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PubMed2002

Interface properties of simplified tear-like fluids in relation to lipid and aqueous layers composition.

The Langmuir trough approach to the study of the physical properties of an in vitro system representing the natural tear lipid-aqueous interface gives useful information on the effect produced by changes of composition of both phases. We found that variations of the composition of the lipid mixture affect more strongly the characteristics of the film rather than changes in the aqueous phase composition. Therefore, future investigations should consider the possibility of searching for and optimising additions of lipid mixtures to the natural tear film. These novel mixtures should stabilise the lipid layer, and thus treat the evaporative Dry Eye Syndrome. More critical and worthy of further investigation is the effect of surface-active water-soluble components that can reduce and ultimately destroy the lipid film integrity and effectiveness. The beneficial effect of water-soluble components, either naturally occurring or artificially added, may be more precisely compared with possible side effects on the stability of the lipid tear layer. In any case, these side effects may be largely compensated by the presence of stability enhanced lipid composition. The present work may be considered as an introductory investigation that takes the physical-chemical approach into the realm of debated data about the tear film structure and properties. Refining the model we have adopted in the present work is certainly necessary. For instance, introducing into the model tear composition other components such as ceramides and cerebrosides will provide insight to their contribution to the packing structure. We may also couple different techniques such as measuring elastic and rheological properties of the films that may be relevant to its physiological behaviour.

Humans↗
PubMed1978

Studies of isolated, maintained oligodendroglia: biochemistry, metabolism, and in vitro myelin synthesis.

Oligodendroglia can be isolated in bulk from dissected white matter of lamb or bovine brain. Studies of the composition of the whole cell and of glial subfractions were performed to detect similarities to mature myelin. With care isolated oligodendroglia can now be maintained in culture for three to four days. While in culture the cells elaborate a form of glial myelin which has characteristics of both the intact cell and of mature myelin. Glial myelin reacts with both the antiserum to oligodendroglial surface components and with antiserum to galacto-cerebroside; it increases in amount with time in culture; if various radiolabeled substrates are added to the cells in culture, the glial myelin has both lipids and proteins which are extensively radiolabeled; the glial myelin has both basic protein and 2',3'-cyclic AMPase associated with it. Thus this model system may be an excellent system for studying myelin assembly in vitro.

Animals↗
PubMed1986

Membrane lipid changes in organic solvent tolerant neural cells.

Although, organic solvents are known to interact with neural membranes and to possess acute anesthetic properties, very little is known about the chronic effects of organic solvents on neural membranes. In the present study lipid compositional changes were examined after chronic exposure to the chlorinated organic solvents, trichloroethylene (TCE) and perchloroethylene (PCE). Animals were exposed continuously in inhalation chambers. Each experimental group had its own control group exposed simultaneously to air under identical conditions. Exposure to these organic solvents had only minor effects on lipid class composition. A tendency towards a decreased cholesterol to phospholipid ratio was observed, whereas the content of cerebrosides was unaffected. However, the proportions of the polyunsaturated fatty acids of ethanolaminephosphoglyceride (EPG) was consistently changed after exposure to either of these solvents for three months at (320 ppm). After longer exposure periods such alterations were observed at even lower solvent concentrations. This change in fatty acid pattern was characterized by an increase in linolenic acid derived fatty acids, with a concomitant decrease in fatty acids of the linolenic acid family. These changes may be an effort to compensate for the increased hydrophobic volume of membranes induced by dissolved solvent molecules. This compensation could be achieved by insertion of less coned lipid components into the membrane. The observed decrease in cholesterol to phospholipid ratio and the increase in the less saturated linoleic acid derived fatty acids could serve this function. Another possibility could be that chlorinated organic solvents interfere with the protein structure of desaturases, resulting in an alteration in the speed of desaturation and a changed fatty acid composition.

Animals↗
PubMed1990

Role of membrane phospholipids and glycolipids in the Vero cell surface receptor for rubella virus.

