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Biomedical subjects

W R Gibson

Publications and source records attributed to W R Gibson.

At least 19 recordsLinked to original sources
PubMed1991

Prevalence of hearing loss in adults with sickle cell disease.

Hearing status in 75 adult subjects with sickle cell disease was examined. Thirty-one (or 41%) of the subjects failed the hearing screening. When examined by hemoglobin type, it was found that persons with sickle cell C disease had the greatest incidence of hearing loss, although all subject groups exhibited greater prevalence rates than the general population. The results suggest that routine audiologic assessment be incorporated into the regular medical examination for adults with sickle cell disease.

Adolescent↗
PubMed1991

Hearing disorders in sickle cell disease: cochlear and retrocochlear findings.

The auditory system was assessed in 34 adult subjects with sickle cell disease using standard audiometric test techniques. The study results indicate that patients with sickle cell disease are at risk for retro-cochlear as well as cochlear dysfunction of the auditory system. However, there is no consistent audiometric pattern that is pathognomonic of sickle cell disease. The test results indicate that auditory status should be carefully monitored in all adult patients with sickle cell disease.

Acoustic Impedance Tests↗
PubMed1986

Daunomycin-induced cardiomyopathy in rabbits: isolated heart and papillary muscle energetics.

Daunomycin was administered to one of each pair of litter mate rabbits at a weekly dosage rate of 40 mg/m2. Treated animals were killed when their pre-ejection period: left ventricular ejection time ratio (PEP:LVET) reached 0.4 and there was other evidence of cardiac abnormalities or when they had received 12 doses of daunomycin. Langendorff-perfused hearts from the treated animals had lower intrinsic heart rates (16%) and decreased coronary resistance (31%) in the arrested state. There was no significant difference between the basal metabolism of the arrested control and treated hearts but the magnitude of the activation component, measured under beating non-working conditions, was depressed by daunomycin. After the whole heart perfusion studies were complete, approximately 2 h after cardiectomy, papillary muscles were dissected out from the right ventricles and mechanical, myothermic and polarographic studies were undertaken. The resting heat production, in support of the whole heart metabolic data, was practically unchanged by the treatment regime. Peak stress development and work output were similar in both the control and treated groups. In energetic terms the slope of the relationship between total stress development and active heat production per beat was unchanged but there was a 21% depression of the activation heat component in the treated animals. Daunomycin treatment had not altered the work output per contraction or significantly changed energy output and hence mechanical efficiency was unaltered. It is clear that 2 h of Langendorff perfusion does not produce any depression of contractile or energetic properties in papillary muscles.

Animals↗
PubMed1986

Blood flow in the ovary and oviduct of rats after sympathetic denervation.

The effect of sympathetic denervation on blood flow in the ovary and oviduct was studied in rats undergoing oestrous cycles or at Day 14 of pregnancy. The ovary and oviduct on one side were denervated by briefly freezing the ovarian vascular pedicle and the ovarian suspensory ligament. Blood flow was measured using 15 microns 57Co-labelled microspheres while the rats were under barbiturate anaesthesia. In cyclic rats denervation raised blood flow to the oviduct by 90% the next day (P less than 0.01) and 39% at 4-10 days (0.05 less than P less than 0.1). Blood flow to the ovary was not affected. Denervation on Day 13 of pregnancy raised blood flow in the oviduct 5-fold at Day 14 (P less than 0.01) and denervation on Day 7 raised blood flow 3-fold on Day 14 (P less than 0.05). Blood flow to the luteal and non-luteal components of the ovary was not affected. Sham-operation did not affect blood flow in the oviduct or ovary. It is concluded that sympathetic nerves exert tonic vasoconstrictor control on the vasculature of the oviduct but not on that of the ovary, and that these nerves do not regulate the major changes in blood flow that occur in ovaries in various physiological states.

Animals↗
PubMed1985

Follicular dynamics throughout the oestrous cycle in sheep. A review.

Whatever the stage of the cycle, follicles of various sizes are apparent on the surface of the ovary of sheep. No evidence of waves of follicular growth at fixed-time intervals has been found during the luteal phase, and growth probably occurs at random until the follicle attains a size of 4 to 7 mm. This shows that follicles can enlarge under a wide range of hormonal levels. The recruitment of a crop of follicles, including the one which will ovulate, occurs at variable times around luteolysis due to the interaction of endocrine and follicular factors (FSH priming, sensitizing the follicle to increased LH pulsatility). All healthy follicles greater than 2 mm in diameter are recruited. Selection of the follicle due to ovulate can be defined by morphological criteria (size) or by its "killing" ability. In all cases, the timing of follicle selection is highly variable, and it is due to this variability that the mechanisms of selection are not fully known. They are presumably intraovarian, one of the follicles actively inhibiting the growth of the others. The dominant follicle is probably maintained because of its high oestradiol content, while the others undergo atresia. The main feature of terminal follicular development is its flexibility in terms of hormonal requirements, follicle size and the timing of the main events.

