Nongravid Uterine Horns Research Articles

Factors influencing circular muscle activity in the pregnant rat uterus.

Near the end of pregnancy the circular muscle of the rat uterus exhibits characteristic changes that are apparently prerequisite for normal delivery. This study concerns the effects on the circular muscle of some intrinsic factors believed to regulate the myometrium during pregnancy, namely, uterine volume (stretch), the ovarian steroids, and the fetoplacental unit. We compared the activity of circular muscle isolated from 1) gravid and nongravid uterine horns of unilaterally pregnant rats, 2) normal and dislocated horns of unilaterally placental-dislocated rats, 3) ovariectomized rats, and 4) normal pregnant rats. Microelectrode and tension recordings were made on the circular muscle segments obtained from these groups of animals at the end of gestation and during parturition. The results show that uterine volume and circulating estrogens are more important than the fetoplacental unit in the evolution of circular muscle activity in the pregnant rat.

Oxytocin receptors and parturition. II. Concentrations of receptors for oxytocin and estrogen in the gravid and nongravid uterus at term.

It has been postulated that intrauterine volume plays a role in the timing of parturition. In previous studies we found that the onset of parturition in the rat was associated with marked increases in the concentrations of receptors for estrogen and oxytocin in the myometrium. To determine the effects of intrauterine volume on the concentrations of these myometrial receptors, we compared receptor levels in gravid and nongravid uterine horns from unilaterally pregnant rats at or near the time of parturition. Myometria from gravid horns contained substantially greater concentrations of DNA and protein per horn than did myometria from the contralateral nongravid horns. The amounts of receptors per horn for estrogen in the nuclear and cytosol fractions and for oxytocin were 7.5, 5.2, and 4.5 times greater, respectively, in myometria from gravid horns. However, the concentration of receptors per cell was the same in gravid and nongravid horns at or near parturition. These results suggest that uterine stretch causes hyperplasia and hypertrophy of the myometrium, indicative of more DNA and protein per gravid horn than nongravid horn. The sharp rise in concentration per cell of receptors for estrogen and oxytocin occurring about the time of labor, however, appears to be induced by hormonal and not physical factors.

Method for obtaining ovine uterine secretions from unilaterally pregnant ewes.

Development of the ovine conceptus was confined to the uterine horn ipsilateral to the corpus luteum (CL) by placing a ligature around that uterine horn at a point near the uterine body on day 5 of pregnancy. On day 140 of gestation, seven of 10 ewes were still pregnant and from 21 to 815 ml of uterine fluid (488 +/- 94 ml, X +/- SEM) were collected from the nongravid uterine horn. Total recoverable protein (X +/- SEM) was 13.4 +/- 3.4 grams. Polyacrylamide gel electrophoresis of the reduced proteins in presence of sodium dodecyl sulfate indicated that protein composition of uterine fluid was distinct from that of colostrum, serum, amniotic fluid, and allantoic fluid, and revealed the presence of two major polypeptides with molecular weights of about 57,000 and 58,500, respectively, plus numerous other minor components. Gel filtration on columns of Sephadex G-200 and Sepharose CL-6B suggested that these polypeptides formed a series of aggregates of high molecular weight when kept under nonreducing conditions. Glucose (.18 +/- .03 mg/ml), but not fructose, was present in uterine fluid. In addition, high levels of prostaglandin F (451.4 +/- 83.3 ng/ml) were present.

Blood flow to uteri of sows during the estrous cycle and early pregnancy: local effect of the conceptus on the uterine blood supply.

