Posttraumatic stress and pain-related anxiety among trauma-exposed adults with chronic pain in terms of opioid misuse and dependence

Trauma-exposure and posttraumatic stress symptoms increase risk for opioid-related problems in the context of chronic pain. Yet, there has been little exploration of moderators of the posttraumatic stress-opioid misuse association. Pain-related anxiety, defined as worry about pain and the negative consequences of pain, has shown relations to both posttraumatic stress symptoms and opioid misuse, and it may moderate the association between posttraumatic stress symptoms and opioid misuse, as well as dependence. The current study examined the moderating role of pain-related anxiety on the relationship between posttraumatic stress symptoms and opioid misuse and dependence among 292 (71.6 % female, M_age = 38.03 years, SD = 10.93) trauma exposed adults with chronic pain. Results indicated that pain-related anxiety significantly moderated the observed relations, such that compared to those with low pain-related anxiety, the relationship between posttraumatic stress symptoms and opioid misuse and dependence was stronger for those with elevated pain-related anxiety. These results highlight the importance of assessing and targeting pain-related anxiety among this trauma-exposed segment of the chronic pain population with elevated posttraumatic stress symptoms.

Manganese enhanced magnetic resonance imaging in type 1 and type 2 diabetes mellitus

Background

The pathophysiology of diabetic cardiomyopathy has yet to be established although pre-clinical studies suggest a role for altered myocardial calcium handling. Manganese-enhanced magnetic resonance imaging (MEMRI) is a novel non-invasive method of assessing in vivo myocardial calcium handling.

Purpose

To investigate whether myocardial calcium handling is impaired in patients with either type 1 or type 2 diabetes mellitus in the absence of underlying heart disease.

Methods

In a prospective case-control study, patients with type 1 (n=19) or type 2 (n=10) diabetes mellitus and healthy volunteers (n=15) underwent MEMRI. Participants with prior coronary artery disease, cardiomyopathy or an abnormal electrocardiogram were excluded. Manganese dipyridoxyl diphosphate (0.1 mL/kg) was administered over 10 min and myocardial T1 mapping was performed prior to and every 2.5 min for 30 min after contrast infusion (Figure 1). Quantitative manganese uptake analysis was performed by measuring T1 relaxation times in a region of interest within the interventricular septum and compared to the left ventricular blood pool. The rate of myocardial manganese uptake was determined by Patlak modelling [1].

Results

Participants with type 1 and type 2 diabetes mellitus were older (50±13 and 55±15.3 years) than the healthy volunteers (32±10 years). All participants had preserved left ventricular ejection fraction (type 1 diabetes mellitus, 67.7±6.1%; type 2 diabetes mellitus, 66.8±3.2%; healthy volunteers, 65±3.5%). Mean myocardial manganese uptake was reduced in participants with both type 1 (6.4±0.6 mL/100 g of tissue/min) and type 2 (6.4±0.5 mL/100 g of tissue/min) diabetes mellitus compared with healthy volunteers (8.3±0.5 mL/100 g of tissue/min; p<0.0001 for both, Figure 2). There were no differences in myocardial manganese uptake between those with type 1 or type 2 diabetes mellitus (p=0.22). There was no statistically significant correlation between myocardial manganese uptake and age in the study population (r=−0.28, p=0.07).

Conclusion

Using MEMRI, we have demonstrated that myocardial calcium handling is impaired in patients with either type 1 or type 2 diabetes mellitus even in the absence of left ventricular systolic dysfunction. This suggests altered myocardial calcium handling may underlie, or contribute to, diabetic cardiomyopathy which has implications developing novel therapeutic targets for the prevention and treatment of diabetic cardiomyopathy.

Funding Acknowledgement

Type of funding sources: Other. Main funding source(s): British Heart Foundation - Clinical Research Training Fellowship (FS/CRTF/20/24087)AstraZeneca - Investigator initiated award (ESR-19-20118)

Post-Traumatic Headache is Associated with Worse Anxiety and Mood Symptoms in Adolescent Mild Traumatic Brain Injury

This study examined the relationships between post-traumatic headache (PTH) and mental health symptoms after concussions to inform adolescent concussion management. Headache is the most common complaint following adolescent concussion. In this sample of 123 adolescents with concussion, there was a 5-fold increase in odds of clinically elevated anxiety, as well as increased mental health symptoms (anxiety, depression, anger, and disruptive behaviours), among adolescents with PTH relative to those without PTH. Adolescents with headache following concussions are vulnerable to worse mental health outcomes, particularly anxiety, and may benefit from routine monitoring of mental health symptoms for early detection and intervention.

Pre-Injury headache and post-traumatic headache in patients with mild traumatic brain injury: neuropsychological, psychiatric, and post-concussion symptom outcomes

PRIMARY OBJECTIVE

Headache, both before and after injury, has been associated with worse outcome following mild traumatic brain injury (MTBI). This study examined whether three MTBI patient groups - no headache (reported no pre-/post-injury headache), pre-injury headache (reported pre-injury headache, nearly all of whom also reported post-injury headache), and post-traumatic headache only (denied pre-injury headache and reported post-injury headache) - differed in acute-to-subacute outcomes.

RESEARCH DESIGN

Cross-sectional observational study.

METHODS AND PROCEDURES

Patients within 21 days of a MTBI (n = 291) completed neuropsychological tests and questionnaires evaluating depression, anxiety, and post-concussion symptoms.

MAIN OUTCOMES AND RESULTS

Neuropsychological test performances did not differ between headache groups. Participants with pre-injury headache and participants with post-traumatic headache only reported greater change in self-reported physical and cognitive symptoms than participants with no headache. Participants with pre-injury headache reported worse post-injury anxiety symptoms than participants with post-traumatic headache only.

CONCLUSIONS

The pre-injury headache and post-traumatic headache only groups did not meaningfully differ in outcome within 21 days of MTBI, but they had worse physical and cognitive symptoms than participants with no headache. Future research should assess whether differences in outcome emerge further from injury and whether specific headache subtypes are differentially associated with outcome.

A-97 Headache before and after Mild Traumatic Brain Injury: Acute-to-Subacute Outcomes in Patients with no Headache, Pre-Existing Headache, and Post-Traumatic Headache

Objective

Patients who experience a mild traumatic brain injury (MTBI) may have a headache condition preceding injury, develop a post-traumatic headache after injury, or experience headache neither before nor after injury. This study examined whether MTBI patients with no headache, pre-existing headache, and post-traumatic headache differed in acute-to-subacute outcomes.

Method

Patients with MTBI were recruited from an outpatient neurosurgery clinic in Taipei, Taiwan after emergency department referral (N = 291; 40.2% men; M = 37.9 ± 13.9 years-old; Mdn = 7 days-since-injury, range = 0–21), completing neuropsychological tests of attention, memory, and verbal fluency and questionnaires evaluating depression, anxiety, and post-concussion symptoms. Participants with no headache (reported neither pre- or post-injury), pre-existing headache (reported pre-injury headache, of whom some reported worsened post-injury headache), and post-traumatic headache (denied pre-injury headache, reported post-injury headache) were compared using non-parametric ANCOVA, controlling for gender and days-since-injury.

Results

Neuropsychological test performances did not differ between headache groups. Participants with pre-injury headache and post-traumatic headache had greater change in self-reported physical (F = 25.52, p < 0.011, η2 = 0.15) and cognitive symptoms (F = 3.74, p = 0.025, η2 = 0.03) than participants with no headache. Participants with pre-injury headache reported worse post-injury anxiety symptoms than participants with post-traumatic headache (F = 12.02, p < 0.011, η2 = 0.08).

Conclusion(s)

Participants with pre-injury and post-traumatic headache did not differ in outcome within 21 days of injury but had worse self-reported physical and cognitive symptoms than participants with no headache. Most participants with pre-injury headache experienced worsened headache following MTBI (53.7%). Future research is needed to assess whether more specific headache subtypes are differentially associated with MTBI outcome.

Understanding loss to follow-up in a longitudinal study of people with traumatic brain injury

OBJECTIVE

To examine factors related to attrition in a traumatic brain injury (TBI) study sample assessed up to 15 years after injury.

PARTICIPANTS

One thousand twenty-eight participants with TBI who completed the year 1 follow-up assessment at a TBI Model Systems Center between 1992 and 2018.

