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PubMed1989

Lipogenesis by isolated human apocrine sweat glands: testosterone has no effect during long-term organ maintenance.

Lipid synthesis by freshly isolated human apocrine glands has been measured by the incorporation of [U-14C] acetate. Incorporation is linear over 6 h at 1010 +/- 282 pmol/mg wet weight/h (n = 11; mean +/- sem). The lipid classes, as percentages of the total lipid synthesized, were found by TLC to be cholesterol 12.3 +/- 2.0, mono-glycerides 7.5 +/- 1.5, 1,2 di-glycerides 3.0 +/- 0.9, 1,3 di-glycerides 3.5 +/- 0.5, tri-glycerides 28.4 +/- 1.8, free fatty acids 2.0 +/- 0.4, lysolecithin 15.4 +/- 3.9, sphingomyelin 9.9 +/- 4.3, phosphatidyl-choline 8.4 +/- 0.4, phosphatidyl-ethanolamine -inositol and -serine 1.8 +/- 0.1, phosphatidic acid and cardiolipin 3.3 +/- 0.5, and unidentified 3.3 +/- 0.5 (mean +/- sem, n = 5). Glands were maintained on permeable supports. After 10 d maintenance, electron microscopy showed that the cellular architecture had been preserved, that the ATP contents were the same as in freshly isolated glands, and that [U-14C] acetate incorporation was not significantly altered at 851 +/- 237 pmol/mg/h (n = 18). The addition of 3 microM testosterone had no effect on acetate incorporation at 844 +/- 231 pmol/mg/h (n = 18). The lipid classes and their proportions were similar to the values for fresh glands after 10 d maintenance both with and without testosterone.

Acetates↗
PubMed1979

Uptake and metabolism of long chain fatty acids in isolated chicken intestinal epithelial cells.

The uptake and metabolism of long chain fatty acids in isolated mucosal cells from chicken small intestine are studied. The viability of the isolated enterocytes is proven by linear oxygen consumption, CO2 and lactate formation form glucose and the active transport of glucose. The transport of palmitic and oleic acid is mediated by passive diffusion. This is demonstrated by the following results: (1) no saturation kinetics in the concentration range of 0.1--10.0 mM; (2) no competitive inhibition of the uptake by structurally related compounds; (3) no influence of 2,4-DNP and cyanide of the uptake; (4) the uptake is independent of sodium ions. Uptake rates of palmitic and oleic acid from suspensions are significantly higher than from the corresponding fatty acid-bovine serum albumin complexes. In both cases the uptake of palmitic acid proceeds faster than the uptake of oleic acid. Palmitic acid is oxidized to CO2 and incorporated into glycerides by enterocytes. Glucose serves as a glyceride-glycerol precursor. Its addition decreases the oxidation of the fatty acids and enhances glyceride synthesis markedly. Free glycerol is phosphorylated by enterocytes and can also serve as a glyceride-glycerol precursor.

Animals↗
PubMed1985

Roles of glucose and its interactions with acetate in maintenance and biosynthesis in bovine mammary tissue.

Mammary gland tissues from three lactating Holstein cows were sampled and slices incubated with various concentrations of glucose and in combinations with other substrates in Krebs-Ringer bicarbonate-based media. Conversions of 1-and 2-carbon-14 glucose to carbon dioxide, lactose, glyceride-glycerol, citrate, and fatty acids were determined. Glucose utilization increased asymptotically with glucose availability. Carbon dioxide, lactose, and glyceride glycerol production accounted for nearly 90% of glucose recovered. Only trace quantities of glucose were recovered as fatty acids. Estimates of apparent affinities for glucose use were in a physiological concentration range of glucose. Oxidation of glucose was positively correlated with availability of acetate. Acetate availability increased the ratio of 1-carbon-14 glucose to 2-carbon-14 glucose oxidation and decreased glucose conversion to fatty acids. Glucose conversion to glyceride-glycerol was not affected by acetate availability. Primary uses of glucose are in lactose and glyceride glycerol synthesis and formation of reduced nicotinamide adenine dinucleotide phosphate for lipogenesis. Extensive use of glucose for these purposes may limit amounts available for fatty acid synthesis.

