Similar patterns of hsp gene message were found with both cDNA probes for each temperature (Figs. 2 and 3). However, the patterns differed between temperatures. At 34 °C, there was the expected increase in message from 15 min onwards, being highest with the 1h treatment (Fig. 2). After the cells were returned to 25°C, there was a progressive loss of message over the subsequent 3 h. This loss was proportionally
greater after the 1h treatment, i.e. whilst there was a greater increase in message after 1 h at 34 °C, the subsequent loss at 25 °C was also greater. This pattern was more marked with the hsp70 (Mdhsp2) than the hsp17 (Mdhsp1) RNA. This pattern of increasing expression with duration of heat and then loss over 3 h at 25 °C was largely lost when cells were first heated to 38 °C (Fig. 3) rather than 34 °C (Fig. 2). At this higher temperature, message homologous to both probes continued to accumulate for up to 1.5h at 25°C for the shorter heat durations, and the loss over 3 h was not obvious.In other words, the higher temperature appeared to have a stronger and more lasting effect on hsp transcript levels.