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PubMed1976

Renal sugar transport in the winter flounder. II. Galactose transport system.

The structural specificity of the transport of 0.5 mM D-galactose and 2-deoxy-D-galactose by teased renal tubules of the winter flounder Pseudopleuronectes americanus was investigated. The sugar uptake reflects preponderantly transport at the antiluminal membrane of tubular cells. Both sugars compete for the transport sites, indicating the sharing of a common carrier. 1) The structural requirements for the hexose-carrier interaction were defined by an inhibiton analysis using 12 structurally analogous sugars (5 mM): a (pyranose) ring structure; a free hydroxyl on C1; free hydroxyls (equatorial configuration) on C3 and C4; an oxygen on C6. Close packing in the vicinity of C2 is indicated. 2) Consonant with the requirement of a free C1-OH, beta-methyl-D-galactoside is not transported 3) Increasing concentrations (0.05-0.5 mM) of phlorizin and phloretin inhibit sugar uptake by lowering cellular levels of phosphorylated hexoses, whereas the levels of free sugars are not depressed. The possibility of an interaction of the sugar at C1-0H with a phosphorylated group at the carrier as the first step in the translocation process of both hexoses across the basal membrane is raised.

Animals↗
PubMed1978

Renal sugar transport in the winter flounder: V. secretion of 2-deoxy-D-galactose.

Isolated renal tubules and renal clearance techniques were used to characterize the renal handling of 2-deoxy-D-galactose (2-d-Gal) by the winter flounder (Pseudopleuronectes americanus). In vitro, energy-dependent, pH-sensitive uptake of 2-d-Gal (2-100 micron) was seen at the antiluminal face of the cell. Clearance measurements showed net secretion of 2-d-Gal in vivo. The mean clearance of 2-d-Gal in 18 fish was 0.98 +/- 0.16 ml/h while the glomerular filtration rate (GFR) was only 0.37 +/- 0.10 ml/h. Secretion was associated with marked renal accumulation of both 2-d-Gal and phosphorylated derivatives (2-d-Gal-1-phosphate). Tissue-to-plasma ratios (T/P) averaged 19 for free sugar and 59 for total sugar. Both clearance ratio and T/P were reduced to approximately 1 by injection of galactose (2.5 mmol/kg) simultaneously with 2-d-Gal (25 mumol/kg). Phlorizin (2.5 mumol/kg) increased net 2-d-Gal secretion, whereas glucose (2.5 mmol/kg) produced no change in secretion. Both compounds depressed 2-d-Gal T/P. This result suggests the presence of readsorptive transport at the brush border, sensitive to glucose and phlorizin.

Anaerobiosis↗
PubMed1976

Effect of hydrocortisone on response of human lymphocytes to galactose oxidase stimulation.

Hydrocortisone at 10(-4)M concentration could inhibit the response of human lymphocytes to galactose oxidase stimulation. Removal of the hydrocortisone after 4 h of culture did not reverse this inhibition. On the other hand, removal of monocytes greatly enhanced it, so that it could be observed at 10(-6)M concentration. Next, tonsil cells were separated into two fractions relatively rich in either T or B cells. Both fractions could respond to galactose oxidase and the response could be inhibited by hydrocortisone.

Alcohol Oxidoreductases↗
PubMed1982

Acid phosphatase. I. Cytochemical localization in lenses of normal and galactose-fed rats.

In the present investigation we have examined the presence, distribution and probable role of acid phosphatase in lenses of normal and galactose-fed rats. Acid phosphatase was localized in lenses using two separate cytochemical procedures (Gomori and Barka-Anderson methods) and examined at the ultrastructural level. Both procedures, in general, provided similar sites of acid phosphatase activity, although with the Barka-Anderson method finer and larger amounts of well-defined reaction product were observable at the site of reaction. The reaction product was observed in lenses of both rats fed on regular laboratory chow and galactose-fed rats. The intracellular location of the reaction of this enzyme was primarily in lysosomes and occasionally in the endoplasmic reticulum cisternae. At the extracellular sites, it was near the epithelial cell membranes which abut each other and cortical fibers. However, in the cortical fibers the extracellular localization was at various sites on the entire intercellular space between neighboring fibers. The possible role of hydrolases in the lens tissue is discussed.

