Phospholipids and acyl groups in subcellular fractions from human cerebral cortex

Subcellular fractionation of human brain cortex obtained at autopsy yielded microsomal and synaptosome-rich fractions from the gray matter and microsomal and purified myelin fractions from the white matter. The phospholipids of myelin were high in plasmalogens, and the molar ratio of alkenyl acyl sn-glycero-3-phosphorylethanolamine to diacyl sn-glycero-3-phosphorylethanolamine was 4. The acyl groups of the myelin phosphoglycerides were enriched in monoenes (mainly 18:1 and 20:1) and a tetraene, 22:4(n - 6). The phospholipids in the synaptosome-rich fraction were high in diacyl sn-glycero-3-phosphorylcholine, and the molar ratio of the alkenyl acyl sn-glycero-3-phosphorylethanolamine to diacyl sn-glycero-3-phosphorylethanolamine was 0.88. The acyl groups of synaptosomal ethanolamine phosphoglycerides were rich in 22:6(n - 3) but contained a very low amount of 20:1. The lipid composition of microsomes from the gray matter was different from that of microsomes from the white matter but was nearly identical with that of the synaptosome-rich fraction. Except for a slightly lower proportion of alkenyl acyl sn-glycero-3-phosphorylethanolamine and sphingomyelin, the lipid composition of microsomes from the white matter was also similar to that of the myelin. There were also species-related differences between the brain lipid composition of human and subhuman primates and that of the rodents. Furthermore, the brain lipid composition in normal human subjects is rather constant and does not seem to be affected much by individual variations.     

Regional and Subcellular Distribution of Thy-1 in Human Brain Assayed by a Solid-Phase Radioimmunoassay

A solid-phase radioimmunoassay, specific for the monomeric form of human Thy-1, was developed and used for quantitation of the Thy-1 antigen in human brain tissue. Determination of Thy-1 in homogenates of 12 anatomically defined brain regions showed that Thy-1 is present throughout the human brain. However, significant variation was found in the expression of the glycoprotein in different regions. Thy-1 appears to be generally enriched within gray matter: caudate nucleus, cerebral cortex, and putamen were found to contain the highest Thy-1 concentration (approximately 2.5 micrograms Thy-1/mg protein). Interestingly, the cerebellar cortex contained only 25% of the Thy-1 concentration of cerebral gray matter. Cerebral subcortical white matter contained half the amount of Thy-1 compared to cerebral cortex. Determination of Thy-1 in subcellular fractions prepared from human brain biopsy tissue indicated that the highest relative concentration of Thy-1 is associated with synaptosomal membranes and myelin/axonal membrane fractions.     

Rapid synthesis and turnover of brain microsomal ether phospholipids in the adult rat.

The rates of synthesis, turnover, and half-lives were determined for brain microsomal ether phospholipids in the awake adult unanesthetized rat. A multicompartmental kinetic model of phospholipid metabolism, based on known pathways of synthesis, was applied to data generated by a 5 min intravenous infusion of [1,1-(3)H]hexadecanol. At 2 h post-infusion, 29%, 33%, and 31% of the total labeled brain phospholipid was found in the 1-O-alkyl-2-acyl-sn-glycero-3-phosphate, ethanolamine, and choline ether phospholipid fractions, respectively. Autoradiography and membrane fractionation showed that 3% of the net incorporated radiotracer was in myelin at 2 h, compared to 97% in gray matter microsomal and synaptosomal fractions. Based on evidence that ether phospholipid synthesis occurs in the microsomal membrane fraction, we calculated the synthesis rates of plasmanylcholine, plasmanylethanolamine, plasmenylethanolamine, and plasmenylcholine equal to 1.2, 9.3, 27.6, and 21.5 nmol. g(-1). min(-1), respectively. Therefore, 8% of the total brain ether phospholipids have half-lives of about 36.5, 26.7, 23.1, and 15.1 min, respectively. Furthermore, we clearly demonstrate that there are at least two pools of ether phospholipids in the adult rat brain. One is the static myelin pool with a slow rate of tracer incorporation and the other is a dynamic pool found in gray matter.The short half-lives of microsomal ether phospholipids and the rapid transfer to synaptosomes are consistent with evidence of the marked involvement of these lipids in brain signal transduction and synaptic function.     

