[Gravidic kidney disease, gravidic pyelonephritis, infected kidney cyst].
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Adult↗
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[The effects of cathepsin on collagen and casein in the gravid and non-gravid uterus in rats].
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Aging↗
[Enzyme activity patterns in the corpus luteum of gravid and non-gravid swine].
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Alcohol Oxidoreductases↗
Evaluation of various attributes of gravid female traps for collection of Culex in Florida.
Gravid female traps are used for surveillance of populations of Culex spp. and arboviruses such as West Nile virus. Field trials evaluating various attributes of gravid female traps for collection of gravid Culex were conducted in rural habitats in Alachua and Marion Counties, FL. Screened cage tests in the field were also used to compare trap models. Three trap models were evaluated: two based on the original Reiter design (Gravid CDC traps A and B) and one based on the revised Reiter design (gravid box trap). Trap model significantly affected collection of Culex quinquefasciatus and Culex nigripalpus; the greatest numbers were collected by the CDC gravid trap Aand CDC gravid trap B traps compared to the gravid box traps. There were no statistically significant differences between the collections with CDC gravid traps A and B. These patterns were similar at both sites and between early and late summer collections in Marion Co. In trials conducted in screened field cages with gravid Cx. quinquefasciatus, significantly more mosquitoes were collected in the CDC gravid trap A and B than in box gravid traps. Size of pan associated with the gravid traps was important and traps with larger pans collected more mosquitoes. Pan color was also important in efficacy of traps, and traps with darker pans (black, green) collected more mosquitoes than traps with lighter pans (tan, white). The percentages of gravid mosquitoes in trap collections of Culex females ranged from 54.0% to 89.6% with no clear differences between model of trap, size of pan, or pan color. Various attributes of gravid female traps impact the efficacy of the traps for Culex spp. and these should be considered in trapping programs.
Animals↗
Compartmentation of creatine kinase isoenzymes in myometrium of gravid guinea-pig.
1. This study was performed to investigate the possible presence and role of the creatine kinase (CK) system in the contraction and relaxation of skinned guinea-pig uterus as well as the changes of the CK system during gestation. Experiments were performed on isolated longitudinal fibres of gravid and non-gravid myometrium. 2. Total CK activity increased from 74 +/- 11 to 196 +/- 39 IU (g wet wt)-1 during gestation. 3. The four isoenzymes of CK: muscle (MM), muscle-brain (MB), brain (BB) and mitochondrial (mt-CK) were found in myometrium. MM, MB and BB isoenzymes represented respectively 20.3 +/- 2.6, 10.3 +/- 4.4 and 72.7 +/- 2.2% of total activity. The distribution of isoenzymes did not significantly change with gestation, the contribution of mt-CK increasing from trace to 5% of total activity. 4. BB-CK was specifically bound to Triton X-100-skinned fibres with the non-gravid uterus containing 6.7 +/- 1.9 IU (g wet wt)-1 and the gravid uterus containing 44 +/- 13 IU (g wet wt)-1. 5. Active tension of Triton X-100-treated fibres increased from 6.06 +/- 0.68 to 19.3 +/- 1.9 mM mm-2 during gestation. 6. Submaximal tension (43.3 +/- 4.4% of maximal tension) can be developed in the absence of ATP and in the presence of 12 mM phosphocreatine (PCr) and 250 microM MgADP from endogenous CK in non-gravid uterine fibres while the gravid uterus was able to generate 65.4 +/- 3.9% of maximal tension via the CK system. 7. The endogenous CK system was able to relax the skinned fibres from high-tension rigor conditions by 47.3 +/- 4.2% of total relaxation in non-gravid fibres and 60.6 +/- 3.2% of total relaxation in gravid fibres. 8. Non-gravid and gravid uteri both contained mt-CK of 17.5 +/- 8.4 and 140 +/- 22 micrograms (g wet wt)-1 respectively as determined with antibodies against mt-CK. 9. Oxygen consumption was studied in fibres where the plasmalemma was solubilized with 50 micrograms ml-1 saponin. Maximal respiration was increased from 0.91 +/- 0.05 to 2.61 +/- 0.16 mumol oxygen min-1 (g dry wt)-1 in the gravid uterine fibres. However, creatine did not stimulate respiration in the uterine fibres treated with saponin. 10. It is concluded that the CK system undergoes qualitative as well as quantitative changes during gestation. BB-CK is specifically localized in the myofilaments and mt-CK is present in the uterine mitochondria.(ABSTRACT TRUNCATED AT 400 WORDS)
Actin Cytoskeleton↗
Do female collared lizards change field use of maximal sprint speed capacity when gravid?
