Biomedical subjects

H A Garverick

Publications and source records attributed to H A Garverick.

At least 37 records · Page 2Linked to original sources

PubMed1999

Molecular mechanisms regulating follicular recruitment and selection.

Ovarian follicular growth and development is an integrated process encompassing both extraovarian signals, such as gonadotrophins and metabolic hormones, and intraovarian factors. Follicular development has been classified into gonadotrophin-independent and -dependent phases. In the latter, FSH provides the primary drive for follicular recruitment and LH is required for continued development of follicles to the preovulatory stage. A transient increase in circulating FSH precedes the recruitment of a group of follicles, and these recruited follicles are characterized by expression of mRNAs encoding P450scc and P450arom in granulosal cells. As follicles mature, there is a transfer of dependency from FSH to LH, which may be part of the mechanism(s) involved in selection of follicles for continued growth. Indeed, changes in the pattern of expression of mRNA for gonadotrophin receptors and steroid enzymes within follicular cells appear to be closely linked to changes in peripheral concentrations of gonadotrophins. The mechanism of selection of dominant follicles still requires clarification, but seems to be linked to the timing of mRNA expression encoding LHr and 3 beta-hydroxysteroid dehydrogenase (3 beta HSD) in granulosal cells. Additional intraovarian systems, including the ovarian IGF and activin/inhibin systems, also exert a role. For example, it appears that the development of follicular dominance in cows is associated with the FSH-dependent inhibition of the expression of mRNA encoding insulin-like growth factor binding protein 2 (IGFBP-2) in granulosal cells. In conclusion, the integration of these endocrine signals and intraovarian factors within follicles determines whether follicles continue to develop and become dominant or are diverted into apoptotic pathways leading to atresia.

3-Hydroxysteroid Dehydrogenases↗

PubMed1998

Follicular dominance in cattle is associated with divergent patterns of ovarian gene expression for insulin-like growth factor (IGF)-I, IGF-II, and IGF binding protein-2 in dominant and subordinate follicles.

A decrease in insulin-like growth factor (IGF) binding protein (BP) amount occurs within the follicular fluid of dominant ovarian follicles. At the same time, concentrations of follicular fluid IGF-I do not change. The mRNA for IGF-I, IGF-II, IGFBP-2, and IGFBP-3, in dominant and subordinate follicles were measured to determine if changes in IGF or IGFBP gene expression are associated with follicular dominance. Heifers were ovariectomized during a follicular wave, either during early-dominance (emerging dominant follicle, 9 mm diameter) or mid-dominance (established dominant follicle, 14-16 mm diameter). Follicles were classified as either dominant (DF), subordinate (SF), or not-recruited (NRF; small antral follicles). mRNA was localized by in situ hybridization and measured by image analyses. The IGF-I mRNA (granulosa cells) was greatest in DF and increased in DF, SF, and NRF from early- to mid-dominance. Likewise, IGF-II mRNA (theca cells) was greatest in DF compared with SF or NRF. The IGFBP-2 mRNA (granulosa cells), however, was nearly undetectable in DF, whereas adjacent SF expressed abundant IGFBP-2 mRNA. The NRF were not uniform in their IGFBP-2 expression because only 5 of 13 NRF had IGFBP-2 mRNA. The IGFBP-3 mRNA (granulosa cells) was found only in two NRF, suggesting that local synthesis is not a predominant source of follicular fluid IGFBP-3. These data show that changes in gene expression for IGFBP-2 are opposite to those for IGF-I or IGF-II. Increased IGF-I and IGF-II mRNA and decreased IGFBP-2 mRNA within the DF may be one mechanism leading to follicular dominance. The opposite pattern of IGFBP-2 gene expression in SF and some NRF may lead to follicular atresia.

Animals↗

PubMed1998

Expression of steroidogenic acute regulatory protein messenger ribonucleic acid is limited to theca of healthy bovine follicles collected during recruitment, selection, and dominance of follicles of the first follicular wave.

