Marcelo Gomes - Academia.edu (original) (raw)

Papers by Marcelo Gomes

Research paper thumbnail of The low energy limit of the non-commutative Wess-Zumino model

The non-commutative Wess-Zumino model is used as a prototype for studying the low energy behaviou... more The non-commutative Wess-Zumino model is used as a prototype for studying the low energy behaviour of a renormalizable non-commutative field theory. We start by deriving the potential mediating the fermion-fermion and boson-boson interactions in the non-relativistic regime. The quantum counterparts of these potentials are afflicted by irdering ambiguities but we show that there exists an ordering prescription which makes them hermitean. For space/space noncommutativity it turns out that Majorana fermions may be pictured as rods oriented perpendicularly to the direction of motion showing a lack of localituy, while bosons remain insensitive to the effects of noncommutativity. For time/space noncommutativity bosopns and fermions can be regarded as rods oriented along the direction of motion. For both cases of noncommutativity the scattering state described scattered waves, with at least one wave having negative time delay signalizing the underlying nonlocality. The superfield formulation of the model is used to compute the corresponding effective action in the one- and two-loop approximations. In the case of time/space noncommutativity, unitarity is violated in the relativistic regime. However, this does not preclude the existence of the unitary low energy limit.

Research paper thumbnail of Zirconium alloys for supercritical water reactor applications: Challenges and possibilities

Journal of Nuclear Materials, 2007

The corrosion behavior of model Zr-based alloys at 500°C is assessed by long term (up to 400 days... more The corrosion behavior of model Zr-based alloys at 500°C is assessed by long term (up to 400 days) corrosion testing in an effort to evaluate their potential for use in the supercritical water reactor and to assess the influence of alloying elements on corrosion behavior. The corrosion weight gains from such systematic testing are seen to be a factor of five higher than those measured at 360°C but the protectiveness ranking of the alloys is similar. Detailed characterization of the oxide layers to rationalize the differences in corrosion behavior was performed using synchrotron radiation and systematic differences are observed in protective and non-protective oxides, especially near the oxide-metal interface. The overall corrosion rate of the best Zr-based alloys compared favorably with those of other alloys being considered for use in the supercritical water reactor.

Research paper thumbnail of Patterns of gene expression in atrophying skeletal muscles: response to food deprivation

Faseb Journal, 2002

During fasting and many systemic diseases, muscle undergoes rapid loss of protein and functional ... more During fasting and many systemic diseases, muscle undergoes rapid loss of protein and functional capacity. To define the transcriptional changes triggering muscle atrophy and energy conservation in fasting, we used cDNA microarrays to compare mRNAs from muscles of control and food-deprived mice. Expression of >94% of genes did not change, but interesting patterns emerged among genes that were differentially expressed: 1) mRNAs encoding polyubiquitin, ubiquitin extension proteins, and many (but not all) proteasome subunits increased, which presumably contributes to accelerated protein breakdown; 2) a dramatic increase in mRNA for the ubiquitin ligase, atrogin-1, but not most E3s; 3) a significant suppression of mRNA for myosin binding protein H (but not other myofibrillar proteins) and IGF binding protein 5, which may favor cell protein loss; 4) decreases in mRNAs for several glycolytic enzymes and phosphorylase kinase subunits, and dramatic increases in mRNAs for pyruvate dehydrogenase kinase 4 and glutamine synthase, which should promote glucose sparing and gluconeogenesis. During fasting, metallothionein mRNA increased dramatically, mRNAs for extracellular matrix components fell, and mRNAs that may favor cap-independent mRNA translation rose. Significant changes occurred in mRNAs for many growth-related proteins and transcriptional regulators. These transcriptional changes indicate a complex adaptive program that should favor protein degradation and suppress glucose oxidation in muscle. Similar analysis of muscles atrophying for other causes is allowing us to identify a set of atrophy-specific changes in gene expression.-Jagoe, R. T., Lecker, S. H., Gomes, M., Goldberg, A. L. Patterns of gene expression in atrophying skeletal muscles: response to food deprivation.