Glycopeptide fractions prepared from purified central and peripheral rat myelin

Myelin was purified from rat brain and sciatic nerve after invivo labeling with [³H]fucose and [¹⁴C]glucosamine to provide a radioactive marker for glycoproteins. The glycoproteins in the isolated myelin were digested exhaustively with pronase, and glycopeptides were isolated from the digest by gel filtration on Bio-Gel P-10. The glycopeptides from brain myelin separated into large and small molecular weight fractions, whereas the glycopeptides of sciatic nerve myelin eluted as a single symmetrical peak. The large and small glycopeptide fractions from central myelin and the single glycopeptide fraction from peripheral myelin were analyzed for carbohydrate by colorimetric and gas liquid chromatographic techniques. The glycopeptides from brain myelin contained 2.4 μg of neutral sugar and 0.59 μg of sialic acid per mg total myelin protein, whereas sciatic nerve myelin glycopeptides contained 10 μg of neutral sugar and 3.8 μg of sialic acid per mg total protein. Similarly, the gas-liquid chromatographic analyses showed that the glycopeptides from peripheral myelin contained 4- to 7-fold more of each individual per mg total myelin protein than those from central myelin. Most of the sialic acid and galactose in the glycopeptides from central myelin were in the large molecular weight fraction, and the small molecular weight glycopeptides contained primarily mannose and $\text{N-}\text{acetylglucosamine}$. The considerably higher content of glycoprotein-carbohydrate in peripheral myelin supports the results of gel electrophoretic studies, which indicate that the major protein in peripheral myelin in glycosylated while the glycoproteins in purified central myelin are quantitatevely minor components.     

Structure of glycoproteins of human erythrocytes. Alkali-stable oligosaccharides

Studies have been made on the oligosaccharide residues of the alkali-stable carbohydrate-protein linkage of sialoglycopeptides derived from human erythrocytes. Four glycopeptides were isolated after alkaline borohydride treatment and Pronase digestion of MN-active sialoglycopeptides. The structure of one of these glycopeptides (GPIV) has been studied by sequential hydrolysis with specific glycosidases. Glycopeptide GPIV contained (per mol): 1mol of fucose, 1mol of sialic acid, 3mol of galactose, 3mol of mannose, 4mol of acetylglucosamine, 1mol of aspartic acid and fractional amounts of threonine, serine and glycine. The molecular weight of the glycopeptide was estimated to be 2330 by gel filtration. On the basis of glycosidase-digestion results, a tentative structure is proposed for the oligosaccharide moiety of glycopeptide GPIV.     

THE CHARACTERIZATION OF SPHINGOLIPIDS OF OLIGODENDROGLIA FROM CALF BRAIN

Abstract— Purified oligodendroglia isolated from bovine brain white matter were found to contain, in addition to galactosylceramide, sulfatide and sphingomyelin, significant quantities of glucosylcerai-mide, dihexosylceramide and esterified galactosylceramide. These sphingolipids were isolated and quan-titated and their fatty acid and long chain base patterns compared with those from sphingolipids isolated from bovine myelin, white matter and gray matter.
The minor glycosphingolipids, glucosylceramide, dihexosylceramide and esterified galactosylceramide, constituted a higher percentage of glial lipids than of myelin lipids. Glucosylceramide accounted for 12% of the total glial monohexosylceramide fraction and 0.8% of total lipids; dihexosylceramide was 0.9% of total glial lipids. Both of these lipids had small quantities of α-hydroxy fatty acids. The unsubstituted fatty acids of glucosylceramide were mostly short chain (16 and 18 carbons) and were different from those of the dihexosylceramides which were a mixture of short and long chain. The hydroxy acids of each of these lipids were, however, similar and resembled those of galactosylceramide.
The fatty acid patterns of galactosylceramide, sulfatide and sphingomyelin from glial cells resembled those of the corresponding lipids from myelin and white matter. The amide-linked acids of esterified galactosylceramide contained both unsubstituted and α-hydroxy chains. Their patterns were not identical to those of galactosylceramide, but were similar in all brain fractions.
With the exception of sphingomyelin and dihexosylceramide, which contained small amounts of C₂₀-sphingosine, all sphingolipids analyzed contained mostly sphingosine and dihydrosphingosine.
We conclude that the distribution of sphingolipids in the oligodendroglia is characteristic, but the lipophilic residues of these lipids are not cell-specific.     

Glycoproteins of avian tumor virus recombinants: evidence for intragenic crossing-over.

