PubMed Health⌕ Search

Biomedical subjects

G Carvalho

Publications and source records attributed to G Carvalho.

At least 19 recordsLinked to original sources
PubMed2007

NF-kappaB inhibition sensitizes to starvation-induced cell death in high-risk myelodysplastic syndrome and acute myeloid leukemia.

CD34(+) bone marrow blasts from high-risk myelodysplastic syndrome (MDS) patients as well as MDS patient-derived cell lines (P39 and MOLM13) constitutively activate the nuclear factor-kappaB (NF-kappaB) pathway and undergo apoptosis when NF-kappaB is inhibited. Here, we show that the combination of conventional chemotherapeutic agents (daunorubicin, mitoxantrone, 5-azacytidine or camptothecin) with the NF-kappaB inhibitor BAY11-7082 did not yield a synergistic cytotoxicity. In contrast, BAY11-7082 (which targets the NF-kappaB-activating I-kappaB kinase (IKK) complex) or knockdown of essential components of the NF-kappaB system (such as the IKK1 and IKK2 subunits of the IKK complex and the p65 subunit of NF-kappaB), by small interfering RNAs sensitized MDS cell lines to starvation-induced apoptosis. The combination of BAY11-7082 and nutrient depletion synergistically killed the acute myeloid leukemia (AML) cell line U937 as well as primary CD34(+) bone marrow blasts from AML and high-risk MDS patients. The synergistic killing by BAY11-7082, combined with nutrient depletion, led to cell death accompanied by all hallmarks of apoptosis, including an early loss of the mitochondrial transmembrane potential, the release of cytochrome c and apoptosis-inducing factor (AIF) from mitochondria, activation of caspase-3, phosphatidylserine exposure on the plasma membrane surface and nuclear chromatin condensation. Transmission electron microscopy revealed the presence of numerous autophagic vacuoles in the cytoplasm before cells underwent nuclear apoptosis. Nonetheless, cell death was neither inhibited by the pan-caspase inhibitor z-VAD-fmk nor by knockdown of AIF or of essential components of the autophagy pathway (ATG5, ATG6/Beclin-1, ATG10, ATG12). In contrast, external supply of glucose, insulin or insulin-like growth factor-I could retard the cell death induced by BAY11-7082 combined with starvation. These results suggest that in MDS cells, NF-kappaB inhibition can precipitate a bioenergetic crisis that leads to an autophagic stress response followed by apoptotic cell death.

Acute Disease↗
PubMed2006

Inhibition of NEMO, the regulatory subunit of the IKK complex, induces apoptosis in high-risk myelodysplastic syndrome and acute myeloid leukemia.

In high-risk myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML), blasts constitutively activate the antiapoptotic transcription factor nuclear factor-kappaB (NF-kappaB). Here, we show that this NF-kappaB activation relies on the constitutive activation of the IkappaB kinase (IKK) complex, which is formed by the IKKalpha, IKKbeta and IKKgamma/NF-kappaB essential modulator (NEMO) subunits. A cell-permeable peptide that mimics the leucine zipper subdomain of IKKgamma, thus preventing its oligomerization, inhibited the constitutive NF-kappaB activation and induced apoptotic cell death in a panel of human MDS and AML cell lines (P39, MOLM13, THP1 and MV4-11). Small interfering RNA-mediated knockdown of the p65 NF-kappaB subunit or the three IKK subunits including IKKgamma/NEMO also induced apoptotic cell death in P39 cells. Cell death induced by the IKKgamma/NEMO-antagonistic peptide involved the caspase-independent loss of the mitochondrial transmembrane potential as well as signs of outer mitochondrial membrane permeabilization with the consequent release of cytochrome c, apoptosis-inducing factor and endonuclease G. Primary bone marrow CD34(+) cells from high-risk MDS and AML patients also succumbed to the IKKgamma/NEMO-antagonistic peptide, but not to a mutated control peptide. Altogether, these data indicate that malignant cells in high-risk MDS and AML cells critically depend on IKKgamma/NEMO to survive. Moreover, our data delineate a novel procedure for their therapeutic removal, through inhibition of IKKgamma/NEMO oligomerization.

