Nonpregnant Rabbits Research Articles

Some Requirements for Mating in the Rabbit Flea, Spilopsyllus Cuniculi (Dale)

ABSTRACT Rabbit fleas Spilopsyllus cuniculi (Dale) do not mate while on adult rabbits; copulation is usually initiated when the fleas are on the body of a new-born rabbit and at least the close proximity of such a nestling is essential. The female probably becomes receptive only after close contact, but not necessarily probing contact, with a young nestling. Fleas with mature ovaries mate much more readily than immature fleas. Male fleas must be in a suitable ‘physiological state’ before they can mate and inseminate females. This state is reached by probing contact with rabbits in the final stages of pregnancy or, for a relatively shorter period, with new-born rabbits. Spermatozoa of such fleas show much greater mobility within the genital ducts than those from fleas kept on male or non-pregnant rabbits.

Serum "Angiotensinase activity" and female steroidal hormones.

Angiotensinase activity was measured in the third trimester of normal pregnancy (15) and preeclampsia (6) in women taking taking contraceptive pills (Oracon) (21) in males who also took these pills (3) and in serum and uterine tissue from pregnant and nonpregnant rabbits serving as controls. The findings of decreased angiotensin II amide survival and increased alpha-L-aspartyl-beta-naphthylamide hydrolysis in women during the third trimester of normal pregnancy suggests a possible relationship between serum angiotensinase activity and female steroidal hormones. Confirmatory evidence was provided by similar results with the latter substrate in women receiving contraceptive pills. Synthetic estrogen but not progestogen induced increased serum naphthylamidase activity in male volunteers. Starch gel electrophoresis was similar in normal women pregnant women and women on contraceptives in the patterns of proteins and this enzyme activity. Electrophoretic studies of enzyme activity in serum and uterine tissue extracts were not demonstrated in the electrophoresis studies and increased enzyme activity in human subjects could not be correlated with plasma renin activity blood pressure or liver cell damage it seems likely that the increased aspartic naphthylamidase hydrolysis is part of a nonspecific naphthylamidase increase induced by estrogens.(Authors modified)

Studies in the regulation of uterine activity.

IN 1956, Csapo put forward the theory of the local action of placental progesterone in an attempt to explain the separate delivery of human twins, several weeks apart. This theory, which holds that progesterone from the placenta can reach the overlying myometrium by a direct route and produce a functional asymmetry ofthe uterus, has been criticised (Short, 1960) on the ground that such progesterone would be absorbed by the maternal blood stream, and distributed uniformly to the myometrium, thus precluding an asymmetric effect. In order to determine whether progesterone absorbed from an intrauterine site is distributed asymmetrically, we chose the bicornuate uterus as an experimental model, since one horn could be used as a control for the other in the same animal. Finger-cot balloons were inserted into each uterine horn of ovariectomized non-pregnant rabbits. A perforated catheter accompanied each balloon, permitting the introduction of progesterone into the uterine lumen. After the animals had recovered from surgery, the balloons in each horn were filled to an equal volume with water. This volume varied among the rabbits between 2 and 10 ml depending upon the size of the uterus. In each case a final volume was selected which produced a high activity with a resting pressure of not more than 10 mmHg. Progesterone in sesame oil was injected into the lumen of the experimental horn, and sesame oil alone into the control horn. Intra-uterine pressure was monitored before, during and after progesterone treatment. Although both horns underwent a loss of active intra-uterine pressure, the loss was significantly greater (P<0025) and recoverv significantly prolonged, in the horns treated with progesterone. When the technique was applied to pregnant animals, it was possible to induce unilateral deliveries (Porter, 1968). In four rabbits thus treated, the control horns delivered a total of twelve out of fourteen foetuses before the first foetus was delivered from the treated horns. These results can best be explained on the basis that some progesterone reached the myometrium of the treated horn by a direct route, not involving the systemic circulation, and in sufficient quantity to produce a significant difference in the mechanical activity of the two horns. The anatomical basis of this direct route is not known. These results support the feasibility of the 'local placental progesterone' hypothesis since if progesterone from an oil droplet in the uterine lumen can pass through the endometrium to the uterine muscle, it would be expected that steroids secreted by the placenta, which is more intimately related to the myometrium, would also pass directly. Zarrow, Anderson & Callantine (1963) and Schofield (1964) have reported failure to prolong pregnancy in the guinea-pig with systemically administered progestogens. In view of the 'local' theory of placental progesterone, and the fact that the placenta of the guinea-pig is known to secrete progesterone (Heap & Deanesly, 1966), local application of progesterone, or medroxyprogesterone acetate (Depo-Provera, Upjohn) to the uterus of the pregnant guinea-pig, might be expected to prolong pregnancy, where intra-muscular injections failed. Accordingly, pregnant guinea-pigs were given single intra-amniotic injections of large doses of progesterone or medroxyprogesterone acetate (MAP), some 5 or 6 days before term. The results are shown in Table 1.

