PubMed Health⌕ Search

Biomedical subjects

R Bais

Publications and source records attributed to R Bais.

At least 19 recordsLinked to original sources
PubMed1992

Lipid parameters and apolipoprotein B RFLP studies: comparison of normal and coronary heart disease groups as defined by angiography.

We have compared the lipid and apolipoprotein values and the frequency of DNA polymorphisms of the apolipoprotein B gene detected with the restriction enzymes, Xba I and Eco RI in 122 patients with coronary heart disease (CHD) and 80 control subjects. The patients with coronary heart disease (CHD) were defined by > 70% stenosis in at least one major coronary artery whereas the controls showed no signs of coronary artery narrowing at angiography. When males and females were considered separately, differences in triglyceride, total cholesterol and high density lipoprotein-cholesterol (HDL-cholesterol) between CHD and control subjects were significant only for females. The polymorphism studies showed no significant differences between the control and CHD subjects except for a difference in the frequency in the females of the Xba I polymorphism (p < 0.05). The X1 allele (absence of the restriction enzyme cutting site) occurred significantly more often in the patient group than in the controls. Individuals with the X1X2 genotype had the highest serum total cholesterol whereas those with the X1X1 genotype had the lowest HDL-cholesterol value. Generally, the associations between the Xba I and Eco RI alleles and serum lipid levels were weak and inconsistent. Furthermore, even after careful selection of disease and control groups, a useful role for restriction fragment length polymorphism studies in assessing CHD risk in individual patients was not demonstrated.

Aged↗
PubMed1991

New method for the determination of pancreatic amylase evaluated.

We have carried out a multicenter evaluation of a new reagent carrier for Reflotron, specific for pancreatic amylase where the salivary isoenzyme is inhibited by two specific monoclonal antibodies. This new procedure combines easy handling with low imprecision (median CV less than 3%) in control material, serum, heparinized blood, and plasma) and close correlation (r = 0.991 to 0.999) with established manual and automated methods. The same close correlation was found with values obtained from either venous or capillary finger-stick blood. Salivary amylase up to 54 kU/L (37 degrees C) was inhibited to about 97%. Endogenous interference by hemoglobin, bilirubin, triglycerides, cholesterol, or hematocrit was found to be negligible within a wide range of interferent concentrations. Out of a panel of 28 commonly used drugs it was shown that only two (ascorbic acid and paracetamol), and then only at toxic concentrations, caused a deviation in amylase activity of greater than 10%. From the results of this study we conclude that this new method is suitable for highly precise and accurate measurements of pancreatic amylase in emergency and routine laboratories.

Amylases↗
PubMed1991

The inhibition of metabolic oxalate production by sulfhydryl compounds.

A number of sulfhydryl compounds were shown to inhibit CO2 and oxalate formation from glyoxylate by rat liver homogenates and hepatocytes. The most significant inhibition occurred with cysteine and this inhibition was concentration-dependent. In rats made hyperoxaluric by administering ethylene glycol in their drinking water, daily intraperitoneal injections of cysteine caused a rapid and marked decrease in urinary oxalate excretion which was maintained over the duration of the treatment (28 days). Over this time period, the level of urinary oxalate excretion in these ethylene glycol-treated rats was reduced to that of the controls. It is postulated that the decrease is due to the formation of a cysteine-glyoxylate adduct, 2-carboxy-4-thiazolidine carboxylate, which prevents glyoxylate being further oxidized to oxalate. Cysteine or similar sulphydryl compounds may therefore have potential as therapeutic agents in the prevention of renal stones.

Aluminum↗
PubMed1991

Investigations into the effect of glyoxylate decarboxylation and transamination on oxalate formation in the rat.

