Effects of the N-acetylgalactosaminyltransferase inhibitor on cultured cerebral cells.

The inhibitor preparation of the UDP-N-acetylgalactosamine: GM3, N-acetylgalactosaminyltransferase (EC 2.4.1.

Internalization of the inhibitor of the N-acetylgalactosaminyltransferase by chicken embryonic retina cells: reversibility of the inhibitor effects.

Retina cells from 6-day-old chicken embryos were cultured in the presence of an 125I-labeled protein inhibitor of the UDP-N-acetylgalactosamine:GM3,N-acetylgalactosaminyltransferase. The cells were labeled and did not lose the incorporated radioactivity when treated with 0.125% trypsin or 1 M NaCl at 37 degrees C for 1 hr, indicating that the iodinated inhibitor was inside the cells.

An endogenous inhibitor of N-acetylgalactosaminyltransferase inhibits retina neuron differentiation in culture.

An inhibitor of N-acetylgalactosamine:GM3, N-acetylgalactosaminyltransferase (EC 2.4.1.

Purification and characterization of an endogenous inhibitor of the sialyltransferase CMP-N-acetylneuraminate: lactosylceramide alpha 2,6-N-acetylneuraminyltransferase (EC 2.4.99.-).

The presence in the 100,000 g supernatant of rat brain homogenate of an inhibitor of the sialyltransferase has been confirmed. It is also present in chicken and bovine brain and in other rat and bovine organs. The inhibitor has been purified, a preparation with a specific activity 130-fold higher than that of the original 100,000 g supernatant of brain being obtained.

An inhibitor of the UDP-N-acetylgalactosamine:GM3, N-acetylgalactosaminyltransferase: purification and properties, and preparation of an antibody to this inhibitor.

An inhibitor of the UDP-N-acetylgalactosamine:GM3, N-acetylgalactosaminyltransferase (EC 2.4.1.

Synthesis and translocation of gangliosides and glycoproteins during urethane anesthesia.

In this work, we have studied (a) the contents of gangliosides, glycoproteins, and phospholipids of the vesicle and plasma membrane fractions from brains of anesthetized and control rats and chickens and (b) the labeling of gangliosides and glycoproteins in the retina ganglion cell layer and optic tectum of urethane-anesthetized and control chickens after intraocular injection of a labeled N-acetylneuraminic acid precursor and the distribution of the label after subcellular fractionation. We found an increase in the content of gangliosides relative to protein in the vesicle fraction of both anesthetized rats and chickens relative to their controls. Other values were not affected by anesthesia.

Optic nerve integrity is required for light to affect retina ganglion cell gangliosides.

The labeling of retina ganglion cell and optic tectum gangliosides after an intraocular injection of N-[3H]acetylmannosamine ([3H]ManNAc) is higher in chickens exposed to light than in those maintained in darkness. In the present work we studied whether the signal for the higher labeling of ganglion cells in light originates in the photoreceptor layer or comes from the nerve terminal. For this purpose the labeling of ganglion cell gangliosides was determined in light and dark in chickens with one optic nerve severed.

Regulation of ganglioside and sialoglycoprotein biosynthesis-Effect of drugs affecting membrane flow.

The labelling of gangliosides and sialoglycoproteins (SGP) after injecting intraocularly 30 ?Ci of [(3)H]ManNAc was studied in chickens that had previously received, also intraocularly, 30 or 70 nmol of monensin in 10 ?l of ethanol or 24 ?g of colchicine in 10 ?l saline. Controls received ethanol or saline only. Colchicine at doses that almost completely block the axonal transport to the optic tectum does not affect the labelling of those sialocompounds.

Posttranslational incorporation of [14C]arginine into rat brain proteins. Acceptor changes during development.

Many of the cytosolic proteins of the rat brain appear to have the capacity to incorporate L-[14C]arginine posttranslationally. Scanning of the electrophoretic pattern of the labeled proteins showed two main radioactive peaks: peak A, found in the region of proteins of MW above 200 kD, and peak B, found in the region of 33 kD. The ratio of peaks A/B tends to decrease with the age of the rats.

Inhibition of the UDP-N-acetylgalactosamine: GM3, N-acetylgalactosaminyl transferase by gangliosides.

Gangliosides in the range of 0.1-0.4 mM inhibited the UDP-N-acetylgalactosamine:GM3, N-acetylgalactosaminyl transferase (EC 2.

Ganglioside glycosyltransferase activities in the cerebral hemispheres from developing rat embryos.

The developmental patterns of three ganglioside glycosyltransferases were determined in the embryonic rat cerebral hemispheres from day 14 of gestation until birth. Considering the values of day 14 of gestation as 100%, the activity per μg of DNA at birth of the CMP-NeuAc:GM3 sialosyltransferase decreased to 40%, that of UDP-GalNAc:GM3 N-acetylgalactosaminyltransferase increased to 230% and that of UDP-Gal:GM2 galactosyltransferase showed minor variations. The changes in the activities of these enzymes correlated with the changes occurring in this embryonic period in the complexity of the oligosaccharide chain of gangliosides which result in a relative increase of gangliosides having the gangliotetraosyl backbone.

