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Biomedical subjects

S M Hall

Publications and source records attributed to S M Hall.

At least 199 records · Page 11Linked to original sources
PubMed1982

Saltatory conduction precedes remyelination in axons demyelinated with lysophosphatidyl choline.

The changing electrical and morphological properties of demyelinating and remyelinating nerve fibres have been studied in rat ventral roots after intrathecal injection of lysophosphatidyl choline (LPC). The spatial distribution of electrical excitability within the lesion has been studied in undissected single fibres using high-resolution longitudinal current analysis. The distribution of excitability has been correlated with the ultrastructure of the fibres and with the distribution of the surrounding Schwann cells. Demyelinated axolemma was initially not excited, but conduction across demyelinated internodes appeared progressively from the 4th day after LPC injection. Conduction was never continuous, but proceeded via new foci of inward membrane current as early as 4 days after LPC injection, i.e. 3 days before the onset of remyelination. It is suggested that these foci (termed phi-nodes to distinguish them from the nodes of Ranvier distributed along myelinated nerve fibres) are precursors of nodes of Ranvier, and may indicate aggregates of sodium channels which form along the demyelinated axolemma prior to remyelination.

Animals↗
PubMed1982

The effects of 2,5-hexane dione on remyelination in the peripheral nervous system of the mouse.

We compared the development and resolution of a demyelinating lesion (produced by the intraneural injection of lysophosphatidyl choline) in mice exposed to a known neurotoxic agent (2,5-hexane dione) with similar events in control animals. A prolongation of the pro-myelin stage was observed in the hexane dione-treated animals: the suppression of remyelination became progressively more marked with the length of exposure to hexane dione. Prolongation of the pro-myelin stage is an indication of a disturbance in some component of the complex interaction between Schwann cell and axon, and presumably reflects the neurotoxicity of 2,5-hexane dione.

Animals↗
PubMed1982

Effect of baroreceptor reflex stimulation on blood flow to an atelectatic lung.

The effect of baroreceptor reflex stimulation by carotid sinus hypotension on the pulmonary vascular response to atelectasis was studied in eight dogs anesthetized with chloralose. Closed-chest dogs with electromagnetic flow probes previously implanted on their left (QL) and main (QT) pulmonary arteries had their left and right lungs ventilated separately. Their carotid sinuses were isolated bilaterally and perfused by a pulsatile pump with a physiological salt solution. After an initial period of bilateral 100% O2 ventilation with carotid sinus perfusion pressures (CSPP) set at each animal's initial mean arterial pressure (98 +/- 19 Torr), the left airway was occluded, QL/QT fell from 0.33 +/- 0.01 to 0.24 +/- 0.02 and PO2 fell from 323 +/- 35 Torr to 74 + 7 Torr. When CSPP was lowered to 21 +/- 3 Torr, there were no changes in QL/QT and PO2. These results suggest that stimulation of the baroreceptor reflex by carotid sinus hypotension does not interfere with the diversion of pulmonary blood flow away from a unilaterally atelectatic lung.

Animals↗
PubMed1981

Ibuprofen and diflunisal in rheumatoid arthritis: a double-blind comparative trial.

Both diflunisal (750 mg/day) and ibuprofen (1600 mg/day) were shown to be superior to placebo in the treatment of rheumatoid arthritis in a double-blind cross-over trial. Neither drug affected lymphocyte transformation to plant mitogens. Diflunisal scored better than ibuprofen at the dose levels chosen but the differences did not reach significance.

Arthritis, Rheumatoid↗
PubMed1980

Nerve conduction during peripheral demyelination and remyelination.

The changes in the conduction properties of peripheral nerve fibres of the mouse were examined during the phases of segmental demyelination, and remyelination, following the intraneural injection of lysophosphatidyl choline (LPC). In this lesion the sequence of the morphological changes was well synchronised in the different calibre fibres and this permitted a closer correlation to be made between the histological and physiological events than has been possible with other experimental models. Conduction in the nerve fibres was blocked during demyelination and for 1--2 days after the axons were completely free of myelin. In many fibres, however, conduction was later restored at about the time the demyelinated axon membrane became reassociated with debris-free Schwann cells, but prior to remyelination; at this time the fibres were unable to conduct closely spaced impulses and the conduction velocity was low. During the subsequent period of remyelination the ability of the fibres to conduct closely spaced impulses was fully restored and the conduction velocity progressively increased; the remyelinated internodes remained both thinner and shorter than normal. The physiological properties of the fibres were described in terms of their refractory periods of transmission (RPTs) as well as their conduction velocities; only the description in terms of the RPT correlated well with the histological events and with the degree of the behavioural deficit.

Action Potentials↗
PubMed1978

Late treatment of paracetamol poisoning with mercaptamine.

Forty patients who had taken overdoses of paracetamol were treated with mercaptamine. Twenty-three patients given mercaptamine within 10 hours of poisoning had normal liver function tests at follow-up, and one could not be traced. In 16 patients mecraptamine was begun more than 10 hours after ingestion of paracetamol ("late" mercaptamine). Eight of these patients developed severe liver damage, which in six was moderate or severe before mercaptamine administration. Acute renal failure occurred in two patients; in one other renal function was temporarily severely impaired. At follow-up two patients were not available, and one admitted moribund had died soon after admission. The remaining 13 all had normal liver function tests. It is concluded that late mercaptamine is not dangerous and may prevent further liver damage.

Acetaminophen↗
PubMed1978

Effects of rapid smoking. Physiologic evaluation of a smoking-cessation therapy.

We studied 24 healthy young male smokers to ascertain the medical safety of a highly effective smoking-abatement technique called rapid smoking. In comparison with results obtained after a 12-h cigarette fast or after normal smoking, statistically significant increases occurred after rapid smoking in heart and respiratory rates, systolic blood pressure, carboxyhemoglobin, and pH (p less than 0.05), while arterial PCO2, HCO3-, and serum [K+] fell (p less than 0.05). Rapid smoking produced alveolar hyperventilation in all subjects. In eight, arterial PO2 increased appropriately, but in 16, fell paradoxically (p less than 0.01); seven had arterial PO2 below 80 torr. Because this fall could represent ventilation/perfusion mismatch due to early bronchoconstrictive disease, in subjects with normal flow/volume loops and spirometry rapid smoking may be a simple, provocative screening test for early airway disease. Despite the changes produced there were no arrhythmias. Rapid smoking is safe for healthy subjects but should not now be used for higher-risk patients.

Adult↗
PubMed1977

Post-hypophysectomy insulin response in patients with advanced breast cancer.

Seven postmenopausal women with metastic breast cancer underwent transsphenoidal hypophysectomy. The rate of disappearance, k*, of iv glucose and insulin following iv glucose and l-arginine infusion was determined before and after the ablation. The k* was estimated with a linear least squares weighted regression method. The insulin secretory capacity of the pancreas before and after the ablation was evaluated with the index of insulinogenic reserve, the index representing the quantity of insulin secreted per unit of glycemic stimulus. Following iv glucose and arginine, there was no significant difference in the mean k* for glucose and insulin, before and after the ablation. The insulinogenic index before was lower than the normal. After hypophysectomy, the index decreased further for the first 30 min following iv glucose. In patients with advanced cancer the index of insulinogenic reserve is lower than normal and is suppressed further by hypophysectomy.

Blood Glucose↗