[The influence of dental health examination in primary school on caries situation].

The purpose of the present epidemiological study was to clarify the influence of regular dental health examination practiced as school dental health care on the caries situation. The data analyzed were the result of dental examinations for 272 1st year pupils attending a junior high school which was attached to a private educational institution with pupils and students ranging from the kindergarten to university level. The institution is conducting regular dental health examination for all but the primary school. We analyzed the differences in the situation of caries between pupils who had graduated from the primary school which was attached to the institution and pupils from other primary schools. The former group was composed of the pupils who had not received regular dental health examination in primary school and the latter was composed of the pupils who had received it. Then, including the factor of the dental health care in kindergarten, we obtained the following results. 1) No significant difference in caries prevalence was found between the pupils who had not received regular dental health examination in primary school and the pupils who had received it, among male and female pupils respectively. 2) Both male and female pupils who had received regular dental health examination revealed a significantly higher rate of filling than pupils who had not received it. 3) Concerning pupils who had not received regular dental health examinations, the caries prevalence only among male pupils who had graduated from kindergarten attached to the institution was higher than that of the pupils from other kindergartens.(ABSTRACT TRUNCATED AT 250 WORDS)

Lyotropic-salt-induced changes in monomer/dimer/tetramer association equilibrium of formyltransferase from the hyperthermophilic Methanopyrus kandleri in relation to the activity and thermostability of the enzyme.

Formyltransferase from Methanopyrus kandleri is composed of only one type of subunits of molecular mass 32 kDa. The enzyme requires the presence of lyotropic salts for activity and thermostability. We report here that the enzyme is in a monomer/dimer/tetramer association equilibrium, the association constant being affected by lyotropic salts. At 0.01 M K2HPO4/KH2PO4, pH 7.2, the enzyme (0.4 mg/ml) was mainly present in a monomeric form. Upon increase of the phosphate concentration, the concentration of the dimer increased up to a phosphate concentration of 0.6 M, then decrease at the expense of tetramer formation up to a phosphate concentration of 1.0 M. The specific activity at 4 C increased from <0.1 U/mg at 0.01 M, over 1.5 U/mg at 0.6 M to 3.6 U/mg at 1.0 M. Similar results were obtained with ammonium sulfate as lyotropic salt. The findings indicate that both oligomerization and activity increase with increasing salt concentrations, suggesting that there is a causal connection. To determine this, we exploited the observation that oligomer formation was not induced by the weak lyotropic salt NaCl up to a concentration of 1.5 M and that the dissociation of the dimer into the monomer at 4 degrees C proceeded very slowly (50% in approximately 6 h). This allowed us to study the effect of NaCl on the activity of the oligomers at NaCl concentrations not sufficient to induce oligomerization. At 4 degrees C, the activity of the oligomers increased from 0.3 U/mg at 0.25 M NaCl to 3.4 U/mg at 1.0 M NaCl. At these NaCl concentrations, the monomers were inactive. The findings indicate that oligomerization is a prerequisite for enzyme activity in the presence of NaCl. The salt-dependent induction of oligomerization was parallelled by an increase in thermostability; strong lyotropic salts conferred thermostability at much lower concentrations than the weak lyotropic NaCl.