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Biomedical subjects

M P Boland

Publications and source records attributed to M P Boland.

At least 19 recordsLinked to original sources
PubMed1997

Daunorubicin activates NFkappaB and induces kappaB-dependent gene expression in HL-60 promyelocytic and Jurkat T lymphoma cells.

The anthracycline antibiotic, daunorubicin, can induce programmed cell death (apoptosis) in cells. Recent work suggests that this event is mediated by ceramide via enhanced ceramide synthase activity. Since the generation of ceramide has been directly linked with the activation of the transcription factor, NFkappaB, this was investigated as a novel target for the action of daunorubicin. Here we describe how treatment of HL-60 promyelocytes and Jurkat T lymphoma cells with daunorubicin results in the activation of the transcription factor NFkappaB. The effect of daunorubicin was evident following 1-2 h treatment, which was in contrast to the time course of activation obtained with the cytokine, tumor necrosis factor, where NFkappaB activation was detected within minutes of cellular stimulation. Activated complexes were shown to contain predominantly p50 and p65/RelA subunit components. Daunorubicin also induced IkappaB degradation and increased the expression of an NFkappaB-linked reporter gene. In addition, the drug was found to strongly potentiate the ability of tumor necrosis factor to induce an NFkappaB-linked reporter gene, suggesting a synergy between these two agents in this response. These events were sensitive to the iron chelator, deferoxamine mesylate (desferal), and the anti-oxidant and metal chelator pyrrolidine dithiocarbamate. A structurally related compound, mitoxantrone, which, unlike daunorubicin, is unable to undergo redox cycling in cells, also activated NFkappaB in a pyrrolidine dithiocarbamate-sensitive manner. A specific inhibitor of ceramide synthase, fumonisin B1, had no effect on daunorubicin induced NFkappaB activation at a range of concentrations previously reported to block apoptosis induced by this drug. However, this agent could inhibit increases in ceramide induced by daunorubicin, in addition to blocking ceramide synthase activity from HL-60 cells which was activated in response to daunorubicin treatment. These data therefore suggest that the effect of daunorubicin on NFkappaB is unlikely to involve ceramide, but may involve reactive oxygen species generated as a result of endogenous cellular processes rather than reductive metabolism of the drug. As NFkappaB may be involved in apoptosis, this effect may be an important aspect of the cellular responses to this agent.

Antibiotics, Antineoplastic↗
PubMed1997

Influence of ovine oviducal amino acid concentrations and an ovine oestrus-associated glycoprotein on development and viability of bovine embryos.

This study examined the effects of incorporating an ovine oviducal oestrus-associated glycoprotein (oEGP) and amino acids, at the concentrations present in the ovine oviduct around the time of oestrus, on in vitro production and subsequent viability of bovine embryos. The first experiment compared the influence of ovine oviducal concentrations of amino acids with MEM and BME amino acids. There was no treatment effect on cleavage rate (74.9% vs. 75.5%), but there was a higher (P < 0.05) blastocyst yield (30.4 vs. 25.2) and a shorter time (P < 0.05) to blastocyst formation (7.16 +/- 0.64 vs. 7.27 +/- 0.56 days) following use of oviducal concentrations of amino acids. Experiment 2 examined the influence of oEGP in combination with each of the amino acid treatments. oEGP had no effect on cleavage or blastocyst yield within amino acid treatments. Day of blastocyst formation significantly influenced nuclei numbers (P < 0.001) with higher numbers being obtained on day 7 than on either day 6 or day 8. There was also a significant (P < 0.01) interaction between day of blastocyst formation and amino acid treatment on blastocyst nuclei numbers. The third experiment studied the effects of the amino acid treatments on embryo viability. There was no effect of amino acid treatment of embryos on pregnancy rates (34.5 vs. 44.4%) following transfer of days 6 and 7 blastocysts to synchronized recipients. oEGP did not influence any of the parameters of bovine embryo development that were measured, suggesting that effects of this protein observed on ovine embryos are species specific. It is concluded that ovine oviducal amino acid concentrations are beneficial to blastocyst development in vitro but do not have any further beneficial effect following transfer of blastocysts to recipients.

Amino Acids↗
PubMed1997

Superovulation in cattle: effect of FSH type and method of administration on follicular growth, ovulatory response and endocrine patterns.

