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R K Christenson

Publications and source records attributed to R K Christenson.

At least 73 records · Page 4Linked to original sources
PubMed1995

Effect of treatment with retinyl palmitate, progesterone, oestradiol and tamoxifen on secretion of a protein similar to retinol-binding protein during uterine gland development in neonatal pigs.

Previous work has demonstrated that uterine secretion of a protein with M(r) 20,000 and pI 5.5 increases during neonatal endometrial gland development. Uterine tissue was collected from a 60-day-old gilt and cultured in 0.1 x leucine minimum essential medium (MEM) plus 50 muCi [3H]leucine to determine whether this protein is related to retinol-binding protein (RBP). Conditioned medium was immunoprecipitated using anti-human RBP antiserum. A radioactive protein with M(r) 20,000 and pI 5.5 was specifically immunoprecipitated from the conditioned medium. Uteri from neonatal gilts were collected at birth (day 0) and on days 3, 6, 9 and 12, cultured, and secreted proteins were immunoprecipitated as described above to determine whether secretion of immunoreactive RBP increased coincident with initiation of endometrial gland development. Immunoprecipitation demonstrated that the secretion of immunoreactive RBP increased by day 3. Finally, gilts were treated each day with corn oil, retinyl palmitate (10,000 iu day-1), progesterone (20 mg day-1), oestradiol (100 micrograms day-1) or tamoxifen (1 mg day-1 or 0.1 mg day-1) for 14 days beginning at birth to determine the effects of these treatments on endometrial gland development and uterine secretion of immunoreactive RBP. On day 14, gilts were killed and uteri collected. Uterine tissue samples were prepared for histology (to evaluate uterine development using morphometry) and for culture in 0.1 x methionine MEM plus 25 muCi [35S]methionine (to evaluate uterine protein synthesis).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Effect of the conceptus and lack of effect of uterine space on endometrial protein secretion during mid-gestation in swine.

The effect of the conceptus and of reduced uterine space on endometrial protein secretion was examined on Days 40, 60, and 80 of gestation in white crossbred gilts. Twenty-nine gilts were checked daily for estrus, and 15 were given 5 mg estradiol valerate daily from Days 11 to 15 (Day 0 = day of estrus) of the estrous cycle to induce pseudopregnancy. The remaining 14 pigs were mated during estrus. All pigs were laparotomized on Day 4, and one uterine horn was ligated to produce one crowded and one roomy uterine environment. Pigs were killed on Days 40, 60, and 80 of pregnancy or pseudopregnancy. The reproductive tracts were collected, and placental tissues from pregnant pigs and endometrial tissues from all pigs were cultured in the presence of 3H-leucine to evaluate protein secretion. Conditioned medium was dialyzed, measured for incorporation of radioactivity into nondialyzable macromolecules, and then subjected to two-dimensional (2D)-PAGE to determine the effect of uterine space and day of pregnancy or pseudopregnancy on overall protein secretion rate and secretion of specific proteins. Fetal survival, fetal weight, and placental weight were decreased (p < 0.01) in the crowded uterine environment compared to the roomy uterine environment. Incorporation of 3H-leucine into nondialyzable macromolecules by endometrial tissue in culture was not affected by uterine space. Secretion of nondialyzable macromolecules by endometrium from pregnant pigs was not different from that by endometrium from pseudopregnant pigs on Day 40 but was greater (p < 0.01) on Days 60 and 80.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Immunocytochemical localization of cytochromes P450 17 alpha-hydroxylase and aromatase in embryonic cell layers of elongating porcine blastocysts.

