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Biomedical subjects

J P Ryan

Publications and source records attributed to J P Ryan.

At least 19 recordsLinked to original sources
PubMed1992

Time of ovulation in merino ewes superovulated with PMSG and FSH-P.

An experiment examined the effects of treatment with gonadotrophin releasing hormone (100 micrograms GnRH injected 24 h after progestagen sponge removal), season of treatment (autumn v. spring), the effect of supplementary feeding with lupin grain (in autumn only, from 12 days before until 8 days after sponge removal) on the time of ovulation in 182 mature Merino ewes superovulated with a combination of 400 I.U. pregnant mare serum gonadotrophin (PMSG) and 12 mg follicle stimulating hormone (FSH-P). Time of ovulation was influenced by both season and the administration of GnRH. Two peaks of ovulation were observed in spring, the first between 24 and 30 h after sponge removal, and the second commencing 42 h after sponge removal. In autumn, there was one peak of ovulation between 42 and 54 h after sponge removal. Treatment with GnRH advanced the time of ovulation in autumn (P less than 0.05), but had no apparent effect in spring. In contrast to the effect of GnRH, time of ovulation for ewes treated in autumn was delayed (P less than 0.001) by supplementary feeding with lupins.

Animal Feed↗
PubMed1992

Metabolic and developmental responses of preimplantation embryos to platelet activating factor (PAF).

Platelet activating factor (PAF) is an ether phospholipid produced by preimplantation embryos of a number of species. Production of PAF by embryos has been measured by detecting thrombocytopenia in a splenectomized mouse bioassay, platelet aggregation bioassays in vitro and a specific radioimmunoassay. Production is highly variable and is adversely affected by culture in vitro. It has, however, been correlated with morphology, development rates in vitro and the pregnancy potential of embryos following transfer. Investigations using PAF-antagonists have established an essential role for PAF in early pregnancy. Together with studies that have shown PAF to have direct effects on embryonic metabolism during culture in vitro, these observations suggest that PAF acts as an embryonic autocoid. Hence, a major site of action for embryo-derived PAF in vivo is the embryo itself. Supplementation of embryo culture media with PAF had no effect on the rate of development in vitro of 2-cell mouse embryos through to the blastocyst stage. However, PAF increased cell numbers of blastocysts cultured from the 2-cell stage and the mitotic index of embryos at both the 8-cell and blastocyst stages. Supplementation of culture media with PAF has also been shown to increase the implantation potential of both mouse and human embryos cultured in vitro. In the mouse, the effect of PAF in enhancing implantation rates was most evident when the developmental potential of untreated embryos was suboptimal. These observations suggest that the production of embryo-derived PAF is one limiting factor in maintaining the viability of embryos cultured in vitro.

Animals↗
PubMed1992

A nasal CPAP system. Description and comparison with facemask CPAP.

Nasopharyngeal pressures were compared in eight subjects breathing through either a nasal CPAP system or facemask CPAP system at a fresh gas flow of 50, 75 and 100 l.min-1. During nose breathing there was no significant difference in nasopharyngeal pressure between the two systems. During mouth breathing pressures were significantly lower with nasal CPAP. During nose breathing at 75 l.min-1 the mean inspiratory and expiratory pressures in cmH2O (SD) were 3.4 (0.68) and 5.9 (0.55) for nasal CPAP and 3.3 (0.71) and 6.3 (0.73) for facemask CPAP. The respective pressures during mouth breathing were 0.3 (0.73) and 2.9 (1.74) for nasal CPAP and 3.9 (0.73) and 5.8 (0.82) for facemask CPAP.

Adult↗
PubMed1992

Nasal CPAP after coronary artery surgery.

Two groups of 14 patients were compared after coronary artery bypass surgery where the left internal mammary artery had been used as a conduit. One group received nasal continuous positive airway pressure for 1 h, the other group acted as a control. Mean pulmonary shunt fraction was 16.3% before, 12.6% during and 15.7% after continuous positive airways pressure. In the control group the shunt fraction fell from 17.3% to 16.8%. The reduction in shunt fraction was significantly greater with nasal continuous positive airways pressure than in the control group (p = 0.016). There was a significant reduction (p = 0.025) in respiratory rate from 18.3 to 16.7 breath.min-1 during continuous positive airway pressure. Other measured cardiorespiratory variables did not differ significantly between the groups. Visual analogue scores showed no significant difference in chest pain or mask comfort between the groups. The ease of breathing score was, however, significantly better in the continuous positive airways pressure group, 7.5 (SD 1.8) cm and control 5.6 (SD 2.6) cm.

