Biomedical subjects

C R Leveille

Publications and source records attributed to C R Leveille.

9 recordsLinked to original sources

PubMed1995

The expression of P-glycoprotein in canine lymphoma and its association with multidrug resistance.

Canine lymphoma is a spontaneous, naturally occurring disease that is a model for non-Hodgkin's lymphoma in humans. Chemotherapy with antineoplastics results in a high rate of remission; however, relapse and clinical drug resistance are usually seen within 8-10 months. The P-glycoprotein product of the mdr gene is thought to function as an ATP-driven membrane drug efflux pump and appears to play an important role in tumor cell resistance. To assess the role of mdr gene products in drug resistance in canine lymphoma, membrane preparations of lymphoma cells from 31 dogs with high- or intermediate-grade lymphoma were subjected to Western blotting for detection of P-glycoprotein. In this study, one of 30 samples taken from dogs prior to receiving chemotherapy expressed detectable levels of P-glycoprotein. P-glycoprotein was also detected in biopsy samples from 3 of 8 dogs that had become resistant to chemotherapy. This pattern of expression is similar to that in human non-Hodgkin's lymphoma. These studies suggest that canine lymphoma is a useful model for studying multidrug resistance.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1993

Multiple drug resistance.

Explore the source record for details and available documents.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1991

Treatment of posttraumatic carinal stenosis by balloon dilation during thoracotomy in a cat.

A cat with posttraumatic stenosis of the terminal part of the thoracic portion of the trachea and carina was successfully treated by balloon dilation of the stenosis during thoracotomy. Thoracotomy was performed at the right fifth intercostal space, and the stenosis was dilated, using a balloon-tipped catheter passed through an endotracheal tube. A 6-week course of orally administered corticosteroids was instituted after surgery. Balloon dilation during thoracotomy is a technically simple procedure for treatment of stenosis of the thoracic portion of the trachea.

Animals↗

PubMed1987

Serum bile acid determination for assessment of hepatic injury in the woodchuck.

A direct spectrophotometric assay for determination of the serum bile acid concentration in the woodchuck (Marmota monax) has been validated. The assay relies on the conversion of 3-hydroxy bile acids to 3-oxo bile acids by 3 alpha-hydroxysteroid dehydrogenase with concomitant reduction of NAD+ to NADH. Reduction of NAD+ is coupled via a diaphorase catalyst to the formation of a diformazan dye from nitrotetrazolium blue and the diformazan product is measured spectrophotometrically at 540 nm. Interfering endogenous dehydrogenase activity present in woodchuck sera was inactivated with sodium pyruvate. Mean recovery of seven exogenous bile acids added to woodchuck sera was 102.0 +/- 2.2%. Intra-assay precision was determined with ten replicate samples giving a mean +/- standard error of the mean of 1.94 +/- 0.12 micron/L with a coefficient of variation of 3.9%. The mean serum bile acid concentration determined in 33 clinically healthy animals was 5.52 +/- 0.81 micron/L. The serum bile acid concentration increased following surgical ligation of the bile duct from 3.78 +/- 0.58 micron/L to a maximum value of 148.0 +/- 30.7 micron/L and remained increased for the 42 day study period. In woodchucks treated with carbon tetrachloride, the serum bile acid concentration peaked at 16 hours following treatment at 72.7 +/- 29.3 micron/L, and returned to pretreatment concentration within 6 days. The serum bile acid concentration therefore appears to be a sensitive biochemical test of cholestasis and hepatocellular forms of hepatic injury and of potential value in the clinical assessment of hepatic disease associated with woodchuck hepatitis virus infection.

Animals↗

PubMed1984

Direct spectrometric determination of serum bile acids in the dog and cat.

Serum bile acid concentrations have been shown to be a predictive indicator of hepatobiliary disease in persons. However, there has been only limited use of bile acid values in the clinical diagnosis of hepatobiliary disease in the dog and cat because of technical difficulties associated with many bile acid assays. A rapid enzymatic method previously developed for the quantitation of 3-hydroxy bile acids in persons has been adapted for use in the dog and cat. Nonsulfated 3-hydroxy bile acids are converted to 3-oxo bile acids by 3 alpha-hydroxysteroid dehydrogenase and reduction of NAD+ to NADH. In a coupled diaphorase catalyzed reaction, H+ is transferred to nitrotetrazolium blue to produce a diformazan dye, which is measured spectrophotometrically at 540 nm. Nonspecific interfering dehydrogenase activities present in the dog and the cat serums were inhibited by heating the serum to 60 C for 30 minutes or by the addition of sodium pyruvate. Standard curves prepared from various serum sodium taurocholate concentrations in dogs and cats are linear to 250 mumol/L. The assay is sensitive for the detection of bile acid concentrations as low as 2.5 mumol/L in sera from dogs and cats. In validation studies quantitative recovery of known concentrations of 7 primary and secondary, conjugated and unconjugated, 3-hydroxy bile acids from pooled canine serum was 95.3 +/- 7.9% (mean +/- SEM) and that from pooled feline serum was 101.4 +/- 8.2%.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1982

Effect of ascorbate on lysosomal enzyme activities in guinea pig cartilage and adrenals.