The envelope glycoproteins of several avian tumor virus recombinants selected for the host range of a leukosis virus and the transforming function of a sarcoma virus were compared with each other and with those of their parents. It was found that the glycoproteins of different recombinant viruses, derived from the same parents, differed in their electrophoretic mobilities measured in polyacrylmide gels. The glycoproteins that had lower electrophoretic mobilities had higher precentages of carbohydrate. The carbohydrate of viral glycoproteins was estimated to range between 8 and 18% from their buoyant densities in CsCl, using known glycoproteins as standards. After exhaustive Pronase digestion, the carbohydrate was recovered from viral glycoproteins as a mixture of glycopeptides with molecular weights ranging from 2,500 to 5,000. It was estimated that distinct viral glycoproteins contained between two and five such oligosaccharide chains and that the glycoproteins of different recombinants expressing the same host range marker may differ in the number of oligosaccharide chains and consequently also in their polypeptide structure. Those with lower electrophoretic mobility contain more oligosaccharide chains per molecule than those with higher electrophoretic mobilities. It is suggested that not oligosaccharide chains define the viral host range.     

THE REGIONAL DISTRIBUTION OF SIALOGLYCOPROTEINS, GANGLIOSIDES AND SIALIDASE IN BOVINE BRAIN

Abstract— Sialoglycoproteins and gangliosides were characterized in various bovine brain regions by determining the amount of sialic acid. Expressed per g dry weight, the gangliosidic sialic acid ranged from 11·20 to 1·93 μmol and the glycoprotein sialic acid from 8·93 to 1·84 μmol in grey and white matter respectively (values not corrected for incomplete release and breakdown during hydrolysis). Both the sialoglycoproteins and the gangliosides occur in highest concentration in areas predominating in neuronal cell bodies (cerebral grey, cerebellar grey, caudate nucleus). The lowest concentrations are found in those areas, consisting largely of myelinated fibre tracts and glial cells (pons, medulla, corpus callosum, cerebral white). Relative to the gangliosides the sialoglycoproteins are somewhat more concentrated in white matter.
The sialidase activity was investigated with endogenous substrate as well as with additional gangliosides or sialoglycopeptides. In all conditions the activity was much greater in grey matter than in white matter. The regional sialidase distribution more or less parallels the distribution of sialic acid in the various regions. At high substrate level the sialoglycopeptides inhibit the sialidase activity. There are indications that gangliosides are a far better substrate for brain sialidase than glycoproteins or glycopeptides. The possible significance of this phenomenon is discussed.     

CARBOHYDRATE-PEPTIDE LINKAGES IN GLYCOPROTEINS AND MUCOPOLYSACCHARIDES FROM BRAIN

Abstract— Treatment of glycopeptides, prepared from glycoproteins of rat and rabbit brain, with NaOH-NaBH₄ leads to the destruction of a portion of the serine, threonine and galactosamine present, and the appearance in acid hydrolysates of alanine, α-aminobutyric acid and galactosaminitol. These results indicate that N-acetylgalactosamine at the reducing end of oligosaccharide chains in brain glycoproteins is linked O-glycosidically to the hydroxyl groups of serine and threonine residues. 2-acetamido-1-(L-β-aspartamido)-l,2-dideoxy-β-D-glucose was also detected after partial acid hydrolysis of the alkali-stable glycopeptides, and most of the carbohydrate in brain glycoproteins appears to be linked by N-acetylglucosaminylasparagine linkages. The results of the treatment of the sulphated mucopolysaccharides from bovine brain with alkaline-borohydride indicate that the polysaccharide chains in chondroitin sulphate and heparan sulphate are linked exclusively to serine.     

COMPARISON OF THE FATTY ACIDS OF LIPIDS OF SUBCELLULAR BRAIN FRACTIONS

Abstract— Rat brain grey and white matter were fractionated to yield myelin, nerve terminal, synaptic vesicle, nerve terminal 'ghost', and microsomal fractions of white and grey matter. Ester-type glycolipids were found in all fractions except myelin, while cerebrosides occurred in significant concentrations only in myelin and white microsomes. Comparison of the fatty acid profile of the ethanolamine- and serine-containing phospholipids showed marked differences between myelin and the particles from grey matter, while the microsomes of white matter were of intermediate composition. Docosahexaenoic acid, a minor acid in myelin, was a major fatty acid in microsomes of grey and white matter. The fatty acid composition of sphingomyelin was distinctly different in the fractions derived from grey and white matter, clustering about stearate and nervonate in the latter, but only about stearate in the grey. Marked differences in the positional distribution of fatty acids were seen within phosphatidyl choline from myelin and nerve terminals. Ribonucleic acid was found in nerve terminal and synaptic vesicle fractions. The sphingosine found in the ganglioside from microsomes of both grey and white matter was similar with respect to distribution of the C₁₈ and C₂₀ homologues.
The possibility is discussed that microsomes furnish characteristic lipids for the synthesis or renewal of specific membranes, and that these lipids are accumulated somewhat before being released.     