Acetates↗
PubMed1977

[A Study On The Lipids Of Ascaris Suum Ova]

The present study was undertaken to observe the quality and quantity of lipid constituents by the developing Ascaris suum eggs. The collected eggs from the uterus of A. suum were classified into 3 groups, i.e., single cell stage, morula stage and embryonated eggs, and were subjected to analyse their lipid fractions. To obtain the morula stage eggs, 10 to 11 incubation days at 30 degree C were needed and for the embryonated eggs, 30 to 31 days were lasted. At the time of experiment, their indices of development by Hoffman were 285(morula stage) and 42 (embryonated stage) respectively. Lipid extraction was done by the methods of Folch et a1. (1957) and Kenny (1952), and then the extracted lipid fractions from the above 3 groups of eggs were separated by thin layer chromatography. Those fractions were also subjected to perform the quantitative analyses of fatty acids, glycerides, cholesterol and phospholipids. The results obtained were summarized as follows. 1. Total amount of fatty acid was decreased from 12.9 mg per gram of eggs (single cell stage) to 6.6 mg/gm (embryonated eggs), whereas the proportion of free fatty acid to total fatty acid was constantly increased from 77.5% to 89.4% during the period of egg development. 2. Total amount of glycerides was also increased from 33.0 mg/gm of single cell stage to 55.9 mg/gm of the embryonated eggs. The most abundant glyceride among 3 glycerides discovered from A. suum eggs was triglyceride, and the least was monoglyceride. 3. The amount of free cholesterol was much larger than that of ester form in general, and it reached maximum in the eggs of morula stage (4.6 mg/gm). The increase of total cholesterol was monitored during the development of A. suum eggs from 3.3 mg/gm to 5.4 mg/gm. 4. The following 8 phospholipids were detected in the embryonated eggs, i.e., lysophosphatidyl choline, phosphatidyl inositol, sphingomyelin, phosphatidyl choline, phosphatidyl glycerol, phosphatidyl serine, phosphatidyl ethanolamine and unknown phospholipid. But in the single cell stage eggs, 4 kinds out of the above 8 phopholipids were not observed, and in the morula stage eggs, 2 kinds were absent among the 8 phospholipids.

Journal Article↗
PubMed1989

Effects of prolactin and androgens on seminal vesicular lipids of castrated mature bonnet monkeys Macaca radiata.

Effects of prolactin (PRL), bromocriptine (Br), testosterone propionate (TP), dihydrotestosterone (DHT) and the combination of these androgens with PRL/Br on the total lipid, total cholesterol, total glyceride glycerols, total phospholipid and their fractions in seminal vesicles of castrated mature monkeys were studied. Glyceride glycerols formed the major portion (50%) of total lipids in normal monkeys. Cholesterol and phospholipids were of equal share (25%). Esterified cholesterol formed major share (75%) of total cholesterol. Diacyl glycerol was the major (60%) glyceride glycerol and phosphatidyl choline and ethanolamine were the major phospholipid classes. Except triacyl glycerol castration markedly decreased all the lipid classes. PRL restored normal free and esterified cholesterol and phosphatidyl inositol but Br invariably decreased all the lipid classes. TP/DHT treatment stimulated the free and esterified cholesterol more than the control; it restored the normal glyceride glycerols. Phosphatidyl inositol, choline and ethanolamine were stimulated by androgens and other phospholipid classes were brought to normal. Addition of PRL + TP/DHT markedly increased esterified cholesterol, phosphatidyl inositol, choline, ethanolamine and phosphatidic acid. In all these aspects, Br counteracted the effects of androgens and PRL.

Animals↗
PubMed1984

Radioisotopic method for the measurement of lipolysis in small samples of human adipose tissue.

