D(+)catechin enhances heparan sulphate content in rat liver

Administration of (D+) catechin (100 mg/kg body wt) to rats resulted in an increase in the amount of total sulphated glycosaminoglycans (GAG) in liver. The increase was more pronounced in the case of heparan sulphate than chondroitin sulphate and dermatan sulphate. The liver slices prepared from catechin-treated rats showed a significant increase in the rate of incorporation of 35S-sulphate into GAG. Similarly there was a concentration-dependent increase in the rate of 35S-sulphate incorporation into GAG by normal liver slices in presence of catechin in vitro. Susceptibility to nitrous acid degradation and chondroitinase ABC digestion showed that more than 80% of the GAG labelled in vivo with 35S-sulphate, was heparan sulphate and about 10% chondroitin sulphate and dermatan sulphate. Gel filtration of the 35S-labelled material isolated from livers of normal and catechin-treated animals over sephacryl S-300 did not show any difference probably excluding the possibility of free GAG chains initiated on catechin or any of its metabolites in vivo. These results indicate that catechin stimulates the synthesis of sulphated GAG, particularly heparan sulphate in liver.     

A comparative study of glycosaminoglycans in cultures of human, normal and malignant glial cells.

The glycosaminoglycans (GAG) of human cultured normal glial and malignant glioma cell lines were studied using 35S-sulphate or 3H-glucosamine as markers. 35S-labelled GAG were assayed by precipitation with cetylpyridinium chloride; 3H-labelled sulphated GAG and 3H-labelled hyaluronic acid were quantitated after separation on a DEAE-cellulos column. The net production of GAG and the distribution, composition and turnover of GAG were similar in all of the normal cell lines tested, but showed a great variability in the malignant cell lines. Most of the glioma cell lines produced more hyaluronic acid and less sulphated GAG than the normal cell lines, but exceptions were noted. The GAG of the trypsin susceptible (pericellular pool of normal glial cells consisted mainly of heparan sulphate with only minor amounts of other GAG. The analogous material of most glioma cells showed hyaluronic acid as the major GAG. Material liberated by trypsin from EDTA-detached cells (membrane fraction) was enriched in heparan sulphate as compared to the entire pericellular pool. Substrate attached material (SAM) left with the plastic dish after EDTA treatment of normal cultures was rich in heparan sulphate, whereas SAM of glioma cells lacked heparan sulphate or showed greatly reduced amounts of this component. Release of newly synthesized GAG to the extracellular medium was a rapid process in the normal cells but was more or less delayed in the glioma cells. The extracellular medium of the malignant glioma cultures was consistently poor in dermatan sulphate, as compared to that of normal cultures.     

ISOLATION AND CHARACTERIZATION OF GLYCOSAMINOGLYCANS FROM BRAIN OF CHILDREN WITH PROTEIN-CALORIE MALNUTRITION

Abstract— The uronic acid containing glycosaminoglycans (GAGs) were isolated from the brains of 1-year-old and 4-year-old kwashiorkor children and characterised by constituent analyses. A marked reduction is the total GAG concentration of brain was noticed in both cases of kwashiorkor. In the 1-year-old kwashiorkor brain, hyaluronic acid is the most predominant GAG (73.5 per cent) whereas heparan sulphate, chondroitin sulphates and low sulphated chondroitin sulphate constituted less than 10 per cent. In the 4-year-old kwashiorkor brain, the proportion of hyaluronic acid was 27.5 per cent, low sulphated chondroitin sulphate 31.2 per cent, chondroitin sulphates 28.3 per cent and heparan sulphate 10 per cent. This marked reduction in the concentration as well as qualitative changes in GAG in protein-calorie malnutrition as compared to the normal is discussed in relation to brain function.     

