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D R Wing

Publications and source records attributed to D R Wing.

36 records · Page 2Linked to original sources
PubMed1992

Detection of multisulphated N-linked glycans in the L2/HNK-1 carbohydrate epitope expressing neural adhesion molecule P0.

P0, the most abundant glycoprotein of PNS myelin, is a homophilic and heterophilic adhesion molecule. P0 is known to contain a glycoform population that expresses the L2/HNK-1 carbohydrate epitope found on other neural adhesion molecules, and to be functionally implicated centrally in neural cell adhesion and neurite outgrowth. This carbohydrate epitope has been characterized previously from glycolipid structures and contains a sulphated glucuronic acid residue. However, the L2/HNK-1 carbohydrate epitope has not been characterized in glycoproteins. Because P0 possesses only one glycosylation sequon, the number of P0 glycoforms is equal to the heterogeneity of the glycan species. Here we report that the carbohydrate analysis of L2/HNK-1-reactive P0 showed the presence of anionic structures containing sialic acid and sulphate in various combinations. At least one sulphate residue was present in 80% of the monosaccharide sequences, and 20% contained three sulphates. High-resolution P4 gel chromatography of the desialylated and desulphated oligosaccharides showed substantial heterogeneity of monosaccharide sequences. Sequential exoglycosidase digestions indicated that the majority of the structures were of the hybrid class, although the sulphated structures were found to be endoglycosidase H-resistant.

Antigens, Differentiation↗
PubMed1986

Examination of the esterified fatty acids from mouse erythrocyte and synaptosomal membrane phospholipids and their distribution between the various phospholipid types.

Esterified fatty acids from mouse erythrocyte and synaptosomal membranes were characterised by fused-silica capillary gas-liquid chromatography and gas chromatography-mass spectrometry. Structural information was obtained from the mass spectra of a number of derivatives including trimethylsilyl (TMS), methyl and picolinyl esters together with the TMS ethers of glycols derived from the unsaturated acids. In addition to previously characterised acids, small concentrations of several acids previously unreported from these membranes were identified. These included branched chain acids and several unsaturated acids.

Animals↗
PubMed1984

The partitioning of delta 1-tetrahydrocannabinol into erythrocyte membranes in vivo and its effect on membrane fluidity.

delta 1-Tetrahydrocannabinol (delta 1-THC) has been quantified directly in erythrocyte membranes from drug-treated mice using gas chromatography/mass spectrometry. Concentrations of approximately 6 ng delta 1-THC/mg membrane protein (10(-5) M) were found when effects of the drug on behavior were prevalent. At these concentrations the drug produced a decrease in membrane order as measured by ESR.

Animals↗
PubMed1984

Changes in membrane lipid content after chronic ethanol administration with respect to fatty acyl compositions and phospholipid type.

Changes in the relative proportions of the phospholipid fatty acids of erythrocyte membranes in mice after chronic ethanol treatment (4.5 g/kg, i.p. twice daily for one week) were shown to vary with the differing control profiles observed. It is suggested that certain changes in membrane lipid composition after ethanol administration may not be interpreted simply in terms of an adaptation to a disordering effect of the drug. The fatty acid changes were, in addition, distributed asymmetrically within the individual phospholipid classes. Depending on the control profile, the effects varied from being mainly in phosphatidylethanolamine (PE; 80%) and phosphatidylserine-inositol (PS + PI; 10%), phospholipids primarily located on the inner half of the membrane bilayer, to being more evenly distributed between PE and phosphatidylcholine (PC) and probably, therefore, between the two halves of the bilayer. Changes in the monounsaturated acid remained primarily with PE, suggesting a specific functional role for this species. The remaining results are discussed in the light of possible effects on cell morphology and their potentially similar consequences of increasing cell volume.

Animals↗
PubMed1982

Effects of chronic ethanol administration on the composition of membrane lipids in the mouse.