METHOD

Secondary analysis of data from a prospective longitudinal cohort study considering follow-up data collection completion status at years 1, 2, 5, 10, and 15.

RESULTS

In univariable analyses, multiple factors were associated with loss to follow-up (LOFU) including being a member of a socially disadvantaged group, substance use history, residence, payor, cause of injury, and results of earlier follow-up attempts. In a multiple logistic regression analysis examining the prediction of follow-up condition at 10 or 15 years post-injury, only payor and race/ethnicity were significant predictors. Hispanic ethnicity was associated with higher odds of LOFU, and these participants often spoke Spanish and were born outside of the United States.

CONCLUSIONS

The findings suggest a need to understand sociodemographic variables and their influence on participant attrition in longitudinal TBI research. With a better understanding of these predictors, procedures can be developed to address retention of participants who are identified as being at increased risk for study drop out.

Semantic Clustering During Verbal List Learning Is Associated With Employment Status in a Community Sample

The ability to learn and remember verbal information is highly relevant to many work roles and environments, but we know little about the underlying cognitive mechanisms of those associations. This study examined the hypothesis that unemployment is associated with decreased spontaneous use of higher-order encoding strategies deployed during list learning and recall. Participants were 120 employed and 59 unemployed community-dwelling adults who completed the California Verbal Learning Test-Second Edition (CVLT-II) as part of a broader neuropsychological assessment. Standardized measures of semantic, serial, and subjective clustering were generated from the CVLT-II. After adjusting for data-driven covariates, a significant interaction emerged between employment status and clustering strategy, whereby participants in the employed group exhibited significantly higher scores on semantic clustering, but not serial or subjective clustering, than the unemployed group. The semantic clustering slope score was higher among the employed group and was positively associated with executive functions and declarative memory. These findings suggest that higher-order semantic organizational strategies during supraspan list learning may be relevant to maintaining gainful employment (e.g., mentally organizing work-related instructions and task lists). Future studies might examine semantic clustering in relation to employment changes and work performance, as well as the potential benefit of metacognitive interventions for learning and employment success.

Pain anxiety and rehabilitation outcomes after acquired brain injury

Purpose: The purpose of this study was to examine pain anxiety after acquired brain injury (ABI) and its relationship to rehabilitation outcomes.Materials and Method: Participants consisted of 89 adults with an ABI participating in outpatient rehabilitation therapy. They completed a battery of neuropsychological tests at baseline along with surveys of mood, health-related self-efficacy, and pain anxiety. Separately, occupational therapists assessed basic and instrumental activities of daily living (ADLs) as well as therapy engagement across treatment after the sixth session.Results: Individuals who reported high pain anxiety had fewer years of formal education, lower self-efficacy, and more emotional distress than those with low pain anxiety. Although Blacks were about half (56%) of the study sample, they comprised the majority (73.1%) of individuals in the high pain anxiety group. Pain anxiety was negatively related to therapy engagement. Moderation analysis using linear regression indicated that pain anxiety moderated the influence of self-efficacy on basic ADLs.Conclusions: Pain anxiety, particularly when high, is negatively associated with rehabilitation outcomes for individuals with ABI. Among those with high pain anxiety, health-related self-efficacy is an important resilience characteristic to improve functional outcomes. In rehabilitation therapy, pain anxiety provides a novel intervention target to enhance ABI recovery.

Validation of the 10-item Center for Epidemiologic Studies Depression Scale Post Stroke

OBJECTIVE

To establish reliability and validity of the abbreviated (10-item) Center for Epidemiologic Studies Depression Scale (CESD-10) among individuals post stroke.

METHOD

The psychometric properties of the CESD-10 were evaluated in 1219 adults with stroke admitted to an eligible inpatient rehabilitation facilities (n = 11) across 9 different states post stroke during 2005 to 2006. This study was a secondary data analysis of the existing publicly available clinical trial dataset, Stroke Recovery in Underserved Populations study. Reliability, validity, factory structure and item-level psychometrics of the CESD-10 were examined. In addition, the predictive accuracy of the CESD-10 was compared against the CESD-20 (criterion).

RESULTS

The CESD-10 was highly correlated with the CESD-20 (r = 0.97). The CESD-10 had good internal reliability (Cronbach's α = 0.86). The CESD-20 and CESD-10 had similar accuracy in classifying individuals as depressed (Kappa = 0.85).

CONCLUSION

The 10-item CESD is a valid measure of depression for individuals post stroke.

Complicated versus uncomplicated mild traumatic brain injuries: A comparison of psychological, cognitive, and post-concussion symptom outcomes

INTRODUCTION

A complicated mild traumatic brain injury (MTBI) is defined as mild by all clinical severity indicators but is complicated due to a traumatic intracranial abnormality visible on neuroimaging. Researchers have reported mixed findings regarding whether neuropsychological and functional outcomes following complicated MTBI are worse than, or similar to, outcomes following uncomplicated MTBI. This study examined patients referred from a Taiwanese emergency department to a neurosurgical outpatient clinic. Participants with complicated MTBI, uncomplicated MTBI, and those who did not undergo head computed tomography (CT) were compared on psychological, neuropsychological, and post-concussion symptom outcomes within 21 days of injury.

METHOD

Participants with complicated MTBI (n = 42), uncomplicated MTBI (n = 77), and no head CT (n = 172) completed the Paced Auditory Serial Attention Test, Taiwanese Word Sequence Learning Test, a semantic Verbal Fluency Test, the Checklist of Post-Concussion Symptoms, and the Beck Depression and Anxiety Inventories.

RESULTS

No significant differences were observed between groups on any measure. For individual post-concussion symptoms, dizziness, anxiety, and attention difficulty were endorsed more often after uncomplicated MTBIs, but these group differences were not significant after controlling for multiple comparisons.

CONCLUSIONS

Participants with complicated MTBIs did not have worse acute or subacute outcomes than participants with uncomplicated MTBIs or no head CT. These results are consistent with many studies finding comparable outcomes between those with complicated and uncomplicated MTBIs. This study is limited by small sample size and minimal information on intracranial abnormalities, broadly categorizing groups based on positive or negative neuroimaging as opposed to specific lesion types and locations.

Systematic Review of Preinjury Mental Health Problems as a Vulnerability Factor for Worse Outcome After Sport-Related Concussion

Background:

It is difficult to predict who will experience prolonged health problems after sustaining a sport-related concussion.

Purpose:

To synthesize the literature and conduct a gap analysis on the association between preinjury mental health problems and clinical outcome from sport-related concussion.

Study Design:

Systematic review; Level of evidence, 4.

Methods:

Data sources were PubMed, PsycINFO, MEDLINE (and MEDLINE in Process), CINAHL, Cochrane Library, EMBASE, SPORTDiscus, Scopus, and Web of Science. Studies published before February 2019 that addressed preinjury mental health problems as a possible predictor of worse clinical outcome or clinical recovery from concussion were eligible for inclusion.

Results:

Of 4013 studies screened, 358 full texts were reviewed, and 12 studies involving 3761 participants (n = 471 [12.5%] with preexisting mental health problems) were ultimately included. The participants with a preinjury history of mental health problems were at greater risk for having persistent symptoms or worse outcome in 9 of 12 studies. The studies had major methodological differences, and most studies were not focused on mental health as a primary predictor or prognostic factor. Rather, they included it as a secondary or tertiary predictor. The sample sizes with preinjury mental health problems in most studies were small or very small (ie, <25). The age of onset, type, course, severity, and duration of mental health problems were not defined. The extent to which mental health problems were present before the season, during baseline testing, was not reported.

Conclusion:

Preinjury mental health problems appear to confer risk for worse clinical outcome after sport-related concussion. Future research is needed to (1) examine this risk factor in large representative populations of middle school students, high school students, and collegiate athletes; (2) quantify the risk for each mental health condition; (3) understand the mechanisms underlying this increased risk; and (4) develop more refined treatment and rehabilitation approaches for these student-athletes.