Locomotor ability is well-documented to decrease in gravid female lizards. However, no studies have examined what proportion of maximal sprint speed capacity gravid females use in nature or how a reduction in maximal capacity translates to changes in sprint speeds used in nature. Gravid females may compensate for reduced locomotor ability by increasing the proportion of their maximal capacity used in nature, or by changing their antipredator behaviour. I measured maximal sprint speed in the laboratory for female collared lizards (Crotaphytus collaris) while gravid and nongravid and then compared those to speeds used in the field while foraging and escaping predators, and also while gravid and nongravid. Females had significantly lower maximal sprint speed capacity while gravid, and they ran slower while foraging and escaping predators. However, gravid females did not increase the proportion of maximal capacity used in those contexts compared to when not gravid. Gravid females compensated for reduced locomotor capacity by staying closer to refugia but not by remaining more cryptic. These results suggest that the costs of reduced locomotor capacity may not be associated with direct costs while foraging or escaping predators, but instead with potential indirect effects associated with the change in antipredator behaviour.
Animals↗
Differential expression of myometrial oxytocin receptor and prostaglandin H synthase 2, but not estrogen receptor alpha and heat shock protein 90 messenger ribonucleic acid in the gravid horn and nongravid horn in sheep during betamethasone-induced labor.
In the present study, we characterized four myometrial contraction-associated proteins (mCAPs): oxytocin receptor (OTR), prostaglandin H synthase 2 (PGHS2), estrogen receptor alpha (ERalpha), and heat shock protein 90 (Hsp90) messenger RNA (mRNA) expression in the nongravid horn of pregnant sheep and compared them with their expression in the gravid horn that is exposed to a greater degree of stretch. We also examined the regulatory effects of estrogen and progesterone on OTR mRNA expression in ovariectomized nonpregnant sheep. In addition, we determined the ontogeny of mCAP expression in the gravid horn throughout late pregnancy and during spontaneous term labor. Gravid horn and nongravid horn myometria were removed under general anesthesia from control ewes not in labor at 130-140 days gestational age (dGA; n = 3) and during betamethasone-induced labor (n = 6) at the same gestational age. Gravid horn myometrium was also collected from ewes not in labor at 95 dGA (n = 3), 101-110 dGA (n = 3), 111-120 dGA (n = 3), 121-130 dGA (n = 3), 131-140 dGA (n = 3), and 141-145 dGA (n = 4) and from ewes in spontaneous term labor (n = 4). All ewes were carrying single fetuses. Myometrium was also collected from ovariectomized nonpregnant ewes treated with saline (n = 5), estradiol (50 microg/day; n = 5), progesterone (0.3 g, intravaginally; n = 5), and estradiol plus progesterone (n = 5). Myometrial RNA was extracted and analyzed by Northern blot for OTR, PGHS2, ERalpha, and Hsp90 mRNA, normalized for 18S ribosomal RNA or beta-actin. ERalpha, Hsp90, OTR, and PGHS2 mRNA were all significantly up-regulated during betamethasone-induced labor (P < 0.01) in gravid and nongravid horn myometrium. The level of gravid horn OTR mRNA during labor was 3 times the level of nongravid horn OTR mRNA (P < 0.0001). Gravid horn PGHS2 mRNA was also higher than nongravid horn PGHS2 (P < 0.02). In contrast, in spontaneous term labor nongravid horn, ERalpha and Hsp90 mRNA were similar to gravid horn. Myometrial ERalpha and Hsp90 mRNA remained unchanged throughout late pregnancy and increased at spontaneous term labor (P < 0.05). In contrast, myometrial OTR increased around 130 dGA (P < 0.01) and further increased at spontaneous term labor (P < 0.02). Progesterone significantly inhibited myometrial OTR mRNA expression in nonpregnant sheep and estradiol antagonized progesterone's inhibitory effect. Mechanical stretch differentially regulated mCAP mRNA expression in the ovine gravid horn and nongravid horn. Mechanical stretch appears largely responsible for increased OTR mRNA and to a lesser degree PGHS2 mRNA. In addition, endocrine factors may be required for full activation of OTR and PGHS2 mRNA associated with labor. ERalpha and Hsp90 mRNA are not under the control of uterine stretch in keeping with our previous results, indicating that systemic hormones such as estradiol, are prime regulators for these two mCAP mRNA expression during labor.
