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Biomedical subjects

P Janssen

Publications and source records attributed to P Janssen.

At least 19 recordsLinked to original sources

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.

Belgium↗

"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.

Analysis of Variance↗

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.

Animals↗

Bioinformatic insight into the unity and diversity of cytochromes P450.

For the past few decades, cytochromes P450 (CYPs) have been the subject of extensive research, owing to the ability of these enzymes to serve as drug targets as well as to their active participation in drug metabolism. Other varieties and functions of CYPs have been discovered and this superfamily currently comprises over 2000 different protein species. In the present study, the protein sequences of CYPs were submitted to computer analysis for elucidation of the structural basis of their pronounced functional diversity. The basic local alignment search tool (BLAST) was used to demonstrate that CYP protein sequences share a certain general similarity; at the same time, it was shown that the CYP superfamily may be split into a number of groups of intimately related proteins. These groups, the families, were revealed by means of cluster analysis, which demonstrated a strong hierarchy among the animal, bacterial and fungal P450s, and the lack of such a hierarchy for plant enzymes. Multiple alignment and consensus sequence analysis were the approaches taken to find out which structural peculiarities of P450s are responsible for the deviations from the random picture. Proteins within each family were aligned and collapsed to the corresponding consensus sequences, the alignment of which produced the consensus for the whole superfamily. The latter consensus yielded a number of unity motifs (most of which being related to the heme-fixing assembly), while the cross-family comparison of consensus sequences enabled the retrieval of some diversity motifs. Three consensus sequences (for the CYP51 and CYP2 families and for the superfamily) were compared, to line up the unity and diversity motifs with the appropriate X-ray data.

Amino Acid Sequence↗

Treatment outcome studies. pitfalls in current methods and practice.

The objective of a treatment outcome study is to investigate the heterogeneity in outcome between patients according to factors other than treatment, such as country, institution or physician. Results of treatment outcome studies have already been extensively presented in the medical literature. However, no clear methodology has emerged to perform treatment outcome studies and various methods have been used. This paper reviews the different types of questions addressed in treatment outcome studies, the different methodologies and the different endpoints used. Statistical techniques are mainly descriptive including tables, estimates of survival curves, but regression models have also been used. Most of the studies use registry data, while only a few use discharge data or data available from clinical trials.

Clinical Trials as Topic↗

Pharmacological characterization of the 5-HT receptors mediating contraction and relaxation of canine isolated proximal stomach smooth muscle.

1. We aimed to characterize 5-HT receptors mediating contraction and relaxation to 5-HT in dog proximal stomach longitudinal muscle (LM) strips. 2. Of the tryptamine analogues tested, 5-HT was the most potent contractile agent at basal length, while 5-CT was the most potent relaxant of PGF(2alpha)-induced contraction. Neither the contractions to 5-HT, nor the relaxations to 5-CT were influenced by tetrodotoxin, illustrating that action potential propagation is not involved. 3. The 5-HT-induced contraction was antagonized by mesulergine (0.03 to 0.3 microM) and ketanserin (2 - 20 nM), but the antagonism was not of a simple competitive nature, indicating multiple receptor involvement. Ketanserin (3 to 30 nM) and mesulergine (30 nM) competitively antagonized the alpha-Me-5-HT-induced contraction (pK(B): 8.83+/-0.09 and pA(2): 8.25+/-0.06 respectively). These affinity values are in line with literature affinities of ketanserin and mesulergine at 5-HT(2A) receptors in various bioassays. 4. The 5-CT-induced inhibition of PGF(2alpha)-induced contraction was competitively antagonized by mesulergine (pK(B) estimate: 8.52+/-0.12) and by the selective 5-HT(7) receptor antagonist SB-269970 (pK(B) estimate: 9.36+/-0.14). Both pK(B) estimates are in line with literature affinities of these compounds for 5-HT(7) receptors. Mesulergine (30 nM) and SB-269970 (10 nM) shifted the relaxant curve to 5-HT parallel to the right in the presence of ketanserin (0.3 microM) (pA(2) estimates of 8.08+/-0.10 and 8.75+/-0.14 respectively), indicative of 5-HT(7) receptor involvement. 5. It is concluded that 5-HT induces dog proximal stomach (LM) contraction via smooth muscle 5-HT(2A) receptors and relaxation via smooth muscle 5-HT(7) receptors.