Uterine blood flow (UBF) of 6 sows was monitored throughout an estrous cycle and the first 30 days of pregnancy using electromagnetic blood flow probes. Probes were placed around both uterine arteries of each sow on Day 12, 13 or 14 of the estrous cycle (first day of estrus = Day 0). The UBF (ml/min) was recorded twice daily for 15 min at 0700 and 1600 h. Values were averaged over both 15 min periods on each day for each artery and considered an estimate of UBF. Blood flow to uteri of nonpregnant sows was highest from Day −5 to estrus and this was followed by a gradual decline during the remainder of the estrous cycle. The pattern of blood flow to uteri of the sows during early pregnancy was similar to that observed during the previous estrous cycle until Day 11 after mating. On Days 12 and 13 of pregnancy, UBF increased (P<0.0l) 3-fold to 4-fold. No corresponding increase in UBF was observed in nonpregnant sows during this 2 day period. By Day 14 of pregnancy, UBF had returned to a level slightly higher than that observed on Day 11, remained relatively constant from Day 14 to 19, then increased (P<0.01) dramatically to Day 30. a second study was conducted using 7 sows made unilaterally pregnant on day 2 postmating (first day of mating = day 0). fertilized ova were flushed from one oviduct and the ipsilateral uterine horn was ligated at the uterine body with silk sutures (nongravid horn). blood flow probes were placed around both uterine arteries and ubf was recorded twice daily. sows were slaughtered on day 16 postmating. five of the 7 sows had embryos and/or embryonic tissue in the nonligated uterine horn (gravid horn) at slaughter. sows in which embryonic tissue was found had higher (p<0.05) blood flow to the gravid compared with the nongravid uterine horn on days 12 and 13 of pregnancy. corpora lutea on the ovary ipsilateral to a gravid uterine horn had higher (p<0.05) progesterone concentrations (±sem) than did corpora lutea on the contralateral ovary (5.45 ± 1.69 vs 2.07 ± 0.49 µg/g luteal tissue).

Uterine blood flow of cows during the oestrous cycle and early pregnancy: effect of the conceptus on the uterine blood supply.

Blood flow to each uterine horn of cows during the oestrous cycle and early pregnancy was determined daily by use of electromagnetic blood flow probes placed around both middle uterine arteries. The pattern of blood flow to uteri of pregnant and non-pregnant cows was similar until Day 14 after mating or oestrus. Between Days 14 and 18 of pregnancy blood flow to the uterine horn containing the conceptus increased (P less than 0.01) 2- to 3-fold, whereas blood flow to the non-gravid uterine horn in these cows remained constant. No corresponding increase in blood flow to the uterine horn ipsilateral to the ovary bearing the CL was observed in non-pregnant cows during this 4-day period. By Day 19 of pregnancy, blood flow to the gravid uterine horn had returned to a level similar to that observed on Day 13. Blood flow to both uterine horns of pregnant cows remained constant from Days 19 to 25 and then increased to the gravid horn (P less than 0.01) markedly until Day 30 whereas blood flow to the non-gravid horn remained low. Uterine blood flow during the oestrous cycle of non-pregnant cows was positively correlated (P less than 0.01) with systemic concentrations of oestradiol and the ratio of oestradiol (pg/ml) to progesterone (ng/ml). There was no association between oestradiol concentrations and blood flow to the gravid uterine horn. These data indicate local control of uterine blood flow by the bovine conceptus which may function to create optimal conditions for the continuation of pregnancy.

Colony-stimulating factor (CSF) in the uterus of the pregnant mouse.

During the growth of the pregnant uterus of inbred Balb/c mice uterine colony-stimulating factor (CSF) content increased 800-fold. This corresponded to a 75-fold increase in CSF concentration. The size of the increase was the same in the uteri of inbred Balb/c mice and the uteri of F1 hybrid C57Bl/Balb/c mice mated with F1 males. It was about four times greater in these uteri than it was in the uteri of randomly mated TO mice. After unilateral Fallopian tubal ligation of TO mice the concentration of CSF was as great in the non-gravid uterine horns as it was in the gravid uterine horns. Physicochemical characterization of CSF from extracts of pregnant uterus showed that it differed from that found in foetal extracts and that found in the circulation. Its function in the pregnant uterus is discussed.

Vein size in intact and hysterectomized mice during the estrous cycle and pregnancy.

The diameters of the ovarian, uterine, and femoral veins and the inferior vena cava were measured during stages of the estrous cycle in intact and hysterectomized mice and at intervals during pregnancy in mice with embryos in both uterine horns or in only the left horn. At metestrus I vein sizes were the least and were not significantly different in intact and hysterectomized mice. Ovarian and uterine veins showed the same or increased diameters at other stages of the cycle; veins enlarged progressively during pregnancy in intact mice. Non-gravid uterine horns showed little size increase as compared to gravid horns. Increases in vein diameter appeared to be correlated with local production of reproductive hormones. Evidence for transuterine migration of embryos was observed in 21 of 53 mice in which one uterine tube had been ligated or one ovary had been removed.

Blood flow and progestin levels in the ovaries of the pregnant rabbit.