To facilitate the study of adrenoreceptor response in small needle biopsy samples of human subcutaneous adipose tissue, we developed a dual radioisotopic technique for measuring lipolysis rate. Aliquots (20-75 mg) of adipose tissue fragments were incubated in a buffered albumin medium containing [3H]palmitate and [14C]glucose, each of high specific activity. In neutral glycerides synthesized in this system, [14C]glucose is incorporated exclusively into the glyceride-glycerol moiety and 3H appears solely in the esterified fatty acid. Alpha-2 and beta-1 adrenoreceptor activation of tissue incubated in this system does not alter rates of 14C-labeled glyceride accumulation, but does produce a respective increase or decrease in the specific activity of fatty acids esterified into newly synthesized glycerides. This alteration in esterified fatty acid specific activity is reflected in the ratio of 14C:3H in newly synthesized triglycerides extracted from the incubated adipose tissue. There is a high correlation (r = 0.90) between the 14C:3H ratio in triglycerides and the rate of lipolysis as reflected in glycerol release into the incubation medium. The degree of adrenoreceptor activation by various concentrations of lipolytic and anti-lipolytic substances can be assessed by comparing this ratio in stimulated tissue to that characterizing unstimulated tissue or the incubation medium. This technique permits the study of very small, unweighed tissue biopsy fragments, the only limitation on sensitivity being the specific activity of the medium glucose and palmitate. It is, therefore, useful for serial examinations of adipose tissue adrenoreceptor dose-response characteristics under a variety of clinical circumstances.

Adipose Tissue↗
PubMed1984

Effects of four-day fast on triglyceride mobilization in human adipocytes.

To examine the effect of a four-day fast on neutral glyceride mobilization in human adipocytes, subcutaneous abdominal fat tissue was obtained from ten human volunteers after an overnight fast and then after four days of fasting. Plasma insulin concentration decreased from 31 +/- 5 microU/ml before the four-day fast to 9 +/- 1 microU/ml after the fast (P less than 0.05). Plasma free fatty acid concentration increased from 13.9 +/- 1.3 to 23.6 +/- 3.2 mg/dl (P less than 0.05). Mean average cell size was similar before and after the four-day fast. Basal lipolysis increased threefold (P less than 0.005) regardless of cell size after four days of fasting. In contrast, isoproterenol (2 microM) stimulated maximum lipolysis was not increased after a four-day fast. The concentrations of isoproterenol required for a half maximum stimulation in the presence of 50 (7 microU/ml) and 8000 pM (1150 microU/ml) insulin were lower after a four-day fast (P less than 0.05, P less than 0.03, respectively) and were uninfluenced by average cell size. Basal and maximum insulin-stimulated glucose transport were similar after a four-day fast. However, glucose incorporation into neutral glycerides was reduced by 50 percent (P less than 0.02) following a four-day fast. The reduction was uninfluenced by average cell size. The data indicate that abdominal adipocytes after a four-day fast are metabolically adapted towards increased neutral glyceride mobilization by reducing glucose incorporation into neutral glycerides, increasing sensitivity of lipolysis to isoproterenol, and increasing basal lipolysis.

Adipose Tissue↗
PubMed1977

[Lipids of plasmamembranes and of mitochondria in rat liver after intoxication with paraoxon (author's transl)].

0.426 mg/kg Paraoxon was applicated to female Sprague-Dawley rats. 4, 10 and 24 h after poisoning, cholesterol, glyceride and phospholipid content was measured in liver plasma membranes and mitochondria. After 4 h, cholesterol content of plasma membranes was significantly lower. Phospholipid content of plasma membranes was significantly higher than control values at all times of investigation, contents of neutral lipids and glycerides were also higher, but not significantly. In mitochondria, no significant difference of cholesterol content could be detected. Glyceride content was lower after 4 and 10 h, but phospholipid content higher at all experimental times. Differences found in cholesterol and phospholipid content of plasma membranes are discussed also in view of higher serum GOT, GPT and CPK activities known from other investigations. The differences in cholesterol and phospholipid content, their degree and their timing, which agrees with the timing of enzyme leakage, suggest that lipid composition of the plasma membrane may be one of the parameters which determine membrane permeability after organophosphate poisoning.

Animals↗
PubMed1993

[Determination of mono-, di- and triglycerides using HPLC].