Membrane receptors for rubella virus (RV) in Vero cells were studied by means of two different approaches: (i) by enzyme treatment of the whole cell membrane and (ii) by testing the ability of isolated plasma membrane molecules to compete with cells for virus binding. The replication of RV was studied with both indirect immunofluorescence assay and molecular hybridization techniques. Phospholipases A2 and C digestion of cells greatly reduced the infectivity by the virus, pointing towards the involvement of lipid structures as receptor sites for RV. Furthermore, susceptibility of Vero cells to virus infection was also reduced after beta-N-acetyl-D-glucosaminidase, alpha-glucosidase and beta-galactosidase treatment, suggesting that carbohydrate residues may participate in a complex cellular receptor structure for RV. When the major membrane lipids were examined separately for their ability to inhibit viral infectivity, several phospholipids (phosphatidylserine, phosphatidylinositol, phosphatidylethanolamine, phosphatidylcholine, sphingomyelin) and glycolipids (gangliosides, lactosylceramide, cerebroside sulphate) showed a strong neutralizing activity, confirming the role of membrane lipid moiety in the cell surface receptor for RV.

Animals↗
PubMed1978

The biosynthesis of glycolipids during the differentiation of the slime mold Dictyostelium discoideum.

In the slime mold Dictyostelium discoideum polysioprenylphosphomannosides are substrates for membrane bound mannosyltransferases; the isolated and purified isoprenyl derivatives transfer mannose to protein in vitro in presence of membrane fractions. The biosynthesis of the mannolipids as well as the biosynthesis of a glucose containing cerebroside, which becomes synthesized in an early stage of the cell development proceeds under control of the cell differentiation. The isolation procedure and the properties of the glycolipids are described, and their functions for the cellular development are discussed.

Ceramides↗
PubMed1990

Ultrastructural and biochemical findings in brain cell cultures infected with canine distemper virus.

To study the pathomechanism of demyelination in canine distemper (CD), dog brain cell cultures were infected with virulent A75/17-CD virus (CDV) and examined ultrastructurally. Special attention was paid to the oligodendrocytes, which were specifically immunolabelled. In addition, cerebroside sulfotransferase (CST), an enzyme specific for oligodendrocyte activity was assayed during the course of the infection. Infection and maturation as well as CDV-induced changes were found in astrocytes and brain macrophages. Infection of oligodendrocytes was rarely seen, although CST activity of the culture markedly decreased and vacuolar degeneration of these cells occurred, resulting in their complete disappearance. We concluded that the degeneration of oligodendrocytes and demyelination is not due to direct virus-oligodendrocyte interaction, but due to CDV-induced events in other glial cells.

Animals↗
PubMed1979

Neutral lipid and sphingolipid composition of the brain of a patient with membranous lipodystrophy.

Lipids were extracted from brains of a patient with membranous lipodystrophy (ML) and three normal patients and the neutral lipid and sphingolipid constituents were investigated. The storage of a large amount of free fatty acid was observed in the ML brain, but no cholesterol ester was found. Total lipid, cholesterol and cerebroside contents were slightly decreased in the white matter of the ML brain. The composition of free and sphingolipid fatty acids did not differ between ML and normal brains.

Adult↗
PubMed1977

Prenatal diagnosis of globoid cell leukodystrophy (Krabbe's diseases). Third documented case.

A case of globoid cell leukodystrophy (Krabbe's disease) was diagnosed prenatally by demonstrating a profound deficiency of cerebroside beta-galactosidase in cultured amniotic cells. The diagnosis was confirmed in the fetus aborted in the 19th week. In the cell-free amniotic fluid, normal enzyme activity was found. This finding, which had been demonstrated in a previous case, is discussed.

Amniocentesis↗
PubMed1975

Direct evidence for the specific fixation of Cl. botulinum A neurotoxin to brain matter.