Localized expression of cytochromes P450 17 alpha-hydroxylase (P450c17) and aromatase (P450arom) was investigated in embryonic cell layers of elongating porcine blastocysts by immunocytochemistry. Blastocysts were flushed from the uterus on day 12 of pregnancy, fixed in paraformaldehyde, embedded in paraffin, sectioned, and stained using immunogold- and peroxidase-based techniques. Staining for both P450c17 and P450arom was intense in spherical 7- to 10-mm blastocysts, but was absent in earlier stage 2- to 4-mm blastocysts and less intense or absent in later stage 20-mm and filamentous embryos. Cytochrome P450c17 was limited to the trophoblast of all blastocysts expressing the enzyme, and in spherical 7- to 10-mm blastocysts, essentially all cells of the trophoblast layer stained positively for P450c17. However, as elongation became apparent in 10-mm blastocysts, the cells of the trophoblast became flattened, and the expression of P450c17 declined particularly in those trophoblast cells adjacent to the embryonic disc where mesoderm outgrowth was occurring. In fact, two distinct populations of trophoblast cells became obvious: one that maintained P450c17 expression, and one that did not. Moreover, those trophoblast cells expressing P450c17 were less flattened than neighboring cells in which P450c17 expression was absent. These two morphologically and functionally distinct trophoblastic cell populations were most obvious in areas furthest from the embryonic disc. Cytochrome P450arom was expressed in the trophoblast as well as the hypoblast under the embryonic disc. Neither P450c17 nor P450arom appeared to be expressed in the embryonic disc or the mesoderm of the expanding blastocyst. These functional and structural changes in the embryonic cell layers of the elongating conceptus may be associated with the transient synthesis and secretion of estrogen that occur at the time of maternal recognition of pregnancy in the pig.

Animals↗
PubMed1994

Immunocytochemical localization of cytochromes P450 17 alpha-hydroxylase and aromatase in embryonic cell layers of elongating porcine blastocysts.

Localized expression of cytochromes P450 17 alpha-hydroxylase (P450c17) and aromatase (P450arom) was investigated in embryonic cell layers of elongating porcine blastocysts by immunocytochemistry. Blastocysts were flushed from the uterus on day 12 of pregnancy, fixed in paraformaldehyde, embedded in paraffin, sectioned, and stained using immunogold- and peroxidase-based techniques. Staining for both P450c17 and P450arom was intense in spherical 7- to 10-mm blastocysts, but was absent in earlier stage 2- to 4-mm blastocysts and less intense or absent in later stage 20-mm and filamentous embryos. Cytochrome P450c17 was limited to the trophoblast of all blastocysts expressing the enzyme, and in spherical 7- to 10-mm blastocysts, essentially all cells of the trophoblast layer stained positively for P450c17. However, as elongation became apparent in 10-mm blastocysts, the cells of the trophoblast became flattened, and the expression of P450c17 declined particularly in those trophoblast cells adjacent to the embryonic disc where mesoderm outgrowth was occurring. In fact, two distinct populations of trophoblast cells became obvious: one that maintained P450c17 expression, and one that did not. Moreover, those trophoblast cells expressing P450c17 were less flattened than neighboring cells in which P450c17 expression was absent. These two morphologically and functionally distinct trophoblastic cell populations were most obvious in areas furthest from the embryonic disc. Cytochrome P450arom was expressed in the trophoblast as well as the hypoblast under the embryonic disc. Neither P450c17 nor P450arom appeared to be expressed in the embryonic disc or the mesoderm of the expanding blastocyst. These functional and structural changes in the embryonic cell layers of the elongating conceptus may be associated with the transient synthesis and secretion of estrogen that occur at the time of maternal recognition of pregnancy in the pig.

Animals↗
PubMed1994

Effect of estrone treatment from day 30 to 45 of pregnancy on endometrial protein secretion and uterine capacity.

