Protein breakdown in the masseter induced by the amputation of lower incisor teeth and in the repeated contraction of isolated masseter was investigated in rats.A significant decrease in the protein breakdown was observed in the masseter 7 days after amputation. Furthermore, a similar significant decrease in the protein breakdown was also observed with repeated contraction of the isolated masseter.
These findings appear to reflect the influences of contractile activity on protein breakdown in the masseter.

抄録全体を表示

Many recent studies of neurotransmitter receptors have investigated the processes involved in receptor change and several workers have reported that when tissues become desensitized, receptors are removed from the cell plasma membrane and appear inside the cell. These internalized receptors are detectable as the “light-density vesicular fraction” when cell homogenates are centrifuged to equilibrium on continuous sucrose gradients. In the present study, we examined the effects of antidepressant drugs on the binding of a β-adrenergic antagonist to various fractions of rat brain isolated by density gradient centrifugation. Specifically, the distribution of binding of [³H] -dihydroalprenolol in sucrose gradients (0.2-2.0 M) containing rat brain cortical homogenates centrifuged to equilibrium (110, 000 × g/6 hours), was examined in controls and after various antidepressant drug treatments. There was no significant change in the number or distribution of, β-adrenergic receptors in rat brain following the acute drug treatments. However, there was a significant decrease (29%) in β-adrenergic receptor number following a chronic desipramine regimen, but no apparent alteration in the density of the receptor-containing membranes, each sample having a maximum distribution at approximately 1.1 M sucrose. Non-specific binding was maximal at 0.7 M sucrose. There were two protein peaks in the sucrose gradient, one corresponding to the non-specific and the other to the specific binding maxima; electron microscopy showed that a significant degree of non-specific binding to a myelin-containing fraction occurred and that the fraction containing most of the specific binding was composed of membrane fragments. Na⁺K⁺-ATPase activity gave a single broad peak (maximum at 1.1 M sucrose). Thus, desensitization of the β-adrenergic receptor does not occur following acute exposure to antidepressant drugs. Secondly, desensitization of the β-adrenergic receptor following chronic antidepressant administration does not apparently result in migration of receptors into the “light-density fraction” which has been reported to be present following acute exposure to agonists in vitro.

抄録全体を表示

The present study investigated the development of crown and bridge resin using a new PNC-EMA monomer. MMA monomer has long been used for crown and bridge resins, but the polymer prepared with MMA monomer has certain demerits such as low mechanical strength and abrasion resistance. The authors prepared a polymer by mixing 3PNC-EMA monomer having a P=N bond in its skeleton, previously synthesized by ANZAI et al., with a monomer currently available on the market, in proportions of 14-70% (wt), using PMMA as the polymer. Both the compressive strength and hardness increased in accordance with increased amounts of the mixed 3PNC-EMA monomer, but water sorption reached 1.86 mg/cm² when the mixed amount of 3PNC-EMA was 28%. The degree of abrasion decreased in accordance with the increase in the mixed amount of 3PNC-EMA, showing a value 1/3 that of PM MA, when mixed in a proportion of 70%.

抄録全体を表示

In the previous study, a statistically significant positive correlation between natural background radiation exposure rates and crude (non-age-adjusted) cancer mortality rates was observed in 46 Japanese prefectures over the period from 1968 until 1978. However, the significance of this correlation mostly disappeared through age adjustment. It was suggested that natural radiation levels are positively correlated with population component ratios older than 40, 50 and 65 years, which was considered to be one of the causes of the apparent correlation between exposure rates and crude cancer mortality rates.
In order to confirm these facts, we also examined the correlation between natural background radiation exposure rates and cancer mortality rates over two other periods : 1950-1957 and 1958-1967. Furthermore, we carried out a long-term analysis for the period 1950-1978, including the data of the previous report. In all periods, statistically significant positive correlation coefficients were observed in most cases of cancer with only a few exceptions. However, as in the previous study, the significance of the correlation mostly disappeared through age-adjustment with only one exception of uterine cancer in 1958-1978.

抄録全体を表示

It is well known that the dimensional change occurring in an impression material is an important factor affecting the fitting accuracy of the final restoration. However, no method of directly measuring the dimensional changes in impression materials, from immediately after initial setting, with accuracy and ease has yet been firmly established. In the direct method which necessitates measurement pressure, force may be applied to impression materials which have great plasticity immediately after initial setting, and a flow may thus be created producing dimensional changes. The indirect method is more advantageous in this respect, but its measurement with the passage of time is complicated, and it is difficult to apply under clinical conditions.
In the present report, a method divised by the authors for measuring changes in dimension directly, without the application of pressure, is described, and will hereinafter be referred to as the “non-pressure direct method.” The method was used to measure dimensional changes in powdered alginate impression materials available on the market at 100% relative humidity and in water.

抄録全体を表示

The authors have hitherto reported a series of basic studies on visible light-curing denture base resin with the aim of investigating its clinical applications.
In the present study, the authors examined the application of this resin to the repair of fractured parts of heat-curing denture base resin, examined the shapes of the fractured parts, the shapes of the divided parts to be irradiated and the resulting mechanical strength. As a result, it was shown that specimens having a 45° downward repair plane exhibited the highest values in transverse strength, and that the form of repair plane which was cut at an angle of 45° had large values of tensile strength.

抄録全体を表示