Biomedical subjects

A Heape

Publications and source records attributed to A Heape.

10 recordsLinked to original sources

PubMed1996

Acylation of endogenous acyl acceptors by mouse sciatic nerve microsomes.

Phospholipid (chiefly phosphatidylcholine) labeling from radioactive acyl-CoAs by mouse sciatic nerve microsomes is observed in the absence of added acyl acceptors. The maximal acylation (ca 10% of administered) for 10 micrograms microsomal proteins is observed at relatively low amounts of oleoyl-CoA (0.2-0.3 nmol) and decreases as the acyl-CoA amount increases. Labeled lysophosphatidylcholine (almost exclusively esterified at position 2) is also observed, particularly when the [1-14C]oleoyl-CoA concentration is higher than 0.2-0.3 nmol/50 microliters. The labeled acyl group is mainly inserted in position 2] of the glycerophosphorylcholine. With 0.15 nmol labeled oleoyl-CoA, phosphatidylcholine acylation increases as a function of the protein amount and reaches 25% of the added label at 40 microgram proteins. It is evaluated that, in the presence of 10 microgram proteins, 2% of the microsomal phosphatidylcholine molecules are acylated from 0.1 nmol acyl-CoA. The acylation mechanism seems to involve an acyl exchange between acyl-CoA and phosphatidylcholine.

Acyl Coenzyme A↗

PubMed1995

Cerebroside formation in the peripheral nervous system of normal and Trembler mice.

The formation of cerebrosides by the galactosylation of ceramides was investigated in a microsomal fraction prepared from sciatic nerves of normal and Trembler mice. In the control, cerebroside synthesis is observed in the presence of uridine-diphosphate-galactose both from endogenously synthesized [1-14C]stearoyl-sphingosine (C18-ceramide), and from [1-14C]lignoceroyl-sphingosine (C24-ceramide). Cerebroside formation is also demonstrated by studying the galactosylation of exogenous ceramides with UDP[1-14C]-galactose. In the mutant, only trace amounts of labeled cerebrosides are formed from labeled stearoyl-sphingosine, whereas with lignoceroyl-sphingosine, no cerebroside synthesis is detected under conditions allowing their formation in the control. However, a higher rate of synthesis of short acyl chain-glucosyl ceramides is observed in the Trembler samples.

Animals↗

PubMed1992

Lack of in vitro ceramide formation in the PNS of trembler mice.

The amidification of sphingosine by acyl donors has been investigated in a microsomal fraction prepared from sciatic nerves of normal and Trembler mice. In the control, a ceramide synthesis is observed in the presence of acyl-CoAs and not with free fatty acids. The synthesis increases as a function of the protein amount and the time and is dependent on acyl-CoA concentration. The level of synthesis is highly similar to that observed in vivo after palmitate injection into the sciatic nerves of normal mice. In the mutant, there is a major abnormality because a weak synthesis (20% of the control) is observed only with high acyl-CoA concentration (greater than 200 microM), whereas in the range of the physiological acyl-CoA concentrations (less than 20 microM), there is no ceramide formation from stearoyl-CoA or lignoceroyl-CoA.

Acyl Coenzyme A↗

PubMed1989

Phospholipid and fatty acid composition of erythrocytes in type I and type II diabetes.

Different data have been reported concerning modifications of the erythrocyte lipid composition in the different types of diabetes. The heterogeneity of diabetes could be a cause for such differences. Ten type I and ten type II diabetics were carefully selected. The patients were poorly controlled (the mean glycosylated hemoglobin was 12.8% +/- 0.7%); their mean age was 54 +/- 5 years, with a mean duration of diabetes of 18 +/- 4 years. One half of them had severe diabetic complications (nephropathy, retinopathy, and/or polyneuropathy). The diabetics were compared with ten controls. The phospholipid composition was determined by HPTLC analysis, and the fatty acid moieties of the total phospholipids were measured by gas liquid chromatography associated with mass spectrometry. Under well-defined experimental conditions, these results demonstrated a slight, but significant (P less than .05), increase in the phosphatidylethanolamine (PE)/phosphatidylserine (PS) ratio using a Ninhydrin quantitation method; there was also an increase in two minor lipids content (phosphatidylinositol, phosphatidic acid) and the appearance of a lysolipid (lysoPE) in the patients. Whatever the type of diabetes, the red blood cells of diabetics showed no significant differences in their fatty acid contents.

Adolescent↗

PubMed1988

Decrease of lipid extractability of chloroform-methanol upon water addition to human erythrocytes.

The yield of lipids extractable by chloroform-methanol 2:1 from human erythrocytes decreases as a function of the relative amount of water added to--or present in--the erythrocyte pellet prior to the lipid extraction. Only slight modifications are observed as long as the volume of water does not exceed that of the red blood cell pellet. As the volume of added water increases, the phosphatidylserine recovery drops dramatically and tends to zero while the yield of the other phospholipids remains unchanged. This phenomenon is not observed when the lipids are extracted by a mixture of isopropanol-chloroform.

1-Propanol↗

PubMed1988

Po, MBP, histone, and DNA levels in sciatic nerve. Postnatal accumulation studies in normal and trembler mice.

