A major isoform of the maize plasma membrane H(+)-ATPase: characterization and induction by auxin in coleoptiles

The plasma membrane (PM) H(+)-ATPase has been proposed to play important transport and regulatory roles in plant physiology, including its participation in auxin-induced acidification in coleoptile segments. This enzyme is encoded by a family of genes differing in tissue distribution, regulation, and expression level. A major expressed isoform of the maize PM H(+)-ATPase (MHA2) has been characterized. RNA gel blot analysis indicated that MHA2 is expressed in all maize organs, with highest levels being in the roots. In situ hybridization of sections from maize seedlings indicated enriched expression of MHA2 in stomatal guard cells, phloem cells, and root epidermal cells. MHA2 mRNA was induced threefold when nonvascular parts of the coleoptile segments were treated with auxin. This induction correlates with auxin-triggered proton extrusion by the same part of the segments. The PM H(+)-ATPase in the vascular bundies does not contribute significantly to auxin-induced acidification, is not regulated by auxin, and masks the auxin effect in extracts of whole coleoptile segments. We conclude that auxin-induced acidification in coleoptile segments most often occurs in the nonvascular tissue and is mediated, at least in part, by increased levels of MHA2.     

Fulminant Guillain-Barré syndrome with universal inexcitability of peripheral nerves: a clinicopathological study

The pathological basis of nerve inexcitability in Guillain-Barré syndrome has not been established with certainty. We report the clinicopathological findings in a 67-year-old patient with fulminant Guillain-Barré syndrome who died 18 days after onset. Three serial electrophysiological studies revealed nerve inexcitability. Antibodies to Campylobacter jejuni were present but there was no antiganglioside reactivity. Spinal root sections revealed extensive and almost pure macrophage-associated demyelination with occasional presence of T lymphocytes and neutrophil leukocytes. Conversely, in femoral, median, and sural nerves the outstanding lesion was axonal degeneration, with some denuded axons remaining. Unmyelinated fibers, posterior root ganglia, and dorsal columns were preserved. Endoneurial postcapillary venules showed plump endothelial cells with loss of their tight junctions. We conclude that both primary demyelination and axonal degeneration secondary to inflammation account for nerve inexcitability. Our findings lend support to the hypothesis of increased endoneurial pressure as the cause of wallerian degeneration in nerve trunks.     

Effect of insulin versus sulfonylurea therapy on cardiovascular risk factors and fibrinolysis in type II diabetes

1. The synthesis and release of nitric oxide may play a role in the pathogenesis of peripheral vasodilatation and hyperdynamic circulation observed in liver cirrhosis. In this work, we analysed the synthesis of nitric oxide by the lympho-mononuclear cells of peripheral blood from patients with chronic alcoholic and non-alcoholic liver disease and we identified the isoform of nitric oxide synthase involved in the increased nitric oxide synthesis. 2. Patients were classified following clinical and histological criteria in non-alcoholic cirrhotic, alcoholic cirrhotic and non-cirrhotic chronic liver disease. We studied clinical and analytical characteristics, haemodynamic parameters and endotoxin levels in these patients. 3. Cirrhotic patients showed an increase of cardiac output and a decrease of peripheral vascular resistance. These patients had higher levels of plasma endotoxin than those observed in the control group. N omega-Nitro-L-arginine methyl ester (L-NAME)-inhibitable nitrite production from mononuclear lymphocyte cells was higher in patients than in the control group, the highest levels being in non-alcoholic cirrhotic patients, and the lowest levels in patients with non-cirrhotic alcoholic liver disease. 4. Immunocytochemistry studies revealed a positive immunoreactivity for the inducible isoform of nitric oxide synthase in lympho-mononuclear cells that was more evident in non-alcoholic than in alcoholic cirrhotic patients. By Northern blot, inducible nitric oxide synthase mRNA expression was observed only in lymphomononuclear cells from non-alcoholic cirrhotic patients. 5. Our patients show a correlation between nitric oxide synthesis, endotoxin levels and haemodynamic parameters. 6. These findings indicate that lympho-mononuclear cell stimulation may play a role in elevated nitric oxide production in hepatic cirrhosis. Thus, this increased nitric oxide synthesis could be implicated in the pathogenesis of the haemodynamic disturbances frequently found in cirrhotic patients. This increase seems to be induced, at least in part, by activation of an inducible isoform of nitric oxide synthase.     