Distribution and metabolism of glycoproteins and glycosaminoglycans in subcellular fractions of brain.

The distribution, carbohydrate composition, and metabolism of glycoproteins have been studied in mitochondria, microsomes, axons, and whole rat brain, as well as in various synaptosomal subfractions, including the soluble protein, mitochondria, and synaptic membranes. Approximately 90% of the brain glycoproteins occur in the particulate fraction, and they are present in particularly high amounts in synaptic and microsomal membranes, where the concentration of glycoprotein carbohydrate is 2-3% of the lipid-free dry weight. Treatment of purified synaptic membranes with 0.2% Triton X-100 extracted 70% of the glycoprotein carbohydrate but only 35% of the lipid-free protein residue, and the resulting synaptic membrane subfractions differed significantly in carbohydrate composition. The glycoproteins which are not extracted by Triton X-100 also have a more rapid turnover, as indicated by the 80-155% higher specific activity of hexosamine and sialic acid 1 day after labeling with [3H]glucosamine in vivo. The specific activity of sialic acid in the synaptosomal soluble glycoproteins 2 hr after labeling was greater than 100 times that of the synaptosomal particulate fraction, whereas the difference in hexosamine specific activity in these two fractions was only twofold, and by 22 hr there was little or no difference in the specific activities of sialic acid and hexosamine in synaptosomal soluble as compared to membrane glycoproteins. These data indicate that sialic acid may be added locally to synaptosomal soluble glycoproteins before there is significant labeling of nerve ending glycoproteins by axoplasmic transport. Fifty to sixty percent of the hyaluronic acid and heparan sulfate of brain is located in the various membranes comprising the microsomal fraction, whereas half of the chondroitin sulfate is soluble and only one-third is in microsomal membranes. When microsomes are subfractionated on a discontinuous density gradient over half of the hyaluronic acid and chondroitin sulfate are found in membranes with a density less than that of 0.5 M sucrose (representing a six- to sevenfold enrichment over their concentrations in the membranes applied to the gradient), whereas half of the heparan sulfate is present in membranes with a density greater than that of 0.8 M.     

Regional and subcellular distributions of brain neurotensin.

The regional and subcellular distribution of neurotensin were determined using a newly developed radioimmunoassay for this central nervous system tridecapeptide. Neurotensin immunoreactivity in calf brain is high in the hypothalamus and basal ganglia, unevenly distributed through the cerebral cortex, and low in cerebellar cortex and cerebral white matter. Subcellular fractionation of rat hypothalamus reveals a strong association of neurotensin immunoreactivity with synaptosomal and microsomal fractions. These data, taken along with previously described high affinity selective brain membrane receptor binding, are consistent with a neurotransmitter candidate role for neurotensin in the brain.     

STALOSYLGALACTOSYL CERAMTDE AS A SPECIFIC MARKER FOR HUMAN MYELIN AND OLIGODENDROGLIAL PERIKARYA: GANGLIOSIDES OF HUMAN MYELIN, OLIGODENDROGLIA AND NEURONS

Gangliosides were isolated from human brain myelin, oligodendroglia, and neurons. Quantitative analysis revealed the following ganglioside contents: myelin, 2.0; neurons, 1.3; and oligodendroglia, 0.35 μg ganglioside sialic acid per mg protein. Myclin had a relatively simple ganglioside pattern with G_M4 and G_M1 as the predominant ganglioside species. The ganglioside pattern of oligodendroglia was quite complex and it resembled that of whole white matter rather than that of myelin. A high concentration of G_M4 was found in oligodendroglial fractions in addition to G_M1, G_D1a, G_D1b, and G_T1b. The usually- minor brain gangliosides G_M3, G_M2, and G_M3 were also enriched in oligodendroglia. The neuronal ganglioside pattern was generally similar to the pattern of whole gray matter. Both neurons and whole gray matter contained very low amounts of G_M4. These results indicate that G_M4 is specifically localized in myelin and oligodendroglia of the CNS. Evidence is also presented that myelin, but not oligodendroglia, is the major reservoir of human white matter G_M1 and G_M4.     

