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Biomedical subjects

A Silva

Publications and source records attributed to A Silva.

At least 199 records · Page 11Linked to original sources
PubMedDate not supplied

Secretion and glycosylation of Clostridium thermocellum endoglucanase A encoded by the celA gene in Saccharomyces cerevisiae.

The Clostridium thermocellum celA gene encoding endoglucanase A is expressed in Saccharomyces cerevisiae but the enzyme produced from the native celA gene is not secreted. After removal of the bacterial signal peptide-coding sequence, the gene was fused to the promoter and prepro segment of the S. cerevisiae MF alpha 1 gene. This construction directs secretion of active endoglucanase A into the culture medium when introduced in yeast on either replicating or integrating vectors. Secretion of endoglucanase A required growth of transformants on rich medium. The secreted enzyme is a 97,000 Da glycoprotein containing about half of its molecular weight as carbohydrate. This new gene fusion could facilitate further research on protein secretion in yeast by using a cellulase as a marker enzyme.

Blotting, Southern↗
PubMedDate not supplied

Postnatal development of somatostatin levels and its binding sites in rabbit gastric mucosa.

Using a specific radioimmunoassay technique, we have determined somatostatin-like immunoreactivity (SLI) in acid extracts of gastric (fundic and antral) mucosa as well as the specific binding of 125I-Tyr11-somatostatin to cytosol of the stomach of 0 to 150 days postnatal rabbits. The levels of somatostatin in both fundus and antrum decreased from birth up to day 5 followed by a sharp increase from 5 to 10 days, then decreased progressively until day 35. After this age, the somatostatin concentration remained relatively stable. The number of specific somatostatin binding sites of both high- and low-affinity increased gradually (without changes in the affinity values) with the development of rabbits, reaching the adult level by 35 days. However, there was an apparent lack of high-affinity sites immediately after birth (day 0). The somatostatin binding sites had characteristics identical with those found in adult animals with regard to their respective specific ligands.

Age Factors↗
PubMedDate not supplied

Impaired experience-dependent plasticity in barrel cortex of mice lacking the alpha and delta isoforms of CREB.

The transcription factor cyclic-AMP response element binding protein (CREB) has been implicated in long-term plasticity processes in vertebrate and invertebrate species. In the absence of the alpha/delta CREB isoforms, performance is impaired in long-term memory tasks and the long-term maintenance of long-term potentiation (LTP) is impaired in the hippocampus. However, it is not known whether CREB plays a role in neocortical plasticity. Antibodies to CREB revealed that CREB-immunoreactive nuclei are present in all cortical layers but are more numerous in layers II/III, where they composed at least two-thirds the total population of cells. CREB-immunopositive cells were therefore present and densest in the very cortical layers that exhibit experience-dependent plasticity at this age. In order to assess the role of CREB in neocortical plasticity, we studied the effect of vibrissae deprivation on receptive field plasticity in the barrel cortex of mutant mice lacking the alpha/delta isoforms of CREB. A single vibrissa was spared and the others removed for 18 days. In wild-types this caused potentiation of the spared vibrissa response. However, in adult mutants (>6 months) spared vibrissa responses from homozygotes were potentiated less than in any adolescent animals or in adult wild-type littermates. Surround receptive field responses were abnormally large in homozygotes and failed to increase by the same amount as they did in wild-types. In contrast, the alpha/delta CREB mutation had no discernible effect on plasticity in cortical layers II/III of the younger adolescent age group (1-2 months), suggesting that different plasticity processes may operate at this age. Further tests showed that the beta isoform of CREB was up-regulated in the barrel cortex of the alpha/delta CREB knock-outs, suggesting that this subunit may have compensated partly for the loss of the alpha/delta isoforms. These studies suggests that CREB plays a role in experience-dependent plasticity in the adult neocortex.

Animals↗
PubMedDate not supplied

Evaluating Chicago's success in reaching the Healthy People 2000 goal of reducing health disparities.

OBJECTIVE: This study was designed to assess Chicago's progress from 1980 to 1998 in addressing the Healthy People 2000 goal of reducing health disparities. METHODS: Chicago vital statistics and surveillance data were used to calculate black:white rate ratios of mortality and morbidity for 1980-1998. Mortality and morbidity rate ratios were also used to compare people living in areas with the lowest median household income with those living in the highest for 1979-1981, 1991-1993, and 1996-1998. The health measures included mortality associated with leading causes of death; all-cause mortality, incidence rates for two communicable diseases; and two birth outcomes. RESULTS: Both black:white and low-income:high-income rate ratios monotonically increased for virtually all measures of mortality and morbidity. Almost all of the rate ratios and linear trends were statistically significant. From 1980 to 1998, the black:white rate ratio for all-cause mortality increased by 57% to 2.03. From 1979-1981 to 1996-1998, the low-income:high-income rate ratio for all-cause mortality increased by 56% to 2.68. CONCLUSIONS: These findings provide clear evidence that disparities in health did not decrease in Chicago. Instead, racial and economic disparities increased for almost all measures of mortality and morbidity used in this study. The fact that the Healthy People 2000 campaign to reduce and then eliminate health disparities was not effective must serve as a stimulus for improved strategies.

Adolescent↗