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Biomedical subjects

L Johnston

Publications and source records attributed to L Johnston.

At least 37 records · Page 2Linked to original sources
PubMed2001

Variation in river water temperatures in an upland stream over a 30-year period.

Stream water temperature data from the Girnock burn, a 30-km2 catchment in Scotland were examined for systematic variation across 30 years of record (1968-1997). The data suggest that there has been no change in mean annual temperature with time, but at a seasonal level there is some indication of an increase in mean daily maximum temperatures during the winter (December to February) and spring (March to May) seasons. For the spring season, there is also evidence that mean temperature has increased. There are no apparent or obvious changes in stream flow to account for this. The strong relationship between air and stream temperatures (r2 = 0.96) implies that changes in the stream are the result of changes in the climate. It is possible that this may occur as a result of the effect of increasing air temperatures which may have also reduced the influence of snow and snowmelt on the catchment during the winter and spring seasons.

Journal Article↗
PubMed2001

Suppression of the early and late cutaneous allergic responses using fexofenadine and montelukast.

BACKGROUND: The relative contribution of histamine and the cysteinyl leukotrienes to the early and late cutaneous allergic responses (ECAR and LCAR) can be studied using antagonists of these mediators. OBJECTIVE: To determine the relative suppression of the ECARs and LCARs using standard doses of an H1-receptor antagonist, a cysteinyl leukotriene1-receptor antagonist, and the two antagonists administered concurrently. METHODS: We carried out a prospective, randomized, double-blind, placebo-controlled, four-way crossover study in 12 highly allergic participants. Intradermal tests with standardized allergen, and with histamine phosphate, LTD4, and saline controls were performed on 5 different test days as follows: pretreatment baseline and at steady state immediately after the seventh and last dose of a 1-week course of treatment with once-daily fexofenadine, 120 mg; montelukast, 10 mg; fexofenadine and montelukast administered concurrently; or placebo. On each test day, the skin test results were read at intervals from 0.25 to 24 hours after the intradermal injections were performed. RESULTS: After allergen injection, compared with baseline, all treatment regimens significantly decreased the ECAR and LCAR. After allergen injection, compared with placebo, fexofenadine significantly decreased the ECAR and the LCAR from 0.25 to 2 hours and at 8 hours. Montelukast did not significantly decrease the ECAR or LCAR. Fexofenadine and montelukast administered concurrently were not more effective than fexofenadine alone at any time. In the control skin tests, compared with placebo, fexofenadine, but not montelukast, significantly decreased the histamine-induced response, and montelukast, but not fexofenadine, significantly decreased the LTD4-induced response. CONCLUSIONS: Fexofenadine and montelukast administered concurrently were not significantly more effective than fexofenadine alone in decreasing the ECAR and LCAR. Montelukast does not need to be discontinued before allergen skin testing. Further studies of the effect of concurrent treatment with higher doses of a histamine antagonist and a leukotriene modifier on the allergic response in the skin are needed.

Acetates↗
PubMed2001

The relationship of sleep quality and posttraumatic stress to potential sleep disorders in sexual assault survivors with nightmares, insomnia, and PTSD.

Sleep quality and posttraumatic stress disorder (PTSD) were examined in 151 sexual assault survivors, 77% of whom had previously reported symptoms of sleep-disordered breathing (SDB) or sleep movement disorders (SMD) or both. Participants completed the Pittsburgh Sleep Quality Index (PSQI) and the Posttraumatic Stress Scale (PSS). High PSQI scores reflected extremely poor sleep quality and correlated with PSS scores. PSQI scores were greater in participants with potential SDB or SMD or both. PSQI or PSS scores coupled with body-mass index and use of antidepressants or anxiolytics predicted potential sleep disorders. The relationship between sleep and posttraumatic stress appears to be more complex than can be explained by the current PTSD paradigm; and, sleep breathing and sleep movement disorders may be associated with this complexity.

Adult↗
PubMed2001

Human spinal cord injury: new and emerging approaches to treatment.

