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Papers by Cristina Barradas Barradas

Research paper thumbnail of Serum lipids analysis in septic shock patients

Critical Care, 2007

Critical Care 2007, 11(Suppl 3):P1 (doi: 10.1186/cc5788)

Research paper thumbnail of Potential role of poly(ADP-ribose) activation in myocardial contractile dysfunction of human septic shock

Research paper thumbnail of Monte Carlo Calculations for Neutron and Gamma Radiation Fields on a Fast Neutron Irradiation Device

ABSTRACT We used the Monte Carlo program MCNP to calculate the neutron and gamma fluxes on a fast... more ABSTRACT We used the Monte Carlo program MCNP to calculate the neutron and gamma fluxes on a fast neutron irradiation facility being installed on the Portuguese Research Reactor (RPI). The purpose of this facility is to provide a fast neutron beam for irradiation of electronic circuits. The gamma dose should be minimized. This is achieved by placing a lead shield preceded by a thin layer of boral. A fast neutron flux of the order of 10(9) n/cm(2)s is expected at the exit of the tube, while the gamma radiation is kept below 20 Gy/h. We will present results of the neutron and gamma doses for several locations along the tube and different thickness of the lead shield. We found that the neutron beam is very collimated at the end of the tube with a dominant component on the fast region.

Research paper thumbnail of Rutherford backscattering and X-ray reflectivity analysis of tunnel barriers

Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2005

The properties of the insulating barrier junctions are determinant to the properties of silicon-b... more The properties of the insulating barrier junctions are determinant to the properties of silicon-based spin transistors. They are strongly influenced by their layer thicknesses and composition. Hence, forming the barrier is a key factor in fabricating a functional device. In this work, we investigate the formation of zirconium oxide and mixed zirconium and aluminium oxide ultra-thin barriers, by deposition of

Research paper thumbnail of Analysis of the candidate tumor suppressor Ris-1 in primary human breast carcinomas

Mutation Research-fundamental and Molecular Mechanisms of Mutagenesis, 2006

Frequent chromosome 3 losses have been described in several tumors types, which strongly suggest ... more Frequent chromosome 3 losses have been described in several tumors types, which strongly suggest the presence of one or several tumor suppressor genes. Recently, a novel candidate tumor suppressor gene termed Ris-1 (for Ras-induced senescence 1) has been identified at chromosomal position 3p21.3. Ris-1 has been proposed to participate in anti-tumor responses that resemble cellular senescence and that are elicited by oncogenes such as Ras. To analyze the role of Ris-1 as a putative tumor suppressor gene in human breast cancer, we have performed a real-time quantitative analysis of its mRNA expression in 60 patients. Moreover, we carried out a first approach to evaluate the most common inactivation mechanism that can affect expression levels of tumor suppressor genes (mutation, promoter hypermethylation and allelic losses). Furthermore, a correlation study between expression as well as inactivating mechanisms of Ris-1 and several clinico-pathological parameters of the tumors was designed, with the objective of appraising the prognostic value of Ris-1 status. Decreased expression of Ris-1 was observed in 23% of the cases and overexpressed Ris-1 was detected in 15% of the primary breast tumors. Our data showed high frequency of LOH (30%) at one of the markers used. Nevertheless, a polymorphism related with the expression levels was described. Statistically significant correlations were found between decreased Ris-1 expression and negative progesterone receptors, as well as between overexpressing Ris-1 tumors and high histological grade. Despite all these data, we conclude that the suggested role of Ris-1 as tumor suppressor gene is not evident, at least in breast cancer. Future and larger series studies in different tumor types are necessary to clarify Ris-1 function in human cancer.

