Molecular and chemical neuropathology最新文献

Alzheimer type II astrocytosis is the pathological hallmark of hepatic encephalopathy. These astrocytes undergo a characteristic morphological change and, in addition, lose immunoreactivity for glial fibrillary acidic protein (GFAP). However, a previous study in the portacaval shunted rat, a model of hepatic encephalopathy, revealed increased rather than decreased GFAP immunoreactivity in Bergmann glia, a specialized group of cerebellar astrocytes. In the present study, sections of cerebellar vermis from 15 cirrhotic patients with hepatic encephalopathy and varying degrees of Alzheimer type II astrocytosis were stained using antisera to GFAP. The Bergmann glial cells did not show altered GFAP immunoreactivity compared to controls. In addition, the degree of GFAP immunoreactivity was not correlated with the degree of Alzheimer type II change nor related to the aetiology of the liver disease. These results suggest a differential response of Bergmann glia in human hepatic encephalopathy.

Abnormalities in the dystrophic gene product, dystrophin, have been implicated in initiating the primary membrane defect and excessive intracellular calcium accumulation (EICA), which play fundamental pathogenic roles in hereditary muscular dystrophy (HMD). Two other cytoskeletal proteins, spectrin and utrophin, bear remarkable structural and functional homologies to dystrophin. CHF-146 strain dystrophic hamsters (DH), like patients with Duchenne muscular dystrophy (DMD), die prematurely from cardiopulmonary insufficiency, focal myonecrosis, and progressive degeneration of the cardiac and skeletal muscles with EICA. Although DH present a suitable model for HMD, there are controversies concerning their dystrophin and utrophin status. Using immunocytochemistry and Western blotting, we studied dystrophin, spectrin and utrophin anomalies in the cardiac and skeletal muscles of 6-mo-old male DH. Age- and sex-matched CHF-148 strain albino normal hamsters (NH) served as controls. Sarcolemmal dystrophin staining was much weaker and interruptive in the DH. The densitometric analysis of the immunoblots revealed that dystrophin is reduced in DH by 83% in cardiac muscle (p < 0.0001), and by 50% in skeletal muscle (p < 0.0001). We conclude that sarcolemmal dystrophin distribution is markedly reduced and discontinuous in the cardiac and skeletal muscles of DH, with simultaneous upregulation of utrophin and a varied degree of spectrin labelling. This observation suggests that reduced sarcolemmal dystrophin is associated with membrane hyperpermeability, which leads to progressive muscle degeneration via EICA and segmental necrosis in DH. As in DMD, utrophin appears to play an important compensatory role in hamster dystrophinopathy.

There is mounting evidence, primarily from research in experimental animals, that the dipeptide N-acetylaspartylglutamate (NAAG) and its metabolic enzyme, N-acetylated alpha-linked acid dipeptidase (NAALADase), are involved in glutamatergic neurotransmission. Previous studies in neuropsychiatric disorders associated with the dysregulation of glutamatergic neurotransmission, such as schizophrenia, seizure disorders, and amyotrophic lateral sclerosis (ALS), have revealed region-specific alterations in the levels of NAAG and in the activity of NAALADase. To establish better the cellular localization of these and related parameters in human brain, we have examined their alterations in two well-characterized selective neurodengenerative disorders, Huntington Disease (HD) and Alzheimer Disease (AD). Brain regions from postmortem controls and HD- or AD-affected individuals were assayed to determine the activity of NAALADase as well as the levels of NAAG, N-acetylaspartate (NAA), and several amino acids. The relationships between changes in these neurochemical parameters and changes in neuronal and glial cell density were determined. The present report demonstrates that the decreases in the levels of NAAG and NAA and in the activity of NAALADase in AD and HD brain correlate primarily with neuronal loss. By inference, the results suggest that NAAG and NAA have primarily a neuronal localization in human brain and that there is a close relationship between NAAG and the dipeptidase NAALADase in populations of affected neurons.

