The Silent Period in the EMG of the Jaw Muscles During Mastication and its Relationship to Tooth Contact

Abstract

Objective. This study aimed to evaluate the occurrence of chromosomal abnormalities, through micronuclei, and apoptosis by the sum of karyorrhexis, pyknosis and condensed chromatin in individuals with chronic periodontitis, gingivitis associated with biofilm and no periodontal disease. Materials and methods. This study included 72 individuals divided into three groups: gingivitis (n = 21), periodontitis (n = 24) and control (n = 27). Information on sociodemographic characteristics, health and lifestyle was obtained. Full mouth clinical examination was performed to define the periodontal condition. Exfoliated cells from gingival mucosa were collected for computation of micronuclei and nuclear changes indicative of apoptosis. The differences in the occurrence of endpoints (micronucleus, karyorrhexis, pyknosis and condensed chromatin) were evaluated using the conditional test to compare proportions in a rare events situation. Results. There was no statistically significant difference in the occurrence of micronucleus (p > 0.1) between gingivitis, periodontitis and control groups. The occurrence of apoptosis was significantly higher among individuals with periodontitis compared to individuals with gingivitis (p < 0.05) and controls (p < 0.025). Conclusions. The findings showed that the inflammatory process generated by gingivitis and periodontitis is not related to a higher occurrence of chromosomal damage. However, the higher occurrence of apoptosis in individuals with periodontitis points to genotoxic effects induced by periodontal infection.     

Increased micronucleus frequency in phytohaemagglutinin-stimulated blood cells of patients with vitiligo

Background Vitiligo is a relatively common, acquired pigmentary disorder characterized by areas of depigmented skin resulting from loss of melanocytes in the epidermis. Although several hypotheses have been proposed for the aetiology and pathogenesis of vitiligo, the cause of vitiligo remains unclear. Objective To evaluate spontaneous micronucleus (MN) frequency using the cytokinesis block MN assay to determine damages at the DNA or chromosome level in phytohaemagglutinin (PHA)‐stimulated blood cells of patients with vitiligo and healthy control subjects. Methods Peripheral blood samples were obtained and cultured from 21 patients with vitiligo (mean age: 21.48 ± 9.78 years) and 21 age‐ and sex‐matched healthy control subjects (mean age: 21.52 ± 9.80 years). MN values were scored in binucleated cells obtained from whole‐blood cultures of patients and control subjects. Results MN frequencies (mean ± SD) in PHA‐stimulated blood cells of patients with vitiligo and control subjects were 0.94 ± 0.58 and 0.58 ± 0.32, respectively. Compared with control subjects, MN frequencies of patients with vitiligo were found significantly higher than those of the control subjects (P = 0.012). Conclusion Our results indicate unexpectedly some chromosomal/DNA damage in whole‐blood cultures of patients with vitiligo. We do not know, however, if these chromosome/DNA instabilities observed in the cells of vitiligo patients resulted from the cause or from the consequences of the disorder.     

骨髓增生异常综合征患者外周血淋巴细胞微核观察

观察25例骨髓增生异常综合征(MDS)和30例正常人外周血淋巴细胞微核。MDS患者外周血微核淋巴细胞出现率为84.00%,淋巴细胞微核率为6.68‰,显著高于对照组(P<0.005)。RAEB和RAEB-T亚型淋巴细胞微核率显著高于RA亚型(P<0.005)。MDS微核淋巴细胞多微核率与对照组差异无显著性(P>0.05)。同时检查外周血淋巴细胞染色体,MDS染色体畸变率为14.68%,显著高于对照组,且与微核率呈直线正相关(r=0.76,P0.001)。本文就MDS微核检测的意义进行了讨论。     

用紫露草微核技术检测大厂锡矿环境诱变物的研究

用紫露草微核技术检测了大厂锡矿的空气和矿尘.有两点发现:1.生产作业区的空气中有致植物细胞染色体损伤的诱变物质污染,其污染水平的高低与职工肺癌的流行特征一致;2.矿尘有很强的诱变性,且显示出良好的剂量-效应关系.研究结果表明,该矿职工肺癌高发与生产环境有关.     

