Nonpregnant Rabbits Research Articles

The effect of pregnancy on experimental hypertension: With observations on the effects of deciduomas

To shed light on factors possibly concerned with the unfavorable influence of pregnancy upon human hypertension, rats and rabbits with experimental hypertension were studied during pregnancy or pseudopregnancy with deciduomas.Blood pressures were measured in rats by the tail plethysmograph and in rabbits by the ear capsule method. Hypertension was induced by partial ligation of renal arteries, or in some rats by painting one kidney with collodion and removing the opposite kidney later. Deciduomas were induced by placing silk threads in the uterine mucosa during pseudopregnancy.During pregnancy in normal rabbits, the changes in blood pressure as shown by these methods are negligible. Renal ischemia produced during pregnancy was followed by hypertension, but the onset was delayed until after delivery. Pregnancy produced an early fall in blood pressure in all of 10 hypertensive rats and a less constant fall in 12 hypertensive rabbits. No untoward effects were observed. An increase of protein content in the diet caused sickness or death in hypertensive nonpregnant rabbits. Pseudopregnancy with deciduomas in all of 11 hypertensive rats caused a decline in blood pressure corresponding roughly in time and extent with that caused by pregnancy.These findings suggest that the cause for the blood pressure fall observed more likely results from endocrine changes than from any action of fetal kidneys. Doubt is thrown on the concept that a “load on the maternal kidneys” plays a significant part in the exacerbation of hypertension usually observed in human pregnancy.

VALUE OF FRIEDMAN TEST IN DIAGNOSIS OF INTRA-UTERINE AND EXTRA-UTERINE PREGNANCY

In a review 1 of 4,595 Friedman tests performed by twenty-six different clinical pathologists, it was shown that 5.1 per cent of the tests were false negatives and 0.95 per cent were false positives. In ectopic pregnancy 77.8 per cent were correct positives and 22.2 per cent were incorrect negatives. The technic employed in this series consisted of the injection of 10 cc. of urine into one nonpregnant mature female rabbit followed by gross inspection of the ovaries forty-eight hours later. At Mount Sinai Hospital, 1,137 Friedman tests have been performed to date. The technic employed differs from that reported by others in that 20 cc. of freshly voided morning urine is used and the test is done in duplicate; i. e., two mature nonpregnant female rabbits are used for each case. Five cubic centimeters of urine is injected in the morning and afternoon on two successive clays and the ovaries are inspected grossly forty-eight hours after the first injection.

Observations on the living eggs of the rabbit

In the course of certain observations on the fertilisation of rabbit ova in vitro it soon became evident that, contrary to normal expectation, unfertilised ova will undergo varying degrees of development, much of the development being indistinguishable morphologically from the development of fertilised ova in vivo . It was decided, therefore, to undertake a comprehensive study of the history of tubal ova and of their behaviour in vitro . Advantage was taken of the fact that the rabbit ovulates regularly at about 10 hours after copulation ( e. g. , Heape, 1905; Hammond and Marshall, 1925; Walton and Hammond, 1928) to obtain ova of known age. Unfertilised ova were obtained by mating non-pregnant rabbit does to vasectomised bucks, and the eggs liberated from the ovary were recovered from the tubes by washing them out with sterile isotonic Pannett-Compton solution (Pannett and Compton, 1924). By this method eggs were obtained from the tubes from 11 to 72 hours after copulation. Between 72 and 96 hours after copulation the unfertilised ova enter the uterus and similar uterine washings were made to recover such eggs. Each doe used was mated to two or three vasectomised bucks. That these animals had been successfully operated upon and were incapable of ejaculating spermatozoa was already shown by the fact that no spermatozoa were found in smears taken from the vulva of the doe immediately after copulation and eggs obtained from these matings never showed the characteristic features, to be described later, of normally fertilised eggs. Some, moreover, showed no evidence of development in vivo . Ova fertilised in vivo and used for control experiments were similarly obtained, but from matings made to normal fertile bucks. To obtain the uterus and tubes the doe was killed and these organs removed with the ordinary precautions for attaining sterile conditions. In the few experiments in which ovarian ova were employed the eggs were obtained by pricking ripe follicles with a sterile needle and floating the emerging eggs into sterile Pannett-Compton solution.

What determines the duration of pregnancy

A.S. Hagedoorn and A. L. Hagedoorn (according to Ber. U. D. G. Gyn. Bd. XIV, H. 8) cite observations of rabbits and hares. It is known that pregnancy in rabbits lasts 4 weeks. Shortly before giving birth, the rabbit prepares a nest and displays her cubs in it; young rabbits are naked and blind. In hares, the duration of pregnancy is 8 weeks; hares are born larger than rabbits, sighted, covered with hair and can move freely. When a rabbit is mated with a hare, naked, blind rabbits similar to each other are born, in an adult state, the instinct of a rabbit is found in females (they prepare nests), and pregnancy lasts 4 weeks. When a hare is mated with a rabbit, pregnancy lasts 8 weeks, animals are born, similar to rabbits, but covered with wool, sighted, much larger and capable of movement. From these observations, the authors conclude that the duration of pregnancy and the term of delivery do not depend on the development of the fetus and not on its hormones, this, apparently, is the reaction of the maternal organism, which is determined by the genotype. This reaction, apparently, depends on the development of a special tissue or group of cells in the mother's body, since sometimes a non-pregnant rabbit, after mating, prepares a nest and covers it with wool.

On the Epinephrine in the Blood of the Suprarenal Vein and in the Suprarenal Extract from the Rabbit during Pregnancy

The cava pocket blood sample of rabbits was taken at various stages of pregnancy, and was tested against adrenalin chloride of the Sankyo Co. by means of the rabbit intestine strip method and the paradoxical eye reaction in parallel. From the suprarenals left behind in the cava pocket experiment the acid extract was prepared and also tested by both the biological methods and the colorimetrical method of Folin, Cannon and Denis. While the suprarenal vein blood of the non-pregnant rabbit involves a greater ability of dilating the denervated pupil than of inhibiting the rabbit intestine movement, the pregnancy alters the ability, and this becomes remarkable with the advancement of the same, the ratio of the value obtainable by the denervated pupil to that by the rabbit intestine being recorded as 1:1.5 in this stage on an average against the average of 2.2:1 for the non-pregnant rabbit. The ratio becomes reverse. In respect of the ratio of the values obtained by both biological methods, the suprarenal vein blood and the extract of the suprarenal gland left behind after the cava pocket experiment show a reciprocal relation; it is readily intelligible when it is taken into consideration that the over-seeretion of a substance can act to diminish its storage in the gland.