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Biomedical subjects

J L Rabinowitz

Publications and source records attributed to J L Rabinowitz.

At least 73 records · Page 4Linked to original sources
PubMed1977

Iodinated phospholipids and the in vitro iodination of proteins of dog thyroid gland.

Slices of dog thyroid gland were incubated with liposomes consisting of (125)I-labelled phosphatidylcholine (the iodine was covalently linked to unsaturated fatty acyl chains). The (125)I label of (125)I-labelled liposomes was incorporated into thyroid protein and/or thyroglobulin at a higher rate than was the (131)I label of either Na(131)I or (131)I(2). The iodine was shown to be protein-bound by the co-migration of the labelled iodine with protein under conditions where free iodine, iodide and lipid-bound iodine were removed from protein. The uptake of iodine from the iodinated phospholipid was probably due to phospholipid exchange between the iodinated liposomes and the thyroid cell membrane, since (a) (14)C-labelled phospholipid was metabolized to (14)CO(2) and (b) many lipids in the tissue slice became (14)C-labelled. A very strong inhibition of iodide ;uptake' from Na(131)I, caused by thiosulphate, produced only a minor inhibition of the incorporation of (125)I from (125)I-labelled liposomes into thyroid protein and/or thyroglobulin. This implies that free iodide may not necessarily be formed from the iodinated phospholipids before their entrance or utilization in the cell. Synthetic polytyrosine polypeptide suspensions showed some iodination by (131)I-labelled liposomes. In tissues with low tyrosine contents, such as liver and kidney, only a trace uptake was observed. Salivary gland showed some uptake. Endoplasmic reticulum of thyroid gland showed a higher iodine uptake than that of the corresponding plasma membranes. These experiments, together with the demonstration of the diet-dependent presence of iodinated phospholipids in dog thyroid, leads us to suggest that iodination of the membrane phospholipids of thyroid cells may be directly or indirectly involved at some stage in the synthesis of thyroglobulin, or exists as a scavenger mechanism, to re-utilize and/or recover released iodine from unstable compounds inside the thyroid cell.

Animals↗
PubMed1977

A method for serum octanoate in hepatic cirrhosis and hepatic encephalopathy.

We describe a new, more efficient, and more reproducible method for determination of octanoate in serum. This method involves ethanol extraction, followed immediately by alkali addition before concentration of the extract. The concentrate is made acidic only before it is to be steam distilled (in a special all-glass apparatus with an alkali trap). The material is acidified again just before separation by gas-liquid chromatography. The yield is 89-107%. When assayed by mass spectrometry, only octanoate was found in the fraction from chromatography. Previous methods yielded only 30-55% of the expected octanoate value and the recovered materials showed impurities by mass spectrometry. Octanoate concentrations were determined in the serum of 24 fasting controls and that of 85 fasting cirrhotic patients, of whom 50 had encephalopathy. Concentrations in arterial and venous blood were significantly higher in cirrhotic patients in coma than in those not in coma, and arterial concentrations were statistically higher than venous concentrations in the cirrhotic patients.

Caprylates↗
PubMed1976

Total plasmalogens and O-(acylalkylglycerophosphoryl) ethanolamine from labelled hexadecanol and palmitate during hypoxia and anoxia in rat heart.

By the use of the Langendorff technique, surviving isolated rat hearts were perfused with [1-14 C] palmitate, [1-14C] hexadecanol or [1-14C,1-3H] hexadecanol under normal or anoxic conditions. After perfusion for 30min with either precursor, when oxygenated or in an hypoxic condition, or when 1mM-KCN was included in the system, the heart tissues showed no significant chemical changes in their content of total lipids, total phospholipids or total ethanolamine-containing phospholipids. Changes were observed in the ratio of alkyl-to alk-1-enyl-glycerophosphorylethanolamine in the tissue perfused with N2+CO1 plus CN-. A slight increase from 4.0+/-0.3 to 4.9+/-0.2% in alkyl derivatives and a decrease from 11.2+/-0.4 to 9.4+/-0.3% in alk-1-enyl derivatives was observed. The incorporation of the [14C] palmitate and the [14C] hexadecanol into the recovered phospholipids and plasmalogens was severely decreased in the tissues perfused with CN-: in the hypoxic state only a mild inhibition was observed compared with the oxygenated systems. Considerable 3H from [1-14C, 1-3H] hexadecanol was retained (25-35%) in the alk-1-enylether chains of plasmalogens under both the oxygenated conditions and with CN-, suggesting that the same mechanism of incorporation is operational at high or low O2 concentrations. The results are consistent with an O2-dependent, CN-sensitive step in the biosynthesis of plasmalogens in the rat heart.

