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Biomedical subjects

D A Gibson

Publications and source records attributed to D A Gibson.

At least 19 recordsLinked to original sources
PubMed2001

Endogenous indoles as novel polyamine site ligands at the N-methyl-D-aspartate receptor complex.

High-throughput ligand displacement screens of a series of endogenous indoles revealed that tryptamine, serotonin and 5-methoxytryptamine readily displace [3H]spermidine and [3H]MK-801 from their respective binding sites in rat brain homogenate. These data, coupled with their potent inhibition of spermidine-potentiated [3H]MK-801 binding, suggest that certain endogenous indoles may act as ligands to one or more polyamine binding sites in the brain, including those on the N-methyl-D-aspartate receptor complex.

Animals↗
PubMed2000

In vitro effects of ethanol withdrawal and spermidine on viability of hippocampus from male and female rat.

BACKGROUND: Long-term ethanol dependence results in neuronal adaptation that likely contributes to ethanol withdrawal-induced central nervous system excitability and, potentially, neurotoxicity. This has been suggested to result, in part, from increased release of or response to endogenous polyamines. Furthermore, it has been reported that neurological difficulties related to ethanol dependence and withdrawal may be more severe in female than in male alcoholics. Thus, we designed this study to examine effects of the polyamine spermidine on neurotoxicity associated with withdrawal from long-term ethanol exposure by using organotypic hippocampal slice cultures derived from male and female rats. METHODS AND RESULTS: Twenty-four hours of withdrawal after continuous 10 day ethanol exposure (100 mM in culture medium) resulted in cytotoxicity in hippocampal slice explants obtained from both sexes. This was most evident in pyramidal cell layers of the CA1 region, and no sex differences were observed in the severity of damage. Exposure of explants from both sexes to the NMDA blocker MK-801 during ethanol withdrawal significantly reduced this toxicity. In control cultures, exposure to spermidine (100 microM) alone produced significant and similar cytotoxicity in hippocampal explants of male and female rats. Exposure to spermidine (100 microM) during ethanol withdrawal significantly increased cytotoxicity in all regions of explants. In the CA3 region, spermidine-potentiation of ethanol withdrawal damage was significantly greater in explants from female rats compared with those from male rats. CONCLUSIONS: These data demonstrate the presence of significant hippocampal neurotoxicity during withdrawal from long-term ethanol exposure that is mediated, in part, by overactivation of NMDA receptors. Furthermore, these findings suggest that the central nervous system of females may be more susceptible than that of males to polyamine-mediated neuronal damage during withdrawal from long-term ethanol exposure.

Alcohol Withdrawal Delirium↗
PubMed1991

Media for the education of health professionals.

The benefits and pitfalls of applying media and communications techniques to the education of health professionals are considered in the context of their use in the classroom, for independent study and for distance education. The difficulties are emphasized for managing learning materials of this kind, and for keeping them up-to-date.

Audiovisual Aids↗
PubMed1990

Geographic variations in Medicare utilization of short-stay hospital services, 1981-88.

The change in Federal fiscal year 1984 from cost-based reimbursement to prospective payment at a fixed price for a known and defined product--the hospital stay--represents a fundamental change in the role of the Medicare program within the health care delivery system. In this article, national and selected geographic trends in Medicare short-stay hospital inpatient discharges since 1981 are presented, and they show the impact of the implementation of the prospective payment system.

Catchment Area, Health↗
PubMed1990

The effects of naloxone on the changes in breathing and behaviour induced by morphine in the foetal sheep.

In the foetal sheep, administration of morphine induces apnoea followed by hyperpnoea; during hyperpnoea the foetus arouses. We tested the hypothesis that naloxone, an opiate antagonist, would block these responses. In 14 foetal sheep between 123 and 140 days of gestation, we measured electrocortical activity (ECoG), eye movements (EOG), diaphragmatic activity (EMGdi), blood pressure and amniotic pressure. Morphine (1 mg/kg) was injected in the foetal jugular vein during low-voltage ECoG. Saline or naloxone (0.1, 0.5 and 2.0 mg) were given, in randomized order, before the morphine injection, shortly after morphine injection during apnoea, and during maximum hyperpnoea. Saline alone had no effect on breathing or behaviour. When saline and naloxone preceded the morphine injection the length of apnoea was 26.6 +/- 7.7 and 19.5 +/- 7.0 min (SEM, P = 0.25) while the length of sustained hyperpnoea was 104.8 +/- 11.4 and 29.6 +/- 8.4 min respectively (P = 0.001). When administered during the maximum breathing response, naloxone decreased the length of breathing from 92.2 +/- 8.4 (saline) to 8.8 +/- 2.9 min (P = 0.001). Respiratory output (fEMGdi x f) also decreased from 6545 +/- 912 arbitrary units post saline to 3841 +/- 629 arbitrary units after naloxone (P = 0.05). Arousal disappeared with the decrease in breathing response. The negligible effect of naloxone on apnoea and its strong inhibition of hyperpnoea suggest that morphine may act on two distinct central regions or on two subtypes of opioid receptors to produce apnoea, hyperpnoea and arousal.

