Identification of quantitative trait loci for chemical/inflammatory nociception in mice

Sensitivity to pain is widely variable, and much of this variability is genetic in origin. The specific genes responsible have begun to be identified, but only for thermal nociception. In order to facilitate the identification of polymorphic, pain-related genes with more clinical relevance, we performed quantitative trait locus (QTL) mapping studies of the most common assay of inflammatory nociception, the formalin test. QTL mapping is a technique that exploits naturally occurring variability among inbred strains for the identification of genomic locations containing genes contributing to that variability. An F2 intercross was constructed using inbred A/J and C57BL/6J mice as progenitors, strains previously shown to display resistance and sensitivity, respectively, to formalin-induced nociception. Following phenotypic testing (5% formalin, 25 microl intraplantar injection), mice were genotyped at 90 microsatellite markers spanning the genome. We provide evidence for two statistically significant formalin test QTLs - chromosomal regions whose inheritance is associated with trait variability - on distal mouse chromosomes 9 and 10. Identification of the genes underlying these QTLs may illuminate the basis of individual differences in inflammatory pain, and lead to novel analgesic treatment strategies.     

The effect of prestorage irradiation on posttransfusion red cell survival

Transfusion-associated graft-versus-host disease (TA-GVHD) may occur whenever immunologically competent allogeneic lymphocytes are transfused to an immunocompromised recipient. Irradiation of blood components eliminates the risk of TA-GVHD but may damage the cellular elements in the transfused component, particularly if the cells are stored for prolonged periods in the irradiated state. To study the effect of irradiation on long-term storage of red cells, AS-1 red cells from eight normal subjects were prepared on two occasions. On one occasion, the units were stored as standard AS-1 red cells for 42 days at 4 degrees C; on the other, they were exposed to 3000 cGy radiation within 4 hours of collection and then were stored as AS-1 red cells for 42 days at 4 degrees C. The donations were at least 12 weeks apart. Irradiated units demonstrated significant elevations in poststorage plasma hemoglobin (Hb) (623 +/- 206 vs. 429 +/- 194 g/dL [6230 +/- 2060 vs. 4290 +/- 1940 g/L], p less than 0.02) and plasma potassium (78 +/- 4 vs. 43 +/- 9 mEq/L [78 +/- 4 vs. 43 +/- 9 mmol/L], p less than 0.01) and significant decreases in red cell ATP (1.9 +/- 0.2 vs. 2.1 +/- 0.3 microM/g Hb, p less than 0.04) and 24-hour posttransfusion red cell recovery (68.5 vs. 78.4%, p less than 0.02), as compared to nonirradiated units. It can be concluded that irradiation with 3000 cGy damages red cells and that long-term storage in the irradiated state may enhance this damage. Red cells should not be stored for 42 days after irradiation with 3000 cGy.     

Fractionation of Spatial Memory in GRM2/3 (mGlu2/mGlu3) Double Knockout Mice Reveals a Role for Group II Metabotropic Glutamate Receptors at the Interface Between Arousal and Cognition

Group II metabotropic glutamate receptors (mGluR2 and mGluR3, encoded by GRM2 and GRM3) are implicated in hippocampal function and cognition, and in the pathophysiology and treatment of schizophrenia and other psychiatric disorders. However, pharmacological and behavioral studies with group II mGluR agonists and antagonists have produced complex results. Here, we studied hippocampus-dependent memory in GRM2/3 double knockout (GRM2/3^−/−) mice in an iterative sequence of experiments. We found that they were impaired on appetitively motivated spatial reference and working memory tasks, and on a spatial novelty preference task that relies on animals'' exploratory drive, but were unimpaired on aversively motivated spatial memory paradigms. GRM2/3^−/− mice also performed normally on an appetitively motivated, non-spatial, visual discrimination task. These results likely reflect an interaction between GRM2/3 genotype and the arousal-inducing properties of the experimental paradigm. The deficit seen on appetitive and exploratory spatial memory tasks may be absent in aversive tasks because the latter induce higher levels of arousal, which rescue spatial learning. Consistent with an altered arousal–cognition relationship in GRM2/3^−/− mice, injection stress worsened appetitively motivated, spatial working memory in wild-types, but enhanced performance in GRM2/3^−/− mice. GRM2/3^−/− mice were also hypoactive in response to amphetamine. This fractionation of hippocampus-dependent memory depending on the appetitive-aversive context is to our knowledge unique, and suggests a role for group II mGluRs at the interface of arousal and cognition. These arousal-dependent effects may explain apparently conflicting data from previous studies, and have translational relevance for the involvement of these receptors in schizophrenia and other disorders.     