Acid Phosphatase↗
PubMed1985

Changes of some biochemical parameters of the lens in galactose-treated weaned rats with and without vitamin E therapy.

We tried to counteract the appearance of galactosemic cataracts in weaned rats by high doses of vitamin E. Rats were fed a diet containing 33% galactose. Cataract development was monitored by biomicroscopy and by several biochemical parameters: K+/Na+ ratio, aldose reductase activity, level of protein and non-protein sulfhydryl (SH) groups. Vitamin E was given parenterally at a dose of 100 mg/kg/day. The K+/Na+ ratio drops after 15 days of galactosemia, while the level of the aldose reductase rises after only 5 days of treatment. The non-protein SH groups lens contents fall from the 5th day of treatment onwards, while protein SH groups are not affected. In short-term experiments vitamin E does not prevent biochemical changes caused by galactosemia. The oxidative insult does not seem to be primarily involved in galactose cataract.

Aldehyde Reductase↗
PubMed1970

Renal and intestinal hexose transport in familial glucose-galactose malabsorption.

Glucose transport by jejunal mucosa in vitro and kidney in vivo was investigated in a 3 yr old patient with congenital glucose-galactose malabsorption, her family, and 16 normal volunteers. Glucose transport by normal human jejunal mucosa was concentrative, saturable, sodium and energy dependent, and exhibited competitive inhibition. Biopsy specimens from six normal controls and an asymptomatic 5 yr old brother of the proband accumulated glucose to concentrations 16 times that in the incubation medium. The proband's mucosa was unable to concentrate glucose throughout a 60 min incubation period. Both of her parents and a half sister demonstrated impaired glucose transport. Their values fell between normal and those of the proband. Influx of glucose was impaired but efflux of glucose from the mucosa of these three heterozygotes was identical with that in three normal controls. A kinetic analysis indicated a reduced capacity (V(max)), but a normal affinity (K(m)) for glucose transport by their intestinal mucosa. All subjects accumulated fructose similarly.Renal glucose transport was investigated using renal glucose titration techniques. A partial defect in renal glucose reabsorption was found in the proband. Her brother's titration curve was similar to that of seven normal volunteers. We conclude that familial glucose-galactose malabsorption is inherited as an autosomal recessive trait, that heterozygotes for this disorder are detectable and demonstrate a reduced capacity for glucose transport, and that absent intestinal glucose transport is accompanied by partial impairment of renal glucose transport.

Adolescent↗
PubMed1977

Enhanced UDP-galactose:glycoprotein galactosyl transferase activity in cultivated skin fibroblasts from patients with cystic fibrosis and its possible relationship to the pathogenesis of the disease.

Homogenates of cultivated skin fibroblasts derived from patients with cystic fibrosis had a higher level of UDP-galactose:ovalbumin galactosyl transferase activity compared to fibroblasts derived from control subjects. The activity in control subjects was 1.82 +/- 0.43 nmol galactose transferred/hr/mg protein, whereas the activity in fibroblasts of patients was 2.95 +/- 0.77. The difference was significant at P less than 0.01. Activity in the fibroblasts of obligate heterozygotes was 2.15 +/- 0.60. The difference between the activities in fibroblasts of heterozygotes and patients was significant at P less than 0.05. The activity in control fibroblasts could be enhanced by basic polypeptides like polylysine, polyarginine, histone, and protamine but not by neutral or acidic polypeptides. Fibroblasts from patients released significantly higher amounts of a soluble form of the enzyme activity into the culture medium than control fibroblasts.

Cells, Cultured↗
PubMed1978

Absorption of glucose and maltose in congenital glucose-galactose malabsorption.

An intestinal perfusion technique has been used to study absorption of glucose from free glucose and the disacchairde maltose in a patient with congenital glucose-galactose malabsorption. Minimal absorption of glucose occurred from high luminal concentrations of either free glucose (100 mmole/liter) or maltose (50 mmole/liter). Glucose diffused into the intestinal lumen during perfusion of a 2 mmole/liter glucose solution. These observations offer no support for nutritionally important glucose absorption in congenital glucose-galactose malabsorption by either passive diffusion or via a "disaccharidase-related" transport system.