Animals↗
PubMed1990

The effects of brain-stem section on the breathing and behavioural response to morphine in the fetal sheep.

In the unanesthetized fetal sheep the administration of morphine causes initial apnoea followed by hyperpnoea. We thought that a section of the brain at midcollicular level might separate these two effects. Therefore we sectioned the brain stem of five fetuses at 132 +/- 1 (SEM) days of gestation and compared their responses to morphine (17 experiments) with that observed in seven intact fetuses at similar gestational ages (15 experiments). Brain stem sections were confirmed morphologically and histologically. Morphine, 1 mg/kg was injected in the fetal jugular vein during low-voltage electrocortical activity (ECoG). We measured ECoG, eye movements, diaphragmatic activity, blood pressure and amniotic pressure. Sectioned fetuses before the administration of morphine had a complete dissociation between ECoG and breathing activity. With the administration of morphine we found: (i) the length of the apnoea was 139.8 +/- 15.5 min in sectioned fetuses and 17.0 +/- 5.8 min in intact fetuses (P less than 0.01); and (ii) there was no hyperpneic response in the sectioned fetus whereas the length of hyperpnoea in the intact group was 99.1 +/- 11.8 min (P less than 0.001). The results support the idea of two central distinct areas of action of morphine in the fetal brain. The absence of hyperpnoea in the sectioned fetuses suggests that neurons inhibiting the 'respiratory neurons' are located rostrally to the mid-collicular line.

Animals↗
PubMed1988

Effect of morphine on breathing and behavior in fetal sheep.

To define the dose response of apnea and breathing to morphine we studied 12 fetuses at 116-141 days of gestation using our window technique. We instrumented the fetus to record electrocortical activity (ECoG), eye movements (EOG), diaphragmatic activity (integral of EMGdi), heart rate, carotid blood pressure, and amniotic pressure. Saline and morphine in doses of 0.03, 0.1, 0.5, 1, and 3 mg/kg were injected in random order in the jugular vein of the fetus during low-voltage ECoG. Fetuses were videotaped for evaluation of fetal behavior. We found 1) that saline did not elicit a response; 2) apnea, associated with a change from low- to high-voltage ECoG, increased from 2.2 +/- 1.5 (SE) min in two fetuses at a dose of 0.03 mg to 20 +/- 6.3 min in seven fetuses at 3 mg/kg (P less than 0.005); 3) the length of the breathing responses, associated with a change from high- to low-voltage ECoG, were 15 +/- 1.8 and 135.9 +/- 18.1 min (P less than 0.0005); 4) integral of EMGdi X frequency, an index equivalent to minute ventilation, increased from 1,763 +/- 317 arbitrary units to 10,658 +/- 1,843 at 1.0 mg/kg and then decreased to 7,997 +/- 1,335 at 3.0 mg/kg. These changes were related to a steady increase in integral of EMGdi, whereas frequency decreased at 3 mg/kg. There was an increase in breathing response to morphine plasma concentrations or morphine doses.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Medicare discharges by facility status under the prospective payment system, 1984-86.

When the Health Care Financing Administration implemented the Medicare prospective payment system (PPS), several types of hospitals and hospital units were excluded from the new reimbursement system, and they remained under the reasonable cost reimbursement system, subject to the target rate of increase limits. The implementation of PPS has been accompanied by several changes in hospital classification and in utilization patterns. This article examines some of these changes based on excluded facility counts and discharges by facility status under the PPS for fiscal years 1984-86.

Data Collection↗
PubMed1983

Effects of N-LAAM on [3H]etorphine binding in neuronal-enriched cell cultures.

Stereospecific [3H]etorphine binding sites are present in neuronal-enriched cell cultures dissociated from 7-day-old chick embryonic brain. Moreover, binding was regulated by both ions and GTP in a manner similar to that of in vivo brain tissue. When cultures were exposed to N-LAAM (10(-6) M) from day 6 to day 7 or 8 and assayed for binding at day 8, Bmax was decreased and KD was increased. These findings support our view that primary neuronal cultures are a suitable model with which to study interactions of drugs with opiate receptors.

Animals↗
PubMed1983

Surgical stabilization of the spine in Duchenne muscular dystrophy.

The problem of real distress from the discomfort of collapsing scoliosis is predictable in Duchenne muscular dystrophy (DMD). Once the lumbar curve has exceeded 35 degrees, further progression is inevitable. A vital capacity, then, of 35% or more permits consideration of spinal surgery. Using these indications, 24 patients with DMD had long Harrington instrumentations and spinal fusions from S1 up to the upper thoracic spine (T4, 5, or 6). After two weeks recumbent, they were mobilized wearing a light spinal support in their wheelchairs. The complications encountered are described in detail. One patient died two years after his operation from dystrophic cardiomyopathy. With a follow-up period of four months to 42 months, the rest of these patients are well and sitting with comfort. The authors think that this experience indicates that prophylactic spinal fusion deserves consideration in the care planned for these patients.

