Involvement of canonical Wnt/Wingless signaling in the determination of the positional values within the leg segment of the cricket Gryllus bimaculatus

The cricket Gryllus bimaculatus is a hemimetabolous insect whose nymphs possess the ability to regenerate amputated legs. Previously, we showed that Gryllus orthologues of Drosophila hedgehog (Gb'hh), wingless (Gb'wg) and decapentaplegic (Gb'dpp) are expressed during leg regeneration and play essential roles in the establishment of the proximal-distal axis. Here, we examined their roles during intercalary regeneration: when a distally amputated tibia with disparate positional values is placed next to a proximally amputated host, intercalary growth occurs in order to regenerate the missing part. In this process, we examined expression patterns of Gb'hh and Gb'wg. We found that expressions of Gb'hh and Gb'wg were induced in a regenerate and the host proximal to the amputated region, but not in the grafted donor distal to the regenerate. This directional induction occurs even in the reversed intercalation. Because these results are consistent with a distal-to-proximal respecification of the regenerate, Gb'wg may be involved in the re-establishment of the positional values in the regenerate. Furthermore, we found that no regeneration occurs when Gb'armadillo (the orthologue of beta-catenin) was knocked down by RNA interference. These results indicate that the canonical Wnt/Wingless signaling pathway is involved in the process of leg regeneration and determination of positional information in the leg segment.     

Dissolved oxygen concentration in river sediment of the Lake Biwa tributaries, Japan

The dissolved oxygen concentration in the sediment pore water downstream of rivers in the Lake Biwa basin was measured, and the factors affecting the dissolved oxygen concentration were analyzed. In August 2003, nine rivers (Sakai, Nakanoi, Hebisuna, Anziki, Yasu, Echi, Ane, Oh, and Ohura) were surveyed. The dissolved oxygen was depleted in the sediment pore water of the rivers with a high proportion of particles less than 250 μm in size. For these rivers, the difference between the dissolved oxygen concentrations of the river surface water and the pore water was large, ranging from −9.54 to −5.26 mg L⁻¹. It was found that the proportion of land turned to paddy fields has an effect on the percentage of the particles below 250 μm (standard partial regression coefficient = 0.807, p = 0.023). These results suggest that, in the Lake Biwa basin, the sedimentation of the fine particles released from paddy fields results in poor dissolved oxygen in the river sediment downstream. In addition, the water flow conditions in small- and medium-scale rivers without headwaters also affect the sedimentation of suspended particles.     

A phase-locking theory of matching between rotated images by dynamic link matching

Pattern recognition invariant to deformation or translation can be performed with the dynamic link matching proposed by von der Malsburg. Dynamic link matching has been applied to some engineering examples efficiently, but has not yet been analyzed mathematically. We propose two models of dynamic link matching, both of which are mathematically tractable. The first model can perform matching between rotated images. The second model can also do that and additionally detect common parts in a template image and in a data image. To analyze these models mathematically, we reduce each model's equation to a phase equation, showing the mathematical principle behind the rotating invariant matching process. We also carry out computer simulations to verify the mathematical theories involved. Received: 23 July 1987 / Accepted in revised form: 12 January 1998     

Stress platelets in normal individuals and patients with idiopathic thrombocytopenic purpura.

To test the hypothesis that stress platelets (SPs) described by Tong et al. in rats may be a parameter of young platelets in humans, we examined and characterized SPs in normal individuals and in patients with idiopathic thrombocytopenic purpura (ITP). Our results indicated that SPs comprise about 1.2% of the circulating platelets in normal individuals and 2.6% in ITP patients. The configuration of SPs as well as of various irregular forms of circulating platelets was found to be supported by synergism of both the platelet microfilaments and microtubules. SPs showed some segmentation, the degree of which was similar in normal individuals and ITP patients, and they underwent further segmentation during in vitro incubation, mainly promoted by microtubules, so that they sometimes appeared like discoid platelets in a chain. These observations suggest a new mode of production of discoid platelets in the circulation. Thus, identification and enumeration of SPs may be useful for evaluating thrombocytopoiesis in humans.