Although different FSH preparations and injection regimens are used to superovulate cattle, the optimum treatment regimen and blood concentrations of FSH to induce effective superovulatory responses are currently not known. The current objective was to evaluate the pattern of follicular growth, oestradiol-17 beta(E2) concentrations and yield of embryos in heifers following superovulation with two different pFSH preparations reportedly differing in LH content. In experiment 1, 90 synchronised heifers were superovulated at mid-cycle using a 2 x 2 factorial design comparing Folltropin (Vetrepharm; low LH) with Pluset (Serovet; FSH:LH ratio 1:1) administered either as a single or multiple (8 for Folltropin, MF and 10 for Pluset, MP) injections. Animals were inseminated during oestrus which was induced with prostaglandin F2 alpha analogue and embryos were recovered 7 days later. Overall, Pluset treatments compared with Folltropin resulted in more ovulations and unfertilized or degenerate embryos (P < 0.05). Multiple injections resulted in more (P < 0.05) freezable (MF = 55 +/- 1.2; MP = 3.8 +/- 1.0) and transferable embryos (MF = 2.68 +/- 0.9; MP = 2.71 +/- 0.9) than single injections (SF = 2.2 +/- 0.5 and 1.0 +/- 0.3 respectively; SP = 2.6 +/- 0.8 and 1.3 +/- 0.4 respectively); there was also a higher (P < 0.05) percentage embryo recovery rate. In two subsequent experiments, animals (n = 17) were superovulated with either single or multiple injections of Folltropin or Pluset as described and blood samples were collected and analysed for E2 concentrations. Ovarian scanning was carried out until 72 h after the first FSH injection, to count medium (5-9 mm) and large (> or = 10 mm) follicles. Heifers treated with SP had higher E2 concentrations in comparison with heifers treated with SF at 18, 36-48 and 84-96 h after the FSH injection. There were no differences in E2 concentrations in heifers treated with MF or MP treatments. Heifers treated with SP had greater numbers of follicles compared to SF treated heifers (21.0 +/- 3.1 vs 13.9 +/- 2.2; P = 0.089) on the third day after FSH injection. There were no differences between the numbers of medium and large follicles in heifers treated with MF or MP at any time throughout the experimental period. These data indicate that a single injection of Folltropin or Pluset can result in multiple ovulations and that the E2 profiles are different following single injections of either Folltropin or Pluset.

Animals↗
PubMed1997

Effect of immunization of rams against bovine inhibin alpha 1-26 on semen characteristics, scrotal size, FSH, LH and testosterone concentrations.

The effects of inhibin immunization on inhibin antibody titres, semen characteristics, scrotal size, fertility, FSH, LH and testosterone concentrations were determined by immunizing adult rams against bovine inhibin alpha 1-26-Gly-Tyr conjugated to human serum albumin (n = 16) in non-ulcerative Freund's adjuvant and DEAE:dextran (1:1) or adjuvant alone (n = 16) on days 0 (29 June), 30, 60, 191, 303 and 394. Blood samples were collected and bovine inhibin alpha 1-26-Gly-Tyr antibody titres and serum testosterone concentrations were determined. Each month, between days 174 and 417, semen was collected every 30 min to a maximum of 15 ejaculates over 7 h and scrotal circumference was measured. Ram fertility was recorded during natural service. FSH, LH and testosterone concentrations and GnRH-induced FSH and LH release were measured in a subgroup of immunized (n = 5) and control (n = 5) rams at frequent intervals. Antibody titres were variable among immunized rams (0-46% 125I-labelled bovine inhibin alpha 1-26-Gly-Tyr at 1:1600 serum dilution) but mean titres were consistently higher than in control rams (P < or = 0.001). Immunization did not alter the semen volume, output or quality of spermatozoa or ram fertility, but increased the mean scrotal circumference (37.6 +/- 0.8 cm versus 34.4 +/- 0.7 cm, P < 0.001). Mean FSH concentrations were higher in immunized rams during two intensive blood sampling periods (in June and August) (5.8 +/- 0.7 ng ml-1 versus 3.0 +/- 0.3 ng ml-1, P < 0.001 in June; and 4.8 +/- 0.9 ng ml-1 versus 2.0 +/- 0.3 ng ml-1, P < 0.02 in August), and were correlated with antibody titres (r2 = 0.3, P < 0.05 in June; and r2 = 0.8, P < 0.001 in August). Discrete FSH pulses were not detected. Immunization did not alter mean or basal testosterone or LH concentrations, or LH pulse frequency; LH pulse amplitude was increased (1.6 +/- 0.2 ng ml-1 versus 0.8 +/- 0.2 ng ml-1, P < 0.02) and was correlated with antibody titres (r2 = 0.6, P < 0.01). Immunization enhanced GnRH-induced FSH (P < 0.05) but not LH release. In conclusion, immunization of adult rams against bovine inhibin alpha 1-26 Gly-Tyr increased scrotal circumference, mean FSH concentrations and LH pulse amplitude, without altering semen characteristics, fertility, mean LH concentrations, LH pulse frequency or mean testosterone concentrations.

