Biomedical subjects

J J Ford

Publications and source records attributed to J J Ford.

At least 37 records · Page 2Linked to original sources

PubMed2001

Increased plasma follicle-stimulating hormone concentrations in prepubertal gilts from lines selected for increased number of corpora lutea.

Plasma follicle-stimulating hormone (FSH) was evaluated in gilts from two studies in which ovulation rate was increased through direct selection for number of corpora lutea (CL) to determine whether selection for ovulation rate affected FSH secretion during prepubertal development. In the first study, 76 control and 110 selected gilts of University of Nebraska gene pool lines were bled twice during prepubertal development. Plasma FSH concentrations were greater (P < 0.05) at 53 (13.5%) and 75 (21.3%) d of age in selected than in control gilts. In the second study, 254 control gilts, 261 gilts from a line selected for ovulation rate, and 256 gilts from a line selected for uterine capacity were bled at three prepubertal ages. Plasma FSH was greater (P < 0.05), relative to controls, on d 34 (> 24%), 55 (> 13%), and 85 (> 10%) in White Composite gilts selected for either increased ovulation rate or for greater uterine capacity. Unilateral ovariectomy and hysterectomy were performed at 160 d of age on random gilts in these three lines (n = 377); weights of these organs were evaluated to determine whether selection affected their development. Ovarian and uterine weights were less (P < 0.01) in the control than in the ovulation rate line. Subsequently, ovulation rate was determined during pregnancy (n > or = 130 gilts/line). Controls had fewer (P < 0.01) CL (14.6) than gilts of the ovulation rate line (17.7) but numbers similar (P > 0.10) to those of gilts of the uterine capacity line (14.7). Within each line, plasma FSH only on d 85 correlated positively with subsequent ovulation rate (P < 0.03, 0.001, and 0.08; r = 0.17, 0.30, and 0.15 for control, ovulation rate, and uterine capacity lines, respectively). Ovarian weight at 160 d of age also correlated with subsequent ovulation rate (P < 0.03 and 0.001; r = 0.23 and 0.38) in control and ovulation rate gilts but not in uterine capacity gilts (P > 0.10; r = 0.11). Gilts selected for increased number of CL, in two independent studies, had greater concentrations of FSH during prepubertal development than respective controls. The modest but significant, positive association of FSH at 85 d of age with subsequent ovulation rate provides additional support for using plasma FSH in prepubertal gilts to indirectly select for ovulation rate.

Animals↗

PubMed2000

Luteinizing hormone secretion as affected by hypophyseal stalk transection and estradiol-17beta in ovariectomized gilts.

