A biochemical comparison of Xenopus laevis and mammalian myelin from the central and peripheral nervous systems

Myelin purified from the central nervous system of Xenopus laevis contained the same major lipid and protein components as human myelin. However, some minor differences in the myelin proteins were noted. The Xenopus basic protein had a higher apparent mol wt. on sodium dodecyl sulfate gels than the corresponding mammalian protein. The absolute specific activity of 2′,3′-cyclic nucleotide 3′-phosphohydrolase in the Xenopus myelin was considerably higher than in mammals. There were differences in the high mol wt. proteins, and the glycoproteins in Xenopus myelin were more heterogeneous than those in mammals. Peripheral myelin from Xenopus sciatic nerve was compared with that from the rat. The lipids in the two types of myelin were similar. There was a major glycoprotein in the Xenopus myelin corresponding to the P₀ protein and a basic protein of slightly larger mol wt. than the P₁ protein of rat myelin.     

Evidence for the presence of cytosolic inhibitors for phospholipid/Ca2+-dependent protein kinase in mastocytoma cell

1. Two kinds of C-kinase inhibitors were indicated to be present in mastocytoma cells. 2. One is a protein (mol. wt 64,000) which is weak but specific for C-kinase. 3. The other component (mol. wt 23,000) does not seem to be a protein and inhibits A-kinase as well as C-kinase.     

Cytoskeletal proteins of the cell surface in Tetrahymena : I. Identification and localization of major proteins

Isolated pellicles (cell ‘ghosts’) have been prepared from Tetrahymena thermophila strain B by two different methods. Using differential solubilization in combination with polyacrylamide gel electrophoresis and electron microscopy, we have tentatively identified the major proteins found in the surface-associated cytoskeleton. The ‘epiplasm’, a continuous layer of fibrous material found just beneath the surface membranes, appears to contain two major proteins. The smaller of the two (mol. wt 122 000 D) is believed to be present throughout the layer, whereas the larger protein (mol. wt 145 000 D) appears to be localized in the regions where ciliary basal bodies connect to the epiplasmic layer and to surface membranes. Evidence is presented which suggests that actin may also be present in this structure. Tubulin has been isolated from the cytosol of Tetrahymena and compared with cytoskeletal tubulin and porcine brain tubulin. A major protein of mol. wt 250 000 D which is found in Tetrahymena pellicles appears to be the major component of kinetodesmal fibers (striated elements which attach to the ciliary basal bodies).     

Acetyl-coenzyme A carboxylase from avocado (Persea americana) plastids and spinach (Spinacia oleracea) chloroplasts.

1. Protein synthesis has been investigated in different regions of the rat epididymis by measuring incorporation of [35S]methionine in tissue minces incubated in vitro followed by analysis of labelled proteins on polyacrylamide gels containing sodium dodecyl sulphate. Rates of synthesis were highest in the proximal cauda > distal cauda > initial segment > ductuli efferentes > corpus > distal caput > proximal caput. One protein (mol.wt. 23 000) characterized the initial segment, three proteins (mol.wts. 18 500, 19 000 and 32 000) the caput and one protein (mol.wt. 47 000) the cauda. 2. After castration, [35S]methionine incorporation in all regions of the epididymis was reduced to < 10% of that in normal animals but could be restored to control levels within 5 days by testosterone treatment. Other steroids (corticosterone, oestrogen or progesterone) were ineffective. 3. The synthesis of the 18 500, 19 000, and 32 000 mol.wt. proteins in the caput and the 47 000 mol.wt. protein in the cauda were preferentially regulated by androgens, whilst the synthesis of 23 000 and approx. 80 000 mol.wt. proteins in the initial segment was dependent upon factors present in testicular fluid. 4. The androgen-dependent and testicular fluid-dependent proteins were major components of epididymal secretion. Purification and characterization of the 18 500, 19 000, 23 000 and 32 000 mol.wt. proteins showed them to be acidic glycoproteins with a carbohydrate content of 7.6-13.2%. The 47 000 mol.wt. protein, on the other hand, is highly basic. 5. A possible role for these proteins in the acquisition of motility, fertilizing capacity and storage of spermatozoa in the epididymis is discussed.     

Protein composition and structure of human placental microvillous membrane. External surface, sialic acid containing, extrinsic and intrinsic components.

