RESUMO
Rare-earth orthochromites with distorted perovskite structure (e.g. RCrO3, R = Sm, Gd) have been under strong debate with respect to the origin of their ferroelectric order. Of particular interest is the question of whether such orthochromites are, in fact, magnetically driven improper ferroelectrics, as many rare-earth manganites or orthoferrites. Here we show, by studying at the atomic scale the rare-earth SmCrO3 system that a distortion of the Sm local environment emerges within the paramagnetic phase, near room temperature. Our Electric Field Gradient measurements combined with first-principles calculations show that the emergent phase cannot be simply ascribed to the Pna21 structure as reported for GdCrO3 or SmCrO3. Instead a local inhomogeneous state, where regular non-polar and polar distorted environments coexist, develops at low temperatures.
RESUMO
The 21-hydroxylase deficiency (21OHD) is caused by CYP21A2 mutations resulting in severe or moderate enzymatic impairments. 21OHD females carrying similar genotypes present different degrees of external genitalia virilization, suggesting the influence of other genetic factors. Single nucleotide variants (SNVs) in the CYP3A7 gene and in its transcription factors, related to fetal 19-carbon steroid metabolism, could modulate the genital phenotype. To evaluate the influence of the 21OHD genotypes and the CYP3A7, PXR and CAR SNVs on the genital phenotype in 21OHD females. Prader scores were evaluated in 183 patients. The CYP3A7, PXR and CAR SNVs were screened and the 21OHD genotypes were classified according to their severity: severe and moderate groups. Patients with severe genotype showed higher degree of genital virilization (Prader median III, IQR III-IV) than those with moderate genotype (III, IQR II-III) (p < 0.001). However, a great overlap was observed between genotype groups. Among all the SNVs tested, only the CAR rs2307424 variant correlated with Prader scores (r(2) = 0.253; p = 0.023). The CYP21A2 genotypes influence the severity of genital virilization in 21OHD females. We also suggest that the CAR variant, which results in a poor metabolizer phenotype, could account for a higher degree of external genitalia virilization.
