Age and beta adrenoceptor-mediated function

Beta adrenoceptor-mediated responsiveness to isoproterenol was compared in young and old subjects using the production of cyclic adenosine monophosphate (cyclic AMP) by lymphocytes as an index. The mean log dose-response curve for the elderly group was displaced to the right and the mean maximum response was less than that for the young subjects. The results corroborate evidence of a decreased response to isoproterenol-induced increases in heart rate in the elderly and raise the possibility of a generalized decrease in beta adrenoceptor-mediated functions in old age.

Characterization of the integration protein of bacteriophage lambda as a site-specific DNA-binding protein

The Int protein specified by bacteriophage lambda is required for the recombination event that integrates the viral DNA into the host genome at its specific attachment site. Using a DNA-binding assay, we have partially purified the Int protein and studied some of the features of its binding specificity and regulation. The DNA-binding activity is attributed to Int protein because the activity is eliminated by a nonsense mutation or a deletion in the int gene, and is rendered thermolabile by temperature-sensitive mutations in the int gene. The DNA-binding activity is specific for DNA carrying an appropriate attachment site, suggesting that Int protein directs the sequence-specific recognition essential for integrative recombination. The specific DNA-binding activity is also missing after infection by phage carrying mutations in the cII and cIII regulatory genes of lambda. This finding corroborates the conclusion from other types of experiments that regulation of the int and cI genes by cII/cIII provides for coordinate regulation of both major events of the lysogenic response, establishment of repression and insertion of viral DNA.

Utility of gaussian-type orbitals in molecular collisions: electronic excitation of the first positive system of the nitrogen molecule

The use of gaussian-type orbitals (GTO) as basis sets of electronic wave functions of molecules for calculating electron-collision excitation cross sections is discussed. A test calculation of the electron excitation cross section of the 2p state of atomic hydrogen at 60-1000 eV in which the hydrogenic wave functions were expressed as linear combinations of GTO indicates that an expansion of the is wave function by six GTO's and the 2p by four GTO's gives quite accurate results. Methods for evaluating the multicenter integrals which appear in the expressions of electron-excitation cross section (by the Born-type approximation) of diatomic molecules are described. Cross sections of direct electron excitation of the B(3)II(g) state (the first positive bands) of the N(2) molecule are calculated by this scheme, and the results are in good agreement with experiments.