The microvillous membrane of human placenta is in direct contact with maternal blood and thus plays a vital role in many essential functions of the placenta. As an initial step in understanding the membrane proteins, and their relationship to these functions and to the structure of the membrane, we have investigated an isolated membrane preparation. Ten major peptide bands and an approximately equal number of minor bands were seen with sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. Sialoglycoproteins were labeled with periodate (PA-³H) borohydride and external surface components with lactoperoxidase-[¹²⁵I] (LP-¹²⁵I). One principal (69 000 mol. wt) and several minor (100 000, 45 000, and 38–40 000 mol. wt) bands were labeled as Sialoglycoproteins and found to be exposed on the surface of the membrane. Approx. 50% of the membrane protein and all of the sialic acid was tightly bound to membrane lipid and resistant to extraction with dimethyl maleic anhydride (DMMA). Electron microscopy demonstrated extraction by DMMA of microfilaments presumptively identified as actin and other electron dense components from the villous core. The extracted supernate and the residual pellet differed markedly in protein composition. The supernatant contained bands of 180 000, 115 000, 85 000, 70–72 000, 45 000, and 38–40 000 mol. wt whereas the lipid pellet contained components of 200 000, 150 000, 100 000, 69 000, and 64 000 mol. wt. The lipid matrix with which these proteins were associated contained phosphatidyl choline and sphingomyelin and was similar in composition to other plasma membranes. Thus by using a variety of experimental approaches the proteins of the human placental microvillous membrane can be divided into groups based on their sialic acid content, exposure on the external surface, tightness of binding to the membrane lipid, and relation to membrane structure.     

Molecular weights and metabolism of rat brain proteins

1. Rats were injected with [U-¹⁴C]glucose and after various intervals extracts of whole brain proteins (and in some cases proteins from liver, blood and heart) were prepared by high-speed centrifugation of homogenates in 0.9% sodium chloride or 0.5% sodium deoxycholate. 2. The extracts were subjected to gel filtration on columns of Sephadex G-200 equilibrated with 0.9% sodium chloride or 0.5% sodium deoxycholate. 3. Extracts prepared with both solvents displayed on gel filtration a continuous range of proteins of approximate molecular weights ranging from less than 2×10⁴ to more than 8×10⁵. 4. The relative amount of the large proteins (mol.wt.>8×10⁵) was conspicuously higher in brain and liver than in blood. 5. At 15min after the injection of [U-¹⁴C]glucose the smaller protein molecules (mol.wt.<2×10⁴) were significantly radioactive, whereas no ¹⁴C could be detected in the larger (mol.wt.>2×10⁴) protein molecules. The labelling of all protein samples was similar within 4h after injection of [U-¹⁴C]glucose. Fractionation of brain proteins into distinctly different groups by the methods used in the present work yielded protein samples with a specific radioactivity comparable with that of total brain protein. 6. No evidence could be obtained by the methods used in the present and previous work to indicate the presence of a significant amount of `metabolically inert protein' in the brain. 7. It is concluded that: (a) most or all of the brain proteins are in a dynamic state of equilibrium between continuous catabolism and anabolism; (b) the continuous conversion of glucose into protein is an important part of the maintenance of this equilibrium and of the homoeostasis of brain proteins in vivo.     

New actin-binding proteins from Dictyostelium discoideum

Dictyostelium discoideum contains a soluble actin-binding protein that caps actin filaments at their fast growing ends. The purified protein consists of two subunits with 34 kd and 32 kd apparent mol. wts. Like similar proteins from Acanthamoeba and bovine brain the capping protein from D. discoideum acts in a Ca²⁺ -independent manner. It lacks severing activity as indicated by its inability to disrupt the stress fibers and the microfilament network in detergent-extracted cells. Two actin-binding proteins from a plasma membrane-enriched fraction were labeled with [¹²⁵I]actin using a gel overlay technique. One of these proteins, with an apparent mol. wt. of 17 kd in SDS-polyacrylamide gels, has been purified from high-salt extracts, the other protein with an apparent mol. wt. of 31 kd has been purified from Triton X-100 extracted membranes. Monoclonal antibodies were raised against D. discoideum severin, α-actinin, the larger subunit of the capping protein, and the 17-kd membrane-associated protein. Immunoblotting of proteins from whole cell lysates showed that all these actin-binding proteins were present in both growth phase and aggregation-competent cells.     

