Neurochemical pathology最新文献

We studied the quantitative changes in proteins (total, Po, MBP, and histones) and DNA from sciatic nerves of normal and Trembler mice during postnatal development. Polyacrylamide gel electrophoresis and immunoblotting procedures allowed an accurate characterization of Po, MBP, and histones, as well as the comparison of their respective amounts from d 2 to d 120 after birth. It was found that 1. The immunoblotting procedure ascertains the presence of Po in the sciatic nerve of Trembler. In the 2-d-old mice, Po is detected in essentially similar amounts in Trembler and normal PNS, whereas its level in adult mutant sciatic nerves is never greater than 20% of the control. The sharp increase in Po levels observed during the third week in the normal nerves is not observed in those of the mutant; 2. MBP species are at most 4% of the control in the 10- to 12-d-old Trembler mice, whereas they were not detectable in adult nerves. The distribution of the different MBP species is the same in both mutant and control mice; 3. In normal mice, Po and MBP accumulate at similar rates, but the 14 kDa MBP accumulates faster than the 18.5 kDa MBP; and 4. Histone and DNA contents decrease 3- to 5-fold in normal nerves, whereas they remain constant, or increase slightly, in the mutant.

Following cryogenic lesions of the brain in the rabbit, ictal activity appears within min with a maximum at 2 h. Brain edema increases rapidly between 2-4 h with a maximum at 8 h. The glutamate concentration reaches 209% of control in the perilesional area at 2 h and the time course of glutamate/GABA ratio parallels the time course of epileptic activity. The impairment of Na+-K+-ATPase activity (rise of KMapp for K+) in the glial fraction coincides with the increase of edema. A positive correlation is found between the total amount of ictal activity and the total amount of edema in individual animals, suggesting that epilepsy may enhance edema formation.

Studying in vitro incorporation of [3H]galactose into biopsied sural endoneurium, we have demonstrated biosynthesis of glucocerebroside and its homologs, lactosylceramide, trihexosylceramide, and tetrahexosylceramide, in normal adult human sural nerve. Such in vitro biosynthesis of oligohexosylceramides is markedly increased in biopsied sural nerve from patients with various types of peripheral neuropathy. Since this altered glycosphingolipid biosynthesis occurs in several diversely caused polyneuropathies, it presumably relates to degenerative or regenerative events characteristic of neuropathy rather than a specific variety of neuropathy.

The drug sensitivity of synaptosomal high-affinity dopamine (DA) uptake was investigated in post-mortem brain regions of schizophrenics, in comparison to controls matched for age, sex, and post-mortem delay, and in model experiments in rats. DA uptake was inhibited by nomifensine in the investigated regions of rat brain in a concentration-dependent manner; the regional rank order of inhibitory potency was: nucleus (n) caudatus greater than n. accumbens greater than frontal cortex. Furthermore, it was shown that the inhibitory potency of nomifensine is unchanged after in situ storage of rat brain tissue for 48 h and after the cryopreservation method used. In post-mortem brain of human controls, nomifensine inhibited DA uptake with the same regional differences as in rats; however, the inhibitory potencies were three-fourfold weaker. In schizophrenia, on the other hand, synaptosomal DA uptake inhibition by nomifensine was significantly weaker than in the corresponding control brains for all regions studied. This suggests a decreased affinity of the DA uptake carrier to nomifensine, similar to DA shown in recent studies with schizophrenic patients. The possible relevance of investigating functional parameters for understanding patho-biochemical mechanisms in schizophrenia is discussed.

Cation-dependent acid protease activity associated with isolated human myelin was inhibited by pepstatin A, or enzymatic reactions were suppressed altogether by maintaining samples at 0 degrees C rather than 37 degrees C to examine whether or not they are involved in the extraction of myelin basic protein (MBP) by increased ionic strength. These measures largely abolished the degradation of MBP by acid protease activity associated with myelin, whereas the extraction of protein was only slightly diminished. Electrophoresis revealed that soluble protein was exclusively accounted for by undegraded MBP. Acid proteolysis, therefore, appears not to be involved in the cation-mediated removal of MBP from myelin. It is suggested that this mechanism may account for the appearance of undegraded MBP in body fluids, as well as for its pathologically increased degradation once it has become soluble.

