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.

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

Ultrastructural criteria that prove the similarities between amphibian and human tumors.

Toads fed with 0.5 mg 7,12-dimethylbenz(a)anthracene twice a week for 12 weeks displayed liver tumors in 27 out of 100 cases. Electron micrographs of liver tumors showed some criteria of malignancy, such as the presence of nuclear pockets, pseudoinclusions, dilatation of the cisternae of rough endoplasmic reticulum and loss of cell junctions. These features are closely similar to those of true malignancy described in humans and other mammals.

Carcinogenic effect of gibberellin A3 in Swiss albino mice.

Gibberellin A3 is a plant growth regulator used in many countries, including Egypt, to increase the growth of fruits and vegetables. The carcinogenic effect of gibberellin A3 was investigated in this study with Swiss albino mice. Administration of gibberellin A3 by gavage for 22 months induced a significant increase in their body weights. Tumors were induced in 18% of the males and 36% of the females and were located in the skin of the axillary region (sebaceous adenomas), breast (adenocarcinomas), and lung (adenocarcinomas and secondary metastatic deposits from breast tumors). Bronchocentric granulomas were induced in animals exposed to gibberellin A3 for 14 months. These results indicate that gibberellin A3 was carcinogenic in mice.

Preventive action of garlic on aflatoxin B1-induced carcinogenesis in the toad Bufo regularis.

The action of fresh minced garlic and garlic oil on aflatoxin B1- (AFB1) induced carcinogenesis in the toad Bufo regularis was studied. Feeding toads with AFB1 induced tumors in 19% of the animals. Animals given AFB1 together with fresh garlic or garlic oil showed a significant reduction in tumor incidence. The tumor incidences were 3% and 9% in animals given AFB1 plus garlic and AFB1 plus garlic oil, respectively. In all three groups, the tumors were located in the liver (hepatocellular carcinomas), in addition to the kidney in animals treated with AFB1 alone and together with garlic. The kidney tumors were diagnosed as metastatic deposits from the primary liver tumors. It is speculated that one or more constituents of garlic may be responsible for inhibition of AFB1-induced carcinogenesis in B. regularis.

Induction of hepatocellular carcinomas in the Egyptian toad Bufo regularis by an antifungal drug (griseofulvin).

Neoplastic lesions (hepatocellular carcinomas) were induced in the liver in 18 of 100 experimental toads (Bufo regularis) force fed with the antifungal drug griseofulvin, at a dose level of 0.4 mg/50 g every day. Maximal time of exposure and observation was 12 weeks. The first tumors appeared in 2 male toads 4 weeks after the initiation of feeding.

Carcinogenicity testing of some constituents of black pepper (Piper nigrum).

In mice, injection of safrole, tannic acid or methylcholanthrene (MCA) during the preweaning period induced tumors in different organs. Safrole and tannic acid (constituents of black pepper) were weak carcinogens when compared with MCA which was used as a carcinogenic control substance. Force feeding of d-limonene (one of the pepper terpenoids) for a long time to the mice which were injected with any of the above 3 substances reduced their carcinogenic activity, while force feeding of piperine (one of black pepper alkaloids) was ineffective.

The carcinogenicity of some antimalarial drugs using the Egyptian toad Bufo regularis as a biological test animal.

Feeding Egyptian toads (Bufo regularis) with chloroquine and primaquine separately induced tumor formation in 14% and 19% of the animals, respectively. When chloroquine and primaquine were given in combination, the tumor incidence increased to 23.5%. Chloroquine feeding resulted in tumors located in the liver (lymphosarcomas) and primaquine in tumors in the kidney (histiocytic sarcomas). Toads fed chloroquine plus primaquine developed tumors in the liver, kidney, lung, and urinary bladder, and all the tumors were diagnosed as histiocytic sarcomas. It is speculated that one or more metabolites of chloroquine and primaquine (e.g., quinone) may be responsible for tumor induction in the toads.

Induction of neoplasms in Egyptian toads Bufo regularis by oil of chenopodium.

