Immunoperoxidase localization of elastin in the human aorta

Summary Use of the peroxidase-antiperoxidase technique with preliminary trypsinization has allowed immunolocalization of elastin in human aorta. By this method it is possible to utilize formalin-fixed and paraffin-embedded tissue. The advantages in studying a strongly-autofluorescent material are discussed.     

The Drosophila clock gene per affects intercellular junctional communication

The per locus of Drosophila has been implicated in the control of behavioural rhythms. In fruitfly embryos and larvae per is expressed in salivary glands. Per mutations have striking effects on intercellular communication in salivary glands: gap junction channels are modulated so that their conductance varies inversely with the period of behavioural rhythms in the mutants. A similar effect on junctional communication in the nervous system may explain how per influences behavioural rhythms.     

Constitutive synthesis of interleukin-3 by leukaemia cell line WEHI-3B is due to retroviral insertion near the gene

Interleukin-3 (multi-CSF) is a multilineage haematopoietic growth regulator that initiates the proliferation and differentiation of multipotential stem cells. Complementary DNA clones encoding interleukin-3 (IL-3) have recently been isolated and the structure of the IL-3 gene determined. IL-3 is produced by T lymphocytes or T lymphomas only after stimulation with antigens, mitogens or chemical activators such as phorbol esters. The myelomonocytic leukaemia line WEHI-3B also produces IL-3 but its production is constitutive and the WEHI-3B cells do not appear to produce significant levels of any of the other lymphokines normally secreted by T lymphocytes after stimulation. It has been proposed that the genetic change leading to the constitutive expression of IL-3 may have been a key event in the development of this leukaemia. We report here that the constitutive synthesis of IL-3 by the WEHI-3B cell line is due to the insertion of an endogenous retrovirus-like element close to the 5' end of the gene. The insertion, an intracisternal A particle (IAP) genome, is positioned with its 5' long terminal repeat (LTR) close to the promoter region of the IL-3 gene, resulting in constitutive synthesis of IL-3.     

Pollen-collecting by stingless bees on cacao flowers

Summary Stingless bees (Trigona jaty) routinely visit the flowers ofTheobroma cacao (Sterculiaceae) in the Atlantic lowlands of Costa Rica. The bees collect pollen and behave as pollen thieves in flowers well exposed to direct sunlight in cacao plantations, and avoid flowers in heavy shade. Pollination rates are maximized, however, in heavy shade due to the high abundance of the small-bodied pollinating midges (Ceratopogonidae and Cecidomyiidae) found in such places. Pollen-thieving by stingless bees, therefore, may only impact on fruit set in cacao trees in direct sunlight, with only minimal to no impact in areas of cacao where natural pollinator activity is high.This research was funded by grants from The American Cocoa Research Institute of the United States of America. I thank T. Noeske for statistical assistance.     

γ辐射剂量计的响应函数及特征参量

本文导出一次击中和二次击中相叠加的响应函数,作为描述各种γ辐射剂量计响应的基本方程,引入特征剂量D_0和一次击中因子R,并阐明了辐射剂量响应的线性、超线性和亚线性与这两个参量的关系。模型计算与实验结果相符合。