Expression of mRNA encoding steroidogenic acute regulatory protein (StAR) in bovine follicles during recruitment and selection was examined. Dairy heifers (4-5/time period) were ovariectomized at 12, 24, 36, 48, 60, 72, 84, or 96 h after initiation of the first follicular wave (Time 0) after estrus. Follicles were collected and stored at -80 degrees C until sectioning. Expression of StAR mRNA was localized by in situ hybridization and quantified by image analysis. Expression of StAR mRNA was first detected in theca interna of antral follicles as small as 0.5 mm in diameter and increased with increasing follicular size (>/= 4 mm; r = 0.75; p < 0.001). StAR mRNA was undetectable in granulosa of healthy follicles at any size or stage of follicular wave examined. However, granulosa or luteinized granulosa of some advanced or late atretic follicles expressed StAR mRNA. During recruitment, StAR mRNA expression in theca cells was similar among recruited follicles (4-8 mm). During selection of dominant follicles (36-48 h), StAR mRNA was expressed in theca of more than one follicle (7-9 mm); therefore, expression of StAR mRNA may not be associated with dominant follicle selection. StAR mRNA in theca was higher (p < 0.05) at 48 h after initiation of the first follicular wave than at 12, 24, and 36 h, and it remained elevated thereafter through 96 h. Dominant follicles expressed more (p < 0.01) StAR mRNA in theca than did subordinate healthy follicles. Healthy follicles expressed higher (p < 0.05) StAR mRNA in theca than atretic follicles. In summary, levels of StAR mRNA increased in theca with stage of follicular wave and size of follicles. Follicular atresia was associated with reduced expression of StAR mRNA in theca cells. The results indicate that expression of StAR mRNA in theca may not be the primary limiting factor for follicular recruitment and selection.

Animals↗

PubMed1998

Expression of steroidogenic enzyme and gonadotropin receptor genes in bovine follicles during ovarian follicular waves: a review.

Ovarian follicular development in cattle is characterized by waves of growth during the prepubertal and postpartum periods and during estrous cycles. Each wave of follicular growth is characterized by recruitment of a cohort of follicles 4 to 5 mm in diameter. From the cohort, one follicle is selected for continued growth and becomes dominant. If luteolysis occurs during the growth phase of dominant follicles, final maturation and ovulation occurs. If luteolysis does not occur during the growing and maintenance phase of follicles, the fate is atresia. Changes in mRNA expression for the gonadotropin receptors (FSHr and LHr), key steroidogenic enzymes (cytochrome P450 side chain cleavage [P450scc], cytochrome P450 17alpha-hydroxylase-[P450c17], cytochrome P450 aromatase [P450arom], and 3beta-hydroxysteroid dehydrogenase [3beta-HSD]), and growth factors (IGF-I and -II) and their binding proteins (IGFBP) have been associated with different stages of follicular growth and atresia. In general, expression of mRNA for the gonadotropin receptors, steroidogenic enzymes, and steroidogenic acute regulatory protein (StAR) increase with progressive follicular development and is highest when dominant follicles approach maximum size. Expression of mRNA declines rapidly and becomes low or undetectable in atretic follicles. The IGF-I (granulosal cells) and IGF-II (thecal cells) are increased, whereas IGFBP-2 (granulosal cells) is reduced, in dominant follicles. Recruitment of a cohort of follicles is associated with initiation of expression of mRNA for P450scc and P450arom in granulosal cells. Selection of dominant follicles is associated with expression of mRNA for LHr and 3beta-HSD in granulosal cells. Thus, changes in gene expression likely are important to recruitment, selection, dominance, and atresia in ovarian follicles.

3-Hydroxysteroid Dehydrogenases↗

PubMed1997

Changes in messenger ribonucleic acid encoding luteinizing hormone receptor, cytochrome P450-side chain cleavage, and aromatase are associated with recruitment and selection of bovine ovarian follicles.

