Evidence for direct arrhythmogenic action of endothelin.

We studied electrophysiological effects of endothelin on canine cardiac tissues. Endothelin prolonged action potential duration and decreased spontaneous firing rate of the right bundle branch cells. At a concentration of 2 x 10(-7)M the plateau phase of action potentials was flattened, followed by the abrupt occurrence of early afterdepolarizations (EADs). ET, at a concentration as low as 2 x 10(-9)M, was capable of inducing EADs although their incidence was low. The EADs were initiated from the membrane potential less negative than -30mV and were suppressed by nicardipine, suggesting the involvement of dihydropyridine-sensitive Ca2+ channels in the induction of EADs. Because EADs are considered to underlie certain types of arrhythmias endothelin per se may have arrhythmogenic action.     

Modulation of glutamate-induced uncompetitive blocker binding to the NMDA receptor by temperature and by glycine

The effect of temperature on the binding of [3H]-N-[1-(2-thienyl)cyclohexyl]piperidine [( 3H]TCP) to the ion channel of the N-methyl-D-aspartate (NMDA) receptors was studied in washed rat brain-cortex membranes. Raising the temperature from 5 to 33 degrees C resulted in a significant increase in the association rates of [3H]TCP binding measured in the presence of 1 microM glutamate and 1 microM glycine, but was less effective in the absence of the added agonists. No such effects of temperature on the dissociation rates of [3H]TCP-receptor complexes were observed. In the absence of agonists, neither the association nor the dissociation binding components varied with temperature, suggesting a diffusion-controlled limitation of access of the ligand to its site within the nonactivated NMDA receptor. No evidence was found for a temperature-dependent change in the density of [3H]TCP binding sites or for heterogeneity of [3H]TCP binding sites associated with the NMDA receptor, even though when approaching equilibrium the binding kinetics in the presence of glutamate and glycine deviated from an ordinary bimolecular reaction scheme. The data were fitted instead to a two-exponent binding function, comprising the sum of a fast and a slow binding component. Their corresponding time constants exhibited an increase with temperature, and the increase of each one was correlated significantly with the corresponding decrease in the equilibrium binding constant; however, there was no temperature-related change in the relative proportions of the two components, with the fast binding component (alpha) accounting for 50-70% of the site population.(ABSTRACT TRUNCATED AT 250 WORDS)     

Curvularia clavata as an aetiological agent of human skin infection

Curvularza cfavata was cultured from skin lesions in a 20-year-old female. The morphological characteristics of the isolate are described. The isolate was sensitive to clotrimazole at a minimum inhibitory concentration of 5 μg/ml.     

Effects of hyperthermia and photodynamic therapy on BALB/c mice bearing subcutaneous tumors

The therapeutic effects of photodynamic therapy and hyperthermia on mice bearing subcutaneous tumors were investigated. Ehrlich ascites tumor cells (1 x 10(7)) were implanted subcutaneously into the femoral area of BALB/c mice. A total of 134 tumor-bearing mice were treated with photodynamic therapy, i.e., administration of laser irradiation (514.5 nm, 112.5 mW/cm2 for 11.12 min with a total energy 75 J/cm2) after injection (i.p.) of hematoporphyrin derivative (HPD, 7.5 and 10.0 mg/kg body weight) and/or hyperthermia (by electric heating needles to 44 and 45 degrees C for 30 min) once a day for three successive days. The results revealed that the therapeutic effects of the combination of photodynamic therapy and hyperthermia were improved when compared with photodynamic therapy or hyperthermia alone. A combination of photodynamic therapy (10.0 mg HPD/kg body weight and 75 J/cm2 of total laser irradiation energy) and hyperthermia (44 degrees C for 30 min) had the best therapeutic effect, indicating that the mortality rate within 120 days (MR120) was 12.5% and the mean survival time (MST120) was 113.8 days.     

Reinvestigation of phosphorylation of tRNA in Escherichia coli.

This report shows the results of the reinvestigation of tRNA phosphorylation in E. coli. The phosphorylation did not occur on suppressor seryl-tRNA but occurred on other tRNA species. The activity of tRNA phosphorylation was found in E. coli extracts and partially purified. On DEAE-Sephadex A50 and PAGE gel, the phosphorylated-tRNA showed a pattern different from that the natural suppressor serine tRNA.     

