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Biomedical subjects

R Douglas

Publications and source records attributed to R Douglas.

9 recordsLinked to original sources
PubMed1992

Effect of amygdaloid kindling on [3H]dopamine and [14C]acetylcholine release from rat prefrontal cortex and striatal slices.

The involvement of the dopaminergic (DA) systems in the control of limbic kindled seizures is ill defined. The effects of kindling on DA activity may have been overlooked in the past, because of its subtle unilateral occurrence and/or the variance of the endogenous imbalance of DA activity in normal animals. In the present study rats were screened for their endogenous DA imbalance using amphetamine-induced rotational behaviour. Electrical or sham kindling was applied in the hemisphere with the higher endogenous DA activity. Sections of the bilateral prefrontal cortex and dorsal and ventral striatum were dissected either 2 hours or 21 days after the final seizure and the electrically stimulated release of [3H]DA and [14C]acetylcholine (ACh) determined. Release was also measured in the presence of quinpirole or sulpiride to assess the activity of pre- and postsynaptic DA D2-receptors. Long-term effects of kindling consisted of facilitation of ACh release in the ventral striatum contralateral to the kindled amygdala and bilateral depression of DA release in the prefrontal cortex. Kindling therefore produced area specific changes in neurotransmitter systems giving rise to increased pro-convulsive cholinergic activity in the ventral striatum and decreased anti-convulsive dopaminergic activity in the prefrontal cortex.

Acetylcholine↗
PubMed1992

Ambulation using the reciprocating gait orthosis and functional electrical stimulation.

Until recently, rehabilitation engineering offered 2 different methods to improve daily living independence for spinal cord paralyzed subjects. One, the use of various orthotics and the other, the application of functional electrical stimulation. In the present work we chose to combine reciprocating gait orthosis (RGO) with functional electrical stimulation (FES) into one hybrid system. A detailed biomechanical and clinical instruction for the use of this system is given. Results obtained from application of the hybrid system on a complete T4 paraplegic patient demonstrate that the most significant contribution was the reduced invested energy cost required for stand-up and for ambulation.

Adult↗
PubMed1990

Visibility of synaptically induced conductance changes: theory and simulations of anatomically characterized cortical pyramidal cells.

A recent report has provided evidence that there are no significant increases in the neuronal input conductance during the response of cortical cells in cat visual cortex to non-preferred visual stimuli (Douglas et al., 1988). A criticism of experiments of this kind is that changes in the membrane conductance occurring in the dendritic tree may not be visible from electrodes that impale the soma. Our paper describes theoretical and numerical results concerning the visibility of synaptically induced conductance changes from intracellular electrodes, in both ideal and anatomically well-characterized cortical neurons. Based on earlier work by Rall (1967), we here derive theoretical expressions for the change in input conductance at any location in a passive dendritic tree resulting from activation of a single synapse and obtain bounds for the effects of multiple synapses. We find that the conductance change measured at the cell body is always less than the sum of the synaptic conductance changes and that this observed conductance change does not depend on the synaptic reversal potential. For the case of an infinite dendritic cylinder, the change in input resistance due to a single synaptic input decays exponentially with distance of the synapse from the recording site. Numerical simulations of synaptic inputs that change approximately as fast as the membrane time-constant produce an increase in input conductance that is only slightly less visible than that of a constant input. We also compute the changes in somatic input conductance of 2 morphologically identified pyramidal cells from cat visual cortex during activity of a single inhibitory basket cell with known synaptic input locations. We find that the increase in conductance due to the activity of the inhibitory basket cells is clearly visible from the cell body of the pyramidal cells and that a 70% reduction in the amplitude of excitation is associated with at least a 30% increase in somatic input conductance, which would be visible in intracellular recordings. Taken together with the negative experimental evidence of Douglas et al. (1988), our results cast doubt on a large class of models of direction selectivity that rely on synaptically mediated inhibitory conductance increases to veto or block excitatory conductances increases.

Animals↗
PubMed1979

Transfer factor and hepatitis B: a double blind study.

A prospective, double blind placebo-controlled trial was carried out on twenty-nine patients with hepatitis B. Thirteen received transfer factor and sixteen placebo. There were no significant differences between the two groups in any clinical or laboratory measurements made, although a rapid early reduction of serum aspartate transaminase levels by transfer factor is possible. Similarly, no significant changes were delineated by the in vitro measurements of lymphocyte function. Transfer factor did not alter the natural course of hepatitis B.

Adult↗
PubMed1977

Transfer factor therapy: clinical experience and the role of the E rosette assay.

Transfer factor has been administered to 17 patients, most with infectious diseases of various kinds. In 12 patients the therapy was followed by a definite clinical improvement although in most cases conventional chemotherapy was given concomitantly. In all cases where clinical improvement followed the sheep red cell or E rosette assay showed low values initially, with an improvement following therapy. This test of T lymphocyte function may be useful both in predicting patients likely to respond to transfer factor, and in monitoring response to treatment. As no specific assay of transfer factor activity is available, an in vivo rise in E rosette formation following transfer factor administration serves as a crude indicator that the injected material has some biological activity.

Abscess↗
PubMed1976

The distribution of HLA in a Polynesian population-Western Samoans.

HLA and gene frequencies are presented for a Polynesian population-the Western Samoans. Within the HLA-A locus A2, A9 and A11 have the highest frequencies and account for 55% of the alleles in this locus. The alleles BW22 and BW40 had the highest frequencies in the HLA-B locus and accounted for 51% of the alleles. The blank gene frequencies for the HLA-A and B loci are .382 and .373 respectively. Significant linkage disequilibrium was found with the haplotypes A1,B7; A3,B7;A2, BW40; A9, BW40 A9, BW22. The most frequent haplotype was A2,BW40. Comparatively low values within this population and between this and other Polynesian populations are discussed in terms of selection, migration and drift.

Alleles↗
PubMed1975

HL-A antigens in Europeans and Maoris with rheumatic fever and rheumatic heart disease.

Using a standard microtoxicity technique of tissue typing, the distribution of tissue antigens in 75 Maoris and 514 European disease-free blood donors was determined. Fifty Maori and 50 Europeans with rheumatic fever or rheumatic heart disease were compared with each control group. Normal Maoris had HL-A3 less frequently than Europeans (P less than .0005). HL-A28 was reduced (P less than .005) and HL-A17 increased in European patients (P less than .0005). In Maori patients there were minor differences in the frequency of HL-A3 and 8, which were increased, and HL-A10, which was diminished.

Europe↗
PubMedDate not supplied

A silicon neuron.

By combining neurophysiological principles with silicon engineering, we have produced an analog integrated circuit with the functional characteristics of real nerve cells. Because the physics underlying the conductivity of silicon devices and biological membranes is similar, the 'silicon neuron' is able to emulate efficiently the ion currents that cause nerve impulses and control the dynamics of their discharge. It operates in real-time and consumes little power, and many 'neurons' can be fabricated on a single silicon chip. The silicon neuron represents a step towards constructing artificial nervous systems that use more realistic principles of neuronal computation than do existing electronic neuronal networks.

Animals↗