Biochimica et Biophysica Acta (BBA) - Specialized Section on Lipids and Related Subjects最新文献

• 1.

  1. Following the incubation of nonlipemic human serum (serum glyceride concentration, 49 mg%) at 38° for 36 h, the major lipoprotein species (S_f 20-10⁵, S_f 0–20, high-density lipoproteins) have been isolated ultracentrifugally and their lipid compositions determined. In all three lipoprotein species, the molar concentrations of cholesterol and phospholipids decrease, while those of the cholesteryl esters increase. The data indicate that during the course of the incubation some of the cholesteryl esters are released from the S_f 0–20 lipoproteins and, subsequently, are associated with the S_f 20-10⁵ lipoproteins and the high-density lipoproteins.

• 2.

  2. Although the total glyceride content in the serum remains constant, it decrease in the S_f 20-10⁵ lipoproteins and increases in the high-density lipoproteins and the S_f 0–20 lipoproteins. The observed reduction in the S_f 20-10⁵ lipoprotein is attributed to the transfer of glyceride to the other lipoproteins during incubation.

• 3.

  3. The fatty acid distributions to the glyceride and cholesteryl ester fractions have been determined by gas-chromatographic techniques. Significant changes are observed only in the glyceride fatty acids of the S_f 20-10⁵ lopoproteins.

Study at the subcellular level of the renewal of the hepatic phospholipid fatty acids by the endogenous fatty acids shows particularly the activity of the free fat phsophoglycerides. The fact that the incorporation intensities, the fastest for palmitic acid (half-life about 3 h), are similar, is in accordance with rapid intracellular exchanges.

The renewal of only the fatty acids in the phosphoglycerid molecule satisfies a function of intracellular transfer of fatty acids. The slower renewal of the intact molecule, joined to the renewal of the proteins, suggests a mechanism of disintegration and rebuilding of the membranes (endoplasmic reticulum and mitochondria) which leads to equilibrium of the cellular lipoproteins and permits entrance to the metabolites.

• 1.

  1. Four chromatographically homogenous gangliosides (FM, 1-G, 3-G, 4-G) and the ceramide-tetrose (asialoganglioside) were isolated and subjected to periodate oxidation.

• 2.

  2. Periodate reduction was quantitatively determined with the mon-, di-, and trisialoganglioside (1-G, 3-G, 4-G) preparations.

• 3.

  3. The periodate-resistant carbohydrate residues were determined in all five preparations.

• 4.

  4. The results are consistent with the structure monosialoganglioside proposed by Kuhn and Wiegandt.

• 5.

  5. The disialo- and trisialongangliosides (3-G and 4-G) isolated contained a sialic acid residue resistant to periodate oxiation. Ganglioside 4-G is apparently a previously unreported trisialogangliosides, since one of the galactose residues was subject to periodate oxidation.

• 6.

  6. Structures for the ganglioside preparations are proposed.

Palmitic acid, stearic acid, oleic acid and linoleic acid assimilated by epididymal fat pads of mice are primarily esterified at the α-positions of triglycerides. A similar glyceride distribution is observed for fatty acids synthesized from acetate or glucose. Increasing the supply of α-glycerylphosphate by glucose addition did not appreciably affect the fatty acid distribution of the saturated fatty acids. In the presence of glucose the distribution of linoleic acid was uniform and oleic was variable. With palmitate, oleate and stearate, tissues from fasted animals demonstrated an increased disproportionality in α-esterification. This trend was only partially reversed by the addition of glucose to the medium. These results indicate at least two modes of incorporation of fatty acids into the triglycerides by adipose tissue. One provides for complete synthesis de novo and the other carries a high degree of specificity toward incorporation at the α-positions.

• 1.

  1. In order to effectivey explore the physiologic role of lipids in skeletal muscle, a method of analysis is needed to permit the separation and subsequent detailed examinatin of the lipid components. Such a method is described for the quantitative determination of the major and minor classes of lipids present in monkey skeletal muscle. Since the various lipid classes are quantitatively isolated, radioactivity in the lipid components is also easily determined.

• 2.

  2. About one-third of the lipid is neutral lipid and two-thirds phospholipid. The neutral lipid is primarily triglyceride and cholesterol. More than 50% of the phospholipid is lecithin and about 25% is phosphatidylethanolamine. Appreciable quantities of phosphatidylinositol and “polyglycerophosphatide” are also present. The plasmalogen/lipid-phosphorus molar ratio is considerably greater than that reported for muscles of other species.

• 3.

  3. The method was applied to an analysis of monkey gastrocnemius and soleus muscles. The lipid composition of a bilateral pair of muscles is found to be sufficiently similar to permit physiological investigation in which one of the bilateral pair serves as a control as the other undergoes contraction. While the functionally different soleus and gastrocnemius muscles are found to have similar lipid compositions, certain definite differences in the nature of their lipids are uncovered.

• 1.

  1. The fatty acid composition of triglycerides and phospholipids isolated from the lungs, adipose tissue, intestine and liver was determined in newborn rats, in rats aged 1, 10 and 30 days, and in adult animals.

• 2.

  2. Only the myristic and lauric acid contents of the triglycerides were found to change with changes in their content in the diet (milk against the solid diet for adult animals). Marked changes occurred in the fatty acid composition of the triglycerides during development in the different organs but these could not always be related to changes in the composition of the diet.

• 3.

  3. The composition of fatty acids in the phospholipids differed with age and between organs. The lungs had the most specialized phospholipids, containing the aldehydes of stearic and palmitic acids and differing from the other organs also in their content of the other acids. Changes in the fatty acid composition of the diet were not reflected in the fatty acid composition of the phospholipids, although pronounced developmental changes were observed.

• 1.

  1. Erythrocyte ghosts incubated with [γ-³²P]ATP incorporate radioactivity into diphosphoinositide, triphosphoinositide, phosphatidic acid, and into at least one unidentified lipid.

• 2.

  2. Over 90% of the radioactivity incorporated into the polyphosphoinositides is in the monoesterified phosphates.

• 3.

  3. Exogenous phosphatidyl inositol increases the labeling in diphosphoinositide by about 30% and in the unidentified compound by about 200%. The labeling in triphosphoinositide is inhibited.

• 4.

  4. Kinetic studies of the labeling of the polyphosphoinsitides fail to provide evidence that the exchange of phosphate in the monoesterified positions is an intermediate reaction in the magnesium-dependent, sodium and potassium-activated ATPase.