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Biomedical subjects

M C Lucy

Publications and source records attributed to M C Lucy.

At least 73 records · Page 4Linked to original sources
PubMed1998

Effects of controlled heat stress on ovarian function of dairy cattle. 1. Lactating cows.

The objective of this experiment was to determine the effects of controlled heat stress on ovarian function of lactating dairy cows. Estrus was synchronized (estrus = d 0), and cows were randomly assigned to either heat stress (n = 11; 29 degrees C, 60% relative humidity) or thermoneutral (n = 11; 19 degrees C, 60% relative humidity) treatment. For cows undergoing heat stress, ambient temperature (19 degrees C) was increased from d 11 to 13 of the estrous cycle (3.3 degrees C/d increase) and remained at 29 degrees C until d 21. Beginning on d 11, the growth and regression of ovarian follicles and corpora lutea were measured by using ultrasonography. Blood was collected daily by coccygeal venipuncture for measurement of serum concentrations of progesterone and estradiol. The second wave dominant follicle was more likely to ovulate in cows in the thermoneutral treatment than in cows undergoing heat stress (91 vs. 18% ovulation, respectively). Patterns of follicular growth in cows under-going heat stress were associated with decreased serum estradiol from d 11 to 21 and on the day of luteolysis. The average day of luteolysis was delayed by 9 d in heat-stressed cows. Conclusions were that follicular growth and development and luteolytic mechanisms were compromised in heat-stressed cows; as a result, luteolysis was delayed, and second wave dominant follicles did not ovulate.

Animals↗
PubMed1998

Effects of controlled heat stress on ovarian function of dairy cattle. 2. Heifers.

The objective of this experiment was to determine the effects of controlled heat stress on ovarian function of dairy heifers. Estrus was synchronized in Holstein heifers (estrus = d 0), and heifers then were randomly assigned to either heat stress (n = 10; 33 degrees C, 60% relative humidity) or thermoneutral (n = 11; 21 degrees C, 60% relative humidity) treatment. For heat-stressed heifers, ambient temperature was increased from thermoneutrality to heat stress (33 degrees C) between d 9 and 14 (2.4 degrees C/d increase) after the synchronized estrus and remained between 31 and 33.5 degrees C until d 22. From d 11 to 21, the growth and regression of ovarian follicles and corpora lutea were measured by using ultrasonography, and blood was collected daily for serum progesterone and estradiol analyses. The second wave dominant follicle was larger for the heifers in the thermoneutral environment than for heat-stressed heifers, and ovulation of the second wave dominant follicle occurred in 9 of 11 thermoneutral heifers. For 6 of 10 heat-stressed heifers, the second wave dominant follicle regressed and was replaced by an ovulatory third wave dominant follicle. Smaller follicular size in heat stressed heifers was associated with decreased serum estradiol concentrations between d 11 and 21. Serum concentrations of progesterone during the luteal phase were similar, but luteolysis was delayed in heat-stressed heifers compared with onset in heifers in the thermoneutral treatment. Conclusions were that heat stress inhibited the growth and function of the dominant follicle so that most of the heat-stressed heifers had three follicular waves and a delay in corpus luteum regression.

Animals↗
PubMed1997

Follicular function in lactating dairy cows treated with sustained-release bovine somatotropin.

The objective of this study was to determine the long-term, short-term, and residual effects of bovine somatotropin (bST) on ovarian function. Twenty-six Holstein cows were assigned to one of four groups and given either bST (500 mg) or saline for seven injection cycles (14 d between injections). Groups were 1) seven injection cycles of saline (control), 2) seven injection cycles of bST, 3) three injection cycles of bST followed by four injection cycles of saline, and 4) three injection cycles of saline followed by four injection cycles of bST. Beginning in the middle of the fourth injection cycle, an estrous cycle was synchronized for study. Serum concentrations of bST and insulin-like growth factor I were lowest during saline injections and increased after bST injections. Growth of the first wave dominant follicle was similar; however, start of the second follicular wave was approximately 48 h earlier in those cows treated with bST (groups 2, 3, and 4). Cows treated with somatotropin had a similar pattern of follicular growth, but tended to have more class 1 (3 to 5 mm) follicles and had more class 2 (6 to 9 mm) follicles than did the control cows. Peak concentrations of serum FSH were lower and occurred earlier for the cows treated with bST. There were no differences in the long-term or short-term effects of bST on ovarian function. Furthermore, cows that were switched from bST to saline (group 3) showed a residual effect of bST for up to 3 wk.

