Levels of sulfogalactosylglycerolipid in capacitated motile and immotile mouse spermatozoa

The purpose of this study was to determine whether sulfogalactosylglycerolipid (SGG) was desulfated during mouse sperm capacitation. Levels of [35S]SGG were determined in freshly retrieved caudal epididymal sperm, motile capacitated sperm, and immotile sperm, after feeding mature male mice with [35S]sulfate-laced chow for 32 days. Caudal epididymal sperm and coisolated epididymal cells were separated into pellet and interphase fractions by centrifugation through a two-step Percoll gradient (45 and 90%). Upon resuspension in Krebs-Ringer bicarbonate medium supplemented with 0.4% bovine serum albumin, the Percoll-gradient pellet fraction consisted mainly of motile capacitated sperm, whereas the interphase fraction comprised largely immotile sperm and fragmented epididymal epithelial cells. The level of [35S]SGG in the Percoll-gradient-pelleted sperm appeared to be much higher than that in the Percoll-gradient interphase sperm. Percoll-gradient-pelleted sperm were further incubated in the culture medium for 2 h. The level of [35S]SGG showed little or no change after 1 h, but was reduced appreciably after 2 h. At this time point, sperm motility was also decreased. Reduction of sperm SGG is correlated with sperm immotility and (or) senescence and may have no direct relation to the capacitation process.     

Synthesis and characterization of deoxy analogues of diphytanylglycerol phospholipids

Novel analogues of diphytanyl phospholipids, 2,3-diphytanyl sn-1-glycerol-1-phosphoryl-1'-(1',3'-propanediol) (dPG), 2,3-diphytanyl-sn-glycerol-1-phosphoryl-1'-propanol (ddPG) and 2,3-diphytanyl-sn-glycerol-1-phosphoryl-1'-(1',3'-propanediol-3'-p hosphate) (dPGP), were synthesized according to modifications of previously published procedures. The samples were TLC and analytically pure and were characterized by 13C- and 1H-NMR and negative FAB/MS. The pK values of dPGP in aqueous dispersions or in methanol/water (1:1, v/v) were determined by potentiometric titration and compared with those of 2,3-diphytanyl-sn-glycerol-1-phosphoryl-3'-sn-glycerol-1'-phosphat e (PGP). The dissociation constant of the third ionizable POH group of dPGP was more than 2 pK units higher than that of PGP, indicating that the free glycerol hydroxyl group plays an important role in headgroup conformation and stabilization, perhaps through hydrogen bonding with the phosphate group(s).     

Occurrence of squalene, di- and tetrahydrosqualenes, and vitamin MK8 in an extremely halophilic bacterium, Halobacterium cutirubrun

The nonpolar (acetone-soluble) lipids of the extremely halophilic bacterium, Halobacterium cutirubrum, were found to consist of red carotenoid pigments (43%) and squalenes (48%) with a small amount of a vitamin K-type quinone. The squalenes were shown by n.m.r. and mass spectra to consist of the fully isoprenoid squalene (S; C(30)H(50)), dihydrosqualene (S(2); C(30)H(52)), and tetrahydrosqualene (S(4); C(30)H(54)) in the ratio of 1.0:0.4:0.1. S(2) probably has one reduced internal isoprenoid group, and S(4) has one internal and one terminal reduced isoprenyl group. The vitamin K-type quinone was shown by n.m.r. and mass spectra to have a C(40) isoprenoid side chain, and is thus identified as menaquinone-8 (MK-8).     

Synthesis of monoacid 2,3-diacyl-sn-glycerols via 1,6-ditrityl-d-mannitol

Stereochemically pure 2,3-dipalmitoyl-sn-glycerol and 2,3-dioleoyl-sn-glycerol were prepared in an overall yield of 20% by a new and facile method starting from D-mannitol. The synthetic intermediates were 1,6-ditrityl-D-mannitol (1), 1-trityl-sn-glycerol (2), and 1-trityl-2,3-diacyl-sn-glycerol (3). The key reaction was the oxidation of 1 with lead tetraacetate followed by reduction with sodium borohydride. The product (2) was readily separated from the only byproduct, tritylethyleneglycol.     