Biological Transport↗
PubMed1989

Activity of hepatic galactose-metabolizing enzymes in the pregnant rat and fetus.

The sp act of hepatic galactose-metabolizing enzymes, galactokinase, galactose-1-phosphate uridyltransferase, and uridine diphosphate-4-epimerase were measured in female rats during pregnancy and lactation as well as in fetuses and pups after parturition. Sp act for transferase and epimerase in pregnant rat liver are about 50% higher than that of virgin females, and with the increase in organ size during pregnancy the total hepatic activity is double that of nonpregnant animals. Galactokinase activity decreases somewhat during pregnancy, but total activity is 25% higher than in virgin liver. A Michaelis-Menten kinetic analysis of liver transferase indicates an increase in the maximum velocity of the reaction without a change in Km. Isoelectricfocusing on a high-resolution IEF gel demonstrated similar isozyme patterns. The sp act of the fetal liver enzymes increase to about twice that of the maternal tissue, but total activities are low due to the very small fetal liver size. Sp act of these enzymes in maternal liver fall after delivery, but sp act of galactokinase and transferase are programmed to increase in liver of the growing neonatal animals, reaching levels almost 5-fold higher than found in nonpregnant adult liver. An understanding of factors contributing to the enhanced transferase activity of the liver of pregnant and neonatal rats may contribute to possible ways of augmenting the residual transferase activity of patients with transferase-deficient galactosemia as a therapeutic strategy.

Animals↗
PubMed1977

Extracellular matrix synthesis in blastula and gastrula stages of normal and hybrid frog embryos. II. Autoradiographic observations on the sites of synthesis and mode of transport of galactose- and glucosamine-labelled materials.

Pulse-chase labelling experiments and light- and electron-microscopic autoradiography were used to examine the sites of synthesis, mode of transport, and sites of deposition of galactose- and glucosamine-labelled materials in different developmental stages of normal developing Rana pipiens embryos and interspecific hybrid embryos formed by fertilizing the eggs of R. pipiens with the sperm of R. catesbeiana. In both normal and hybrid embryos, after 15-min pulse, grains are closely associated with juxtanuclear and cytoplasmic collections of membrane-bound vesicles which resemble the Golgi apparatus. In normal embryos following a 15-30 min pulse and a 60-min chase, grains are largely cleared from the cytoplasmic vesicles and deposited in the extracellular spaces or along cell surfaces where the extracellular spaces are relatively large. In contrast, arrested hybrid embryos given a 15-30-min pulse and a 60-min chase show a marked accumulation of grains over cytoplasmic structures such as the Golgi apparatus and vesicular elements in the cell cortex. Finally, early gastrula stage normal embryos are most active in the synthesis of galactose-labelled materials in cells above the dorsal lip of the blastopore, where cell migration is initiated.

Animals↗
PubMed1977

Extracellular matrix synthesis in blastula and gastrula stages of normal and hybrid frog embryos. III. Characterization of galactose- and glucosamine-labelled materials.

Normal Rana pipiens gastrulae show more incorporation of isotopically-labelled galactose and glucosamine into TCA-insoluble materials than blastulae. Interspecific hybrid embryos which undergo developmental arrest at the onset of gastrulation often synthesize reduced amounts of galactose- and glucosamine-labelled materials. These materials are high-molecular weight, but not collagen. After pronase digestion, labelled materials elute in the void volume of Sephadex G-50. Labelled materials migrate slowly on cellulose acetate, bind to several kinds of anion exchangers and elute at low ionic strength, are precipitated by cetyl pyridinium chloride (CPC) when mixed with carrier compounds, and are not degraded by Clostridium neuraminidase or Streptomyces, leech, and bovine testicular hyaluronidases.

Animals↗
PubMedDate not supplied

The effect of galactose metabolic disorders on rat brain acetylcholinesterase activity.

