Specificity protein 1 regulates topoisomerase IIß expression in SH-SY5Y cells during neuronal differentiation.

Topoisomerase IIß (top IIß) is a nuclear enzyme with an essential role in neural development. The regulation of top IIß gene expression during neural differentiation is poorly understood. Functional analysis of top IIß gene structure displayed a GC box sequence in its transcription promoter, which binds the nuclear transcription factor specificity protein 1 (Sp1). Sp1 regulates gene expression via multiple mechanisms and is essential for early embryonic development. This study seeks to determine whether Sp1 regulates top IIß gene expression during neuronal differentiation. For this purpose, human neuroblastoma SH-SY5Y cells were induced to neuronal differentiation in the presence of all-trans retinoic acid (RA) for 5 days. After incubation with 10 µM RA for 3-5 days, a majority of the cells exited the cell cycle to become postmitotic neurons, characterized by the presence of longer neurite outgrowths and expression of the neuronal marker microtubule-associated protein-2 (MAP2). Elevated Sp1 and top IIß mRNA and protein levels were detected and found to be positively correlated with the differentiation stage. Chromatin immunoprecipitation assay demonstrated an increased recruitment of Sp1 to the top IIß promoter after RA treatment. Mithramycin A, a compound that interferes with Sp1 binding to GC-rich DNA sequences, downregulated the expression of top IIß, resulting in reduced expression of MAP2 and decreased neurite length compared with the control group. Our results indicate that Sp1 regulates top IIß expression by binding to the GC box of the gene promoter during neuronal differentiation in SH-SY5Y cells.

[A study on the penetration abilities of natural initial caries lesions with resin infiltration].

OBJECTIVE: To compare the penetration abilities of resin infiltration into natural initial caries lesions with those of adhesive in vitro. METHODS: Thirty-six extracted human molars and premolars showing proximal white spot lesions were selected. Teeth roots were removed, and the crowns were cut across the caries lesions perpendicular to the surface. Corresponding lesion halves were etched for 2 min with 15% hydrochloric acid gel and were subsequently treated with either adhesive or resin infiltration. Specimens were observed with confocal laser scanning microscopy (CLSM) in dual fluorescence mode. In confocal microscopic images, penetration depth (PD) and lesion depth (LD) were defined as the distance from the surface to the deepest point of red and green fluorescence, respectively. The penetration percentages (PP) were calculated. RESULTS: At the same level of caries, mean maximum lesion LD were comparable for both lesion halves (P > 0.05). But mean maximum PD and PP of the resin infiltration were significantly higher than those of the adhesive (P < 0.01). CONCLUSION: Penetration of enamel caries lesions is observed in the adhesive and the resin infiltration. But the resin infiltration is capable of penetrating almost completely into enamel parts of natural caries lesions.

[An experimental study on the penetration abilities of resin infiltration into proximal caries lesions in primary molars].

OBJECTIVE: To compare the penetration abilities of resin infiltration into proximal lesions in primary molars with those of adhesive in vitro. METHODS: Thirty-two extracted or exfoliated primary molars showing proximal white spot lesions were selected. Roots of the teeth were removed, and the crowns were cut across the white spot lesions perpendicular to the surface. Cut surfaces were examined (by stereo microscopy) and classified with respect to histological lesion extension (C1-C4): lesions confined to the outer half on enamel (C1), lesions confined to the inner half on enamel (C2), lesions confined to the outer half on dentin (C3), lesions extending into the inner half of dentin (C4). Corresponding lesion halves were etched for 120 s with 15% hydrochloric acid gel and were subsequently treated with either adhesive or resin infiltration. Specimens were observed with laser scanning confocal microscope (LSCM) in dual fluorescence mode. In confocal microscopic images, lesion depth and penetration depth of the resin infiltration or the adhesive in corresponding halves were measured, and penetration percentages were calculated respectively. Differences of the data between two groups were analyzed by Wilcoxon signed rank test. Variations of histological caries extensions were detected with Kruskal-Wallis H test. RESULTS: At the same grading level (C1-C3) in histological caries extension, penetration depths of the resin infiltration group and the adhesive group were 240 (230, 260) µm vs 190 (150, 210) µm, 405 (300, 523) µm vs 180 (160, 200) µm, and 590 (430, 640) µm vs 180 (160, 200) µm respectively. There was significant statistical difference in the data between two groups (P < 0.05). Statistically significant difference in penetration depths of the resin infiltration group (at C1-C3) were found (P < 0.01). At the same grading level (C1-C3) in histological caries extension, percentage penetrations of the resin infiltration group and the adhesive group were [100.0% (96.2%, 100.0%)], [99.1% (95.7%, 100.0%)], [82.0% (81.1%, 92.2%)] and [79.2% (68.4%, 87.5%)], [41.8% (29.1%, 74.5%)], [30.2% (29.2%, 39.6%)], respectively. The difference between the above data was also significant (P < 0.05). Percentage penetrations of the resin infiltration group at C1 and C2 level was higher than those at C3 level (P < 0.05). CONCLUSIONS: The resin infiltration is capable of penetrating almost completely into proximal lesions in primary molars.

[Left lower first premolar with 3 root canals: a case report].

3 root canals were found when a left lower first premolar, which preoperative radiograph showing root canal variety, was treated and were verified by postoperative radiograph. The root canal variety of lower premolars should be paid more attention to prevent root canal from losing.