Characterization of Mass Transfer within the Crystal-Solution Boundary Layer of l-Alanine {120} Faces Using Laser Interferometry during Growth and Dissolution.

Crystallization and dissolution are important processes to consider in drug development as well as many other industrial processes. Many current growth and dissolution models are based on bulk solution properties and do not implicitly consider concentration variation close to the crystal surface-solution interface and how this is mediated by solute diffusive mass transfer. Solution boundary layer thickness and concentration distribution, for the {120} crystal habit face of single crystals of l-alanine in saturated aqueous solutions during both growth and dissolution processes, is measured as a function of super/undersaturation using a Mach-Zehnder optical interferometer system. Further analysis allows determination of the diffusion coefficient and mass flux within the boundary layer as well as whether the processes are controlled by mass transfer or crystal interfacial kinetics. The measurement of this study revealed that the {120} face was not saturated at its surface during growth or dissolution meaning both processes were somewhat limited by their crystal interfacial kinetics. Growth was limited by crystal interfacial kinetics at all supersaturations to the same degree, whereas dissolution had a mixed dependency on crystal interfacial kinetics and mass transfer at lower undersaturations becoming more limited by mass transfer at higher undersaturations. Boundary layer thickness increased with super/undersaturation but to a lesser degree than the increase in the concentration difference between the crystal surface and bulk solution leading to a higher mass flux of solute molecules through the boundary layer. At the same relative super/undersaturation mass flux of solute molecules was faster during dissolution which was concurrent with its increased surface to bulk solution concentration difference and boundary layer thickness.

Southeastern plants toxic to ruminants.

Selected toxic plants affecting cattle, sheep, and goats in the southeastern United States are presented. The author's intention is to provide veterinary practitioners and students with an overview of plant poisoning in the region. Plants are grouped by body system affected, based on clinical signs and/or lesions.

Concentration and bioavailability of ciprofloxacin and teicoplanin in the cornea.

PURPOSE: To investigate the concentration and bioavailability of ciprofloxacin and teicoplanin in the cornea. METHODS: A biological assay was developed with corneal tissue used as a carrier for the antimicrobial. Concentration and biological activity were determined with a chemical assay and zone of inhibition (ZOI) around corneal samples with epithelial and endothelial surfaces in contact with the indicator organism. Patients undergoing penetrating keratoplasty received ciprofloxacin 0.3% or teicoplanin 1%. RESULTS: There were good correlations between antimicrobial concentration and ZOI, when either filter paper or corneal discs were used (R(2) > 92%). Of 33 patients, the mean (median) concentration of ciprofloxacin in the cornea was 1.37 mg/L (0.46 mg/L) and 1.89 mg/L (1.44 mg/L; bioassay) in the epithelial and endothelial orientations, respectively, and 14.87 mg/L (7.41) in the cornea and 0.51 mg/L (0.42) in the aqueous (chemical assay). For teicoplanin, the mean (median) concentration in the cornea was 9.58 mg/L (0 mg/L) in the epithelial and 4.78 mg/L (0 mg/L) in the endothelial orientations (bioassay). In the chemical assay, teicoplanin could not be detected in the cornea or aqueous at the lower limit of detection of 3.6 mg/L. CONCLUSIONS: The ZOI produced by corneal tissue provides a potential bioassay of antimicrobial activity and concentration. Although in contrast to teicoplanin ciprofloxacin shows good corneal penetration, with high endothelial-to-epithelial levels, only approximately 10% of measured levels in a chemical assay are available, according to a bioassay. Teicoplanin shows relatively poor corneal penetration through intact epithelium. These methods may be useful in evaluating the biological activity across the cornea of antimicrobials introduced into ophthalmic practice to deal with changing bacterial resistance.

Pharmacokinetics of vancomycin following intracameral bolus injection in patients undergoing phacoemulsification cataract surgery.

AIM: To determine the elimination kinetics of intracameral vancomycin administered as a bolus injection at the end of phacoemulsification cataract surgery. METHODS: Vancomycin 1 mg/0.1 ml saline solution was administered to 19 patients by intracameral bolus injection at the end of routine cataract surgery. The aqueous concentration of vancomycin was determined in nine patients 1 minute after administration and in 10 patients 18-24 hours postoperatively. Aqueous samples were obtained by inserting a Rycroft cannula into the anterior chamber via the side port incision. Fluorescence polarisation immunoassay was used to calculate the aqueous vancomycin concentration. RESULTS: The median (interquartile range) vancomycin concentration was 5458 (4756-6389) mg/l at 1 minute and 40.6 (25.9-47.1) mg/l 18 to 24 hours (median 19 hours) postoperatively. The vancomycin concentration exceeded the minimum inhibitory concentration (MIC) of endophthalmitis-causing gram-positive bacteria by a factor of 4 for up to 26 hours postoperatively. No adverse event or reaction was noted. CONCLUSION: Following bolus intracameral injection at the end of cataract surgery the concentration of vancomycin in the anterior chamber vastly exceeds its MIC for at least 24 hours but is predicted to fall below the MIC after 33 hours.

Treatment of refractory vernal ulcers with large-diameter bandage contact lenses.

