Myelin Deficiency Research Articles

Neurochemistry as a Diagnostic Aid in the Congenital Tremor Syndrome of Piglets

SUMMARY A knowledge of the chemical composition of the central nervous system can assist the neuropathologist in detecting, describing and differentiating developmental myelin disorders of the neonate. In particular, the analysis of spinal cord lipids can be used as an aid in the diagnosis of the congenital tremor syndrome (CT) of piglets. An abnormally low content of lipid (especially cerebrosides) reflects a deficiency of myelin which occurs in all four known CT types. The presence of cholesterol esters having a particular fatty acid profile denotes demyelination and this distinguishes one of two types of CT that result from transplacental virus infection and one of the two hereditary types. Thus, a fairly simple neurochemical examination of the cord taken together with the epidemiological features of outbreaks and the gross pathology of affected piglets is shown to form a reliable system for the diagnosis of the congenital tremor syndrome.

X-ray diffraction study of myelin structure in immature and mutant mice

X-ray diffraction patterns were obtained from freshly dissected central and peripheral nerves of quaking, myelin synthesis deficiency ( msd), and trembler mutants, as well as immature and adult normal mice. The patterns were compared with respect to strength of myelin diffraction, background scatter level, repeat period, and intensity and linewidth of Bragg reflections. The deficiency of myelin in optic nerves was found to be (in decreasing severity): quaking > immature > trembler ⋍ normal adult; and in sciatic nerves: trembler > immature > quaking msd ⋍ normal adult. Repeat periods about 3 Å less than that for normal adult sciatic myelin were detected in corresponding nerves from immature, quaking, and trembler mice. In some trembler sciatic nerves a second phase having a 190–200 Å period and accounting for about 60% of the total ordered myelin was also evident. Comparison of electron density profiles of membrane units calculated from the repeat periods and diffracted intensities for sciatic myelins indicate structural differences at the molecular level. The main findings are: (1) quaking myelin shows a significant elevation of density in the external protein-water layer between membrane bilayers; (2) the membrane bilayer of immature myelin is ≈ 2 Å thinner than that for normal adult; (3) the membrane bilayer of the more compact phase in trembler myelin is ≈ 5 Å thinner than for normal; and (4) the difference in repeat periods for the two phases present in some of the trembler nerves can be accounted for predominantly by distinct membrane bilayer separations at the external boundary.

The (Na+ + K+)-ATPase activity in brain of Quaking mice.

The (Na+ 4 K+)- and Mg2+-dependent ATPase distribution in several brain areas has been investigated in Quaking mutant mice characterized by myelin deficiency. A marked decrease of (Na+ + K+)-ATPase activity has been found in limbic structures, hypothalamus and cerebellum. The Mg2+-dependent activity did not change. A possible involvement of the impairment of the (Na+ + K+)-ATPase activity in the seizure susceptibility of this mice is discussed.

Effect of serum deprivation on myelinating mouse cerebellum cultures.

In order to investigate the effect of nutrient deprivation on brain development, mouse cerebellum cultures were grown in nutrient media with reduced serum concentration. After 9--18 days in vitro, experimental cultures grown in media with low serum concentration exhibited a delayed and retarded myelination. Electron microscopic examination of experimental cultures revealed profiles of deficient myelination, but showed normal neuronal and synaptic structures. The amount of myelin basic protein measured by radioimmunoassay was markedly reduced in experimental cultures. Activity of cholinesterase in these experimental cultures was also decreased.

Myelin deficiency in hereditary pituitary dwarfism: a biochemical and morphological study.

Myelin in the central nervous system of 19-day-old Snell's dwarf mice was studied morphologically and biochemically. The number of myelinated axons per unit area in the corticospinal tract and anterior commissure of dwarf mice was significantly decreased. The distribution of myelinated fibers based upon sheath thickness was normal. The yield of isolated myelin was decreased by 56% in the dwarf but its compositions of lipids, proteins, glycoproteins and 2', 3'-cyclic nucleotide 3'-phosphohydrolase activity was nearly equivalent to that of control myelin.

Alpha hydroxylation of lignoceric acid to cerebronic acid during brain development. Diminished hydroxylase activity in myelin-deficient mouse mutants.