The decarboxylation and transamination reactions of glyoxylate, which divert this precursor from oxalate formation, have been investigated. Decarboxylation of glyoxylate is synergistic with 2-oxoglutarate and catalysed by 2-oxoglutarate:glyoxylate carboligase which co-chromatographs with the 2-oxoglutarate dehydrogenase complex. The activity is located in the mitochondrial fraction and is probably due to the E1 subunit of the complex. A greater amount of decarboxylation occurs from 2-oxoglutarate than from glyoxylate but the presence of 2-oxoglutarate does not affect oxalate formation from glyoxylate. There is no oxalate formation from 2-oxoglutarate. Studies with rat liver homogenates showed that a number of amino acids can participate in glyoxylate transamination. However, using isolated rat hepatocytes, these reactions did not have a significant effect on oxalate formation from glyoxylate with the exception of cysteine which caused an 80% reduction in oxalate formation. Investigation of this inhibition indicated that it was most likely due to the formation of a cysteine-glyoxylate adduct which makes glyoxylate unavailable for oxidation to oxalate. This cysteine inhibition of oxalate formation was also demonstrated in normal rats and rats made hyperoxaluric by injecting them with either glyoxylate or glycolate. The results indicate that sulphydryl compounds, which can have a therapeutic role as oxalate-lowering agents, may be able to be developed.

Aldehyde-Ketone Transferases↗
PubMed1990

Macromolecular lactate dehydrogenase: an innocent bystander.

Lactate dehydrogenase (LD) activity is often increased in malignancy, and may occasionally be a useful tumor marker. In the case reported here, a persistently increased LD activity led to an extensive search for a neoplasm. Results of routine investigations were normal, but LD electrophoresis followed by gel filtration and immunofixation confirmed the presence of a circulating macromolecular LD, comprising IgAK bound to LD. Altogether it may provoke unnecessary investigations, the LD-IgA complex currently has no diagnostic significance.

Adult↗
PubMed1990

The relation of clinical catastrophes, endogenous oxalate production, and urolithiasis.

A dose-related toxicity syndrome of renal, cerebral, and liver dysfunction; metabolic acidosis; and deposition of calcium oxalate crystals in tissues is reported in association with various apparently unrelated treatments for a wide range of diseases. The parenteral nutrient xylitol, the hyperosmolar agent glycerol, the polysorbate emulsifiers (e.g., in vitamin E preparations), the anesthetic methoxyflurane, and possibly the experimental hypoglycemic agent dichloroacetate all produce a toxicity syndrome very similar to that of ethylene glycol poisoning. In long-term, high-dose oral toxicity studies with rodents, these or similar agents also produce calcium oxalate bladder stones and bladder tumors. Studies with both unlabeled and labeled agents in humans and animals and in vitro experiments with purified enzymes, tissue homogenates, and isolated hepatocytes have provided both strong circumstantial and direct evidence for the existence of minor pathways of carbohydrate metabolism and of oxidative dealkylation and dehalogenation reactions in drug biotransformations that link these agents to endogenous oxalate production. Because urinary oxalate is now considered to be a critical factor in stone formation and because it is increasingly accepted that 80-90% of urinary oxalate is produced endogenously, it is now possible to formulate pathways that link oxalate production with dietary macronutrients. Therapeutic modifications of diet, in vivo hormonal milieu, and intracellular metabolic controls in relation to endogenous oxalate production may provide new forms of treatment for urolithiasis.

Animals↗
PubMed1989

Metabolic response to insulin and glucose infusions in starved tumor-bearing rats.

Tumor-induced alterations in insulin sensitivity and glucose metabolism were investigated by examining the effect of glucose and insulin infusions in 72-h-starved tumor-bearing (TB) rats. Following glucose infusion, the rate of glucose disappearance from the blood was similar in TB and non-tumor-bearing (NTB) rats, even though insulin concentrations were lower in TB rats. Blood lactate was increased in TB rats prior to treatment and increased immediately following glucose infusion. Insulin alone decreased blood glucose in NTB but not TB rats. When insulin was infused together with glucose, the rate of glucose disappearance increased similarly in both TB and NTB rats. The immediate increase in blood lactate seen in TB rats following glucose infusion was not apparent in the TB rats receiving insulin and glucose. TB rats infused with glucose and insulin showed a greater rise in blood alanine concentrations, compared with all other infusion regimens. While ketone body concentrations decreased in both TB and NTB rats in response to the different infusion regimens, plasma free fatty acids in TB rats were not decreased by insulin and glucose treatments. TB rats therefore not only have decreased insulin release, but adipose tissue is also less sensitive to insulin action. In vivo studies using 2-deoxy[U-14C]glucose showed that glucose uptake by the muscle and adipose tissue, but not the tumor, was significantly increased by the infusion of insulin, thereby demonstrating one of the mechanisms by which insulin may act to conserve host tissue.

