Lipids in Cryptomonas CR-1. II. Biosynthesis of Betaine Lipids and Galactolipids

The biosynthesis of lipids in Cryptomonas strain CR-1 was studiedusing radioactive tracers. For studies of general aspects ofthe biosynthesis of lipids, the cells were labelled with [¹⁴C]NaHCO₃or with [l,3-¹⁴]glycerol. In both cases, monogalactosyl diacylglycerol(MGDG) was the most heavily labelled lipid. Phosphatidylcholineand the alanine lipid DGTA were not labelled to specific activitiescomparable to those of MGDG and DGDG. It is improbable thatthe so-called "eukaryotic pathway", which has been suggestedas the pathway for the synthesis of " eukaryotic" molecularspecies of MGDG from PC in higher plants, is operative in Cryptomonascells which contain typical "eukaryotic" MGDG. The homoserinelipid DGTS was labelled to a significant level only in its polargroup. The C-3 and C-4 atoms of methionine, as well as the methylcarbon of methionine, were incorporated into both DGTS and DGTA,whereas the C-l carbon of methionine was incorporated uniquelyinto DGTS. Results of pulse-chase experiments with [3,4-¹⁴C]methionineand [methyl.-^l4C]methionine suggest the conversion of DGTS toDGTA. (Received April 22, 1991; Accepted June 12, 1991)     

Water-soluble lipoproteins from yolk granules in sea urchin eggs. II. Chemical composition.

The chemical composition of yolk lipoproteins (YLP-1, 2, and 3) was determined. YLP-1, 2, and 3 were quite similar as regards the chemical composition of lipids, proteins, and carbohydrate moieties. Each lipoprotein has an average dry weight composition of lipids (55--72%) and apo-lipoproteins (28--45%) containing protein, hexose, hexosamine, and sialic acid. In each lipoprotein, triacylglycerol is a major lipid component (70--83%), followed by phospholipid (8--16%), cholesterol (free and esterified, 8--10%), and free fatty acid (3--4%). Phosphatidylcholine and phosphatidylserine account for 68--74% and 16--24% of the phospholipids, respectively. The fatty acid compositions of total lipids from each lipoprotein are quite similar, with a high degree of unsaturation (63--65%). The carbohydrate content of apolipoprotiens from each lipoprotein is remarkably high (27--31% of apo-lipoproteins) and their composition is very simple: mannose and glucosamine are major constituents in the polysaccharide moiety of each lipoprotein and sialic acid is all in the N-glycolyl form. The amino acid compositions of apo-lipoproteins are quite similar in YLP-1, 2, and 3, with high contents of aspartic acid, glutamic acid, threonine, serine, and leucine. Furthermore, a small amount of glycolipids is present in the yolk lipoproteins. They were separated into six components on TLC. All of them are resorcinol-positive, indicating the presence of sialoglycolipids.     

Chemical composition distribution of bacterial copolyesters.

Poly(3-hydroxybutyrate) [P(3HB)] and its copolymers with hydroxyalkanoates are naturally occurring thermoplastic materials produced by bacteria. There are many potential uses for these copolyesters owing to their biodegradability and biocompatibility. The physical properties of the copolyesters vary depending on the chemical structure as well as the composition of the comonomers. Usually, we expect, copolymers to have a narrow chemical composition distribution (CCD). Several reports, however, have pointed out that some bacterial copolyesters have broad and/or multimodal CCD. Fractionation based on the chemical composition has also been reported for several bacterial copolyester samples. In this review, the literature concerning CCD and fractionation based on chemical composition is summarized. The width of CCD is approximated based on the data of diad sequence distribution. Generality of the complex CCD in bacterial copolyesters is also discussed.     