Glycosaminoglycans in early chick embryo

The developmental profile of glycosaminoglycans (GAGs) were examined by cellulose acetate electrophoresis and high performance liquid chromatography in the early chick embryo from late blastula (stage XIII+) to early somite developmental stages (stage HH7-9). Sulphated GAGs were present from the earliest stages. They were more abundant than the non-sulphated forms and showed stage-related changes. Chondroitin sulphate and especially dermatan sulphate appeared to be the predominant GAGs in embryos at stage XIII+. Dermatan sulphate was about three times as abundant as chondroitin sulphate at stage XII+. In contrast, embryos at the definitive streak stage (stage HH4) produced about twice as much chondroitin sulphate as dermatan sulphate. At the head process stage (stage HH5), the level of chondroitin sulphate was reduced and its relative content in the embryo was about the same as dermatan sulphate. Levels of dermatan sulphate were more than five times those of heparan sulphate from stage XIII through to stage HH5 and three times more at stage HH7-9. The 4- and 6- sulphation of chondroitin sulphate increased 14- and 10-fold respectively, from stage XIII+ to stage HH 7-9. The sulphation pattern of chondroitin sulphate had a delta(di)-4S:delta(di)-6S molar ratio ranging from 4 to 8:1 and a delta(di)-4S:delta(di)-OS molar ratio ranging from 9 to 16:1 and was developmentally regulated. Thus, chondroitin sulphate in the early chick embryo was sulphated predominately in the 4-position in all stages studied. The presence of both 4- and 6-sulphated disaccharides in chondroitin sulphate indicated that both 4 and 6 sulfotransferases were active in the early embryo. Hyaluronate and sulphated GAG content increased markedly at gastrulation when the first major cellular migrations and tissue interactions begin.     

Release of diamine oxidase into plasma by glycosaminoglycans in rats

Plasma diamine oxidase (DAO) values are enhanced by intravenous injection of heparin which releases the enzyme, synthesized in small bowel enterocytes, from binding sites located on endothelial cells of the intestinal microvasculature. Intestinal DAO, in analogy with lipoprotein lipase (another heparin-released enzyme), is believed to be electrostatically linked to endothelial binding sites composed of a glycosaminoglycan (GAG) which is presumably heparan sulphate, but the complete mechanism of enzyme release is not known. In this study we assayed in rats the DAO-releasing capability of heparan sulphate, dermatan sulphate, chondroitin sulphate A and hyaluronic acid, all heparin related compounds. Heparan sulphate, a compound with the same hexosamine as heparin but with a lower concentration of sulphated iduronic acid, induced a very high release of DAO (3-fold less than heparin), while the other tested GAGs, composed of higher proportions of non sulphated uronic acid and with galactosamine instead of glucosamine, induced a significantly lower release. In rats treated with 60 mg heparan sulphate the significant decrease in ileal mucosal DAO activity indicates that, in analogy with heparin, the high plasma enzymatic activity induced is of enterocytic origin. It is suggested that the high charge density of the compounds tested, due to the degree of sulphatation, is the decisive factor in promoting the release of intestinal DAO.     

Changes in the morphology and synthetic activity of cultured rat tail tendon

Summary Isolated single fascicles from tail tendons of young rats were freed of epitenon cells and cultured in vitro for up to 7 days. The tissue remained viable, as judged by the structural integrity of cell organelles and the ability to synthesize DNA and glycosaminoglycans (GAG). The rate of DNA synthesis peaked after 2 days in culture and decreased slowly thereafter. Concomitantly, an increase in cell number was noted at the periphery of the fascicle. GAG production also increased during culture, sulphated GAG being increased proportionately more than hyaluronic acid. Dermatan sulphate was the predominant sulphated GAG in freshly isolated fascicles, but in cultured tissue, the newly synthesized sulphated GAG was more sensitive to degradation by chondroitinase AC and had an increased electrophoretic mobility. Fine structural changes were observed in cultured tissues such as the retraction of cell processes. rounding up of cell bodies and the appearance of gaps between collagen fibrils. Cultured tenocytes also frequently contained apparently phagocytized collagen fibrils which were not seen in freshly isolated fascicles, and this appearance was suggestive of collagen degradation occurring in vitro, although no change in the total hydroxyproline content was noted. The data show that when individual fascicles are cultured in vitro they undergo a process of matrix remodelling which has features in common with events occurring in vivo when tendons have been surgically manipulated.     

