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M C Da Silva

Publications and source records attributed to M C Da Silva.

8 recordsLinked to original sources
PubMed2000

Analysis of structural and physico-chemical parameters involved in the specificity of binding between alpha-amylases and their inhibitors.

Enzyme-inhibitor specificity was studied for alpha-amylases and their inhibitors. We purified and cloned the cDNAs of two different alpha-amylase inhibitors from the common bean (Phaseolus vulgaris) and have recently cloned the cDNA of an alpha-amylase of the Mexican bean weevil (Zabrotes subfasciatus), which is inhibited by alpha-amylase inhibitor 2 but not by alpha-amylase inhibitor 1. The crystal structure of AI-1 complexed with pancreatic porcine alpha-amylase allowed us to model the structure of AI-2. The structure of Zabrotes subfasciatus alpha-amylase was modeled based on the crystal structure of Tenebrio molitor alpha-amylase. Pairwise AI-1 and AI-2 with PPA and ZSA complexes were modeled. For these complexes we first identified the interface forming residues. In addition, we identified the hydrogen bonds, ionic interactions and loss of hydrophobic surface area resulting from complex formation. The parameters we studied provide insight into the general scheme of binding, but fall short of explaining the specificity of the inhibition. We also introduce three new tools-software packages STING, HORNET and STINGPaint-which efficiently determine the interface forming residues and the ionic interaction data, the hydrogen bond net as well as aid in interpretation of multiple sequence alignment, respectively.

Amino Acid Sequence↗
PubMed1997

Age-related effects of diazepam on retention of inhibitory avoidance and shuttle avoidance tasks in rats.

We investigated the effect of diazepam on memory of 30 days-old and 60-70 days-old female Wistar rats, using two behavioral tasks: step-down inhibitory avoidance (IA) and shuttle avoidance (SA). Diazepam (0.2, 1.0 or 5.0 mg/kg) or its vehicle were given i.p., 60 min prior to the training session. Training-test interval was 24 h. Diazepam impaired the retention of IA in 30 days-old rats at the three doses used, while retention of SA was not impaired by any dose. In the 60-70 days-old animals, diazepam at the dose of 0.2 mg/kg was facilitatory in IA and had no effect on SA, while doses of 1.0 mg/kg and 5.0 mg/kg impaired retention of both tasks. We suggest that these age-dependent effects of diazepam on memory of IA and SA could be related to developmental changes in brain GABAA receptors.

Age Factors↗
PubMed1996

Surgery of the sympathetic nervous system.

This article reviews the innervation of the arterial system of the lower extremity, lumbar sympathectomy in vascular surgery, lumbar sympathectomy for digital gangrene and in the prevention of major amputation of the lower extremity and substance P's role in neurogenic inflammatory modulation. Long-term results of lumbar sympathectomy and direct arterial bypass surgery have also been reviewed. In addition to the pilomotor, sudomotor and vasomotor actions of the sympathetic nervous system via its neurotransmitters, the molecular basis of the chronic neurogenic inflammatory reaction have been addressed with special attention to the discovery of substance P in the lumbar sympathetic chain and ganglia of human beings.

Amputation, Surgical↗
PubMed1990

Xylem-to-Phloem Transfer of Organic Nitrogen in Young Soybean Plants.

Xylem-to-phloem transfer in young vegetative soybean (Glycine max [L.] Merr.) plants (V4 stage) was identified as the difference in the distribution of [(14)C]inulin, a xylem marker, and [(14)C]aminoisobutyric acid (AIB), a synthetic amino acid, fed via the transpiration stream. Since [(14)C]AIB was retained in the stem to some extent, whereas [(14)C]inulin was not, the distribution of these marker compounds in each leaf was expressed as a percentage of the total [(14)C] radioactivity recovered in the foliage. The developing third trifoliolate was a consistent and reliable indicator of xylem-to-phloem transfer. The phloem stream provided to the developing trifoliolate up to fourfold the relative proportion of solute received from the xylem stream; this was markedly reduced by increased light intensity and consequently water flow through the xylem. Evidence from heat girdling experiments is discussed with respect to the vascular anatomy of the soybean plant, and interpreted to suggest that direct xylem-to-phloem transfer in the stem, in the region of the second node, accounted for about one-half of the AIB supplied to the developing trifoliolate, with the remainder being provided from the second trifoliolate. Since AIB is not metabolized it seems likely that rapid transfer within the second trifoliolate occurred as direct veinal transfer rather than indirect cycling through the mesophyll. This study confirmed that xylem-to-phloem transfer plays a major role in the partitioning of nitrogen for early leaf development.

Journal Article↗
PubMed1990

Distribution and metabolism of xylem-borne ureido and amino compounds in developing soybean shoots.

Pulse-chase feeding (30-120 minutes) of (14)C-labeled nitrogenous compounds to cut transpiring shoots was used to investigate the early fate of the major xylem-borne solutes in N(2)-fixing soybean (Glycine max) plants at the V(4) growth stage. By comparison with the foliar distribution of [(14)C]inulin (a xylem marker), it was determined that the phloem supply of allantoin, allantoic acid, asparagine, glutamine, aspartate, and arginine, respectively, provided about 20, 10, three, two, five, and 20 times the (14)C delivered to the developing trifoliolate in the xylem stream. Recovery of unmetabolized asparagine, aspartate, and arginine in this indicator trifoliolate, and significant declines in the percentage of (14)C from allantoic acid and allantoin recovered in the first trifoliolate, provided some support for the direct xylem-to-phloem transfer of these compounds, but did not preclude the involvement of indirect transfer. Data on stem retention and foliar distribution, expressed as a function of the relative xylem sap composition, indicated that ureides provide the major sources of nitrogen to all plant parts. There was no consistent distinction in distribution patterns between pairs of similar anionic and neutral compounds. The extent of xylem-to-phloem transfer among the ureido or the amino compounds was inversely related to its prominence in xylem sap.

Journal Article↗
PubMed1980

Distribution of abnormal hemoglobins and glucose-6-phosphate dehydrogenase variants in 1200 school children of Bahia, Brazil.

School children from Bahia, Brazil were studied for hemoglobin and glucose-6-phosphate dehydrogenase electrophoretic variants. Eighty-nine heterozygotes Hb AS and 41 Hb AC were identified out of 1200 children. In a subsample of 369 male children there were 38 Gd A-, 38 Gd A, and six Gd Med. An example of Gd MG was identified and evidence is added to the suggestion that this allele is not rare in Brazil.

Brazil↗
PubMed1979

Human aconitase polymorphism in three samples from northeastern Brazil.

Human aconitase (ACONS) polymorphism was studied in three samples from northeastern Brazil. Two of the samples were collected in the State of Bahia and one in the State of Sergipe. The main characteristic of the samples was given by different degrees of Black admixture. The results showed that the more negroid the samples the higher the frequencies of the alleles ACONS4, ACONS2 and ACONS6. These findings fit well with the known ACONS gene frequencies in present-day Nigerians and with the past history of Yoruba slaves in Bahia.

Aconitate Hydratase↗