Hybrid microprobes for chronic implantation in the cerebral cortex

This paper reports on a neural device for chronic implantation into the cerebral cortex. Silicon microprobes with 36 electrodes arranged on four shafts are fabricated using MEMS technology. The hybrid integration of a ribbon cable with high flexibility provides the connection of the electrodes to external instrumentation. Crosstalk between the channels is investigated, as well as the electrode stability for a time period of one month in vitro. Due to the geometry and the mechanical stability of these microprobes, insertions are possible without the need for prior opening of the dura mater. A dedicated insertion tool has been fabricated to achieve a precise insertion of the microprobes and their subsequent mechanical decoupling. Additionally, a protection chamber allowing the secure attachment of two connector units on the skull is introduced. The short-time chronic implantation of microprobes showed that neural activity can be recorded, including single unit activity, which was present after four days.

Validation of prognostic indices using the frailty model

A major issue when proposing a new prognostic index is its generalisibility to daily clinical practice. Validation is therefore required. Most validation techniques assess whether "on average" the results obtained by the prognostic index in classifying patients in a new sample of patients are similar to the results obtained in the construction set. We introduce a new important aspect of the generalisibility of a prognostic index: the heterogeneity of the prognostic index risk group hazard ratios over different centers. If substantial variability between centers exists, the prognostic index may have no discriminatory capability in some of the centers. To model such heterogeneity, we use a frailty model including a random center effect and a random prognostic index by center interaction. Statistical inference is based on a Bayesian approach using a Laplacian approximation for the marginal posterior distribution of the variances of the random effects. We investigate different ways to summarize the information available from this marginal posterior distribution. Our approach is applied to a real bladder cancer database for which we demonstrate how to investigate and interpret heterogeneity in prognostic index effect over centers.

Anterior regions of monkey parietal cortex process visual 3D shape

The intraparietal cortex is involved in the control of visually guided actions, like reach-to-grasp movements, which require extracting the 3D shape and position of objects from 2D retinal images. Using fMRI in behaving monkeys, we investigated the role of the intraparietal cortex in processing stereoscopic information for recovering the depth structure and the position in depth of objects. We found that while several areas (CIP, LIP, and AIP on the lateral bank; PIP and MIP on the medial bank) are activated by stereoscopic stimuli, AIP and an adjoining portion of LIP are sensitive only to depth structure. Furthermore, only these two regions are sensitive to both the depth structure and the 2D shape of small objects. These results indicate that extracting 3D spatial information from stereo involves several intraparietal areas, among which AIP and anterior LIP are more specifically engaged in extracting the 3D shape of objects.

A randomized trial to assess the effectiveness of an infant home safety programme

The aim of this study was to test an intervention aimed at addressing the risk of injury in infants 2 - 12 months of age. A non-blinded, randomized controlled trial was conducted, whereby parents were randomly assigned to either a control or one of two intervention groups. Parents completed questionnaires regarding safety behaviours and injuries at the 2 (baseline), 6 and 12 month immunization visit at the community health unit. During the 2 month visit to the health unit, the two intervention groups received a home safety kit containing nine items, an instructional brochure and a risk assessment checklist. Subjects randomized to the safety kit plus home visit group also received a standardized home visit from a community health nurse. Two of the 14 parental safety behaviours showed a significant increase in use among parents in the intervention groups. Neither of the interventions was associated with a reduction in parent-reported injuries among children. It was concluded that home visitation may provide a beneficial adjunct to the provision of safety devices and may increase use by parents.

Is laparoscopic appendectomy an effective procedure?

AIM

To compare the results of open and laparoscopic appendectomy and to determine if the laparoscopic approach might be more effective for some subgroups of patients.

MATERIAL AND METHODS

We retrospectively analysed the computerised data of 326 consecutive adult patients operated on for suspected appendicitis between 2001 and 2005. The series consisted of 166 men and 160 women with a mean age of 32 +/- 16 years and a mean Body Mass Index (BMI) of 24 +/- 4. There were 265 ASA I, 46 ASA II and 5 ASA III patients. According to the surgeon's preference, 176 patients had an open appendectomy (OA) and 150 a laparoscopic appendectomy (LA).