Identification of diacylglycerol-O-(N,N,N-trimethyl)-homoserine in the halotolerant alga, Dunaliella parva

An unusual zwitterionic polar lipid component isolated from the halotolerant alga, Dunaliella parva Lerche, has been identified as 1(3),2-diacylglyceryl-3(1)-O-4′-(N,N,N-trimethyl) homoserine by means of infrared spectrometry, ¹H- and ¹³C-NMR spectrometry and field desorption mass spectrometry of the intact lipid, as well as by its TLC mobilities and staining behaviour. Mass spectrometry of this lipid indicated the presence of the following major molecular species: 16:0–18:0 (24%); 18:3–18:3 (19%); 16:0–18:2 (16%); 16:0–18:1 (8%).     

Effects of cold acclimation and fasting on thyroxine 5'-deiodinase in brown adipose tissue of ob/ob mice.

Gradual acclimation to mild cold for 6 weeks increases the total activity of thyroxine 5'-deiodinase in brown adipose tissue (BAT) of genetically obese (ob/ob) mice to a level greater than that in similarly acclimated lean mice. This increase is largely due to the growth of the BAT in the ob/ob mouse, because specific activity of the enzyme is only slightly increased. In similarly cold-acclimated lean mice, the specific activity of thyroxine 5'-deiodinase was not altered. BAT mitochondrial GDP binding increased to the same high level in the gradually cold-acclimated ob/ob mouse as in cold-acclimated lean mice. We conclude that the growth and maintenance of BAT in the cold-acclimated ob/ob mouse, as in the cold-acclimated lean mouse, does not require greatly increased activity of thyroxine 5'-deiodinase. Fasting for 48 hr did not alter thyroxine 5'-deiodinase activity of BAT in either lean or ob/ob mice. The fasting-induced increase in activity seen by others in lean mice is probably due to thermoregulatory stimulation of BAT occasioned by the low environmental temperature at which the fasting occurred.     

The lipid composition of a halotolerant species of Staphylococcus epidermidis.

Studies were carried out on the lipid composition of a halotolerant Staphylococcus epidermidis isolated in pure culture from a growth medium for extreme halophiles containing 25% NaCl. The four major polar lipid components in this bacterium were found to be: (a) glycerophosphoryl diglucosyl diglyceride (10% by weight) with structure 3(1)-O-(-sn-glycerol-1-phosphoryl-6'-O=(beta-D glucopyranosyl-(1 leads to 6)- O-beta-D-glucopyranosyl)-1(3),2-diacyl-sn-glycerol; (b) diglucosyl diglyceride (15% by weight) with structure 3(1)-O-(beta-D-glucopyranosyl (1 leads to 6)-O-beta-D-glucopyranosyl)-1(3),2-diacyl-sn-glycerol; (c) monoglucosyl diglyceride (3% by weight) with structure 3(1)-O-(beta-D-glucopyranosyl)-1(3),2-diacyl-sn-glycerol, and (d) phosphatidylglycerol (60% by weight) with structure 1,2 diacyl-sn-glycero-3-phosphoryl-1'-sn-glycerol. Phosphatidic acid, cardiolipin, lysophosphatidylglycerol and three unidentified phospholipids were also detected in small amounts. Each lipid component had essentially the same fatty acid composition namely, anteiso-15:0 (60-75%), anteiso-17:0 (18-24%), iso-17:0 (8--10%), and small amounts of palmitic and stearic acids (2-5%). The fatty acids were non-randomly distributed in phosphatidylglycerol, the shorter chain anteiso 15:0 fatty acid being exclusively esterified to the 2-position and the longer chain anteiso- and iso-17:0 fatty acids at the 1-position. The fatty acid composition was not affected by increaseing NaCl content in the medium in the rande 0--15% but the proportion of anteiso-15:0 increased greatly when the salt concentration was increased to 25%. The proportions of ionic polar lipids were modified to give an increased net negative charge per mol ionic lipids when NaCl in the medium was increased from 15 to 25%, but the proportions of neutral glycolipids remained fairly constant.