Flow cytometric measurements and electron microscopy of cell surface glycosaminoglycans using Acridine Orange

Summary Cell surface glycosaminoglycans (GAGs) were measured, after various treatments, by their binding to Acridine Organge using flow cytometry. Using a critical electrolyte concentration and combining it with specific degradation of individual GAG elements, it was found possible to differentiate between GAG components. The technique was adapted for electron microscopy level to reveal characteristics of membrane-associated GAG. By this means, the cell membrane of the human leukaemic cell line K562 was shown to contain a large amount of GAG; 75% of it was highly sulphated GAG, mostly heparan sulphate. This component was evenly distributed in the outer plasma membrane layer. In the presence of other GAGs, the appearance of complex proteoglycan granules was detected.     

The biosynthesis of sulphogalactosyldiacylglycerol of rat brain in vitro

Triton X-100 extracts of rat brain microsomal fraction catalyse the formation of sulphogalactosyldiacylglycerol from galactosyldiacylglycerol and adenosine 3'-phosphate 5'-sulphatophosphate. Of the various subcellular fractions of brain assayed, the microsomal fraction contained most (79%) of the adenosine 3'-phosphate 5'-sulphatophosphate-galactosyldiacylglycerol sulphotransferase activity. The enzyme activity was stimulated by Triton X-100 and showed linearity with increasing time, concentrations of enzyme and added substrates. ATP and KF prolonged the linearity of the activity with time, but ATP had an overall inhibitory effect on the sulphotransferase. Both ATP and KF inhibit the degradation of adenosine 3'-phosphate 5'-sulphatophosphate, which probably causes the increased linearity of the sulphotransferase reaction with time. The enzyme preparation did not catalyse the transfer of sulphate from adenosine 3'-phosphate 5'-sulphatophosphate to either cholesterol or galabiosyldiacylglycerol (galactosylgalactosyldiacylglycerol). Significant differences between the formation of sulphogalactosyldiacylglycerol and cerebroside sulphate catalysed by the same enzyme preparation were noted. ATP and Mg(2+) strongly inhibit the formation of sulphogalactosyldiacylglycerol but equally strongly stimulate the synthesis of cerebroside sulphate. The apparent K(m) for galactosyldiacylglycerol is 200mum, and that for cerebroside is 45mum. Galactosyldiacylglycerol and cerebroside are mutually inhibitory toward the synthesis of sulphated derivatives of each. These data do not necessarily lead to the conclusion that two sulphotransferases are present, but they do indicate a possible means of controlling the synthesis of these two sulpholipids.     

Biochemical studies on the sulphated glycosaminoglycan fraction of skin fibroblasts cultured from a patient with the Hurler syndrome

1. The metabolism of the sulphated glycosaminoglycan fraction in cultured skin fibroblasts derived from a patient with the Hurler syndrome and from a normal subject was studied. Two labelled precursors, Na(2) (35)SO(4) and d-[2-(3)H]glucose, were used and their intracellular fates during uptake and ;chase' periods were assessed after separation of sulphated glycosaminoglycans from hyaluronic acid. After 4 or 8h of exposure to culture medium containing both labels, [(35)S]sulphate incorporation into the sulphated glycosaminoglycan fraction was twofold greater in Hurler-syndrome cells than in normal cells. At the same time, the rate of incorporation of [(3)H]glucose into the sulphated glycosaminoglycan fraction was approximately the same for both cell types. Consequently, an increased (35)S/(3)H ratio (nmol of [(35)S]sulphate incorporated/nmol of [(3)H]glucose incorporated) was observed for Hurler-syndrome cells compared with normal cells. 2. The results of ;chase' experiments revealed that although the expected loss and relative retention of labelled sulphate occurred in the sulphated glycosaminoglycan fraction of normal and Hurler-syndrome cells, both cell types retained all of their radioactivity derived from [(3)H]glucose. 3. After 34h exposure to a ;corrective-factor' preparation from urine, the sulphated glycosaminoglycan content (as hexosamine and [(35)S]sulphate) of the Hurler-syndrome cells approached normal values. At the same time, there was an increase in specific radioactivity of ;corrected' Hurler-syndrome cells.     

