Accuracy of ultrasound in counting and measuring gallstones

A prospective study of accuracy of ultrasound in measuring and counting gallstones was undertaken in 30 patients undergoing cholecystectomy. Stones were correctly counted (up to five) in 27 of 30 patients. Ninety-three of 106 stones (88%) examined were measured accurately (with a 2 mm error margin). The size of the smaller stones tended to be overestimated, whereas the size of the larger stones tended to be underestimated. When nonoperative treatment of gallstones is considered, ultrasound can be used as the first examination to identify patients who will not be eligible for one or another protocol on the basis of size or number of stones.     

Recent drug use and suicidal behaviour among young offenders

Patterns of psychoactive substance use were examined among 216 young offenders in South Australian secure care facilities. Compared to four student samples (n = 1525), young offenders reported recent use of most substances considerably more often than did student peers. Almost one-half used a substance at the time of committing their last offence. A subgroup of offenders (n = 126) was questioned about suicide attempts, mood, recent suicidal ideation and deliberate self-injury. Past suicide attempts and deliberate self-injury were found to be associated with increased substance use. Drawing on evidence from other studies it is argued that impulsiveness often underlies these behaviours and contributes to their covariation. Substance use can further increase impulsiveness and thereby exacerbate offending and suicide risk. Not only should substance use be considered in all assessments of antisocial and self-destructive behaviour but innovative approaches to developing effective interventions for the reduction of substance misuse need to be encouraged.     

Neural correlates of long-term object memory in the mouse anterior cingulate cortex

Damage to the hippocampal formation results in a profound temporally graded retrograde amnesia, implying that it is necessary for memory acquisition but not its long-term storage. It is therefore thought that memories are transferred from the hippocampus to the cortex for long-term storage in a process called systems consolidation (Dudai and Morris, 2000). Where in the cortex this occurs remains an open question. Recent work (Frankland et al., 2005; Vetere et al., 2011) suggests the anterior cingulate cortex (ACC) as a likely candidate area, but there is little direct electrophysiological evidence to support this claim. Previously, we demonstrated object-associated firing correlates in caudal ACC during tests of recognition memory and described evidence of neuronal responses to where an object had been following a brief delay. However, long-term memory requires evidence of more durable representations. Here we examined the activity of ACC neurons while testing for long-term memory of an absent object. Mice explored two objects in an arena and then were returned 6 h later with one of the objects removed. Mice continued to explore where the object had been, demonstrating memory for that object. Remarkably, some ACC neurons continued to respond where the object had been, while others developed new responses in the absent object's location. The incidence of absent-object responses by ACC neurons was greatly increased with increased familiarization to the objects, and such responses were still evident 1 month later. These data strongly suggest that the ACC contains neural correlates of consolidated object/place association memory.     

Ultrasmall superparamagnetic iron oxide nanoparticle prelabelling of human neural precursor cells

Stem cells prelabelled with iron oxide nanoparticles can be visualised using magnetic resonance imaging (MRI). This technique allows for noninvasive long-term monitoring of migration, integration and stem cell fate following transplantation into living animals. In order to determine biocompatibility, the present study investigated the biological impact of introducing ultrasmall superparamagnetic iron oxide nanoparticles (USPIOs) into primary human fetal neural precursor cells (hNPCs) in vitro. USPIOs with a mean diameter of 10–15 nm maghemite iron oxide core were sterically stabilised by 95% methoxy-poly(ethylene glycol) (MPEG) and either 5% cationic (NH₂) end-functionalised, or 5% Rhodamine B end-functionalised, polyacrylamide. The stabilising polymer diblocks were synthesised by reversible addition-fragmentation chain transfer (RAFT) polymerisation. Upon loading, cellular viability, total iron capacity, differentiation, average distance of migration and changes in intracellular calcium ion concentration were measured to determine optimal loading conditions. Taken together we demonstrate that prelabelling of hNPCs with USPIOs has no significant detrimental effect on cell biology and that USPIOs, when utilised at an optimised dosage, are an effective means of noninvasively tracking prelabelled hNPCs.     

Activity profiles of single neurons in caudal anterior cingulate cortex during trace eyeblink conditioning in the rabbit

Acquisition of trace eyeblink conditioning involves the association of a conditioned stimulus (CS) with an unconditioned stimulus (US) separated by a stimulus-free trace interval. This form of conditioning is dependent upon the hippocampus and the caudal anterior cingulate cortex (AC), in addition to brain stem and cerebellar circuitry. Hippocampal involvement in trace eyeblink conditioning has been studied extensively, but the involvement of caudal AC is less well understood. In the present study, we compared neuronal responses from rabbits given either paired (trace conditioning) or unpaired (pseudoconditioning) presentations of the CS and US. Presentation of the CS elicited significant increases in neuronal activity at the onset of both trace conditioning and pseudoconditioning. A robust CS-elicited neuronal response persisted throughout the first 2 days of trace conditioning, declining gradually across subsequent training sessions. In contrast, the magnitude of the CS-elicited excitatory response during pseudoconditioning began to decline within the first 10 trials. Neurons exhibiting excitatory responses to the CS during trace conditioning also exhibited excitatory responses to the US that were significantly greater in magnitude than US-elicited responses during pseudoconditioning. CS-elicited decreases in neuronal activity became more robust over the course of trace conditioning compared to pseudoconditioning. Reductions in activity during the CS interval consistently preceded excitation in both training groups, suggesting that the CS-elicited decreases in neuronal activity may serve to increase the signal-to-noise ratio of the excitatory response to the tone. Taken together, these data suggest that the caudal AC is involved early in trace eyeblink conditioning and that maintenance of the CS-elicited excitatory response may serve to signal the salience of the tone.