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PubMed2006

Immobilization of UDP-galactose 4-epimerase from Escherichia coli on the yeast cell surface.

UDP-galactose 4-epimerase (EC 5.1.3.2, Gal E) from Escherichia coli catalyzes the reversible reaction between UDP-galactose and UDP-glucose. In this study, the Gal E gene from E. coli, coding UDP-galactose 4-epimerase, was cloned into pYD1 plasmid and then transformed into Saccharomyces cerevisiae EBY100 for expression of Gal E on the cell surface. Enzyme activity analyses with EBY100 cells showed that the enzyme displayed on the yeast cell surface was very active in the conversion between UDP-Glc and UDP-Gal. It took about 3 min to reach equilibrium from UDP-galactose to UDP-glucose.

Cloning, Molecular↗
PubMed1981

Involvement of membrane galactose in the in vivo and in vitro sequestration of desialylated erythrocytes.

The influence of terminal beta-galactose residues for the in vitro and in vivo sequestration of sialidase-treated erythrocytes by macrophages was investigated. Preincubation of rat peritoneal macrophages with galactose, oligosaccharides, glycoproteins and glycolipids with terminal beta-galactose residues inhibits both binding and phagocytosis of sialidase-treated erythrocytes by masking a beta-galactose-specific lectin on the macrophage cell membrane. These inhibition studies show that binding via demasked erythrocyte surface beta-galactosyl residues to this lectin is necessary for the subsequent phagocytosis step. According to these observations, repeated injections of lactose (30mM serum concentration) and asialo-fetuin (10-30 microM serum concentration) into the blood stream of rabbits led to a reduction of the rapid sequestration rate of sialidase-treated erythrocytes. Asialo-fetuin proved to be a much more potent inhibitor than lactose, in accordance with the in vitro experiments. This inhibition is reversible, as after the disappearance of the inhibitory effect, the sialidase-treated erythrocytes were again rapidly removed from the circulation to an extent similar to that of the experiments without inhibitors. No significant influence on binding and phagocytosis was measured in the presence of sialyllactose and native fetuin in vitro, or of native fetuin on sequestration in vivo. The experiments with rabbits show that a beta-galactosyl-specific lectin seems to be involved in the mechanism of sequestration of desialylated erythrocytes in vivo, as has been observed in vitro with rat peritoneal macrophages.

Animals↗
PubMed1983

A new mass screening method for determining UDP-galactose in blood.

We devised a new microfluorometric mass screening method for determining UDP-galactose by using only one blood disc of 3 mm in diameter. This method contains two coupling enzymes of UDP-galactose-4-epimerase and UDP-glucose dehydrogenase, and conversion of NAD to NADH. The assay ranges are 0 to 1 mM or 0 to 0.2 mM UDP-galactose in blood. UDP-galactose contents were determined in galactosemia of epimerase-, transferase- and kinase-deficiencies, and several cases with high or low Paigen's values.

Galactosemias↗
PubMed1987

Galactose neuropathy. Structural changes evaluated by nuclear magnetic resonance spectroscopy.

We examined the hypothesis that the polyol accumulation resulting from chronic galactose supplementation in the diet produces endoneurial edema that can be prevented by inhibition of aldose reductase. We explored the potential of nuclear magnetic resonance (NMR) spectroscopy to quantitate and characterize the water accumulation in the sciatic nerve in this "galactose neuropathy." The data demonstrate a 16% increase in gravimetrically determined total water content of nerve in the galactose-fed rat after 8 mo of this diet and a 50% increase in the T1 relaxation time for nerve water as determined by NMR spectroscopy. Prolongation of the T1 relaxation time reflects increased rotation of water in a magnetic field, consistent with an extracellular site of the additional water. Simultaneous feeding of sorbinil to inhibit aldose reductase resulted in normalization of both total nerve water and of the prolongation of T1 relaxation time. These data define the NMR-spectroscopic state of endoneurial edema in the galactose-fed rat and suggest specific application to the investigation of the role of aldose reductase in human diabetic neuropathy.