Characterization of phycoerythrin from a Cryptomonas sp.

Summary Two closely similar phycoerythrins were purified from Cryptomonas sp. The two proteins were indistinguishable with respect to native molecular weight, subunit structure, photolability and immunological specificity, and differed only in their isoelectric points (pH 5.74 and 6.35), as determined by isoelectric focussing in polyacrylamide gels. Each protein consisted of two unequal subunits, (mol. wt. 11,800) and (mol. wt. 19,000), and each subunit contained covalently bound chromophore. In contrast to the blue-green and red algal phycoerythrins studied thus far, the Cryptomonas sp. phycoerythrins are extremely photolabile; exposure of the purified proteins to relatively short periods of intense illumination with visible light produces a marked decrease in fluorescence and in absorbance at 567 m.Abbreviation used SDS sodium dodecyl sulfate     

Protein phosphorylation in normal and neoplastic development. Phosphorylation of proteins endogenous to foetal tissues and tumours.

The abilities of proteins endogenous to normal and neoplastic tissues to serve as substrates in a protein-phosphorylation reaction in vitro were compared. After the tissue extracts were incubated with [gamma-32P]ATP, the phosphorylated proteins were separated by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and the dried gels were subjected to radioautography. Considerable incorporation of 32P into a protein of mol.wt. 135000 was observed with extracts from foetal tissues and tumours, but only minimal incorporation into this protein occurred when extracts from adult tissues were used. The ability of this protein to become phosphorylated in vitro may be related to cell proliferation. When ascites cells were incubated with [32P]Pi, one of the major phosphoproteins migrated on sodium dodecyl suphate/polyacrylamide gels at mol.wt. 135000, suggesting that this protein can be phosphorylated both in intact cells and broken-cell preparations. A protein of mol.wt. 87000 was highly phosphorylatable in extracts from solid tumours, but was not phosphorylated in extracts from ascites tumours, foetal or adult tissues. The phosphorylation pattern of these two proteins can thus distinguish solid neoplasms and normal adult tissues from ascites tumours and from foetal tissues. A protein of mol.wt. 49000, which was the most labelled protein in adult tissues, was also one of the major phosphoproteins in foetal and neoplastic tissues. Numerous mechanisms are postulated to explain how the extent of 32P incorporation into a protein could vary as a function of biological state.     

Purification and some properties of a new strain of cowpea mild mottle virus in Israel*

The virus responsible for tomato pale chlorosis disease in Israel was purified from Nicotiana glutinosa plants. Purified virus contained a single stranded RN A of mol. wt 2.5 × 10⁶ and a single coat protein subunit of mol. wt 31 000. Enzyme-linked immunosorbent assay and an immunoelectron microscopy decoration test demonstrated a serological relationship with cowpea mild mottle virus (CMMV). Based on the present study and previously reported data the virus was identified as a new strain of CMMV designated CMMV/I.     

The b-32 protein from maize endosperm, an albumin regulated by the O2 locus: Nucleic acid (cDNA) and amino acid sequences

Summary The cDNA coding for the b-32 protein, an albumin expressed in maize endosperm cells under the control of the O2 and O6 loci, has been cloned and the complete amino acid sequence of the protein derived. A lambda gt11 cDNA library from mRNA of immature maize endosperm was screened for the expression of the b-32 protein using antibodies against the purified protein. One of the positive clones obtained was used to isolate a full-length cDNA clone. By Northern analysis, the size of the b-32 mRNA was estimated to be 1.2 kb. Hybrid-selected translation assays show that the message codes for a protein with an apparent molecular weight of 30–35 kDa. The nucleotide sequence shows that several internal repeats are present. The protein has a length of 303 amino acid residues (mol. wt. 32430 dalton) and its sequence shows the following features: no signal peptide is observable; it contains seven tryptophan residues, an amino acid absent in maize storage proteins; polar and hydrophobic residues are spread along the sequence; several pairs of basic residues are present in the N-terminal region; the secondary structure allows the prediction of two structural domains for the b-32 protein that would fold up giving rise to a globular shape. The cloning of this gene may help in understanding the role of the O2 and O6 loci in regulating the deposition of zein, the major storage protein of maize endosperm.     