Engagement in rehabilitation therapy and functional outcomes among individuals with acquired brain injuries

Purpose : The purpose was to examine the role of therapy engagement as a potential mediator for the relationship between neuropsychological performance and functional outcomes. Materials and method : Participants were 94 adults with medically documented ABI recruited from three outpatient rehabilitation clinics at the start of occupational therapy. Participants (57% men) ranged from 18 to 82 in age, with the majority (81%) having completed 12 or more years of education. They completed a comprehensive neuropsychological assessment at baseline. Separately, occupational therapists (OTs) assessed functional independence and disability at baseline and follow up. The OTs also rated the participants' therapy engagement. Results : Therapy engagement predicted functional outcomes and mediated the relationship between neuropsychological performance and outcomes. Moreover, therapy engagement accounted for unique variance in functional outcome, even after accounting for education, comorbid health conditions, emotional distress, apathy, and baseline functional ability. Conclusions : Engagement in therapy is a crucial patient characteristic in successful rehabilitation outcome. Cognitive deficits associated with ABI undermine full engagement in rehabilitation therapy, which in turn diminishes potential gains made in therapy and functional recovery. Neuropsychological assessment can enhance rehabilitation outcomes by identifying characteristics that underlie therapy engagement, which can ultimately be used to maximize the effectiveness of individualized treatment plans. Implications for rehabilitation Neuropsychological assessment can identify cognitive abilities that are strongly related to functional outcomes during occupational therapy for acquired brain injury. Therapy engagement is an important pathway by which neuropsychological impairment predicts functional outcomes after acquired brain injuries.

Health literacy, sociodemographic factors, and cognitive training in the active study of older adults

OBJECTIVE

Health literacy is critical for understanding information from health-care providers and correct use of medications and includes the capacity to filter other information in navigating health care systems. Older adults with low health literacy exhibit more chronic health conditions, worse physical functioning, and poorer mental health. This study examined the relationship between sociodemographic variables and health literacy, and the impact of cognitive training on change in health literacy over 10 years in older adults.

METHODS

Participants (N = 2,802) aged 65 years and older completed assessments, including reading and numeracy health literacy items, as part of the Advanced Cognitive Training for Independent and Vital Elderly (ACTIVE) study. We evaluated baseline sociodemographic variables and change in health literacy over a 10-year period in individuals exposed to cognitive training in reasoning, processing speed, memory, or a no-contact control condition.

RESULTS

Age, sex, race, education level, and general cognitive functioning at baseline were all associated with baseline health literacy in older adults. Predictors of change in health literacy over the 10-year follow-up were age, race, education level, general cognitive functioning, and neighborhood income; disparities in health literacy because of race attenuated over time, while the effect of age increased over time. Health literacy was generally stable across the ACTIVE intervention groups over 10 years.

CONCLUSIONS

The present study showed important disparities in health literacy level and change over 10 years. Cognitive training did not significantly impact health literacy, suggesting that alternative approaches are needed to reduce the disparities.

Brief and cost-effective tool for assessing verbal learning in multiple sclerosis: Comparison of the Rey Auditory Verbal Learning Test (RAVLT) to the California Verbal Learning Test - II (CVLT-II)

BACKGROUND

The Brief International Cognitive Assessment for Multiple Sclerosis (BICAMS) is a common cognitive screening tool. However, administration and scoring can be time-consuming, and its use of proprietary subtests like the California Verbal Learning Test - II (CVLT-II) is financially limiting. Use of the non-proprietary Rey Auditory Verbal Learning Test (RAVLT) may be provide a valid alternative.

OBJECTIVES

To compare the RAVLT and CVLT-II in terms of diagnostic accuracy for detecting cognitive impairment, and to determine optimal cut-scores for the RAVLT.

METHODS

100 participants with MS completed the five learning trials from the RAVLT and CVLT-II. Receiver operating characteristic analyses were used to compare the measures' sensitivities, specificities, positive predictive values (PPV) and negative predictive values (NPV), and to identify optimal cut-scores.

RESULTS

Using a criterion of 1.5 SD below the normative sample mean, the RAVLT showed fair to good (κs = 0.21-0.41) agreement with the CVLT-II. A cut-score of 12 on Trials 1 + 2 of the RAVLT showed fair sensitivity (75%) and specificity (76%) and did not differ significantly from the CVLT-II (p > .05).

CONCLUSIONS

Performance on initial learning trials of the RAVLT may provide a brief, valid, and cost-effective alternative to the CVLT-II for screening verbal learning impairments in MS.

Functional independence after acquired brain injury: Prospective effects of health self-efficacy and cognitive impairment

OBJECTIVE

To examine how health self-efficacy and cognitive impairment severity relate to functional independence after acquired brain injury (ABI).

DESIGN

Observational.

SETTING

Outpatient rehabilitation hospital.

PARTICIPANTS

Seventy-five adults with predominately stroke or traumatic brain injury who were beginning a course of occupational therapy.

MAIN MEASURES

Health self-efficacy was assessed with the Self-Rated Abilities for Health Practices. Cognitive functioning was assessed via a composite z score of neuropsychological tests. Trait affectivity was assessed with the Positive and Negative Affect Schedule. Functional independence was assessed with the Barthel Index and Lawton Instrumental Activities of Daily Living Scale.

RESULTS

Health self-efficacy correlated moderately with functional independence. A moderation threshold effect was detected that revealed for whom health self-efficacy predicted functional independence. Among participants with normal to mildly impaired cognition (>-2 z cognitive composite), health self-efficacy correlated positively with functional independence, which held after accounting for trait affectivity. In contrast, health self-efficacy was not correlated with functional independence among participants with greater impairment (<-2 z cognitive composite).

CONCLUSIONS

Health self-efficacy predicts functional independence and may serve as a protective factor after ABI among individuals with relatively intact cognition. However, health self-efficacy does not predict functional independence among individuals with moderate or severe cognitive impairment, possibly due to limited self-awareness. This study extends the literature linking health self-efficacy with rehabilitation outcomes and reinforces the need for promoting self-management in ABI. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Rasch analysis of the coping inventory for stressful situations in individuals with moderate to severe traumatic brain injury

OBJECTIVE

To evaluate psychometric properties of the Coping Inventory for Stressful Situations (CISS) in individuals with traumatic brain injury (TBI).

DESIGN

Archival study using Rasch analysis.

SETTING

Postacute rehabilitation hospital.

PARTICIPANTS

Adults (N=331) 1 to 15 years after moderate to severe TBI, recruited consecutively.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURE

CISS.

RESULTS

Indices of unidimensionality and model fit supported the scale's proposed multidimensional structure consisting of Task, Emotion, and Avoidant coping style; 3 unidimensional scales showed better fit than a single combined scale. The 3 scales met Rasch expectations of reliability and separation for persons and items, as well as adequate response category functioning. The scales were generally well targeted but showed some evidence of ceiling effect for Task, and floor effects for Emotion and Avoidant coping; item difficulties did not fully capture extreme ranges demonstrated by some participants, suggesting that measurement of coping after TBI on the CISS would be improved with additional items at low and high ranges of difficulty. Results were generally equivalent for cross-sectional groups representing short-term (1y), intermediate (2y), and long-term (5-15y).

CONCLUSIONS

The CISS showed good psychometric properties as a measure of coping style among persons with moderate to severe TBI in acute and chronic phases of recovery, and showed evidence of multidimensionality as predicted by theory, consistent with 3 unidimensional scales. Added items tapping broader (or more accessible, less cognitively complex) ranges of coping responses would likely benefit the scale overall and improve correspondence with the response needs of people with TBI.

Incremental validity of neuropsychological evaluations to computed tomography in predicting long-term outcomes after traumatic brain injury

This study evaluated the incremental utility of neuropsychological tests to computed tomography (CT) in predicting long-term outcomes of adults with moderate to severe traumatic brain injury (TBI). Participants were 288 adults with mild complicated, moderate, and severe TBI. Longitudinal data were evaluated during inpatient status in an urban rehabilitation hospital with a TBI Model System, as well as 1 and 2 years post injury. Predictors including demographic characteristics, injury severity, CT characteristics, and neuropsychological evaluations were regressed to outcomes of disability, life satisfaction, and employment at 1 and 2 years post injury. Prediction of life satisfaction was not improved with the use of CT characteristics or neuropsychological tests, but prediction of return to work was improved by these variables at 2 years post injury. Neuropsychological evaluations uniquely contributed to outcome predictions of functional disability, even after considering demographic and injury severity characteristics, including information from CT. In contrast, CT characteristics were not predictive of long-term functional disability at 1 or 2 years post TBI. Taken together, the findings indicate that neuropsychological tests add unique predictive information for long-term functional outcomes after TBI.

