Gabriel Romero - Academia.edu (original) (raw)

Papers by Gabriel Romero

International Journal of Biological Macromolecules, 2000

Isozymes of glycosyl hydrolase Family 17 hydrolyze 1,3-b-glucan polysaccharides found in the cell... more Isozymes of glycosyl hydrolase Family 17 hydrolyze 1,3-b-glucan polysaccharides found in the cell wall matrix of plants and fungi, enabling these plant enzymes to serve diverse roles in plant defense and plant development. Fourteen genes from Family 17 have been characterized in the genome of rice. A sequence dendrogram analysis divided these genes into four subfamilies. The recombinant GNS1 enzyme from subfamily B had 1,3;1,4-b-glucanase activity, suggesting a role for this isozyme in plant development.

The Sociedad Universitaria de Astronomia (SUNA) is a group of astronomy amateurs which works insi... more The Sociedad Universitaria de Astronomia (SUNA) is a group of astronomy amateurs which works inside the Universidad Central de Venezuela (Venezuelas Central University)s campus. The initiative is originated during the path through the perihelion of Comet Halley in 1986, and since then their goals are promotion of astronomical information to all the university community. Observational works are also carried out,

ACS chemical neuroscience, Jan 17, 2014

D-Serine, an N-methyl D-aspartate receptor coagonist, and its regulatory enzymes, D-amino acid ox... more D-Serine, an N-methyl D-aspartate receptor coagonist, and its regulatory enzymes, D-amino acid oxidase (DAO; degradation) and serine racemase (SR; synthesis), have been implicated in crucial roles of the developing central nervous system, yet the functional position that they play in regulating the availability of d-serine throughout development of the mammalian retina is not well-known. Using capillary electrophoresis and a sensitive method of enantiomeric amino acid separation, we were able to determine total levels of d-serine at specific ages during postnatal development of the mouse retina in two different strains of mice, one of which contained a loss-of-function point mutation for DAO while the other was a SR knockout line. Each mouse line was tested against conspecific wild type (WT) mice for each genetic strain. The universal trend in all WT and transgenic mice was a large amount of total retinal d-serine at postnatal age 2 (P2), followed by a dramatic decrease as the mice ...

Agronomy, 2014

Traditional rice varieties maintained and cultivated by farmers are likely sources of germplasm f... more Traditional rice varieties maintained and cultivated by farmers are likely sources of germplasm for breeding new rice varieties. They possess traits potentially adaptable to a wide range of abiotic and biotic stresses. Characterization of these germplasms is essential in rice breeding and provides valued information on developing new rice cultivars. In this study, 307 traditional rice varieties newly conserved at the PhilRice genebank were characterized to assess their phenotypic diversity using 57 morphological traits. Using the standardized Shannon-Weaver diversity index, phenotypic diversity indices averaged at 0.73 and 0.45 for quantitative and qualitative traits, respectively. Correlation analyses among agro-morphological traits showed a high positive correlation in some traits such as culm number and panicle number, flag leaf width and leaf blade width, grain width and caryopsis width. Cluster analysis separated the different varieties into various groups. Principal component analysis (PCA) showed that seven independent principal components accounted for 74.95% of the total variation. Component loadings for each principal component showed morphological characters, such as culm number, panicle number and caryopsis ratio that were among the phenotypic traits contributing positive projections in three principal components that explained 48% of variation. Analyses of results showed high diversity in major traits assessed in farmers' rice varieties. Based on plant height and maturity, 11 accessions could be potential donor parents in a rice breeding

Theoretical optimization of ARC (antireflecting coating) for both, single and double ARC has been... more Theoretical optimization of ARC (antireflecting coating) for both, single and double ARC has been done in the order to obtain minimum reflectance on crystalline silicon surface. Experimental corroboration has been made with the deposition of a simple SiN/sub x/ (silicon nitride) and double SiN/sub x//SiO/sub 2/ (silicon nitride/silicon oxide) ARC on silicon substrates using PECVD (Plasma enhanced chemical vapor deposition)

