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Biomedical subjects

G H Mudge

Publications and source records attributed to G H Mudge.

At least 91 records · Page 5Linked to original sources
PubMed1978

Chronic hepatic inflammation and fibrosis due to low doses of paracetamol.

Chronic hepatic necrosis developed in a man who had been taking 4 g of paracetamol daily for about a year (cumulative dose 1700 g). Liver biopsy done 23 days after the drug was stopped showed prominent diffuse central necrosis and portal changes. Repeat biopsy 5 months later showed chronic active hepatitis. This prompted anti-inflammatory treatment, with subsequent improvement in liver histology. Liver concentrations of reduced glutathione and paracetamol metabolism, assessed 1-1 1/2 years after drug was stopped, were normal; the basis for this patient's drug sensitivity is thus unclear. In some patients, chronic ingestion of therapeutic doses of paracetamol may produce hepatic necrosis and hepatitis which persist long after the drug has been discontinued.

Acetaminophen↗
PubMed1978

Synthesis of N-hydroxyacetaminophen, a postulated toxic metabolite of acetaminophen, and its phenolic sulfate conjugate.

The synthesis of N-hydroxyacetaminophen (N-acetyl-N-hydroxy-p-aminophenol, 4), a postulated toxic metabolite of acetaminophen (N-acetyl-p-aminophenol, 3), and its phenolic sulfate conjugate (potassium N-acetyl-N-hydroxy-p-aminophenyl sulfate) (13) is described. Potassium p-nitrophenyl sulfate was reduced to the hydroxylamine, acetylated, and treated with sulfatase to yield N-hydroxyacetaminophen. The structures assigned are supported by the spectral data (IR, UV, MS, 1H NMR, and 13C NMR). N-Hydroxyacetaminophen was found to be moderately unstable at physiological pH and temperature, whereas it phenolic sulfate conjugate was stable.

Acetaminophen↗
PubMed1978

Inotropic and toxic effects of a polar cardiac glycoside derivative in the dog.

It has been suggested that central nervous system (CNS) neuroexcitation plays an important role in digitalis-induced cardiac arrhythmias. To elucidate further the role of the CNS in digitalis-induced arrhythmias, the inotropic and toxic effects of a highly polar semisynthetic cardiac glycoside, 3beta-O-(4 amino-4,6 dideoxy-beta-D-galactopyranosyl)-digitoxigenin (ASI-222) were compared to those of digoxin and correlated with plasma and cerebrospinal fluid (CSF) concentrations of each drug. Thirteen dogs anesthetized with sodium pentobarbital were given repeated intravenous doses of digoxin or ASI-222. Ventricular tachycardia was elicited at a mean dose of digoxin of 0.12 mg/kg, compared with 0.09 mg/kg for ASI-222 (not significant). Terminal ventricular fibrillation occurred after 0.18 mg/kg of digoxin, a value significantly larger than the ASI-222 dose (0.14 mg/kg, P less than 0.05) required to produce lethal arrhythmias. Digoxin produced a 21% increase in LV dP/dt at a plasma digoxin concentration of 20.0 +/- 2 ng/ml (mean +/- SEM) 30 minutes after 0.05 mg/kg; the CSF digoxin concentration at this time averaged 0.7 +/- 0.1 ng/ml. At death, the plasma digoxin concentration was 88 +/- 16 ng/ml and CSF digoxin concentration was 5.7 +/- 1.6 ng/ml. ASI-222 produced a similar 25% increase in LV dP/dt 30 minutes after administration of 0.05 mg/kg, with a plasma concentration of 18 +/- 2 ng/ml as determined by a newly developed radioimmunoassay. The plasma ASI-222 concentration at death, 95 +/- 18 ng/ml, was similar to that of digoxin. However, CSF samples at 30 minutes and at death showed no detectable levels of ASI-222. Thus, despite similar inotropic and toxic responses and similar plasma drug concentrations compared to digoxin, ASI-222 was demonstrated to have limited if any access to the CNS as judged by CSF concentrations. These findings suggest that direct CNS stimulation does not play a primary part in the genesis of digitalis-induced cardiac arrhythmias in this experimental model, or that CNS effects are mediated by an area or areas lacking an effective blood-brain barrier.

Aminoglycosides↗
PubMed1978

Covalent binding of metabolites of acetaminophen to kidney protein and depletion of renal glutathione.