The objectives were to determine hypothalamic regulation of pulsatile luteinizing hormone (LH) secretion in female pigs and the biphasic feedback actions of estradiol-17beta (E(2)-17beta). In the first study, the minimum effective dosage of E(2)-17beta that would induce estrus in ovariectomized gilts was determined to be 20microg/kg body weight. In the second study, ovariectomized gilts were assigned randomly on day 0 to treatments: (a) hypophyseal stalk transection (HST), (b) cranial sham-operated control (SOC), and (c) unoperated control (UOC). On day 3, gilts from each group received a single i.m. injection of either E(2)-17beta (20microg/kg body weight) or sesame oil. Blood was collected from an indwelling jugular cannula at 15min intervals for 3h before (day -2) and after treatment (day 2) from HST, SOC and UOC gilts. On day 3, blood was collected at 2h intervals for 12h after E(2)-17beta or sesame oil injection and at 4h intervals thereafter for 108h. Pulsatile LH secretion in all gilts 2 days after ovariectomy exhibited a frequency of 0.9+/-0.06peaks/h, amplitude of 1.3+/-0.13ng/ml, baseline of 0.8+/-0.07. Serum LH concentrations from SOC and UOC gilts were similar on day 2 and profiles did not differ from those on day -2. In HST gilts pulsatile LH release was abolished and mean LH concentration decreased compared with controls (0 versus 0.9+/-0. 06peaks/h and 0.77+/-0.03 versus 1.07+/-0.07ng/ml, respectively; P<0. 05). E(2)-17beta or sesame oil did not affect serum LH concentration in HST gilts, and LH remained constant throughout 120h (0.7+/-0. 07ng/ml). In SOC and UOC control gilts, E(2)-17beta induced a 60% decrease (P<0.05) in LH concentration within 12h, and LH remained low until 48h, then increased to peak values (P<0.05) by 72h, followed by a gradual decline to 120h. Although pituitary weight decreased 31% in HST gilts compared with controls (228 versus 332mg, P<0.05), an abundance of normal basophils was evident in coronal sections of the adenohypophysis of HST comparable to that seen in control gilts. The third and fourth studies determined that hourly i. v. infusions of LHRH (2microg) and a second injection of E(2)-17beta 48h after the first had no effect on the positive feedback action of estrogen in UOC. However, in HST gilts that received LHRH hourly, the first injection of E(2)-17beta decreased (P<0.05) plasma LH concentrations while the second injection of E(2)-17beta failed to induce a positive response to estrogen. These results indicate that both pulsatile LH secretion and the biphasic feedback action of E(2)-17beta on LH secretion depend on hypothalamic regulatory mechanisms in the gilts. The isolated pituitary of HST gilts is capable of autonomous secretion of LH; E(2)-17beta will elicit direct negative feedback action on the isolated pituitary gland if the gonadotropes are supported by exogenous LHRH, but E(2)-17beta at high concentrations will not induce positive feedback in isolated pituitaries. Thus, the direct effect of E(2)-17beta on the pituitary of monkeys cannot be mimicked in pigs.

Animals↗

PubMed2000

Identification and characterization of a new allele for the beta subunit of follicle-stimulating hormone in Chinese pig breeds.

During evaluation of follicle-stimulating hormone-beta (FSHB) expression in anterior pituitary glands by an RNase protection assay (RPA), the expected fragment of 205 nucleotides at positions 759-963 was not detected in one boar that had moderate plasma and pituitary FSH concentrations. After subcloning and sequencing, mRNA from this boar lacked an 11-bp fragment (5'-CATTTGGAAAC-3') at nucleotide positions 807-817 of the 3'-untranslated region (3'-UTR, D allele). Wild-type FSHB (WT allele) was present in pituitary RNA and genomic DNA in both Meishan (MS) and White Composite (WC) pigs; whereas the D allele was present only in MS pigs (P < 0.01; 5/6 MS vs. 0/6 WC). Also, we found the D allele in five other Chinese breeds but absent in ten American Landrace, 11 Yorkshire and 17 Berkshire pigs. Additionally, the D allele had one silent nucleotide change in the coding region plus six, single nucleotide changes in the 3'-UTR.

3' Untranslated Regions↗

PubMed2000

Comparison of plasma FSH concentration in boars and gilts from lines selected for ovulation rate and embryonal survival, and litter size and estimation of (co)variance components for FSH and ovulation rate.

