SEARCH · Search PubMed

Results for “GALACTOSE”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 505 records · Page 28Linked to original sources

PubMed1966

Glucose effect and the galactose enzymes of Escherichia coli: correlation between glucose inhibition of induction and inducer transport.

Adhya, Sankar (University of Wisconsin, Madison), and Harrison Echols. Glucose effect and the galactose enzymes of Escherichia coli: correlation between glucose inhibition of induction and inducer transport. J. Bacteriol. 92:601-608. 1966.-The inhibitory effect of glucose on the induction of the enzymes required for galactose utilization ("glucose effect") was studied in Escherichia coli. Experiments on the uptake into the cell of labeled inducers (d-galactose-C(14) and d-fucose-H(3)) pointed to inhibition at the level of inducer transport as the possible primary mechanism of the glucose effect in the case of the gal enzymes. This interpretation was supported by the finding that a mutant constitutive for the lac enzymes was resistant to glucose inhibition of galactose induction of the gal enzymes; the mutant had acquired a glucose-resistant alternative transport mechanism for galactose via the constitutively synthesized galactoside permease. Further support for the transport inhibition model was provided by the finding that glucose did not substantially inhibit induction of the gal enzymes when glucose and galactose were produced intracellularly by beta-galactosidase hydrolysis of lactose, even if excess glucose was added. The inducer uptake experiments also showed that d-galactose and d-fucose probably enter the cell via different transport systems, although uptake of both compounds was inhibited by glucose.

Carbon Isotopes↗

PubMed1969

Role of lac genes in induction of beta-galactosidase synthesis by galactose.

Strain BL1003, a lacO mutant, synthesizes beta-galactosidase constitutively at a low rate. The enzyme is further inducible by d-galactose to the same differential rate as is seen in the presence of an optimal concentration of thiomethylgalactoside. lacY Mutants derived from strain BL1003 are not inducible by galactose, although they synthesize beta-galactosidase at the low constitutive rate characteristic of the parent. Galactose is a weak inducer of beta-galactosidase synthesis in wild-type Escherichia coli K-12, but it is more effective when the wild type has been preinduced with isopropyl-beta-d-thiogalactoside. Nevertheless, the rise in the differential rate of synthesis in response to galactose in a preinduced wild-type culture is much lower than in strain BL1003. Thus, two factors are involved in the induction of strain BL1003 by galactose: the mutant operator and the constitutive permease. The operator has an altered sensitivity to the i product-galactose complex. The low constitutive level of permease enabled the cells, at the high concentrations of galactose used (5 x 10(-2)m), to maintain a sufficient internal concentration for further induction.

Carbon Isotopes↗

PubMed1982

Galactose intolerance and the risk of cataract.

Cataracts may arise in association with various major and minor disorders restricting galactose metabolism, and the risk is broadly associated with the degree of galactose intolerance. A family is described in which a girl presented at the age of 7 3/4 years with cataracts, galactosuria, and partial deficiencies of the enzymes galactokinase and galactose-1-phosphate uridyl transferase. Galactose intolerance as determined by an oral test was impaired and fluctuated with variation in activity of the above galactose enzymes. Minor defects were also present in the parents and a maternal half-brother. The child has a compound disorder of galactose metabolism differing from those previously described. Assessment of galactose tolerance may be useful in the investigation of families with an incidence of cataract.

Carbohydrate Metabolism, Inborn Errors↗

PubMed1995

Galactosylated proteins are recognized by the liver according to the surface density of galactose moieties.

