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Biomedical subjects

A M Rofe

Publications and source records attributed to A M Rofe.

At least 19 recordsLinked to original sources
PubMed1992

Changes in plasma zinc, copper, iron, and hepatic metallothionein in adjuvant-induced arthritis treated with cyclosporin.

The early changes in hepatic metallothionein (MT) and plasma zinc (Zn), copper (Cu), and iron (Fe) were investigated during the induction of adjuvant (AJ) arthritis in rats in conjunction with cyclosporin (CsA) treatment. Plasma Zn decreased after AJ injection (60% of control values at 8 h), and this was associated with a 4.5-fold increase in hepatic MT at 8 h. Plasma Zn was lowest at 16 h (40% of control), whereas hepatic MT concentrations increased to a maximum of 20-fold at 16 h. Changes in plasma Fe paralleled those of Zn, whereas plasma Cu levels were increased. Plasma metal and hepatic MT concentrations returned toward normal from d 1-7. At d 14, when marked paw swelling was apparent, hepatic MT and plasma Cu were again increased and plasma Zn decreased. Administration of CsA decreased MT induction in rats injected with AJ and also caused a marked recovery in plasma Zn and Fe levels. These changes were small but significant even in the early stages (up to 24 h) after AJ injection and were followed by a sustained improvement in all parameters, corresponding to the nonappearance of clinical arthropathy in CsA-treated rats. TNF-alpha and IL-6 production by peritoneal macrophages isolated from AJ-injected rats was significantly decreased by CsA treatment at d 7 and 14. The inhibition of hepatic MT induction during acute and chronic inflammation by cyclosporin emphasizes the role of the immune system in altered metal homeostasis in inflammation.

Animals↗
PubMed1992

Beneficial effects of endotoxin treatment on metabolism in tumour-bearing rats.

The effects of endotoxin treatment on host metabolism in tumour-bearing rats were investigated. Metabolism in control rats (non-tumour-bearing) was slightly altered by endotoxin treatment, whereas in tumour-bearing rats a number of biochemical parameters that were initially perturbed by the presence of the tumour had returned to normal at 48 h post-treatment. The beneficial effects included increased blood glucose and insulin concentrations, and decreased ketone body, triglyceride and lactate concentrations. Potentially non-beneficial effects of endotoxin observed in both tumour-bearing and control rats included decreased plasma cholesterol, and increased plasma phosphate, potassium and alkaline phosphatase levels. Endotoxin caused haemorrhaging in the encapsulated tumour, and this was associated with histological evidence of endothelial damage, red cell infiltration into surrounding tumour tissue and a marked decrease in cell viability. The in vivo uptake of glucose by the tumour, measured by 2-deoxy [U-14C]glucose uptake, was decreased by 96% following endotoxin treatment, and this was associated with a two-fold increase in glucose uptake by muscle. It is concluded that endotoxin treatment has major effects on cell viability and the integrity of vasculature in the tumour, which limits glucose uptake by the tumour and thereby decreases the energy and substrate requirements of the tumour, thus benefiting the host. It is suggested that tumour cytotoxicity and intra-tumour haemorrhage are the result of endotoxin stimulating cytokine release from macrophages that are already activated by the presence of the tumour.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenocarcinoma↗
PubMed1992

Hemoglobin A1c by HPLC with the Pharmacia Mono S HR 5/N cation-exchange column: influence of sample protein load on optimal chromatographic conditions.

The Pharmacia Mono S HR 5/5 column has been optimized for hemoglobin A1c analysis by HPLC by using a much smaller column load, decreased buffer flow rate, and a steeper gradient than was used in previously described methods. Superior chromatographic separation, shorter analysis time, and a greatly extended column life have resulted.

Cations↗
PubMed1992

Determinants of synovial fluid lactate concentration.

The resting intraarticular pressure and the type of arthropathy [rheumatoid arthritis (RA) or non-RA] have been examined for their importance as determinants of synovial fluid (SF) lactate concentration in patients with knee effusions. SF lactate concentration was higher in RA than in non-RA knees. This difference was not related to the resting intraarticular pressure at the time of sampling. After drainage of SF and saline lavage of the joint, the rate of increase of lactate in a fixed volume of intraarticular saline was examined under resting conditions. The rate of increase of the lactate concentration was significantly greater in RA joints. It is most likely that SF lactate concentration under resting conditions will reflect the lactate concentration during the preceding period of activity which, in turn, is probably a composite function of the extent of synovial hypoxia due to hypoperfusion and the type of arthropathy.