The objective of this research was to determine whether plasma concentration of FSH was genetically correlated with ovulation rate and thus was a useful trait for indirect selection. Blood samples were collected from 619 animals from five lines of pigs. Line I was selected for increased index of ovulation rate and embryonal survival, and Line C was its randomly selected control. Pigs sampled from Lines I and C were from generations 12 and 13. Pigs from three additional lines that were derived from eighth-generation pigs of Lines I and C also were used. These lines were Line C2, a randomly selected control derived from Line C, Line COL, derived from Line C, and Line IOL, derived from Line I; each of these lines was selected an additional five generations for increased ovulation rate and increased litter size. A single blood sample was collected from each pig between 46 to 63 (d 58), 86 to 98 (d 90), 110 to 133 (d 124), and 147 to 153 (d 150) d of age. The heritability of ovulation rate was .28 and heritabilities of plasma concentration of FSH at d 58, 90, 124, and 150 were .41, .25, .12, and 0, respectively. Genetic correlations between ovulation rate and d-58, d-90, and d-124 plasma concentration of FSH were .31, .23, and 0, respectively. Line I gilts had greater estimated breeding values for plasma concentration of FSH at d 58 and 90 than Line C gilts (P < .01). Line COL gilts had greater estimated breeding values for plasma concentration of FSH at d 58 than Line C2 gilts (P < .01). Line I boars had greater estimated breeding values for plasma concentration of FSH at d 90 than Line C boars (P < .05). Even though genetic correlations were low, selection for increased plasma concentration of FSH was estimated to be 93% as effective in changing ovulation rate as direct selection because selection for FSH can be practiced in both sexes. Thus, selection for increased plasma concentration of FSH seems to be a practical method for increasing ovulation rate in pig breeding programs without using laparoscopy.

Animals↗

PubMed2000

Relationships of gonadotropins, testosterone, and cortisol in response to GnRH and GnRH antagonist in boars selected for high and low follicle-stimulating hormone levels.

Considerable variation exists in the serum levels of gonadotropins in boars; this results in differential testicular function. Boars (Chinese Meishan, European White composite, and crosses of the two breeds) selected for high and low circulating FSH concentrations were used to define possible differences in pituitary sensitivity to GnRH and GnRH antagonist and gonadal and adrenal responses. After a 2-h pretreatment sampling period, boars were injected with GnRH or GnRH antagonist and repetitively sampled via jugular cannula for changes in serum concentrations of FSH, LH, testosterone, and cortisol. In response to varying doses of GnRH or GnRH antagonist, FSH, LH, or testosterone changes were not different in high- or low-FSH boars. Declines in LH after GnRH stimulation were consistently faster in boars selected for high FSH. Chinese Meishan boars had considerably higher cortisol concentrations than White composite boars (132.2 +/- 28.5 vs 67.4 +/- 26.8 ng/mL, respectively; P < .01). When select high- and low-gonadotropin Meishan:White composite crossbreds were sampled, cortisol levels were elevated but comparable between the two groups (126.5 +/- 13.7 vs 131.4 +/- 13.4 ng/mL, respectively). After GnRH antagonist lowered LH concentrations, administration of hCG resulted in increased testosterone and cortisol concentrations. Although testosterone concentrations remained high for 30 h, cortisol concentrations returned to normal levels within 10 h after hCG injection. The mechanism by which boars selected for high gonadotropins achieve increased levels of LH and FSH may not be due to differences in pituitary sensitivity to GnRH but to differences in clearance from the circulation.

Animals↗

PubMed2000

GnRH antagonist inhibition of gonadotropin and steroid secretion in boars in vivo and steroid production in vitro.

The hormone GnRH has a stimulatory effect on gonadotropin synthesis and secretion. The objective of the first study was to evaluate concentrations of FSH and LH in plasma of boars after successive treatment with SB75, a GnRH antagonist. Thirteen boars greater than 1 yr of age (eight White Composite [WC] and five Meishan [MS]) were injected once daily with SB75 (10 microg/kg of body weight) for 4 d. Plasma concentrations of LH and testosterone (T) decreased after 1 h from the first dose of SB75. After 12 h of treatment, LH gradually returned to pretreatment concentrations, but T remained suppressed (< 2 ng/mL) until after the last injection of SB75. There was a modest, but significant, reduction in FSH during treatment with SB75. The prolonged inhibitory effect of SB75 on suppression of plasma T concentrations, in the presence of pretreatment concentrations of LH, implied direct effects of SB75 at the testis. In the second experiment, testicular tissue from adult boars was incubated in the presence of three doses of human chorionic gonadotropin (hCG; 0, .5, and 5 IU) with SB75 (250 ng/mL) or with Deslorelin, a GnRH agonist (500 ng/mL). Samples of media were collected every hour for 3 h, and concentrations of T and estrone (E1) were determined by RIA. Concentrations of T and E1 increased with time in response to treatment with hCG. Co-treatment with SB75 decreased media concentrations of T (P < .01) and E1 (P < .03) compared to controls (77.9 vs 85.7 +/- 2.0 and 4.7 vs 5.3 +/- .2 ng/g). In contrast, treatment with Deslorelin had no effect on the amount of T (P > .50) or E1 (P > .26) released with all dosages of hCG. These results indicate that a GnRH antagonist has a direct effect on the testis, decreasing amounts of T and E1 released from the Leydig cells; however, treatment with a GnRH agonist had no direct effect on release of these gonadal steroids. Thus, it remains unresolved whether the site of action of GnRH antagonist on testicular steroidogenesis is through a testicular GnRH receptor or through some other mechanism.