Coronary Artery Bypass↗
PubMed1992

Modulation of cat antral slow waves by ion substitution, Ca2+ and K+ channel blockade, and ACh stimulation.

Two distinct slow waves can be recorded from smooth muscle cells on the submucosal border (submucosal cells) and the myenteric border (myenteric cells) in the circular layer of the cat antrum. The present studies examined the effects of decreasing extracellular Na+ ([Na+]o) or Ca2+ concentration ([Ca2+]o), Ca2+ and K+ channel blockade, and acetylcholine (ACh) stimulation on "submucosal" and "myenteric" slow waves using intracellular recording techniques. Decreasing [Na+]o (30 mM) reduced the upstroke depolarization of slow waves from submucosal cells but had no effect on the upstroke depolarization of myenteric cells. Decreasing [Ca2+]o (0.5 mM) decreased the upstroke depolarization in cells from each area. Neither cadmium (200 microM) nor nifedipine (100 microM) had any effect on the upstroke depolarizations from both submucosal and myenteric slow waves. In contrast, nickel (5 mM), a nonselective Ca2+ channel blocker, decreased the upstroke depolarizations of slow waves from submucosal and myenteric cells. Slow waves from myenteric cells normally exhibit a plateau phase of several seconds duration. The amplitude of the plateau potential could be decreased by lowering [Na+]o or [Ca2+]o or by nickel, cadmium or nifedipine. In the presence of 30 mM Na+ slow waves from submucosal cells appeared to develop plateau potentials. K+ channel blockade with tetrabutylammonium (TBA, 5 mM) or cesium (10 mM) increased the upstroke depolarization and delayed membrane repolarization in slow waves from submucosal cells. TBA and cesium also increased the upstroke depolarization from myenteric cells but did not delay membrane repolarization. ACh (1 and 3 microM) caused the generation of plateau potentials in slow waves from submucosal cells and increased slow-wave duration.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1992

Upper airway disease in systemic lupus erythematosus: a report of 4 cases and a review of the literature.

We report the occurrence of life threatening upper airway complications in 4 of 158 patients with systemic lupus erythematosus (SLE) admitted to our hospital over a 6-year period and review published reports on this complication. The patients included in our study were identified through a computer search of our hospital medical records. Patients' charts were reviewed and the diagnosis confirmed by currently accepted criteria. The clinical features of SLE in all the published cases were assessed and compared to those found in our patients. We found that although upper airway involvement is uncommon in SLE, occurring with a relative frequency of 4/158 patient admissions, endotracheal intubation in patients with active SLE may result in the development of life threatening upper airway complications. We suggest that patients with active SLE who require intubation should be observed for the development of upper airway symptoms.

Adult↗
PubMed1991

Increased production of sheep embryos following superovulation of Merino ewes with a combination of pregnant mare serum gonadotrophin and follicle stimulating hormone.

In a factorially designed experiment (N = 321), 0, 800 or 1600 I.U. pregnant mare serum gonadotrophin (PMSG) were administered in combination with 0, 12 or 18 mg follicle stimulating hormone (FSH-P) to superovulate Merino ewes in autumn and spring. A moderate dose of PMSG (800 I.U.) in conjunction with 12 or 18 mg FSH-P increased the ovulation rate above that observed when FSH-P was used alone. This was accomplished by (i) increasing the proportion of ewes that exhibited a superovulatory response (greater than 3 corpora lutea (CL) or persistent large follicles (LF): 69/70 (99%) v. 55/74 (74%), P less than 0.001), and (ii) in those ewes that exhibited a superovulatory response, by an additive effect of exogenous gonadotrophin (14.8 +/- 0.9 CL (69) v. 11.3 +/- 0.9 CL (55), P less than 0.01) without increasing the incidence of LF. The use of 1600 I.U. PMSG in conjunction with 12 or 18 mg FSH-P was characterized by an increase in the number of LF and, in comparison with 800 I.U. PMSG, a reduction in ovulation rate. Season had no effect on the numbers of CL, but total ovarian response (CL + LF) was higher in autumn than in spring (P less than 0.01), because of a greater incidence of LF (P less than 0.001). The proportion of ewes with regressed CL was higher in autumn than in spring (53/143 (37%) v. 32/156 (21%), P less than 0.01), and increased with increased dose of gonadotrophin. Furthermore, a nutritional component to the incidence of ewes with regressed CL was suggested by the observation that the mean concentration of plasma glucose was higher for ewes with normal CL than for ewes with regressed CL (P less than 0.05). Rates of ova or embryo recovery, fertilization and embryo development generally declined with an increase in the incidence of LF as a result of increases in the dose of gonadotrophin and season of administration.

