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Biomedical subjects

M H Roberts

Publications and source records attributed to M H Roberts.

At least 91 records · Page 5Linked to original sources
PubMed1981

The effects of chronic section of dorsal roots on the responsiveness of motoneurones to 5-hydroxytryptamine and a substance P analogue.

1 Experiments were performed on rats 14-21 days after unilateral dorsal root section in order to determine if the effects on motoneurone excitability of a substance P analogue, 5-hydroxytryptamine (5-HT) and noradrenaline were altered by section of primary afferents. 2 The effects of iontophoretic applications of these agents on motoneurone excitability were quantified by measuring the change in amplitude of the short latency field potentials evoked antidromically, by ventral root stimulation. 3 Iontophoretic application of the substance P analogue (eledoisin-related peptide, ERP) always produced an increase in the amplitude of the field potential. These increases in amplitude were 25.9% larger on the sides of the cords with sectioned dorsal roots. This was not statistically significant difference (P greater than 0.05). 4 Section of dorsal roots did not alter responses to noradrenaline. 5 Responses to 5-HT were significantly larger following section of dorsal roots. There is very little evidence for the release of 5-HT by primary afferents and denervation supersensitivity is an improbable explanation. It is possible that descending 5-HT systems directly excite motoneurones and indirectly inhibit primary afferent transmission. Dorsal root section would alter the balance between these actions of 5-HT in favour of an excitatory effect.

Animals↗
PubMed1980

Responses of spinal neurones to a substance P analogue, noxious pinch and bradykinin.

It is likely that substance P is a neurotransmitter at the first afferent synapse. These synapses may mediate pain sensations from thermal, mechanical or chemical (bradykinin) stimulation of nociceptors. Correlation of the responsiveness of dorsal horn neurones to iontophoretic application of a substance P analogue and mechanical or chemical stimulation of the hind limb suggested that sensitivity to substance P was shown by cells responding to chemical but not mechanical noxious stimulation.

Animals↗
PubMed1980

A new look at peripheral vascular disease in blacks: a two-year update.

A comprehensive overview of 66 patients-the majority of whom were black-undergoing distal lower extremity revascularization for severe atherosclerotic ischemia with impending limb loss is presented. Twenty-five patients are presently two-years postoperative, 19 are one-year post revascularization, and 22 are new additions having undergone revascularization within the last year.Patients in the study group are presented according to race, sex, and age. Their histories and pre-operative clinical conditions, along with angiographic and operative findings lead to the identification of a previously undescribed atherosclerotic phenomenon present among blacks. The impact of an aggressive program for limb salvage is reported and the prospect of avoiding needless limb loss is discussed.

Black or African American↗
PubMed1979

Cell surface charge correlation of partition with electrophoresis.

Critical mixtures of aqueous solutions of polymers separate into two or more immiscible phases. Particulate materials distribute in such phase systems generally between one bulk phase and the interface between bulk phases. The distribution is described by a simple partition law, and is quantitatively determined by, inter alia, the nature of the particle surface, particularly net electrical charge. The partition behaviour of various cells, native or modified by treatment with trypsin, neuraminidase or maleic anhydride, correlate strongly with electrophoretic mobility. Partition behaviour and electrophoretic mobility are both dependent upon cell surface charge. Thus, in appropriate conditions, changes in surface charge may be registered as changes in partition.

Cell Membrane↗
PubMed1979

Potentiation of responses to monoamines by antidepressants after destruction of monoamine afferents.

1 Stereotaxic lesioning and microiontophoretic techniques were used to study the effects of lesions of the medial forebrain bundle (MFB) on the potentiation by antidepressant drugs of responses to monoamines of cortical neurones.2 Active uptake of noradrenaline (NA) and 5 hydroxytryptamine (5-HT) by synaptosomes from the motor and somatosensory cortex was reduced to approximately 20%, 10 to 14 days following lesion of the MFB in rats.3 Unilateral lesions of the MFB caused changes in responsiveness of neurones to NA and 5-HT, applied by iontophoresis, in the cortex ipsilateral to the lesion. Excitatory responses to both amines were observed less frequently and depression was the predominant response. Excitatory responses on the lesioned side were significantly smaller than on the unlesioned side, but the size of depressant responses was unaltered.4 Viloxazine strongly potentiated responses of cortical neurones to NA and 5-HT on both sides of the brain of MFB-lesioned rats. There were no significant differences in the potentiation of responses to monoamines on the lesioned or unlesioned sides of the brain.5 Desipramine potentiated responses to NA of neurones in the cortex ipsilateral to MFB lesions.6 Chlorimipramine potentiated responses to 5-HT of neurones in the cortex ipsilateral to MFB lesions.7 It is concluded that antidepressants can potentiate responses to monoamines despite a profound reduction in presynaptic terminals. The potentiation is unlikely to be the result of blockade of monoamine uptake into presynaptic terminals, and is probably a postsynaptic effect of the antidepressant drugs.

Animals↗
PubMed1979

Modification of cortical neuron responses to acetylcholine by viloxazine.

Viloxazine, an antidepressant with no peripheral antiacetylcholine activity, was capable of reducing responses of single cortical neurons to acetylcholine. Acetylcholine responses could also be potentiated by viloxazine. Both potentiation and reduction by viloxazine were often seen in the same study, reduction of responses invariably preceding potentiation. These results suggest that viloxazine may have selective effects on central cholinergic receptors. Responses of cortical neurons to monoamines could also be potentiated by viloxazine although it has little effect on monoamine uptake. These results are compatible with the idea that potentiation of monoamine responses may occur by a postsynaptic mechanism.

Acetylcholine↗
PubMed1977

Report of large kinship with familial translocation between chromosomes 21 and 22.

This paper reports a large kinship with a familial (21;22) translocation occurring in both the balanced and the unbalanced states. Recurrence risks for the (21;22) translocation in the unbalanced state are high (14%) for the offspring of female carriers as compared with those for the offspring of male carriers (4%), but the offspring of male carriers appear to have a much higher risk (50%) of being balanced carriers than those of female carriers (30%).

Chromosomes, Human, 21-22 and Y↗