The World Health Organization together with the Iceland Ministry of Health and Social Security sponsored a conference entitled 'Human Spinal Cord Injury: New and Emerging Approaches to Treatment' held on May 31-June 2, 2001 in Reykjavik, Iceland. To help catalyze the development of new paradigms to address spinal cord injury, the conference's overall goal was to bring in a diversity of perspectives, ranging from state-of-the-art stem cell biology to the ancient wisdom of Eastern Medicine. The purpose of this paper is to summarize the presentations of the conference's 26 speakers.

Complementary Therapies↗
PubMed2001

A comparison of life satisfaction and mood in nursing home residents and community-dwelling elders.

This study compared life satisfaction and mood in a sample of 138 cognitively intact and ambulatory elders, including 70 who lived in nursing homes and 68 who lived independently in the community. Community-dwelling elders reported greater life satisfaction, and scored higher on the Vigor-Activity subscale of the Profile of Mood States (POMS) than those who lived in a nursing home. Nursing home residents scored higher on the Depression-Dejection, Tension-Anxiety, and Confusion-Bewilderment subscales of the POMS. No between group differences were shown on the Anger-Hostility and Fatigue-Inertia subscales of the POMS. The diminished life satisfaction and high depression found in the nursing home residents hold immediate implications for professionals who work in this area.

Activities of Daily Living↗
PubMed2001

Mechanisms of carvedilol action in human congestive heart failure.

The precise mechanism by which beta-adrenoceptor blockers exert their beneficial actions in patients with heart failure remains unclear. Several possibilities have been proposed, including heart rate reduction, beta2-adrenoceptor-mediated modulation of catecholamine release, antagonism of the receptor-mediated toxic actions of norepinephrine on the myocardium, and favorable effects on myocardial energetics. In the present study we evaluated the effect of 3 months of carvedilol therapy on hemodynamics, total systemic and cardiac norepinephrine spillover (isotope dilution method), and myocardial metabolism (myocardial oxygen consumption and carbon dioxide release) in 10 patients with severe congestive heart failure. Although carvedilol treatment was associated with a significant improvement in left ventricular ejection fraction (17+/-1% to 28+/-3%; P<0.01) and left ventricular stroke work (87+/-13 to 119+/-21 g. m per beat; P<0.05), this effect was unrelated to changes in total systemic or cardiac norepinephrine spillover. The rise in left ventricular stroke work was accompanied by a modest rise in myocardial oxygen consumption per beat (0.33+/-0.04 to 0.42+/-0.04; P=0.05), although contractile efficiency was unchanged. The favorable effects of carvedilol on ventricular function in the failing heart are not explained by alterations in norepinephrine release or by changes in myocardial contractile efficiency.

Antihypertensive Agents↗
PubMed2001

An open-label trial of evidence-based cognitive behavior therapy for nightmares and insomnia in crime victims with PTSD.

OBJECTIVE: Insomnia and nightmares are perceived as secondary phenomena in posttraumatic stress disorder (PTSD). Scant treatment research has targeted these two sleep disturbances. This study reports on an open-label trial of cognitive behavior therapy for insomnia and disturbing dreams in crime victims with PTSD. The relationship among nightmares, sleep disturbances, and PTSD symptoms is discussed. METHOD: Sixty-two participants completed a 10-hour group treatment consisting of imagery rehearsal for nightmares and sleep hygiene, stimulus control, and sleep restriction for insomnia. Nightmare frequency, sleep quality, sleep impairment, and ratings for PTSD, anxiety, and depression symptoms were assessed at baseline and at the 3-month follow-up. RESULTS: All measures demonstrated improvement that was roughly equivalent to changes in clinical severity from severe to moderate for sleep quality, sleep impairment, and nightmare frequency, from borderline severe to borderline moderate for PTSD symptoms, and from extremely severe to borderline severe for anxiety and depression symptoms. CONCLUSIONS: In this uncontrolled study, successful treatment for insomnia and nightmares in crime victims was associated with improvement in symptoms of PTSD, anxiety, and depression. Participants with clinical improvements in PTSD symptoms demonstrated significantly greater improvement in sleep quality and nightmare frequency than those whose PTSD symptoms did not improve.

Adult↗
PubMed2000

A retrospective study on improvements in nightmares and post-traumatic stress disorder following treatment for co-morbid sleep-disordered breathing.

