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Biomedical subjects

R J MacGregor

Publications and source records attributed to R J MacGregor.

32 records · Page 2Linked to original sources
PubMed1979

Self-catheterization for decompensated bladder: a review of 100 cases.

The non-neurogenic decompensated bladder is a poorly defined entity. In an attempt to elucidate this condition 100 consecutive patients with non-neurogenic decompensated bladders were studied, etiology was sought and treatment with intermittent self-catheterization was done. Of the patients 34 per cent were able to resume voiding. Bacteriuria and pyuria were decreased from 90 to 18 per cent. Complications were few and over-all acceptance was excellent. A definition of non-neurogenic decompensated bladder was established.

Adolescent↗
PubMed1977

Systems simulation: theory of monosynaptic transfer between neuron populations.

This paper presents a theory for the input-output transformation involved in diffuse monosynaptic activation in a neural tissue or organ system of one population of neurons by another. Main findings are: (1) highly diffuse monosynaptic linkages act very much like filters, selectively sensitive to synchronized clusters of action potentials among the fibers of the input population; (2) partially diffuse monosynaptic linkages are capable of effecting either an amplification or diminution of the number of pulses involved in a single synchronized cluster, depending on parameters of the system; and (3) partially diffuse and spatially organized monosynaptic linkages are capable of effecting a spatial inversion of fine-grained spatial patterns. Theoretical predictions are clarified by mathematical analysis and computer simulation.

Action Potentials↗
PubMed1968

A model for responses to activation by axodendritic synapses.

A simple mathematical model of synaptic activation shows that the response to synaptic activation depends inversely on the size of the subsynaptic process. This provides a theoretical foundation for: the relationship between excitability and cell size; a possible source of plasticity in nerve cell behavior; and the hypothesis that postsynaptic responses to activation at axodendritic synapses are of large amplitude. The last-mentioned idea provides for flexible nonlinear interaction in dendritic regions because the diminution of postsynaptic potentials (PSPs) by prior potential becomes significant at high levels of depolarization. Digital-computer simulations of nerve cell input-output behavior for axodendritic activation based on these ideas reveal: frequency-transfer curves for axodendritic activation saturate; activations combined on different dendritic branches sum approximately linearly while those on the same branch occlude; simultaneous activation of several synapses on a previously inactive dendritic branch results in a large "peak" response at the onset of stimulation; and such an initial peak may be markedly mitigated by a prior depolarization of the branch. The third-mentioned finding may represent a widespread mode of hypersensitivity to stimulus onset in neural systems and in particular may contribute to the "on" responses of sensory channels, and the fourth suggests that depolarizing synapses at extreme peripheries of dendritic fibers might in some cases serve an inhibitory function.

Axons↗