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Biomedical subjects

J W Moore

Publications and source records attributed to J W Moore.

At least 127 records · Page 7Linked to original sources
PubMed1989

Adaptively timed conditioned responses and the cerebellum: a neural network approach.

Conditioned responses often reflect knowledge about the timing of a US. This knowledge is manifested in the dependence of response topography on the CS-US interval employed in training. A neural network model and set of learning rules capable of simulating temporally adaptive features of conditioned responses is reviewed, and simulations are presented. In addition, we present a neural network implementation of the model which is designed to reconcile empirical studies of long-term synaptic depression in the cerebellum with neurobiological evidence from studies of the classically conditioned nictitating membrane response of the rabbit.

Animals↗
PubMed1989

Aortic root dilatation associated with partial trisomy 7(q31.2----qter).

Aortic root dilatation and mitral valve prolapse are cardiac findings sometimes seen in disorders of connective tissue, most often in the Marfan syndrome. This report describes an infant with these cardiac anomalies and a specific chromosomal abnormality, partial trisomy of chromosome 7 associated with partial monosomy of chromosome 22. This association may have significance with respect to the etiology of cardiac disease in connective tissue disorders such as Marfan syndrome.

Aorta, Thoracic↗
PubMed1989

Neuropsychological deficits and morphological MRI brain scan abnormalities in apparently healthy non-encephalopathic patients with cirrhosis. A controlled study.

By means of psychometric testing, we have determined the frequency of latent hepatic encephalopathy in a group of 19 cirrhotics with no clinical evidence of encephalopathy. Magnetic resonance imaging (MRI) of the brain was performed in order to determine whether morphological cerebral abnormalities were associated with latent encephalopathy. Nineteen age and educationally matched patients with normal liver function acted as controls. Significant differences (P less than 0.05) between cirrhotics and controls were found in tests of short-term visual memory and speed of reaction to light (cirrhotics 316 +/- 132 ms vs. controls 225 +/- 36 ms), sound (cirrhotics 361 +/- 152 ms vs. controls 236 +/- 52 ms) and choice (cirrhotics 651 +/- 190 ms vs. controls 406 +/- 101 ms) stimuli (all values mean +/- S.D.). Reitan trail test performance, however, was similar in both groups. (Trail A: cirrhotics 43 +/- 19 s vs. controls 35 +/- 13 s; Trail B: cirrhotics 105 +/- 66 s vs. controls 93 +/- 36 s.) In patients with cirrhosis, MRI revealed statistically significant increases in the maximum fissure width of right frontal sulci, right and left parietal sulci, inter-hemispheric fissure width and in bicaudate index. These changes, indicating cerebral atrophy, were largely confined to alcoholics. There was poor correlation between measurements of cerebral morphology and neuropsychological performance, only 10% of associations achieving statistical significance.

Adult↗
PubMed1989

The relationships of SHBG with current and previous use of oral contraceptives and oestrogen replacement therapy.

Sex hormone binding globulin (SHBG) concentration was measured in serum samples from 2077 premenopausal and 901 naturally postmenopausal women who had no history of disease or of recent drug use likely to affect SHBG. Current users of oral contraceptives (OCs) and of oestrogen replacement therapy had higher mean SHBG values than non-current users. Both premenopausal and postmenopausal women who had previously used OCs had a lower mean SHBG concentration than never users of OCs. Previous use of oestrogen replacement therapy was not related to SHBG.

Adult↗
PubMed1989

Demonstration of savings on the AVLT and development of a parallel form.

The purposes of the present study were (1) to investigate whether significant savings occur with repeat testing on Rey's Auditory-Verbal Learning Test and (2) to develop a parallel version of the AVLT. Subjects (N = 60) were divided into pairs (individually matched for sex, age, and education) to form two groups and were administered either the AVLT or a parallel version. Results indicated no significant differences on all AVLT measures of learning, recall, and recognition, suggesting that the parallel version can be used as an equivalent form of the AVLT. Subjects were retested after an interval of 27 (+/- 3) days, with half receiving the same version and half receiving a different version. In contrast to subjects receiving different lists, those who were retested with the same version demonstrated a significant improvement in performance on the majority of AVLT variables.

Adult↗
PubMed1989

Identification of ionic currents at presynaptic nerve endings of the lizard.

