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Biomedical subjects

R Hess

Publications and source records attributed to R Hess.

At least 127 records · Page 7Linked to original sources
PubMed1977

A study of long-term effects of guanethidine on peripheral noradrenergic neurones of the rat.

In long-term experiments in rats the effects of guanethidine sulphate on peripheral adrenergic neurons in the heart, the vas deferens, the superior cervical ganglion and the ganglion innervating the vas deferens were studied in relation to the dosage and route of administration of the drug by biochemical, histofluorimetric and electron-microscopic methods. When administered daily in very high doses, i.e. 180 mg/kg orally or 25 mg/kg intraperitoneally, for several weeks guanethidine was found to induce toxic effects which appeared to be a result of mitochondrial changes in the ganglion cells. These changes were not directly related to the decrease in catecholamine content and the capacity of the neurones to retain exogeneous transmitter. The short neurones innervating the vas deferens appeared to be the structures most sensitive to guanethidine. As in the other tissues, however, the changes in these structures proved reversible to a considerable extent upon cessation of high-dose treatment. The structural changes induced in the animal by toxic doses of guanethidine are considered to have no bearing upon the pharmacological action of the drug under practical conditions.

Administration, Oral↗
PubMed1977

[Epilepsy and headaches (author's transl)].

The controversial relations between migraine and vascular headache on one hand, epilepsy on the other hand are once more discussed: survey of the arguments for a more than fortuitous connexion, taken from literature and general experience. Critical analysis of the personal case material. Discussion of some specific groups of patients with various combinations of both syndromes: long antecedents of headaches, leading up to sporadic epileptic attacks, focal or generalized; clinical seizures under photic stimulation (10% of the cases with chronic headaches without organic lesions); headaches in the latency period of symptomatic epilepsy; cases of seeming transition between the two syndromes; headaches as a substitute, an aura or as a component of the epileptic seizure, with clearly distinctive features between generalized and focal epilepsy: in patients with bilateral EEG paroxysms, headaches are usually diffuse or bilateral, in those with epileptogenic foci, headaches, if consistently localized, are always reported to be homolateral to the focus. Considerations concerning pathogenesis include the familiar hypothesis of hypoxic discharges following migrainous vasoconstriction, as well as secondary vascular headaches induced by focal epileptic activity. Headaches caused by excessive discharges in the sensory representation areas (H. Jackson) must be rare. Whether increased neuronal activity in the hypothalamus may be responsible for the migraine syndrome (Herberg), possibly in connection with biogenic amines, remains in open question.

Adolescent↗
PubMed1976

Tetrodotoxin-resistant dendritic spikes in avian Purkinje cells.

Electrophysiological evidence for the existence of dendritic spikes in the Purkinje cells of pigeon cerebellar cortex is presented. Intradendritic records indicate that the electroresponsive properties of the dendrites linger after voltage-dependent sodium and potassium conductances are reduced by superfusion of the cortex with Ringer's solution containing 20 mug/ml tetrodotoxin and 5 mM 3-aminopyridine. Dendritic spikes could be evoked, in the complete absence of activity from all cerebellar afferents and from the soma and axon of the Purkinje cells, by direct electrical activation of the surface of the cerebellar cortex or by intracellular injection of current via the recording electrode. The denritic electroresponsiveness was blocked by superfusion with 20 mM Mn2+ or Co2+. It is thus concluded that dendrites of Purkinje cells in birds are capable of generating calcium-dependent spikes. The possible role of such a calcium current in neuronal function is discussed.

Action Potentials↗
PubMed1975

The optimization test in the guinea-pig. A method for the predictive evaluation of the contact allergenicity of chemicals.

Guinea-pigs were sensitized with various substances (DNCB, penicillin G, PPL, ethylaminobenzoate, formalin) by the Draize method, the maximization method and the new optimization method (intracutaneous test employing adjuvant). The advantages of the optimization method favouring its adoption as a standard sensitization test are discussed in the light of the results obtained by this method and with the two established tests.

Adjuvants, Immunologic↗