Animals↗
Tumor formation and sister chromatid exchange induction by ethyl carbamate: relationships among non-pregnant murine females, gravid dams, and transplacentally exposed offspring.
Sister-chromatid exchange (SCE) induction and cell cycle kinetics alterations by ethyl carbamate in bone marrow of non-gravid murine Swiss Webster, ICR/Jcl, and C57Bl/6J dams were evaluated, and data from non-gravid females were compared with those previously reported for pregnant dams of the same strains. In addition, lung adenoma induction by ethyl carbamate in gravid Swiss Webster dams, their offspring, and in non-pregnant Swiss Webster females was also determined. Relative cytogenetic and tumor responses in non-gravid and gravid Swiss Webster females and their offspring were compared. In contrast to the increased sensitivity reported for gravid Swiss Webster dams versus ICR/Jcl and C57Bl/6J dams, SCE responses to 1.1, 2.2, or 3.3 mmol/kg of ethyl carbamate in non-gravid females were approximately equivalent among strains. In Swiss Webster and C57Bl/6J (but not ICR/Jcl) strains, SCE responses in non-gravid females at 2.2 and 3.3 were significantly lower than those of their pregnant counterparts. Tumor induction by 3.3 mmol/kg ethyl carbamate paralleled relative SCE induction with Swiss Webster dams, demonstrating a 5-fold increase in the number of tumors relative to their offspring and a 4-fold enhancement of tumor induction relative to their non-pregnant counterparts.
Adenoma↗
Sampling gravid Culex quinquefasciatus (Diptera: Culicidae) in Tanzania with traps baited with synthetic oviposition pheromone and grass infusions.
The effectiveness of traps baited with (5R,6S)-6-acetoxy-5-hexadecanolide (the synthetic oviposition pheromone) and grass infusions in sampling a population of gravid Culex quinquefasciatus Say was conducted in Muheza, Northeast Tanzania. A counterflow geometry (CFG) trap baited with pheromone and set outdoors, adjacent to a pit latrine building, collected more gravid Cx. quinquefasciatus than a CDC trap baited with pheromone and operated without light. Inside pit latrine buildings, significantly more gravid Cx. quinquefasciatus were collected in a CFG trap-baited with pheromone or grass infusion than in traps baited with tap water. CFG traps baited with either grass infusion or pheromone and set outdoors, away from known breeding sites, caught significantly more gravid Cx. quinquefasciatus than traps baited with tap water. CFG traps baited with pheromone + grass infusion caught significantly more gravid Cx. quinquefasciatus than CFG traps baited with either grass infusion or pheromone. In both cases, the proportion of gravid mosquitoes increased as traps were moved away from a natural emergence site. More gravid Cx. quinquefasciatus were collected in a pheromone-baited CFG trap than were egg rafts deposited in a jar with pheromone-treated water. It is concluded that CFG traps baited with oviposition attractants can be used effectively to sample gravid Cx. quinquefasciatus.
Animals↗
Muscarinic receptor subtypes in normal, fetal, and gravid rabbit bladder, heart and uterus.
In the rabbit bladder, pregnancy has been shown to induce a significant decrease in both muscarinic receptor density and response to muscarinic stimulation. Neonatal rabbit bladders have a high muscarinic receptor density and contractile response to bethanechol stimulation. The bladders from 7 gravid rabbits, 7 age-matched virgin controls, and 32 fetal rabbits of 3 week gestation were studied. Compared to control tissue, filtration binding demonstrated receptor density to be 24.3% lower in gravid bladder dome, 41.2% lower in gravid bladder base, and 114.8% higher in fetal bladders. While total receptor density was not different from control in gravid heart, fetal hearts showed a 2.5 fold increased receptor density. There was also a 61% reduction in muscarinic receptor density in the gravid uterus. Immunoprecipitation assays using muscarinic receptor subtype specific antisera were used to measure the relative levels of m1, m2, m3 and m4 receptors. The m2 receptor was the predominant subtype in the bladder and uterus, and the only subtype detected in rabbit heart. The m3 receptor protein was also present, but in lower levels in the bladder and uterus. The m1 and m4 receptors were not detected in any of the tissues studied. Furthermore, the relative percent of each receptor did not statistically change for the gravid or fetal rabbit bladder, uterus, or heart, when compared to its control. Differences in the contractile response to cholinergic stimulation of the gravid bladder and uterus, and of the fetal bladder then, can be attributed to changes in muscarinic receptor density and not to changes in receptor subtype.
