[Effects of an Amendment on Cadmium Transportation in the Rhizosphere Soil-Rice System].

The remediation of cadmium (Cd) contaminated paddy soils has become an important issue in the field of remediation of agricultural soils contaminated by heavy metals. The iron (Fe) redox cycle (referring to the fluctuation of iron between the ferrous (Ⅱ) and ferric (Ⅲ) oxidation states) exhibits a unique role in the transportation of Cd in the soil-rice system. The exploration of practical remediation strategies for Cd from the perspective of the Fe redox cycle is expected to obtain some state-of-the-art technologies and products to reduce Cd accumulation in rice grains. In this study, an amendment was selected and a field experiment was carried out to investigate the effects of this amendment on Cd transportation from the rhizosphere soil to the Fe plaque, and further to different rice tissues at four different growth stages, and to highlight some possible mechanisms by which the Fe redox cycle controls Cd availability in rice paddy fields. The results showed that the amendment induced the formation of Fe sulfides, which co-precipitated with Cd, reducing the NH4Ac-extractable Cd content in rhizosphere soils at the tillering, jointing, and filling stages; the oxidation of Fe sulfides increased the NH4Ac-extractable Cd content in the rhizosphere soil at the maturing stage; the formation of Fe sulfides in rhizosphere soils impeded the migration of Fe(Ⅱ) from the rhizosphere soil to the root surface, decreasing the content of DCB-extractable Fe and Cd in Fe plaques at the tillering and filling stages; the amendment inhibited Cd transportation from the roots to other tissues, increasing the proportion of Cd in the roots at the jointing, filling, and maturing stages, but decreasing the proportion in the straws at the jointing, filling, and maturing stages, and in the rice grain at the maturing stage. These findings provide a theoretical basis for the exploration and application of the amendment, and have significance in the field of remediation of Cd-contaminated paddy soils.

Subclinical hypothyroidism and risk of cerebral small vessel disease: A hospital-based observational study.

OBJECTIVE: Subclinical hypothyroidism (SCH) has been associated with atherosclerosis and increased risk of ischaemic stroke. However, whether SCH is associated with cerebral small vessel disease (cSVD) remains largely unexplored. This study aimed to investigate the relationship between SCH and total cSVD burden, a composite measurement detected with magnetic resonance imaging (MRI), in patients with minor ischaemic stroke or transient ischaemic attack (TIA). DESIGN: This was a prospective observational cohort study conducted in a tertiary referral hospital. METHODS: Subclinical hypothyroidism (SCH) was defined as with mildly or moderately increased thyroid-stimulating hormone levels (TSH, 4.5-10.0 mIU/L), but with normal free thyroxine levels. Brain MRI presence of silent lacunar infarcts (LIs), white matter lesions (WMLs), cerebral microbleeds (CMBs) and enlarged perivascular spaces (EPVs) were summed to a validated scales ranging from 0 to 4 to represent the load of cSVD. The associations between SCH and cSVD were analysed by logistic regression analyses. RESULTS: Subclinical hypothyroidism (SCH) was identified in 43 of 229 (18.8%) patients with minor stroke or TIA. Compared with patients without SCH, those with SCH had higher risks of WMLs, CMBs and total cSVD burden. Adjustment of potential confounders did not change these associations. CONCLUSIONS: These findings showed that SCH might be associated with the presence of WMLs, CMBs, as well as cSVD burden in patients with minor stroke or TIA.