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Biomedical subjects

D T Plummer

Publications and source records attributed to D T Plummer.

At least 19 recordsLinked to original sources
PubMed2000

The combined effect of cyclosporine a and gentamicin on enzymuria in the Sprague-Dawley rat.

Male Sprague-Dawley rats (8 per group) were administered a single oral dose of cyclosporine A (10, 30 and 50 mg/day) for 5 days or vehicle (corn oil, 1.5 mL/kg) and urinary enzymes excretion was monitored. Only minor changes in enzymuria were observed in the 10 and 30 mg/kg group. However, in the 50 mg/kg group, nephrotoxicity was evident by significant increase in the excretion of N-acetyl-beta-D-glucosaminidase (NAG), glutamate dehydrogenase (GDH), and lactate dehydrogenase (LDH on day 2 of treatment. As chemotherapeutic drug interaction with cyclosporine A (CyA) is thought to aggravate its nephrotoxicity, the effect of combined CyA (30 mg/kg) and the antibiotic gentamicin (50 mg/kg) for 5 days was investigated. Gentamicin alone caused a significant enzymuria, whilst co-treatment of rats with CyA gave rise to increased changes in enzymuria on days 1 and 2, between the groups receiving gentamicin+vehicle and those receiving CyA+gentamicin. This was particularly marked by significant changes in LDH excretion. In contrast these observed differences were not paralleled by changes in serum creatinine and other functional parameters. Treatment with gentamicin, appears to enhance CyA nephrotoxicity, but only in the first 2 days, after this there was no significant differences between the two groups. Our data suggest that urinary enzyme measurements could serve as a valuable non-invasive means of monitoring renal performance in animals or humans who may be exposed to combination of drugs. CyA is found not to potentiate the nephrotoxic effect of gentamicin in the animal model used in this study. It therefore appears safe to use the combined therapy particularly in the treatment of transplant patients.

Acetylglucosaminidase↗
PubMed1995

Renal damage caused by gentamicin: a study of the effect in vitro using isolated rat proximal tubular fragments.

The clinical use of gentamicin (G) is limited because of its nephrotoxic potential. The administration of G (50 mg/kg) to rats in a 10-day daily treatment gave a biphasic pattern of lactate dehydrogenase (LDH) and N-acetyl-beta-D-glucosaminidase (NAG) excretion. Alkaline phosphatase (ALP) was highly elevated during the corresponding second phase while a slight and statistically insignificant increase in glutamate dehydrogenase (GDH) was obtained. The kidneys of such rats were isolated and tubules prepared and incubated for a specific period of time at 37 degrees C in Kreb's Henseleit bicarbonate buffer, pH 7.4. Results indicate a considerable loss of protein (P < 0.01) after the 3rd and 10th days of treatment with G, elevated and significant increase of ALP after the 1st (P < 0.05) and 3rd (P < 0.01) days and significant increase (P < 0.05) of GDH after the 10th day of treatment. The release of GDH, LDH and NAG from tubules of rats after a single dose of G was lower than the control rats while other treatments produced a significant increase in ALP, LDH and NAG over the period of incubation. In vitro incubation of tubules in the presence of several concentrations (5, 50, 500, 5000 micrograms/g of wet cortex) of G indicated a time-dependent leakage of enzyme only at the highest concentration of G. Our results clearly indicate that cellular damage caused by G as evidenced by urinary enzyme excretion and marker enzyme release from isolated tubules occurs at very high concentration in vivo or in vitro and is time-dependent.

Acetylglucosaminidase↗
PubMed1993

Influence of hydration states on the acute nephrotoxic effect of gentamicin in the rat.

The influence of acute water loading and water deprivation on gentamicin-induced nephrotoxicity was examined in rats by administering the drug (50 mg kg-1) into a group of hydrated rats and another 24 h-dehydrated group. Renal damage was assessed by measuring urinary enzymes, protein, urine flow rate and cell excretion in urine. Water loading alone caused significant alterations (2-5-fold) of the parameters under observation while these parameters were either lower or of comparable values to the untreated controls in water-deprived rats. Gentamicin administration further resulted in the elevation of all parameters in water-loaded rats. However, elevated alkaline phosphatase (P < 0.01), similar excretion of muramidase and decreased excretion of N-acetyl-beta-D-glucosaminidase compared to the controls was observed in water-deprived rats given gentamicin. Cells excreted in the urine were mainly renal tubular and squamous epithelial types in the control and all treated rats. These cells contain between 2 and 10% of the total enzyme activity in the urine of untreated-control rats. Increases in the percentage of these enzymes were observed as follows: in water-loaded (12-24%); water-deprived (4-26%); gentamicin alone (16-27%); water-loaded rats given gentamicin (11-30%); and water-deprived rats receiving gentamicin (8-15%). These observations demonstrate that the toxicity of gentamicin could be aggravated by both water loading and water deprivation. Water load alone is also associated with physiopathological changes in the kidney cells.