On the mechanism of action of intra-amniotic hypertonic saline treatment in rabbits.

Summary. A study was made into the effects of hypertonic saline upon the intra-uterine pressure in non-pregnant and pregnant rabbits. In non-pregnant rabbits intra-luminal administration of hypertonic saline caused an almost immediate transient increase in amplitude and frequency of uterine pressure cycles, a response which was abolished by prior treatment with progesterone. In pregnant rabbits, provided all placentae were damaged by the treatment, intra-amniotic administration of 20% NaCl resulted in abortion of all foetuses in 56 ± 7·3 hr SE. If one conceptus escaped damage pregnancy was not interrupted. Furthermore, treatment with 25 μg/day oestradiol propionate prevented abortion. Of the procedures carried out, only dislocation of the placentae also caused abortion, whereas pregnancy was not terminated by extra-amniotic administration of hypertonic saline, by cutting the umbilical cords (i.e. causing foetal death), nor by the intra-amniotic administration of normal (0·9%) saline. The abortion produced by both intra-amniotic hypertonic saline and dislocation of the placentae could be prevented by oestrogen administration, but not if ovariectomy were combined with placental dislocation. From these results, it is concluded that intra-amniotic hypertonic saline induced abortion in rabbits by interrupting the luteotrophic function of the placenta which resulted in loss of the luteal function essential for the defence of pregnancy.

THE LOCAL EFFECT OF INTRA-UTERINE PROGESTERONE TREATMENT ON MYOMETRIAL ACTIVITY IN RABBITS

Summary. The instillation of progesterone into the lumen of one uterine horn of unanaesthetized non-pregnant rabbits caused a more profound loss of intra-uterine pressure in the treated than in the placeboinjected control horn. The recovery of active pressure by the treated horn was significantly slower than by the control. The magnitude of the effect of progesterone, but not the rate of onset, was dose dependent. When progesterone was administered to one uterine horn of pregnant rabbits, asymmetrical delivery ensued, in which the control horns invariably expelled most of their foetuses before the treated horns commenced delivery. Autoradiographic study indicated that progesterone is very rapidly absorbed from the uterine lumen. The implication of these findings is discussed in relation to previous work.

Changes in lipids (especially phospholipids) and lipoprotein lipase activity in nonpregnant rabbit ovaries under the influence of human chorionic gonadotrophin

成熟非妊家兎を用い, HCGを投与して間質腺細胞の脂質の変動を調べ, ステロイド分泌との関連を見た.定量では燐脂質は増加し, コレステロールは減少した.又32Pのとりこみはマイクロゾームに著しかつた.脂肪酸もincorporationが促進した.卵巣燐脂質構成脂酸中アラキドン酸が減少し, 血漿NEFA中でも著減した.考案した1ipase活性測定法により, 卵巣リパーゼ活性の上昇を認めた.HCG投与後脂質変動は活発で, リパーゼとも関係が深くsteroidgenesisに密接に関連している事を論じた.

Rabbit uterus as a source of renin.

Rabbit uterus as a source of renin.

The activity of post-ganglionic sympathetic nerves to the uterus of the rabbit.

