Regenerating soleus and extensor digitorum longus muscles of the rat show elevated levels of TNF-alpha and its receptors, TNFR-60 and TNFR-80.

We measured the mRNA and protein levels of tumor necrosis factor-alpha (TNF-alpha) and the transcript levels of its receptors (TNFR-60 and TNFR-80) in the rat soleus (slow twitch) and extensor digitorum longus (EDL; fast twitch) muscles regenerating from notexin-induced necrosis. On the first day after administration of the toxin, when most fibers were necrotic and invaded by inflammatory cells/macrophages, dramatic increases of transcript and protein levels of TNF-alpha and of the mRNA levels of its receptors were observed. The transcript levels of TNF-alpha and TNFR-60, but not of TNFR-80, showed a second but smaller increase at the time when newly formed muscle fibers became reinnervated. In situ hybridization showed that on day 1, during the phase of extensive necrosis, the transcript of TNF-alpha was abundantly present and on day 4 of regeneration it was most often seen in areas devoid of desmin. The mRNA level of TNF-alpha was not detectable in BC(3)H1- and C2C12-cultured myoblasts and it was low in freeze-injured muscle, corresponding to the relatively mild degree of inflammation elicited by freezing. Therefore, our results are most consistent with the view that inflammatory cells/macrophages are the main source of TNF-alpha.

Development of an in vitro wound healing model for periodontal cells.

BACKGROUND: Periodontal wound healing and regeneration are influenced by a multitude of factors. While many in vitro investigations have compared the proliferation of periodontal ligament (PDL) cells and gingival fibroblasts (GF), there are no reports directly comparing the abilities of these 2 cell types to fill a wound site. As such, the goals of this research were: 1) to develop an in vitro model of wound healing which would allow for the investigation of the biologic basis of periodontal wound healing and regeneration and 2) to compare the rates of PDL cells and GF to fill an in vitro wound site. METHODS: Using both human PDL cells and GF confluent cultures, in vitro wounds were mechanically created, removing a 3 mm wide band of the cell layer. Wounded cultures were then incubated for time periods up to 12 days in media containing fetal bovine serum (FBS) concentrations (0, 0.1, 1, 5, 10, and 20%) as appropriate for each experiment. Slides were fixed, stained, and cells quantified within the wound boundaries by computer-assisted histomorphometry. The effect of wounding a cell layer was determined by comparing wounded cells as described above with a cell layer margin created without physically disrupting the cell layer. RESULTS: The in vitro model for periodontal wound healing established in this study showed that GF fill in the wound site at a significantly (P <0.0025) faster rate than PDL cells over 12 days of healing. In addition, PDL cells and GF were found to have unique concentration-dependent responses to FBS (P<0.0025). It was also shown that wounding resulted in a significant delay (P <0.01) in the initial healing response of an in vitro wound. CONCLUSION: This in vitro model demonstrated that the characteristics of wound healing are dependent on cell type, disruption (wounding) of the cell layer, and serum concentration. In addition, this model has incorporated both proliferation and migration to provide the first direct evidence demonstrating GF has a significantly greater ability to fill a wound site than PDL cells. This in vitro model may be utilized in future investigations of the biologic basis of periodontal wound healing.

Efficacy of 5 machining instruments in scaling of molar furcations.

The scaling efficacy of machining instruments was studied in the furcations of 100 extracted molars. The molars were divided into 5 groups with similar furcation anatomy, painted with artificial calculus, partly submerged in stone blocks, and the furcation entrances covered with a heavy rubber dam material. Ten mandibular and 10 maxillary molars were scaled by an experienced operator with each of the following instruments/inserts: ultrasonic instrument with either a prototype ball point insert or with a new pointed insert; ultrasonic instrument with a ball point insert; reciprocating hand-piece with new inserts for furcations; and a sonic scaler with a universal insert. The molar groups were coded and graded in a stereomicroscope by 2 independent examiners, and the rankings were tested with the Kruskal-Wallis test and the multiple comparisons between treatments test. The results revealed statistically significant differences between the instruments, as well as between different topographical areas of the furcations. The sonic scaler with a universal insert and the ultrasonic instrument with ball point inserts were significantly more efficient (P < 0.05) than the reciprocating handpiece with inserts in most of the areas studied. For mandibular molars, significantly better results (P < 0.05) were obtained for lingual furcation entrances than for furcation roofs. For maxillary molars, significantly better results (P < 0.05) were obtained for distal and buccal entrance areas than for furcation roofs and inside of mesial roots. The present study may give some guidance to the practitioner in choosing machining instruments for furcation cleaning as well as identifying the most difficult topographical areas to instrument.