The objective of this study was to investigate changes in expression of mRNAs encoding FSH receptor (FSHr), LH receptor (LHr), cytochrome P450 side-chain cleavage (P450(scc)), cytochrome P450 17alpha-hydroxylase (P450(c17)), and cytochrome P450 aromatase (P450(arom)) during recruitment and selection of bovine ovarian follicles. Dairy heifers (4-5 per group) were ovariectomized at 12, 24, 36, 48, 60, 72, 84, or 96 h after initiation of the first follicular wave following estrus as determined by ultrasonography (Time 0 = initiation of follicular wave; mean +/- SEM = 42.0 +/- 2.6 h after estrus). Expression of mRNAs encoding FSHr, LHr, P450(scc), P450(c17), and P450(arom) was detected by in situ hybridization and quantified by image analysis. Antral follicles were classified as healthy or atretic. Healthy follicles expressed higher (p < 0.01) amounts of mRNAs for gonadotropin receptors and steroidogenic enzymes than did atretic follicles, and expression of LHr, FSHr, P450(scc), P450(c17), and P450(arom) increased (p < 0.01) with follicular size and stage of the follicular wave. Expression of mRNAs for P450(scc), P450(arom), and LHr was time- and size-dependent during recruitment and selection. During recruitment, expression of mRNAs for P450(scc) and P450(arom) was first detected in granulosa cells of 16 of 21 of the follicles 4-6 mm in diameter at 12 h. At 24 and 36 h, almost all follicles 6-9 mm in diameter, but not those 4-5 mm in diameter, expressed both P450(scc) and P450(arom) mRNA in the granulosa cells. At 48 h and thereafter, P450(scc) and P450(arom) mRNA were expressed predominantly in one healthy large follicle per cow with a few exceptions. Expression of LHr mRNA was first detected in granulosa cells at 36 h and was always found in granulosa cells of one follicle > or = 8 mm per cow with exception of one cow at 36 h (no expression) and another two cows, one each at 36 and at 84 h (expression in 2 follicles). In addition, LHr mRNA expression in the granulosa cell layer was limited to follicles that also expressed mRNAs for P450(scc) and P450(arom) in the granulosa cells. In summary, follicular recruitment in cattle was associated with expression of P450(scc) and P450(arom) mRNA within granulosa cells, and the process of follicular selection was associated with initiation of LHr mRNA expression in granulosa cells.

Animals↗

PubMed1997

Expression of messenger ribonucleic acid (mRNA) encoding 3beta-hydroxysteroid dehydrogenase delta4,delta5 isomerase (3beta-HSD) during recruitment and selection of bovine ovarian follicles: identification of dominant follicles by expression of 3beta-HSD mRNA within the granulosa cell layer.

The objective of the present study was to examine changes in expression of mRNA encoding 3beta-hydroxysteroid dehydrogenase delta4,delta5 isomerase (3beta-HSD) during recruitment and selection of bovine ovarian follicles. Dairy heifers (4-5/time period) were ovariectomized at 12, 24, 36, 48, 60, 72, 84, or 96 h after initiation of the first follicular wave (Time 0) following estrus. Expression of 3beta-HSD mRNA was localized by in situ hybridization and quantified by image analysis. Expression of 3beta-HSD mRNA was first detected in theca interna cells of preantral follicles with a well-developed theca layer and in granulosa cells of follicles > or = 8 mm in diameter. Regardless of stage of follicular wave, expression of 3beta-HSD mRNA in granulosa cells of follicles > or = 8 mm was correlated with follicular size (r = 0.665; p < 0.01). The 36-h time period appeared to be a transition period for selection since dominant follicles were detected by size and expression of 3beta-HSD mRNA in some cows but not in others. By 48 h after wave initiation, dominant follicles could be identified by both size and expression of 3beta-HSD mRNA. Expression of mRNA for 3beta-HSD in theca cells was higher (p < 0.05) at 24 h than at 12 h and remained elevated thereafter through 96 h. In contrast to theca cells, expression of mRNA for 3beta-HSD was undetectable within granulosa cells at 12 and 24 h. At 36 h, 3beta-HSD mRNA was expressed in granulosa cells of healthy follicles > or = 8 mm, and expression was higher (p < 0.05) at 48 h compared with 36 h. Expression of 3beta-HSD mRNA levels increased further in granulosa cells (p < 0.05) at 84 and 96 h compared to 48 h. Upon detection of mRNA for 3beta-HSD in granulosa cells, high levels of expression were always found in one (dominant) follicle/cow with the exception of two cows at 36 and 84 h that expressed 3beta-HSD mRNA in two large healthy follicles. Expression of 3beta-HSD mRNA was also detectable in granulosa cells of a few large atretic follicles in which remnant granulosa cells appeared to be luteinized. Healthy follicles expressed higher (p < 0.05) levels of 3beta-HSD mRNA in both theca and granulosa cells than did atretic follicles. Expression of 3beta-HSD mRNA in theca cells was higher (p < 0.01) in dominant follicles than in other subordinate healthy follicles. These results indicate that only selected dominant follicles express 3beta-HSD mRNA within granulosa cells, and expression increased in both thecal and granulosa cells during the follicular wave. Therefore, expression of 3beta-HSD mRNA within granulosa cells may be associated with the mechanism of selection of the dominant follicle during a follicular wave and may be required for maximum steroid production during follicular dominance.

