Bicarbonate uptake by basolateral membrane vesicles from rat jejunum

Basolateral membranes from rat jejunal enterocytes have been obtained by self-orienting Percoll-gradient centrifugation. Bicarbonate and L-glucose uptake into osmotically active basolateral membrane vesicles has been studied by a rapid filtration technique. In closed vessels and at pH 8.2 the uptake kinetics of both [14C]bicarbonate and L[3H]glucose have been followed for 30 min at 18 degrees C. Bicarbonate uptake seems to be fast and in efflux experiments SITS and DIDS effect is negligible. This work demonstrates that it is possible to determine bicarbonate flux across basolateral membrane vesicles at pH and temperature values close to usual experimental conditions.     

Enzyme-linked immunosorbent assay (ELISA) for the identification of mosquito bloodmeals

An ELISA for the identification of mosquito bloodmeals (MBM) is described. The technique makes use of commercial antisera and allows to investigate at least three different animal sources on the same MBM. The efficiency of identification is 100% for up to 20 hrs-digested MBM.     

Structural Genes for a Newly Recognized Acetolactate Synthase in Escherichia coli K-12

Evidence is reported that shows the presence in Escherichia coli K-12 of a newly found acetolactate synthase. This enzyme is the product of two genes, ilvH and ilvI, both located very close to leu. Amber mutations have been found in both genes and therefore their products are polypeptides. Mutations in the ilvH gene cause the appearance of an acetolactate synthase activity which is relatively resistant to valine inhibition and can be separated by adsorption on hydroxylapatite from another activity present in the extract and more sensitive to valine inhibition than the former. A mutant altered in the ilvI gene was isolated among the revertants sensitive to valine inhibition of an ilvH mutant. Such a mutant lacks the resistant acetolactate synthase. A temperature-sensitive revertant of the ilvI mutant contained a temperature-sensitive acetolactate synthase. Thus ilvI is the structural gene for a specific acetolactate synthase. The activity of the ilvH gene product has been measured by adding an extract containing it to a purified ilvI acetolactate synthase, which, upon incubation, became more sensitive to valine inhibition. Conversely, a valine-sensitive acetolactate synthase (the product of the ilvH and the ilvI genes) became more resistant to valine inhibition upon incubation with an extract of a strain containing a missense ilvH gene product.