Alain F. Pelfrene

Effect of sodium ascorbate on tumor induction in rats treated with morpholine and sodium nitrite, and with nitrosomorpholine

Groups of male MRC Wistar rats were treated for 2 years either with morpholine (10 g/kg food) together with sodium nitrite (3 g/l drinking water) or with N-nitrosomorpholine (NM, 0.15g/l drinking water). In both cases, a group of rats was given sodium ascorbate (22.7 g/kg food) in addition to these treatments. When ascorbate was present, the liver tumors induced by morpholine and nitrite showed a 1.7-fold longer induction period, a slightly lower incidence, and an absence of metastases in the lungs, indicating that ascorbate had inhibited the in vivo formation of NM. Ascorbate did not affect liver tumor induction by the performed NM. The group treated with morpholine, nitrite, and ascorbate had a 54% incidence of forestomach tumors, including an 18% incidence of squamous cell carcinomas, possibly because ascorbate promoted NM action in this organ.

Carcinogenic activity of anthanthrene on mouse skin.

Dibenzo [cd, jk] pyrene (anthanthrene), considered to be noncarcinogenic, was examined for carcinogenicity in a comparative study with other polycyclic hydrocarbons. Anthanthrene induced benign and malignant epidermal neoplasms in female Swiss mice after repeated skin application. The incidence of these tumors (47%) was lower and the latency longer than those found after benzo[a]pyrene or dibenzo[a,h]pyrene treatment. Since the proportion of malignant neoplasms was similar (60%) in these three groups, the results indicate that anthanthrene is a relatively strong carcinogen. A rationale accounting for previous negative results in percutaneous experiments with this compound is suggested. Das als nicht-carcinogen erachtete Dibenzo [cd,jk] pyrene (Anthanthren) wurde auf seine carcinogene Wirkung in einer vergleichenden Untersuchung mit anderen polycyclischen Kohlenwasserstoffen untersucht. Nach wiederholten Gaben auf die Haut führte Anthanthrene zu gutund bösartigen epidermalen Geschwülsten bei weiblichen Swiss Mäusen. Die Häufigkeit dieser Tumoren (47%) war geringer, und die Latenzzeit war länger als bei Neoplasmen der Haut, die nach Behandlung mit Benzo[a]pyren oder Dibenzo[a,h]pyren gefunden wurden. Da der Anteil bösartiger Geschwülste in diesen drei Behandlungsgruppen ähnlich war (60%), zeigen die Ergebnisse, daß Anthanthren ein relativ starkes Carcinogen ist. Auf eine Erklärung vorher negativer Befunde nach percutaner Behandlung mit dieser Verbindung wird hingewiesen.

Histology of chemically induced mesotheliomas in MRC-Wistar rats.

Two peritoneal mesotheliomas were induced in rats during a carcinogenicity study of 1-nitroso-5,6-dihydrouracil (NO-DHU) injected intraperitoneally. A review of literature concerning experimental induction of such tumors indicated that they seldom produced with organic compounds and rarely occur spontaneously. In the present study, several reports of chemically induced mesotheliomas of the testes are analyzed and the diagnoses critically reviewed along with other differential diagnoses.

Arsenic and cancer: the still unanswered question.

For some 2,500 years, arsenic was considered an important element of pharmacopeias and was praised for its medicinal qualities. However, an incidental link with cancer was suggested during the nineteenth century, and since that time a controversy has ensued with regard to the compounds tumorigenicity. Several epidemiological surveys, for example, have suggested that arsenic induces lung, liver, or skin cancer in humans. On the other hand, all experimental attempts to reproduce such neoplasms in laboratory animals have consistently failed, thereby denying support to the human data. Recently arsenic was reported to be mutagenic. However, because of the inconsistency of most mutagenesis findings at present, this also cannot be regarded as supporting evidence. Furthermore, a recent trend has been to consider arsenic as beneficial in cancer prevention and in maintaining the health of farm animals, and, perhaps, humans. A critical review of epidemiological and experimental data from the literature has been made in an attempt to present an objective picture of this controversial and sensitive question and to encourage further research, which may ultimately determine whether arsenic deserves its execrable reputation.

