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Biomedical subjects

M O'Shea

Publications and source records attributed to M O'Shea.

At least 91 records · Page 5Linked to original sources
PubMed1981

Neuropeptide proctolin (H-Arg-Tyr-Leu-Pro-Thr-OH): immunological detection and neuronal localization in insect central nervous system.

Proctolin (H-Arg-Tyr-Leu-Pro-Thr-OH) is a pentapeptide first extracted from cockroaches. It is known to have many neurohormonal effects and has been associated with specific, identified cockroach neurons. We have produced proctolin antisera and report here on their application in detecting proctolin-like immunoreactivity (PLI) in the cockroach central nervous system. Radioimmunoassay, capable of detectable 50 fmol of proctolin, was used to quantify the distribution of PLI. Highest concentrations were detected in the genital ganglia and lowest in the cerebral ganglia. Immunohistochemistry on the cockroach central nervous system demonstrated that PLI is localized to neurons. Neurons stained by using immunohistochemistry were widespread in the ganglia. Cell bodies were found to be in constant positions from animal to animal and to occur in bilaterally symmetrical pairs. These neurons are potentially identifiable.

Animals↗
PubMed1981

Disopyramide and neuromuscular transmission.

The effect of disopyramide on neuromuscular transmission has been studied using the rat isolated phrenic nerve-diaphragm preparation. The response of the muscle to indirect nerve stimulation was decreased in the presence of disopyramide 5.6 x 10(-6) mol litre-1 (P less than 0.05), total blockade occurring at 5.6 x 10(-4) mol litre-1. Marked augmentation of the response to direct muscle stimulation was recorded in the presence of disopyramide 1.8 x 10(-4)-5.6 x 10(-4) mol litre-1. Disopyramide 5.6 x 10(-6) mol litre-1 caused a leftward shift of the log concentration response for tubocurarine and decreased the antagonist effect of neostigmine.

Animals↗
PubMed1979

Embryonic development of identified neurons: temporal pattern of morphological and biochemical differentiation.

Individually identified neurons can be recognized in grasshopper embryos, and are accessible to examination by morphological, physiological, and biochemical techniques from their birth to their maturation. Only after the axon of an identified neuron reaches its postsynaptic target does the neurotransmitter accumulate, the soma rapidly enlarge, and the central arborizations greatly expand.

Animals↗
PubMed1978

The identification of an octopaminergic neurone and the modulation of a myogenic rhythm in the locust.

An octopaminergic neurone in an insect is demonstrated. This cell (DUMETi) is the dorsal unpaired median neurone which projects to the extensor tibiae muscle of the locust metathoracic leg. Its soma was physiologically identified, isolated and shown to contain about 0.1 pmol of octopamine. Octopamine is about four times more concentrated in the axon than in the soma. The concentration in the soma is at least 800 times more than that in the soma of an identified motoneurone (which controls the fast extensor of the tibia). The effects of DUMETi on a myogenic rhythm in the extensor muscle of the locust metathoracic leg can be mimicked by superfusion with low concentrations of octopamine. The myogenic bundle possesses at least two types of aminergic receptor: one which slows the rhythm (and has a high-affinity for octopamine) and a second which accelerates the rhythm (and has a low-affinity for octopamine but a high-affinity for the indolalkylamine, 5-hydroxytryptamine). The roles of the two receptor types in modulating the rhythm are discussed in relation to the function of the rhythm.

Action Potentials↗
PubMed1976

Neuronal basis of a sensory analyser, the acridid movement detector system. III. Control of response amplitude by tonic lateral inhibition.

1. The Lobular Giant Movement Detector neurone (LGMD) of Schistocerca responds with spikes when small areas of the visual field change in luminance. Previous work has shown that changes of +/- 1 log 10 unit are enough to produce maximal ON and OFF responses. 2. Using a 5 degree test area, it is shown that the number of spikes generated by such a stimulus depends on the luminance of the surrounding area. When the surround is dark, the response is maximal; when it is brightly lit, the response is minimal. Intermediate intensities produce intermediate values of response. A X 2 change in response is produced by about 3 log 10 units change in surround intensity. 3. A bright annulus, with diameters of 10-5 degrees and 25-8 degrees, inhibits both ON and OFF responses when concentric with the 5 degree test area, but not when it is 30 degrees eccentric to the test area. The inhibitory effect shows no decrease after 4 min. 4. These results are interpreted to indicate a tonic lateral inhibitory network, sited peripherally in the optic lobe prior to the divergence of the separate ON and OFF channels found in the projection from the medulla to the LGMD. It is probably identical with that described for the lamina by previous workers.

Action Potentials↗
PubMed1975

Serum ferritin assay and iron status in chronic renal failure and haemodialysis.

Forty-four patients with chronic renal failure on haemodialysis for four months to eight years were studied. All recieved intravenous iron dextran 100 mg on alternate weeks. Serum ferritin concentrations correlated well with body iron stores estimated by grading the bone marrow stainable iron. Altogether 34 patients showed increased bone marrow iron stores and serum ferritin concentrations greater than controls; four patients showed absence of iron in the marrow, and three of these had subnormal serum ferritin concentrations. Serum ferritin assay represents the best method of repeatedly monitoring the exact amount of iron therapy needed by patients with chronic renal failure, particularly those on regular haemodialysis.

Adult↗
PubMed1970

Altered dihydrofolate reductase associated with drug-resistance transfer between rodent plasmodia.

Resistance to pyrimethamine in strains of Plasmodium vinckei and of Plasmodium berghei is attributed to changes in amounts and properties of the dihydrofolate reductases. The resistant strain of Plasmodium berghei was isolated from an experimentally induced mixed infection of drug-resistant Plasmodium vinckei and drug-sensitive Plasmodium berghei, through biological filtration in hamsters. The drug resistance in Plasmodium berghei appears to have been acquired through transfer of part of the gene or genes coding for dihydrofolate reductase from the resistant Plasmodium vinckei to the sensitive Plasmodium berghei.

Animals↗
PubMed1969

Treatment of deep vein thrombosis. A trial of heparin, streptokinase, and arvin.

Thirty patients with deep vein thrombosis of the legs of less than four days' duration were allocated at random to treatment with heparin, streptokinase, or Arvin under laboratory control. When the fate of the thrombi was assessed by objective techniques-phlebography and the (125)I-labelled fibrinogen test-the incidence of complete thrombolysis was greatest in the streptokinase group. Complications arose during treatment in each group but were least with Arvin. The natural history of the disease favours clinical but not always anatomical recovery.

Adult↗