Lipid composition in ganglia of Mollusca

Why Is N-Glycolylneuraminic Acid Rare in the Vertebrate Brain?

The sialic acids N-acetylneuraminic acid (Neu5Ac) and N-glycolylneuraminic acid (Neu5Gc) differ by a single oxygen atom and are widely found at the terminal position of glycans on vertebrate cell surfaces. In animals capable of synthesizing Neu5Gc, most tissues and cell types express both sialic acids, in proportions that vary between species. However, it has long been noted that Neu5Gc is consistently expressed at trace to absent levels in the brains of all vertebrates studied to date. Although several reports have claimed to find low levels of Neu5Gc-containing glycans in neural tissue, no study definitively excludes the possibility of contamination with glycans from non-neural cell types. This distribution of a molecule - prominently but variably expressed in extraneural tissues but very low or absent in the brain - is, to our knowledge, unique. The evolutionarily conserved brain-specific suppression of Neu5Gc may indicate that its presence is toxic to this organ; however, no studies to date have directly addressed this very interesting question. Here we provide a historical background to this issue and discuss potential mechanisms causing the suppression of Neu5Gc expression in brain tissue, as well as mechanisms by which Neu5Gc may exert the presumed toxicity. Finally, we discuss future approaches towards understanding the mechanisms and implications of this unusual finding.

Arylsulphatase A activity and sulphatide concentration in placenta, membranes and cord after delivery

AIM

We evaluated variations in behavior of arylsulphatase A activity (an enzyme that catabolizes sulphatides) and of sulphatide concentration in the placenta, cord and membranes of healthy gravidas at term pregnancy, following spontaneous birth.

METHODS

We extracted and biochemically determined arylsulphatase A and sulphatide concentration in placenta, cord and membranes (far from and close to internal uterine os) in 14 patients.

RESULTS

Activity of arylsulphatase A decreased in the cord, in membranes far from the internal uterine os, in membranes close to the internal uterine os and in the placenta. Sulphatide concentration was minimal in the cord and maximal in placenta, with intermediate values in the membranes. No correlation was found between arylsulphatase A activity and sulphatide concentration, nor among arylsulphatase A activities, nor among sulphatide concentrations among the different tissues. It seems that multiparity may increase and the duration of active labor may decrease arylsulphatase A activity in membranes far from the internal uterine os, while active labor duration does not appear to have any implication on sulphatide concentration in membranes close to the internal uterine os.

CONCLUSIONS

Arylsulphatase A activities and sulphatide concentrations in fetal adnexa show significant differences.

Biochemical determinations of arylsulphatase A activity and sulphatide concentrations in decidua of women at 41 and 42 weeks of gestation

OBJECTIVE

To evaluate arylsulphatase A activity and sulphatide concentrations in decidua of women at 41 and 42 weeks of gestation.

STUDY DESIGN

Enzyme activity and sulphatide concentrations were determined by biochemical procedures on samples of women at 41 and 42 weeks of gestation; thin-layer chromatography was also prepared to separate and visualize sulphatides and other lipid fractions.

RESULTS

The spectrophotometric values of arylsulphatase A showed very low values at 41 weeks, which reduced to a half at 42 weeks of gestation, while values of sulphatide concentrations increased in 42 weeks.

CONCLUSIONS

The behavior of two parameters examined could be due to the amount of placental estriol reduction, because of sudden placental aging.

Sulfatides and arylsulfatase A activity in major salivary glands of hamster (Mesocricetus auratus) after adenocarcinoma induction in oral cavity

A biochemical study of sulfatides and arylsulfatase A (ASA) was carried out in the submandibular and sublingual glands of the male and female hamster Mesocricetus auratus after experimental induction of oral adenocarcinoma by 7,12-dimethylbenzanthracene (DMBA). Hamster experimental groups included control animals, animals treated with beta-carotene, animals treated with DMBA, and animals treated with DMBA plus beta-carotene. Oral cavity treatment with DMBA induced carcinogenesis in the buccal mucosa, but not in the major salivary glands, where nevertheless, the morphology and expression of both parameters examined changed. In fact, sulfatide concentrations and enzyme activity increased significantly, while in control and beta-carotene-treated hamsters they were similar in both glands and sexes. After administration of DMBA plus beta-carotene, sulfatide concentration decreased, as did ASA activity, slightly in the submandibular gland and remarkably so in the sublingual one of female hamsters. Thin-layer chromatography (TLC) analysis of lipid patterns, after DMBA treatment, revealed considerable differences, not only in sulfatides, but also in other lipid fractions, as well as between the two glands and two sexes. These findings show that oral cavity treatment with DMBA is not able to induce carcinogenesis in the major salivary glands examined; however, it does cause considerable metabolic changes.