Animals↗

PubMed1999

Identification of quantitative trait loci affecting female reproductive traits in a multigeneration Meishan-White composite swine population.

A multigeneration crossbred Meishan-White composite resource population was used to identify quantitative trait loci (QTL) for age at first estrus (AP) and the components of litter size: ovulation rate (OR; number of ova released in an estrous period) and uterine capacity (UC). The population was established by reciprocally mating Meishan (ME) and White composite (WC) pigs. Resultant F1 females were mated to either ME or WC boars to produce backcross progeny (BC) of either 3/4 WC 1/4 ME or 1/4 WC 3/4 ME. To produce the next generation (F3), 3/4 WC 1/4 ME animals were mated to 1/4 WC 3/4 ME animals yielding half-blood (1/2 WC 1/2 ME) progeny. A final generation (F4) was produced by inter se mating F3 animals. Measurements for AP and OR were recorded on 101 BC, 389 F3, and 110 F4 gilts, and UC data were from 101 BC and 110 F4 first parity litters. A genomic scan was conducted with markers (n = 157) spaced approximately 20 cM apart. All parental, F1, BC, and F4 animals but only 84 F3 animals were genotyped and included in this study. The QTL analysis fitted a QTL at 1-cM intervals throughout the genome, and QTL effects were tested using approximate genome-wide significance levels. For OR, a significant (E[false positive] < .05) QTL was detected on chromosome 8, suggestive (E[false positive] < 1.0) QTL were detected on chromosomes 3 and 10, and two additional regions were detected that may possess a QTL (E[false positive] < 2.0) on chromosomes 9 and 15. Two regions possessed suggestive evidence for QTL affecting AP on chromosomes 1 and 10, and one suggestive region on chromosome 8 was identified for UC. Further analyses of other populations of swine are necessary to determine the extent of allelic variation at the identified QTL.

Animals↗

PubMed1999

Effects of the thymic peptide thymulin on in vitro and in vivo testicular steroid concentrations in white composite and Meishan boars.