Animals↗
Pregnancy rates and gravid uterine parameters in single, twin and triplet pregnancies in naturally bred ewes and ewes after transfer of in vitro produced embryos.
The objectives of this study were to: (1) evaluate the pregnancy rates after transfer of embryos produced in the presence or absence of epidermal growth factor (EGF) during in vitro maturation, and (2) compare several variables of the gravid uterus on day 140 after fertilization in single, twin and triplet pregnancies in ewes (n = 12) bred naturally and in ewes (n = 18) after transfer of embryos produced in vitro. Oocytes collected from FSH-treated ewes (n = 18) were collected from all visible follicles and cultured in maturation medium with or without EGF. Oocytes were then fertilized in vitro by frozen-thawed semen. On day 5 after fertilization, embryos with > or = 16 cells were transferred to recipient ewes (n = 39). In addition 12 ewes were bred naturally. Pregnancy was verified by real-time ultrasonography on day 45 or later after embryo transfer (ET) or breeding. On day 140 of pregnancy, the reproductive tract was collected from all ewes and the following parameters were determined: the number, sex, weight and crown to rump length (CRL) of fetuses, weights of gravid uterus and fetal membranes, and weight and number of placentomes. Presence of EGF in maturation medium increased (P < 0.04) cleavage rates (78% versus 59%) and percentage of > or = 16 cell embryos on day 5 after fertilization (62% versus 40%). Pregnancy rates tended to be greater (P < 0.1) after transfer of embryos matured in the presence of EGF (52%) than in the absence of EGF (39%). EGF presence in maturation medium did not affect any variables of gravid uterus or fetal weight. For single pregnancies in naturally bred ewes and ewes after ET all uterine variables were similar. For twin pregnancies, weight of gravid uterus, weight of uterus plus fetal membranes, total weight of placentomes/ewe, mean weight of individual placentome, mean weight of fetus, total fetal weight/ewe and CRL were greater (P < 0.0001-0.04) for ewes after ET than for ewes bred naturally. The weights of gravid uterus, fluid, uterus plus fetal membranes, fetal membranes, total placentomes/ewe, mean weight of individual placentome and total fetal weight/ewe were greater (P < 0.0001-0.08) for triplet pregnancies in ewes after ET than single and twin pregnancies in ewes naturally bred or after ET. The number of placentomes/fetus was greatest (P < 0.0001-0.06) in single pregnancies in ewes bred naturally and after ET fewer in twin pregnancies in ewes bred naturally and after ET and fewest in triplet pregnancies in ewes after ET. The total number of placentomes/ewe was greatest (P < 0.0001-0.06) for twin pregnancies in ewes naturally bred, fewer in single pregnancies in ewes naturally bred and twin and triplet pregnancies after ET, and fewest in single pregnancies in ewes after ET. The mean weight of fetus was greater (P < 0.0001-0.07) in single pregnancies in ewes naturally bred or after ET than in twin or triplet pregnancies in ewes naturally bred or after ET. The CRL was the lowest (P < 0.01) in twin pregnancies in ewes bred naturally. For pregnancies after natural breeding and after ET, the number of fetuses/ewe was negatively correlated (P < 0.03-0.0001) with the weight of placentomes/fetus, the number of placentomes/fetus, the mean weight of the fetus and CRL, and was positively correlated (P < 0.0001-0.05) with weight of gravid uterus, the total number of placentomes/ewe and total fetal weight/ewe. These data demonstrate that the presence of EGF in maturation medium increases the rates of cleavage and early embryonic development, and has a tendency to enhance rates of pregnancy but does not affect variables of the gravid uteri in ewes after transfer of in vitro produced embryos. Transfer of embryos produced in vitro affected some uterine variables in twin but not single pregnancies to compare with pregnancies after natural breeding. In addition, culture conditions in the present experiment did not create large offspring syndrome. The low number of placentomes/fetus seen in triple pregnancies appears to be compensated for by the increase in the weight of each individual placentome.
