Synthesis and preliminary antimicrobial screening of two thiosulfonates

Tetramethylene bis(methanethiosulfonate), the S-ester analog of busulfan, was prepared by reacting 1,4-dibromobutane with potassium methanethiosulfonate. 2,4-Dichlorophenyl methanethiosulfonate was prepared by reacting sodium methanesulfinate with 2,4-dichlorobenzenesulfenyl chloride. Neither compound showed antifungal activity against Microsporum audouini or Trichophyton mentagrophytes. Although tetramethylene bis(methanethiosulfonate) was more active against Staphylococcus aureus than was 2,4-dichlorophenyl methanethiosulfonate, neither compound was as active as the streptomycin control.     

Core domain mutation (S86Y) selectively inactivates polyubiquitin chain synthesis catalyzed by E2-25K

The mammalian ubiquitin conjugating enzyme known as E2-25K catalyzes the synthesis of polyubiquitin chains linked exclusively through K48-G76 isopeptide bonds. The properties of truncated and chimeric forms of E2-25K suggest that the polyubiquitin chain synthesis activity of this E2 depends on specific interactions between its conserved 150-residue core domain and its unique 50-residue tail domain [Haldeman, M. T., Xia, G., Kasperek, E. M., and Pickart, C. M. (1997) Biochemistry 36, 10526-10537]. In the present study, we provide strong support for this model by showing that a point mutation in the core domain (S86Y) mimics the effect of deleting the entire tail domain: the ability to form an E2 approximately ubiquitin thiol ester is intact, while conjugation activity is severely inhibited (>/=100-fold reduction in kcat/Km). The properties of E2-25K enzymes carrying the S86Y mutation indicate that this mutation strengthens the interaction between the core and tail domains: both free and ubiquitin-bound forms of S86Y-25K are completely resistant to tryptic cleavage at K164 in the tail domain, whereas wild-type enzyme is rapidly cleaved at this site. Other properties of S86Y-26K suggest that the active site of this mutant enzyme is more occluded than the active site of the wild-type enzyme. (1) Free S86Y-25K is alkylated by iodoacetamide 2-fold more slowly than the wild-type enzyme. (2) In assays of E2 approximately ubiquitin thiol ester formation, S86Y-25K shows a 4-fold reduced affinity for E1. (3) The ubiquitin thiol ester adduct of S86Y-25K undergoes (uncatalyzed) reaction with dithiothreitol 3-fold more slowly than the wild-type thiol ester adduct. One model to accommodate these findings postulates that an enhanced interaction between the core and tail domains, induced by the S86Y mutation, causes a steric blockade at the active site which prevents access of the incoming ubiquitin acceptor to the thiol ester bond. Consistent with this model, the S86Y mutation inhibits ubiquitin transfer to macromolecular acceptors (ubiquitin and polylysine) more strongly than transfer to small-molecule acceptors (free lysine and short peptides). These results suggest that unique residues proximal to E2 active sites may influence specific function by mediating intramolecular interactions.     

Mesenchyme specifies epithelial differentiation in reciprocal recombinants of embryonic lung and trachea

Normal lung morphogenesis and cytodifferentiation require interactions between epithelium and mesenchyme. We have previously shown that distal lung mesenchyme (LgM) is capable of reprogramming tracheal epithelium (TrE) from day 13-14 rat fetuses to branch in a lung-like pattern and express a distal lung epithelial phenotype. In the present study, we have assessed the effects of tracheal mesenchyme (TrM) on branching and cytodifferentiation of distal lung epithelium (LgE). Tracheae and distal lung tips from day 13 rat fetuses were separated into purified epithelial and mesenchymal components, then recombined as homotypic (LgM + LgE or TrM + TrE) or heterotypic (LgM + TrE or TrM + LgE) recombinants and cultured for 5 days; unseparated lung tips and tracheae served as controls. Control lung tips, LgM + LgE, and LgM + TrE recombinants all branched in an identical pattern. Epithelial cells, including those from the induced TrE, contained abundant glycogen deposits and lamellar bodies, and expressed surfactant protein C (SP-C) mRNA. Trachea controls, and both TrM + TrE, and TrM + LgE recombinants did not branch, but instead formed cysts. The epithelium contained ciliated and mucous secretory cells; importantly, no cells containing lamellar bodies were observed, nor was SP-C mRNA detected. Mucin immunostaining showed copious production of mucous in both LgE and TrE when recombined with TrM. These results demonstrate that epithelial differentiation in the recombinants appears to be wholly dependent on the type of mesenchyme used, and that the entire respiratory epithelium has significant plasticity in eventual phenotype at this stage in development.     

Physical fitness and psychological benefits of strength training in community dwelling older adults

Previous studies concerning psychological benefits of exercise among the elderly has focused predominantly on the effects of aerobic exercise. In the present study, psychological and behavioral adaptations in response to 12-weeks of strength training were examined in medically healthy but sedentary 42 older adults (mean age = 68 years). The purpose of this study was to evaluate the effects of high and low intensity resistance training intensity on a) muscular fitness, b) psychological affect, and c) neurocognitive functioning. Subjects were randomly assigned to high intensity/low volume (EXH: 2 sets of 8 to 10 repetitions for 75 to 85% of 1 RM), low intensity/high volume (EXL: 2 sets of 14 to 16 repetitions for 55 to 65% of 1 RM), or no exercise control programs. Prior to and following the 12-week program, subjects underwent comprehensive physiological and psychological evaluations. Physiological assessment included measurements of blood pressure, heart rate, arm and leg muscle strength, body composition, and oxygen consumption (VO2max). Psychological measures included evaluations of mood, anxiety, and physical self-efficacy as well as cognitive functioning. The results of this study indicated that both high and low intensity strength programs were associated with marked improvements in physiological fitness and psychological functioning. Specifically, subjects in the strength training programs increased overall muscle strength by 38.6% and reduced percent body fat by 3.0%. Favorable psychological changes in the strength-trained subjects included improvements in positive and negative mood, trait anxiety, and perceived confidence for physical capability. The treatment effects of neurocognitive functioning were not significant. In summary, this study demonstrated that participation in 12-weeks of high or low intensity strength training can improve overall physical fitness, mood, and physical self-efficacy in older adults while cognitive functioning remains constant.