Animals↗
PubMed1997

Response of dairy cows treated with bovine somatotropin to a luteolytic dose of prostaglandin F2 alpha.

The objective of this study was to evaluate the timing of follicular waves in cows treated with bovine somatotropin (bST) by measuring ovarian responses to a luteolytic dose of PGF 2 alpha on d 12 of the estrous cycle. Thirty lactating cows (26 Holstein and 4 Guernsey) were assigned to receive bST (500 mg; n = 18) or saline (control; 1.5 ml; n = 12) every 14 d for three injection cycles. On d 12 of a synchronized estrous cycle, cows were injected with PGF 2 alpha to induce luteolysis. Following PGF 2 alpha, 9 cows ovulated from the dominant follicle during the first follicular wave (4 cows treated with bST and 5 control cows), and 14 cows ovulated from the dominant follicle during the second follicular wave (8 cows treated with bST and 6 control cows). Of the cows that ovulated during the second follicular wave, cows treated with bST had more class 3 follicles (> or = 10 mm) than did control cows. Concentrations of estradiol rose earlier after PGF 2 alpha injection in cows treated with bST than in control cows. This rise in estradiol was parallel to the development of dominant follicles. Serum concentrations of FSH were decreased in cows treated with bST. During the first and second estruses, equivalent numbers of cows treated with bST and control cows ovulated, but fewer cows treated with bST expressed estrus. These results are consistent with the hypothesis that cows treated with bST have reduced FSH, a faster turnover of dominant follicles, and differences in the timing of follicular waves. Treatment of cows with bST also increased the incidence of undetected estrus.

Animals↗
PubMed1996

Effects of administering progesterone at selected intervals after insemination of synchronized heifers on pregnancy rates and resynchronization of returns to service.

In 3 separate trials at 2 locations, dairy heifers (n = 396) were treated with a Controlled Internal Drug Release (CIDR) progesterone device for 9 d. On Day 7 of CIDR treatment, all heifers were injected with PGF(2alpha). Synchronized estruses were detected using a tailpaint and chalk (TPC) scoring system. An animal's tailhead was painted at device insertion, and this strip was covered with a contrasting color of chalk at device removal. Over all trials, 85.1% of the heifers were detected in estrus and were inseminated at 48 or 72 hours after CIDR removal. These synchronized and inseminated heifers were divided into the following treatment groups: 1) untreated controls, receiving no further treatment (n = 138); 2) post-insemination progesterone supplementation with a new (n = 59) or used (n = 29) CIDR device for Days 1 to 8 or 2 to 9, respectively, following insemination; or 3) resynchronization of return to service with a used CIDR device for Days 17 to 22 after insemination (n = 112). The pregnancy rate to first insemination in the control and resynchronized groups (Groups 1 and 3) was 46.4%, but decreased to 18.2% with the post-insemination progesterone supplementation. Resynchronization of returns to service (estrus detected 1 to 4 d following removal of second CIDR) occurred in 58.9% of all nonpregnant heifers in Group 3. In summary, CIDR devices used in conjunction with PGF(2alpha) effectively synchronize estrus in dairy heifers. Progesterone supplementation within 2 d of first insemination for 7 d suppressed fertility. Used CIDR devices inserted for Days 17 to 22 after first insemination resynchronized heifers not pregnant to first insemination.

Journal Article↗
PubMed1996

Expression of alternate growth hormone receptor messenger RNA in ovary and uterus of cattle.