Alpha Hydroxylation of lignoceric acid (n-tetracosanoic acid) to cerebronic acid (2-hydroxylignoceric acid) by postnuclear preparations of brains from developing rat, mouse, and several neurological mouse mutants was studied. The preparations of brains from jimpy and myelin synthesis deficiency (msd) mice were found to synthesize cerebronic acid at less than 10 percent of their control rates, and those from quaking and dilute-lethal approximately 30 and 50 percent, respectively. The apparent low rate of in vitro hydroxylation by brains of the mutant mice appeared to be due to decreased synthesis rather than increased oxidation of cerebronic acid. Mixing experiments eliminated the possibility of an inhibitor in the mutant or an activator in normal animals. The preparations of brains from wabbler-lethal, ducky, and weaver mice showed normal activity. The developmental pattern of the hydroxylase activity was examined in quaking, jimpy, and their control mice. In normal brains the hydroxylase activity was low in the immediate postnatal period, increased sharply between 10 and 20 days after birth, and fell to a low level following maturation of the brain. The hydroxylase activity in quaking mice changed similarly during brain development but at a much reduced level. The brains of jimpy mice had barely detectable hydroxylase activity which changed little with age and reached a peak at about 15 days postpartum. The subnormal hydroxylase activity in brains of quaking mice and the near absence in brains of jimpy and msd mice correlate with the observations that myelin deficiency is more severe in jimpy and msd than in quaking. These results suggest a close association of the synthesis of cerebronic acid with the synthesis of the characteristic myelin lipid that is cerebroside (N-acyl sphingosine beta-D-galactoside).

Deficient myelination by 2, 4-dinitrophenol administration in the early stage of development

Deficient myelination by 2, 4-dinitrophenol administration in the early stage of development

CHEMICAL PATHOLOGY OF KRABBE'S DISEASE II. Futty Acid Composition of Cerebrosides, Sulfatides and Sphingomyrlins in Brain

ABSTRACT: Vanier, M.‐Th. and Svennerholm, L. (Department of Neurochemistry, Psychiatric Research Centre, University of Göeborg, Göteborg, Sweden). Chemical Pathology of Krabbe's Disease. II. Fatty acid composition of cerebrosides, sulfatides and sphingomyelins in brain. Acta Paediatr Scand, 63: 501, 1974.—The fatty acid composition of sphingomyelins, cerebrosides and sulfatides was determined in cerebral tissue from 18 Swedish children aged 7–32 months, with Krabbe's disease. Sphingomyelins of the white matter had a fatty acid pattern which indicated a serious deficiency of myelin. The fatty acid pattern also suggested that a substantial amount of the sphingomyelins was derived from cells of mesenchymal origin. The cerebrosides, and to a certain extent the sulfatides of cerebral cortex and white matter, had a higher concentration of saturated very‐long‐chain C23‐C26 acids than normal brains. The difference from the normal fatty acid pattern of cerebrosides was smaller in myelin. This suggests that the cerebrosides stored in the globoid cells have an abnormal fatty acid composition.

Chemical pathology of Krabbe's disease. I. Lipid composition and fatty acid patterns of phosphoglycerides in brain.

ABSTRACT. Vanier, M.‐Th. and Svennerhohn, L. (Department of Neurochemistry, Psychiatric Research Centre, University of Göteborg, Göteborg, Sweden). Chemical pathology of Krabbe's Disease. I. Lipid composition and fatty acid patterns of phosphoglycerides in brain. Acta Paediatr Scand, 63: 494, 1974.—Lipid biochemical determinations were performed on autopsy material from 18 cases of Krabbe's disease, aged 7–23 months, collected in Sweden between 1960 and 1972.Cerebral white matter. The lipid concentration of the cerebral white matter was found substantially reduced. It was the same in 17 cases, independent of age at death, and rather similar to that of cerebral cortex. All major lipids were diminished, but the myelin lipids, cholesterol and particularly galactolipids (cerebrosides and sulfatides) were reduced more than the phospholipids. The ratio cerebroside/sulfatide was significantly increased, but this. was not a constant finding. The relative percentage of ethanolamine phosphoglycerides was decreased and that of choline phosphoglycerides increased. The fatty acid composition of the phosphoglycerides shifted towards values found in the white matter of 2 to 4 month‐old infants. In addition, a characteristic significant increase of arachidonic acid occurred.Cerebral cortex. Only minor changes were observed, but they were of the same type as some of the changes of the white matter: a decrease in the relative percentage of ethanolamine phosphoglycerides and an increase of arachidonic acid.The lipid changes in Krabbe's disease are suggested to be the result of the combined effect of a serious myelin deficiency, and the replacement of the normal brain cytoarchi‐tecture by proliferated astroglial cells, ephitheliod cells and globoid bodies.