Animals↗
PubMed1996

Oestradiol potentiates a prolonged progesterone-induced suppression of LH release in ovariectomised cows.

Our working hypothesis was that the negative feedback effect of progesterone on LH secretion in ovariectomised cows is greatly enhanced by oestradiol when both hormones are administered intravaginally. Each of eight ovariectomised cows had a progesterone releasing device ('CIDR-1'; Eazi-breed CIDR-B. InterAg, Hamilton, New Zealand) inserted into the vagina for 3 days, followed by an injection of 1 mg oestradiol benzoate (ODB) in peanut oil 24 h after device removal. The timing of this injection was designated as Day 0. The CIDR-1 was reinserted concurrently with an injection of 0.4 mg ODB on Day 5. An additional device ('CIDR-2') was inserted 4 days later (Day 9). In four of the cows, an ODB capsule (CIDIROL), Douglas Pharmaceuticals. Auckland, New Zealand) was placed into a groove on the surface of CIDR-2 preceding insertion. CIDR-2 was withdrawn after 5 days (Day 14) and CIDR-1 was withdrawn 2 days later (Day 16). The treatment regimen was repeated in a cross-over design where each cow received CIDR-2 with or without an ODB capsule. Blood samples were collected at intervals of 15 min for a period of 16 h beginning 8 h before insertion of CIDR-2 to determine changes in LH secretion pattern, and then at intervals of 8 h until 48 h after removal of CIDR-1 to determine mean LH and steroid concentrations. Concentrations of progesterone in plasma reflected the effects of inserting and removing each CIDR device. The insertion of CIDR-2 elevated progesterone from 2.0 +/- 0.1 ng ml-1 to 4.9 +/- 0.1 ng ml-1 within 30 min (P < 0.01) and maintained levels > 3 ng ml-1. Withdrawal of CIDR-2 produced a new baseline level of 1.8 +/- 0.1 ng ml-1 within 4 h (P < 0.01). Concentrations of oestradiol-17 beta in plasma increased from a baseline of < 1 pg ml-1 to-a-maximum of 12.6 +/- 2.2 pg ml-1 at 22 h after insertion of an ODB capsule. Initial pulse frequency of LH (1.2 +/- 0.05 pulses h-1) and mean concentration of LH (1.6 +/- 0.1 ng ml-1) declined (P < 0.05) to 0.2 +/- 0.1 pulses h-1 and 0.5 +/- 0.1 ng ml-1 during the period from 2 to 8 h following insertion of CIDR-2. Mean concentrations recovered to pre-treatment levels (> 1 ng ml-1) within 48 h if CIDR-2 was inserted without an ODB capsule. In contrast, LH levels remained less than 0.7 ng ml-1 for 5 days following this form of ODB treatment. A subsequent increase in mean LH of 1.4 +/- 0.2 ng ml-1 (P < 0.05) was inversely synchronised with the precipitous decline in progesterone of 1.2 +/- 0.1 ng ml-1, following removal of CIDR-2. The inclusion of an ODB capsule with insertion of CIDR-2 reduced concentrations of FSH from 166 +/- 17 ng ml-1 to a new baseline of 105 +/- 16 ng ml-1 within 24 h (P < 0.05). In conclusion, an acute increase in progesterone induced a transient suppression of LH lasting less than 48 h. This suppression was prolonged to 5 days by the concurrent insertion of a capsule containing 10 mg ODB. The subsequent recovery of LH was coincident with the decline in progesterone following removal of CIDR-2.