Animals↗

PubMed1997

Pregnancy rates per artificial insemination for cows and heifers inseminated at a synchronized ovulation or synchronized estrus.

Two synchronization protocols were tested for lactating dairy cows and heifers. Nulliparous dairy heifers (13 to 23 mo; n = 155) and primiparous and multiparous dairy cows (60 to 289 d postpartum; n = 310) were assigned randomly to two treatments. Controls received 25 mg of PGF2 alpha and were artificially inseminated according to the a.m.-p.m. rule following detected estrus. All controls that were not detected in estrus were injected with 25 mg of PGF2 alpha at 14-d intervals until artificial insemination (AI) at a detected estrus or until timed AI at 72 to 80 h after a third sequential injection of PGF2 alpha. Treated cows and heifers received a protocol that used GnRH and PGF2 alpha to synchronize ovulation (Ovsynch). Cows and heifers that were treated with Ovsynch were injected i.m. with 100 micrograms of GnRH at a random stage of the estrous cycle. Seven days later, cows and heifers in this group received 25 mg of PGF2 alpha followed by a second injection of 100 micrograms of GnRH 30 to 36 h later. Subsequently, the treated cows and heifers received AI 16 to 20 h after the second injection of GnRH. Pregnancy rates per AI were similar (38.9% vs. 37.8%) for control cows and cows treated with the Ovsynch protocol, respectively. However, pregnancy rate per AI was greater for control heifers (74.4%) than for heifers treated with Ovsynch (35.1%). Evaluation of serum progesterone concentrations at each hormonal injection indicated that the first injection of GnRH synchronized luteal function of lactating dairy cows but not of heifers. In summary, one fixed-time AI at a synchronized ovulation provided similar pregnancy rates per AI as did AI following the a.m-p.m. rule after estrus had been induced by PGF2 alpha in lactating cows, but the fixed-time AI was not effective for heifers because of the lack of synchronization.

Animals↗

PubMed1997

Ovarian follicular cysts in dairy cows.

Ovarian follicular cysts are anovulatory follicular structures that occur in 10 to 13% of dairy cows. This review focuses upon the dynamics of cyst growth, development, and persistence as well as on associated endocrine and cellular mechanisms. During the estrous cycle of cows, two to four waves of follicular growth occur. From a cohort of recruited follicles, one is selected for continued growth and dominance while the other undergo atresia and regress. In contrast, cysts have long been thought to be static structures that persist for extended periods. Although cysts can persist for extended periods, most regress over time and are replaced during subsequent follicular waves. The next dominant follicle either ovulates or develops into a new cyst. The recruitment of a cohort of follicles from which a cyst develops and the growth rate of cysts to ovulatory size are similar to ovulatory follicular waves, but the cyst continues to grow for a longer period. The interval between waves of follicular growth is longer for cows with cysts than for cows with normal estrous cycles. Each wave is preceded by a transient increase in circulating FSH. Near the time of cyst development and persistence, the concentration of FSH is not different from that during normal estrous cycles. Serum concentrations of LH and estradiol-17 beta are higher in cows that develop cysts than in cows that do not. Conversely, hypothalamic content of GnRH is lower in cows with cysts. Thus, cysts are dynamic structures, and their development and lifespan are likely associated with altered hypothalamic-hypophysial-ovarian function.