To evaluate whether in classical galactosemia galactose (Gal), galactose-1-phosphate (Gal-1-P) and galactitol (Galtol) affect brain acetylcholinesterase (AChE) activity, various concentrations (1-16 mM) of these compounds were preincubated with brain homogenates of suckling rats as well as with pure eel Electroforus electricus AChE at 37 degrees C for 1 h. Initially, Galtol (up to 2.0 mM) increased (25%) AChE activity which decreased. thereafter, reaching the control value in high Galtol concentrations. Gal-1-P decreased gradually the enzyme activity reaching a plateau (38%), when incubated with 8-16 mM. However, when the usually found 2 mM of Galtol and 2 mM of Gal-1-P, concentrations in galactosemia were added in the incubation mixture simultaneously, brain AChE was stimulated (16%). Galtol or Gal-1-P modulated brain AChE as well as enzyme activity of E.electricus in the same way. Gal, Glucose (Glu) and glucose-1-phosphate (Glu-1-P) had no effect on AChE activity. It is suggested that Galtol as well as Gal-1-P can affect acetylcholine degradation acting directly on AChE molecule. Consequently the direct action of these substances on the enzyme might explain the brain cholinergic dysfunction in untreated galactosemia patients.

Acetylcholinesterase↗
PubMed1980

The effect of galactose oxidase treatment on the hepatic binding and biological activity of desialylated human chorionic gonadotrophin.

125I labelled desialylated hCG (asialo-hCG) was treated with galactose oxidase, in order to find out whether oxidation of the terminal galactosyl residues would diminish the hepatic uptake of asialo-hCG. Specific binding to the hepatic asialo-glycoprotein receptor was monitored in vitro by a rat liver radioligand receptor assay (RRA). Hormonal activities were compared by ovarian RRA and by in vitro bioassay. Uptake studies were done in superovulated immature rats. Galactose oxidase treatment had hardly any influence on the in vitro ovarian binding and biological activity of [125I]asialo-hCG. Binding in the liver RRA was virtually abolished. In vivo hepatic uptake, however, was considerably above the level of [125I]hCG, as was the uptake in the kidneys. The hepatic uptake was inhibited by the administration of a high dose of asialo-fetuin. It is concluded that oxidation of the terminal galactosyl residues reduces the binding of asialo-hCG to the hepatic asialo-glycoprotein receptor, without affecting its hormonal properties. The ovarian uptake in vivo, however, is still limited by the high hepatic and renal clearance.

Animals↗
PubMed1976

Measurement of intrahepatic shunted blood flow by ethanol-1-14C method as compared with D-galactose-1-14C method.

Ethanol-1-14C method for the measurement of intrahepatic shunted blood flow was compared with the method of continuous infusion of D-galactose-1-14C. In controls, in chronic hepatitis, and in hepatic cirrhosis, per cent intrahepatic shunt measured by the ethanol-1-14C- method was about a half or one-third of that measured by the D-galactose-1-14C method. Study of radioactivity-dye concentration ratio of the blood sampled from the inferior vena cava showed that per cent intrahepatic shunt was underestimated by the ethanol-1-14C method because of permeability of ethanol-1-14C through the capillaries. In patients with hepatic carcinoma, in whom the carcinomatous tissue was supplied mainly by the hepatic artery, there was no significant difference in per cent intrahepatic shunt between both methods.

Ethanol↗
PubMed1981

Pancreatic D-cell recognition of D-glucose: studies with D-glucose, D-glyceraldehyde, dihydroxyacetone, D-mannoheptulose, D-fructose, D-galactose, and D-ribose.