Blood flow and progestin levels in corpora lutea and in the ovaries minus corpora lutea (interstitial gland) were determined in pregnant New Zealand rabbits having one nongravid uterine horn. Corpora lutea weight, interstitial gland weight, progestin levels in the ovary and blood flow in the corpora lutea and interstitial gland were similar in the 2 ovaries between days 5 and 25. The ratio of 20a-hydroxypregn- 4-en-3-one (20a-OH) to progesterone was 4-16 times higher in the interstitial gland than in the corpora lutea. Blood flow rates in the corpora lutea were highest at day 10, decreasing significantly at later stages. Blood flow rates in the interstitial gland were relatively constant throughout pregnancy. These results indicate that one nongravid horn has no differential or local effect on the ipsilateral ovary during pregnancy in the rabbit. (Endocrinology 88: 821, 1971)

Local relationship between the ovary and uterus of rats and guinea pigs.

The nongravid uterus limits the life span of corpora lutea in both guinea pigs and rats. Experiments with these 2 species demonstrate that this effect has a local component which is dependent upon the normal physical connections between the uterine horn and ovary, that the amount of uterine tissue is inversely related to length of luteal persistence, and that in rats a nongravid uterine horn does not interfere with pregnancy in the other horn. Removal of one uterine horn in guinea pigs on day 5 of the estrous cycle extended the life span of corpora lutea only in the ovary on the operated side. Cutting all physical connections between an ovary and adjacent uterine horn, without removing any tissue, had a similar effect. In rats, cutting all connections between the uterine horn and ovary on one or both sides lengthened pseudopregnancy (15.7 and 18.5 days, respectively, vs. 14.0 days in controls). Removal of the anterior or posterior half of one uterine horn was equally effective in lengthening pseudopregnan...

Regression of corpora lutea in unilaterally pregnant guinea-pigs.

SUMMARY Corpora lutea of unilaterally pregnant guinea-pigs regressed in the ovary adjacent to a non-gravid uterine horn while luteal maintenance occurred in the opposite ovary adjacent to a gravid horn. Severence of the utero-ovarian vascular and tissue connexions of the non-gravid uterine horn prevented unilateral regression during unilateral pregnancy and also appeared to cause asynchronous maintenance of cyclic corpora lutea that prolonged the length of oestrous cycles. Unilateral hysterectomy also prevented luteal regression during unilateral pregnancy. One-third of the females in which the vascular and tissue connexions between the ovary and non-gravid horn were left intact did not contain corpora lutea in the ovary adjacent to the non-gravid horn. Most of the remaining females in the same treatment groups contained smaller corpora lutea in the ovary adjacent to a non-gravid horn than in the ovary adjacent to a gravid horn. The presence of a sterile uterine horn tended to cause a decrease in the size of corpora lutea located in the contralateral ovary during the last half of pregnancy.

A Study of 1,000 Bovine Genitalia

Summary The average measurement (length, unless otherwise stated; for the various parts of apparently normal reproductive tracts from 100 parous cows were as follows: vulva, 3.8 ± 0.49 in.; vagina, 6.9 ± 0.72 in.; cervix, 3.1 ± 0.54 in. (2 to 4 transverse folds; diam. 1.3 ± 0.3 in.) ; uterine horns, 15.46 ± 2.80 in. (diam. 0.9 ± 0.2 in.) ; oviducts, 8.1 ± 0.9 in. (diam. 0.1 ± 0.01 in.) ; and ovaries, about 1.4 × 0.9 × 0.65 in. The right ovary and right uterine horn were, on the average, slightly larger than their counterparts on the left. Among 255 pregnant specimens studied, 57.3 r /r of the fetuses were found in the right uterine horn. The corpus luteum of pregnancy was found in the ovary opposite the horn carrying the fetus in four cases. Fetal membranes were studied in 153 specimens having single fetuses of varying sizes. Though there were obvious variations, the membranes appeared to extend into the nongravid uterine horn when the fetus was about 1.2 cm. long (35 days) and showed evidence of attachment in the gravid horn when the fetus was about 2.5 cm. long (40 days). Among 1,000 slaughter-house specimens, about 54% showed visible evidence of one or more abnormalities. Of the 1,000 organs examined, 3.3% had abnormalities which definitely would have rendered the cow sterile, and another 8.6% had abnormalities severe enough probably to cause lowered fertility. Granular vaginitis was present in 28.3% of the specimens and was the most frequent abnormality found. Yaginitis (nongranular), cervicitis, and metritis were much more frequent in specimens from cows than in those from heifers. Among specimens from heifers, granular vaginitis, persistent hymens, and other anatomical abnormalities were most often found. In general (all specimens), the incidence of abnormalities decreased as the distance from the exterior increased. (The ovaries were an exception to this rule, however.)