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Biomedical subjects

E M Quinn

Publications and source records attributed to E M Quinn.

4 recordsLinked to original sources
PubMed1989

Carbon dynamics of logarithmetic and stationary phase phytoplankton as determined by track autoradiography.

Track autoradiographic analysis of photosynthetic radiocarbon incorporation at the cellular level indicated that the carbon uptake rate and carbon pool size of exponentially growing (log phase) Scenedesmus cells was threefold that of stationary phase cells, while carbon turnover rates were similar. Carbon fixation was uncoupled from growth and cell division in the stationary phase cells, which were larger and contained less chlorophyll per unit volume than log phase cells. Changes in the temporal pattern of isotope incorporation were evident at the cell level prior to the cessation of division and transition to stationary phase, while bulk carbon fixation responded only the second day after cell division ceased. The carbon uptake patterns of a marine nanoplankter from a nutrient-enriched natural sample resembled that of log phase cells while the control population pattern resembled that of stationary cells. The physical, biochemical, and metabolic differences between log and stationary phase cells are potentially measurable by flow cytometry procedures currently in use and under development. The use of flow cytometry to sort cell types for analysis by track autoradiography and subsequent correlation of metabolic characteristics with flow cytometry signatures is a feasible means of investigating the heterogeneity of phytoplankton metabolic state in the marine environment.

Autoradiography↗
PubMed1989

The expression of sequences similar to the human c-erb-A oncogene are regulated in a tissue and stage specific manner in Drosophila melanogaster.

The gene encoding the human thyroid hormone receptor, c-erb-A, is hypothesized to be a member of a superfamily of genes, which originated from a primordial receptor encoding gene. To trace the molecular evolutionary background of this gene, we initiated the search for it in the genome of Drosophila melanogaster by using low stringency hybridization analysis. We report here the presence of more than one gene in Drosophila with varying degrees of sequence similarity. By RNA blot hybridization analyses utilizing both wild type and a temperature sensitive ecdysone deficient mutant strain, ecd1, with a human c-erb-A probe, we show that a single high molecular weight RNA of 6.8kb in size is recognized by human c-erb-A, is regulated in a stage and tissue specific manner, and is also inducible in organisms of the ecd1 mutant strain in the presence of exogeneous ecdysone.

Animals↗
PubMed1988

Induction of alcohol dehydrogenase by ethanol in Drosophila melanogaster.

When Drosophila melanogaster larvae were fed a defined fat-free, low sucrose medium, alcohol dehydrogenase (ADH) was increased to a higher activity with a moderate, nontoxic level of ethanol (2.5% vol/vol) within 5 h. Ethanol-stimulated increases in ADH activity and cross-reacting material in late third-instar larvae were paralleled by increases in the larval ADH mRNA as indicated by dot blot analysis. Northern blot observations indicated that both adult and larval ADH messages were increased by dietary ethanol. The increased levels of the ADH mRNA transcribed from the proximal and distal promoters of ethanol-fed larvae argue that the induction is a consequence of elevated levels of mRNA, not a result of changes in enzyme stability or synthesis. To determine whether the induction is of nutritional significance to larvae, the rate of flux from ethanol to lipid was estimated in control larvae and larvae that were pre-fed ethanol. Flux changes occurred; the rate of incorporation of [14C]ethanol into body lipid showed a strong association with larval ADH activity. Because the induced increase in larval ADH activity did not extend into the adult stage and attempts to stimulate ADH activity by exposing adults to ethanol were unsuccessful, the modulation of ADH activity by dietary ethanol may be a mechanism by which larvae utilize environmental ethanol as a resource, especially when free sugar levels are low. In addition, ADH in larvae is postulated to perform a second, nonethanol function that expedites the conversion of sugars to lipid when habitats are low in fats, low in ethanol and high in sugars.

Age Factors↗