Animals↗
Administration of N(omega)-L-arginine methyl ester (L-NAME) impairs endothelium-dependent relaxation in gravid but not nongravid rats.
OBJECTIVE: To characterize the impairment of endothelium-dependent relaxation induced by administration of the nitric oxide synthase (NOS) inhibitor N(omega)-L-arginine methyl ester (L-NAME) to gravid rats and to determine whether L-NAME affects nongravid rats in a similar manner. METHODS: Acetylcholine (ACh; 0.01-10 microM) relaxation was studied in aortic segments (contracted with 10 nM norepinephrine) from Wistar rats that were hypertensive after receiving L-NAME (0.5 mg/mL in drinking water) before gravidity (hypertensive virgin rats [HVR]), during gravidity (hypertensive gravid rats [HGR]), or during the last 10 days of gravidity to 24 hours postpartum (hypertensive puerperal rats [HPR]). We also studied aortic segments from corresponding groups of untreated normotensive rats (normotensive gravid rats [NGR], normotensive puerperal rats [NPR], and normotensive virgin rats [NVR]). The approximate participations of NO and the hyperpolarizing mechanisms in ACh relaxation were calculated from the reduction of relaxation observed, respectively, after incubation with the NOS inhibitor N(G)-monomethyl-L-arginine (L-NMMA, 0.1 mM) or after contraction with 50 mM of potassium chloride. Expression of endothelial NOS protein was studied by Western blot in segments of HGR and NGR. RESULTS: Acetylcholine relaxation was reduced in HGR compared with NGR, and this reduction correlated with the severity of hypertension. In contrast, ACh relaxation in HVR was similar to that in NVR, and that of HPR was similar to that in NPR. The NO component of relaxation was reduced in HGR but preserved in the other groups. Nevertheless, there were no differences in endothelial NOS protein expression between NGR and HGR. The hyperpolarizing component in relaxation was enhanced in HVR and HPR but not HGR. CONCLUSION: Administration of L-NAME induced an impairment of endothelium-dependent relaxation, involving both nitric oxide- and hyperpolarizing-dependent mechanisms in gravid but not virgin rats; this impairment resolved with delivery.
Acetylcholine↗
Effects of adult body size on fecundity and the pre-gravid rate of Anopheles gambiae females in Tanzania.
The influence of adult body size on the pre-gravid state and fecundity was studied in Anopheles gambiae Giles females hand-caught inside houses and virgin females collected as pupae in Tanzania. Blood-fed mosquitoes were kept for 2-3 days before dissection and examination for insemination and ovarian condition. Those females which did not develop eggs were classified as pre-gravid. The number of mature eggs in those mosquitoes which became gravid was counted. Virgin females were fed and kept for egg maturation in the laboratory. Wing-length of females was measured as an index of mosquito size. The overall pre-gravid rate in the resting An.gambiae population was found to be 21% and, of these, 66% had been inseminated. In the virgin females the pre-gravid rate was 92.6%. The mean wing-length of wild females which became gravid was significantly larger than those which remained pre-gravid. There was a positive correlation between fecundity and wing-length. Smaller females tended to require two or three bloodmeals to facilitate completion of the first gonotrophic cycle. The critical size permitting oviposition from the first blood-meal was a wing-length of 3 mm.
Animals↗
Evaluation of the CDC gravid trap for the surveillance of St. Louis encephalitis vectors in Memphis, Tennessee.
Collections with CDC Gravid Mosquito Traps on 954 trap-nights from May through September 1983 are compared to 2,608 concurrent resting site collections made in the same area of Memphis, Tennessee. Gravid Traps yielded 88 times more Culex per collection and 96 times more Culex per man hour. The total Gravid Trap catch was 135,724 mosquitoes, 99% of which were either Culex pipiens or Cx. restuans, whereas these species comprised only 63% of the 6,613 mosquitoes collected from resting sites. Gravid Traps also collected significant numbers of Aedes aegypti and Ae. triseriatus. On most nights, more than 95% of mosquitoes in the Gravid Trap catch were gravid females. These results demonstrate that the trap is an effective and efficient device for collecting several important vector species. The preponderance of gravid mosquitoes should enhance the probability of encountering pathogens acquired by blood-feeding.
