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Biomedical subjects

B O'Connor

Publications and source records attributed to B O'Connor.

102 records · Page 6Linked to original sources
PubMed1984

Localization of a narrow-specificity thyroliberin hydrolyzing pyroglutamate aminopeptidase in synaptosomal membranes of guinea-pig brain.

In this paper we report the presence of a particulate pyroglutamate aminopeptidase in guinea-pig brain tissue. This activity appears to reside in the synaptosomal membrane and could be released from the membrane by treatment with papain or Triton X-100. By contrast with a previously described broad-specificity soluble pyroglutamate aminopeptidase from guinea-pig brain tissue, the enzyme released from the synaptosomal membrane preparation removed pyroglutamic acid from thyroliberin, acid thyroliberin and less than Glu-His-Gly alone of the peptides tested. Unlike the soluble tissue enzyme the present enzyme was inhibited by the presence of EDTA and the activity released from synaptosomal membranes by papain was found to have a relative molecular mass of 230 000, almost one order of magnitude greater than that reported for the soluble enzyme.

Aminopeptidases↗
PubMed1984

Left ventricular function at rest and during Raynaud's phenomenon in patients with scleroderma.

We evaluated left ventricular function in 10 scleroderma patients with signs and symptoms suggestive of congestive heart failure. M-mode and two-dimensional echocardiography demonstrated normal to increased systolic function in all patients. The presence of pulmonary venous congestion on the chest radiograph was not useful in assessing left ventricular systolic function. Five of nine patients with normal to increased left ventricular ejection fraction (LVEF) had increased cardiothoracic ratios and increased pulmonary vascular markings. Left ventricular hypertrophy was associated with a worse New York Heart Association functional class, more pulmonary vascular congestion, and greater left atrial size. In the presence of normal systolic function and ventricular hypertrophy, diminished left ventricular diastolic compliance may account for the cardiac dysfunction in these patients. Cold pressor testing induced peripheral Raynaud's phenomenon in nine of nine patients; however, no ST segment changes or chest pain was provoked. In seven of nine patients there was no abnormal fall in LVEF. The mechanism for the fall in ejection fraction seen in two patients may be related to an increase in afterload or myocardial ischemia secondary to coronary atherosclerosis. We found little to suggest that a myocardial Raynaud's phenomenon affects left ventricular perfusion or systolic function. Clinical signs and symptoms of congestive failure as well as chest radiographs are poor indicators of impaired systolic function in scleroderma patients. Based on these findings, it appears that evaluation of left ventricular systolic function should include echocardiographic or angiographic study before such patients are treated for heart failure with inotropic agents.

Adult↗
PubMed1984

Potencies of barbiturates in mice selectively bred for resistance or susceptibility to nitrous oxide anesthesia.

To test the possibility that mice selectively bred for resistance (HI mice) and susceptibility (LO mice) to nitrous oxide anesthesia have general differences in central nervous system sensitivity to other depressants, we examined the effects of four barbiturates in these two lines of mice. LO mice given intraperitoneal injections of barbital (275 mg/kg), hexobarbital (120 mg/kg), pentobarbital (65 mg/kg), or secobarbital (50 mg/kg) had significantly (16-46%) longer sleep times than HI mice. Concentrations of barbiturates were significantly (12-73%) greater in the serum and 3-55% greater in the brain on awakening in HI mice than in LO mice. The largest separations in potency between the HI and LO lines occurred with pentobarbital and hexobarbital and the smallest separations with barbital and secobarbital. We concluded that HI and LO mice do have a general resistance and susceptibility to barbiturates, but that the magnitude of the difference in central nervous system sensitivity between the two lines varies among barbiturates.

Anesthesia↗
PubMed1982

Potencies of convulsant drugs in mice selectively bred for resistance and susceptibility to nitrous oxide anesthesia.

To test the possibility that mice selectively bred for resistance (HI mice) and susceptibility (LO mice) to nitrous oxide anesthesia have general differences in central nervous system excitability, we examined the effects of six convulsant agents in these two lines in mice. Using high-pressure helium, flurothyl, pentylenetetrazol, strychnine, (+)-bicuculline, and picrotoxin, we induced convulsions in HI and LO mice. For all of the agents tested, HI mice were significantly more susceptible to convulsions than LO mice. LO mice convulsed at a 13 to 25 per cent higher dose of convulsant agent than did HI mice. In contrast, nitrous oxide requirements (as measured by the partial pressure of nitrous oxide required to abolish the righting reflex), were 49 to 65 per cent higher in HI mice. Therefore, the higher nitrous oxide requirement in HI mice is probably due, at least in part to a generalized increase in central nervous system excitability.

Animals↗
PubMed1980

Effect of diabetes upon penile sympathetic nerves in impotent patients.

Samples of erectile tissue taken from the corpora cavernosa of 16 male diabetic patients suffering from impotence were studied. The content of norepinephrine, which reflects sympathetic nerve activity of that tissue, was significantly lower in insulin-dependent patients 104.2 +/- 24.8 (SE) pg/mg wet weight (P less than .001) and diet-controlled patients 483.7 +/- 103.7 (P less than .01) than the normal men (881.7 +/- 62.0). Myelinated and unmyelinated nerve fibers were observed intact and unaltered in each group of patients. The results indicated that normally a dense adrenergic innervation of human erectile tissue is present, but that a reduction occurs in norepinephrine content in diabetic patients with impotence. It appears, however, that the anatomic integrity of the sympathetic nerves is intact. The presence of intact nerve fibers along with a diminished content of neurotransmitter suggests the possibility of pharmacologic treatment of impotence.

Diabetes Complications↗
PubMed1975

Insular biogeography: of mice and mites.

The number of mite species using cricetid rodents in North America is related to the host distributional areas. The age and latitude of the distributional areas have unimportant effects on the number of mite species using a rodent species. The relation between species and areas is analogous to species equilibrium numbers of island faunas.

Animals↗
PubMedDate not supplied

Adenovirus pathogenicity in immature ostriches.

Two group I avian adenoviruses implicated as the possible cause of "fading chick syndrome" in ostriches less than 8 wk of age were isolated in primary chicken embryo liver cells. These viruses were identified by virus neutralization and further characterized by a pathogenicity trial in immature ostriches. The results showed that these isolates were noninfectious in ostrich chicks.

Adenoviridae Infections↗
PubMedDate not supplied

Inhaler devices: compliance with steroid therapy.

Many people with asthma do not take their medication as prescribed. The use of inhaler devices is an important factor in patient compliance with steroid therapy. Some of the features that influence compliance are discussed and the characteristics of inhaler devices are compared.

Administration, Inhalation↗
PubMedDate not supplied

Hazards associated with the recreational drug 'ecstasy'.

The amphetamine analogue 'ecstasy' is a popular 'designer' drug and is perceived by its users to be relatively harmless. However, it has been associated with several fatalities through a disorder of thermoregulation, and severe reactions have been reported across many disciplines. This article emphasises the hazardous nature of the drug and highlights the urgency and nature of treatment in the acutely toxic state.

Adolescent↗