Experiments in CD-1 mice and Sprague-Dawley rats were carried out to determine the extent to which biochemical changes described previously for acute acetaminophen-induced hepatotoxicity might be applicable to the kidney. After intraperitoneal injection of acetaminophen, tissue glutathione and covalent binding of tritiated metabolites of acetaminophen to tissue protein were measured for liver, kidney cortex and kidney papilla. Glutathione was reduced more in mice than in rats, and more in liver than in kidney, without appearance of oxidized glutathione in either tissue. Covalent binding was likewise greater in mice than in rats and greater in liver than in kidney. The determination of covalent binding was extremely sensitive to the trace radiochemical impurities of the labeled drug. With prior administration of 3-methyl-cholanthrene, the induced changes were far greater in liver than in kidney, suggesting that the formation of a reactive metabolite from acetaminophen occurred in each organ by slightly different mechanisms. At doses less than those associated with demonstrable acute toxicity, the duration of covalent binding to protein was longer for renal papilla than for renal cortex or for liver. The results may be applicable to the pathogenesis of both acute and chronic nephrotoxicity.

Acetaminophen↗
PubMed1976

Reflex increase in coronary vascular resistance in patients with ischemic heart disease.

To assess possible coronary vasoconstriction in patients with ischemic heart disease, we measured coronary vascular resistance in 12 patients with normal hearts and 12 with coronary disease before and during the initial 50 seconds of cold pressor test, a stimulus known to produce systemic vasoconstriction. Control coronary vascular resistance was similar in the two groups, and although it did not change in patients with normal vessels, it rose by 27 per cent (P less than 0.005) in the group with coronary disease during the cold pressor test. In three of 12 patients with coronary disease coronary flow actually declined despite an increase in arterial pressure; in four, angina was precipitated. Phentolamine abolished increases in arterial pressure and coronary vascular resistance during the test in three patients with coronary disease. Adrenergically mediated coronary vascular tone may be an important determinant of coronary blood flow and may contribute to ischemia in patients with coronary disease.

Adrenergic alpha-Antagonists↗
PubMed1976

Alterations of myocardial amino acid metabolism in chronic ischemic heart disease.

Arteriovenous differences (A-V) of all naturally occurring amino acids, lactate, and oxygen were measured simultaneously with coronary sinus blood flow (CSBF) in 8 normal subjects and 11 patients with coronary artery disease at rest and during pacing stress. Mean values for CSBF and myocardial oxygen consumptions (MVO2) for the two groups were similar at rest and during pacing, although mean CSBF and MVO2 increased significantly in both groups in the paced as compared to the rest state. Alanine (ala) was the only amino acid released by the myocardium, while only glutamic acid(glu) demonstrated uptake. Mean A-V ala was negative at rest in the control and coronary disease groups (-4.8+/-3.8 vs. -22.0+/-3.0 nmol/ml, respectively), but was significantly more negative in the coronary group (P less than 0.001) and not statistically different than zero in the normals. A-V ala became significantly negative with pacing in the normals (-10.0+/-4.3 nmol/ml), remained unchanged in the coronary group (-23.0+/-2.9 nmol/ml), and was significantly more negative in the coronary group (P less than 0.05). Calculation of data on the basis of net ala flux ([A-V] X [CSBF X hematocrit]) yielded similar results as that obtained with A-V differences. A-V glu was significantly positive in normals (27.7 +/- 8.9 nmol/ml, P less than 0.01) and coronary patients (59.9 +/- 8.9 nmol/ml, P less than 0.01) at rest but significantly greater in the latter group (P less than 0.001). With pacing, A-V glu remained significantly greater than zero in coronary patients (35.3 +/- 6.3 nmol/ml) and decreased to zero in the normals (4.3 +/- 11.8 nmol/ml). Calculation of net glu flux (nmol/min) at rest yielded data similar to that based on A-V difference. With pacing, net glu flux in the coronary patients did not decrease due to the augmentation of CSBF. No relation between A-V glu or ala and CSBF, MVO2 or A-V lactate was noted. The data demonstrate that specific alterations of myocardial amino acid metabolism characterize patients with chronic ischemic heart disease.

Adult↗
PubMed1976

Phenacetin: renal tubular transport and intrarenal distribution in the dog.

In a total of 22 studies in the anesthetized dog, the renal clearnace of phenacetin was measured over a range of plasma concentrations and at different urinary pH and rates of urine flow. Phenacetin is reabsorbed by passive diffusion. The urine/plasma ratio is essentially unity under all conditions. As measured by ultraviolet-spectrophotometric and colorometric methods and by high-pressure liquid chromatography, a labile metabolite appears in urine and renal papilla which upon hydrolysis gives rise to falsely high values for phenacetin. Renal cortical and papillary concentrations were determined in six dogs during hydropenia or diuresis. All tissue/plasma concentration ratios for phenacetin were essentially unity. The results indicate that the papillary localization of the earliest lesions of analgesic nephropathy cannot be attributed to high phenacetin concentrations within the papilla. This is in contrast to acetaminophen, the major metabolite of phenacetin.

Animals↗
PubMed1976

Analgesic nephropathy: renal distribution of acetaminophen and its conjugates.