Secretion of proteins by the endometrium of pigs during pregnancy is reported to be influenced by progesterone and estrogen. The effect of estrone treatment from d 30 to 45 of pregnancy on endometrial protein secretion and uterine capacity was tested in unilaterally hysterectomized-ovariectomized (UHO) gilts. Ten intact and 16 UHO crossbred gilts were mated and assigned to the following treatments: 1) intact controls, n = 10; 2) UHO, n = 8; and 3) UHO + estrone (E; two 150-mg implants, 60-d release, implanted on d 30 of gestation), n = 8. Gilts were killed on d 45 of pregnancy. A sample of allantoic fluid was collected from each conceptus. Blood and endometrial tissue samples were collected to evaluate estrone concentrations, and placental and endometrial tissues were incubated to evaluate protein secretion. Estrone treatment increased (P < .01) plasma and endometrial tissue estrone concentrations. Unilateral hysterectomy-ovariectomy decreased (P < .01) fetal survival. No effect of estrone was detected on the number of live fetuses, protein secretion by endometrial tissue in culture, or allantoic fluid protein, acid phosphatase, retinol binding protein, or retinol. Estrone treatment decreased uterine weight (P = .05) and allantoic fluid fructose concentrations (P < .05). After correction for allantoic fluid volume, allantoic fluid protein, retinol, and acid phosphatase activity were decreased (P < .05) in UHO-treated pigs. The UHO treatment did not affect allantoic fluid fructose concentrations. These results indicate that 1) estrone treatment from d 30 to 45 of pregnancy and at the dosage used did not alter endometrial protein secretion or fetal survival, and 2) UHO decreased the amount of endometrial proteins available to conceptuses.

Acid Phosphatase↗
PubMed1993

Uterine space affects placental protein secretion in swine.

The effect of altering uterine space available to developing conceptuses on placental and endometrial protein secretion and endometrial 3H-thymidine incorporation on Days 25 and 35 of gestation was tested. Gilts bred at estrus (Day 0) were laparotomized on Day 4, and the uterine horn ipsilateral to the ovary with the most ovulations was ligated midway between the uterine tip and uterine bifurcation to create a crowded and a roomy uterine environment. On Day 25 (n = 7) or 35 (n = 6), gilts were killed and the reproductive tract was dissected from each. Each placenta and fetus was weighed, and a sample of endometrium adjacent to each placenta was collected. Within each uterine environment, tissues (500 mg) from the heaviest and lightest (by weight) placentae and adjacent endometrial tissue were cultured for 24 h at 37 degrees C in 15 ml Minimal Essential Medium having 0.1 times the normal amount of leucine plus 50 microCi 3H-leucine. Aliquots (2 ml) of dialyzed medium were subjected to two-dimensional PAGE and fluorography to examine proteins with molecular weight ranges of approximately M(r) 20,000-130,000, and a further aliquot was subjected to SDS-PAGE to examine low molecular weight proteins (M(r) 2000-20,000). In addition, endometrium (200 mg in duplicate) adjacent to the heaviest and lightest placentae within each uterine environment was incubated for 4 h in 5 ml MEM plus 1 microCi 3H-thymidine to measure DNA synthesis. After culture, 3H-thymidine incorporation and total DNA were determined. Fetal survival in the crowded uterine environment decreased (p < 0.05) on Day 35 compared to Day 25. On both days, the heaviest and lightest placentae from the crowded uterine environment weighed less (p < 0.01) than the heaviest and lightest placentae from the roomy uterine environment. The fetuses associated with the heaviest and lightest placentae from the crowded uterine environment also weighed less (p < 0.05) than fetuses associated with the heaviest and lightest placentae from the roomy uterine environment. Nondialyzable radioactivity in medium per gram of tissue cultured from placental cultures decreased (p < 0.05) and from endometrial culture increased (p < 0.05) between Days 25 and 35. Placental secretion of a protein with M(r) 46,000, pI 5, decreased between Days 25 and 35. Endometrial secretion of three proteins (M(r) 35,000, pI 6.2; M(r) 25,000, pI 4.9; and M(r) 14,000, pI unknown) increased, and secretion of three other proteins (M(r) 24,000, pI 6.5 doublet; M(r) 22,000, pI 7.5, and M(r) 7000, pI unknown) decreased from Day 25 to Day 35 of pregnancy.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

Differential expression of distinct mRNAs for ovine trophoblast protein-1 and related sheep type I interferons.