Animals↗

Smooth muscle 5-HT2A receptors mediating contraction of porcine isolated proximal stomach strips.

1. The aim of this study was to characterize the 5-HT receptors involved in the 5-HT-induced contraction of longitudinal muscle (LM) strips of porcine proximal stomach. This was done in a classical organ bath set-up for isotonic measurement. 2. The concentration-contraction curve to 5-HT was not modified by 5-HT(3) and 5-HT(4) receptor antagonism. Methysergide, ketanserin and mesulergine antagonized the curve to 5-HT. Concomitantly, increasing concentrations of ketanserin and mesulergine progressively revealed a biphasic nature of the 5-HT curve. Ketanserin antagonized the low-affinity receptor while it did not modify the high-affinity receptor. 3. Tetrodotoxin did not influence the concentration-contraction curve to 5-HT neither in the absence nor presence of ketanserin, indicating that nerves are not involved. 4. Ketanserin competitively antagonized the monophasic concentration-response curve to alpha-Methyl-5-HT, yielding a Schild slope that was not significantly different from unity. After constraining the Schild slope to unity, a pK(B) estimate of 8.23+/-0.90 was obtained. This affinity estimate of ketanserin closely approximates previously reported affinities at 5-HT(2A) receptors. 5. In the presence of ketanserin (0.1 microM; exposing the high-affinity receptor), a wide range of 5-HT receptor antagonists covering all 5-HT receptors known, was tested. Only methysergide and ritanserin inhibited the response to 5-HT, thus expressing affinity for the high-affinity receptor. This did not reveal the identity of the receptor involved. 6 It can be concluded that 5-HT induces pig proximal stomach (LM) contraction via 5-HT(2A) receptors located on smooth muscle. A ketanserin-insensitive phase of contractions could not be characterized between the actually known classes of 5-HT receptors with the pharmacological tools that were used.

Animals↗

Macaque inferior temporal neurons are selective for three-dimensional boundaries and surfaces.

The lower bank of the superior temporal sulcus (TEs), part of the inferior temporal cortex, contains neurons selective for disparity-defined three-dimensional (3-D) shape. The large majority of these TEs neurons respond to the spatial variation of disparity, i.e., are higher-order disparity selective. To determine whether curved boundaries or curved surfaces by themselves are sufficient to elicit 3-D shape selectivity, we recorded the responses of single higher-order disparity-selective TEs neurons to concave and convex 3-D shapes in which the disparity varied either along the boundary of the shape, or only along its surface. For a majority of neurons, a 3-D boundary was sufficient for 3-D shape selectivity. At least as many neurons responded selectively to 3-D surfaces, and a number of neurons exhibited both surface and boundary selectivity. The second aim of this study was to determine whether TEs neurons can represent differences in second-order disparities along the horizontal axis. The results revealed that TEs neurons can also be selective for horizontal 3-D shapes and can code the direction of curvature (vertical or horizontal). Thus, TEs neurons represent both boundaries and surfaces curved in depth and can signal the direction of curvature along a surface. These results show that TEs neurons use not only boundary but also surface information to encode 3-D shape properties.

Animals↗

Serum bile acids in liver transplantation--early indicator for acute rejection and monitor for antirejection therapy.

We studied the course of serum bile acids to investigate its reliability in the diagnosis of acute rejection after liver transplantation in relation to pathohistological findings. Serum bile acid concentration, bilirubin and transaminases were measured in 41 patients who underwent liver transplantation. Their course was correlated to liver biopsy. Group I (n = 19) patients were without acute rejection, whereas group II (n = 22) patients showed acute rejection. Bile acid concentrations in group II showed a statistically highly significant (P < or = 0.001) threefold increase 3 days prior to biopsy. Successful antirejection treatment was correlated with a statistically significant (P = 0.008) decrease of serum bile acid 1 day after initiation of therapy. Patients without acute rejection showed a baseline bile acid concentration at the time of biopsy. Bilirubin and transaminases did not show any statistically significant correlation to acute rejection. Infection did not lead to a significant bile acid increase. Our study shows that serum bile acids monitored after liver transplantation can easily be used to detect acute rejection and at the same time they reflect the success of antirejection therapy.