Is Na + K ATPase a Myelin-Associated Enzyme?

The Na + K ATPase activity associated with purified myelin has been investigated. On the basis of marker enzyme studies, the Na + K ATPase activity of myelin was higher than could be accounted for by microsomal contamination. Fractions prepared from white matter-enriched areas of rat brain showed a threefold enrichment in Na + K ATPase activity in myelin as compared with the white matter homogenate. The ATPase activity in myelin was stimulated fourfold by treatment with sodium deoxycholate, but the activity in the whole brain homogenate and the microsomal fraction was only doubled. This discontinuity temperature for Na + K ATPase activity was significantly higher for the myelin fraction (29 degrees C) than for the microsomal fraction (21 degrees C), but the energies of activation, both above and below the discontinuity temperature, were the same for both fractions, Myelin Na + K ATPase had a lower affinity for strophanthidin than the microsomal enzyme, but both fractions were inhibited to the same extent by 10-3 M-strophanthidin. The evidence thus indicated that much of the ATPase activity of myelin is not the result of microsomal contamination. Although the possibility of axolemmal contamination cannot be ruled out conclusively, indirect evidence suggest that this is not a significant factor and that Na + K ATPase may be a myelin-associated enzyme.     

THE ACTION OF CALF BRAIN SIALIDASE ON GANGLIOSIDES, SIALOGLYCOPROTEINS AND SIALOGLYCOPEPTIDES

Abstract— In agreement with other investigators it has been shown that endogenous as well as added gangliosides are a substrate for brain sialidase. The release of sialic acid was enhanced in the presence of Triton X-100; this might be due to the action of the detergent on the ganglioside micelles. The sialic acid release from endogenous gangliosides was observed over 48 h and compared with the effect of the sialidase on the endogenous glycoproteins. Though the hydrolysis of sialic acid from gangliosides is much faster in the first hours, after 48 h 40 per cent of the total bound sialic was released from both substrates at pH 4.0 and 37°C.
Sialoglycopeptides obtained from brain glycoproteins are also metabolized by the sialidase. No effect of Triton X-100 on this substrate has been observed. From sialoglycopeptides, fractions can be obtained by DEAE-Sephadex A-50 column chromatography with a sialic acid content from 8 to 26 per cent. The fractions with a high sialic acid content were about equally active towards brain sialidase as gangliosides. The results agree with the similar turnover rate observed for the carbohydrate chains from gangliosides and glycoproteins, but are in contrast to the observations of other investigators who have stated that glycoproteins are a poor substrate for brain sialidase. In our experiments bovine and ovine submaxillary mucins and sialyl-lactoses showed only slight activity compared to gangliosides and selected brain sialoglycopeptides.     

A comparison of the glycoproteins and the proteins from multiple sclerosis and normal brain tissue

Two highly sensitive techniques were used to identify glycoproteins and proteins in several tissue fractions from two normal brains and five brains from multiple sclerosis (MS) patients. Comparison of glycoproteins and proteins in white and gray matter, myelin and a myelin-related fraction between normal and MS brains not only showed the presence in all fractions of many more minor components than has previously been reported, but also subtle differences in some of these components. However, no change was unequivocally MS-specific. This provides additional evidence that MS is a demyelinating rather than a dysmyelimating disorder and may lead to some insight into the etiology and/or progression of this disease. Moreover, this study has served to characterize further the proteins and glycoproteins of human brain tissue.     

Differences between the carbohydrate units of cell-surface glycoproteins of moust B- and T-lymphocytes.

Carbohydrate units of cell-surface glycoproteins of mouse B- and T-lymphocytes, labelled in their sialic acid residues by the periodate/NaB3H4 method and in their galactose residues by the galactose oxidase/NaB3H4 method after neuraminidase treatment, have been studied. Glycopeptides were prepared from the labelled cells by Pronase digestion and fractionated by concanavalin A affinity chromatography into two fractions (A and B). Alkali-labile oligosaccharides were isolated after mild NaOH/NaBH4 treatment by gel filtration. The alkali-labile oligosaccharides were further analysed by t.l.c. To study the relative proportion of neutral mannose-rich carbohydrate units (fraction C) in lymphocyte glycoproteins, glycopeptides were also prepared from unlabelled cells and subjected to concanavalin A affinity chromatography after N-[3H]acetylation of their peptide moiety. The major alkali-labile oligosaccharide component of both cell types was identified as galactosyl-(beta 1 leads to 3)-N-acetylgalactosaminitol. T-Lymphocytes were characterized by a high proportion of this oligosaccharide and a lower proportion of alkali-stable fraction A glycopeptides, whereas the opposite was observed for B-lymphocytes. The relative proportions of the concanavalin A-binding fractions B and C were similar in both cell types. The differences observed may correlate with the different surface properties of B- and T-lymphocytes.     