An antiluteolytic substance secreted by the ovine conceptus and primarily responsible for maternal recognition of pregnancy is ovine trophoblast protein-1 (oTP-1), a new type I interferon (IFN). The objectives of this research were 1) to investigate whether multiple, distinct genes encode oTP-1 and other type I IFNs in the ovine genome and 2) to examine expression of oTP-1 and other IFN mRNAs during conceptus development. Genes for type I IFNs were isolated from a subgenomic library constructed from Day 25 (Day 0 = estrus) ovine conceptus high-molecular-weight DNA. Six clones were isolated and nucleotide-sequenced from -1000 to +900 (bases relative to cap site). Comparisons of inferred amino acid sequences demonstrated that four clones were distinct oTP-1 genes and that two clones, defined as o9 and o12, were related type 1 IFNs (deduced aa homology of o9 and o12 to oTP-1 was 71% and 54%, respectively). The presence of mRNAs encoded by oTP-1 and type I IFN genes was examined quantitatively via reverse transcription-polymerase chain reaction (RT-PCR) analysis of total cellular RNA (tcRNA) extracted from Day 13-45 concepti. Total cellular RNA obtained from Day 75 placenta and adult lymphocytes was also analyzed by RT-PCR, coupled with Southern blot hybridization of the PCR reaction products with specific DNA probes. PCR products were sequenced in order to confirm primer specificity, and mRNAs corresponding to two of the four oTP-1 genes and to both related IFN clones (o9 and o12) were identified. Furthermore, quantitation of the PCR products revealed that of the two oTP-1 genes examined, one was highly expressed on Days 13-20 and transcripts were weakly detectable on Days 30 and 45. In contrast, the other oTP-1 gene examined was weakly expressed on Days 13-20 only. Densitometric analysis of hybridization signals revealed that IFN o9 mRNA was detected in Day 75 placenta but only weakly detected in conceptus (Days 13-45) and adult lymphocytes. IFN o12 mRNA was abundant in lymphocytes relative to the other tissues examined. Collectively, these results demonstrate the existence of distinct oTP-1 and related type I IFN genes. The data suggest that these genes display differential, tissue-specific expression and developmental regulation during pregnancy.

Amino Acid Sequence↗
PubMed1993

Semen characteristics, testicular size, and reproductive hormone concentrations in mature duroc, meishan, fengjing, and minzhu boars.

Chinese breeds of swine are known for their reproductive prolificacy and are noted for large litter size. The current investigation evaluated reproductive components of three breeds of Chinese boars in comparison to a contemporary site breed common in the U.S. Semen from postpubertal Duroc, Meishan, Fengjing, and Minzhu boars was collected during four seasons of the year. After each semen collection and evaluation period, boars were weighted and placed in a restraining chute for testicular measurements and blood sampling for measurement of FSH, testosterone, and inhibin. Although Duroc boars were 2 mo younger than Chinese boars, initial and final body weight and paired testis volume in Durocs were greater (p < 0.05) than in Chinese boars. Total spermatozoa per ejaculate was similar for Duroc and Minzhu boars, but was lower (p < 0.05) in Fengjing and Meishan boars. Progressive motility and sperm morphological characteristics were not affected by breed of boar. Serum FSH concentrations were markedly higher (p < 0.01) in Meishan and Fengjing boars than in other breeds, and concentrations were nearly 8-fold higher in Meishan than in Duroc boars. Breed differences in serum inhibin were essentially the inverse of those observed for FSH, with Durocs exhibiting the highest inhibin concentrations and Meishans exhibiting the lowest. Testosterone values were not different between breeds. However, testosterone concentrations fluctuated with season, and serum testosterone was highest during the fall of the year in all breeds. These results indicated that some reproductive characteristics differ dramatically between Duroc and Chinese breeds of boars. Breed differences existed in body size, testis size, sperm per ejaculate, ejaculate volume, and serum FSH and inhibin concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

A novel role for GM-CSF: enhancement of pregnancy specific interferon production, ovine trophoblast protein-1.

