An in vitro model of ischemia: metabolic and electrical alterations in the hippocampal slice

The transverse guinea pig hippocampal slice preparation was used to model the metabolic changes which occur in vivo during ischemia and recovery. Perfusing brain slices with medium devoid of glucose and oxygen elicits rapid decreases in phosphocreatine, ATP, intracellular pH, and in the evoked field potential recorded in the dentate gyrus. AMP and creatine rise during this period, while ADP and lactate levels remain unchanged. Cyclic AMP exhibits a transient increase in concentration. With the exception of ADP and lactate, these responses are very similar to those observed during in vivo ischemia. The return of glucose and oxygen to the incubation medium reverses these metabolic and electrophysiological effects and also leads to pronounced elevations in cyclic nucleotide concentrations. Metabolite concentrations approach, but do not reach, in vitro steady state levels during the first 30 min of recovery. Total adenylate and creatine steady state levels are approximately 50% of in vivo concentrations. The results suggest that, although hippocampal slices differ metabolically from in vivo tissue, they exhibit a similar pattern of metabolic responses to ischemic and reflow conditions.     

Pre-implantation diagnosis of HPRT-deficient male and carrier female mouse embryos by trophectoderm biopsy

In an animal model for Lesch-Nyhan syndrome, the affected maleembryos, as well as the carrier female embryos, have been successfullyidentified by biochemical microassay of a sample of trophectodermcells taken from the mouse embryos at the blastocyst stage.The embryos were removed from the uterus, diagnosed and returnedto the uterus within 2 days without the need for cryopreservation.The diagnosis was con firmed at 14 days gestation by analysisof the hypoxanthine phosphoribosyl transferase (HPRT) statusof the fetuses. Live young were obtained from biopsied embryosafter transfer.     

A portable radiation-force balance for use with diagnostic ultrasonic equipment

It is desirable to be able to measure power output of diagnostic ultrasonic transducers for both technical and biological reasons. Design criteria for an instrument to fulfill this purpose on a routine basis are suggested. Previous approaches are discussed in relation to these criteria and a new instrument design is presented. This is based on a measurement of radiation force using a null system, with a magnetic restoring force controlled by a pair of photo-detectors. The method of calibration is described and a selection of field results obtained with the prototype instrument are presented. Methods for applying the same principal to beam plotting, and modifying the instrument for use with therapy machines are also described.