Chronic fistulation and cannulation of the rabbit caecum.

A PTFE cannula was introduced into the rabbit abdomen through the right flank. A purse string suture was used to fix a small plastic flange within the caecum. A larger flange was sutured under the skin to fix the cannula. Caecal contents could be collected from the chronic fistula via a threaded stainless steel cap on the cannula. Animals tolerated the fistulation well and sepsis was never seen.

The major role of glutathione in the metabolism and excretion of N,N-dimethyl-4-aminoazobenzene in the rat.

In the normal rat given a single dose of one mg N,N-dimethyl-4-aminoazobenzene (DAB) via the hepatic portal vein the following biliary metabolites reached their maximal rates of excretion in the sequence: 4'-sulphonyloxy-DAB, N-(glutathione-S-methylene)-4-aminoazobenzene (GSCH2AB), 4'-sulphonyloxy-N-methyl-4-aminoazobenzene (4'-sulphonyloxy-MAB) 4'-sulphonyloxy-GSCH2AB and MAB-4'-beta-glucuronide. The unusual and relatively unstable N-methylene glutathione conjugates were major metabolites accounting for up to 70% of the whole. It was shown that all the 4-aminoazobenzene (AB) and perhaps all of the 4'-sulphonyloxy-AB, which may be observed in bile, are artefacts due to decomposition of GSCH2AB and 4'-sulphonyloxy-GSCH2AB respectively and that biliary excretion of N-methyl oxidised products of MAB and 4'-hydroxy-MAB is dependent on their conversion to the GSH conjugates, GSCH2AB and 4'-hydroxy-GSCH2AB respectively. Sulphotransferase inhibition by pentachlorophenol caused a reduction in the excretion of all sulphate conjugates, but biliary excretion as a whole was not reduced significantly due to a compensatory increase in the excretion of MAB-4'-beta-glucuronide and the appearance of 4'-OH-GSCH2AB. Glutathione (GSH) depletion by diethylmaleate caused a reduction in biliary metabolites of DAB by lowering the levels of GSH conjugates. This was because the amount of N-methyl oxidation of MAB and 4'-hydroxy-MAB were proportional to the amount of GSH present. The fall in N-methyl oxidation was not compensated for by an increase in 4'-hydroxylation and was accompanied by a delay in the appearance of 4'-hydroxylated metabolites. The administration of potential precursors of 4'-sulphonyloxy-GSCH2AB establishes the sequence of reactions resulting in its formation to be 4'-hydroxylation, N-methyl oxidation, GSH conjugation and O-sulphation.

The Eker renal tumor rat. General immune status in relation to a varying tumor burden.

Evidence was obtained that the response of blood lymphocytes to phytohemagglutinin was reduced in some but not all rats with massive hereditary renal tumors (less than 50 mm mean diameter). Erythrocyte-antibody sensitized, complement dependent (EAC) rosette formation by sensitized spleen cells was also depressed in these animals, but plaque forming cell activity was essentially normal. Lesser tumor growth was associated with general cell-mediated and humoral immune responses which were within the range found for non-tumor-bearing syngeneic rats.

The Eker renal tumor rat. Tumor transplantability and a re-evaluation of tumor histology.

Further histological findings for the naturally occurring kidney tumor of the Eker rat included the unusual location of the tumor entirely within the medulla rather than in the more usual site within the kidney cortex; the presence of psammoma bodies, and metastases of the tumor in one animal. The kidney tumors were shown to be transplantable with a latent period of about nine months. Histologically, the transplanted tumor, even at the twenty-eight transplant generation, maintained the cellular characteristics of the primary. The histological and transplant data allow the classification of the definitive tumor as a primary adenocarcinoma. The suitability of the tumor as an animal model for human renal carcinoma is suggested.

The effect of a protein-free diet, a sugar diet and of carbon tetrachloride administration on the toxicity and rate of metabolism of dimethylnitrosamine in different rat strains.

A Porton and a hooded rat strain showed a raised LD50 for dimethylnitrosamine (DMN) when pre-conditioned on a protein-free and/or a sugar diet. Little or no such differential toxicity between normal and diet-fed animals was found for rats of the Wistar, BDIX and CFY strains. Pre-treatment with CCl4 did not alter significantly the toxicity of DMN in the Wistar strain. All 5 rat strains treated by diet or CCl4 administration metabolized DMN at a very much slower rate than did the controls, the rates for the different strains being quantitatively similar. It is concluded that the toxicity of DMN is not necessarily related to its rate of metabolism and that the effect of diet or CCl4 treatment of DMN toxicity is dependent on the strain of rat used.

The effect of N-nitroso-N-methylurea and N-dimethylnitrosamine on cell mediated and humoral immune responses in rats and mice.

N-Nitroso-N-methylurea (NMU) induced a marked dose dependent leucopoenia which was associated with an increased survival of skin allografts in adult rats and in 2 strains of mice. The humoral immune response to NMU as assessed by haemolytic plaque formation and haemagglutination was also much reduced. Dimethylnitrosamine (DMN) which, like NMU is a powerful carcinogen and an alkylating agent, showed no immunosuppressive activity after a single dose in rats on either a normal diet or fed a protein-free diet which enhances kidney tumourigenesis. In mice DMN at a near LD(50) dose (14 mg/kg) had no effect on skin graft survival but did reduce the humoral response. At half this dose level, however, no immunosuppressive effect was seen. The results support the conclusion that the immunosuppressive activity of a chemical carcinogen is not necessarily associated with the expression of its carcinogenicity.

Studies on metabolism of vitamin A. The effect of vitamin A status on the secretion rates of some steroids into the ovarian venous blood of pregnant rats.

1. Rats raised on a vitamin A-deficient diet supplemented with either retinyl acetate or retinoic acid were mated and became pregnant. 2. The rates of secretion of progesterone, 20alpha-hydroxypregn-4-en-3-one, oestradiol-17beta and oestrone into the ovarian-venous blood of rats in these two groups were measured on days 9 and 15 of pregnancy. 3. Rates of secretion of progesterone and 20alpha-hydroxypregn-4-en-3-one, both on days 9 and 15, were lower for the rats given retinoic acid. No such differences were found in ovarian oestrogen secretion. 4. The implications of these results are discussed in the light of the previous demonstration that the activity of ovarian 3beta-hydroxy-Delta(5)-steroid dehydrogenase was markedly less in pregnant rats given retinoic acid.

Changes in the concentration of high-affinity oestradiol receptor in rat uterine supernatant preparations during the oestrous ycle, pseudopregnancy, pregnancy, maturation and after ovariectomy.

A quantitative method was used to determine the concentration of high-affinity oestradiol-receptor sites in rat uterine supernatant preparations under various physiological conditions. Cyclic changes in concentration were observed during the oestrous cycle, with a maximum occurring in late dioestrus. The changes followed a similar pattern in endometrium and myometrium, although concentrations were higher in the former. In pseudopregnancy the concentration was initially low, rising to a maximum on the tenth day. In early pregnancy a high concentration of receptor was found to be associated with the developing placenta, but this declined in later stages of pregnancy. After ovariectomy or combined ovariectomy and adrenalectomy the receptor concentration remained at a constant low value that could be increased by treatment with oestradiol. The receptor concentration was considerably higher in immature than in adult uteri.