Normal skeletal pattern formation in chick limb bud with a mesenchymal hole is mediated by adjustment of cellular properties along the anterior-posterior axis in the limb bud.

The chick limb bud has plasticity to reconstruct a normal skeletal pattern after a part of mesenchymal mass is excised to make a hole in its early stage of development. To understand the details of hole closure and re-establishment of normal limb axes to reconstruct a normal limb skeleton, we focused on cellular and molecular changes during hole repair and limb restoration. We excised a cube-shaped mass of mesenchymal cells from the medial region of chick hindlimb bud (stage 23) and observed the following morphogenesis. The hole had closed by 15 â€‹h after excision, followed by restoration of the limb bud morphology, and the cartilage pattern was largely restored by 48 â€‹h. Lineage analysis of the mesenchymal cells showed that cells at the anterior and posterior margins of the hole were adjoined at the hole closure site, whereas cells at the proximal and distal margins were not. To investigate cell polarity during hole repair, we analyzed intracellular positioning of the Golgi apparatus relative to the nuclei. We found that the Golgi apparatus tended to be directed toward the hole among cells at the anterior and posterior margins but not among cells at identical positions in normal limb buds or cells at the proximal and distal hole margins. In the manipulated limb buds, the frequency of cell proliferation was maintained compared with the control side. Tbx3 expression, which was usually restricted to anterior and posterior margins of the limb bud, was temporarily expanded medially and then reverted to a normal pattern as limb reconstruction proceeded, with Tbx3 negative cells reappearing in the medial regions of the limb buds. Thus, mesenchymal hole closure and limb reconstruction are mainly mediated by cells at the anterior and posterior hole margins. These results suggest that adjustment of cellular properties along the anteroposterior axis is crucial to restore limb damage and reconstruct normal skeletal patterns.

Anesthetic Management of a Patient With Catecholaminergic Polymorphic Ventricular Tachycardia.

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a rare inherited arrhythmogenic disorder induced by adrenergic stress. Electrophysiologically, it is characterized by emotional stress- or exercise-induced bidirectional ventricular tachycardia that may result in cardiac arrest. Minimizing perioperative stress is critical as it can reduce fatal arrhythmias in patients with CPVT. Dexmedetomidine (DEX), a centrally acting sympatholytic anesthetic agent, was used in the successful intravenous (IV) moderate sedation of a 27-year-old female patient with CPVT, a history of cardiac events, and significant dental fear and anxiety scheduled to undergo mandibular left third molar extraction. Oral surgery was successfully performed under DEX-based IV sedation to reduce stress, and no arrhythmias were observed. IV sedation with DEX provided a sympatholytic effect with respiratory and cardiovascular stability in this patient with CPVT who underwent oral surgery.

[The effect of working memory on learning from texts].

This study examined the effect of working memory on learning from texts. In Experiment 1, participants preformed a word clustering task involving key words from an explanatory text (pretest), and then read the text, which was presented sentence-by-sentence. Next, they performed a second clustering task (post-test), a problem solving task, and a reading span test (RST). The results suggested that the individual differences of the RST scores correlated with the scores for problem solving. In Experiment 2, the results suggested that the individual differences of the RST scores influenced the clustering performance at the level of the situation model when the text was presented all together. Moreover, the result of multiple dimension scaling suggested that the situation models of high-span readers reflected the structure of the text more than those of low-span readers. These results indicate that readers with high reading span scores construct coherent situation models of texts and make use of them for learning from texts.