Proteose-peptone fractions of human and bovine milk

• 1.1. Human milk proteose-peptone fraction contained an average of 45% carbohydrate compared to about 11% carbohydrate present in the bovine milk fraction.
• 2.2. The human milk proteose-peptone fraction contained Lactobacillus bifidus var. Penn. growthpromoting factors, whereas there was very little such growth-promoting activity in the bovine milk material.
• 3.3. Polyacrylamide gel electrophoresis showed that human milk proteose-peptone fraction contained 4 major protein components with the respective mol. wts of approx 100,000, 70,000, 30,000, and 13,000. The latter was the most abundant component of human milk proteose-peptone fraction. There was, in addition a very low mol. wt carbohydrate-containing component. Bovine milk proteose-peptone fraction had 3 major protein components with mol. wts of 30,000, 18,000 and 12,000.
• 4.4. The human milk proteose-peptone component with the mol. wt of 13,000 was identified as α-lactalbumin, the component with the mol. wt of 30,000 was identified as a temperature-sensitive protein probably similar to galactothermin, and the components having mol. wts of 100,000 and 70,000 were closely associated to give a protein of a very high mol. wt. This complex also contained carbohydrate and was thus glycoprotein in nature.
• 5.5. The low-mol. wt carbohydrate-containing material was identified as being similar if not identical to glycoprotein B previously described.

     

Penicillin-binding proteins of protoplast and sporoplast membranes of Streptomyces griseus strains

Membrane-bound penicillin-binding proteins (PBPs) of two Streptomyces griseus strains that sporulate well in liquid and solid medium have been investigated during the course of their life-cycle. The PBP patterns were analyzed by sodium dodecylsulphate polyacrylamide-gel electrophoresis and fluorography. One strain (No. 45 H) has only a single band (mol wt: 27,000) in early log phase, and two additional PBPs of higher mol wt (69,000 and 80,000) in the late log phase. The other strain (No. 2682) possessed two bands with mol wts 27,000 and 38,000 which did not change during its vegetative phase. In strain No. 2682, a new PBP with a mol wt of 58,000 appeared in spore membranes while one of those (mol wt 38,000) present in mycelial membranes disappeared. Our results suggest that appearance of the new PBP in the spore may be associated with the sporulation process. The major PBP band (mol wt: 27,000) present in all stages of the life cycle of these strains, may be characteristic of S. griseus while the other PBPs reflect certain stages of the life cycle. A new method was developed for the production of spore protoplasts by consecutive enzymatic treatments.Abbreviation PBP penicillin-binding protein     

A biochemical comparison of Xenopus laevis and mammalian myelin from the central and peripheral nervous systems.

Myelin purified from the central nervous system of Xenopus laevis contained the same major lipid and protein components as human myelin. However, some minor differences in the myelin proteins were noted. The Xenopus basic protein had a higher apparent mol wt. on sodium dodecyl sulfate gels than the corresponding mammalian protein. The absolute specific activity of 2',3'-cyclic nucleotide 3'-phosphohydrolase in the Xenopus myelin was considerably higher than in mammals. There were differences in the high mol wt. proteins, and the glycoproteins in Xenopus myelin were more heterogeneous than those in mammals. Peripheral myelin from Xenopus sciatic nerve was compared with that from the rat. The lipids in the two types of myelin were similar. There was a major glycoprotein in the Xenopus myelin corresponding to the P0 protein and a basic protein of slightly larger mol wt. than the P1 protein of rat myelin.     

Cleavage of bacterial flagellin with cyanogen bromide. Antigenic properties of the protein fragments

1. Four polypeptide fragments, obtained by cyanogen bromide treatment of the protein flagellin from Salmonella adelaide, were tested for their antigenic activity by using them as inhibitors in three different assays: bacterial immobilization, haemagglutination of sensitized erythrocytes and quantitative micro precipitation. Immunodiffusion studies were also performed on the protein fragments. 2. Cleavage of the flagellin molecule in this way gave no detectable loss of antigenic determinants. Fragment A (mol.wt. 18000), the largest of the polypeptides, contained all the antigenic specificities present on flagellin that were recognized by the antisera used. In one test, fragment B (mol.wt. 12000) also contained antigenic activity to an extent not easily explainable by contamination with fragment A. Fragments C (mol.wt. 5500) and D (mol.wt. 4500) appeared to be antigenically inactive.     