Research paper thumbnail of Compositional and structural characterisation of GaSb and GaInSb

Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2005

Low band gap III-V semiconductors are researched for applications in thermophotovoltaic technolog... more Low band gap III-V semiconductors are researched for applications in thermophotovoltaic technology. GaSb crystal is often used as a substrate. Ga 1Àx In x Sb is also a promising substrate material, because its lattice parameters can be adjusted by controlling x. We used a new method to synthesise GaSb and GaInSb, in which a high frequency alternate magnetic field is used to heat, to melt and to mix the elements. We present a compositional and structural characterisation of the materials using a combination of complementary techniques. Rutherford backscattering was used to determine accurately the composition of the GaSb. With proton induced X-ray emission in conjunction with a 3 · 3 lm 2 micro-beam we studied the homogeneity of the samples. Structural analysis and phase identification were done with X-ray diffraction. The results for GaSb show a homogeneous composition while the GaInSb samples were found to be strongly heterogeneous at the end of the ingot. The ingots produced are competitive feed material, when compared to other growth techniques, to be used in a second step for the production of good quality ternary crystals.

Research paper thumbnail of MAPEAMENTO E QUANTIFICA˙ˆO DO REFLORESTAMENTO NO ESTADO DE SO PAULO / REFORESTATION INVENTORY OF THE SO PAULO STATE

Research paper thumbnail of Capture Conditions in the Restricted Three-Body Problem

Research paper thumbnail of Lipid metabolism and organ dysfunction in septic patients during intensive glycemic control

Critical Care, 2007

Hydrogen sulfide is produced endogenously by a variety of enzymes involved in cysteine metabolism... more Hydrogen sulfide is produced endogenously by a variety of enzymes involved in cysteine metabolism. Clinical data indicate that endogenous levels of hydrogen sulfide are diminished in various forms of cardiovascular diseases. The aim of the current study was to investigate the effects of hydrogen sulfide supplementation on cardiac function during reperfusion in a clinically relevant experimental model of cardiopulmonary bypass. Twelve anesthetized dogs underwent hypothermic cardiopulmonary bypass. After 60 minutes of hypothermic cardiac arrest, reperfusion was started after application of either saline vehicle (control, n = 6), or the sodium sulfide infusion (1 mg/kg/hour, n = 6). Biventricular hemodynamic variables were measured by combined pressure-volume-conductance catheters. Coronary and pulmonary blood flow, vasodilator responses to acetylcholine and sodiumnitroprusside and pulmonary function were also determined. Administration of sodium sulfide led to a significantly better recovery of left and right ventricular systolic function (P < 0.05) after 60 minutes of reperfusion. Coronary blood flow was also significantly higher in the sodium sulfide-treated group (P < 0.05). Sodium sulfide treatment improved coronary blood flow, and preserved the acetylcholine-induced increases in coronary and pulmonary blood (P < 0.05). Myocardial ATP levels were markedly improved in the sulfide-treated group. Thus, supplementation of sulfide improves the recovery of myocardial and endothelial function and energetic status after hypothermic cardiac arrest during cardiopulmonary bypass. These beneficial effects occurred without any detectable adverse hemodynamic or cardiovascular effects of sulfide at the dose used in the current study.

Research paper thumbnail of Septic lipidic dysregulation is related to heart rate variability alteration

Research paper thumbnail of Maternal malnutrition during lactation alters gonadotropin-releasing hormone expression in the hypothalamus of weaned male rat pups

Nutritional Neuroscience, 2010

Gonadotropin-releasing hormone (GnRH) is the key hormone regulating reproduction. Its feedback re... more Gonadotropin-releasing hormone (GnRH) is the key hormone regulating reproduction. Its feedback regulation is exercised by estradiol. The early postnatal period is critical for sexual differentiation. Despite the fact that malnutrition-related reproductive suppression in rats is a well-documented phenomenon, we had no knowledge, until now, on how maternal malnutrition affects GnRH expression and estradiol serum concentrations of weaned pups. Six pregnant Wistar rats were separated into three groups at delivery with 6 pups each: control group (C) with free access to a standard diet containing 23% protein; protein energy restricted group (PER) with free access to an isoenergy and 8% protein diet; and an energy-restricted (ER) group receiving a standard diet in restricted quantities, which were calculated according to the mean ingestion of the PER group. At 21 days post partum, the animals were killed and the serum estradiol was evaluated by radioimmunoassay. Immunohistochemistry for GNRH was performed. The serum estradiol concentration was decreased in PER and ER groups compared with C (PER, 34%; ER, 19%;P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01) and the staining of GNRH was restricted to arcuate nucleus and median eminence in the control group while in PER and ER stained processes aligned with the third ventricle wall (periventricular nucleus) were present. In conclusion, our data reinforce the concept that the maternal nutritional state during lactation is critical for sexual maturation since maternal malnutrition resulted in a neuron migration delay evidenced by an altered GnRH expression profile, probably a consequence of low estradiol serum levels.