Acute Disease↗
PubMed2006

Targeting NF-kappaB in hematologic malignancies.

The transcription factor nuclear factor kappa B (NF-kappaB) can intervene in oncogenesis by virtue of its capacity to regulate the expression of a plethora of genes that modulate apoptosis, and cell survival as well as proliferation, inflammation, tumor metastasis and angiogenesis. Different reports demonstrate the intrinsic activation of NF-kappaB in lymphoid and myeloid malignancies, including preneoplastic conditions such as myelodysplastic syndromes, underscoring its implication in malignant transformation. Targeting intrinsic NF-kappaB activation, as well as its upstream and downstream regulators, may hence constitute an additional approach to the oncologist's armamentarium. Several small inhibitors of the NF-kappaB-activatory kinase IkappaB kinase, of the proteasome, or of the DNA binding of NF-kappaB subunits are under intensive investigation. Currently used cytotoxic agents can induce NF-kappaB activation as an unwarranted side effect, which confers apoptosis suppression and hence resistance to these drugs. Thus, NF-kappaB inhibitory molecules may be clinically useful, either as single therapeutic agents or in combination with classical chemotherapeutic agents, for the treatment of hematological malignancies.

Hematologic Neoplasms↗
PubMed2005

[Natural history of fetal pyelocaliectasia].

INTRODUCTION: It is estimated that genitourinary anomalies comprise 20% of all antenatally detected fetal anomalies, and pyelocaliectasia is the most common one. Detection of antenatal dilatation of the urinary tract does not always indicate postnatal urinary tract obstruction or even a significant genitourinary anomaly. Most cases will improve spontaneously, representing a temporary physiologic impedence and do not require surgery. MATERIALS AND METHODS: In a two-year period we studied 197 newborns, with prenatal pyelocaliectasia, without concomitant anomaly, delivered at Maternidade Dr. Daniel de Matos. In the postnatal follow-up period, the infants were followed at Pediatrics Department, at our Center. RESULTS: A male predilection was found. Ultrasonic follow-up of the 197 infants showed that pyelocaliectasia resolved in 97%, while 3% still presented it in the postnatal ultrasound. Complementary renal evaluation, with voiding cystourethrography and radionuclide imaging, was realised in 29 (15%) infants to further characterize the abnormality detected in postnatal ultrasound. Surgery was performed in four (2%) children. CONCLUSION: Prenatally diagnosed pyelocaliectasia may be safely observed, and surgical correction should be performed only if renal compromise occurs.

Clinical Protocols↗
PubMed2004

Model development and application for surfactant biodegradation in an acclimatising activated sludge system.

A model for the biodegradation of non-ionic surfactants in an activated sludge system during acclimatisation was developed, based on respirometric and titrimetric experimental data. The data were obtained in a sequencing batch reactor (SBR) using a non-ionic surfactant as sole carbon source and sludge previously acclimatised to a different surfactant. The model was successfully applied to successive SBR-cycles of sludge acclimatisation processes subjected to two ethoxylated surfactants. The model was validated using the corresponding total organic carbon data. The evolution of the model parameters along the acclimatisation process was examined. An acclimatisation model was developed using the evolution of two of these parameters (affinity constant and inhibition constant), supported by two independently calculated acclimatisation indicators. This acclimatisation model was then applied to determine an optimal surfactant concentration sequence to feed non-acclimatised sludge during a period of 41 days, in order to induce pre-acclimatisation to this surfactant before it replaces another one in the wastewater. The model was also useful in the economical assessment of this and alternative procedures to cope with frequent changes in activated sludge feed composition.

Biodegradation, Environmental↗
PubMed2003

Potentiation of tumour apoptosis by human growth hormone via glutathione production and decreased NF-kappaB activity.