Lipids of nervous tissue: composition and metabolism

As indicated in the Introduction, the many significant developments in the recent past in our knowledge of the lipids of the nervous system have been collated in this article. That there is a sustained interest in this field is evident from the rather long bibliography which is itself selective. Obviously, it is not possible to summarize a review in which the chemistry, distribution and metabolism of a great variety of lipids have been discussed. However, from the progress of research, some general conclusions may be drawn. The period of discovery of new lipids in the nervous system appears to be over. All the major lipid components have been discovered and a great deal is now known about their structure and metabolism. Analytical data on the lipid composition of the CNS are available for a number of species and such data on the major areas of the brain are also at hand but information on the various subregions is meagre. Such investigations may yet provide clues to the role of lipids in brain function. Compared to CNS, information on PNS is less adequate. Further research on PNS would be worthwhile as it is amenable for experimental manipulation and complex mechanisms such as myelination can be investigated in this tissue. There are reports correlating lipid constituents with the increased complexity in the organization of the nervous system during evolution. This line of investigation may prove useful. The basic aim of research on the lipids of the nervous tissue is to unravel their functional significance. Most of the hydrophobic moieties of the nervous tissue lipids are comprised of very long chain, highly unsaturated and in some cases hydroxylated residues, and recent studies have shown that each lipid class contains characteristic molecular species. Their contribution to the properties of neural membranes such as excitability remains to be elucidated. Similarly, a large proportion of the phospholipid molecules in the myelin membrane are ethanolamine plasmalogens and their importance in this membrane is not known. It is firmly established that phosphatidylinositol and possibly polyphosphoinositides are involved with events at the synapse during impulse propagation, but their precise role in molecular terms is not clear. Gangliosides, with their structural complexity and amphipathic nature, have been implicated in a number of biological events which include cellular recognition and acting as adjuncts at receptor sites. More recently, growth promoting and neuritogenic functions have been ascribed to gangliosides. These interesting properties of gangliosides wIll undoubtedly attract greater attention in the future.(ABSTRACT TRUNCATED AT 400 WORDS)     

Immunocytochemistry of Lipids: Chemical Fixatives have Dramatic Effects on the Preservation of Tissue Lipids

We report here the effects of chemical fixatives on lipids studied under conditions simulating the immunogold labelling of phosphatidylserine. Using anti-phosphatidylserine antibodies, it is shown that the labelling intensity of a phosphatidyl-serine/phosphatidylcholine coating depends largely on the conditions of fixation. In fact, the usual aldehydic fixatives washed out most of the phostphatidylserine, thus preventing the binding of anti-phosphatidylserine antibodies. This was confirmed on biological samples such as rat liver and brain by measuring the loss of radiolabelled lipids during the fixation procedure. Furthermore, the complete procedure of tissue preparation for electron microscopical observation was investigated. The loss of (radiolabelled) lipids was studied in tissue samples during fixation and resin embedding. The results showed that the classical procedure (glutaraldehyde fixation followed by epoxy resin embedding) results in the loss of 73–91% of the tissue lipids whereas in unfixed, freeze-substituted samples, more than 76% of the tissue lipids are preserved.     

Lipids in the Harder's gland of certain rodents. II: Phospholipids

The phospholipid components of Harder's glands of rats and mice were investigated. The content of phosphatidylcholine and of sphyngomyelin is notably less in the rat than in the mouse difference among the other components, being negligible. In the male rat the total phospholipid content is larger than in the female, while in mice the opposite is true. The presence of a large red fluorescent spot, which is not phospholipid, has been shown.     

Deoxyribonucleoproteins of herring sperm nuclei. I. Chemical composition

The chemical composition of deoxyribonucleoproteins from herring sperm nuclei was analyzed and the results are summarized as follows: 1. Chemical analysis of nuclear proteins and nucleic acids revealed that arginine/P molar ratio in herring sperm nuclei is unity but the ratio of arginine residues in protamine to phosphorus in the total DNA is 0.86. 2. The deoxyribonucleoproteins were isolated and their composition showed that about 14% of the total DNA in herring sperm nuclei is free from protamine and is bound with nonprotamine proteins in the weight ratio of nonprotamine proteins to DNA of 0.25-0.30. The remaining 86% of the total DNA is combined mainly with protamine and a small amount of nonprotamine proteins; the weight ratios of protamine and nonprotamine proteins to DNA are 0.75 and 0.08, respectively. In the latter complex, the molar ratio of arginine residues in protamine to phosphorus in DNA is unity.