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  • 1980-1984  (4)
  • 1975-1979  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 28 (1977), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The biosynthesis and accumulation of monogalactosyl diglyceride, galacto-cerebrosides and sulfatides were studied in the brain of quaking mouse during myelination. The specific activity of monogalactosyl diglyceride synthesis of the mutant mouse was reduced to 50% of the control of the same age, comparable to the reduction in the biosynthesis of galactosylcerebrosides and sulfatides. The three galactolipids were largely associated with the myelin and microsomal fractions in the normal and quaking mice at the ages studied. Although the concentrations of microsomal galactolipids (expressed as nmol/g wet wt of brain) were lower in quaking mice than in the controls at all ages, the percentage of total brain monogalactosyl diglyceride recovered in the microsomes of the mutant mouse was always larger than in the microsomes of the controls. Between 16 and 41 days, the monogalactosyl diglyceride content of the control myelin increased 10-fold, whereas the concentrations in the mutant increased only 2-fold. In normal animals, the percentage of total myelin galactolipids in the ‘small myelin’ decreased over the age of 1841 days with concomitant increase in the ‘large myelin’. In contrast, in the mutant, large percentages of these compounds remained associated with the small myelin even at late periods of myelin development. These findings indicate that the slow rate of deposition of myelin in the brain of quaking mouse may be due to a defective transport mechanism of the galactolipids from the site of synthesis (microsomes) to the site of deposition (myelin), or to a defect in the mechanism of final myelin assembly, rather than to a lipid-specific genetic error.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 30 (1978), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 36 (1981), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: At intervals ranging from 1 to 10 min after injection of 32Pi into rat brain, myelin was prepared and separated into three subfractions: heavy, medium, and light. The radioactivity of total phospholipids and polyphospho-inositides (PPI) was then determined. There was rapid incorporation of 32Pi into PPI, which contained 50–70% of the radioactivity among total brain lipids and more than 70% among myelin lipids. The myelin fraction had incorporated 32Pi into total recovered PPI in the order of medium 〉 heavy 〉 light fraction: however, the order of relative specific radioactivities was heavy 〉 light 〉 medium. Labeling of the PPI precursors, phosphatidic acid (PA) and phos-phatidylinositol (PI), was considerably lower in the purified myelin than in total brain. The di- (DPI) and triphosphoinositides (TPI) in heavy myelin exchanged 32Pi at rates 2 to 3 times faster than those in medium and light myelin. DPI of all subfractions of myelin exchanged much faster than TPI. The results show that the most active phosphate turnover of myelin PPI occurs in the heavy myelin fraction (probably largely consisting of myelin appurtenant regions). However, medium and light myelin (most probably representing the closely packed layers of myelin sheaths) also showed rapid turnover of PPI.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Neurochemical research 5 (1980), S. 617-628 
    ISSN: 1573-6903
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We describe an attempt to incorporate a metabolically inert phospholipid analog into animal membranes, especially myelin, in vivo, with the view of eventual long-term membrane modification or membrane engineering. A sonicated suspension of a mixture of [14C] phosphatidylcholine and its dialkyl analog, [3H] tetradecyloctadecano(1)phosphocholine, was injected into the brain of weanling rats. Samples were counted of whole brain, myelin, liver, and carcass, at intervals from 1 to 63 days, and the composition of the extracted labeled lipid was determined by thin-layer chromatography. Both lipid labels were found to be cleared from the body at similar rates, but while phosphatidylcholine was metabolized within a day, with the label appearing mainly in the phosphatidylethanolamine fraction and in nonpolar lipids, the dialkylphosphatidylcholine remained intact, with retention in myelin of a small but almost constant amount for a month. Ways will have to be found to enhance uptake of the lipids by the brain.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-6903
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract When unilamellar “stable” liposomes composed of a dialkyl analog of phosphatidylcholine, tetradecyloctadec-11-eno(1)phosphocholine (dialkyl-PC), plus cholesterol at 1∶1 molar ratio, and a trace of [3H]dialkyl-PC were injected into the vitreous of the rabbit eye, macrophage infiltration and phagocytosis of lipid were observed in retina including the epiretinal myelinated nerve fiber bundles, with no other neurotoxic effects. Little or no incorporation of [3H]dialkyl-PC was observed in the distal tissues of the optic system. With “labile” vesicles composed of egg lecithin, trace amounts of [3H]dialkyl-PC, and phosphatidic acid, no morphological changes occurred. After a lag of more than 7 days [3H]dialkyl-PC appeared in superior colliculus, indicating axonal transport of the lipid in an anterograde direction. Experiments with submandibular and parotid gland indicated retrograde transport of the lipid. The data do not suggest axonal transport of intact (stable) liposomes, but suggest that intact phospholipid molecules can be axonally transported.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-6903
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Phosphomonoesterase and diesterase that cleave phosphatidylinositol-4-phosphate (diphosphoinositide, DPI) and phosphatidylinositol-4,5-bisphosphate (triphosphoinositide, TPI) were detected in three subfractions of purified rat brain myelin, and some properties of the enzymes were studied. Monoesterase activity was stimulated by KCl, maximally at a concentration of 25 mM, and inhibited at KCl concentrations above 50 mM. Addition of boiled pH 5 supernatant of rat brain homogenate doubled the enzymic activity; EDTA was inhibitory. The specific activities were nearly equal in the “low density”, “medium density”, and “heavy density” myelin fractions but about 30% lower than in whole brain homogenate. The monophosphatase could be solubilized by extraction with 0.2% Triton X-100. The phosphodiesterase activity was inhibited by EDTA and EGTA and not stimulated by KCl or pH 5 supernatant. Specific activities were nearly equal in whole brain and myelin but were by about 60 percent elevated in the “heavy density” over the “low density” myelin fraction. These results show that the hydrolases operative in the fast turnover of the inositide phosphate groups are distributed over the entire myelin structure.
    Type of Medium: Electronic Resource
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