Chemo- and karyotaxonomic studies on some rhizomatous species of the genusSymphytum (Boraginaceae)

InS. tuberosum subspp.tuberosum andnodosum, S. grandiflorum andS. ibericum the presence of the pyrrolizidine alkaloids lycopsamine, echimidine and symphytine could be demonstrated. The taxonS. tuberosum contains an unknown compound that seems to be specific for this taxon. This compound is not the pyrrolizidine alkaloid anadoline which has previously been reported for this species. It is possibly represented by a peak on GC/MS with a molecular ion peak at m/z 623 (as TMS derivative) and can be used as a chemotaxonomic marker for the speciesS. tuberosum. The pyrrolizidine alkaloid pattern of the two subspecies ofS. tuberosum reinforces the close relationship. Fresh material ofS. tuberosum contained the triterpene isobauerenol, but in herbarium material isobauerenol was lacking. InS. grandiflorum, neither fresh nor dried material contains isobauerenol. In herbarium material ofS. ibericum also no isobauerenol could be found. More extensive chemotaxonomical research is necessary to support the view thatS. abchasicum is more closely related toS. ibericum than toS. grandiflorum.     

Cionin: a disulfotyrosyl hybrid of cholecystokinin and gastrin from the neural ganglion of the protochordate Ciona intestinalis

We have purified an acidic octapeptide from the neural ganglion of the protochordate Ciona intestinalis by a three-step procedure including C18 Sep-Pak fractionation, MonoQ ion-exchange chromatography, and C4 reversed-phase high-performance liquid chromatography. The purification was monitored by an immunoassay specific for the alpha-carboxyamidated COOH terminus common to the mammalian brain-gut hormones, cholecystokinin and gastrin. Automated Edman degradation revealed the sequence Asn-Tyr-Tyr-Gly-Trp-Met-Asp-Phe. In accordance with the high acidity of the peptide, amino acid analysis after cleavage with aminopeptidase M showed that both tyrosyl residues are sulfated. Hence, the structure is Asn-Tyr(SO3)-Tyr(SO3)-Gly-Trp-Met-Asp-Phe-NH2, as also confirmed by identity with the synthetic disulfated peptide in different chromatographic systems. The occurrence of two consecutively sulfated tyrosyl residues after a neutral residue challenges present concepts of consensus sites for tyrosyl sulfation. We conclude that the structure of the peptide, named cionin, suits that of a common ancestor for cholecystokinin and gastrin.     

Side reaction in peptide synthesis. Formation of oxazolidone derivatives

2-Oxazolidone derivatives formed through an intramolecular reaction in the process of alkaline treatment of urethane-type N-protected peptides of which the N-terminal residues were Ser or Thr having unprotected hydroxyl groups. In oder to avoid this side reaction, the esters of these peptides could be cleaved by enzymatic hydrolyses instead of saponification.     

Salt tolerant sugarbeet progeny from tissue cultures challenged with multiple salts

Lines of sugarbeet (Beta vulgaris L.) tolerant of multiple salts was accomplished by an in vitro multiple salt challenge. Petioles were placed on RV medium amended with 5 different salts along with Murashige and Skoog base salts for one month. Surviving shoots were cultured on RV medium to obtain petioles for subsequent challenges. During the first, second and third challenges, organogenically regenerated shoots developed from 5%, 46%, and 80% of the petioles, respectively. After the third multiple salt challenge, tolerant shoots were rooted and transplanted in soil. Salt was added to this soil at 1.0% by weight and plants were observed for 2 months. The ten most salt tolerant plants were vernalized to obtain seed. The R₁ seed and controls were planted in soil containing 0%, 0.61% or 0.77% multiple salts per dry soil weight. Emergence of R₁ seedlings was significantly greater than the controls under salt stress. Multiple salt tolerant R₁ plants were maintained in salt amended soil to the 8–10 leaf stage and appeared as healthy and vigorous as the control growing in salt free soil.Contribution from Missouri Agricultural Experiment Station Journal Series No. 10948. University of Missouri, Columbia, MO, USA Mention of trade names does not constitute a guarantee or warranty of the product by University of Missouri of Holly Sugar Corporation and does not imply their approval to the exclusion of other products.