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Biomedical subjects

R G Price

Publications and source records attributed to R G Price.

At least 19 recordsLinked to original sources
PubMed1979

Studies on the nephrotoxicity of p-nitrophenylarsonic acid: changes in rat kidney and urinary enzyme activities following the administration of p-nitrophenylarsonic acid.

Histological studies showed that the administration of p-nitrophenylarsonic acid to rats resulted in renal tubular necrosis. The nephrotoxin was administered intraperitoneally and doses greater than 30 mg/kg were found to be fatal. The severity of the renal lesion depended on the amount of the nephrotoxin used. Elevated serum urea levels, urinary protein and volume were recorded over an 8-day period following the injection of the nephrotoxin. These changes were paralleled by an increase in the activity of lactate dehydrogenase, acid and alkaline phosphatase, N-acetyl-beta-glucosaminidase and beta-glucosidase in the urine. beta-Glycosidase activities increased in kidney homogenates, immediately after the injection of the nephrotoxin, but this eventually fell to well below the normal range. Subcellular fractions were prepared from sucrose homogenates by differential centrifugation and beta-glycosidases and cytochrome oxidase were used as enzyme markers. Only minor changes in the activity of cytochrome oxidase activity resulted from the administration of p-nitrophenylarsonic acid. One of the earliest indications of renal damage was a decrease in lysosomal latency. The activities of the lysosomal and soluble enzymes were elevated above normal during the first two days after the injection of p-nitrophenylarsonic acid, but they fell to values, significantly lower than normal, on the third day. The isoenzymic forms of beta-galactosidase, beta-glucosidase and N-acetyl-beta-glucosaminidase in normal and damaged kidneys were studied, using starch gel electrophoresis. The activities of both the lysosomal and the soluble forms of these enzymes decreased following the injection of the nephrotoxin, confirming the results obtained with whole homogenates. The relationship between the changes in renal enzyme activity and urinary enzyme excretion during the nephrotoxic process is discussed.

Animals↗
PubMed1979

Urinary enzyme assays in toxicological studies in the rat and marmoset.

The relative merits of the automated, fluorimetric assay of urinary enzymes and cell exfoliation were compared with other commonly used tests for renal damage. Two types of nephrotoxic agent were used, causing crystal nephropathy and acute tubular necrosis respectively. Groups of marmosets were given one of two drugs known to cause crystal nephropathy. One agent caused intermittent increases in urinary enzyme excretion and an early increase in cell excretion which was not sustained. The second agent in contrast caused elevated cell and enzyme excretion, increasing throughout the period of administration. A nephrotoxic anti-tumour agent also caused increases in cell and enzyme excretion when given to marmosets. The early changes produced by this agent were studied using catheterised rats. Hourly samples of urine were collected and urinary beta-glycosidase excretion was found to give an early indication of renal damage, which correlated with albuminuria and glycosuria. The fluorimetric assay of urinary enzymes provides a sensitive, non-invasive test of nephrotoxicity.

Acetylglucosaminidase↗
PubMed1979

Urinary N-acetyl-beta-D-glucosaminidase (NAG) as an indicator of renal disease.

The automated fluorimetric assay of N-acetyl-beta-D-glucosaminidase (NAG) has proved to be of value in the detection of rejection in transplant patients and in monitoring the course of renal disease. The urine can be diluted prior to assay, due to the sensitivity of the fluorimetric method and this reduces the effect of endogenous inhibitors. Time consuming dialysis or gel filtration steps are therefore unnecessary. Results are available to the physician within hours of the collection of the urine sample, since factoring the enzyme activity by the creatinine concentration avoids the necessity of collecting twenty-four hour or timed urine samples. Over one hundred samples can be assayed in a day using the automated procedure. The excretion of NAG in normal individuals varies with age and the activity found in pathological samples should always be compared with age-matched controls. The development of a new series of colorimetric substrates has allowed the production of a simple 'Dipstick' which should be of value in the screening of at-risk populations for renal disease. The diagnostic potential of the estimation of urinary NAG activity is enhanced by the separation of its isoenzymic forms by ion-exchange chromatography on DEAE-cellulose.

Acetylglucosaminidase↗
PubMed1978

N-acetyl-beta-d-glucosaminidase in marmoset kidney, serum and urine.