Animals↗
Fecundity and proportions of gravid females in populations of the bluetongue vector Culicoides imicola (Diptera: Ceratopogonidae) and several other species in Israel.
The gravid proportions of five Culicoides spp. in Israel were determined based on a suction light trap placed above calves in a cowshed and on two similar traps hung in a Eucalyptus tree at elevations of 1.4 and 26 m. In the cowshed, the proportion of gravid Culicoides distinctipennis Austen showed no significant variation between seasons; C. imicola Kieffer (the dominant species) was caught in significantly smaller proportions in winter; C. schultzei gp (second most dominant) showed no significant seasonal variation. In the Eucalyptus tree, a significantly smaller percentage was gravid in winter at the lower trap, but at the higher trap there was no significant variation between seasons. Culicoides circumscriptus Kieffer showed no significant seasonal variation at either height. C. distinctipennis was present with a significantly higher proportion gravid at the lower level in spring, but no significant variation between seasons was observed in the higher level trap. In C. imicola, gravids were proportionately more numerous in the lower trap in summer and autumn, but, in the higher trap, there was no significant variation between seasons. A significantly greater proportion of gravid C. schultzei gp females occurred at the higher level trap in spring, whereas no significant variation occurred in the lower level trap. Counts of eggs were made for C. cataneii, C. circumscriptus, C. distinctipennis, C. imicola, C. newsteadi Austen, C. obsoletus Meigen, C. saevanicus Dzhafarov, C. schultzei gp, and C. univittatus Vimmer. Counts for all four seasons were made only for C. circumscriptus and C. imicola, and only C. imicola showed significant variation between seasons (fecundity lower in autmn and winter).
Analysis of Variance↗
Unilateral luteotropic effect of uterine venous effluent of a gravid uterine horn in sheep.
The involvement of the main uterine vein in the unilateral maintenance of CL was studied in bilaterally ovulating unilaterally pregnant ewes. Ewes were mated at estrus (Day 0) and bilaterally ovulating ewes were randomized into three groups at surgery on Day 5. In all ewes, the uterine horns were separated through the intercornual area and one was ligated and transected near the internal bifurcation to produce a nongravid horn. One group served as controls (five ewes). In the other two groups the main uterine vein on one side was surgically anastomosed (end to side) to the corresponding vein of the opposite side (gravid side to nongravid side in one group--three ewes, and nongravid side to gravid side in the other--three ewes). Necropsies were done on Day 20. Mean CL weight was less, (P less than .01) on the nongravid side in control ewes than on the gravid side in control ewes or for either side in the other two groups. There were no significant differences among mean weights of CL on the gravid side in control ewes and either side in the other two groups. The CL regressed when the ipsilateral uterine vein contained blood from only the nongravid horn whereas the CL was maintained when the ipsilateral uterine vein contained venous blood from a gravid horn, whether or not it also contained blood from a nongravid horn. Results indicate that the uterine venous effluent from a gravid uterine horn in sheep has a luteotropic effect on the ipsilateral CL.
Animals↗
Changes in caridac output and hemolymph flow during hypoxic exposure in the gravid grass shrimp, Palaemonetes pugio.
The cardiovascular response of decapod crustaceans to hypoxic exposure is well documented; however, information is limited concerning the influence of reproductive state on cardiovascular demands during hypoxic exposure. Given the additional metabolic demand of reproduction, we investigated the cardiovascular adjustments employed by gravid grass shrimp Palaemonetes pugio to maintain oxygen delivery during hypoxic stress. Cardiac output values were elevated in gravid compared to nongravid grass shrimp. Gravid grass shrimp were exposed to hypoxia and the stroke volume, heart rate, cardiac output and hemolymph flow were determined using video-microscopy and dimensional analysis. Oxygen consumption rates were determined using respirometry. There where no changes in the cardiac output values of gravid females until reaching 6.8 kPa O2, with a significant redistribution of hemolymph flow at 13.7 kPa O2. Flow was significantly decreased to the anterior lateral arteries that supply the ovaries and hepatopancreas, the anterior aorta and the posterior aorta. The redistribution of hemolymph flow away from these vessels results in an enhanced hemolymph flow to the sternal artery that supplies the ventral segmental system, the gills, the buccal apparatus and the ventral nerve cord. The data suggest that during hypoxic stress, gravid females place a priority on survival.
Animals↗
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.
Animals↗