1. Ionic currents associated with the invasion of an action potential into the motor nerve ending of the lizard, Anolis carolinensis, were measured with a focal extracellular electrode at several locations along the nerve ending. 2. These experimentally observed currents could be matched with computer simulations of action potential propagation into the nerve ending. They revealed that while Na+ channels are the major ionic current pathway in the heminode, K+ channels provide the major pathway in the terminal branches and boutons. 3. Calcium current in the presynaptic ending was unmasked by the application of tetraethylammonium (TEA). This current was blocked by: (a) cadmium, (b) omega-conotoxin GVIA and (c) nifedipine, but was unaffected by nickel at concentrations less than or equal to 100 microM. Nifedipine's action became more definitive when the duration of the action potential was greatly extended by pre-treatment with TEA. The effect of Bay K 8644 was inconsistent. 4. Transmitter release, as measured by postsynaptic current, had a pharmacological response profile similar to that of the Ca2+ current, with the exception that transmitter release was increased reliably and reversibly by Bay K 8644. 5. This pharmacological response profile is identical to that of the L type Ca2+ channel identified by Fox, Nowycky & Tsien (1987 alpha) in chick dorsal root ganglion neurones. We saw no evidence for more than a single type of Ca2+ channel in lizard motor nerve endings. 6. A calcium-activated K+ current IK(Ca) was revealed by application of 3,4-diaminopyridine (DAP), a delayed-rectifier K+ channel blocker. This K(Ca) current was blocked by TEA, charybdotoxin and by substitution of cobalt for extracellular calcium.

Animals↗
PubMed1989

Classical conditioning reduces amplitude and duration of calcium-dependent afterhyperpolarization in rabbit hippocampal pyramidal cells.

1. The afterhyperpolarization (AHP) that follows action potentials was studied in CA1 hippocampal pyramidal cells from classically conditioned and control rabbits. Measurements of the AHP were obtained with intracellular recordings from CA1 cells within hippocampal slices. 2. The AHP of rabbit CA1 pyramidal cells was found to be accompanied by a conductance increase. The AHP was reduced by bath applications of the calcium channel blockers, cadmium and cobalt, by bath application of the cholinergic agonist, carbamylcholine chloride, and intracellular injection of the calcium chelator, ethylene glycol-bis(B-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA). 3. The AHP was markedly reduced in cells from rabbits that were well-trained with the nictitating membrane conditioning procedure, as compared with cells from pseudoconditioned or naive control animals. The difference in AHP amplitudes between conditioned and control groups increased as the number of spikes elicited by the stimulation pulse increased from one to four. Both the duration (measured as the time constant of AHP decay) and amplitude of the AHP were reduced in cells from conditioned animals. 4. The reduced AHP in cells from conditioned animals remained reduced in a medium that contained 0.5 microM tetrodotoxin (TTX) and 5.0 mM tetraethylammonium chloride (TEA); the AHP following calcium spikes was measured under these conditions. Since this medium eliminated synaptic transmission elicited by Schaeffer collateral stimulation, the AHP reduction in pyramidal cells from conditioned animals was not due to a modification in synaptic properties. There were no significant differences in the mean voltage thresholds, amplitudes, or durations of calcium spikes between cells from animals in the three groups. Thus the AHP reduction appears to be due to a modification of a Ca2+ -dependent K+ conductance and was not due to a secondary effect of reductions in calcium conductances underlying the spike. 5. In medium containing TTX and TEA, the amount of injected current required to elicit a calcium spike (current threshold) was significantly greater in cells from conditioned animals than in cells from control animals. This increase in current threshold persisted in 4-aminopyridine (4-AP)-containing medium and so cannot be attributed entirely to conditioning-specific increases in the A-current. 6. The conditioning-specific AHP reduction resulted in increased excitability in cells from conditioned animals versus pseudoconditioned control animals. Cells from conditioned animals fired more spikes to trains of 100-ms depolarizing current pulses than did cells from controls.

4-Aminopyridine↗
PubMed1989

Development of pulmonary arteriovenous malformations after modified Fontan operations.

Two patients with complex cyanotic congenital heart disease and without previous Glenn anastomosis underwent modified Fontan operations. Postoperatively, pulmonary arteriovenous malformations developed that resulted in cyanosis from significant intrapulmonary right-to-left shunting. These malformations were detected by pulmonary angiograms and contrast echocardiograms. Pulmonary arteriovenous malformations may be a major cause of late clinical deterioration in patients treated with modified Fontan operations.

Arteriovenous Fistula↗
PubMed1988

Intraosseous infusion of hypertonic glucose and dopamine.

Intraosseous infusion of drugs for resuscitation and of fluids has been advocated as an alternate emergency technique to intravenous infusion. The reliability of intraosseous infusion of many substances has not been established. Glucose and dopamine hydrochloride are two commonly used emergency drugs in pediatric practice that have not been carefully studied when administered into the bone marrow. In an animal model, we compared the response of an intraosseous injection of hypertonic glucose with that of an intravenous injection of hypertonic glucose. Serum glucose measurements following the injection revealed both routes of administration to be effective. A dopamine infusion was then administered through the bone marrow for 20 minutes. A statistically significant rise in blood pressure was observed two minutes after initiation of the infusion. Intraosseous infusion of hypertonic glucose and dopamine is an effective route by which to administer these medications and is potentially useful in emergency situations in which intravascular access is delayed.