Animals↗

PubMed1996

Ontogenies of messenger RNA encoding tissue inhibitor of metalloproteinases 1 and 2 within bovine periovulatory follicles and luteal tissue.

Tissue inhibitors of metalloproteinases 1 and 2 (TIMP-1 and TIMP-2) are important regulators of extracellular matrix remodeling and also possess growth factor activity. The objective of these studies was to characterize TIMP-1 and TIMP-2 mRNA expression by bovine periovulatory follicles/ corpora hemorrhagica (Experiment 1) and luteal tissue (Experiment 2). In Experiment 1, beef heifers (n = 27) were ovariectomized at-16 (n = 6), 0 (n = 5), 8 (n = 3), 16 (n = 4), 24 (n = 4), or 48 (n = 5) hr relative to a gonadotropin-releasing hormone induced gonadotropin surge (40 hr after prostaglandin F2 alpha-induced luteolysis). Total cellular RNA was isolated from the large steroidogenically active follicle or corpus hemorrhagicum obtained from each animal, and the expression of TIMP-1 and TIMP-2 mRNA was subsequently examined by northern and dot blot analysis. The expression of TIMP-1 or TIMP-2 mRNa did not differ in preovulatory follicles collected at -16 vs. 0 hr. Concentrations of both TIMP-1 and TIMP-2 mRNA (picograms per microgram of tissue DNA) were increased (P < 0.05) at 8 hr postgonadotropin surge, had declined to presurge levels by 24 hr (P < 0.05), and were increased (P < 0.05) in corpora hemorrhagica collected at 48 hr after a gonadotropin surge. In Experiment 2, corpora lutea were collected from beef heifers on Days 4, 10, 15 (n = 4 each), or 19 (n = 3) postestrus (Day 0 = estrus). Concentrations of TIMP-1 mRNA (picograms per microgram of tissue DNA) were greater in corpora lutea collected on Day 4 (P < 0.05) vs. Day 10, 15, or 19. Concentrations of TIMP-2 mRNA increased (P < 0.05) from Day 4 to 15 and decreased (P < 0.05) by Day 19. We conclude that: 1) during the periovulatory period, the ontogenies of TIMP-1 and TIMP-2 mRNA expression are similar, whereas 2) during luteal phase, TIMP-1 mRNA expression is maximal during the early luteal phase, whereas concentrations of TIMP-2 mRNA peak during the midluteal phase. TIMP-1 and TIMP-2 may play important roles in the regulation of extracellular matrix remodeling during the periovulatory period and the subsequent luteal phase.

Animals↗

PubMed1995

Use of umbilical cord clamps for ovariectomy in cows.

Bilateral ovariectomy was performed in 45 beef cows through a left paralumbar fossa laparotomy. Umbilical cord clamps were used to ligate the ovarian pedicle and were found to provide reliable hemostasis. Examination of the uterus by palpation per rectum 10 to 33 days after surgery revealed that the procedure resulted in minimal formation of adhesions, and, in all but 1 cow, the uterine horns were freely movable.

Animals↗

PubMed1995

Characterization of ovarian follicular cysts and associated endocrine profiles in dairy cows.

It is generally accepted that ovarian follicular cysts (cysts) are nonovulatory follicular structures that contribute to extended calving intervals. Follicle/cyst dynamics and the etiology of cysts are unclear. The present study was conducted to characterize follicle/cyst dynamics and to define endocrine changes (etiology) associated with cyst development. Thirty-two dairy cows were studied: controls (n = 6), cows with spontaneously occurring cysts (n = 14), and cows in which cysts were induced by exogenous steroid treatment (n = 12). Ovaries of cows were scanned daily by ultrasonography to record follicle/cyst dynamics. Blood was collected to determine endocrine changes associated with follicle/cyst life span. Three ovarian responses in cows with cysts were observed: persistence of cysts, turnover of cysts, or spontaneous recovery (self-recovered; turnover of cysts and replacement with a follicle that ovulated). Mean maximum size of cysts was larger (p < 0.05) than that of ovulatory follicles (2.80 +/- 0.19 vs. 1.60 +/- 0.05 cm). Mean interval from initial detection of follicle/cyst wave to detection of a new follicle/cyst wave in cows with cysts was longer (13.0 +/- 1.1 days; p < 0.05) and more variable (6 to 26 days; p < 0.05) than in controls (8.5 +/- 0.5 days and 6-14 days, respectively). Cysts grew at the same rate as follicles but continued to grow for an additional period of time. A transient increase in FSH preceded detection of all follicle/cyst waves.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