Transient and massive production of ovine trophoblast protein-1 (oTP-1) by preimplantation conceptuses seems to be a critical event required for the establishment of successful pregnancy. We have previously demonstrated that one of several oTP-1 genes is predominantly expressed between days 13 and 20 of pregnancy and that this oTP-1 gene contains an AP-1 site, a transcription enhancer element, in the 5'-flanking region. We have obtained evidence, indicating a linkage between cytokine granulocyte macrophage-colony stimulating factor (GM-CSF) and conceptus production of the trophoblast interferon (IFN), oTP-1. These are: 1) oTP-1 production (both polypeptide and mRNA) is enhanced by the addition of GM-CSF in vitro and 2) GM-CSF mRNA is localized in the luminal and glandular epithelium of the uterine endometrium. Based on these observations, we propose that the massive amounts of oTP-1 produced during the period of pregnancy establishment is stimulated at least in part by maternal GM-CSF.

Animals↗
PubMed1993

Ovulation rate and embryonic survival in Chinese Meishan and white crossbred pigs.

Two component traits of litter size of pigs, ovulation rate and embryonic survival, were examined in Meishan and composite white crossbred gilts and sows. At puberty, an ovulation rate of 12.5 was similar for Meishan (118 +/- 3 d of age) and crossbred gilts (217 +/- 3 d of age). The number of corpora lutea (CL) increased (4.3 CL) markedly (P < .01) from puberty to the sixth estrous period (220 d of age) in Meishan gilts but increased (1.2 CL) slightly from puberty to the fourth estrous period in crossbred gilts. At 220 and 280 d of age, Meishan gilts had a greater (P < .01) number of CL than did crossbred gilts (220 d, 16.7 +/- .5 vs 12.7 +/- .4; 280 d, 16.5 +/- .7 vs 13.9 +/- .6 CL). Ovulation rate was greater (P < .01) in Meishan than in crossbred sows examined at 417 (18.1 +/- 1.2 vs 15.2 +/- .4 CL), 608 (20.1 +/- 1.3 vs 17.1 +/- .6 CL), and 735 d of age (24.6 +/- .8 vs 16.6 +/- .8 CL). Early embryonic survival was not significantly different in this study for Meishan and crossbred gilts (73 vs 81% , respectively). However, at 30 d of gestation embryo weight and length, placental weight, and allantoic fluid volume were less (P < .01) in Meishan than in crossbred gilts. The effect of small embryo size and reduced placenta weights and allantoic fluid volumes at d 30 of gestation on subsequent fetal survival and development (uterine capacity) is unknown but may be an enhancement to the prolificacy of Meishan pigs. This observation indicates the need for further study of fetal-maternal interactions after d 30 of gestation in both Meishan and European pigs because of potential breed differences in uterine and placental function.

Age Factors↗
PubMed1993

Association between low birth weight and increased adrenocortical function in neonatal pigs.

This study examined differences in adrenocortical function between low- and high-birth-weight female neonatal pigs. Pigs born to unilaterally hysterectomized, ovariectomized sows were grouped by birth weight; "small" were < or = 1.2 kg and "large" were > 1.2 kg. Pigs were cross-fostered such that each sow had six to eight pigs that were either small or large. At 3 or 7 d of age a blood sample was obtained by venipuncture, pigs were killed, and adrenocortical cells were isolated. Adrenal weights (milligrams/kilogram BW) in small pigs were 46% greater (P = .001) than those in large pigs at both ages. Compared with those in large pigs, plasma cortisol concentrations were 70% greater (P = .006) in small pigs at 3 d and 199% greater at 7 d of age. Sensitivity of adrenocortical cell response to ACTH was enhanced at both ages in small pigs (P = .001). Corticosteroid binding globulin (CBG) binding capacity in small pigs was 75% greater (P = .03) than that in large pigs at 3 d and 26% greater at 7 d of age. Significant negative correlations existed between birth weight and relative adrenal weight, plasma cortisol, slopes of in vitro adrenocortical cell response curves to ACTH, and CBG binding capacity, irrespective of birth weight group classification. Such data indicate an association between adrenal function during early neonatal life and birth weight in female pigs. The current study does not indicate whether increased adrenal function causes or merely reflects conditions associated with low birth weight. However, we hypothesize that increased adrenal function is initiated prenatally and causes some instances of low birth weight.

