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The behaviour of Varroa jacobsoni mites, with respect to orientation and site of their preferred temperature range, was studied as a function of age with the help of a temperature gradient apparatus. Groups of 20–30 animals were introduced into various temperatures upon a linear gradient ranging from 16–43 °C. It was determined that the range of preference for winter mites lay between 33.6–36.6 °C while that for the young summer mites lay between 31.8–37.2 °C. Zusammenfassung Untersuchungen über die Temperaturabbängigkeit des Verhaltens der Honigbienen‐Milbe Varroa jacobsoni O. In einem Temperaturgradienten wurde das Orientierungsverhalten von Varroa jacobsoni und die Lage des Präferenzbereiches in Abhängigkeit vom Alter untersucht. Gruppen von 20–30 Tieren wurden in die verschiedenen Temperaturbereiche des linearen Gradienten von 16–43 °C eingesetzt. Dabei wurde ermittelt, daß der Präferenzbereich der Wintermilben zwischen 33,6 und 36,6 °C lag, der der jungen Sommermilben dagegen zwischen 31,8 und 37,3 °C.

Bovine alveolar macrophages were incubated up to 20 h with DQ12 quartz particles, either in untreated native form or pretreated with dipalmitoyl lecithin. The content of cathepsin B and N-acetylglucosaminidase was measured in the culture supernatant and in the cells. After incubation, a loss of about 50% of the total cathepsin B activity in the culture dish was observed, whereas no influence on total N-acetylglucosaminidase content occurred. Loss of cathepsin B activity was completely prevented by the pretreatment of quartz with the surfactant component dipalmitoyl lecithin. Similarly, a complete abrogation of the quartz effect on cathepsin B was noted when the cells were incubated with quartz in the presence of NH4Cl in order to prevent phagosome-lysosome fusion. There was also no influence on cathepsin B activity when a lysosome-rich fraction, prepared from alveolar macrophages, was incubated together with quartz. It was concluded that the reduction of cathepsin B activity was related with the intralysosomal deposition of quartz particles.

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