Administration, Intravaginal↗
PubMed1996

Alterations in intrafollicular levels of different molecular mass forms of inhibin during development of follicular- and luteal-phase dominant follicles in heifers.

The experiment reported here characterized changes in serum concentrations of FSH, follicular fluid (FF) concentrations of immunoreactive alpha inhibins and dimeric inhibins, and different molecular forms of inhibin during development of dominant follicles in both luteal and follicular phases of the estrous cycle in heifers. Follicular status was determined daily by ultrasound examination of ovaries, and blood samples were taken at 4-6-h intervals. Heifers (5-6 per treatment) were ovariectomized on Days 0 (follicular phase, pre-LH surge), 1-Ov (post-LH surge, preovulation), 1 + Ov (postovulation), 3 (selection phase), 6 (dominance phase), and 12 (atretic phase) of the estrous cycle. Follicles were classified on the basis of FF estradiol (E) to progesterone (P) ratio and by ultrasound morphology. Concentrations of E, P, immunoreactive alpha inhibin, LH, and FSH were determined by RIA, and concentrations of dimeric inhibins were determined by a two-site dimeric-specific immunoradiometric assay (IRMA); the different molecular mass forms of inhibin were determined by immunoblot analysis. Serum FSH was transiently elevated during Days 0.5-1.5 and 8-10.5, in association with emergence of each new wave of follicular growth. The follicular-phase dominant follicle of heifers before the preovulatory LH/FSH surge had less immunoreactive alpha inhibin and 29-kDa inhibin but more 110-kDa inhibin compared with concentrations after the surge (p < 0.05). During growth of the dominant follicle between Days 3 and 6, there were no changes in either proportions or amounts of any inhibin forms (p > 0.05). However, while concentrations of dimeric inhibins decreased between Days 1 and 6, the concentration of immunoreactive alpha inhibin increased (p < 0.05). Atresia of the luteal-phase dominant follicle during Days 6-12 was associated with a decrease in amounts and proportions of the 110- and > 160-kDa forms, an increase in amounts and proportions of the 34-kDa form, and an increase in dimeric inhibin concentration (p < 0.05). Alterations in FF E concentrations were positively correlated with changes in amounts of the 77- and 110-kDa precursor forms of inhibin, but negatively correlated with 34-kDa inhibin. The results of this experiment demonstrate that 1) seven different molecular mass forms of inhibin were present in bovine FF during all stages of development of follicular- and luteal-phase dominant follicles examined, 2) amounts and proportions of most inhibin forms are altered differently in follicular- and luteal-phase dominant follicles, 3) FF inhibins and E are regulated by different factors, and 4) RIA, IRMA, and immunoblot measurements of inhibin in bovine FF produced divergent results.

Animals↗
PubMed1995

Effect of photoperiod before and after birth on puberty in ewe lambs.

Previous studies have shown that exposure to long days followed by short days after 12 wk of age advances the onset of puberty in ewe lambs. The aim of this experiment was to determine whether or not puberty would be advanced by exposure of lambs to such a photoperiodic regime when the long days were given before birth and the short days immediately after birth. Ewes kept in natural photoperiod (NP) were housed on January 15 and allocated at random to one of four treatments: 1) NP/NP, natural photoperiod before and after parturition (n = 26); 2) SD/SD, short days (SD; 9L:15D) before and after parturition (n = 27); 3) LD/NP, long days (LD; 18L:6D) before parturition and NP after parturition (n = 27); and 4) LD/SD, LD before parturition and SD after parturition (n = 26). Mean (+/- SEM) birth date for all lambs was March 20 +/- 1 day, and the number of days of exposure to long and short days prior to parturition was 64 +/- 2 and 67 +/- 2 days, respectively. From ewes on the four treatments, 24, 20, 14, and 16 female lambs, respectively, were reared. Lambs were weighed at birth and at weekly intervals after weaning. Reproductive activity in ewe lambs was assessed from serum progesterone concentrations in blood samples collected twice weekly from August 1 until puberty was reached or the experiment terminated on November 17 (34 wk after birth).(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1994

A capillary electrophoresis-based assay for protein kinases and protein phosphatases using peptide substrates.