In addition to its primary role as growth factor, human growth hormone (hGH) can also participate in cell survival, as already documented by its protective effect on human monocytes or human promyelocytic leukaemia U937 cells exposed to a Fas-mediated cell death signal. However, despite similarities in the molecular events following Fas and TNF-alpha receptor engagement, we report that U937 cells, genetically engineered to constitutively produce hGH, were made more sensitive to TNF-alpha-induced apoptosis than parental cells. This was due to overproduction of the antioxidant glutathione, which decreased the nuclear factor (NF)-kappaB activity known to control the expression of survival genes. These findings were confirmed in vivo, in nude mice bearing U937 tumours coinjected with recombinant hGH and the NF-kappaB -inducing anticancer drug daunorubicin, to avoid the in vivo toxicity of TNF-alpha. This study therefore highlights one of the various properties of hGH that may have potential clinical implications.

Animals↗
PubMed2003

Activated sludge acclimatisation kinetics to non-ionic surfactants.

The biodegradation of surfactants is a frequent and complex problem in domestic and industrial wastewater treatment processes. In addition to the resulting metabolites being sometimes refractory, the complete biodegradation of many of the most employed non-ionic surfactants requires long hydraulic retention times and the presence of specialised bacterial consortia. Preliminary acclimatisation tests highlighted the importance of the sludge acclimatisation state to a specific surfactant substrate for biotreatment efficiency. This paper reports on studies aimed at quantifying activated sludge acclimatisation and memory retention levels when subjected to changes in the type of surfactant included in the feed. Several transitions were tested, namely from an alkylphenol ethoxylate to a linear alkyl ethoxylate and the reverse, and between alkyl ethoxylates with different hydrophobic and hydrophilic molecular chain lengths. The kinetic results showed that sludge activation and memory loss were more dynamic for primary biodegradation It was found that the sludge was harder to adapt to alkylphenol ethoxylate than to alkyl ethoxylate. The former also apparently introduced an inhibitory effect, resulting in very slow degradation kinetics when imposed to alkyl ethoxylate acclimatised sludge. When replacing an alkyl ethoxylate with another surfactant of the same family, a longer ethoxylate chain reduced the degradation rates. This effect was further enhanced by simultaneously increasing the hydrophobic chain length of the substrate. The acclimatisation kinetic after the replacement of an alkyl ethoxylate by a longer counterpart was slower than the reverse case, and memory was also more easily lost.

Biodegradation, Environmental↗
PubMed2002

Optimal operation for timely adaptation of activated sludge plants to changes in the surfactant composition of wastewater.

The composition of a textile industry wastewater is highly variable, as the industrial process has to follow fashion and season trends. Surfactants represent one of the largest COD fractions in a typical textile wastewater. Therefore, it was the aim of this paper to model the acclimatisation behaviour of an activated sludge system when subjected to composition variations in the surfactant containing feed. The model was based on data obtained in SBR experiments in which a linear alkyl ethoxylate as sole carbon source in the feed was replaced by another with a longer ethoxylate chain. A previously developed model (Fractionated Degradation Model) was applied to each of the 21 SBR cycles carried out in this study. The resulting best-fit parameters were investigated and sub-models were further developed, to create an acclimatisation model, able to predict the sludge acclimatisation level. Using the information given by this model, it was possible to propose an optimal operation scheme to pre-acclimatise the sludge before a surfactant replacement is made in the textile process. A cost analysis was carried out to compare different scenarios, with and without the application of this operation scheme. It was concluded that the proposed pre-acclimatisation process may be cost effective as compared to other scenarios if a cheap surfactant-containing product was employed.

Calibration↗
PubMed2001

River basin-related genetic structuring in an endangered fish species, Chondrostoma lusitanicum, based on mtDNA sequencing and RFLP analysis.

