Oscillations of cortical oxidative metabolism and microcirculation in the ischaemic brain.

A new in vivo model for studying brain metabolic and haemodynamic oscillatory phenomena during ischaemia is described. In this model acute or chronic occlusion of one or two carotid arteries in the rat is performed. Due to the partial ischaemia developed, oscillations in the level of intramitochondrial pyridine nucleotides (NADH) as well as flavoproteins (Fp) were recorded from the brain by monitoring the fluorescence of these respiratory chain components. The two fluorescent signals (NADH and Fp) were measured by using the time sharing or DC fluorometer/reflectometer. The changes in the reflected light at the excitation wavelengths (366 and 450 nm) were recorded simultaneously. Bilateral carotid artery occlusion induced immediate oscillations (6-9 waves per min) in the mitochondrial redox state as well as in tissue blood volume in both hemispheres. To verify the accuracy of the NADH monitoring system, including the correction technique for haemodynamic and other artifacts, we used the intracarotid artery saline bolus injection approach. The results could be summarized as follows: (1) unilateral carotid artery occlusion resulted in delayed development of oscillations, particularly in the ipsilateral hemisphere; (2) the oscillation phenomenon was reversible if recirculation restarted within 5 min. Occlusion for more than 30 min resulted in irreversible oscillations; (3) the oscillation appearances and intensities were affected by various physiological conditions. Vasoconstriction, induced by hyperoxia, stimulated the oscillations while vasodilation, induced by hypercapnia, depressed them. Anoxia, hypoxia and spreading depression (SD) abolished the oscillations. Glucose injection was not effective.(ABSTRACT TRUNCATED AT 250 WORDS)     

Kainic acid-mediated increase of preprotachykinin-A messenger RNA expression in the rat hippocampus and a region-selective attenuation by dexamethasone.

The hippocampus contains the highest number of glucocorticoid-sensitive neurons in the rat brain and excessive exposure to glucocorticoids can cause damage to hippocampal neurons and impair the capacity of the hippocampus to survive neuronal insults. In this study in situ hybridization combined with quantitative image analysis was used to study preprotachykinin-A mRNA levels after administration of a toxic dose of kainic acid in animals pretreated with glucocorticoids. Kainic acid was injected into dorsal hippocampus CA3 region in animals pretreated with the synthetic glucocorticoid receptor agonist dexamethasone and in control animals. Preprotachykinin-A mRNA was not detected in the hippocampus of untreated animals or in animals analysed 30 min after a kainic acid injection. However, 4 h after injection of kainic acid, the level of preprotachykinin-A mRNA increased to 20-times above the detection limit both in the dentate gyrus and the CA3 region of the hippocampus. Treatment of kainic acid-injected animals with dexamethasone 30 min before and 2 h after the injection attenuated the increase in the granule cells of the dentate gyrus by 50%. In contrast, dexamethasone pretreatment had no significant effect on the kainic acid-induced increase of preprotachykinin-A mRNA in pyramidal cells in regions CA3 or CA1. These results show that an excitatory stimulus within the hippocampus causes a substantial increase in the level of preprotachykinin-A mRNA in hippocampal granule and pyramidal cells and suggest that in granule cells of the dentate gyrus this increase can be modulated by glucocorticoids.     

Cellular and molecular characteristics of an immortalized ataxia-telangiectasia (group AB) cell line

Ataxia-telangiectasia (A-T) is a multisystem hereditary disease featuring neurodegeneration, immunodeficiency, extreme cancer proneness, chromosomal instability, and radiosensitivity. A-T is found in many ethnic groups, and is genetically heterogeneous: four complementation groups have been identified in A-T so far. Attempts to isolate the A-T gene are based in part on gene transfer experiments, using permanent A-T fibroblast lines, obtained by transformation with SV40. "Immortalization" of A-T primary diploid fibroblasts using SV40 is difficult, possibly because of the chromosomal instability of these cells. The number of currently available permanent A-T fibroblast lines is small, and not all of them have been assigned to specific complementation groups. Using the assay of X-ray induced inhibition of DNA synthesis, we have assigned the A-T strain AT22IJE to complementation group AB. Origin-defective SV40 was used to transfect these cells, and one transformant (AT22IJE-T), which survived crisis, was found to have the typical characteristics of permanent cell lines obtained in this way. "In-gel renaturation" analysis did not show any DNA amplification of high degree in AT22IJE-T. Cytogenetic analysis showed considerable chromosomal instability in the new cell line, and medium conditioned by these cells contained the clastogenic activity which is characteristic of the parental strain as well. Other parameters of the "cellular A-T phenotype" have also been retained in the immortalized cells: hypersensitivity to the lethal effects of X-rays and neocarzinostatin, as well as "radioresistant" DNA synthesis. However, the sensitivity of AT22IJE-T to both DNA-damaging agents is less pronounced than that of the parental cells. The capacity of the cells for uptake of foreign DNA was tested by introducing into them the plasmid pRSVneo, using three different transfection methods. Satisfactory frequency of G418-resistant transfectants (0.66%) was achieved using a protocol recently published by Chen and Okayama (Mol. Cell Biol., 7: 2745-2752, 1987), which was found to be superior to the traditional calcium phosphate transfection method and to the polybrene-based method.     

Increased yield of full GBA sequencing in Ashkenazi Jews with Parkinson's disease

Background

Variants in GBA are the most common genetic risk factor for Parkinson's disease (PD), and are especially prevalent in the Ashkenazi Jewish (AJ) population. However, most studies on GBA in AJ genotype only seven selected Gaucher-associated pathogenic variants rather than sequencing the whole gene, which may leave carriers of PD-associated GBA variants undiscovered.

Defective potassium currents in ataxia telangiectasia fibroblasts

Similarities exist between the progressive cerebellar ataxia in ataxia telangiectasia (AT) patients and a number of neurodegenerative diseases in both mouse and man involving specific mutations in ion channels and/or ion channel activity. These relationships led us to investigate the possibility of defective ion channel activity in AT cells. We examined changes in the membrane potential of AT fibroblasts in response to extracellular cation addition and found that the ability of AT fibroblasts to depolarize in response to increasing concentrations of extracellular K⁺ is significantly reduced when compared with control fibroblasts. Electrophysiological measurements performed with a number of AT cell lines, as well as two matched sets of primary AT fibroblast cultures, reveal that outward rectifier K⁺ currents are largely absent in AT fibroblasts in comparison with control cells. These K⁺ current defects can be corrected in AT fibroblasts transfected with the full-length ATM cDNA. These data implicate, for the first time, a role for ATM in the regulation of K⁺ channel activity and membrane potential.