Immuno-peptides may have positive or negative effects on gonadal steroidogenesis, but few have been tested outside of rodent species or in vivo. In Exp. 1, thymulin, a secreted nonapeptide of the thymus, was incubated (1, 10, 100, or 1,000 ng/mL) with testicular minces (sampled at 3, 6, or 12 h) from Chinese Meishan boars of high gonadotropin/testicular steroidogenic function (n = 8) and White composite boars of European origin (n = 8 ) to test the hypothesis that thymulin could augment hCG stimulation of testicular androgen concentrations. Thymulin alone had few effects on androgen concentrations (testosterone, dehydroepiandrosterone+dehydroepiandrosterone sulfate [DHEA+DHEASO4]) in Meishan boar testicular incubates. In minces from White composites incubated with thymulin, testosterone concentrations were generally below control values (P<.05), but DHEA+DHEASO4 concentrations were unaffected. Thymulin had no effect on estrone concentrations in testicular incubates of White composite boars but stimulated estrone concentrations in Meishan testicular incubates. Thymulin plus hCG increased testosterone (3 and 6 h of incubation; P<.05) but not DHEA+DHEASO4 concentrations in White composite testicular incubates. Thymulin plus hCG did not alter androgen or estrogen concentrations from control values in Meishan testicular incubates. In Exp.2 with a protocol similar to that of Exp. 1 for testicular minces from White composite boars (n = 30), thymulin increased testosterone concentrations during the early incubation period (1 to 3 h; P<.05) and depressed testosterone concentrations at later times (6 h; P<.05). Thymulin synergized with hCG in stimulating increases in testosterone and DHEA+DHEASO4 concentrations (P<.05) but had no effect on estrone concentrations in vitro. Thymulin was tested in vivo in boars from three genetic lines selected for high, medium, or normal circulating LH concentrations (Meishan, select White composites, and control White composites, respectively). Injection of thymulin i.v. (4.4, 44.4, or 444.4 ng/kg BW) generally increased circulating testosterone concentrations (2 to 3 h later; P<.01), but the response was dependent on the boar's general circulating LH concentrations and dose of thymulin. Overall results from these studies support the hypothesis of a thymulin augmentation of LH stimulation of androgen increases in vitro and in vivo in the testis of boars.

Animals↗

PubMed1998

Concentrations of gonadotropins, estradiol and progesterone in sows selected on an index of ovulation rate and embryo survival.

The objective of this study was to determine concentrations of follicle stimulating hormone (FSH), luteinizing hormone (LH), progesterone (P4) and 17beta-estradiol (E2) in sows from a line selected on an index which emphasized ovulation rate (Select) and from a control line. A further classification of the sows in each line was made according to the estimated number of ovulations during an estrous cycle. Sows in the Select line were ranked into a high (HI) or low group (LI) when their estimated number of ovulations were 25 or more and 14 to 15, respectively. Sows of the control line were classified into groups as high (HC) or low (LC) when the estimated values for ovulation rate were 14-15 and 8-9 ovulations, respectively. Blood samples were collected every 12 h during a complete estrous cycle and samples were analyzed for concentrations of FSH and LH. Samples collected every 24 h were assayed for P4 and E2. Mean concentrations of FSH, LH, P4 and E2 did not differ (P > 0.10) between lines or between HI and LI or HC and LC groups. Selection of pigs for ovulation rate and embryonal survival did not affect concentrations of FSH, LH, P4 and E2 in sows during the estrous cycle.

Animals↗

PubMed1998

Relationships of liver weight, cholesterol, albumin and alpha2-macroglobulin concentrations with ovarian function in swine.

In two genetic swine models selected for diversity in ovulation rates (White composite controls and ovulation rate selection line, n = 131; 1/2 White composite: 1/2 Meishan crossbreds, n = 387), a positive relationship was established with liver weight and ovulation rate (P < 0.01). Serum changes of cholesterol, albumin and alpha2-macroglobulin were monitored during various stages of the luteal phase and follicular phase (days 17 and 19 of the estrous cycle; 1/2 White composite: 1/2 Meishan gilts). Serum cholesterol concentrations increased with liver weights (r = 0.19; P < 0.01) and corpora lutea numbers (r = 0.14; P < 0.01). Albumin concentrations were negatively correlated with corpora luteal numbers (r = -0.3; P < 0.01) but had no relationship with liver weight. Serum concentrations of alpha2-macroglobulin were not related to liver weight or corpora lutea numbers. Circulating concentrations of cholesterol and alpha2-macroglobulin increased with day of the estrous cycle (P < 0.01). Testosterone concentrations were inversely related to circulating cholesterol concentrations during the estrous cycle, but testosterone concentrations on day 17 or 19 of the cycle were unrelated to corpora lutea numbers. Concentrations of estrone on day 17 or 19 (as an index of follicles destined to ovulate) were also not related to numbers of corpora lutea. Many interactions between liver and ovarian function involving metabolic and endocrine systems are plausible, but defined mechanisms resulting in coordinate increases in liver weight and ovulation rates are presently unelucidated.