Chemically induced esthesioneuroblastomas in rats

Malignant tumours of the nasal cavity were induced in 19 of 56 (34%) female MRC-Wistar rats by 1-nitrosopiperazine administered orally for life. These tumours were of neurogenic origin, according to classical histologicriteria. Bösartige Geschwülste der Nasenhöhle wurden in 19 von 56 (34%) weiblichen MRC-Wistar-Ratten durch orale Gabe von 1-Nitrosopiperazin induziert. Nach histologischen Kriterien waren diese Tumoren neurogener Herkunft.

Early vascular modifications induced by asbestos fibers in the hamster cheek pouch

Abstract The vascular response of the hamster cheek pouch to direct application of five UICC-standardized types of asbestos fibers was studied in vivo by the transparent chamber technique. The resulting vascular modifications were different from those in studies of the inflammatory process, but similar to changes induced in the cheek pouch by several chemical carcinogens or transplanted malignant tumors. Although definite conclusions may not yet be drawn as to the mechanism and/or significance of the induced vascular response, its relationship to the respective abilities of the various fiber types to induce mesothelial tumors is considered.

Experimental induction of melanotic tumors in Syrian golden hamsters by transplacental and topical application of ethylnitrosourea

Pregnant Syrian golden hamsters were treated with a single intraperitoneal injection of ethylnitrosourea (ENU) solution a few hours pre-parturition. Offspring either received no further treatment or from 6 weeks of age, bi-weekly application of ENU solution in acetone for 20 consecutive weeks. Progeny from non, transplacentally treated mothers were also treated topically. Among all treated groups, 8.6% of the animals developed pigmented skin tumors, most of these animals having received the combined treatment. This group also showed a significantly decreased latency period in females compared to males. One of the skin tumors, which was histologically and clinically benign, was transplanted several times and subsequently exhibited malignant features. Experimentelle Induktion von melanotischen Hauttumoren in Syrischen Goldhamstern durch örtliche Anwendung von Äthylnitrosoharnstoff. Trächtige syrische Goldhamster wurden durch einmalige intraperitoneale Injektion von Äthylnitrosoharnstofflösung (ENU) einige Stunden vor der Geburt behandelt. Die Jungen erhielten entweder keine weitere Behandlung oder es wurde, von der sechsten Lebenswoche ab, zweimal pro Woche eine ENU-Lösung in Aceton während 20 aufeinanderfolgenden Wochen appliziert. Die Nachkommenschaft von nicht-transplacental behandelten Müttern wurde nach gleichem Muster örtlich behandelt. Von allen behandelten Gruppen entwickelten 8.6% der Tiere pigmentierte Hauttumoren, wobei die meisten Tumoren in der Gruppe mit Kombinationsbehandlung vorkamen. Diese Gruppe zeigte auch eine signifikant erniedrigte Latenzzeit im weiblichen Geschlecht. Einer der Hauttumoren, der histologisch und klinisch gutartig war, wurde mehrere Male transplantiert. Dabei trat eine maligne Transformation auf.

Acinar adenomas of the pancreas in MRC-Wistar rats

Abstract Acinar cell adenomas of the pancreas, rarely found neoplasms, have been observed in MRC-Wistar rats randomly bred in the Eppley Institute for the last 6 years. Over 9000 rat pancreas were examined histologically. These were from rats treated with various chemicals (carcinogens and non-carcinogens) and from non-treated animals, all of which were maintained under similar standard conditions. The frequency of this lesion was 0·6 per cent and was apparently unrelated to administration of chemical carcinogens.

Experimental evaluation of the clearance of 3,4-benzo(a)pyrene in association with talc from hamster lungs

B(a)P was administered intratracheally either alone or in association with 3 mg or 9 mg of talc, to Syrian golden hamsters. The clearance rate of the polycyclic hydrocarbon from the lungs was measured at regular intervals. It was found that talc was an effective factor in depressing the clearance of carcinogen from the lung tissue.