The generation of dental caries in humans is thought to be regulated by many intrinsic and social factors. In this study, we examined the effect of MHC on susceptibility to dental caries in mice. The mean carious score of BALB.K/Ola, a H-2 congenic strain in which the H-2 region derived from C3H/HeJ (H-2k/k) is introduced into BALB/cJ (H-2d/d), was markedly reduced as compared with that of its recipient strain (BALB/cJ). Mating experiments confirmed a strong genetic linkage between H-2 haplotype and caries susceptibility. These results demonstrate that one of the genetic factors of the susceptibility in the mouse is mapped within the H-2 region. This finding of a host genetic factor influencing the generation of dental caries will help in developing clinical preventive strategies.
In this study, we demonstrate that
the localized surface plasmon
(LSP) resonance of metal nanoparticles, depending strictly on the
generating wavelength of LSP resonance, can have both beneficial enhancement
and harmful quenching effects on a triplet–triplet annihilation-based
upconversion (TTA-UC) emission. When the LSP resonance band of anisotropic
silver nanoprisms spectrally overlapped with the photoexcitation wavelength
of a sensitizer and the fluorescence of an emitter, an increase in
the photoexcitation efficiency and an acceleration of the radiative
decay rate were respectively induced, resulting in an effective enhancement
in the TTA-UC emission. Furthermore, the overlapping with the photoexcitation
wavelength led to a significant decrease (93%) in the threshold light
excitation intensity, which greatly enhances the figure-of-merit in
TTA-UC systems. However, when the LSP resonance band overlapped with
the phosphorescence band of the sensitizer, the TTA-UC emission was
extremely quenched, accompanied by the enhanced phosphorescence and
the decreased phosphorescence lifetime. These results suggest that
the decrease in the TTA-UC emission is a result of the competition
between the triplet–triplet energy transfer to the emitter
and the LSP-induced nonradiative energy transfer to the silver nanoprisms
from the triplet-excited sensitizer. This discovery of the conflicting
effects of LSP resonance provides an important guideline: a precise
adjustment of LSP resonance wavelengths is needed for the efficient
enhancement of TTA-UC emission. This requirement is different from
those of other fluorescence systems such as single downconverted fluorophores
and lanthanide-based upconversion nanoparticles.
We studied dental caries susceptibility in various inbred mice strains infected with Streptococcus mutans and the inheritance pattern in the F1 and the N2 backcross animals. A high caries score was observed in four laboratory strains, BALB/cAJcl, C57BL/6NJcl, C57BL/10Slc and DBA/2NJcl. Three strains, C3H/HeNJcl, AKR/JSlc and CBA/JNCrj, showed less caries. Males of strain C57BL/10Slc (mean caries score = 112.2) and females of strain C3H/HeNJcl (mean caries score = 24.0) were chosen for examinations of the inheritance of the caries susceptibility. The mean caries score in (C57BL/10Slc×C3H/HeNJcl) F1 hybrids was 98.4, demonstrating that F1 progenies were susceptible. A number of N2 mice were obtained by mating the F1 male and the C3H/HeNJcl female. The caries scores of these N2 male mice had an extensive range, from 14 to 194. Assuming that a caries score over 74 (median of the scores between C57BL/10Slc and C3H/HeNJcl) belonged to the highly caries-susceptible group, N2 mice could be divided into groups with low or high caries susceptibility. Furthermore, the effect of nu/nu mutation on caries susceptibility in mice was also examined.
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