Animals↗
PubMed1988

Nephrotoxicity of high- and low-osmolality contrast media.

Nephrotoxicity of radio-opaque contrast media (CM) is generally believed to involve toxic injury of proximal tubular cells. Measurement of urinary tubular enzyme excretion has been advocated as a sensitive marker of such toxic injury. It has been claimed that the new low-osmolality or nonionic CM reduce the incidence of nephrotoxicity but this remains uncertain. We studied 23 patients with normal renal function undergoing coronary angiography; patients were randomized into three groups receiving either diatrizoate (1,800 mmol/kg H2O), ioxaglate (600 mmol/kg H2O) or iohexol (850 mmol/kg H2O). Urinary excretion of a panel of enzymes increased significantly in all groups by 20 h (p less than 0.05 to less than 0.005). Alanine aminopeptidase excretion at 20 h was greater after the administration of high osmolality ionic CM than with the others but all three CM produced a similar pattern of enzyme excretion. No significant change in glomerular filtration rate was found in any group so the significance of the enzymuria remains uncertain.

Adult↗
PubMed1981

Affinity chromatography of acetylcholinesterase. The use of Amberlite CG-120 for dissociating the enzyme-inhibitor complex.

Acetylcholinesterase from rat brain was solubilized with 1% (w/v) Triton X-100 and purified by affinity chromatography. Two different ligands were investigated. The most efficient purification was obtained when the enzyme was eluted from a column containing the acetylcholinesterase inhibitor N-methyl-3-aminopyridinium iodide covalently linked to Sepharose 2B. An initial recovery of 6% of the applied enzyme increased to 70% after treatment with Amberlite CG-120. The partially purified enzyme had a specific activity of 205 mumoles min-1 mg-1 and a purification of 162-fold with respect to the brain homogenate and 44-fold with respect to the Triton solubilized enzyme. The effect of metal cations on the stability of the partially purified enzyme during storage at --20 degrees C was also investigated. The addition of MgCl2 to the purified enzyme prevented the rapid loss of enzyme activity.

Acetylcholinesterase↗
PubMed1980

The effect of insulin on the electrophoretic mobility of rat hepatocytes.

The addition of insulin (10 microU) to a suspension of isolated hepatocytes in Krebs-Ringer bicarbonate solution, causes an increase in the negative electrophoretic mobility of the cells from - 1.68 micrometer sec-1 V-1 cm to 2.26 micrometer sec-1 V-1 cm. This observation supports the findings by other workers that the binding of insulin to its receptor leads to a marked change in the membrane.

Animals↗
PubMed1979

The effect of cephaloridine on the stability of rat kidney lysosomes.

The administration of cephaloridine to rats caused a decrease in the excretion of acid phosphatase into the urine. The antibiotic itself had no effect on urinary acid phosphatase and inhibitors or proteolytic enzymes were not present in the urine from treated rats. Cephaloridine may therefore be stabilizing the lysosomal membrane in vivo and experiments with isolated lysosomes confirm this hypothesis. The lysosomal integrity was followed by measuring the acid phosphatase activity and the light scattering properties of the particles. A good correlation was obtained between these parameters in the case of thermal disruption and progesterone induced lysis of the lysosomes and low concentrations of cephaloridine (0.1-1.0 mmol/1) protected the lysosomes against this form of damage.

Acid Phosphatase↗
PubMed1979

The monitoring of lysosomal integrity by pH-stat and light scattering measurements.

Light scattering measurements were used to monitor the integrity of isolated rat kidney lysosomes during prolonged incubation at 37 degrees C or following the addition of lysolecithin. The fall in extinction at 520 nm (E520) was shown to correlate very well with the fall in the particulate enzyme activity and the corresponding rise in the soluble enzyme activity. Measurements were also made of the release of H+ from the lysosomes into the suspending medium following treatment with lysolecithin. A good relationship was obtained between acidification of the medium and changes in the light scattering (E520) of the lysosomal suspension. The value of these techniques in following rapid changes in the integrity of lysosomes is discussed.