Adolescent↗
PubMed1982

Effects of methadone on ornithine decarboxylase and cyclic nucleotide phosphohydrolase in neuronal and glial cell cultures.

Mixed neuronal and nonneuronal cell cultures were obtained from 8-day-old chick embryos cerebral hemispheres and glial-enriched cultures were obtained from fifteen-day-old chick embryo cerebral hemispheres. Cultures were exposed to methadone, a narcotic drug, from days four to six. The activity of ornithine decarboxylase (ODC) was determined at day eight and the activity of cyclic nucleotide phosphohydrolase (CNP) was determined at day fifteen. Both ODC and CNP activity were higher in mixed neuronal-nonneuronal cell cultures treated with methadone as compared to control. No effect was observed in the neuronal-enriched or glial-enriched cultures. These findings are interpreted to reflect that neuronal-glial interaction is important in the response of primary neural cells to methadone.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1982

[3H]Etorphine binding activity in early chick embryos: brain and body tissue.

Stereospecific [3H]etorphine binding has been detected in chick embryos as early as day 4 of incubation in both brain and body tissue. By day 10 of incubation [3H]etorphine stereospecific binding activity is not detectable in nonneuronal tissue. The ubiquitous opiate binding sites early in embryogenesis are high affinity and respond to ion and GTP regulation in a manner similar to adult brain tissue. We interpret our observations to indicate all embryonic cells prior to cell differentiation contain opiate receptors. Therefore, we propose that opiate receptors play a dual role; one function early in embryogenesis not associated with neurotransmitter regulation, and another function later in embryonic development and in the adult: the classical neurotransmitter regulatory function.

Animals↗
PubMed1980

Clinical evaluation of UNB 3-state myoelectric control for arm prostheses.

This report describes an attempt to conduct (in 1978 during a period of one week) an intensive, thorough, and objective evaluation of a prosthetic control system in such a manner that the evaluation avoids what are seen as shortcomings common among evaluation procedures described in the literature. The evaluation, in terms of benefits to patients, involved consideration on an interdisciplinary basis among an engineering team, prosthetics team, and therapy team. Nine below-elbow and two forequarter amputees participated. The device evaluated was the University of New Brunswick 3-state myoelectric control system, in the 12-volt version designed in 1975. This system is intended for use where there are not enough control sites to permit use of an Otto Bock or similar control system, and permits on/off control of a powered hand or other device in two directions from a single muscle. Observations on each patient by the 14-person evaluation team are summarized, and an Appendix presents questionnaires with summarized responses of the subjects and their families.

Adolescent↗
PubMed1979

Sensory feedback in a myoelectric upper limb prosthesis: a preliminary report.

Upper limb prostheses are often rejected because they do not provide the sensory feedback available from a normal hand. A system for providing sensory feedback has been developed at the University of New Brunswick for use with the three-state myoelectric controls prepared in the Bioengineering Institute there. Strain gauges mounted on the forefinger of an electric hand provide information which is processed electronically to cause a tingling sensation in the patient's stump, proportional in its intensity to the pinch force in the finger. This system has been used by a patient at the Ontario Crippled Children's Centre in Toronto, since June 1976. She uses it consistently with great satisfaction and enthusiasm. It gives her a sense of competence and confidence she does not have without it.

Arm↗
PubMed1978

Activities of types A and B MAO and catechol-o-methyltransferase in blood cells and skin fibroblasts of normal and chronic schizophrenic subjects.

We assayed activities of monoamine oxidase (MAO) type B in blood platelets and type A (and B) in fibroblasts cultured from punch biopsy specimens of skin, as well as of catechol-O-methyltransferase (COMT) in erythrocytes and fibroblasts. Fibroblasts contained moderate amounts of both forms of MAO (types A and B) found in human brain and large amounts of COMT activity. Activities of both enzymes correlated poorly between fibroblasts and blood cells. Comparing carefully diagnosed chronic schizophrenics with age-matched normal young men, we found no difference in these biochemical variables, nor could we distinguish patients with paranoid symptoms. In contrast, we confirmed markedly lower MAO activities in platelet samples from chronic patients provided by colleagues at the National Institute of Mental Health. Results concerning MAO and COMT activities are now sufficiently inconsistently characteristic of schizophrenics as to question their clinical applicability and to indicate a need for further critical evaluation, with special attention to diagnosis, matching of subjects, and effects of possible spurious environmental variables.

Adolescent↗
PubMed1978

Saying goodbye.

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Aged↗