Neurochemical pathology最新文献

[9,10-3H] palmitic (C16:0) and [1-14C] lignoceric (C24:0) acid dissolved in 10 microL of ethanol were injected subperineurially into the sciatic nerve of rats. Both C16:0 and C24:0 were incorporated into lipids, and in most lipid fractions C16:0 incorporation exceeded that of C24:0. Free ceramide and cholesterol ester were the only lipid moieties in which C24:0 incorporation was equal to or greater than that of C16:0. This finding is of particular interest since the very-long-chain fatty acid excess is by far the most striking in the cholesterol ester fraction in adrenoleukodystrophy. Furthermore, incorporation into cerebroside and sulfatide indicates that at least some of the injected fatty acids were metabolized in the Schwann cell. Subperineurial injections of either very-long-chain fatty acids or medium-chain fatty acids into rat sciatic nerve caused demyelination, and this morphological change does not occur following injection of pure solvent.

A variety of pharmacological agents were used as experimental probes to determine with greater precision the site(s) of damage to cerebral adenylate cyclase as a consequence of postischemic reperfusion in the gerbil. A paradigm of 60-min bilateral ischemia followed by 40-min reperfusion results in a decreased sensitivity of the catalytic site of adenylate cyclase to Mn2+. Likewise, the GTP-transducer site (guanine nucleotide regulatory or G protein) revealed depressed responses to GTP in the absence or presence of norepinephrine, dopamine agonists, substance P, yohimbine, and cholera and pertussis toxins. Moreover, a crude preparation of GTPase disclosed that damage elicited by postischemic reperfusion was directed to the higher-affinity form of this enzyme, which is associated with the overall function of the guanine nucleotide regulatory protein. Injury to adenylate cyclase was unrelated either to the ability of adrenergic ligands to bind to associated receptor sites or to the capacity of the brain to generate visual evoked potentials in response to visual stimuli.

Biochemical markers are crucial to the development of early diagnosis of infantile autism. The blood concentrations of neuroanalytes epinephrine, norepinephrine, dopamine, and serotonin were elevated in autistic subjects (n = 13) as compared to normal controls (n = 10). Autistic subjects had peptide patterns (peaks I-V, Sephadex G-25) that were different from those of normal controls. Methionine-enkephalin has been tentatively identified from fraction I of autistic subjects by HPLC as one of a large number of peptides that appears to be elevated. The HPLC chromatographic patterns of fraction V from all autistic subjects show a peak with retention time of 7.6 min. The HPLC of control urine fraction V revealed no comparable peaks.

Rabbits were subjected to 3 h of hyperthermia at 40 degrees C. The phospholipid content of the brain was unchanged, whereas the free fatty acids increased by about 73% over control levels. Hyperthermia also induced inhibition of fatty acid peroxidation processes. The last products of fatty acid peroxidation, the thiobarbituric acid reactive substances, diminished significantly during hyperthermia, whereas the level of the first intermediate of this pathway, the conjugated double bonds, remained unchanged. Simultaneously, the levels of lipid-soluble antioxidants decreased significantly. The content of free fatty acids, malondialdehyde, and lipid-soluble anti-oxidant returned toward control levels during 3 h of recovery. The content of gangliosides was 10-20% above control values in the groups of animals examined immediately and 3 h after hyperthermia. The ganglioside-specific enzymes, neuraminidase and sialyltransferase, both directed toward endogenous lipid substrates, were activated by hyperthermia, suggesting the stimulation of turnover of the gangliosides during the course of hyperthermia. Lipid alterations resulting from short-term hyperthermia may influence the physicochemical properties of neuronal membranes.

Samples of rat and human cerebral cortex were frozen, stored, and thawed under a variety of conditions to define further the optimal procedure for storing human brain samples for subsequent metabolic and functional studies that use incubated synaptosomes. Tissue samples were best preserved by immersing them in isotonic sucrose prior to slow freezing, but there was no advantage in first chopping up the material. High concentrations of sucrose, rather than exerting a cryoprotective effect, were detrimental to subsequent synaptosomal performance (oxygen uptake, K+ accumulation, stimulus-induced release of amino acid neurotransmitters). However, good activity was observed in preparations from rat brain frozen in the absence of fluid. This result was confirmed by studies on the uptake of gamma-aminobutyrate (GABA) into an osmotically sensitive compartment in synaptosomes prepared from frozen human autopsy material transshipped from the brain tissue collection ("brain bank") at Harvard Medical School, MA, USA, to Sydney, Australia. Although activity was slowly lost over a 3-mo period in rat tissue samples stored at -20 degrees C, there was little or no such loss at -70 degrees C.

