Nicotinic mechanisms influencing synaptic plasticity in the hippocampus

Nicotinic acetylcholine receptors （nAChRs） are expressed throughout the hippocampus, and nicotinic signaling plays an important role in neuronal function. In the context of learning and memory related behaviors associated with hippocampal function, a potentially significant feature of nAChR activity is the impact it has on synaptic plasticity. Synaptic plasticity in hippocampal neurons has long been considered a contributing cellular mechanism of learning and memory. These same kinds ofcellular mechanisms are a factor in the development of nicotine addiction. Nicotinic signaling has been demonstrated by in vitro studies to affect synaptic plasticity in hippocampal neurons via multiple steps, and the signaling has also been shown to evoke synaptic plasticity in vivo. This review focuses on the nAChRs subtypes that contribute to hippocampal synaptic plasticity at the cellular and circuit level. It also considers nicotinic influences over long-term changes in the hippocampus that may contribute to addiction.     

Permanent Pacemaker Implantation Following Cardiac Surgery: Indications and Long-Term Follow-Up

Background: Conduction disturbances requiring permanent pacemaker implantation after heart surgery occur in about 1.5% of patients. Early pacemaker implantation may reduce morbidity and postoperative hospital stay. We reviewed our experience with patients undergoing surgery to try and identify predictors for pacemaker requirements and patients who will remain pacemaker dependent.
Methods: We performed a retrospective review of 4,999 patients undergoing surgery between the years 1993 and 2005. Patient age was 64 ± 12 years, and 71% were males. Coronary bypass was performed in 4,071 (81%), aortic valve replacement in 675 (14%), and mitral valve replacement in 968 (18%) patients.
Results: Seventy-two patients (1.4%) required implantation of a permanent pacemaker after surgery. Indications for pacemaker implantation included complete atrioventricular block in 59, symptomatic bradycardia/slow atrial fibrillation in nine, second-degree atrioventricular block in two, and other conduction disturbances in two patients. Predictors for pacemaker requirement by multivariate analysis were left bundle branch block and aortic valve replacement (P < 0.001). Late follow-up was available in 58 patients, at 72 ± 32 months. Thirty-seven (63%) were pacemaker dependent. Predictors for late pacemaker dependency were third-degree atrioventricular block after surgery and preoperative left bundle branch block (P < 0.001).
Conclusions: Patients at high risk for pacemaker implantation after heart surgery include those with preexisting conduction disturbances, and those undergoing aortic valve replacement. Of those receiving a pacemaker, about one-third will recover at late follow-up. For patients in the high-risk group who are pacemaker dependent after surgery, we recommend implanting a permanent pacemaker at 5 days after surgery, thus enabling early mobilization and early discharge.     

Performance evaluation of the PENTRA 60C+ automated hematology analyzer and comparison with the ADVIA 2120

The PENTRA 60C⁺ hematology analyzer provides a complete blood cell (CBC) count, including a five‐part differential (5‐DIFF) count and two leukocyte subpopulations, i.e. large immature cells (LIC’s) and atypical lymphocytes (ALY’s). We evaluated its analytical performance and assessed agreement with the ADVIA 2120, in order to install the analyzer in a small satellite hematology laboratory. First we assessed repeatability, reproducibility and carry‐over to evaluate the analytical performance. Then we used Pearson correlation coefficients, Passing and Bablok regression analysis and a graphical approach (n = 209) to evaluate agreement with the ADVIA 2120. Repeatability and reproducibility were excellent for the majority of CBC and 5‐DIFF count parameters. Carry‐over was negligible. Our data showed very good correlation for most CBC count parameters. Lower correlation coefficients were observed for red cell distribution width, mean corpuscular volume and mean platelet volume. As compared to the ADVIA 2120, the 5‐DIFF count performed very well. Agreement was poorer for low‐level eosinophils and basophils. Furthermore, the PENTRA 60C⁺ was equally able to identify pathological blood samples through the determination of LIC’s and ALY’s. Therefore, the PENTRA 60C⁺ is an eligible blood cell counter to be operational in a satellite laboratory setting.     

