Search

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.

SUMMARY Extracts of jugular-vein blood of pregnant cows and of cows in oestrus were treated with methanolic HCl and phenolic fractions prepared. Assay by the mouse uterine-weight method failed to detect oestrogen in fractions from cows in oestrus or 2–3 months pregnant but indicated the presence of oestrogen, equivalent to about 1 μg. of oestrone/l. in blood from cows 5–6 months pregnant and about 7 μg./l. in blood from cows 7–9 months pregnant. The activity of the phenolic fraction from blood of late pregnancy was shown to be due mainly to oestrone, most of which had been present in the blood as a water-soluble derivative. Similar fractions from blood of cows in oestrus, assayed by the tetrazolium method of Martin, showed a total of 1–10 ng./l. (expressed as oestrone) activity being in the non-ketone and ketone fractions.

Oral, subcutaneous and intratracheal administration of carcinogenic lactones and related substances: the intratracheal administration of cigarette tar in the rat.

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.

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.

Images Fig. 1

SUMMARY Oestradiol-17β in ovarian venous blood and ovarian tissue was assayed by a competitive protein-binding method. Oestradiol was found in similar amounts in the ovarian vein blood of pregnant rats hypophysectomized on Day 12 and killed on Days 16 and 21 and in pregnant rats sham-hypophysectomized on Day 12 and killed on Day 16. The pituitary therefore plays no part in oestrogen production after mid-pregnancy until some time between Day 16 and Day 21, when it gives rise to an increased ovarian venous blood oestradiol content just before parturition, in intact sham-hypophysectomized rats. It is suggested that this increase is associated with the advent of the post-partum ovulation. The corpus luteum and the extraluteal component of the ovary in hypophysectomized rats autopsied on Days 16 and 21 and in sham-hypophysectomized rats autopsied on Day 16, contain similar amounts of oestradiol within each group. The extraluteal component contains about five times more oestradiol than corpora lutea in sham-hypophysectomized intact rats autopsied on Day 21. The ovaries of these animals also show an increased amount of oestradiol over that of the ovaries in the other three groups. It is suggested that secretion of oestradiol after mid-pregnancy in rats involves concurrently both the corpus luteum and the extraluteal component of the ovary.

Summary. The secretion rates of oestradiol-17\g=b\ and oestrone into the ovarian venous blood of rats on the day of pro-oestrus and on nine different occasions in pregnancy have been measured by collection of blood samples and assay of extracts by the intravaginal, tetrazolium\x=req-\ reduction method in mice. Secretion rate of oestradiol-17\g=b\at pro-oestrus and 1 to 2 days before parturition was about 3 ng/ovary/hr but was much lower at other times in pregnancy. There was a significant rise in oestradiol-17\g=b\secretion rate from the 3rd to the 4th day post coitum (81 to 500 pg/ovary/hr). Secretion rates of oestrone were always less than 300 pg/ovary/hr and did not show marked rises at pro-oestrus and before parturition. The physiological significance of the changes in ovarian oestrogen secretion rate is discussed.

SUMMARY Free and total acid phosphatase activity has been measured in individual corpora lutea from rat ovaries in various reproductive states (both natural and experimentally induced). Significant changes both in weight and enzymic activity were found, and an attempt has been made to correlate these with the growth and regression of the corpora lutea. A possible connexion between acid phosphatase activity, progesterone secretion and/or cellular composition of the corpus luteum is suggested.

An apparatus easily manufactured in the laboratory is described for the continuous infusion of substances into the stomach of the unanaesthetised rat.

