A reaction route graph analysis of the electrochemical hydrogen oxidation and evolution reactions

The reaction route (RR) graph approach recently developed by us for complex, non-linear kinetic mechanisms is applied to the hydrogen oxidation and evolution reactions. A corresponding RR graph is constructed and translated into an equivalent electrical circuit network by associating each elementary step with a characteristic resistance for the steady-state case and considering the overall reaction as a power source. It is further shown that the steady-state kinetics of the reaction can be investigated employing the conventional methods of the electrical network theory. Using a set of rate constants for the hydrogen evolution reaction (her) in alkaline solutions from the literature, the dominant RRs are identified and simplified mechanisms and kinetics derived.     

Color Stability of Dry Earth Pigmented Maxillofacial Silicone A-2186 Subjected to Microwave Energy Exposure

PURPOSE: The purpose of this study was to measure spectrophotometrically the color stability of pigmented A-2186 silicone maxillofacial elastomer with 10% by volume of titanium white dry earth opacifier before and after exposure to microwave energy over a simulated 1.5-year period of microwave sterilization. Materials AND METHODS: A-2186 silicone elastomer opacified with titanium white dry earth pigment, pigmented with 5 cosmetic dry earth pigment colors [no pigment (control) group (Pc), red (Pr), yellow ochre (Py), burnt sienna (Po), and a mixture of Pr + Py + Po color group (P3)], was used in this study. Each of the 5 experimental groups consisted of 5 specimens. All specimens were placed in a 250 ml glass beaker filled with 150 ml of water (replenished for each microwave exposure). An exposure of 6 minutes was used 18 times (simulating 1.5 years of microwave sterilization with one 6 minute exposure monthly). Reflectance values were measured by spectrophotometer. Three- and two-way analyses of variance with repeated measures were performed for the color difference (DeltaE*) with the factors of group/color/months, and group/months, respectively. Means were compared by Tukey Honest Significant Difference (HSD) multiple range test calculated at the 0.05 level of significance using SPSS. RESULTS: The trained human eye can detect color changes (DeltaE*) greater than 1.0. Most DeltaE* values of the red pigment group at all intervals and the mixed pigment group at 15- and 18- month intervals increased significantly greater than 1.0 (p < 0.001) compared with the control group. Yellow and burnt sienna groups remained the most color stable over time with DeltaE* values below 0.35. CONCLUSIONS: Lack of color stability of red dry earth pigmented A-2186 silicone maxillofacial elastomers was clinically significant after 12-month exposure to microwave energy as compared with yellow, burnt sienna, and opacified A-2186 dry earth pigments.     

Phosphorus Oxychloride in Organic Synthesis. Part 3: Synthesis of α-Benzoylaminocinnamic Acids

A new approach to the activation of reactants during the condensation of aromatic aldehydes with N-aroylglycines (acting as CH-acids) is described. The condensation reaction carried out on heating in phosphorus oxychloride leads to a high yield of 4-benzylideneoxazol-5-one derivatives. The hydrolysis of these intermediate products yields the target α-benzoylaminocinnamic acids. __________ Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 39, No. 7, pp. 41 – 42, July, 2005.     

Transplantation of microencapsulated bovine chromaffin cells reduces lesion-induced rotational asymmetry in rats

Surrounding bovine chromaffin cells by a semipermeable membrane may protect the transplanted cells from a host immune response and shield them from the inflammatory process resulting from the surgical trauma. Encapsulation of the chromaffin cells was achieved by inter-facial adsorption of a polycation on a polyanionic colloid matrix in which the chromaffin cells were entrapped. Basal and potassium-evoked release of catecholamines from encapsulated bovine chromaffin cells was analyzed over a 4-week period in vitro. Norepinephrine and dopamine release remained constant over time whereas epinephrine release significantly decreased. The chromaffin cells also retained the capacity for depolarization-elicited catecholamine release 4 weeks following the encapsulation procedure. Morphological analysis revealed the presence of intact chromaffin cells with well-preserved secretory granules. Striatial implantation of chromaffin cell-loaded capsules significantly reduced apomorphine-induced rotation compared to empty polymer capsules in animals lesioned with 6-hydroxydopamne frr at least 4 weeks. Intact chromaffin cells expressing tyrosine hydroxylase and dopamine-β-hydroxylase were observed in all capsules implanted in the striatum for 4 weeks. The assessment of the clinical potential of transplanting encapsulated adrenal chromaffin cells of either allo- or xenogeneic origin for Parkinson's disease will require long-term behavioral studies. The present study suggests, however, that the polymer encapsulation procedure may offer an alternative to adrenal autografts as a source of dopaminergic tissue.     

Steroids in Duchenne muscular dystrophy--deflazacort trial

We conducted a double blind controlled trial in 28 Duchenne muscular dystrophy (DMD) patients with Deflazacort (DF), an oxazoline derivative of prednisolone which reduces its side-effects. Myometric muscle strength measurements, Scott Score and timed tests showed statistically significant improvement for the treated group (P less than 0.05). Side-effects after 9 months of treatment included mild cushingoid appearance in four patients (28%) and moderate in only one (7%), increased appetite in seven (50%), increased body hair in four (28%), irritability and hyperactivity in three (21%). Increased body weight was not prominent and was controlled with dietary measures. No patient had to be withdrawn from medication. More research and long-term follow-up are needed in order to establish the mechanism of improvement and the consequences of long-term steroid administration in DMD. In this regard DF appears as an alternative to prednisone preserving its benefits but with fewer side-effects.     

