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Biomedical subjects

M Duarte

Publications and source records attributed to M Duarte.

At least 55 records · Page 3Linked to original sources
PubMed1999

Instant equilibrium point and its migration in standing tasks: rambling and trembling components of the stabilogram.

A method of decomposing stabilograms into two components, termed rambling, was developed. The rambling component reveals the motion of a moving reference point with respect to which the body's equilibrium is instantly maintained. The trembling component reflects body oscillation around the reference point trajectory. The concepts of instant equilibrium point (IEP) and discrete IEP trajectory are introduced. The rambling trajectory was computed by interpolating the discrete IEP trajectory with cubic spline functions. The trembling trajectory is found as a difference between the approximated rambling trajectory and the COP trajectory. Instant values of the horizontal ground reaction force at a zero time lag. It suggests that trembling is strongly influenced by a restoring force proportional to the magnitude of COP deviation from the rambling trajectory and acts without a time delay. An increment in relative COP position per unit of the restoring force in mm/N, was on average 1.4 +/- 0.4. The contribution of rambling and trembling components in the stabilogram was ascertained. The rambling variability is approximately three times larger than the trembling variability.

Adult↗
PubMed1998

Effect of ranitidine on gastric intramucosal pH in critically ill patients.

OBJECTIVE: To determine whether ranitidine a) increases the values of gastric intramucosal pH (pHi) in critically ill patients, as determined by tonometry; b) reduces the variability of these measurements. DESIGN: Prospective, double blind, randomized, placebo-controlled study. SETTING: General Intensive Care Unit of a teaching hospital. PATIENTS: Twenty-five critically ill, mechanically ventilated patients requiring arterial catheter and nasogastric tube. INTERVENTIONS: Tonometer placement; blind, random administration of intravenous ranitidine (50 mg) or placebo. MEASUREMENTS AND MAIN RESULTS: Tonometer saline PCO2 (PCO2i), arterial blood gases, gastric juice pH and pHi were determined immediately before, and 2, 4, 6 and 8 h after, ranitidine (12 patients) or placebo (13 patients). Ranitidine significantly increased gastric juice pH, but did not affect PCO2i or pHi; pHi was 7.34 +/- 0.14 before ranitidine, and 7.30 +/- 0.12, 7.31 +/- 0.11, 7.31 +/- 0.14 and 7.31 +/- 0.12-2, 4, 6 and 8 h, respectively, after ranitidine administration (p = 0.55). Ranitidine did not modify the coefficients of variation of PCO2i or pHi, either. No significant changes in gastric juice pH, PCO2i or pHi were observed in the placebo group. CONCLUSIONS: In critically ill patients, ranitidine has no effect on pHi values, and does not increase the reproducibility of pHi measurements.

APACHE↗
PubMed1998

Inactivation of the gene coding for the 30.4-kDa subunit of respiratory chain NADH dehydrogenase: is the enzyme essential for Neurospora?

We have isolated and characterised the nuclear gene that codes for the 30.4-kDa subunit of the peripheral arm of complex I from Neurospora crassa. The single-copy gene was localised on chromosome VI of the fungal genome by restriction fragment length polymorphism mapping. An extra copy of the gene was introduced into a strain of N. crassa by transformation. This strain was crossed with another strain in order to inactivate, by repeat-induced point mutations, both copies of the duplication carried by the parental transformant. Ascospore progeny from the cross were analysed and a mutant strain lacking the 30.4-kDa protein, nuo30.4, was isolated and further characterised. The mutant appears to assemble the membrane arm of complex I, while formation of the peripheral arm is prevented. Nevertheless, the mutant grows reasonably well--indicating that this well conserved protein is not essential for vegetative growth--and is able to mate with other strains both as male or female. Strains with multiple mutations are readily obtained from heterozygous crosses between different complex I mutants of N. crassa. On the other hand, homozygous crosses between several mutants, including nuo30.4, fail to produce ascospores. These results suggest that complex I plays an essential role during the sexual phase of the life cycle of the fungus.

Fungal Proteins↗
PubMed1998

[Treatment of mucocutaneous leishmaniasis with pentamidine isothionate].