Research paper thumbnail of Composted municipal waste effects on chemical properties of a Brazilian soil

Bioresource Technology, 2007

The spread of composted municipal waste (CMW) on land can be used for sustainable crop production... more The spread of composted municipal waste (CMW) on land can be used for sustainable crop production. Nevertheless, heavy metals availability may be a problem. Therefore, the main objective of this study was to assess the impact of CMW disposal on heavy metal accumulation in soil and plants. The treatments consisted of an untreated plot (control) and four rates of CMW application. All plots were cultivated in succession of carrot, cauliXower, sweet corn, and radish. Cu and Pb signiWcantly accumulated in the topsoil (0-5 cm) with a similar pattern in the depths of 5-10 cm and 10-20 cm. CauliXower, for Fe and Cu, and radish, for Pb and Cu, had their tissue analysis sig-niWcantly aVected due to the increasing rates of application of CMW. Nevertheless, the levels of accumulation in both, soil and plant, are within permissible limits. The evidences provided by this experiment indicated that heavy metals are less likely to cause problems for the estimation of CMW loadings to Brazilian agricultural land.

Research paper thumbnail of Morphological Evidence for the Existence of Two Distinct Types of Mitochondria Rich Cells in the Gill of the Crayfish Astacus leptodactylus Eschscholtz

Acta Zoologica, 1997

An ultrastructural study was performed on gill epithelia of the crayfish Astacus leptodactylus. T... more An ultrastructural study was performed on gill epithelia of the crayfish Astacus leptodactylus. The filament and the lamina of the podobranch were examined. In both structures a vascular system is lined by a specialized epithelium covered by a cuticle. Different types of epithelium were described in the gill filaments: either a thin epithelium with few organelles and probably involved in gas exchange or, in other filaments, a thick epithelium with characteristics of a transporting epithelium (abundant mitochondria in close association with plasma membrane infoldings). The epithelium of the lamina is also of a transporting type but in this case the complex of membrane infoldings and mitochondria is in an opposite orientation to that of the filament epithelium suggesting a different role in osmoregulation. © 1997 Published by Elsevier Science Ltd on behalf of The Royal Swedish Academy of Sciences.

Research paper thumbnail of High prevalence of ST121 in community-associated methicillin-susceptible Staphylococcus aureus lineages responsible for skin and soft tissue infections in Portuguese children

European Journal of Clinical Microbiology & Infectious Diseases, 2011

In order to evaluate the incidence of community-associated methicillin-resistant Staphylococcus a... more In order to evaluate the incidence of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) in Portugal, we analyzed a collection of 38 S. aureus isolates recovered from 30 children attending the pediatric emergency department of a central hospital in Lisbon due to skin and soft tissue infections. Molecular characterization identified seven clonal lineages among the 35 methicillin-susceptible S. aureus (MSSA) isolates, of which the major lineage PFGE A/t159/ST121 included 63% of the isolates. The three MRSA isolates belonged to the Pediatric clone PFGE D/t535/ST5-IV (n = 2) and to the European CA-MRSA clone PFGE G/t044/ST80-IVc (n = 1). All isolates harbored several virulence factors, namely, leukocidins. Panton–Valentine leukocidin (PVL) was produced by isolates from five MSSA lineages and by the ST80 MRSA. Of interest, this is the first reported isolation of CA-MRSA ST80 in Portugal.