1. The spontaneous activity recorded from the central ends of the uterine nerves of the rabbit is described. The discharges resembled those reported from other post-ganglionic sympathetic nerves; the individual units appeared to discharge remarkably regularly at frequencies between 4/sec and 1 per 3 sec.2. The resting discharge in late pregnant rabbits was usually more intense than in non-pregnant rabbits; otherwise no clear relation existed between variations in the discharges and in the sexual state.3. The discharge was reduced by stimulation of the central end of the depressor nerve and increased by asphyxia.4. Stimulation of either the preganglionic or the post-ganglionic nerve by a single shock evoked a long after-discharge in the post-ganglionic nerve. It is shown that this after-discharge is a property of some of the post-ganglionic neurones supplying the rabbit's uterus which does not depend on the integrity of the preganglionic nerves or of the spinal cord, or on transmission through the ganglia, and that it is not a general property of the sympathetic post-ganglionic neurones of the rabbit.5. Repetitive stimulation of the preganglionic nerve at low frequencies augmented the after-discharge in some cases and depressed it in others; stimulation at high frequencies invariably depressed the after-discharge. Repetitive stimulation of the post-ganglionic nerve at low or high frequencies depressed the after-discharge.6. If the normal preganglionic activity was interrupted abruptly by an anode block, the post-ganglionic discharge also stopped abruptly.7. A ganglion-stimulating action of hexamethonium is described.8. Adrenaline inhibited the post-ganglionic neurones with no sign of excitation. This effect was antagonized by Rogitine without affecting the resting discharge, the action of the depressor nerve or the after-discharge in any way.

Some observations on the behaviour of hypothalamic enzymes during the time of blastocyst implantation in the rabbit.

1. Hypothalami from pregnant and non-pregnant rabbits were homogenized in sucrose and separated into fractions by differential and density-gradient centrifugation. 2. The fractions were examined for enzymes capable of inactivating oxytocin. 3. Enzyme activity was detected in the supernatant and one particulate fraction of both pregnant and non-pregnant animals. 4. The specific activity of the enzymes increased during early pregnancy, and coincided with the time of blastocyst spacing and implantation in the uterus.

Fetal and maternal temperatures in rabbits.

The differences between fetal deep body temperature and maternal aortic temperature were measured in 10 New Zealand white rabbits of 22—29 days gestation with thermocouples thrust into the fetuses immediately after the animals had been killed by a warmed overdose of sodium pentobarbital. Fetal temperatures exceeded maternal temperatures by —2.51 + 0.099.X °C, where X is the gestational age in days. There is 95% confidence that fetal temperatures exceeded maternal temperature by at least 0.25 °C at a fetal age of 29 days. Permanently implanted thermocouples in six nonpregnant rabbits showed that the ventral surface of the abdominal cavity is colder than the aorta, and that the dorsal surface is slightly warmer. Fetal heat loss is partly via the umbilical circulation and partly via the fetal body surface. tissue temperatures in rabbits; fetal heat loss Submitted on September 28, 1964

The Reproductive Biology of the Rabbit Flea Spilopsyllus Cuniculi (Dale) and the Dependence of this Species Upon the Breeding of Its Host

ABSTRACT Unlike any other species of flea which has been cultured successfully Spilopsyllus cuniculi (Dale) is entirely dependent for its own reproduction upon its host becoming pregnant. The ovaries of fleas kept on male or non-pregnant female rabbits remain immature whereas those on a pregnant host are mature at the time of parturition. Vitellogenesis commences at a critical point approximately 7 days pre-partum, irrespective of how long the fleas have been on the host. It is postulated that a factor required by the flea for ovarian development is only available during the final week of pregnancy, and not at all in male or non-pregnant rabbits. The factor disappears from the adult after parturition but is present in her nestlings for at least 7 days. Most fleas desert the adult doe shortly after the young are born and enter her nest, where copulation and oviposition occur. The factor does not act solely as a trigger initiating in the flea developmental processes which then continue in its absence; ovarian regression occurs among maturing fleas transferred to hosts that do not supply the factor. The processes of vitellogenesis, not those of oogenesis, fail in the absence of the factor. It is suggested that the ‘yolk-forming hormone’ normally secreted by the corpus allatum of the adult insect may only be produced by rabbit fleas when they can obtain the postulated factor. Variations in the quantity of this factor available to fleas on different hosts could explain the observed variations in ovarian activity. Some parallels between the factor and steroid hormone levels in the host’s blood are discussed.