The comparative chemical morphology of the mammalian cornea

A simple model of mammalian corneal stroma has been tested against biochemical and ultrastructural measurements performed on a number of species. Contents of water, collagen and total sulphated polyanion were constant, as predicted from the model. Alcian blue CEC results showed great variability between species, with a rise in CEC as corneal size and thickness increased. These variations were due to changes in keratan sulphate content, and particularly to its oversulphated terminal domain, which is absent from mouse cornea. The increase in keratan sulphate content with corneal thickness was balanced by an increase in dermatan sulphate in thin corneas, thus maintaining total sulphated GAG levels at a constant "average", in all the mammals investigated. This balance is probably decided by oxygen tension, which will vary with corneal thickness.     

Lipid changes in central nervous system membranes in experimental allergic encephalomyelitis (EAE)

Lipid composition of myelin fractions isolated from Lewis rats during the early stage of the development of experimental allergic encephalomyelitis (EAE) were determined by high-performance thin layer chromatography (HPTLC). When comparing the myelin fractions of EAE-affected animals with those of controls, the main differences were observed in the light fraction, where a decrease in the percentage of phospholipids (PH) relative to the total lipids was observed. These findings give further support that the light myelin fraction being the most sensitive at the onset of clinical symptoms must play a key role in demyelinating process.Abbreviations used EAE experimental allergic encephalomyelitis - PH phospholipids - CH cholesterol - GL galactolipid - PE phosphatidylethanolamine - SPM sphingomyelin - PC phosphatidylcholine - PS phosphatidylserine - PI phosphatidylinositol - CB cerebroside - CB-OH hydroxy-cerebroside - SULF sulfatides - BP basic proteins     

Ultrastructural localization of keratinocyte surface associated heparan sulphate proteoglycans in human epidermis

Fixation and staining procedures were developed for the electron microscopic demonstration of glycosaminoglycans (GAGs) in human epidermis. En bloc staining with cuprolinic blue (CB), ruthenium red (RR) and tannic acid (TA) in the primary fixative were applied for the localization of the GAGs. Removal of the epidermal basal lamina and underlying dermis was a prerequisite for stain penetration. In CB-fixed specimens 50 nm long, rod-like granules were found attached to keratinocyte cell surfaces, while the RR- and TA-fixed specimens contained round granules (luminal diameter 10 and 30 nm, respectively). The stainability of the CB-positive granules in the presence of 0.3 mol/l MgCl2 indicated that they contained sulphated GAGs. Prefixation digestions of epidermal sheets with chondroitinase ABC. Streptomyces hyaluronidase, and heparitinase showed that the RR-positive granules also contained sulphated GAGs, mostly heparan sulphate. The granules visualized with TA on keratinocytes were susceptible to heparitinase treatment, but the abundance of TA-staining suggested that TA also stained structures other than heparan sulphate. The EM data was in accordance with the 35SO4 labelling experiments showing that heparan sulphate was the major sulphated GAG synthesized in epidermis, whereas chondroitin/dermatan sulphates comprised about one fifth of the total activity incorporated. The distributions of the CB-, RR- and TA-positive granules on cell surfaces were similar. The morphology of the proteoglycan granules was probably determined by the extent of the GAG-chain collapse following binding to each of the dyes.     

Comparison of the cerebroside sulphatase and the arylsulphatase activity of human sulphatase A in the absence of activators.