The recognition of 111In-labeled galactosylated superoxide dismutase (Gal-SOD) and galactosylated bovine serum albumin (Gal-BSA) by the liver was investigated in mice after intravenous injection. 111In-labeled galactosylated proteins were recovered in the liver by amounts that were highly dependent on the degree of galactose modification and the administered dose. The distribution patterns were analyzed based on a physiological pharmacokinetic model including an uptake process with Michaelis-Menten kinetics in the liver and hepatic plasma flow. The Michaelis constant of hepatic uptake of 111In-Gal-SOD was observed to inversely correlate with the number of galactose residues, without a significant change in maximum rate of uptake or extrahepatic clearance. This relation could be applied to 111In-Gal-BSA and other galactosylated proteins by using the surface density of galactose residues as a degree of modification, suggesting galactose density controls ligand recognition by the asialoglycoprotein receptor. The analysis also indicated that increasing galactose density higher than 1.0 x 10(-3) molecules/A2 did not affect the distribution of galactosylated proteins due to limitation by the hepatic plasma flow rate. In conclusion, efficient delivery of proteins modified with galactose to the liver will be achieved by controlling both the galactose density on the protein surface and the administered dose.

Animals↗

PubMed1995

Oxidation of exogenous [13C]galactose and [13C]glucose during exercise.

The present study examined the oxidation of exogenous galactose or glucose during prolonged submaximal cycling exercise. Eight highly trained volunteers exercised on two occasions on a cycle ergometer at 65% of maximal workload for 120 min, followed by a 60-min rest period and a second exercise bout of 30 min at 60% maximal workload. At random, subjects ingested a 8% galactose solution to which an [1-13C]galactose tracer was added or a 8% glucose solution to which an [U-13C]glucose tracer was added. Drinks were provided at the end of the warm-up period (8 ml/kg) and every 15 min (2 ml/kg) during the first 120 min of the test. Blood and breath samples were collected every 30 and 15 min, respectively, during the test. The exogenous carbohydrate (CHO) oxidation was calculated from the 13CO2/12CO2 ratio and CO2 production of the expired air. Peak exogenous CHO oxidation during exercise for galactose and glucose was 0.41 +/- 0.03 and 0.85 +/- 0.04 g/min, respectively. Total CHO and fat oxidation were not significantly different between the treatments. Forty-six percent of the ingested glucose was oxidized, whereas only 21% of the ingested galactose was oxidized. As a consequence, more endogenous CHO was utilized with galactose than with glucose (124.4 +/- 6.7 and 100.1 +/- 3.6 g, respectively). These results indicate that the oxidation rate of orally ingested galactose is maximally approximately 50% of the oxidation rate of a comparable amount of orally ingested glucose during 120 min of exercise.

Administration, Oral↗

PubMed1991

A membrane-bound form of the acute-phase protein C-reactive protein is the galactose-specific particle receptor on rat liver macrophages.

Rat liver macrophages express a galactose-specific receptor which mediates endocytosis of particles or neuraminidase-treated blood cells. From rat serum we now have isolated a galactose-specific lectin by affinity chromatography. Comparative analysis of this serum galactose-binding protein with the galactose-specific particle receptor protein purified from rat liver macrophages and with the acute-phase protein C-reactive protein (CRP) revealed a close relation or identity of these proteins. An apparent molecular weight of 30 kilodaltons was determined for all three proteins by SDS-PAGE under reducing conditions and of about 130 kilodaltons by native PAGE. All three proteins exhibit the same pentameric, ring-shaped structure. Antibodies raised against the serum galactose-binding protein or against the macrophage receptor did cross-react. Monoclonal antibodies raised against rat CRP labeled liver macrophage but not hepatocyte surfaces and reacted with all three isolated proteins in a Western blot assay. Furthermore, the galactose-specific particle receptor could be functionally replaced by purified CRP. Northern blot analysis showed that the CRP is not synthesized in the macrophages but appears to be acquired from hepatocytes or blood. We now conclude that a membrane-bound form of CRP functions as the recycling galactose-specific particle receptor in rat liver Kupffer cells.

Animals↗

PubMed1997

Uncertainty in liver function assessment on the basis of single-point galactose concentration.