Research paper thumbnail of Multiple types of skeletal muscle atrophy involve a common program of changes in gene expression

Faseb Journal, 2004

Skeletal muscle atrophy is a debilitating response to starvation and many systemic diseases inclu... more Skeletal muscle atrophy is a debilitating response to starvation and many systemic diseases including diabetes, cancer, and renal failure. We had proposed that a common set of transcriptional adaptations underlie the loss of muscle mass in these different states. To test this hypothesis, we used cDNA microarrays to compare the changes in content of specific mRNAs in muscles atrophying from different causes. We compared muscles from fasted mice, from rats with cancer cachexia, streptozotocin-induced diabetes mellitus, uremia induced by subtotal nephrectomy, and from pair-fed control rats. Although the content of >90% of mRNAs did not change, including those for the myofibrillar apparatus, we found a common set of genes (termed atrogins) that were induced or suppressed in muscles in these four catabolic states. Among the strongly induced genes were many involved in protein degradation, including polyubiquitins, Ub fusion proteins, the Ub ligases atrogin-1/MAFbx and MuRF-1, multiple but not all subunits of the 20S proteasome and its 19S regulator, and cathepsin L. Many genes required for ATP production and late steps in glycolysis were down-regulated, as were many transcripts for extracellular matrix proteins. Some genes not previously implicated in muscle atrophy were dramatically up-regulated (lipin, metallothionein, AMP deaminase, RNA helicase-related protein, TG interacting factor) and several growth-related mRNAs were down-regulated (P311, JUN, IGF-1-BP5). Thus, different types of muscle atrophy share a common transcriptional program that is activated in many systemic diseases.

Research paper thumbnail of Substitution of Methotrexate for Cyclophosphamide in Wegener Granulomatosis: A 12Year Single-Practice Experience

Medicine, 2007

We conducted a retrospective review to assess outcomes of therapy in patients with newly diagnose... more We conducted a retrospective review to assess outcomes of therapy in patients with newly diagnosed Wegener granulomatosis (WG) using methotrexate (MTX) for mild to moderate disease and short-term treatment with cyclophosphamide (CYC) followed by MTX for severe disease. Patients with WG were included if their initial plan of therapy and subsequent care were directly supervised by the Cleveland Clinic Center for Vasculitis Care and Research. Severe disease (immediately life-threatening or involving critical organs) was initially treated with CYC and glucocorticoids. Mild to moderate disease was initially treated with MTX and glucocorticoids if serum creatinine was less than 2 mg/dL. Following initial improvement of severe disease, treatment was changed to MTX if serum creatinine was originally less than 2 mg/dL or had diminished to less than 2 mg/dL. Disease activity was determined at each visit and later converted to a Birmingham Vasculitis Activity Score, as modified for Wegener granulomatosis (BVAS/WG). Laboratory monitoring of disease and treatment toxicity was initially weekly and never less than monthly.Eighty-two (32%) of 253 patients with WG referred to the Center for Vasculitis Care and Research met eligibility criteria. Ineligible patients did not have new-onset disease or were not able to be followed principally in our center. Seventy percent of patients (57/82) initially had severe disease and received a short course of CYC for remission induction. In over half of these patients, illness was judged to be severe because of pulmonary hemorrhage; rapidly progressive glomerulonephritis, including need for dialysis; or neurologic abnormalities. All patients improved: remission was achieved in 50% (41/82) of patients within 6 months and in 72% (59/82) within 12 months. Sustained remission (BVAS/WG = 0 for at least 6 consecutive months) was ultimately achieved in 78% (64/82) of patients. Among the 75 (91%) patients who achieved remission of any duration, 45% relapsed within 1 year and 66% relapsed within 2 years following remission. Eighty-two percent of relapsed patients achieved subsequent remissions after additional treatment. About three-quarters of relapses were mild and promptly responded to treatment. Seventeen percent of patients developed serious infections. CYC-associated cystitis or bladder cancer did not occur in any patients. At least 1 form of permanent morbidity from WG alone was noted in 74.0% of patients. Three patients (3.7%) died over a median follow-up period of 4.5 years; no deaths were due to active disease. Although treatment was primarily directed toward achieving clinical improvement and not calculated to achieve marked lymphopenia, patients in whom treatment produced lymphocyte counts of <or=500/mm3, sustained over a median time of 4 (quartiles: 1, 8.5) months, were 3.8 times more likely to achieve a sustained remission (p = 0.015). Conversely, following remission, an absolute lymphocyte count of >1000/mm was associated with a hazard ratio for relapse of 3.0, although the latter difference was not statistically significant. In patients with WG, a strategy that limits or avoids CYC therapy produced a frequency of remission comparable to that achieved with conventional CYC protocols, excellent survival, and avoidance of long-term CYC toxicity. However, relapses were common and incremental permanent morbidity occurred in most patients. While not a goal of therapy, when treatment produced marked lymphopenia, prolonged remissions were more likely.

