ASSESSMENT OF OVERRANGING AS A FUNCTION OF PITCH, COLLIMATION AND ROTATION TIME FOR THREE OF THE MOST RECENT AND WIDESPREAD CT SCANS IN FRANCE.

PURPOSE: to assess overranging (OR) as a function of pitch, collimation and rotation time for three commonly used CT models in France. METHODS: OR was measured using XR-SP2 Gafchromic films (Ashland, USA) and computed from exposure data for three widely used CT models in France. The impact of collimation, pitch and rotation time on OR was analyzed while comparing the three CT models. RESULTS: for a typical head protocol, measured OR was found to be equal to 1.64 cm for CT scan A, 0.5 cm for CT scan B and 3.44 cm for CT scan C. OR values were respectively of 4.47, 3.24 and 7.81 cm for the typical chest protocol and the 3 CT models. OR was lowest at pitch values <1 for CT scan A, while it linearly increased with pitch for CT scan B and was lowest for high pitch values for CT scan C. Additionally, OR increase with collimation (24 mm to 38.4 mm) was most pronounced for CT scan B (factor of 2.2 for low pitch (0.5) and 2.8 for high pitch (1.2)) while it increased linearly regardless of the pitch for CT scans A and C. Rotation time also proved to slightly affect OR mainly for CT scan B (up to 2.2 mm). CONCLUSION: the present study shows that overranging remains an issue in modern CT scanners with large disparities across the vendors.

A comparative study of two cooling protocols on stallion sperm cryosurvival.

There are many protocols for horse sperm cryopreservation, but results are inconsistent; sperm survival after freeze-thawing is usually poor; in consequence, fertility is low. The objective of this work was to see whether slow cooling before freezing to minus 3 °C instead of +5 °C, the traditional target temperature, could improve horse sperm cryosurvival, capability to carry out capacitation and the acrosome reaction induced by progesterone. Spermatozoa from five stallions were packaged in straws and slowly cooled to +5 °C. Half of the straws were frozen directly and the other half was further cooled to -3 °C before freezing. Progressive motility, viability, plasma membrane integrity, acrosome integrity and capacitation status were assessed. After thawing, there were no differences between cooling treatments on motility, viability, acrosome integrity and capacitation status; however, there was difference (P < 0.05) regarding plasma membrane integrity. Acrosome integrity decreased as incubation, without or with progesterone (2 µg ml(-1) ), progressed, but there were no differences between cooling treatments regardless of progesterone. Both capacitated and acrosome-reacted spermatozoa increased as incubation progressed, but there were no differences between cooling treatments regardless of progesterone. Slow cooling to -3 °C before freezing did not improve horse sperm cryosurvival or capability to undergo the acrosome reaction.

Estudio de mosaicismo y seudomosaicismo en diagnóstico prenatal citogenético. Experiencias en Ciudad de La Habana / Mosaicism and pseudomosaicism in prenatal diagnosis. Experience in Havana City

Introducción. Se hace un estudio de la incidencia y repercusión fenotípica del mosaicismo y seudomosaicismo cromosómico en diagnóstico prenatal en 18 años de labor en el laboratorio de Ciudad de La Habana.Métodos. Se incluyeron 10.676 amniocentesis cultivadas principalmente en frascos. El seguimiento de los casos se hace a través de especialistas y enfermeras en genética.Resultados y conclusiones. Se halló un 0,33 por ciento de mosaicismo en el muestreo, 4,50 por ciento de seudomosaicismo tipo I y 0,40 por ciento seudomosaicismo tipo II. Se detectaron 36 casos de mosaicos cromosómicos. El 70 por ciento del mosaicismo correspondió a aberraciones numéricas con paridad de aparición para los autosomas y los cromosomas sexuales; los mosaicos de aberraciones estructurales se hallaron en un 13,8 por ciento y los de marcadores cromosómicos supernumerarios en un 16,2 por ciento. El 42,2 por ciento de los fetos abortados o recién nacidos vivos con mosaicos cromosómicos fueron fenotípicamente normales a grosso modo. Se alcanzó un 63 por ciento de seguimiento citogenético en los casos de mosaicos cromosómicos. Las aberraciones cromosómicas mayormente involucradas en mosaicismo fueron la trisomía 21, la monosomía de la X y el cromosoma marcador supernumerario. Se hallaron 459 aberraciones cromosómicas asociadas al seudomosaicismo tipo I (327 aberraciones estructurales y 132 aberraciones numéricas). Fueron encontradas 48 aberraciones cromosómicas en el seudomosacismo tipo II, de las cuales 25 eran estructurales, 21 numéricas y 2 casos 46,XX/46,XY. Los cromosomas más frecuentemente hallados en seudomosaico fueron el 2, el 13, el 17, el 18, el 20 y el 21. La mayoría de los casos de seudomosaico el recién nacido fue normal. (AU)