The copia retrotransposon and horizontal transfer in Drosophila willistoni.

The copia element is a retrotransposon that is hypothesized to have been horizontally transferred from Drosophila melanogaster to some populations of Drosophila willistoni in Florida. Here we have used PCR and Southern blots to screen for sequences similar to copia element in South American populations of D. willistoni, as well as in strains previously shown to be carriers of the element. We have not found the canonical copia element in any of these populations. Unlike the P element, which invaded the D. melanogaster genome from D. willistoni and quickly spread worldwide, the canonical copia element appears to have transferred in the opposite direction and has not spread. This may be explained by differences in the requirements for transposition and in the host control of transposition.

[Laser Doppler flowmetry in differential diagnosis of organic erectile dysfunction].

The aim of this study was to investigate penile microcirculation in patients with erectile dysfunction. Laser doppler flowmetry was performed in 67 patients (mean age 43.9 +/- 1.53 years) with organic erectile dysfunction and in 20 men without erectile dysfunction. It was found that in patients with arteriogenic erectile dysfunction blood flow parameters were subnormal including flux motions. The occlusive test revealed reduced postocclusive reactive hyperemia in patients with arteriogenic erectile dysfunction. Patients with neurogenic erectile dysfunction have signs of sympathetic denervation of microcirculation and decreased respiratory response.

Plant pyruvate dehydrogenase complex purification, characterization and regulation by metabolites and phosphorylation.

The pyruvate dehydrogenase complex was purified from mitochondria of cauliflower, Brassica oleracea var. botrytis floral buds to a specific activity of 5.4 mumol of NADH/min per mg of protein. The pyruvate dehydrogenase complex required CoASH, NAD+, thiamine pyrophosphate and Mg2+ for the oxidative decarboxylation of pyruvate. The kinetic analysis of the complex gave a series of parallel lines for all substrates. Product interaction patterns showed that NADH is competitive with NAD+; acetyl-CoA is competitive with CoASH; and NADH and acetyl-CoA uncompetitive with pyruvate. These kinetic patterns suggest a multisite ping-pong mechanism as described by Cleveland ((1973) J. Biol. Chem 248, 8353). The noncompetitive inhibition of NADH versus CoASH, and acetyl-CoASH versus NAD are not predicted by this mechanism. Regulation of the complex was more sensitive to the NADH/NAD+ ratio than acetyl-CoA/CoASH ratio. Hydroxypyruvate and glyoxylate inhibited the complex noncompetitively versus pyruvate. The pyruvate dehydrogenase complex was inactivated and phosphorylated by ATP. The ATP dependent inactivation is believed to be enzyme catalyzed by a pyruvate dehydrogenase complex kinase. However, no evidence was found for a plant pyruvate dehydrogenase complex phosphatase. The results suggest that the cauliflower pyruvate dehydrogenase complex is regulated by a phosphorylation-dephosphorylation mechanism.

Uptake and Utilization of Sugar Phosphates by Anabaena flos-aquae.

The effect of various sugar phosphates on CO(2) fixation in Anabaena flos-aquae was investigated and found to be very similar to that found for isolated spinach chloroplasts. One exception, glucose 6-phosphate, has a stimulatory effect on CO(2) fixation in Anabaena but not in isolated chloroplasts.Further examination of the role of glucose 6-phosphate metabolism in Anabaena indicates that: (a) this sugar phosphate can be taken up; (b) its uptake is greater in the light than the dark; (c) turnover of glucose 6-phosphate is inhibited in the light; and (d) glucose 6-phosphate can support dark CO(2) fixation. These results are discussed with reference to photosynthesis-related control of glucose 6-phosphate metabolism and the role of glucose 6-phosphate as a source for reducing equivalents and ATP in blue-green algae.

Regulation of plant pyruvate dehydrogenase complex by phosphorylation.

The ATP-dependent inactivation of the pyruvate dehydrogenase complex (PDC) was examined using ruptured mitochondria and partially purified pyruvate dehydrogenase complex isolated from broccoli and cauliflower (Brassica oleracea) bud mitochondria. The ATP-dependent inactivation was temperature- and pH-dependent. [(32)P]ATP experiments show a specific transphosphorylation of the gamma-PO(4) of ATP to the complex. The phosphate attached to the PDC was labile under mild alkaline but not under mild acidic conditions. The inactivated-phosphorylated PDC was not reactivated by 20 mm MgCl(2), dialysis, Sephadex G-25 treatment, apyrase action, or potato acid phosphatase action. However, partially purified bovine heart PDC phosphatase catalyzed the reactivation and dephosphorylation of the isolated plant PDC. The ATP-dependent inactivation-phosphorylation of the PDC was inhibited by pyruvate. It is concluded that the ATP-dependent inactivation-phosphorylation of broccoli and cauliflower mitochondrial PDC is catalyzed by a PDC kinase. It is further concluded that the PDC from broccoli and cauliflower mitochondria is capable of interconversion between an active (dephosphorylated) and an inactive (phosphorylated) form.

Plant Pyruvate Dehydrogenase Complex: II. ATP-Dependent Inactivation and Phosphorylation.

ATP inactivated plant pyruvate dehydrogenase complex (PDC) from broccoli (Brassica oleracea) mitochondria. ATP inactivation of the complex was time-dependent and proportional to the ATP concentration. Time-dependent incorporation of (32)P from [gamma(32)P]ATP into trichloroacetic acid-precipitable protein corresponded to the inactivation of the PDC. It is concluded that plant PDC is phosphorylated and inactivated by a PDC kinase.