Brain catecholamine metabolism in catechol-O-methyltransferase (COMT)-deficient mice

Catechol-O-methyltransferase (COMT) catalyses the O-methylation of compounds having a catechol structure and its main function involves the elimination of biologically active or toxic catechols and their metabolites. By means of homologous recombination in embryonic stem cells, a strain of mice has been produced in which the gene encoding the COMT enzyme is disrupted. We report here the levels of catecholamines and their metabolites in striatal extracellular fluid in these mice as well as in homogenates from different parts of the brain, under normal conditions and after acute levodopa administration. In immunoblotting studies, COMT-knockout mice had no COMT protein in brain or kidney tissues but the amounts of catecholamine synthesizing and other metabolizing enzyme proteins were normal. Under normal conditions, COMT deficiency does not appear to affect significantly brain dopamine and noradrenaline levels in spite of relevant changes in their metabolites. This finding is consistent with previous pharmacological studies with COMT inhibitors and confirms the pivotal role of synaptic reuptake processes and monoamine oxidase-dependent metabolism in terminating the actions of catecholamines at nerve terminals. In contrast, when COMT-deficient mice are challenged with l-dihydroxyphenylalanine, they show an extensive accumulation of 3,4-dihydroxyphenylacetic acid and dihydroxyphenylglycol and even dopamine, revealing an important role for COMT under such situations. Notably, in some cases these changes appear to be Comt gene dosage-dependent, brain-region specific and sexually dimorphic. Our results may have implications for improving the treatment of Parkinson's disease and for understanding the contribution of the natural variation in COMT activity to psychiatric phenotypes.     

Meat consumption and meat preparation in relation to colorectal adenomas among sporadic and HNPCC family patients in The Netherlands

Meat consumption and meat preparation methods are thought to be associated with the risk of sporadic colorectal cancer, and possibly adenomas. As the same somatic mutations occur in sporadic adenomas and hereditary non-polyposis colorectal cancer (HNPCC)-related adenomas, similar exogenous factors may play a role in the development of both types of adenoma. In a case control study among 57 sporadic colorectal adenoma cases and 62 adenoma cases from HNPCC families (and 148 adenoma-free controls) from the Netherlands, we examined whether meat consumption and preparation are similarly associated with sporadic and suspected HNPCC colorectal adenomas. Frequency of meat consumption was not significantly associated with adenoma risk in our population of sporadic and HNPCC family cases and controls (Odds Ratios (OR) for high versus low consumption were 1.0 and 0.6, respectively). Interestingly, consumption of red meat and specific preparation methods (i.e., "not adding any water" and " closed lid with most meat types") slightly, but non-significantly, increased the risk of adenomas in the sporadic group only (OR, 95% Confidence Interval (CI): 4.1, 0.7-23.0, 2.0, 0.6-6.5 and 2.6, 0.9-7.2, respectively). This is the first study to examine possible differences or similarities in risk factors for sporadic and HNPCC colorectal carcinogenesis. Our results do not provide support for meat consumption as a risk factor for adenoma formation in HNPCC family members. Some characteristics of habitual meat preparation in the Netherlands may, however, increase the risk of sporadic adenomas.     

Concurrent LOH at multiple loci in human malignant mesothelioma with preferential loss of NF2 gene region

Human malignant mesothelioma (MM) is a highly aggressive neoplasm related to occupational asbestos exposure and characterised by a long latency period between the exposure and onset of disease. Previous studies indicate that losses at different genomic regions are present in MM. We examined allele loss at three known tumour suppressor gene regions (22q/NF2 gene, 9p/p16 gene, and 3p/FHIT gene) and at two other frequently deleted areas (14q and 6q) in MM. Loss of heterozygosity (LOH) was investigated in cell cultures and primary tumours with several highly polymorphic markers for each site. To study if LOH of the NF2 gene is a consistent feature in MM, we performed a more detailed analysis of chromosome 22q that included a NF2 marker (NF2CA3). We observed a high frequency of LOH occurring simultaneously at multiple loci. In particular, 100% of the cultured MM cells exhibited LOH at the NF2 gene region. From the other chromosomal sites analysed, recurrent allele loss was detected at 9p (5/7; 71%), 3p (4/7; 57%), 14q (3/7; 43%), and 6q (3/7; 43%). Of the 32 tumours, even those trimmed to exclude normal tissue, few showed LOH, suggesting consielment by normal cells within MM tumours, whereas tumour cells in primary cultures showed LOH already in passages 1-2. In conclusion, our present LOH data indicate that MM cells exhibit allele losses at multiple tumour suppressor gene sites concurrently, involving NF2 gene preferentially. This supports the view that the accumulation of multiple genetic hits is characteristic to malignant transformation of MM cells.     