OBJECTIVE: To assess the impact of treatment for co-morbid sleep-disordered breathing (SDB) on patients with nightmares and post-traumatic stress. METHODS: Twenty-three chronic nightmare sufferers (15 with post-traumatic stress disorder, PTSD) who also suffered co-morbid SDB (obstructive sleep apnea, OSA, n=16; upper airway resistance syndrome, UARS, n=7) completed a telephone interview, on average, 21 months after having been offered treatment for SDB at a university sleep disorders clinic. RESULTS: At follow-up, 14 reported maintaining treatment (Treatment Group) and 9 reported discontinuing treatment (No-Treatment Group). More patients in the Treatment Group reported improvement in sleep (93% vs. 33%) and in daytime well being (93% vs. 33%) compared with those in the No-Treatment group. The Treatment Group reported a median improvement in nightmares of 85% compared with a median 10% worsening in the No-Treatment Group. In the PTSD subset (n=15), nine in the Treatment Group reported a median 75% improvement in PTSD symptoms whereas six in the No-Treatment Group reported a median 43% worsening. CONCLUSION: In this small sample of patients, treatment of SDB was associated with improvements in nightmares and PTSD. Relationships between nightmares, PTSD and SDB are discussed.

Adult↗
PubMed2000

Sleep disorder, depression, and suicidality in female sexual assault survivors.

The role of sleep in psychiatric illness in general, and depression and suicidality in particular, is poorly understood and has not been well researched despite the pervasiveness of sleep complaints in these conditions. As an exploratory, hypothesis-generating study, female sexual assault survivors with posttraumatic stress disorder (n = 153) who had enrolled in a nightmare-treatment program were assessed for subjectively determined sleep breathing and sleep movement disorders. Diagnoses of potential disorders were based on clinical practice parameters and research algorithms from thefield of sleep disorders medicine. Potential sleep breathing and sleep movement disorders were present in 80% of the participants (n = 123) and included three subgroups: sleep-disordered breathing only (n = 23); sleep movement disorder only (n = 45); and both sleep disorders (n = 55). Based on the Hamilton Depression Rating Scale and Suicide subscale, participants with potential sleep disorders suffered greater depression (Cohen's d = .73-.96; p < .01) and greater suicidality (Cohen's d = .57-.78; p < .05) in comparison to participants without potential sleep disorders. The group with both sleep disorders suffered from the most severe depression and suicidality. A provisional hypothesis is formulated that describes how sleep disorders may exacerbate depression and suicidality through the effects of chronic sleep fragmentation.

Depression↗
PubMed2000

Clinical pharmacology of the H1-receptor antagonists cetirizine and loratadine in children.

H1-receptor antagonists are widely used in children but are not as well-studied in children as they are in adults. Our objective was to determine the onset and duration of action and the relative potency of the H1-receptor antagonists cetirizine and loratadine in children. We performed a prospective, randomized, placebo-controlled, double-blind, crossover, single-dose study of cetirizine and loratadine using suppression of the histamine-induced wheal and flare as the primary outcome. In 15 allergic children, mean age 9 years, compared with baseline, cetirizine (10 mg) suppressed the wheals and flares significantly from 0.25 to 24 h, achieving nearly 100% of flare suppression from 2 to 24 h, inclusive, and loratadine (10 mg) suppressed the wheals and flares significantly from 0.75 to 24 h, inclusive. Cetirizine suppressed the wheals and flares significantly more than loratadine from 0.25 to 1 h, inclusive, and at 0.5, 1, 2, 3, 5, 6, 7, and 24 h, respectively. Placebo also suppressed the wheal and flare significantly at some assessment times. Cetirizine and loratadine both have excellent antihistaminic activity in children, with a rapid onset of action and a 24-h duration of action in this population.

Anti-Allergic Agents↗
PubMed1999

Suppressing thoughts about chocolate.

OBJECTIVE: Thought suppression frequently results in subsequent hyperaccessibility of the suppressed thoughts. This study investigated whether this effect transfers to behavior. Does suppressing thoughts result in a subsequent increase in the performance of behaviors related to those thoughts? METHODS: Twenty chocolate cravers and 22 noncravers were instructed to suppress chocolate-related thoughts in an articulated thoughts task or they were given no specific instructions. Participants then completed a computer-based task which yielded chocolate rewards. RESULTS: Both cravers and noncravers could suppress chocolate-related thoughts when instructed to do so. Both groups of participants showed greater performance, and hence earned more chocolate, in the suppression than control condition (p < .05). DISCUSSION: Behavioral control may follow many of the same ironic pathways traced by mental control.

