor-alpha and interleukin-1 beta during leprosy reactional states.

The possible role of cytokines in leprosy reactions was investigated by analysing the levels of tumour necrosis factor (TNF) and interleukin-1 (IL-1) in serum samples from 39 leprosy patients, 22 of them presenting either type I (upgrading) or type II (ENL) reactions. Fifty per cent of the patients showed elevated concentrations of TNF and IL-1 in at least one of the serum samples tested. This included all four patients undergoing type I reversal reaction and nine (50%) of the ENL patients studied. Concentrations of TNF above 1000 pg/ml were found in four patients with ENL. Development of erythema multiforme in these ENL patients represented an aggravating factor and all four patients suffering from this type of lesion demonstrated increased serum TNF levels. All BT patients tested presented elevated IL-1 levels, while only half of them presented elevated levels of TNF. No correlation was found between any particular systemic symptoms and the levels of TNF and IL-1. These results suggest that TNF and IL-1 may be implicated in leprosy reactions, either acting directly or in synergism with other cytokines.

Adolescent↗
PubMed1988

[Correlation of skin tests and the production of gamma-interferon in leprosy patients].

The responsiveness of 25 leprosy patients to an in vitro correlate of cell-mediated immunity to M. leprae antigen, (the production of Y-IFN by peripheral blood mononuclear cells) was compared to their response to skin tests routinely used to evaluate cell-mediated immunity to a number of antigens including M. leprae. The results indicate that among the polar lepromatous patients (LL) there was a clear correlation between low responses in the in vitro assay (Y-IFN production), negative skin test to the specific antigen (Mitsuda reaction) and low responses to skin tests to a related antigen (PPD). There was no correlation in the other clinical groups with skin tests to other unrelated antigens.

Antigens, Bacterial↗
PubMed1988

Immunological responsiveness to M. leprae and BCG antigens in 98 leprosy patients and their household contacts.

1. The cellular immune response to M. leprae and BCG antigens was evaluated in 98 leprosy patients and 143 household contacts lacking clinical manifestation of the disease. 2. The proliferative responses and release of Interferon-gamma by peripheral blood mononuclear cells were assessed and both patients and contacts were classified as low or high responders to M. leprae. 3. The high responder contacts constituted 54.8% of the population analyzed, a three times higher proportion when compared to the controls, indicating the possible existence of active infection among them. 4. The correlation coefficient between the immunological response to M. leprae and BCG was found to be higher within the contact group than in the patients, suggesting that cross-reactivity defense mechanisms against mycobacteria exist even before the onset of clinically detectable disease.

Adolescent↗
PubMed1983

Analysis of cell populations in crescentic glomerulonephritis.

The cell types present in the crescents were studied in 5 human patients with crescentic glomerulonephritis: two cases of systemic lupus erythematosus, one case of hemolytic uremic syndrome and two cases of rapidly progressive glomerulonephritis. Frozen sections of renal biopsies were studied by immunofluorescence, using murine monoclonal antibodies (orthoclones) against specific antigens on the membrane of human peripheral blood cells, and by histochemical methods. Monocytes (OKM1+, OKIa+ cells) but no lymphocytes (OKT+ cells), were detected in the crescentic glomeruli. Subsets of T lymphocytes (inducer-helper and cytotoxic-suppressor) were detected in the interstitium. Non-specific esterase-positive cells were observed in the glomeruli and in small numbers in the crescents. Fibrinogen deposits were present in the crescents of four of the five cases studied. No immunoglobulins (IgG, IgM, IgA) or complement (C1q, C3) deposits were detected in the crescents. Fibrinogen, immunoglobulins and complement were present in the glomerular tufts.

Antibodies, Monoclonal↗