To investigate how the D-cell recognizes the glucose stimulus, the hormone response to (1) glucose, (2) the trioses glyceraldehyde and dihydroxyacetone, (3) the metabolic blocker, mannoheptulose, and (4) the low- or nonmetabolized sugars galactose, fructose, or ribose were studied using the isolated dog pancreas. We found (1) a sigmoidal relationship between extracellular glucose concentrations and the somatostatin release. The threshold concentration was around 5 mM and the largest increase in somatostatin release occurs between 5 and 10 mM of glucose. (2) Glyceraldehyde at concentrations ranging between 1.25 and 5 mM stimulated the release of somatostatin, whereas the higher concentrations of 10 and 20 mM were suppressive. Dihydroxyacetone (11 mM), also initiated somatostatin release in the absence of glucose. Both of the trioses stimulated B- and inhibited A-cell secretion. (3) Mannoheptulose (5 mM) attenuated somatostatin and insulin secretion to 8.3 mM glucose, while it augmented glucagon output. In contrast, mannoheptulose (5 mM) did not affect D-, A-, or B-cell responses to glyceraldehyde (5 mM) in the absence of glucose. (4) The somatostatin, insulin, and glucagon release remained unchanged when 8.3 mM of either galactose, fructose, or ribose was added. The results suggest that the initiation of glucose-mediated D- as well as A- and B-cell responses depends on the metabolism of the sugar.

Animals↗
PubMed1986

Changes in the hepatic capacity of urea-N synthesis, galactose elimination and antipyrine clearance following 70% hepatectomy in the rat.

The capacity of urea-N synthesis (CUNS), galactose elimination capacity (GEC), and antipyrine clearance (APC) was investigated in rats 0, 3, 6, 24, 96, and 240 h after 70% hepatectomy. Sham-operated animals were used as controls. The CUNS was assessed during alanine infusion as urea accumulation in total body water, corrected for intestinal hydrolysis, GEC was measured during constant galactose infusion, and APC by the one-sample method. Immediately after the 70% hepatectomy, CUNS was reduced from 8.9 +/- 2.4 to 3.9 +/- 1.1 mumol (min X 100 g body wt)-1 (mean +/- SD, p less than 0.05), that is, 0.43 times the control value. The corresponding reduction in liver weight was 0.36. After 6 h CUNS rose to 0.62 times the control values versus 0.36 for the liver weight. The recovery of GEC and APC was slower than the recovery of the liver weight, and was only restored to 0.81 and 0.59 times the control value (p less than 0.05), respectively, after 240 h. This study demonstrates that after partial hepatectomy the capacity of urea-N synthesis rate is increased, that is, a compensatory hyperfunction of the remnant liver, and that this function is restored to normal more rapidly than other measures of functional liver mass.

Animals↗
PubMed1977

Rates and mechanisms of glucose, galactose, and xylose absorption in man in vivo.

Jejunal absorption-rates of glucose, galactose, and xylose were determined consecutively, using a double-lumen tube perfusion technique, in 6 Arab subjects in vivo; perfusion solutions contained 200 mmol/l of each monosaccharide. Mean xylose absorption rate was significantly lower than that for glucose (P less than 0.001) and galactose (P less than 0.001). In order to investigate evidence that glucose and xylose share the same jejunal transfer mechanism, their absorption-rates when given alone and together, at high concentrations, were determined in 6 other Arabs; perfusion solutions contained (1) 200 mmol/l glucose, (2) 100 mmol/l xylose, and (3) 200 mmol/l glucose + 100 mmol/l xylose. Rates of glucose and xylose absorption were not significantly influenced by the other monosaccharide. This study does not therefore confirm existence of a common transfer mechanism. A significant correlation between absorption rate of glucose and weight of xylose excreted after a 25 g oral load (P less than 0.05) was demonstrated.

Adolescent↗
PubMed1990

Reversal of the limited proteolysis of MP26 during the reversal and prevention of the galactose cataract in rat lenses.

The reversal and prevention of the galactose-induced cataract in rats were employed to study their effects on the acceleration of the limited proteolysis of MP26 into MP23-24 previously observed in cataractous lenses of galactose-fed animals. Lenses of rats on a cataract reversal-diet demonstrated the reversal of MP23-24 and MP26 levels to control levels in the clearing cortical areas but not in remaining cataractous nuclear areas. Acceleration of the limited proteolysis of MP26 was observed in the nucleus but not the cortex in the clear lenses of animals on a cataract prevention-diet. The results demonstrated that the limited proteolysis of MP26 may form part of a gradual aging process that although not directly (causally) related to cataractogenesis may at least be accelerated by cataractogenic agents or conditions.

Aging↗