Antonio Duarte | UFAL - Universidade Federal de Alagoas (original) (raw)

Papers by Antonio Duarte

Research paper thumbnail of mDll1 and mDll3 expression in the developing mouse brain: Role in the establishment of the early cortex

Journal of Neuroscience Research, 2001

The Delta/Notch signalling system is involved in several developmental processes. During fly neur... more The Delta/Notch signalling system is involved in several developmental processes. During fly neurogenesis, Delta expression defines the fate of neuronal precursors and inhibits neighboring Notch-expressing cells from acquiring a neural fate, a process known as lateral inhibition. In vertebrates, recent evidence demonstrates that Notch activation can positively determine cell fate and affect neuronal process extension. Nevertheless, Delta-like expression patterns during brain development are relatively unknown. Using a transgenic mouse, which expresses LacZ under the mDll1 promoter, we show by immunofluorescence that in the developing telencephalon mDll1 is expressed in undifferentiated cells in close contact with radial glial cells. Based on in situ hybridization data on mDll1 and mDll3 mRNA expression and on the immunohistochemical detection of β-galactosidase in the Dll1-lacZ transgenic mouse, we suggest that mDll1 and mDll3 are involved in the establishment of the early cortical plate and that mDll1-expressing cells are in close contact with radial glial cells, thereby modulating the latter population, which is known to express Notch1. Furthermore, we suggest that the decrease in mDll1 mRNA found toward the end of gestation could be related, first, to the slowing of neurogenesis and, second, to the differentiation of the radial glial cell population into astrocytes. J. Neurosci. Res. 64:590–598, 2001. © 2001 Wiley-Liss, Inc.

Research paper thumbnail of The forkhead transcription factors, Foxc1 and Foxc2, are required for arterial specification and lymphatic sprouting during vascular development

Developmental Biology, 2006

Accumulating evidence suggests that in the vertebrate embryo, acquisition of arterial and venous ... more Accumulating evidence suggests that in the vertebrate embryo, acquisition of arterial and venous identity is established early by genetic mechanisms, including those regulated by vascular endothelial growth factor (VEGF) and Notch signaling. However, although the COUP-TFII nuclear receptor has recently been shown to regulate vein identity, very little is known about the molecular mechanisms of transcriptional regulation in arterial specification. Here, we show that mouse embryos compound mutant for Foxc1 and Foxc2, two closely related Fox transcription factors, exhibit arteriovenous malformations and lack of induction of arterial markers whereas venous markers such as COUP-TFII are normally expressed, suggesting that mutant endothelial cells fail to acquire an arterial fate. Notably, consistent with this observation, overexpression of Foxc genes in vitro induces expression of arterial markers such as Notch1 and its ligand Delta-like 4 (Dll4), and Foxc1 and Foxc2 directly activate the Dll4 promoter via a Foxc-binding site. Moreover, compound Foxc mutants show a defect in sprouting of lymphatic endothelial cells from veins in early lymphatic development, due to reduced expression of VEGF-C. Taken together, our results demonstrate that Foxc transcription factors are novel regulators of arterial cell specification upstream of Notch signaling and lymphatic sprouting during embryonic development.

Research paper thumbnail of On the relative position of multiple eigenvalues in the spectrum of an Hermitian matrix with a given graph

Linear Algebra and Its Applications, 2003

For Hermitian matrices, whose graph is a given tree, the relationships among vertex degrees, mult... more For Hermitian matrices, whose graph is a given tree, the relationships among vertex degrees, multiple eigenvalues and the relative position of the underlying eigenvalue in the ordered spectrum are discussed in detail. In the process, certain aspects of special vertices, whose removal results in an increase in multiplicity are investigated.

Research paper thumbnail of The maximum multiplicity of an eigenvalue in a matrix whose graph is a tree

Linear & Multilinear Algebra, 1999

It is well known that every eigenvalue of an irreducible tridiagonal matrix has geometric multipl... more It is well known that every eigenvalue of an irreducible tridiagonal matrix has geometric multiplicity one. Thus, the maximum (algebraic) multiplicity of an eigenvalue of a (real) symmetric matrix, the graph of whose (off-diagonal) entries is a path, is one. It follows that the same ...

