Hector Figueroa - Academia.edu (original) (raw)

Uploads

Papers by Hector Figueroa

Research paper thumbnail of Subtidal Benthic Macroinfauna in an Estuary of South Chile: Distribution Pattern in Relation to Sediment Types

Marine Ecology, 1984

Abstract. A quantitative survey (18 stations) of the subtidal soft bottom macroinfauna in an estu... more Abstract. A quantitative survey (18 stations) of the subtidal soft bottom macroinfauna in an estuary of the south Chilean coast was conducted during January, 1980. The map of sedimentological facies elaborated for the Queule River Estuary shows sandy bottoms in the outlet and upper part of the area studied, while the middle part is occupied by muddy sand. The ordination of stations by Principal Component Analysis is fundamentally defined by mud and gravel percentage and is, in general, concordant with the distribution of sediments in the facies map. A total of 17,405 animals was collected (16 taxa), Polychaeta being the dominant group in density (77.47%) and biomass (73.4%). The maximum number of species was obtained outside the mouth of the estuary, while maximum densities and biomass were obtained in the middle of the estuary.The Factor Analysis performed with the abundances data of the most abundant species rendered the ordination of two groups of stations (concordant with a Cluster Analysis) in the Q-mode and two groups of species in the R-mode. One group of stations is restricted to sandy habitats of the outlet area and is dominated by suspension feeders. The other, in the middle and upper part of the estuary (muddy sand or sandy bottoms with a higher percentage of organic matter), is dominated by deposit feeders. Between these two groups, significant differences in sedimentological variables (sand, mud, and organic matter percentage) were detected. Each of the two delineated groups of species corresponds to the groups of stations, showing that most of the taxa can be combined in faunal assemblages with preference for different types of substrate.

Research paper thumbnail of A nonperturbative form of the spectral action principle in noncommutative geometry

Journal of Geometry and Physics, 1998

Using the formalism of superconnections, we show the existence of a bosonic action functional for... more Using the formalism of superconnections, we show the existence of a bosonic action functional for the standard K-cycle in noncommutative geometry, giving rise, through the spectral action principle, only to the Einstein gravity and Standard Model Yang-Mills-Higgs terms. It provides an effective nonminimal coupling in the bosonic sector of the Lagrangian.

Research paper thumbnail of Advanced Glycation and ROS: A Link between Diabetes and Heart Failure

Current Vascular Pharmacology, 2008

Despite many advances achieved to date, heart failure (HF) remains a leading cause of morbidity a... more Despite many advances achieved to date, heart failure (HF) remains a leading cause of morbidity and mortality. There is a widely-accepted consensus that HF and diabetes are strongly linked by at least 3 mechanisms: associated comorbidities, coronary atherosclerosis or a specific diabetic cardiomiopathy. For the last 2 mechanisms, advanced glycation end-products may contribute to trigger key processes relevant to HF by affecting cardiac function through cross-linking or receptor engagement.

Research paper thumbnail of Oxidative Stress at the Vascular Wall. Mechanistic and Pharmacological Aspects

Archives of Medical Research, 2006

During the process of energy production in aerobic respiration, vascular cells produce reactive o... more During the process of energy production in aerobic respiration, vascular cells produce reactive oxygen species (ROS). A growing body of evidence indicates that oxidative stress refers to a condition in which cells are subjected to excessive levels of ROS. Overall vascular function is dependent upon a fine balance of oxidant and antioxidant mechanisms, which determine endothelial functions. Considerable experimental and clinical data indicate that intracellular oxidant milieu is also involved in several redox-sensitive cellular signaling pathways such as ion transport systems, protein phosphorylation, and gene expression and thus also plays important roles as modulator of vascular cell functions such as cell growth, apoptosis, migration, angiogenesis and cell adhesion. Overproduction of ROS under pathophysiologic conditions is integral in the development of cardiovascular diseases. This fact has raised an intensive search of new pharmacological approaches to improve vascular hemostasis and particularly those intended to decrease oxidative stress or augm ent the antioxi dant defe nse mechani sms.

