Transformation and regeneration of Brassica rapa using Agrobacterium tumefaciens

Summary Transformation and regeneration procedures for obtaining transgenic Brassica rapa ssp. oleifera plants are described. Regeneration frequencies were increasedby using silver nitrate and by adjusting the duration of exposure to 2,4-D. For transformation, Agrobacterium tumefaciens strain EHA101 containing a binary plasmid with the neomycin phosphotransferase gene (NPT II) and the b-glucuronidase gene (GUS) was cocultivated with hypocotyl explants from the oilseed B. rapa cvs. Tobin and Emma. Transformed plants were obtained within three months of cocultivation. Transformation frequencies for the cultivars Tobin and Emma were 1–9%. Evidence for transformation was shown by NPT II dot blot assay, the GUS fluorometric assay, Southern analysis, and segregation of the kanamycin-resistance trait in the progeny. The transformation and regeneration procedure described here has been used routinely to transform two cultivars of B. rapa and 18 cultivars of B. napus.     

Prostaglandin D2, another renal prostaglandin?

Prostaglandin (PG) D₂ was biosynthesized by rabbit renal papillae incubates in vitro. Quantification of the renal prostaglandins by gas chromatography-mass spectroscopy demonstrated that the concentration of PGD₂ generated by renal papillae was to the amount of PGE₂ or about 1 μg/g tissue/30 min. Infusion of the sodium salt of PGD₂ into the renal artery of the dog produced a dose related increase in renal blood flow and urine flow, free water clearance, sodium excretion and potassium excretion without changes in systemic hemodynamics. At low doses PGD₂ increased renal blood flow to all cortical zones. Higher concentrations of PGD₂ produced a shift in the intrarenal distribution of blood flow toward the juxtamedullary nephrons.     

Nitrogen fixation in hardwood forests of the northeastern United States

Summary Nitrogen-fixing activity in hardwood forests of the northeastern United States occurred in wood litter, greater than 2 cm in diameter. Activity in large dead wood was independent of species, in the case of deciduous wood litter, but was restricted to partially decayed wood with a high moisture content. Maximum rates of activity were observed in the summer months, minimum rates in the winter. Evidence from six stands of varying ages showed that fixation in large wood litter occurred in only 25% of the samples assayed.Fixation was highest in the youngest, 4 years, and oldest, over 200 years, stands; being about 2 kg/ha/yr. The quantity of nitrogen fixed appears to be related to the biomass of dead wood. Large amounts of wood litter in the youngest stands were from slash left after cutting. As the supply of slash is exhausted by decay, nitrogen fixation decreases, with a low around year 20. Fixation then gradually increases as natural thinning adds wood to the litter compartment.Apparently, the amount of nitrogen fixed in dead wood the first 20 years following clearcutting can only replace a modest fraction of the amount lost as a result of the cutting and product removal. Finally, the results indicate that nitrogen fixation in wood litter does not equal nitrogen fixation in a northern hardwood forest calculated using a mass balance approach, suggesting that additional nitrogen inputs exist.     

Piroxicam, a structurally novel anti-inflammatory compound. Mode of prostaglandin synthesis inhibition

Piroxicam is a potent inhibitor of prostaglandin biosynthesis. Experiments utilizing cell culture and microsomes derived from various sources have demonstrated that piroxicam is a selective inhibitor of the cyclooxygenase step of arachidonic acid metabolism. Little blocking activity is observed at the phospholipase, thromboxane or prostacyclin synthetase, and arachidonic acid lipoxygenase steps.     

Ribonucleotide reductase: A structural study of the dimeric iron site

The iron-containing B2 subunit of ribonucleotide reductase from Escherichia coli has been investigated by Raman spectroscopy. Both the tyrosyl radical-containing native protein and the radical-free protein exhibit a resonance-enhanced Raman band at 500 cm^?1. This band is assigned to an Fe-O vibrational mode arising from an oxygen-containing ligand. The failure to observe any tyrosinate ring modes makes it unlikely that ribonucleotide reductase is an iron-tyrosinate protein and rules out tyrosinate oxygen as a ligand. It is proposed that the 500 cm^?1 band in ribonucleotide reductase is analogous to the 510 cm^?1 Fe-O vibrational mode of methemerythrin and arises from an oxo- or carboxylate-bridge between the antiferromagnetically-coupled Fe(III) ions.