Research paper thumbnail of The Parter-Wiener Theorem: Refinement and Generalization

Siam Journal on Matrix Analysis and Applications, 2003

An important theorem about the existence of principal submatrices of a Hermitian matrix whose gra... more An important theorem about the existence of principal submatrices of a Hermitian matrix whose graph is a tree, in which the multiplicity of an eigenvalue increases, was largely developed in separate papers by Parter and Wiener. Here, the prior work is fully stated, then generalized with a self-contained proof. The more complete result is then used to better understand the eigenvalue possibilities of reducible principal submatrices of Hermitian tridiagonal matrices. Sets of vertices, for which the multiplicity increases, are also studied.

Research paper thumbnail of Inverse eigenvalue problems and lists of multiplicities of eigenvalues for matrices whose graph is a tree: the case of generalized stars and double generalized stars

Linear Algebra and Its Applications, 2003

We characterize the possible lists of ordered multiplicities among matrices whose graph is a gene... more We characterize the possible lists of ordered multiplicities among matrices whose graph is a generalized star (a tree in which at most one vertex has degree greater than 2) or a double generalized star. Here, the inverse eigenvalue problem (IEP) for symmetric matrices whose graph is a generalized star is settled. The answer is consistent with a conjecture that determination of the possible ordered multiplicities is equivalent to the IEP for a given tree. Moreover, a key spectral feature of the IEP in the case of generalized stars is shown to characterize them among trees.

Research paper thumbnail of On the possible multiplicities of the eigenvalues of a Hermitian matrix whose graph is a tree

Linear Algebra and Its Applications, 2002

We consider the general problem of determining which lists of multiplicities for the eigenvalues ... more We consider the general problem of determining which lists of multiplicities for the eigenvalues occur among Hermitian matrices the graph of whose off-diagonal entries is a given tree. Several restrictions are cited and a construction strategy is given. Together, these are sufficient to characterize all lists for each tree in two infinite classes: the double paths and generalized stars, and to tabulate all lists for trees on fewer than nine vertices. Such tables should be useful for formulating and dispelling general conjectures.

Research paper thumbnail of Metabolic effects of dietary sucrose and fructose in type II diabetic subjects

Diabetes Care, 1996

To investigate the metabolic effects of dietary fructose and sucrose in type II diabetic patients... more To investigate the metabolic effects of dietary fructose and sucrose in type II diabetic patients. Sixteen well-controlled type II diabetic subjects were fed three isocaloric diets for 28 days each. The three diets provided 50-55, 15, and 30-35% of total energy from carbohydrate, protein, and fat, respectively. In one diet, 20% of total calories were derived from fructose; in another, 19% of total calories were derived from sucrose; and in the control diet, only 5% of daily calories were derived from sugars, all other carbohydrates being supplied as polysaccharides. No significant differences were observed between either the fructose or the sucrose diet and the control polysaccharide diet in any of the measures of glycemic control, serum lipid levels, or insulin and C-peptide secretion. Our data suggest that in the short and middle terms, high fructose and sucrose diets do not adversely affect glycemia, lipemia, or insulin and C-peptide secretion in well-controlled type II diabetic subjects.

Research paper thumbnail of 1 psicopedagogia como alicercer

Nada é fixo para aquele que alternadamente pensa e sonha." Bachelard RESUMO: Esse artigo tem como... more Nada é fixo para aquele que alternadamente pensa e sonha." Bachelard RESUMO: Esse artigo tem como objetivo apresentar aos profissionais da psicopedagogia as possibilidades de um trabalho psicopedagógico direcionado a desenvolver a competência e habilidade dos alunos, visto que os mesmos trazem consigo um desejo inerente do ser humano, que é aprender e dialogar. PALAVRAS-CHAVE: Psicopedagogo. Prevenção. Diagnóstico. Devolutiva.