Sulphatides in the brain of spontaneously hypertensive rats

Sulphatides were assayed in preparations of frontal cortex, neostriatum and hippocampus of 6-month-old male spontaneously hypertensive rats (SHR, systolic pressure 215 +/- 6 mmHg) and age-matched normotensive Wistar-Kyoto (WKY) rats (systolic pressure 143 +/- 6 mmHg) by thin layer chromatography associated with spectrophotometry and histochemistry. The volume of gray and white matter of the above areas was also measured by microanatomical techniques associated with image analysis. Sulphatide levels were unchanged in the frontal cortex and neostriatum and decreased in the hippocampus of SHR in comparison with WKY rats. No changes of metachromatic sulphatide staining were found in the different brain areas investigated of SHR, whereas a decrease of positive metachromatic areas was noticeable in the frontal cortex and neostriatum, but not in the hippocampus of SHR. A reduction of volume of frontal cortex gray and white matter as well as of striosomes and of gray matter of hippocampus was found in SHR. No changes in the total volume of neostriatum and in the volume of white matter of hippocampus were observed between SHR and normotensive WKY rats. These findings, which are consistent with recent evidence of the occurrence of atrophic changes in the brain of SHR, showed that sulphatide levels were decreased in the hippocampus of SHR. In this area no reduction of white matter was observed. Sulphatide concentrations are thought to reflect the status of brain myelinated fibers. The not parallel decrease of sulphatide levels and white matter volume in the majority of brain areas investigated suggests the occurrence in SHR of sulphatide changes not corresponding simply to a reduction of myelinated pathways.

Arylsulphatase A activity and sulphatide concentration in the female rabbit oviduct are under physiological hormonal influence

Oviduct samples of female rabbits in different phases of the reproductive cycle were analysed to establish the role of sex steroid hormones in the regulation of sulphatide concentration and arylsulphatase A activity. In addition to biochemical procedures, histochemical techniques were used to localize both enzyme activity and the natural substrate. The plasma concentrations of progesterone and 17 beta-oestradiol were determined by radioimmunoassay (RIA). The findings show that the parameters examined undergo considerable changes during the different phases of the reproductive cycle. Oestrogens exert an inducing action on arylsulphatase A activity, while progesterone inhibits it. Fluctuations of the catabolic arylsulphatase activity condition the sulphatide concentration, which reaches maximum values at the eighth post-ovulatory day when progesterone dominance is consolidated. In this phase of the reproductive cycle, thin-layer chromatography confirms the presence not only of larger quantities of sulphatides, but also of all other lipid fractions.

Expression of acidic glycosphingolipids and arylsulphatase A activity in human pathological endometrium

Endometrium biopsic samples from women with cystic hyperplasia or adenocarcinoma were analysed by biochemical procedures to verify fluctuations in the acidic glycosphingolipid (sulphatide) concentration and arylsulphatase A (ASA) activity. Comparing the values of the considered parameters with those obtained in normal subjects, it was observed that ASA activity significantly increased in both pathologies; in contrast, sulphatide concentration underwent a non-significant decrease in hyperplasia and a statistically significant increase in neoplasia. The thin-layer chromatography (TLC) images revealed not only quantitative, but also qualitative differences in the lipid fractions. In fact, compared with controls, the sulphatides showed one more marked fraction in the neoplastic endometrium, and two fractions with different Rf values in the hyperplastic one. Moreover, two new unknown fractions also appeared in some subjects with cystic hyperplasia. The findings suggest the lipid metabolism undergoes considerable changes under the pathological conditions examined. The fluctuations observed, in particular, in the sulphatide concentration are believed to be related to changes in the biosynthetic and catabolic activities of the key enzymes directly involved in their metabolism, i.e. arylsulphatase A and sulphotransferase, which are regulated by sex hormones.

Identification of muramyl derivatives in Mollusca Gastropoda tissue

Previous findings have demonstrated the presence of muramic acid and the lack of sialic acid in gastropod glycoconjugates from different tissues. The present study investigated the composition of muramyl derivatives in Mollusca Gastropoda tissue from the foot, mantle and periesophageal ganglia, using HRP-labeled lectins (LTA, UEA I, GSA IB4, GSA II, DBA, SBA, RCA II, WGA, PNA, ConA) and glycosidase digestion (neuraminidase, lysozyme, alpha-L-fucosidase, beta-N-acetylglucosaminidase, alpha-N-acetylgalactosaminidase). Muramyl derivatives from the tissue examined showed some differences related to the composition of the terminal disaccharides. Indeed, foot and mantle mucocytes exhibited muramic acid in a terminal position, linked to (subterminal) N-acetylgalactosamine, whereas in neuron cells muramic acid was present in an internal position and linked to N-acetylglucosamine. Diversities also occurred between foot and mantle mucocytes with respect to the receptor sugar for penultimate N-acetylgalactosamine.