Acute Disease↗

Genetic polymorphisms of microsomal and soluble epoxide hydrolase and the risk of Parkinson's disease.

Oxidative stress is hypothesized to play a major role in the destruction of dopaminergic neurons, which is associated with Parkinson's disease. Epoxides are potentially reactive intermediates formed through the oxidative metabolism of both exogenous and endogenous substances that contribute to cytotoxic damage mediated by oxidative stress. The microsomal (EPHX1) and soluble (EPHX2) epoxide hydrolases function to regulate the oxidation status of a wide range of xenobiotic- and lipid-derived substrates; therefore, interindividual variation in these pathways may mitigate epoxide-related cellular injury. In this investigation, we examined the potential association between the risk of Parkinson's disease and genetic variation within the EPHX1 and EPHX2 genes. Fluorescent 5' nuclease-based assays were developed to identify the allelic status of individuals with respect to specific single nucleotide polymorphisms in exons 3 and 4 of the EPHX1 gene and exons 8 and 13 of the EPHX2 gene. EPHX1 and EPHX2 genotype data were obtained from 133 idiopathic Parkinson's disease patients and 212 control subjects matched on age, gender and ethnicity. No statistically significant differences were found in the distribution of the reference and variant alleles between Parkinson's disease and control subjects, or when results were stratified by gender. Therefore, common polymorphisms within EPHX1 and EPHX2 do not appear to be important risk factors for Parkinson's disease.

Adult↗

Solubilization and purification of the human ETB endothelin receptor produced by high-level fermentation in Pichia pastoris.

In the present report, the successful solubilization and purification of the ETB receptor heterologously produced in the methylotrophic yeast P. pastoris is described for the first time. In comparison to the baculovirus system where successful production, solubilization and purification have already been reported, handling and up-scaling of recombinant P. pastoris cells was much easier and less time consuming. Recombinant P. pastoris clones producing two different ETB receptor constructs were grown in a fermenter to a density of about 360 g/l. After induction with methanol, a production level of maximally 45 pmol/mg was obtained, a value which is in the range of that reported for baculovirus-infected insect cells. A method for the large-scale preparation of membranes was established. Solubilization of the recombinant ETB receptor was achieved with the detergent n-dodecyl-/beta-D-maltopyranoside. The stability of the solubilized and ligand-bound receptor was examined in detail. Subsequently, two purification methods for two different receptor constructs were tested and a large-scale procedure for isolation of recombinant receptor was established. In general, the purification methods described herein will be adaptable to other G protein-coupled receptors heterologously produced in heterologous expression systems including P. pastoris.

Binding Sites↗

Genome sequences and great expectations.

To assess how automatic function assignment will contribute to genome annotation in the next five years, we have performed an analysis of 31 available genome sequences. An emerging pattern is that function can be predicted for almost two-thirds of the 73,500 genes that were analyzed. Despite progress in computational biology, there will always be a great need for large-scale experimental determination of protein function.

Animals↗

Induction of labour: a continuous quality improvement and peer review program to improve the quality of care.

This article describes a program developed to improve the process of planned induction of labour and to reduce the rates of inappropriate induction. The setting is a tertiary-care maternity hospital in urban Vancouver, BC, in which 7000 deliveries take place annually. Approximately 65% of these can be considered primary care; the remainder are secondary- or tertiary-level cases. Continuous quality improvement (CQI) methods were used by a multidisciplinary team, which included nursing staff, physicians, health records personnel and a CQI facilitator. Interventions included the development of a new induction-booking process, clear criteria for induction, feedback to caregivers about changes and a peer review system to oversee and maintain improvement. The overall induction rate for the institution decreased, and this change has been maintained.