The determination of monoglycerides, diglycerides and triglycerides in the normal phase system: Separon SGX-CN (silica gel with phase-bonded cyanoethyl) and mobile phase hexane-isopropanol-formic acid by HPLC with refractometric detection, is described. It was found that the separation was according to the molecular mass of glycerides, i.e. in groups. This was demonstrated with palmitic, oleic and linoleic acids. The diglycerides and especially monoglycerides of olive and sunflower oils were partly separated according to the ECN1 values of the glycerides. The response factors related to triglycerides were estimated for the glycerides of the fatty acids and oils mentioned above. The value of response factors depends on the number of double bonds of the fatty acids.

Chromatography, High Pressure Liquid↗
PubMed1986

Glycerolipid biosynthesis in rat adipose tissue. Influence of age and cell size on substrate utilization.

The conversion of [14C]-labeled compounds such as acetate, glucose, pyruvate and palmitate into CO2, glyceride-glycerol, glyceride fatty acids and total lipids was monitored in the average and matching adipocyte (with respect to size) preparations from young (6-9 wk) and old (age 56-60 wk) male Sprague-Dawley rats. The average cell size populations from young and old rats were 46 +/- 3 and 83 +/- 11 microns in diameter, respectively. The incorporation of [14C]acetate, pyruvate and glucose into fatty acids was significantly reduced in the adipocytes from older rats, irrespective of their sizes. The production of CO2 and glyceride-glycerol did not change significantly as a function of either cell size or animal age. Palmitate incorporation into lipids was similar in the average cell population derived from old and young rats, but it was considerably lower in the smaller adipocytes (46-50 microns diameter) from old animals. Irrespective of the cell size, triacylglycerol formation from sn-glycerol-3-phosphate was also significantly diminished in the adipocytes from older animals compared to younger ones as evidenced by decreases in activities of several enzymes, including sn-glycerol-3-phosphate acyltransferase, Mg2+-dependent phosphatidate phosphohydrolase and diacylglycerol acyltransferase. However, triacylglycerol formation from monoacylglycerol did not change as a function of either cell size or age. These measurements of the metabolic and enzymic activities provide evidence that the synthesis of fatty acids from various precursors and triacylglycerol formation from sn-glycerol-3-phosphate are significantly reduced in adipocytes from older animals and that such changes occur independently of adipocyte size.

Adipose Tissue↗
PubMed1978

Glyceroneogenesis in rat and guinea pig adipose tissue during the fed and fasted states.

While both pyruvate and lactate are good substrates for glyceride-glycerol synthesis in isolated adipocytes from fed rats and guinea pigs, neither alanine nor serine appear to support glyceroneogenesis. Fasting increases the proportion of radioactive pyruvate or lactate incorporated into glyceride-glycerol and reciprocally decreases the proportion incorporated into fatty acids. However, the total incorporation of radioactivity into triacylglycerol is considerably lower in isolated adipocytes from fasted than from fed animals. Addition of glucose to the incubation medium promotes the incorporation of radioactive lactate into both fatty acids and glyceride-glycerol by adipocytes from fasted as well as fed animals. The concentration of alpha-glycerolphosphate is considerably higher in adipose tissue of fed than fasted animals. In general, these results support the presence of a glyceroneogenic pathway in rat and guinea pig adipose tissue. However, it would appear that the physiologic significance of this pathway is less important in the fasted than the fed state, where it may play some role in the esterification of intracellular fatty acids.

Adipose Tissue↗
PubMed1967

Esterification of glycerol 3-phosphate in lactating guinea-pig mammary gland.

1. The presence of palmitoyl-CoA-l-glycerol 3-phosphate palmitoyltransferase (EC 2.3.1.15) has been demonstrated in a particulate fraction of mammary tissue from lactating guinea pigs. 2. Cell-free preparations also catalysed the activation of palmitate and oleate, and the conversion of enzymically formed phosphatidic acid into glycerides, in accord with the Kennedy pathway of glyceride formation. 3. The properties of the system that esterifies l-glycerol 3-phosphate were studied with respect to substrates and cofactors, and the reaction product was shown to be phosphatidic acid (1,2-diacyl glycerol 3-phosphate). 4. The extent to which newly formed phosphatidic acid was converted into glyceride in a cell-free system was dependent on the nature of the acyl donor, the concentration of subcellular particles, the time of incubation and the concentration of Mg(2+).

