The occurrence of long chain α,ω-diols in the lipids of steer and human meibomian glands

A group of long chain α,ω-diols (C₂₉ to C₃₄) has been identified in the lipids of steer and human meibomian gland excreta (meibum). These new lipids were isolated from the steer meibum unsaponifiables. Proof of structure was provided by 1) the column chromatographic behavior and TLC of the diols and their diacetates; 2) GLC on glass capillary columns; 3) fragmentation patterns in GC-MS; 4) NMR data, and 5) ozonolysis studies of the unsaturates. Chain types for the steer sample were 51% straight monoenes, 8.5% straight saturates, 39% iso and anteiso saturates and 1.5% iso and anteiso unsaturates. GC for the human sample gave straight monoenes 83%, straight saturates 8%, and iso plus anteiso saturates 9%. Close correspondence of the α,ω-diol chain lengths and types with meibum ω-hydroxy fatty acids suggests a biochemical precursor relationship.     

Double-bond patterns of fatty acids and alcohols in steer and human meibomian gland lipids

Ozonolysis studies of the monoenes of the fatty chain types in lipids of steer meibomian gland excreta (meibum) have confirmed earlier structural assignments based on gas liquid chromatography (GLC) retention data and have assisted in assigning complete structures to a group of recently identified ω-hydroxy fatty acids. The ω-hydroxy acids include straight-chain monoenoic acids (85%), saturated anteiso and iso acids (13%), monoenoic acids of the latter group (1%) and, finally, saturates of the normal monoenoic acids (1%). All the fatty chains of meibum can be biosynthesized by a unified process of chain buildup to primary chain lengths of 12∶0–20∶0 for the straight evens, with 16∶0 predominating, 13∶0–21∶0 for the straight odds with 17∶0 predominating, i16∶0 to i28∶0 for the iso and ai17∶0 to ai29∶0 for the anteiso chain types; then Δ9 desaturation of each of these chain types; and finally chain elongation of 1–10 C₂ units. Some chain degradation may also occur. The meibum lipid components involved are unsubstituted fatty acids, α-OH fatty acids, ω-OH fatty acids, fatty alcohols and some other lipid components incompletely characterized. The carbon skeletons are straight even, straight odd, iso and anteiso except that the α-OH fatty acids are only straight even and straight odd and these chains are not elongated. All fatty chains are almost entirely saturated and monoenoic, the polyenes occurring in only trace amounts. Biosynthesis of the fatty chains of human meibum evidently occurs similarly, except that considerably more 18∶0 than 16∶0 fatty acids are built up by the fatty acid synthetase, before desaturation and extension.     

Biosynthesis of lipids by bovine meibomian glands

Isolated bovine meibomian glands incorporated exogenous [1-¹⁴C] acetate into lipids. Thin layer chromatographic analysis of the lipids showed that wax esters and sterol esters contained 61% of the total label. Radio gas liquid chromatographic analysis of the acid and alcohol moieties of both ester fractions showed the label was distributed equally between the two portions of the ester in both cases. Cholesterol and 5-α-cholest-7-en-3β-ol were the major labeled sterols, and anteiso-C25, anteiso-C27 and anteiso-C23 were the most highly labeled alcohols. The major labeled fatty acids in the wax esters were anteiso-C15,n-C16, anteiso-C17 andn-C18∶1, whereas anteiso-C25 and anteiso-C27 were the major labeled acids in the sterol esters. The diester region with 6% of the total label contained labeled fatty acids and fatty alcohols each with anteiso-C25 as the major component and ω-hydroxy acids in whichn-C32∶1 was the major labeled component. The trigly ceride fraction which contained 8% of the total lipids was composed of labeled fatty acids similar to those found in both sterol and wax ester fractions. Chromatographic analyses of the labeled lipids derived from exogenous labeled isoleucine showed that anteiso-branched products were preferentially labeled. The labeled triglyceride fraction derived from [U-¹⁴C] isoleucine also contained esterified C15, C13, C11, C9, C7 and possibly shorter anteisobranched acids.     

The lipids of the aging human brain

Lipid compositions of the brains of human beings of different ages from 26 to 80 years have been determined by a combination of chromatographic techniques. No significant differences in composition were found among any of the adult agegroups, and it thus appears that the decline in brain weight and function with age is not associated with loss of any particular type of lipid. These studies were supported by Contract AT(04-1) GEN-12 between the Atomic Energy Commission and the University of California. Supported in part by a USPHS Research Career Award (GM-K6-19,177) from the Division of General Medical Sciences.     

