Effects of a brassinosteroid on growth and electrogenic proton extrusion in maize root segments

In apical or subapical root segments of maize ( Zea mays L. cv. Dekalb XL640), 10⁻⁷–10⁻⁵ M 24-epibrassinolide (BR), a physiologically active synthetic epimer of the pollen hormone brassinolide, induces a significant stimulation of root growth, associated with an increase of acid secretion. The increase in acid secretion is enhanced by the presence of K⁺ in the medium and is accompanied by an early, significant hyperpolarization of the transmembrane electric potential (PD), which is completely suppressed by the addition of the protonophore uncoupler FCCP. Similar effects of BR have earlier been reported for shoots, and also for IAA in shoots. Contrariwise, 10⁻⁸–10⁻⁷ M IAA inhibits acid secretion and depolarizes the PD in the maize root segments. This suggests different pathways for the action of the two different hormones on the proton pump.     

Periodate oxidation products derived from methylated alpha-amanitin: evidence for distinct aldehydic and non-aldehydic forms.

Amatoxins are cyclic octapeptides which can be purified from various mushroom species. They have found widespread use due to their potent inhibition of eukaryotic RNA polymerase II. In the course of our efforts to prepare additional semisynthetic derivatives of the amatoxin, alpha-amanitin, we examined the products formed through the periodate oxidation of 6'-O-methyl-alpha-amanitin. Periodate oxidation under conditions of near-neutral pH yielded two chemically similar, yet chromatographically separable, products. On the basis of their proton NMR spectra and their lack of reactivity with sodium chlorite these products did not contain a free aldehydic group. However, both forms were interconvertible in aqueous neutral solution and could be converted to the same product, 6'-O-methyldemethyl-gamma-amanitin, through reduction with sodium borohydride. Periodate oxidation under mildly acidic conditions generated a single product which has properties of a free aldehyde. It exhibited a proton NMR spectrum with signals characteristic of an aliphatic aldehyde and was readily oxidized to the carboxylic acid with sodium chlorite. Conditions have been defined to synthesize the free aldehyde derivative of 6'-O-methyl-alpha-amanitin in generous yield to provide a precursor for oxidation and further derivatization.     

GISH-based comparative genomic analysis in Urochloa P. Beauv.

The genus Urochloa P. Beauv. [syn. Brachiaria (Trin.) Griseb.] comprises species of great economic relevance as forages. The genomic constitution for the allotetraploid species Urochloa brizantha (cv. Marandu) and Urochloa decumbens (cv. Basilisk) and the diploid Urochloa ruziziensis was previously proposed as BBB¹B¹, B¹B¹B²B² and B²B², respectively. Evidence indicates U. ruziziensis as the ancestral donor of genome B² in U. decumbens allotetraploidy, but the origin of the genomes B and B¹ is still unknown. There are diploid genotypes of U. brizantha and U. decumbens that may be potential ancestors of the tetraploids. The aim of this study was to determine the genomic constitution and relationships between genotypes of U. brizantha (2x and 4x), U. decumbens (2x and 4x) and U. ruziziensis (2x) via genomic in situ hybridization (GISH). Additionally, chromosome number and genome size were verified for the diploid genotypes. The diploids U. brizantha and U. decumbens presented 2n?=?2x?=?18 chromosomes and DNA content of 1.79 and 1.44 pg, respectively. The GISH analysis revealed high homology between the diploids U. brizantha and U. decumbens, which suggests relatively short divergence time. The GISH using genomic probes from the diploid accessions on the tetraploid accessions’ chromosomes presented similar patterns, highlighting the genome B¹ present in both of the tetraploids. Based on GISH results, the genomic constitution was proposed for the diploid genotypes of U. brizantha (B¹B¹) and U. decumbens (B¹′B¹′) and both were pointed as donors of genome B¹ (or B¹′), present in the allotetraploid genotypes.

     

Effect of lyso-phosphatidylserine on rat hypothalamic cAMP, in vivo

Lyso-Phosphatidylserine, like its precursor phosphatidylserine, increases the concentration of cAMP in the rat hypothalamus. The effect is dose-dependent and reaches its maximum 10–20 minutes from the injection. Antiadrenergic drugs, such as reserpine, α-methyl-p-tyrosine (α-MpT), haloperidol and chlorpromazine, but not phentolamine or propranolol, prevent the accumulation of hypothalamic cAMP induced by lysophosphati dylserine. Serotoninergic, histaminergic, cholinergic and GABAergic drugs do not modify the lyso-phosphatidylserine effect. The obtained results suggest a primary involvement of the dopaminergic system in the mediation of the pharmacological effect of lyso-phosphatidylserine.     