Research paper thumbnail of Facing Up the ROS Labyrinth - Where To Go

Current Vascular Pharmacology, 2006

Evidence indicates that oxidative stress refers to a condition where cells are subjected to exces... more Evidence indicates that oxidative stress refers to a condition where cells are subjected to excessive levels of reactive oxygen species (ROS). Overall vascular function is dependent upon a fine balance between oxidant and antioxidant mechanisms which is required, at least in part, for proper functioning of the endothelium. Considerable experimental and clinical data indicate that the intracellular oxidant milieu is also involved in several redox-sensitive cellular signaling pathways, such as ion transport systems, protein phosphorylation, and gene expression and thus also plays important roles as modulator of vascular cell function, such as cell growth, apoptosis, migration, angiogenesis and cell adhesion. Overproduction of ROS under pathophysiologic conditions is integral in the development of vascular disease. This fact stimulated an intensive search of new pharmacological approaches to improve vascular hemeostasis and, particularly those intended to decrease oxidative stress or augment the antioxidant defense mechanisms.

Research paper thumbnail of Pinealectomy and melatonin effects on daily variations of the hypothalamic serotonergic system in the goldfish

Comparative Biochemistry and Physiology Part A: Physiology, 1981

Day-night variations of hypothalamic serotonergic activity were noted in goldfish maintained on a... more Day-night variations of hypothalamic serotonergic activity were noted in goldfish maintained on a 16L/84 20°C regime but were not found in fish kept on an 8Lj16D, 20°C regime.

Research paper thumbnail of Changes in mouse brain serotonin turnover following chronic imipramine administration

General Pharmacology-the Vascular System, 1985

1. Mice were injected daily for 2 weeks with saline, tryptophan or p-chlorophenylalanine, alone o... more 1. Mice were injected daily for 2 weeks with saline, tryptophan or p-chlorophenylalanine, alone or in combination with the tricyclic antidepressant imipramine.

Research paper thumbnail of In vivo and in vitro effects of temperature on monoamine oxidase activity in brain and other tissues of the goldfish, carassius auratus L

Comparative Biochemistry and Physiology Part C: Comparative Pharmacology, 1982

1. The maximum velocity (Vmax) and apparent Michaelis constant (Km) of brain and liver monoamine ... more 1. The maximum velocity (Vmax) and apparent Michaelis constant (Km) of brain and liver monoamine oxidase (MAO) in goldfish were different in fish acclimated to 22 degrees C and to 7 degrees C ambient temperature. 2. In brain, Vmax and Km were dependent upon incubation temperature, but both parameters were lower in 7 degrees C, adapted fish over most of the incubation temperature range. 3. The values obtained for Km showed a plateau at incubation temperatures at and below 25 degrees C for warm water fish, and at and below 20 degrees C for cold water fish. The activation energy of brain MAO was lower in fish adapted to the colder water. 4. These results show that goldfish MAO displays changes in functional activity in response to a change in environmental temperature. Apparently the purpose of this adaptation is to compensate for a reduction in enzyme concentration.

Research paper thumbnail of Hypothalamic monoamine oxidase, a component in the serotonergic control of pituitary prolactin content in Carassius auratus L

General and Comparative Endocrinology, 1979

The role of the enzyme monoamine oxidase (MAO) was examined with regard to the control of pituita... more The role of the enzyme monoamine oxidase (MAO) was examined with regard to the control of pituitary prolactin content in the goldfish. Inhibition of MAO by means of intraperitoneal injection of pargyline resulted in significantly elevated brain serotonin content. Concomitantly, pituitary prolactin stores were also significantly elevated. Time-course and dose-response experiments revealed that pargyline at doses 225 r&kg completely inhibited MAO and significantly increased brain serotonin and pituitary prolactin content within 12 hr. It is concluded that the enzyme MAO may be a significant component of the monoaminergic system of the goldfish, serving to modulate the serotonergic inputs to centers involved in the control of pituitary prolactin secretion.

Research paper thumbnail of Monoamine oxidase types A and B in the vertebrate brain

Comparative Biochemistry and Physiology Part C: Comparative Pharmacology, 1982

1. Monoamine oxidase (MAO) activity was measured in brains of teleosts, amphibians, a reptile, bi... more 1. Monoamine oxidase (MAO) activity was measured in brains of teleosts, amphibians, a reptile, birds and mammals. Selective inhibitors were used to determine the relative proportion of MAO type A and MAO type B.