Behavior↗
PubMed1999

Cross-Canada spread of methicillin-resistant Staphylococcus aureus via transplant organs.

We report our investigation of the transmission of methicillin-resistant Staphylococcus aureus (MRSA) through transplantation. The kidneys, liver, and corneas were harvested from a child who died in Nova Scotia. Several days postmortem it was learned that culture of a premortem endotracheal tube aspirate from the donor yielded MRSA. Both kidneys were transplanted into a child in Nova Scotia and the liver into a child in Alberta. Both recipients subsequently became blood culture-positive for MRSA. One corneal ring from the donor was MRSA-positive. All four MRSA isolates were mecA-positive by polymerase chain reaction (PCR). The relatedness of the MRSA isolates was examined by restriction fragment length polymorphism (RFLP) analysis, a 16S-23S ribosomal PCR typing method, and comparison of antibiograms. Results were identical for all four MRSA isolates. These findings indicate that MRSA from the donor was transferred to recipients during implantation of harvested organs in Alberta and Nova Scotia, a cross-Canada spread.

Adolescent↗
PubMed1999

The advanced practice nurse. Changing the practice law: what did we learn?

The nurse practice statute was changed in Connecticut during the 1999 Legislative session in an effort to more accurately reflect the current practice of advanced practice nurses. The effort to make changes began in 1990, when the psychiatric clinical nurse specialists organized and incorporated to improve the practice status of this nurse specialty group and to improve patient accessibility to their services. This article describes the changes that were made in the practice statute and the lessons that were learned along the way. It elaborates on the need for strong organizational identification, coalition building, choosing legal and lobbying support carefully, negotiating with the opposition, and grassroots lobbying. Compromise was reached and statutory changes were made so that advanced practice nurses moved from being under the direction of physicians to a mutually agreed-on collaborative relationship with physicians. The article provides insights and learning experiences that may help others moving along the road to more independent practice laws.

Connecticut↗
PubMed1997

Cognitive distortions in sex offenders: an integrative review.

Clinicians and researchers have noted that maladaptive beliefs and distorted thinking play an important role in facilitating or justifying sexual offenses. There have been a number of attempts to describe the nature of these beliefs and to develop ways of measuring them, but in the absence of any integrating theory. We suggest that an understanding of the cognitive processes underlying the initiation, maintenance, and justification of sexual offending is a vital prerequisite to the development of successful treatment programs. In this paper, we use a social cognition framework to review the literature on the role of cognition in sexual offending. Pertinent research in the sexual offending domain, specifically cognitive products, information processing, cognitive change, and the impact of affective and motivational factors on cognitive processes, is described and related to the social cognitive approach. Implications for future research and clinical practice are discussed in light of the major issues and problems highlighted in our review.

Adult↗
PubMed1996

Fetal placental embolization in the late-gestation ovine fetus: alterations in umbilical blood flow and fetal heart rate patterns.