THE ACTIVATION OF VARIOUS TYPES OF UTERINE MUSCLE DURING STRETCH-INDUCED CONTRACTION

The electrical and mechanical activity of uterine strips from human beings, cats, rats, and rabbits was studied using glass pore surface electrodes and isometric recording of tension. Uterine strips from animals treated with estrogen, or with estrogen and progesterone, were compared with those from pregnant animals. Marked differences in both electrical and mechanical activity were found among the various strips studied. Strips from estrogen or pregnant cats were activated primarily by propagated "ail-or-none" action potentials. Propagated action potentials were recorded from rat uterine strips of all types, but they originated from several sites during the same burst, and did not spread over the entire uterus or even a few millimeters in some strips. Mechanical strain appeared to play a role in activation in rat uterus. In strips from uteri of nonpregnant rabbits, action potentials were small, and propagation was slow and limited in extent. Action potential conduction played a minor role in activation in these tissues. Uterine strips from pregnant rabbits resembled those from cats and rats. Action potentials similar to those of animal uteri were recorded from strips of pregnant human uterus. Progesterone pretreatment and pregnancy increased the number of action potentials and duration of contraction. Progesterone pretreatment reduced the sensitivity of cat uterus to stretch. The effect of reduction of external sodium concentration on propagation of uterine action potentials was studied. The results are discussed in relation to the mechanisms underlying electrical activity and to the question of whether electrical activity is a determinant of mechanical activity in the uterus.

Further Studies on Growth-promoting Factor of Exudates.

SummaryThere is present in inflammatory exudates a diffusible growth-promoting factor which can be purified further from concentrated diffusate by precipitation at pH 4.5 with N acetic acid. Repeated injections of the fraction in its present state of purification induce in non-pregnant rabbits conspicuous hyperplasia of epithelial structures as well as a condition in breast tissue simulating that seen in chronic cystic mastitis. A state of irreversibility is established upon termination of a prolonged course of injections of growth-promoting factor of exudates. The enlarged nipples fail to regress in size, though administration of the active material is discontinued. By enzymatic inactivation, evidence is advanced that both nucleotide and peptide structures appear to play a role in biological activity of the growth-promoting factor of exudates.

THE ACTIVATION OF VARIOUS TYPES OF UTERINE MUSCLE DURING STRETCH-INDUCED CONTRACTION

The electrical and mechanical activity of uterine strips from human beings, cats, rats, and rabbits was studied using glass pore surface electrodes and isometric recording of tension. Uterine strips from animals treated with estrogen, or with estrogen and progesterone, were compared with those from pregnant animals. Marked differences in both electrical and mechanical activity were found among the various strips studied. Strips from estrogen or pregnant cats were activated primarily by propagated "ail-or-none" action potentials. Propagated action potentials were recorded from rat uterine strips of all types, but they originated from several sites during the same burst, and did not spread over the entire uterus or even a few millimeters in some strips. Mechanical strain appeared to play a role in activation in rat uterus. In strips from uteri of nonpregnant rabbits, action potentials were small, and propagation was slow and limited in extent. Action potential conduction played a minor role in activation in these tissues. Uterine strips from pregnant rabbits resembled those from cats and rats. Action potentials similar to those of animal uteri were recorded from strips of pregnant human uterus. Progesterone pretreatment and pregnancy increased the number of action potentials and duration of contraction. Progesterone pretreatment reduced the sensitivity of cat uterus to stretch. The effect of reduction of external sodium concentration on propagation of uterine action potentials was studied. The results are discussed in relation to the mechanisms underlying electrical activity and to the question of whether electrical activity is a determinant of mechanical activity in the uterus.

