3H]Methoxymethyl-3-[(2-methyl-1,3-thiazol-4-yl)ethynyl]pyridine binding to metabotropic glutamate receptor subtype 5 in rodent brain: in vitro and in vivo characterization

The binding of [3H]methoxymethyl-3-[(2-methyl-1,3-thiazol-4-yl)ethynyl]pyridine (methoxymethyl-MTEP), a potent and selective antagonist for metabotropic glutamate (mGlu)5 receptors, was characterized in rat brain both in vitro and in vivo. Nonspecific binding, as defined with 10 microM 2-methyl-6-(phenylethynyl)-pyridine (MPEP), was less than 10% of total binding in rat brain membranes. The binding of [3H]methoxymethyl-MTEP was of high affinity (K(d) = 20 +/- 2.7 nM), saturable (B(max) = 487 +/- 48 fmol/mg protein), and to a single site. The mGlu5 antagonists methoxymethyl-MTEP and MPEP displaced [3H]methoxymethyl-MTEP binding with IC50 values of 30 and 15 nM, respectively. In vivo administration of [3H]methoxymethyl-MTEP (50 microCi/kg i.v.) revealed 12-fold higher binding in hippocampus (an area enriched in mGlu5 receptors) relative to cerebellum (an area with few mGlu5 receptors) in rats. Similarly, administration of [3H]methoxymethyl-MTEP to mGlu5-deficient mice demonstrated binding at background levels in forebrain, whereas wild-type littermates exhibited 17-fold higher binding in forebrain relative to cerebellum. Systemic administration of unlabeled mGlu5 antagonists methoxymethyl-MTEP and MPEP to rats reduced the binding of [3H]methoxymethyl-MTEP with ID50 values of 0.8 and 2 mg/kg i.p., respectively, 1 h post-treatment. The mGlu5 agonist 2-chloro-5-hydroxyphenylglycine (CHPG) (0.3, 1, and 3 micromol) dose-dependently increased phosphoinositide (PI) hydrolysis in the hippocampus after i.c.v. administration in rats. CHPG-evoked increases in PI hydrolysis were blocked with MPEP at a dose (10 mg/kg i.p.) that markedly reduced [3H]methoxymethyl-MTEP binding in vivo. These results indicate that [3H]methoxymethyl-MTEP is a selective radioligand for labeling mGlu5 and is useful for studying the binding of mGlu5 receptors in rat brain in vitro and in vivo.     

Comparison of cardiac troponin I and creatine kinase ratios in the detection of myocardial injury after aortic surgery

BACKGROUND: Perioperative myocardial infarction may not be diagnosed correctly because World Health Organization criteria are often not met and creatinine kinase myocardial fraction (creatinine kinase/creatinine kinase MB isoenzyme; CK/CK-MB) ratios can be difficult to interpret. Cardiac troponin (cTn) I and cTnT are the most sensitive and specific markers of myocardial cell necrosis currently available but are not widely used in surgical practice. The aim was to compare cTnI and CK/CK-MB ratios in the detection of myocardial injury following aortic surgery. METHODS: This was a prospective study of 59 patients undergoing elective (n = 28) or ruptured (n = 24) abdominal aortic aneurysm repair or elective aortofemoral bypass (n = 7). cTnI level was measured before operation and at 6, 24 and 48 h after surgery. The CK/CK-MB ratio was measured where cTnI was detectable. RESULTS: Some 14 of 24 emergency and ten of 35 elective patients had detectable cTnI (greater than 0.5 ng/ml) at one or more time-points. The CK/CK-MB ratio was greater than 5 per cent in only four of 24 patients having an emergency operation and in none of the elective patients with detectable cTnI. CONCLUSION: Over half of patients undergoing emergency operation and more than a quarter of those having elective aortic surgery suffered myocardial necrosis as determined by detectable cTnI levels. This was accompanied by a raised CK/CK-MB ratio in less than one-fifth of patients.     

Oral anticoagulation in paediatric patients: dose requirements and complications

The lack of oral anticoagulant guidelines specific to paediatric practice has led to the adoption of adult regimens, often without scientific evidence of efficacy or safety. A two year prospective study of anticoagulant control was carried out in 45 children aged 9 months to 18 years, the majority of whom were receiving primary prophylactic anticoagulation. The main indication was congenital heart disease, either with (n = 8) or without (n = 34) mechanical valve prosthesis. During a follow up period of 602 patient months the average interval between visits was three weeks. Target international normalised ratios (INRs) were achieved on 62% and 39% of visits for children with low target INR (2.0-3.0) and high target INR (3.0-4.0) respectively. However warfarin dose was altered on only 22% of visits. Warfarin doses required to achieve a stable INR of 2.0-3.0 in 33 children were strongly correlated with weight [dose (mg/d) = 0.07 x weight (kg) + 0.54] but independently influenced by age. No thrombotic complications were recorded, and haemorrhagic events were infrequent (2.1% of visits) and, with one exception, minor. Safe outpatient oral anticoagulation is feasible in children, whose warfarin requirements appear moderately predictable and whose control is no more erratic than that of adults.     

