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Biomedical subjects

M C Walker

Publications and source records attributed to M C Walker.

116 records · Page 7Linked to original sources
PubMed1977

The purification of antimorphine antibodies by affinity chromatography.

Affinity chromatography was employed successfully to purify extensively antimorphine antibodies produced in rabbits. Morphine succinylated at position 6 was attached to bovine serum albumin to make it immunogenic and to Sepharose beads for affinity chromatography. A crude gamma-globulin fraction of antimorphine serum, prepared by salt fractionation, was used for purification. After unbound gamma-globulin was washed off the column with phosphate-buffered saline, two populations of antimorphine antibodies were eluted in succession by two low pH buffers. Each of these two purified antibody fractions had an index of heterogeneity of approximately 1. Immunoelectrophoresis indicated that the antibodies were immunoglobulin G and that they formed a single precipitation band with antirabbit serum. The average association constants for morphine of the two purified antibody fractions were similar and ranged from 4.5 to 4.8 X 10(7) LITERS/MOL-1. A 67-fold purification of the antimorphine antibodies could be achieved by a single pass through an affinity column.

Antibodies↗
PubMedDate not supplied

Postprandial venous ammonia concentrations in the diagnosis of hepatobiliary disease in dogs.

A postprandial ammonia tolerance test (PPATT) was performed on normal dogs and dogs with signs that suggested they may have liver disease. All dogs underwent transcolonic scintigraphy, liver biopsy, or both and were assigned to extrahepatic disease, primary hepatocellular, and congenital portosystemic vascular anomalies (PSVA) groups. Each dog was fed a chicken and rice diet providing 25% of its estimated daily metabolizable energy requirement (MER) as an ammonia challenge. This is practical in patients with liver disease because ammonium chloride administration often causes vomiting or ammonia toxicity. Venous ammonia concentrations were measured before feeding and every 2 hours after feeding for 8 hours. No difference in mean ammonia concentrations between dogs with extrahepatic disease and control dogs was found. Therefore, the specificity of the PPATT was 100%. Dogs with hepatocellular disease showed no change in mean ammonia concentration at any time point, before or after feeding, but sensitivity was greatest when venous ammonia was measured 6 hours after feeding (sensitivity before feeding, 28%, and after feeding, 36%). Among dogs with congenital PSVA, mean ammonia concentrations were higher than the reference range at all time points before and after feeding, and peak mean ammonia concentration occurred 6 hours after feeding. In this group, the sensitivity of the PPATT was 81% before feeding and 91% 6 hours after feeding. This study demonstrates that the measurement of venous ammonia concentration is a useful test to detect congenital PSVA, and the sensitivity of the test may be improved by sampling 6 hours after feeding. The PPATT has poor sensitivity in detecting primary hepatocellular disease.

Ammonia↗