Estrus synchronization of beef cattle with a combination of melengestrol acetate and an injection of progesterone and 17beta-estradiol.

Our hypothesis was that estrus synchronization in beef cattle using melengestrol acetate (MGA) and an injection of progesterone (P4) and 17beta-estradiol (E2) to regress dominant ovarian follicles would improve pregnancy rate (number conceived/number in group) to AI compared with feeding only MGA or injecting PGF2alpha. During 2 yr, peripubertal heifers (n = 52) and cows (n = 327) received either 1) MGA for 18 d (d 0 = 1st d of MGA) plus an injection of P4 and E2 in sesame oil (vehicle) on d 11 to regress persistent ovarian follicles (MGA+P4), 2) MGA for 18 d plus vehicle on d 11 (MGA), or 3) two injections of PGF2alpha 10 d apart (d 7 and 17, PG). Concentration of P4 was assessed in blood samples obtained on d 0, 7, and 17 to indicate estrual status (anestrual or estrual) during treatment to induce estrus synchrony.

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.

Fluostatins A and B, new inhibitors of dipeptidyl peptidase III, produced by Streptomyces sp. TA-3391. I. Taxonomy of producing strain, production, isolation, physico-chemical properties and biological properties.

New inhibitors of dipeptidyl peptidaseIII (EC 3.4.14.

Epostatin, new inhibitor of dipeptidyl peptidase II, produced by Streptomyces sp. MJ995-OF5. I. Taxonomy of producing strain, fermentation, isolation, physico-chemical properties and biological properties.

A new inhibitor of dipeptidyl peptidase II (DPP-II, EC 3.4.14.

Gonadotropin secretion and development of ovarian follicles during oestrous cycles in heifers treated with luteinizing hormone releasing hormone antagonist.

The hypothesis tested was that reduced LHRH stimulation of the anterior pituitary would lead to attenuated development of ovarian follicles as a result of reduced gonadotropin secretion during oestrous cycles of cattle. Twenty heifers were randomly assigned to be treated ( n = 5/treatment) with an antagonist to LHRH (LHRH-Ant) 1) from Day 2 to 7 (Day 0 = behavioural oestrus), 2) Day 7 to 12, 3) Day 12 to 17, 4) or serve as untreated control animals. LHRH-Ant suppressed LH pulses of heifers in all treatment groups from treatment initiation through Day 17 as compared with untreated control heifers [Peters et al.

Characterization of filamentous phages of Vibrio cholerae O139 and O1.

We have analyzed our collection of Vibrio cholerae O139 strains to determine whether filamentous phages are produced in their culture supernatants, and whether any replicative form of DNA is detectable in cell lysates. Two types of filamentous phage, designated fs1 (6.4 kb) and fs2 (8.

Development of a persistent ovarian follicle and associated elevated concentrations of 17beta-estradiol preceding ovulation does not alter the pregnancy rate after embryo transfer in cattle.

It was hypothesized that prolonged elevation in 17beta-estradiol (E(2)) preceding ovulation as a result of a persistent ovarian follicle would have a detrimental effect on pregnancy rate after Day 7 (behavioral estrus = Day 0) of the estrous cycle. Cows were either treated with exogenous progesterone (P(4)) for 10 d or remained untreated (CON; n = 76). Cows were treated with 1 of 2 doses of P(4) from Day 6 to 16 which was intended to result in either elevated E(2) (EE(2); n = 76) or normal E(2) (NE(2); n = 76) concentration in the circulation.

Prolonged increased concentrations of 17beta-estradiol associated with development of persistent ovarian follicles do not influence conception rates in beef cattle.

Objectives were to evaluate conception rates and time to estrus following cessation of treatments designed to either cause prolonged elevated concentrations of 17beta-estradiol associated with development of persistent ovarian follicles or to inhibit elevated concentrations of 17beta-estradiol and development of persistent ovarian follicles. Beef heifers (n = 80) and 2-yr-old nonlactating cows (n = 39) were stratified by age, blocked by estrual status (previously exhibited estrus or anestrus) and assigned to receive either 1) four norgestomet implants (4 Norg; n = 59) for 9 d (d 0 = treatment initiation) or 2) one norgestomet implant from d 0 to 7 and three additional norgestomet implants from d 7 to 9 (1 + 3 Norg; n = 60). All animals received PGF2alpha on d 0 to lyse corpora lutea.

Morphological features of a filamentous phage of Vibrio cholerae O139 Bengal.