Allosteric modulators of NR2B-containing NMDA receptors: molecular mechanisms and therapeutic potential

N-methyl-D-aspartate receptors (NMDARs) are ion channels gated by glutamate, the major excitatory neurotransmitter in the mammalian central nervous system (CNS). They are widespread in the CNS and are involved in numerous physiological and pathological processes including synaptic plasticity, chronic pain and psychosis. Aberrant NMDAR activity also plays an important role in the neuronal loss associated with ischaemic insults and major degenerative disorders including Parkinson''s and Alzheimer''s disease. Agents that target and alter NMDAR function may, thus, have therapeutic benefit. Interestingly, NMDARs are endowed with multiple extracellular regulatory sites that recognize ions or small molecule ligands, some of which are likely to regulate receptor function in vivo. These allosteric sites, which differ from agonist-binding and channel-permeation sites, provide means to modulate, either positively or negatively, NMDAR activity. The present review focuses on allosteric modulation of NMDARs containing the NR2B subunit. Indeed, the NR2B subunit confers a particularly rich pharmacology with distinct recognition sites for exogenous and endogenous allosteric ligands. Moreover, NR2B-containing receptors, compared with other NMDAR subtypes, appear to contribute preferentially to pathological processes linked to overexcitation of glutamatergic pathways. The actions of extracellular H⁺, Mg²⁺, Zn²⁺, of polyamines and neurosteroids, and of the synthetic compounds ifenprodil and derivatives (‘prodils’) are presented. Particular emphasis is put upon the structural determinants and molecular mechanisms that underlie the effects exerted by these agents. A better understanding of how NR2B-containing NMDARs (and NMDARs in general) operate and how they can be modulated should help define new strategies to counteract the deleterious effects of dysregulated NMDAR activity.     

Pitfalls in MR measurement of tissue blood flow with intravascular tracers: Which mean transit time?

Measuring tissue blood flow with NMR imaging of intravascular tracers is more difficult than measurements of tissue blood volume. One major obstacle to the application of the Central Volume Principle is the direct measurement of the mean transit time. In this note, we demonstrate that mean transit time (MTT), which relates tissue blood volume to blood flow via the Central Volume Principle, is not the first moment of the concentration-time curve for MR or CT imaging of purely intravascular tracers. However, while first moment methods cannot be used by themselves to determine absolute flow, we show that transit curves may provide a useful relative measure of flow, for example, by considering ratios of the first moments.     

Ponseti technique of correcting idiopathic clubfoot deformity

The efficacy of the Ponseti method of clubfoot treatment at Queen Elizabeth Central Hospital (QECH) was analysed from December 2000 to December 2001. Ninety one patients, 60 boys and 31 girls were prospectively and consecutively enrolled. 31 patients had a unilateral clubfoot and 60 had bilateral clubfeet. 77 patients had primary idiopathic clubfoot and 14 patients had clubfeet associated with other congenital anomalies such as arthrogryposis. 32 patients (35%) were lost to follow up; records were inadequate for 6 patients leaving 54 patients (59%) available for analysis. Three main groups were assessed. Group 1 (24 patients): virgin previously untreated primary idiopathic clubfeet: Ponseti method used from outset. Group 2 (19 patients): complex, primary idiopathic clubfeet: Ponseti method introduced after other manipulation techniques. Group 3 (11 patients): clubfeet associated with other congenital anomalies. In group 1, the mean age at start of treatment was 9.7 weeks and the mean time to correction of deformity was 7.4 weeks. 20 out of 24 patients (84%) had correction of deformity and remained corrected. 4 patients had recurrence of deformity mainly due to non compliance with treatment and correction was achieved once treatment restarted. In group 2, 19 patients had been on treatment for a mean period of 32 weeks prior to commencement of Ponseti treatment. In 17 of these patients the deformity was still uncorrected. Ponseti treatment was commenced at a mean age of 36 weeks and correction was achieved in all 17 patients after a mean treatment duration of 7.1 weeks. In group 3, correction of deformity was initially achieved in only 60%. The period to achieve correction was long and incidence of recurrence of deformity was high.The success of conservative treatment of clubfeet using the Ponseti method has resulted in large decrease in the number of surgical procedures performed under general anaesthaesia such as posteromedial releases in the treatment of clubfeet at QECH. This method has now been adopted as the Standard treatment of clubfoot and is being advocated nationwide.     