Animals↗
PubMed1991

Restoration of Na(+)-K+ pump activity and resting membrane potential by myo-inositol supplementation in neuroblastoma cells chronically exposed to glucose or galactose.

myo-Inositol uptake by culture neuroblastoma cells at a concentration of myo-inositol less than 50 microM was largely Na+ dependent. Exposing neuroblastoma cells to media supplemented with increasing concentrations of myo-inositol resulted in an increase in myo-inositol accumulation and intracellular content, but myo-inositol incorporation into phospholipids was not increased. The data indicate that myo-inositol exists as separate pools in neuroblastoma cells, and one or more of these pools may contribute to phospholipid synthesis. Exposing neuroblastoma cells to an increased concentration of glucose caused a decrease in myo-inositol uptake by two separate mechanisms. Acute exposure of the cells to 30 mM glucose caused a myo-inositol concentration-dependent decrease in Na(+)-dependent myo-inositol uptake. We propose that the acute inhibition of myo-inositol uptake by glucose is likely due to a competitive type of inhibition. Chronic exposure of cells to media containing 30 mM glucose or 30 mM galactose also caused decreases in myo-inositol uptake and incorporation into inositol phospholipids and intracellular myo-inositol content. This decrease in myo-inositol metabolism persisted at a higher concentration of external myo-inositol than the acute inhibition. Supplementing media containing 30 mM glucose or 30 mM galactose with 250 microM myo-inositol restored myo-inositol metabolism and content. The inhibition of myo-inositol uptake by cells chronically exposed to increased concentrations of glucose or galactose was due to a noncompetitive type of inhibition that was blocked by the addition of sorbinil. Chronic exposure of neuroblastoma cells to media containing 30 mM glucose or 30 mM galactose caused a decrease in Na(+)-K(+)-ATPase transport activity and resting membrane potential.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2000

Endothelin receptor blockade prevents augmented extracellular matrix component mRNA expression and capillary basement membrane thickening in the retina of diabetic and galactose-fed rats.

Endothelins (ETs) are a family of vasoactive peptides that have mitogenic properties and have also been associated with altered long-term nuclear signaling. We have previously shown that mRNA levels for ET-1, ET-3, and their receptors are upregulated under hyperhexosemic conditions. In this study, an endothelin antagonist was used to assess the effects of endothelin blockage on the production of two basement membrane transcripts, fibronectin and collagen alpha1 (IV). The microvascular basement membranes were analyzed using ultrastructural morphometry. Streptozotocin-induced diabetic rats, galactose-fed rats (30% galactose in diet), and nondiabetic, non-galactose-fed control rats were studied after 1-month and 6-month follow-up. Simultaneously, similar animal groups were treated with a general ET receptor blocker (bosentan, 100 mg x kg(-1) x day(-1)) and investigated. Semiquantitative reverse transcription-polymerase chain reaction for fibronectin and collagen alpha1 (IV) was conducted after 1 month of follow-up with comparison to beta-actin housekeeping gene using slot blot hybridization and densitometry. Basement membrane thickness was assessed after 6 months of follow-up in diabetic rats, using the orthogonal intercept method. After 1 month of follow-up, increased fibronectin and collagen alpha1 (IV) mRNA were present in the retina of diabetic and galactosemic animals, and the bosentan-treated groups exhibited mRNA levels similar to the control animals. After 6 months of follow-up, diabetes and galactose feeding induced basement membrane thickening, which was partially prevented by bosentan treatment. The above findings indicate that increased production of extracellular matrix proteins leading to thickening of microvascular basement membrane, secondary to hyperhexosemia, may be mediated via augmented ET production.

Animals↗
PubMed2003

Downregulation of fibronectin overexpression reduces basement membrane thickening and vascular lesions in retinas of galactose-fed rats.

Overexpression of extracellular matrix (ECM) components is closely associated with the development of vascular basement membrane (BM) thickening, a histological hallmark of diabetic microangiopathy. To determine whether BM thickening of retinal capillaries could be prevented by down regulating synthesis of fibronectin, an ECM component, we used antisense oligos targeted against translation initiation site of the fibronectin transcript in galactose-fed rat, an animal model of diabetic retinopathy. After 2 months of galactose-feeding, intravitreal administration of 3 micro mol/l antisense fibronectin oligos was initiated at monthly intervals for 3 months. The antisense strategy significantly reduced fibronectin mRNA and protein level in the retinas of treated eyes compared with untreated eyes of galactose-fed rats (130 +/- 16 vs. 179 +/- 18% of control, P < 0.01, and 144 +/- 28 vs. 204 +/- 22% of control, respectively, r = 0.9) and resulted in partial reduction of retinal capillary BM width (123 +/- 16 vs. 201 +/- 12 nm, P < 0.03). In eyes treated with antisense fibronectin oligos, approximately 35% reduction in both pericyte loss and acellular retinal capillaries was observed (P < 0.04 and P < 0.03, respectively). Glycohemoglobin level was consistently elevated in the treated (6.9 +/- 0.6%) and untreated (6.5 +/- 0.7%) galactose-fed rats compared with control rats (4.5 +/- 0.8%). Overall, these results indicate that downregulation of fibronectin synthesis reduces BM thickening in retinal capillaries with beneficial effect to retinal lesions. The antisense fibronectin oligos may provide a useful approach for reducing vascular lesions in diabetic retinopathy. The thickened vascular BM may be a potential therapeutic target for preventing retinal lesions in diabetic retinopathy.