A novel procedure for detection and assay of protein kinase and phosphatase activities in complex biological mixtures was developed. By means of capillary zone electrophoresis (CZE) methodology, the phosphorylated and dephosphorylated forms of the peptide Kemptide, a 46-amino-acid fragment from protein phosphatase inhibitor-1 and a peptide fragment corresponding to the RII subunit of cAMP-dependent protein kinase (PKA), were rapidly resolved. This facilitated nonradioactive detection of PKA and protein phosphatase-2B (calcineurin) in rabbit skeletal muscle extracts. In addition, the CZE procedure enabled a site-specific assay of a 14-amino-acid peptide from the glycogen-binding subunit of protein phosphatase-1 monophosphorylated on distinct sites by PKA and casein kinase-II. These results suggest that CZE may prove to be extremely useful for the analysis of peptides that are phosphorylated at multiple sites in vivo.

Animals↗
PubMed1994

Effect of follicle size on bovine oocyte quality and developmental competence following maturation, fertilization, and culture in vitro.

The aim of the present series of experiments was to investigate the effect of the size of follicle from which the oocytes originate on their subsequent in vitro developmental ability. Ovarian follicles were isolated and grouped according to size (2-6 mm, > 6 mm). Primary oocytes were carefully liberated and grouped according to morphology into one of five categories: denuded; expanded; with two or three layers of cumulus; with four or five layers; and with many (six or more) layers. Following in vitro maturation (IVM), fertilization (IVF), and culture (IVC), more oocytes with many layers of cumulus (P < 0.01, 70.2%, 73/104 vs. 46.8%, 87/186, respectively) and a higher proportion of blastocysts were obtained from follicles > 6 mm compared to 2-6 mm follicles (P < 0.01, 65.9%, 60/91 from > 6 mm follicles vs. 34.3%, 34/99 from 2-6 mm follicles, respectively). Use of follicular fluid (BFF) from follicles of different sizes in the IVM medium did not significantly increase the cleavage rate or blastocyst yield compared to controls. Administration of porcine follicle-stimulating hormone (pFSH) to donors prior to slaughter was investigated as a possible means of increasing the number of larger sized follicles in the ovaries and, thereby, the quality of the recovered oocytes. It was found that administration of six injections of pFSH beginning 3 days prior to slaughter resulted in a significant increase (P < 0.001) in the proportion of follicles > 6 mm in diameter (31.6%) compared to that in nontreated controls (6.6%) and to animals that received only four injection groups (9.4%).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Infrequent structures in cattle oocytes.

Uncommon and controversial structures in cattle oocytes were studied in dominant and subordinate follicles of unstimulated Bos taurus and zebu (Bos indicus), and in FSH-stimulated B. taurus cattle, before or after administration of cloprostenol. Growing oocytes were very rare in follicles more than or equal to 5 mm in diameter. For the first time, special vesicles that may be involved in cortical granule synthesis were observed. Classical rough endoplasmic reticulum was very rare in unstimulated oocytes, but was seen at superovulation. Vacuolation of the nucleolus was a common feature in dominant oocytes that were collected after cloprostenol injection, except in superovulated cattle. Annulate lamellae were very rare or absent in oocytes of B. taurus, while they were more frequent in zebu oocytes.

Animals↗
PubMed1994

Prorenin and active renin concentrations in ovarian follicular fluid increase after the LH peak in superovulated heifers.

1. The aim was to analyse the in vivo variations with time of prorenin and active renin and their relationship to steroid hormones in ovarian follicular fluid during follicular growth in heifers. 2. Thirty one beef heifers were assigned to two groups after oestrous synchronization: an unstimulated and a follicle-stimulating hormone (FSH)-treated (superovulated) group. Within each group, animals were slaughtered at different times of the follicular phase of the oestrous cycle. Ovarian follicular fluids were aspirated and analysed for the concentrations of active renin, prorenin, oestradiol-17 beta (E2) and progesterone (P4). 3. Prorenin and active renin concentrations in follicular fluid remained constant until the luteinizing hormone (LH) peak, after which time they increased four- and two-fold, respectively, in superovulated heifers. 4. In follicular fluid, prorenin and active renin correlated negatively with oestradiol and E2/P4 ratio but positively with progesterone during follicular growth in superovulated heifers. Prorenin also correlated negatively with oestradiol and E2/P4 ratio in unstimulated heifers. 5. The increase of renin concentrations in ovarian follicles after the LH peak and the correlations to steroid hormones suggest an important role of the ovarian renin-angiotensin system in bovine follicular growth and maturation.