Growth hormone (GH) receptor mRNA is found within the corpus luteum and endometrium of cattle. However, binding sites for placental lactogen (PL) but not GH are found within these tissues. The objectives were to isolate cDNA for the GH receptor within the reproductive tissues of cattle and to examine these cDNA as potential variants of the GH receptor that bind PL. Ten cDNA clones were isolated from a bovine endometrial cDNA library with a 32P-labeled cDNA of the GH receptor extracellular domain. On the basis of restriction enzyme digestion, 2 of the 10 cDNA clones contained exon 1. The DNA sequence of these clones was determined by dideoxy nucleotide sequencing. The exon 1 DNA sequence of each clone (exon 1B) was different from the previously reported exon 1 for the bovine GH receptor cDNA isolated from liver (exon 1A). Analyses of these cDNA sequences showed that exon 1B contained significant homology with placental forms of the GH receptor found in mouse and human. Unlike the human cDNA, the bovine cDNA isolated from endometrium contained an intact third exon. Amplification of GH receptor mRNA by reverse transcriptase polymerase chain reaction, with exon 1A- and 1B-specific forward primers, showed that exon 1B was expressed in liver, corpus luteum, ovary, endometrium, and myometrium. Exon 1A was found almost exclusively in liver, and little was found in reproductive tissues. The predicted initiation of protein coding for the GH receptor was within the second exon and was not changed by the splicing of the alternate first exon. This suggests that the alternate mRNA results in the expression of intact GH receptor protein that is similar to that found within liver. Alternative promoters (1B) may control the expression of the receptor outside the liver. Furthermore, mechanisms other than the differential splicing of GH receptor protein may dictate the specificity of PL binding within the endometrium and corpus luteum.

Animals↗
PubMed1996

Messenger ribonucleic acid expression for growth hormone receptor, luteinizing hormone receptor, and steroidogenic enzymes during the estrous cycle and pregnancy in porcine and bovine corpora lutea.

Growth hormone (GH) and luteinizing hormone (LH) are pituitary hormones involved in steroidogenesis in the corpus luteum (CL). The objectives of Experiment I were to determine mRNA expression for GH receptor (GHR) and LH receptor (LHR) in porcine luteal tissues during the estrous cycle and pregnancy and to relate changes in these receptor mRNA with changes in steroidogenic enzyme mRNA for cytochrome P450 side-chain cleavage enzyme (P450sec) and 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD). Ovaries were collected from gilts during the estrous cycle (day 10 [n = 3] and Day 19 [n = 3, regressed CL) and pregnancy (Day 25 [n = 3] and Day 44 [n = 3]). Tissues were frozen in liquid nitrogen and sectioned. Messenger RNA was detected by in situ hybridization, and relative mRNA amounts were determined by image analysis. The mRNA for GHR, LHR, P450sec, and 3 beta-HSD were detected in the CL on Day 10 of the estrous cycle. None of these mRNA were specific to cither large luteal cells (LLC) or small luteal cells (SLC). On Day 19 of the estrous cycle (regressed CL), mRNA for GHR, P450sec, and 3 beta-HSD were decreased (P < 0.01) whereas LHR mRNA disappeared (P < 0.01). During pregnancy, mRNA expression increased 2.1-, 1.4-, 1.4-, and 1.2-fold for GHR, LHR, P450sec, and 3 beta-HSD, respectively (P < 0.05). The luteal location of GHR mRNA in the pig did not agree with that found in our previous studies of GHR mRNA or protein in cattle. Therefore, the objective of Experiment 2 was to measure GHR mRNA by the use of in situ hybridization in bovine CL during the estrous cycle (Day 14; n = 2) and pregnancy (Day 25; n = 2). In situ hybridization demonstrated specific expression of GHR mRNA in the LLC of cattle. Furthermore, GHR mRNA increased 1.8-fold in CL on Day 25 of pregnancy compared with GHR mRNA on Day 14 of the estrous cycle (P < 0.01). In adjacent sections, the LHR mRNA was most highly expressed in clusters of SLC with 1.6-fold more mRNA on Day 25 of pregnancy compared with Day 14 of the estrous cycle (P < 0.01). These results suggest that: 1) mRNA for LHR, GHR, P450sec, and 3 beta-HSD are differentially regulated during the estrous cycle and pregnancy and 2) the cellular location of GHR differs for pigs and cattle, with highly specific expression of GHR in bovine LLC but not porcine LLC. This may suggest different functions for GH in the CL of these species.

