[Characteristics of cervical vestibular evoked myogenic potential in different test positions].

Objective: To investigate the characteristics of cervical vestibular evoked myogenic potential (cVEMP) of normal youth with different test positions, to study the relationship between test positions and test parameters, and to explore the suitable test position for clinical practice. Methods: Fifty healthy young volunteers (25 males, 25 females, 100 ears) were enrolled in this study. Two test positions were used, including sitting with the head turned away from the test (SIT) and supine with the head held straight up (SUP). The derivation rate, latency and amplitude were analyzed. Results: The derivation rates of both SIT and SUP were 100%. The VEMP threshold in SIT was (93.5±4.3)dBnHL. The latency of P1 and N2 in SIT was longer than that in SUP, with significant different (P< 0.05), the amplitude of P1-N2 in SIT was less than that in SUP, with significant different (P< 0.05). Regarding to the latency of P1 and N2 in SIT, the left was longer that right, with (P=0.013) and (P=0.015) respectively. The latency in SUP between sides was not significant (P>0.05). The amplitude ratio and asymmetry in SIT were more obvious than in supine position (P=0.009 and 0.016). In SIT position the P1-N2 amplitude in males was larger than in females, with significant difference (P=0.031); In SUP position the P1-N2 amplitude in males was less than in females, with significant difference (P=0.043). Conclusion: The cVEMP can be affected by the different test positions, it is recommended to select a more suitable test position according to the condition of the subject and the purpose of the test.

MTHFR C677T polymorphism and osteoporotic fracture in postmenopausal women: a meta-analysis.

Numerous studies have evaluated the association between MTHFR C677T polymorphism and osteoporotic fracture risk in postmenopausal women. However, the results have been inconsistent. We performed a meta-analysis of the association between MTHFR C677T polymorphism and osteoporotic fracture risk in postmenopausal women. Only seven case-control studies were retrieved, with a total of 4258 patients and 3454 healthy controls. Meta-analysis results showed no significant association between MTHFR C677T polymorphism and osteoporotic fracture risk in postmenopausal women for all genetic models (for TT vs CC: OR=0.99, 95%CI=0.72-1.39; for TT vs TC: OR=1.02, 95%CI=0.87-1.20; for CC+TC vs TT: OR=0.96, 95%CI=0.71-1.28; for TT+TC vs CC: OR=0.93, 95%CI=0.84-1.03). In the subgroup analysis by ethnicity, the results also showed no significant association between MTHFR C677T polymorphism and susceptibility to osteoporotic fracture in postmenopausal women in both Caucasian and Asian populations. In conclusion, this meta-analysis suggests that MTHFR C677T polymorphism may not be associated with susceptibility to osteoporotic fracture in postmenopausal women.

Cytomixis and meiotic abnormalities during microsporogenesis are responsible for male sterility and chromosome variations in Houttuynia cordata.

Houttuynia cordata (Saururaceae) is a leaf vegetable and a medicinal herb througout much of Asia. Cytomixis and meiotic abnormalities during microsporogenesis were found in two populations of H. cordata with different ploidy levels (2n = 38, 96). Cytomixis occurred in pollen mother cells during meiosis at high frequencies and with variable degrees of chromatin/chromosome transfer. Meiotic abnormalities, such as chromosome laggards, asymmetric segregation and polyads, also prevailed in pollen mother cells at metaphase of the first division and later stages. They were caused by cytomixis and resulted in very low pollen viability and male sterility. Pollen mother cells from the population with 2n = 38 showed only simultaneous cytokinesis, but most pollen mother cells from the population with 2n = 96 showed successive cytokinesis; a minority underwent simultaneous cytokinesis. Cytomixis and irregular meiotic divisions appear to be the origin of the intraspecific polyploidy in this species, which has large variations in chromosome numbers.