The relative proportions of the phospholipid fatty acids of erythrocyte membranes in mice were changed by chronic ethanol treatment and were not related to effects of the drug on nutrition, body temperature or experimental stress. Similar changes were observed using two different routes of ethanol administration and they did not reflect the metabolic effects of ethanol seen in the phospholipid fatty acids of whole liver. The observed increased content of saturated fatty acids and decreased content of polyunsaturated acids support the concept of adaptive changes taking place in the membrane during tolerance development to compensate for an increased membrane fluidity caused by ethanol. However, an increased content of the mono-unsaturated acid, octadecenoic (oleic), was found and there was no change in the cholesterol/phospholipid ratio. Other contrasting types of plasma membrane in mice showed different patterns of change in their phospholipid fatty acids during chronic ethanol administration. It is suggested that changes in membrane lipid composition could only partly account for an adaptation to ethanol-induced membrane disordering.

Alcoholism↗
PubMed1981

Effects of halothane on the incorporation of [14C]-serine into phospholipid in the guinea-pig ileum.

1 The effects of halothane on the incorporation of L-[3-14C]-serine into phospholipid were studied in the resting, innervated longitudinal muscle preparation of the guinea-pig ileum. 2 The anaesthetic, at clinical concentrations, caused a dose-dependent, partial inhibition of incorporation. The effect was rapid and reversible, and did not show characteristics of competitive inhibition. 3 The incorporation was reduced by a decrease in the Ca2+ concentration of the Krebs incubation buffer. Part of the activity persisted in the absence of added Ca2+ and this was most susceptible to inhibition by halothane. Sensitivity to external Ca2+ was not influenced at the halothane concentrations studied. 4 Evidence in support of the 14C-incorporation being due to L-[3-14C]-serine-phospholipid base-exchange activity included: (a) the rapid appearance of radioactivity in phosphatidylserine; (b) the kinetics of this incorporation in relation to that in phosphatidylethanolamine; (c) its dependence on Ca2+, and (d) its sensitivity to 2,4-dinitrophenol and its sensitivity to temperature. 5 It is concluded that this preparation makes it possible for a membrane-bound lipid-dependent activity (L-serine-phospholipid base-exchange) to be studied in conditions of cellular integrity under which the normal functional effects of lipophilic drugs can be simultaneously tested. 6 A rapid gas-chromatographic assay for halothane from an aqueous medium is also described.

Animals↗
PubMed1978

The effects of delta1-tetrahydrocannabinol on mammary gland growth, enzyme activity and plasma prolactin levels in the mouse.

DELTA1-tetrahydrocannabinol (delta1-THC), a highly lipid soluble and active principle of cannabis, was injected each day (25 mg/kg) s.c. in mice from the estimated 13th day of pregnancy. Delta1-THC-treated mice showed no increase in the wet weight or DNA content of their mammary glands during the period of investigation from before parturition until the 12th day post-partum. A marked increase in mammary-gland lipoprotein lipase activity w,s found in control mice at parturition and this was suppressed by delta1-THC. Prolactin rose to a peak level in plasma earlier in lactation in the control mice than in the delta1-THC-treated mice. This delayed rise in plasma prolactin due to delta1-THC may account for the depression of mammary gland growth and development by the drug and for the delay in the appearance of high activities of lipoprotein lipase until later in lactation.

Animals↗
PubMed1973

The effect of cycloheximide on adipose-tissue clearing-factor lipase.

The progressive increase in clearing-factor lipase activity that occurs during the incubation of adipose tissue from starved rats in an appropriate medium at 25 degrees C is shown to occur in two stages. The first of these is not inhibited by cycloheximide, whereas the second is.

Adipose Tissue↗
PubMed1968

Clearing-factor lipase in adipose tissue. Studies with puromycin and actinomycin.