Update on Percutaneous Mechanical Mitral Commissurotomy

A reusable metallic valvotomy device has been developed with the goals of improving the results of percutaneous mitral valvotomy and increasing the cost-effectiveness of the procedure. The device consists of a detachable and reusable metallic dilator with two articulated bars screwed at the distal end of a catheter. Using transseptal catheterization, the device is placed across the valve over a traction guidewire and then opened gradually by means of pliers up to a maximum of 40 mm. To date, the device was used in 168 patients with a broad spectrum of mitral valve disease. The procedure was successful in 95% of cases and resulted in an increase in mitral valve area from 1.01 ± 0.8 to 2.20 ± 0.7 cm². No increase in mitral regurgitation was noted in 87% of cases. Bilateral splitting of the commissures was observed in 89%. Complications included the following: 2 severe mitral regurgitations (one requiring surgery), 1 pericardial tamponade, 1 transient cerebrovascular embolic event. The maximum number of consecutive patients treated with the same device was 35. The results obtained are at least comparable to those of current balloon techniques and confirm the possibility of safe multiple reuses of the device after sterilization.     

Evidence of impaired neurocognitive functioning in school‐age children awaiting cardiac surgery

Aim Children with congenital heart disease (CHD) are at risk of developing neurocognitive problems. However, as these problems are usually identified after cardiac surgery, it is unclear whether they resulted from the surgery or whether they pre‐existed and hence might be explained by complications and events associated with the heart disease itself. The purpose of this study was to examine whether neurocognitive deficits commonly reported after cardiac surgery are present before surgery. Method Forty‐five children (22 males, 23 females; mean age 11y 6mo, SD 3y 0mo) with cyanotic and acyanotic heart diseases scheduled for elective cardiac surgery were compared with 41 healthy peers (17 males, 24 females; mean age 11y 10mo, SD 2y 10mo) for attention and processing speed, construction, motor speed, motor planning and fluency, and visual memory. Twenty‐three children in the patient group were awaiting their first cardiac surgery and 22 were awaiting follow‐up surgery. Results The patients showed manifest neurocognitive difficulties. Their performance was inferior to that of the healthy comparison group for motor planning (p=0.02) and visual memory (p=0.01). The same neurocognitive profile was found in the group of patients awaiting their first cardiac operation. Interpretation School‐age children with various forms of CHD are at risk of neurocognitive impairments before cardiac surgery.     

Decreased spontaneous arousability in preterm newborns with impaired neurological outcome

Preterm newborns are at high risk of neurological injury. In this population, we investigated the link between neurological complications and sleep architecture. At term‐corrected gestational age, we studied retrospectively the polysomnography of 45 preterm infants born at < 28 weeks or weighting < 1 kg. These infants were followed‐up by a neuropaediatrician (median age at last follow‐up 50.4 months). Two groups of children were constituted: a group without neurological disorder and a second group with at least one of the following: cerebral palsy, language or mental retardation, visual or hearing disability or attention disorder. A Multiple Indicators and Multiple Causes model assessed the relationship between the neurological outcome and two sleep components: spontaneous arousability [number of awakenings and movements per hour of quiet sleep (QS) and active sleep] and QS characteristics (median duration of QS cycles and percentage of QS over total sleep time). Twenty‐six infants had an impaired neurological outcome. There were no statistical differences between the two groups regarding clinical characteristics. Compared to preterm neonates with normal neurological outcome, those with impaired outcomes had a lower spontaneous arousability; i.e. 0.7 (0.5–1) times less awakenings and movements per hour of QS and 0.9 (0.8–1) times less per hour of active sleep than infants with normal outcomes (P = 0.05). The differences in QS characteristics did not reach statistical significance. These findings suggested that, in preterm infants, perinatal neurological injuries could be associated with an abnormal sleep architecture characterized by altered spontaneous arousability.