Research paper thumbnail of The low energy limit of the non-commutative Wess-Zumino model

The non-commutative Wess-Zumino model is used as a prototype for studying the low energy behaviou... more The non-commutative Wess-Zumino model is used as a prototype for studying the low energy behaviour of a renormalizable non-commutative field theory. We start by deriving the potential mediating the fermion-fermion and boson-boson interactions in the non-relativistic regime. The quantum counterparts of these potentials are afflicted by irdering ambiguities but we show that there exists an ordering prescription which makes them hermitean. For space/space noncommutativity it turns out that Majorana fermions may be pictured as rods oriented perpendicularly to the direction of motion showing a lack of localituy, while bosons remain insensitive to the effects of noncommutativity. For time/space noncommutativity bosopns and fermions can be regarded as rods oriented along the direction of motion. For both cases of noncommutativity the scattering state described scattered waves, with at least one wave having negative time delay signalizing the underlying nonlocality. The superfield formulation of the model is used to compute the corresponding effective action in the one- and two-loop approximations. In the case of time/space noncommutativity, unitarity is violated in the relativistic regime. However, this does not preclude the existence of the unitary low energy limit.

Research paper thumbnail of Zirconium alloys for supercritical water reactor applications: Challenges and possibilities

Journal of Nuclear Materials, 2007

The corrosion behavior of model Zr-based alloys at 500°C is assessed by long term (up to 400 days... more The corrosion behavior of model Zr-based alloys at 500°C is assessed by long term (up to 400 days) corrosion testing in an effort to evaluate their potential for use in the supercritical water reactor and to assess the influence of alloying elements on corrosion behavior. The corrosion weight gains from such systematic testing are seen to be a factor of five higher than those measured at 360°C but the protectiveness ranking of the alloys is similar. Detailed characterization of the oxide layers to rationalize the differences in corrosion behavior was performed using synchrotron radiation and systematic differences are observed in protective and non-protective oxides, especially near the oxide-metal interface. The overall corrosion rate of the best Zr-based alloys compared favorably with those of other alloys being considered for use in the supercritical water reactor.

Research paper thumbnail of Patterns of gene expression in atrophying skeletal muscles: response to food deprivation

Faseb Journal, 2002

During fasting and many systemic diseases, muscle undergoes rapid loss of protein and functional ... more During fasting and many systemic diseases, muscle undergoes rapid loss of protein and functional capacity. To define the transcriptional changes triggering muscle atrophy and energy conservation in fasting, we used cDNA microarrays to compare mRNAs from muscles of control and food-deprived mice. Expression of >94% of genes did not change, but interesting patterns emerged among genes that were differentially expressed: 1) mRNAs encoding polyubiquitin, ubiquitin extension proteins, and many (but not all) proteasome subunits increased, which presumably contributes to accelerated protein breakdown; 2) a dramatic increase in mRNA for the ubiquitin ligase, atrogin-1, but not most E3s; 3) a significant suppression of mRNA for myosin binding protein H (but not other myofibrillar proteins) and IGF binding protein 5, which may favor cell protein loss; 4) decreases in mRNAs for several glycolytic enzymes and phosphorylase kinase subunits, and dramatic increases in mRNAs for pyruvate dehydrogenase kinase 4 and glutamine synthase, which should promote glucose sparing and gluconeogenesis. During fasting, metallothionein mRNA increased dramatically, mRNAs for extracellular matrix components fell, and mRNAs that may favor cap-independent mRNA translation rose. Significant changes occurred in mRNAs for many growth-related proteins and transcriptional regulators. These transcriptional changes indicate a complex adaptive program that should favor protein degradation and suppress glucose oxidation in muscle. Similar analysis of muscles atrophying for other causes is allowing us to identify a set of atrophy-specific changes in gene expression.-Jagoe, R. T., Lecker, S. H., Gomes, M., Goldberg, A. L. Patterns of gene expression in atrophying skeletal muscles: response to food deprivation.

