The use of clip cages to restrain insects reduces leaf expansion systemically in Rumex obtusifolius

Abstract. 1. Clip cages have been used widely by experimental ecologists to contain insects on plants.
2. Under controlled conditions, the effect of applying clip cages alone and clip cages and the chrysomelid beetle Gastrophysa viridula on systemic leaf expansion of Rumex obtusifolius was investigated. Treatments were applied to the fully expanded fourth leaf and expansion of leaf 8 was measured over a period of 22 days.
3. The application of clip cages reduced the rate at which leaf area increased and led to reductions in final leaf areas.
4. Clip cages have systemic effects on plant development and these effects are sustained even after the clip cage is removed. Investigators should take this into account in designing experiments.     

Book Reviews

Book reviewed in this article:
Applied Anthropology: The Aboriginal Arts and Crafts Industry . Jon Altman
Marketing Aboriginal Art in the 1990s . Jon Altman and Luke Taylor     

Three C. elegans Rac proteins and several alternative Rac regulators control axon guidance, cell migration and apoptotic cell phagocytosis.

The Caenorhabditis elegans genome contains three rac-like genes, ced-10, mig-2, and rac-2. We report that ced-10, mig-2 and rac-2 act redundantly in axon pathfinding: inactivating one gene had little effect, but inactivating two or more genes perturbed both axon outgrowth and guidance. mig-2 and ced-10 also have redundant functions in some cell migrations. By contrast, ced-10 is uniquely required for cell-corpse phagocytosis, and mig-2 and rac-2 have only subtle roles in this process. Rac activators are also used differentially. The UNC-73 Trio Rac GTP exchange factor affected all Rac pathways in axon pathfinding and cell migration but did not affect cell-corpse phagocytosis. CED-5 DOCK180, which acts with CED-10 Rac in cell-corpse phagocytosis, acted with MIG-2 but not CED-10 in axon pathfinding. Thus, distinct regulatory proteins modulate Rac activation and function in different developmental processes.     

Expansion of repetitive DNA into cytogenetically visible elements.

Two cases of amplified repetitive elements accidentally identified in cancer samples are reported. In both cases, repeated DNA that is normally not visible by traditional chromosome banding had increased in amount to become cytogenetically visible. In one case, an addition to the short arm of chromosome 1 was originally diagnosed. However, upon molecular analysis the diagnosis could be corrected to an amplification of the D1Z2 repeat. In the second case, a strongly DAPI-positive band was visible at the top of the short arm of chromosome 22, and the original diagnosis was add(22). Staining for telomeric repeats revealed their presence inside the DAPI-positive element, thus confirming that the element in question was truly added to the end of the chromosome. Curiously, no telomeric repeats could be detected distal to the DAPI-positive element. The identity of the DAPI-positive element could not be established, as it was not stained by any of the specific probes applied, nor in a scanning hybridization with labeled Cot-1 DNA. It thus seems to represent an expansion from some lowly repetitive AT-rich DNA translocated to the tip of chromosome 22.