Animals↗
PubMed1991

Effects of season, GnRH administration and lupin supplementation on the ovarian and endocrine responses of merino ewes treated with PMSG and FSH-P to induce superovulation.

Administration of gonadotrophin releasing hormone (GnRH) 24 h after sponge withdrawal did not affect the numbers of corpora lutea (CL) or persistent large follicles (LF) in ewes superovulated with 400 I.U. pregnant mare serum gonadotrophin and 12 mg follicle stimulating hormone in spring (11.6 +/- 0.9 v. 13.0 +/- 0.9 CL and 0.8 +/- 0.9 v. 0.9 +/- 0.3 LF, for +GnRH and -GnRH ewes, respectively). However, it did increase the ovulatory response of ewes superovulated in autumn (15.8 +/- 1.2 v. 11.8 +/- 1.1 CL). The incidence of ewes with prematurely regressed CL was also greater in autumn than in spring (21/89 v. 5/88). Supplementary feeding with lupin grain in autumn had no effect on numbers of CL but did increase the incidence of ewes with LF (18/48 v. 7/46) and caused a marked reduction in the incidence of ewes with regressed CL (1/44 v. 20/45). For ewes treated in autumn, there were no effects of lupin supplementation or GnRH administration on peak oestradiol-17 beta (E2) or peak luteinizing hormone (LH) levels. However, when peak E2 concentrations in the plasma were adjusted for numbers of preovulatory follicles, higher concentrations were observed for ewes in the +lupin/-GnRH group (12.4 +/- 2.9 pg mL-1) than in other treatment groups (range 4.3 +/- 0.4 to 5.7 +/- 0.3 pg mL-1). Moreover, the time of the LH peak was advanced by both lupin supplementation and GnRH treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗
PubMed1991

Effect of muscle length on isometric stress and myosin light chain phosphorylation in gallbladder smooth muscle.

These experiments were designed to characterize the effect of muscle length on isometric stress, sensitivity to stimulation, and phosphorylation of the 20,000-Da myosin light chains in guinea pig gallbladder smooth muscle. Basal, active, and total isometric stress were determined in acetylcholine- or K(+)-treated (10(-4) M ACh, 80 mM KCl) muscle strips at 0.6-1.3 times the optimal muscle length (Lo) for isometric stress development. The effect of muscle length on the sensitivity to ACh and K+ was determined in cumulative dose-response experiments (10(-8) to 10(-4) M ACh, 10-80 mM KCl) at 0.7, 1.0, and 1.3 Lo. The effect of muscle length on myosin light chain phosphorylation was determined in ACh- or K(+)-treated (10(-4) M ACh, 80 mM KCl) muscle strips at 0.7, 1.0, and 1.3 Lo. In gallbladder smooth muscle, 1) active isometric stresses at 0.7 and 1.3 Lo were less than active isometric stress at 1.0 Lo; 2) the sensitivity of developed stress was similar at 1.0 and 1.3 Lo but decreased at 0.7 Lo; 3) the decline in isometric stress and sensitivity at 0.7 Lo was associated with reduced levels of phosphorylated myosin light chain; and 4) the decline in isometric stress at 1.3 Lo was not associated with reduced amounts of phosphorylated myosin light chain. These results suggest that the decline in active stress and sensitivity at short muscle lengths (L less than Lo) in gallbladder smooth muscle is due, at least in part, to decreases in the activation of the myofilaments. The decline in active isometric stress at long muscle lengths (L greater than Lo) is not due to changes in myofilament activation.

Acetylcholine↗
PubMed1991

Electrical slow-wave activity from the circular layer of cat terminal antrum.