Expression of follicle-stimulating hormone and luteinizing hormone receptor messenger ribonucleic acids in bovine follicles during the first follicular wave.

The objective of the present study was to characterize expression of mRNAs encoding FSH and LH receptors during follicular development and at different stages of the first follicular wave in cattle. Following estrus, groups of heifers (3-5 per group) were ovariectomized on the day of initiation of the first follicular wave (as determined by ultrasonography; Day 0), or on Days 2, 4, 6, 8, or 10 after initiation of the first wave. FSH and LH receptor mRNAs were detected within follicles > or = 4 mm and in some smaller follicles by in situ hybridization and were quantified by image analysis. FSH receptor mRNA was expressed in granulosa cells of all growing follicles, starting in some follicles with only one layer of granulosa cells. Irrespective of day of the follicular wave, the level of expression of FSH receptor mRNA in granulosa cells of healthy antral follicles ranging from 0.5 to 14 mm in diameter did not vary significantly with follicular size (r = 0.02, p > 0.10). Expression of LH receptor mRNA was first observed in theca interna cells of follicles shortly after antral formation. Irrespective of day of the follicular wave, the levels of LH receptor mRNA in theca interna cells of healthy antral follicles ranging from 0.5 to 14 mm increased with follicular size (r = 0.39, p < 0.01). In granulosa cells, LH receptor mRNA was expressed only in healthy follicles > 9 mm in diameter and was first observed in the dominant follicles collected on Day 4. Expression of mRNA for LH receptor, but not for FSH receptor, changed (p < 0.01) with the stage of the first follicular wave.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

Expression of messenger ribonucleic acid encoding cytochrome P450 side-chain cleavage, cytochrome p450 17 alpha-hydroxylase, and cytochrome P450 aromatase in bovine follicles during the first follicular wave.

The objective of the present study was to investigate changes in the expression of messenger RNAs (mRNAs) encoding cytochrome P450 side-chain cleavage (P450scc), cytochrome P450 17 alpha-hydroxylase (P450c17), and cytochrome P450 aromatase (P450arom) at different stages of the first follicular wave of the bovine estrous cycle. Groups of heifers (three to five per group) were ovariectomized on the day of initiation of the first follicular wave (as determined by ultrasonography, day 0) or on days 2, 4, 6, 8, and 10 after initiation of the first follicular wave following estrus. Expression of mRNAs encoding P450scc, P450c17, and P450arom was detected by in situ hybridization and quantified by image analysis. P450scc mRNA was localized to theca interna cells of large preantral follicles and also to granulosa cells of follicles 4 mm or greater in diameter. mRNA for P450c17 was localized exclusively to theca interna cells, whereas P450arom mRNA was localized to granulosa cells of follicles 4 mm or greater in diameter. There were changes in mRNA levels for all three enzymes in thecal and/or granulosa cells at different times of the first follicular wave. Before identification of the dominant follicle (i.e. on days 0 and 2), there was no change in expression of P450scc and P450c17 mRNAs, whereas expression of P450arom mRNA was higher on day 2 than on day 0. Maximal mRNA levels for all three enzymes were observed on day 4. By day 6, P450scc and P450c17 mRNA levels were reduced compared to those on day 4, whereas P450arom mRNA levels remained elevated. On day 8, mRNA levels for all three enzymes were reduced. After initiation of the second follicular wave (day 10), dominant follicles from the first wave were at an advanced stage of atresia. P450scc and P450arom mRNAs were undetectable in granulosa cells, and very low levels of P450scc and P450c17 mRNAs were observed in theca interna cells. Before identification of the dominant follicle, mRNA levels for all three enzymes were similar within a cohort of follicles. Therefore, expression of these enzymes may not be associated with the mechanism of selection of the dominant follicle during a follicular wave.

