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Biomedical subjects

D L Davidson

Publications and source records attributed to D L Davidson.

53 records · Page 3Linked to original sources
PubMed1978

Ouabain induced seizures: site of production and response to anticonvulsants.

Ouabain, an inhibitor of Na+ -K" -ATP'ase, has been administered intraventricularly to rats to study the effect of impairment of membrane transport mechanisms on the genesis of seizures. Running and leaping seizures occur rapidly after injection of ouabain in a low volume (10 microliter) when the maximal uptake of ouabain (39.8%) is the hippocampus. Generalized clonic-tonic seizures are induced by higher volume injections (50 microliter) associated with wider distribution of ouabain, including the cerebellum and brainstem. Ouabain was injected into cerebral cortex, caudate nucleus, dorsal hippocampus, fastigeal nucleus, ventrolateral mesencephalic reticular formation and cerebellar cortex. The cerebellar injections produced both running and leaping and generalized clonic-tonic seizures. It is suggested that this results from decreased inhibitory effect of vermal and paravermal Purkinje cells on intra-cerebellar nuclei, which alters cerebellar influence on the reticular formation and the limbic system. Diphenylhydantoin, phenobarbitone, phenacemide, carbamezepine and clonazepam but not ethosuximide are effective against generalized clonic-tonic seizures, suggesting that this is a model for "grand mal" but not "petit mal" seizure mechanisms. It is furthermore suggested that running and leaping are subcortical, probably limbic, seizures that are most relevant as a model for temporal lobe seizures.

Animals↗
PubMed1977

Methotrexate hepatotoxicity in children with leukemia.

Percutaneous liver biopsy was performed on seven children with acute lymphocytic leukemia who had received maintanance chemotherapy with high-dose intravenous methotrexate for 1 1/2 to 2 1/2 years. Portal fibrosis was found in four of the seven children and in an additional patient treated with oral methotrexate. Serial tests of liver function and 99mtechnetium-sulfur-colloid scans did not accurately identify children with hepatic fibrosis. Clinical evidence of liver disease was not seen.

Adolescent↗
PubMed1977

CSF studies on the relationship between dopamine and 5-hydroxytryptamine in Parkinsonism and other movement disorders.

In Parkinson's disease, the concentration of homovanillic acid (HVA) was reduced in lumbar CSF from patients with idiopathic Parkinsonism (n = 54, P less than 0.05) and post-encephalitic Parkinsonism (n = 19, P less than 0.01). The reduction in the concentrations of 5-hydroxyindolylacetic acid (5-HIAA) was not significant, and there was no alteration in the levels of 4-hydroxy-3-methoxyphenylethylene glycol (MHPG). Treatment with L-dopa increased the concentration of HVA in the CSF (P less than 0.05) but had no effect on the levels of 5-HIAA and MHPG. Carbidopa given in combinations with L-dopa produced similar CSF concentrations of dopa as did L-dopa alone but caused less than half the rise in HVA. Fourteen patients who became functionally independent on treatment with L-dopa had higher 5-HIAA levels than 23 patients who showed no such improvement (P less than 0.001), suggesting that intact 5-hydroxyltryptamine neurones may be important in the therapeutic response to L-dopa. In a variety of movement disorders, the levels of HVA, 5-HIAA, and MHPG were not significantly different from age-matched controls. Treatment with tetrabenazine did not significantly alter the metabolite levels in patients in whom it produced either improvement, or side effects.

Aged↗
PubMed1977

Hypertension and papilloedema in the Guillain-Barré syndrome.

Three patients with the Guillain-Barré Syndrome are described, one of whom was relapsing. Hypertension persisted for three to four months in two patients, associated with increased urinary excretion of catecholamines. Baroreceptor sensitivity, although depressed, did not explain the hypertension. It may be due to lesions affecting either central vasomotor control or peripheral sympathetic nerve activity. Two patients had papilloedema. This has been attributed in the literature to defective reabsorption of CSF due to high protein concentration. Normal reabsorption of isotope labelled albumin from the subrachnoid space argues against this explanation in our cases.