PURPOSE: To report two cases of refractory vernal ulcers in which the fitting of a large-diameter (22 mm) hydrogel (Contaflex T75) bandage contact lens (BCL) ameliorated the signs and symptoms of the condition. METHODS: Two patients with refractory vernal ulcers are described. Mechanisms of the effect of a large-diameter lens across the ocular surface are discussed in this condition. RESULTS: The first patient is a 10-year-old boy who had been treated unsuccessfully for a left vernal corneal ulcer with topical prednisolone 0.5% and olopatadine. The vernal ulcer resolved 2 weeks after the fitting of a large-diameter BCL. The second patient is a 4-year-old boy who had been intolerant of all his previous topical medications partly because of his ocular discomfort in association with the right vernal ulcer. A large-diameter BCL was fitted in his right eye. The BCL was removed 2 weeks later with complete healing of the corneal vernal ulcer. Owing to his improved comfort, the patient was able to tolerate topical prednisolone 0.5% drops. CONCLUSIONS: Large-diameter BCLs may be a useful treatment option in the management of refractory vernal ulcers.

Toxicity of Insecticides and Skin Care Products of Botanical Origin.

Abstract- Toxicoses associated with products which are derived from plants and then used as insecticides and skin care/grooming aids on animals, are reviewed. These include pyrethrins, pyrethroids, rotenone, pennyroyal oil, d-limonene, linalool and melaleuca oil. Poisoning is uncommon and generally results from exposure to concentrations stronger than that recommended by the manufacturer. Pyrethrins and pyrethroids may cause excessive salivation, tremors, ataxia, depression, hyperexcitability/hyperactivity, seizures, dyspnea and rarely death of the animal. Ingestion of rotenone by licking may induce vomiting in dogs and cats. d-Limonene may cause excess salivation, marked hypothermia, shivering and ataxia in cats, and dermal exposure of cats to a spray containing linalool, d-limonene and piperonyl butoxide at 5 and 10 times normal concentration has caused depression and recumbency lasting for several DAys. This was followed by recovery without treatment. Melaleuca oil has been associated with ataxia, incoordination, weakness, tremors and depression. Bathing with a mild detergent, treatment of associated signs, and providing supportive care are usually adequate therapy for these toxicoses. An exception is pennyroyal oil which is hepatotoxic. Résumé- Les toxicités des produits d'origine végétale utilisés comme insecticides et comme topiques dermatologiques chez l'animal sont présentées. Ces produits comprennent les pyréthrines, les pyrethinoïdes, la roténone, l'huile de poulior, la citronnelle, le linalcool, et l'huile de melaleuca. Les intoxications sont rares et résultent généralement de l'exposition à des concentrations supérieures à celles recommandées par le fabricant. Les pyréthrines et les pyrethrinoïdes peuvent entraïner une siallhorée, des tremblements, une ataxie, un abattement, une hyperexcitabilité/hyperréactivité, des convulsions, une dyspnée, et rarement la siallhorée, une hypothermie marquée, des tremblements, et une ataxie chez le chat, et la pulvérisation de chats avec un aérosol contenant du linalool, de la citronnelle et du butoxyde de piperonyl à des concentrations 5 à 10 fois supérieures à la normale à provoqué un abattement et une prostration qui a duré plusieurs jours. Ceci a été suivi par une guérison sans traitement. L'huile de melalcuca a provoqué parfois ataxie, incoordination, faiblesse, tremelements et abattement. Les traitements indiqués lors d'intoxication associent un lavage avec un détergent doux, un traitement symptomatique et une réanimation. L'huile de poulior est une exception car elle est hépatotoxique. [Nicholson, S. S. Toxicity of insecticides and skin care products of botanical origin (Toxicité des insecticides et des produits dermatologiques d'origine végétale). Resumen- Se revisan las toxicosis asociadas a compuestos derivados de plantas y utilizados como insecticidas y productos dermatológicos o de cuidado de la piel en animales. En éstos se incluyen piretrinas, piretroides, rotenona, aceite de Mentha pulegium, D-limoneno, linanol y aceite de maleleuca. Las intoxicaciones son infrecuentes y son a menudo debidas uso de concentraciones mayores a las recomendadas por el productor. Las piretrinas y los piretroides pueden causar hipersialia, temblores, ataxia, depresión, hiperexcitabilidad, hiperactividad, ataques, dispnea y ocasionalmente muerte del animal. La ingestión de rotenona por lamido puede inducir el vómito en perros y gatos. El D-limoneno puede causar exceso de salivación, fuerte hipotermia, temblores y ataxia en gatos; la exposición de la piel del gato a un pulverizador con linalol, D-limoneno y butóxido de piperonilo a concentraciones 5 o 10 veces superior a la normal provocó depresión y postración de varios dias de duración. La recuperación a este cuadro fue completa sin tratamiento. El aceite de malaleuca se ha asociado con ataxia, incoordinación, debilidad, temblores y depresión. El traitamiento de estas toxicosis consiste en bañar al animal con un detergente suave, un tratamiento sintomático y teriapia de soporte. Una excepción a ésto es el aceite de Mentha pulegium, que es hepatotóxico. [Nicholson, S. S. Toxicity of insecticides and skin care products of botanical origin (Toxicidad de los insecticidas y productos dermatológicos de origen botánico).