Arthritis, Rheumatoid↗
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

Biochemical manifestations of a rat mammary adenocarcinoma-producing cachexia: in vivo and in vitro studies.

The physical and metabolic characteristics of a Dark Agouti rat mammary adenocarcinoma and its effects on host metabolism are described. The tumour was characterized by a lack of glandular differentiation, tetraploidy, a rapid mitotic index and a high rate of glycolysis. The adenocarcinoma was readily maintained in tissue culture and could be passaged through the host by inoculating either cell suspensions or tissue explants. In the rat, tumour growth resulted in a loss of adipose tissue at a tumour mass of less than 5% body weight indicating that increased energy expenditure was already present at that stage. In addition the tumour caused anaemia, hypercalcaemia and hypoglycaemia. Hyperketonaemia was also observed in fasted tumour-bearing rats. Methotrexate arrested tumour growth in vivo. These aspects of the tumour model make it useful for investigations into host-tumour competition and mechanisms of cachexia.

Adenocarcinoma↗
PubMed1990

Prevention of adjuvant-induced cachexia in rats by cyclosporin A.

The changes in food intake and biochemistry following Freund's adjuvant (AJ)-induced inflammation in rats were investigated. Injection of AJ into rats resulted in a transient anorexia but a sustained decrease in body weight. Within 14 days, body weight decreased by 12% (P less than 0.05) and adipose tissue (retroperitoneal fat pads) decreased by more than 50%. Biochemical changes seen in association with the AJ-induced wasting included decreased plasma concentrations of triglyceride and cholesterol. Injection of cyclosporin-A (CS) (20 mg/kg) with the AJ decreased the anorexia, prevented the sustained loss of body weight and adipose tissue and reversed the effects on plasma triglyceride and cholesterol concentrations. Insulin concentrations were not significantly affected by the AJ or AJ/CS treatments. Peritoneal macrophages from AJ-treated rats produced 3-fold more tumour necrosis factor-alpha (cachectin) than control rats. This effect was not observed in rats treated with AJ plus CS. The results are consistent with CS preventing the release of cytokines which have anorectic and catabolic actions (IL-1, TNF), although there is also the possibility that CS has effects involving endocrine mechanisms.

Adipose Tissue↗
PubMed1990

Intraarticular pressure and the relationship between synovial perfusion and metabolic demand.

We examined the influence of intraarticular pressure on products of synovial energy metabolism in patients with knee effusions. A range of intraarticular pressures was generated by controlled flexion. Pressures greater than or equal to 45 mm Hg were associated with increased synovial fluid lactate concentrations and pCO2, and decreased pH. Our results suggest that pressures greater than or equal to 45 mm Hg, which we also observed during standing and walking, can cause synovial ischemia and hypoxia manifest in a perfusion/metabolic demand mismatch. Monitoring changes in SF concentrations of uric acid did not provide consistent evidence for accelerated purine degradation following periods of inadequate perfusion. Overall, our results suggest that synovial blood flow can be compromised by modest elevations in intraarticular pressure in the range encountered during daily activity in patients with knee effusions.

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↗
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↗
PubMed1987

The effects of recombinant tumour necrosis factor (cachectin) on metabolism in isolated rat adipocyte, hepatocyte and muscle preparations.

Tumour necrosis factor (TNF) did not stimulate lipolysis in isolated rat adipocytes, though preincubation with TNF increased adrenaline-stimulated fatty acid release. Glycogenolysis, gluconeogenesis and ketogenesis in isolated rat hepatocytes were not influenced by TNF in short-term (30-60 min) incubations. TNF stimulated 14CO2 production from [U-14C]glucose in rat hemidiaphragm preparations, but lactate production and alanine release were not significantly altered. It is concluded that TNF does not regulate short-term metabolism in adipocytes, hepatocytes and muscle preparations in the manner of a catabolic hormone.

Adipose Tissue↗
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↗