Intrathymic expression of genes involved in organ specific autoimmune disease.

Insulin, thyroglobulin and myelin basic protein (MBP) are implicated as autoantigens in the autoimmune diseases, insulin-dependent diabetes mellitus (IDDM), autoimmune thyroid-disease and multiple sclerosis. Self tolerance to these antigens, until recently only thought to be present extrathymically, is generally considered to be maintained by 'peripheral' mechanisms, such as clonal anergy or clonal ignorance. The techniques of reverse transcription and polymerase chain reaction (RT-PCR) were used to investigate the intrathymic expression of these genes. Expression was examined in mRNA isolated from complete adult rat thymus, various mouse thymic cell-types isolated from fetal thymic-organ cultures and from neonatal-mouse thymocyte subsets. mRNA for insulin, thyroglobulin and MBP were detected in unfractionated adult rat and embryonic mouse thymus. Rat thymus expressed both insulin I and II, while mouse thymus only expressed insulin II. Thyroglobulin and MBP, but not insulin mRNA were detected in mouse MHC class II+ thymic epthelial cells and class II+ dendritic cells and in certain thymocyte subsets. The presence of insulin, thyroglobubin and MBP mRNA in the thymus has important implications for the development of the T-cell repertoire, particularly for the mechanisms of tolerance that prevent autoreactivity to these antigens in healthy individuals.

The importance of measurement of effective transducers radiating area in the testing and calibration of "therapeutic" ultrasonic instruments.

The data presented show early results from a longitudinal survey of "therapeutic" ultrasonic instrument performance in clinical physiotherapy. Previous studies undertaken in North America and the United Kingdom have shown that these units tend not to be scientifically tested and recalibrated, and have been found to have measured outputs at variance with the metered values if tests have been undertaken. This study measured effective transducer radiating area and, concurrently, the total power output at the metered intensity used for the area estimations. Actual output, in terms of total power and space averaged intensity was then compared with expected values derived both from manufacturers' data and from measured transducer radiating area. Only four of eighteen transducers (22%) were within the specified tolerance when actual transducer area was taken into account. Range was 179-31% of expected values. False assumptions of acceptable and unacceptable output can arise from failure to measure actual transducer radiating area.