Research paper thumbnail of mDll1 and mDll3 expression in the developing mouse brain: Role in the establishment of the early cortex

Journal of Neuroscience Research, 2001

The Delta/Notch signalling system is involved in several developmental processes. During fly neur... more The Delta/Notch signalling system is involved in several developmental processes. During fly neurogenesis, Delta expression defines the fate of neuronal precursors and inhibits neighboring Notch-expressing cells from acquiring a neural fate, a process known as lateral inhibition. In vertebrates, recent evidence demonstrates that Notch activation can positively determine cell fate and affect neuronal process extension. Nevertheless, Delta-like expression patterns during brain development are relatively unknown. Using a transgenic mouse, which expresses LacZ under the mDll1 promoter, we show by immunofluorescence that in the developing telencephalon mDll1 is expressed in undifferentiated cells in close contact with radial glial cells. Based on in situ hybridization data on mDll1 and mDll3 mRNA expression and on the immunohistochemical detection of β-galactosidase in the Dll1-lacZ transgenic mouse, we suggest that mDll1 and mDll3 are involved in the establishment of the early cortical plate and that mDll1-expressing cells are in close contact with radial glial cells, thereby modulating the latter population, which is known to express Notch1. Furthermore, we suggest that the decrease in mDll1 mRNA found toward the end of gestation could be related, first, to the slowing of neurogenesis and, second, to the differentiation of the radial glial cell population into astrocytes. J. Neurosci. Res. 64:590–598, 2001. © 2001 Wiley-Liss, Inc.

Research paper thumbnail of The forkhead transcription factors, Foxc1 and Foxc2, are required for arterial specification and lymphatic sprouting during vascular development

Developmental Biology, 2006

Accumulating evidence suggests that in the vertebrate embryo, acquisition of arterial and venous ... more Accumulating evidence suggests that in the vertebrate embryo, acquisition of arterial and venous identity is established early by genetic mechanisms, including those regulated by vascular endothelial growth factor (VEGF) and Notch signaling. However, although the COUP-TFII nuclear receptor has recently been shown to regulate vein identity, very little is known about the molecular mechanisms of transcriptional regulation in arterial specification. Here, we show that mouse embryos compound mutant for Foxc1 and Foxc2, two closely related Fox transcription factors, exhibit arteriovenous malformations and lack of induction of arterial markers whereas venous markers such as COUP-TFII are normally expressed, suggesting that mutant endothelial cells fail to acquire an arterial fate. Notably, consistent with this observation, overexpression of Foxc genes in vitro induces expression of arterial markers such as Notch1 and its ligand Delta-like 4 (Dll4), and Foxc1 and Foxc2 directly activate the Dll4 promoter via a Foxc-binding site. Moreover, compound Foxc mutants show a defect in sprouting of lymphatic endothelial cells from veins in early lymphatic development, due to reduced expression of VEGF-C. Taken together, our results demonstrate that Foxc transcription factors are novel regulators of arterial cell specification upstream of Notch signaling and lymphatic sprouting during embryonic development.

Research paper thumbnail of On the relative position of multiple eigenvalues in the spectrum of an Hermitian matrix with a given graph

Linear Algebra and Its Applications, 2003

For Hermitian matrices, whose graph is a given tree, the relationships among vertex degrees, mult... more For Hermitian matrices, whose graph is a given tree, the relationships among vertex degrees, multiple eigenvalues and the relative position of the underlying eigenvalue in the ordered spectrum are discussed in detail. In the process, certain aspects of special vertices, whose removal results in an increase in multiplicity are investigated.

Research paper thumbnail of The maximum multiplicity of an eigenvalue in a matrix whose graph is a tree

Linear & Multilinear Algebra, 1999

It is well known that every eigenvalue of an irreducible tridiagonal matrix has geometric multipl... more It is well known that every eigenvalue of an irreducible tridiagonal matrix has geometric multiplicity one. Thus, the maximum (algebraic) multiplicity of an eigenvalue of a (real) symmetric matrix, the graph of whose (off-diagonal) entries is a path, is one. It follows that the same ...