Animals↗

PubMed1994

Pattern of protein production by bovine corpora lutea during luteolysis and characterization of expression of two major secretory products of regressing corpora lutea.

Although the decrease of progesterone in serum and in luteal tissue during luteal regression is well characterized, relatively little is known about changes in proteins produced by the corpus luteum during this time. The first objective was to examine changes in patterns of protein secretion that might be associated with functional and structural luteal regression. The second objective was to characterize the expression of two major secretory products of regressing corpora lutea. Thirty normally cyclic heifers were randomly assigned at day 15-16 of the oestrous cycle (oestrus = day 0) to be ovariectomized at 0 h (no PGF2 alpha; n = 5) or at 4, 8, 12, 24 or 48 h after PGF2 alpha-induced luteal regression (n = 5 per time point). Total cellular RNA was isolated from tissue frozen at the time of ovariectomy. Thin slices (< 1 mm) of tissue were placed in methionine-deficient minimum essential media with [35S]methionine and placed in a humidified CO2 incubator at 38 degrees C. Media and tissues were collected 6 h later. Changes in profiles of secreted proteins were analysed by one-dimensional SDS-PAGE. A number of proteins (relative molecular mass ranging from 14,300 to 200,000) were produced by luteal tissue at each time point (0-48 h). The major secretory proteins had relative molecular masses of approximately 21,500, 28,200, 43,700 and 46,000. Secretion of the relative molecular mass 46,000 protein(s) increased (P < 0.05) between 4 and 24 h after PGF2 alpha injection compared with the 0 h group.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Estrus, ovulation, luteinizing hormone, and suckling-induced hormones in mastectomized cows with and without unrestricted presence of the calf.

Angus x Hereford multiparous cows were assigned to four treatments: 1) mastectomized+calf weaned at birth (MCW; n = 7); 2) mastectomized+calf presence restricted to noninguinal contact (MCR; n = 7); 3) mastectomized+unrestricted calf presence (MCP; n = 7); and 4) udder-intact cows+unrestricted calf presence (UICP; n = 8). Except for MCW cows, cow-calf pairs were penned together individually from parturition (d 0) until d 35 when calves were weaned. On d 7, calves in MCP and UICP treatments were separated overnight from their dams, and before and upon reunion, blood samples were collected from the cows to assess changes in oxytocin, cortisol, and prolactin. Calves in the MCP and UICP treatments attempted to or suckled their dams for a similar duration upon reunion, respectively. Concentrations of cortisol and percentage of change in oxytoxin and prolactin were increased (P < .05) for up to 12 min in MCP cows after reunion with their calves. Average concentrations of serum LH in samples collected on d 14, 21, 28, and 35 did not differ in noncyclic cows among treatments within day postpartum (except for greater [P < .05] LH in MCW cows on d 21). However, MCP cows had more (P < .05) LH pulses (d 21), greater (P < .05) variability in LH pulses (d 21), greater (P < .05) variability in LH concentrations, and greater (P < .05) average maximum concentrations of LH than UICP cows after d 14. Intervals to first ovulation were similar in MCW and MCR cows but shorter (P < .01) than those in MCP and UICP cows. Attempted suckling of mastectomized dams by their calves was associated with increased serum cortisol and percentage of increase in serum oxytocin and prolactin. Despite increased LH in MCP cows, intervals to first ovulation did not differ from those of UICP cows.

Animals↗

PubMed1993

Basis of norgestomet action as a progestogen in cattle.