N-Acetyl-beta-D-glucosaminidase activities were determined in homogenates of marmoset kidney, in serum and in urine by using the 4-methylumbelliferyl substrate. The enzyme activity was separated into several components by DEAE-cellulose ion-exchange chromatography, starch-gel electrophoresis and isoelectric focusing. The kidney contained two major forms of the enzyme, A and B, which had similar pH optima and Km values. The A-form bound to DEAE-cellulose at pH 6.8, migrated towards the anode on starch-gel electrophoresis and had a pI of 5.0. The B-form did not bind to DEAE-cellulose at pH 6.8, remained near the origin on starch-gel electrophoresis and had a pI of 7.64. The isoenzymes also differed in heat stability, the B-form being the more stable. Serum contained B-form activity and, in addition, two intermediate forms (I1 and I2) were loosely bound to DEAE-cellulose. The serum A-form activity was less firmly bound to DEAE-cellulose than was the tissue A-form and was designated As. Serum from a pregnant marmoset contained a form which may be analogous to the human P-isoenzyme. Urine contained only a small amount of B-form activity, the majority being present in the A-form. The kidney A- and B-forms both had mol.wts. of 96000--100000 and the activity was predominantly lysosomal. Partial purification of the kidney A isoenzyme was undertaken. Immunoprecipitation studies indicated a relationship between marmoset kidney A-form and human liver A-form activity.

Acetylglucosaminidase↗
PubMed1977

Studies on the metabolism of the renal glomerular basement membrane. Turnover measurements in the rat with the use of radiolabeled amino acids.

The synthesis and degradation of the renal glomerular basement membrane have been investigated in the rat with the aid of injected tracer doses of various tritiated amino acids including L-proline, L-lysine, L-phenylalanine, L-leucine, and glycine. After incorporation into the basement membrane the turnover times of these amino acid constituents, as well as of hydroxyproline and hydroxylysine, were determined from the decay in their specific radioactivities. The loss of radioactivity from the proline and hydroxyproline of the glomerular basement membrane was as slow as that from tail tendon collagen in the same animals (turnover time of more than 100 days) and contrasted with the radiodecay of the proline in other glomerular proteins (turnover time of 9 days). The glycine of the membrane similarly turned over at this very slow rate. The total replacement times of the leucine, hydroxylysine, lysine, and phenylalanine constituents of the basement membrane were determined to be somewhat shorter with a range of 65 to 23 days. The nonuniform turnover of these membrane components may be a function of the polydispersity of the peptide subunits of the basement membrane observed by polyacrylamide gel electrophoresis and may reflect a subtle morphological and functional heterogeneity. The amino acid and saccharide composition of the rat glomerular basement membrane used in these studies are also reported.

Amino Acids↗
PubMed1977

The separation and characterization of marmoset kidney beta-D-galactosidase and beta-D-glucosidase.

beta-D-Galactosidase and beta-D-glucosidase activities were determined in homogenates of marmoset kidney by using the appropriate 4-methylumbelliferyl glycoside, beta-D-Galactosidase activity was separated into two main components by ion-exchange chromatography on DEAE-cellulose, starch-gel electrophoresis, isoelectric focusing and gel filtration on Sephadex G-200. One form designated A had a pI of 5.1, was loosely bound to DEAE-cellulose at pH7.0, remained near the origin on starch-gel electrophoresis at pH 7.0 and had an apparent molecular weight of 160000. The second beta-D-galactosidase component, designated B, was associated with the total beta-D-glucosidase activity, had a pI of 4.3, was firmly bound to DEAE-cellulose, migrated rapidly towards the anode on starch-gel electrophoresis and had an apparent molecular weight of 50000. The optimum pH values of beta-D-galactosidase A and B were 4.5 and 6.0 respectively. beta-D-Galactosidase A was activated by 0.1 M-NaC1 but the activity of the B form was inhibited by 1 M-NaC1 at pH 4.5. beta-D-galactosidase had a bimodal distribution, the A form being recovered in the lysosomal fraction whereas the B form was present in the soluble fraction, as was the major portion of the beta-D-glucosidase activity. The lysosomal and soluble forms were further characterized by DEAE-cellulose chromatography.

Animals↗
PubMed1977

Changes in rat renal cortex, isolated plasma membranes and urinary enzymes following the injection of mercuric chloride.

Some of the biochemical changes in rat kidney following the administration of mercuric chloride have been determined. Mercuric chloride had an immediate effect on the renal brush border resulting in rapid loss of the microvilli. Plasma membranes were isolated and characterised at various stages in the necrotic process, mircovilli were absent from these preparations and the activities of marker enzymes for the brush border were significantly decreased. In contrast the basal plasma membranes were unaffected by the nephrotoxin during the early stages and no change occurred in the activity of (Na+ + K+)-ATPase, a marker enzyme for the basal membranes. The change in the pattern of urinary enzyme excertion closely paralleled the ultrastructural changes in the tubular cells. The sequence of subcellular change following the administration of mercuric chloride is discussed in relation to the known mechanism of action of this agent.

Acid Phosphatase↗