Anestrus↗
PubMed1985

Ovulation after sympathetic denervation of the rat ovary produced by freezing its nerve supply.

The ovaries of cyclic female rats were unilaterally or bilaterally denervated or sham-operated. Denervation was achieved by freezing the ovarian vascular pedicle and suspensory ligament about 1 cm from the ovary; this technique renders the ovary devoid of innervation for up to 10 days. Denervated ovaries from 6 unilaterally and 7 bilaterally operated animals exhibited normal ovulation rates (5.8 +/- 1.0 and 5.2 +/- 1.2 respectively, mean +/- s.e.m.) compared with intact (5.6 +/- 0.4) and sham-operated controls (4.4 +/- 0.6 unilaterally sham-operated; 4.1 +/- 0.8 bilaterally sham-operated). It is concluded that the mechanism of follicular rupture is unaffected by the absence of ovarian sympathetic innervation.

Animals↗
PubMed1985

Pregnancy and parturition in rats after sympathetic denervation of the ovary, oviduct and utero-tubal junction.

The ovarian vascular pedicle and ovarian suspensory ligament were briefly frozen to destroy the nerves. Examination of sections from the ovary, oviduct and utero-tubal junction by fluorescence histochemistry showed that they were usually devoid of adrenergic nerves. Measurement of noradrenaline in segments of the uterine horn by high-performance liquid chromatography showed that the transmitter was eliminated from the upper third but not the middle or lower thirds of the uterine horn. Unilateral or bilateral denervations at metoestrus in cyclic rats did not affect either the number of ovulations or the numbers or spacing of conceptuses at Day 7 of pregnancy. Bilateral denervations on Days 4, 7 or 11 of pregnancy did not affect ovarian weights or numbers of conceptuses observed 1 week later. Plasma progesterone concentrations were at least as high in the denervated groups as in the sham-operated control groups. After unilateral or bilateral denervations at Day 15, pregnancy continued normally and birth of normal young occurred, without apparent problems, at the same time as for sham-operated rats. The mothers tended their young and allowed them to suck. It is concluded that the adrenergic innervation of the ovary in the rat is not required for its normal function during pregnancy; that of the oviduct and mesosalpinx is not required for ovum pick-up or for transport of oocytes, spermatozoa or early embryos; and that of the utero-tubal junction is not required for uterine motility involved in embryo spacing and parturition.

Adrenergic Fibers↗
PubMed1985

Ovulation rate and inhibin levels in gonadotrophin-treated mice.

Ovarian follicular growth was induced in immature female mice with varying doses of pregnant mare's serum gonadotrophin. The numbers of ovulations were determined either by counting tubal oocytes or corpora lutea in the ovary. Ovarian and circulatory levels of inhibin rose progressively with increasing doses of PMSG and a positive correlation (P less than 0.01) was found between circulating inhibin levels and ovulation rate. The latter correlation makes it likely that the growing preovulatory ovarian follicles are the predominant source for the secretion of inhibin into the circulatory system.

Animals↗
PubMed1984

Cardiac energetics in daunorubicin-induced cardiomyopathy.

Daunorubicin (DNR) was administered to one of each pair of litter mate rabbits at a weekly dosage rate of 40 mg/m2. Treated animals were killed when their pre-ejection period: left ventricular ejection time ratio (PEP:LVET) reached or exceeded 0.4. Mechanical, myothermic and polarographic measurements were made upon papillary muscles obtained from the right ventricle of DNR treated rabbits and their litter mate controls. DNR treatment significantly increased the PEP:LVET ratio (41%) and increased the left ventricular: body weight ratio (24%). Basal metabolism, measured 2 h after cardiectomy, was significantly reduced whether measured myothermically or polarographically: both measurements were highly correlated but the O2 consumption values were higher. Peak stress development was 31% lower in the DNR treated rabbits but this reduction was largely accounted for by a larger cross-sectional area (CSA) of the papillary muscles in this group. There was no change in the slope of the active heat: stress relationships but the stress-independent (activation) heat intercept was depressed. In isotonic studies DNR treatment caused a 57% reduction in work output per beat (relative to controls) and a 39% decline in active energy output. Because of the approximately parallel shift in work and total energy output mechanical efficiency was not significantly changed. It is suggested that part of the basal energy production fall produced by DNR relates to protein synthesis inhibition but that most of the other mechanical and energetic effects are probably explicable in terms of the intrinsic hypertrophic response of the 'failing' heart.

Animals↗
PubMed1984

Action of PMSG on follicular populations in the heifer.