Phylogeography of microbial phototrophs in the dry valleys of the high Himalayas and Antarctica

High-elevation valleys in dry areas of the Himalayas are among the most extreme, yet least explored environments on Earth. These barren, rocky valleys are subjected to year-round temperature fluctuations across the freezing point and very low availability of water and nutrients, causing previous workers to hypothesize that no photoautotrophic life (primary producers) exists in these locations. However, there has been no work using modern biogeochemical or culture-independent molecular methods to test the hypothesis that photoautotrophs are absent from high Himalayan soil systems. Here, we show that although microbial biomass levels are as low as those of the Dry Valleys of Antarctica, there are abundant microbial photoautotrophs, displaying unexpected phylogenetic diversity, in barren soils from just below the permanent ice line of the central Himalayas. Furthermore, we discovered that one of the dominant algal clades from the high Himalayas also contains the dominant algae in culture-independent surveys of both soil and ice samples from the Dry Valleys of Antarctica, revealing an unexpected link between these environmentally similar but geographically very distant systems. Phylogenetic and biogeographic analyses demonstrated that although this algal clade is globally distributed to other high-altitude and high-latitude soils, it shows significant genetic isolation by geographical distance patterns, indicating local adaptation and perhaps speciation in each region. Our results are the first to demonstrate the remarkable similarities of microbial life of arid soils of Antarctica and the high Himalayas. Our findings are a starting point for future comparative studies of the dry valleys of the Himalayas and Antarctica that will yield new insights into the cold and dry limits to life on Earth.

Assessment of lake sensitivity to acidic deposition in national parks of the Rocky Mountains

The sensitivity of high-elevation lakes to acidic deposition was evaluated in five national parks of the Rocky Mountains based on statistical relations between lake acid-neutralizing capacity concentrations and basin characteristics. Acid-neutralizing capacity (ANC) of 151 lakes sampled during synoptic surveys and basin-characteristic information derived from geographic information system (GIS) data sets were used to calibrate the statistical models. The explanatory basin variables that were considered included topographic parameters, bedrock type, and vegetation type. A logistic regression model was developed, and modeling results were cross-validated through lake sampling during fall 2004 at 58 lakes. The model was applied to lake basins greater than 1 ha in area in Glacier National Park (n = 244 lakes), Grand Teton National Park (n = 106 lakes), Great Sand Dunes National Park and Preserve (n = 11 lakes), Rocky Mountain National Park (n = 114 lakes), and Yellowstone National Park (n = 294 lakes). Lakes that had a high probability of having an ANC concentration <100 microeq/L, and therefore sensitive to acidic deposition, are located in basins with elevations >3000 m, with <30% of the catchment having northeast aspect and with >80% of the catchment bedrock having low buffering capacity. The modeling results indicate that the most sensitive lakes are located in Rocky Mountain National Park and Grand Teton National Park. This technique for evaluating the lake sensitivity to acidic deposition is useful for designing long-term monitoring plans and is potentially transferable to other remote mountain areas of the United States and the world.

Class I areas at risk: event-based nitrogen deposition to a high-elevation, western site

Between June 1, 2000 and September 30, 2000, 32 precipitation events were sampled near Telluride, CO at an elevation of 3200 m. The wet deposition site was operated following protocols of the Atmospheric Integrated Research Monitoring Network (AIRMoN), a network of the National Atmospheric Deposition Network (NADP). Inorganic nitrogen deposition at the Telluride site of 1.41 kg ha(-1) during the study period was 25 to 50% higher than nearby NADP sites. In turn, nitrogen deposition at these NADP sites was similar to high-elevation sites in and near the Colorado Front Range that have been shown to be impacted by atmospheric deposition of inorganic nitrogen in wetfall. Power plant emissions are a likely source of a major portion of this elevated inorganic nitrogen in wetfall to the San Juan Mountains. Principal component analysis (PCA) shows that solutes formed by gases that are emitted from power plants were clustered tightly together, including nitrate, ammonium, sulfate, and chloride. Trajectory analysis, including both backward and forward trajectories, shows that the air masses that contributed to the precipitation events with high amounts of nitrogen deposition at the Telluride site passed directly over or near power plants. Our results suggest that Class I Wilderness Areas in and near the San Juan Mountains are at risk to ecosystem impairment at present rates of atmospheric deposition of inorganic nitrogen in wetfall. Deployment of proposed power plants to this area will likely increase the risk of degradation of resource values in nearby Class I areas. While these data were collected over a short time span, they indicate that establishment of an official AIRMoN site in the southwestern U.S. may be warranted.

Seasonal changes in the character and nitrogen content of dissolved organic matter in an alpine/subalpine headwater catchment

We are studying the chemical quality of dissolved organic nitrogen (DON) in a high-elevation watershed in the Colorado Front Range. Samples were collected over the 2000 snowmelt runoff season at two sites across an alpine/subalpine ecotone to understand how the transition between the lightly vegetated alpine and forested reaches of the catchment influences the chemical character of DON. Samples were analyzed approximately weekly for dissolved organic material (DOM) content and chemical character. A subset of samples was analyzed for the elemental content of fulvic and hydrophilic acids. Concentrations of DON at both sites were highest in the spring at the initiation of snowmelt, decreased during snowmelt, and increased again during the late summer and fall. In contrast, concentrations of dissolved organic carbon (DOC) peaked on the ascending limb of the hydrograph and declined to seasonal minima on the descending limb of the hydrograph. The ratio of DOC:DON showed a seasonal shift at both sites with high values (40 to 55) during peak runoff in early summer and lower values (15 to 25) during low flows late in the runoff season. These results indicate that there was a seasonal change in the relative N content of DOM at both sites. Chemical fractionation of DOC showed that there were temporal and longitudinal changes in the chemical character of DOC. At the alpine site, the fulvic acid content of DOC decreased from 57% in June to 35% in September. The change in fulvic acid was less pronounced at the forested site, from 66% in June to 54% in September. Elemental analysis of fulvic and hydrophilic acids indicated that hydrophilic acids were N rich compared to fulvic acids. Additionally, fulvic and hydrophilic acids isolated at the alpine site had a lower C:N ratio than those isolated at the forested site. Similarly, the C:N ratio of organic acids at both sites was lower in September than in June during peak runoff. These differences appear to be a result of changes in both DOM precursor material and hydrologic flowpaths. Using C:N ratios of fulvic and hydrophilic acids, we estimate that nonhumic material carried between 54 to 73% of the organic N in surface water at the alpine site and 44 to 58% of the organic N in surface water at the subalpine site.

Na,K-ATPase in skeletal muscle: two populations of beta-spectrin control localization in the sarcolemma but not partitioning between the sarcolemma and the transverse tubules

We used immunological approaches to study the factors controlling the distribution of the Na,K-ATPase in fast twitch skeletal muscle of the rat. Both alpha subunits of the Na,K-ATPase colocalize with beta-spectrin and ankyrin 3 in costameres, structures at the sarcolemma that lie over Z and M-lines and in longitudinal strands. In immunoprecipitates, the alpha1 and alpha2 subunits of the Na,K-ATPase as well as ankyrin 3 associate with beta-spectrin/alpha- fodrin heteromers and with a pool of beta-spectrin at the sarcolemma that does not contain alpha-fodrin. Myofibers of mutant mice lacking beta-spectrin (ja/ja) have a more uniform distribution of both the alpha1 and alpha2 subunits of the Na,K-ATPase in the sarcolemma, supporting the idea that the rectilinear sarcomeric pattern assumed by the Na,K-ATPase in wild-type muscle requires beta-spectrin. The Na,K-ATPase and beta-spectrin are distributed normally in muscle fibers of the nb/nb mouse, which lacks ankyrin 1, suggesting that this isoform of ankyrin is not necessary to link the Na,K-ATPase to the spectrin-based membrane skeleton. In immunofluorescence and subcellular fractionation experiments, the alpha2 but not the alpha1 subunit of the Na,K-ATPase is present in transverse (t-) tubules. The alpha1 subunit of the pump is not detected in increased amounts in the t-tubules of muscle from the ja/ja mouse, however. Our results suggest that the spectrin-based membrane skeleton, including ankyrin 3, concentrates both isoforms of the Na,K-ATPase in costameres, but that it does not play a significant role in restricting the entry of the alpha1 subunit into the t-tubules.