Adenocarcinoma↗
PubMed1989

Inhibition of endogenous oxalate production: biochemical considerations of the roles of glycollate oxidase and lactate dehydrogenase.

1. Both the peroxisomal, flavin-linked glycollate oxidase [(S)-2-hydroxy-acid oxidase; EC 1.1.3.15] and the cytosolic, nicotinamide-adenine dinucleotide (NAD)-linked lactate dehydrogenase (L-lactate dehydrogenase; EC 1.1.1.27) are thought to contribute to the formation of oxalate from its immediate precursors, glycollate and glyoxylate, but the relative contributions of each enzyme to endogenous oxalate production is not known. 2. In rat liver homogenates, [14C]oxalate production from labelled glycollate is halved and that from labelled glyoxylate is increased fourfold by the addition of either NAD or NADH. 3. In isolated rat hepatocytes, the 3-hydroxy-1H-pyrrole-2,5-dione derivatives of glycollate, which are specific inhibitors of glycollate oxidase, have a greater effect on glycollate metabolism than on glyoxylate metabolism. 4. These findings are consistent with an important role for lactate dehydrogenase in oxalate formation from glyoxylate. 5. With human and rat liver homogenates and with purified human liver glycollate oxidase and rabbit muscle lactate dehydrogenase, DL-phenyl-lactate (2 mmol/l) completely inhibits glycollate oxidase but has not effect on lactate dehydrogenase. On the other hand, the reduced form of a chemically synthesized, NAD-pyruvate adduct (1 mmol/l) almost completely inhibited lactate dehydrogenase but had no effect on glycollate oxidase. 6. Either alone or in combination, DL-phenyl-lactate and reduced NAD-pyruvate adduct reduce oxalate production from glycollate and glyoxylate in isolated rat hepatocytes, but do not abolish it completely. 7. These findings support a role for another enzyme, probably glycollate dehydrogenase (EC 1.1.99.14), in oxalate production in integrated cell metabolism.(ABSTRACT TRUNCATED AT 250 WORDS)

Alcohol Oxidoreductases↗
PubMed1989

Alpha-amylase determination with the Reflotron reagent carrier system: use of whole blood, plasma, and serum, and effect of isoenzymes.

In the Reflotron Amylase dry-reagent carrier system (Boehringer Mannheim GmbH) a new substrate is used for determining total amylase (EC 3.2.1.1) activity:indolyl-alpha-D-maltoheptaoside. The procedure shows low imprecision (median CV less than 3.2%), and results for sera, plasma, and capillary and venous blood (y) correlate well with those of a conventional alpha-amylase method involving p-nitrophenyl (PNP)-maltoheptaoside substrate (x) (for 209 blood samples: y = 0.981x + 9.7; r = 0.994). Correlation was also excellent with a method involving maltotetraose as substrate (r = 0.987). Attachment of an indoxyl residue rather than a PNP group to the maltoheptaoside did not affect the substrate response to pancreatic or salivary isoenzyme activity. Therefore, the relative proportion of these isoenzymes did not affect the correlation between the Reflotron Amylase reagent carrier and the alpha-amylase PNP-maltoheptaoside method. With a reaction time of less than 3 min, this system is especially suitable for amylase determination in situations where a prompt result is required.

Humans↗
PubMed1988

The effect of tumour-bearing on 2-deoxy[U-14C]glucose uptake in normal and neoplastic tissues in the rat.