The short-term action of PMSG on the population of growing follicles in cattle was studied using histological methods. On Day 7 of a synchronized oestrous cycle 10 Friesian heifers were unilaterally ovariectomized. The remaining ovary was immediately stimulated by an injection of PMSG (2000 i.u.) and was removed 48 h after the preovulatory discharge of LH. Control animals did not receive any injection of PMSG. In all ovaries, follicles greater than 70 micron diameter were counted, measured and checked for atresia. The mitotic index in granulosa cells of follicles of different sizes was estimated in both ovaries of all the PMSG-injected animals. Unilateral ovariectomy alone had no significant effect on follicular populations. In the interval between PMSG injection and removal of the second ovary (148 +/- 22.7 h), PMSG significantly increased the number of normal preantral follicles but did not change the number of normal antral follicles. The mitotic index doubled in preantral and early antral follicles but remained unchanged in large antral follicles. PMSG stimulated slightly the growth of the antrum in large antral follicles but did not stimulate its formation in preantral follicles. The incidence of atresia among antral follicles, particularly the largest ones (diam. greater than 1.7 mm), was significantly reduced after PMSG, suggesting some 'rescue' of follicles from atresia.

Animals↗
PubMed1984

Time course of sympathetic denervation of the rat ovary after freezing its nerve supply.

Brief freezing of the ovarian vascular pedicle in rats reduced ovarian noradrenaline concentration, measured with HPLC, by 67% (P less than 0.01). Freezing of the ovarian suspensory ligament caused a 22% reduction (P less than 0.01) and 33% reduction (P less than 0.05) in 2 experiments. The numbers of adrenergic nerve terminals detected by fluorescence microscopy after these procedures were similarly reduced (P less than 0.01). Freezing of both the pedicle and the ligament produced complete sympathetic denervation in about 50% of the ovaries. From Days 2 to 10 after operation no noradrenaline or nerve terminals were detected in 14 out of 27 ovaries. Nerve terminals were also eliminated from the oviduct. Reinnervation of the ovary began between Days 12 and 30. It is concluded that the adrenergic innervation of the ovary is predominantly through nerves that accompany the vascular supply to the ovary and the ovarian suspensory ligament. Freezing of these routes is a simple and relatively atraumatic means of denervating the ovary for experimental studies.

Animals↗
PubMed1982

Effects of pancreatectomy, tolbutamide and insulin on glucose fluxes in chickens.

The effects of pancreatectomy and of injection of insulin or Tolbutamide on glucose fluxes in chickens were examined. This was prompted by earlier observations that Tolbutamide seems not to require the presence of pancreatic insulin for its acute hypoglycaemic action in this species. Rates of appearance (Ra) and disappearance (Rd) of glucose were estimated by isotope dilution using [14C]glucose in single-injection experiments and [14C]glucose and [6-3H]glucose in priming-injection + constant-infusion experiments. Six hours after sub-total pancreatectomy (splenic lobe remained in situ), chickens were hyperglycaemic (16.7 v. 10-4 mmol glucose/1 in controls), had a larger sampled glucose pool (4.41 v. 3.10 mmol) and a higher average rate of glucose utilization (41.7 v. 33.3 micron mol/kg per min) than sham-operated controls as estimated in single-injection experiments. Tolbutamide (50 mg/kg injected i.v.) reduced Ra in intact chickens from 33.9 to 1.1 micro mol/kg per min and reduced Ra in pancreatectomized chickens from 42.2 to 10.2 micro mol/kg per min. in priming-injection + constant-infusion experiments tolbutamide again reduced Ra significantly. In all case Rd tended to fall, apparently as a result of the developing hypoglycaemia. tolbutamide did not affect the volume of extracellular fluid (sucrose space). In single-injection experiments , insulin (1 unit/kg injected i.v.) reduced Ra by 56% and transiently increased Rd by 39%. It was concluded that pancreatectomy and injection of insulin or tolbutamide produce responses in glucose movements in chickens that are qualitatively similar to those in mammals. In chickens the hypoglcaemic action of tolbutamide, which persists in the absence of the pancreas, depends on an inhibition of glucose release by the liver.

Animals↗
PubMed1979

Can reduced consumption of gonadotrophins account for ovarian compensation in unilaterally ovariectomized, immature mice injected with gonadotrophins?

The effect of unilateral ovariectomy on ovulation rates in immature mice was studied. Ovulations were induced by injecting PMSG and hCG and their number was determined by counting tubal oocytes. A 2--3-fold increase in number of ovulations per ovary was observed after unilateral ovariectomy, and daily injections of progesterone abolished this ovulatory compensation. No significant increase in serum concentrations of immunoreactive FSH and LH was observed at 4, 8, 32 and 51 h after unilateral ovariectomy. Progesterone treatment lowered FSH levels at all times, while LH was unaffected. In intact mice, ovarian sensitivity to PMSG and hCG was not substantially affected by progesterone. Ovulatory compensation in immature gonadotrophin-injected mice appears to arise through a negative feedback mechanism and transiently increased secretion of pituitary gonadotrophin rather than through a greater utilization of a fixed amount of gonadotrophin.

Animals↗