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Biomedical subjects

K J O'Connor

Publications and source records attributed to K J O'Connor.

At least 19 recordsLinked to original sources
PubMed2001

Angiography of potential cardiac donors.

OBJECTIVES: This retrospective review of organ donor records was designed to evaluate the practice of donor angiography in one organ procurement organization and determine the outcomes of angiography and its impact on the timing of the organ donation process. BACKGROUND: Concerns about transmission of atherosclerosis from donor to recipient have been heightened by the increasing prevalence of older donors. Guidelines that advocate the use of angiography in specific settings have been published, but no formal large-scale review has been performed. METHODS: For the period January 1993 through June 1997, we reviewed all New England Organ Bank records of donors between the ages of 40 and 65 including any from whom at least one solid organ was procured. Data abstracted included the presence of risk factors, timing of the evaluation process and angiographic findings. RESULTS: Coronary angiography was performed in 119 donors aged 40 and older; 64.7% of these hearts were transplanted. Thirty-eight hearts were transplanted from donors not subjected to angiography and outcomes were poorer compared with donors who underwent angiography. Advanced donor age was the only significant predictor of coronary artery disease. The duration of the procurement process was not prolonged by the performance of angiography. CONCLUSIONS: Donor coronary angiography does not complicate the donation process. Older donor age is the most powerful predictor of coronary artery disease and may explain prior observations of poorer outcome with older donor hearts. These factors should be considered when angiography is performed as part of the heart donor evaluation.

Adult↗
PubMed2001

Activation of the left amygdala to a cognitive representation of fear.

We examined the neural substrates involved when subjects encountered an event linked verbally, but not experientially, to an aversive outcome. This instructed fear task models a primary way humans learn about the emotional nature of events. Subjects were told that one stimulus (threat) represents an aversive event (a shock may be given), whereas another (safe) represents safety (no shock will be given). Using functional magnetic resonance imaging (fMRI), activation of the left amygdala was observed in response to threat versus safe conditions, which correlated with the expression of the fear response as measured by skin conductance. Additional activation observed in the insular cortex is proposed to be involved in conveying a cortical representation of fear to the amygdala. These results suggest that the neural substrates that support conditioned fear across species have a similar but somewhat different role in more abstract representations of fear in humans.

Amygdala↗
PubMed2000

Performance on indirect measures of race evaluation predicts amygdala activation.

We used fMRI to explore the neural substrates involved in the unconscious evaluation of Black and White social groups. Specifically, we focused on the amygdala, a subcortical structure known to play a role in emotional learning and evaluation. In Experiment 1, White American subjects observed faces of unfamiliar Black and White males. The strength of amygdala activation to Black-versus-White faces was correlated with two indirect (unconscious) measures of race evaluation (Implicit Association Test [IAT] and potentiated startle), but not with the direct (conscious) expression of race attitudes. In Experiment 2, these patterns were not obtained when the stimulus faces belonged to familiar and positively regarded Black and White individuals. Together, these results suggest that amygdala and behavioral responses to Black-versus-White faces in White subjects reflect cultural evaluations of social groups modified by individual experience.

Black or African American↗
PubMed2000

Use of electrostimulation in the treatment of diabetic neuroarthropathy.

Charcot's joint is a difficult and sometimes frustrating condition to treat, for both the patient and the physician. The authors give a brief overview of Charcot's joint and the treatment options available. They discuss the use of bone stimulators and how electrostimulation may be used to help arrest the progression of Charcot's deformity. To the authors' knowledge, the use of electrostimulation for the treatment of Charcot's joint has been described only once in the literature; three patients were evaluated in that study. In the current study, 11 patients were evaluated, with promising results obtained, thus supporting the findings of the previous study.

Arthropathy, Neurogenic↗
PubMed1991

Glucocorticoids inhibit the induction of nitric oxide synthase and the related cell damage in adenocarcinoma cells.

