Occurrence of phosphatidylsulfocholine, the sulfonium analog of phosphatidylcholine in some diatoms and algae.

A survey of seven species of diatoms, one Euglena sp. and one dinoflagellate sp. for the presence of phosphatidylsulfocholine (PSC), the sulfonium analog of phosphatidylcholine (PC), was carried out using 1H-NMR spectroscopy and ammonia desorption chemical ionization mass spectrometry. PSC alone was found only in a non-photosynthetic diatom, Nitzschia alba. PSC, together with PC, was found in four of the diatoms (Nitzschia angularis, Cylindrotheca fusiformis, Phaeodactylum tricornutum and Navicula pelliculosa) in proportions of 6-24% of the total PC + PSC fraction, but little or no PSC (less than 2%) was detected in the remaining two (Cyclotella nana and Navicula incerta). Little or no PSC (less than 2%) was detected in a Euglena sp. by 1H-NMR but its presence was confirmed by 35S-labeling. The amount of PSC, if any, in the dinoflagellate (Amphidinium carterae) was below the level of detection by 1H-NMR.

Distribution of GABA in the periaqueductal gray matter. Effects of medial hypothalamic lesions.

Gas chromatography and chemical ionization mass spectrometry were used in order to measure the GABA (gamma-aminobutyric acid) concentration in a series of successive horizontal slices of the mesencephalic periaqueductal gray (CG) as well as in a series of successive frontal CG slices in the rat. Along the dorso-ventral axis, the GABA concentration (3.5-7 microgram/mg protein) was found first to increase and then to decrease, a maximum concentration being found at the level of the aqueduct. In contrast, no concentration gradient was found along the caudo-rostral axis. In an additional experiment, the medial hypothalamus (MH) was lesioned on one side and the effect of such a unilateral MH lesion on the caudo-rostral distribution of GABA was investigated. Fifteen days after performing the lesion, a graded decrease in GABA concentration--with a maximum in the rostral CG--was found to occur mainly on the lesioned side.

[Turnover of gamma-aminobutyric acid (GABA) in neurons and glial cells of the chick embryo in culture]. / Renouvellement de l'acide gamma-aminobutyrique (GABA) dans les neurones et les cellules gliales d'embryon de poulet en culture.

The turnover rates of gamma-aminobutyric acid (GABA) in cultured neurons and glial cells of Chicken embryo were measured by using a gas chromatography/mass spectrometric method. The method followed involved monitoring of the time course of changes in the enrichment of deuterium in GABA following incubation with pentadeuterated glutamate in the medium. The GABA turnover rate in neurons was found to be nearly eight fold greater than in glial cells.

Fast-heating mass spectrometry of phosphatidylcholine, lysophosphatidylcholine, phosphatidylethanolamine, and sphingomyelin.

A fast-heating probe and chemical ionization have been used to obtain mass spectra of the synthetic glycerophospholipids 1,2-diacyl-sn-glycero-3-phosphocholine, 1,2-diacyl-sn-glycero-3-phosphoethanolamine, and 1-monoacyl-2-lyso-sn-glycero-3-phosphocholine. The phospholipids investigated gave quasimolecular peaks and fragment ions, with preferential cleavage of the C-O bond (beta position to the phosphorus atom) and loss of phosphoethanolamine or phosphocholine. This technique makes possible the analysis of mixtures of intact phosphatidylethanolamine, phosphatidylcholine, 2-lysophosphatidylcholine, and sphingomyelin isolated from natural sources such as egg yolk or brain. Only minor and inexpensive modifications of a standard mass spectrometer are required.

Biodegradation of refractory hydrocarbon biomarkers from petroleum under laboratory conditions.

Biomarkers are of great value in petroleum exploration because they provide essential information about the geological history of oils and source rocks. Steranes are of particular importance as they can be related to naturally occurring precursors. These compounds generally experience intense biodegradation, however, which alters their original distribution and obscures the information that they carry regarding oil maturity and source material. In an attempt to identify the microorganisms responsible for this degradation, we have investigated the capacity of 73 aerobic bacteria to degrade steranes present in Rozel Point (Utah) oil. Seven Gram-positive strains, belonging to a limited number of genera, were found to be active. Using Nocardia sp. SEBR 16, which caused the most extensive alteration, we have determined biodegradation rates for several isomers of steranes and methylsteranes. The preference for alteration of different isomers reflects that observed in natural environments, suggesting that the degradation intermediates could be used as indicators of the extent of the biodegradation in an oil. In addition, the microorganisms used here might be effective in biodegrading oil spills.