Increase of striatal dopamine release by cadmium in nursing rats and its prevention by dexamethasone-induced metallothionein

Repeated daily intraperitoneal (i.p.) administrations of cadmium (CdCl2, 1 mg/kg per day for 5 days) increased striatal dopamine (DA) release (180% of controls) and turnover (150% of controls) in 13-day-old rats. Cd treatment also increased striatal metallothionein (MT) content (161%), Cd (127%) and lipid peroxidation (LPO, 190%). In addition, Cd treatment decreased striatal tyrosine hydroxylase (TH) activity (-28%), and such an effect may result from D-2 receptor blockade as a consequence of excessive dopamine release, since sulpiride (a specific D-2 receptor antagonist) administration to Cd-treated rats abolished the effect of Cd on TH. No effect was observed on striatal monoamine oxidase (MAO) activity. Dexamethasone (Dx) treatment increased striatal MT content and caused no effect on either DA release or turnover. However, Dx administration prevented the effects caused by Cd, including the increased DA release and enhanced striatal lipid peroxidation. These results indicate that toxic effects on the brain are to be expected as a result of Cd exposure and that Dx administration can attenuate them.     

Aromatic nitrations by mixed acid. Slow liquid-liquid reaction regime

Aromatic nitrations by mixed acid have been selected as a specific case of a heterogeneous liquid-liquid reaction. An extensive experimental programme has been followed using adiabatic and heat-flow calorimetry and pilot reactor experiments, supported by chemical analysis. A series of nitration experiments has been carried out to study the influences of different initial and operating conditions such as temperature, stirring speed and sulphuric acid concentration. In parallel, a mathematical model to predict the overall conversion rate has been developed. In this paper the mathematical modelling and the implementation and experimental validation for benzene, toluene and chlorobenzene mononitration in the kinetic control regime (slow liquid-liquid reaction) are presented and discussed.     

In-laboratory removal of femoral sheath following protamine administration in patients having intracoronary stent implantation

Two hundred twenty-eight patients with successful coronary stent implantation were randomized either to protamine administration and femoral sheath removal (group I, n = 117) or no heparin neutralization and delayed sheath removal (group II, n = 111). The hospital stay after treatment was shorter in patients receiving protamine; therefore, protamine use for neutralizing circulating heparin may be safely administered immediately after stent implantation.     

Membrane-bound calmodulin in Xenopus laevis oocytes as a novel binding site for melatonin

Melatonin has been suggested as a physiological antagonist of calmodulin. In this work, we have characterized melatonin binding sites in Xenopus laevis oocyte membranes. Binding of [125I]melatonin by X. laevis oocyte membranes fulfills all criteria for binding to a receptor site. Binding was dependent on time, temperature, and membrane concentration and was stable, reversible, saturable, and specific. The binding site was also pharmacologically characterized. Stoichiometric studies showed a high-affinity binding site with a Kd of 1.18 nM. These data are in close agreement with data obtained from kinetic studies (Kd=0.12 nM). In competition studies, we observed a low-affinity binding site (Kd=63.41 microM). Moreover, the binding site was characterized as calmodulin. Thus, binding was dependent on calcium and blocked by anti-CaM antibodies in a concentration-dependent manner. Calmodulin inhibitor chlorpromazine also inhibited binding of the tracer. From these results, it is suggested that membrane-bound calmodulin acts as a melatonin binding site in Xenopus laevis oocytes, where it might couple cellular activities to rhythmic circulating levels of melatonin. This hypothesis correlates with the previous findings describing melatonin as a physiological antagonist of calmodulin.