3-Hydroxysteroid Dehydrogenases↗
PubMed1996

Messenger ribonucleic acid for insulin-like growth factors-I and -II, insulin-like growth factor-binding protein-2, gonadotropin receptors, and steroidogenic enzymes in porcine follicles.

Several aspects of growth, development, and steroidogenesis in ovarian follicles are controlled by the interaction of insulin-like growth factors (IGF-I and IGF-II) and gonadotropins (LH and FSH). The objective of this study was to determine the developmental stage and location at which mRNA for IGF, IGF-binding protein (IGFBP)-2, gonadotropin receptors, and steroidogenic enzyme genes are expressed within porcine follicles. Ovaries from pigs on Days 10 (n = 3; midluteal phase) and 19 (n = 3; preovulatory phase) of the estrous cycle were collected, frozen, and sectioned. The mRNA for IGF-I, IGF-II, IGFBP-2, LH receptor, FSH receptor, cytochrome P450 side-chain cleavage (P450scc), 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD), 17 alpha-hydroxylase (P45017 alpha), and aromatase (P450arom) were detected by in situ hybridization, and relative amounts were determined by image analysis. Expression of mRNA for IGF-I and IGF-II was cell specific (granulosa and theca interna cells, respectively) and increased with follicular size. The IGFBP-2 mRNA was expressed in greater amounts for theca interna cells than for granulosa cells. The pattern of expression for LH and FSH receptors diverged as follicles grew. For LH receptor, mRNA was detected in the theca interna cells of small antral follicles and in both the theca interna and granulosa cells of large antral follicles. Amount of LH receptor mRNA increased with follicular diameter. For FSH receptor, mRNA increased as follicles grew to a small antral size. However, FSH receptor mRNA disappeared in large antral follicles on Day 19 of the estrous cycle. Steroidogenic enzyme mRNA for 3 beta-HSD (theca interna cells), P450scc (theca interna cells), P45017 alpha (theca interna cells), and P450arom (granulosa cells) increased with follicular diameter. In summary, coordinated expression of IGF, IGFBP-2, gonadotropin receptors, and steroidogenic enzyme mRNA throughout different stages of follicular development was observed. Changes in mRNA suggested increased IGF-I and -II action and a switch from FSH to LH dependence in porcine preovulatory follicles.

3-Hydroxysteroid Dehydrogenases↗
PubMed1996

Effects of growth hormone and pregnancy on expression of growth hormone receptor, insulin-like growth factor-I, and insulin-like growth factor binding protein-2 and -3 genes in bovine uterus, ovary, and oviduct.

The effects of growth hormone (GH) and pregnancy on insulin-like growth factor (IGF)-I, IGF binding protein (IGFBP)-2, and IGFBP-3 mRNA in reproductive tissues were studied in cattle. Lactating dairy cows were inseminated at estrus and treated with 25 mg/day GH (n = 8) or saline (n = 8) for 16 days. Corpus luteum (CL), ovary (CL removed), oviduct, endometrium, and myometrium were collected at the end of treatment. Messenger RNA for GH receptor, IGF-I, IGFBP-2, IGFBP-3, and actin were measured by nuclease protection assays. The CL contained more GH receptor mRNA than the other reproductive tissues examined. Expression of IGF-I mRNA was highest in myometrium, with lower amounts found in endometrium; the CL expressed the least amount of IGF-I mRNA. The IGFBP-2 mRNA was most abundant in endometrium and least abundant in CL. Expression of IGFBP-3 mRNA was detected in all reproductive tissues examined. However, endometrium, a tissue that expressed the most IGFBP-2 mRNA, had the lowest amount of IGFBP-3 mRNA. The GH receptor mRNA was decreased in cows treated with GH whereas the mRNA for IGF-I, IGFBP-2, or IGFBP-3 was not changed. In the reproductive tissues evaluated, cows that contained a conceptus at tissue collection (pregnant) had higher amounts of IGF-I mRNA than did nonpregnant cows. In summary, the level of mRNA encoding GH receptor, IGF-I, IGFBP-2, and IGFBP-3 varied within the tissues examined, suggesting that these genes may play a variety of roles in the bovine female reproductive tract. Supplemental GH failed to change the expression of IGF-I, IGFBP-2, and IGFBP-3 mRNA, possibly because of low GH receptor mRNA levels in tissues other than CL. A direct action of GH on IGF-I, IGFBP-2, or IGFBP-3 gene expression within cow reproductive tissues was not supported because the amount of IGF-I, IGFBP-2, or IGFBP-3 mRNA was not altered by GH.