Intracellular recording techniques were used to characterize the electrical slow-wave activity through the thickness of the circular muscle layer of the cat terminal antrum. Muscle strips were pinned out in cross section to the floor of a recording chamber perfused with Krebs buffer. Circular muscle cells from the myenteric to the submucosal border then were impaled with 20- to 40-M omega glass microelectrodes, and slow-wave activity was recorded. Slow waves from the myenteric side of the circular layer consisted of an upstroke depolarization, a prominent plateau phase, and a downstroke repolarization. Slow-wave characteristics for cells along the myenteric border were Em, -74.2 +/- 1.3 mV; duration, 5.3 +/- 0.5 s; upstroke amplitude, 29.4 +/- 3.4 mV; upstroke velocity, 0.20 +/- 0.03 V/s; and frequency, 5.8 +/- 0.5/min. Slow waves from muscle cells along the submucosal side of the preparation lacked a discernible plateau phase. Slow waves from submucosal border cells had the following characteristics: Em, -80.4 +/- 1.4 mV (P less than 0.01); duration, 3.5 +/- 0.4 s (P less than 0.01); upstroke amplitude, 44.0 +/- 2.4 mV (P less than 0.01); upstroke velocity, 0.56 +/- 0.06 V/s (P less than 0.01); and frequency, 4.2 +/- 0.4/min (P less than 0.05). Slow waves were not affected by 10(-7)M tetrodotoxin and 10(-6)M atropine or by removal of the longitudinal muscle layer. Slow-wave activity within each region was maintained after dissecting the circular layer into submucosal and myenteric segments. The results suggest that two distinct slow waves exist within the circular muscle layer of the cat terminal antrum.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Myosin light chain phosphorylation and contraction of guinea pig gallbladder smooth muscle.

These experiments were designed to determine 1) whether acetylcholine (ACh) stimulation is accompanied by changes in myosin light chain phosphorylation in gallbladder smooth muscle and 2) whether dephosphorylated noncycling cross bridges (latch bridges) exist in gallbladder smooth muscle. Isometric stress, isotonic shortening velocity, and myosin light chain phosphorylation were determined under conditions of contraction and relaxation in ACh-stimulated guinea pig gallbladder smooth muscle. Unstimulated muscle contained 6.8 +/- 2.0% phosphorylated myosin light chain. ACh stimulation (5 x 10(-5) or 10(-4) M) was associated with a rapid increase in myosin light chain phosphorylation to a value that was maintained throughout the tonic contraction. In contrast, isotonic shortening velocity was maximal at 30 s of stimulation and then declined over time to a steady-state level that was 25-30% of the peak velocity. Upon agonist washout (relaxation), dephosphorylation of the myosin light chain occurred at about the same rate as the decline in shortening velocity and preceded the decline in isometric stress. These data suggest that ACh stimulation is accompanied by changes in myosin light chain phosphorylation but that dephosphorylation of cross bridges is not necessary for the slowing of cross-bridge cycling rates in gallbladder smooth muscle.

Acetylcholine↗
PubMed1990

The residual spatial abilities of hippocampally lesioned rats can be enhanced by peripheral sympathetic-adrenal interventions.

In order to test the possible effectiveness of peripheral interventions with the adrenergic system for the alleviation of certain disorders that typically follow bilateral hippocampal lesions, rats with bilateral lesions of the hippocampus, the overlying neocortex, or sham operations were tested at two postoperative times in the Morris water maze, a frequently used "spatial task." Half of the animals in all groups were exposed to the adrenergic manipulations, i.e., a chronic, 7-day, systemic bretylium regime (5 mg/kg) and, in addition, a peripheral injection of norepinephrine (4 micrograms/kg) 30 min before the start of each training day. The other half received saline chronically and a single saline injection before each training day. Five days of training were given at each of the two training periods. The first began 7 days after surgery while the second began 33 days after surgery. As expected, the hippocampally lesioned animals were severely impaired in the task. The adrenergic treatment produced enhanced performances in the rats with hippocampal lesions at both training sessions, although the improvement was greatest at the later period. Although the animals receiving the pharmacologic treatment located the general area of the hidden platform better than the saline-treated animals with hippocampal lesions, the treated animals were still impaired, swimming directly to the hidden platform on fewer trials than did animals in the other groups.

Adrenal Glands↗