Short term labeling of proteins, gangliosides and glycoproteins of the optic tract of chickens exposed to light or darkness.

In contrast with previous findings of the labeling of the glycosidic moieties of the gangliosides and glycoproteins in chickens injected with N-[ (3)H ] acetylmannosamine , the labeling of the ganglion cell layer and optic tectum proteins of chicks exposed to light after an intraocular injection of [(3)H]proline showed no differences with those of their counterpart chickens that remained in darkness. The same failure in finding a difference was met when the cytosolic or the particulate proteins or the acid soluble fraction in the retina were compared. Cycloheximide and puromycin inhibited the labeling of retina and optic tectum proteins, gangliosides and glycoproteins in both illumination conditions.

Inhibition of brain tubulinyl-tyrosine carboxypeptidase by endogenous proteins.

When a 25-50% ammonium-sulphate-insoluble fraction from a bovine brain preparation was chromatographed on a cellulose phosphate column, several protein fractions which inhibit the activity of tubulinyl-tyrosine carboxypeptidase were obtained. One of these fractions exhibited activity of fructose-bisphosphate aldolase (EC 4.1.

Inhibition of the chicken retinal UDP-GaINAc:GM3, N-acetylgalactosaminyl-transferase by blood serum and by pineal gland extracts.

The effects of the pineal gland extract and blood serum on the activity of the UDP-GalNAc:GM3, N-acetylgalactosaminyltransferase (GM3:GalNAc-T) from chicken retina were studied. Both preparations have inhibitory capability on the enzyme activity. Two types of inhibitory capabilities were found: one is heat labile and decomposes UDP-GalNAc and another is heat stable.

The labeling of the retina and optic tectum gangliosides and glycoproteins of chickens in darkness or exposed to light.

Chickens that received an intraocular injection of 3H-ManNAc and were exposed to light had more labeled gangliosides in the retina ganglion cell layer and in the contralateral optic tectum than similarly treated animals that remained in darkness. The effect is not due to the turning on or off of the light. The sialyl groups of sialoglycoproteins showed similar effect but the labeling of proteins in chickens that received 3H-proline did not show significant differences.

The effect of light exposure following an intraocular injection of [3H]N-acetylmannosamine on the labeling of gangliosides and glycoproteins of retina ganglion cells and optic tectum of singly caged chickens.

Ten-day-old chickens that after a 2-day-period of adaptation to dark received an intraocular injection of [3H]N-acetylamannosamine ([3H]ManNAc) and were exposed, individually housed, to light, have more labeling in the gangliosides and glycoproteins of the ganglion cell layer of retina and in the contralateral optic tectum compared to their counterparts that remained in darkness. No differences were found in the labeling of the acid soluble fraction of the ganglion cell layer between the animals in dark and light at 0.5 and 5 h after the injection of [3H]ManNAc.

Ganglioside-cholera toxin interactions: a binding and lipid monolayer study.

On t.l.c.

Enzymatic detyrosination of tubulin tyrosinated in rat brain slices and extracts.

Tubulin was tyrosinated in slices and in extracts of brain of rats of 3, 25, and 120 days of age by successive incorporation of [14C]tyrosine and [3H]tyrosine, respectively. The release of the incorporated amino acid was measured by using tubulinyl-tyrosine carboxypeptidase, carboxypeptidase A, and tubulin-tyrosine ligase. With the carboxypeptidases no differences in either the rates or the extents of the release of tyrosine between these two differently labeled tubulins were found.

Disposition of gangliosides and sialosylglycoproteins in neuronal membranes.

Labeled gangliosides and glycoproteins were obtained by incubation of homogenized neuronal perikarya from rat brain with CMP-[3H]N-acetyl neuraminic acid. The highest degree of labelling was observed in a subcellular fraction that also showed the highest specific activities for several ganglioside glycosyltransferases. The [3H]sialosylglycoconjugates of this fraction remained associated with the membranes after treatment with 1 M-KCl, 125 mM-EDTA, repeated freezing and thawing, or controlled sonication, but were solubilized by sodium deoxycholate (DOC) at a concentration high enough to solubilize the choline phospholipids.

Interaction of glycosphingolipids with melittin and myelin basis protein in monolayers.

The penetration of melittin and myelin basic protein into glycosphingolipid monolayers depends on the lipid polar head group, the protein concentration available and the initial surface pressure. The lipid-protein interaction leads to modification of the surface properties of both the glycosphingolipid and the proteins.

Inhibition of tubulinyl-tyrosine carboxypeptidase by brain soluble RNA and proteoglycan.

Rat brain extracts contain two heat-stable, nondialyzable inhibitors of tubulinyl-tyrosine carboxypeptidase. One of the inhibitors was sensitive to ribonuclease and insensitive to trypsin and pronase, indicating that the inhibitor is RNA. This is supported by the observation that purified RNA from rat brain inhibited the enzyme activity to the same extent as similar amounts of the endogenous RNA.

Configuration and interaction of the polar head group in gangliosides.

1. The interactions of gangliosides with Ca(2+) and some polar-head-group requirements for establishment of particular interactions with phosphatidylcholine were studied in monolayers at the air/145mm-NaCl interface. 2.