Animals↗
PubMed1977

Effect of sites of blood sampling in determination of the galactose elimination capacity.

The galactose elimination capacity was calculated from both arterial and capillary or peripheral venous curves in twenty patients. The capillary curves on the average were delayed 1.4 min in relation to the arterial curves. No significant difference was found between the calculated galactose elimination capacity from either curve. On the average the slope of the venous curves was smaller than that of the arterial curve, and their time delay was very variable (from 1.55 to 5.27 min). Galactose elimination capacity calculated from venous curves was smaller than those calculated from arterial curves, especially in patients with a high galactose elimination capacity. Capillary blood sampling may replace arterial puncture for routine use, whereas venous blood sampling introduces a significant bias.

Adult↗
PubMed1984

Galactose elimination kinetics in perfused rat liver after two thirds hepatectomy.

Galactose elimination kinetics was studied in isolated perfused livers (single pass) from rats subjected to two thirds partial hepatectomy 6 h earlier or immediately before investigation. No difference was found between the two groups in the maximum galactose elimination rate or in the half saturation galactose concentration. This is in contrast with in vivo observation of restored galactose elimination capacity 6 h after two thirds hepatectomy. The discrepancy indicates that extrahepatic factors may be of importance for the metabolic regulation in the liver during regeneration.

Animals↗
PubMed1986

Use of galactose oxidase in labelling hydroxylysine glycosides of collagen.

Commercial preparations of galactose oxidase were shown to contain a proteolytic component active against collagen and collagen CNBr peptides which could not be inhibited by reagents such as EDTA, PMSF, PCMB and TLCK nor activated by Ca++ or Mn++. 30% of the total galactose oxidase activity could be recovered free of proteolytic activity in a simple one-step combined gel filtration/affinity chromatography procedure. The biological activity of such preparations was tested with reference to collagen hydroxylysine glycosides. It was shown that over 70% of the covalently linked tritium label introduced by KB3H4 reduction after galactose oxidase treatment was not associated with galactose but was present in the same non-specifically labelled components in control experiments. The enzyme could be used in a controlled manner to label hydroxylysine glycosides in collagen by immobilising it on agarose beads. In this form it was easy to store, re-usable and retained 95% of its original activity even after prolonged (18 h) incubation with substrates.

Collagen↗
PubMed1994

Impairment of afferent arteriolar myogenic responsiveness in the galactose-fed rat.

Previous studies from our laboratory have demonstrated impaired afferent arteriolar responsiveness to pressure in rats 4-6 weeks after the induction of diabetes mellitus. Although the responsible mechanisms mediating this renal autoregulatory defect have not been fully defined, increased polyol metabolism has been implicated as a possible factor involved in the pathogenesis of diabetic complications. We therefore investigated the possible role of this metabolic disturbance in renal autoregulation using the galactose-fed rat, a model characterized by increased polyol pathway activity independent of hyperglycemia or insulin deficiency. Hydronephrosis was induced to permit direct visualization of renal microvessels. Pressure-induced vasoconstriction of afferent arterioles was assessed by quantitating vessel diameter following stepwise increments of renal perfusion pressure (RAP; from 80 to 180 mm Hg) in the hydronephrotic kidneys from control rats and rats fed a 50% galactose diet for 2 or 4 weeks. Vessel diameters were measured from video images by computer-assisted image processing. Control rats exhibited progressive afferent arteriolar vasoconstriction when RAP was increased from 80 to 180 mm Hg (-17.3% +/- 1.0%; P < 0.001). In contrast, myogenic responses to increases in pressure were absent in the afferent arterioles of rats fed a 50% galactose diet for either 2 (-4.1% +/- 1.9%; not significant) or 4 weeks (-2.9 +/- 3.4%; not significant). Our demonstration that the impairment of afferent arteriolar responsiveness to increasing RAP in the normoglycemic galactose-fed rat was identical to that observed in the STZ-diabetic rat suggests that increased polyol accumulation may contribute to the impairment of renal autoregulation in the diabetic rat.

Animals↗
PubMed2003

[Effect of Boschniakia rossica extract on free radicals in brain of D-galactose induced senile rats].

