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Biomedical subjects

F Antunes

Publications and source records attributed to F Antunes.

At least 19 recordsLinked to original sources
PubMed2006

Changes in blood cell membrane properties in HIV type-1-infected patients.

To evaluate the possible HIV-1 infection-induced changes in cell membrane properties and in calcium signaling, membrane fluidity, acetylcholinesterase (AChE, a glycosylphosphatidylinositol-anchored protein) activity, and intracellular calcium concentration ([Ca2(+)](int)) were evaluated in lymphocytes and erythrocytes of infected individuals, previous to their engagement in antiretroviral therapy. Membrane fluidity was assessed by fluorescence spectroscopy measurements, using the fluorescence probes 1,6-diphenyl-1,3,5-hexatriene (DPH) and 1-[4-(trimethylamino)-phenyl]-6-phenyl-1,3,5-hexatriene (TMA-DPH). AChE activity was determined by the colorimetric Ellman's method and [Ca2(+)](int) using the fluorescent fura-2 acetoxymethyl ester. When compared with the control group, lymphocytes of infected patients presented significantly decreased membrane fluidity, decreased AChE activity, and increased [Ca2(+)](int). Erythrocytes from HIV-infected patients presented decreased [Ca2(+)](int) when compared with the control group and decreased membrane fluidity near the lipid/water interface. Our data show that HIV-1 infection leads to biochemical and biophysical changes in the membrane itself and in membrane protein activity in lymphocytes (average of infected and noninfected subpopulations) and even in erythrocytes. The present observations are in agreement with a process of facilitated propagation of the infection to new cells, stimulation of virion production, and maintenance of a reservoir of erythrocyte-bound infectious virus.

Acetylcholinesterase↗
PubMed2006

The feasibility of clinical endpoint trials in HIV infection in the highly active antiretroviral treatment (HAART) era.

BACKGROUND: Planning clinical-endpoint trials in patients with HIV remain difficult as long-term follow-up of many patients is required. Cohort studies of patients with HIV can provide key estimates of the likely disease progression, required sample size and follow-up. OBJECTIVES: To verify the assumptions used in designing ESPRIT, a large randomized clinical trial assessing the clinical benefit of interleukin-2 treatment in patients with HIV infection, to use EuroSIDA to mimic the inclusion criterion of ESPRIT in order to compare the observed event rate in ESPRIT with the projected rate in EuroSIDA, and to project the required length of ESPRIT. METHODS: Patients in EuroSIDA who satisfied the ESPRIT recruitment criteria were selected. Patients were followed from baseline to new AIDS or death. RESULTS: The incidence of clinical progression in the selected EuroSIDA patients (N = 4482) was 1.5 per 100 PYFU (95% CI 1.3-1.7), and did not increase with increasing time from baseline, contrary to what was assumed in the design of the ESPRIT trial. In ESPRIT (N = 4150), for which the comparative data remain blinded, the incidence was 1.1 per 100 PYFU (95% CI 0.9-1.3), with no increase over time. The average follow-up required to complete ESPRIT and accrue the 320 events required by protocol would be seven years, 10 months using the projected rates from the EuroSIDA study, and seven years, 11 months if the observed event rate in ESPRIT continued unchanged. LIMITATIONS: Differences between patients recruited to observational studies or clinical trials cannot always be adjusted for. CONCLUSIONS: Event rates in EuroSIDA were similar in the first two years to those used in the design of ESPRIT, but did not increase over time, leading to an increase in the expected duration of ESPRIT. Clinical endpoint trials in HIV infection remain feasible, and large cohort studies are critical to the planning and ongoing assessment of design assumptions in such trials. The underlying assumptions of the clinical trial should be re-examined to ensure the original trial assumptions remain valid.

Acquired Immunodeficiency Syndrome↗
PubMed2005

Detection of Pneumocystis jirovecii dihydropteroate synthase polymorphisms in patients with Pneumocystis pneumonia.