Research paper thumbnail of Serum lipids analysis in septic shock patients

Critical Care, 2007

Critical Care 2007, 11(Suppl 3):P1 (doi: 10.1186/cc5788)

Research paper thumbnail of Potential role of poly(ADP-ribose) activation in myocardial contractile dysfunction of human septic shock

Research paper thumbnail of Monte Carlo Calculations for Neutron and Gamma Radiation Fields on a Fast Neutron Irradiation Device

ABSTRACT We used the Monte Carlo program MCNP to calculate the neutron and gamma fluxes on a fast... more ABSTRACT We used the Monte Carlo program MCNP to calculate the neutron and gamma fluxes on a fast neutron irradiation facility being installed on the Portuguese Research Reactor (RPI). The purpose of this facility is to provide a fast neutron beam for irradiation of electronic circuits. The gamma dose should be minimized. This is achieved by placing a lead shield preceded by a thin layer of boral. A fast neutron flux of the order of 10(9) n/cm(2)s is expected at the exit of the tube, while the gamma radiation is kept below 20 Gy/h. We will present results of the neutron and gamma doses for several locations along the tube and different thickness of the lead shield. We found that the neutron beam is very collimated at the end of the tube with a dominant component on the fast region.

Research paper thumbnail of Rutherford backscattering and X-ray reflectivity analysis of tunnel barriers

Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2005

The properties of the insulating barrier junctions are determinant to the properties of silicon-b... more The properties of the insulating barrier junctions are determinant to the properties of silicon-based spin transistors. They are strongly influenced by their layer thicknesses and composition. Hence, forming the barrier is a key factor in fabricating a functional device. In this work, we investigate the formation of zirconium oxide and mixed zirconium and aluminium oxide ultra-thin barriers, by deposition of

Research paper thumbnail of Analysis of the candidate tumor suppressor Ris-1 in primary human breast carcinomas

Mutation Research-fundamental and Molecular Mechanisms of Mutagenesis, 2006

Frequent chromosome 3 losses have been described in several tumors types, which strongly suggest ... more Frequent chromosome 3 losses have been described in several tumors types, which strongly suggest the presence of one or several tumor suppressor genes. Recently, a novel candidate tumor suppressor gene termed Ris-1 (for Ras-induced senescence 1) has been identified at chromosomal position 3p21.3. Ris-1 has been proposed to participate in anti-tumor responses that resemble cellular senescence and that are elicited by oncogenes such as Ras. To analyze the role of Ris-1 as a putative tumor suppressor gene in human breast cancer, we have performed a real-time quantitative analysis of its mRNA expression in 60 patients. Moreover, we carried out a first approach to evaluate the most common inactivation mechanism that can affect expression levels of tumor suppressor genes (mutation, promoter hypermethylation and allelic losses). Furthermore, a correlation study between expression as well as inactivating mechanisms of Ris-1 and several clinico-pathological parameters of the tumors was designed, with the objective of appraising the prognostic value of Ris-1 status. Decreased expression of Ris-1 was observed in 23% of the cases and overexpressed Ris-1 was detected in 15% of the primary breast tumors. Our data showed high frequency of LOH (30%) at one of the markers used. Nevertheless, a polymorphism related with the expression levels was described. Statistically significant correlations were found between decreased Ris-1 expression and negative progesterone receptors, as well as between overexpressing Ris-1 tumors and high histological grade. Despite all these data, we conclude that the suggested role of Ris-1 as tumor suppressor gene is not evident, at least in breast cancer. Future and larger series studies in different tumor types are necessary to clarify Ris-1 function in human cancer.