Actins↗
PubMed1996

Ovarian expression of insulin-like growth factor-I (IGF-I), IGF binding proteins, and growth hormone (GH) receptor in heifers actively immunized against GH-releasing factors.

Active immunization against GRF at 6 months of age delays puberty in beef heifers. The objectives of the present study were to determine whether active immunization against GRF at an earlier age would affect normal onset of puberty and follicular growth and to determine whether these changes were related to alterations in ovarian insulin-like growth factor I (IGF-I) or IGF binding protein (IG-FBP) messenger RNA (mRNA) levels. Heifers were immunized against human serum albumin (HSAi; n = 15) or against GRF conjugated to HSA (GRFi; n = 18) at 3 months of age. A third group of heifers was not immunized (CON; n = 16). Immunization against GRF delayed puberty beyond 13 months of age in 75% of treated heifers. Unilateral ovariectomy at 191 days of age revealed that the delay in puberty was associated with a reduction in the number of large ( > or = 7 mm in diameter) follicles. Large follicles were present in only 22% of GRFi heifers compared to 77% of HSAi heifers. The number of small ( < or = 3 mm in diameter) and medium (4 to 6 mm in diameter) follicles was not affected by GRFi. The percentage of 1- to 3-mm follicles that were atretic was not different between HSAi (65%) and GRFi (62%) heifers. Unilateral ovariectomy had no effect on age at puberty. Immunization against GRF decreased (P < 0.01) concentrations of IGF-I in serum (23 +/- 2 ng/ml) compared to HSAi heifers (109 +/- 11 ng/ml). IGF-I levels in follicular fluid (FFL) of medium and small follicles were also decreased by GRFi from 82 +/- 3 ng/ml in HSAi heifers to 48 +/- 6 ng/ml (P < 0.01). Levels of IGFBP-3 (determined by ligand blot analysis) in serum and FFL of small follicles were decreased by GRFi (P < 0.01). In contrast, IGFBP-2 serum levels were increased from 422 +/- 32 ng/ml in HSAi heifers to 657 +/- 6 ng/ml in GRFi heifers (P < 0.05). Likewise, IGFBP-2 levels in FFL from small and medium follicles were increased from 785 +/- 44 ng/ml to 926 +/- 44 ng/ml (P < 0.05). Ligand blot analysis indicated that IGFBP levels were lower in FFL from large vs. small follicles. The band intensities of IGFBP-4 and -5 were drastically reduced ( > 80%) while the decreases in IGFBP-2 and -3 were less marked ( < 50%). The decreased levels of IGFBP-5 in FFL from large follicles was not associated with an increase in proteolytic fragments detectable by immunoblot analysis. While mRNA transcripts for IGF-I, GH receptor, and IGFBP-2, -3, -4, and -5 were readily detectable in ovarian tissue, GRFi had no effect on ovarian levels of mRNA for each of these proteins. This suggests that the decrease in follicular development associated with GRFi may be related to changes in circulating IGF-I and/or IGFBPs.

Animals↗
PubMed1996

Effects of growth hormone, prolactin, insulin-like growth factors, and gonadotropins on progesterone secretion by porcine luteal cells.

