The in vivo incorporation of linolenic acid into neuronal and glial cells and myelin

Abstract— Neurons, astrocytes, oligodendrocytes, and myelin were prepared from 21-day-old rat brain at various times after intracerebral injection of [1-¹⁴C]linolenate. Comparisons of phospholipid specific radioactivity demonstrated that the oligodendrocytes were much more active than neuronal, astroglial, or myelin fractions. This is consistent with the concept that the oligodendrocyte is responsible for synthesis of the relatively large mass of myelin sheath. Initially the phosphatidylcholine fraction was more active than the phosphatidylethanolamine fraction, but during the 36 h after injection the former decreased in radioactivity while the latter fraction showed an increase. Fatty acid elongation occurred rapidly. Within 2h after injection, 2/3 of the label had been converted to elongated products (20:4. 20:5, 22:5 and 22:6). All three cell types apparently contained the enzymes necessary to incorporate, elongate, and desaturate linolenic acid and this occurred at similar rates in each cell type. No direct precursor-product relationship was found between the lipids of oligodendrocytes and myelin. There was, however, a lag in the appearance of elongated fatty acids in the phosphoglycerides of myelin. indicating that the polyunsaturated fatty acids in myelin were synthesized elsewhere and transported into the myelin sheath.     

THE INCORPORATION OF [1-14C]LINOLENATE INTO LIPIDS OF DEVELOPING RAT BRAIN DURING ESSENTIAL FATTY ACID DEPRIVATION

Abstract— Twenty-one-day old essential fatty acid (EFA) deprived rats incorporated about twice the radioactivity from [1-¹⁴C]linolenate into brain lipid fractions as did controls. At 5 min after injection, 2/3 of the radioactivity was associated with the less polar lipid fraction of both control and EFA deprived animals. By 30 min after injection, 70% of the radioactivity was in the phospholipid fraction. This value increased to 90% at later time points.
The specific activity of brain phospholipids from EFA deprived rats was always greater than that of controls. This held true for the individual phosphatide fractions also. In general, phosphatidylcholine (PC) was labeled most rapidly. With increasing time intervals, radioactivity was transferred to phospha-tidylethanolamine (PE) and phosphatidylserine + phosphatidylinositol (PS + PI).
The transfer of fatty acid radioactivity into phospholipid and the distribution of radioactivity among individual phosphatides did not appear to be affected by the dietary state. However, the total amount of radioactivity incorporated was related to the amount initially retained by brain after injection. Our data suggest that one or more components of the less polar lipid fraction may act as a 'trap' or reservoir for fatty acids which are required for phospholipid synthesis.     

Four-Hour Urease Test for Distinguishing Between Klebsiella and Enterobacter

Infections with Klebsiella and Enterobacter have increased among hospitalized patients. To study such infections, relatively simple but precise methods are needed for clinical laboratories to identify the two genera accurately. Moreover, a rapid identification is essential for assisting with the therapy of the patients. For this purpose, a new 4-hr urease test was developed so that colonies could be tested directly from blood-agar plates which have been inoculated with clinical material and allowed to incubate overnight. This 4-hr test was positive with 98.5% of 202 Klebsiella species and negative with 80 Enterobacter species. As a single criterion for distinguishing between the two major genera, the new 4-hr urease test was just as accurate as a motility test (99% of the 282 isolates were accurately identified with either). The 4-hr urease test represents a simple, rapid, and reliable technique which is ideally suited for use in clinical microbiology laboratories.     

Fatty acids of glycerophosphatides in developing chick embryonic brain and liver

Fatty acid compositions of glycerophosphatides of developing chick embryonic brain and liver were compared. In brain, ethanolamine and serine glycerophosphatides contained 30-40% polyunsaturated fatty acids, lecithin almost none (except for arachidonic). In the liver, these acids were equally distributed in the phospholipid fractions. The principal polyunsaturated fatty acids of the ethanolamine and serine glycerophosphatides in brain, liver, and yolk were 22:6, 20:4, and 18:2, respectively. During embryonic development of brain from the 8th day of incubation to hatching, the fatty acid composition of individual glycerophosphatide fractions remained constant. Because of the relative increase of ethanolamine glycerophosphatides and decrease of lecithin, total glycerophosphatides showed a decrease in 16:0 and an increase in 18:0. Substantial amounts of palmitaldehyde and stearaldehyde were present on the 8th day of incubation in the brain ethanolamine glycerophosphatide fraction. During the 3rd week of incubation, the liver showed a two-fold increase in the relative amount of 18:2 in all glycerophosphatide fractions. A decrease of 16:0 in the lecithin fraction and consequently in total glycerophosphatides was also observed during this period. No significant changes in glycerophosphatide fatty acids were observed in the yolk throughout incubation.