Animal products and K-ras codon 12 and 13 mutations in colon carcinomas

K-ras gene mutations (codons 12 and 13) were determined by PCR-based mutant allele-specific amplification (MASA) in tumour tissue of 185 colon cancer patients: 36% harboured mutations, of which 82% were located in codon 12. High intakes of animal protein, calcium and poultry were differently associated with codon 12 and 13 mutations: odds ratios (OR) and 95% confidence intervals (95% CI) for codon 12 versus codon 13 were 9.0 (2.0-42), 4.1 (1.4-12) and 15 (1.4-160), respectively. In case-control comparisons, high intakes of animal protein and calcium were positively associated with colon tumours harbouring codon 12 mutations [for animal protein per 17 g, OR (95% CI) = 1.5 (1.0-2.1); for calcium per 459 mg, 1.2 (0.9-1.6)], while inverse associations were observed for tumours with K-ras mutations in codon 13 [for animal protein 0.4 (0.2-1.0); for calcium 0.6 (0. 3-1.2)]. Transition and transversion mutations were not differently associated with these dietary factors. These data suggest a different dietary aetiology of colon tumours harbouring K-ras codon 12 and 13 mutations.     

Cell cycle-dependent nucleocytoplasmic shuttling of the neurofibromatosis 2 tumour suppressor merlin

The neurofibromatosis 2 tumour suppressor merlin/schwannomin is structurally related to the ezrin-radixin-moesin family of proteins, which anchor actin cytoskeleton to specific membrane proteins and participate in cell signalling. Merlin inhibits cell growth with a yet unknown mechanism. As most tumour suppressors are linked to cell cycle control, we investigated merlin's behaviour during cell cycle. In glioma and osteosarcoma cells, endogenous merlin was targeted to the nucleus in a cell cycle-specific manner. Merlin accumulated perinuclearly at the G2/M phase, and shifted to the nucleus at early G1. During mitosis, merlin localized to mitotic spindles and at the contractile ring. Nuclear merlin was strongly reduced in confluent cells. Blocking of the CRM1/exportin nuclear export pathway led to accumulation of merlin in the nucleus. Activation of the p21-activated kinase or protein kinase A, which result in phosphorylation of merlin, did not affect its nuclear localization. Merlin regulates the activity of extracellular signal-regulated kinase 2 (ERK2) and nuclear localization of both proteins was induced by cell adhesion. Unlike ERK2, nuclear localization of merlin was not, however, dependent on intact actin cytoskeleton. These results link merlin to events related to cell cycle control and may help to resolve its tumour suppressor function.     

Is the learning curve for laparoscopic fundoplication determined by the teacher or the pupil?

BACKGROUND: For all surgical procedures, a surgeons' learning curve can be anticipated during which complication rates are increased. The aims of this study were to evaluate individual learning curves for a group of surgeons performing laparoscopic fundoplication and to evaluate if the Procedicus MIST-simulator (Mentice Inc., G?teborg, Sweden) accurately predicts surgical performance. METHODS: Twelve Nordic centers participated, each contributing with a "master" and a "pupil" surgeon. The pupils were tested in the simulator and thereafter performed their first 20 supervised operations. All procedures were videotaped and evaluated by 3 independent reviewers. RESULTS: A significant decrease in operative time (P <0.001) and a trend (P = 0.12) toward improved score were seen during the series. The master significantly affected the pupil's score (P =0.0137). The simulator-test showed no correlation with the operative score. CONCLUSIONS: Individual learning curves varied, and the teacher was shown to be the most important factor influencing the pupil's performance score. The correlation between assessed performance and patient outcome will be further investigated.     