Growth hormone (GH) and IGF-I have receptors within the corpus luteum (CL) and stimulate CL function. Our objective was to investigate the effects of GH, prolactin (PRL), IGF-I, IGF-II, LH, and FSH on progesterone secretion by porcine luteal cells during mid-pregnancy. Gilts (crossbred Yorkshire/Landrace) were slaughtered on d 44 of pregnancy and CL were collected. Large and small luteal cells (LLC and SLC, respectively) were obtained from dissociated CL and separated by elutriation. Luteal cells were incubated with 0, 1, 10, or 100 ng/mL of GH, PRL, IGF-I, IGF-II, LH, and FSH or combinations of 10 ng/mL of these reagents for 24 or 48 h. Culture media were harvested and concentrations of progesterone analyzed by radioimmunoassay. Growth hormone, PRL, and IGF-I increased (P < .05; 100 ng/mL dose) concentrations of progesterone in media of LLC. Insulin-like growth factor-II, LH, and FSH had no effect on progesterone in LLC cultures. In SLC cultures, GH, PRL, IGF-I, IGF-II, and FSH failed to stimulate progesterone secretion, whereas LH increased progesterone secretion (linear effect of dose; P < .05). Combinations (10 ng/mL each hormone) of GH and IGF-I or PRL and IGF-I increased progesterone secretion by LLC compared with control, GH, PRL, or IGF-I alone (P < .05). Similar combinations of GH or PRL with IGF-I had no effect on SLC. Conclusions are that GH and PRL are stimulatory to progesterone secretion by LLC (location of GH receptor) and SLC are responsive to LH during mid-pregnancy. Both GH and PRL are synergistic with IGF-I for increased progesterone secretion.

Animals↗
PubMed1996

Responses of porcine corpora lutea to somatotropin administration during pregnancy.

The effects of somatotropin (ST) on functions of porcine corpora lutea (CL) during pregnancy were investigated. Twenty-four crossbred (Yorkshire/Landrace) gilts from d 30 to 43 of pregnancy were injected daily with 5 mg of recombinant porcine somatotropin (rpST; n = 12) or 1 mL of saline (control, n = 12). Blood was collected on d 30, 37, and 43 for analyses of plasma progesterone. Gilts were killed on d 44 of pregnancy, and mRNA were isolated from CL, ovary, and liver. Messenger RNA expression for LH receptor, FSH receptor, ST receptor, 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD), and cytochrome P450 side-chain cleavage enzyme (SCC) were measured. Liver, CL, and ovary contained a 4.7-kb mRNA of ST receptor, but the liver contained more mRNA for ST receptor than did CL or ovary (.97 +/- .18, .47 +/- .04, and .25 +/- .04 units, respectively). There were two variants of LH receptor mRNA in CL (6.8 and 4.4 kb). The CL also contained a 1.8-kb mRNA of SCC and a 1.7-kb mRNA of 3 beta-HSD. No FSH receptor mRNA was detected in CL of the pig. The rpST treatment did not affect the mRNA level of ST receptor, 3 beta-HSD, SCC, or 4.4-kb mRNA of the LH receptor. The 6.8-kb mRNA for the LH receptor was decreased (P < .05) by rpST (.56 +/- .04 vs .78 +/- .05 units). Furthermore, concentrations of plasma progesterone decreased (P < .001) in gilts treated with rpST. Decreased luteal function was associated with decreased expression of LH receptor in rpST-treated gilts. The luteotropic effects of ST observed in vitro do not necessarily occur in vivo when gilts are administered rpST during pregnancy.

3-Hydroxysteroid Dehydrogenases↗
PubMed1995

Effects of somatotropin on the conceptus, uterus, and ovary during maternal recognition of pregnancy in cattle.

Effects of recombinant bovine somatotropin (rbST) on ovarian and uterine function and the production of components of the insulin-like growth factor (IGF) system were examined during the period of maternal recognition of pregnancy in cattle. Lactating dairy cows were treated with 25 mg/d rbST (n = 8) or saline (n = 8) for 16 d after estrus. Ovaries, uteri, and conceptuses were collected on Day 17 after estrus. The length (millimeters) of the conceptus was recorded. The concentration of IGF-I and the content of IGF-binding proteins (BP) in uterine flushings were determined. Corpora lutea (CL) were weighed, and the number of follicles (> or = 2 mm in diameter) were counted. Follicular fluid from the largest and second-largest follicles was assayed for the concentration of IGF-I, IGFBP, progesterone, and estradiol. The length of the conceptus and the total amount of IGF-I in uterine fluid were similar for rbST and control. Recombinant bST increased 1) the weight of the CL, 2) the number of largest follicles (10 to 15 mm in diameter), 3) the concentration of IGF-I in the follicular fluid, 4) the follicular fluid content of IGFBP of the largest estrogenic follicle, and 5) the quantity of IGFBP in uterine flushings. The concentration of progesterone in the follicular fluid tended to be increased in rbST-treated cows, whereas the concentration of estradiol was similar to that of control cows. The concentration of progesterone in plasma was similar for rbST compared with control. In conclusion, the administration of rbST in lactating dairy cows for 16 d after estrus did not alter the growth of the conceptus collected on Day 17. The greatest responses to rbST were found within the ovary, where rbST increased the weight of the CL and altered the amount of IGF-I and IGFBP in the follicular fluid.