Research paper thumbnail of Compositional and structural characterisation of GaSb and GaInSb

Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2005

Low band gap III-V semiconductors are researched for applications in thermophotovoltaic technolog... more Low band gap III-V semiconductors are researched for applications in thermophotovoltaic technology. GaSb crystal is often used as a substrate. Ga 1Àx In x Sb is also a promising substrate material, because its lattice parameters can be adjusted by controlling x. We used a new method to synthesise GaSb and GaInSb, in which a high frequency alternate magnetic field is used to heat, to melt and to mix the elements. We present a compositional and structural characterisation of the materials using a combination of complementary techniques. Rutherford backscattering was used to determine accurately the composition of the GaSb. With proton induced X-ray emission in conjunction with a 3 · 3 lm 2 micro-beam we studied the homogeneity of the samples. Structural analysis and phase identification were done with X-ray diffraction. The results for GaSb show a homogeneous composition while the GaInSb samples were found to be strongly heterogeneous at the end of the ingot. The ingots produced are competitive feed material, when compared to other growth techniques, to be used in a second step for the production of good quality ternary crystals.

Research paper thumbnail of MAPEAMENTO E QUANTIFICA˙ˆO DO REFLORESTAMENTO NO ESTADO DE SO PAULO / REFORESTATION INVENTORY OF THE SO PAULO STATE

Research paper thumbnail of Capture Conditions in the Restricted Three-Body Problem

Research paper thumbnail of Lipid metabolism and organ dysfunction in septic patients during intensive glycemic control

Critical Care, 2007

Hydrogen sulfide is produced endogenously by a variety of enzymes involved in cysteine metabolism... more Hydrogen sulfide is produced endogenously by a variety of enzymes involved in cysteine metabolism. Clinical data indicate that endogenous levels of hydrogen sulfide are diminished in various forms of cardiovascular diseases. The aim of the current study was to investigate the effects of hydrogen sulfide supplementation on cardiac function during reperfusion in a clinically relevant experimental model of cardiopulmonary bypass. Twelve anesthetized dogs underwent hypothermic cardiopulmonary bypass. After 60 minutes of hypothermic cardiac arrest, reperfusion was started after application of either saline vehicle (control, n = 6), or the sodium sulfide infusion (1 mg/kg/hour, n = 6). Biventricular hemodynamic variables were measured by combined pressure-volume-conductance catheters. Coronary and pulmonary blood flow, vasodilator responses to acetylcholine and sodiumnitroprusside and pulmonary function were also determined. Administration of sodium sulfide led to a significantly better recovery of left and right ventricular systolic function (P < 0.05) after 60 minutes of reperfusion. Coronary blood flow was also significantly higher in the sodium sulfide-treated group (P < 0.05). Sodium sulfide treatment improved coronary blood flow, and preserved the acetylcholine-induced increases in coronary and pulmonary blood (P < 0.05). Myocardial ATP levels were markedly improved in the sulfide-treated group. Thus, supplementation of sulfide improves the recovery of myocardial and endothelial function and energetic status after hypothermic cardiac arrest during cardiopulmonary bypass. These beneficial effects occurred without any detectable adverse hemodynamic or cardiovascular effects of sulfide at the dose used in the current study.

Research paper thumbnail of Septic lipidic dysregulation is related to heart rate variability alteration

Research paper thumbnail of Maternal malnutrition during lactation alters gonadotropin-releasing hormone expression in the hypothalamus of weaned male rat pups

Nutritional Neuroscience, 2010

Gonadotropin-releasing hormone (GnRH) is the key hormone regulating reproduction. Its feedback re... more Gonadotropin-releasing hormone (GnRH) is the key hormone regulating reproduction. Its feedback regulation is exercised by estradiol. The early postnatal period is critical for sexual differentiation. Despite the fact that malnutrition-related reproductive suppression in rats is a well-documented phenomenon, we had no knowledge, until now, on how maternal malnutrition affects GnRH expression and estradiol serum concentrations of weaned pups. Six pregnant Wistar rats were separated into three groups at delivery with 6 pups each: control group (C) with free access to a standard diet containing 23% protein; protein energy restricted group (PER) with free access to an isoenergy and 8% protein diet; and an energy-restricted (ER) group receiving a standard diet in restricted quantities, which were calculated according to the mean ingestion of the PER group. At 21 days post partum, the animals were killed and the serum estradiol was evaluated by radioimmunoassay. Immunohistochemistry for GNRH was performed. The serum estradiol concentration was decreased in PER and ER groups compared with C (PER, 34%; ER, 19%;P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01) and the staining of GNRH was restricted to arcuate nucleus and median eminence in the control group while in PER and ER stained processes aligned with the third ventricle wall (periventricular nucleus) were present. In conclusion, our data reinforce the concept that the maternal nutritional state during lactation is critical for sexual maturation since maternal malnutrition resulted in a neuron migration delay evidenced by an altered GnRH expression profile, probably a consequence of low estradiol serum levels.