Animals↗
PubMed1994

Effect of the presence of male and female flockmates on reproductive activity in ewes.

Four experiments were carried out to determine the effect of the presence of ewes and rams on the reproductive state of ewes. In Expt 1, the breeding season of ewes kept with a vasectomized ram ended later (April 18 +/- 8 days; mean +/- SEM) than that of ewes isolated from rams (6 March +/- 7 days; P < 0.01). In Expt 2, the end of the breeding season was later (5 May +/- 6 days; P < 0.05) and the onset of the next breeding season earlier (29 September +/- 2 days; P < 0.001) in ewes maintained with rams, compared with ewes isolated from rams (14 April +/- 7 days and 1 November +/- 2 days, respectively). There was no difference in the timing of, or variation in, reproductive transitions between ewes maintained either as individuals or in groups. In Expt 3, all ewes exposed to artificial short days from the date of the winter solstice and interrupted with 35 long days in spring resumed cyclicity (median date, 7 September; range, 59 days). Most ewes (seven of nine) exposed to short days from the date of the winter solstice and isolated from other ewes did not resume cyclicity in the following 11 months. In contrast, all ewes resumed cyclicity (median date, 19 October; range, 144 days) when exposed to short days but housed in social contact with other ewes that became reproductively active in early September; however, the onset of cyclicity was later than in ewes exposed to long days (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Effect of exogenous progesterone on superovulatory response in heifers inseminated with fresh or frozen semen.

Superovulation in cattle normally involves the administration of gonadotrophins at specific times of the oestrous cycle, followed by the induction of luteolysis and insemination with high quality semen. The first aim of this experiment was to examine the effect of supplementary progesterone when used in conjunction with porcine FSH (pFSH) to induce superovulation in heifers. The methods compared were PGF2 alpha given at mid-cycle or a progesterone-releasing intravaginal device (PRID) inserted at different phases of the cycle. The second aim was to determine whether site of insemination or use of fresh or frozen semen affected embryo production. A factorial design was used involving 185 beef heifers. The main factors were (i) synchronization methods (PGF2 alpha or PRID); (ii) semen type (fresh or frozen); (iii) insemination regimens (involving two inseminations and variations in the sites) and number of straws used (one or two) at the second insemination. Eight injections of pFSH were given twice a day for 4 days starting either on days 9, 10 or 11 of the oestrous cycle or on the fourth day after insertion of a PRID. Heifers were checked for oestrus, inseminated twice and embryos were recovered on day 7 of the superovulated cycle. There was no difference between heifers given either PRID or PGF2 alpha in the oestrous response (93% versus 96%), number of ovulations (15.9 +/- 1.11 versus 13.4 +/- 1.06), large follicles (2.5 +/- 0.24 versus 2.3 +/- 0.23) or embryos recovered (9.1 +/- 0.77 versus 9.1 +/- 0.74).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Selection, dominance and atresia of follicles during the oestrous cycle of heifers.

This study examined the correlation between measurement of follicle growth by ultrasound, and measurement of intrafollicular ratios of oestradiol and progesterone concentrations and the serum concentrations of FSH during selection, dominance and atresia or ovulation of dominant follicles in heifers. Heifers were ovariectomized on days 0 (before LH surge), 1 (after LH surge, preovulation), 1 (postovulation), 3, 6 and 12 of the oestrous cycle. Blood samples were collected at 4-6 h intervals. After ovariectomy all follicles > or = 5 mm were measured and follicular fluid was aspirated. Follicles were classified by size according to ultrasound (F1, largest; F2, second largest; F3, all remaining follicles > or = 5 mm) and by the ratio of oestradiol:progesterone concentrations. During the follicular phase, a single dominant oestrogen-active follicle increased in diameter while serum concentrations of LH increased and FSH decreased (P < 0.05). On day 1 (after LH surge, preovulation), serum LH and FSH decreased to pre-surge concentrations (P < 0.0001), while follicle size and intrafollicular progesterone concentration increased and oestradiol concentration decreased (P < 0.05). A dominant nonovulatory follicle, classified as oestrogen-active on days 1, 3 and 6 and oestrogen-inactive on day 12, increased in size from day 1 to day 7 and lost dominance during days 10-12, coincident with the growth of multiple oestrogen-active follicles. The serum FSH concentration increased transiently (P < 0.05) before each new wave of dominant follicular growth. The overall correlation of ultrasound measurements of follicle diameter with measures of follicle size after ovariectomy was high.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Association between the duration of dominance of the ovulatory follicle and pregnancy rate in beef heifers.