Glial fibrillary acidic protein in mutant mice with deficiency of myelination: quaking and jimpy.

Fibrous neuroglia has been studied by immunofluorescence with GFA protein antibodies in the spinal cord of mutant mice with deficient myelination: quaking and jimpy. In both these mutants a well formed astrocytic framework was observed in the non-myelinated white matter, indicating that the arrest of myelination in quaking and jimpy mice is associated with defects of the oligodendroglial cell line, rather than with an abnormality of glioblast differentiation.

The enduring behavioral changes in rats with experimental phenylketonuria.

The biochemical features of phenylketonuria have been reproduced in developing rat pups by administering to them a combination of p-chloro-DL-phenylalanine plus L-phenylalanine for the first 21 days after birth. During the treatment period, the experimental animals show delayed eye opening and decreased brain weight compared with controls given saline. Neuropathological examination of developing animals reveals deficient myelination and some inhibition of cerebellar maturation. When tested as adults, after a long recovery period, animals with phenylketonuria are hyperactive in activity wheels. Adult rats are deficient in reversing a position choice and demonstrate impaired performance in a Y-maze. Rats treated with p-chloro-DL-phenylalanine plus L-phenylalanine during the vulnerable period of rapid brain development thus have enduring behavioral changes that persist throughout life.

Turnover of brain adrenergic transmitters in Quaking mice.

Quaking mice, neurological mutants of the C57 BL/6J strain have a markedly deficient myelination of the CNS(Sidman, Dickie and Appel, 1964). Many studies have been carried out on their lipids (Jacque, Harpin and Baumann, 1969; Neskovic, Nussbaum and Mandel, 1969, 1970; Kurihara, Nussbaum and Mandel, 1970; Sarlieve, Neskovic and Mandel, 1971; Singh, Spritz and Geyer, 1971) for this reason, but little attention has been paid to other aspects of their aminergic transmitters metabolism. During the course of our work, Tillement, Debarle, Simon and Boissier (1970) reported on the transmitter levels in Quaking mice. The reasons for thinking that the monoamine metabolism of these mice might be altered are as follows. The trembling might be associated with a change in the activity and therefore metabolism of dopaminergic structures. Chronic stress due to permanent tremor might induce changes in norepinephrine metabolism. Since there are changes in the sleep patterns of Quaking mice (Valatx and Jouvet, 1971), there might be changes in brain serotonin metabolism. This study of the turnover of norepinephrine, dopamine and serotonin in the whole brains of control and Quaking mice is the preliminary to detailed examination of the turnover of the transmitters in well‐defined brain regions.

The white matter in $${\text{G}}_{{\text{M}}_{\text{2}} } $$ gangliosidosis

The white matter in 4 cases of\({\text{G}}_{{\text{M}}_{\text{2}} } \) gangliosidosis was studied with particular regard to the question of a primary versus secondary character of myelin alteration. Histopathologically, the cases were characterized by extremely severe and extensive myelin deficiency in cases 1 and 2, very severe in case 3, and mild in case 1. The characteristic myelin lipid alteration was an 80–85% decrease in cerebrosides in cases 1, 2 and 3, and a 50% decrease in case 4. These findings are considered to be the results of more than one process. It is postulated that arrested myelinogenesis played a chief role in the pathomechanism of white matter involvement and secondary myelin degeneration was a contributory factor. The failure in myelin development is attributed to interference with cerebroside synthesis in the „vulnerable” period of brain development. Neuronal degeneration, on the other hand, in this particular period may promote the secondary degeneration of the already deposited but metabolically still unstable myelin. A relationship was suggested between myelin lipid, as indicated by the cerebroside content, and axonal and/or glial constituents, as indicated by the glycoproteins and glycosaminoglycans.