Adrenal Cortex↗
PubMed1993

Investigations into the control of litter size in swine: II. Comparisons of morphological and functional embryonic diversity between Chinese and American breeds.

It has been suggested previously that the increased litter size of the prolific Chinese Meishan pig may result from an increased littermate embryonic synchrony. This study compared embryonic diversity in Meishan and domestic (white line crossbred) sows. Third-parity Meishan sows (n = 14) and second-parity domestic sows (n = 15) were observed for estrus every 6 h and were hand-mated at 24 and 30 h after first observed estrus (d 0) to boars of the same breed. The sows were slaughtered on d 11.9 +/- .1 (mean +/- SEM). Embryos were flushed from each uterine horn and were individually sonicated, lyophilized, and frozen (-86 degrees C) until they were assayed for estradiol-17 beta (E2 beta), DNA, and protein content. Ovulation rate was higher (P < .001) in Meishan (24.9 +/- 1.1) than in domestic sows (15.2 +/- .7). The average littermate embryonic diameter was smaller (P < .001) for Meishan than for domestic sows, although morphological embryonic diversity (standard deviation for diameter) did not differ (P > .10) between the two breeds. In addition, for embryos of the same diameter, no differences (P > .10) in number of embryonic cells (micrograms of DNA/embryo) or in cell size (protein:DNA ratio) were observed for either breed. The more advanced (> 6 mm) embryos from Meishan sows contained less (P < .001) E2 beta (picograms/embryo) than did embryos of the same size from domestic sows. The prolificacy of the Meishan sow may result from both an increased ovulation rate and reduced E2 beta production by Meishan embryos.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Uterine function in Meishan pigs.

The Meishan pig provides a biological model with the genetic capacity to express a high prolificacy. This prolificacy can be partially attributed to a higher ovulation rate and a higher rate of prenatal survival at a given ovulation rate throughout gestation than in European breeds. Both early embryonic survival (factors inherent to the ovum and uterus, which occur before day 25 of gestation) and uterine capacity (factors inherent to uterine limitation, which occur from 30 days of gestation to parturition) may contribute to prenatal survival. Crossbreeding studies show that the prolificacy of Meishan pigs is primarily of maternal origin, but not whether the effects occur via the ovum, uterus or systemic factors. Although there have been few comparative studies on uterine function for prolific pigs, experiments relating to three general areas have been reported. During neonatal uterine development, endometrial gland development occurs shortly after birth in Meishan and European breeds. Tissue culture for 24 h showed that secretion of at least three uterine proteins (one identified as retinol-binding protein) increased in clear temporal association with development of the endometrial gland. The secretion of two additional proteins appears to change in a breed-specific manner. Although regulatory roles for uterine proteins remain to be defined, biochemical events associated with neonatal endometrial gland development may affect subsequent adult uterine function. During the time of maternal recognition of pregnancy or early gestation, reports suggest that uterine secretions are enhanced in Meishan pigs, which may partially explain their increased prolificacy. However, other studies show smaller embryo and placental weights at day 30 of gestation, suggesting that prolificacy of Meishan females is related to a maternal ability to control embryo/fetal and placental growth. During the later fetal period (uterine capacity) in European pigs, endometrial response to a crowded uterine environment is minimal, but the conceptus responds to a crowded uterine environment by altering placental function; similar experiments using Meishan pigs are in progress. Once the regulatory determinants of uterine function are understood, improvements can possibly be made in the reproductive efficiency of all swine.

Animals↗
PubMed1993

Early uterine development in pigs.