OBJECTIVE: Our goal was to determine the effect of chronic and acute umbilical-placental embolization on placental hemodynamic and fetal heart rate patterns in relation to fetal oxygenation in the near-term ovine fetus. STUDY DESIGN: Daily fetal placental embolization was performed during 10 days in 9 sheep fetuses until fetal arterial oxygen content decreased by approximately 30%. Nine control fetuses received saline solution. Mean and pulsatile umbilical blood flow, perfusion pressure, placental vascular resistance, fundamental impedance, pressure pulsatility index, and umbilical artery resistance index corrected to a fetal heart rate of 160 beats/min were measured. On day 10 both groups were acutely embolized until fetal arterial pH decreased to approximately 7.00. Fetal heart rate was measured with the Sonicaid System 8000 (Oxford Sonicaid, Oxford, United Kingdom). RESULTS: Chronic fetal placental embolization was associated with a progressive reduction in umbilical blood flow (p < 0.00001) and fetal arterial oxygen content (p < 0.001) whereas fetal heart rate patterns remained unaltered. A chronic increase in umbilical artery resistance index corrected to a fetal heart rate of 160 beats/min could be entirely explained only if the changes in umbilical artery pressure pulsatility index and the fundamental impedance were taken into account, in addition to the changes observed in placental vascular resistance. During acute embolization leading to a 50% reduction in umbilical blood flow (p < 0.0002) and a three times increase in placental vascular resistance (p < 0.0001), the most consistent change in fetal heart rate patterns related to progressive metabolic acidosis was an 84% decrease in absolute acceleration frequency (p < 0.0001) whereas short-term fetal heart rate variability remained unaltered. CONCLUSION: Changes in umbilical artery resistance index induced by chronic umbilical-placental embolization resulting in fetal hypoxemia occurred before any changes in fetal heart rate patterns were detectable. A decrease in the absolute acceleration frequency was the only component of fetal heart rate patterns related to progressive metabolic acidosis in the near-term ovine fetus.

Animals↗
PubMed1996

Fetal cerebral, circulatory, and metabolic responses during heart rate decelerations with umbilical cord compression.

OBJECTIVE: The purpose of this study was to determine the cerebral, circulatory, and metabolic responses of the ovine fetus near term to umbilical cord compression with variable-type fetal heart rate decelerations. STUDY DESIGN: Nine fetal sheep, at 0.9 of gestation, were studied before, during, and after umbilical cord occlusion for 1-minute and again after repetitive 1-minute cord occlusions every 5 minutes for 1 hour, with resultant fetal heart rate decelerations of approximately 90 beats/min. Brachiocephalic arterial and sagittal venous blood was analyzed for oxygen content, blood gases and pH, glucose, and lactate. Cerebral and upper body blood flow was measured with the microsphere technique. RESULTS: Umbilical cord occlusion with moderate to severe variable-type fetal heart rate deceleration resulted in an immediate drop in arterial PO2 by approximately 7 torr, an increase in PCO2 by approximately 9 torr, and a small but significant increase in lactate levels. Cerebral oxidative metabolism was well maintained but required an increase in fractional oxygen extraction because the variable change in cerebral blood flow was insufficient to maintain oxygen delivery. A redistribution of upper body blood flow was evident, with that to the bran and heart variably maintained or increased whereas that to muscle tissue was markedly decreased. Repetitive umbilical cord occlusion over 1 hour resulted in a significant drop in fetal arterial pH, with the acidemia mixed as PCO2 increased approximately 6 torr, whereas lactate levels increased almost fourfold. CONCLUSION: Although cerebral oxidative metabolism appears to be well maintained during moderate to severe variable-type fetal heart rate decelerations with umbilical cord occlusion, the need to increase fractional oxygen extraction and the redistribution of blood flow from carcass tissues may contribute to an accumulation of lactic acid both within the brain and systemically when such an insult occurs repeatedly.

Animals↗
PubMed1995

Increased fetal plasma prostaglandin E2 concentrations during fetal placental embolization in pregnant sheep.

OBJECTIVE: The purpose of this study was to examine the effect of chronic fetal placental embolization on fetal plasma prostaglandin E2 concentrations. STUDY DESIGN: Fourteen pregnant sheep were studied (seven embolized and seven controls) for 10 days between 0.84 and 0.91 of gestation. Daily injections of nonradioactive microspheres were made to decrease fetal arterial oxygen content by 30% to 35% of preembolization values. RESULTS: In response to repeated embolization, fetal plasma prostaglandin E2 concentrations increased significantly on day 1, declined to near control levels on days 2 to 6, but were significantly elevated again after day 7. Maternal prostaglandin E2 levels remained unchanged throughout the study. Fetal plasma prostaglandin E2 levels increased significantly with decreasing fetal oxygenation when fetal arterial oxygen content was < 2.0 mmol/L. CONCLUSION: We conclude that there is increased production of prostaglandin E2 by the placenta during progressive fetal hypoxemia induced by fetal placental embolization. We speculate that the progressive increase in prostaglandin E2 may be an important hormonal adaptive mechanism to maintain fetal homeostasis during the development of placental insufficiency.

Animals↗