Motor activity and neurotransmitter release in the gastric fundus of streptozotocin-diabetic rats.

As deficiencies of the cholinergic and non-adrenergic non-cholinergic innervation of the gastrointestinal tract have been described in diabetic rats, we studied the simultaneous release of, and muscular response to, acetylcholine, vasoactive intestinal polypeptide and adenosine-5'-triphosphate in isolated preparations of gastric fundus from control and 8-week streptozotocin-treated diabetic rats. Muscular responses were measured in longitudinal muscle strips prepared from one half of the gastric fundus and release was studied in the other half. The contractile response to acetylcholine and electrical field stimulation was not different in control and diabetic rats. In the presence of atropine, and when tone was increased with prostaglandin F2 alpha, electrical field stimulation, vasoactive intestinal polypeptide and adenosine-5'-triphosphate induced relaxation with a similar response in control and diabetic rats. The basal release of acetylcholine, vasoactive intestinal polypeptide and adenosine-5'-triphosphate was not significantly different in control and diabetic rats. Electrical field stimulation significantly increased the release of the three substances and this increase was tetrodotoxin-sensitive. While the stimulation-induced increase of acetylcholine and vasoactive intestinal polypeptide was not different in control and in diabetic rats, the stimulation-induced release of adenosine-5'-triphosphate increased 3-fold in diabetic compared to control gastric fundus. Desensitization to alpha,beta-methylene adenosine-5'-triphosphate reduced the relaxant response to adenosine-5'-triphosphate and to electrical field stimulation, suggesting a role of adenosine-5'-triphosphate in non-adrenergic non-cholinergic neurotransmission of rat gastric fundus. The reduction of the non-adrenergic non-cholinergic relaxation by alpha,beta-methylene adenosine-5'-triphosphate was greater in diabetic tissues. This, with the increase in stimulation-induced adenosine-5'-triphosphate release, suggests that the purinergic component of the vagal non-adrenergic non-cholinergic response of the stomach may be increased in diabetics.     

Altered excitatory and inhibitory amino acid receptor binding in hippocampus of patients with temporal lobe epilepsy.

We examined binding to excitatory amino acid and inhibitory amino acid receptors in frozen hippocampal sections prepared from surgical specimens resected from 8 individuals with medically refractory temporal lobe epilepsy. The excitatory receptors studied included N-methyl-D-aspartate (NMDA), strychnine-insensitive glycine, phencyclidine, and quisqualate. The inhibitory receptors studied were gamma-aminobutyric acid type A (GABAA) and benzodiazepine. Excitatory and inhibitory amino acid receptor binding were differentially altered in the patients with temporal lobe epilepsy in comparison to 8 age-comparable autopsy control subjects, and changes in receptor binding were regionally selective in four areas. Binding to phencyclidine receptors associated with the NMDA channel was reduced by 35 to 70% in all regions in the hippocampi of the patients. In contrast, binding to the NMDA recognition site and its associated glycine modulatory site was elevated by 20 to 110% in the cornu ammonis (CA) 1 area and dentate gyrus of the hippocampus of the patients. Binding to these sites was unaffected in area CA4. Binding to the quisqualate-type excitatory amino acid receptor was unchanged in all regions except the stratum lacunosum moleculare CA1, where it was increased by 63%. GABAA and benzodiazepine receptor binding was reduced by 20 to 60% in CA1 and CA4, but unchanged in dentate gyrus. The data indicate that excitatory and inhibitory amino acid receptors are altered in the hippocampus of patients with temporal lobe epilepsy.     

Increased lymphocyte beta-adrenergic receptor density in progressive multiple sclerosis is specific for the CD8+, CD28- suppressor cell.

Beta-adrenergic receptor density on T cells from healthy humans is greatest on suppressor cells (CD8+, CD28-) and the effect of catecholamines, secreted by the sympathetic nervous system, predominates on this subset. The sympathetic skin response, a measure of sympathetic nervous system function, is absent in most patients with chronic progressive multiple sclerosis (MS). We measured beta-adrenergic receptor density on suppressor cells, cytotoxic cells, and monocytes from patients with chronic progressive MS and healthy control subjects. Control receptor density on suppressor cells was 2.8 +/- 0.3 fmol/10(6) cells versus a density of 5.1 +/- 0.7 fmol/10(6) cells for patients. Cytotoxic cell (CD8+, CD28+) receptor density was 1.4 +/- 0.4 fmol/10(6) cells in control subjects and 0.9 +/- 0.3 fmol/10(6) cells in the patients. Monocytes displayed beta-adrenergic receptor densities of 2.6 +/- 0.4 fmol/10(6) cells in normal individuals and 2.7 +/- 0.4 fmol/10(6) cells in the patient group. CD8 lymphocyte beta-adrenergic receptor densities in patients with relapsing-remitting and those with stable MS were not different from control values, yet were significantly less than the values for patients with chronic progressive MS. We find that mononuclear cells from healthy control subjects and patients with chronic progressive MS proliferate in response to 200 units/ml of recombinant human interleukin-2 (IL-2) similarly. However, IL-2 treatment increased beta-adrenergic receptor density on normal mononuclear cells, but failed to increase it on mononuclear cells from patients with chronic progressive MS.(ABSTRACT TRUNCATED AT 250 WORDS)