Cyclooxygenase-2 inhibition prevents delayed death of CA1 hippocampal neurons following global ischemia

The inducible isoform of the enzyme cyclooxygenase-2 (COX2) is an immediate early gene induced by synaptic activity in the brain. COX2 activity is an important mediator of inflammation, but it is not known whether COX2 activity is pathogenic in brain. To study the role of COX2 activity in ischemic injury in brain, expression of COX2 mRNA and protein and the effect of treatment with a COX2 inhibitor on neuronal survival in a rat model of global ischemia were determined. Expression of both COX2 mRNA and protein was increased after ischemia in CA1 hippocampal neurons before their death. There was increased survival of CA1 neurons in rats treated with the COX2-selective inhibitor SC58125 [1-[(4-methylsulfonyl) phenyl]-3-trifluoro-methyl-5-[(4-fluoro)phenyl] pyrazole] before or after global ischemia compared with vehicle controls. Furthermore, hippocampal prostaglandin E2 concentrations 24 h after global ischemia were decreased in drug-treated animals compared with vehicle-treated controls. These results suggest that COX2 activity contributes to CA1 neuronal death after global ischemia.     

Cognitive ability and cerebral lateralisation in transsexuals

INTRODUCTION: The application of high-frequency current to the AV junctional area results in a temperature rise in the myocardium and may cause accelerated junctional rhythm (AJR). The aim of the study was to characterize heat-induced AJR in an in vitro animal model. METHODS AND RESULTS: Studies were performed in isolated perfused pig and rabbit hearts. Using a small heating probe, we could induce AJR from a discrete area located in the middle of the triangle of Koch, which was smaller than the area from which RF energy application could elicit AJR. Histology showed that the heat-sensitive area was located over, or close to, the compact AV node. It did not correspond with the areas where double potentials were found or with the site(s) of earliest atrial activation during VA conduction. Microelectrode recordings revealed that AJR arose in nodal-type cells. Heat increased the slope of the phase 4 depolarization and shortened the action potential duration. Two types of AJR were observed: the first one was regular and the second one showed irregularity in the intervals. Interaction of multiple foci and the presence of conduction block between the foci and the His bundle caused the irregularity of the His-His intervals during the second type of AJR. CONCLUSION: AJR observed during heat and RF application in the AV nodal area results from the effect of heat on AV nodal cells with underlying pacemaker activity. The heat-sensitive area is located over, or very close to, the compact AV node.     

DNA polymerase fidelity: from genetics toward a biochemical understanding

This review summarizes mutagenesis studies, emphasizing the use of bacteriophage T4 mutator and antimutator strains. Early genetic studies on T4 identified mutator and antimutator variants of DNA polymerase that, in turn, stimulated the development of model systems for the study of DNA polymerase fidelity in vitro. Later enzymatic studies using purified T4 mutator and antimutator polymerases were essential in elucidating mechanisms of base selection and exonuclease proofreading. In both cases, the base analogue 2-aminopurine (2AP) proved tremendously useful-first as a mutagen in vivo and then as a probe of DNA polymerase fidelity in vitro. Investigations into mechanisms of DNA polymerase fidelity inspired theoretical models that, in turn, called for kinetic and thermodynamic analyses. Thus, the field of DNA synthesis fidelity has grown from many directions: genetics, enzymology, kinetics, physical biochemistry, and thermodynamics, and today the interplay continues. The relative contributions of hydrogen bonding and base stacking to the accuracy of DNA synthesis are beginning to be deciphered. For the future, the main challenges lie in understanding the origins of mutational hot and cold spots.     

Chromosomal duplication accompanies allelic loss in non-small cell lung carcinoma

Hemizygous deletion in the short (p) arm of chromosome 3 is a common finding in non-small cell lung carcinoma (NSCLC) and is postulated to be a crucial early change in lung tumorigenesis. Yet one of the most frequent nuclear abnormalities in both NSCLC and premalignant bronchial epithelium is increase in chromosomal copy number. Deletion and duplication have not been assessed in the same tumor set by both molecular and cytogenetic methods to determine whether allelic loss correlates with chromosomal duplication in the same tumor cell populations. It is also not established what biological mechanisms might lead to allelic deletion and chromosomal duplication. We have investigated changes in the copy number of chromosome 3 in touch preparations of 38 NSCLCs (19 adenocarcinomas and 19 squamous cell carcinomas) using dual-target, dual-color fluorescence in situ hybridization (FISH) assays. Chromosome 3 centromere probe was matched with a 3p14.2 probe [intron 4 of the fragile histidine triad (FHIT) gene] and a 3p21.31 probe (HSemaIV gene). We then correlated FISH results with results of molecular analyses for allelic losses at loci in the regions to which the FISH probes mapped in 20 of these cases. Although various combinations of FISH abnormalities were sometimes detected within the same specimens, individual cases could be classified according to the predominant FISH pattern, usually with one abnormality present in >60% of tumor cells. Chromosomal duplication, indicated by the presence of more than two centromeric signals, was the most frequent abnormality observed by FISH and was accompanied by loss of specific sequences on 3p in approximately one-half of the specimens in which it was observed. The most frequent abnormality observed by molecular analysis was loss of heterozygosity (LOH) in both of the chromosomal regions tested and was demonstrated in 83% of cases with chromosomal duplication. We conclude that LOH may occur in the presence of chromosomal duplication, suggesting that the duplicated chromosome is homozygous. Our findings imply that LOH occurs before chromosomal duplication during lung carcinogenesis.     

