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  • 1
    Electronic Resource
    Electronic Resource
    Fatty Acids from Degenerating Myelin Lipids Are Conserved and Reutilized for Myelin Synthesis During Regeneration in Peripheral Nerve (1995)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 65 (1995), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Following nerve crush, cholesterol from degenerating myelin is conserved and reutilized for new myelin synthesis during nerve regeneration. The possibility that other myelin lipids are salvaged and reutilized has not been investigated previously. We examined the fate of myelin phospholipids and their fatty acyl moieties following nerve crush by electron microscopic autoradiography of myelin lipids prelabeled with [3H]oleate or [2-3H]-glycerol. Both precursors were incorporated predominantly (〉90%) into phospholipids; 〉85% of the [3H]oleate was incorporated as oleate, with the remainder in longer-chain fatty acids. Before nerve crush, both labels were restricted to myelin sheaths. Following nerve crush and subsequent regeneration, over half the label from [3H]oleate, but little from [2-3H]glycerol, remained in nerve. The oleate label was present as fatty acyl moieties in phospholipids and was localized to newly formed myelin sheaths. Among the extracellular soluble lipids within the degenerating nerve, the bulk of the labeled phospholipids floated at the same density as lipoprotein particles. These data indicate that myelin phospholipids are completely hydrolyzed during nerve degeneration, that at least half the resultant free fatty acids are salvaged and reutilized for new myelin synthesis, and that these salvaged fatty acids are transported by a lipoprotein-mediated mechanism similar to that functioning in cholesterol reutilization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1995.65041752.x
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  • 2
    Electronic Resource
    Electronic Resource
    Nerve Regeneration and Cholesterol Reutilization Occur in the Absence of Apolipoproteins E and A-I in Mice (1995)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 64 (1995), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Apolipoproteins have been implicated in the salvage and reutilization of myelin cholesterol during Wallerian degeneration and the subsequent nerve regeneration. Current evidence suggests that myelin cholesterol complexes with apolipoproteins E and A-I to form lipoproteins that are taken up via low-density lipoprotein receptors on myelinating Schwann cells. We recently reported, however, that apolipoprotein E is not required for nerve regeneration or reutilization of myelin cholesterol. We have now investigated nerve regeneration and the reutilization of cholesterol in mutant mice deficient in both apolipoproteins E and A-I. Morphologic examination of nerves 4 and 12 weeks after crush injury revealed that regeneration proceeded at a normal rate in the absence of these apolipoproteins. Autoradiography of regenerating nerves indicated that prelabeled myelin lipid was reutilized in the regenerating myelin. 3-Hydroxy-3-methylglutaryl-CoA reductase, the rate-limiting enzyme in cholesterol synthesis, was down-regulated in the regenerating nerves, indicative of cholesterol uptake via lipoproteins. Prelabeled myelin cholesterol was present in lipoprotein fractions isolated from crushed nerves of mutant mice. These data suggest that there is considerable redundancy in the process of cholesterol reutilization within nerve, and that apolipoproteins other than apolipoproteins E and A-I may be involved in the recycling of myelin cholesterol.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1995.64010408.x
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  • 3
    Electronic Resource
    Electronic Resource
    Lipid Droplets in Schwann Cells During Tellurium Neuropathy Are Derived from Newly Synthesized Lipid (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 55 (1990), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Exposure of weanling rats to a diet containing elemental tellurium results in a peripheral neuropathy characterized by segmental demyelination and minimal axonal degeneration. One of the earliest ultrastructural abnormalities in tellurium neuropathy is an increased number of cytoplasmic lipid droplets in myelinating Schwann cells. The pathogenesis of these lipid droplets was investigated using light and electron microscopic autoradiography. Nerve lipids were either “prelabeled” with [3H]acetate via in vivo intraneural injection 3 days before a 2-day exposure to tellurium, or “postlabeled” via in vivo intraneural injection or in vitro incubation with [3H]acetate following a 2-day exposure to tellurium. In the prelabeled nerves, myelin became heavily labeled, but the tellurium-induced cytoplasmic lipid droplets were rarely labeled. In the postlabeled nerves, the tellurium induced cytoplasmic lipid droplets were the most heavily labeled structures within the nerve. These data indicate that the tellurium-induced lipid droplets in Schwann cells are derived from newly synthesized lipid rather than from the early breakdown and internalization of myelin lipids. The earliest biochemical abnormality observed in tellurium neuropathy is an inhibition of cholesterol synthesis at the squalene epoxidase step. This leads to an accumulation of squalene within the nerve. We conclude that the cytoplasmic lipid droplets in Schwann cells contain this accumulated lipid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1990.tb05778.x