Acetaminophen (APAP) and its conjugates (APAP-conj) are the major metabolites of phenacetin. To study their significance in the pathogenesis of analgesic nephropathy, their concentrations in the renal parenchyma were determined in conjunction with clearance measurements in 15 dogs with inulin as a reference marker. Particular attention was given to interpretation of the mechanisms responsible for the concentrations generated within the papilla. For APAP, APAP-conj and inulin there is a significant corticomedullary gradient which is inversely related to the rate of urine flow. For inulin and APAP-conj, this gradient may be explained by their concentrations within the tubular fluid of the distal nephron. With concentration in the urine as a reference, the apparent volume of distribution of inulin within the papilla is not fixed, but varies with the rate of urine flow. Using several different types of comparison with inulin, we found that the results with APAP are consistent with its penetration by diffusion into the cellular compartment of the papilla. Dehydration leads to maximal concentrations of APAP in the urine as well as in the tubular fluid and the cells of the distal nephron. This is consistent with the kinetics of diffusion.

Acetaminophen↗
PubMed1975

Renal tubular transport of paracetamol and its conjugates in the dog.

1 The renal tubular transport of paracetamol and its conjugates was investigated with renal clearance and stop flow studies in the dog. Paracetamol is sparingly bound to plasma proteins and therefore undergoes glomerular filtration. It is reabosrbed in the renal tubules by simple diffusion. 2 The conjugates of paracetamol, the sulphate and the glucuronide, both undergo glomerular filtration being weakly protein bound. At low concentrations in plasma both compounds are secreted by an active transport process. At higher concentrations both compounds are reabsorbed. Clearances are not dependent on urinary pH or flow rate. It is concluded that reabsorption is not a passive process but that there is an active bidirectional transport of the conjugates. 3 Net tubular secretion of the sulphate, but not the glucuronide, conjugate was inhibited by the administration of probenecid.

Acetaminophen↗
PubMed1975

Electrolyte excretion and free-water production during onset of acute diuresis.

The concentration of major urinary solutes was studied in ureteral urine collected at 15- to 30-s intervals at the onset of acute diuresis induced in anesthetized dogs either by high-ceiling diuretics (mainly ethacrynic acid) or by osmotic diuretics. Phosphate/inulin clearance ratios remained unchanged; potassium/inulin clearance ratios rose rapidly. Principal attention is given to the mechanisms underlying a transient rise in urinary sodium and chloride concentrations during the onset of diuresis. When the data are corrected for washout artifacts from the pelvis and ureter, it can be shown that the initial collection periods are associated with a transient increase in free-water production and by the simultaneous secretion of urea from the interstitium into the tubular fluid. The former coincides in time with the rise in urinary chloride concentration and represents an augmentation of water reabsorbed in the collecting duct, which is relatively impermeable to chloride. Both responses are quantitatively consistent with the transition from a hyperosmotic to isosmotic medullary interstitium.

Animals↗
PubMed1975

Effect of biliary stasis and hepatotoxins on the excretion of iopanoate in the rat.

In rats, hepatic dysfunction was induced with CCl4, SKF 525-A, taurolithocholic acid and alpha-naphthylisothiocyanate and by acute and chronic surgical ligation of the bile duct. Biliary and urinary excretion of 125I-labeled iopanoate was measured after a standard i.v. dose. In the absence of normal biliary excretion, the amount excreted in the urine varied over a wide range (0.25-11.2 percent of the dose), with highest rates of urinary excretion occurring after alpha-naphthylisothiocyanate and chronic stasis. Drug disposition was further determined by tissue analysis of liver and kidney. The results indicate that, for a drug that is normally almost exclusively excreted by the bile, in the presence of hepatic dysfunction the amount excreted by the alternate urinary route depends on the type of the induced hepatic disorder. The intrarenal distribution of 125I-radioactivity is strongly influenced by its plasma concentration rather than just by the rate of excretion in the urine.

Animals↗
PubMed1975

Oral cholecystography: osmotic activity of iopanoic glucuronide in bile.

The cholecystographic agent iopanoic acid (Telepaque) is excreted in high concentrations in the bile as the glucuronide, but produces little or no choleresis. In order to determine the osmotic characteristics of the excretory product, bile was collected from treated and untreated anesthetized dogs and the major solute concentrations and biliary osmolality were determined. After iopanoic acid, there was no change in biliary osmolality or in chloride or bicarbonate concentration. However, the calculated osmolality exceeded the measured osmolality to a significant degree. The data suggest that iopanoic glucuronide, like bile salts, is osmotically inactive because of micelle formation. From physiological considerations, low osmotic activity of the excreted contrast agent might enhance radiographic quality.

Administration, Oral↗