Views of hospital staff on the management of hypertension

A questionnaire concerning the detection and management of hypertension was presented to 265 hospital doctors, 114 medical students and 59 student nurses. Of these 75% were completed. Although only 76% thought that routine measurement was necessary in outpatients, 92% of respondents thought that blood pressure (BP) should be measured routinely in all in-patients. A total of 17% of all doctors and 11% of physicians indicated that they would not use drug treatment until the diastolic BP exceeded 105 mmHg. Thirty-four per cent of respondents still use diastolic phase IV and 84% felt that BP should be measured 2-4 times before deciding on treatment but the posture of the patient (lying, sitting or standing) during recording was inconsistent. Seventy-seven per cent of respondents indicated that they recorded BP to the nearest 5 mmHg and 4% to the nearest 10 mmHg. Despite the literature on the subject, there are still widely differing opinions amongst medical staff on how to record BP and at what level it should be treated.     

Effects of central and peripheral administration of kynurenic acid on hippocampal evoked responses in vivo and in vitro

Kynurenic acid is an excitatory amino acid antagonist with preferential activity at the N-methyl-D-aspartate subtype of glutamate receptors. It is produced endogenously in the brain, but is synthesized more effectively in the periphery. The influence of peripheral kynurenic acid on brain function is unclear because kynurenic acid is likely to penetrate the blood-brain barrier poorly. To determine the potential central effects of peripheral kynurenic acid, we compared its effects in the hippocampus after peripheral or direct administration. The hippocampus of the rat was chosen as a test system because this region receives glutamatergic inputs, and because responses to stimulation of these inputs can be compared after peripheral drug administration in vivo, and after direct administration of drugs in vitro. Peripherally-administered kynurenic acid was injected via a catheter in the jugular vein. Bath-application to hippocampal slices was used to test effects of direct administration. Area CA1 pyramidal cells and dentate gyrus granule cells were examined by extracellular recording and stimulation of area CA3 or the perforant path, respectively. Pairs of identical stimuli were used to assess paired-pulse inhibition and paired-pulse facilitation. Kynurenic acid decreased evoked responses in area CA1 and the dentate gyrus, both in vivo and in vitro. Effective concentrations were in the low micromolar range, and therefore were likely to be mediated by antagonism of N-methyl-D-aspartate receptors. In both preparations, area CA1 was more sensitive than the dentate gyrus, and paired-pulse facilitation was affected, but not paired-pulse inhibition. Control solutions had no effect. We conclude that kynurenic acid can enter the brain after peripheral administration, and that peripheral and direct effects in the hippocampus are qualitatively similar. Therefore, we predict that effects of endogenous kynurenic acid that was synthesized peripherally or centrally would be similar. Furthermore, the results suggest that modulation of the glycine site of the N-methyl-D-aspartate receptor, for example by kynurenic acid, may vary considerably among different brain areas.     

Participation of AT1 and AT2 receptor subtypes in the tonic inhibitory modulation of baroreceptor reflex response by endogenous angiotensins at the nucleus tractus solitarii in the rat

Although myelin basic protein (MBP)-recognizing T cells are not readily obtained after immunization of BALB/c mice with MBP (reflecting the BALB/c resistance to actively induced experimental autoimmune encephalomyelitis (EAE)), they can be expanded and cloned after several rounds of in vitro culture. The majority of BALB/c-derived clones recognize an epitope defined by MBP peptide 59-76. When transferred to naive BALB/c recipients, these clones cause classical EAE, with characteristic inflammation and demyelination of the central nervous system (CNS). We previously showed that two related clones recognizing a minor epitope, defined by MBP peptide 151-168, cause inflammation and demyelination preferentially of the peripheral nervous system (PNS). Because MBP has alternatively spliced isoforms, residues 151-168 are not present contiguously in all MBP isoforms. In order to determine whether induction of PNS disease is idiosyncratic to these sister clones, or related to their properties of epitope recognition, an independent T-cell line with similar recognition properties was studied. Clone 116F, derived from a BALB/c shiverer mouse, expresses a different T-cell receptor (TCR), with distinct TCR contact residues, but like the previously described T cells, this clone requires residues from both exons 6 and 7 for optimal stimulation. When adoptively transferred to BALB/c recipients, this clone preferentially induces disease of the PNS. A control BALB/c shiverer-derived MBP 59-76-recognizing clone, in contrast, induces CNS disease. These data strongly suggest that the site of disease initiation may correlate with epitope recognition, particularly when alternative isoforms are involved.     

Overexpression of phospholipase C-gamma1 in rat 3Y1 fibroblast cells leads to malignant transformation

Phospholipase C-gamma1 (PLC-gamma1) mediates signals from various extracellular origins to evoke cellular events such as mitogenesis. Previously, we reported that PLC-gamma1 was highly expressed in colorectal cancer and familial adenomatous polyposis, suggesting that PLC-gamma1 might be oncogenic. In this study, we have established rat 3Y1 fibroblasts that overexpress whole PLC-gamma1 and src homology 2 (SH2)-SH2-SH3 domain of PLC-gamma1. These cells showed a transformed phenotype and were tumorigenic when transplanted into nude mice. These results indicate that overexpression of PLC-gamma1 could transform rat fibroblasts, and the transformation is mediated by SH2-SH2-SH3 domain of PLC-gamma1.