OBJECTIVE: To study the effect of Boschniakia rossica extract on free radicals in the brain of D-galactose induced senile rats. METHODS: Sixty Wistar rats were randomly divided into normal group, model group (48 mg.kg(-1).d(-1) D-galactose, SC), Boschniakia rossica group (100, 150, 200 mg/kg ig and 48 mg.kg(-1).d(-1) D-galactose, SC). After 40 days, the activities of SOD, MAO and the content of MDA were measured with colorimetric method, and the histological changes were synchronously observed by electronic microscope. RESULTS: Boschniakia rossica extract significantly increased the SOD activity, decreased the MDA content, and inhibited the MAO activity in the brain tissue. It was observed under microscope that Boschniakia rossica extract could retrieve the degeneration of mitochondrion. CONCLUSION: Boschniakia rossica extract can clear the free radicals for D-galactose induced senile rats.

Aging↗
PubMed2005

Cross-linked leucaena seed gum matrix: an affinity chromatography tool for galactose-specific lectins.

A cross-linked leucaena (Leucaena leucocephala) seed gum (CLLSG) matrix was prepared for the isolation of galactose-specific lectins by affinity chromatography. The matrix was evaluated for affinity with a known galactose-specific lectin from the seeds of snake gourd (Trichosanthes anguina). The matrix preparation was simple and inexpensive when compared to commercial galactose-specific matrices (i.e. about 1.5 US dollars/100 ml of matrix). The current method is also useful for the demonstration of the affinity chromatography technique in laboratories. Since leucaena seeds are abundant and inexpensive, and the matrix preparation is easy, CLLSG appears to be a promising tool for the separation of galactose-specific lectins.

Chromatography, Affinity↗
PubMed1999

Galactose transport inhibition by cytochalasin E in rat intestine in vitro.

Cytochalasins are cytoskeleton disrupters, and cytochalasin E has been reported to increase intestinal paracellular permeability. In this study, the cytochalasin E effect on galactose transport has been investigated. Ussing-type chamber experiments show an inhibitory effect of 20 microM cytochalasin E on unidirectional mucosal to serosal flux of galactose. On the contrary, the opposite unidirectional flux is not modified by the inhibitor. Results using intestinal everted sacs and rings confirm that galactose uptake by the tissue is diminished by cytochalasin E. The effect appears already after 5 min incubation, depends on cytochalasin E concentration, and does not occur in the absence of Na+. The inhibition is accompanied by an increase in the apparent K(m) of the active sugar transport (11.5 vs.15.8 mM) without significant change in the VmaX (10.6 vs. 9.1 micromol x g(-1) wet weight x 5 min(-1)). Cytochalasin E does not modify either galactose uptake by brush border membrane vesicles or Na(+)-K(+) ATPase activity in the enterocytes, indicating that the inhibitory effect on the Na(+)-dependent sugar transport cannot be explained as a direct effect on SGLT1 activity or as an indirect effect through the Na(+)-K(+) ATPase. Thus, our results suggest that cytochalasin E decreases SGLTI activity indirectly through cytoskeleton disruption.

Animals↗
PubMed1976

A galactose-inhibitable mitogen for human lymphocytes from the sponge axinella polypoides.

Of two galactose-binding hemagglutinins isolated from the sponge Axinella polypoides, axinella I was strongly mitogenic for human peripheral blood lymphocytes, and axinella II was not. Purified T cells responded strongly and B cells weakly to axinella I. Mitogenic response, as monitored by rate of 3H-thymidine incorporation on the third day of culture, was specifically inhibited by Dgalactose, Dfucose, raffinose, or 2-deoxy-D-galactose added within 5 hr of the mitogen. Mitogenic response was correlated with degree of lymphocyte agglutination. The effectiveness of a given sugar in inhibiting mitogenic response to axinella I paralleled its potency in inhibiting precipitation of lectin by blood group substances. If an inhibitory concentration of Dgalactose was add 24 to 40 hr after mitogenic activation, rate of 3H-thymadine uptake at 72 hr was two to twenty times above the rate induced in cultures to which no galactose was added. Dgalactose at a subinhibitory concentration (10mug/ml) enhanced 3H-thymidine incorportion incorporation induced by phytohemagglutinin or Con A, an effect reversible by Dgalactose. These findings suggest that axinella I has tow antagonistic effects on human lymphocytes: a) mitogenic activation and b) depressive activity resulting from depletion of essential galactose moieties.