Lipopolysaccharide (LPS) induced a time-dependent synthesis of nitric oxide (NO) in EMT6 adenocarcinoma cells, assayed by accumulation of NO-derived nitrite in the medium. The induction of NO synthesis was inhibited in a concentration-dependent manner by the glucocorticoids dexamethasone (IC50 = 5 nM) and hydrocortisone (IC50 = 20 nM) and this effect was partially antagonized by progesterone and cortexolone. If addition of dexamethasone was delayed 6 h or more, inhibition of nitrite accumulation over 24 h was substantially reduced, indicating a lack of direct effect of glucocorticoids on the NO synthase. Nitrite accumulation was accompanied by cell damage, which was increased by L-arginine and inhibited by NG-monomethyl-L-arginine (L-NMMA) and dexamethasone. These data show that NO is a primary cytotoxic mediator and that suppression of its formation by glucocorticoids explains some of their anti-inflammatory and cytoprotective effects.

Amino Acid Oxidoreductases↗
PubMed1988

CT scanography for limb length determination.

The authors present an alternative to classic techniques used to measure limb length discrepancy radiographically. CT scanography seems to have advantages over currently-used Bell-Thompson roentgenography in that it uses less radiation and is of no increase in cost.

Adult↗
PubMed1988

Duplication methods for replacement of broken orthoses.

The methods presented for replacement of broken orthoses have proved very effective (Fig. 9). In more than 5 years of employing such duplication techniques, we have found patient satisfaction in the product to be commensurate with that for their originally prescribed devices. The techniques presented are not the only methods by which orthoses can be duplicated. We recognize that the clinician should refabricate the same orthosis only when the cause of breakage has been determined to be material fatigue or stress. Should the patient's weight, foot structure, or activities have changed, new orthoses should be fabricated with those factors in mind.

Equipment Design↗
PubMed1986

Organ procurement.

The growth of organ transplantation has led to increased physician assistant involvement in the organ procurement process. Consent for organ donation must be obtained from the family of the brain-dead patient prior to discontinuation of life-support systems. This is a complex and difficult task for the counseling clinician. It requires a sound understanding of brain death, the mechanics of the procurement system, and the needs of the donor family. In this article, a specialist offers practical guidelines to PAs who wish to help these families make informed decisions about organ donation.

Brain Death↗
PubMed1982

125I-labelled insulin degradation by isolated rat hepatocytes: the roles of glutathione-insulin transhydrogenase and insulin-specific protease.

Isolated rat hepatocytes degraded 125I-insulin with a Km of 150 nmol/l. Degradation was stimulated by the addition of glutathione and dithiothreitol. In cells incubated with diamide, glutathione was oxidised to the disulphide. Regeneration of reduced glutathione commenced after a further 30 min incubation at 37 degrees C. Diamide (1 mmol/l) significantly inhibited insulin degradation by hepatocytes (p less than 0.001). The 'apparent Vmax' for insulin degradation was decreased tenfold and the Km decreased to 25 nmol/l. The diamide-insensitive degrading activity was cell-associated and produced an intermediate of hormone degradation that was apparently of a higher molecular weight than insulin A chain. The biological activity of the intermediate was 0.03% of that of insulin. The diamide-insensitive activity was not due to release of protease into the medium by cell lysis. We conclude that there are at least two pathways capable of degrading insulin existing in rat hepatocytes.

Animals↗
PubMed1982

The internalisation of [125I] insulin by isolated rat hepatocytes.

This work was undertaken to examine the relationship between the binding, internalisation and degradation of insulin by isolated rat hepatocytes. Internalisation of hormone reached a maximum after 5-7 minutes at 37 degrees C; at an insulin concentration of 0.1 nM, 25% of the specifically bound hormone was internalised. Internalisation and the degradation of internalised insulin were inhibited by the intralysosomal protease inhibitors chloroquine and methylamine but not by the thiol oxidant diamide. It is concluded that internalisation of insulin by rat hepatocytes is not a necessary step in the degradation of the hormone molecule.

Animals↗
PubMed1981

The metabolism of 125I-labelled insulin by isolated Zucker rat hepatocytes.

The metabolism of 125I-labelled insulin by hepatocytes isolated from 48-h-starved Zucker lean and obese rats was studied. Hepatocytes from the lean animals bound significantly more 125I-labelled insulin and had a greater receptor number per cell than did cells from obese littermates. Hepatocytes from the lean animals degraded and internalized more hormone than did those from obese ones. Increased degradation and internalization correlated with the increased receptor number.

Animals↗