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M Grealy

Publications and source records attributed to M Grealy.

10 recordsLinked to original sources
PubMed2004

Plakoglobin expression and localization in zebrafish embryo development.

Plakoglobin (gamma-catenin) and beta-catenin are major components of the adherens junctions and can be localized to the nucleus by activation of the Wnt signalling pathway. In addition, plakoglobin is also found in desmosomes, a vertebrate-specific cell-cell adhesion structure. Plakoglobin expression and localization were examined at the protein level during zebrafish embryonic development by Western blotting and confocal microscopy. Plakoglobin was expressed throughout embryo development at the protein level. Western blotting revealed that embryonic plakoglobin protein content increased between 12- and 24-h post-fertilization (hpf). Confocal microscopy showed that at stages up to 12 hpf, plakoglobin and beta-catenin were co-localized and expressed in both the nucleus and in cell-cell junctions. At 24- and 72-hpf, separate patterns were seen for plakoglobin and beta-catenin. These data indicate that plakoglobin localization in the heart region shifts from adherens junctions to desmosomes during heart chamber development.

Adherens Junctions↗
PubMed1999

Effect of adenylyl cyclase activation on intracellular and extracellular cAMP and cGMP in preimplantation cattle blastocysts.

The effects of direct and indirect activation of adenylyl cyclase on the production of intracellular and extracellular cAMP and cGMP by 13- to 16-day-old cattle embryos were determined. Embryos were incubated for 2 h in a Krebs Ringer bicarbonate medium containing the phosphodiesterase inhibitor isobutyl-methylxanthine, to which stimulating agents forskolin (100 mumol l-1), cholera toxin (2 micrograms ml-1), or both were added. Total (intra- and extracellular) basal cAMP and cGMP concentrations ranged from 6.65 +/- 0.895 to 3.4 +/- 0.708 fmol microgram-1 protein in 13-day-old embryos and from 4.05 +/- 1.151 to 0.19 +/- 0.041 fmol microgram-1 protein in 16-day-old embryos. Forskolin induced an increase (P < 0.001) in cAMP that ranged from 5.4-fold on day 13 to 2.7-fold on day 16, whereas cholera toxin induced an increase (P < 0.001) that ranged from 30-fold at day 13 to 21-fold at day 16, similar to the effect of forskolin and cholera toxin combined. Individually, forskolin and cholera toxin had no effect on cGMP concentrations, but together they induced an increase (P < 0.05). cAMP (P < 0.01) and cGMP (P < 0.001) concentrations decreased with embryo age from day 13 to day 16 for all treatments; the decrease was greater for cGMP than cAMP (5-24-fold versus 1.6-3.3-fold, respectively). It is concluded that inducible adenylyl cyclase is present in 13- to 16-day-old cattle embryos and that the embryos secrete cAMP and cGMP into the incubation medium. In addition, basal and inducible concentrations of cAMP and cGMP decrease with embryo age from day 13 to day 16. These observations indicate that cAMP and cGMP may have a role in the rapid embryonic cell proliferation that occurs at this time or in signalling to the endometrium.

Adenylyl Cyclases↗
PubMed1998

Epidermal growth factor receptor and ligands in elongating bovine blastocysts.

Preimplantation development depends on multiple interactions between mother and embryo. The Epidermal Growth Factor Receptor (EGF-R) and its ligands are potential components of the embryo-maternal cross-talk: Employing RT-PCR, in situ hybridization, and immunohistochemistry, we investigated on mRNA and protein level the expression of EGF-R, Epidermal Growth Factor (EGF), Transforming Growth Factor alpha (TGF-alpha), and Heparin-binding EGF-like Growth Factor (HB-EGF) in spherical and elongating bovine blastocysts between day 13 and day 16 of gestation, and in endometrium at day 13 of gestation. EGF-R mRNA and protein were detected in trophoblast and endoderm cells of all blastocyst stages that were studied, and in luminal and some glandular epithelial cells of the endometrium at day 13. EGF protein was detected in both blastocysts and endometrial epithelium. TGF-alpha transcripts and protein were present in blastocysts prior to and after elongation and in uterine glandular and luminal epithelium at day 13 of gestation. HB-EGF mRNA and protein was shown in the endoderm, and the protein also was detected immunohistochemically in about 45% of the blastocysts. This presence of the EGF receptor-ligand system in the endometrium and the preimplantation embryo at the time of blastocyst elongation suggests an important role for these growth factors during bovine preimplantation development.

Animals↗
PubMed1997

Volitional control of anticipatory ocular smooth pursuit after viewing, but not pursuing, a moving target: evidence for a re-afferent velocity store.