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  • 4
    Electronic Resource
    Electronic Resource
    Nerve Regeneration Occurs in the Absence of Apolipoprotein E in Mice (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 60 (1993), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The concentration of apolipoprotein E (apoE), a high-affinity ligand for the low-density lipoprotein receptor, increases dramatically in peripheral nerve following injury. This endoneurial apoE is thought to play an important role in the redistribution of lipids from the degenerating axonal and myelin membranes to the regenerating axons and myelin sheaths. The importance of apoE in nerve repair was examined using mutant mice that lack apoE. We show that at 2 and 4 weeks following sciatic nerve crush, regenerating nerves in apoE-deficient mice were morphologically similar to regenerating nerves in control animals, indicating that apoE is not essential for peripheral nerve repair. Moreover, cholesterol synthesis was reduced in regenerating nerves of apoE-deficient mice as much as in regenerating nerves of control animals. These results suggest that the intraneural conservation and reutilization of cholesterol following nerve injury do not require apoE.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1993.tb03268.x
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  • 5
    Electronic Resource
    Electronic Resource
    Lipid Metabolism During Early Stages of Wallerian Degeneration in the Rat Sciatic Nerve (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 52 (1989), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract We examined changes in biosynthetic capacity of sciatic nerve during the early stages of Wallerian degeneration, utilizing a model that permits exclusion of nonresident cells from degenerating nerve. Sciatic nerve segments were placed in either 5-μm pore (allowing infiltration of nonresident cells) or 0.22-μm pore (excluding nonresident cells) Millipore diffusion chambers and then implanted in the peritoneal cavity of the same 32-34-day-old rat. At times up to 7 days post-surgery, nerve segments from the chambers, as well as control segments from the contralateral sciatic nerve, were removed and their capacity to incorporate radioactive precursors into lipids and proteins assayed in vitro. In nerve segments from both the 0.22- and 5-μm pore chambers, incorporation of [14C]acetate into total lipids was decreased relative to control by 50% at 12 h postsurgery and by 85% at day 3. This decreased incorporation of [14C]acetate reflects primarily decreased de novo synthesis of cholesterol and of fatty acyl residues incorporated into glycerolipids and sphingolipids. There was a preferentially decreased synthesis of cerebrosides and cholesterol (components enriched in myelin) relative to other lipids, while cholesterol esters and free fatty acids (products of membrane degradation) accounted for a greater proportion of the greatly reduced levels of total lipid label. In contrast to [14C]acetate, incorporation of [3H]glycerol into lipids was increased up to fourfold, relative to control, 1 day after nerve transection. This increased incorporation of [3H]glycerol does not reflect de novo synthesis of lipids (which is decreased), but rather removal of toxic fatty acyl residues derived from degradation of myelin lipids; these toxic compounds must be removed by resynthesis into nonmyelin glycerolipids and cholesterol esters. The inhibition of de novo synthesis of myelin lipids in Schwann cells during the early stages of Wallerian degeneration occurs independently of hematogenously-derived cells. We suggest that Wallerian degeneration rapidly results in some breakdown of myelin, and that the increased free fatty acid levels resulting from degradation of myelin lipids inhibit the de novo synthesis of new myelin lipid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1989.tb01851.x
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  • 6
    Electronic Resource
    Electronic Resource
    Acute lead encephalopathy in the guinea pig (1975)
    Springer
    Acta neuropathologica 33 (1975), S. 185-190 
    Details
    ISSN: 1432-0533
    Keywords: Guinea pig ; Lead ; Encephalopathy ; Blood-brain barrier
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Acute lead encephalopathy was induced in adult guinea pigs with daily oral doses of lead carbonate. Cerebral capillaries were examined by electron microscopy, and the blood-brain barrier (B-BB) evaluated with Evans blue and horseradish peroxidase. Brain lead levels were also determined during the developing encephalopathy. There was no cerebral capillary alteration or demonstrable B-BB dysfunction. Brain lead concentrations increased over the 5-day period. The encephalopathy in the absence of any vascular alteration suggests that lead can produce a primary toxic effect at the neuronal level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00688392
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  • 7
    Electronic Resource
    Electronic Resource
    Regenerating Sciatic Nerve Does Not Utilize Circulating Cholesterol (1998)
    Springer
    Neurochemical research 23 (1998), S. 401-406 
    Details
    ISSN: 1573-6903