Animals↗

PubMed1998

Positive association between expression of follicle-stimulating hormone beta and activin betaB-subunit genes in boars.

This study tested our hypothesis that inhibin/activin (I/A) betaB subunit and not follistatin (FS) gene expression relates positively to plasma FSH concentrations in the anterior pituitary gland of boars. Mature crossbred boars (n = 12) were selected for divergence in plasma FSH concentrations, and their anterior pituitary glands were evaluated for expression of the FSHbeta, I/A ssB, FS, calmodulin, and GnRH receptor (GnRH-R) genes by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) and/or RNase protection assays (RPAs). Expression of I/A ssB was greater (p < 0. 01) in the six boars with high FSH than in the six with low FSH; expression of the I/A betaB-subunit gene was positively correlated to that of the FSHbeta gene (RT-PCR: r = 0.96; p < 0.01; RPA: r = 0.68; p < 0.05). In contrast, expression of the FS (p > 0.10), GnRH-R (p > 0. 08), and calmodulin (p > 0.10) genes was similar in the two groups of boars. Additionally, expression of the FSHbeta gene was correlated positively with pituitary and plasma FSH concentrations (r = 0.69 and 0.88, respectively; p < 0.05). These results support the hypothesis that activin B is partially responsible for elevated FSH concentrations in boars. Furthermore, the expression difference of the calmodulin gene observed previously between Meishan and White Composite boars represents a breed difference unrelated to FSH.

Activins↗

PubMed1998

A comprehensive evolutionary analysis based on nucleotide and amino acid sequences of the alpha- and beta-subunits of glycoprotein hormone gene family.

On the basis of nucleotide sequences of the coding region and their predicted amino acid sequences, 58 glycoprotein hormone subunit genes were compared, aligned and used to construct phylogenetic trees for this family. The analysis included 17 alpha-subunits, eight TSH beta-, six FSH beta-, 17 LH beta/CG beta-, four fish gonadotropin (GTH)-I beta-, five fish GTH-II beta- and one additional fish GTH beta-subunit. The reliability of the phylogenetic trees was probed with the bootstrapping test. Our results indicated that: both the alpha- and beta-subunits of the family diverged from a common ancestral gene about 927 million years ago, the initial precursor of the beta-subunit duplicated to give rise to the LH beta and a second hormone, the latter then duplicating to FSH beta and TSH beta, so that FSH beta is related more to TSH beta than to LH beta; and bony fish GTH-I beta is highly related to mammalian FSH beta, whereas the bony fish GTH-II beta is more related to mammalian LH beta. For scientific consistency and convenience, we propose that the following nomenclature be adopted, all fish gonadotropins of type I be classified as FSH and all type II be classified as LH hormones. In addition, on the basis of results from this and other studies, we propose an evolutionary history for this glycoprotein hormone family. Reconstruction of the evolutionary history of this family would not only provide clues to understanding thyrotropin and gonadotropin functions, but would also allow further revision of the present nomenclature of the gonadotropins in fish.

Amino Acid Sequence↗

PubMed1997

Effect of gonadotropin treatment on size, number, and cell proliferation of antral follicles in cows.