Power frequency magnetic field exposure and gap junctional communication in Clone 9 cells

Exposure to a power-frequency magnetic field has been reported to produce a statistically significant inhibition of gap junctional communication (GJC) in Clone 9 cells that have been pre-stressed by treatment with low concentrations of chloral hydrate (CH) [C.F. Blackman, J.P. Blanchard, S.G. Benane, D.E. House, J.A. Elder, Double blind test of magnetic field effects on neurite outgrowth, Bioelectromagnetics, 19 (1998) 204-209]. This observation might provide mechanistic insight into the possible role of electromagnetic fields (EMFs) in the carcinogenic process, since cancer cells frequently show decreased or absent GJC, and tumor promoting chemicals have been observed to inhibit GJC. Magnetic field exposure conditions were 45 Hz, 23.8 microT rms + parallel DC 36.6 microT, for 30 min of exposure. The responses of Clone 9 cells to the GJC-inhibiting effects of the tumor promoter 12-O-tetradecanoylphorbol 13-acetate and the chemical CH were evaluated and compared to reported results [S.G. Benane, C.F. Blackman, D.E. House, Effects of perchloroethylene and its metabolites on intercellular communication in Clone 9 rat liver cells, J. Toxicol. Environ. Health, 48 (1996) 427-437]. Before magnetic field exposure, cells were exposed for 24 h to either 3 (nine experiments) or 5 mM (11 experiments) CH to produce GJC of 67% or 50%, respectively, relative to unexposed controls. GJC was assessed microscopically using the scrape-loading technique and a blinded protocol. No statistically significant effect was observed due to magnetic field exposure with either CH concentration.

Cellular communication in clone 9 cells exposed to magnetic fields

Magnetic-field exposure (45 Hz B(a.c.) over a flux density range of 7.7 to 49.9 microT r.m.s. with parallel B(d.c.) of 36.6 microT) has been reported by Blackman and coworkers to inhibit gap junction intercellular communication in Clone 9 cells treated with chloral hydrate for 24 h prior to field exposure in accord with predictions of the ion parametric resonance model. The study reported here is an attempt to reproduce this effect. Baseline experiments showed that growth in culture and state of confluence at time of addition of chloral hydrate were comparable in both laboratories. PMA inhibited cell-cell communication in a dose-dependent manner, similar to the results of Blackman and coworkers, whereas cells in the present study were somewhat more sensitive to chloral hydrate than reported by Blackman and coworkers. A total of 38 exposure experiments were undertaken using a 45 Hz magnetic field with a flux density of 23.8 microT r.m.s., in parallel with a 36.6-microT static magnetic field for 40 to 45 min, after pretreatment with 2.5 mM chloral hydrate for 24 h. In 14 unblinded experiments, a small but statistically significant effect of magnetic-field exposure was observed, but due to the subjective nature of the assay, it was deemed essential to carry out blinded experiments. The remaining 24 experiments were blinded. In 15 blinded experiments, cells purchased from the American Type Culture Collection and grown only in this laboratory were used, while in 9 experiments, the cells had originally been grown in Blackman's laboratory and were subsequently sent to this laboratory. There was no statistically significant effect of magnetic-field exposure on gap junction intercellular communication in these blinded experiments using either cell line.

Membrane skeleton of innervated and denervated fast- and slow-twitch muscle

We used confocal microscopy and immunoblotting to study membrane skeletal proteins of fast-twitch (extensor digitorum longus) and slow-twitch (soleus) muscles of the adult rat. In the extensor digitorum longus (EDL), beta-spectrin concentrates in costameres, whereas dystrophin is enriched at costameres but is also present in intercostameric regions. In the soleus, beta-spectrin and dystrophin underlie much of the sarcolemma, and intercostameric regions are difficult to detect. The EDL sarcolemma reorganizes following denervation to resemble soleus sarcolemma, but denervation does not significantly affect the latter. Consistent with these observations, soleus contains similar amounts of dystrophin but more beta-spectrin than EDL. Denervation increases beta-spectrin levels only in the EDL and dystrophin levels in both muscles. Denervation does not affect beta-fodrin, a beta-spectrin homolog expressed in embryonic myofibers. Thus, neuromuscular activity controls sarcolemmal organization and the levels of beta-spectrin and dystrophin, but not postnatal downregulation of beta-fodrin. The differences in organization of the sarcolemma may underlie the differential susceptibility of fast and slow myofibers to dystrophinopathies.

Differential distribution of dystrophin and beta-spectrin at the sarcolemma of fast twitch skeletal muscle fibers

We used double label immunofluorescence and confocal microscopy to examine the organization of beta-spectrin and dystrophin at the sarcolemma of fast twitch myofibers in the Extensor Digitorum Longus (EDL) of the rat. Both beta-spectrin and dystrophin are concentrated in costameres, a rectilinear sarcolemmal array composed of longitudinal strands and transverse elements overlying Z and M lines. In contrast, intercostameric regions, lying between these linear structures, contain significant levels of dystrophin but little detectable beta-spectrin. The dystrophin-associated proteins, syntrophin and beta-dystroglycan, are also concentrated at costameres but, like dystrophin, are present in intercostameric regions as well. Dystrophin is present at costameres and intercostameric regions in fast twitch muscles of the mouse but is absent from all regions of the sarcolemma in the mdx mouse, which lacks dystrophin. Areas of the sarcolemma near myonuclei also contain dystrophin without beta-spectrin, consistent with the idea that the distribution of dystrophin at the sarcolemma is not dependent on beta-spectrin. We conclude that dystrophin is present under all areas of the sarcolemma. The increased fragility of the sarcolemma in patients with Duchennes muscular dystrophy may be explained in part by the absence of dystrophin not only from costameres, but also from intercostameric regions.

Extensive but coordinated reorganization of the membrane skeleton in myofibers of dystrophic (mdx) mice

We used immunofluorescence techniques and confocal imaging to study the organization of the membrane skeleton of skeletal muscle fibers of mdx mice, which lack dystrophin. beta-Spectrin is normally found at the sarcolemma in costameres, a rectilinear array of longitudinal strands and elements overlying Z and M lines. However, in the skeletal muscle of mdx mice, beta-spectrin tends to be absent from the sarcolemma over M lines and the longitudinal strands may be disrupted or missing. Other proteins of the membrane and associated cytoskeleton, including syntrophin, beta-dystroglycan, vinculin, and Na,K-ATPase are also concentrated in costameres, in control myofibers, and mdx muscle. They also distribute into the same altered sarcolemmal arrays that contain beta-spectrin. Utrophin, which is expressed in mdx muscle, also codistributes with beta-spectrin at the mutant sarcolemma. By contrast, the distribution of structural and intracellular membrane proteins, including alpha-actinin, the Ca-ATPase and dihydropyridine receptors, is not affected, even at sites close to the sarcolemma. Our results suggest that in myofibers of the mdx mouse, the membrane- associated cytoskeleton, but not the nearby myoplasm, undergoes widespread coordinated changes in organization. These changes may contribute to the fragility of the sarcolemma of dystrophic muscle.

