Triiodothyronamine--a beta-adrenergic metabolite of triiodothyronine?

Triiodothyronamine (Triam) is a potential metabolite of triidothyronine (T3), resulting from decarboxylation of the side-chain. In an attempt to elucidate the physiological properties of Triam we have investigated the binding of Triam to beta-adrenergic receptors, using turkey-erythrocytes and performing binding studies with ( (-)(3H)-dihydroalprenolol) ( (-)(3H)-DHA) as a specific beta-adrenergic ligand. The inhibition constant Ki for Triam was determined as 5 X 10(-6) M, compared to dopamine (Ki = 1,3 X 10(-2) M), norepinephrine (Ki = 3 X 10(-4) M), epinephrine (Ki = 5 X 10(-5) M) and isoproterenol (Ki = 3 X 10(-6) M). The inhibition of ( (-)(3H)-DHA)-binding by Triam was further compared with other iodothyronines thyroxine (T4), T3, 3,3',5'-triiodothyronine (rT3) and 3,3'-diiodothyronine (3,3'-T2). It is concluded that Triam binds to beta-adrenergic receptors like naturally occurring amines but different from typical circulating iodothyronines.     

Physical analysis of the genomes of hybrid phages between phage P1 and plasmid p15B

The genomes of three plaque-forming recombinant phages between phage P1 and plasmid p15B were characterized by restriction cleavage analysis and electron microscopic heteroduplex studies. The structure of all three P1-15 hybrid genomes differs from that of P1 DNA in the res mod region coding for restriction and modification systems EcoP15 and EcoP1, respectively. P1-15 hybrid 2 shows an additional major difference to P1 around the site of the residential IS1 element of P1 and it does not carry an IS1 in its genome.     

Cell cycle associated changes in histamine release from rat basophilic leukemia cells separated by counterflow centrifugal elutriation

This study evaluated histamine release from cells at different stages of the cell cycle. Cells from the cloned rat basophilic leukemia subline (RBL-2H3) were fractionated by counterflow elutriation according to size and density. The smallest cells were predominantly in the G1 phase of the cell cycle. These cells contained the least histamine and after IgE-mediated triggering released the lowest fraction of their total histamine. In contrast cells in the S, G2, and M stages were larger, contained more histamine and released more of their histamine after activation. When G1 stage cells were recultured, there was an increase in cell size, in histamine content and histamine release. Therefore, there is heterogeneity in the capacity of cells for IgE-mediated triggering at different stages in the cell cycle, with optimal release from the more mature cells.     

Gas mixing in the airways of dog lungs during high-frequency ventilation

Washout of insoluble inert test gases of different diffusivity (He and SF6 or He and Ar) from dog lungs was studied during high-frequency ventilation (HFV). Test gas equilibrium and subsequent washout were performed with HFV, succeeding measurements being performed at different stroke volumes (1.5-2.5 ml/kg body wt), oscillation frequencies (10-30 Hz), and with different lung volumes (32-74 ml X kg-1). Test gas concentrations were continuously measured by a mass spectrometer. The time course of washout could be described as the sum of two exponentials. There were no consistent differences in the time courses of washout between He and SF6 or between He and Ar. It is concluded that gas mixing in the airways during HFV is not significantly limited by diffusion, and this is suggested to apply during HFV to steady-state transport of respiratory gases (e.g., O2 and CO2) as well as to the transient state of inert gas washout.     

Polymeric structure of a high-molecular-weight glycoprotein from bovine cervical mucus.

A 16 X 10(6)-Mr glycoprotein isolated from bovine oestrus cervical mucus when reduced under conditions where disulphide-bond cleavage is essentially quantitative produces chains whose Mr from light-scattering and from sedimentation and diffusion data is some 4 X 10(6)-5 X 10(6). Pronase digestion of the chains indicates that glycosylated sequences of Mr 0.3 X 10(6)-0.5 X 10(6) are interspersed with enzyme-susceptible non-glycosylated peptide sequences.     

Saturated Fatty Acid Mutant of Saccharomyces cerevisiae with an Intact Fatty Acid Synthetase

To determine directly the effects of streptomycin on translational fidelity in intact cells, we studied the synthesis of beta-galactosidase and of the coat protein of bacteriophage R17 in an Escherichia coli mutant in which the bactericidal effects of streptomycin are delayed. After the addition of streptomycin to exponentially growing mutant cells, protein synthesis continues at an undiminished rate for approximately an hour; however, as measured by enzyme assays, little functional protein is produced. Serological assays designed to detect beta-galactosidase and bacteriophage R17 coat protein show that substantial amounts of the protein synthesized can react with antisera prepared against active beta-galactosidase and phage R17, indicating the aberrance of the protein produced in the presence of the antibiotic. The polypeptides synthesized in the presence of streptomycin are degraded in the cell to a much greater extent than protein synthesized in the absence of the antibiotic. The proteolytic attack on this protein is not affected by inhibitors of serine proteases, suggesting that enzymes other than those involved in "normal turnover" of cellular protein are responsible. In this strain, certain of the multiple effects of streptomycin are separated in time and the production of abnormal protein (enzymatically inactive and susceptible to proteolytic attack) could be studied in the absence of the lethal effect of the drug.