Rat brain homogenate and synaptosomes from rat brain bind botulinum toxin. The binding is accompanied by partial inactivation. The binding decreases with increasing ionic strength. A considerable fixation of tetanus toxin can still be demonstrated under conditions which prevent the fixation of botulinum toxin. 2. Only the grey substance, not the white substance from bovine brain is able to bind the toxin. 3. Upon pretreatment with neuraminidase, synaptosomes lose nearly all of their binding capacity. However, neither gangliosides nor ganglioside-cerebroside mixtures nor brain extracts could replace the synaptosomes. Thus botulinum A toxin closely resembles tetanus toxin in its ability to react with (a) neuraminidase-sensitive site(s) of the grey matter of the CNS. It differs from tetanus toxin by its stronger sensitivity against ionic forces and by its failure to react with certain gangliosides.

Animals↗
PubMed1985

Postnatal sudanophilic leukodystrophy in two siblings.

Reported here are two siblings with sudanophilic leukodystrophy occurring in early infancy. Soon after birth, high fever, distension of the abdomen and spasticity of the extremities were noted. Neurologic disorders, frequent convulsive seizures, and malnutrition caused both siblings to die at the age of 3 and 6 months, respectively. Neuropathologic examination of the brain revealed diffuse demyelination in the cerebral and cerebellar white matter as well as a disturbance of the myelination, especially in the descending pathway. Numerous sudanophilic lipids and glial fibers proliferated in the demyelinated areas. Neurochemically, there was a marked decrease in all lipid components, cholesterol, phospholipids, and glycolipids and an increase in cholesterol ester. Fatty-acid composition of cerebroside and sulfatide, especially that of long-chain acids, was within normal range, unlike the fatty-acid composition found in connatal Pelizaeus-Merzbacher disease. The brain damage in postnatal infant caused by frequent convulsive seizures and the severe demyelination in the cerebral and cerebellar white matter in both patients are discussed. The cases of sudanophilic leukodystrophy and Pelizaeus-Merzbacher disease occurring in children under 5 years of age are reviewed.

Brain↗
PubMed1982

Biochemical studies of the late infantile form of metachromatic leukodystrophy.

Biochemical studies from a patient with the late infantile form of metachromatic leukodystrophy are presented. Since the autopsy was performed soon after death, viable cells were isolated from brain. The purified cells had altered densities and unusual appearances. The cells when placed in culture were able to incorporate radiolabeled substrates into cerebrosides, indicating that some of the cells were of oligodendroglial origin. Myelin was isolated using several different methods, and the degree of abnormality appeared to be dependent upon the method of isolation. Nonetheless, MLD myelin, while still retaining its characteristic-morphology, had increased levels of sulfatides (two to four times that normally found). Other membrane subfractions were isolated that were not present in control tissue and that were more abnormal in composition than myelin. Finally, the glycoproteins in MLD tissue also appeared to be altered. There were losses in MLD myelin glycoproteins that bind to Concanavalin A (Con A) and additional prominent glycoproteins that bind to wheat germ agglutinin.

Autopsy↗
PubMed1975

[Malignant granular-cell tumor of the cerebral white matter: morphological, cytophotometrical and neurochemical studies (author's transl)].

This is a report of the second known case of a primary malignant granular-cell tumor of the cerebral hemispherical white matter. Two cell types may be distinguished apparently representing different developmental stages of otherwise identical tumor cells. Quantitative histochemical and biochemical studies have shown that tumor cells were containing markedly elevated levels of DNA and RNA. Only few ribosomes and polysomes could be detected, however, by electron microscopy. While cytophotometry disclosed only slightly elevated cytoplasmic proteins, there was a distinct increase in total protein concentration of tumor tissue per unit weight, as measured by conventional techniques. It is suggested that this increase is mainly attributable to structural proteins of cellular and subcellular elements of multiplicating malignant cells. A ratio of RNA to DNA in excess of 1 was found for white matter derived from the central tumor, while the ratios of control tissue were lowered to values far below one due to postmortem changes greatly reducing tissue concentrations of RNA. No detailed characterization of RNA was attempted. The nuclear DNA content of tumor cells reached values equivalent to chromosomal hexadekaploidy. This was in sharp contrast to control data from an Abrikossoff tumor of the oral cavity and from a neurohypophyseal tumorette ("choristoma"), respectively, displaying diploidy only associated with a much lesser increase of cytoplasmic RNA and proteins. Qualitative lipid studies were consistent with a marked active demyelination of the tumor centre as indicated by a severe reduction of cerebrosides and sulfatides and the presence of cholesterol esters. In addition there was a striking loss of phosphatidylethanolamine and a lesser one of sphingomyelin of white matter of both the tumor-stricken and the contralateral unaffected hemispherical regions, possibly suggesting a generally disturbed metabolism of myelin. It is not clear whether these general changes were resulting from the presence of the unilateral tumor or from precocious cerebral involution.