We studied the quantitative changes in proteins (total, Po, MBP, and histones) and DNA from sciatic nerves of normal and Trembler mice during postnatal development. Polyacrylamide gel electrophoresis and immunoblotting procedures allowed an accurate characterization of Po, MBP, and histones, as well as the comparison of their respective amounts from d 2 to d 120 after birth. It was found that 1. The immunoblotting procedure ascertains the presence of Po in the sciatic nerve of Trembler. In the 2-d-old mice, Po is detected in essentially similar amounts in Trembler and normal PNS, whereas its level in adult mutant sciatic nerves is never greater than 20% of the control. The sharp increase in Po levels observed during the third week in the normal nerves is not observed in those of the mutant; 2. MBP species are at most 4% of the control in the 10- to 12-d-old Trembler mice, whereas they were not detectable in adult nerves. The distribution of the different MBP species is the same in both mutant and control mice; 3. In normal mice, Po and MBP accumulate at similar rates, but the 14 kDa MBP accumulates faster than the 18.5 kDa MBP; and 4. Histone and DNA contents decrease 3- to 5-fold in normal nerves, whereas they remain constant, or increase slightly, in the mutant.

Animals↗

PubMed1987

A developmental study of fatty acyl group contents in the peripheral nervous system of normal and trembler mice.

We quantitated the content of the fatty acyl groups of sciatic nerves from normal and Trembler mice between the postnatal ages of 5 and 60 d. Palmitoyl, stearoyl, and unsaturated 18-carbon groups increased normally in Trembler nerves during the first 9 d, after which their levels were notably lower than those observed for the normal littermates. In good agreement, the synthesis of palmitic acid by the fatty acid synthetase was normal in the PNS of 9-d-old Trembler mice. "Myelin-specific" saturated very long chain fatty acyl groups (VLCFAG) were deficient at all ages studied, the deficiency increasing from about 2.5-fold at 5 d, to 26-fold at 60 d, compared to the maximal 3- to 4-fold decrease observed for the more ubiquitous shorter chains. The results presented in this paper suggest that the highly abnormal VLCFAG content of the mutant nerves cannot be accounted for by an abnormal fatty acid synthetase activity. For the fatty acyl chains with 18 carbon atoms, however, the deficiency observed after 9 d of age can be almost entirely explained by the diminished levels of palmitic acid. The relatively late occurrence of the palmitic acid deficiency compared with that of the VLCFAG and the normal palmitate synthetase activity observed in young mutant mice indicates that the former is an indirect consequence of the Trembler mutation.

Aging↗

PubMed1986

Correlation between the morphology and the lipid and protein compositions in the peripheral nervous system of individual 8-day-old normal and trembler mice.

The hereditary, hypertrophic interstitial neuropathy which afflicts the trembler mouse manifests itself about two weeks after birth. Consequently, the identification of these mutant mice was not possible before this age, except when double mutants were available. We show that the trembler mice can be easily distinguished from their normal littermates before the clinical symptoms appear by using an HPTLC/densitometry technique that allows the simple and rapid analysis of the polar lipids extracted from one sciatic nerve. The results presented in this paper demonstrate important differences between the polar lipid compositions of sciatic nerves from 8-day-old normal and trembler littermates, whose phenotypes were confirmed by the morphological analysis of the contralateral sciatic nerves. The small amount of material that is needed for this identification makes it possible to use the remaining nerve material for other studies. Furthermore, important differences between the sciatic nerve protein compositions of normal and trembler mice, identified according to their polar lipid composition, were also observed and these differences can, therefore, also be employed for the identification of the mutants before the manifestation of the clinical symptoms of the trembler neuropathy.

Animals↗

PubMed1986

A quantitative developmental study of the peripheral nerve lipid composition during myelinogenesis in normal and trembler mice.

The quantitative evolution of 10 polar lipids was examined in the sciatic nerves of normal and trembler mice between the ages of 3 days and 60 days. In normal nerves, the polar lipids accumulated slowly until the age of 9 days. A period of rapid accumulation then took place until 18 days of age, after which the phospholipids plateaued, while the glycolipid content continued to increase at a slower rate. The results obtained for the sciatic nerves of trembler mice show that the accumulation of all the polar lipids studied, except phosphatidylcholine and hydroxysulfatides, is abnormal from the earliest stages of postnatal development, and strongly support the view that the primary disorder in the trembler peripheral nervous system is one of dysmyelination. With the exception of cardiolipin, all the lipids in the trembler nerves stopped accumulating at the age of 18 days. The cerebrosides were the lipids the most affected severely at all ages.

Aging↗

PubMed1986

A quantitative developmental study of neutral lipids during myelinogenesis in the peripheral nervous system of normal and trembler mice.

The quantitative accumulation of neutral lipids during the period of myelination in the peripheral nervous system was studied in normal and trembler mouse sciatic nerves, between the ages of 5 and 27 days. Neutral lipids were resolved by high-performance thin-layer chromatography, using the solvent mixture hexane/diethyl ether/acetic acid (90:15:2, v/v/v). The lipids were quantitated, after copper acetate/phosphoric acid charring, by densitometric scanning, using an external standard technique. Cholesterol and triacylglycerols accumulated in normal nerves throughout the period studied, while cholesteryl esters were not observed at any age. In trembler nerves, the accumulation of cholesterol took place at a much lower rate than in normal nerves and this lipid was deficient from the earliest stages of development. Triacylglycerols were not significantly deficient in trembler nerves during the first 2-3 weeks, but, after the age of 18 days, their quantity diminished significantly. Cholesteryl esters were first detected in the mutant nerves at the age of 18 days. These results, in agreement with those of a previous developmental study of the polar lipids, are strongly in favour of the view that the trembler mutation directly induces a process of dysmyelination and that demyelination is a secondary event.

Aging↗