Research paper thumbnail of The Parter-Wiener Theorem: Refinement and Generalization

Siam Journal on Matrix Analysis and Applications, 2003

An important theorem about the existence of principal submatrices of a Hermitian matrix whose gra... more An important theorem about the existence of principal submatrices of a Hermitian matrix whose graph is a tree, in which the multiplicity of an eigenvalue increases, was largely developed in separate papers by Parter and Wiener. Here, the prior work is fully stated, then generalized with a self-contained proof. The more complete result is then used to better understand the eigenvalue possibilities of reducible principal submatrices of Hermitian tridiagonal matrices. Sets of vertices, for which the multiplicity increases, are also studied.

Research paper thumbnail of Inverse eigenvalue problems and lists of multiplicities of eigenvalues for matrices whose graph is a tree: the case of generalized stars and double generalized stars

Linear Algebra and Its Applications, 2003

We characterize the possible lists of ordered multiplicities among matrices whose graph is a gene... more We characterize the possible lists of ordered multiplicities among matrices whose graph is a generalized star (a tree in which at most one vertex has degree greater than 2) or a double generalized star. Here, the inverse eigenvalue problem (IEP) for symmetric matrices whose graph is a generalized star is settled. The answer is consistent with a conjecture that determination of the possible ordered multiplicities is equivalent to the IEP for a given tree. Moreover, a key spectral feature of the IEP in the case of generalized stars is shown to characterize them among trees.

Research paper thumbnail of On the possible multiplicities of the eigenvalues of a Hermitian matrix whose graph is a tree

Linear Algebra and Its Applications, 2002

We consider the general problem of determining which lists of multiplicities for the eigenvalues ... more We consider the general problem of determining which lists of multiplicities for the eigenvalues occur among Hermitian matrices the graph of whose off-diagonal entries is a given tree. Several restrictions are cited and a construction strategy is given. Together, these are sufficient to characterize all lists for each tree in two infinite classes: the double paths and generalized stars, and to tabulate all lists for trees on fewer than nine vertices. Such tables should be useful for formulating and dispelling general conjectures.

Research paper thumbnail of Metabolic effects of dietary sucrose and fructose in type II diabetic subjects

Diabetes Care, 1996

To investigate the metabolic effects of dietary fructose and sucrose in type II diabetic patients... more To investigate the metabolic effects of dietary fructose and sucrose in type II diabetic patients. Sixteen well-controlled type II diabetic subjects were fed three isocaloric diets for 28 days each. The three diets provided 50-55, 15, and 30-35% of total energy from carbohydrate, protein, and fat, respectively. In one diet, 20% of total calories were derived from fructose; in another, 19% of total calories were derived from sucrose; and in the control diet, only 5% of daily calories were derived from sugars, all other carbohydrates being supplied as polysaccharides. No significant differences were observed between either the fructose or the sucrose diet and the control polysaccharide diet in any of the measures of glycemic control, serum lipid levels, or insulin and C-peptide secretion. Our data suggest that in the short and middle terms, high fructose and sucrose diets do not adversely affect glycemia, lipemia, or insulin and C-peptide secretion in well-controlled type II diabetic subjects.

Research paper thumbnail of 1 psicopedagogia como alicercer

Nada é fixo para aquele que alternadamente pensa e sonha." Bachelard RESUMO: Esse artigo tem como... more Nada é fixo para aquele que alternadamente pensa e sonha." Bachelard RESUMO: Esse artigo tem como objetivo apresentar aos profissionais da psicopedagogia as possibilidades de um trabalho psicopedagógico direcionado a desenvolver a competência e habilidade dos alunos, visto que os mesmos trazem consigo um desejo inerente do ser humano, que é aprender e dialogar. PALAVRAS-CHAVE: Psicopedagogo. Prevenção. Diagnóstico. Devolutiva.