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Biomedical subjects

M J Sullivan

Publications and source records attributed to M J Sullivan.

205 records · Page 12Linked to original sources
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Mechanisms of baroreceptor activation.

The determinants of the nerve activity generated at the baroreceptor endings have been examined. 1) In the isolated carotid sinus, the placement of activated bovine aortic endothelial cells decreased baroreceptor activity (BRA) in a reversible manner. Both endothelin and nitric oxide (NO) suppress BRA, whereas prostacyclin (PGI2) increases activity. 2) The BRA in single units declines and often ceases during non-pulsatile increases in carotid sinus pressure sustained over several minutes. This "adaptation" is attenuated by the transient potassium channel (IA) blocker 4-aminopyridine (4-AP) and not by inhibition of the Na+/K+ pump. 3) In preliminary studies, mechano-electrical transduction was examined in isolated and cultured nodose ganglion neurons. Opening of stretch-activated (SA) channels by suction on the cell-attached patch was seen infrequently; however, probing the neurons consistently increased their intracellular calcium [Ca++]i measured with fura-2. This increase in [Ca++]i is blocked by gadolinium (Gd3+), a trivalent lanthanide reported to block SA channels. Gd3+ also blocks the BRA in the carotid sinus. We conclude that paracrine factors significantly modulate BR sensitivity, that selective ionic mechanisms (the 4-AP sensitive K+ channels) determine the degree of "adaptation" of BR to elevated pressure, and that SA channels sensitive to Gd3+ may be the mechano-electrical transducers in BR neurons.

4-Aminopyridine↗
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A psychological intervention for reducing pain during dental hygiene treatment.

Previous research has shown that individuals who "catastrophize" are more likely to experience high levels of pain and emotional distress during dental treatment. In the present study, we examined the effects of emotional disclosure on the pain and emotional distress experienced by "catastrophizers" and "noncatastrophizers" during dental hygiene treatment. Eighty undergraduate students were randomly assigned to a dental-worry disclosure condition or a control condition prior to scaling. In the disclosure condition, participants were asked to write about their dental worries before having dental hygiene treatment. In the control condition, participants were asked to write about their activities of the previous day. Consistent with previous research, catastrophizers in the control condition reported significantly more pain and emotional distress than noncatastrophizers, F (1, 76) = 9.86, P < .001. Disclosure reduced the pain and emotional distress of catastrophizers, but increased the pain and emotional distress of noncatastrophizers, F (1, 76) = 6.1, P < .01. While catastrophizers benefited from disclosure in regard to their immediate physical and emotional experience, their levels of catastrophizing and dental anxiety remained essentially unchanged. Clinical implications of the findings are discussed.

Adult↗
PubMedDate not supplied

Catastrophic thinking and the experience of pain during dental procedures.

In recent years, considerable research has addressed psychological predictors of pain, emotional distress, and avoidance in relation to dental treatment. Our work has focused on how "pain catastrophizing" impacts on the physical and emotional distress experienced during dental procedures. Pain catastrophizing refers to individuals' tendency to focus excessively on pain sensations and exaggerate their threat value, and to feel helpless in their efforts to reduce or manage their pain. Several studies reveal that pain catastrophizers report extreme pain even in response to dental procedures not typically considered to be painful. In this paper, we also discuss how practitioners who foster the disclosure of dental worries and concerns can significantly reduce the physical and emotional distress of patients who engage in catastrophic thinking.

Age Factors↗
PubMedDate not supplied

The effects of cobra venom factor, an inhibitor of the complement system, on the sequence of morphological events in the rat kidney in experimental pyelonephritis.

Acute experimental pyelonephritis has been produced by a combination of mechanical ureteral obstruction and intravenous injection of E. coli (strain IMRU-54). The effects of administration of cobra venom factor, an inhibitor of the complement system, on the sequence of morphologic events in the kidneys have been studied by light and electron microscopy.Pronounced bacterial colonization and suppression of the infiltration of acute inflammatory cells into the kidney were present in the cobra venom factor treated rats on day 2. In these rats, in which the infiltration of polymorphonuclear leukocytes was inhibited, renal structural damage was significantly reduced. The findings appear to indicate that the polymorphonuclear leukocytes infiltrating into the kidney play some role in damaging the renal parenchymal tissue in the early phase of E. coli induced acute pyelonephritis in rats.

Animals↗
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In vivo validation of a thermodilution system designed to measure peripheral blood flow.

A 5F triple-lumen thermodilution catheter was evaluated in a canine vena cava model to determine whether this catheter and the thermodilution technique provide valid in vivo determinations of blood flow. Our ultimate goal is to develop methods for studying limb blood flow in humans. Seven dogs were studied. Blood flow was provided and regulated by a calibrated roller pump. Flow rate determinations by thermodilution were made over a range of 0.5 to 5.01 1/minute. Excellent correlation (r = 0.98, r2 = 0.96, P less than 0.01) was found between actual flow and flow measured by thermodilution. The mean (+/- SD) coefficient of variation for the thermodilution method was 9.97 +/- 5.72 per cent over the flow range tested. The coefficient of variation tended to be higher at low flow rates. The thermodilution technique with this catheter provides valid in vivo determinations of blood flow through large vessels. This technology can be rationally applied to the study of limb blood flow in humans.

Animals↗
PubMedDate not supplied

Psychological predictors of pain during dental hygiene treatment.

This study examined the role of catastrophizing (i.e. a tendency to exaggerate the threat value of potentially painful situations) in predicting pain experience during dental hygiene treatment. Participants in the research were 100 patients undergoing scaling and/or root planing procedures at Dalhousie University's Dental Clinic. Following treatment, participants completed the Pain Catastrophizing Scale, a measure of emotional distress, a pain scale, and the Dental Anxiety Scale-Revised. Participants who scored above the median on the Pain Catastrophizing Scale were classified as catastrophizers, participants who scored below the median were classified as noncatastrophizers. Results showed that catastrophizers reported significantly more dental anxiety, emotional distress and pain than noncatastrophizers; and that distress reactions were more pronounced in men that in women. Discussion focuses on the importance of addressing psychological factors in dental hygiene practice, particularly as they relate to reactions to dental hygiene procedures, and avoidance of dental care.

Adult↗