Acyltransferases↗
PubMed1968

Lipid composition of the isolated rat intestinal microvillus membrane.

1. Rat intestinal microvillus plasma membranes were prepared from previously isolated brush borders and the lipid composition was analysed. 2. The molar ratio of cholesterol to phospholipid was greatest in the membranes and closely resembled that reported for myelin. 3. Unesterified cholesterol was the major neutral lipid. However, 30% of the neutral lipid fraction was accounted for by glycerides and fatty acid. 4. Five phospholipid components were identified and measured, including phosphatidylethanolamine, phosphatidylcholine, phosphatidylserine, sphingomyelin and lysophosphatidylcholine. Though phosphatidylethanolamine was the chief phospholipid, no plasmalogen was detected. 5. In contrast with other plasma membranes in the rat, the polar lipids of the microvillus membrane were rich in glycolipid. The cholesterol:polar lipid (phospholipid+glycolipid) ratio was about 1:3 for the microvillus membrane. Published data suggest that this ratio resembles that of the liver plasma membrane more closely than myelin or the erythrocyte membrane. 6. The fatty acid composition of membrane lipids was altered markedly by a single feeding of safflower oil. Membrane polar lipids did not contain significantly more saturated fatty acids than cellular polar lipids. Differences in the proportion of some fatty acids in membrane and cellular glycerides were noted. These differences may reflect the presence of specific membrane glycerides.

Animals↗
PubMed1972

The activities of lipases and carnitine palmitoyltransferase in muscles from vertebrates and invertebrates.

1. The activities of tri-, di- and mono-glyceride lipase and carnitine palmitoyltransferase were measured in homogenates of a variety of muscles. These activities were used to estimate the rate of utilization of glycerides and fatty acids by muscle. In muscles whose estimated rates of fat utilization can be compared with rates calculated for the intact muscle from such information as O(2) uptake, there is reasonable agreement between the estimated and calculated rates. 2. In all muscles investigated the maximum rates of hydrolysis of glycerides increase in the order triglyceride, diglyceride, monoglyceride. The activity of diglyceride lipase is highest in the flight muscles of insects such as the locust, waterbug and some moths and is lowest in the flight muscles of flies, bees and the wasp. These results are consistent with the utilization of diglyceride as a fuel for some insect flight muscles. 3. In many muscles from both vertebrates and invertebrates the activity of glycerol kinase is similar to that of lipase. It is concluded that in these muscles the metabolic role of glycerol kinase is the removal of glycerol produced during lipolysis. However, in some insect flight muscles the activity of glycerol kinase is much greater than that of lipase, which suggests a different role for glycerol kinase in these muscles.

Animals↗
PubMedDate not supplied

Physical state of membrane lipids of Mycoplasma capricolum.

The physical state of the lipids in Mycoplasma capricolum membranes was studied by differential scanning calorimetry. Cells grown in the presence of horse serum incorporated large amounts of cholesterol esters into their membranes. After incubation at a low temperature, the cholesterol ester-containing membranes showed an endotherm characteristic of a cholesterol ester transition from a crystalline state to an isotropic liquid that was identical in membranes both before and after thermal protein denaturation. This transition was not observed in membranes of cells grown in medium in which the horse serum was replaced by bovine albumin, fatty acids, and unesterified cholesterol unless cholesterol esters were added to the growth medium. In membrane preparations obtained from both horse serum-grown cells and from cells grown with bovine albumin plus cholesterol and fatty acids, the free cholesterol content was sufficient to eliminate the bilayer order/disorder transition observed in isolated membrane phospholipids. Our calorimetric studies indicate that the majority of cholesterol esters in M. capricolum membranes is not present in attached serum lipoprotein particles nor is it intimately associated with membrane protein but exists as relatively large droplets of cholesterol ester or as pockets in the membrane. The cholesterol esters in these pockets exist in a liquid-like state at growth temperature and appear to be relatively pure, although the presence of small amounts of other membrane components, especially glycerides, is likely. The existence of a low-temperature endotherm in membrane attributable to glycerides suggests there may be glyceride-rich regions in the membranes.