To determine the effects of gonadotropins on the size, number, and cell proliferation of antral ovarian follicles, cows received FSH-P or vehicle beginning on Day 2 after estrus, and ovaries were collected 6, 12, 24, or 48 hr after the initiation of FSH-P treatment or 24 or 48 hr after the initiation of vehicle treatment. Ovaries also were collected from untreated cows on Day 2 after estrus (pretreatment). Before fixation, all visible antral follicles were counted and their surface diameters were recorded. Proliferating cells were immunolocalized in fixed follicles by using a specific primary antibody against proliferating cell nuclear antigen (PCNA), and the labeling index (LI; percentage of cells staining positively for PCNA) was determined for granulosa and thecal cells. After 48 hr of treatment, FSH-P-treated cows had fewer (P < 0.01) small antral follicles and more medium and large antral follicles (P < 0.01 and P < 0.05, respectively) compared with vehicle-treated cows. Granulosa cell LI was negatively correlated (P < 0.05) with follicular diameter for vehicle-treated but not for FSH-P-treated cows. Analysis of covariance using follicular diameter as a covariate to adjust to a common diameter indicated that granulosa cell LI was greater (P < 0.05) at 24 and 48 hr in FSH-P-treated than in vehicle-treated cows; conversely, thecal cell LI was greater (P < 0.01) at 48 hr in FSH-P-treated compared with vehicle-treated cows but did not differ at 24 hr. Across all groups, the LI of cells located within the antral half of the granulosa cell layer was greater (P < 0.01) than that of cells located within the basal half. In conclusion, the stimulation of follicular development by exogenous gonadotropins increased or maintained the proliferation of granulosa and thecal cells concomitant with continued follicular growth. Therefore, enhanced follicular cell proliferation may be an important mechanism by which FSH-P superinduces the growth of antral follicles in cows.

Animals↗

PubMed1997

Expression of follistatin and inhibin/activin subunit genes in porcine follicles.

Expression of the follistatin (FS) and inhibin/activin (I/A) alpha, beta(A), and beta(B) subunit genes in porcine ovarian follicles was evaluated by reverse transcriptase polymerase chain reaction and/or RNase protection procedures to establish changes during the final stages of follicular development. For the I/A alpha and beta(A) subunits, expression increased (p < 0.05) as follicles progressed to the mid-stage of the follicular phase. The beta(B) subunit was expressed in lower concentrations, and all three I/A subunits showed a marked reduction (p < 0.01) in expression by the late stage of follicular development. In contrast to this pattern, FS gene expression decreased (p < 0.05) as follicles developed from the early (low estradiol) to the mid stage (high estradiol) and continued to decline in advanced follicles (after estrus). The predominant mRNA encoded for FS-315, and the ratio of mRNA for FS-315 to mRNA for FS-288 did not differ significantly during the three stages. Within an animal, concentration of FS mRNAs was related more to stage of the follicular phase than to follicular size. Follicular fluid concentration of FS changed in a manner similar to that observed for expression of its gene. We conclude that expression of the FS gene and translation of its mRNA decrease as follicles approach ovulatory status.

Animals↗

PubMed1997

Breed differences in expression of inhibin/activin subunits in porcine anterior pituitary glands.

Chinese Meishan (MS) boars have greater plasma FSH concentrations than European White Composite boars, but this difference does not occur in females of these breeds. To understand this disparity, we studied expression of the follistatin gene and of genes for the inhibin/activin alpha-, beta A-, and beta B-subunits in porcine anterior pituitary glands using quantitative reverse transcription-PCR and ribonuclease protection techniques. We found that 1) the inhibin/activin beta A- and beta B-subunits and follistatin were expressed in porcine pituitary, 2) the alpha-subunit was not detected in the porcine pituitary, but was highly expressed in porcine follicles; and 3) the beta B-subunit gene is more abundantly expressed (2-fold greater) in MS boar pituitaries than in pituitaries of White Composite boars. We conclude that this is not due to a breed difference, because the expression levels of this gene were similar in pituitaries of females of these breeds. No breed differences were detected for other genes screened in this study. From these observations, we propose that activin B, a dimer of beta B-subunits and a stimulator of FSH secretion, may be partially responsible for the elevated plasma FSH concentrations in MS boars, and intrapituitary inhibin plays no or a very minimal role.

Activins↗

PubMed1997

An evaluation of three methods for assessing sexual behavior in boars.