Brain Neoplasms↗
PubMed1991

Cell regulation by sphingosine and more complex sphingolipids.

Sphingolipids have the potential to regulate cell behavior at essentially all levels of signal transduction. They serve as cell surface receptors for cytoskeletal proteins, immunoglobulins, and some bacteria; as modifiers of the properties of cell receptors for growth factors (and perhaps other agents); and as activators and inhibitors of protein kinases, ion transporters, and other proteins. Furthermore, the biological activity of these compounds resides not only in the more complex species (e.g., sphingomyelin, cerebrosides, gangliosides, and sulfatides), but also in their turnover products, such as the sphingosine backbone which inhibits protein kinase C and activates the EGF-receptor kinase, inter alia. Since sphingolipids change with cell growth, differentiation, and neoplastic transformation, they could be vital participants in the regulation of these processes.

Animals↗
PubMed1981

Composition of axolemma-enriched fractions isolated from bovine CNS myelinated axons.

Axolemma-enriched fractions were isolated from the white matter of bovine corpus callosum via a purified preparation of myelinated axons which were osmotically shocked and fractionated on a discontinuous density gradient. Two membrane fractions of differing density were obtained: both were somewhat enriched over white matter whole homogenate in specific activity of acetylcholinesterase and 5'-nucleotidase and maximal binding capacity for saxitoxin. Both membrane fractions contained appreciable amounts of 2', 3'-cyclic nucleotide 3'-phosphohydrolase; the specific activity of antimycin-sensitive NAPH-cytochrome c reductase and cytochrome c oxidase indicated low levels of contamination by microsomal and mitochondrial membrane. The myelin which is concomitantly isolated with the axolemma-enriched fractions has a lipid and protein composition comparable to that of myelin isolated by other procedures. Both axolemma-enriched fractions contain about one half of their dry weight as lipid comprised of approximately 25% cholesterol, 25% galactolipid (cerebrosides and sulfatides in a molar ratio of about 4:1) and 50% phospholipid, mostly choline phosphatides and ethanolamine phospholes in an equimolar ratio. The axolemma fractions are also enriched in ganglioside content relative to the myelin fraction. The polypeptides of the axolemma-enriched fractions range from 20,000 to over 200,000 in molecular weight; the predominant proteins are in the range from 50,000 to 69,000. The most dense axolemma-enriched fraction is over fourfold enriched in glycoprotein content compared with myelin, with at least 10 different molecular-weight classes of glycoproteins as identified by Schiff stain of polyacrylamide gel protein profiles. The differences and similarities in the molecular composition of axolemma-enriched preparations which have been characterized to date are discussed.

Animals↗
PubMed1979

Large-scale preparation of synaptosomes from bovine brain using a zonal rotor technique.

A zonal rotor technique for the preparation of synaptosomes in bulk from bovine brain frontal cortex based on an impirical transformation of a small-volume discontinuous sucrose density gradient arrangement is presented in detail. The procedure yields new information concerning synaptosomes prepared in sucrose gradients. Cerebroside analysis and electron microscopy show myelin contamination to be restricted to the leading, less dense edge of the synaptosomal profile, free mitochondria to the trailing, more dense edge. Exclusion of fringe areas yields a highly purified synaptosome preparation which entirely enters the next dense layer beyond the 0.8 : 1.2 M sucrose interface. This interface collects most of the oubain-sensitive (Na+, K+) adenosine triphosphatase activity. The purified synaptosomes display very high intrinsic sialidase activity and are rich in di-, tri-, and tetrasialogangliosides, the preferred substrates for the enzyme. Up to 90% of the cholinesterase activity in the zonal rotor synaptosome preparation is specific acetylcholinesterase.