Feeding the Egyptian toad Bufo regularis with oil of the chenopodium plant induced hepatocellular carcinomas in 23% of the animals, and metastases of the primary liver tumors appeared in the kidneys of 6 toads. The earliest evidence of tumors appeared after 3 months of treatment. The average latent period of tumor induction was 3.6 +/- 0.4 months. It is speculated that oil of chenopodium may be one of the constituents of Chenopodium ambrosoides which is responsible for tumor induction in the toads B. regularis.

Effect of adriamycin on the morphology of the erythrocytes and blood parameters of the toad Bufo regularis.

The effect of the anticancer drug adriamycin on the morphology of the erythrocytes as well as some blood parameters were studied in the Egyptian toad Bufo regularis. Injecting the toads subcutaneously in the dorsal lymph sac with adriamycin at a dose level of 2 mg/kg body weight once every three weeks for 12 weeks induced the formation of abnormalities in the cytoplasm and nuclei of the erythrocytes. Its administration also caused severe anaemia, since the number of red blood corpuscles, haemoglobin content and haematocrit values were obviously decreased throughout the whole experimental period. The total leucocytic count was also diminished. On the other hand, the erythrocyte sedimentation rate was increased all over the experiment.

Flour infested with Tribolium castaneum, biscuits made of this flour, and 1,4-benzoquinone induce neoplastic lesions in Swiss albino mice.

The carcinogenic effect of flour infested with beetles (Tribolium castaneum), biscuits made of this flour, and 1,4-benzoquinone (a quinoid secretion of this beetle) was investigated using Swiss albino mice. Force feeding flour infested with T. castaneum induced liver and spleen tumors (lympholeukemia) in 35.2% of the animals. The tumor incidence was 29% in mice force fed biscuits made of infested flour, and the tumors were located in the liver (lympholeukemia) and breast (adenocarcinoma type A). In animals fed 1,4-benzoquinone, the tumor incidence was 33.6%, and the tumors were located in the liver and spleen (lympholeukemia). It is speculated that 1,4-benzoquinone, alone or in combination with other quinoid secretions of the beetles present in the flour, may be responsible for tumor induction in the organs of mice.

Adriamycin-induced neoplastic lesions in the Egyptian toad Bufo regularis.

Injecting adult toads (Bufo regularis) subcutaneously in the dorsal lymph sac with adriamycin at a dose of 2 mg/kg body weight, once every 3 weeks for 20 weeks, induced hepatocellular carcinomas in 20 out of 100 animals. Metastases of the primary liver tumors appeared in the kidneys of 7 toads.

Carcinogenic effect of force-feeding an extract of black pepper (Piper nigrum) in Egyptian toads (Bufo regularis).

50 male and 50 female Bufo regularis were treated, by force-feeding, with an extract of black pepper, at a dose level of 2 mg, 3 times a week for 5 months. The first tumors appeared after 2 months. Liver tumors (hepatocellular carcinomas, lymphosarcomas and fibrosarcomas) were found in 12 males and 18 females. Metastatic deposits of hepatocellular carcinomas were registered in the spleen, kidney, fat body and ovary.

Carcinogenesis induced by black pepper (Piper nigrum) and modulated by vitamin A.

Painting and feeding of mice with 2mg of an extract from black pepper on 3 days a week for 3 months results in a significant increase of the number of tumor-bearing mice. Tumor incidence is reduced in those groups of experimental animals receiving 5 or 10mg Vitamin A-palmitate twice weekly for 3 months by feeding or painting during and subsequent to application of pepper extract. Feeding of mice with powder of black pepper in diet (50g/3kg food) has no impact on carcinogenesis.

Aflatoxin-B1 inhibition of spermatogenesis in the toad Bufo regularis.

Aflatoxin-B1 was injected in a dose of 0.01 mg/50 g body weight into the dorsal lymph sac of male toads (Bufo regularis) to evaluate its effect on the testes. After three and six weeks' treatment the diameters of the seminiferous tubules were significantly reduced. Furthermore, spermatogenic cells were almost completely absent. The histological evidence also showed complete suppression of spermatogenesis. It is suggested that one or several AFB1 metabolites may be responsible for suppression of spermatogenesis in the given toads, through inhibition of testicular androgenic activity.

