Effects of phorbol dibutyrate on M currents and M current inhibition in bullfrog sympathetic neurons

1. Effects of bath-applied phorbol dibutyrate (PDBu) on M currents (IM) and on the inhibition of IM by muscarine and luteinizing hormone-releasing hormone (LHRH) were recorded in voltage-clamped bullfrog lumbar sympathetic ganglion cells. 2. PDBu (0.1-30 microM) produced a slowly developing, irreversible and partial (less than or equal to 60%) inhibition of IM. This effect was not replicated by 4-alpha-phorbol or by vehicle. 3. After treatment with PDBu, residual IM showed a reduced sensitivity to inhibition by muscarine or LHRH but not by Ba2+. The reduced response to muscarine appeared to result from a 10-fold shift in the concentration dependence for inhibition. 4. PDBu did not clearly reproduce the ability of muscarine to inhibit the slow, Ca-activated K current IAHP or to increase the leak conductance at hyperpolarized potentials. The latter effect of muscarine was enhanced, rather than inhibited, by PDBu. 5. IM and IAHP were not inhibited by 1 mM dibutyryl cyclic AMP or by 20 microM forskolin. 6. It is concluded that activation of protein kinase C, but not protein kinase A, partly replicates the effect of muscarine on frog sympathetic neurons.     

Assessing the consultation: methods of observing trainees in general practice.

We compared two different methods of observing trainees at work in general practice: the traditional one of a senior or training general practitioner sitting in during selected surgeries and the more modern video recording, with the patients'' written consent. Patients who had experienced the presence of a second doctor during the consultation were less likely to show an increase in arousal after their consultations than those who had been recorded on video. Patients who refused consent to be recorded were more highly stressed than those who agreed and showed smaller decreases in stress after consultations. The presence of two doctors generated fewer reductions in stress after the consultation than video recording did, but this was a non-significant trend. The group that was recorded on video did not differ appreciably from a control group in changes in stress or arousal.     

Xyloside inhibits synthesis of the class II-associated chondroitin sulfate proteoglycan and antigen presentation events

An alternative form of the human invariant chain exists as a chondroitin sulfate proteoglycan (CSPG) with invariant chain as the core protein. The selective inhibitor of proteoglycan synthesis, p-nitrophenyl beta-D-xyloside was used to study the role of this CSPG in class II biology. At xyloside concentrations of 2.5 and 5.0 mM, CSPG synthesis was completely inhibited with marginal inhibition of protein synthesis. The inhibitory effect on CSPG synthesis was completely reversible. The number of class II molecules on the cell surface was not affected by xyloside, but biosynthesis and appearance of newly synthesized class II molecules at the cell surface were both decreased by xyloside. Recognition of influenza virus-infected cells by class II-restricted, virus-specific cytotoxic T lymphocytes was not diminished by the presence of xyloside in the effector phase of the cytotoxicity assay. However, sensitization of target cells was markedly inhibited when target cells were exposed to virus in the presence of xyloside. These results are consistent with the hypothesis that the CSPG form of invariant chain has a role in antigen processing.     

Preferential repair of N-acetoxy-acetylaminofluorene lesions in the nuclease-hypersensitive region of simian virus 40

We exposed simian virus 40-infected CV-1 monkey cells to the carcinogen N-acetoxy-acetylaminofluorene and monitored the removal of lesions from cellular DNA and from various regions of viral DNA. Exposure to 5.5 microM 3H-labeled carcinogen produced 20-80 adducts per 10(6) bases in cellular DNA in different experiments. The initial adduct concentration in viral DNA was always approximately half that in cellular DNA. At various times after treatment, cellular and viral DNA, and restriction fragments of viral DNA, were purified and examined for adduct density. Independent of the initial adduct concentration three rates of repair were observed. Cellular DNA was repaired at the lowest rate. Viral DNA was repaired about 50% more rapidly than was cellular DNA isolated from the same carcinogen-treated monolayers. Within the viral DNA a 366-base pair region containing the major nuclease-hypersensitive site was repaired at twice the rate of the rest of the viral genome. This region contains regulatory sequences that govern the initiation of DNA replication and viral gene expression. As reported previously this region was initially modified 1.71 +/- 0.20-fold higher than expected from its guanine content. Selective repair diminished the extent of hypermodification of this region by 6.0 +/- 2.1% per hour, partly compensating for the higher initial level of adducts.