Adenosine Triphosphatases↗
PubMed1990

Lipid profile of rat myelin subfractions.

Myelin from adult rat brains was separated on a discontinuous sucrose gradient into three subfractions. Analysis of "light", "heavy" and "membrane fraction" lipid classes was performed by HPTLC and densitometry while fatty acid composition was determinated by GLC. The more interesting results observed are: i) the "membrane fraction" resembles in its lipid and fatty acid composition other cell membranes (particularly oligodentrocytes); ii) "light" and "heavy" myelin are quite similar between them but the former has a higher content of sphingomyelin, a lower hydroxy/nonhydroxy cerebrosides ratio and a lower content of monoenoic fatty acids than the "heavy" subfraction. The results obtained could explain the different structures observed in each myelin subfraction since fatty acid composition, hydroxy fatty acids, sphingomyelin and cholesterol play a key role in the stability and structure of membranes.

Animals↗
PubMed1986

Effects of pre-weaning undernutrition and post-weaning rehabilitation on polyphosphoinositide pools in rat brain regions.

In order to assess the effects of undernutrition during the pre-weaning period on polyphosphoinositide (PolyPI) pools in rat cerebral cortex, brain stem, and cerebellum, dams were fed 5% (L-) or 22% (L+) protein diets from birth to weaning and the pups were used at this age for analyses. To examine rehabilitation post-weaning, L- and L+ pups were fed 22% protein diets (P+) for an additional six week period. Rats were decapitated and the dissection begun either immediately ("0 min" samples) or 10 min later (10 min samples). Body and tissue weights, and cerebroside levels were determined in addition ot PolyPI concentrations. In brain the extent of disappearance of PolyPI during the 10 min post-mortem period paralleled the content of gray matter: cerebral cortex greater than cerebellum greater than brain stem in all groups regardless of diet. Levels of PtdIns4P and PtdIns4,5P2 were decreased by 40% and 70% respectively in cerebral cortex of L- "0 min" samples. Deficits of both lipids in brain stem and cerebellum were 40-50%. In the L- 10 min samples, deficits were 20-30% in all three regions as compared with L+ 10 min levels, indicating the presence of a portion of both lipids affected only moderately by nutritional insufficiency. The effects on this relatively inert pool, much of it localized in myelin, were reversed on nutritional rehabilitation. The PolyPI pool lost post-mortem in L+ brain regions was practically absent in L- brain regions and was not restored in L-P+ animals. Thus, this study indicates that a metabolically labile pool, primarily located in gray matter structures, is more sensitive to nutritional deprivation during the pre-weaning period than the more stable pool. The precise role and function of these pools remain to be determined.

Animals↗
PubMed1993

Neurotoxicity of 2,4-dichlorophenoxyacetic butyl ester in chick embryos.

Fertilized hens' eggs were externally treated, before starting incubation, with a single dose of 2,4-Dichlorophenoxyacetic butyl ester (2,4-D b.e., 3.1 mg/egg). Chicks at different developmental stages were examined, extending from 10 day embryos to one day after hatching. Previously, we demonstrated that 2,4-D b.e. produces hypomyelination in chicks born from treated eggs. In search of the causes of this hypomyelination, "myelin markers" such as sulphatides, cerebrosides and 2'3'-cyclic nucleotide 3'-phosphohydrolase (CNPase) activity, as well as protein and nucleic acid contents were determined in the embryonic brains. We have shown in the present study that the chemical alterations occurred even before the period of active myelination, since myelin appears in chicken brain stem and cerebrum approximately after 17 days of incubation, and most of the chemical parameters studied are diminished before that time. The DNA content in brain of treated group is increased from the 14th embryonic day (with a transient diminution at 12th day) to the first hatching day, when compared to the control, suggesting a proliferation of glial cells, possibly oligodendrocytes.

2,4-Dichlorophenoxyacetic Acid↗