BACKGROUND: The mucocutaneous form of New World cutaneous leishmaniasis is caused, theoretically, by Leishmania (viannia) braziliensis. Pentad valency antimonic compounds are widely used for treatment of New World cutaneous leishmaniasis. The rate of recurrence is often high when these drugs are used for mucocutaneous forms. Pentamidine has been considered as a second line treatment although little data is available. PATIENTS AND METHODS: Seventeen patients with mucocutaneous leishmaniasis were treated with pentamidine isothionate, 4 mg/kg every 48 hours. A complete oto-rhino-laryngological examination was performed once a week to determine the course of the lesions. Treatment was discontinued when the lesions healed. A follow-up oto-rhinolaryngological examination was also performed after treatment withdrawal and every three months thereafter for an undetermined period. RESULTS: Lesions healed with pentamidine isothionate in 16 patients (94%). Mean dosage required was 2872 mg (2025-4320 mg) for a mean treatment duration of 22 days (12-32 days). Mean follow-up was 13.3 months (3-37 months). Leishmaniasis relapsed in one patient 4 months after treatment withdrawal. DISCUSSION: Pentamidine isothionate is an effective treatment for mucocutaneous leishmaniasis, providing cure with a low rate of recurrence.

Adult↗
PubMed1997

Identification of the TYKY homologous subunit of complex I from Neurospora crassa.

A polypeptide subunit of complex I from Neurospora crassa, homologous to bovine TYKY, was expressed in Escherichia coli, purified and used for the production of rabbit antiserum. The mature mitochondrial protein displays a molecular mass of 21280 Da and results from cleavage of a presequence consisting of the first 34 N-terminal amino acids of the precursor. This protein was found closely associated with the peripheral arm of complex I.

Animals↗
PubMed1997

Alteration of macrophage function by a Trypanosoma cruzi membrane mucin.

Cytokines secreted by macrophages play important roles in the immune response to Trypanosoma cruzi. Here, we report that a purified glycosylphosphatidylinositol (GPI)-anchored mucin from the T. cruzi membrane, Ag C10, is able to bind to the macrophage cell surface and blocks the subsequent binding of mAb against CD62L/L-selectin, whereas binding of mAbs directed against other monocyte surface molecules is unaffected. In addition, Ag C10 binding to macrophages triggered a CD54/ICAM-1-mediated cell adhesion as well as an increase in intracellular Ca2+, which was further augmented by cross-linking the Ag C10-bound surface receptors by mAb against Ag C10. Interestingly, Ag C10-treated monocytes secreted IL-1beta, but not TNF-alpha or IL-12. Moreover, these cells could secrete IL-1beta, but not TNF-alpha or IL-12, after activation with LPS. T. cruzi-infected macrophages displayed similar alterations in cytokine secretion, with an impaired ability to secrete IL-12 and TNF-alpha, but not IL-1beta, upon LPS activation. These effects were substantially inhibited by neutralizing mAb against Ag C10. These effects appeared to take place at the transcriptional level, since mRNA for TNF-alpha, but not that for IL-1beta, was drastically reduced in LPS-stimulated infected cells treated with Ag C10. Conceivably, inhibition of TNF-alpha and IL-12 by T. cruzi could be involved in the evasion of the immune response by this parasite.

Animals↗
PubMed1997

Effect of sucralfate on gastric intramucosal pH in critically ill patients.

OBJECTIVE: To determine whether sucralfate administration affects the tonometric measurement of gastric intramucosal pH (pHi). DESIGN: Non-randomized observational study. SETTING: General intensive care unit of a teaching hospital. PATIENTS: Twenty critically ill, mechanically ventilated, consecutively admitted patients requiring an arterial catheter and nasogastric tube. INTERVENTIONS: Tonometer placement and sucralfate administration. MEASUREMENTS AND MAIN RESULTS: We simultaneously determined tonometer saline PCO2 (PCO2i), arterial blood gases, pH of gastric juice and pHi. These parameters were evaluated immediately before sucralfate administration, and 2 h and 4 h after. We did not detect any change in either PCO2i or pHi after sucralfate administration (PCO2i: basal 6.4 +/- 1.7, 2 h 6.3 +/- 1.7, 4 h 6.3 +/- 1.7; pHi: basal 7.35 +/- 0.13, 2 h 7.36 +/- 0.12, 4 h 7.36 +/- 0.12). CONCLUSIONS: Sucralfate does not affect the tonometric measurement of PCO2i and pHi.