N-acetylmuramic acid in Mollusca Gastropoda: a histochemical and immunocytochemical study

The presence of N-acetylmuramic acid in glycoconjugates in various mollusc tissues was investigated by histochemical and immunocytochemical techniques. The tissues studied included foot, mantle, digestive gland, ganglia and haemocytes of Helix aspersa, Planorbarius corneus, Murex brandaris and Trunculariposis trunculus. Sialic acid residues were found to be absent. The possibility that N-acetylmuramic acid replaces sialic acid in acid glycoconjugates of gastropods with similar properties is discussed.

Changes induced by progesterone treatment in the sulphatides of the frog oviduct

Sulphatides have been studied by histochemical and biochemical procedures in the oviduct of the frog in different experimental conditions. In ovariectomized or hypophysectomized animals, compared to sham-operated, an increase in sulphatides was observed. The progesterone treatment did not significantly modify this lipid fraction in ovariectomized frogs, while in hypophysectomized frogs it induced a further increase. Densitographic profiles of the sulphatides, obtained by thin-layer chromatography (TLC) and also recorded by Tesak equipment, were similar in ovariectomized or hypophysectomized frogs following hormone treatment because they showed three distinct fractions in both experimental groups of animals. The appearance of a third fraction never previously observed was probably induced by the progesterone treatment. Moreover, under the effects of this hormone, the phospholipid fractions (phosphatidylcholine and phosphatidylethanolamine) also showed different densitographic profiles.

Sialic acid and neuraminidase activity in the frog oviduct: comparative biochemical investigation in the different tracts during the reproductive cycle

1. A biochemical study was carried out on the protein-bound and lipid-bound sialic acid, and neuraminidase activity in the different tracts of the oviduct of the frog Rana esculenta during the reproductive cycle. 2. Plasma sexual steroids were also investigated by RIA. 3. Fluctuations in neuraminidase activity are related to that of glycoprotein sialic acid and plasma estradiol. Glycolipid sialic acid does not have a close relationship either with neuraminidase or plasma estradiol. 4. Very high plasma concentration of progesterone before ovulation and, on the contrary, its drop after ovulation were observed. 5. The results are discussed and hypotheses advanced to explain fluctuations of the studied parameters during the reproductive cycle.

Immunodetection of haemocyte subpopulations by N-acetylmuramic acid antibody in Planorbarius corneus (L.) (Gastropoda, Pulmonata)

The cell subpopulations in the haemolymph of Planorbarius corneus were distinguished by means of flow cytometry. An antibody against N-acetylmuramic acid was prepared and used as a cellular marker to recognize the cell types forming the subpopulations. The spreading haemocytes showed a positive reaction for anti-N-acetylmuramic acid; round haemocytes gave a negative reaction.

Age-related changes in the function of somatic membrane potassium channels of neurons in the mollusc Lymnaea stagnalis

The function of the membrane potassium channels of the identified neurons of the small parietal ganglion was investigated in the adult (10-12-month) and old (22-24-month) molluscs Lymnaea stagnalis. Old molluscan neurons showed a decrease in maximal amplitude of fast and delayed potassium currents, in maximal potassium conductance, and in kinetics of inactivation of the delayed outward current. These features may be conditioned by the age changes in phospholipid composition of the membranes, rather than by the shifts of neuronal surface area during aging. Age dynamics in the function of potassium channels is thought to cause changes in the neuronal function.

Lectin binding to neurosecretory cells of Helicella virgata (Gastropoda, Pulmonata)

The neurosecretory cells of Helicella virgata, irrespective of specific neurosecretory activity, react in the same manner against each lectin (concanavalin A, soybean agglutinin, Pisum sativum agglutinin, Ricinus communis agglutinin I, wheat germ agglutinin, Ulex europaeus agglutinin I), but with different intensity. The possible neuromodulatory function is discussed in relation to surface reactivity to lectins.

Arylsulphatase activity and cerebroside sulphates in the frog oviduct during the reproductive cycle

The presence of arylsulphatase A and cerebroside sulphates in different tracts of Rana esculenta oviduct during different phases of the reproductive cycle were investigated by histochemical and biochemical procedures. The results indicate that enzyme activity shows seasonal fluctuations connected with the phase of the sexual cycle. The concentrations of cerebroside sulphates (the natural substrates of arylsulphatase A) is related to the activity of this hydrolytic enzyme. The role of arylsulphatase A activity in regulating the substrate concentration, and particularly that of sulphatides, is discussed.