In the present study, in order to improve the detection of Pneumocystis jirovecii dihydropteroate synthase (DHPS) mutations in pulmonary specimens of HIV-infected patients with P. jirovecii pneumonia, we evaluated a microfiltration procedure for the removal of human cell contamination and a nested-PCR method, for amplification in specimens with low parasite load. In the studied population, PCR amplification of the DHPS gene was more successful in unfiltered than in filtered specimens, with both touchdown-PCR and nested-PCR procedures (p<0.05 and p<0.001, respectively), but the amount of host DNA in the samples analysed seems to be inversely related with the successful PCR parasite detection. Amplification of P. jirovecii DHPS gene with nested-PCR was achieved in 77.5% of the specimens studied, demonstrating that this is a useful method for the identification of mutations in pulmonary specimens, including samples with low parasite loads, and will facilitate the evaluation of the relationship between the P. jirovecii DHPS polymorphisms and clinical resistance to sulfa drugs.

Bronchoalveolar Lavage Fluid↗
PubMed2004

Decreased cellular permeability to H2O2 protects Saccharomyces cerevisiae cells in stationary phase against oxidative stress.

The higher resistance of stationary-phase Saccharomyces cerevisiae to H2O2 when compared with exponential phase is well characterized, but the molecular mechanisms underlying it remain mostly unknown. By applying the steady-state H2O2-delivery model, we show that (a) cellular permeability to H2O2 is five times lower in stationary--than in exponential phase; (b) cell survival to H2O2 correlates with H2O2 cellular gradients for a variety of cells; and, (c) cells in stationary phase are predicted to be more susceptible to intracellular H2O2 than in exponential phase. In conclusion, limiting H2O2 diffusion into cells is a key protective mechanism against extracellular H2O2.

Cell Cycle↗
PubMed2004

Central nervous system AIDS--related diseases.

The neurological complications of HIV contribute importantly to patient morbidity and mortality. Major common AIDS-related CNS diseases are ADC, metabolic encephalopaties, CMV encephalitis, TE, PCNSL, PML, criptococcal meningitis, and aseptic meningitis. After HAART, declines in incidence and improved outcome of several HIV-1 related opportunistic infections, including CNS-ADIs have been reported. The differential diagnosis of CNS complications of AIDS is routinely established according to temporal evolution, clinical data, and neuroradiological imaging. Combining neuroradiological imaging with the new CSF PCR tests may improve the diagnostic accuracy of some CNS-ADIs without the need of stereotactic brain biopsy, that may become limited to the situations where data remain conflicting.

AIDS Dementia Complex↗
PubMed2003

Mutations in the dihydropteroate synthase gene of Pneumocystis jiroveci isolates from Portuguese patients with Pneumocystis pneumonia.

The aim of this study was to evaluate the frequency of mutations of the P. jiroveci dihydropteroate synthase (DHPS) gene in an immunocompromised Portuguese population and to investigate the possible association between DHPS mutations and sulpha exposure. In the studied population, DHPS gene mutations were not significantly more frequent in patients exposed to sulpha drugs compared with patients not exposed (P=0.390). The results of this study suggest that DHPS gene mutations are frequent in the Portuguese immunocompromised population but do not seem associated with previous sulpha exposure. These results are consistent with the possibility of an incidental acquisition and transmission of P. jiroveci mutant types, either by person to person transmission or from an environmental source.

AIDS-Related Opportunistic Infections↗
PubMed2003

Smear microscopy to diagnose tuberculosis early and prevent further transmission in a population with a high prevalence of HIV infection.

In western Europe, Portugal has the highest incidence of tuberculosis (TB). The quickest way to diagnose TB is with a positive smear. To evaluate the usefulness of smear microscopy in a population with a high HIV seroprevalence, TB patients admitted during the year 2000 were retrospectively analyzed. Of the 74 TB patients admitted, 45 (61%) had pulmonary TB, 11 having multiresistant (MR)-TB. Considering that only half of the patients with pulmonary TB had a positive smear, a high degree of clinical suspicion is of great importance. Appropriate isolation facilities for TB are much needed, in order to prevent nosocomial TB spread.

