Molecular and chemical neuropathology最新文献

To address the problem of the pathogenesis in diabetic neuropathy, rats were made diabetic by streptozotocin administration, and discrete brain regions, such as cortex, cerebellum, brainstem, thalamus, and hypothalamus, were sampled for assay of activities of electron transport chain complexes I-IV at 1 and 3 mo after induction of diabetes. Significant decrease was seen in activities of dinitrophenylhydrazine DNPH-coenzyme Q reductase (complex I), coenzyme Q cytochrome-c reductase (complex III), and cytochrome-c oxidase (complex IV) from discrete brain regions with more pronounced changes in complex I. The decline in the complex I, III, and IV activity was more severe in the 3-mo group. Succinate dehydrogenase (SDH) coenzyme Q reductase (complex II), which is an enzyme shared by tricarboxylic acid (TCA) cycle and electron transport chain, showed a significant increase under the same set of conditions. These results suggest that the bioenergetic impairment has an important role in the pathophysiology of diabetes.

GTPase-activating protein is known to regulate the conversion between ras-GTP and ras-GDP. We studied the basal expression of GTPase-activating protein-like immunoreactivity in mouse cerebral regions using a polyclonal anti-GTPase-activating protein antibody. Cells with GTPase-activating protein-like immunoreactivity were distributed in frontal cortical layers IV and V, and in the parietal cortex, piriform cortex, amygdaloid area, septum, lateral thalamus, and hypothalamus. The GTPase-activating protein-like immunoreactivity was also observed in fiber-like structures in the caudate putamen, stria terminalis, internal capsule, and medial forebrain bundle, and around CA2 pyramidal cells in Ammon's horn. These results imply that GTPase-activating protein is constitutively expressed in mouse brain regions and may have physiological functions in specific neuronal pathways in the brain.

Total acetylcholinesterase (AChE) and the molecular forms of the enzyme from six brain regions were compared in young adult (6 mo) and aged (24 mo) Fischer 344 rats. Total AChE activity was significantly reduced in aged striatum (48.7%), parietal cortex (39%), cerebellum (30.2%), and medulla/pons (23.1%). Forebrain of aged rats showed nonsignificant reduction of AChE (18.4%), but olfactory bulbs exhibited no differences in aged rats. The ratio of G4/G1 molecular forms, as isolated on sucrose density gradients, was unaltered in all aged rat brain tissues examined. These results indicate that aged rats exhibit reduced brain AChE, but there is no evidence for selective effects on individual molecular forms.

The regulation of C1q expression was examined in the human monocytic cell line THP-1. Since these cells can be differentiated into cells with macrophage properties and induced to express C1q, they were used as models for mature human monocyte/macrophages and indirectly microglia. Interferon-gamma (IFN-gamma) and the anti-inflammatory steroid agents dexamethasone and prednisone were powerful stimulators of C1q production, alone or in combination. Interleukin-6 (IL-6) and lipopolysaccharide (LPS) also had significant stimulatory activity. Phorbol myristate acetate, a protein kinase C activator, reduced C1q expression. Four additional classes of pharmacological agents were tested for their effect on C1q secretion. Tacrine, but not indomethacin, cimetidine, or propentofylline, showed activity in inhibiting C1q secretion by IFN-gamma treated THP-1-derived macrophages.

The effect of transient cerebral ischemia on phosphorylation of the microtubule-associated protein (MAP) tau was investigated using the rat four-vessel occlusion model. Phosphorylation of tau is proposed to regulate its binding to microtubules, influencing the dynamics of microtubule assembly necessary for axonal growth and neurite plasticity. In this study, tau was rapidly dephosphorylated during ischemia in the hippocampus, neocortex, and striatum. Dephosphorylation of tau was observed within 5 min of occlusion and increased after 15 min in all three brain regions, regardless of their relative vulnerability to the insult. Thus, dephosphorylation of tau is an early marker of ischemia and precedes the occlusion time required to cause extensive neuronal cell death in this model. On restoration of blood flow for a little as 15 min, tau was phosphorylated at a site(s) that causes a reduction in its electrophoretic mobility. The dephosphorylation/phosphorylation of tau may alter its distribution between axon and cell body, and affect its susceptibility to proteolysis. These changes would be expected to influence microtubule stability, possibly contributing to disruption of axonal transport, but also allowing neurite remodeling in a regenerative response.

We have determined ammonia in cerebrospinal fluid (CSF) with the indophenol direct method. The results were compared with an enzymatic method. The method is very simple, and precision (coefficient of variation 1.6%) and linearity (r = 0.9999, p < 0.001) of the method are excellent. The recoveries of the method are very good (within-sample recovery: range 88-93, median 93%; between-sample recovery: 88-93, median 91%). In a population of 23 neurological patients not suffering from liver disease, the reference values ranged from 8 to 26, median 18 microM. Males and females did not differ (p = 0.5). The values obtained with the indophenol method were equal to the enzymatic method (range 9-28, median 18 microM, p = 0.6). On storage in the deep freeze (-20 degrees C), there was no change in CSF ammonia concentration for at least 1 mo. When stored at 4 degrees C (refrigerator), ammonia determinations have to be performed within 2 d. CSF storage at room temperature results in artificially elevated ammonia levels and should be avoided.