Research paper thumbnail of Multiple types of skeletal muscle atrophy involve a common program of changes in gene expression

Faseb Journal, 2004

Skeletal muscle atrophy is a debilitating response to starvation and many systemic diseases inclu... more Skeletal muscle atrophy is a debilitating response to starvation and many systemic diseases including diabetes, cancer, and renal failure. We had proposed that a common set of transcriptional adaptations underlie the loss of muscle mass in these different states. To test this hypothesis, we used cDNA microarrays to compare the changes in content of specific mRNAs in muscles atrophying from different causes. We compared muscles from fasted mice, from rats with cancer cachexia, streptozotocin-induced diabetes mellitus, uremia induced by subtotal nephrectomy, and from pair-fed control rats. Although the content of >90% of mRNAs did not change, including those for the myofibrillar apparatus, we found a common set of genes (termed atrogins) that were induced or suppressed in muscles in these four catabolic states. Among the strongly induced genes were many involved in protein degradation, including polyubiquitins, Ub fusion proteins, the Ub ligases atrogin-1/MAFbx and MuRF-1, multiple but not all subunits of the 20S proteasome and its 19S regulator, and cathepsin L. Many genes required for ATP production and late steps in glycolysis were down-regulated, as were many transcripts for extracellular matrix proteins. Some genes not previously implicated in muscle atrophy were dramatically up-regulated (lipin, metallothionein, AMP deaminase, RNA helicase-related protein, TG interacting factor) and several growth-related mRNAs were down-regulated (P311, JUN, IGF-1-BP5). Thus, different types of muscle atrophy share a common transcriptional program that is activated in many systemic diseases.

Research paper thumbnail of Substitution of Methotrexate for Cyclophosphamide in Wegener Granulomatosis: A 12Year Single-Practice Experience

Medicine, 2007

We conducted a retrospective review to assess outcomes of therapy in patients with newly diagnose... more We conducted a retrospective review to assess outcomes of therapy in patients with newly diagnosed Wegener granulomatosis (WG) using methotrexate (MTX) for mild to moderate disease and short-term treatment with cyclophosphamide (CYC) followed by MTX for severe disease. Patients with WG were included if their initial plan of therapy and subsequent care were directly supervised by the Cleveland Clinic Center for Vasculitis Care and Research. Severe disease (immediately life-threatening or involving critical organs) was initially treated with CYC and glucocorticoids. Mild to moderate disease was initially treated with MTX and glucocorticoids if serum creatinine was less than 2 mg/dL. Following initial improvement of severe disease, treatment was changed to MTX if serum creatinine was originally less than 2 mg/dL or had diminished to less than 2 mg/dL. Disease activity was determined at each visit and later converted to a Birmingham Vasculitis Activity Score, as modified for Wegener granulomatosis (BVAS/WG). Laboratory monitoring of disease and treatment toxicity was initially weekly and never less than monthly.Eighty-two (32%) of 253 patients with WG referred to the Center for Vasculitis Care and Research met eligibility criteria. Ineligible patients did not have new-onset disease or were not able to be followed principally in our center. Seventy percent of patients (57/82) initially had severe disease and received a short course of CYC for remission induction. In over half of these patients, illness was judged to be severe because of pulmonary hemorrhage; rapidly progressive glomerulonephritis, including need for dialysis; or neurologic abnormalities. All patients improved: remission was achieved in 50% (41/82) of patients within 6 months and in 72% (59/82) within 12 months. Sustained remission (BVAS/WG = 0 for at least 6 consecutive months) was ultimately achieved in 78% (64/82) of patients. Among the 75 (91%) patients who achieved remission of any duration, 45% relapsed within 1 year and 66% relapsed within 2 years following remission. Eighty-two percent of relapsed patients achieved subsequent remissions after additional treatment. About three-quarters of relapses were mild and promptly responded to treatment. Seventeen percent of patients developed serious infections. CYC-associated cystitis or bladder cancer did not occur in any patients. At least 1 form of permanent morbidity from WG alone was noted in 74.0% of patients. Three patients (3.7%) died over a median follow-up period of 4.5 years; no deaths were due to active disease. Although treatment was primarily directed toward achieving clinical improvement and not calculated to achieve marked lymphopenia, patients in whom treatment produced lymphocyte counts of <or=500/mm3, sustained over a median time of 4 (quartiles: 1, 8.5) months, were 3.8 times more likely to achieve a sustained remission (p = 0.015). Conversely, following remission, an absolute lymphocyte count of >1000/mm was associated with a hazard ratio for relapse of 3.0, although the latter difference was not statistically significant. In patients with WG, a strategy that limits or avoids CYC therapy produced a frequency of remission comparable to that achieved with conventional CYC protocols, excellent survival, and avoidance of long-term CYC toxicity. However, relapses were common and incremental permanent morbidity occurred in most patients. While not a goal of therapy, when treatment produced marked lymphopenia, prolonged remissions were more likely.