The Journal of Physiology, 2011

Retinal ganglion cells represent a population of neurons that relay information from the retina t... more Retinal ganglion cells represent a population of neurons that relay information from the retina to the brain. During retinal light responses, the spiking activity of retinal ganglion cells is shaped in part by NMDA receptors, which require a coagonist for activation. There is debate over if glycine or D-serine serves as the endogenous coagonist to retinal ganglion cell NMDA receptors. To address this question, we used a mutant mouse lacking functional serine racemase, the D-serine-synthesizing enzyme. In this study we show that D-serine is required to activate retinal ganglion cell NMDA receptors during light stimulation. Mice lacking serine racemase also appeared to have alterations in the relative contribution of NMDA and AMPA receptors to light responses. Interestingly, behavioural tests showed that mice lacking serine racemase had no apparent visual deficits. Collectively, these findings raise interesting questions about the role of D-serine in shaping excitatory synapses and in visual processing.

Behavioural Brain Research, 2013

Head movement is a novel behavioral endpoint in the FST and TST. Reproducible in 129 and C57 mous... more Head movement is a novel behavioral endpoint in the FST and TST. Reproducible in 129 and C57 mouse strains. Inversely correlated to swimming and selectively enhanced by SSRIs. Weighted TST analysis differentiates 5-HT and norepinephrine responsive behaviors. 5-HT 2A and 5-HT 2C postsynaptic receptor activation diminish TST head movement. Available online xxx Keywords: TST FST Antidepressant SSRI Serotonin subtype receptor Bin sample analysis a b s t r a c t

Alcohol, 2012

a b s t r a c t NMDA receptors become a major contributor to acute ethanol intoxication effects a... more a b s t r a c t NMDA receptors become a major contributor to acute ethanol intoxication effects at high concentrations as ethanol binds to a unique site on the receptor and inhibits glutamatergic activity in multiple brain areas. Although a convincing body of literature exists on the ability of NMDA receptor antagonists to mimic and worsen cellular and behavioral ethanol effects, receptor agonists have been less well-studied. In addition to a primary agonist site for glutamate, the NMDA receptor contains a separate co-agonist site that responds to endogenous amino acids glycine and D-serine. D-serine is both selective for this co-agonist site and potent in boosting NMDA dependent activity even after systemic administration. In this study, we hypothesized that exogenous D-serine might ameliorate some acute ethanol behaviors by opposing NMDA receptor inhibition. We injected adult male C57 mice with a high concentration of D-serine at various time windows relative to ethanol administration and monitored sedation, motor coordination and voluntary ethanol drinking. D-serine (2.7 g/kg, ip) prolonged latency to a loss of righting reflex (LoRR) and shortened LoRR duration when given 15 min before ethanol (3 g/kg) but not when it was injected with or shortly after ethanol. Blood samples taken at sedative recovery and at fixed time intervals revealed no effect of D-serine on ethanol concentration but an ethanol-induced decrease in L-serine and glycine content was prevented by acute D-serine pre-administration. D-serine had no effect on ethanol-induced (2 g/kg) rotarod deficits in young adult animals but independently and interactively degraded motor performance in a subset of older mice. Finally, a week-long series of daily ip injections resulted in a 50% decrease in free choice ethanol preference for D-serine treated animals compared to saline-injected controls in a two-bottle choice experiment.

Germplasm materials are the building blocks for the construction of improved rice varieties. Howe... more Germplasm materials are the building blocks for the construction of improved rice varieties. However, as farmers turn to few modern varieties, extant germplasm undergoes a narrowing of diversity. There is therefore a great need to conserve the rice biodiversity found in nature and also those developed through plant breeding. Ex-situ conservation in genebanks provides a safe storage system for the germplasm. It is also important to have a systematic and sufficient characterization of these materials. In selecting plants for breeding, information on their morpho-agronomic traits, grain quality, and reaction to pests and diseases are primary considerations. As more information is available about the germplasm, the wider selection and diversity of materials can be utilized for varietal improvement. In PhilRice Genebank, rice germplasm are collected, conserved, and evaluated to support plant breeding programs. Emphasis is on conserving Philippine traditional varieties to safeguard this n...