Functional properties of Hb-J Calabria, beta 64 (E8) Gly-Asp

A young male from Apulia region (Southern Italy), heterozygous carrier of Hb-J Calabria (beta 64(E8) Gly-Asp), was described here. He showed mild polycythemia, and his whole blood dissociation curve for oxygen was clearly left-shifted, with a decreased p50. But these characteristics were not only due to the hyperaffinity of the abnormal pigment, accounting for about one third of the total Hb; in fact, also Hb-A, the main pigment present, had relative hyperaffinity. Nevertheless, this subject was completely symptomless, suggesting that the abnormal Hb was almost completely excluded from respiratory exchange and traveled always oxygenated also in the venous-capillary bed. However, the level reached by Hb-A furnished a satisfactory functional compensation against tissue hypoxia.     

Caffeine antagonizes several central effects of diazepam

In spinal cats, caffeine (3–30 mg·kg^?1 i.v.) reduced the increase of dorsal root potentials (DRPs) caused by diazepam (0.1–1 mg·kg^?1 i.v.) without affecting the prolongation of DRPs evoked by phenobarbitone (10–20 mg·kg^?1 i.v.). Caffeine antagonized the depression by diazepam, but not that by phenobarbitone, of the ventral root-evoked Renshaw cell discharge. In unrestrained cats, 50 mg·kg^?1 caffeine i.p. abolished the elevation induced by 1 mg·kg^?1 diazepam i.p. of the threshold for eliciting a rage reaction by stimulation of the lateral hypothalamus, but was ineffective against the threshold increase caused by 20 mg·kg^?1 phenobarbitine i.p. In the horizontal wire test in mice, caffeine was more potent in reversing the depression of performance induced by diazepam that that by phenobarbitone (ED50 1.8 mg·kg^?1 and 139 mg·kg^?1 p.o., respectively). The reduction of skeletal muscle tone in mice produced by diazepam was antagonized by low doses of caffeine (ED50 0.53 mg·kg^?1 p.o.). While caffeine at low doses (0.3-3 mg·kg^?1 p.o.) abolished the anticonflict effect of diazepam in rats, high doses (ED50 160 mg·kg^?1 p.o.) were necessary to antagonize the anticonvulsant effect of diazepam on pentylene-tetrazole-induced seizures in mice. The interaction between caffeine and diazepam is not due to a competition at the benzodiazepine receptors but may involve purinergic mechanisms.     

Brain cortex phosphatidylserine inhibits phosphatidylinositol turnover in rat anterior pituitary glands

The in vitro effect of bovine brain cortex phosphatidylserine on 32Pi incorporation into phosphatidylinositol, phosphatidylcholine, and phosphatidylethanolamine of rat anterior pituitary glands was studied. Phosphatidylserine (0.1 to 66.6 microM) decreased the incorporation of 32Pi into phosphatidylinositol, but not phosphatidylcholine or phosphatidylethanolamine, in a concentration-related manner. The inhibitory effect of phosphatidylinositol was similar to that of dopamine in the same experimental conditions. The combined effects of submaximal concentrations of dopamine and phosphatidylserine elicited an apparently additive inhibitory effect on phosphatidylinositol synthesis. The inhibitory effect of phosphatidylserine was completely reversed by haloperidol and sulpiride and only partially by pimozide, antidopaminergic agents which per se do not affect phosphatidylinositol synthesis. The stimulatory effect of TRH to increase 32Pi incorporation into phosphatidylinositol was decreased by phosphatidylserine. These observations suggest that the decrease in prolactin release in the presence of phosphatidylserine may be evoked through a dopaminergic mechanism.     

Induction by carrot allelochemicals of insecticide-metabolising enzymes in the southern armyworm (Spodoptera eridania)

Carrot foliage monoterpenes induce cytochrome P-450 up to 2.9-fold, NADPH cytochrome c (P-450) reductase up to 1.6-fold, NADPH-oxidation up to 3.8-fold, aldrin epoxidation up to 1.5-fold in southern armyworm larval midgut tissues when incorporated in their diet at 0.2% for 3 days. Stigmasterol and ergosterol did not substantially induce microsomal oxidase activities and significantly inhibited GSH S-aryltransferase activity and sulfotransferase activity. Coumarin did not substantially affect microsomal oxidase and sulfotransferase activity but is the most potent inducer of GSH S-aryltransferase activity, increasing this activity 7-fold. None of the chemicals is acutely toxic to the sixth instar larvae or affect the larval weight gain except coumarin which significantly depressed the maximal body weight attained.     

Improved synthesis and purification of methylated amanitins using diazomethane

We have examined the conditions of methylating alpha-amanitin with diazomethane with the intent of producing 6'-O-methyl-alpha-amanitin (meAMA). Under the appropriate conditions meAMA was afforded as the sole product in nearly quantitative yield. By exceeding the stoichiometries designed for optimal meAMA synthesis, a dimethylated amanitin, 1'-N-, 6'-O-dimethyl-alpha-amanitin (dimeAMA), was also produced. Both products were characterized, following HPLC, by ultraviolet and n.m.r. spectroscopy. Based upon their inhibitory potential against wheat germ RNA polymerase II, apparent dissociation constants of 4.3 nM and 5.4 nM were estimated for meAMA and dimeAMA, respectively.