Conduction failure of action potentials in sensory sural nerves of undernourished rats.

In order to determine possible functional and morphometrical alterations produced by perinatal undernourishment on peripheral nerves, sensory sural nerves from control and undernourished rats of 30 and 90 postnatal days of age were dissected and divided in two segments, one for recording the compound action potential (CAP) and the other for histological examination. Nerves from undernourished animals showed maximal CAP responses of smaller amplitude and area, larger trial-to-trial variability in area, and a significant reduction in axonal myelin sheath thickness than nerves from control animals. It is suggested that perinatal undernourishment produces changes in axonal myelin sheath structure, resulting in severe alterations in the generation and propagation of action potentials (block and/or intermittent conduction) in sensory afferent fibers in the rat.

Acarbose vs. bedtime NPH insulin in the treatment of secondary failures to sulphonylurea-metformin therapy in type 2 diabetes mellitus.

OBJECTIVE: To evaluate the efficacy of acarbose in the treatment of secondary failures to sulphonylurea-metformin therapy, its comparison against bedtime NPH insulin, and to measure the changes in postprandial metabolism resulting from both treatments. METHODS: One hundred type 2 diabetic patients in a secondary failure were included. The study begun with a run-in diet period of 6 weeks, in which an isocaloric diet was prescribed. Only subjects who continued hyperglycaemic were randomly assigned to placebo and acarbose (n = 17) or bedtime NPH insulin (n = 12). Acarbose (300 mg/day) or placebo were administered using a randomized, double blind, crossover design. Treatment periods of 3 months were separated by a 3-week washout period. Insulin was administered during 3 months. At the beginning and the end of each treatment period, an i.v. glucose tolerance test and a meal test were performed. Safety tests were done every 4 weeks. RESULTS: Acarbose resulted in a small but significant improvement in fasting plasma glucose (13.5 +/- 2.4 vs. 11.3 +/- 3.9 mmol/l, p = 0.05), HbA1c (11.1 +/- 3.4 vs. 10.3 +/- 2.5%, P = 0.3) and in a decreased plasma glucose during the meal test. Bedtime insulin significantly decreased fasting plasma glucose (13.1 +/- 2.9 vs. 8.2 +/- 2.3 mmol/l, p < 0.01), HbA1c (11.7 +/- 2.9 vs. 9.4 +/- 2.7%, p < 0.01) and plasma cholesterol. No change in insulin secretion resulted from insulin and acarbose treatment. CONCLUSIONS: Acarbose decreases blood glucose in secondary failure to sulphonylurea-metformin therapy; however, the decrease is not enough to reach the desired metabolic control. Bedtime NPH insulin is, by far, a more effective alternative.

Inmunocaracterización enzimática del endotelio capilar cerebral / Enzymatic immunocharacterization of brain capillary endothelium

La barrera hematoencefálica formada principalmente por los microvasos cerebrales, limita y controla el movimiento de iones y solutos entre la sangre y el cerebro. La enzima Na+K+ATSasa constituye una de las más importantes bombas de membrana, dispuesta para mantener las composiciones iónicas intra y extracelulares. esta bomba ha sido localizada en la membrana abluminal de distintos epitelios y se ha determinado que su funcionalidad depende de la fosforilación en residuos de aspartato. Por otra parte, la enzima aspartato quinasa (AK), desempeña el papel de fosforilar ácido aspártico, formando un compuesto altamente inestable. En trabajos anteriores, hemos inmunodetectado esa quinasa, asociada tanto a membranas como al citoplasma, en células de diferentes tejidos. En este estudio, basado en la inmunodetección de las enzimas por anticuerpos policlonales específicos, en secciones ultrafinas de cerebro de rata, hemos notado una asociación en la ubicación de Na+/K+APTasa y AK, en la membrana luminal de los endotelios de los capilares cerebrales. También, hemos observado vesículas en el citoplasma de los vasos, que tienen una reacción positiva al anticuerpo de AK marcado con peroxidasa. La presencia de Na+/K+APTasa en la membrana luminal y abluminal del endotelio de los microvasos cerebrales, indica una falta de polaridad de esta enzima. El análisis de las observaciones sugiere que ambas enzimas podrían estar funcionalmente relacionadas