International Journal of Biological Macromolecules, 2000

Isozymes of glycosyl hydrolase Family 17 hydrolyze 1,3-b-glucan polysaccharides found in the cell... more Isozymes of glycosyl hydrolase Family 17 hydrolyze 1,3-b-glucan polysaccharides found in the cell wall matrix of plants and fungi, enabling these plant enzymes to serve diverse roles in plant defense and plant development. Fourteen genes from Family 17 have been characterized in the genome of rice. A sequence dendrogram analysis divided these genes into four subfamilies. The recombinant GNS1 enzyme from subfamily B had 1,3;1,4-b-glucanase activity, suggesting a role for this isozyme in plant development.

The Sociedad Universitaria de Astronomia (SUNA) is a group of astronomy amateurs which works insi... more The Sociedad Universitaria de Astronomia (SUNA) is a group of astronomy amateurs which works inside the Universidad Central de Venezuela (Venezuelas Central University)s campus. The initiative is originated during the path through the perihelion of Comet Halley in 1986, and since then their goals are promotion of astronomical information to all the university community. Observational works are also carried out,

ACS chemical neuroscience, Jan 17, 2014

D-Serine, an N-methyl D-aspartate receptor coagonist, and its regulatory enzymes, D-amino acid ox... more D-Serine, an N-methyl D-aspartate receptor coagonist, and its regulatory enzymes, D-amino acid oxidase (DAO; degradation) and serine racemase (SR; synthesis), have been implicated in crucial roles of the developing central nervous system, yet the functional position that they play in regulating the availability of d-serine throughout development of the mammalian retina is not well-known. Using capillary electrophoresis and a sensitive method of enantiomeric amino acid separation, we were able to determine total levels of d-serine at specific ages during postnatal development of the mouse retina in two different strains of mice, one of which contained a loss-of-function point mutation for DAO while the other was a SR knockout line. Each mouse line was tested against conspecific wild type (WT) mice for each genetic strain. The universal trend in all WT and transgenic mice was a large amount of total retinal d-serine at postnatal age 2 (P2), followed by a dramatic decrease as the mice ...

Agronomy, 2014

Traditional rice varieties maintained and cultivated by farmers are likely sources of germplasm f... more Traditional rice varieties maintained and cultivated by farmers are likely sources of germplasm for breeding new rice varieties. They possess traits potentially adaptable to a wide range of abiotic and biotic stresses. Characterization of these germplasms is essential in rice breeding and provides valued information on developing new rice cultivars. In this study, 307 traditional rice varieties newly conserved at the PhilRice genebank were characterized to assess their phenotypic diversity using 57 morphological traits. Using the standardized Shannon-Weaver diversity index, phenotypic diversity indices averaged at 0.73 and 0.45 for quantitative and qualitative traits, respectively. Correlation analyses among agro-morphological traits showed a high positive correlation in some traits such as culm number and panicle number, flag leaf width and leaf blade width, grain width and caryopsis width. Cluster analysis separated the different varieties into various groups. Principal component analysis (PCA) showed that seven independent principal components accounted for 74.95% of the total variation. Component loadings for each principal component showed morphological characters, such as culm number, panicle number and caryopsis ratio that were among the phenotypic traits contributing positive projections in three principal components that explained 48% of variation. Analyses of results showed high diversity in major traits assessed in farmers' rice varieties. Based on plant height and maturity, 11 accessions could be potential donor parents in a rice breeding

Theoretical optimization of ARC (antireflecting coating) for both, single and double ARC has been... more Theoretical optimization of ARC (antireflecting coating) for both, single and double ARC has been done in the order to obtain minimum reflectance on crystalline silicon surface. Experimental corroboration has been made with the deposition of a simple SiN/sub x/ (silicon nitride) and double SiN/sub x//SiO/sub 2/ (silicon nitride/silicon oxide) ARC on silicon substrates using PECVD (Plasma enhanced chemical vapor deposition)