Small, membrane-bound, alternatively spliced forms of ankyrin 1 associated with the sarcoplasmic reticulum of mammalian skeletal muscle

We have recently found that the erythroid ankyrin gene, Ank1, expresses isoforms in mouse skeletal muscle, several of which share COOH-terminal sequence with previously known Ank1 isoforms but have a novel, highly hydrophobic 72-amino acid segment at their NH2 termini. Here, through the use of domain-specific peptide antibodies, we report the presence of the small ankyrins in rat and rabbit skeletal muscle and demonstrate their selective association with the sarcoplasmic reticulum. In frozen sections of rat skeletal muscle, antibodies to the spectrin-binding domain (anti-p65) react only with a 210-kD Ank1 and label the sarcolemma and nuclei, while antibodies to the COOH terminus of the small ankyrin (anti-p6) react with peptides of 20 to 26 kD on immunoblots and decorate the myoplasm in a reticular pattern. Mice homozygous for the normoblastosis mutation (gene symbol nb) are deficient in the 210-kD ankyrin but contain normal levels of the small ankyrins in the myoplasm. In nb/nb skeletal muscle, anti-p65 label is absent from the sarcolemma, whereas anti-p6 label shows the same distribution as in control skeletal muscle. In normal skeletal muscle of the rat, anti-p6 decorates Z lines, as defined by antidesmin distribution, and is also present at M lines where it surrounds the thick myosin filaments. Immunoblots of the proteins isolated with rabbit sarcoplasmic reticulum indicate that the small ankyrins are highly enriched in this fraction. When expressed in transfected HEK 293 cells, the small ankyrins are distributed in a reticular pattern resembling the ER if the NH2-terminal hydrophobic domain is present, but they are uniformly distributed in the cytosol if this domain is absent. These results suggest that the small ankyrins are integral membrane proteins of the sarcoplasmic reticulum. We propose that, unlike the 210-kD form of Ank1, previously localized to the sarcolemma and believed to be a part of the supporting cytoskeleton, the small Ank1 isoforms may stabilize the sarcoplasmic reticulum by linking it to the contractile apparatus.

Cloricromene reduces myocardial infarct size in rabbits when administered during the early reperfusion period

Cloricromene is a coumarin derivative without anticoagulant activities that has recently been found to decrease myocardial infarct size after an ischemic-reperfusion injury. This study seeks to determine when the cardioprotective action of cloricromene is exerted in an in vivo rabbit model of ischemic-reperfusion injury. Forty-nine rabbits subjected to 30 min of coronary occlusion and 120 min of reperfusion were randomized into five groups: VEH (n = 11) received saline vehicle; IR (n = 9) received an infusion of cloricromene starting at the onset of ischemia at 8 micrograms.kg-1.min-1; R(-5)(n = 9) and R(+30)(n = 9) received an infusion of cloricromene at 8 micrograms.kg-1.min-1 starting 5 min before reperfusion and 30 min after reperfusion, respectively; and RB(-5)(n = 11) received 300 micrograms/kg bolus of cloricromene 5 min before reperfusion followed by an infusion of 8 micrograms.kg-1.min-1. All infusions were continued until the end of the reperfusion period. Myocardial infarct size was significantly reduced in groups IR, R(-5), and RB(-5). We conclude that cloricromene's effective time of action occurs prior to the first 30 min of the reperfusion period.

Intravascular adenosine at reperfusion reduces infarct size and neutrophil adherence

BACKGROUND

Adenosine has been shown to reduce infarct size predominantly during reperfusion by adenosine A2-receptor-mediated processes. This cardioprotection may involve inhibition of events in the vascular compartment, such as adherence-independent and adherence-dependent actions of neutrophils. This study tested the hypothesis that adenosine exerts its cardioprotection during reperfusion by targeting effectors in the vascular compartment.

METHODS

Polyadenylic acid (molecular weight, 230,000 daltons) was used as an intravascularly confined adenosine mimetic. In anesthetized New Zealand white rabbits, the left coronary artery was occluded for 30 minutes and reperfused for 120 minutes.

RESULTS

Polyadenylic acid (1 mg/kg bolus, 0.5 mg kg-1 h-1) given 5 minutes before reperfusion significantly (p < 0.05) reduced infarct size compared with vehicle (23% +/- 2% versus 37% +/- 2% area at risk). The A1-antagonist KW-3902 had no effect on this polyadenylic acid-induced protection (17% +/- 3%), whereas the A1-A2 antagonist sulfophenytheophylline blocked this infarct size reduction (41% +/- 2%). In vitro adherence of platelet-activating factor-activated neutrophils to thoracic aortic endothelium was significantly diminished by polyadenylic acid (185 +/- 12 neutrophils/mm2 versus 36 +/- 4 neutrophils/mm2 endothelial surface). Sulfophenytheophylline inhibited this effect (280 +/- 6 neutrophils/mm2), whereas KW-3902 did not (31 +/- 7 neutrophils/mm2).

CONCLUSIONS

An intravascular adenosine mimetic agent exerts cardioprotection during reperfusion by targeting receptor-mediated mechanisms in the intravascular compartment, possibly involving inhibition of neutrophil-related processes.

Adenosine A2-receptor activation inhibits neutrophil-mediated injury to coronary endothelium

Adenosine (ADO) attenuates polymorphonuclear neutrophil (PMN)-mediated damage, partly by inhibiting superoxide anion (O2-.) generation and PMN adherence to the coronary artery endothelium. This study tests the hypothesis that the antineutrophil effects of ADO are mediated by A2-receptor activation. Isolated canine PMN were activated by 100 nM platelet-activating factor (PAF). Compared with untreated activated PMN (100%), ADO attenuated O2-. production (46 +/- 9% of activated PMN), which was mimicked by the A2 agonist CGS-21680 (50 +/- 6% of activated PMN), unaltered by A1-selective antagonism with KW-3902 in the presence of ADO (40 +/- 7%), but blocked by combined A1-A2 blockade with 8-p-sulfophenyl theophylline (8-SPT, 94 +/- 14%). ADO reduced adherence of fluorescent PMN to endothelial surfaces of isolated canine coronary artery segments from 174 +/- 12 to 29 +/- 9/mm2 (P < 0.01), which was unaltered by A1 antagonism (35 +/- 7/mm2) but was reversed by 8-SPT (150 +/- 11/mm2). CGS-21680 inhibited adherence (48 +/- 8/mm2), comparable to that of ADO. Canine coronary artery rings were incubated with activated PMN to induce injury to the endothelium. The concentration of drug required to elicit 50% of maximal relaxation (-log M) derived from dose-relaxation responses to acetylcholine in PMN-damaged rings was significantly (P < 0.05) less in ADO-treated (6.88 +/- 0.08) and CGS-21680-treated (7.12 +/- 0.09) rings than untreated rings (6.54 +/- 0.10). This protection with ADO was reversed by inclusion of 8-SPT (6.49 +/- 0.12) but not KW-3902 (6.96 +/- 0.07). We conclude that ADO reduces PMN-induced coronary endothelial injury by A2-receptor-mediated inhibition of O2-. generation and adherence.

Supplemental L-arginine during cardioplegic arrest and reperfusion avoids regional postischemic injury

Unenhanced hypothermic cardioplegia does not prevent postischemic endothelial and contractile dysfunction in hearts subjected to antecedent regional or global ischemia. This study tested the hypothesis that supplementing blood cardioplegic solution and reperfusion with the nitric oxide precursor L-arginine would preserve endothelial function, reduce infarct size, and reverse postcardioplegia regional contractile dysfunction by the L-arginine-nitric oxide pathway. In 23 anesthetized dogs, the left anterior descending coronary artery was ligated for 90 minutes, after which total bypass was established for surgical "revascularization." In 10 dogs, unsupplemented multidose hypothermic blood cardioplegic solution was administered for a total of 60 minutes of cardioplegic arrest. In eight dogs, L-arginine was given intravenously (4 mg/kg per minute) and in blood cardioplegic solution (10 mmol) during arrest. In five dogs, the nitric oxide synthesis blocker N omega-nitro-L-arginine (1 mmol) was used to block the L-arginine-nitric oxide pathway during cardioplegia and reperfusion. Infarct size (triphenyltetrazolium chloride) as percent of the area at risk was significantly reduced by L-arginine compared with blood cardioplegic solution (28.2% +/- 4.1% versus 40.5% +/- 3.5%) and was reversed by N omega-nitro-L-arginine to 68.9% +/- 3.0% (p < 0.05). Postischemic regional segmental work in millimeters of mercury per millimeter (sonomicrometry) was significantly better with L-arginine (92 +/- 15) versus blood cardioplegic solution (28 +/- 3) and N omega-nitro-L-arginine (26 +/- 6). Segmental diastolic stiffness was significantly lower with L-arginine (0.46 +/- 0.06) compared with blood cardioplegic solution (1.10 +/- 0.11) and was significantly greater with N omega-nitro-L-arginine (2.70 +/- 0.43). In ischemic-reperfused left anterior descending coronary arterial vascular rings, maximum relaxation responses to acetylcholine, the stimulator of endothelial nitric oxide, was depressed in the blood cardioplegic solution group (77% +/- 4%) and was significantly reversed by L-arginine (92% +/- 3%). Smooth muscle function was unaffected in all groups. We conclude that cardioplegic solution supplemented with L-arginine reduces infarct size, preserves postischemic systolic and diastolic regional function, and prevents arterial endothelial dysfunction via the L-arginine-nitric oxide pathway.

