Clouds, shadows, or twilight? Mayfly nymphs recognise the difference

1. We examined the relative changes in light intensity that initiate night-time locomotor activity changes in nymphs of the mayfly, Stenonema modestum (Heptageniidae). Tests were carried out in a laboratory stream to examine the hypothesis that nymphs increase their locomotion in response to the large and sustained reductions in relative light intensity that take place during twilight but not to short-term daytime light fluctuations or a minimum light intensity threshold. Ambient light intensity was reduced over a range of values representative of evening twilight. Light was reduced over the same range of intensities either continuously or in discrete intervals while at the same time nymph activity on unglazed tile substrata was video recorded. 2. Nymphs increased their locomotor activity during darkness in response to large, sustained relative light decreases, but not in response to short-term, interrupted periods of light decrease. Nymphs did not recognise darkness unless an adequate light stimulus, such as large and sustained relative decrease in light intensity, had taken place. 3. We show that nymphs perceive light change over time and respond only after a lengthy period of accumulation of light stimulus. The response is much lengthier than reported for other aquatic organisms and is highly adaptive to heterogeneous stream environments

Childhood malignant lymphoma. Favourable outlook with aggressive combination chemotherapy and radiotherapy.

From 1963-1974, 62 cases of malignant lymphoma were treated: 24 patients with Hodgkin's lymphoma (HL) and 38 with non-Hodgkin's lymphoma (NHL). Relapse rate in children with HD before 1971 (pre-laparotomy data) was significantly higher than in the group after 1971, when explorative laparotomy, splenectomy and more aggressive radio- and chemotherapy were applied ( 10 15 vs 2 9). Since 1970 all children with NHL were entered in a modified leukaemia protocol combining radiotherapy to the primary site, prophylactic C.N.S.-irradiation and aggressive multiple drug chemotherapy. In this group 23 26 patients achieved complete remission vs 7 12 before 1970, when therapy consisted of low dose irradiation to the primary site, and/or single agent chemotherapy. Median survival in the group before 1970 was 5 months compared with 34+ months after 1970. Only 1 patient receiving prophylactic C.N.S.-irradiation developed C.N.S.-leukaemia vs 5 12 in the group before 1970