A cerebroside sulphatase (cerebroside-3-sulphate 3 sulphohydrolase, EC 3.1.6.8) assay based on radio thin-layer chromatography is described. The substrate was labelled by the catalytic addition of tritium to cerebroside sulphate. Using this assay the cerebroside sulphatase activity of sulphatase A (Aryl-sulphate sulphohydrolase, EC 3.1.6.1) from human liver and kidney in the absence of activators was investigated. The pH optimum of this reaction depends on the buffer concentration, being pH 4.5 at 50 mM and 5.3 at 10 mM sodium formate. With the latter concentration the apparent Km for cerebroside sulphate is 0.06 mM; SO2-4 and nitrocatechol sulphate inhibit noncompetitively with a Ki of 4.51 mM for Na2SO4 and 0.43 mM for nitrocatechol sulphate. The cerebroside sulphatase activity of sulphatase A is highly dependent on the ionic strength. The optimum sodium formate concentration is 10 mM, and the cerebroside suophatase activity decreases rapidly with increasing buffer concentration. The same concentration dependence is observed in the inhibitory effect of cerebroside sulphate on the arylsulphatase reaction. The inhibition decreases at increasing buffer concentrations, becoming an activation at 70 mM sodium formate. The progress curve of the cerebroside sulphatase reaction shows a deviation from linearity similar to that of the arylsulphatase reaction. Investigation of the effect of preincubation with cerebroside sulphate on the arylsulphatase activity of the enzyme shows that cerebroside sluphatase activity and inactivation of the enzyme by cerebroside sulphate occur simultaneously. These observations are interpreted as supporting the assumption that cerebroside suophate and arylsulphates are degraded at an identical active site on the same enzyme. Differences in the properties of the cerebroside sulphatase and the arylsulphatase reaction of the enzyme may be attributed to the differences in the physiocochemical state of the two substrates.     

Isolation of heparan sulfate proteoglycan from beneath the monolayers of rat hepatocytes and its binding to type IV collagen

Primary cultures of rat hepatocytes maintained as monolayer in a serum-free medium synthesise and secrete sulphated proteoglycans. Nearly 5% of the total 35(S)-sulphated material was obtained in a soluble form from beneath the cell layer. A shift in gel filtration pattern on beta-elimination with alkali suggested that it is a sulphated proteoglycan. On ion exchange chromatography over Dowex AG 1 x 2, the major fraction was eluted with 1.25 M NaCl. Further, nearly 80% of the 35(S)-labeled material was susceptible to nitrous acid degradation and more than 90% of the material was resistant to chondroitinase ABC digestion suggesting that it is predominantly a heparan sulphate proteoglycan (HSPG). Since HSPG is a major component of basement membrane, its binding with collagen was studied by a solid phase binding assay. About 75% of the 35(S) HSPG bound to wells coated with type IV collagen whereas only about 20% bound to type I collagen at physiological pH. Binding to collagen IV was reduced by about 50% when free GAG chains were used indicating that the protein core is also involved in interaction with the collagen. These results indicate the possible role of this basal extracellular heparan sulphate proteoglycan in the basal lamina formation.     

Brain and Spinal Cord Levels of Histamine in Lewis Rats with Acute Experimental Autoimmune Encephalomyelitis

Acute experimental autoimmune encephalomyelitis (EAE) was induced in Lewis rats by inoculation with guinea pig spinal cord homogenate emulsified with Mycobacterium tuberculosis-enriched complete Freund's adjuvant (CFA). Control rats were inoculated with CFA alone. Control and EAE rats were killed on days 7, 9, 11, and 13 postinoculation, and regional brain and spinal cord levels of histamine were determined. No regional differences in histamine content between control and EAE rats were seen on day 7 or 9 postinoculation. However, depending on the region, EAE rats exhibited significantly higher levels of histamine in their CNS on day 11 or 13 postinoculation or on both. Thus, regionally and temporally specific increases in brain and spinal cord levels of histamine develop concomitant with or just after the appearance (on day 10 postinoculation) of clinical signs of acute EAE, a finding suggesting that histamine may be involved in the development or expression of acute EAE in Lewis rats.     