SUMMARY A simple and rapid technique for intravenous IllJection into the sublingual veins of common laboratory rodents is described. No prior preparation other than light anaesthesia is required and repeated injections can be made into the same vein. 35 The major problem associated with intravenous administration in common laboratory rodents is the inaccessibility of the veins. In most instances, either a considerable degree of skill has to be acquired, as for tail-vein injection, or time-consuming preparative procedures such as shaving the hair from the injection area, or actual surgery, must be carried out before the veins can be entered. Even when accessibility is little in question as with the penile vein and, to the skilled, the tail vein, these vessels are not universally present in all rodents. It is somewhat surprising that the sublingual veins, with their ease of accessibility, have been almost completely overlooked in the literature on rodent injection techniques. Green & Wade (1967) have described a method for the rat, but they use a procedure for anchoring the to~gue by the insertion of a thread through its tip which, it would seem, is both relatively timeconsuming and unnecessary. The two sublingual veins are to be found one on each lateral aspect of the ventqil surface of the tongue. They are extremely superficial and can be entered quickly and easily. Haematoma formation is rarely seen and the veins can be used repeatedly over a number of days. METHOD The animal is anaesthetised with ether and placed in dorsal recumbence with its head towards the operator. A gauze pad is placed over its nose and anaesthesia is continued by drop application of ether. The tongue is pulled out with forceps and held on the antero-lateral surface of the index finger

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.

Fifty recent clinical isolates of the B.fragilis group were tested to determine their susceptibility to ampicillin, carbenicillin, mezlocillin, azlocillin and piperacillin using an agar dilution technique. The influence of clavulanic acid on the penicillin susceptibility of these strains was determined by incorporating 2 mg/1 of clavulanic acid into test media. The production of beta-lactamase by the strains was determined by the nitrocefin test and their isoelectric points by focusing on Polyacrylamide gel. Piperacillin was generally the most active of the penicillins tested and carbenicillin the least active with MIC50 values of 8 and 32 respectively. Although mezlocillin was slightly more active than piperacillin against highly resistant strains (MIC 64 mg/1 ampicillin) it was less active against strains with moderate resistance (16–32 mg/1 ampicillin). The majority of resistant strains became at least fivefold more susceptible to ampicillin and carbenicillin in the presence of clavulanic acid, while this effect was less marked for the acylureidopenicillins. In 18% of strains the susceptibility to all five penicillins tested was virtually unaffected by the presence of clavulanic acid.

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.

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.

An increase in luteal volume was seen between Day 11 and 16 of pregnancy in the rat. In particular, a high rate of growth of the corpus luteum was found between the 11th and 12th day and it is suggested that this may be due to a »surge« of placental LTH at this time. A marked reduction in luteal volume, concomitant with an early return to oestrus, was observed after caesarian section on Day 12 of pregnancy. The maternal placenta, surgically separated from the foetal placenta, was unable to maintain either the dioestrous period of pregnancy or the growth of the corpus luteum. Neither decidualisation nor hysterectomy had any effect on luteal volume.

SUMMARY 1. The effectiveness of miroestrol in causing cornification of the vagina of the ovariectomized rat, inhibiting pituitary activity of the adult male rat and preventing pregnancy in the mated female rat has been compared with that of hexoestrol and stilboestrol when each oestrogen is administered either subcutaneously or orally. 2. Inhibition of pituitary function and prevention of pregnancy by these substances are directly related to their activity in producing cornification of the vaginal epithelium. Only large doses of oestrogen produce the first two responses fully. 3. When administered subcutaneously miroestrol has about 0·3 of the potency of stilboestrol and 0·25 of that of hexoestrol in each response studied. By oral administration it is 0·8 as potent as stilboestrol and more potent than hexoestrol. Since the potency of miroestrol compared with a given oestrogen administered in the same way is of the same order in each response, it is concluded that these substances are only capable of inhibiting the function of the pituitary and of preventing pregnancy because of their oestrogenic activity.

Rats hypophysectomised on Day 8 of pregnancy showed no growth or involution of the corpus luteum four days later but there was a significant increase in the total and free acid phosphatase activities. Hypophysectomy on Day 12 did not affect the expected changes in luteal weight and acid phosphatase activity but did increase the volume of the corpus luteum on Day 16 compared to intact pregnant rats. Concurrently performed hypophysectomy and Caesarian section caused a greater rate of luteal regression and a greater increase in acid phosphatase activity than did Caesarian section alone. Although involution of the corpus luteum was progressively advanced by 32 days after the initiation of gestation in rats hypophysectomised or hypophysectomised plus Caesarian sectioned on Day 8 and 12 respectively, there was no proportional increase in the acid phosphatase activity. The role of acid phosphatase in the structural regression of the rat corpus luteum is considered to be minimal.