Forebrain muscarinic control of micturition reflex in rats.

Functional contribution of the cholinergic pathway between the frontal cortex and basal nucleus of Meynert to micturition reflex was investigated. Male Wistar rats were subjected to bilateral lesion of the basal forebrain by ibotenic acid (IA) injection (7.5 microg/rat on each side) (BF rats). Phosphate buffered saline (PBS) was injected into control rats (sham operated rats; SO rats). Cystometrograms were obtained from conscious BF and SO rats 7-10 days after IA/PBS injection. Bladder capacity (BC) of BF rats was significantly smaller than that of SO rats (approximately 43.7%) and was accompanied by decrease in choline-acetyltransferase activity in the frontal cortices. Oxotremorine M, a muscarinic receptor agonist, increased BC in BF rats, while pirenzepine, an M1 muscarinic receptor antagonist, counteracted the effect of the oxotremorine M-induced increase in BC. Injection of oxotremorine M into the dorsal pontine tegmentum (DPT) reduced BC in BF and SO rats, while injection of pirenzepine had no effect on cystometrograms. These findings indicate that the M1 muscarinic receptor plays a part in the forebrain inhibitory mechanisms involved in the micturition reflex and that muscarinic receptor in the DPT contributes to excitatory control of micturition reflex.

Removal of dissolved 85Kr by vacuum degassing method.

In the irradiation apparatus where unsealed 85Kr gas is used as an internal radiation source for liquid-phase chemical reaction, the 85Kr gas dissolved in a liquid reactant must be removed after irradiation. Experiments on removal of dissolved 85Kr by the vacuum degassing method were carried out to examine the influence of degassing temperature, initial 85Kr concentration and stirring of a solution on the removal. The liquid reactant used was a water of 500 ml in which 85Kr gas was dissolved. The removal effect became greater with increasing temperature. The dissolved 85Kr concentration after removal decreased exponentially with the reciprocal of degassing temperature. Further, the removal effect was intensely affected by stirring of the solution and was independent of the initial 85Kr concentration. The removal factor of dissolved 85Kr at 33 degrees C reached 5 X 10(3) after a 30 minute lapse.

Radiation decomposition of trichlorofluoromethane in flow system under 60Co gamma-ray irradiation.

Irradiation experiments of CCl3F were carried out with 60Co gamma-rays using the irradiation facility of the flow system. In the system, CCl3F was irradiated at 5.7 kGg/h (5.7 X 10(5) rad/h) and -30 degrees C. The decomposition behavior of CCl3F and the influence of impurities in the circulating gas on the decomposition were examined. The result was compared with that of ampoule scale. The decomposition yield of CCl3F and the yields of radiolytic products (fluorocarbons) increased in proportion to the absorbed dose. The decomposition yield per Mrad of CCl3F was 0.0246 mol%/Mrad (G = 2.9). This value was equal to 1.8 times that of the ampoule scale. The marked influence of impurities (air, CH4, I2) was recognized for the yields of halogen ions.

[Recovery and purification of leakage radioactive krypton].

A recovery-purification system for radioactive Kr was constructed by enclosing an 85Kr testing apparatus with an airtight vessel. Experiments were carried out to examine the recovery rate of leakage Kr and the purity of Kr recovered with the system. The concentration of the leakage Kr in the airtight vessel was decreased to a detection limit of 0.3 ppm by the system. The recovery rate corresponded to 99.976%. The concentration of the Kr recovered was over 99.9908%. It shows that almost 100% of the radioactive Kr leaked out into the airtight vessel could be recovered and the He content in the Kr recovered could be reduced to less than 100 ppm.

Dose measurement of 90Sr source for radiation chemical reaction.

The irradiation characteristics for a plate source of 90 Sr 222GBq (6 Ci) were examined with the blue cellophane dosimeter and the thermoluminescence dosimeter. The 90Sr source used has the active area of 35x20mm2 and the surface concentration of 31.5 GBq (0.85 Ci)/cm2. The high dose rate of 1.1 kGy (1.1x10(5) rad)/h was obtained at the distance of 5 cm from this source. At that time, the isodose curve determined by the blue cellophane was similar to a circle. The peak in depth dose curve was fairly displaced to the shallow direction in comparison with that obtained from the irradiation with an electron beam accelerator (2 MeV). The calculated dose rate attains to 800 kGy (i.0x10(7) rad)/h at the distance of 5 cm from the source when the infinite plate source with the maximum surface concentration (1.51 TBq(40.7Ci)/cm2) is placed on a plane.

[Concentration measurement of 85Kr dissolved in the solution with GM counter (author's transl)].

When 85Kr gas is used as an internal radiation source for chemical reactions in liquid phase, it is necessary to check after irradiation whether the radioactive concentration of 85Kr dissolved in the solution is below permissible level or not. Measurements were made on solutions ranging in concentration from 1 X 10(-3) approximately 1 X 10(0)kBq/g (1 X10(-4) to 1 X 10(-1) microCi/g) by the use of an end-window GM counter for beta-rays. In the present paper, the method of making up the calibration curve for 85Kr solution is studied, together with some problems in measurement. The calibration curve for 85Kr solution was represented as N = 1.8 X 10(5) C. In addition, the method for measuring concentration of dissolved 85Kr was established by resolving problems relating to the volatilization of 85Kr in measurement.