RESULTS

The mean operative time and hospital stay were equivalent in the two groups : respectively 49 +/- 19 min. and 4.1 +/- 2.5 days in OA and 50 +/- 16 min. and 3.5 +/- 1.8 days in LA. However, subgroup analysis revealed that overweight (BMI > 25) patients (n = 102) and patients with ectopic appendices (n = 86) had an obvious benefit from LA. In cases of OA, operative time and hospital stay were longer in overweight patients than in normal weight patients: respectively 63 +/- 20 min. and 5.3 +/- 2.9 days versus 44 +/- 16 min. (p < 0.01) and 3.7 +/- 2.2 days (p < 0.01). On the contrary, no difference was observed in the LA group. Operative time and hospital stay were also longer in patients with ectopic appendices submitted to OA than in patients with an appendix in the normal position: respectively 60 +/- 18 min. and 4.7 +/- 2.7 days versus 45 +/- 18 min. (p < 0.01) and 3.9 +/- 2.4 days (p < 0.01). Again, such a difference was not observed in cases of LA. We noted no mortality, but 24 patients (7%) developed an abdominal complication : 18 wound infections and 6 intra-abdominal abscesses. Wound infections were more common in the OA than in the LA group : 7.3% (13/176) versus 3.3% (5/150) (p = 0.1). In the LA group, 4 wound infections were observed in our early experience, at a time where no endoscopic bag was used for the removal of the appendix. The rate of intra-abdominal abscesses was similar: 1.7% (3/176) in the OA group and 2% (3/150) in the LA group.

CONCLUSIONS

LA is an effective procedure with a reduced risk of developing wound infection. The laparoscopic approach is particularly effective for overweight patients and/or patients with ectopic appendices as far as shortening the operative time and hospital stay is concerned.

Extracting 3D structure from disparity

The neural mechanisms of stereoscopic 3D shape perception have only recently been investigated. Here we review the two cortical regions in which these mechanisms have been studied so far in macaques: a small subpart of inferotemporal cortex called TEs, and the caudal intraparietal (CIP) region. Neurons in TEs respond selectively to the orientation and curvature in depth of stereoscopic surfaces and this region provides a detailed 3D shape description of surface boundaries and surface content. This description is evoked only by binocular stimuli in which subjects see depth and it does not vary if depth is specified by different cues. Neurons in CIP are a selective for orientation in depth of surfaces and elongated objects, and their responses are also unaffected by changes in depth cues. Thus, stereoscopic 3D shape is processed in both the dorsal, occipito-parietal and the ventral, occipito-temporal streams.

Time and the brain: how subjective time relates to neural time

Most of the actions our brains perform on a daily basis, such as perceiving, speaking, and driving a car, require timing on the scale of tens to hundreds of milliseconds. New discoveries in psychophysics, electrophysiology, imaging, and computational modeling are contributing to an emerging picture of how the brain processes, learns, and perceives time.

"Bounce at the Bell": a novel program of short bouts of exercise improves proximal femur bone mass in early pubertal children

OBJECTIVES

To examine the effects of a simple and inexpensive physical activity intervention on change in bone mass and structure in school aged children.

METHODS

Fifty one children (n = 23 boys and 28 girls; mean age 10.1 years) participated in "Bounce at the Bell" which consisted of 10 counter-movement jumps 3x per day (total approximately 3 min/day). Controls were 71 matched children who followed usual school practice. We assessed dietary calcium, physical activity, physical performance, and anthropometry in September and after 8 months of intervention (June). We measured bone mineral content (BMC) and bone area at the lumbar spine, total body, and proximal femur. Proximal femur scans were also analysed for bone geometry and structural strength using the hip structural analysis program. Lean and fat mass (g) were also calculated.

RESULTS

Groups were similar at baseline and did not differ in weight, height, total body, lumbar spine, proximal femur, or femoral neck BMC. Control children had a greater increase in adjusted total body BMC (1.4%). Intervention children gained significantly more BMC at the total proximal femur (2%) and the intertrochanteric region (27%). Change in bone structural parameters did not differ between groups.

CONCLUSIONS

This novel, easily implemented exercise program, took only a few minutes each day and enhanced bone mass at the weight bearing proximal femur in early pubertal children. A large, randomised study of boys and girls should be undertaken powered to test the effectiveness of Bounce at the Bell in children at different stages of maturity, and in boys and girls independently.