A filamentous phage was isolated from carrier strain AI-1841 of Vibrio cholerae 0139 Bengal and thus was termed fs phage. The phage was measured to be approximately 1 microm in length and 6 nm in width. One end of the phage was slightly tapered and had a fibrous appendage.

Incidence of precocious puberty in developing beef heifers.

The objectives of this study were to determine the incidence of precocious puberty and effect of exposure to a bull on the incidence of precocious puberty in beef heifers. The experiment was conducted using 120 heifers during 1990 and 1991. Heifer calves were randomly assigned to be pastured in the presence (n = 30 heifers/yr) or absence (n = 30 heifers/yr) of a bull starting at 140 +/- 14 d of age for the duration of the study.

Comparison of circulating concentrations of reproductive hormones in boars of lines selected for size of testes or number of ovulations and embryonal survival to concentrations in respective control lines.

The objectives of this study were to determine whether circulating concentrations of genadotropins and gonadal hormones of boars were altered as a result of selection of pigs for size of testes or for embryonal survival and(or) number of ovulations. Included in Exp. 1 and 2 were boars with the greatest estimated paired weight of testes (TS) and boars from a control (C) line.

Progestin and estrogen regulation of pulsatile LH release and development of persistent ovarian follicles in cattle.

When doses of progestin used commercially are administered to synchronize the stage of the estrous cycle among bovine females, fertility is reduced compared with that of untreated controls. The reduced fertility that results from the use of progestin based estrus synchrony regimens is associated with the development of persistent ovarian follicles. Persistent ovarian follicles develop as a result of the greater frequency of LH pulses that occurs during the period of treatment with progestins.

Changing dose of progesterone results in sudden changes in frequency of luteinizing hormone pulses and secretion of 17 beta-estradiol in bovine females.

The aim of the present study was to elucidate the time course according to which changes in circulating concentrations of progesterone influence pulsatile secretion of LH and secretion of 17 beta-estradiol. Our working hypothesis was that changing the dose of progesterone would result in changes in frequency of LH pulses and secretion of 17 beta-estradiol within 72 h. Five days after behavioral estrus, thirty-three cows were randomly assigned to one of five groups: 1) control, no treatment (CONT, n = 5); 2) treatment with two progesterone-releasing intravaginal devices (PRIDs) for 11 days (2PRID, 5-6 ng/ml plasma progesterone, n = 7); 3) treatment with a 0.

Development of persistent ovarian follicles during synchronization of estrus influences the superovulatory response to FSH treatment in cattle.

The synchronization of estrus with synthetic progestins or progesterone (P(4)) results in the development of a large, persistent ovarian follicle. The objectives of the present study were to determine if development of a persistent ovarian follicle during synchronization of estrus suppresses recruitment of additional follicles during FSH treatment. On Day 5 of the estrous cycle (estrus = Day 0), beef cows were treated with 0.

Dosage of the synthetic progestin, norgestomet, influences luteinizing hormone pulse frequency and endogenous secretion of 17 beta-estradiol in heifers.

The objective of this study was to determine whether there were doses at which the synthetic progestin, norgestomet, could mimic midluteal phase concentrations of progesterone in regulating the secretion of LH and 17 beta-estradiol in bovine females. Heifers were randomly assigned to one of five groups to receive: 1) one (1Norg, n = 5), 2) two (2Norg, n = 5), 3) four (4Norg, n = 5), or 4) eight (8Norg, n = 5) norgestomet implants or to serve as untreated control heifers (control, n = 5). On Day 7 (Day 0 = behavioral estrus), implants containing norgestomet were inserted, and they remained in place for 10 days.

Melengestrol acetate at greater doses than typically used for estrous synchrony in bovine females does not mimic endogenous progesterone in regulation of secretion of luteinizing hormone and 17 beta-estradiol.

Our working hypothesis was that doses of melengestrol acetate (MGA) greater than those typically administered in estrous synchrony regimens would regulate secretion of LH and 17 beta-estradiol (E2) as endogenous progesterone (P4) does during the midluteal phase of the estrous cycle. We also hypothesized that endogenous P4 from the CL would interact with MGA to further decrease the frequency of LH pulses and E2. Cows on Day 5 of their estrous cycle (Day 0 = estrus) were randomly assigned to an untreated control group (CONT, n = 5) or to one of six MGA treatment groups (n = 5 per group): 1) MGA administered orally each day via a gelatin capsule at a dose of 0.

Effects of 17 beta-estradiol on distribution of pituitary isoforms of luteinizing hormone and follicle-stimulating hormone during the follicular phase of the bovine estrous cycle.