Adolescent↗
PubMed2002

Changes in the cause of death among HIV positive subjects across Europe: results from the EuroSIDA study.

OBJECTIVES: The causes of death among HIV-positive patients may have changed since the introduction of highly active antiretroviral therapy (HAART). We investigated these changes, patients who died without an AIDS diagnosis and factors relating to pre-AIDS deaths. METHODS: Analyses of 1826 deaths among EuroSIDA patients, an observational study of 8556 patients. Incidence rates of pre-AIDS deaths were compared to overall rates. Factors relating to pre-AIDS deaths were identified using Cox regression. RESULTS: Death rates declined from 15.6 to 2.7 per 100 person-years of follow-up (PYFU) between 1994 and 2001. Pre-AIDS incidence declined from 2.4 to 1.1 per 100 PYFU. The ratio of overall to pre-AIDS deaths peaked in 1996 at 8.4 and dropped to < 3 after 1998. The adjusted odds of dying following one AIDS defining event (ADE) increased yearly (odds ratio, 1.53; P < 0.001), conversely the odds of dying following three or more ADE decreased yearly (odds ratio, 0.79; P < 0.001). The proportion of deaths that followed an HIV-related disease decreased by 23% annually; in contrast there was a 32% yearly increase in the proportion of deaths due to known causes other than HIV-related or suicides. Injecting drug users (IDU) were significantly more likely to die before an ADE than homosexuals (relative hazard, 2.97; P < 0.0001) and patients from northern/eastern Europe (relative hazard, 2.01; P < 0.0001) were more likely to die pre-AIDS than southern patients. CONCLUSIONS: The proportion of pre-AIDS deaths increased from 1994 to 2001; however, the incidence of pre-AIDS deaths and deaths overall declined. IDU and subjects from northern/eastern Europe had an increased risk of pre-AIDS death. HIV-positive patients live longer therefore it is essential to continue to monitor all causes of mortality to identify changes.

Cause of Death↗
PubMed2002

DNA-lipid systems. A physical chemistry study.

It is well known that the interaction of polyelectrolytes with oppositely charged surfactants leads to an associative phase separation; however, the phase behavior of DNA and oppositely charged surfactants is more strongly associative than observed in other systems. A precipitate is formed with very low amounts of surfactant and DNA. DNA compaction is a general phenomenon in the presence of multivalent ions and positively charged surfaces; because of the high charge density there are strong attractive ion correlation effects. Techniques like phase diagram determinations, fluorescence microscopy, and ellipsometry were used to study these systems. The interaction between DNA and catanionic mixtures (i.e., mixtures of cationic and anionic surfactants) was also investigated. We observed that DNA compacts and adsorbs onto the surface of positively charged vesicles, and that the addition of an anionic surfactant can release DNA back into solution from a compact globular complex between DNA and the cationic surfactant. Finally, DNA interactions with polycations, chitosans with different chain lengths, were studied by fluorescence microscopy, in vivo transfection assays and cryogenic transmission electron microscopy. The general conclusion is that a chitosan effective in promoting compaction is also efficient in transfection.

Cations↗
PubMed2001

Viral load outcome of non-nucleoside reverse transcriptase inhibitor regimens for 2203 mainly antiretroviral-experienced patients.