Endogenous nitric oxide (NO) protects against ischaemia-reperfusion injury in the rabbit

OBJECTIVES

Recent studies suggest that nitric oxide (NO) is deleterious in models of shock and hypoxia-reoxygenation However, the role of endogenous NO in ischaemia-reperfusion injury in vivo remains controversial. We tested the hypothesis that blockade of endogenous NO produced during myocardial ischaemia-reperfusion or during reperfusion alone in vivo increases infarct size after coronary occlusion in the rabbit, and conversely, supplementation with L-arginine would reduce infarct size.

METHODS

Ketamine-xylazine anaesthetised New Zealand white rabbits were subjected to left coronary artery occlusion for 30 min and reperfusion for 120 min. The rabbits were divided into five groups: (1) saline (VEH); (2) L-nitro arginine (L-NA), a NO-synthase inhibitor, was infused intravenously (15 mg/kg bolus followed by 7.5 mg/kg h-1) before coronary occlusion to block NO synthase activity during ischaemia and reperfusion (IR); (3) L-NA was administered during reperfusion only (R) at the same dose as in the IR group; (4) D-arginine (D-ARG) (25 mg/kg bolus followed by 4 mg/kg min-1), the non-metabolised enantiomer of L-arginine was infused intravenously during reperfusion only; (5) L-arginine (L-ARG) (25 mg/kg bolus followed by 4 mg/kg min-1), the physiological precursor of NO, was infused intravenously during reperfusion only.

RESULTS

L-NA infusion in the IR and R groups caused an increase in mean arterial pressure and a decrease in heart rate; however, no significant change in pressure rate product (PRP) occurred immediately after drug infusion. PRP did not change significantly during the experiment across groups except at the end of reperfusion. The area at risk was comparable in all groups, averaging 29(1)%. The infarct size (triphenyltetrazolium chloride) expressed as a percent of area at risk was 27(2)% for the untreated vehicle group. In contrast, L-NA significantly (P < 0.05) increased infarct size in the IR group, 51(2)%; this augmented infarct size persisted when NO synthase activity was blocked during reperfusion only in the R group, 50(2)%. There was no significant (P < 0.05) difference in infarct size between the IR and the R groups. D-ARG-treated group showed a comparable increase in infarct size 48(2)% versus the IR and R groups. However, supplementation of NO with L-arginine (L-ARG) showed no reduction in infarct size, 24(3)%, over vehicle group (VEH).

CONCLUSIONS

We conclude that (1) blockade of NO synthase activity with L-NA increases infarct size, (2) this effect was expressed primarily during reperfusion, (3) D-arginine mimicked the infarct augmentation of L-NA, while (4) L-arginine supplementation did not reduce infarct size. These data imply that endogenous NO production exerts a tonic cardioprotective effect on myocardial infarct following coronary reperfusion.

Acadesine reduces myocardial infarct size by an adenosine mediated mechanism

OBJECTIVE

The aim was to test the hypotheses that acadesine (1) augments endogenous interstitial fluid (ISF) adenosine during ischaemia, and (2) reduces infarct size by adenosine receptor mediated mechanisms.

METHODS

To test these hypotheses, the left coronary artery of anaesthetised rabbits (n = 33) was occluded for 30 min and reperfused for 120 min. Acadesine (1 mg.kg-1.min-1 for 5 min, then 0.2 mg.kg-1.min-1) was infused intravenously beginning 30 min before coronary occlusion and ending 30 min after reperfusion. The area at risk was comparable in all groups, averaging 34.7 (SEM 2.2%) of the left ventricle. In separate studies (n = 22), estimates of ISF adenosine and adenosine metabolites were obtained by cardiac microdialysis. Although dialysate adenosine levels increased significantly in the area at risk during ischaemia in the untreated group [from 0.044(0.008) to 0.339(0.146) microM], acadesine did not significantly augment dialysate adenosine levels before or during ischaemia [preischaemia = 0.094(0.032) microM; ischaemia = 0.542(0.262) microM]. In addition, there was no significant difference in dialysate adenosine concentrations during the first 10 min of reperfusion, after which adenosine levels returned to baseline levels. A 2.5-fold large dose failed to increase interstitial fluid adenosine. However, the adenosine receptor blocker 8-p-sulphophenyltheophylline (SPT) in the presence of acadesine increased ISF adenosine fourfold. Acadesine significantly (P < 0.05) reduced infarct size [n = 8, 19.7(2.9)% of risk area] compared with the untreated group [n = 8, 29.4(1.3)%]. This infarct size reduction with acadesine was antagonised by SPT given during ischaemia-reperfusion [n = 8, 46.2(3.0)%] or only during reperfusion [n = 9, 42.7(2.6)%.

CONCLUSIONS

Acadesine reduces infarct size by an adenosine mediated mechanism, but this cardioprotective action is not associated with significantly augmented interstitial fluid adenosine levels.

Adenosine in blood cardioplegia prevents postischemic dysfunction in ischemically injured hearts

Adenosine (ADO) is an endogenous cardioprotective autacoid that exerts receptor-mediated cardioprotection from ischemic-reperfusion injury. This study tested the hypothesis that blood cardioplegia (BCP) supplemented with ADO reduces postischemic left ventricular dysfunction in ischemically injured hearts. Twenty-one anesthetized dogs on total bypass were subjected to 30 minutes of normothermic global ischemia. Cold (4 degrees C) potassium BCP was then delivered every 20 minutes for 60 minutes of cardioplegic arrest. In 7 dogs, unsupplemented BCP was used; in 7 dogs, BCP was supplemented with 400 mumol/L ADO; and, in 7 dogs, ADO receptors were blocked with 8-p-sulfophenyltheophylline (30 mg/kg) given with 400 mumol/L ADO in BCP. Preischemic and postischemic left ventricular systolic function was assessed by the slope and volume axis intercept of the end-systolic pressure-volume (impedance catheter) relationship (ESPVR). In unsupplemented BCP, the postischemic slope of the ESPVR was significantly depressed by 42% versus the preischemic value (from 6.8 +/- 1.2 mm Hg/mL to 3.9 +/- 0.4 mm Hg/mL; p < 0.05 versus the preischemic value). In contrast, BCP supplemented with ADO was found to restore the postischemic ESPVR slope to preischemic levels (7.7 +/- 1.0 mm Hg/mL versus 7.4 +/- 1.2 mm Hg/mL, respectively). This cardioprotection was reversed by 8-p-sulfophenyltheophylline (9.9 +/- 1.5 mm Hg/mL versus 4.5 +/- 0.7 mm Hg/mL; p < 0.05 versus the preischemic value). Postischemic plasma creatinine kinase activity was elevated equally in all groups over the baseline values. We conclude that ADO in BCP attenuates postcardioplegia dysfunction in severely injured hearts through the operation of receptor-mediated mechanisms.

Pentostatin-augmented interstitial adenosine prevents postcardioplegia injury in damaged hearts

This study tests the hypothesis that the adenosine deaminase inhibitor pentostatin (2-deoxycoformycin), when given before ischemia or during infusions of blood cardioplegia, augments interstitial adenosine levels and prevents postcardioplegia dysfunction in hearts with antecedent ischemia. Twenty-one anesthetized dogs were placed on cardiopulmonary bypass, and the hearts were made globally ischemic for 30 minutes. Dogs received blood cardioplegia with no pentostatin (BCP group, n = 6), pretreatment pentostatin (0.2 mg/kg) infused 5 minutes before global ischemia (PS-PTx group, n = 7), or pentostatin included only in the blood cardioplegia without pretreatment (PS-BCP group, n = 8). Microdialysate myocardial adenosine levels (an index of interstitial fluid levels) increased only modestly in the BCP group (from 0.55 +/- 0.13 microM to 2.64 +/- 0.50 microM) and the PS-BCP group (from 0.55 +/- 0.18 microM to 1.08 +/- 0.48 microM) during normothermic ischemia, but interstitial adenosine levels were not augmented further during cardioplegic arrest in either group. In contrast, the adenosine level in the PS-PTx group was significantly (p < 0.05) augmented during global ischemia (from 0.50 +/- 0.13 microM to 63.16 +/- 28.08 microM) and cardioplegia infusion (to 15.26 microM +/- 5.61 microM). Relative to baseline, postischemic left ventricular performance (end-systolic pressure-volume relation) was depressed in both the BCP (from 5.5 +/- 1.2 mm Hg/mL to 3.8 +/- 0.4 mm Hg/mL) and PS-BCP groups (from 7.1 +/- 0.9 mm Hg/mL to 3.8 +/- 0.7 mm Hg/mL). In contrast, PS-PTx restored postischemic performance (from 6.2 +/- 0.5 mm Hg/mL to 7.5 +/- 0.9 mm Hg/mL).(ABSTRACT TRUNCATED AT 250 WORDS)

Prevention of falls among older people at home

The high incidence of falls among older people and the subsequent high rates of potentially preventable morbidity and mortality highlight the need for early identification of risk factors. This article discusses the major contributory factors and the role of community nurses in accident prevention assessment of older people.