Although human subjects cannot normally initiate smooth eye movements in the absence of a moving target, previous experiments have established that such movements can be evoked if the subject is required to pursue a regularly repeated, transient target motion stimulus. We sought to determine whether active pursuit was necessary to evoke such an anticipatory response or whether it could be induced after merely viewing the target motion. Subjects were presented with a succession of ramp target motion stimuli of identical velocity and alternating direction in the horizontal axis. In initial experiments, the target was exposed for only 120 ms as it passed through centre, with a constant interval between presentations. Ramp velocity was varied from +/- 9 to 45 degrees/s in one set of trials; the interval between ramp presentations was varied from 640 to 1920 ms in another. Subjects were instructed either to pursue the moving target from the first presentation or to hold fixation on another, stationary target during the first one, two or three presentations of the moving display. Without fixation, the first smooth movement was initiated with a mean latency of 95 ms after target onset, but with repeated presentations anticipatory smooth movements started to build up before target onset. In contrast, when the subjects fixated the stationary target for three presentations of the moving target, the first movement they made was already anticipatory and had a peak velocity that was significantly greater than that of the first response without prior fixation. The conditions of experiment 1 were repeated in experiment 3 with a longer duration of target exposure (480 ms), to allow higher eye velocities to build up. Again, after three prior fixations, the anticipatory velocity measured at 100 ms after target onset (when visual feedback would be expected to start) was not significantly different to that evoked after the subjects had made three active pursuit responses to the same target motion, reaching a mean of 20 degrees/s for a 50 degrees/s target movement. In a further experiment, we determined whether subjects could use stored information from prior active pursuit to generate anticipatory pursuit in darkness if there was a high expectancy that the target would reappear with identical velocity. Subjects made one predictive response immediately after target disappearance, but very little response thereafter until the time at which they expected the target to reappear, when they were again able to re-vitalize the anticipatory response before target appearance. The findings of these experiments provide evidence that information related to target velocity can be stored and used to generate future anticipatory responses even in the absence of eye movement. This suggests that information for storage is probably derived from a common pre-motor drive signal that is inhibited during fixation, rather than an efference copy of eye movement itself. Furthermore, a high level of expectancy of target appearance can facilitate the release of this stored information in darkness.

Afferent Pathways↗
PubMed1997

Cyclic AMP and cyclic GMP concentrations in, and efflux from, preimplantation cattle embryos.

Basal embryonic cAMP and cGMP concentrations and cAMP and cGMP accumulation in embryos and in the incubation medium were measured in cattle blastocysts recovered at days 14 (n = 23), 15 (n = 29) and 16 (n = 23) of pregnancy. Cyclic AMP and cGMP concentrations were measured by radioimmunoassay and the results expressed per microgram of protein, which was determined by the Pierce Micro BCA protein assay. Cyclic AMP and cGMP were present on each day. Basal embryonic cAMP was similar on days 14, 15, and 16, at 2.3., 2.5 and 2.6 fmol per microgram protein, respectively, while the concentration of cGMP was higher at day 14 (0.14 fmol per microgram protein than at either day 15 or 16 (0.06 and 0.05 fmol per microgram protein, respectively; P < 0.05), which were similar (P > 0.10). Basal embryonic cAMP concentrations were 15 to 60-fold higher than cGMP concentrations. Following a 2 h culture period in the presence or absence of the phosphodiesterase (PDE) inhibitor, isobutylmethylxanthine (IBMX), the accumulated concentrations of cAMP and cGMP were measured in the embryos and in the incubation medium. IBMX did not affect the concentrations of either cAMP or cGMP in the embryos but increased the concentrations of cAMP (P < 0.005) and cGMP (P < 0.01) in the incubation medium. There was no effect of day on either embryonic or medium cAMP, but both embryonic and medium cGMP were higher at day 14 than at day 15 (P < 0.05) or 16 (P < 0.005). Differences between embryonic and medium cAMP and cGMP accumulation were examined. There was no effect of day or treatment. cGMP accumulation in the medium was higher than in the embryos (P < 0.005) whereas cAMP accumulation in the medium was lower than in the embryos (P < 0.05). Whether the efflux of cAMP and cGMP is active or passive is not clear but it may indicate a possible role in embryo-maternal signalling.

1-Methyl-3-isobutylxanthine↗
PubMed1996

Protein content of cattle oocytes and embryos from the two-cell to the elongated blastocyst stage at day 16.

The protein content of cattle oocytes and preimplantation embryos produced in vivo, from the two-cell to the elongated blastocyst at day 16, was determined. From the oocyte to the expanded blastocyst stage (day 8), protein determination was carried out on zona pellucida-enclosed embryos. Protein content was measured by the Pierce Micro BCA protein assay. The mean protein content of oocytes was 0.126 micrograms, with no significant increase at the two-cell stage (0.132 micrograms). Protein content was higher at the morula stage (0.183 micrograms; P < 0.05) with a further increase at the expanded blastocyst stage (0.367 micrograms; P < 0.05). There was a 160-fold increase in protein content from the expanded blastocyst to the hatched day 13 stage. Spherical, ovoid and elongated blastocysts were collected on days 13 and 14. The mean protein content of day 13 (59.8 micrograms) and day 14 (92.4 micrograms) embryos was similar (P > 0.1), but the protein content of the elongated embryos was higher than that of ovoid or spherical embryos collected on the same day. Protein content of day 15 embryos (362.2 micrograms) was higher than that on day 14, with a further increase to 946.6 micrograms by day 16. The correlation between protein content and day of development contained both a linear and a quadratic component. Embryo length and width increased from day 13 (5.24 mm and 0.89 mm, respectively) to day 16 (51.6 mm and 1.82 mm, respectively). From day 13 to day 16, the protein content was correlated with both embryo length and width (r2 = 0.89 and 0.51, respectively; P < 0.001) and was highly correlated (r2 = 0.95) with the product of embryo length by width, indicating that protein content increases as a function of surface area.