Animals↗
PubMed1995

Effects of recombinant porcine somatotropin on placental size, fetal growth, and IGF-I and IGF-II concentrations in pigs.

The objective of this study was to determine the effects of recombinant porcine somatotropin (rpST) on placental size, fetal growth, and maternal and fetal IGF-I and IGF-II concentrations. Twenty-four pregnant gilts received daily injections of either 1 mL of saline (control) (n = 12) or 5 mg of rpST (n = 12) from d 30 to 43 of gestation. Gilts were slaughtered on d 44 of gestation, reproductive tracts were removed, and fetal weight and length, placental weight, and implantation length were recorded. There was no effect of rpST on fetal or implantation length. Placental weight increased with rpST administration (71.20 +/- 3.52 vs 58.35 +/- 3.41 g; P < .02), as did fetal weight (18.06 +/- .55 vs 16.44 +/- .53 g; rpST vs control, respectively; P < .05). Implantation lengths were partitioned into quartiles to determine the effect of rpST on fetuses with different implantation lengths. The effect of rpST of fetal weight was greater in the first quartile ( < 137.5 mm) than in the fourth quartile ( > 240 mm) (16.04 vs 13.86 g compared with 19.47 vs 18.21 g, respectively). Analysis using a modified Brody curve suggests that the effect of rpST treatment on fetal weight is equivalent to the effect of increasing implantation length by 58.8 mm. Administration of rpST numerically raised IGF-I (P = .07) and IGF-II (P = .12) concentrations in fetal serum. Although maternal serum IGF-I concentrations were similar at d 30, treatment with rpST increased these concentrations over time (77.76, 247.75, 267.85 vs 82.59, 79.59, 77.97 ng/mL on d 30, 37, 43, respectively; P < .001, SE = 14.09). Maternal IGF-II concentrations were also similar at d 30 but decreased over time with rpST treatment (265.78, 219.61, 191.05 vs 285.44, 284.72, 283.05 ng/mL; P < .03, SE = 14.03). Increased maternal IGF-I concentrations may exhibit negative feedback on maternal IGF-II concentrations. The more pronounced effect of rpST on growth in fetuses with shorter implantation lengths suggests that rpST may increase uptake or utilization of nutrients by fetuses. In addition, nutrient transfer across placental membranes may be enhanced by rpST.

Animals↗
PubMed1994

Extended function of the corpus luteum and earlier development of the second follicular wave in heifers treated with bovine somatotropin.

Effects of recombinant bovine somatotropin (bST) on growth of the corpus luteum (CL) and development of ovarian follicles were tested. Starting at estrus (Day=0), the following treatments were administered: control (saline injected Days 0 to 19, n=5); bST[0-9] (25 mg bST injected Days 0 to 9, saline injected Days 10 to 19, n=5); bST[10-19] (saline injected Days 0 to 9, 25 mg bST injected Days 10 to 19, n=5); and bST[0-19] (25 mg bST injected Days 0 to 19, n=6). Blood was collected daily for progesterone analysis, and ultrasound examinations were performed daily for measurement of follicles and CL. Compared with the heifers treated with saline, those treated with bST had larger CL and more progesterone during the early (</= Day 10) and late (Days 15 to 21) phases of the estrous cycle. At mid-cycle (Days 10 to 15), luteal tissue area and progesterone levels were similar for bST- and saline-treated heifers. Ovarian follicular growth was similar for bST- and saline-treated heifers during the first follicular wave. However, during recruitment for the second follicular wave (Days 10 to 14), second largest follicles emerged sooner (P<0.001), the number of Class-3 (>/=10 mm) follicles was greater (P<0.01) and largest follicles were smaller (P<0.001) in bST than in saline-treated heifers. Estrous cycle length and ovulation rate were similar for each group. In conclusion, bST increased initial development of the CL and extended its function. Furthermore, the second follicular wave was earlier with bST.