Reversal learning and RNA labeling in neurological mutant mice and normal littermates

Incorporation of radioactive uridine into five brain areas, following reversal learning, was explored for neurological mutant mice with a deficit of myelin in the brain and spinal cord (quaking, qkqk) and normal littermates (?/+) from strain C57BL/6-qk (Jackson Laboratory). Both groups mastered the reversal task, although the mutants performed at a lower level. There was a Genotype × Test Conditions × Brain Area interaction with littermates exhibiting increased labeling of RNA in the amygdala and the hippocampus, and the quaking mice exhibiting no significant changes in these two areas following learning. Findings suggest that a genetic defect in the integrity of the CNS, a deficiency of myelin, affects reversal learning, and that this effect may be reflected in changes in RNA synthesis, or specific activity, for structures which are critical to reversal learning ability.

Enzymic synthesis of psychosine sulphate.

Abstract—An enzyme which catalyses the synthesis of psychosine sulphate by the transfer of [35S]sulphate from 3′‐phosphoadenosine 5′‐phosphosulphate to galactosyl‐sphingosine has been demonstrated in the brain of the young mouse. The enzyme activity appears to be bound to a microsomal fraction which is spun down with the synaptosomes. The product of the incubation mixture has been characterized as psychosine sulphate by a variety of TLC separations and other chemical procedures. Several parameters (detergent, cations, substrate and 3′‐phosphoadenosine 5′‐phosphosulphate concentrations, pH and incubation time), affecting the 3′‐phosphoadenosine 5′‐phosphosulphate‐psychosine sulphotrans‐ferase activity, have also been investigated. In the normal mouse brain there is a maximum enzyme activity at 17–19 days after birth, which is the period of most rapid myelin formation. In the brains of Jimpy mice, mutants with myelin deficiency, the activity is reduced and reaches a maximum around the 13th day. The lower activity correlates with the small amounts of sulphatides in Jimpy mouse brains. The results are discussed and related to present knowledge of galactolipid biosynthesis.

The composition of myelin from the mutant mouse 'quaking'.

Abstract— Myelin was isolated from the brains of adult Quaking mice, a mutant showing a deficiency of myelin in the central nervous system, and normal controls. The mutant myelin was found to have a higher flotation density than that of the control and showed marked differences in lipid composition. The myelin from Quaking mice was found to be deficient in cerebroside and ethanolamine phospholipid. Acrylamide gel electrophoresis of total myelin protein demonstrated a pronounced deficiency of proteolipid protein. The activity of cyclic 2′,3′‐AMP phosphohydrolase was normal.

Sterol and fatty acid synthesis in developing brains of three myelin-deficient mouse mutants

1. 1. The rate of sterol synthesis and the level of hydroxymethylglutaryl-CoA (HMG-CoA) reductase were previously shown to be subnormal in the myelin-deficient brains of jimpy ( jp/Y) mutants. To determine whether these changes were specific for the jimpy mutation, rates of sterol synthesis and other aspects of lipid synthesis in jimpy brains were compared with those in the brains of two other mutants with defective myelination of the central nervous system, quaking ( qk/qk) and myelin synthesis deficiency ( msd/Y). 2. 2. The rate of sterol synthesis from [1- 14C]acetate or from [2- 14C]mevalonic acid and the level of HMG-CoA reductase were depressed in all three mutations at the earliest age at which clinical symptoms of the disorders were apparent. Ratios of cholesterol to desmosterol in developing brains of the three mutations were normal. 3. 3. The heat stability and the K m (HMG-CoA) of brain HMG-CoA reductase were not affected by the three mutations. 4. 4. The rate of fatty acid synthesis from [1- 14C]acetate was depressed in qk/qk brains but not in jp/Y or msd/Y brains. 5. 5. Rates of sterol, fatty acid, and CO 2 production in brain were not reduced in two neuromuscular mutants (reeler ( rl/rl) and oscillator ot/ot) with depressed growth rates but without known myelin deficiencies or in normal immature mice deprived of food, indicating that inadequate nutrition was not a cause for the observed deficiencies in lipid synthesis rates.

