Abnormal strategies during visual discrimination reversal learning in ephrin-A2(-/-) mice.

Eph receptors and ephrins are involved in establishing topographic connectivity in primary sensory brain regions, but also in higher order structures including the cortex and hippocampus. Ephrin-A2(-/-) mice have abnormal topography in the primary visual system but have normal visual and learning performance on a simple visual discrimination task. Here we use signal detection theory to analyse learning behaviour of these mice. Wild-type (WT) and ephrin-A2(-/-) (KO) mice performed equally well in a two-stimulus visual discrimination task, with similar learning rates and response latencies. However, during reversal learning, when the rewarded stimulus was switched, the two genotypes exhibited differences in response strategies: while WTs favoured a win-stay strategy, KOs remained relatively neutral. KOs also exhibited a stronger lateralization bias in the initial stages of learning, choosing the same arm of the maze with high probability. In addition, use of a Bayesian "optimal observer" revealed that compared to WT, KO mice adapted their decisions less rapidly to a change in stimulus-reward relationship. We suggest that the misexpression of ephrin-A2 may lead to abnormal connectivity in regions known for their involvement in reversal learning and perseverative behaviours, including thalamic-prefrontal cortical-striatal circuitry and particularly orbitofrontal cortex. The implication is that topographic organisation of higher order brain regions may play an important role in learning and decision making.

Mycobiota and concentration of ochratoxin A in concentrated poultry feed from Venezuela.

The main objective of this study was to evaluate the frequency distribution of mycobiota and the concentration of Ochratoxin A (OTA) in 50 samples from one company of commercial brand poultry feed produced in Venezuela. The concentration of OTA in the samples analyzed was determined using the competitive ELISA method. The most frequently isolated genera of moulds were Aspergillus (36%) and Penicillium (20%). Of these genera, the most frequently isolated species were Aspergillus flavus, Aspergillus terreus and Penicillium citrinum. Ochratoxigenic species such as Eurotium herbariorum, Aspergillus niger, Aspergillus ochraceus and Aspergillus glaucus, were also found with lower frequency. Rhodotorula mucilaginosa was the only yeast isolated. 94% of the samples presented contamination by OTA in a range between 2.558 and 31.978 microg kg(-1) feed and 42% of them presented OTA levels from 10 up to 20 microg kg(-1). The findings of this investigation show that 84% of the samples of concentrated feed for meat poultry surpass the maximum permitted limit for OTA of 5 microg kg(-1), established in the majority of countries in which regulations are placed.

Catéter intratecal con reservorio en el síndrome postlaminectomia vía clínica y protocolo / Intrathecal catheter with reservoir in pos-tlatninectotnp syndrome. Clinical guidelines and protocol

El síndrome de la espalda operada es una patología frecuente que cursa con lumbalgia y/o radiculalgia crónica tras la cirugía. Las recomendaciones para su manejo son variadas y controvertidas debido a su cronicidad y necesidad de tratamiento paliativo a largo plazo. La necesidad de nuevas técnicas terapéuticas nos hará reducir costes y mejorar la calidad de vida de los pacientes. Describimos la utilización, con éxito, de la implantación de un sistema intratecal con reservorio subcutáneo en un paciente con síndrome de espalda operada complicada como tratamiento de cuarto escalón según criterios de la OMS como modelo de protocolo de actuación en nuestro centro hospitalario (AU)

The operated back syndrome is a frequent pathology that presents chronic lumbalgia and/or radiculalgia after surgery. Its management recommendations are varied and controversial due to its chronicity and its need for palliative treatment in the long term. The new therapies will lead to a reduction in costs and to an improvement of the quality of life. We describe the successful use of an intrathecal system with subcutaneous reservoir in a patient with complicated operated back syndrome, as fourth level treatment according to WHO criteria. We use this case report as a means of presenting the treatment guideline in our hospital (AU)

Desviación traqueal secundaria a un bocio / No disponible

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Soft toric lenses fitting for the ophthalmic technician.

1. Many ophthalmic technicians are familiar with fitting standard soft lenses that correct hyperopia and myopia. There is less confidence, however, in their proficiency with fitting soft toric lenses that correct astigmatism. 2. Performing accurate keratometry and refraction is an essential first step in fitting soft toric lenses. Familiarity with the different types of toric lenses is integral to an effective fit. 3. Knowledge of front and back surface toric lenses and their indications is of primary concern and allows for an effortless and successful fit.

Soft toric lenses: correcting cylinder greater than sphere.

We reviewed soft toric contact lens fitting success in 100 eyes that required greater astigmatic correction than spherical power correction. We found a significantly greater rate of success with lenses having back surface cylinder correction than lenses with front surface cylinder. When back surface optics are used to correct astigmatism with soft toric lenses, the success rate approaches that obtained in random studies of soft lens fitting success.

Penlight test for glare disability of cataracts.

We describe an alternative glare test using a simple penlight. When the glare and decrease in vision created by the penlight were compared on Snellen chart recordings, 92% of eyes within 20/50 or less visual acuity were no longer able to see even the 20/200 Snellen figure. This penlight test is suggested as an adjunct to standard Snellen testing in the evaluation of the cataract surgery patient.