Fractionation and characterization of rapidly phosphorylated nuclear proteins in salivary gland cells of Chironomus tentans

Rapidly phosphorylated nuclear proteins were investigated in explanted salivary gland cells of Chironomus tentans after labeling with ³²P_i. After sonication nuclei were fractionated by centrifugation at 18,000 g into sedimentable (80% of ³²P) and not sedimentable (supernatant) material. About 90% of ³²P in the supernatant fraction was sedimentable at 100,000 g (disperse chromatin). The disperse chromatin contained 20%–40% of the total nuclear DNA but only 5%–20% of ³²P. The ³²P-labeled phosphoproteins in the material pelleted at 20,000 g were further fractionated by differential solubility in lysis buffer. Electrophoretic analyses on SDS polyacrylamide gels resolved the ³²P-labeled nuclear proteins into 12 major bands in the M_r range of 12,000–120,000. The incorporation of ³²P into most bands reached a steady-state within 5–10 min of incubation with ³²P_i and was not measurably influenced by cycloheximide, an inhibitor of protein synthesis. The phosphate groups are linked to polypeptide chains by bonds vulnerable to pronase and alkaline phosphatase. All major bands in the pelleted chromatin were also present in the disperse chromatin except for an M_r 95,000 phosphoprotein. Two of the fastest moving ³²P-bands comigrated with the core histones H2A and H4. Both possessed a high pI value and were insoluble in 0.35 M NaCl. The H2A-like protein was partially soluble in lysis buffer while the H4-like one was not. The two fast moving ³²P-labeled bands with rapidly turned over phosphates may be fractions or variants of the core histones H2A and H4.     

Cell-specific expression of heat shock proteins in chicken reticulocytes and lymphocytes

We have found that chicken reticulocytes respond to elevated temperatures by the induction of only one heat shock protein, HSP70, whereas lymphocytes induce the synthesis of all four heat shock proteins (89,000 mol wt, HSP89; 70,000 mol wt, HSP70; 23,000 mol wt, HSP23; and 22,000 mol wt, HSP22). The synthesis of HSP70 in lymphocytes was rapidly induced by small increases in temperature (2 degrees-3 degrees C) and blocked by preincubation with actinomycin D. Proteins normally translated at control temperatures in reticulocytes or lymphocytes were not efficiently translated after incubation at elevated temperatures. The preferential translation of mRNAs that encode the heat shock proteins paralleled a block in the translation of other cellular proteins. This effect was most prominently observed in reticulocytes where heat shock almost completely repressed alpha- and beta-globin synthesis. HSP70 is one of the major nonglobin proteins in chicken reticulocytes, present in the non-heat-shocked cell at approximately 3 X 10(6) molecules per cell. We compared HSP70 from normal and heat-shocked reticulocytes by two-dimensional gel electrophoresis and by digestion with Staphylococcus aureus V8 protease and found no detectable differences to suggest that the P70 in the normal cell is different from the heat shock-induced protein, HSP70. P70 separated by isoelectric focusing gel electrophoresis into two major protein spots, an acidic P70A (apparent pl = 5.95) and a basic P70B (apparent pl = 6.2). We observed a tissue-specific expression of P70A and P70B in lymphocytes and reticulocytes. In lymphocytes, P70A is the major 70,000-mol-wt protein synthesized at normal temperatures whereas only P70B is synthesized at normal temperatures in reticulocytes. Following incubation at elevated temperatures, the synthesis of both HSP70A and HSP70B was rapidly induced in lymphocytes, but synthesis of only HSP70B was induced in reticulocytes.     