Journal Article↗
PubMed1994

The effect of a GnRH analogue on the dynamics of follicular development and synchronization of estrus in lactating cyclic dairy cows.

A GnRH analogue was used to synchronize ovarian follicular development prior to an injection of PGF(2alpha) for the synchronization of estrus in lactating Holstein cows. On Day 12 (estrus = Day 0) of the experimental cycle, cows (n = 8) were injected with 8 mug Buserelin (BUS group), followed by 25 mg PGF(2alpha) 7 d later (Day 19). Control cows (n = 7) received PGF(2alpha) on Day 12 (PGF group). Ovaries were scanned daily via ultrasonography, and plasma progesterone and estradiol concentrations were determined. Sizes of all visible follicles were recorded. Follicles were classified as small (3 to 5 mm), medium (6 to 9 mm), or large (> or = 10 mm). Between Days 12 and 16 of the cycle, the number of large follicles in PGF cows remained unchanged (1.2), whereas in the BUS group, the number of large follicles decreased from 1.3 on Day 12 to 0.5 on Day 15. Only 4 of 7 PGF cows ovulated a second-wave dominant follicle. In the BUS group, 7 of 8 cows ovulated a GnRH analogue induced dominant follicle that was first identified on Day 15. During the follicular phase (last 5 d prior to estrus), plasma progesterone declined in association with CL regression in both groups, and estradiol concentrations increased, reaching higher (P<.0.05) preovulatory peak concentration in BUS cows than in PGF cows (14.0 +/- 1.0 vs 10.4 +/- 1.1 pg/ml). The number of medium-size follicles was smaller and the number of small-size follicles tended to be higher in BUS cows than in the PGF-treated group. On the day of estrus, the size of the ovulatory follicle (16.1 vs 13.3 mm) and the size difference between the ovulatory and second largest follicle (11.4 vs 6.2 mm) were both larger in BUS cows than in PGF-treated cows, suggesting a more potent dominance effect of the ovulatory follicle in the BUS cows. This study suggests that a GnRH analogue can alter follicular development prior to synchronization of estrus with an injection of PGF(2alpha) in lactating dairy cows.

Journal Article↗
PubMed1994

Placental lactogen and somatotropin: hormone binding to the corpus luteum and effects on the growth and functions of the ovary in heifers.

The effects of recombinant bovine placental lactogen (rbPL) and recombinant bovine somatotropin (rbST) on development of ovarian follicles and CL were tested in heifers. Estrus (day = 0) was synchronized and heifers were treated (Days 0-21) with either saline (control; n = 7), rbST (25 mg/day; n = 6), or rbPL. (50 mg/day; n = 8). Blood was collected daily for analyses of progesterone, estradiol, ST, PL, and insulin-like growth factor (IGF)-I; ultrasound was performed daily for measurement of follicles and CL. PL in plasma (mean +/- SE; ng/ml) averaged 4.1 +/- 0.2 for rbPL-treated heifers, and ST in plasma (ng/ml) averaged 2.7 +/- 0.3 for rbST-treated heifers. IGF-I in plasma (ng/ml) was increased for rbST-treated (198 +/- 10; p < 0.001) and rbPL-treated (143 +/- 9; p < 0.06) heifers compared to controls (117 +/- 9). After Day 9 of the estrous cycle, heifers treated with rbPL had larger CL (p < 0.001) and more progesterone in plasma (p < 0.001) than controls, whereas rbST-treated heifers were intermediate for these measures. Largest follicles were decreased in size (mm) throughout the estrous cycle for rbPL-treated heifers (12.9 +/- 0.4) compared to controls (14.2 +/- 0.5; p < 0.06) or heifers given rbST (14.0 +/- 0.5; p < 0.11). After Day 17 (preovulatory period), concentrations of estradiol in serum (pg/ml) were decreased for rbST-treated (2.7 +/- 0.3; p < 0.01) and rbPL-treated (2.9 +/- 0.2; p < 0.02) heifers compared to controls (3.8 +/- 0.3).(ABSTRACT TRUNCATED AT 250 WORDS)

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