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Biomedical subjects

P Mercer

Publications and source records attributed to P Mercer.

16 recordsLinked to original sources
PubMed2003

Detection of juvenile sleep deprivation by stochastic optimization of pupillographic records.

OBJECTIVE: To address the challenging problem of measuring juvenile sleep deprivation, we test the hypothesis that a pupillographic method found successful for adult narcoleptics might also discriminate between sleep deprived juveniles acting as their own controls. METHODS: A linear, nonstationary model relating pupillary diameter and a random photic stimulus are estimated by recursive regressions from pupillographic records of 8 juveniles of median age 7 years acting as their own rested controls. The estimated pupillary impulse response noise functions are stochastically optimized using the Kullback divergence measure to maximally separate the sleep deprived records from the control records. RESULTS: Both the average and covariance statistics of the estimated pupillary noise functions exhibit statistically significant differences between sleep deprived and rested subjects. The main result is that sleep deprivation decreases pupillary noise variance; a finding consistent with a previous study of adult narcoleptics. Further, it was found that virtually the same stochastic parameters were optimal for the juvenile sleep deprived data and for the previous adult narcoleptic study. CONCLUSIONS: Although our results are preliminary, the consistent reduction of pupillary noise appears to justify a comprehensive clinical trial across a broad range of age classes. In addition, the finding that the same parameters stochastically optimize both juvenile and adult recordings suggests the procedure holds promise as a clinical test which could produce sleep deprivation measures simultaneous with data collection.

Algorithms↗
PubMed2000

Pulmonary effects induced by ultrafine PTFE particles.

PTFE (polytetrafluoroethylene) fumes consisting of large numbers of ultrafine (uf) particles and low concentrations of gas-phase compounds can cause severe acute lung injury. Our studies were designed to test three hypotheses: (i) uf PTFE fume particles are causally involved in the induction of acute lung injury, (ii) uf PTFE elicit greater pulmonary effects than larger sized PTFE accumulation mode particles, and (iii) preexposure to the uf PTFE fume particles will induce tolerance. We used uf Teflon (PTFE) fumes (count median particle size approximately 16 nm) generated by heating PTFE in a tube furnace to 486 degrees C to evaluate principles of ultrafine particle toxicity. Teflon fumes at ultrafine particle concentrations of 50 microg/m(3) were extremely toxic to rats when inhaled for only 15 min. We found that when generated in argon, the ultrafine Teflon particles alone are not toxic at these exposure conditions; neither were Teflon fume gas-phase constituents when generated in air. Only the combination of both phases when generated in air caused high toxicity, suggesting either the existence of radicals on the surface or a carrier mechanism of the ultrafine particles for adsorbed gas compounds. Aging of the fresh Teflon fumes for 3.5 min led to a predicted coagulation to >100 nm particles which no longer caused toxicity in exposed animals. This result is consistent with a greater toxicity of ultrafine particles compared to accumulation mode particles, although changes in particle surface chemistry during the aging process may have contributed to the diminished toxicity. Furthermore, the pulmonary toxicity of the ultrafine Teflon fumes could be prevented by adapting the animals with short 5-min exposures on 3 days prior to a 15-min exposure. Messages encoding antioxidants and chemokines were increased substantially in nonadapted animals, yet were unaltered in adapted animals. This study shows the importance of preexposure history for the susceptibility to acute ultrafine particle effects.

Administration, Inhalation↗
PubMed1998

Role of REM sleep and dream affect in overnight mood regulation: a study of normal volunteers.

To test that REM sleep and/or dreaming aid in the overnight regulation of negative mood, 60 student subjects, selected to have no current or past episodes of depression, were tested with the Profile of Mood States (POMS) before and after two nights of laboratory sleep. There was a significant overnight effect of sleep on the Depression scale (Dep) both on a sleep-through night and a night of REM awakenings for dream recall. Pre-sleep Dep was significantly correlated with the affect in the first REM report. Although Dep scores were truncated due to the screening criteria, a subgroup of the 10 highest scorers differed from the 50 low scorers in the distribution of dream affect categories across the night. Low scorers displayed a flat distribution of positive and negative affect in dreams, while those with some pre-sleep depressed mood showed a pattern of decreasing negative and increasing positive affect in dreams reported from successive REM periods. This suggests that dreaming may actively moderate mood overnight in normal subjects.

Adult↗
PubMed1998

Role of REM sleep and dream variables in the prediction of remission from depression.

