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C F Wu

Publications and source records attributed to C F Wu.

137 records · Page 8Linked to original sources
PubMed1975

Quantal basis of photoreceptor spectral sensitivity of Drosophila melanogaster.

Small potential fluctuations ("bumps"), boyh spontaneous and light induced, can be recorded intracellularly from the photoreceptors of Drosophila melanogaster. Statistical analyses of these bumps in the spectral range, 400-600 nm, lead to the following interpretations; (a) For weak stimuli at least, these bumps are the quantal units of the receptor potential. (b) Quanta of various wavelengths, when effectively absorbed, will elicit bumps of the same average size. (c) The spectral sensitivity of the receptor potential appears to have its origin in the relative efficiency of quantum bump production at different wavelengths, and not in the intrinsic difference in the properties of bumps produced by quanta of differenct wavelengths.

Animals↗
PubMed1975

Acute myocardial infarction in toxic cardiomyopathy without coronary obstruction.

Confluent left ventricular scar without significant coronary obstruction has been found in alcoholic subjects at autopsy. To evaluate the pathogenesis, 12 patients with chronic alcoholism and severe precordial pain persisting 4-24 hours were observed clinically. Cardiac isoenzymes of lactic dehydrogenase rose in serum. ST segment was elevated in anterior or posterior ECG leads, and abnormal Q waves appeared. Hypertnesion and hypercholesterolemia were present in two (group B) but not in the ten (group A). The latter exhibited no significant obstructive disease, based on coronary angiography in seven survivors and postmortem examination of the remaining three. Clinical evidence, as well as the quantitative assessment of platelets, made arterial thromboembolism an unlikely cause for the symptoms. Neither hemotologic or systemic disease affecting myocardium was present. The morphology of the left ventricle in three autopsies was compared with that of patients with alcoholism who had no cardiac disease, cardiomyopathy, or an asymptomatic scar. All had accumulation of Alcian positive glycoprotein in the interstitium. The patients with cardiac disease also had interstitial fibrosis which was characterized, particularly in the acute infarction group, by concentric periarterial fibrosis. Restriction of coronary vasodilation by this process during periods of high blood flow requirements was postulated as a basis for infarction.

Adult↗
PubMedDate not supplied

Decrease of brain acetylcholine release in aging freely-moving rats detected by microdialysis.

In vivo extracellular acetylcholine release from brain hemispheric areas of 2-, 9-, and 18-month-old rats was measured by intracerebral microdialysis coupled with a radioenzymatic assay. Dialysis tubing was inserted transversally through both striata, frontal cortices and dorsal hippocampi 24 hours before the experiments. In the 2-month-old rats, the net average acetylcholine output, corrected for recovery and expressed in fmoles/min/single striatum, cortex and hippocampus, was 902.4 +/- 67, 303.9 +/- 14 and 334 +/- 32, respectively. In 18-month-old rats acetylcholine output was 53, 35 and 37% lower in striatum, cortex and hippocampus, respectively, than in young rats. The release from the striatum in the 9-month-old was intermediate between those of the 2- and 18-month-old rats. The intracerebroventricular injection of hemicholinium-3 caused a marked decrease in acetylcholine release from the striata of 2- and 18-month-old rats. If the decrease with hemicholinium was expressed as percent of the basal release there was no age-related difference between the young and old rats, indicating that the differences observed were due to the lower basal release found in the old rats. The possibility that the deficit in basal acetylcholine release with age may depend on a reduction of acetylcholine synthesis is discussed.

Acetylcholine↗
PubMedDate not supplied

Effects of in situ cobalt ion addition on the activity of a gfp-oph fusion protein: the fermentation kinetics.

The effects of cobalt ion addition and inducer concentration were studied in the fermentation of E. coli BL21 expressing a GFP (green fluorescent protein)-OPH (organophosphorus hydrolase) fusion protein. It was found that cobalt ion addition improved the OPH activity significantly. When 2 mM of CoCl(2) was supplied during the IPTG-induction phase, OPH activity was enhanced approximately 10-fold compared to the case without cobalt or by the addition of cobalt to the cell extracts. Results indicate, therefore, that incorporation of the cobalt during synthesis is needed for enhanced activity. Also, the maximum OPH activity was not linearly related to inducer concentration. A mathematical model was then constructed to simulate these phenomena. Model parameters were determined by constrained least-squares and optimal IPTG and cobalt addition concentrations were obtained, pinpointing the conditions for the maximum productivity. Finally, the GFP fluorescence intensity was found linear to the OPH activity in each fermentation, demonstrating the function of GFP for monitoring its fusion partner's quantity in the bioreactor.

Aryldialkylphosphatase↗
PubMedDate not supplied

A cGMP-dependent protein kinase gene, foraging, modifies habituation-like response decrement of the giant fiber escape circuit in Drosophila.

The Drosophila giant fiber jump-and-flight escape response is a model for genetic analysis of both the physiology and the plasticity of a sensorimotor behavioral pathway. We previously established the electrically induced giant fiber response in intact tethered flies as a model for habituation, a form of nonassociative learning. Here, we show that the rate of stimulus-dependent response decrement of this neural pathway in a habituation protocol is correlated with PKG (cGMP-Dependent Protein Kinase) activity and foraging behavior. We assayed response decrement for natural and mutant rover and sitter alleles of the foraging (for) gene that encodes a Drosophila PKG. Rover larvae and adults, which have higher PKG activities, travel significantly farther while foraging than sitters with lower PKG activities. Response decrement was most rapid in genotypes previously shown to have low PKG activities and sitter-like foraging behavior. We also found differences in spontaneous recovery (the reversal of response decrement during a rest from stimulation) and a dishabituation-like phenomenon (the reversal of response decrement evoked by a novel stimulus). This electrophysiological study in an intact animal preparation provides one of the first direct demonstrations that PKG can affect plasticity in a simple learning paradigm. It increases our understanding of the complex interplay of factors that can modulate the sensitivity of the giant fiber escape response, and it defines a new adult-stage phenotype of the foraging locus. Finally, these results show that behaviorally relevant neural plasticity in an identified circuit can be influenced by a single-locus genetic polymorphism existing in a natural population of Drosophila.

Animals↗