Urinary excretion of sulphated N-acetylhexosamines in patients with various mucopolysaccharidoses.

Sulphated N-acetylhexosamines have been isolated from human urine and tentatively identified as N-acetylglucosamine 6-sulphate (GlcNAc6S), N-acetylgalactosamine 6-sulphate (GalNAc6S), N-acetylgalactosamine 4-sulphate (GalNAc4S) and N-acetylgalactosamine 4,6-disulphate (GalNAc4,6diS). Urine from mucopolysaccharidosis-Type-IIID, -IVA and -VI patients compared with that from normal individuals contains elevated levels of GlcNAc6S (380-fold), GalNAc6S (180-fold) and GalNAc4S (420-fold) respectively. Urine from mucopolysaccharidosis-Type-VI patients also contain more than 600 times the normal level of GalNAc4,6diS. Urine from a mucolipidosis-Type-II and a multiple-sulphatase-deficient patient, and, in general, all mucopolysaccharidosis patients studied, contain at least 5-10-fold elevations of sulphated N-acetylhexosamines over the levels detected in urine from normal controls and a alpha-mannosidosis patient. Urine from patients with clinically mild phenotypes contains less sulphated N-acetylhexosamines than isolated from urine of clinically severe mucopolysaccharidosis patients. The source of the four sulphated N-acetylhexosamines is not known. However, incubation of a series of oligosaccharide substrates, derived from keratan sulphate and chondroitin 6-sulphate and containing non-reducing-end beta-linked 6-sulphated N-acetylhexosamine residues, with homogenates of cultured human skin fibroblasts has indirectly been shown to release GlcNA6S and GalNAc6S respectively. Release of GalNAc4S could not be demonstrated in similar incubations of oligosaccharide substrates derived from chondroitin 4-sulphate and containing non-reducing-end beta-linked GalNAc4S residues. We propose that some, if not all, of the sulphated N-acetylhexosamine present in human urine is derived from the action of beta-N-acetylhexosaminidase on sulphated GlcNAc or GalNAc residues at the non-reducing end of keratan sulphate, dermatan sulphate or chondroitin sulphate.     

Ultrastructural localization of keratinocyte surface associated heparan sulphate proteoglycans in human epidermis

Summary Fixation and staining procedures were developed for the electron microscopic demonstration of glycosaminoglycans (GAGs) in human epidermis. En bloc staining with cuprolinic blue (CB), ruthenium red (RR) and tannic acid (TA) in the primary fixative were applied for the localization of the GAGs. Removal of the epidermal basal lamina and underlying dermis was a prerequisite for stain penetration. In CB-fixed specimens 50 nm long, rod-like granules were found attached to keratinocyte cell surfaces, while the RR- and TA-fixed specimens containd round granules ( 10 and 30 nm, respectively). The stainability of the CB-positive granules in the presence of 0.3 mol/l MgCl₂ indicated that they contained sulphated GAGs. Prefixation digestions of epidermal sheets with chondroitinase ABC, Streptomyces hyaluronidase, and heparitinase showed that the RR-positive granules also contained sulphated GAGs, mostly heparan sulphate. The granules visualized with TA on keratinocytes were susceptible to heparitinase treatment, but the abundance of TA-staining suggested that TA also stained structures other than heparan sulphate. The EM data was in accordance with the ³⁵SO₄ labelling experiments showing that heparan sulphate was the major sulphated GAG synthesized in epidermis, whereas chondroitin/ dermatan sulphates comprised about one fifth of the total activity incorporated. The distribution of the CB-, RR- and TA-positive granules on cell surfaces were similar. The morphology of the proteoglycan granules was probably determined by the extent of the GAG-chain collapse following binding to each of the dyes.     