Animals↗
PubMed1994

Microvascular anastomoses utilizing new intravascular stents.

Evolving microsurgical technique has allowed for the anastomosis of smaller diameter vessels. Standard suture anastomoses cause a measure of stenosis and intimal damage during application and therefore cannot be dependably used in the anastomosis of very small vessels. We developed and tested a fibrin glue-based anastomosis applied over a meltable stent made of mono- di- and tri-glycerides. In vivo rodent studies using the 0.35 mm diameter inferior epigastric artery have shown immediate and short-term patency rates better than those associated with suture technique. The stent technique is significantly faster and easier than the suture technique. The glyceride stent method suffers from decreased late patency due to aneurysm formation. In addition, we developed a glyceride-coated polyethylene glycol-based stent for use in lasered anastomoses. Work on both projects is ongoing.

Anastomosis, Surgical↗
PubMed1969

Characterization and biological activity of the monocytosis-producing agent of Listeria monocytogenes.

Experiments directed toward determining the lipids in extracts of Listeria monocytogenes containing monocytosis-producing agent (MPA) and the effect of these extracts on several biochemical parameters previously shown to change during experimental Listeria infection were conducted. MPA-containing extracts were found to be a complex of lipids with glycerides, glycolipids, and phospholipid being present. No common cell wall carbohydrates were found. A glyceride, designated glyceride A, was determined to cause the characteristic mononuclear response observed in mice injected with MPA-containing extracts. Fasted MPA-treated animals showed less gluconeogenesis than did controls. Blood glucose levels declined in MPA-treated animals. Increases observed in both blood urea nitrogen and plasma glutamic-pyruvic transaminase were greater in the control groups. Incorporation of (14)C-alanine into liver glycogen was depressed in MPA-treated animals. Liver steroid levels in the control groups increased during fasting and remained elevated for the duration of the experiments, while levels in the MPA-treated groups declined initially and showed no increase until 72 hr after injection. MPA appears to affect steroid metabolism and consequently the animals' homeostatic mechanisms seem to be impaired. Possibly as a consequence, carbohydrate metabolism is altered. The apparent effect of MPA on steroid metabolism and on the gluconeogenic process may indicate participation in the carbohydrate derangement observed in experimental Listeria infection.

Alanine↗
PubMed1967

The monoglyceride pathway of fat absorption in man.

The absorption of fat was studied in five male subjects with cannulation of the thoracic duct in the neck by the administration of doubly labeled monoglycerides, or triglyceride as well as labeled free glycerol or labeled free oleic acid, by gastric or duodenal intubation.Total recoveries of the administered glyceride radioactivity from the lymph lipids ranged from 35 to 53% for the glycerol label (tritium) and from 35 to 57% for the fatty acid label ((14)C). The recovery of administered radioactive free glycerol in lymph lipids was only 4.1%, even when given in mixture with bile salts, fatty acid, and monoglyceride.A comparison of the isotope ratios of the two components (glycerol and fatty acid) of the lymph glycerides with the ratios of these components of the original meal glyceride showed little change during the initial period of fat absorption, indicating that the doubly labeled monoglycerides passed into the lymph intact. During the later part of the period of major fat absorption, the ratios in lymph lipids changed due to loss of glycerol representation, indicating monoglyceride hydrolysis and portal venous diversion of free glycerol. Confirmation of the intact nature of 2-monoglyceride during absorption was made by analyzing the amount and position of the labeled fatty acid in the lymph triglycerides. The percentage of labeled fatty acid in the various positions of the lymph triglycerides was virtually identical with that of the meal during the initial period of fat absorption and then changed reflecting isomerization of fatty acids and subsequent complete hydrolysis of the glycerides.The 2-monoglyceride pathway appears to be the major route of fat absorption for man during normal digestion and absorption of dietary triglyceride.

Adult↗