Modulation of high-dose methotrexate toxicity by a non-toxic level of 5-fluorouracil

High-dose methotrexate (MTX) toxicity is reduced by a non-toxic dose of 5-fluorouracil (FU) when these agents are used in combination. Changes in the hematopoietic system (platelets, erythrocytes, leukocytes, hemoglobin, and hematocrit), ileal tissue, body weight, and mean survival were used as parameters to assess toxicity. For all parameters studied, there were no significant differences between the scheduling of MTX (245 mg/kg) after a priming dose of FU (25 mg/kg), simultaneous MTX and FU, FU alone, and control. However, sequential treatment with MTX followed by FU, and MTX alone resulted in: a marked decrease in the hematopoietic parameters; significant morphological changes in ileal tissue; a reduction of body weight; and increased mortality of animals. Hence, this study suggests that FU, a cytotoxic agent, may protect against MTX toxicity and improve its therapeutic index when FU administration precedes MTX or when these agents are given simultaneously.     

Characteristics of different isolates of Schistosoma japonicum from China in the final hosts

The present paper deals with the susceptibility of common laboratory animals, such as mouse, rat, hamster, jird, rabbit and rhesus monkey, to infection with different isolates of Schistosoma japonicum in the mainland of China under laboratory conditions. With the exception of the rat, all the animals under study were permissive hosts for different isolates though their worm recovery rates varied. The mean body length of pair-worms of the Yunnan isolate was considerably smaller than that of the Anhui, Hubei, Guangxi and Sichuan isolates, and the percentage of male specimens with 7 testes in the Yunnan isolate was also significantly less than that in the other 4 isolates. Judging from the egg index (width/length x 100), the eggs of the Sichuan isolate were broad and short in shape, giving a high index; those of Guangxi and Hubei isolates were oblong, giving the lowest index; the other two isolates from Yunnan and Anhui, lay between these two extremes. The mean prepatent periods were longer in mice, hamsters and rhesus monkeys infected with Yunnan and Guangxi isolates, than those with Sichuan isolate. A dendrogram of the 5 isolates of S. japonicum was constructed on the basis of similarity coefficients by means of fuzzy cluster analysis on the biological characters mentioned above. Our results provide evidence of the existence of different strains of S. japonicum in the mainland of China as shown by comparative studies of their characteristics in the final hosts.