Biomedical subjects

J M Doblin

Publications and source records attributed to J M Doblin.

5 recordsLinked to original sources

PubMed1996

A histologic evaluation of localized ridge augmentation utilizing DFDBA in combination with e-PTFE membranes and stainless steel bone pins in humans.

This study evaluated histologically and clinically the use of decalcified freeze-dried bone allograft in conjunction with Gore-Tex Augmentation Material and Memfix bone pins for localized ridge augmentation in three cases. Biopsies taken at 3, 6, and 9 months were evaluated. It was concluded that: (1) guided bone regeneration may be performed at local immediate extraction sites when flap design permits primary wound closure; (2) decalcified freeze-dried bone allografts used in conjunction with supporting pins may contribute to successful bone regeneration either by osseoinduction or osseoconduction, and/or by maintaining the membrane-created space during the early events in wound healing; and (3) at 9 months, guided bone regeneration utilizing Gore-Tex Augmentation Material membranes and decalcified freeze-dried bone allografts resulted in the formation of dense, viable new bone.

Adult↗

PubMed1993

Comparison between mechanical cleaning and an antimicrobial rinse for the treatment and prevention of interdental gingivitis.

This study compared the efficacy of an antimicrobial mouthrinse (0.12% chlorhexidine gluconate) plus toothbrushing (mouthrinse group), mechanical interdental cleaning plus toothbrushing (mechanical group), and toothbrushing alone (control group), at reducing and preventing interdental gingival inflammation. 92 male subjects were examined for interdental inflammation using the Eastman interdental bleeding index at baseline, then monthly for 3 months after using one of the above oral hygiene regimens. The mechanical cleaning group had significant reductions in bleeding sites compared to baseline at 1 month (56.90% versus 13.17%) that persisted throughout the study (2 months = 6.65%, 3 months = 5.70%). The other regimens showed no significant bleeding reduction at any time point in the study. The mechanical interdental cleaning group showed improvement over baseline at 1 month with the full benefit apparent after 2 months. The effect of location in the mouth on bleeding reduction was also assessed. The % of posterior sites which bled was always higher than anterior sites. Analysis of maxillary versus mandibular, and buccal versus lingual sites showed no significant differences. Additional observations of the data demonstrated that sites which bled at baseline were more likely to stop bleeding in the mechanical cleaning group. Also, sites which did not bleed at baseline were unlikely to bleed subsequently when mechanical cleaning was used. Neither of these observations were true for the other cleaning regimens. These data show that only mechanical interdental plaque removal combined with toothbrushing is effective at reducing or preventing interdental inflammation. This underscores the importance of instituting mechanical interdental cleaning to eliminate interdental inflammation.

Adolescent↗

PubMed1983

Factors modifying the synergistic toxicity of deoxycytidine in combination with thymidine plus 5-fluorouracil in HeLa cells.

We reported previously that deoxycytidine (CdR) enhances the cytotoxic effects of the drug combination thymidine (TdR) plus 5-fluorouracil (FUra) against HeLa S-3 cells. We have now examined the relationships between the concentration of CdR and its cytotoxic and cytokinetic effects, and have also investigated the role of certain other components of the culture medium in this phenomenon. Cell survival was determined by a colony-forming assay; cytokinetic effects were monitored by flow cytometry. In the initial experiments, cells were grown in Ham's F12 medium and exposed for 22 hr to 4 mM TdR, 0 X 025 mM FUra, and dCyd ranging from 1 microM to 4 X 0 mM. The individual drugs were at most only slightly toxic under these conditions; for TdR plus FUra, the survival decreased to 50% (in 5% FCS), and in the three-drug combination it varied from 8% at 1 microM CdR to 28% at 0 X 10 mM and back to a low of 3% at 4 X 0 mM CdR. Results from flow cytometry appeared correlated with the survival data, in that cells accumulated in the S phase to a greater extent in the region around 0 X 10 mM CdR than at higher or lower concentrations. When cells were exposed to the drugs in MEM medium in place of F12, their sensitivity to FUra and the TdR-FUra combination was enhanced, although the additional synergistic effect of CdR was reduced. We found that hypoxanthine, present in F12 but not in MEM, was the principal compound responsible for the observed differences between media.

Cell Survival↗

PubMed1981

Cytotoxic and cytokinetic effects of thymidine, 5-fluorouracil, and deoxycytidine on HeLa cells in culture.

Exponentially growing HeLa cells were exposed to thymidine (dThd), 5-fluorouracil (FUra), and deoxycytidine (dCyd) singly and in combination for up to 3 days. Survivals were measured using a colony forming assay, and cytokinetic effects of the drugs were evaluated by flow cytometry and by determination of population growth rates. Increasing concentrations of dThd alone (up to 4 mM) progressively slowed the movement of cells through the cycle; dThd was toxic above 1 mM. Nontoxic levels of FUra (10(-5) M) inhibited cell progression, but this was abolished by very low concentrations (3 microM) of dThd. The cytotoxic effects of FUra were not reversed by dThd; in fact, the lethality of FUra was enhanced in some cases. dCyd alone had neither cytotoxic nor cytokinetic effects on HeLa cells up to 4 mM, but low concentrations reversed the cytotoxic effects of 4 mM dThd and high concentrations reversed its cytokinetic effects. When dCyd was added to the combination of dThd and FUra, synergistic lethality resulted even at 10(-5) M FUra. The mechanism by which this synergism was achieved was not simply increased incorporation of FUra into RNA since, while dThd did enhance this incorporation, dCyd did not further increase it. Our results suggest instead that dCyd either directly or indirectly inhibited the repair of FUra-associated damage or else enabled the cells to progress into a more sensitive phase of the cell cycle during exposure.

Cell Division↗

PubMed1981

Cytotoxic and cytokinetic effects of 1-beta-D-arabinofuranosylcytosine, daunorubicin, and 6-thioguanine on HeLa cells in culture.

Exponentially growing HeLa cells were exposed to 1-beta-D-arabinofuranosylcytosine, daunorubicin, and 6-thioguanine singly and in combination for 21 hr. Survivals were determined by a colony-counting assay, and cytokinetic effects of the drugs were evaluated by flow cytometry. When used in two-drug combinations (concurrent exposures). 1-beta-D-arabinofuranosylcytosine was found to protect cells against both 6-thioguanine- and daunorubicin-induced lethality, the former to a greater extent than the latter. Protection against 6-thioguanine appeared to be related to the degree of inhibition of DNA synthesis by 1-beta-D-arabinofuranosylcytosine, but this was not the case with daunorubicin. When cells were exposed to the three drugs simultaneously, survivals were in agreement with those predicted from the various two-drug combinations. This implies that no additional drug interactions occurred when a third drug was added to the two-drug combinations.

Cell Cycle↗