The capacity of pig uterine tissues to recognize and respond to maternal and conceptus signals determines whether pregnancy can be established and defines the environment in which embryonic and fetal growth occur. Limits of uterine capacity may be defined genetically. However, the extent to which functional uterine capacity approaches genetic potential may be determined, in part, by the success of organizational events associated with growth, morphogenesis and cytodifferentiation of uterine tissues. It is important, therefore, that these events be identified and evaluated with respect to their potential effect on adult uterine function. Histogenesis of the pig uterus begins prenatally, but is completed postnatally. Transformation of the uterine wall from histoarchitectural infancy to maturity occurs between birth and day 120. Morphogenetic events characteristic of the first 60 days of neonatal life proceed normally in gilts ovariectomized at birth. These events include appearance and proliferation of uterine glands, development of endometrial folds, and growth of the myometrium. Endometrial development during this period involves alterations in patterns of epithelial and stromal DNA synthesis, coordinated changes in the distribution and biosynthesis of extracellular matrix glycosaminoglycans and cell surface glycoconjugates, and specific alterations in patterns of uterine protein secretion. The ovary-independent, spatially coordinated nature of these events suggests that neonatal uterine development is regulated locally via dynamic cell-cell and cell-extracellular matrix interactions. The extent to which such potentially critical interactions must be preserved to ensure developmental success remains unknown. However, the normal pattern of ovary-independent cellular and molecular events associated with development of the uterine wall was disrupted by treating neonatal gilts with oestradiol valerate, and daily administration of oestrogen to gilts from birth to day 13 did not affect ovulation rate, but did reduce embryonic survival by 22% on day 45 of gestation in adults that were exposed to oestrogen neonatally. These observations support the idea that some organizational events associated with development of the neonatal uterine wall must be allowed to proceed without interruption to ensure that adult uterine function is not compromised. Efforts to identify specific developmental determinants of uterine capacity may be facilitated by examining the consequences of xenobiotically induced interruption of uterine development on adult uterine function. Such studies may also contribute to identification of uterine factors affecting embryonic survival and fetal growth.

Animals↗
PubMed1992

Steroidogenic enzyme expression in porcine conceptuses during and after elongation.

The following studies were performed to investigate levels of expression of steroidogenic enzymes in porcine conceptuses between days 12 and 21 postmating and to correlate these findings with estrogen levels in conceptus tissues. In the first experiment, levels of steroidogenic enzymes in individual day 12 blastocysts were examined by Western immunoblot analyses. In a second experiment, Northern blot, slot blot, and Western immunoblot analyses for 17 alpha-hydroxylase cytochrome P450 (P450(17) alpha) were performed on conceptus tissue pooled for each uterine horn of sows on days 12, 14, 16, and 21 postmating. On day 12, P450(17) alpha) protein was detectable in 6-mm blastocysts, with highest levels apparent in 10- to 15-mm (tubular) blastocysts. Filamentous blastocysts appeared to have less P450(17) alpha) protein than did littermate tubular blastocysts. Side-chain cleavage cytochrome P450 (P450scc) and aromatase cytochrome P450 (P450arom) followed a pattern similar to that of P450(17) alpha. 3 beta-Hydroxysteroid dehydrogenase was undetectable by Western analysis in blastocysts at the stages examined, but was detectable in placenta from fetuses at later stages of gestation. In pooled tissue, P450(17) alpha) protein and mRNA were greater in day 12 conceptuses than in conceptuses from all other days. However, transition from the tubular to the filamentous form on day 12 postmating was associated with a dramatic decline in the level of P450(17) alpha) mRNA. The conceptus 17 beta-estradiol concentration was highly correlated with immunoreactive P450(17) alpha) protein and hybridizable P450(17) alpha) mRNA over days 12, 14, 16, and 21 postmating. These data suggest that the decrease in blastocyst estrogen secretion occurring after the time of elongation in porcine conceptuses may be due to a decrease in P450(17) alpha expression.

3-Hydroxysteroid Dehydrogenases↗
PubMed1992

Effects of weaning on concentrations of inhibin in follicular fluid and plasma of sows.