To test the hypothesis that REM sleep and/or dreams contribute to overnight mood regulation, 61 subjects were tested on the Beck Depression Inventory (BDI), and for 3 nights of monitored sleep on two occasions, once close to, and 1 year after, a marital separation. Forty-nine percent of the variance in the follow-up BDI could be accounted for by the initial BDI score, and three sleep and dream variables associated with the mood regulatory hypothesis: eye movement density in the first REM, strength of the affect in the first dream and total number of negative dreams recalled from REM awakenings. Among the 39 who met BDI depression criteria initially, 71.8% could be classified correctly as remitted or not remitted at follow-up by discriminant function analysis based on the presence of negative dreams the first vs. second half of the night. Subjects reporting more negative dreams at the beginning and fewer at the night's end were more likely to be in remission 1 year later than were those with fewer negative dreams at the beginning and more at the end of the night. Early negative dreams may reflect a within-sleep mood regulation process taking place, while those that occur later may indicate a failure in the completion of this process.

Adult↗
PubMed1998

Evaluating the donor pool: impact of using hearts from donors over the age of 49 years.

The shortage of hearts for transplantation has led to the use of organs from older donors in many centres. Despite the lack of coronary angiography on potential organ donors, hearts from carefully selected donors over 49 years of age have been used at this centre since 1988. In the study reported here looked at the impact of this strategy on morbidity and mortality. Between May 1988 and August 1996, 400 first heart transplants were performed, 35 recipients (31 male, 4 female; age 51 +/- 5.9 years) received hearts from donors over 49 years of age (group 1) while 365 (310 male, 55 female; age 49 +/- 9.7 years) had younger donors (group 2). The mean ischaemic time was 189 min (+/- 63.1) in group 1 and 180 min (+/- 59.2) in group 2 (n.s.). The main aetiology of heart failure in groups 1 and 2 was coronary artery disease in 46% and 51%, and dilated cardiomyopathy in 40% and 45% respectively (n.s.). There were no differences in the duration of stay on the intensive care unit or in hospital between the groups. One-year survival was 79% in group 1 and 82% in group 2 (n.s.) and actuarial 5-year survival 69% and 67%, respectively. Six patients in group 1 (17%) and 45 patients in group 2 (12%) died in the first 3 months; of these primary donor organ failure accounted for 50% in group 1 and 13.3% in group 2 (n.s.). Episodes of acute rejection (in the first 3 months) were similar in the two groups: 1.4 and 1.6 per 100 patient days, respectively. Infection rates were also similar: 0.5 and 0.6 per 100 patient days, respectively. The prevalence of coronary artery disease on surveillance coronary angiography at 2 years was 23% in group 1 and 9% in group 2 (P < 0.005). There was a greater proportion of CMV antibody donors in the older donor group, but the association between donor age and coronary artery disease persisted after adjusting for CMV status in multivariate analysis. Too few patients underwent angiography thereafter for valid comparisons. In summary, recipients of organs from donors aged 49 years and over can expect comparable survival rates and morbidity levels to recipients of organs from younger donors, at least in the first 2 years postoperation. There is evidence that older donors confer a significantly higher risk of cardiac allograft vasculopathy which may result in a greater attrition rate thereafter. Careful follow-up of these patients after 2 years is required.

Age Factors↗
PubMed1997

Bevel-down superior to bevel-up in intradermal skin testing.

BACKGROUND: Intradermal skin testing is one of the most widely used procedures in the diagnosis of hypersensitivity diseases in vivo. It is critical to perform the test accurately and expediently. Yet, there are few articles describing its detailed technique or proficiency available. OBJECTIVES: To identify the better method for intradermal testing between the bevel-up and bevel-down techniques. METHODS: Three inexperienced testers performed intradermal injections using both methods. Four sets of paired trails each consisting of ten injections were applied randomly, alternating between the same volunteer subject's contralateral arms. Duration to complete ten injections was measured. Numbers of injection sites that bled, that squirted into the air, and failed to form a bleb were counted. The overall comfort level was determined. RESULTS: The time to complete the injections by bevel-up and by bevel-down methods were 165.5 +/- 31.3 and 152.5 +/- 27.4 seconds, respectively (P < .015). The number of injection sites that bled was higher in the bevel-up method, particularily on trial one (P < .001). Completion rate of successful bleb formation in bevel-down was 27.3 as compared with 23.3 in bevel-up method (P = .013). The comfort level was higher with the bevel-down than the bevel-up method (P = .0001). CONCLUSION: The bevel-down method of intradermal testing is superior to the bevel-up method.

Equipment and Supplies↗
PubMed1994

Audit of complete axillary dissection in early breast cancer.