The extent to which normal and neoplastic tissues of the rate take up glucose was assessed by the 2-deoxy[U-14C]glucose tracer technique. Measurements of glucose uptake were made over 40 min in anaesthetized rats under conditions where the blood glucose concentration was constant. In fed tumour-bearing rats, the relative rates of glucose uptake per g wet wt. of tissue were tumour (100), small intestine (72), brain (61), heart (61), spleen (50), lung (42), adipose tissue (11) and muscle (8). Normal tissues of the fed tumour-bearing rats had decreased rates of glucose uptake as compared with the same tissues in fed non-tumour-bearing control rats. Blood glucose concentrations were similar in both groups, but insulin concentrations were decreased in tumour-bearing rats. Starvation decreased the rates of glucose uptake by normal tissues in both control and tumour-bearing rats, but the difference between the fed and starved states was greater in the control rats. Starvation did not decrease glucose uptake by the tumour. On an organ basis, the tumour (12-14% of body wt.) took up 4 times more glucose than did muscle (40% of body wt.).

Adenocarcinoma↗
PubMed1988

Creatine kinase reference intervals determined from a multi-centre data pool.

Reference intervals for creatine kinase assayed at 37 degrees C using N-acetyl cysteine-activated methods have been determined on data obtained from 10 laboratories throughout Australia. The pooled distributions for males and females are skewed towards higher values and cannot be transformed to Gaussian distributions. The reference interval for females was calculated to be 34 to 180 U/l and for males it was 46 to 300 U/l. However, if creatine kinase is to be used in the diagnosis of myocardial infarction, the upper limit of the reference interval for males is considered to be too high. It is concluded that for males, the upper limit may need to be determined on specific populations such as hospital inpatients.

Australia↗
PubMed1985

The purification and properties of human liver ketohexokinase. A role for ketohexokinase and fructose-bisphosphate aldolase in the metabolic production of oxalate from xylitol.

Ketohexokinase (EC 2.7.1.3) was purified to homogeneity from human liver, and fructose-bisphosphate aldolase (EC 4.1.2.13) was partially purified from the same source. Ketohexokinase was shown, by column chromatography and polyacrylamide-gel electrophoresis, to be a dimer of Mr 75000. Inhibition studies with p-chloromercuribenzoate and N-ethylmaleimide indicate that ketohexokinase contains thiol groups, which are required for full activity. With D-xylulose as substrate, ketohexokinase and aldolase can catalyse a reaction sequence which forms glycolaldehyde, a known precursor of oxalate. The distribution of both enzymes in human tissues indicates that this reaction sequence occurs mainly in the liver, to a lesser extent in the kidney, and very little in heart, brain and muscle. The kinetic properties of ketohexokinase show that this enzyme can phosphorylate D-xylulose as readily as D-fructose, except that higher concentrations of D-xylulose are required. The kinetic properties of aldolase show that the enzyme has a higher affinity for D-xylulose 1-phosphate than for D-fructose 1-phosphate. These findings support a role for ketohexokinase and aldolase in the formation of glycolaldehyde. The effect of various metabolites on the activity of the two enzymes was tested to determine the conditions that favour the formation of glycolaldehyde from xylitol. The results indicate that few of these metabolites affect the activity of ketohexokinase, but that aldolase can be inhibited by several phosphorylated compounds. This work suggests that, although the formation of oxalate from xylitol is normally a minor pathway, under certain conditions of increased xylitol metabolism oxalate production can become significant and may result in oxalosis.

Electrophoresis, Polyacrylamide Gel↗
PubMed1979

Oxalate excretion in rats injected with xylitol or glycollate: stimulation by phenobarbitone pre-treatment.

The hypothesis that the prior intake of barbiturates may predispose patients to form increased amounts of oxalate following the intravenous infusion of xylitol was investigated in the rat. Phenobarbitone pre-treatment resulted in a 2-3 fold increase in urinary [14C] oxalate concentration following the intraperitoneal injection of [U-14C] xylitol or [l -14C] glycollate. The absence of any marked changes in urine volumes and creatinine excretion implied that this increase in urinary oxalate excretion was due to the enhanced synthesis of oxalate. The activities of key enzymes in hepatic oxalate synthesis, glycollate oxidase, lactate dehydrogenase, catalase and alanine aminotransferase were not altered by phenobarbitone pre-treatment. It is suggested that the increased activity of the microsomal mixed function oxidases, following phenobarbitone treatment, may facilitate the oxidation of glycollate and possibly xylitol. This communication leads experimental support to the concept that the prior intake of drugs, such as barbiturates, may predispose patients to form increased amounts of oxalate.

Animals↗