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  • Author: Hiroshi Mukai x
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Seasonal variations in vegetative growth and production of two seagrass species, Zostera asiatica and Z. marina, were investigated in Akkeshi Bay, northern Japan. Z. asiatica, a threatened species in Japan, was dominant, occurring from the intertidal zone to the deepest edge of the seagrass bed (5 m deep), whereas Z. marina was restricted to the shallower edge of the bed (<2 m). Above ground biomass and above ground net production per shoot were greater for Z. asiatica than for Z. marina. In contrast, shoot density was 3- to 4-fold higher for Z. marina. Biomass and production were minimum in winter to early spring (January to March), and maximum in summer (June to July) for both species. Annual production per unit area of Z. asiatica was larger than that of Z. marina (2033 and 1354 g DW m-2 y-1, respectively). Our findings reveal contrasting growth patterns for the two species: Z. asiatica allocates more resources to enlarging shoot size, whereas Z. marina allocates more to increasing shoot density by clonal propagation of rhizomes. Seagrass beds consisting of Z. asiatica contributed importantly to coastal ecosystems in Akkeshi Bay area because of high productivity.


Background: Dual oxidase 2 (DUOX2) mutations are a cause of dyshormonogenesis (DH) and have been identified in patients with permanent congenital hypothyroidism (PH) and with transient hypothyroidism (TH). We aimed to elucidate the prevalence and phenotypical variations of DUOX2 mutations.

Methods: Forty-eight Japanese DH patients were enroled and analysed for sequence variants of DUOX2, DUOXA2, and TPO using polymerase chain reaction-amplified direct sequencing.

Results: Fourteen sequence variants of DUOX2, including 10 novel variants, were identified in 11 patients. DUOX2 variants were more prevalent (11/48, 22.9%) than TPO (3/48, 6.3%) (p=0.020). The prevalence of DUOX2 variants in TH was slightly, but not significantly, higher than in PH. Furthermore, one patient had digenic heterozygous sequence variants of both DUOX2 and TPO.

Conclusions: Our results suggest that DUOX2 mutations might be the most common cause of both PH and TH, and that phenotypes of these mutations might be milder than those of other causes.