Adult↗
PubMed1977

Scanning electron microscopy of integumental surfaces of Schistosoma intercalatum.

Scanning electron microscopy was employed to study critical point dried Schistosoma intercalatum adults at 120 to 6,000 X magnifications. Well-developed integrumental elevations, or bosses, with variable spination account for the roughness of the male schistosome. The female is relatively smooth even though it possesses minute spines on the posterior part of the body. SEM reveals that the gynecophoral canal of the male, especially the presence of a gynecophoral fold, provides an effective means for clasping the female when in copula.

Animals↗
PubMed1976

Scanning electron microscopy of the integumental surfaces of Schistosoma haematobium.

The integumental surfaces of critical point dried S. haematobium were studied by scanning electron microscopy at 34 to 8,000 magnifications. There are marked differences between the surface structures of male and female as well as from one part of the same parasite to another. The surface of the male schistosome is moderately rough while that of the female is relatively smooth. SEM reveals certain basic features such as spines in the oral sucker and the acetabulum of both sexes which may facilitate rasping and/or attachment of the parasite for residence in the bloodstream of the definitive host. The lining of the gynecophoral canal is roughened by minute spines. The presence of a gynecophoral fold may enhance anchorage of the female in the grasp of the male. The significance of visualization of surface features by SEM as a means for differentiating species is not yet known.

Animals↗
PubMed1975

Hepatic disease in erythropoietic protoporphyria.

Two sisters had erythropoietic protoporphyria and a spectrum of liver disease. One (F.B.) died in hepatic failure within 3 months after the development of jaundice. Only 10 months before she died, she had exhibited only bromsulfalein retention and a borderline increase in serum transaminase. Surgical exploration because of the jaundice revealed patency of the bile ducts which was confirmed at autopsy. Wedge biopsy and autopsy specimens of liver showed an active cirrhosis with massive amounts of protoporphyrin in Kupffer cells, portal histiocytes, bile canaliculi and parenchymal cytoplasm. The other sister (L.R.) had never had symptomatic liver disease and only a slight increase in serum transaminase and bromsulfalein retention. On needle biopsy, the liver specimen showed portal inflammation with erosion of limiting plates, occasional bridging between triads and central areas of cell dropout. Protoporphyrin pigment was present in portal histiocytes, areas of central collapse and, more rarely, in parenchymal cytoplasm. These studies demonstrate that significant, progressive hepatic disease may occur insidiously in erythropoietic protoporphyria, and that once jaundice appears it may be followed rapidly by fatal hepatic failure.

Adult↗
PubMedDate not supplied

Abnormal aluminium, cobalt, manganese, strontium and zinc concentrations in untreated epilepsy.

The concentration of 38 trace and bulk elements in the serum from 19 patients with recent onset of epilepsy and 20 age- and sex-matched controls was estimated by neutron activation analysis or inductively coupled plasma source by mass spectrometry. The concentrations of aluminium, strontium and zinc were significantly higher and the concentrations of cobalt and manganese were significantly lower than controls. Low concentrations of manganese and high concentrations of zinc in epilepsy have been previously reported but the abnormalities of aluminium, cobalt and strontium are new findings. The possible significance of these results in the pathogenesis of epilepsy is discussed.

Adult↗
PubMedDate not supplied

Reduced ouabain binding to erythrocytes in epilepsy--evidence for a membrane abnormality.

The number of sodium pump sites on erythrocytes was measured using tritiated ouabain in 20 untreated fasted patients with recent-onset untreated primary generalised or partial seizures and in 22 age- and sex-matched controls. The ouabain binding was significantly lower at 1393 +/- 392 molecules ouabain/pl cells compared to 1677 +/- 366 molecules ouabain/pl cells in the group with epilepsy (P less than 0.02). The differences between ouabain binding in patient and control groups were greater for males than for females. There were no significant differences between patients with generalised and those with partial seizures. These results are consistent with a generalised membrane abnormality in epilepsy which, if present in the brain, might predispose to seizures.

Adolescent↗