Erythrocytes express chondroitin sulphate/dermatan sulphate, which undergoes quantitative changes during diabetes and mediate erythrocyte adhesion to extracellular matrix components

Glycosaminoglycans (GAGs) such as chondroitin sulphate/dermatan sulphate (CS/DS) are complex molecules that are widely expressed on the cell membrane and extracellular matrix (ECM). They play an important role in wide range of biological activities especially during pathological conditions. Diabetes, a metabolic disorder characterized by sustained hyperglycemia, is known to affect GAGs in different tissues and affect erythrocyte adhesion. The present investigation was aimed at exploring the nature of GAGs present in erythrocytes and its role on adhesion of erythrocytes from control and diabetic rats to major extracellular matrix components. GAGs isolated from erythrocytes were demonstrated to be CS/DS and a 2-fold increase was observed in erythrocytes from diabetic rats. Disaccharide composition analysis by HPLC after depolymerization by the enzyme, chondroitinase ABC showed the presence of 4-O sulphated disaccharide units with small amounts of non-sulphated disaccharides, in both control and diabetic erythrocytes. Erythrocytes from diabetic rats, however, showed significantly increased binding to poly-l-ornithine (P-orn), type IV collagen, laminin and fibronectin, which was abrogated on treatment with chondroitinase ABC to various degrees. This study sheds new light on CS/DS in erythrocytes and its likely biological implications in vivo.     

Extracellular matrix components in uterine leiomyoma and their alteration during the tumour growth

It was found that both normal human myometrium and uterine leiomyoma contain several glycosaminoglycans. In contrast to many normal and tumour tissues the amount of hyaluronic acid is very low and the proportional amount of sulphated glycosaminoglycans is distinctly higher. It is of interest that heparan sulphate is the major glycosaminoglycan component both in normal myometrium, and in leiomyoma. The amount of hyaluronic acid in myometrium and in the leiomyoma is very low. No significant change in hyaluronate content was observed during the tumour growth. In contrast to that the amount of some sulphated glycosaminoglycans (heparan sulphate, keratan sulphate, chondroitin sulphates and heparin) distinctly increased. It is suggested that some of the GAGs participate in the creation of a storage depot for biologically active molecules (growth factors, enzymes) which are thereby stabilized and protected. Hydrolytic degradation of some GAGs may result in the release of some cytokines which may promote the tumour growth and stimulate collagen biosynthesis by tumour cells.     

PHOSPHOLIPID METABOLISM IN EXPERIMENTAL ALLERGIC ENCEPHALOMYELITIS: ACTIVITY OF MITOCHONDRIAL PHOSPHOLIPASE A2 OF RAT BRAIN TOWARDS SPECIFICALLY LABELLED 1,2-DIACYL-, 1-ALK-1''-ENYL-2-ACYL- AND 1-ALKYL-2-ACYL-SN-GLYCERO- 3-PHOSPHORYLCHOLINE

—1,2-Diacyl-, 1-alk-1′-enyl-2-acyl-and 1-alkyl-2-acyl-sn-glycero-3-phosphorylcholine, specifically labelled with different fatty acids at the 2 position, were prepared enzymically using the acyltransferase system of rabbit sarcoplasmic reticulum. The substrates were submitted to hydrolysis by mitochondrial phospholipase A₂ (phosphatide acyl-hydrolase, EC 3.1.1.4) obtained from normal and from rat brain afflicted with EAE. In the acute stage of the disease an increase of approximately 25 per cent in phospholipase A ₂ activity could be observed in comparison to that from the control animals for all investigated substrates. Phospholipase A₂ obtained from normal rat brains and from those afflicted with EAE had a higher affinity for 1,2-diacyl-sn-glycero-3-phosphorylcholine when compared to the corresponding alkyl acyl- and alkenyl acyl-analogues. Choline plasmalogen was cleaved more slowly than the corresponding alkyl acyl derivative. The enzyme activity returned to the control level in the recovery stage of the demyelinating disease.