The uncertainty in liver function assessment based on single-sample galactose levels after galactose injection, in comparison to the standard procedure using the galactose elimination capacity (GEC), was assessed in 905 tests performed in a wide range of liver functions. The 45-min galactose levels significantly correlated with GEC, the correlation being better in subjects with a good liver function. In cirrhosis, the prediction using the 60-min galactose value was better than when the 45-min value was used. In the whole series, the 95% confidence interval of GEC predicted by 45-min galactose was as large as +/- 1.55mg x kg(-1) x min(-1) as absolute value, corresponding to a range from -41 to +47% of measured GEC. In cirrhosis, the 95% confidence interval was +/- 1.42 mg x kg(-1) x min(-1) and between -40 and +46% of measured GEC. The 60-min values were more predictive, but in Child class C patients the average error was 0.42 mg x kg(-1) x min(-1) (95% confidence interval -0.64 to +1.49, corresponding to -39 to +76% of measured GEC). The uncertainty was maintained within +/- 10% of measured values only in 50% of the tests. We conclude that the single-point galactose test introduces a considerable error, mainly in patients with more advanced liver disease, which may bias the decision-making process.

Analysis of Variance↗

PubMed1994

Dose-response characteristics of galactose-induced cataract in the rat.

The onset and progression of cataract was investigated in weanling Sprague-Dawley rats fed 10, 15, 20 and 30% dietary galactose (groups 1-4) for 45-226 days. Cataracts were graded on a 0-5 scale. After 226 days, 9% of the rats fed 10% galactose developed lesions beyond the very early stage of cataractogenesis (grade 1). After 154 days 50% of the rats fed 15% galactose developed subcortical cataract (grade 3) with no nuclear cataract. In the rats fed 20% galactose, an initial rapid development by 31 days of a grade 3 cataract was observed in 50% of the eyes. Advancement to grade 4 and grade 5 cataract proceeded more slowly; by 207 days, 45% of the eyes had grade 5 cataract. In rats fed 30% galactose, rapid vacuolization and development of nuclear cataracts (grade 5) were observed by day 44. Dietary galactose at levels of 20 and 30% was associated with a significant reduction in weight gain at the early stage of dietary treatment. These observations demonstrate that 10-30% dietary galactose induces cataract in rat lens in a dose- and time-dependent fashion. These data serve to further establish this animal model as a useful model for studying the sequelae of cataractogenesis.

Animals↗

PubMed1983

Light microscopic histochemical detection of sugar residues in secretory glycoproteins of rodent and human tracheal glands with lectin-horseradish peroxidase conjugates and the galactose oxidase-Schiff sequence.

Lectins conjugated to horseradish peroxidase were used to stain paraffin sections of mouse, rat, and human respiratory tract tissues. An additional method was applied utilizing galactose oxidase to oxidize the C-6 hydroxyl of galactose and N-acetylgalactosamine residues and the resulting aldehyde was visualized with 2% Schiff's reagent. Sections were stained prior to and after removal of sialic acid residues. Oligosaccharides with terminal beta-galactose and alpha-N-acetylgalactosamine residues were found in all serous cells in the mouse trachea but were never seen in human tracheal serous cells. About 5-10% of serous cells in the rat trachea contained terminal beta-galactose, whereas all human tracheal serous cells and the remainder of those in the rat contained oligosaccharides with terminal sialic acid and penultimate beta-galactose residues. Fucose was not detected in tracheal serous cells of any species. Mucous cells in the mouse and rat trachea produced heterogeneous oligosaccharides containing terminal alpha-N-acetylgalactosamine and/or terminal sialic acid residues in various proportions. The structure of oligosaccharides in human tracheal mucous cells varied between individuals and was related to ABO blood group reactivity. The majority of oligosaccharides in type A individuals contained terminal alpha-N-acetylgalactosamine, whereas type AB individuals had approximately equal amounts of terminal alpha-galactose and alpha-N-acetylgalactosamine residues. Mucous cells in the two type O specimens examined contained a large amount of terminal beta-galactose and surprisingly, terminal fucose was not detected in these individuals. These results support biochemical studies showing structural diversity in oligosaccharide chains of respiratory tract secretions and reveal differences in glycoprotein secretion of different cell types.

Animals↗

PubMed1989

Gonadal function and ovarian galactose metabolism in classic galactosemia.