British Columbia↗

Selectivity for 3D shape that reveals distinct areas within macaque inferior temporal cortex.

The anterior part of the macaque inferior temporal cortex, area TE, occupies a large portion of the temporal lobe and is critical for object recognition. Thus far, no relation between anatomical subdivisions of TE and neuronal selectivity has been described. Here, we present evidence that neurons selective for three-dimensional (3D) shape are concentrated in the lower bank of the superior temporal sulcus, whereas neurons in lateral TE are generally unselective for 3D shape, though equally selective for 2D shape. These findings reveal that TE consists of at least two distinct areas, one of which processes a specific object property.

Animals↗

Three-dimensional shape coding in inferior temporal cortex.

Neurons in the rostral lower bank of the superior temporal sulcus (TEs), part of the inferior temporal cortex, respond selectively to three-dimensional (3D) shapes. We have investigated how these neurons represent disparity-defined 3D structure. Most neurons were selective for either first-order (disparity gradients) or second-order (disparity curvature) disparities. The latter selectivity proved remarkably vulnerable to disparity discontinuities, such as sharp edges or steps in disparity. The majority of the neurons remained selective for small disparity variations within the stimulus. 3D shape selectivity was preserved when the frontoparallel position or the stimulus size was altered. Thus, in TEs, 3D shape is coded by first- and second-order disparity-selective neurons, which are highly sensitive to spatial variations of disparity.

Action Potentials↗

Metastatic breast cancer presenting with diabetes insipidus.

We present a case of acute-onset diabetes insipidus in a 60-year-old woman who had been treated for breast cancer. MR images showed a thickened and enhancing pituitary stalk and an asymmetrical hypophysis. The clinical diagnosis of a pituitary metastasis of the breast carcinoma was made.

Bone Neoplasms↗

The human ET(B) endothelin receptor heterologously produced in the methylotrophic yeast Pichia pastoris shows high-affinity binding and induction of stacked membranes.

The human endothelin B receptor (ET(B) receptor) was produced in the methylotrophic yeast Pichia pastoris under transcriptional control of the highly inducible alcohol oxidase 1 (AOX1) gene promoter. In the expression plasmids pPIC9KFlagET(B)Bio and pPIC9KFlag deltaGPET(B)Bio the ET(B) receptor coding region was fused in frame to the Saccharomyces cerevisiae alpha-factor prepropeptide and the FLAG-tag. In both constructs, the receptor was also fused to a biotinylation domain. Additionally, in pPIC9KFlag deltaGPET(B)Bio the putative N-glycosylation site and a protease site have been deleted by site directed mutagenesis. Crude membranes prepared from recombinant P. pastoris revealed specific and saturable binding of [125I]ET-1 with a K(D) of about 42 pM. Receptor levels of 60 pmol/mg and 35 pmol/mg for the Flag deltaGPET(B)Bio and the FlagET(B)Bio construct, respectively, were determined. The pharmacological profile for ET-1, ET-2 and ET-3 were as expected for a subtype B endothelin (ET) receptor. Immunoblot analysis showed an apparent molecular mass of 55 kDa for the Kex2-processed and about 74 kDa for the Kex2-unprocessed receptor. Contrary to the Flag deltaGPET(B)Bio construct, the FlagET(B)Bio construct was not correctly processed by the internal Kex2 endopeptidase. As was detected by ultrastructural analysis of recombinant yeast cells, high-level production of the receptor resulted in the formation of stacked membranes.

Amino Acid Sequence↗

Macaque inferior temporal neurons are selective for disparity-defined three-dimensional shapes.

Real-world objects are three-dimensional (3D). Yet, it is unknown whether the neurons of the inferior temporal cortex, which is critical for object recognition, are selective for the 3D shape of objects. We tested for such selectivity by comparing responses to stereo-defined curved 3D shapes derived from identical pairs of monocular images. More than one-third of macaque inferior temporal neurons were selective for 3D shape. In the vast majority of those neurons, this selectivity depended on the global binocular disparity gradient and not on the local disparity. Thus, inferior temporal cortex processes not only two-dimensional but also 3D shape information.

Animals↗