B-Lymphocytes↗
PubMed1975

Biosynthesis of chondroitin sulfate. Solubilization of chondroitin sulfate glycosyltransferases and partial purification of uridine diphosphate-D-galactose:D-xylose galactosyltrans.

UDP-D-Galactose:D-xylose galactosyltransferase, a membrane-bound enzyme which catalyzes the second glycosyl transfer reaction in the biosynthesis of chondroitin sulfate chains, has been solubilized and partially purified from embryonic chick cartilage. Solubilization was effected by treatment of a particulate fraction of a homogenate (sedimenting between 10,000 and 100,000 times g) with the nonionic detergent Nonidet P-40 (0.5%) and KCl (0.5 M) or by the alkali-detergent method described previously (Helting, T. (1971) J. Biol. Chem. 246, 815-822). The applicability of the salt-detergent procedure as a general method for solubilization of membrane-bound glycosyltransferases was tested by assay of four other glycosyltransferases involved in chondroitin sulfate synthesis (UDP-D-xylose:core protein xylosyltransferase, UDP-D-galactose:4-O-beta-D-galactosyl-D-xylose galactosyltransferase, UDP-D-glucuronic acid: 3-O-beta-D-galactosyl-D-galactose glucuronosyltransferase, and UDP-N-acetyl-D-galactosamine: (GlcUA-GalNAc-4-sulfate)4 N-acetylgalactosaminyltransferase). In each case, greater than 70% of the activity was solubilized and, on gel chromatography on Sephadex G-200, the enzymes appeared largely in included positions and partially separated from each other. After partial purification by gel chromatography on Sephadex G-200, UDP-D-galactose:D-xylose galactosyltransferase was purified further by chromatography on one of several affinity matrices, i.e. xylosylated core protein of cartilage proteoglycan coupled to CNBr-activated Sepharose, a core protein matrix saturated with UDP-D-xylose:core protein xylosyltransferase or UDP-D-xylose:core protein xylosyltransferase covalently bound to Sepharose. The specific activities of the enzyme preparations obtained by these procedures were approximately 1000-fold greater than that of the crude homogenate.

Animals↗
PubMed1975

Effect of anaerobiosis, dinitrophenol and fluoride on the active intestinal transport of galactose in snail.

The active transport of galactose across the intestinal wall (everted sacs) of the snail Cryptomphalus hortensis Müller has been studied in vitro, under several metabolic conditions. Anaerobiosis does not change the serosal/mucosal galactose gradients which are developed in oxygen atmosphere. Dinitrophenol (10(-4) M) greatly increased the O2 uptake by the tissue and clearly inhibits the sugar transport. At 5 times 10(-4) M concentration, DNP totally prevents the uphill transport while the O2 uptake is normal. The inhibition produced by DNP does not increase by anaerobiosis. Fluoride inhibits the galactose transport and also the O2 uptake. It is deduced that in snail intestine the energy for the active transport of galactose can be supplied by aerobic as much as by anaerobic metabolism. The inhibition by dinitrophenol seems to be independent of its uncoupling action on the oxidative phosphorylation. The inhibitory effect of NaF may be due both to glycolisis inhibition and to alteration of the digestive epithelium.

Anaerobiosis↗
PubMed1976

External labeling of galactose in surface membrane glycoproteins of the intact myelin sheath.

The molecular organization of surface galactose residues in glycoproteins of the intact myelin sheath was investigated using the enzymatic membrane probe, galactose oxidase. Rat spinal cords treated under physiological conditions with this nonpermanent probe were labeled specifically in galactose residues by reduction with tritiated sodium borohydride. The enzymatically modified proteins from isolated myelin were analyzed electrophoretically and their specific radioactivities determined. Results indicated tritium label associated with a surprising variety of high molecular weight proteins. The most extensively labeled peak corresponded to the major myelin glycoprotein as indicated by the coincidence of tritium label with that of [14C]fucose used as an internal marker for the glycoproteins. The radioactivity associated with this protein was 1.1 to 2.7 times higher after treatment with galactose oxidase when compared to reduction in the absence of the enzyme and 1.4 to 4.8 times higher when oxidized and reduced after prior treatment with neuraminidase. The results suggest a complex heterogeneity of minor glycoproteins associated with isolated myelin. It is concluded that from this complexity of glycoproteins, a major glycoprotein is at least partially localized on the external surface of either the intact myelin sheath or the closely associated oligodendroglial plasma membrane. Such a localization of this glycoprotein and the probable localization of the other glycoproteins enhances their potential role in specific interactions in the process of mpyelination or myelin maintenance.

Animals↗