Adult↗
PubMed1997

Co-Infection of Tuberculosis and HIV/HTLV Retroviruses: Frequency and Prognosis Among Patients Admitted in a Brazilian Hospital.

During 2 1/2 year period,378 patients diagnosed with tuberculosis and admitted to a general hospital for care of the poor in Salvador, Bahia, were tested serologically for HIV-1, HTLV-I, and HTLV-II. The patients' mean age was 41.8 (range 14-89); they were hospitalized for a mean of 62 +/- 43 days; 70% were being treated for the first time; most of the remainder were being retreated after non-compliance with previously recommended anti-tuberculosis medication and a few required second-line therapy for relapsed disease. None had had previous serologic testing for retroviruses. Among the study population, 59 (16%) were found to be positive for retroviral infection. The distribution was as follows: 18 (4.8%) had HIV-1, 32 (8.5%) had HTLV-I, 2 of these had both HTLV-l and HTLV-II, 9 (2.4%) had both HIV-1 and HTLV-I. The rates of positive serologic tests for retroviral infection in this Salvador is 0.2% for HIV-1 and 1.0% for HTLV-I. Thus, there is a higher than expected frequency of retroviral infections among patients hospitalized for treatment of tuberculosis. The prognosis for treated patients was determined by recording the cause of death and the mortality rate. In the 319 patients with negative serologic testing for retroviruses there were 25 deaths (8%). In 32 patients with HTLV-I infection there were 8 deaths (25%), and in 18 patients with HIV-1 infection there were 6 deaths (33%). In 9 patients with both HIV-1 and HTLV-I there were 5 deaths (56%). The causes of death in each serological group were primarily related to progression of tuberculosis rather than complications of rapid progression of the retroviral infection. We conclude that co-infection and disease due to either HIV-1 or HTLV-I/II infection and tuberculosis is common, that the occurrence of HTLV-I in this population is higher than previously recognized, and that prognosis associated with the management of tuberculosis is adversely affected by the presence of either retroviral infection. In a few patients with both retroviral infections, mortality was very high. All patients with tuberculosis should be tested for retroviral infection because of the prognostic and therapeutic implications.

Journal Article↗
PubMed1996

Disruption of the nuclear gene encoding the 20.8-kDa subunit of NADH: ubiquinone reductase of Neurospora mitochondria.

The nuclear gene coding for the 20.8-kDa subunit of the membrane arm of respiratory chain NADH: ubiquinone reductase (Complex I) from Neurospora crassa, nuo-20.8, was localized on linkage group I of the fungal genome. A genomic DNA fragment containing this gene was cloned and a duplication was created in a strain of N. crassa by transformation. To generate RIP (repeat-induced point) mutations in the duplicated sequence, the transformant was crossed with another strain carrying an auxotrophic marker on chromosome I. To increase the chance of finding an isolate with a non-functional nuo-20.8 gene, random progeny from the cross were selected against this auxotrophy since RIP of the target gene will only occur in the nucleus carrying the duplication. Among these, we isolated and characterised a mutant strain that lacks the 20.8 kDa mitochondrial protein, indicating that this cysteine-rich polypeptide is not essential. Nevertheless, the absence of the 20.8-kDa subunit prevents the full assembly of complex I. It appears that the peripheral arm and two intermediates of the membrane arm of the enzyme are still formed in the mutant mitochondria. The NADH: ubiquinone reductase activity of sonicated mitochondria from the mutant is rotenone insensitive. Electron microscopy of mutant mitochondria does not reveal any alteration in the structure or numbers of the organelles.

Base Sequence↗
PubMed1996

Primary structure of a ferredoxin-like iron-sulfur subunit of complex I from Neurospora crassa.

We have isolated cDNA clones encoding an iron-sulfur polypeptide subunit of the mitochondrial complex I of Neurospora crassa. The fungal cDNA library was screened by hybridisation with an heterologous probe from Paracoccus denitrificans. The DNA sequence of relevant isolates was determined and revealed an open reading frame encoding a precursor protein of 219 amino acid residues. The gene product is a ferredoxin-like protein that contains two cysteine-rich motives that may each bind a tetranuclear iron-sulfur cluster. The primary structure of the protein is highly homologous to the 23 kDa iron-sulfur subunit of complex I from bovine and P. denitrificans. Interestingly, an alanine residue within the second cluster-binding motif, which is conserved in complex I but replaced by tyrosine in similar chloroplast genes, is substituted for serine in N. crassa.