Chondrostoma lusitanicum is a Portuguese endemic cyprinid with a restricted distribution and reduced numbers in some basins, justifying its status as a threatened species. We examined genetic population structure using samples from throughout its geographical range in Portugal, using sequencing of b cytochrome and restriction fragment length polymorphism analysis of the NADH subunits 5 and 6. There was reduced within-population genetic variability but considerable among-population differentiation, particularly marked between both the Mira and Arade basins in the extreme south and other populations. These results confirm phylogeographic relationships suggested by previous fragmentary allozyme studies for C. lusitanicum, and are in accordance with allozyme and mitochondrial DNA data on phylogeography of coexisting cyprinid species of the genus Leuciscus. The levels of genetic divergence revealed by sequence and RFLP data showed strongly concordant patterns: geographical genetic structuring, with the definition of three distinct groups, was observed. The high values of nucleotide divergence and pairwise sequence divergence of the Mira and Arade groups, when compared with all other samples, support a distinct taxonomic status probably at the species level. Results are also discussed in relation to conservation of this highly fragmented species, in terms of Evolutionary Significant Units and Management Units.

Analysis of Variance↗
PubMed2001

Modelling of activated sludge acclimisation to a non-ionic surfactant.

A model is proposed to describe activated sludge acclimatisation to a non-ionic surfactant. The model was calibrated automatically, using WEST, a specific software environment for wastewater treatment model building, simulation and parameter estimation. The assays have been performed in a sequencing-batch reactor (SBR), using a non-ionic surfactant as sole carbon source and non-acclimatised sludge. The best fitting model was based on the assumption of three sequentially degraded COD fractions, where the second fraction is a metabolite of the original molecule and the third fraction is a more slowly biodegradable metabolite resulting from the secondary degradation. For primary degradation, hydrolysis with no associated growth was assumed. The growth of microorganisms responsible for degradation of the second and third COD fractions was presumed to follow Haldane and first order kinetics, respectively. The model was able to fit four consecutive assays of the same acclimatisation process, using Brij 30 as carbon source, with different food/microorganism ratios. The parameters obtained showed that the (self-)inhibition of the growth on the second COD fraction decreased along acclimatisation.

Bacteria↗
PubMed1998

Contraceptive use and pregnancy before and after introducing lactational amenorrhea (LAM) in a postpartum program.

There is good evidence that lactational amenorrhea (LAM) is an effective method of fertility regulation during the first 6 months postpartum, provided no other food is given to the baby and the mother remains amenorrheic. However, although breast-feeding is strongly promoted in many maternity hospitals that also run postpartum family planning programs, LAM is rarely included among the contraceptive options being offered. This paper presents the results of an operational study which compared the prevalence of contraceptive use and the cumulative pregnancy rate at 12-months postpartum among 350 women observed before and 348 women studied after introducing LAM as an alternative contraceptive option offered to women following delivery at the Instituto Materno Infantil de Pernambuco (IMIP), in Recife, Brazil. The percentage of women not using any contraceptive method was significantly lower (p<0.0001) after the intervention (7.4%) than before (17.7%). This difference remained statistically significant after controlling for age, number of living children, marital status and years of schooling. The proportion pregnant one year postpartum was also significantly lower (p<0.0001) after the introduction of LAM (7.4%) than before (14.3%), but the difference was no longer significant after controlling for the same variables. It is concluded that LAM is a useful addition to family planning postpartum programs.

Adolescent↗
PubMed1998

Long-term in vivo cochlear transgene expression mediated by recombinant adeno-associated virus.

Adeno-associated virus (AAV) integrated transgene expression within guinea pig cochlea has been previously documented. This article extends these studies by characterizing the AAV-mediated gene transfer for duration of transgene expression within the cochlea and its effect upon cochlear cytoarchitecture over a period of 6 months. All animals infused with AAV expressed the transgene product, bacterial beta-galactosidase (beta-gal) enzyme, in the spiral limbus, spiral ligament, spiral ganglion cells and the organ of Corti at 2-24 weeks after infusion. However, the level of beta-gal expression, as determined from intensity of immunoreactivity, was relatively lower at 24 weeks as compared with 2 weeks. The cellular and tissue architecture within the AAV-beta-gal perfused cochleae, harvested 2-8 weeks after AAV infusion, was generally intact, ie free from inflammation and cellular degeneration. However, cellular degeneration and degradation was apparent in the cochleae of some but not all animals harvested at 12 and 24 weeks after AAV infusion.

Animals↗