OBJECTIVE: To assess the factors associated with virologic response to non-nucleoside reverse transcriptase inhibitor (NNRTI)-containing regimens in a large clinic cohort. DESIGN: Inception cohort. SETTING: HIV clinics in Europe PATIENTS: We identified all patients in EuroSIDA who began a regimen including either nevirapine or efavirenz (not both) after July 1997 and for whom pre-therapy viral load and CD4 cell count were known. MAIN OUTCOME MEASURES: Virological failure. RESULTS: A total of 1325 patients initiated nevirapine and 878 efavirenz. Respectively, median start dates were October 1998 and May 1999. Other factors at baseline, including CD4 cell count, viral load, previous AIDS, previous antiretroviral drug use and make-up of the NNRTI-containing regimen were all approximately similar between the nevirapine and efavirenz groups. A total of 669 patients experienced virological failure during follow-up. In a Cox model, less protease inhibitors and nucleoside reverse transcriptase inhibitors (NRTIs) previously used, higher CD4 nadir, lower viral load at baseline, a previous AIDS diagnosis and less NRTIs in the regimen were associated with lower risk of virological failure. The relative hazard of virological failure comparing those on efavirenz with those on nevirapine was 0.57 (95% confidence interval, 0.47-0.69; P < 0.0001). CONCLUSIONS: The difference in virologic outcome between those using nevirapine and efavirenz in this almost entirely drug-experienced population could reflect differences in effectiveness of the drugs in this setting but, despite the similarity between groups at baseline, bias cannot be excluded as an explanation. Replication of these findings in randomized trials and other cohort studies is required.

Adult↗
PubMed2001

Non-Hodgkin lymphoma in HIV-infected patients in the era of highly active antiretroviral therapy.

This study was designed to assess the influence of highly active antiretroviral therapy (HAART) on non-Hodgkin lymphoma (NHL) among patients infected with human immunodeficiency virus (HIV). Within EuroSIDA, a multicenter observational cohort of more than 8500 patients from across Europe, the incidences of NHL and subtypes (Burkitt, immunoblastic, primary brain lymphoma [PBL], and other/unknown histology) were determined according to calendar time of follow-up, and for those who initiated HAART (> or =3 drugs) also time on HAART. Potential predictive factors of NHL were evaluated in Cox proportional hazard models. Over 26 764 person-years of prospective follow-up (PYF) from May 1994 to December 2000, the incidence of NHL decreased from 1.99 (95% confidence interval, 1.51-2.47) before September 1995 to 0.30 (0.19-0.42) cases/100 (PYF) after March 1999 (P <.001). The incidence of all subtypes of NHL decreased significantly and most pronouncedly for PBL. Among patients who started HAART, the incidence of NHL decreased from 0.88 (0.60-1.16) within the first 12 months after starting HAART to 0.45 (0.31-0.60) cases/100 PYF after more than 24 months (P =.004). In an adjusted Cox model for patients on HAART, the latest CD4 cell count and plasma viral load were both significantly associated with diagnosis of NHL; the relative hazard was 1.39 (range, 1.14-1.69) per 50% lower CD4 cell count, and 1.51 (range, 1.21-1.88) per 1 log higher plasma viral load. In conclusion, the incidence of NHL among HIV-infected patients has decreased significantly after the introduction of HAART, and the decline was most pronounced for PBL. After starting HAART, patients with insufficient immunologic and virologic responses were at highest risk of NHL.

Acquired Immunodeficiency Syndrome↗
PubMed2001

Apoptosis induced by exposure to a low steady-state concentration of H2O2 is a consequence of lysosomal rupture.

We have re-examined the lysosomal hypothesis of oxidative-stress-induced apoptosis using a new technique for exposing cells in culture to a low steady-state concentration of H(2)O(2). This steady-state technique mimics the situation in vivo better than the bolus-administration method. A key aspect of H(2)O(2)-induced apoptosis is that the apoptosis is evident only after several hours, although cells may become committed within a few minutes of exposure to this particular reactive oxygen species. In the present work, we were able to show, for the first time, several correlative links between the triggering effect of H(2)O(2) and the later onset of apoptosis: (i) a short (15 min) exposure to H(2)O(2) caused almost immediate, albeit limited, lysosomal rupture; (ii) early lysosomal damage, and later apoptosis, showed a similar dose-related response to H(2)O(2); (iii) both events were inhibited by pre-treatment with iron chelators, including desferrioxamine. This compound is known to be taken up by endocytosis only and thus to become localized in the lysosomal compartment. After exposure to oxidative stress, when cells were again in standard culture conditions, a time-dependent continuous increase in lysosomal rupture was observed, resulting in a considerably lowered number of intact lysosomes in apoptotic cells, whereas non-apoptotic cells from the same batch of oxidative-stress-exposed cells showed mainly intact lysosomes. Taken together, our results reinforce earlier findings and strongly suggest that lysosomal rupture is an early upstream initiating event, and a consequence of intralysosomal iron-catalysed oxidative processes, when apoptosis is induced by oxidative stress.