CHARACTERIZATION AND PROTEIN ANALYSIS OF MYELIN SUBFRACTIONS IN RAT BRAIN: DEVELOPMENTAL AND REGIONAL COMPARISONS

—Myelin preparations from the whole brains of 16-day-old rats and from cortical regions and brainstem, respectively, of 40-day-old rats were separated into light, medium and heavy subfractions on a discontinuous sucrose gradient by a procedure previously used for whole adult rat brain (Matthieu, et al., 1973). The total dry weight of myelin recovered from the 16-day-old rats was only 2·4mg/g fresh brain in comparison to 20 mg from adult brains. In 16-day-old rat brains, the percentage of the total myelin protein in the light fraction was higher than that found in adult brains; the percentage in the medium fraction was only one-third that in adults; while the percentage in the heavy fraction was about the same at both ages. The heavy fraction from the 16-day-old rats contained less basic protein and proteolipid than the light fraction, and the levels of the 2′3′-cyclic nucleotide 3′-phosphohydrolase (CNP) and glycoprotein were less than half those in the light and medium fractions. Double labelling experiments with radioactive fucose indicated that the major labelled glycoprotein in the heavy and medium fractions had a slightly higher apparent mol. wt than that in the light fraction. Electron microscopy showed much readily identifiable, compact myelin in the light and medium fractions from the 16-day-old rats, whereas the heavy fraction contained more single membranous structures and much less multilamellar myelin. The yield of myelin/g fresh wt from brainstem of 40-day-old rats was 4-fold higher than from cortical regions, and the percentage recovered in the light fraction was greater in the brainstem. In both regions basic proteins decreased from the light to the heavy fraction, whereas high mol. wt proteins, the glycoprotein and CNP increased. The biochemical and morphological results suggest that in both 16-day-old and young adult rats the light fraction is enriched multilamellar, compact myelin. In contrast, the heavy fraction at both ages is enriched in loose, uncompacted myelin and myelin-related membranes, although the heavy fraction from 16-day-old rats also may be substantially contaminated with membranes which are unrelated to myelin.     

Inhibitor analysis of protein phosphorylation/dephosphorylation in maize mitochondria in relation to redox conditions

The role of protein phosphorylation/ dephosphorylation in the redox regulation of mitochondrial functioning was investigated. Incubation of isolated mitochondria of maize (Zea mays L.) in the presence of γ-³²P-ATP revealed phosphorylation of polypeptides with mol wt of 66, 60, 55, 48/50 doublet, 45, 29, 22, and 19 kD. The presence in the incubation medium of oxidized glutathione significantly reduced the level of protein phosphorylation. The addition of reduced glutathione diminished phosphorylation of proteins with mol wt of 60 and 48/50 kD and slightly increased phosphorylation of proteins with mol wt of 66, 55, and 45 kD. The reducing agent, sodium dithionite decreased phosphorylation of proteins with mol wt of 60, 45, 29, 22, and 19 kD but increased phosphorylation of 55 kD protein. The inhibitors of protein kinases and protein phosphatases significantly modified the effects of redox agents. For example, simultaneous action of an oxidant K₃[Fe(CN)₆] and NaF enhanced phosphorylation level compared to separate treatments with these agents. The combined application of sodium dithionite and NaF elevated phosphorylation level of 55 kD protein. Phosphoprotein with mol wt of about 66 kD was identified immunochemically as a heat shock protein (HSP 60). The results indicate the presence in mitochondria of redox-sensitive protein kinases and protein phosphatases. Differential changes in the pattern of mitochondrial phosphoproteins under the action of various redox agents suggest that phosphorylation is probably involved in the transduction of redox signal in plant mitochondria.     

THE ISOLATION AND LIPID COMPOSITION OF MYELIN-FREE AXONS FROM RAT CNS1

—Myelin-free axons were isolated from rat CNS using a modification of the method of De Vries et al. (1972). On a dry weight basis, the axons contained 15·2% lipid composed of 19·4% cholesterol, 56·9% phospholipid and 23·7% galactolipid with a weight ratio of cerebroside to sulfatide of 3·6-1. The phospholipid was composed of 11·0% ethanolamine phosphatides (44·4% in the plasmalogen form), 21·0% choline phosphatides (9·3% in the plasmalogen form), 4·5% sphingomyelin, 4·5% phosphatidyl serine, 4·3% phosphatidyl inositol, 3·0% diphosphatidyl glycerol and 8·5% unidentified phospholipid. The rat axons contained 0·18 μg ganglioside NeuNAc/mg dry wt. In addition to the 4 major brain gangliosides, the rat axons contained gangliosides G_D2 and G_D3. The axonal galactolipid could not be accounted for by myelin contamination as revealed by electron microscopy, absence of the characteristic ratio of myelin specific proteins in the axonal protein profile as shown by polyacrylamide gel electrophoresis, and the axonal level of the myelin marker enzyme 2′,3′-cyclic nucleotide-3′-phosphohydrolase. The relationship between lipids of axons isolated from rat and bovine CNS, and rat whole brain and CNS myelin is discussed.