Xenopus glucose transporter 1 (xGLUT1) is required for gastrulation movement in Xenopus laevis

Glucose transporters (GLUTs) are transmembrane proteins that play an essential role in sugar uptake and energy supply. Thirteen GLUT genes have been described and GLUT1 is the most abundantly expressed member of the family in animal tissues. Deficiencies in human GLUT1 are associated with many diseases, such as metabolic abnormalities, congenital brain defects and oncogenesis. It was suggested recently that Xenopus GLUT1 (xGLUT1) is upregulated by Activin/Nodal signaling, although the developmental role of xGLUT1 remains unclear. Here, we investigated the expression pattern and function of xGLUT1 during Xenopus development. Whole-mount in situ hybridization analysis showed expression of xGLUT1 in the mesodermal region of Xenopus embryos, especially in the dorsal blastopore lip at the gastrula stage. From the neurula stage, it was expressed in the neural plate, eye field, cement gland and somites. Loss-of-function analyses using morpholino antisense oligonucleotides against xGLUT1 (xGLUT1MO) caused microcephaly and axis elongation error. This elongation defect of activin-treated animal caps occurred without downregulation of early mesodermal markers. Moreover, dorsal-marginal explant analysis revealed that cell movement was suppressed in dorsal marginal zones injected with xGLUT1MO. These findings implicate xGLUT1 as an important player during gastrulation cell movement in Xenopus.

Comparison of induction during development between Xenopus tropicalis and Xenopus laevis

Several in vitro systems exist for the induction of animal caps using growth factors such as activin. In this paper, we compared the competence of activin-treated animal cap cells dissected from the late blastulae of Xenopus tropicalis and Xenopus laevis. The resultant tissue explants from both species differentiated into mesodermal and endodermal tissues in a dose-dependent manner. In addition, RT-PCR analysis revealed that organizer and mesoderm markers were expressed in a similar temporal and dose-dependent manner in tissues from both organisms. These results indicate that animal cap cells from Xenopus tropicalis have the same competence in response to activin as those from Xenopus laevis.

[A case of sleep apnea syndrome with significant alteration of apnea index by sleep position]

An obese 37-year-old man (130% ideal body weight) was admitted to our hospital with the complaint of excessive daytime sleepiness. During all-night polysomnography, he showed predominantly obstructive sleep apnea and an apnea index (AI) of 57.5, and was diagnosed as having obstructive sleep apnea syndrome (OSAS). However, AI values calculated separately for the time in the supine position (AI-S) and in the lateral decubitus position (AI-L) were 82.4 and 5.9, respectively. Moreover, duration of apnea, lowest SaO2, and the quality of sleep were improved when sleeping in the lateral compared to the supine position. After weight reduction of 7 kg, AI in total decreased to 33.2, although AI-S was 77.3 and AI-L was 3.8. The improvement of AI in total to be due to a relative increase during sleep in the lateral position. These results suggest that in some OSAS patients, the sleep position should be taken into account in assessing the severity of the disease or in evaluating the effects of therapy. This study also suggests the efficacy of sleep position adjustment in the treatment of OSAS.