Animals↗
PubMed1979

The interaction of cephaloridine with model membrane systems and rat kidney lysosomes.

The antibiotic cephaloridine has been shown to interact with phospholipid structures, using the techniques of ultraviolet difference spectroscopy, surface pressure measurements and liposome models. The results indicate that this interaction is at least partly hydrophobic in nature and help explain the disruptive effects of high concentrations of cephaloridine on both artificial and natural phospholipid structures (lysosomes). Low concentrations of cephaloridine were shown to inhibit a lysosomal membrane-bound phospholipase 2 and it is suggested that such an inhibition may explain the cephaloridine-induced stabilization of rat-kidney lysosomes.

Animals↗
PubMed1979

The sensitivity of urinary enzyme measurements for detecting renal injury.

The relative sensitivity of urinary enzyme measurements for detecting renal damage was determined for two nephrotoxins. Injection of a single dose of sodium phosphate (10 mmoles/kg) caused damage to the proximal tubules and led to a 15 fold increase in lactate dehydrogenase (LDH) activity excreted into the urine. In contrast to this change the serum LDH remained normal. Similar results were obtained following the injection of cephaloridine (2 g/kg) with an 18 fold increase in urinary LDH and a marginal increase in urinary glutamate dehydrogenase (GDH). By contrast the serum LDH was unchanged. Urinary enzymes are therefore more sensitive for detecting renal injury than enzymes. The four enzymes investigated are located in specific regions of the cell so that the involvement of the organelles and regions of the cell can be followed. Damage to the organelles does not appear to occur as the excretion of the lysosomal enzymes remained normal and only in the case of cephaloridine were marginal changes in the mitochondrial GDH excretion seen. The average alkaline phosphatase was also normal suggesting no gross damage to the plasma membrane although a few individual rats excreted abnormal activities of alkaline phosphatase. These rats however, also excreted high activities of LDH. This suggests that damage to the membrane causes leakage of LDH and in severe cases release of the plasma membrane enzyme alkaline phosphatase. The administration of cephaloridine at various doses showed that urinary enzyme measurements were as sensitive as histology for demonstrating renal damage and that of these enzymes, LDH was by far the most useful.

Acid Phosphatase↗
PubMed1978

Purification of acetylcholinesterase from pig cerebral cortex by affinity chromatography.

Acetylcholinesterase from pig cerebral cortex was solubilised with 1% (w/v) Triton X-100 and purified by affinity chromatography. Three different ligands were investigated and details are given for their preparation. The elution profile depended on the presence of Triton X-100, the ionic strength and the inhibitor used to remove the enzyme from the column as well as the nature of the affinity material. The most efficient purification was obtained when the enzyme was eluted from a column containing the acetylcholinesterase inhibitor [1-methyl-9-(Nbeta-epsilon-amino-caproyl)-beta-aminopropylamino] acridinium bromide hydrobromide covalently linked to Sepharose 4B. A recovery of 44% of the applied enzyme was eluted from the column with a specific activity of 148 mumoles min-1 mg-1 and a purification of 900-fold.

Acetylcholinesterase↗
PubMed1978

The interaction of purified acetylcholinesterase from pig brain with liposomes.

The binding of pig brain acetylcholinesterase to artificial phospholipid membranes was investigated at different temperatures. Calculation of the thermodynamic parameters revealed a small negative enthalpy change, but a large negative change in the free energy and a large positive change in the entropy on binding. The large entropy change might be interpreted as being responsible for forming the enzyme-membrane complex and was indicative of hydrophobic interactions between lipid and protein. This conclusion would also favour the hypothesis that the enzyme was an integral protein. Further support for this theory was provided by the study of acetylcholinesterase binding to liposomes containing the phospholipid 1,2-dimyristoyl-sn-glycero-3-phosphocholine. Lowering the temperature below the transition temperature or incorporating cholesterol into the liposomes decreased enzyme binding. Both factors could be interpreted as decreasing the fluidity of the hydrocarbon side chains of the phospholipids, causing an increase in bilayer thickness due to closer packing of side chains. This membrane condensation would certainly not favour the binding of integral protein molecules.

Acetylcholinesterase↗