PubMed Health⌕ Search

Biomedical subjects

Sylvia Fischer

Publications and source records attributed to Sylvia Fischer.

5 recordsLinked to original sources
PubMed2006

Genetic screen for signal peptides in Hydra reveals novel secreted proteins and evidence for non-classical protein secretion.

We have screened a Hydra cDNA library for sequences encoding N-terminal signal peptides using the yeast invertase secretion vector pSUC [Jacobs et al., 1997. A genetic selection for isolating cDNAs encoding secreted proteins. Gene 198, 289-296]. We isolated and sequenced 907 positive clones; 88% encoded signal peptides; 12% lacked signal peptides. By searching the Hydra EST database we identified full-length sequences for the selected clones. These encoded 37 known proteins with signal peptides and 40 novel Hydra-specific proteins with signal peptides. Localization of two signal peptide-containing sequences, VEGF and ferritin, to the secretory pathway was confirmed with GFP fusion proteins. In addition, we isolated 105 clones which lacked signal peptides but which supported invertase secretion from yeast. Isolation of plasmids from these clones and retransformation in invertase-negative yeast cells confirmed the phenotype. A GFP fusion protein of one such clone encoding the foot morphogen pedibin was localized to the cytoplasm in transfected Hydra cells and did not enter the ER/Golgi secretory pathway. Secretion of pedibin and other proteins lacking signal peptides appears to occur by a non-classical protein secretion route.

Amino Acid Sequence↗
PubMed2004

Culex mosquitoes in temporary urban rain pools: seasonal dynamics and relation to environmental variables.

The study was conducted in a park of Buenos Aires City, where a total of 89 rain pools were sampled weekly for mosquito immature stages over a one-year period. The aim of the present paper was to investigate the seasonal dynamics of three Culex species breeding in temporary rain pools and to analyze the relationships of the presence of these species to pool dimensions, pool age, vegetation, and insolation degree. The three species showed differences in their seasonal patterns, Culex dolosus being present during the whole year, Culex pipiens mainly in the summer season, and Culex maxi almost exclusively during the fall. The variable explaining most of the variation among sampling dates in species composition was weekly mean temperature. A significant positive association was detected among mosquito species, as they were recorded together more frequently than expected by chance. The statistical analyses performed revealed significant positive relationships of all three mosquito species to increasing surface area, whereas no relationship to insolation degree was detected in the studied pools. Culex pipiens and Culex dolosus showed positive relationships to increasing vegetation cover, whereas the presence of Culex dolosus was also related to pool age.

Animals↗
PubMed2003

[Bone mineral density in school age children born preterm ].

BACKGROUND: The age at which children born preterm normalize their bone mineral density, is not well known. AIM: To study if children born preterm have normalized their bone mineral density at age 5 to 7 years. PATIENTS AND METHODS: Twenty six infants born preterm (14 male), were studied at age 5 to 7 years. Birth weight, present weight and height, bone age, calcium and phosphate intake at the first year of life and at the current age were assessed. Bone mineral density was measured by single photon X ray absorptiometry in the dominant forearm. A blood sample was obtained to measure insulin growth factor 1 (IGF-1). As a control group, 105 healthy age-paired infants born at term, were studied. RESULTS: Bone mineral density was significantly lower in infants born preterm than in their term counterparts (0.273 +/- 0.01 g/cm2 and 0.302 +/- 0.01 g/cm2 respectively, p < 0.001). There was a positive correlation between bone mineral density and IGF-1 (r = 0.49, p = 0.01). No correlation with the other measured parameters was observed. CONCLUSIONS: Infants that were born preterm have a lower bone mineral density at 5 to 7 years of age than their term controls. Bone mineral density correlates with IGF-1.

Anthropometry↗
PubMed2002

Ochlerotatus albifasciatus in rain pools of Buenos Aires: seasonal dynamics and relation to environmental variables.

The immature stages of Ochlerotatus albifasciatus develop in temporary pools. The present study aims at evaluating the seasonal dynamics of the aquatic stages of this mosquito, also analyzing the relationship among their presence and breeding success to some relevant climatic and environmental variables in the ephemeral rain pools of an urban park. Nineteen cohorts of O. albifasciatus that developed synchronously after rain events were recorded in all seasons. The proportions of mosquito-positive pools were significantly higher during the fall-winter period than in the spring-summer months (p < 0.001). The presence of this mosquito species was positively related to the amount of rain (p < 0.001), whereas negatively correlated to air temperature (p < 0.05) within a 5.2 to 29.7 degrees C range. The distribution of the number of cohorts per pool throughout the year was grouped (variance/mean: 3.96), indicating that these habitats were not equally suitable as breeding sites. The immature stages of O. albifasciatus were detected in pools belonging to all of the categories of surface area, depth, duration, vegetation cover, and insolation. However, the proportion of pools where immature mosquitoes were detected was positively and significantly related to surface, depth, duration, and vegetation cover. On the other hand, the proportion of mosquito-positive pools was higher at an intermediate insolation degree. Our results suggest that although preimaginal stages were present in all seasons, high temperatures may be unfavorable to larval development, and substrate vegetation may regulate water temperature. The positive relationship between the proportion of mosquito-positive pools and pool size and duration might reflect a strategy of O. albifasciatus to accomplish immature development.

Animals↗