A new methodology for teaching clinical reasoning skills: problem solving clinical seminars

In the final year of the medical curriculum of the Faculty of Medicine of the Katholieke Universiteit Leuven (Belgium), a new methodology for teaching clinical skills was introduced: Problem Solving Clinical Seminars (PSCS). Two eight-week series of 70 seminars were offered. Students prepared for the seminars in groups of five students who worked on one or more clinical cases followed by half-open questions. Additional information was collected individually. At the clinical seminar the solutions were presented and discussed, guided by a clinical teacher. A questionnaire was administered to investigate whether students perceive the new type of clinical seminars as a powerful learning environment. Students were satisfied with the new methodology. The importance of the postulated educational aspects--preparation, clinical case and the seminar--was confirmed. The preparation phase (self-study and group work) and the clinical seminar were experienced as two separate and important learning events. The implementation of the problem solving clinical seminars is considered by students to be a powerful learning environment and therefore a broader applicability of the PSCS methodology is recommended.

A representation of the hazard rate of elapsed time in macaque area LIP

The capacity to anticipate the timing of environmental cues allows us to allocate sensory resources at the right time and prepare actions. Such anticipation requires knowledge of elapsed time and of the probability that an event will occur. Here we show that neurons in the parietal cortex represent the probability, as a function of time, that a salient event is likely to occur. Rhesus monkeys were trained to make eye movements to peripheral targets after a light dimmed. Within a block of trials, the 'go' times were drawn from either a bimodal or unimodal distribution of random numbers. Neurons in the lateral intraparietal area showed anticipatory activity that revealed an internal representation of both elapsed time and the probability that the 'go' signal was about to occur (termed the hazard rate). The results indicate that the parietal cortex contains circuitry for representing the time structure of environmental cues over a range of seconds.

In vivo characterization of 5-HT1A receptor-mediated gastric relaxation in conscious dogs

Accumulating data have been published emphasizing the important role of 5-hydroxytryptamine (5-HT) receptors in proximal stomach relaxation. However, a proper in vivo characterization of 5-HT receptors mediating gastric relaxation is still missing. In the current study, we focus on the in vivo characterization of 5-HT1A receptors mediating relaxation of the proximal stomach in conscious dogs. Beagle dogs were equipped with a gastric fistula. In the conscious state, volume changes within an intragastric bag were measured at constant pressure by means of a barostat. Results are presented as the maximum volume increase after treatment (mean+/-s.e.m.). All drugs were injected intravenously. The 5-HT1A receptor agonist flesinoxan (10, 50, 100 and 150 microg kg-1) induced a dose-dependent relaxation of the canine proximal stomach (50+/-10, 230+/-51, 290+/-38 and 275+/-33 ml, respectively; n=9-11). The selective 5-HT1A receptor antagonist WAY-100635 dose-dependently inhibited the flesinoxan-induced relaxation. NG-nitro-l-arginine methyl ester did not affect this relaxation, suggesting that nitrergic nerves are not involved. After supradiaphragmatic vagotomy, the baseline of the intragastric volume was larger compared to that before vagotomy (317+/-50 vs 142+/-28 ml, respectively; n=5). Compensation for this by either reduction of the intraballoon pressure or infusion of a contractile dose of bethanechol did not establish a condition in which flesinoxan was able to relax the stomach. In contrast, nitroprusside induced a significant gastric relaxation when tone was increased by bethanechol. It is concluded that flesinoxan induces proximal gastric relaxation in conscious dogs via 5-HT1A receptors. The response is mediated through a vagal pathway without involvement of nitrergic nerves.

[Expression of the Mycobacterium tuberculosis cytochrome CYP51 gene in Escherichia coli]

Mycobacterium tuberculosis sterol 14 alpha-demethylase CYP51 is currently considered a promising target for a new generation of antitubercular drugs. Similarly to eucaryotic sterol 14 alpha-demethylases, candidate selective inhibitors of M. tuberculosis CYP51 belong to azoles, the N-substituted derivatives of imidazole and triazole. We have constructed a highly effective system for heterologous expression of MT CYP51 in E. coli. The recombinant protein was purified by metalloaffinity chromatography for primary in vitro screening of novel antitubercular azole compounds for their high affinity to the molecular target. Yield of the purified recombinant MT CYP51 was about 1.5 micromoles of the purified native protein per 1 l of E. coli cell culture. The recombinant protein interacted with ketoconazole with a Kd of 7.7 microM. MT CYP51 produced by our system for heterologous expression in E. coli may be used for initial testing of novel antimycobacterial azole drugs.