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Biomedical subjects

B Meldrum

Publications and source records attributed to B Meldrum.

9 recordsLinked to original sources
PubMed1978

Blockade of epileptic responses in the photosensitive baboon, Papio papio, by two irreversible inhibitors of GABA-transaminase, gamma-acetylenic GABA (4-amino-hex-5-ynoic acid) and gamma-vinyl GABA (4-amino-hex-5-enoic acid).

The anticonvulsant potency and neurological toxicity of two new catalytic inhibitors of GABA-transaminase have been assessed in acute experiments in baboons with a natural syndrome of photic epilepsy. gamma-Acetylenic GABA, 160--200 mg/kg, or gamma-vinyl GABA, 450--950 mg/kg, intravenously, gave complete protection against generalised myoclonus or seizure responses induced by photic stimulation (in baboons without or with priming with subconvulsant doses of allylglycine). The protection became maximal 1--3 h after injection, and continued for 7--24 h. Signs characteristic of the acute toxicity of anticonvulsant drugs (nystagmus and ataxia) were not seen. The potential use of these compounds in human epilepsy deserves investigation.

4-Aminobutyrate Transaminase↗
PubMed1978

Blockade of photically induced epilepsy by 'dopamine agonist' ergot alkaloids.

The effect of the intravenous administration of ergot alkaloids on epileptic responses to intermittent photic stimulation )IPS) has been studied in adolescent baboons, Papio papio, from Senegal. Ergocornine, 1--2 mg/kg, produced marked autonomic and behavioural effects, slowed the EEG, and abolished myoclonic responses to IPS for 30--90 min. Ergometrine, 1 mg/kg, activated the EEG and blocked the induction of myoclonic responses for 1--3 h. Bromocriptine, 0.5--4 mg/kg, did not consistently prevent myoclonic responses to IPS. After pretreatment with a subconvulsant dose of allylglycine (180--200 mg/kg), lysergic acid diethylamide, 0.1 mg/kg, retained the capacity to block myoclonic responses to IPS, and ergocornine 1 mg/kg reduced such responses. The convulsant effect of allylglycine was enhanced, however, so that prolonged seizure sequences began 19--96 min after ergocornine administration. The protective action of ergot alkaloids against epileptic responses induced by sensory stimulation is interpreted in terms of effects at several sites, including dopaminergic and serotoninergic synapses.

Allyl Compounds↗
PubMed1978

Physiological changes during prolonged seizures and epileptic brain damage.

The role of physiological changes occurring during prolonged seizures in the causation of epileptic brain damage has been investigated experimentally in baboons and rats. Prolonged drug-induced myoclonic seizure activity is associated with initial arterial hypertension and subsequent hypotension, increased venous pressure, early hyperglycaemia and subsequent hypoglycaemia, variable arterial hypoxia and lactacidosis, and hyperpyrexia. Cerebral metabolic rate for oxygen and glucose is increased 2--3 fold throughout prolonged seizures provided the physiological status of the animal is well maintained. Ischaemic neuronal change is found after seizures lasting 1.5--7 hours, involving the small neurones of the third cortical lamina, Purkinje and basket cells in the cerebellum, and pyramidal neurons in the endfolium and Sommer sector of the hippocampus. Muscular paralysis and artificial ventilation minimise late physiological changes such as arterial hypotension and hyperpyrexia, and protect against cerebellar damage, but only slightly against neocortical and hippocampal damage. When arterial hypotension, hypoxia or hypoglycaemia lead to a reduction in the intensity of seizure discharge in paralysed, ventilated rats, there is also a reduction in hippocampal and neocortical damage. Factors intimately related to the intensity and duration of the neuronal discharge are responsible for neocortical and hippocampal lesions.

Animals↗
PubMed1977

Seizure activity in photosensitive baboons following antidepressant drugs and the role of serotoninergic mechanisms.

Laboratroy and clinical evidence indicates that tricyclic antidepressants lower seizure threshold and in high doses may induce generalised seizures. In baboons with photosensitive epilepsy (Papio papio) the effects of 2 tricyclic antidepressants (imipramine and chlorimipramine) and of maprotiline and Nomi fensine have been studied (i.v. dose range 1-20 mg/kg. Imipramine, chlorimipramine and maprotiline (10 mg/kg i.v.) lowered seizure threshold to a comparable extent, whereas Nomifensine (10 mg/kg i.v-) did not enhance myoclinic responses to photic stimulation. Generalised seizures were seen 15-30 min after imipramine or chlorimipramine (20 mg/kg), and these two drugs showed no difference in their epileptogenicity. Administration of 5-hydroxytryptophan (25 mg/kg i.v.) 90 min before chlorimipramine or imipramine (10 mg/kg) completely blocked the usual augmentation of photically-induced epileptic responses. It is concluded that enhancement of serotoninergic activity following blockade of 5-HT re-uptake within the brain is unlikely to be responsible for enhanced myoclonic responses and epileptogenic seizures seen after tricyclic antidepressants. Nomifensine is significantly less epileptogenic than imipramine or chlorimipramine.

5-Hydroxytryptophan↗
PubMed1975

Survey of antibiotic residues in Canadian slaughter animals.

Kidneys and urine of cattle, swine, sheep and chickens were tested for bacterial growth inhibitors using Bacillus subtilis and Sarcina lutea as test organisms. Results were as follows: 211 beef kidneys four positive, 611 swine kidneys five positive, 27 sheep and 120 chicken kidneys all negative, 2108 beef urine 76 positive, 2409 swine urine 186 positive, 176 sheep urine 17 positive. Strongest reactions were obtained with B. subtilis on phosphate buffered pH 6.0 plates. Larger zones were produced by urine from injected animals than by tissue samples.

Abattoirs↗