Evaluation of ovarian steroid secretion, histologic examination of ovarian tissue, and incubation studies with radiolabelled galactose in ovarian tissue slices were performed in a 21-year-old woman with galactosemia and incipient ovarian failure. After exogenous gonadotropin administration in an attempt to achieve fertility, there was no evidence of ovulation by ultrasound; estrogen and androgen production were deficient indicating ovarian unresponsiveness. Histologic examination of the ovary revealed that the ovarian stroma had an increase in fibrous tissue and that a few hyalinized atretic follicles were present with no intermediate or evolving Graafian follicles. After incubation with galactose-1-14C, there was absence of labelled CO2 production and only labelled galactose-1-phosphate was identified as compared to controls in which several labelled intermediates could be seen. The incorporation of galactose into the TCA-insoluble fraction was drastically reduced in the patient compared to controls, suggesting that there may be a deficiency of ovarian galactose-containing glycolipids, glycoproteins and mucopolysaccharides in the galactosemic ovary. Deficiency in the production of galactose containing compounds, or galactose-1-phosphate accumulation or both, may lead to the development of hypergonadotropic hypogonadism seen in women with galactosemia.

Adolescent↗

PubMed1986

Limited proteolysis of MP26 in lens fiber plasma membranes of the galactose-induced cataract in the rat.

Lenses of rats maintained on a 50% galactose diet displayed the development of a progressive cataract which was cortical at 3-11 days, and progressively internalized (nuclear as well) and mature at 16-20 days of feeding. Lens fiber plasma membranes were isolated from female rats subjected to the galactose diet and from controls at 11, 19, and 31 days of feeding, and analyzed by SDS-PAGE. Examination of the fiber plasma membranes from whole lenses of galactose-fed rats demonstrated the limited proteolysis of MP26 into MP23-24, in both the cortical and mature stages of the resultant cataracts. The limited proteolysis of MP26 was first evident in the lens cortex at 11 days of galactose feeding, and was evident as well, and more severe in proportion, in the lens nucleus at 19 days of feeding. The greatest proportion in MP26 limited proteolysis was observed in whole lenses at 31 days of galactose feeding. The regional progression of MP26 limited proteolysis closely paralleled the morphological progression of the galactose-induced cataract in the rat. The proportion of lens MP26 which underwent limited proteolysis into MP23-24 increased the longer the animals were kept on the galactose diet.

Animals↗

PubMed1992

Myo-inositol transport in the lens of galactose-maintained rats.

Lens myo-inositol (MI) content is regulated by a pump-leak system consisting of an active Na-dependent MI transport and its passive permeability through the membrane. We measured the active MI uptake and membrane permeability in lenses of rats maintained on a 50% galactose diet for 1, 3 and 7 days. After only 1 day of galactose feeding, active MI uptake in the lens was reduced dramatically by 74% compared to age-matched control lenses; by day 3, active MI transport was decreased by 89% and it was undetectable by day 7. The passive membrane permeability was determined by measuring (a) the passive MI influx and (b) the 3H-sorbitol flux. After 1 day of galactose feeding, the membrane permeability increased such that within 3 days it increased to 5-6 fold. Galactose feeding also led to a rapid increase in lens polyol content. After 1 day, lens polyol increased to 53 mumol/g wet wt compared to a control value of 0.35 mumol/g wet wt and increased further to 65 and 72 mumol/g wet wt after 3 and 7 days of galactose feeding respectively. Lens galactose accumulation was low (3 mumol/g wet wt) up to 7 days; however, it was rapidly increased after 7 days. Our results indicate that galactose feeding rapidly interfered with MI homeostasis by a severe depression of active MI transport and a rapid increase in membrane permeability. These interferences of MI homeostasis correlate with the appearance of high polyol levels.

Animals↗

PubMed2004

Changes in galactose and lactic acid content of sweet whey during storage.