Amino Acid Sequence↗
PubMed1996

Sequential steps in Tat trans-activation of HIV-1 mediated through cellular DNA, RNA, and protein binding factors.

The regulation of HIV expression is controlled by the activity of the Long Terminal Repeat (LTR). Trans-activation by the virally encoded Tat protein is one of the main mechanisms of LTR activation. Tat binds to its target, TAR RNA, and cellular proteins that bind the LTR, Tat, or TAR RNA are important components of the trans-activation process. We will review the factors that have been characterized for a possible involvement in this mechanism. Whereas LTR binding proteins consist of Sp1 and TBP, a large number of factors that bind TAR RNA have been isolated. We have previously cloned two of them by RNA probe recognition: TRBP and La. We have shown that the in vitro and in vivo binding of TRBP to TAR RNA correlates with a constant expression of the protein during HIV-1 infection. Several proteins that interact with Tat have mainly positive, but some negative, effects on trans-activation. Genetic studies have defined that human chromosome 12 encodes a protein that will allow trans-activation in rodent cells. The binding and the functional data about these proteins suggest sequential steps for the Tat trans-activation mechanism. Each of these intracellular molecular events could be the target for molecular intervention against the virus.

Amino Acid Sequence↗
PubMed1996

[Lipid changes of fibrinogen and of platelet aggregation induced by etofibrate].

PURPOSE: To evaluate modifications on lipid profile, fibrinogen and platelet aggregation induced by etofibrate. METHODS: Twenty-one adult patients were studied. They all had primary hyperlipidemia and had already been on the AHA step I diet and placebo. Etofibrate (500mg/day) was administered for 60 days in the active phase, when lipid parameters, fibrinogen and platelet aggregation were measured. RESULTS: The % significant reductions were: total cholesterol (-9.50%), LDL-cholesterol (-7.88%), triglycerides (-19.07%), total cholesterol/HDL-cholesterol(-11.90%), LDL-cholesterol/HDL-cholesterol (-10.20%), fibrinogen (-12.79%), platelet aggregation with adrenaline (-24.02%), with ADP 1 mumol (-30.13%), and ADP 3 mumol (-24.51%). CONCLUSION: The beneficial effects of etofibrate were observed not only on the lipid profile but also on the thrombogenic parameters measured by fibrinogen and platelet aggregation.

Adult↗
PubMed1996

Multicentric Castleman's disease in HIV infection: a clinical and pathological study of 20 patients.

OBJECTIVES: To describe, in a retrospective study, the clinical and pathological spectrum of multicentric Castleman's disease (MCD) in HIV infection. PATIENTS: The diagnosis of MCD was established by lymph node biopsy in 20 HIV-infected patients. All patients had been HIV-infected by sexual contact. At diagnosis, HIV infection was asymptomatic in eight patients and Kaposi's sarcoma was present in 12. Mean +/- SD CD4+ cell count was 156 +/- 99 x 10(6)/l. RESULTS: Patients were referred with a syndrome of fever and splenomegaly (100%), peripheral lymphadenopathy (90%), hepatomegaly (70%), severe weight loss (70%), respiratory symptoms (65%) and oedema (55%). Anaemia was a constant finding and seven (35%) patients presented with pancytopenia. Serum markers of inflammation were present in most patients: a high level of C reactive protein (90%), polyclonal hypergammaglobulinaemia (89%) and hypoalbuminaemia (56%). The histological pattern of the lymph nodes was characterized by small hyalinized germinal centres surrounded by concentric layers of small lymphocytes, vascular hyperplasia, hyalinized vessels and large interfollicular sheets of plasma cells. Five patients were classified as plasma cell type MCD and 15 as hyaline vascular/plasma cell (mixed) type. Immunophenotyping studies (n = 13) demonstrated a polyclonal B-cell process. No linkage with Epstein-Barr virus (EBV) could be demonstrated immunohistochemically using an anti-latent membrane protein-1 monoclonal antibody (n = 16) or by RNA in situ hybridization with an EBV-encoded RNA transcript-specific probe (n = 13). Remission was obtained with low-dose and usually single agent chemotherapy in 16 patients. During follow-up, non-Hodgkin's lymphoma developed in two patients and Kaposi's sarcoma in three. Fatal outcome occurred in 14 patients with a median survival of 14 months. CONCLUSION: MCD associated with HIV infection is a distinct clinico-pathological entity that can be differentiated from other types of HIV-associated systemic lymphoproliferative disorders. It is very similar to MCD observed in non-HIV-infected patients, except for the high prevalence of pulmonary symptoms and for the stronger association with Kaposi's sarcoma. Single-agent chemotherapy with vinblastine is effective and may prolong survival.