Administration of adenosine A1 receptor agonists in vivo is neuroprotective in various stroke models. Experiments using either mixed cultures of neurons and astrocytes or brain slices, in which several cell types are present, have demonstrated that activation of A1 receptors also id protective against hypoxia and/or hypoglycemia in vitro. In this study, we have examined the effect of the A1 agonist cyclopentyladenosine (CPA) on cellular damage, measured by efflux of lactate dehydrogenase (LDH), in highly enriched primary cultures of either neurons of astrocytes exposed to different metabolic insults. CPA reduced neuronal LDH release induced by a combination of hypoxia and substrate deprivation ("simulated ischemia"; IC50 = 28 nM) of by hypoxia alone (IC50 = 170 nM). In contrast, CPA had no effect on neuronal damage induced by substrate deprivation alone, not did it affect ischemic death to astrocytes. The neuroprotective effect of CPA during simulated ischemia and hypoxia were reversed by the A1 antagonist 1,3-dipropyl-8-cyclopentylxanthine (DPCPX). These data demonstrate that activation of an adenosine A1 receptor on neurons, but not astrocytes, is protective against cellular damage of death induced specifically by hypoxia as opposed to other metabolic insults such as hypoglycemia.

Cuprizone intoxication has been used as a model for reversible demyelination in the CNS. During the course of cuprizone intoxication, the glutathione-S-transferase isoform, Pi, normally and oligodendrocytic marker, appears in reactive astrocytes (Cammer ad Zhang, 1993). The present experiments address the changes in expression of Pi after removal of cuprizone from the diet of the affected mice. In order to localize Pi message, a riboprobe was prepared and in situ hybridization (ISH) performed. Western blots and immunocytochemistry were used to examine Pi protein and other glial cell markers. The data indicated that Pi protein increased during the first 2 d after withdrawal of the toxicant, when the level of the myelin marker, 2',3'-cyclic nucleotide-3'phosphohydrolase, remained minimal. Results of ISH suggested that levels of Pi message in the corpus striatum decreased during cuprizone feeding and began to recover within 2d after withdrawal of the toxicant. Both microglia and astrocytes appeared during the first week of cuprizone administration and persisted during two to three additional weeks on cuprizone. Reactive astrocytes remained in the tissue for at least 6 wk after cuprizone was withdrawn, while microglia receded within days. The findings suggest that astrocytes continue to express Pi after withdrawal of cuprizone.

Wistar rats were lesioned into the nigrostriatal pathway with 6-OHDA. The D-amphetamine-induced circling behavior test was performed to evaluated lesion efficiency. Animals that showed more than 620 turns/90 min were named totally lesioned animals (TLA). The group of rats that performed less than 620 turns/90 min were named partially lesioned animals (PLA). The contents of DA and its catabolites in the striata of these groups, and in the same tissue of the untreated animals, were measured. Moreover, the striatal glutathione-S-transferase (GST) specific activity for all groups was tested, and the kinetics parameters for GST purified from the whole brain were evaluated from other three similar groups. The striatal DA depletion on TLA was greater than in PLA. Striatal GST activity showed a significantly bilateral increase in PLA, whereas TLA exhibited only and ipsilateral augment. There were also differences between groups about the kinetic parameters of the purified brain enzyme. The possible role of GST on the interindividual lesion response difference was analyzed.