Animals↗
PubMed1995

Effect of immunization against synthetic peptide sequences of the alpha N-subunit of bovine inhibin on ovulation rate, gonadotrophin concentrations and fertility in heifers.

The effects of immunizing cattle against either of two peptides from the amino terminal peptide (alpha N) of the alpha 43-subunit of bovine inhibin on ovulation rate, gonadotrophin concentration and fertility were investigated. Two peptide sequences from the alpha N-subunit of bovine inhibin (P1N, bI alpha-(8-20) and P2N, bI alpha-(153-167)) were synthesized and conjugated to human serum albumin (HSA). Hereford-cross heifers (n = 5 per group) were given an initial injection of 3 mg of one of the peptide conjugates, followed by three booster injections (1.5 mg) at intervals of 11 weeks. Control heifers (n = 5) were injected with HSA only. Blood samples were taken once a week to measure antibody titre and every hour at about the time of the first oestrus and during the mid-luteal phase after the second booster injection, to measure FSH and LH concentrations. Ovulation rate was measured by ultrasonography. Gonadotrophin concentrations were analysed for four periods relative to the peak (time = 0 h) of the preovulatory LH surge as follows: pre-surge: -16 to -5 h; surge: -4 to 4 h; post-surge: 5 to 16 h and a period of 12 h during the mid-luteal (days 10-12) phase. Antibodies that bound to the individual peptides were generated and the ovulation rate increased (P < 0.05) in immunized heifers. Control heifers had one ovulation at all ovulatory cycles monitored. In group P1N, one heifer had two ovulations at each of the six cycles monitored, while another heifer had two ovulations at one cycle.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1992

Neuroendocrine response to clonidine and 8-OH-DPAT in rats following chronic administration of desipramine or sertraline.

1. Rats were administered either desipramine (DMI) or sertraline daily at doses 7.5 mg kg-1 or 10 mg kg-1, i.p., respectively and the effects on the functional state of hypothalamic neuroendocrine control mechanisms assessed by measurements of plasma hormones following acute drug challenge. The effects of treatment on gross behaviour and brain adrenoceptor density were also determined. 2. Both DMI and sertraline caused significant reduction in activity measured as ambulation and rearing at 14 days of treatment. 3. All animals were chronically cannulated after 14 days of treatment and tested for neuroendocrine response to acute i.v. clonidine (50 micrograms kg-1) or 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT, 250 micrograms kg-1) after 21 or more days of treatment. 4. Rats treated with DMI but not sertraline showed a virtually complete suppression of the growth hormone (GH) secretion elicited by clonidine in controls, while the secretion of corticosterone was augmented. 5. Treatment with DMI but not sertraline led to a significantly greater 8-OH-DPAT-induced secretion of prolactin than in the control rats, while the plasma concentrations of corticosterone following 8-OH-DPAT were not influenced by either DMI or sertraline treatment. 6. The density (but not the affinity) of cerebral cortical binding of [3H]-dihydroalprenolol was significantly reduced by DMI treatment. 7. These results show that DMI treatment blunted the sensitivity of post-synaptic alpha 2-adrenoceptors, accompanied by complex interactions manifested as increased responsiveness of alpha 1-adrenoceptors and 5-HT1A receptors. Sertraline had no significant neurendocrine effects at a dose which significantly reduced gross activity.

1-Naphthylamine↗
PubMed1991

Secretion of growth hormone elicited by intravenous desipramine in the conscious, unrestrained rat.

1. Acute intravenous administration of either clonidine (Clon) (50 micrograms kg-1) or desipramine (DMI) (5 mg kg-1) elicited a pulse of growth hormone (GH) and corticosterone secretion in conscious, unrestrained rats. 2. The responses to DMI were similar to those with Clon, except that the GH pulse following DMI was delayed and was not dose-dependent. 3. The GH response to DMI was inhibited by prior administration of idazoxan (1 mg kg-1) or yohimbine (0.5 mg kg-1), but not by atropine (10 micrograms kg-1), sulpiride (5 mg kg-1) or prazosin (1 mg kg-1). 4. The corticosterone secretion following DMI was not altered by prior atropine, sulpiride or prazosin, but was augmented by idazoxan (1 mg kg-1). 5. GH secretion was not influenced by atropine, sulpiride, prazosin or idazoxan given alone. Idazoxan or yohimbine given alone elicited significant secretion of corticosterone. 6. It is concluded that i.v. DMI caused an activation through indirect mechanisms of alpha 2-adrenoceptors specifically involved in hypothalamic-pituitary regulation of GH release and also a distinct, independent and transient generalized activation of the pituitary-adrenal axis.

Animals↗