Growth of Enveloped RNA Viruses in a Line of Chinese Hamster Ovary Cells with Deficient N-Acetyl-glucosaminyltransferase Activity

Sindbis and vesicular stomatitis viruses were grown in a line (termed 15B) of Chinese hamster ovary (CHO) cells that is deficient in a specific UDP-N-acetylglucosamine:glycoprotein N-acetylglucosaminyltransferase. Both viruses replicated normally in the cell line, but the glycoproteins of the released virus migrated faster on sodium dodecyl sulfate-polyacrylamide gels than did glycoproteins of virus grown in parent CHO cells. Digestion of the viral glycoproteins with Pronase followed by gel filtration demonstrated that the glycopeptides of Sindbis-15B virus were much smaller than the glycopeptides of Sindbis-CHO virus. In addition, Sindbis-15B viral glycopeptides but not Sindbis-CHO viral glycopeptides contained terminal α-mannose residues as shown by their susceptibility to α-mannosidase digestion. These findings demonstrate that the oligosaccharide units of the glycoproteins of vesicular stomatitis and Sindbis viruses are altered when the viruses are grown in 15B cells. We conclude that the N-acetylglucosaminyltransferase that is missing in 15B cells normally participates in the biosynthesis of the oligosaccharide units of the viral glycoproteins, and in the absence of this enzyme incomplete oligosaccharide chains are produced. Viruses released from 15B cells appear to retain full infectivity; Sindbis-15B virus, however, showed a significant decrease in hemagglutination titer compared with that of Sindbis-CHO virus.     

METABOLISM OF ARACHIDONOYL PHOSPHOGLYCERIDES IN MOUSE BRAIN SUBCELLULAR FRACTIONS

Abstract— Mouse brain subcellular fractions were prepared at 1, 12, and 24 h and 3 and 8 days after intracerebral injections of [1-¹⁴C]arachidonate. Initially, radioactivity was mainly distributed in the microsomal and synaptosomal fractions, but the proportion of radioactivity in the myelin increased from 5 to 16% within 8 days. Radioactivity of the microsomal lipids started to decline at 1 h after injection, and the decay was represented by two pools with half-lives of 19 h and 10 days, respectively. Radioactivity in the synaptosomal and myelin fractions did not reach a maximum until 24 h after injections. The half-life for turnover of synaptosomal lipids was 9 days.
The decline of radioactivity measured in the microsomal fraction was due mainly to diacyl-GPC and diacyl-GPI, since radioactivity of other phosphoglycerides (diacyl-GPS, diacyl-GPE and alkenyl-acyl-GPE) continued to increase for 12-24 h. In this fraction, half-lives of 10-14 h were obtained for the fast turnover pools of diacyl-GPC and diacyl-GPI, and slow turnover pools with half-lives of 7 days for diacyl-GPI and 10-14 days for other phosphoglycerides were also present. Among the synaptosomal phosphoglycerides, radioactivity of diacyl-GPI declined in a biphasic mode, thus exhibiting half-lives of 5 h and 5 days. Incorporation of labelled arachidonate into diacyl-GPE and diacyl-GPS in the synaptosomal fractions was observed for a period of 24 h. The half-lives for these phosphoglycerides ranged from 8 to 12 days. Results of the study have demonstrated the presence of small pools of arachidonoyl-GPI in synaptosomal and microsomal fractions which were metabolically more active than other arachidonoyl containing phosphoglycerides.     

Oligosaccharides of the glycoprotein of rabies virus.

The number of oligosaccharide side chains on rabies virus glycoprotein (G-protein) was investigated. Analysis of glycopeptides obtained by protease digestion of desialated G-protein revealed three discrete glycopeptides. Comparison of the protease digestion products from desialated and from untreated G-protein indicated a heterogeneity among the glycopeptides in the sialic acid content. Two major tryptic glycopeptides were isolated from desialated rabies virus G-protein and analyzed after protease digestion; one contained two oligosaccharide side chains and the other contained a single oligosaccharide side chain.