Research paper thumbnail of Subtidal Benthic Macroinfauna in an Estuary of South Chile: Distribution Pattern in Relation to Sediment Types

Marine Ecology, 1984

Abstract. A quantitative survey (18 stations) of the subtidal soft bottom macroinfauna in an estu... more Abstract. A quantitative survey (18 stations) of the subtidal soft bottom macroinfauna in an estuary of the south Chilean coast was conducted during January, 1980. The map of sedimentological facies elaborated for the Queule River Estuary shows sandy bottoms in the outlet and upper part of the area studied, while the middle part is occupied by muddy sand. The ordination of stations by Principal Component Analysis is fundamentally defined by mud and gravel percentage and is, in general, concordant with the distribution of sediments in the facies map. A total of 17,405 animals was collected (16 taxa), Polychaeta being the dominant group in density (77.47%) and biomass (73.4%). The maximum number of species was obtained outside the mouth of the estuary, while maximum densities and biomass were obtained in the middle of the estuary.The Factor Analysis performed with the abundances data of the most abundant species rendered the ordination of two groups of stations (concordant with a Cluster Analysis) in the Q-mode and two groups of species in the R-mode. One group of stations is restricted to sandy habitats of the outlet area and is dominated by suspension feeders. The other, in the middle and upper part of the estuary (muddy sand or sandy bottoms with a higher percentage of organic matter), is dominated by deposit feeders. Between these two groups, significant differences in sedimentological variables (sand, mud, and organic matter percentage) were detected. Each of the two delineated groups of species corresponds to the groups of stations, showing that most of the taxa can be combined in faunal assemblages with preference for different types of substrate.

Research paper thumbnail of A nonperturbative form of the spectral action principle in noncommutative geometry

Journal of Geometry and Physics, 1998

Using the formalism of superconnections, we show the existence of a bosonic action functional for... more Using the formalism of superconnections, we show the existence of a bosonic action functional for the standard K-cycle in noncommutative geometry, giving rise, through the spectral action principle, only to the Einstein gravity and Standard Model Yang-Mills-Higgs terms. It provides an effective nonminimal coupling in the bosonic sector of the Lagrangian.

Research paper thumbnail of Advanced Glycation and ROS: A Link between Diabetes and Heart Failure

Current Vascular Pharmacology, 2008

Despite many advances achieved to date, heart failure (HF) remains a leading cause of morbidity a... more Despite many advances achieved to date, heart failure (HF) remains a leading cause of morbidity and mortality. There is a widely-accepted consensus that HF and diabetes are strongly linked by at least 3 mechanisms: associated comorbidities, coronary atherosclerosis or a specific diabetic cardiomiopathy. For the last 2 mechanisms, advanced glycation end-products may contribute to trigger key processes relevant to HF by affecting cardiac function through cross-linking or receptor engagement.

Research paper thumbnail of Oxidative Stress at the Vascular Wall. Mechanistic and Pharmacological Aspects

Archives of Medical Research, 2006

During the process of energy production in aerobic respiration, vascular cells produce reactive o... more During the process of energy production in aerobic respiration, vascular cells produce reactive oxygen species (ROS). A growing body of evidence indicates that oxidative stress refers to a condition in which cells are subjected to excessive levels of ROS. Overall vascular function is dependent upon a fine balance of oxidant and antioxidant mechanisms, which determine endothelial functions. Considerable experimental and clinical data indicate that intracellular oxidant milieu is also involved in several redox-sensitive cellular signaling pathways such as ion transport systems, protein phosphorylation, and gene expression and thus also plays important roles as modulator of vascular cell functions such as cell growth, apoptosis, migration, angiogenesis and cell adhesion. Overproduction of ROS under pathophysiologic conditions is integral in the development of cardiovascular diseases. This fact has raised an intensive search of new pharmacological approaches to improve vascular hemostasis and particularly those intended to decrease oxidative stress or augm ent the antioxi dant defe nse mechani sms.

