Detection of an ascorbate radical in an irradiated mice using electron spin resonance (ESR).

Ascorbate radical (Asc.-) produced by the reaction of AscH- (ascorbic acid) with HO or O2.- after irradiation in mice has been measured. It is possible to measure Asc.- easily using ESR and a dialysis method in which Asc.- is collected at room temperature in the interstitial fluid through the dialysis membrane. After irradiation, Asc.- increases in both normal muscle and tumor tissues (SCC-VII) in proportion to the radiation dose. These results suggest that the amount of HO and O2.- produced is reflected in the Asc.- production. This method has been found more useful for the following reasons, (i) no special treatment, such as freezing of the sample, and no administration of noxious agents are necessary to measure Asc.-, (ii) irradiation using a dose of only a few Gy shows an increase in production of Asc.-, and (iii) this method dose not require removal of organs. Using this method, Asc.- can serve as an indicator of the amount of HO and O2.- produced by irradiation in vivo.

Diethylcarbamazine: inhibitory effect on acetylcholinesterase of Dirofilaria immitis and Brugia pahangi.

Anti-acetylcholinesterase activity of diethylcarbamazine (DEC) was studied. Acethylcholinesterase (AchE) of adult worms of Dirofilaria immitis, those of the 4th-stage larvae, early 5th-stage larvae and adults worms of Brugia pahangi, and that of hamster brain tissue were all inhibited by DEC. Michaelis constant (Km) of D. immitis and B. pahangi adult worm AchE were 1.47 x 10(-4) and 1.81 x 10(-4) M respectively. DEC was a competitive inhibitor of the filarial AchE. Inhibition constant (Ki) for AchE of D. immitis and B. pahangi adult worms were 2.56 x 10(-4) and 6.39 x 10(-4) M, respectively. DEC is a less potent anticholinesterase inhibitor, because Ki of DEC is 10(4) times higher than that of eserine, a potent anti-cholinesterase agent.

Plasma level of diethylcarbamazine in jirds and hamsters.

The relation between the dosage and plasma level of diethylcarbamazine (DEC) in jirds and hamsters was examined by gas-liquid chromatography. When the drug was given intraperitoneally to jirds at 100 mg/kg body weight, the plasma level rose rapidly and reached the maximum level (20-25 micrograms/ml) at 10 minutes and afterwards fell quickly to undetectable level at 4 hours. Even if larger dosage (300 mg/kg) was given, DEC was eliminated completely from the blood circulation within 8 hours. When the same dosages of DEC were given intraperitoneally, the DEC levels remained 2-4 hours longer in the blood of hamsters than in the blood of jirds. DEC given by stomach intubation at 100 mg/kg remained detectable much longer in hamsters (8 hrs) than in jirds (2 hrs). A repeated doses schedule did not show a tendency for the drug to accumulate. DEC was excreted in the urine and feces, but the total amount of drug excreted without metabolic changes was only about 8% of the given dosage. The majority of unmetabolized DEC was excreted in the urine within 0-12 hours.

Studies on Brugia pahangi in inbred hamsters. 1. Susceptibility of inbred GN and APG hamsters.

The susceptibility of inbred GN and APG hamsters to Brugia pahangi infection was studied. Male GN hamsters infected subcutaneously with 100 infective larvae showed 100% patency with the average prepatent period of 69 days. The average microfilarial density was 148/40 c.mm at 26 weeks and reached 1,000/40 c.mm at days 280. The rate of adult recovery was as high as 36%. Most worms were recovered from the heart and lungs (46%) and testes (40%). The male GN hamster-B. pahangi model could be a good substitution for the jird-B. pahangi model. Female GN and male APG hamsters seemed to be less susceptible than male GN hamsters. However, they could still be a better alternative to outbred hamsters due to their high rates of patency (92 and 100%), relatively high microfilarial densities (31 and 39/40 c.mm at 26 weeks) and reasonable rates of adult recovery (23.5 and 17.2%).