Toshihide Matsumoto

The effect of dam's strain on the intrauterine craniofacial growth of mouse fetuses

PurposeThe maternal effect is one of the important factors in mammalian growth in conjunction with the genetic effect. The present study investigated the prenatal maternal effect of a dam on the intrauterine craniofacial growth of a mouse fetus using embryo transfer and cephalometry. DDD/Qdj strain mouse embryos were transferred to four strains of recipient female mice (DDD/Qdj, C3H/Qdj, C57BL/Qdj, and DBA/1J Sea). Just after parturition cephalometric observation of the newborn offspring, which developed in the uteri of the four strains of dams, was performed and then the craniofacial size of the newborn offspring was calculated on the lateral cephalogram. Statistical analyses were performed to examine the correlation between the dams weight and the craniofacial size of the newborn offspring, to test the significance of the effect of the dams strain on the craniofacial size of the newborn offspring, and to evaluate the interstrain difference of the intrauterine craniofacial growth of the mouse fetuses.ResultsIt was disclosed that there were a direct relation between the dams weight and the craniofacial size of the newborn offspring, a significant effect of the dams strain on the craniofacial size of the newborn offspring, and a significant interstrain difference in the craniofacial size of the newborn offspring after eliminating the effects of litter size and gestation period on the craniofacial size of the newborn offspring (DDD/Qdj > C3H/Qdj = C57BL/ Qdj > DBA/1J Sea).ConclusionThus, it could be concluded that the four strains of dams affected differently the intrauterine craniofacial growth of the DDD/Qdj strain fetuses through each uterine condition, indicating that the dams weight played an important role as one of the prenatal maternal effects on the intrauterine craniofacial growth of mouse fetuses.

Genetic study of dentinal growth in mandibular first molars of mice

The dentinal growth of mandibular molars of mice could be determined by genetic and environmental factors as are other quantitative characters, such as crown size and craniofacial size. To study the relative contribution of genetic and environmental factors to dentinal growth, a partial diallel cross was carried out by the mating of one pair from each of six strains of mice. In each F1 offspring, the total amount of dentinal formation in the first molar of the right mandible was quantified as a volume by the time-marking method, using nitrilotri-acetate lead with the computerized image scanning system, and then analyzed by a quantitative genetic method. The result obtained was as follows: In either sex, both additive genetic and nonadditive genetic variance components of the accumulative volume of dentinal formation in the first molar were relatively large throughout the experimental period, while the environmental variance component was much smaller. Thus it could be concluded that the genetic factor contributed more to the whole process of dentinal growth in the first molar rather than the environmental one in this F1 population.

A genetic study of dentin growth in the mandibular second and third molars of male mice.

Although the influence of genetic and environmental factors on the completed crown size of mandibular molars in mice is well known, such influence on the growth process of the mandibular second and third molars of mice has not yet been clarified. The purpose of the present study is to examine the growth pattern of the dentinal formation and evaluate the relative contributions of both genetic and environmental factors to longitudinal dentin formation by the use of the partial diallel cross-genetic approach, the time-marking method and a computerized image measurement system. The following results were obtained: 1) the onset of dentinal formation in the second molar was on the 6-9th day after birth, while that of the third molar was on the 9-12th day after birth; 2) the best fitted growth curve of the dentinal formation for the first molar was the fifth order polynomial equation, while for the second molar the fourth order polynomial equation was best, and for the third molar the third order polynomial equation was best; 3) maternal effect strongly influenced the second and the third molar dentin growth at an early stage of postnatal growth. Thus, it could be concluded that the dentinal formation growth pattern differed among the three kinds of mouse molars while maternal environmental factors, in addition to genetic factors, played an important role in the mouse second and third molar dentin growth during the early stage of postnatal growth.

Phenylthiocarbamide (PTC) Taste Test in Various Ethnic Groups in China

We carried out this investigation to determine taste sensitivity of phenylthiocarbamide (PTC) in various Chinese ethnic groups. While the Han ethnic group accounts for more than 90% of the population in China, there are 55 other ethnic groups, distinguished from each other by their historical origin, customs, language, and religion. Taste sensitivity to PTC is controlled by a gene, and differences in this sensitivity have been investigated in various populations.