Induction of skin papillomas in the rabbit, Oryctologus cuniculus, by bites of a blood-sucking insect, Cimex lectularius, irradiated by gamma rays.

Bed bugs, Cimex lectularius, irradiated with gamma rays were allowed to suck blood from shaved areas of the skin of rabbits, Oryctolagus cuniculus, 2 times/week for 5 months and then once weekly for another 5 months. This significantly induced the formation of skin papillomas and sweat gland hyperplasia in five out of nine experimental animals. It is speculated that the saliva of the irradiated bugs was activated by gamma rays and was responsible for the induction of skin papillomas. Because bed bugs play a significant role in the transmission of virus, it is also speculated that there is a virus in the saliva of bugs; this virus may be activated by gamma radiation and causes the development of papillomas in the skin.

The use of cytoenzymological changes in some parasitic protozoa for screening the carcinogenicity of chemicals.

Changes in the Golgi bodies and in hydrolytic enzymes were observed in parasitic ciliates (Nyctotheroides puytoraci) and flagellates (Opalina sudafricana and Protoopalina sp.) after the administration of a single dose of 0.5 mg beta-naphthylamine (BNA) to their host, Bufo regularis. The experiment was carried out during the host's pre-breeding season, from November to February (when only trophozoites are available); the trophozoites were examined 21 days after the injection of BNA. Use of the silver impregnation technique showed an increase in the size of the granular argentophilic Golgi bodies in all three trophozoites after administering BNA to their host. In addition, a larger number of acid phosphatase and nonspecific esterase granules was found in the endoplasm of the three parasites after the injection. The localization of acid phosphatase and nonspecific esterase was found to be similar to the distribution of the Golgi bodies in both the control and the treated preparations. The results could be useful, in that some protozoans could be employed for the quick detection of chemical carcinogenicity if changes in their hydrolytic enzyme content are used as a diagnostic feature.

Carcinogenic effect of biscuits made of flour infested with Tribolium castaneum in Bufo regularis.

Biscuits made of flour infested with Tribolium castaneum induced the formation of hepatocellular carcinomas (22%) when force-fed to toads (Bufo regularis) at a dose level of 200 mg/50 g 3 times a week. Maximal time of exposure and observation was 16 weeks. Some metastatic deposits from the primary liver tumours were found in the kidneys. Thus, the carcinogenic potency of the biscuits was almost the same as that of the flour previously reported by the authors indicating that the temperature of the oven in which the biscuits were baked did not alter the carcinogenicity of the infested flour.

The use of cytoenzymological changes in certain parasitic protozoans for screening the carcinogenicity of chemicals.

Cytoenzymological changes were observed in parasitic ciliates (Nyctotheroides puytoraci) and flagellates (Opalina sudafricana and Protoopalina sp.) after injection of their host, Bufo regularis, with a single dose of 0.5 mg beta-naphthylamine (BNA) per toad. The experiment was carried out during the host's pre-breeding season. Trophozoites of the given parasites were examined 21 days after the injection. The localization of the mitochondria and the relative intensity of succinic dehydrogenase (SDH) and deoxyribonucleic acid (DNA) activity in the control and BNA-treated trophozoites were compared. The results could prove useful for screening the carcinogenicity of chemicals by means of these parasitic protozoans.

Enhancement of hepatic tumors induced by N-nitrosodimethylamine in female toads Bufo regularis by oestrone.

The effect of oestrone on hepatic tumours induced in the female toads Bufo regularis by N-nitrosodimethylamine (DMNA) was evaluated. Injecting the toads with DMNA induced hepatocellular carcinomas in 17% comparable with 23% in toads injected with DMNA plus oestrone. These results show that oestrone insignificantly enhanced the tumour formation. Oestrone alone induced hepatic tumours in only 4 cases and was considered as a weak initiator.