The effect of ascorbic acid on adrenal and cartilage lysosomal enzyme activity was evaluated in guinea pigs maintained on either 2.4 mg, or 150 mg of ascorbate per day. When compared to adrenal enzyme activities in animals on high dietary levels of ascorbate, the adrenals of animals on 2.4 mg of ascorbate per day expressed 50% increase in the activities of acid phosphatase, arylsulfatase A, and arylsulfatase B (p less than 0.02). In cartilage, the activity of acid phosphatase was significantly elevated in animals on low dietary levels of ascorbate (p less than 0.01), but arylsulfatase A and arylsulfatase B activities were not affected by varying the dietary intake of ascorbate. These data indicate an inverse relationship between tissue vitamin C concentrations and lysosomal enzyme activities.

Acid Phosphatase↗

PubMed1981

Experimentally induced osteoarthritis in guinea pigs: metabolic responses in articular cartilage to developing pathology.

Developing osteoarthritis, surgically induced in the right hind knee joint of guinea pigs by different procedures (A or B), was studied in animals maintained on either minimal or supplemented levels of dietary vitamin C. Procedure A, consisting of transecting the anterior cruciate and major portion of the medial collateral ligaments, resulted in a slower developing and less severe form of the disease than procedure B which also included a partial menisectomy. Regardless of the surgical procedure used, animals on minimal levels of ascorbate always exhibited more severe pathology than those on high levels. When compared with controls, a significant enhancement of acid phosphatase characterized arthritic cartilage in both supplemented and minimal diet groups, although the increase was 2-fold greater in the latter. In addition, a significant elevation of arylsulfatase A and B activities was observed only in the minimal diet group. Early stages of pathology in both diet groups were characterized by formation of repair cartilage which stained strongly with Safranin O on histologic sections. As the disease progressed, pitting, ulcerations, and eburnation occurred in the minimal diet group. Cartilage weight in normal joints was greater for guinea pigs kept on high levels of vitamin C. It is likely that this stimulated synthesis of cartilage in the supplemented animals protected against the erosion of the articular cartilage which characterized the more severe disease process in the guinea pigs on minimal levels of ascorbate.

Animals↗

PubMed1981

Proteoglycan structure and metabolism in normal and osteoarthritic cartilage of guinea pigs.

Sulfated proteoglycan structure and metabolism in osteoarthritic articular cartilage from the hind-limb joints of guinea pigs in which the disease had been surgically induced were evaluated and compared with those from nonoperated or sham-operated controls. In these studies, conducted on animals receiving high and low dietary levels of ascorbic acid, the effect of vitamin C on these variables was also examined. Sulfated proteoglycan biosynthesis per unit of DNA as reflected by in vivo uptake of 35S-sulfate was stimulated both by arthritic development and high dietary vitamin C. Under these conditions, the specific activities, 35S-cpm/micrograms uronic acid, of the proteoglycans were elevated. Neither arthritic development nor variation in dietary levels of vitamin C altered the structure of the proteoglycans. Two species of proteoglycans that exhibited the same electrophoretic mobilities in agarose/acrylamide gels, the same elution profiles on high performance liquid chromatography,, and the same galactosamine/glucosamine ratios were found in all normal and osteoarthritic cartilage specimens tested. The specific activities of these two specimens tested. The specific activities of these two species were dissimilar. In all samples, the larger of the two species had a higher specific activity.

Animals↗

PubMedDate not supplied

Pathophysiology and pharmacologic modulation of hepatic fibrosis.

Most chronic liver disorders are accompanied morphologically by the deposition of fibrous tissue within the hepatic parenchyma. This fibrotic tissue compromises hepatic function and contributes significantly to hepatic failure. Fibrosis is a dynamic process associated with the continual deposition and resorption of connective tissue. Therapeutic strategies are emerging whereby this dynamic process can be modulated. Since collagen is the major component of the extracellular matrix deposited in hepatic fibrosis, most anti-fibrotic therapies have been directed toward the control of collagen metabolism. After collagen genes are transcribed and translated into precursor procollagen proteins, a number of post-translational modifications that ensure the deposition of structurally sound collagen within the extracellular matrix occur. A number of drugs can specifically modulate collagen biosynthesis at the transcriptional level or at various post-translational stages. These anti-fibrotic drugs include corticosteroids, azathioprine, penicillamine, colchicine, zinc, prostaglandins, cyclosporine, and interferons. The pharmacologic action of these drugs and the clinical role in veterinary and human fibrotic hepatopathies will be discussed.

Animals↗