Apoptosis↗
PubMed2001

Cellular titration of apoptosis with steady state concentrations of H(2)O(2): submicromolar levels of H(2)O(2) induce apoptosis through Fenton chemistry independent of the cellular thiol state.

Apoptosis was studied under conditions that mimic the steady state of H(2)O(2) in vivo. This is at variance with previous studies involving a bolus addition of H(2)O(2), a procedure that disrupts the cellular homeostasis. The results allowed us to define three phases for H(2)O(2)-induced apoptosis in Jurkat T-cells with reference to cytosolic steady state concentrations of H(2)O(2) [(H(2)O(2))(ss)]: (H(2)O(2))(ss) values below 0.7 microM elicited no effects; (H(2)O(2))(ss) approximately 0.7-3 microM induced apoptosis; and (H(2)O(2))(ss) > 3 microM yielded no additional apoptosis and a gradual shift towards necrosis as the mode of cell death were observed. H(2)O(2)-induced apoptosis was not affected by either BCNU, an inhibitor of glutathione reductase, or diamide, a compound that reacts both with low-molecular weight and protein thiols, or selenols. Glutathione depletion, accomplished by incubating cells either with buthionine sulfoximine or in cystine-free medium, rendered cells more sensitive to H(2)O(2)-induced apoptosis, but did not change the threshold and saturating concentrations of H(2)O(2) that induced apoptosis. Two unrelated metal chelators, desferrioxamine and dipyridyl, strongly protected against H(2)O(2)-induced apoptosis. It may be concluded that, under conditions of H(2)O(2) delivery that mimic in vivo situations, the oxidative event that triggers the induction of apoptosis by H(2)O(2) is a Fenton-type reaction and is independent of the thiol or selenium states of the cell.

2,2'-Dipyridyl↗
PubMed2001

Effect of oral washes on the diagnosis of Pneumocystis carinii pneumonia with a low parasite burden and on detection of organisms in subclinical infections.

This study was designed to assess the efficacy of using oral washes (OWs) to diagnose Pneumocystis carinii pneumonia (PCP) in patients with a low parasite burden and to detect cases of subclinical infection. A total of 104 paired induced sputum (IS) samples and OWs from 104 HIV-seropositive patients and 32 OWs from immunocompetent healthy controls were studied. All of the control samples were negative. Fifty-two IS specimens were positive for Pneumocystis carinii, and 26 of these cases were also detected in the OWs using conventional stain or polymerase chain reaction. Twenty-four of the PCP cases had a high or a moderate parasite load and 28 had a low parasite load; among them, Pneumocystis carinii was detected in the OWs of 15 and 11 cases, respectively. Fifteen of the 104 IS samples studied belonged to patients who were asymptomatic carriers or who had a subclinical infection, and Pneumocystis carinii was detected in the OWs of 4 of these cases. The parasite was not detected in 37 IS samples and in 74 OWs. The results of this study indicate that in patients with a low pulmonary parasite burden, the number of organisms reaching the oral cavity is insufficient for reliable detection in OWs. Thus, OWs are less useful than IS samples for detecting Pneumocystis carinii in cases of pneumonia in which a low parasite burden and/or subclinical infection are present.

AIDS-Related Opportunistic Infections↗