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R Pownall

Publications and source records attributed to R Pownall.

At least 37 records · Page 2Linked to original sources
PubMed1980

Time of day of taking immunosuppressive agents after renal transplantation: a possible influence on graft survival.

Large-amplitude circadian rhythms in immune responses and the known variations in the effects of glucocorticoids with the time of day of administration suggest that immunosuppressive regimens may need to take this variable into account. In two similar groups of patients with renal transplants functioning satisfactorily after three months subsequent graft failure developed in 66% of those taking all immunosuppressives in the evening, compared with only 22% of those taking immunosuppressives twice daily (p < 0.05). A survey of other transplant units showed that one unit with outstanding results--graft survival at three years 82%--had a unique policy of morning-only administration of immunosuppressives. Doctors need to consider more carefully the time of drug administration when prescribing, as it may be possible to obtain better results with less toxicity.

Adult↗
PubMed1979

Possible effect of time on renal allograft rejection.

The change in plasma creatinine concentrations from decreasing values after successful renal transplantation to increasing values after the onset of rejection occurs as a sudden event. Twenty-two such episodes in 16 renal allograft recipients were studied by extrapolating sequential measurements of plasma creatinine concentrations to see when the change occurred. Seventeen of the episodes occurred between 2300 and 1100 and the rest at other times. This difference was significant. The results suggest that rejection is more common at night and apparently has a circadian rhythm, being likely to first influence creatinine clearance at around 0600.

Circadian Rhythm↗
PubMed1979

The time of day of antigen encounter influences the magnitude of the immune response.

Studies in the rat and in man have shown that the time of day at which an antigen is encountered has an influence on the expression of any subsequent cell-mediated immunity, when the response is measured after a fixed interval. This suggests that immune processes are modulated by intrinsic biological rhythms. Experiments are now reported in which sensitized rats were ear-challenged with oxazolone and studied at intervals during the delayed hypersensitivity reaction. These show that differences in the expression of immunity due to the clock time of challenge became apparent at an early stage and were still present after the maximum response, assessed by the change in ear thickness. The experiments also show that the circadian variations in antigen responsiveness are present during the second recall of immunity and can be manipulated by altering the lighting regimen. The light-dark cycle is often a synchronizer for biological rhythms, although its precise role in the oxazolone system remains to be evaluated. This study demonstrates that phase reversal of the lighting regimen alters the proportions of lymphocytes present in rat blood at two clock times, one of which is the time of day at which the maximum immune response to oxazolone is initiated.

Animals↗
PubMed1978

Circadian rhythmicity of delayed hypersensitivity to oxazolone in the rat.

1. A marked circadian rhythm was detected in the ear swelling of rats immunized and then challenged with oxazolone. 2. The peak response observed at 10.00 hours was over eight times the minimum at 16.00 hours. 3. As related tests are used frequently in man greater attention to clock time is necessary in clinical immunology.

Animals↗