Induction of leukaemia in chloramphenicol-treated toads.

Chloramphenicol has been associated with the development of aplastic anaemia. As it is still widely used in Egypt, we studied its effect on 100 Egyptian toads (Bufo regularis) given a dose of chloramphenicol of 5 mg/40 g body weight for 12 weeks. We found it induced numerous, severe ultrastructural changes in almost all types of leukocytes. These changes were similar to those induced by the chemical carcinogen 7,12-dimethylbenz(a)anthracene in 100 toads used as the carcinogen control group, and similar to those in leukocytes reported in humans with leukaemia. We recommend regulations be applied on the use of this antibiotic in countries where it is still widely used.

Embryotoxic effects of benzo[a]pyrene, chrysene, and 7,12-dimethylbenz[a]anthracene in petroleum hydrocarbon mixtures in mallard ducks.

Studies with different avian species have revealed that surface applications of microliter amounts of some crude and fuel oils that coat less than 10% of the egg surface result in considerable reduction in hatching with teratogenicity and stunted growth. Other studies have shown that the embryotoxicity is dependent on the aromatic hydrocarbon content, further suggesting that the toxicity is due to causes other than asphyxia. In the present study the effects of three polycyclic aromatic hydrocarbons identified in petroleum were examined on mallard (Anas platyrhynchos) embryo development. Addition of benzo[a]pyrene (BaP), chrysene, or 7,12-dimethylbenz[a]anthracene (DMBA) to a synthetic petroleum hydrocarbon mixture of known composition and relatively low embryotoxicity resulted in embryotoxicity that was enhanced or equal to that of crude oil when 10 microliter was applied externally to eggs at 72 h of development. The order of ability to enhance embryotoxicity was DMBA greater than BaP greater than chrysene. The temporal pattern of embryonic death was similar to that reported after exposure to crude oil, with additional mortality occurring after outgrowth of the chorioallantois. Retarded growth, as reflected by embryonic body weight, crown-rump length, and bill length, was accompanied by teratogenicity. Abnormal embryos exhibited extreme stunting; eye, brain, and bill defects; and incomplete ossification. Gas chromatographic-mass spectral analysis of externally treated eggs showed the passage of aromatic hydrocarbons including chrysene through the shell and shell membranes to the developing embryos. These findings suggest that the presence of polycyclic aromatic hydrocarbons in petroleum, including BaP, chrysene, and DMBA, significantly enhances the overall embryotoxicity in avian species.

Neoplasms in strains of splenectomized mice after a single 7,12-dimethylbenz[alpha]anthracene treatment.

The effects of splenectomy on carcinogenesis by a single 10-mg dose of 7,12-dimethylbenz[alpha]anthracene (DMBA) given in olive oil by gavage was tested on BTOs, C57BL/60s, C3H/HeOs, and BALB/cOs mice. The splenectomy, performed a week before the DMBA was given, did not affect physical status or the incidence of acute toxic death of animals. DMBA-treated animals developed neoplasms at a significantly higher rate than did untreated mice. Splenectomy did not influence the overall incidence of neoplasms. Observed tumors in DMBA-treated groups were those of skin, forestomach, colon, liver, lung, adrenal, ovary, breast, hematopoietic-lymphoreticular system, and vascular system, depending on the strain. Types of DMBA-treated neoplasms were affected by prior splenectomy, depending on the strain: Splenectomy inhibited lung adenomas in BALB/cOs females and hepatomas in C57BL/60s females; splenectomy enhanced skin neoplasms in C57BL/60s and squamous cell carcinoma of the forestomach in BTOs males. The most significant change was in the incidence of the group of lymphomas. Myelogenous leukemia was increased in DMBA-treated groups of all strains, but splenectomy inhibited the development of this type of lymphoma.