Transient enhancement of serum somatomedin levels prior to weaning of growth-impaired vasopressin-deficient Brattleboro rats

Somatomedin serum levels of congenitally vasopressin-deficient Brattleboro rats were determined postnatally between day 1 and 55, and compared with heterozygous control values. Assays were performed with a radioimmunoassay of insulin-like growth factor 1 (IGF-1). A transient enhancement of immunoreactive IGF-1 levels between day 8 and 21 of age and a reduction in adulthood was found. This observation shows that the early growth impairments of the Brattleboro mutant are not due to a deficiency of IGF-1.     

Sequence of the ebgA gene of Escherichia coli: comparison with the lacZ gene

We have sequenced the ebgA (evolved beta-galactosidase) gene of Escherichia coli K12. The sequence shows 50% nucleotide identity with the E. coli lacZ gene, demonstrating that the two genes are related by descent from a common ancestral gene. Comparison of the two sequences suggests that the ebgA gene has recently been under selection. A significant excess of identical, rather than synonymous, codons used to encode identical amino acids at the same positions in the aligned sequences implies that some form of selection is operating directly at the DNA level. This selection is independent of, and in addition to, selection based on codon usage or on function of the gene products.      

Plasma esterase polymorphism in the Bank vole, Clethrionomys glareolus, in Britain

Three hundred and eighty-three Clethrionomys glareolus from 20 localities in England, Wales and Scotland were typed for plasma esterase and a genetic polymorphism was discovered. The esterase was named Es-1. Breeding tests suggested that three alleles were segregating: Es-1^o when homozygous results in complete absence of enzyme activity. The active alleles Es-1^f and Es-1^s code for enzyme variants which migrate more rapidly and less rapidly, respectively, under starch gel electrophoresis. Of these active alleles, Es-1^f is morc common in the north of Britain and Es-1⁸ in the south. A 23-month field study on two areas at Wicken Fen, Cambridgeshire, suggested that animals possessing Es-1^s survived less well at high population densities, perhaps through their being more likely to emigrate.     

Actions of synthetic piperidine derivatives on an insect acetylcholine receptor/ion channel complex

The actions of synthetic piperidine derivatives on the response to ionophoretically-applied acetylcholine (ACh) have been tested on the cell body membrane of the fast coxal depressor motoneurone (F_f) of the cockroach Periplaneta americana. The cis form and the cis (80%):trans (20%) mixture of 2-methyl-6-undecyl piperidine were the most effective (the half-maximal blocking action of the mixed isomers was estimated to be 6.3 × 10^?5 M). Less potent was the cis (50%):trans (50%) mixture of 2-methyl-6-tridecyl piperidine. However, pure cis 2-methyl-6-tridecyl piperidine was even less effective than the mixed isomers, indicating that, in the case of the tridecyl derivative, the trans form was largely responsible for the block of the ACh response.Cis 2-Methyl-6-undecyl piperidine failed to inhibit the binding of N-[propionyl-³H] propionylated α-bungarotoxin to metathoracic ganglion homogenates at concentrations up to 1.0 × 10^?4 M. Also, block of ACh-induced current by 2-methyl-6-undecyl piperidine (cis 80%:trans 20%) was largely independent of membrane potential in the range ?120 mV to ?60 mV, indicating an interaction with the closed ACh receptor/ion channel complex at a site which, in the case of the cis isomer, is separate from the binding site for α-bungarotoxin.     

Pressure effects on alamethicin conductance in bilayer membranes.

We report here the first observations of the effects of elevated hydrostatic pressure on the kinetics of bilayer membrane conductance induced by the pore-forming antibiotic, alamethicin. Bacterial phosphatidylethanolamine-squalene bilayer membranes were formed by the apposition of lipid monolayers in a vessel capable of sustaining hydrostatic pressures in the range, 0.1-100 MPa (1-1,000 atm). Principal observations were (a) the lifetimes of discrete conductance states were lengthened with increasing pressure, (b) both the onset and decay of alamethicin conductance accompanying application and removal of supra-threshold voltage pulses were slowed with increasing pressure, (c) the onset of alamethicin conductance at elevated pressure became distinctly sigmoidal, suggesting an electrically silent intermediate state of channel assembly, (d) the magnitudes of the discrete conductance levels observed did not change with pressure, and, (e) the voltage threshold for the onset of alamethicin conductance was not altered by pressure. Apparent activation volumes for both the formation and decay of conducting states were positive and of comparable magnitude, namely, approximately 100 A3/event. Observation d indicates that channel geometry and the kinetics of ion transport through open channels were not affected by pressure in the range employed. The remaining observations indicate that, while the relative positions of free-energy minima characterizing individual conducting states at a given voltage were not modified by pressure, the heights of intervening potential maxima were increased by its application.     

Partial Purification and Characterization of Cystine Lyase from Cabbage (Brassica oleracea var capitata)

Cabbage (Brassica oleracea var capitata) leaves were used as a source of cystine lyase. Diethylaminoethyl-cellulose chromatography resolved two peaks of activity, designated I and II.