In an attempt to delineate the capacity of aluminum (Al) to promote pro-oxidant events, several indices of oxidative stress have been determined in brains and livers of rats exposed to an Al salt, either alone or in combination with an iron (Fe) compound. Treatment with Al over a 3-wk period increased both cortical levels of glutathione (GSH) and the rates of generation of reactive oxygen species (ROS). Dosing with an Fe compound resulted in no parallel changes, and concurrent exposure to Fe together with Al prevented these elevations. Both Fe and Al dosing elevated glutamine synthetase activity in the cortex. Levels of creatine kinase, another enzyme susceptible to oxidative stress, were also elevated in cortices of Al-treated rats. These data are in contrast to the changes found in liver fractions where exposure to Fe greatly enhanced hepatic pro-oxidant events as judged by changes in all three of the test indices used. Concurrent treatment with Al did not potentiate the pro-oxidant effects of Fe in liver. Al treatment had very minor effects on hepatic parameters of oxidative events. The results suggest that the presence of Al may exert deleterious pro-oxidant changes within the brain, which may be related to induction of oxidant species. These changes are tissue-specific and appear to be independent of any promotion of pro-oxidant status induced by exogenous Fe.

There have been repeated reports of a decrease in serotonin2A receptors in the frontal cortex from subjects with schizophrenia. Similarly, in rats treated with antipsychotic drugs, it has been shown that many antipsychotic drugs decrease cortical serotonin2A receptors, an affect not seen with the antipsychotic drug haloperidol. We therefore compared the density of serotonin2A receptors in frontal cortex from schizophrenic subjects treated with haloperidol, schizophrenic subjects treated with other antipsychotic drugs, and nonschizophrenic subjects. Independent of antipsychotic drug treatment, serotonin2A receptors were decreased in the frontal cortex from schizophrenic subjects. Importantly, the density of serotonin2A receptors was not different in schizophrenic subjects whether or not they had been treated with haloperidol. This study suggests that data obtained from treating rats with antipsychotic drugs cannot be simplistically extrapolated to studies on tissue obtained postmortem from schizophrenic subjects treated with the same drugs.

Considerable evidence suggests that oxidative stress plays an important role in tissue damage associated with hypoglycemia and other metabolic disorders. The altered brain neurotransmitters metabolism, cerebral electrolyte contents, and impaired blood-brain barrier function may contribute to CNS dysfunction in hypoglycemia. The present study elucidates the effect of starvation and insulin-induced hypoglycemia on the free radical scavanger system--reduced glutathione (GSH) content, glutathione S-transferase (GST), glutathione peroxidase (GPx), glutathione reductase (GR), gamma-glutamyl transpeptidase (gamma-GTP), gamma-glutamyl cystein synthetase (gamma-GCS), catalase and superoxide dismutase (SOD), and mitochondrial electron transport chain (ETC) complexes I-IV from three different regions of rat brain, namely cerebral hemispheres (CH), cerebellum (CB), and brainstem (BS). Peripheral organs, such as liver and kidney, were also studied. Significant changes in these enzymic activities were observed. The analysis of such alterations is important in ultimately determining the basis of neuronal dysfunction during metabolic stress conditions, such as hypoglycemia, and also defining the nature of these changes may help to develop therapeutic means to cure metabolically stressed tissues.

The concurrent release of myelin basic protein (MBP) and extrinsic proteinases from isolated myelin membranes by aqueous solvents of high ionic strength is considered circumstantial evidence of a presumptive mutual interaction in situ. The joint release of proteins and proteinases from myelin membranes of bovine brain, depending on the ionic strength of aqueous solvents, was therefore examined; 25 mM Tris buffer released an average 1.4% of total myelin protein. It was attributable to about 25 different electrophoretic bands, but no apparent MBP. However, the extract potently mediated the limited proteolysis of added MBP at pH 4.0, 5.6, and 9.0. Because of the pH and the effects of specific inhibitors, proteolysis appears to be owing to activities of cathepsin B and D, and an alkaline metalloproteinase. The subsequent extraction of myelin membranes with buffered 300 mM NaCl released an additional 20% of total myelin protein, mainly MBP. The extracts, unlike those of untreated myelin membranes, no longer cleaved MBP at pH 5.6 and 9.0, and did so only slightly at pH 4.0. The results indicate that the bulk of soluble myelin-associated proteinases is much less tightly bound than MBP. The weak binding of the former and the prevalence of lysosomal cathepsin B- and D-like activities suggest that during their isolation, myelin membranes may adsorb soluble cellular proteins of tissue homogenates. At any rate the washing of myelin membranes with dilute buffer was found to largely remove soluble proteinase activities that are otherwise associated with salt-soluble MBP of myelin.