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Biomedical subjects

J A O'Brien

Publications and source records attributed to J A O'Brien.

At least 91 records · Page 5Linked to original sources
PubMed1987

Inositol trisphosphate and calcium mobilisation in permeabilised enterocytes.

Saponin-permeabilised epithelial cells isolated by hyalurodinase incubation from chicken small intestine were used to study 45Ca uptake into intracellular stores. At low (6.7 X 10(-7) M) free Ca2+ concentration most of the Ca2+ appears to be taken up into non-mitochondrial stores, whilst the mitochondria seem to play a major role at high (2 X 10(-5) M) Ca2+ concentration. Addition of inositol trisphosphate (IP3) causes a rapid and reversible release of 45Ca from non-mitochondrial stores, with a half-maximal effect of approximately 1 microM.

Animals↗
PubMed1987

Localization and accumulation of fibronectin in rabbit fetal lung tissue.

An interaction between mesenchyme and epithelium is required for the normal differentiation of fetal lung tissue. This morphogenic interaction may be mediated, in part, by changes in the composition and/or structure of the extracellular matrix. Therefore, we characterized the localization and accumulation of fibronectin, an extracellular-matrix component, during several stages of lung development in the rabbit fetus in vivo as well as in day-21 rabbit fetal lung explants maintained in vitro. Fibronectin was detected immunocytochemically in the basement-membrane zone beneath the epithelial ducts in lung tissue obtained from rabbit fetuses at 19 and 21 days of gestation. In fetal lung tissue obtained at these early stages of lung development, mesenchymal cells were stained only at their periphery. Immunostaining for connective-tissue fibronectin increased greatly between days 24 and 31 of gestation. A similar increase in the intensity of immunostaining for connective-tissue fibronectin was observed in rabbit fetal lung explants that had been maintained in vitro for 7 days. The concentration of fibronectin in fetal lung tissue obtained at different days of gestation was determined using a specific enzyme-linked immunoadsorbent assay (ELISA) and was found to increase from 1.7 ng/micrograms protein in fetal lung tissue obtained at day 19 of gestation to 7.3 ng/micrograms protein in fetal lung tissue obtained at day 24 of gestation. The levels of fetal lung fibronectin then remained relatively constant through to day 31 of gestation. A similar increase in fibronectin concentration was observed in day-21 fetal lung explants maintained in vitro for 7 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

The English bulldog: a natural model of sleep-disordered breathing.

To establish a natural model of sleep-disordered breathing, we investigated respiration during wakefulness and sleep in the English bulldog. This breed is characterized by an abnormal upper airway anatomy, with enlargement of the soft palate and narrowing of the oropharynx. During sleep, the animals had disordered respiration and episodes of O2 desaturation. These were worst in rapid-eye-movement (REM) sleep, with most bulldogs having O2 saturations of less than 90% for prolonged durations. In contrast, control dogs never desaturated. In REM sleep, the bulldogs had episodes of both central and obstructive apnea, the latter being associated with paradoxical movements of the rib cage and abdomen. During wakefulness, the bulldogs were hypersomnolent as evidenced by a shortened sleep latency (mean of 12 min compared with greater than 150 min for controls). This animal model should facilitate studies of the natural history of the sleep apnea syndrome and its complications.

Animals↗
PubMed1985

Tracheal collapse in two cats.

Two cats examined bronchoscopically to discover the cause of tracheal collapse were found to have tracheal obstruction cranial to the collapse. Cats with this unusual sign should be examined bronchoscopically to ascertain whether there is an obstruction, as the cause in these 2 cats was distinct from the diffuse airway abnormality that causes tracheal collapse in dogs.

Animals↗
PubMed1985

Prepartum diagnosis of traumatic fetal-maternal hemorrhage.

The diagnosis of significant fetal-maternal hemorrhage due to abdominal trauma was made upon detection of fetal red cells in the maternal circulation before delivery, and prompted immediate intervention despite an equivocal fetal monitor tracing. Histologic examination of the placenta identified the area of disruption of the fetal circulation, and the clinical condition of the neonate confirmed the diagnosis. A test for fetal-maternal hemorrhage would be appropriate in the evaluation of any pregnant woman sustaining trauma to the abdomen.

Abdominal Injuries↗
PubMed1982

The effect of veiled cells on lymphocyte function.

The response of lymphocytes to stimulation with Con A has been studied in the presence of veiled cells collected from the afferent lymph. In these enriched cultures the response occurred earlier with smaller numbers of lymphocytes and at lower concentrations of Con A. Veiled cells also caused clumping of lymphocytes in unstimulated cultures. In stimulated cultures small cells with veil-like projections appeared after 48 hr, but were not seen in unstimulated cultures.

Animals↗
PubMed1981

The relationship between the size of mitochondria and the intensity of light that they scatter in different energetic states.

The intensity of light scattered at 90 degrees to the incident beam and the effective hydrodynamic radii of mitochondria incubated under a variety of conditions have been measured. Addition of high concentrations of uncouplers to respiring mitochondria resulted in a decrease in scatter which was not due to swelling. Addition of valinomycin to mitochondria depleted to substrate in K+-free medium produced an increase in scatter that was not due to shrinking. It is concluded that changes in the intensity of scattered light are not reliable indices of changes of volume of mitochondria, and the changes in conformation with changes in metabolic state dominate changes in light scatter. A molecular mechanism for the effect of metabolic state upon the scattered intensity is suggested.

Animals↗
PubMed1975

Creatine release from the isolated perfused rat heart.

Creatine release from the isolated perfused rat heart decreases during the first 40 min of perfusion to a constant rate which is maintained for at least a further 50 min. Reoxygenation after a period of 15 min of anoxia is accompanied by an increase in creatine release. The highest rate of release occurs during preperfusion after the excision of the heart. These losses might contribute to impairment of function after anoxia.

Aerobiosis↗