[Association of fimA genotype to kgp genotype in Porphyromonas gingivalis from infected root canals of primary apical periodontitis].

Objective: To investigate the distribution of fimA and kgp genotypes as well as the common genotype combination of Porphyromonas gingivalis (Pg) in infected root canals of primary apical periodontitis for virulent isolates screening in future. Methods: Thirty-four samples harboring Pg were selected from infected root canals of primary apical periodontitis from patients of the Department of Endodontics, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine from June 2013 to September 2015. FimA type-specific primers were used to amplify the samples, revealing the distribution of various fimA genotypes. The genotypes of kgp were obtained by using Mse Ⅰ restriction endonuclease. The prevalence of each genotype and common genotype combinations were then calculated. Pearson's chi-squared test was performed to analyze the correlation between genotype combinations and clinical symptoms and major signs of apical periodontitis. In addition, the bioflim architectures between Pg isolates with different fimA and kgp genotype combinations were observed compared using confocal laser scanning microscope. Results: Among the 34 Pg-positive samples, fimA Ⅱ was the most prevalent genotype [47% (16/34)] followed by fimA Ⅰ [26% (9/34)], while fimA Ⅴ was detected in only one sample. The prevalence of kgp Ⅰ [56% (19/34)] was slightly higher than that of kgp Ⅱ [44% (15/34)]. Both fimA Ⅱ+kgp Ⅰ and fimAⅡ+kgp Ⅱ were the most prevalent genotype combinations [24% (8/34) each]. No significant correlation was found between specific genotype combination and such major clinical manifestations as gingival swelling and sinus tract of dental origin (P>0.05). Three Pg isolates with different genotype combinations were acquired. Isolate A (fimAⅠ+kgpⅠ) formed densest biofilm, while the biofilm of isolate C (fimAⅤ+kgp Ⅰ) was much looser. The biofilm feature of isolate B (fimAⅢ+kgp Ⅱ) fell in between A and C. Conclusions: Pg with fimA Ⅱ was most frequently detected in infected root canals of primary apical periodontitis. The prevalence of Pg with kgp Ⅰ was slightly higher than that with kgp Ⅱ, and fimAⅡ+kgp Ⅰ as well as fimA Ⅱ+kgp Ⅱ were the commonest genotype combinations. According to the comparison of Pg biofilms formed by clinical isolates, it might be possible that different genotype combinations may lead to distinct biofilm architectures.

[Response of lithium fluoride detector to charged particle LET].

Response of LiF thermoluminescence (TL) detector to charged particle is dependent on particles' LET. High LET can cause reduction of detector response and underestimation of radiation dose. This paper summarized the response of LiF detector to charged particles' LET, and suggested a new approach to solve the dose contribution of high LET charged particles.

[An analysis on thickness effect of lithium fluoride detector in proton measurement].

OBJECTIVE: To theoretically analyze the thickness effect of a LiF detector for proton measurement. METHOD: Thickness effect of the detector was calculated by using the definition of the detector dose under ideal and reasonable hypothesis. RESULT: The thickness effect of the detector was not obvious when protons could penetrate the detector: when proton energy was above 12 MeV, the thickness effect was obvious only on condition that the detector thickness approaches proton range, when proton energy was less than 12 MeV, the thickness effect was not obvious. The thickness effect of the detector was obvious, when protons could not penetrate the detector. CONCLUSION: Thin detectors should be used in low energy proton measurements to avoid thickness effect of the detector.

[Measurements of proton response of two lithium fluoride detectors with different thicknesses].

OBJECTIVE: To study the response characteristics of LiF detectors to proton fluence rate and energy, and to observe the thickness effect of the detector. METHOD: Protons were generated by an accelerator. Proton energy was changed in two ways, i.e. changing the accelerator energy directly, or using detector stacks to absorb the proton energy. The incident proton energy on each chip of detector stacks was calculated according to proton range in LiF. RESULT: The response of the detector to proton fluence rate was almost constant; when proton energy was above 9 MeV, the response of the detector to proton energy was constant (less than 10% errors). When proton energy was below 9 MeV, the response reduced gradually with the decrease of proton energy. Thickness effect for LiF thicknesses of 0.4mm and 0.8mm was not obvious. CONCLUSION: The homemade LiF detector is suitable for measurement of space radiation dose. When proton component (below 9 MeV) was abundant in radiation field, the decrease of the relative thermoluminescence efficiency should be taken into consideration.

Identification of small collagenous proteins with properties of procollagen alpha 1 (I) pN-propeptide in fetal porcine calvarial bone.

Several small collagenous apatite binding (SCAB) proteins have been extracted from the mineralized matrix of fetal porcine calvarial bone. One protein (SCAB 3), released on demineralization of bone with 0.5 M EDTA, appears to represent the alpha 1 pN-propeptide that is normally released during proteolytic processing of type I procollagen. The 28 Kd protein, which stains blue with "Stains-all", is reduced to a 19 Kd fragment by bacterial collagenase digestion, but is not susceptible to cyanogen bromide. The amino acid composition, blocked amino-terminus and immunological properties are all consistent with properties of alpha 1 (I) pN-propeptide. Fractionation on hydroxylapatite in the presence of urea has revealed a nonbinding (SCAB 3a) and a binding (SCAB 3b) form. Extraction of the demineralized matrix of bone with 4 M GuHCl revealed a third form (G2-28) which was similar to SCAB 3a on hydroxylapatite chromatography but showed differences on FPLC "Mono Q" resin. The occurrence of these different forms of pN-propeptide in bone may be of significance in collagen fibril-associated hydroxylapatite formation and in the regulation of osteoblastic function during bone resorption.