1. When adipose tissue from starved rats is incubated in a medium containing glucose, insulin, heparin and actinomycin (5mug./ml.) the total clearing-factor lipase activity of the system increases at least tenfold over a period of 9hr. In the absence of actinomycin, enzyme activity also increases, but to a lesser extent and for only about 3hr. Some enzyme activity appears in the incubation medium in both the presence and the absence of actinomycin. 2. When the glucose and insulin of the incubation medium are replaced by pyruvate and heparin is omitted, an increase in the total clearing-factor lipase activity in the presence of actinomycin still occurs, but only after a lag of several hours. When only heparin is omitted from the medium, the rise in enzyme activity begins immediately, but there is a shoulder in the time-course curve after a few hours. In the absence of heparin, little enzyme activity appears in the incubation medium. 3. The increases in enzyme activity in the presence of actinomycin are prevented if puromycin (0.5mg./ml.) is present in the incubation medium. 4. Catecholamines and corticotrophin inhibit the increase in enzyme activity caused by actinomycin. 5. The clearing-factor lipase activity of adipose tissue from fed animals declines with a half-life of between 1 and 1.5hr. when the tissue is incubated in the presence of puromycin. The clearing-factor lipase activity of adipose tissue from starved animals is stable under similar circumstances, as is the raised activity found after such tissue has been incubated in the presence of actinomycin. 6. Clearing-factor lipase extracted from adipose tissue of fed animals is less stable in solution than that extracted from the tissue of starved animals after this has been incubated in the presence of actinomycin.

Adipose Tissue↗
PubMed1968

Clearing-factor lipase in adipose tissue. A possible role of adenosine 3',5'-(cyclic)-monophosphate in the regulation of its activity.

1. The rise in clearing-factor lipase activity that occurs when epididymal fat bodies from starved rats are incubated in appropriate media in vitro is inhibited in the presence of 6-N-2'-O-dibutyryl-3',5'-(cyclic)-AMP (1mm). 2. Inhibition occurs at a concentration of glucose in the incubation medium of 1.3mg./ml. or less, but not at a glucose concentration of 2.4mg./ml., unless caffeine (1mm), an inhibitor of 3',5'-(cyclic)-nucleotide phosphodiesterase, is also present. Caffeine (5mm) alone inhibits the rise in clearing-factor lipase activity at a glucose concentration of 2.4mg./ml. of medium. 3. The concentration of free fatty acids in the epididymal fat bodies normally falls during incubations in vitro as the rise in clearing-factor lipase activity occurs. In the presence of 1mm-6-N-2'-O-dibutyryl-3',5'-(cyclic)-AMP, however, either the tissue free fatty acid concentration is increased or it does not fall to the same extent. The concentration of glucose in the incubation medium is important in determining the direction and extent of the changes in tissue free fatty acid concentration that occur in the presence of 6-N-2'-O-dibutyryl-3',5'-(cyclic)-AMP. 4. Free fatty acid concentrations in epididymal fat bodies in vivo rise as the clearing-factor lipase activity of the tissue falls during starvation. 5. The possibility that the concentration of 3',5'-(cyclic)-AMP in adipose tissue may regulate clearing-factor lipase activity, and that the regulation may occur through effects of the nucleotide on tissue free fatty acid concentrations, is discussed.

Adenine Nucleotides↗
PubMed1966

Clearing-factor lipase in adipose tissue. Factors influencing the increase in enzyme activity produced on incubation of tissue from starved rats in vitro.

1. Evidence is presented that the increase in clearing-factor lipase activity that occurs when adipose tissue from starved rats is incubated in a defined medium in vitro is due to an increase in the total enzyme content of the system. It is shown that the clearing-factor lipase activity rises to reach a plateau level where, it is suggested, rates of enzyme synthesis and of enzyme destruction become balanced. 2. The presence of heparin in the incubation medium results in the extraction of part of the clearing-factor lipase originally present in the adipose tissue and this could provide the stimulus for the increase in total enzyme content. 3. Glucose is required in the incubation medium at a very low concentration. It can be replaced by fructose, but not by pyruvic acid, lactic acid, glyceric acid or dihydroxyacetone. 4. Adrenaline and corticotrophin inhibit the increase in enzyme activity when they are present in the incubation medium. 5. The high clearing-factor lipase activity associated with adipose tissue of fed rats is decreased by 50% within 3hr. of the injection of puromycin.

Adipose Tissue↗