Norgestomet is the progestational component present in Syncro-Mate-B, which is used to synchronize estrus in cattle. In post-partum cows, luteal phases anticipated to be short following first ovulation are of normal length when cows are pretreated with norgestomet. Because Syncro-Mate-B is used experimentally as a progestogen to affect uterine function, these studies were conducted to investigate how norgestomet acts at the level of the uterus. Receptor binding assays and a sensitive estrogen bioassay in tissue culture were used to address the possibility that some effects of norgestomet might be mediated through interaction of this compound with steroid hormone receptors other than the progesterone receptor (rP). The source of receptors was high-speed cytosol, prepared from bovine uterine endometrium, which was obtained from cyclic cows. Results of single-point and complete competition analyses comparing norgestomet and progesterone indicated that norgestomet competed even more effectively than did progesterone for specific binding of [3H]progesterone to rP. Results of similar studies, which compared the abilities of norgestomet and diethylstilbestrol to compete with [3H]estradiol for binding by uterine endometrial estrogen receptors (rE), provided no evidence for norgestomet competitive binding to rE. In MCF-7 breast cancer cell bioassays, norgestomet showed weak estrogenic activity, but only at concentrations greater than 1 micromolar. Finally, norgestomet did not compete with [3H]triamcinolone acetonide when present in an 100-fold excess, and only competed with [3H]dexamethasone for binding by endometrial glucocorticoid receptors (rG) when present in the micromolar range. We conclude that, at the concentrations used in synchronizing estrus, norgestomet interacts with bovine endometrium as a progestogen and that its biological actions occur through binding of this compound to rP present in target tissues.

Animals↗

PubMed1993

Detection of mRNA for inhibin alpha- and beta A-subunits in bovine ovarian tissues and the effect of in vivo administration of GNRH.

The aims of these studies were to determine which types of bovine ovarian tissue contain mRNA for inhibin/activin subunits and whether administration of GnRH influences concentration of these mRNAs. In experiment (exp.) one, cows in the luteal phase of the estrous cycle were given prostaglandin F2 alpha (PGF2 alpha) to induce luteal regression and injected after 40 hr with saline (n = 5) or 100 micrograms GnRH (n = 6). Ovaries were removed 6 hr later. In exp. two, unilaterally ovariectomized (OVX) heifers (n = 33) in the luteal phase of their estrous cycle were given PGF2 alpha to induce luteal regression. Twelve heifers were OVX without injection of GnRH at 24 (n = 6) or 40 hr (n = 6) after PGF2 alpha. The remaining heifers (n = 21) were given 100 micrograms GnRH at 40 hr after PGF2 alpha injection and OVX 8 (n = 4), 16 (n = 5), 24 (n = 6) or 48 (n = 6) hr after GnRH injection. Total cellular RNA was isolated from large follicles (exp. one and two), small-medium follicles and stromal tissue (SMS) and corpora lutea (CL; exp. one) tissues and analyzed by dot blot and Northern blot techniques by hybridizing with cDNA probes for human inhibin/activin alpha- and beta A-subunits. Large follicles were classified as steroidogenically active (EA) if follicular fluid (FF) concentration of estradiol-17 beta (E2) was greater than progesterone (P4), or if P4 and E2 concentrations in FF were greater than 100 ng/ml, and estrogen inactive (EI) if FF concentration of E2 and P4 did not satisfy these criteria. In exp. one, mRNA for the alpha-subunit was primarily expressed in EA follicles, and detectable in EI follicles, SMS, and CL while beta A-subunit mRNA was detected only in large EA follicles and a few SMS samples. The mRNA (x +/- SEM fmoles/mg DNA) for both subunits of inhibin/activin was higher (P < .05) in EA follicles from GnRH-treated cows (alpha = 210.2 +/- 38.6; beta A = 376.9 +/- 41.0) than in EA follicles from control cows (alpha = 102.5 +/- 28.6; beta A = 170.8 +/- 57.6). Concentration of mRNA for the alpha-subunit of inhibin in other ovarian tissues was not different (P > .10) between saline and GnRH treatments.(ABSTRACT TRUNCATED AT 400 WORDS)

Activins↗

PubMed1993

Female reproductive physiology and endocrinology of cattle.

Maximizing reproductive efficiency is of major economic importance to dairy and beef producers. The development of new and improved methods of increasing reproductive performance depends on our understanding of the physiologic and endocrinologic mechanisms controlling the reproductive process. This article reviews the mechanisms associated with puberty, estrous cycles, pregnancy, parturition, and postpartum return to estrus.

Anestrus↗