The role of complete axillary dissection (CAD) in the management of breast cancer is controversial and largely unresolved. Acceptance of the results of trials incorporating CAD assumes that the axillary dissection is truly complete. To address this point, and also to define quality control criteria for this operation within our unit, we audited 100 consecutive axillary dissections as follows: the primary surgeon performed what he/she felt to be a thorough CAD and submitted separately the contents of level I, II and III for pathological evaluation; a second surgeon then independently assessed the dissection and arbitrarily labelled any further excised tissue as level IV. Level IV nodes were retrieved in 38% of cases. Tumour involvement of level IV nodes was noted in 5% (2/38) of dissections where lymph nodes were retrieved, but in neither instance was pathological staging altered. There was a significant decrease in the incidence of level IV node retrieval from 47% (28/60) in the first 6 months of audit to 20% (8/40) subsequently. This novel approach to our continuing audit identified quality control criteria for this procedure in our unit and suggested that audit of this kind benefits training.

Breast Neoplasms↗
PubMed1993

Clinical theophylline toxicity: acute and chronic.

Reliable methods for measuring serum theophylline levels have provided the clinician with a range of serum theophylline concentrations to maximize therapeutic results while minimizing potential adverse effects. Although serum theophylline levels are often quoted for diagnosing theophylline toxicity, intolerance of this agent is closely associated with clinical features that are more important than an absolute serum value. This report contrasts the two most common settings of theophylline toxicity and presents an approach to the treatment of each type.

Adult↗
PubMed1992

Docking of dogs.

Explore the source record for details and available documents.

Animal Welfare↗
PubMed1991

Endothelium-derived relaxing factor and the vascular reply to systemic hypertension.

Endogenous nitric oxide is an important modulator of vascular smooth muscle tone. The role of nitric oxide in the vascular adaptation to systemic hypertension was examined by using N omega-monomethyl-L-arginine (L-NMMA; 110 micrograms/kg/min), a competitive inhibitor of the conversion of L-arginine to nitric oxide. L-NMMA or saline vehicle (9.6 microL/min) was infused i.v. into several rat models of acute and chronic systemic hypertension. The response to L-NMMA was compared either in uninephrectomized Sprague-Dawley rats treated with deoxycorticosterone on either a high- or low-sodium diet or in untreated uninephrectomized rats on normal chow. Hypertensive deoxycorticosterone rats had a significantly greater pressor response to L-NMMA (139 +/- 2 to 169 +/- 3 mm Hg; N = 9) than did normotensive uninephrectomized rats (112 +/- 4 to 129 +/- 3 mm Hg; N = 7) or deoxycortisterone treated rats on a low-sodium diet (108 +/- 2 to 121 +/- 3 mm Hg; N = 9). By contrast, hypertension induced by the vasoconstrictor angiotensin II did not have an enhanced response (134 +/- 3 to 154 +/- 4 mm Hg; N = 7) nor did spontaneously hypertensive rats (164 +/- 4 to 175 +/- 4 mm Hg; N = 6). This dose of L-NMMA had minimal effects on renal hemodynamics in the normotensive and hypertensive animals, except for those receiving angiotensin II where it led to substantial reductions of inulin and para-aminohippurate clearance. In conclusion, these data point to a role for nitric oxide in the vascular adaptation to volume-mediated hypertension, an effect that was not observed in vasoconstrictor-induced hypertension.

Acute Disease↗
PubMed1986

Inhibition of glycation of albumin and hemoglobin by acetylation in vitro and in vivo.

Aspirin (acetylsalicylic acid or ASA) is known to inhibit glycosylation (glycation) of albumin in vitro. The mechanism has been presumed to be acetylation, but this has never been validated. The new affinity aminophenylboronic acid procedure for determination of glycosylated albumin was used to demonstrate inhibition of glycosylation by aspirin. ASA, but not salicylic acid, inhibited glycation. The inhibition of glycation by equimolar acetic anhydride was greater than that by ASA. Pretreatment of albumin with ASA in the absence of glucose demonstrated that inhibition was extremely rapid, occurring in a matter of minutes. However, the inhibition by ASA could not be prevented by massive acceleration of glycation induced by borohydride reduction. Glycation of hemoglobin was also inhibited by ASA, but the dose requirement was considerably higher. Various analogues of ASA were evaluated for inhibition of glycation. Only acetyl-5-ethylsalicylic acid was more effective than ASA in inhibiting albumin glycation. None of these agents was more potent than ASA in inhibiting glycation of hemoglobin. ASA was fed to diabetic rats in a long-term experiment. Glycohemoglobin and glycoalbumin levels were decreased by ASA administration. We conclude that ASA inhibits glycation by a very rapid acetylation process. This process is apparently quite selective in terms of the protein involved, presumably because of the local environment of affected lysine groups. The phenomenon can be produced in vivo by administration of ASA.

Acetylation↗
PubMedDate not supplied

Post-operative care of transplant patients.

The skills involved in the post-operative management of patients undergoing transplantation are a major factor influencing their survival. This article explores the role of clinicians' assistants in providing care for patients and their families after cardiothoracic transplantation at the pioneering Papworth Hospital in Cambridgeshire.

Humans↗