    Keywords: Nerve regeneration ; demyelination ; remyelination ; peripheral nervous system myelin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The rapid accumulation of myelin in the peripheral nervous system during the early postnatal period requires large amounts of cholesterol, a major myelin lipid. All of the cholesterol accumulating in the developing rat sciatic nerve is synthesized locally within the nerve, rather than being derived from the supply in lipoproteins in the systemic circulation (Jurevics and Morell, J. Lipid Res. 5:112–120; 1994). Since this lack of utilization of circulating cholesterol may relate to exclusion by the blood-nerve barrier, we examined the sources of cholesterol needed for regeneration following nerve injury, when the blood-nerve barrier is breached. One sciatic nerve was crushed or transected, and at various times later, the rate of cholesterol accumulation was compared with the rate of local in vivo synthesis of cholesterol within the nerve, utilizing intraperitoneally injected 3H2O as precursor. The accumulation of additional cholesterol in nerve during regeneration and remyelination could all be accounted for by that locally synthesized within the nerve. There was also an increase in cholesterol esters in injured nerve segments; in crushed nerves, these levels decreased during regeneration and remyelination, consistent with reutilization of cholesterol originally salvaged by phagocytic macrophages and Schwann cells. Thus, regeneration and remyelination following injury in sciatic nerve utilizes both salvaged cholesterol and cholesterol synthesized locally within the nerve, but not cholesterol from the circulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022469803426
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  • 8
    Electronic Resource
    Electronic Resource
    Distribution of testican expression in human brain (2000)
    Springer
    Cell & tissue research 302 (2000), S. 139-144 
    Details
    ISSN: 1432-0878
    Keywords: Extracellular matrix Proteoglycan Ependymal cells Neurons Gliosis Endothelium In situ hybridization Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Testican is a putative extracellular heparan/chondroitin sulfate proteoglycan of unknown function that is expressed in a variety of human tissues at widely different levels but is most abundant in the brain. In mice, testican mRNA has been detected only in brain and it is therefore likely to have an important function in the central nervous system. RNA blot analysis reveals the relative intensity of testican in various regions of the human brain. Levels of testican message are most pronounced in the thalamus, hippocampus, occipital lobe, nucleus accumbens, temporal lobe, and caudate nucleus, with somewhat lower levels in the cerebral cortex, medulla oblongata, frontal lobe, amygdala, putamen, spinal cord, substantia nigra, and cerebellum. In situ hybridization reveals the cellular distribution of the mRNA within these areas to be highest in neurons and in choroid plexus epithelium, and moderately lower in ependymal cells lining the ventricles and in vascular endothelial cells. Testican mRNA is not detected in oligodendrocytes or in most astrocytes. However, astrocytes in regions of reactive gliosis do express testican mRNA. These findings, along with a cysteine-rich pattern similarity to neurocan, brevican, versican, and other proteoglycans found in brain, suggest that testican may be a part of the specialized extracellular matrix of the brain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410000277
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  • 9
    Electronic Resource
    Electronic Resource
    Application of confocal scanning laser microscopy in experimental pathology (1991)
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 18 (1991), S. 38-49 
    Details
    ISSN: 0741-0581
    Keywords: Apoptosis ; Surfactant apoprotein-A ; Blood-nerve barrier ; Pinocytosis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Confocal scanning laser microscopy (CSLM) represents an exciting new tool for scientific disciplines which focus on mechanistic studies such as experimental pathology. Enhanced resolution in the specimen plane and rejection of out-of-focus fluorescence flare allow analysis of specific nucleic acid sequences, enzymes, structural macromolecules, and cellular homeostasis utilizing fluorescent probes. Four different experimental applications are discussed which utilize CSLM to evaluate pathological processes at the subcellular, cellular, and tissue levels. Programmed cell death, or apoptosis, is a natural process of significance both during development and as a response to toxic stimuli. CSLM-imaging of nuclei of human B lymphoblastoid cells following exposure to a monofunctional alkylating agent suggests that the degradation of chromatin characteristic of apoptosis may occur in asymmetric patterns. Surfactant apoprotein-A is the major non-serum protein component of pulmonary surfactant and is essential for the extracellular function of surfactant. CSLM of alveolar type II cells suggests that apoprotein-A is present in both the cytoplasm, predominantly in lamellar bodies, and in the nucleus. The tumor promoter, phorbol myristate acetate, rapidly stimulated the formation of vacuoles in human neutrophils. CSLM using Lucifer Yellow as a probe suggests that cylindrical vacuoles are formed by fluid-phase pinocytosis. The blood-nerve barrier (BNB) in peripheral nerves may be an important target during toxin-induced neuropathies. Ricin-induced permeability of the BNB in the rat was rapidly visualized by CSLM as leakage of fluorescein isothiocynate (FITC)-dextran into the endoneurial compartment.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1060180107
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