Reported increases in brain lactate production in Alzheimer disease led us to test the hypothesis that lactic acid acidosis alters the processing of the beta-amyloid precursor protein, beta PP, in neurons. To test this proposition, embryonic rat hippocampal neurons were first cultures for 4 d in serum-free B27/neurobasal medium. Lactic acid at 0.5 and 1 mg/mL (pH 7.1 and, 6.9, respectively) caused a dose-dependent increase in cellular beta-amyloid immunoreactivity detected with antibody 4G8. Acidosis did not affect secretion of beta PP or its derivatives into the medium. The cytoplasmic production of beta PP was slightly reduced by acidosis without a differential effect on maturation or proteolytic processing. In the substrate-bound material, which was insoluble in nonionic detergent, acidosis caused increases in an N-terminal 75-kDa band, a C-terminal 72-kDa band, and potentially amyloidogenic bands at 35 and 38 kDa. Processing to the 4-kDa amyloid beta protein was not observed in these early pure rat neuronal cultures. These results suggest that mild acidosis id sufficient to alter neuronal processing to the amyloid precursor protein into potentially amyloidogenic forms and increase certain beta PP fragments bound to the substrate. If a similar process occurs in the presence of other cell types in the aging brain, acidosis may stimulate an extracellular deposition of amyloid and contribute to the pathogenesis of Alzheimer disease.

Considerable evidence indicates that ATP, acting intracellularly of as a neurotransmitter, can influence nerve cell physiology in a variety of ways. Defects in the functioning of ATP-metabolizing enzymes could therefore lead to disturbances in neurotransmission and creation of sustained neuronal discharges characteristic of status epilepticus. In this study we investigated synaptosomal ATPase changes in rat brains during lithium/pilocarpine-induced status epilepticus. After 2 h of continuous electroencephalographic spiking, both Mg(2+)- and Ca(2+)-dependent ecto-ATPases were significantly decreased in freshly prepared synaptosomal preparations from the status rats. The intracellularly acting Ca2+Mg(2+)-ATPase (Ca-pump) was also decreased, but no changes occurred in synaptosomal Na+K(+)-ATPase activity. The difference between ecto-ATPase activities of the control and status rat brains was not affected by repeated freezing-thawing and lengthy storage. Possible involvement of reduced synaptosomal divalent cation-dependent ATPases in the pathophysiology of status epilepticus is discussed.

Both mania and bipolar depression have been associated with decrements in the activity of the sodium and potassium-activated adenosine triphosphatase (Na,K-ATPase) membrane pump. Although the role of this observation in the pathophysiology of bipolar illness is unclear, it has been proposed that this defect could be central to the pathogenesis of the illness. In an effort to test this hypothesis, the authors examined the efficacy of lithium pretreatment in attenuating behavioral changes secondary to acute administration of a single intracerebroventricular (i.c.v.) dose of the Na,K-ATPase-inhibiting compound, ouabain, in the Sprague-Dawley rat. Ouabain (10(-3)M) significantly decreased motor activity in automated activity monitors. Lithium pretreatment for 7 d totally prevented this effect. These preliminary data suggest that i.c.v. ouabain administration in the rat may prove to be a viable animal model for bipolar illness.

The gonadal hormone, progesterone, has been shown to have neuroprotective effects in injured nervous system, including the severity of postinjury cerebral edema. Progesterone's attenuation of edema is accompanied by a sparing of neurons from secondary neuronal death and with improvements in cognitive outcome. In addition, we recently reported that postinjury blood-brain barrier (BBB) leakage, as measured by albumin immunostaining, was significantly lower in progesterone treated than in nontreated rats, supporting a possible protective action of progesterone on the BBB. Because lipid membrane peroxidation is a major contributor to BBB breakdown, we hypothesized that progesterone limits this free radical-induced damage. An antioxidant action, neuroprotective in itself, would also account for progesterone's effects on the BBB, edema, and cell survival after traumatic brain injury. To test progesterone's possible antiperoxidation effect, we compared brain levels of 8-isoprostaglandin F2 alpha (8-isoPGF2 alpha), a marker of lipid peroxidation, 24, 48, and 72 h after cortical contusion in male rats treated with either progesterone or the oil vehicle. The brains of progesterone treated rats contained approximately one-third of the 8-isoPGF2 alpha found in oil-treated rats. These data suggest progesterone has antioxidant effects and support its potential as a treatment for brain injury.