The Journal of Physiology, 2011

Retinal ganglion cells represent a population of neurons that relay information from the retina t... more Retinal ganglion cells represent a population of neurons that relay information from the retina to the brain. During retinal light responses, the spiking activity of retinal ganglion cells is shaped in part by NMDA receptors, which require a coagonist for activation. There is debate over if glycine or D-serine serves as the endogenous coagonist to retinal ganglion cell NMDA receptors. To address this question, we used a mutant mouse lacking functional serine racemase, the D-serine-synthesizing enzyme. In this study we show that D-serine is required to activate retinal ganglion cell NMDA receptors during light stimulation. Mice lacking serine racemase also appeared to have alterations in the relative contribution of NMDA and AMPA receptors to light responses. Interestingly, behavioural tests showed that mice lacking serine racemase had no apparent visual deficits. Collectively, these findings raise interesting questions about the role of D-serine in shaping excitatory synapses and in visual processing.

Behavioural Brain Research, 2013

Head movement is a novel behavioral endpoint in the FST and TST. Reproducible in 129 and C57 mous... more Head movement is a novel behavioral endpoint in the FST and TST. Reproducible in 129 and C57 mouse strains. Inversely correlated to swimming and selectively enhanced by SSRIs. Weighted TST analysis differentiates 5-HT and norepinephrine responsive behaviors. 5-HT 2A and 5-HT 2C postsynaptic receptor activation diminish TST head movement. Available online xxx Keywords: TST FST Antidepressant SSRI Serotonin subtype receptor Bin sample analysis a b s t r a c t

Alcohol, 2012

a b s t r a c t NMDA receptors become a major contributor to acute ethanol intoxication effects a... more a b s t r a c t NMDA receptors become a major contributor to acute ethanol intoxication effects at high concentrations as ethanol binds to a unique site on the receptor and inhibits glutamatergic activity in multiple brain areas. Although a convincing body of literature exists on the ability of NMDA receptor antagonists to mimic and worsen cellular and behavioral ethanol effects, receptor agonists have been less well-studied. In addition to a primary agonist site for glutamate, the NMDA receptor contains a separate co-agonist site that responds to endogenous amino acids glycine and D-serine. D-serine is both selective for this co-agonist site and potent in boosting NMDA dependent activity even after systemic administration. In this study, we hypothesized that exogenous D-serine might ameliorate some acute ethanol behaviors by opposing NMDA receptor inhibition. We injected adult male C57 mice with a high concentration of D-serine at various time windows relative to ethanol administration and monitored sedation, motor coordination and voluntary ethanol drinking. D-serine (2.7 g/kg, ip) prolonged latency to a loss of righting reflex (LoRR) and shortened LoRR duration when given 15 min before ethanol (3 g/kg) but not when it was injected with or shortly after ethanol. Blood samples taken at sedative recovery and at fixed time intervals revealed no effect of D-serine on ethanol concentration but an ethanol-induced decrease in L-serine and glycine content was prevented by acute D-serine pre-administration. D-serine had no effect on ethanol-induced (2 g/kg) rotarod deficits in young adult animals but independently and interactively degraded motor performance in a subset of older mice. Finally, a week-long series of daily ip injections resulted in a 50% decrease in free choice ethanol preference for D-serine treated animals compared to saline-injected controls in a two-bottle choice experiment.

Germplasm materials are the building blocks for the construction of improved rice varieties. Howe... more Germplasm materials are the building blocks for the construction of improved rice varieties. However, as farmers turn to few modern varieties, extant germplasm undergoes a narrowing of diversity. There is therefore a great need to conserve the rice biodiversity found in nature and also those developed through plant breeding. Ex-situ conservation in genebanks provides a safe storage system for the germplasm. It is also important to have a systematic and sufficient characterization of these materials. In selecting plants for breeding, information on their morpho-agronomic traits, grain quality, and reaction to pests and diseases are primary considerations. As more information is available about the germplasm, the wider selection and diversity of materials can be utilized for varietal improvement. In PhilRice Genebank, rice germplasm are collected, conserved, and evaluated to support plant breeding programs. Emphasis is on conserving Philippine traditional varieties to safeguard this n...