沥青对人体细胞遗传学效应的研究

采用人体外周血淋巴细胞染色体畸变和微核两项试验对沥青接触者进行细胞遗传学效应研究,结果表明,染色体畸变率和微核检出率接触者均比非接触者高,经泊松检验P<0.01,差异有非常显著意义,说明沥青可导致染色体损伤。但48例的染色体与微核检测的配对卡方检验,X~2=7.84,P<0.01,说明微核检测方法不及染色体检测灵敏。本文还对吸烟者和不吸烟者的染色体畸变分析进行了比较,结果表明,不论在接触组和非接触组中差异均无显著性意义,P>0.05。     

顺铂、樟脑胺氯乙酸铂及碳铂对染色体损伤的比较

以CHL细胞为材料,比较了顺铂(DDP)、碳铂(JM 8)和樟脑胺氯乙酸铂(CCP)的细胞毒作用和对CHL细胞的染色体损伤。实验表明,这三种铂络合物都有较强的细胞毒作用,其中顺铂最强而CCP最弱。DDP,JM-8和CCP的IC~(90)(±SD)分别为0.68±0.21,4.4±0.6,10.8±1.5μmol/L。在微核及染色体畸变实验中,观察到在药物浓度小于或等于IC_(90)时,这三种化合物诱发的微核及染色体损伤相当,但药物浓度增加时,CCP所诱发的微核及染色体畸变均大于DDP而JM-8最轻。     

Cytotoxicity of the β-carboline alkaloids harmine and harmaline in human cell assays in vitro

beta-Carboline alkaloids are natural products widely distributed in plants and also found in alcoholic beverages, well-cooked foods and tobacco smoke. Various authors have reported genotoxic activities of several carboline in prokaryotic and eukaryotic cells that have been attributed to their abilities to intercalate into DNA. But studies on the genotoxic and on the cytotoxic potencies in human cells in vitro are not found in the literature. In the present study the toxicities of one full aromatic beta-carboline alkaloid (harmine) and one dihydro-beta-carboline alkaloid (harmaline) were evaluated by means of two in vitro human cell assays: the cytochalasin-B blocked micronucleus (CBMN) assay and the viability/colony formation assay with four different human cultured non-transformed (CCD18Lu) and transformed (HeLa, C33A and SW480) cells. Neither alkaloid was able to induce micronuclei levels above that of control levels in a wide range of doses tested; although, harmine at the highest concentrations assayed induced apoptotic as well as necrotic cells. Harmine produced a good viability of all cell lines assayed (control and tumor) while harmaline significantly reduced the viability of transformed and non-transformed cell lines in a dose-dependent manner. Harmine displayed a dose-dependent inhibitory effect on cell proliferation against all human carcinoma cells, but the SW480 transformed cell line showed a higher sensitivity. These results suggested that harmine was identified as a useful inhibitor of tumor development.     

The increment of micronucleus frequency in cervical carcinoma during irradiation in vivo and its prognostic value for tumour radiocurability.

A potential usefulness of micronucleus assay for prediction of tumour radiosensitivity has been tested in 64 patients with advanced stage (II B-IV B) cervical carcinoma treated by radiotherapy. The study of cellular radiosensitivity in vitro was conducted in parallel with the study of cellular damage after tumour irradiation in vivo. Radiosensitivity of in vitro cultured primary cells isolated from tumour biopsies taken before radiotherapy was evaluated using cytokinesis-block micronucleus assay. Frequency of micronuclei per binucleated cell (MN/BNC) at 2 Gy was used as a measure of radiosensitivity. Radiation sensitivity in vivo was expressed as per cent increment of micronucleus frequency in cells isolated from biopsy taken after 20 Gy (external irradiation, 10 x 2 Gy) over the pre-treatment spontaneous micronucleus level and was called MN20. Very low correlation (r = 0.324) was observed between micronucleus frequency in vitro and in vivo. Although micronucleus frequency at 2 Gy differed widely between tumours evaluated (mean MN/BNC was 0.224; range 0.08-0.416), no significant correlation was observed between this parameter and clinical outcome. The average increment of micronucleus frequency after 20 Gy amounted to 193% of spontaneous level (range 60-610%) and was independent of spontaneous micronucleation before radiotherapy. In contrast to in vitro results, these from in vivo assay seem to have a predictive value for radiotherapy of cervix cancer. The micronucleus increment in vivo that reached at least 117.5% of pretreatment value (first quartile for MN20 data set) correlated significantly with better tumour local control (P < 0.008) and overall survival (P < 0.045). Our results suggest that evaluation of increment of micronucleus frequency during radiotherapy (after fixed tested dose of 20 Gy) offers a potentially valuable approach to predicting individual radioresponsiveness and may be helpful for individualization of treatment strategy in advanced stage cervical cancer.     

6MV X线照射人离体血细胞遗传学剂量—效应研究——常规法的微核剂量效应曲线

本文应用医用直线加速器6MV X 线照射5例健康成人离体血研究淋巴细胞微核与剂量间的关系,发现微核率及微核细胞率可各配以回归方程 Y=6.6896×10~(-3)+1.2959×10~(-2)D~2及 Y=7.3906×10~(-3)+1.0824×10~(-2)D~2,其 R~2值分别为O.9948及0.9976,有较好的拟合度,可作为预测受照剂量的模型。     

细胞微核形成机理探讨

微核试验是反映染色体损伤，进行遗传毒性评估的重要试验，该文对微核的相关信息进行了分析，并结合自己的研究工作，对微核的形成机理进行了深入探讨。