The simultaneous separation and quantitation of human milk lipids

A protocol using a dry column method was modified for the extraction of total lipids and the simultaneous separation and quantitation of neutral and polar lipids in human milk. The triacylglycerol, cholesterol, phospholipid and vitamin E contents of the lipid extracts were determined and compared with lipids extracted using a modified Folch procedure. Good precision for the extraction of neutral, polar and total lipids, as well as the different lipid classes, was demonstrated. No significant differences were found between the two methods with respect to the amount of cholesterol, phospholipid, total lipid or vitamin E extracted, thus validating the method as an extraction technique. We discuss the relationship between vitamin E and the three major milk lipids as an indicator of the vitamin's place of origin in the mammary gland. Our findings do not support the idea that vitamin E in mature milk has its original location in the apical membrane. Scientific Contribution No. 1254, Storrs Agricultural Experiment Station, University of Connecticut, Storrs, CT 06269.     

The electroreduction mechanism of Di- and tricyanobenzenes

The electroreduction behaviour of 1,2-, 1,4-, 1,3-dicyano- and 1,3,5-tricyanobenzenes in acetonitrile was investigated. The mechanism for the electroreduction of these compounds was proposed using the results of cyclic voltammetry, rotating disc voltammetry, dc and differential pulse polarography and controlled potential electrolysis experiments. The effect of the presence of protons on the mechanism was also elucitated. The products of large scale electrolysis experiments were identified by the aid of electroanalytical and chromatographic methods.     

The lipids of mitochondria of human gray and white matter

Mitochondrial enriched fractions were obtained separately from gray and white matter of human and bovine brains. The preparations differed in that choline and ethanolamine glycerophosphatides were present in higher concentration in mitochondria than in gray or white matter from which they were derived. The fatty acid composition also was at variance, palmitic, palmitoleic and linoleic acids being present in considerably higher concentration in the mitochondria of white matter than in the corresponding homogenate, and fatty acids of C₂₅ and C₂₆ chain length being absent. A deficiency of polyunsaturated fatty acids and the lowest linoleic acid were found in a preparation obtained from a multiple sclerosis brain, a lesser deficiency was noted in the preparation from an emaciated individual.     

Polyprenols of beef and human pituitary glands

An unknown lipid previously isolated in our laboratory from beef and human pituitaries was shown to have the same structure as dolichol from pig liver. Beef pituitaries contained ca. 130 mg/kg wet tissue, of which ca. 25% was esterified to fatty acids. Human pituitaries contained ca. 1.4 g/kg, mainly as the free alcohol.     

Integral lipids of human hair

It has long been recognized that hair is coated with nonpolar lipids originating in the sebaceous glands, and recently it has been shown that hair also contains cholesterol sulfate and small amounts of ceramides, similar to those found in the keratinized portion of the epidermis. In the present study, it is demonstrated that significant amounts of several additional lipids are tightly associated with hair in such a way as to be highly resistant to solvent extraction. These integral hair lipids included cholesterol sulfate (3.3 mg/g of extracted hair), cholesterol (0.6 mg/g), fatty alcohols (0.2 mg/g) and free fatty acids (4.3 mg/g). The principal fatty acid, comprising 40% of the total fatty acids, was identified as 18-methyl-eicosanoic acid by cochromatography with authentic standard on gas-liquid chromatography (GLC) and by mass spectrometry (MS).     

Lipid composition of beef and human pituitary glands

The lipid composition of beef and human pituitary was determined by chromatographic and spectrophotometric methods. Beef pituitary lipid contained about 25% nonpolar lipids and 75% phospholipids whereas nonpolar lipids made up approximately 60% of the total in human pituitaries. The main nonpolar (i.e., low polarity) lipids in human pituitary were triglycerides, cholesterol, free fatty acids and an unidentified component in the triglyceride fraction. Cholesterol was the major nonpolar lipid component in freshly collected beef anterior and posterior pituitary, but the amount of free fatty acids appeared to increase during storage. Preliminary investigation of the unknown nonpolar lipid in human pituitaries suggested that it was an unsaturated hydroxy compound with no carbonyl functions. Thin layer chromatography indicated that it was also present in smaller amounts in freshly collected beef pituitaries. The main phospholipids of beef anterior, posterior and human pituitary were phosphatidyl ethanolamine, phosphatidyl choline, phosphatidyl inositol, phosphatidyl serine and sphingomyelin. The fatty acid composition of total nonpolar lipids, free fatty acids, total phospholipids, phosphatidyl ethanolamine and phosphatidyl choline of beef anterior and posterior pituitary was determined by gas liquid chromatography. Mixtures of saturated and unsaturated fatty acids ranging from C₁₂ to C₂₂ were present; the main fatty acids were palmitic, stearic, oleic, linoleic and arachidonic.     