This study used three separate methods to evaluate sexual behavior in boars previously classified as having high (H), intermediate (INT), or low (L) levels of sexual behavior. Boars were initially evaluated for sexual behavior at 9.6 to 10.6 mo of age with a tethered female for 5 min. Boars were subsequently evaluated with a tethered female for 10 min (TF), a group of females for 10 min (FG), or continuously in a cohabitation environment for 113 h (C). When boars were evaluated with the TF procedure they mounted the female in less time (P < .01) and copulated sooner (P < .01) than when evaluated with the FG procedure. Regardless of whether the TF or FG procedure was used, L boars cumulated less time (P < .01) nosing the sides of females and took longer (P < .01) to first mount than H or INT boars. Proportion of successful matings was not different between the TF and FG procedure; however, the proportion of successful matings by H (91.7%), INT (79.2%), and L (45.8%) boars did differ (P < .001). With the C procedure, sexual behavior classification affected (P < .01) average number of successful matings (H, 4.7; INT, 2.3; and L, .33). This study indicates that sexual behavior traits expressed by a boar are similar when evaluated with a tethered female, a group of females, or a cohabitation environment.

Animals↗

PubMed1997

Activin inhibition of estradiol and progesterone production in porcine granulosa cells.

Two studies evaluated the influence of activin on steroidogenesis in cultured porcine granulosa cells obtained at various stages of differentiation. In granulosa cells isolated from 1- to 3-mm follicles, obtained at random stages of the estrous cycle, treatment with activin or transforming growth factor beta (TGF beta) decreased progesterone production during the first 48 h of culture, but neither had an effect on estradiol production. One-half of these cells received FSH treatment at 48 h, and at 96 and 144 h of culture FSH increased estradiol and progesterone production. Activin or TGF beta reduced, in a dose-dependent manner, both basal and FSH-stimulated production of both steroids. In the second study, granulosa cells were obtained during follicular growth associated with weaning and were separated into two subpopulations (weakly associated [WA] and tightly bound [TB]). Estradiol production in culture increased with time after weaning. Tightly bound cells produced more estradiol than WA cells and maintained FSH-stimulated estradiol production, whereas production of progesterone increased in both cell types after treatment with FSH. Activin depressed FSH-stimulated estradiol production in TB cells and depressed FSH-stimulated progesterone production in both cell types. These results clearly indicate that activin depresses in vitro steroidogenesis by granulosa cells from antral, porcine follicles; thus, activin may participate in atresia of antral follicles of this species.

Activins↗

PubMed1997

Negative relationship between blood concentrations of follicle-stimulating hormone and testicular size in mature boars.

Relationships between blood concentration of FSH and testicular size and daily sperm production were evaluated with data obtained from five studies originally designed to investigate regulation of FSH secretion in Meishan (MS), White composite (WC), and crossbreds of these. A minimum of three blood samples/boar were obtained at greater than 4-d intervals for determination of FSH, and testes were obtained at castration or slaughter. In a random sample of boars, FSH was fivefold greater (P < .01) in MS than in WC boars (n = 22/group). Daily sperm production (DSP)/gram of testis (estimated by counting elongated spermatid nuclei in testicular homogenates) was similar in the groups, but testicular weight (TWT), adjusted for body weight, was less (P < .01) in MS than in WC, yielding lower total daily sperm production (TDSP; P < .05) in MS boars. In four populations (one with MS, one with WC, and two with crossbreds; n = 34 males), boars were selected for extremes in FSH concentrations from larger groups. Across all populations, a threefold greater plasma FSH concentration was associated with a 32% smaller TWT (P < .01). Coincident with increased FSH, TDSP was 33% less (P < .05). In 48 MS x WC boars that were selected for divergence in plasma FSH during pubertal development (4 to 6 mo of age), this divergence was retained at 1 yr (P < .01). Retrospectively, the divergence in FSH was also apparent at 2 and 8 wk of age (P < .05), and the boars with elevated FSH had smaller testicles, lower DSP, and lower TDSP (P < .01). These studies document a negative relationship in mature boars between FSH secretion and testicular size accompanied with decreased TDSP.

Aging↗