The paralytic tremor (pt) rabbit, a neurological mutant, exhibits hypomyelination transmitted in X-linked recessive fashion. This rabbit mutant was used for regional lipid analyses of different brain structures during development. There was a significant decrease of myelin-specific lipids, particularly in the cerebroside and sulfatide in pt rabbits. The decrease of phospholipid and cholesterol was relevant to the total lipids depletion. The molar ratio of galactolipid to phospholipid decreased in the pt rabbit brain in each age group examined. The other lipids typical for myelin, such as ethanolamine glycerophospholipids, sphingomyelin, and GM1 ganglioside, were also diminished in the myelin-rich structures, but were not changed in the cortical gray matter of pt rabbits. In contrast, the total amount of gangliosides was near control levels and, therefore, in the mutant rabbits, the white matter and brain stem contained a higher proportion of lipid, as ganglioside, relative to the control animals. This result suggests that neuronal membranes were not involved in this pathology. The characteristic biochemical abnormalities exhibited in the pt rabbit suggest that a defect of oligodendroglial cell function is primarily responsible for the myelin abnormality.

The assembly of pig brain microtubule proteins was measured in vitro in the presence of serum from control rats and rats that had been rendered diabetic with 50 mg/kg streptozotocin 14 d previously. Control serum inhibited total microtubule assembly and increased the lag time before assembly commenced. Serum from diabetic animals was significantly more potent in both respects. The effect on lag time was reproduced in a predominantly albumin-containing fraction of serum that had been fractionated by affinity chromatography. Glycosylation of rat albumin in vitro led to an increase in its ability to increase polymerization lag time, but the concentration of albumin required was greater than that found in the serum fractions. The results indicate that diabetic serum contains factors that can adversely affect microtubule formation and that part of this effect may be caused by the presence of glycosylated albumin. This phenomenon may underlie some of the complications associated with diabetes.

Cell-mediated immune responses to various nervous antigens were examined in 12 cases of Guillain-Barré syndrome (GBS), 24 cases of noninflammatory peripheral neuropathy (NIPN), and 18 cases of degenerative disorders of central nervous system (CNSDD), using the lymphocyte-transformation technique. Cellular hypersensitivity to bovine P2 protein (P2) and a synthetic peptide, SP66-78, corresponding to the residues 66-78 of P2, was detected in about two-thirds of GBS cases, especially in the active or improving stages, but not in NIPN and CNSDD. The lymphocytes sensitized to these nervous antigens might play an important role in the pathogenesis of GBS.

The material derived from defective degradation of glycoproteins, which accumulates in brain and liver of a patient with GM1 gangliosidosis type I, was investigated, and the structure of the main storage compounds determined. For comparison, brain and liver of a patient with GM1 gangliosidosis type II were also analyzed. Analysis of the glycopeptides obtained after pronase digestion of the defatted residue indicates the storage of glycoprotein-like material in type I, but not in type II. Treatment with endo-beta-galactosidase showed that the stored material contained N-acetyllactosamine repeating units. Two major oligosaccharides, OS I and OS II, were isolated after the enzyme treatment, whose structures are: GlcNAc beta 1----3 Gal (OS I) and Gal beta l----4GlcNAc beta 1----3 Gal (OS II). Treatment with exo-beta-galactosidase transformed the trisaccharide OS II into the disaccharide OS I, indicating that the deficiency of beta-galactosidase in GM1 gangliosidosis type I, but not in type II, also affects glycoprotein catabolism, leading to the accumulation of glycopeptides containing terminal beta-galactosyl residues and N-acetyllactosamine repeating units. These results indicate the severe impairment in the catabolism of glycoconjugates with beta-linked galactose in type I, although this impairment is not as pronounced in type II.

The encephalitogenic potential of rabies vaccines prepared from nervous tissue is a result of the presence of myelin basic protein. Vaccines prepared from duck embryos are economical and efficient, but, occasionally, cases of allergic encephalomyelitis have been reported. An improved rabies vaccine has been developed that contains the classical Pitman Moore strain of rabies virus grown in embryonated duck eggs. This vaccine has been highly purified and enriched in immunologically effective rabies virus glycoprotein antigen. We have searched for the presence of myelin basic protein using sensitive radioimmunological and immunoblotting techniques. Whereas the classical duck embryo rabies vaccine contained small amounts of myelin basic protein, in the improved purified duck embryo rabies vaccine, none could be detected.