Adult↗
PubMed1995

Functional domains in the spike protein of transmissible gastroenteritis virus.

The coronavirus spike protein S is assumed to mediate essential biological functions, including recognition of target cells. Earlier studies from our and other groups identified two regions of the TGEV S (220K) protein possibly implicated in such functions. The first of these corresponds to the 224 amino acid N-terminal region which is deleted in PRCV, the respiratory variant of TGEV. We have examined the pathogenicity for the newborn piglet of a series of neutralization escape mutants encoding an S protein mutated in this region. Several amino acid changes were correlated with a dramatic loss of enterovirulence, thus indicating that crucial determinants are associated with this domain of S. The second region of potential relevance is the major neutralization domain. Baculovirus-vectored expression of 150 to 220 amino acid-long stretches encompassing this region, which is encoded by both TGEV and PRCV, was performed. The resultant recombinant proteins were shown to react with the cognate antibodies and to bind APN specifically, thus localizing the receptor-binding site on the S primary structure. Altogether these data lend support to the view that a domain of S protein structurally distinct from the receptor binding site is required for the virus to express its enteric tropism.

Amino Acid Sequence↗
PubMed1995

Inactivation of genes encoding subunits of the peripheral and membrane arms of neurospora mitochondrial complex I and effects on enzyme assembly.

We have isolated and characterized the nuclear genes encoding the 12.3-kD subunit of the membrane arm and the 29.9-kD subunit of the peripheral arm of complex I from Neurospora crassa. The former gene was known to be located in linkage group I and the latter is now assigned to linkage group IV of the fungal genome. The genes were separately transformed into different N. crassa strains and transformants with duplicated DNA sequences were isolated. Selected transformants were then mated with other strains to generate repeat-induced point mutations in both copies of the genes present in the nucleus of the parental transformant. From the progeny of the crosses, we were then able to recover two individual mutants lacking the 12.3- and 29.9-kD proteins in their mitochondria, mutants nuo12.3 and nuo29.9, respectively. Several other subunits of complex I are present in the mutant organelles, although with altered stoichiometries as compared with those in the wild-type strain. Based on the analysis of Triton-solubilized mitochondrial complexes in sucrose gradients, neither mutant is able to fully assemble complex I. Our results indicate that mutant nuo12.3 separately assembles the peripheral arm and most of the membrane arm of the enzyme. Mutant nuo29.9 seems to accumulate the membrane arm of complex I and being devoid of the peripheral part. This implicates the 29.9-kD protein in an early step of complex I assembly.

Blotting, Southern↗
PubMed1994

Sequence analysis of the porcine epidemic diarrhea virus genome between the nucleocapsid and spike protein genes reveals a polymorphic ORF.

In order to investigate the genome organization of the porcine epidemic diarrhea virus (PEDV) further, cDNA clones covering the region between the nucleocapsid and the spike (S) protein genes were independently constructed and sequenced for the two virulent isolates Br1/87 and CV777. Of the three major ORFs identified, two were found to encode the major and minor coronavirus membrane proteins M and sM. A potentially single ORF, designated ORF3 according to the pattern of the viral subgenomic mRNAs, could be identified between the S and sM genes. A striking variability, essentially generated by short deletions clustered in a few loci, was observed in the ORF3 of both isolates. The largest predicted polypeptide of 223 amino acids showed homology with polypeptides potentially encoded by other members of the same genetic subset, including two shorter polypeptides of human respiratory virus HCV 229E and one of transmissible gastroenteritis virus TGEV. This homology suggests that the two HCV ORFs may have originated from a single precursor. The function of these polypeptides is not known, but the predicted products of the PEDV ORF3 and related ORFs share features suggestive of a membrane-associated protein.

Amino Acid Sequence↗