Mites of the family Phytoseiidae, a diverse and widespread group, occur throughout the world from the Arctic through the tropics. The number of described species has increased from fewer than 20 in 1951 (Nesbitt, 1951) to over 450 in 1965 (Chant, personal communication). Opinion differs among' taxon

SummaryTo understand the process of cardiac aging, it is of crucial importance to gain insight into the age-related changes in gene expression in the senescent failing heart. Age-related cardiac remodeling is known to be accompanied by changes in extracellular matrix (ECM) gene and protein levels. Small noncoding microRNAs regulate gene expression in cardiac development and disease and have been implicated in the aging process and in the regulation of ECM proteins. However, their role in age-related cardiac remodeling and heart failure is unknown. In this study, we investigated the aging-associated microRNA cluster 17-92, which targets the ECM proteins connective tissue growth factor (CTGF) and thrombospondin-1 (TSP-1). We employed aged mice with a failure-resistant (C57Bl6) and failure-prone (C57Bl6 · 129Sv) genetic background and extrapolated our findings to human age-associated heart failure. In aging-associated heart failure, we linked an aging-induced increase in the ECM proteins CTGF and TSP-1 to a decreased expression of their targeting microRNAs 18a, 19a, and 19b, all members of the miR-17-92 cluster. Failure-resistant mice showed an opposite expression pattern for both the ECM proteins and the microRNAs. We showed that these expression changes are specific for cardiomyocytes and are absent in cardiac fibroblasts. In cardiomyocytes, modulation of miR-18 ⁄ 19 changes the levels of ECM proteins CTGF and TSP-1 and collagens type 1 and 3. Together, our data support a role for cardiomyocyte-derived miR-18 ⁄ 19 during cardiac aging, in the fine-tuning of cardiac ECM protein levels. During aging, decreased miR-18 ⁄ 19 and increased CTGF and TSP-1 levels identify the failure-prone heart.

The literature pertalOlOg to the bionomics of some of the mos t important tetranychids is r~viewed. Considerable attention is paid to the possihiliries of spider mites reaching pest le~els /as a 'resu lt of environmental factors. It is concluded that more infor--m ation is needed on economic injury levels of various species on d ifferent crops and under various climatic conditions. The in-I fluences of cultural practices and their interactions as related to population development of tetranychids also need more i tu dy. Furthermore, work is need~d on the influence of climatic conditions on development of retranychid mite populations together with possible predictability 'of outbreak situations. Finally; we need to know more about ·th)e fundamental relations between the host-planr-qualiry and spider mite development, and the, impact of spider mites on the development .of their .host p lants.

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