Cognitive functions in relation to MRI findings 30 years after traumatic brain injury

OBJECTIVE: The aim of the study was to relate cognitive effects of a remote traumatic brain injury (TBI) to MRI findings and severity of injury. METHOD: Sixty-one patients were assessed on average 30 years after a TBI of variable severity. A comprehensive cognitive test battery was used to evaluate memory, executive functions and cognitive overall impairment. Multiple regression analyses were used to examine the relationships between cognitive variables and MRI volumetric findings (the volumes of the hippocampus and the lateral ventricles) and local contusions on MRI. Also, the effect of injury severity on cognitive outcome was evaluated. RESULTS: Reductions in hippocampal volumes and lateral ventricular enlargement were significantly associated with impaired memory functions, memory complaints and executive functions. Of the MRI parameters used, the best predictor for cognitive outcome was the volume of the lateral ventricle. There was only a modest relationship between severity of injury and cognitive performance. CONCLUSIONS: The results show that long-term memory impairments after TBI are associated with MRI volumetric measures. This suggests that the degree of diffuse injury leading to atrophic changes is prognostically more important than the initial severity of TBI.     

Anterior knee pain after intramedullary nailing of a tibial shaft fracture: an ultrasound study of the patellar tendons of 36 patients

OBJECTIVES: Chronic anterior knee pain is a common complication following intramedullary nailing of a tibial shaft fracture. The etiology of pain is often not known. This study sonographically examined the patellar tendons of patients with a nailed tibial shaft fracture. DESIGN: Prospective study. SETTING: University hospital. PATIENTS: Fifty consecutive patients with a nailed tibial shaft fracture were initially included in the study. Thirty-six of them could be measured at an average of 2.5 +/- 0.5 years after nail insertion (1.0 +/- 0.3 years after nail extraction). INTERVENTION: Reamed intramedullary nailing with 2 interlocking bolts at both ends of the nail (Grosse-Kempf-nail, Howmedica). MAIN OUTCOME MEASUREMENTS: The ultrasound investigation of the patellar tendons of the 36 patients. RESULTS: Twelve (33%) patients were painless and 24 (67%) patients had anterior knee pain at follow-up. With the reference to the mean difference in the thickness of the distal part of the patellar tendon in the operated limb versus nonoperated limb, the result was 1.4 +/- 1.1 mm in the chronic pain group and 2.6 +/- 2.5 mm in the painless group (P = 0.135, [95% confidence interval for the group difference = -0.4-2.8]). The corresponding values for the proximal part of the patellar tendon was 1.4 +/- 1.3 mm in the chronic pain group and 2.3 +/- 2.3 mm in the painless group (P = 0.251, [95% confidence interval for the group difference = -0.7-2.4]). There were no statistically significantly differences between study groups in the blood circulation of the patellar tendon or at the entry point, calcification of the patellar tendon, granulation tissue at the entry point, or occurrence of low echo areas in the patellar tendon. CONCLUSION: After intramedullary nailing of a tibial shaft fracture, patients with or without anterior knee pain show similar changes in the ultrasound investigation of their patellar tendons. Based on those findings, it does not appear to make any difference as to the approach used (paratendinous or transtendinous) for intramedullary nailing of the tibia.     

Fixation of syndesmotic ruptures in 38 patients with a malleolar fracture: a randomized study comparing a metallic and a bioabsorbable screw

OBJECTIVES: To compare the performance of a metallic and a biodegradable screw in the fixation of tibia-fibula syndesmotic ruptures. DESIGN: A randomized, prospective, and blinded study. SETTING: Central hospital, Department of Surgery. PATIENTS: Forty consecutive patients with a clinically verified syndesmotic rupture in association with a malleolar fracture, of whom 38 completed the study. INTERVENTION: After syndesmosis rupture was diagnosed, implant selection was performed intraoperatively by a strict randomization with sealed envelopes. Eighteen patients were treated with a metallic screw, and 20 with a bioabsorbable polylevolactic acid screw. The metallic screws were removed in a second operation at 8 weeks postoperatively. All patients had a treatment-blinded clinical and radiographic control after a mean follow-up of 35 (range 17-51) months. MAIN OUTCOME MEASURES: Return to previous physical activity level, evaluation of ankle stability, range of motion, circumference of the ankle, and a radiographic evaluation of both ankles including a measure of the talocrural, medial joint, and syndesmotic space widths. RESULTS: More patients with a polylevolactic acid screw returned to their previous activity level, and there was less swelling in the ankles of these patients, but joint motion was similar between the groups. The mean values of syndesmotic and medial joint spaces were significantly higher in the radiographs of the operated ankles when compared to the uninjured ankle, but there was not a correlation to the type of screw used. CONCLUSIONS: Polylevolactic acid screws worked as well, or slightly better than, metallic ones in syndesmosis fixation in patients with an ankle fracture.