Research paper thumbnail of Facing Up the ROS Labyrinth - Where To Go

Current Vascular Pharmacology, 2006

Evidence indicates that oxidative stress refers to a condition where cells are subjected to exces... more Evidence indicates that oxidative stress refers to a condition where cells are subjected to excessive levels of reactive oxygen species (ROS). Overall vascular function is dependent upon a fine balance between oxidant and antioxidant mechanisms which is required, at least in part, for proper functioning of the endothelium. Considerable experimental and clinical data indicate that the intracellular oxidant milieu is also involved in several redox-sensitive cellular signaling pathways, such as ion transport systems, protein phosphorylation, and gene expression and thus also plays important roles as modulator of vascular cell function, such as cell growth, apoptosis, migration, angiogenesis and cell adhesion. Overproduction of ROS under pathophysiologic conditions is integral in the development of vascular disease. This fact stimulated an intensive search of new pharmacological approaches to improve vascular hemeostasis and, particularly those intended to decrease oxidative stress or augment the antioxidant defense mechanisms.

Research paper thumbnail of Pinealectomy and melatonin effects on daily variations of the hypothalamic serotonergic system in the goldfish

Comparative Biochemistry and Physiology Part A: Physiology, 1981

Day-night variations of hypothalamic serotonergic activity were noted in goldfish maintained on a... more Day-night variations of hypothalamic serotonergic activity were noted in goldfish maintained on a 16L/84 20°C regime but were not found in fish kept on an 8Lj16D, 20°C regime.

Research paper thumbnail of Changes in mouse brain serotonin turnover following chronic imipramine administration

General Pharmacology-the Vascular System, 1985

1. Mice were injected daily for 2 weeks with saline, tryptophan or p-chlorophenylalanine, alone o... more 1. Mice were injected daily for 2 weeks with saline, tryptophan or p-chlorophenylalanine, alone or in combination with the tricyclic antidepressant imipramine.

Research paper thumbnail of In vivo and in vitro effects of temperature on monoamine oxidase activity in brain and other tissues of the goldfish, carassius auratus L

Comparative Biochemistry and Physiology Part C: Comparative Pharmacology, 1982

1. The maximum velocity (Vmax) and apparent Michaelis constant (Km) of brain and liver monoamine ... more 1. The maximum velocity (Vmax) and apparent Michaelis constant (Km) of brain and liver monoamine oxidase (MAO) in goldfish were different in fish acclimated to 22 degrees C and to 7 degrees C ambient temperature. 2. In brain, Vmax and Km were dependent upon incubation temperature, but both parameters were lower in 7 degrees C, adapted fish over most of the incubation temperature range. 3. The values obtained for Km showed a plateau at incubation temperatures at and below 25 degrees C for warm water fish, and at and below 20 degrees C for cold water fish. The activation energy of brain MAO was lower in fish adapted to the colder water. 4. These results show that goldfish MAO displays changes in functional activity in response to a change in environmental temperature. Apparently the purpose of this adaptation is to compensate for a reduction in enzyme concentration.

Research paper thumbnail of Hypothalamic monoamine oxidase, a component in the serotonergic control of pituitary prolactin content in Carassius auratus L

General and Comparative Endocrinology, 1979

The role of the enzyme monoamine oxidase (MAO) was examined with regard to the control of pituita... more The role of the enzyme monoamine oxidase (MAO) was examined with regard to the control of pituitary prolactin content in the goldfish. Inhibition of MAO by means of intraperitoneal injection of pargyline resulted in significantly elevated brain serotonin content. Concomitantly, pituitary prolactin stores were also significantly elevated. Time-course and dose-response experiments revealed that pargyline at doses 225 r&kg completely inhibited MAO and significantly increased brain serotonin and pituitary prolactin content within 12 hr. It is concluded that the enzyme MAO may be a significant component of the monoaminergic system of the goldfish, serving to modulate the serotonergic inputs to centers involved in the control of pituitary prolactin secretion.

Research paper thumbnail of Monoamine oxidase types A and B in the vertebrate brain

Comparative Biochemistry and Physiology Part C: Comparative Pharmacology, 1982

1. Monoamine oxidase (MAO) activity was measured in brains of teleosts, amphibians, a reptile, bi... more 1. Monoamine oxidase (MAO) activity was measured in brains of teleosts, amphibians, a reptile, birds and mammals. Selective inhibitors were used to determine the relative proportion of MAO type A and MAO type B.