Cryopreservation Studies on Silver Carp (Hypophthalmichthys molitrix) Embryos.

BACKGROUND: Cryopreservation is an effective tool for the preservation of live biological materials. OBJECTIVE: This study examined the suitability of cryopreservation protocols and the effectiveness of ultrasound for silver carp embryos. MATERIALS AND METHODS: Embryos at three developmental stages were exposed to 10, 15, 20, and 25% of five cryoprotectants (CPAs), namely propylene glycol (PG), dimethylformamide (DFA), DMSO, MeOH, and ethylene glycol (EG) for 20 min. Embryos were exposed to twelve vitrification solutions (VSs) for 10 (five steps of 2 min), 15 (five steps of 3 min), 20 (five steps of 4 min) min. Embryos were also exposed to ultrasound in VSs prior to cooling for cryopreservation. RESULTS: Hatching rates decreased with increasing CPA concentrations while toxicity varied in the order of PG < DMSO < EG < MeOH < DFA. Tail elongation stage was more tolerant to CPA than 6-somites and morula stages. The survival of embryos exposed to ultrasound in VS was remarkably lower than in water. Embryos exposed to ultrasound in VSs under the best conditions did not response well after attempted vitrification. CONCLUSION: Ultrasound-mediated CPA impregnation could be effective but other innovative methods may be needed to attain successful cryopreservation.

Cocaine decreases cortical cerebral blood flow but does not obscure regional activation in functional magnetic resonance imaging in human subjects.

The authors used functional magnetic resonance imaging (fMRI) to determine whether acute intravenous (i.v.) cocaine use would change global cerebral blood flow (CBF) or visual stimulation-induced functional activation. They used flow-sensitive alternating inversion recovery (FAIR) scan sequences to measure CBF and blood oxygen level-dependent (BOLD) sensitive T2* scan sequences during visual stimulation to measure neuronal activation before and after cocaine and saline infusions. Cocaine (0.6 mg/kg i.v. over 30 seconds) increased heart rate and mean blood pressure and decreased end tidal carbon dioxide (CO2). All measures returned to baseline by 2 hours, the interinfusion interval, and were unchanged by saline. Flow-sensitive alternating inversion recovery imaging demonstrated that cortical gray matter CBF was unchanged after saline infusion (-2.4 +/- 6.5%) but decreased (-14.1 +/- 8.5%) after cocaine infusion (n = 8, P < 0.01). No decreases were detected in white matter, nor were changes found comparing BOLD signal intensity in cortical gray matter immediately before cocaine infusion with that measured 10 minutes after infusion. Visual stimulation resulted in comparable BOLD signal increases in visual cortex in all conditions (before and after cocaine and saline infusion). Despite a small (14%) but significant decrease in global cortical gray matter CBF after acute cocaine infusion, specific regional increases in BOLD imaging, mediated by neurons, can be measured reliably.

Acute effects of cocaine on human brain activity and emotion.

We investigated brain circuitry mediating cocaine-induced euphoria and craving using functional MRI (fMRI). During double-blind cocaine (0.6 mg/kg) and saline infusions in cocaine-dependent subjects, the entire brain was imaged for 5 min before and 13 min after infusion while subjects rated scales for rush, high, low, and craving. Cocaine induced focal signal increases in nucleus accumbens/subcallosal cortex (NAc/SCC), caudate, putamen, basal forebrain, thalamus, insula, hippocampus, parahippocampal gyrus, cingulate, lateral prefrontal and temporal cortices, parietal cortex, striate/extrastriate cortices, ventral tegmentum, and pons and produced signal decreases in amygdala, temporal pole, and medial frontal cortex. Saline produced few positive or negative activations, which were localized to lateral prefrontal cortex and temporo-occipital cortex. Subjects who underwent repeat studies showed good replication of the regional fMRI activation pattern following cocaine and saline infusions, with activations on saline retest that might reflect expectancy. Brain regions that exhibited early and short duration signal maxima showed a higher correlation with rush ratings. These included the ventral tegmentum, pons, basal forebrain, caudate, cingulate, and most regions of lateral prefrontal cortex. In contrast, regions that demonstrated early but sustained signal maxima were more correlated with craving than with rush ratings; such regions included the NAc/SCC, right parahippocampal gyrus, and some regions of lateral prefrontal cortex. Sustained negative signal change was noted in the amygdala, which correlated with craving ratings. Our data demonstrate the ability of fMRI to map dynamic patterns of brain activation following cocaine infusion in cocaine-dependent subjects and provide evidence of dynamically changing brain networks associated with cocaine-induced euphoria and cocaine-induced craving.