The endocrine control of myometrial contractility in the uterus of the pregnant rabbit

The present experiments clarify the following points:1. Provided that extreme care is taken to maintain light anesthesia, undisturbed breathing, constant body temperature, and constant temperature around the uterine segment from which recording is made, furthermore, if the tension is recorded isometrically, there is no significant difference between in vitro and in vivo findings. This suggests that the reactivity of the myometrium is determined by the endocrine state of the animal and that other mechanisms working in the body are of lesser importance.2. That the method here employed is satisfactory has been established in several different ways:a. Between the steps of an experiment in which electrical stimulation was employed, it was always possible to observe the same pattern of spontaneous activity as found at the beginning of the experiment.b. All animals in the same group exhibited the same pattern of uterine behavior, and even the quantitative differences from one animal to another in the same group were slight. Among all the tests employed in these studies, spontaneous activity showed the greatest and the staircase the smallest variation.c. When the patterns of behavior of the two horns of the uterus of one animal were compared, the similarity between the two records obtained was very close.d. When tension was recorded continuously for a period of 5 hours in an estrogen-treated nonpregnant rabbit, the uterus being stimulated electrically with optimum stimulus once every 4 minutes, tension remained unchanged. This, we believe, is one of the most convincing tests of the reliability of the technique and the unchanged condition of the animal during the experiment.3. These experiments demonstrate that until the twenty-ninth day of pregnancy progesterone dominates the myometrium. The effect of progesterone begins to decline only on the twenty-ninth day, its withdrawal being completed on the thirty-second day, the day on which labor occurs.4. A few hours before delivery, on the thirty-second day, the myometrium is clearly estrogen dominated. Its excitability is optimal. Its conductivity appears to be restored, its intrinsic stimulatory system is highly efficient, and development of spontaneous tension is at its best. Working capacity is maximal. It appears, therefore, that all conditions are optimal as required for maximum function, and the uterus is ready to perform its main physiological function, i.e., the delivery of the conceptuses.5. Shortly after delivery estrogen domination approaches an extreme condition so far as excitability of the myometrium is concerned, whereas working capacity begins to decline, and 48 hours after delivery it is similar to the value which can be obtained in the nonpregnant estrogen-dominated animal.It is to be hoped that the findings and methods reported in this paper will be useful in devising means by which studies on the human myometrium can be carried out in order to establish changes in endocrine domination in women during normal and abnormal pregnancies.

Carbonic anhydrase in the female reproductive tract; occurrence, distribution and hormonal dependence.

SUMMARY Carbonic anhydrase was shown to occur in the female reproductive tract of a variety of mammalian species. The uterine endometrium, placental tissue and the Fallopian tubes were established as the main loci of carbonic anhydrase activity. The enzyme was present in the endometrium of the non-pregnant rabbit in a low concentration. Following mating no perceptible increase in enzyme content occurred before the 4th day; from then onwards the activity continued to rise, reaching a maximum by about the 8th day; with advancing foetal development the endometrial activity declined, but at the same time the enzyme could be demonstrated in the placenta, chiefly in the maternal, but to a small extent also in the foetal, part. The behaviour of carbonic anhydrase in the pseudopregnant uterus or in response to ovulating doses of gonadotrophin or copper salts, presented essentially the same picture as in the early phase of pregnancy; excessive doses of gonadotrophin were capable of increasing the enzyme content within 2 days of administration; moreover, their effect persisted for 20–24 days. Progesterone, and to a smaller extent ethisterone and methyltestosterone, injected into oestrous adult or into oestrogen-primed immature rabbits, produced marked increases in the content of uterine carbonic anhydrase, the extent of which depended upon the dose. Whereas the endometrium of rats, hamsters and guinea-pigs was completely devoid of carbonic anhydrase, both in pregnant and non-pregnant females, the placenta of these animals contained the enzyme, again mainly in the maternal portion. The uterine mucosa of the non-pregnant sheep was conspicuously rich in carbonic anhydrase, the activity being largely restricted to the intercotyledonary areas; the uterine portion of the Fallopian tubes was also remarkably active. In this species the uterine carbonic anhydrase was found to be independent of ovarian function: the enzyme was present in the uteri of prepubertal lambs, and it was fully preserved in ovariectomized animals. Considerable enzymic activity was found in the sheep placenta. No carbonic anhydrase was found in the uterus or Fallopian tubes of the non-pregnant pig; the pig placenta, however, was very active, the enzyme being located in the chorion in late pregnancy. In the non-pregnant cow only the fimbrial portion of the Fallopian tubes showed enzymic activity, especially marked in the immediate post-ovulatory phase. No carbonic anhydrase was present in the non-pregnant uteri or Fallopian tubes of mares, cats or dogs. By introducing parenterally large amounts of a sulphonamide inhibitor of carbonic anhydrase it was possible to inhibit the enzyme in vivo, both in the rat placenta and in the progestational rabbit endometrium.