Whey is often stored or transported for a period of time prior to processing. During this time period, galactose and lactic acid concentrations may accumulate, reducing the quality of spray-dried whey powders in regard to stickiness and agglomeration. This study surveyed industry samples of Cheddar and mozzarella cheese whey streams to determine how galactose and lactic acid concentrations changed with storage at appropriate (4 degrees C) and abuse (37.8 degrees C) temperatures. Samples stored at 4 degrees C did not exhibit significant increases in levels of lactic acid or galactose. Mozzarella whey accumulated the greatest amount of galactose and lactic acid with storage at 37.8 degrees C. Whey samples derived from cheese made from single strains of starter culture were also evaluated to determine each culture's contribution to galactose and lactic acid production. Starter cultures evaluated included Streptococcus salivarius ssp. thermophilus. Lactobacillus helveticus, Lactobacillus delbrueckii ssp. bulgaricus, Lactococcus lactis ssp. cremoris, and Lactococcus lactis ssp. lactis. Whey derived from L. helveticus accumulated a significantly greater amount of lactic acid upon storage at 37.8 degrees C as compared with the other cultures. Galactose accumulation was significantly decreased in whey from L. lactis ssp. lactis stored at 37.8 degrees C in comparison with the other cultures. Results from this study indicate that proper storage conditions (4 degrees C) for whey prevent accumulation of galactose and lactic acid while the extent of accumulation during storage at 37.8 degrees C varies depending on the culture(s) used in cheese production.

Cheese↗

PubMed1999

Organophosphate metabolic changes in the rat lens during the development of galactose-induced cataract.

Using phosphorous-31 nuclear magnetic resonance (31P-NMR) spectroscopy, we observed the metabolic kinetics of organophosphate compounds in the rat lens during cataract development induced by different doses of galactose (5%, 15%, 25%, and 40%) added to rat chow. The metabolic and histologic changes in the lenses were compared among the rats fed with different doses of galactose. alpha-Glycerophosphate significantly increased in response to the galactose doses, followed by a decrease to steady values of approximately 120% of the base line value, except in the 40% galactose group, which had a marked decrease to 68% of the base line value. Choline phosphate decreased rapidly during dosing in all but the 5% group, but no changes in those levels were observed after 2 weeks of galactose dosing. ATP decreased significantly when the histologic destruction progressed in the entire lens. Although inorganic phosphate increased significantly in a dose-dependent manner, it did not exceed the peak level. The histologic changes were closely related to the dynamic changes in the phosphorous compounds in the rat lens during formation of the galactose-induced cataract. Our results indicated that the development of a galactose-induced cataract was associated with the metabolic changes of the phosphate compounds.

Adenosine Triphosphate↗

PubMed1991

Proton-motive force-driven D-galactose transport in plasma membrane vesicles from the yeast Kluyveromyces marxianus.

Galactose transport was studied in membrane vesicles, prepared by fusion of plasma membranes from the yeast Kluyveromyces marxianus with proteoliposomes containing beef heart cytochrome c oxidase as a proton-motive force-generating system. Sugar transport studies performed under nonenergized conditions revealed that, even at high protein to phospholipid ratios, not all vesicles contained a D-galactose-specific transporter. The amount of vesicles containing an active carrier proved to be proportional to the amount of plasma membrane protein present in the fusion mixture. By addition of a suitable electron donor system a proton-motive force of -160 mV could be generated, inside alkaline and negative. Moreover, D-galactose accumulation was observed. It was found that D-galactose accumulation was highly dependent on the phospholipid composition of the vesicles, whereas generation of a proton-motive force was not. Best results were obtained with vesicles prepared with Escherichia coli phospholipid, giving a galactose accumulation of 14 times. Uphill transport could be established under conditions where only the pH gradient or the electrical gradient was present. Moreover, kinetic analysis of the galactose transport activity in energized vesicles revealed influx with a Km value of 540 microM, which is in good agreement with the apparent affinity constant obtained with whole cells. These results establish that galactose transport of K. marxianus is a proton-motive force-driven process. Moreover it demonstrates that plasma membrane vesicles co-reconstituted with cytochrome c oxidase are a valuable resource for the analysis of proton-motive force-driven sugar transport systems of yeast.