Animals↗
PubMed1988

Adaptive timing in neural networks: the conditioned response.

A conditioned response not only reflects knowledge of an association between two events, a CS and a US, it also reflects knowledge about the timing of these events. A neural network and set of learning rules that generates appropriately timed conditioned response waveforms is presented. The model is capable of simulating some of the basic temporal properties of conditioned responses exhibited in biological systems, including (1) decreasing onset latency during acquisition training, (2) peak amplitude occurring at the temporal locus of the US, (3) inhibition of delay, and (4) trace conditioning. The model is also capable of simulating complex CR waveforms under certain conditions, and these simulations are compared with the results of behavioral experiments. The temporally adaptive responses are achieved by virtue of stimulus trace processes that are built into the network architecture.

Conditioning, Psychological↗
PubMed1988

Effects of prednisolone on sex hormone binding globulin during primary endocrine treatment of advanced breast cancer.

Serum sex hormone binding globulin (SHBG) was measured in 21 pre and 39 postmenopausal women with advanced breast cancer before treatment and 1, 3, 6, 9 and 12 months after ovarian irradiation or during continuous administration of tamoxifen at a dose of 10 mg twice daily, respectively; some patients received additional prednisolone at a dose of 5 mg twice a day. Ovarian irradiation was associated with a 25% reduction in serum SHBG levels 3 to 6 months after treatment whilst patients on tamoxifen experienced a rise of about 80% in serum SHBG levels after 1 to 3 months. In postmenopausal women prednisolone markedly dampened the effect of tamoxifen, reducing a 80% rise to about 20%. There was no relationship between SHBG levels and response to treatment.

Breast Neoplasms↗
PubMed1988

The distribution of estradiol in the sera of normal Caucasian, Chinese, Filipina, Hawaiian and Japanese women living in Hawaii.

Mean concentrations of sex-hormone-binding-globulin (SHBG) and the percentage distribution of estradiol between the non-protein-bound, albumin-bound and SHBG-bound fractions were not different in Caucasian, Hawaiian, Chinese, Japanese and Filipinas living in Hawaii. The widely varying incidence rates for breast cancer are therefore not explained by variations in the availability of estradiol.

Adult↗
PubMed1988

The permanent effect of reproductive events on blood prolactin levels and its relation to breast cancer risk: a population study of postmenopausal women.

In each of two population-based studies conducted on the Island of Guernsey between 1967-1976 and 1977-1984, respectively, single specimens of blood were taken from over 5000 normal women. From these two studies there were 1173 and 946 postmenopausal women in whom blood prolactin was determined and multivariate analysis was used to establish the association between blood prolactin concentration and possible determinants of risk of breast cancer. Since prolactin levels were log-normally distributed these analyses were done on log-transformed data. The age at menarche or menopause, age at first or last childbirth, length of reproductive life (i.e. time from menarche to menopause) or post-menopausal life (i.e. time from menopause to time of blood sampling), contraceptive use and history of breast cancer were not significantly associated with blood prolactin concentration. Of significance were age, parity, time of blood sampling and assay drift. Ponderosity (Quetelet's Index) was positively associated with prolactin concentration and this was significant using a one-tail criterion. Women with a mammographic pattern designated DY by Wolfe had significantly higher prolactin levels than those with N1 patterns. However, the main finding to emerge was that after standardizing for all the other variables increasing parity was related to a step-wise reduction in blood prolactin levels. Since this had occurred in women who had had their last child up to 35 years previously it implies this effect is permanent. It could therefore be that the protective effect on breast cancer risk of multiparity and early first pregnancy could be mediated by such a life-long reduction in blood prolactin levels.

Age Factors↗
PubMed1988

Urinary epidermal growth factor excretion and breast cancer risk.

The amount of urinary epidermal growth factor (EGF) excreted was determined in 350 normal women of whom 37 subsequently developed breast cancer. These were a group of women selected on a case-control basis from 5000 volunteers who had participated in a prospective epidemiological study. Urinary EGF excretion was not correlated with known risk factors such as age at menarche or menopause, age at first or last full-term child or parity. Neither was it associated with day or length of menstrual cycle, breast mammographic parenchymal pattern or the blood concentration of prolactin, dehydroepiandrosterone or its sulphate ester. Univariate analysis indicated that the amount of urinary EGF was significantly correlated with urinary creatinine (P less than 0.001), age (P less than 0.001), urinary androsterone (P less than 0.02) or aetiocholanolone (P less than 0.02), height (P less than 0.05) and weight (P less than 0.05). However, multivariate analysis showed that the amount of urinary EGF was correlated only with creatinine excretion (P less than 0.001) and age (P less than 0.001) and that the significance of the other correlations were probably due to the confounding influence of creatinine.

Adult↗