Changes in plasma and follicular fluid concentrations of inhibin were examined in sows after weaning at 28-32 days post partum. From 0 to 48 h after weaning, inhibin concentrations were 200-300 times higher in follicular fluid from small (less than 4 mm) and medium-large (greater than or equal to 4 mm) follicles than in ovarian venous plasma. Inhibin concentrations increased in follicular fluid from medium-large follicles at 24 and 48 h after weaning; concentrations in ovarian venous plasma were positively correlated with the number of medium-large follicles (r = 0.40) and with ovarian venous plasma concentrations of oestradiol (r = 0.61). Blood samples were collected for 30 days from sows (n = 6) that exhibited oestrus within 5 days after weaning and from sows (n = 5) that remained anoestrous for 11 days after weaning. Plasma inhibin concentrations rose in oestrous and anoestrous sows by 12 h and continued to rise for 60 h after weaning. Plasma inhibin concentrations rose further and were higher at 3.5-4.5 days after weaning in oestrous sows than in sows that remained anoestrous. After oestrus, plasma inhibin concentrations declined. At weaning, plasma concentrations of follicle-stimulating hormone (FSH) were higher in sows that subsequently exhibited oestrus than in sows that remained anoestrous. After weaning, plasma concentrations of FSH declined in both groups, reached a nadir at 2.5 days, and increased gradually in anoestrous sows; oestrous sows exhibited an FSH surge at oestrus. Plasma FSH returned to preweaning concentrations in both groups of sows at Days 7-8.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Relationship of fetal position within the uterus to fetal weight, placental weight, testosterone, estrogens, and thymosin beta 4 concentrations at 70 and 104 days of gestation in swine.

Fetal intrauterine position relative to the sex of adjacent fetuses has an effect on reproductive performance in rodents. An experiment was conducted to determine whether sex of adjacent fetuses in utero has an influence on fetal and placental weights and whether the hormonal mechanisms documented in rodents are similar in fetal pigs. Sows were slaughtered at 70.1 +/- 1.7 d (n = 123) and 104.5 +/- .05 d (n = 135) of gestation. The fetuses and placentas were removed from the uterus and the position and sex of each fetus was recorded to indicate whether the fetus was between two males, two females, or a male and a female. Fetal blood was sampled for later hormonal analysis. At 70 d of gestation, male fetal and placental weights were heavier than those of females (P less than .05), but no differences were detected relative to the sex of adjacent fetuses. At 104 d of gestation, a fetus surrounded on each side in utero by fetuses of the opposite sex (two males or two females) was lighter in weight than a fetus surrounded by fetuses of the same sex (P less than .01). Differences in fetal weight due to the sex of adjacent fetuses were not related to placental function because placental weights were generally not different at 104 d of gestation. By 104 d of gestation, most placentas were not separated by necrotic regions and were in close apposition with surrounding placentas. No differences in growth or development could be related to hormonal effects (testosterone, estrone, or estrone sulfate) from surrounding fetuses.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Ovarian follicular changes after weaning in sows.

Three experiments investigated ovarian follicular development in sows whose litters were weaned at 28 to 31 d of lactation. Unilateral ovariectomy near the time of weaning was used to assess early follicular characteristics and to identify those sows that would not return to estrus within 10 d after weaning. This allowed segregation of and exclusion from the study those sows that had a prolonged interval from weaning to first estrus. In Exp. 1, 82 and 72% of the large follicles that were marked at 48 or 72 h after weaning (10 sows per time point) were subsequently identified as corpora lutea. In Exp. 2, sows (seven to nine per time point) were unilaterally ovariectomized at 0, 6, 12, 18, 24, or 48 h after weaning, and follicular fluid was evaluated for changes in steroid concentrations. Progesterone concentrations in fluid from medium-sized (4 to 6 mm) follicles increased by 6 h after weaning and then declined through 24 h concomitant with increases in testosterone and estradiol. For Exp. 3, follicular fluid and granulosa cells from individual follicles were obtained from sows (seven to nine per time point) at 0, 6, and 24 h after weaning. In follicular fluid, insulin-like growth factor I (IGF-I) concentrations were not correlated (P greater than .05) with concentrations of progesterone, testosterone, or estradiol, or with granulosa cell production of estradiol during culture in androstenedione-supplemented medium.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