Biological Transport↗

PubMed1990

A membrane-associated form of C-reactive protein is the galactose-specific particle receptor on rat liver macrophages.

Rat liver macrophages express a galactose-specific receptor which mediates endocytosis of particles or neuraminidase-treated blood cells. From rat serum we now have isolated and purified a galactose-specific lectin by affinity chromatography. Comparative analysis of this serum galactose-binding protein with the galactose-particle receptor protein purified from rat liver macrophages and with C-reactive protein (CRP) reveals close relation or identity of these proteins. An apparent m.w. of 30,000 was determined for all three proteins by SDS-PAGE under reducing conditions and m.w. of about 130,000 by native PAGE. All three proteins exhibit the same pentameric, ring-shaped structure in electron microscopy after negative staining. Antibodies raised against the serum galactose-binding protein or against the macrophage receptor cross-react. A mAb specific for rat neo-CRP labels liver macrophages but not hepatocytes and reacts with the isolated protein in a Western blot assay. Furthermore, the galactose-particle receptor can be functionally replaced by purified CRP: the binding capacity for neuraminidase-treated E of receptor-depleted liver macrophages can be restored by preincubation with purified rat CRP. We therefore conclude that CRP occurs as a membrane-associated protein constitutively expressed on liver macrophages functioning as a receptor mediating galactose-specific binding of particulate ligands.

Animals↗

PubMed1989

[Anticaries effectiveness of D(+)-galactose].

The influence of different galactose concentrations on the cariogenic effect of Streptococcus mutans (strains: DSM 20381 and DSM 20523) in a sucrose diet (33%) was examined in an animal experiment. The treated Wistar rats were free of pathogenic germs at the beginning of the experiment. The experimental conditions were approximately in accordance with the "Consensus statement" of the American Dental Association. The sides of the teeth, the amount of film, the abrasion of the chewing surfaces, the amount of surface and fissure caries and the animals general condition were evaluated. The anticaries effectiveness of galactose is dependent on its concentration: 5.0% galactose reduces the amount of caries on a high significance level, lowers the abrasion of the chewing surfaces, possibly because of the increased amount of serum calcium related to this galactose concentration, and diminishes the amount of film. 1.5% galactose prevents caries significantly and strongly reduces the amount of film; 0.5% galactose reduces the amount of caries non-significantly, but diminishes the amount of film. The effect is based on the property of galactose to occupy the receptors of the pellicle (layer of glycoprotein on the tooth enamel), hence the adherence of specific germs (for example, Streptococcus mutans) ceases in whole or in part.

Analysis of Variance↗

PubMed1988

Increased ocular blood flow and 125I-albumin permeation in galactose-fed rats: inhibition by sorbinil.

125I-Albumin permeation and blood flow (assessed with 15 micron, 85Sr-labelled microspheres) were determined in the retina, choroid, anterior uvea, and brain of male Sprague-Dawley rats fed diets containing 50% dextrin (control) or 50% galactose. Blood flow was increased in the retina, choroid, and anterior uvea but not in the brain of rats fed galactose for 3 weeks and 3 months versus controls, and was normalized by sorbinil (an inhibitor of aldose reductase) in the 3-week group. After 8 months of galactose feeding, blood flow was reduced to normal levels in the retina and was slightly below normal in the choroid; blood flow remained elevated in the anterior uvea but was significantly lower than that observed at 3 weeks and at 3 months. In rats fed galactose for 8 months, sorbinil completely normalized blood flow in the choroid, and decreased, but did not normalize, blood flow in the anterior uvea. 125I-Albumin permeation was increased in the retina, choroid, and anterior uvea of rats fed 50% galactose for 3 weeks, 3 months, and 8 months versus controls, but was unchanged in the brain. Sorbinil normalized 125I-albumin permeation in all three ocular tissues in 8-month galactose-fed rats. Polyol levels were increased significantly in all three ocular tissues of 3-week galactose-fed rats; sorbinil markedly decreased, but did not normalize, polyol levels in all three tissues.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