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Biomedical subjects

J O'Callaghan

Publications and source records attributed to J O'Callaghan.

At least 37 records · Page 2Linked to original sources
PubMed1992

Symbiotic interactions in the EVOLVE III ecosystem model.

Parasitic feeding mechanisms were introduced into the EVOLVE III ecosystem model. The modified system exhibited a number of interesting behaviors, including obligative and facultative parasitism, transient facultative mutualism and nonsymbiotic feeding. Speciation and massive die-offs were also observed. The introduction of a symbiotic capability altered the co-evolutionary development of traits that exhibited an arms race when the symbiotic capability was not present. Stable mutualisms were not possible in the present version of the model due to the restriction that organisms were not allowed to feed both on other organisms and from the environment at the same time. The ecosystem biomass increased with increased symbiotic activity. Biomass was influenced by the balance of virulence and resistance traits in the population and decreased as these traits became more disparate.

Animals↗
PubMed1991

5,7-Dihydroxytryptamine injections increase glial fibrillary acidic protein in the hypothalamus of adult rats.

The distribution and levels of glial fibrillary acidic protein (GFAP) were determined in the adult rat hypothalamus following axotomy of serotonin (5-HT) neurons. Seven days after unilateral intrahypothalamic injection of the 5-HT neurotoxin, 5,7-dihydroxytryptamine, there was a marked increase in the number of GFAP-labelled astrocytes in the ipsilateral hypothalamus of 5,7-DHT-treated as compared to sham-treated rats. In addition, levels of GFAP were significantly increased 7 days after 5,7-DHT injection.

5,7-Dihydroxytryptamine↗
PubMed1990

Comparative controlled trial of low-dose weekly methotrexate versus azathioprine in rheumatoid arthritis: 3-year prospective study.

Fifty-three patients with rheumatoid arthritis who required immunosuppressive therapy were commenced in a randomized trial comparing azathioprine to weekly oral pulse methotrexate. After an initial 24-week period, both groups had significantly improved from baseline measures of pain and functional capacity and there were no significant differences in clinical outcomes between the two groups. Laboratory variables of disease activity showed a significant improvement in haemoglobin and ESR in the methotrexate group. Subsequently, the patients were followed for up to 3 years. After one year, more than half of the patients in both groups had discontinued therapy due to inefficacy or adverse events. Adverse effects were more frequent in the patients treated with methotrexate, but withdrawal rates were similar in both groups. From these data, the probability of a patient continuing therapy with either agent for greater than 18 months is low.

Activities of Daily Living↗
PubMed1988

A longitudinal study of cholinesterase changes in pregnancy.

Serum cholinesterase activity was measured at intervals before, during, and after 44 pregnancies in 43 women. Three patterns of change were seen: (a) A decline in activity after conception, with no return towards pre-conception values before delivery (20 pregnancies). (b) A decline in activity accompanied by a partial or complete return to pre-conception values before delivery (19 pregnancies). (c) Either no discernible decline or increased activity during gestation (five pregnancies). We saw no association between these patterns and either the sex of the child, parity, smoking history, or alcohol intake. However, the continuous decrease in cholinesterase activity occurred in the youngest group of women, a decrease followed by an increase in the intermediate age group, and no decrease at all in the oldest group. Although not all the age-related differences quite reached statistical significance, these findings suggest that the patterns of change may be determined by some aspect of maternal physical maturity.

Adult↗
PubMed1986

Radiological assessment of aluminium-related bone disease.

Two hundred and fifty-nine radiological skeletal surveys were reviewed in 67 cases of end-stage renal failure. Fractures were identified in 16 patients, of whom 12 (17.9% of total) had aluminium-related bone disease. Moderate or severe fracturing osteopathy with more than five fractures not explained by trauma was 100% specific for aluminium intoxication. It is sufficient to perform radiological skeletal surveys in the assessment of renal osteodystrophy annually. They should include radiographs of the fingers, a lateral view of the lumbar spine and oblique views of the ribs. The primary aim of reporting on such surveys should be to grade the severity of fracturing osteopathy and of subperiosteal erosions.

Aluminum↗
PubMed1985

Plasma and synovial fluid gentisate in patients receiving salicylate therapy.

Our study was undertaken to assay gentisate, an oxidation metabolite of salicylate, in plasma and synovial fluid (SF) samples from patients taking antiinflammatory doses of aspirin. A close correlation between plasma and SF concentrations was found for (1) salicylate, (2) salicylurate, and (3) gentisate, in 20 patients studied. Our data suggest ready equilibration of these compounds between the plasma and synovial spaces. In vitro experiments confirmed that in the presence of an oxy radical flux, salicylate is oxidized to gentisate. However, no evidence was obtained to implicate peripheral conversion of salicylate to gentisate in inflamed joints where oxy radicals may be produced.

Arthritis, Rheumatoid↗
PubMed1979

The CT scan and subtraction angiography in chemodectomas.

The value of subtraction angiography and CT scanning in the diagnosis of chemodectomas are illustrated by two cases, a glomus jugulare tumour which exhibited true malignant behaviour, and a carotid body tumour. The characteristic early arterial blush of a chemodectoma, which can be obscured by bone, is clearly seen following subtraction techniques revealing tumours as small as 0.5 cm. The chemodectoma appeared as an isodense tumour on the CT scan with uniform contrast enhancement and well-defined margins. The appearances, however, are not diagnostic of a chemodectoma and may be simulated by other tumours.

Adult↗
PubMed1976

Inhibition of H+ secretion in the frog gastric mucosa by ATP and related compounds.

Addition of adenosine triphosphate (ATP) to the nutrient (submucosal-facing) solution of the histamine-stimulated in vitro frog (Rana pipiens) gastric mucosa produces a marked reduction in the H+ secretory rate and an increase in transmucosal potential difference (PD) and resistance in both Cl- and Cl-free media. The effects are reversible upon removal of ATP. The threshold concentration is between 1 and 2 mM, and 5 mM produce maximal inhibition. It is shown that the effects of ATP are not due to a change in pH or osmolarity of the nutrient fluid, or to a decrease in the Ca2+ and/or Mg2+ activities of the nutrient fluid. It is also shown that the inhibitory action of ATP is not dependent on a chelation complex between Ca2+ or Mg2+. Adenosine diphosphate also produces effects essentially the same as ATP whereas 5'-adenosine monophosphate and adenosine produce relatively little or no change.

Adenosine↗