Composition of novel triesters from the skin of the rhino mutant mouse

Composition of two novel triesters, derived from the skin of the rhino mutant mouse, is described. Chemical and spectroscopic analysis of the products of pancreatic hydrolysis of the triesters showed that these are comprised predominantly of isomer I (92.7 mole %). The syntheses of two reference compounds, 1-O-hexadecanoyl-2-[(14-hexadecanoyloxy)O-tetradecanoyl] 1,2-hexadecanediol (Ia) and 2-O-hexadecanoyl-1-[(14-hexadecanoyloxy)O-tetradecanoyl]-1,2-hexadecanediol (IIa), corresponding in their structures to isomers I and II of the triester, wax have also been described. Presented at the AOCS 49th Annual Fall Meeting, Cincinnati, Sept. 1975.     

Genetic variability of human plasma and erythrocyte lipids

Genetic variation of fasting plasma lipids, lipoproteins and erythrocyte membrane lipids was studied in 67 sets of like-sexed twins and 3 sets of triplets. All of the plasma lipids were more variable in dizygotic twins than monozygotic twins with the exception of phosphatidyl ethanolamine, but only cholesteryl esters, lecithin, phosphatidyl inositol and β-lipoprotein showed significant genetic variation. In contrast, no significant genetic variability was found in any of the erythrocyte membrane lipids and erythrocyte phosphatidyl ethanolamine had significantly greater variation in monozygotic twins. Two sets of twins had an extra lipoprotein band (slow α1); in one family the variant appeared to be segregating as a dominant trait. Presented in part at the ISF-AOCS World Congress, Chicago, September 1970.     

Extraction of lipids from cottonseed tissue: VI. Ultrastructural morphology of isolated pigment glands

Cottonseed pigment glands, isolated from the underflow fraction of the liquid cyclone process, were examined with an electron microscope. The glands were circumscribed by a layer of tangentially flattened cells. Subjacent to the flattened cells were partially lysed cells containing recognizable remnants of cell walls. Within the lumens or matrices of the glands were myriads of pigment spherules measuring 0.1–1.5 µ in diameter. These spherules remained within the glands, even though gland walls were ruptured mechanically. Since aggregates of pigment spherules devoid of gland walls were observed in the gland-rich fraction, it was concluded that maintenance of intact pigment glands was not a requisite for successful separation of gossypol from other cottonseed components with the liquid cyclone process. Avoiding dispersion of aggregated spherules from the glandular matrix was probably just as important as maintaining intact gland walls during mechanical separation of gossypol from other cottonseed components.     

Composition of the lipids in human milk: A review

Recent publications on the composition of human milk are reviewed. The importance of proper sampling is discussed. Fat contents of 2.6–4.5% and cholesterol amounts of 200–650 mg/100 g fat were reported. The phytosterols in milk were increased by the consumption of these sterols. Phytosterols could contribute to the “total cholesterol” in milk if analyses are done colorimetrically. The fatty acid composition is remarkably uniform unless bizarre diets are consumed; the amounts of linoleic acid vary the most. Phospholipids contained more long chain polyunsaturated fatty acids than triacylglycerols. Scientific Contribution No. 786, Storrs Agricultural Experiment Station, University of Connecticut, Storrs, CT 06268.     

The lipids of human pancreas with special reference to the presence of fatty acid methyl esters

Total lipids were extracted from human pancreas with chloroform-methanol, chloroform-methanol following acidification, and benzene. A similar proportional amount of total lipid was obtained by each procedure. Regardless of the method of extraction (i.e., whether or not methanol was present), a small proportion (about 1%) of the total lipid was found to consist of fatty acid methyl esters. Triglycerides constituted the major fraction (about 80%) of the pancreatic lipids; in addition to methyl esters, the remaining lipids comprised free fatty acids, phospholipids, cholesterol esters, and traces of free cholesterol. In general, each class of lipid had a similar over-all fatty acid composition with palmitic and oleic acids as predominant components. The methyl esters had a relatively high content of linolenic acid, and the free fatty acids contained a notably high proportion of palmitic acid, in each case accompanied by a corresponding decrease in the proportion of oleic acid present.     

The lipids in pathology of the eye

The lipoidal composition of the human eye is frequently altered in the diseased state. Un-fortunately, most of the literature is unreliable and only recently has adequate methodology been employed to determine the status of the lipids in ocular pathology. The modern studies have been very useful in helping to understand the mech-anism behind some pathological problems and in a few eases, the lipoidal composition of a tissue has been elucidated and is presented herein for the first time.     

The seed lipids of the palm family

The majority of palms, represented byElaeis guineensis, contained mainly neutral lipids (triglycerides) in their seed fats with lauric and myristic acids as the major acids. In certain others, symbolized by theRaphia palms, polar lipids dominated, with the unsaturated acids, oleic and linoleic acids constituting the major fatty acids. Contrary to established belief, lauric and myristic acids were not the principal fatty acids in all palms.