ABSTRACT. The vitamin D receptor (VDR) is involved in the immune response and bone metabolism, both of which are implicated in the pathogenesis of chronic periodontitis (CP). In this study, we investigated the association between the VDR single nucleotide polymorphism rs2228570 and CP susceptibility in a Han Chinese population consisting of 440 moderate or severe CP patients and 324 controls. Genomic DNA was extracted from buccal epithelial cells and genotyped using matrix-assisted laser desorption/ ionization time-of-flight-mass spectrometry. No significant difference in allelic or genotypic frequencies distributions for rs2228570 was found between CP patients and controls. In conclusion, we found no statistically significant association between rs2228570 and CP in our population.

Mechanical periodicity (MP) of the end-diastolic volume (EDV) of the left ventricle (LV) is closely associated with cardiovascular pathophysiology. On the basis of the Starling's law of the LV and Burattini and Gnudi's four-element model of the vascular system, and considering baroreceptor reflex, a non-linear dynamic lumped-parameter model is proposed. This simulates the MP phenomena of the EDV by solving a series of one-dimensional discrete non-linear dynamic equations. The results demonstrate that excessive deviations of some physiological parameters often induce MP -the unstable phenomena of EDV -and verify that the effects of baroreceptor reflex enhance the ability of the human physiological system to maintain stability.

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