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Biomedical subjects

D Jefferson

Publications and source records attributed to D Jefferson.

At least 37 records · Page 2Linked to original sources
PubMed1983

Beta-adrenoreceptor mechanisms in essential tremor; a double-blind placebo controlled trial of metoprolol, sotalol and atenolol.

In order to elucidate the mode of action of beta-adrenoreceptor antagonists in essential tremor, the efficacy of chronic oral administration of metoprolol, atenolol and sotalol was compared in a randomised, double-blind placebo controlled trial in twenty-four patients. Only sotalol proved superior to placebo on both subjective and "objective" assessments. Metoprolol and sotalol produced comparable degrees of beta-adrenoreceptor antagonism as judged by the blockade of standing tachycardia. Atenolol, in the dose used, produced a trend towards a greater cardiac chronotropic effect. These findings provide no support for the concept that central or peripheral beta 1-adrenoreceptor mechanisms are important in essential tremor. The beneficial effect of beta-adrenoreceptor antagonists may be mediated predominantly through peripheral beta 2-adrenoreceptor mechanisms.

Adult↗
PubMed1981

Renaut body distribution at sites of human peripheral nerve entrapment.

In an autopsy study of the pathology of chronic subclinical nerve entrapment Renaut bodies showed a strong predilection for sites of nerve entrapment. They were present at these sites in 43 of 74 peripheral nerves but in none of the control sections of the same nerves. Renaut bodies were most frequently encountered in the median nerve at the wrist and in the lateral femoral cutaneous nerve at the inguinal ligament but were rarely seen in sections of the common peroneal nerve at the neck of the fibula. Renaut bodies were closely associated with thickened subperineurial capillaries, and, in successive transverse sections, they terminated in a fibrous mass of these thickened vessels. In several nerves Renaut bodies showed a similar orientation within adjacent fascicles, suggesting that mechanical factors were related to their pathogenesis; despite this finding there was no relationship between their numbers at entrapment sites and the presence of pathological changes in myelinated nerve fibres at the same level. These findings suggest that while mechanical factors are important in the pathogenesis of Renaut bodies there is no evidence to support the theory that these structures protect nerve fibres from mechanical stress.

Humans↗
PubMed1981

Cerebrospinal fluid concentrations of propranolol, pindolol and atenolol in man: evidence for central actions of beta-adrenoceptor antagonists.

1 Single and multiple oral dose studies of the penetration into CSF of three beta-adrenoceptor antagonists were performed in groups of patients needing lumbar puncture as part of their neurological investigation. Propranolol, pindolol and atenolol were chosen because of their differing physico-chemical properties. 2 The CSF concentration of propranolol (lipid-soluble) and pindolol (moderately lipid-soluble) was proportional to the free plasma concentration and was similar to, although generally lower than, that theoretically predicted. 3 The CSF concentrations of the poorly lipid-soluble atenolol were similar in different patients and were independent of plasma concentration. This may be due to the slow rate of diffusion of atenolol into CSF preventing the predicted concentrations being achieved.

Adrenergic beta-Antagonists↗
PubMed1980

Acute nerve compression during limb ischaemia--an experimental study.

In 6 baboons the deep peroneal nerve was compressed for 1 hr by a weighted cord laid over the leg just above the ankle. The procedure was carried out on both sides in a single experiment. On one side the whole leg was rendered ischaemic by a cuff round the thigh which was maintained for 3 or 4 hr before and during the period of nerve compression at the ankle. As judged by the severity of the conduction block at the ankle 24 hr later, and its subsequent recovery, the compressed nerves which were also made ischaemic fared no worse than those subjected to compression alone. Histological studies showed evidence of selective damage to large myelinated fibres during the compression; this damage was not increased on the ischaemic side. There is thus no evidence that ischaemia increased the susceptibility of nerve fibres to mechanical damage in these experiments.

Acute Disease↗
PubMed1979

beta-Adrenoreceptor antagonists in essential tremor.

Three different beta-adrenoreceptor antagonists--propranolol, sotalol, and atenolol--were compared in a double-blind study with placebo in nine patients with essential tremor. All three drugs produced an equal reduction in standing pulse rate but atenolol was less effective in reducing tremor than propranolol and sotalol. These results suggest that the reduction in tremor produced by beta-adrenoreceptor antagonists is mediated by an effect on peripheral beta 2-adrenoreceptors.

Adult↗
PubMed1979

Relationship between plasma propranolol concentration and relief of essential tremor.

The relationship between plasma propranolol concentration and relief of essential tremor was examined in 11 patients during treatment with oral racemic propranolol in doses of 30 to 640 mg/day. Although propranolol decreased tremor in all 11 patients, the degree of improvement varied widely in individuals (mean 51%, range 25--90%), and was not related directly occurred at plasma propranolol concentrations below 20 ng/ml (0.077 mumol/l) and, in three others, below 40 ng/ml (0.154 mumol/l). It is concluded that the optimum response of essential tremor to propranolol is achieved at relatively low plasma propranolol levels, levels which are obtained by daily propranolol doses of 120--240 mg.

Adult↗
PubMed1972

In vivo formation of H2O2 in red cells during exposure to hyperoxia.

Chow-fed and tocopherol-deficient mice were given aminotriazole (AT), exposed to 100% O(2) at 60 pounds per square inch absolute for 1 hr (OHP), and red blood cells were assayed for catalase activity and lipid peroxide levels. A decrease of catalase activity (CA) in the presence of AT can be taken as evidence of excess formation or accumulation of H(2)O(2). No differences of CA were observed among chow-fed mice, with or without AT and/or OHP. Tocopherol-deficient mice with AT had lower CA (0.174+/-0.040) than chow-fed mice with AT (0.225+/-0.028) P < 0.01. Tocopherol-deficient mice with AT exposed to OHP had even lower CA, 0.137+/-0.024, P < 0.01.The data are consistent with the hypothesis that H(2)O(2) is formed or accumulated in excess in red cells of tocopherol-deficient mice, an effect that is enhanced in the presence of hyperoxia. They imply that tocopherol plays a role in the detoxification of H(2)O(2).

Animals↗
PubMedDate not supplied

Subclinical entrapment of the lateral femoral cutaneous nerve: an autopsy study.

Five out of 12 lateral femoral cutaneous nerves, removed at routine autopsies, showed pathologic changes in myelinated nerve fibers in the vicinity of the inguinal ligament. These changes included both local demyelination and Wallerian degeneration, particularly affecting the fibers with the largest diameters. The presence of polarized internodal swellings on single nerve fibers from two specimens suggested that mechanical factors were involved in pathogenesis. Endoneurial vascular thickening confined to the region of the inguinal ligament was also seen and may be implicated in the production of some of the symptoms of meralgia paresthetica (MP).

Adult↗