Research paper thumbnail of Composted municipal waste effects on chemical properties of a Brazilian soil

Bioresource Technology, 2007

The spread of composted municipal waste (CMW) on land can be used for sustainable crop production... more The spread of composted municipal waste (CMW) on land can be used for sustainable crop production. Nevertheless, heavy metals availability may be a problem. Therefore, the main objective of this study was to assess the impact of CMW disposal on heavy metal accumulation in soil and plants. The treatments consisted of an untreated plot (control) and four rates of CMW application. All plots were cultivated in succession of carrot, cauliXower, sweet corn, and radish. Cu and Pb signiWcantly accumulated in the topsoil (0-5 cm) with a similar pattern in the depths of 5-10 cm and 10-20 cm. CauliXower, for Fe and Cu, and radish, for Pb and Cu, had their tissue analysis sig-niWcantly aVected due to the increasing rates of application of CMW. Nevertheless, the levels of accumulation in both, soil and plant, are within permissible limits. The evidences provided by this experiment indicated that heavy metals are less likely to cause problems for the estimation of CMW loadings to Brazilian agricultural land.

Research paper thumbnail of Morphological Evidence for the Existence of Two Distinct Types of Mitochondria Rich Cells in the Gill of the Crayfish Astacus leptodactylus Eschscholtz

Acta Zoologica, 1997

An ultrastructural study was performed on gill epithelia of the crayfish Astacus leptodactylus. T... more An ultrastructural study was performed on gill epithelia of the crayfish Astacus leptodactylus. The filament and the lamina of the podobranch were examined. In both structures a vascular system is lined by a specialized epithelium covered by a cuticle. Different types of epithelium were described in the gill filaments: either a thin epithelium with few organelles and probably involved in gas exchange or, in other filaments, a thick epithelium with characteristics of a transporting epithelium (abundant mitochondria in close association with plasma membrane infoldings). The epithelium of the lamina is also of a transporting type but in this case the complex of membrane infoldings and mitochondria is in an opposite orientation to that of the filament epithelium suggesting a different role in osmoregulation. © 1997 Published by Elsevier Science Ltd on behalf of The Royal Swedish Academy of Sciences.

Research paper thumbnail of High prevalence of ST121 in community-associated methicillin-susceptible Staphylococcus aureus lineages responsible for skin and soft tissue infections in Portuguese children

European Journal of Clinical Microbiology & Infectious Diseases, 2011

In order to evaluate the incidence of community-associated methicillin-resistant Staphylococcus a... more In order to evaluate the incidence of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) in Portugal, we analyzed a collection of 38 S. aureus isolates recovered from 30 children attending the pediatric emergency department of a central hospital in Lisbon due to skin and soft tissue infections. Molecular characterization identified seven clonal lineages among the 35 methicillin-susceptible S. aureus (MSSA) isolates, of which the major lineage PFGE A/t159/ST121 included 63% of the isolates. The three MRSA isolates belonged to the Pediatric clone PFGE D/t535/ST5-IV (n = 2) and to the European CA-MRSA clone PFGE G/t044/ST80-IVc (n = 1). All isolates harbored several virulence factors, namely, leukocidins. Panton–Valentine leukocidin (PVL) was produced by isolates from five MSSA lineages and by the ST80 MRSA. Of interest, this is the first reported isolation of CA-MRSA ST80 in Portugal.