Geographical variation in leucine aminopeptidase in Mytilus edulis L. From the Irish coasts

Phenotypic variation in leucine aminopeptidase has been demonstrated in Mytilus edulis L. from twelve localities in Ireland. It is proposed that one locus with three common and two rare alleles is responsible for one group of variants. The frequencies of the common alleles are significantly correlated with the relative amount of wave action (exposure) at the sites investigated. M. edulis seems to exhibit an above average amount of genetic variation thereby paralleling the variations in growth rate, shell morphology, filtration rate, and certain kinetic parameters previously recorded amongst individuals of this species. In view of the apparently close correlation between genotype and environmental conditions and since genotype in other species is known to control survival and growth rate, genetic studies of the kind described here could clearly have important implications for the commercial mussel fishery.     

An electron microscopic method for studying and mapping the region of weak sequence homology between simian virus 40 and polyoma DNAs.

A procedure for investigating the possibility of small amounts of partial DNA sequence homology between two defined DNA molecules has been developed and used to test for sequence homology between simian virus 40 and polyoma DNAs. This procedure, which does not necessitate the use of separated viral DNA strands, involves the construction of hybrid DNA molecules containing a simian virus 40 DNA molecule covalently joined to a polyoma DNA molecule, using the sequential action of EcoRI restriction endonuclease and Escherichia coli DNA ligase. Denaturation of such hybrid DNA molecules then makes it possible to examine intramolecularly rather than intermolecularly renatured molecules. Visualization of these intramolecularly renatured “snapback” molecules with duplex regions of homology by electron microscopy reveals a 15% region of weak sequence homology. This region is denatured at about 35 °C below the melting temperature of simian virus 40 DNA and therefore corresponds to about 75% homology. This region was mapped on both the simian virus 40 and polyoma genomes by the use of Hemophilus parainfluenzae II restriction endonuclease cleavage of the simian virus 40 DNA prior to EcoRI cleavage and construction of the hybrid molecule. The 15% region of weak homology maps immediately to the left of the EcoRI restriction endonuclease cleavage site in the simian virus 40 genome and halfway around from the EcoRI restriction endonuclease cleavage site in the polyoma genome.     

A method for determining the adenosine triphosphatase content of energy-transducing membranes. reaction of 4-chloro-7-nitrobenzofurazan with the adenosine triphosphatase of bovine heart submitochondrial particles.

1. Modification of a single amino acid residue by introduction of the nitrobenzofurazan group inactivates mitochondrial ATPase (adenosine triphosphatase) when membrane-bound in submitochondrial particles. The similarity between the reactions of both membrane-bound and isolated ATPase with 4-chloro-7-nitrobenzofurazan indicates that the single essential tryosine residue identified in the isolated enzyme [Ferguson, Loyd, Lyons & Radda (1975) Eur. J. Biochem. 54, 117-126] Is also a feature of the membrane-bound ATPase. 2. A procedure is presented for estimating the ATPase content of the inner mitochondrial membrane. It is based on the specificity of the incorporation of the nitrobenzofurazan group, and the ready removal of this group by compounds that contain a thiol group. This method indicates that 8.5% of the membrane protein is ATPase. The procedure should be applicable to the titration of the energy-transducing ATPases of bacterial plasma membranes and of the thylakoid membranes of chloroplasts. 3. Combination of the data obtained on the ATPase content of the bovine heart inner mitochondrial membrane with a titration of the cytochrome bc1 complex with antimycin indicates that these two components of the membrane are present in approximately equal amounts.     

Selective and reversible inhibition of the ATPase of Micrococcus denitrificans by 7-chloro-4-nitrobenzo-2-oxa-1,3 diazole

The covalent inhibitor of the beef heart mitochondrial ATPase 7-chloro-4-nitrobenzo-2-oxa-1,3 diazole inhibits the ATPase of phosphorylating particles prepared from Micrococcus denitrificans. Inhibition of both ATP synthesis and ATP hydrolysis occurs at similar rates, with a similar pH dependence, and in each case the inhibition is relieved by treatment with dithiothreitol. These results are compared with those previously obtained with the mitochondrial ATPase.     

Precipitins to Dietary Proteins in Serum and Upper Intestinal Secretions of Coeliac Children

We have used precipitin tests to detect antibodies to 10 dietary proteins in the serum (71 cases) and intestinal secretions (51 cases) of a group of children. Thirty-three of the patients had untreated coeliac disease. Our aims were to find out if, in coeliac patients, there was intestinal secretion of antibodies to wheat proteins only or if, as in coeliac serum, antibodies to many food proteins were present; and to confirm that secretion of antibodies to wheat or gluten was specific for coeliac disease.Precipitins to one or more dietary antigens were detected in the intestinal secretions of 26 out of 30 coeliacs and of 11 out of 21 children who did not have coeliac disease. Most of the positive reactions were with the antigens wheat flour, gluten, oatmeal, and egg. Though precipitins to wheat flour or gluten were present in the intestinal secretions of 22 out of 30 coeliacs this was not specific for coeliac disease for these precipitins were also present in 8 out of 21 non-coeliac children.Serum precipitins were detected in 27 out of 33 coeliacs (to the antigens wheat flour, gluten, oatmeal, rice flour, milk, bovine calf serum, sheep serum, and egg) and in 5 out of 33 non-coeliacs (mainly to milk and calf serum, but two infants aged 3 and 5 months had precipitins to several antigens).     

Myoglobin polymorphism in the pollan (Osteichthyes: Coregoninae).

Three electrophoretically separable phenotypes of heart and lateral line muscle myoglobin were found in the Irish pollan (Coregonus pollan). This polymorphism appears to be under the control of two co-dominant alleles. The allele frequencies were found to be virtually identical in samples from two lakes which have probably been isolated since the close of the last Ice Age. A significant excess of heterozygotes was found in samples from both lakes. This myoglobin polymorphism appears to be balanced, maintained due to heterozygote superiority.     

The absence of a growth inhibitor during the log phase of growth of Dictyostelium discoideum

When amebae of the cellular slime mold Dictyostelium discoideum Ax-3 reach stationary phase in liquid nutrient medium, an extracellular factor appears which will inhibit cell multiplication when added to a logarithmically multiplying culture (Yarger et al., 1974). Recently, Hanish (1975) presented evidence that an inhibitor also accumulated during log phase and concluded that the cessation of cell multiplication and the final cell concentration were controlled by the accumulation of this inhibitor to an effective level. We have reexamined this extremely interesting observation, but have found no evidence to support Hanish's conclusions.