HUMAN SKIN PERMEABILITY IN PREGNANCY AND MENSTRUATION

In a previous paper by the present author (1952) it was shown that rabbits towards the end of their pregnancy exhibit a smaller dermal spread and a more rapid dermal absorption (i.e., disappearance of an indicator) than non-pregnant rabbits. The indicators used were a hemoglobin solution for the spreading determinations and a uranin solution for the absorption tests. Similar results were obtained when hyaluronidase was added to the indicator solutions. The fact that an inhibited spread was found also in recently killed pregnant rabbits was considered to indicate a change in the connective tissue proper and not only with regard to the circulation. In a discussion of the findings, attention was drawn to the hormonal regulatory mechanism of the mesenchymal tissue. It was further stated that probably the most important factors influencing the permeability of the connective tissue during pregnancy are the effects of oestrogens, hydration, and stress, and their

ON THE CONTRACTION OF THE VAGINA OF NON-PREGNANT RABBIT

On the phasic contraction of the uterus of the nonpregnant rabbit already reported many authors. But as for the contraction of the vagina, little is known.It is reasonably assumed, when ve consider the anatomical relation of the uterus and vagina and their mechanism, that some similar movement must occur to the vagina as to the uterus. Therefore the author intended to inquire into the contraction, if any, and to compare it with that of uterus.A balloon of proper size made of thin elastic rubber was put deep into the vagina from the introitus vaginae or the canal on the abdominal wall specially prepared for the purpose. If the balloon is expanded previously with adequate pressure, the change of its volume due to contraction of the vagina is recorded by means of the optical lever on the bromide paper.The contraction curve shows in most cases relatively regular phasic contraction, having one or one and half cycle per minute. But in some cases after 7-15 days experiments (one or two hours a day), groups of several contractions appeared, and between the e were observed only small or no contraction. These groups occurred roughly once in 5-10 minutes. This state of contraction is similar to that of uterus, which is observed on the rabbit administered with follicular hormone.From those results, it is concluded that the vagina of a non-pregnant rabbit has phasic contraction, which varies according to conditions.

Tannin und Adrenalin

Tannic acid in concentrations which of themselves have no action potentiates and prolongs the action of adrenaline on the isolated rabbit intestine (inhibitory effect) and on the isolated non-pregnant rabbit uterus (excitatory effect). The adrenaline-pressor effect in the decapitated cat and, in the same species, its stimulant action on the nictitating membrane (either denervated or normal) may also be potentiated by tannic acid. Since the oxidation of adrenalinein vitro is inhibited by tannic acid, it seems that this—in addition to a possible increase of permeability—is mainly responsible for the potentiation of adrenaline.

TOXICITY OF SALINE UTERINE EXTRACTS FROM RABBITS DURING PREGNANCY, PSEUDOPREGNANCY AND AFTER CORPUS LUTEUM HORMONE ADMINISTRATION1

IN PREVIOUS COMMUNICATIONS (1, 2, 3) it was reported that saline extracts of rabbit I uteri from animals immediately post partum contain a histamine-like substance i L which is fatally toxic when injected intravenously into males or females of the same species. Similar extracts prepared from liver, muscle or uteri from nonpregnant animals and administered in the same way were not toxic. It was further reported (4) that saline uterine extracts from estrogen-treated nonpregnant rabbits also con-tain this factor. The present report concerns further investigations on the presence of this toxic substance in the uteri of rabbits during pregnancy, pseudopregnancy and after corpus luteum hormone administration. A total of 108 rabbits were used in this study; 48 young adult females providing uteri for extraction and 60 animals weighing between 2.5 and 4.0 kg., including both sexes, serving as test animals.