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Biomedical subjects

G M Padilla

Publications and source records attributed to G M Padilla.

At least 37 records · Page 2Linked to original sources
PubMed1979

Germination and outgrowth of Schizosaccharomyces pombe spores isolated by a simple batch centrifugation technique.

Spores of the fission yeast Schizosaccharomyces pombe have been separated from vegetative cells by a simple and rapid centrifugation (800 g for 20 min) through a 35% Hypaque solution to a purity greater than 95%. Approximately 35% of the spores were recovered. Regrowth in EMM2 plus glucose showed that over 97% of the spores germinated within the first 2 h and outgrowth continued between 5 and 10 h. Sucrose induced germination in greater than 95% of the spores with a 1 h delay and outgrowth in 50% of the spores with a 3 h delay. There was little protein synthesis during germination but the protein content increased linearly coincident with outgrowth. The RNA content increased slightly during germination, but increased linearly 1 h before the onset of outgrowth and protein synthesis. After 8 h of regrowth, coincident with the onset of DNA synthesis, the rate of RNA synthesis was accelerated. The DNA content had increased 1.7-fold after 10 h of regrowth from a haploid level of 1.36 x 10(-8) microgram spore-1.

Ascomycota↗
PubMed1977

How Gymnodinium breve red tide toxin(s) produces repetitive firing in squid axons.

Partially purified toxin(s), GbTX, extracted from Gymnodinium breve red tide organisms elicits a spontaneous train of action potentials in the squid giant axon. The spikes have a shape similar to that in the normal seawater control except for an increase in the rate of recovery from the afterhyperpolarization. With this more rapid recovery, the membrane potential overshoots the resting potential and threshold, triggers another spike, and thus produces repetitive firing. Voltage-clamp studies revealed that the toxin has no effect on the normal sodium or potassium conductance changes produced by step depolarization. However, consistent with the faster recovery after an action potential, GbTX speeds recovery of the "shut-off" currents to their steady-state values after a depolarization. The most likely mechanism by which the toxin accelerates recovery after an action potential (leading to repetitive firing) is the induction of a small additional inward current which was found to be reduced by prehyperpolarization. This toxin-induced current which speeds recovery is blocked by tetrodotoxin and hence presumably flows through the sodium channel.

Action Potentials↗
PubMed1976

Oxalate, calcium uptake and ATPase activity of sarcoplasmic reticulum vesicles.

Ca++-uptake and Mg++-Ca++-dependent ATPase activity of skeletal muscle sarcoplasmic reticulum vesicles were reciprocally affected by increasing the oxalate concentration from 0 to 4 mM. At 0-0.1 mM oxalate approximately 17% of the calcium was removed by the vesicles from the medium while the ATPase activity was maximal (approximately 0.66 mumoles Pi mg-1 protein min-1). Between 0.1 to 0.2 mM oxalate the ATPase activity was reduced to one-fifth but the uptake rose sharply and 100% of the 45Ca++ was removed from the medium. The uptake was maintained at this level at oxalate concentrations greater than 0.4 mM but the ATPase activity remained inhibited. The kinetics of Ca++-uptake and ATPase activity were also differentially affected by oxalate. In the presence of oxalate, ruthenium red had only a very slight inhibitory effect on the calcium uptake. Addition of 0.1 mM EGTA removed 80% of the Ca++ from preloaded vesicles within 10 min. The formation of insoluble Ca-oxalate salt on the surface of the vesicle is suggested by these results. Calculations based on the Ksp of the calcium oxalate salt are presented to show its formation and the possible speciation of a Ca-oxalate complex which may affect the Ca++-uptake and ATPase activity.

Animals↗