Mary Whittaker

Heterogeneity of the silent gene for plasma cholinesterase. Immunological studies.

Rocket immuno-electrophoresis and enzyme-linked immunosorbent assays were used to estimate the amount of cholinesterase present in 29 apparent silent homozygotes. 26 of these samples were segregated into four groups representing zero, very low, low and high levels of immunoreactive protein. These groups may represent the genotypes E1sE1s, E1sE1t, E1tE1t and a new genotype E1xE1x, respectively. The possible genotypes of the remaining 3 individuals are discussed.

The serum cholinesterase variants. Differentiation by means of formaldehyde

Abstract The effect of varying concentrations of formaldehyde on the activities of “usual” and “atypical” serum cholinesterase using benzoyl choline as substrate has been examined. The “atypical” enzyme has been shown to be more sensitive to inhibition than the “usual” enzyme. The effect of neuraminidase on this differential inhibition has been shown to be negligible.

Evidence for an abnormality in the erythrocyte membranes of patients having paroxysmal nocturnal haemoglobinuria and aplastic anemia

Abstract Triton X 100-solubilised acetylcholinesterase (acetylcholine acetylhydrolase, E.C. 3.1.1.7) has been prepared from the erythrocyte membranes of three healthy adults and three patients with paroxysmal nocturnal haemoglobinuria (PNH). The elution profile of the membranes from one of the PNH bloods after gel filtration on Sepharose 4 B differed from the others in acetylcholinesterase and protein content. Density gradient centrifugation using sucrose has shown that the density of the membranes from the same PNH blood was considerably less than the densities of the other membrane samples. Similar treatment of a mixture of equal volumes of normal and atypical PNH membranes resulted in a clear separation of the two components. Polyacrylamide disc electrophoresis has shown that the protein pattern obtained from erythrocyte membranes of this individual differed from those obtained from the other specimens. Subsequent investigations revealed that the atypical PNH membranes were obtained when the patient was severely aplastic. A repeat specimen obtained when the patient was hyperplastic showed none of the above abnormalities.

Immunological studies of families segregating the silent gene for plasma cholinesterase

Seven families segregating apparently silent gene homozygotes have been investigated by enzyme-linked immunosorbent assays. These families confirm not only the heterogeneity of the silent gene in the form of E1s and E1t but in 3 families there is support for the segregation of the new gene E1x.

Immunological assay of erythrocyte acetylcholinesterase

An immunoassay for the quantitation of erythrocyte surface acetylcholinesterase is described; using a red cell suspension, bound mouse monoclonal acetylcholinesterase antibody is detected by an alkaline phosphatase conjugated rabbit anti mouse IgG. Extraction is not required. In addition, the activity of erythrocyte surface acetylcholinesterase using dithiobisnitrobenzoate to detect released thiocholine has been measured. The coefficient of variation for each method is 7%. Reference ranges have been established for healthy adults and cord blood.

Recognition of the Ek1Ek1 homozygote for plasma cholinesterase.

A family is reported in which the propositus was found to be sensitive to suxamethonium. Both parents were heterozygote each having genotype Ea1Ek1. The sibling of the propositus had the most common phenotype as defined by dibucaine, fluoride and RO2 numbers. Genetic analysis, however, indicated that this sibling must be an Ek1Ek1 homozygote.