The objective of this study was to examine the influence of 17 beta-estradiol (E2) on distribution of LH and FSH isoforms during the follicular phase of the bovine estrous cycle prior to the preovulatory surges of LH and FSH. On Day 16 of the estrous cycle (Day 0 = estrus), intact controls (CONT; n = 4) were treated with prostaglandin F2 alpha (PGF2 alpha) to induce luteal regression and initiation of the follicular phase. Other cows were also treated with PGF2 alpha and either ovariectomized (OVX; n = 5) or ovariectomized and given E2 implants (OVXE; n = 6) to mimic the pattern of increasing E2 concentrations during the follicular phase of the estrous cycle.

Increasing concentrations of 17 beta-estradiol has differential effects on secretion of luteinizing hormone and follicle-stimulating hormone and amounts of mRNA for gonadotropin subunits during the follicular phase of the bovine estrous cycle.

The hypothesis tested was that 17 beta-estradiol (E2) would increase amounts of mRNA for alpha, LH beta, and FSH beta subunits during the follicular phase of the estrous cycle prior to the preovulatory surge of gonadotropins in cows. On Day 16 (Day 0 = estrus) of the estrous cycle, all cows were treated with prostaglandin F2 alpha (PGF2 alpha). Cows served as intact controls (CONT, n = 4) were ovariectomized (OVX, n = 5), or were ovariectomized and administered E2 (OVXE, n = 6) in increasing doses starting at the time of treatment with PGF2 alpha.

Belactins A and B, new serine carboxypeptidase inhibitors produced by Actinomycete. I. Taxonomy, production, isolation and biological activities.

Belactins A and B, new inhibitors of serine carboxypeptidase were discovered in the fermentation broth of Saccharopolyspora sp. MK19-42F6. They were purified by ethyl acetate extraction, silica gel chromatography, Sephadex LH20 chromatography, Capcellpak C18 SG120 reversed phase HPLC and centrifugal partition chromatography (CPC) following their inhibitory activity against carboxypeptidase Y (CP-Y).

Endocrine basis for puberty in heifers and ewes.

Maturation processes that culminate in puberty and sexual maturity are initiated before birth, continue through prepuberty (> 50 days before puberty) and peripuberty (50 days before puberty) and are completed early after puberty. The hypothalamus is the primary site of change during transition to sexual maturity. Maturation of the hypothalamus results from decreased negative feedback of oestradiol that leads to increased frequency of release of LH pulses.

Pyrostatins A and B, new inhibitors of N-acetyl-beta-D-glucosaminidase, produced by Streptomyces sp. SA-3501.

Pyrostatins A and B, new inhibitors of N-acetyl-beta-D-glucosaminidase (GlcNAc-ase), have been purified from the culture broth of Streptomyces sp. SA-3501 isolated from a marine environment. They were purified by chromatography on Dowex 50W, silica gel and Capcell Pak C18 (HPLC) followed treatment with active carbon and then isolated as white powders.

Luteinizing hormone has a role in development of fully functional corpora lutea (CL) but is not required to maintain CL function in heifers.

We tested the hypothesis that endogenous pulses of LH have a role in development and maintenance of CL during the estrous cycle of the bovine female. Twenty heifers were synchronized to estrus by treating two times with prostaglandin F2 alpha 11 days apart (Day 0 = behavioral estrus). Heifers were then randomly assigned to one of four treatments (n = 5/group).

Ovarian follicular development in prepubertal heifers is influenced by level of dietary energy intake.

Objectives were twofold: 1) to determine the chronology of development of dominant ovarian follicles during the peripubertal period in heifers and 2) to determine whether feeding a diet with low energy content that delays onset of puberty alters chronology of dominant ovarian follicular development in peripubertal heifers. Ten heifers of composite breeding (1/4 Angus, 1/4 Hereford, 1/4 Red Poll, 1/4 Pinzgauer) were randomly assigned, at 8 mo of age, to receive a diet designed to produce 0.9 (n = 5) or 0.

Differential regulation of gonadotropin synthesis and release in ovariectomized ewes after treatment with a luteinizing hormone-releasing hormone antagonist.

Our working hypothesis was that synthesis and release of LH, but not FSH, were solely dependent on LHRH. Twenty ovariectomized (OVX) ewes were randomly assigned to one of five treatments (n = 4 per group). Ewes were administered a low (10 micrograms/kg) or high (100 micrograms/kg) dose of LHRH antagonist (LHRH-Ant) at 24-h intervals for 3 or 6 days.