Biomedical subjects

R Alva

Publications and source records attributed to R Alva.

4 recordsLinked to original sources

PubMed2003

Evaluation of fipronil spot-on in the treatment of flea allergic dermatitis in dogs.

The purpose of this study was to evaluate the effectiveness of treatment with 10 per cent fipronil solution for controlling signs of flea allergic dermatitis in dogs under field conditions. Thirty-one client-owned dogs with flea allergic dermatitis were treated with three monthly applications of 10 per cent fipronil solution. Flea counts and pruritus were significantly reduced at all post-treatment visits. At the final visit, on day 90, flea counts were reduced by 98 per cent, and pruritus was reduced or eliminated in 84 per cent of the study dogs. Dermatological lesion scores for erythema, crusts, scales and papules were also significantly improved by the final visit. The overall assessment of efficacy on day 90 was 'excellent' to 'good' for 87 per cent of the study dogs. The results demonstrate that treatment with monthly topical applications of 10 per cent fipronil solution is effective in reducing the prevalence and severity of signs of flea allergic dermatitis in dogs.

Administration, Cutaneous↗

PubMed1999

Efficacy of omeprazole paste in the treatment and prevention of gastric ulcers in horses.

Equine gastric ulcer syndrome (EGUS) is very common among performance horses, with a reported prevalence of approximately 90% in racehorses, and also > 50% in foals. Omeprazole, an acid pump inhibitor 5 times more potent than ranitidine, has been used with great success to treat EGUS. This multicentre study of Thoroughbred racehorses with endoscopically verified gastric ulcers was designed to demonstrate the efficacy of an equine oral paste formulation of omeprazole in the treatment and prevention of recurrence of EGUS. Of the 100 horses entered into the study, 25 were sham-dosed for the full 58 days of the study. The remaining 75 horses all received omeprazole paste, 4 mg/kg bwt/day once daily for 28 days. At Day 28, 25 of treated horses continued on this dosing regimen while 25 received a half dose (2 mg/kg bwt once daily) and 25 horses were sham-dosed. By Day 28, gastric ulcers were completely healed in 77% of omeprazole-treated horses, while 92% were significantly (P < 0.01) improved. In contrast, 96% of the sham-dosed horses still had gastric ulcers at Day 28. The improvement was maintained in horses that continued on either a full dose or half dose of omeprazole paste until Day 58. However, in those horses that were removed from omeprazole treatment at Day 28, the incidence and severity of the gastric ulcers at the end of the study were similar to those horses that did not receive the omeprazole paste. This study demonstrates that omeprazole paste, 4 mg/kg bwt per os, once daily, is highly effective in healing gastric ulcers in Thoroughbred racehorses and that either a full dose or half dose of omeprazole paste effectively prevents the recurrence of EGUS. The study also indicates that gastric ulcers in untreated horses did not demonstrate a significant rate of spontaneous healing.

Administration, Oral↗

PubMed1992

Nigericin forms highly stable complexes with lithium and cesium.

Nigericin is a monocarboxylic polyether molecule described as a mobile K+ ionophore unable to transport Li+ and Cs+ across natural or artificial membranes. This paper shows that the ion carrier molecule forms complexes of equivalent energy demands with Li+, Cs+, Na+, Rb+, and K+. This is in accordance with the similar values of the complex stability constants obtained from nigericin with the five alkali metal cations assayed. On the other hand, nigericin-alkali metal cation binding isotherms show faster rates for Li+ and Cs+ than for Na+, K+, and Rb+, in conditions where the carboxylic proton does not dissociate. Furthermore, proton NMR spectra of nigericin-Li+ and nigericin-Cs+ complexes show wide broadenings, suggesting strong cation interaction with the ionophore; in contrast, the complexes with Na+, K+, and Rb+ show only clear-cut chemical shifts. These latter results support the view that nigericin forms highly stable complexes with Li+ and Cs+ and contribute to the explanation for the inability of this ionophore to transport the former cations in conditions where it catalyzes a fast transport of K+ greater than Rb+ greater than Na+.

Biological Transport↗

PubMed1987

Formation of ion-translocating oligomers by nigericin.

At pH 4.0, greater than 10(-7) M nigericin was found capable of conducting net charge transfer across bimolecular lecithin membranes, with a stoichiometry of three uncharged ionophore moieties per cation. At neutral or alkaline pH, nigericin catalyzed the transfer of net charge through dimer forms. In agreement with these results, quantitative analysis of nigericin-potassium complexes formed at pH 4.0 showed a 3:1 ratio, and a 2:1 ratio at neutral or alkaline pH. A 1:1 stoichiometry was observed when the ionophore complex was not transferred from methanol-water to chloroform. Moreover, 1H-NMR spectra of nigericin-cation complexes formed at pH 4.0, displayed clear-cut chemical shift variations different to those observed at neutral or alkaline pH. Thus, it is apparent that acid pH causes a transition from dimeric to trimeric forms of nigericin-cation complexes. The membrane conductance increased up to ten times when negatively charged phosphatidyl glycerol was used, while the conductance decreased in positively charged cetylpyridinium containing membranes at pH 4.0. These results suggest that the nigericin-K+ oligomeric complex is positively charged. In this respect, pKa values around 8.0 were obtained for the nigericin carboxylate group in media of different dielectric constant, indicating that this chemical group is undissociated under these conditions. Moreover, the values for the complex formation constants as well as the delta G values calculated for the dimers and trimers indicated that such ionophore cation oligomeric complexes are thermodynamically stable.

Anti-Bacterial Agents↗