Surface charge of mammalian neurones as revealed by microelectrophoresis

The surface charge of isolated rat dorsal root ganglion neurones was studied by microelectrophoresis technique. The increase of Ca concentration caused greater reduction of the electrophoretic mobility compared to that produced by an equivalent amount of divalent organic cations, dimethonium or hexamethonium. No charge reversal for Ca concentrations up to 80 mM was observed. These data fit the suggestion that two anion groups of the outer membrane surface can bind one Ca ion with apparent binding constant of about 50 M-1. In solutions of low pH the electrophoretic mobility of cells decreased corresponding to titration of acidic groups with apparent pK = 4.2. Trypsin treatment in mild conditions markedly reduced the surface charge; however, neuraminidase and hyaluronidase did not change it. N-bromosuccinimide (a specific reagent for carboxylic groups of proteins) decreased the electrophoretic mobility about 60%. However, no increase of the surface charge after the action of specific reagents for amino groups (2,4,6-trinitrobenzene-sulfonic acid and maleic anhydride) was observed. It was shown that the surface charge depends also on the intracellular metabolism. If 1 mM dibutyryl cAMP or theophilline was added to the culture medium (thus, raising the concentration of cAMP inside the cell) the surface charge increased. This effect developed slowly and reached its maximum on the third day of incubation. Treatment of cells by 5 mM tolbutamide (an inhibitor of some protein kinases) did not change cell mobility. Addition of 5 mM N-ethylmaleimide (an inhibitor of adenylate cyclase) to the culture medium produced some decrease of the surface charge.(ABSTRACT TRUNCATED AT 250 WORDS)

Lipids of nervous tissue: composition and metabolism

As indicated in the Introduction, the many significant developments in the recent past in our knowledge of the lipids of the nervous system have been collated in this article. That there is a sustained interest in this field is evident from the rather long bibliography which is itself selective. Obviously, it is not possible to summarize a review in which the chemistry, distribution and metabolism of a great variety of lipids have been discussed. However, from the progress of research, some general conclusions may be drawn. The period of discovery of new lipids in the nervous system appears to be over. All the major lipid components have been discovered and a great deal is now known about their structure and metabolism. Analytical data on the lipid composition of the CNS are available for a number of species and such data on the major areas of the brain are also at hand but information on the various subregions is meagre. Such investigations may yet provide clues to the role of lipids in brain function. Compared to CNS, information on PNS is less adequate. Further research on PNS would be worthwhile as it is amenable for experimental manipulation and complex mechanisms such as myelination can be investigated in this tissue. There are reports correlating lipid constituents with the increased complexity in the organization of the nervous system during evolution. This line of investigation may prove useful. The basic aim of research on the lipids of the nervous tissue is to unravel their functional significance. Most of the hydrophobic moieties of the nervous tissue lipids are comprised of very long chain, highly unsaturated and in some cases hydroxylated residues, and recent studies have shown that each lipid class contains characteristic molecular species. Their contribution to the properties of neural membranes such as excitability remains to be elucidated. Similarly, a large proportion of the phospholipid molecules in the myelin membrane are ethanolamine plasmalogens and their importance in this membrane is not known. It is firmly established that phosphatidylinositol and possibly polyphosphoinositides are involved with events at the synapse during impulse propagation, but their precise role in molecular terms is not clear. Gangliosides, with their structural complexity and amphipathic nature, have been implicated in a number of biological events which include cellular recognition and acting as adjuncts at receptor sites. More recently, growth promoting and neuritogenic functions have been ascribed to gangliosides. These interesting properties of gangliosides wIll undoubtedly attract greater attention in the future.(ABSTRACT TRUNCATED AT 400 WORDS)

Histochemical detection of anionic components in the cephalopod brain

Brains obtained from three species of mediterranean cephalopods (Loligo, Sepia, Octopus) were fixed in Bouin's solution. Paraffin sections were cut sequentially at the frontal plane and used for Alcian blue staining (critical electrolyte concentration method), colloidal iron hydroxide staining procedure, the periodic acid Schiff's reagent method, and the lead tetra-acetate-Schiff method. The stained sections were evaluated at 2 regions of different histological composition: the palliovisceral ganglion and the optic lobe. A high concentration of anionic components was found in synaptic regions of the neuropil whereas neuronal cell bodies showed a relatively weak staining of these constituents. There was a significant reaction of the perineuronal glia nets in the cellular rind of the palliovisceral ganglion. From the comparison of staining patterns obtained with the 4 methods in this study and literature data it can be concluded that the detected anionic sites are mainly carboxyl groups of acidic proteins and/or glycoproteins. Sulphate groups may be present in lower concentrations. Their distribution reveals that the role of anionic components other than sialic acids in the invertebrate brain might be discussed in the context of synaptic transmission similar to that in vertebrates. The possible involvement of the glia cell population has to be taken into consideration.