"Paralytic tremor" (pt) rabbit mutant is characterized by a severe hypomyelination of the CNS, however, it is not defined if the defect in myelinogenesis is an "assembly" or "synthesis" type. In this study, we have compared the general metabolic and biosynthetic properties of the myelinating mutant brain with unaffected controls of the same age. In the brain slices of 4 wk old "pt" rabbits the incorporation of U-[14C]glucose, 6-[3H] galactose, and U-[14C] leucine into macromolecules (total lipids and proteins, galactolipids, and myelin basic protein) was substantially elevated. In isolated myelin fraction, the total reduction of the radioactivity was followed by the increased specific activity of all examined macromolecules. The myelin to homogenate specific activity ratio was similar in control and "pt" rabbits. Distribution of the label and myelin marker, cyclic nucleotide 3'-phosphodiesterase (CNP-ase) among the membranous fractions suggests the partial inhibition of myelin formation in "pt" rabbits on the step of premyelin, unilamellar membranes. 14CO2 yields derived from differently labeled glucose were used for the evaluation of the basal oxidative metabolism in "pt" brain slices. 14CO2 production from U-[14C] glucose was normal. The depolarization of the slices by 50 mM K+ stimulated glucose oxidation to a higher extent in "pt" than in control. Hexose monophosphate pathway (HMP), the route providing much of NADPH required for lipid biosynthesis, did not change significantly by mutation. The activity of glucose 6-phosphate dehydrogenase (Glc-6-P DH), an oligodendroglia enriched, HMP connected enzyme, was slightly lower in "pt" homogenates by 13-17%, whereas CNP-ase was lowered more than 30% in the same samples. All this data suggest that the capacity for the synthesis of myelin constituents is well preserved in the mutant brain and the impairment of myelogenesis is probably caused by increased elimination of already synthesized, myelin-related components.

The paradigm of IDPN neuropathy was produced in rats in order to examine the neurofilaments (NFs) that accumulate in the proximal motor and sensory axons of intoxicated animals, and to compare the aggregated NFs with control NFs and with the depleted populations of NFs in the distal portions of the same experimental nerves. NFs were probed biochemically and histochemically, using a large and well-characterized library of monoclonal antibodies that included antibodies that are monospecific for each of the rat NF protein subunits (NF-H, NF-M, and NF-L) as well as antibodies that recognized differential phosphorylated states of rat NF-H and NF-M. All antibodies tested showed enhanced immunostaining of enlarged axons and of large spheroids in the spinal cord and dorsal root ganglia of experimental animals. Biochemical analyses of IDPN-treated animals revealed enrichment of NF-H, NF-M, and NF-L in homogenates of dorsal root ganglia and of proximal motor and sensory nerve roots as well as depletion of the three subunits in distal nerve roots and in sciatic nerves. Immunoblot revealed a uniform enrichment of NF-H, NF-M, and NF-L in NF aggregates as well as the same admixture of phosphorylated and dephosphorylated epitopes of NF-H and NF-M in experimental and in control tissues. The global increase of immunoreactivity in axonal swellings to antibodies that react with phosphorylated, nonphosphorylated, and phosphorylation-independent NF epitopes suggests that IDPN induces an accumulation of NFs in proximal axons without necessarily altering the state of NF phosphorylation.

Levels of ornithine decarboxylase activity were measured in brain regions and in adrenal glands of adult male rats exposed to electroshock. Five hours after shock at levels causing transient loss of consciousness and fore and hindlimb tonic extensor seizures, major increases in ornithine decarboxylase activity were found in adrenals, hippocampus, brain stem, frontal cortex, and cerebellum, but striatal levels were unchanged. These increases were reversed by 24 h after electroshock. When lower levels of shock, which caused no loss of consciousness, were also used, a clear dose-response relationship of shock intensity and ornithine decarboxylase activity was found for hippocampus and brain stem. The ornithine decarboxylase response in brain increased with higher shock levels. However, the changes of ornithine decarboxylase in adrenal glands were maximal at intermediate, and diminished at maximal shock values, as were levels of circulating testosterone. These data suggest a differing role for cerebral and adrenal ornithine decarboxylase in the mature rat. The brain enzyme may be primarily related to metabolic repair processes, whereas adrenal ornithine decarboxylase may function in the activation of secretion.

General anesthesia is often used to immobilize experimental animals prior to the induction of cerebral ischemia. However, anesthetics are known to alter many of the biochemical and physiological parameters used for the assessment of stroke-induced brain damage. We examined the effects of bilateral carotid artery ligations on mortality and the development of cerebral edema in unanesthetized gerbils. We found that increasing the length of the ischemic episode resulted in increased mortality, both during the ischemic period and during cerebral reperfusion. The duration of the ischemic episode was also correlated with the rate and degree of the development of cerebral edema. Both of these estimates of ischemia-induced brain damage were significantly reduced by the pretreatment of the animals with pentobarbital. Based on the variable effects of different anesthetics on CNS activities, and the observed effects of barbiturate anesthesia on ischemia-induced mortality and edema development in the present model, we suggest that it may be inappropriate to anesthetize experimental animals when investigating certain aspects of stroke-induced brain damage.

In the brain of quaking and shiverer mutants, vitamin E content was normal when related to both wet weight and dry weight. When related to lipid extract, phosphorus, and polyunsaturated fatty acids, vitamin E was slightly increased only in the quaking mutant. In the sciatic nerve from trembler mutants, vitamin E was 134% of control values in the dry material, but normal in relation to wet weight. It was 260% in the lipid extract and 716% based on phosphorus. In relation to total fatty acids, there was a threefold increase in trembler mutants. Interestingly, it was increased approximately three times when related to 18:2 n-6, 20:4 n-6, and 20:5 n-3, and seven times when related to 22:6 n-3. The fact that the amount of vitamin E in fresh weight was normal, suggests that vitamin E plays a role in some nonmembrane material, such as the extracellular matrix or the basal lamina.