Relief of transcriptional polarity by a mutation that creates a promoter in the hisG gene of Salmonella typhimurium LT2.

Six mutant strains were independently isolated in Salmonella typhimurium as non-polar revertants of a polar Tn10 insertion in hisG. DNA sequence analysis showed that all six mutants result from the same nucleotide alteration: a G/C to A/T transition 4 bp from the end of the hisG coding sequence. We present data suggesting that the mutation (hisG10225) acts by creating a new transcriptional initiation signal. Furthermore, the hisG10225 mutation renders the hisG gene product cold sensitive.

Effect of Cromoglycate on Gas Changes, During Bronchial Challenge by UNCDW in Children with Asthma.

Eighteen asthmatic children were challenged with ultrasonically nebulized cold distilled water (UNCDW). Blood gas composition was monitored transcutaneously (tcpO(2) and tcpCO(2)) during and after the challenge. Assuming as basal the response to this UNCDW test, nine children (Group A) were then chosen at random to inhale cromoglycate by aerosol delivery for 8 days. Nine children (Group B), acting as a control, inhaled saline for 8 days. At the end of this therapy, each child repeated the UNCDW test. Statistical analysis with t-test for paired data was used to compare the results of each child to both tests. Mean basal tcpO(2) and tcpCO(2) were all within the expected normal range. In all children, both mean tcpO(2) and tcpCO(2) were reduced during and after UNCDW inhalation. Mean tcpCO(2) values during the challenge were significantly (p < 0.001) lower than the corresponding steady state 2 rain after the UNCDW challenge, with a mean drop of -7% (2.1 S.D.). Mean tcpO(2) values remained significantly decreased (p < 0.001) from the fifth mitt of the UNCDW challenge to the end of the observation period, with a mean drop of -20% (15.5 S.D.). After treatment with cromoglycate (Group A), the mean tcpCO(2) values during UNCDW did not change significantly from those ofsteady state conditions: -0.8% (0.5 S.D.); whereas mean tcpO(2) values decreased by -4% (4.9 S.D.). The control children treated with saline (Group B) showed mean tcpCO(2) and tcpO(2) values which were significantly different (p < 0.001) from those of the steady state conditions: mean drop of tcpCO(2), -6% (4.2 S.D.); mean drop of tcpO(2), -20% (4.7 S.D.). In conclusion, it emerges that: UNCDW induces nonspecific broncho-constriction in asthmatic children with a typical drop of tcpCO(2) and tcpO(2); the treatment with cromoglycate normalizes the time course of tcpCO(2) (hyper-reactivity) and reduces dramatically the drop of tcpO(2) time course (hyper-responsivity) during and after the UNCDW test.