Analysis of the cytotoxic properties of linoleic acid metabolites produced by renal and hepatic P450s

Cytochrome P450 epoxidation of linoleic acid produces biologically active metabolites which have been associated with many pathological conditions that often lead to acute renal failure. In the present study, we evaluated the ability of specific cytochrome P450s to produce linoleic acid monoepoxides. We then tested the cytotoxic properties of linoleic acid, linoleic acid monoepoxides, and corresponding diols in a rabbit renal proximal tubule model. CYP1A2, CYP2E1, CYP2J2, CYP2J3, CYP2J5, and CYP2J9 metabolized linoleic acid at rates comparable to arachidonic acid and produced linoleic acid monoepoxides as major products. Cytotoxicity studies showed that linoleic acid, linoleic acid monoepoxides, and corresponding diols are toxic at pathologically relevant concentrations (100-500 microM). Concentration-dependent studies showed that linoleic acid and linoleic acid monoepoxides are the most toxic and induce mitochondrial dysfunction prior to cell death. Cytoprotectants known to block cell death associated with mitochondrial dysfunction and oxidative stress did not prevent cell death induced by linoleic acid and linoleic acid monoepoxides. This study shows that P450s in the CYP1 and CYP2 gene families metabolize linoleic acid to linoleic acid monoepoxides and that the monoepoxides, as well as linoleic acid, disrupt mitochondrial function without causing oxidative stress.     

Pathways of tumor spread through the lung: radiologic correlations with anatomy and pathology

The pathways of tumor spread through the lung are described and their significance for radiographic interpretation is illustrated. A key to understanding the spread of bronchogenic carcinoma is the realization that although the normal flow of lymph in the pulmonary lymphatics is centripetal, lymphatic obstruction can cause reversal of flow. As a result, tumor cells are commonly carried centrifugally to the periphery in lymphatics or the connective tissue around them, and remote pleural involvement, secondary parenchymal masses, or satellite nodules may develop. Failure to appreciate peripheral spread of tumor has negative consequences for tumor staging, surgery, and radiotherapy. In the absence of hilar node involvement causing obstruction, long line shadows more than 0.5 inch (1.25 cm) in length proximal to a peripheral mass very infrequently represent tumor.     

Reduction of dental decay in rampant caries individuals following short-term kanamycin treatment.

A week of kanamycin gel treatment before and after the placement of dental restorations, compared to a placebo gel treatment, significantly reduced the levels of cultivable bacteria, S mutans and S sanguis, in the plaque samples collected immediately after the completion of the gel treatments, and was associated with a 46% reduction in new carious surfaces in the 14- to 37-month period following the gel treatment.     

Differing responses of globin and glycophorin gene expression to hemin in the human leukemia cell line K562

The human leukemia cell line, K562, produces embryonic and fetal hemoglobins and glycophorin A, proteins normally associated only with erythroid cells. Hemoglobin accumulation is enhanced by exposure of the cells to 0.05 mM hemin. We have examined K562 cells before and after exposure to hemin to determine whether expression of these erythroid proteins was shared by all cells or confined to specific subpopulations. Globin gene expression was examined by quantitation of globin mRNA sequences, using a 3H-globin cDNA molecular hybridization probe. Constitutive cells produced globin mRNA, the content of which was increased 3-4-fold by hemin. Cell-to-cell distribution of globin mRNA was determined by in situ hybridization of 3H-globin cDNA to constitutive and hemin-treated K562 cells. Virtually all cells in the culture exhibited grain counts above background, indicating globin gene expression by all cells, rather than a confined subpopulation. Virtually all hemin-treated cells had 3-5-fold higher grain counts, indicating uniformly increased globin gene expression. The glycophorin content of K562 cells was estimated by fluorescence-activated cell sorting (FACS) of cells labeled with fluorescein-labeled antiglycophorin antiserum. The vast majority of constitutive cells contained glycophorin, but exhibited to apparent increase in glycophorin accumulation after hemin exposure. Thus, glycophorin and globin genes exhibited differential responses to hemin. These differences could reflect normal differences in the patterns of specialized gene expression in stem cells. Alternatively, different aberrations of gene expression could be occurring in response to the determinants of the neoplastic properties of K562.     

Percutaneous transjejunal catheterization of Roux-en-Y biliary-jejunal anastomoses

Percutaneous transjejunal biliary interventions were performed in 11 patients with Roux-en-Y jejunobiliary anastomoses that had not been specially constructed for percutaneous puncture. These procedures were performed to evaluate the utility of this approach in patients with complex biliary abnormalities. Catheterization from the jejunal loop into the biliary tree was successful in each case. In three cases, long-term stents were placed; eight other catheters were removed after the intervention. No complications were encountered. This preliminary experience suggests that this approach can provide safe access for biliary intervention.