The Association of the Galactosyl Diglycerides of Brain with Myelination: II. THE INABILITY OF THE MYELIN-DEFICIENT MUTANT, JIMPY MOUSE, TO SYNTHESIZE GALACTOSYL DIGLYCERIDES EFFECTIVELY

Abstract The brain of the jimpy mouse, a mutant with a severe deficiency of myelin in the central nervous system, has little ability to synthesize galactosyl diglyceride. Lipase and α- and β-galactosidase activity in the brain of the jimpy were the same as in normal littermates. Thus the very low concentration of monogalactosyl diglyceride found in the brain of the jimpy (19 nmoles per g, wet wt) compared with the normal (438 nmoles per g, wet wt) must be attributed to low synthesis by a galactosyltransferase pathway rather than to overly active degradative enzymes. The galactosyltransferase involved in the synthesis of psychosine and cerebroside was also reduced in the jimpy brain. The small amount of monogalactosyl diglyceride that is found in the jimpy is restricted predominantly to the microsomal fraction, whereas normal littermates of identical age had monogalactosyl diglyceride in both myelin and microsomal fractions of brain. The jimpy mouse appears to be unable to transfer galactosyl diglyceride from microsomes (site of synthesis) to myelin (site of deposition). The relative inability of the jimpy mouse to make and to transfer galactosyl diglyceride to myelin correlates well with relative absence of myelin in the jimpy and supports the contention that the galactosyl diglycerides are associated with the process of myelination.

The fatty acid composition of phospholipids and glycolipids in Jimpy mouse brain.

Abstract— Phospholipids and sphingolipids from brains of normal and Jimpy mice were isolated in a pure form by thin‐layer chromatographic procedures. The fatty acid composition of the major phospholipids, i.e. ethanolamine glycerophospholipids, serine glycerophospholipids, choline glycerophospholipids and inositol glycerophospholipids, as well as sphingomyelin, cerebrosides and sulphatides was determined by gas‐liquid chromatography. A specific fatty acid pattern for each of the four glycerophospholipids was found. The fatty acid composition of inositol glycerophospholipid, which has not previously been studied in mouse brain, was characterized by a high concentration of arachidonic acid. After 16 days of age, fatty acid analysis showed definite differences between the phospholipids from normal and mutant brains. A small increase of polyunsaturated fatty acids in glycerophospholipids of ethanolamine, serine and choline from the Jimpy central nervous system was found, which has been explained by the myelin deficiency. Sphingomyelin, cerebrosides and sulphatide analyses showed a wide distribution of saturated and mono‐unsaturated fatty acids in both normal and mutant mice. A reduction in the amount of long‐chain fatty acids was demonstrated in mutant brain sphingolipids; in sulphatides and cerebrosides, the amount of non‐hydroxy fatty acids was reduced to a greater extent than in sphingomyelin.The distribution of fatty acids in sphingolipids from the myelin and microsomal fractions was also investigated in both types of mice. Cerebrosides were characterized by a high content of long‐chain fatty acids in myelin as well as in microsomes. Sulphatides and sphingomyelin, on the other hand, showed a higher content of medium‐chain fatty acids in microsomes than in myelin. In the mutant brain, the amount of long‐chain fatty acids was reduced in both subcellular fractions. The deviation from normal in the pattern of fatty acid distribution in Jimpy brain is discussed in relation to the current concepts of glycolipid biosynthesis.

Cerebral phospholipids in 'quaking' mice.

AbstractThe brain of the adult ‘quaking’ mutant mouse is characterized by a reduced phospholipid content which can be ascribed not only to the myelin deficiency but also to a well‐defined hydrocephalus. The mutant brain shows highly significant decreases in the percentage of ethanolamine plasmalogen, triphosphoinositide and phosphatidic acid in the whole phospholipid fraction, while the proportions of phosphatidylcholine, phosphatidyl‐ethanolamine, diphosphatidylglycerol and phosphatidylinositol increase. The changes are consistent with the selective absence of ‘myelinic’ phospholipid although phosphatidylserine, sphingomyelin and diphosphoinositide are unchanged.