ABSTRACT
The effects of retinyl acetate (RA) on the development of carcinogen-induced metaplastic lung nodules were investigated. Four mg of 3-methylcholanthrene were administered intratracheally to F344 rats maintained on a vitamin A-free diet and receiving 31.4 nmoles of RA per week by intragastric intubation. At 3, 5, and 10 weeks after intratracheal instillation of 3-methylcholanthrene, one group of 24 rats each was started on a weekly dose of 31,400 nmoles of RA; a control group was continued on the low-RA dose. Fifty-two weeks after 3-methylcholanthrene injection, the incidence of metaplastic lung nodules was found to be 3% in the combined high-RA-dose groups as compared with 42% in the low-RA-dose group. It is therefore concluded that RA has a significant effects on the postinitiation phase of preneoplastic lung nodules in rats.
Subject(s)
Precancerous Conditions/chemically induced , Vitamin A/analogs & derivatives , Animals , Avitaminosis , Dose-Response Relationship, Drug , Female , Methylcholanthrene , Neoplasms, Experimental/chemically induced , Rats , Rats, Inbred F344 , Vitamin A/pharmacologySubject(s)
Carcinoma, Squamous Cell/chemically induced , Lung Neoplasms/chemically induced , Methylcholanthrene , Vitamin A/pharmacology , Animals , Carcinoma, Squamous Cell/prevention & control , Hyperplasia , Injections , Intubation, Gastrointestinal , Liver/metabolism , Lung Neoplasms/prevention & control , Metaplasia , Methylcholanthrene/antagonists & inhibitors , Precancerous Conditions , Rats , Time Factors , Vitamin A/administration & dosage , Vitamin A/metabolismSubject(s)
Histocytochemistry , Iron/analysis , Microtomy , Animals , Anura , Female , Ferritins/analysis , Injections , Iron-Dextran Complex/analysis , Microscopy, Electron , Ovary/analysisABSTRACT
Ovaries from the spider crab, Libinia emarginata L. were studied to learn more of vitellogenesis in crustaceans. Oogonia and previtellogenic oocytes were found in the core of the ovaries. Vitellogenic oocytes are located more peripherally. Profiles of the endoplasmic reticulum are abundant in the vitellogenic oocytes. The granular and agranular reticulum as well as the Golgi complex are active in yolk synthesis. As vitellogenesis proceeds, yolk precursors are incorporated into the egg by micropinocytosis at the egg surface. Thus, in Libinia, yolk materials appear to be derived from both intra- and extraoocytic sources.