Alcohols↗
PubMed1976

Elongation of (omega-14C)oleic acid and (omega-14C)nervonic acid.

During feeding experiments with [omega-14C]oleic acid and [omega-14c]nervonic acid to adult rats, 14C-labelled C26, C28 and C30 fatty acids were recovered from the intestinal mucosa, liver, plasma, kidney and stools. The structures of these fatty acids were determined by g.l.c., radio-g.l.c. and mass spectrometry. The Schmidt and Ginger degradation methods indicated that most of the 14C found in these extra-long fatty acids remained in the omega position. These radioactive extra-long fatty acids were found mainly in the polar lipids of rats killed 3 or 15 h after being fed on labelled oleic acid or nervonic acid. Rats killed 63 h later yielded only traces of these extra-long fatty acids. When the rats were given antibiotics or received the same radioactive fatty acids by intravenous injection, the labelled extra-long fatty acids could not be detected in any of the tissues. We conclude that they were probably synthesized by elongation of oleic acid and nervonic acid by intestinal micro-organisms (probably yeasts) and then absorbed by the intestinal mucosa.

Animals↗
PubMed1976

Weight reduction and serum insulin levels in hypothalamic obese monkeys.

Two hyperinsulinemic rhesus monkeys, made obsese (body weight 22 kg) by the placement of hypothalamic lesions, were place on a weight reduction diet for a period of approximately eight months. After losing approximately losing approximately 25% body weight, the animals exhibited a fall in serum insulin levels without changes in plasma glucose levels or composition of fat pad tissue. There was evidence that the number of adipocytes remained constant but were reduced in size after the body weight loss.

Adipose Tissue↗
PubMed1976

Evidence for lipid synthesis by the dihydroxyacetone phosphate pathway in rabbit lung subcellular fractions.

Lipid synthesis by the lung requires a 3-carbon skeleton that can be provided by sn-glycerol-3-phosphate derived from glycolysis. This study investigated whether acylation of dihydroxyacetone-phosphate can serve as an alternate pathway for lung lipid synthesis. Rabbit lung microsomal and mitochondrial fractions were incubated with radiolabelled sn-glycerol-3-P and/or dihydroxyacetone-P. Palmitoyl CoA was used as acyl donor. The lipid fraction was subsequently isolated and radioactive incorporation was determined. Glycerol-3-P and dihydroxyacetone-P were both incorporated into the lipid fraction when each substrate was present alone. During incubation in the presence of equimolar concentrations of both substrates dihydroxyacetone-P accounted for 41 per cent of the total incorporation. These results show that acylation of dihydroxyacetone phosphate is a potential alternate to the glycerol-3-phosphate pathway for lung lipid synthesis.

Animals↗
PubMed1975

Aortic mitochondrial synthesis of lipid and its response to cholesterol feeding.

The rates and products of lipid synthesis from acetate-I-14C were studied in mitochondria isolated from control and atherosclerotic rabbit aorta. More acetate was incorporated into fatty acids in the cholesterol-fed animals. The mechanism was one of chain elongation, and the resultant products were longer in chain length. The newly elongated fatty acids were esterified mostly into phospholipids, presumably those turning over most rapidly. A hypothesis is proposed for the pathogenetic sequence: Cholesterol feeding alters transport functions of the mitochondrial membranes of aortic smooth muscle cells. Respiration and redox state are altered and consequently acetate is incorporated more rapidly into fatty acids as an alternate mechanism for oxidation of the reduced form of nicotin-amide-adenine dinucleotide (NADH). Rapidly turning over phospholipids esterify these fatty acids and may transfer them ultimately to cholesterol. Esterified cholesterol is less exchangeable and commences to accumulate.

Acetates↗
PubMed1975

Lipids and other components of human jejunal and ileal mucosa.

Jejunal and ileal intestinal segments were obtained from patients undergoing laparotomy, from peroral jejunal biopsies, and from fresh cadavers. The excised mucosa was weighed and assayed for total lipids, neutral and polar lipids. The lipid families were separated and identified, and their individual fatty acid composition determined. In addition, DNA, RNA, collagen and total protein were measured.

Collagen↗