After luteolysis, subluteal concentrations of progesterone or treatment with a synthetic progestagen result in an extended period of dominance (persistence) of the dominant follicle in cattle. Two experiments studied (1) the relationship between the duration of dominance of the ovulatory follicle and pregnancy rate and (2) the ability of a persistent dominant follicle to ovulate and form a normal functioning corpus luteum. In Expt 1, beef heifers were either untreated (n = 30) or given a synthetic progestagen implant (3 mg norgestomet) for 12 days starting on day 16 of their cycle (n = 32). The mean duration of dominance of the ovulatory follicle differed (P < 0.05) between treated and control heifers (10.8 +/- 1.2 and 3.3 +/- 0.8 days, respectively) and 20 of 26 control and 7 of 30 treated heifers were diagnosed pregnant 28 days after artificial insemination (P < 0.01). In Expt 2, on the first day of dominance of the second dominant follicle, heifers received either a PGF2 alpha analogue alone (controls; n = 18), or prostaglandin and a norgestomet implant for 6 (T6; n = 19) or 10 days (T10; n = 20). Increases in the duration of dominance of the second dominant follicle (controls, 4.1 +/- 0.2 days; T6, 8.6 +/- 0.2 days; T10, 12.1 +/- 0.2 days; P < 0.05) resulted in a decrease in pregnancy rate (controls, 14 of 16; T6, 11 of 19; T10, 0 of 13; P < or = 0.05). Progesterone concentrations on days 7 and 12 and the area of luteal tissue on day 12 after artificial insemination were not different (P > 0.05) between treatments.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Identification and characterisation of a type-1 protein phosphatase from the okadaic acid-producing marine dinoflagellate Prorocentrum lima.

The unicellular marine dinoflagellate, Prorocentrum lima, an established producer of okadaic acid (OA), was shown to contain a type-1 protein phosphatase (PP-1) the biochemical profile of which on Mono-Q and Superdex-75 fast protein liquid chromatography was identical to the catalytic subunit of PP-1 from rabbit skeletal muscle. Purified P. lima PP-1 (apparent molecular mass 37.5 kDa) was highly sensitive to inhibition by mammalian protein phosphatase inhibitor-1 and inhibitor-2, and to OA itself. A 6-7-fold increase in OA production by P. lima, when grown under controlled conditions, correlated with an up to 300-fold increase in P. lima PP-1 activity. Furthermore, P. lima did not contain any detectable type-2A protein phosphatase activity. This study represents the first identification of a serine/threonine protein phosphatase in a dinoflagellate.

Animals↗
PubMed1993

Chromatin and microtubule morphology during the first cell cycle in bovine zygotes.

Chromatin and microtubule configurations during the first cell cycle of bovine zygotes were analyzed by DNA staining and microtubule immunolocalization using an IVM/IVF system and oocytes matured and fertilized in vivo, in order to investigate the origin of the active centrosome and to characterize the nuclear and the cytoplasmic changes following bovine fertilization. Our results suggest that the paternal centrosome is active during early zygotic development, forming a conspicuous sperm aster soon after fertilization. We also report that polyspermy in bovine eggs, leads to the formation of numerous sperm asters with different degrees of association with the chromatin. The maternal structures in both monospermic and polyspermic zygotes can be lost or degenerate. Consequently, these cells may resume the first cell cycle as androgenotes, very often with several types of mitotic activity taking place in different regions of the cell cytoplasm at the same time. As indicated by a comparison of monospermic and polyspermic fertilization rates to rates of development, it is possible that some androgenetic embryos cleave and develop to the blastocyst stage.

Animals↗