Gene Probe Analysis in an Informative Family with Multiple Endocrine Neoplasia Syndrome Type 2A (MEN 2A). Improvement in Carrier Risk Estimation

Gene probe analysis of the MEN 2A locus on chromosome 10 hasbeen undertaken using the markers TB10.163, RBP 3 and TB14.34in a large kindred with familial medullary thyroid carcinomas,with or without phaeochromocytomas or primary hyperparathyroidism.A maximum LOD score of 2.97 gave strong evidence of close linkagewith zero recombination. For 12 members of the family so far not known to be affectedby any form of the disease the estimated risk of carrying thegene has been considerably decreased in all but one, whose riskhas been greatly increased.     

The clinical use of supine left lateral leg cycle ergometry for exercise electrocardiographic testing in women, as used in exercise echocardiography.

BACKGROUND: Two-dimensional exercise echocardiography is commonly performed in the supine (SUP) left lateral posture (SLL) to optimize imaging quality. OBJECTIVES: To assess the clinical use of SLL cycle ergometry, we determined the metabolic, cardiovascular, and hemodynamic responses during graded leg cycle ergometry in women, performed in SLL, commonly used during exercise echocardiography, and compared our findings with those obtained during upright (UP) and SUP leg cycle ergometry. METHODS: A total of 21 apparently healthy women performed leg cycle ergometry in 3 distinct postures (UP, SUP, and SLL). RESULTS: Peak oxygen consumption and peak achieved workload during SLL cycle ergometry were significantly lower compared with UP cycle ergometry, indicating that in SLL physical work capacity would be underestimated compared with that obtained for the UP and SUP postures. The peak heart rate was significantly lower in SLL and the peak systolic blood pressure higher, compared with UP. Maximal rate pressure product was not significantly different among the postures, indicating the equivalent value of SLL with regard to augmenting myocardial oxygen demand during exercise. Stroke volume (calculated from aortic Doppler flow integral) was higher at rest, and increased to a smaller extent during exercise, in the SUP posture and SLL compared with UP. Similar peak values were attained for the 3 postures. CONCLUSIONS: SLL is not a suitable modality for the assessment of functional status or for the derivation of target heart rates for exercise training in UP posture. However, SLL leg cycle ergometry exercise provokes a comparable stimulus for the detection of coronary artery disease, as it will increase myocardial oxygen demand to the same extent as UP leg cycle exercise.     

Risk factors for infection in Malaysian patients with systemic lupus erythematosus

To determine the incidence, types and risk factors for infection in systemic lupus erythematosus (SLE) patients in Kuala Lumpur, Malaysia, we retrospectively reviewed the medical records of 102 patients with definite SLE attending a specialist clinic. Details of major infections (pneumonia or severe infection requiring intravenous therapy) and minor infections, and their time of onset in relation to immunosuppressive therapy and disease flares were recorded. There were 77 major and 163 minor infections during 564 patient-years of follow-up. In the month following a course of pulse methylprednisolone, the incidence of major infection was 20 times higher and the incidence of minor infection was 10 times higher than at other periods (p<0.0001). In the month after disease flare, the incidence of major infection was 10 times higher and the incidence of minor infection six times higher than at other times (p<0.0001). After allowing for methylprednisolone therapy and disease flares, there was no increase in the rate of infections during treatment with azathioprine, oral or intravenous cyclophosphamide. There was no effect of renal involvement on infection rate.