Intestinal absorption and lymphatic transport of peroxidized lipids in rats: effect of exogenous GSH

We previously found that mucosal glutathione (GSH) plays an important role in the intestinal metabolism of luminal peroxidized lipids [T. Y. Aw, M. W. Williams, and L. Gray. Am. J. Physiol. 262 (Gastrointest. Liver Physiol. 25): G99-G106, 1992]. To determine the effects of exogenous GSH on lipid hydroperoxide elimination under conditions in which mucosal GSH was initially depleted with buthionine sulfoximine (BSO), we infused peroxidized lipid solutions without or with GSH into the proximal intestine of rats and monitored the steady-state output of hydroperoxides in lymph and recovery of luminal hydroperoxides. GSH supplementation in BSO-treated rats resulted in a concentration-dependent attenuation of lymphatic output of peroxidized lipids that was correlated with increases in mucosal GSH. Compared with BSO control, the luminal lipid hydroperoxide contents were significantly lower in GSH-supplemented rats, consistent with enhanced elimination of peroxidized lipids by exogenous GSH. The effect of GSH was ameliorated by the inhibitors of GSH uptake, suggesting that the uptake of GSH is required for promotion of intestinal removal of luminal hydroperoxides. Other thiols, either at comparable or higher concentrations than GSH, were without significant effects on lymphatic transport or luminal recovery of lipid hydroperoxides, indicating that these thiols are poor substitutes for GSH. Overall, the data are consistent with exogenous GSH being a source for cellular reduction of peroxidized lipids. Results from these studies could directly impact on future consideration of therapeutic means to increase cellular antioxidant systems to promote intestinal hydroperoxide detoxication.

Absorption and lymphatic transport of peroxidized lipids by rat small intestine in vivo: role of mucosal GSH

The absorption and lymphatic transport of peroxidized MaxEPA fish oil was studied using the lymph fistula rat to determine the role of mucosal glutathione (GSH) in intestinal metabolism of luminal lipid hydroperoxides. Decreasing intestinal GSH concentrations with buthionine sulfoximine (BSO, 1.15 +/- 0.20 nmol/g), diethyl maleate (DEM, 0.93 +/- 0.26 nmol/g), phorone (1.46 +/- 0.14 nmol/g), or 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU, 1.54 +/- 0.18 nmol/g) compared with control (2.60 +/- 0.38 nmol/g) resulted in higher luminal recovery of the infused lipid hydroperoxide (% of infused dose): BSO (87.8 +/- 4.8%), DEM (86.1 +/- 1.3%), phorone (78.1 +/- 2.1%), and BCNU (71.7 +/- 4.8%) compared with control (52.8 +/- 4.3%). These results suggest that decreased elimination of luminal peroxidized lipids is associated with decreased tissue GSH. Treatment of rats with BSO, DEM, phorone, or BCNU resulted in dramatic increases in appearance of peroxidized lipids in lymph over 6-h lipid infusion (54.7 +/- 3.7, 57.7 +/- 4.6, 46.4 +/- 2.7, and 42.1 +/- 3.9 nmol, respectively) compared with control (20.5 +/- 3.4 nmol). The results are consistent with decreased intracellular metabolism of absorbed hydroperoxides and enhanced transport into lymph under GSH-deficient conditions. The current findings suggest that the function of the mucosal GSH peroxidase/oxidized glutathione (GSSG) reductase system may play an important role in intestinal handling of luminal lipid hydroperoxides. A compromised function of this detoxication mechanism in GSH-deficient states can significantly alter the metabolic fate of dietary peroxidized lipids.

Phallic reinnervation via the pudendal nerve

Total phallic reconstruction presents the genitourinary reconstructive surgeon with one of the most difficult surgical challenges. The development of microsurgical techniques and free tissue transfers have advanced phallic reconstruction by reducing the number of surgical procedures and by allowing more selectivity in choosing the best innervated donor tissue. During the last 5 years 16 patients underwent total phallic reconstruction using free tissue transfers from distant donor sites. The pudendal nerve was coapted routinely to the major sensory nerves of the donor free flap. The most accurate objective baseline parameters of penile sensibility are pressure and vibratory thresholds, and electrically evoked potentials. We examined 30 normal subjects and 7 patients at least 1 year postoperatively for penile (phallic) sensibility. A pressure aesthesiometer, a biothesiometer and electrodiagnostic studies were used for testing. The 7 postoperative patients (in all of whom the pudendal nerve was incorporated into the reconstruction) had an encouraging return of tactile and erogenous sensibility compared to normal subjects. This is a promising advance in phallic reconstruction.

Cadmium resistance in Drosophila: a small cadmium binding substance

A small cadmium-binding substance (CdBS) has been observed in adult Drosophila melanogaster that were raised for their entire growth cycle on a diet that contained 0.15 mM CdCl2. Induction of CdBS was observed in strains that differed widely in their sensitivity to CdCl2. This report describes the induction of CdBS and some of its characteristics.

Genetic and physiological parameters associated with cadmium toxicity in Drosophila melanogaster

Two strains of Drosophila melanogaster represent the extremes in resistance and sensitivity to the lethal effects of CdCl2. The strain containing the mutations vermilion and brown (v; bw) and the strain Austin had LC50's of 3.3 and 1.3 mM CdCl2, respectively. The three major chromosomes from these two strains were assorted genetically into the six possible combinations. The measured LC50's for CdCl2 for these six genotypes fell into two groups according to the X chromosome; those containing the X chromosome from v; bw had LC50's 0.5-1.0 mM greater than those in which the X chromosome was from Austin. Since the parent strains differed by 2 mM, we suggest that the X chromosome is a major, but not the sole, site of genes to produce resistance to CdCl2. When 109Cd was in the diet the uptake by v; bw and Austin over 2 days was the same. After 4 days of uptake, the Austin strain excreted the 109Cd five times faster than v; bw but the six genotypes did not differ appreciably in excretion rate from one another and resembled the sensitive parent Austin more than the resistant one. Thus a second process is indicated that distinguishes resistance to CdCl2 that apparently is not associated with the X chromosome.

The toxicity of sixteen metallic compounds in Chinese hamster ovary cells

The toxicity of 16 metal salts to Chinese hamster ovary (CHO) cells was determined by measuring the cloning efficiency (CE) of CHO cells after exposure to the metals. CHO cells differed by a factor of 10(5) to 10(6) in their toxic response to these metal salts. While Cd(II) was the most toxic ion, Mg(II) exhibited the least toxicity based on either CE50 (concentration required to reduce the CE to 50%) or D0 (concentration increment which reduced the CE by 63%). On the basis of CE50, the toxicity ranking was Ag greater than Tl for monovalent metals, Cd greater than Zn greater than Hg greater than Co greater Cu greater than Mn greater than Ni greater than Be greater than Pd greater than Sr greater than Mg for divalent metals, and In greater than Rh greater than Y for trivalent metals. A similar ranking was found for D0. For the 11 divalent metals, correlations of CE50 and D0 in the CHO cell assay and the Pearson-Mawby softness parameter for metals (sigma p) were reasonably strong. A good correlation exists between the results of this study on the toxic response in CHO cells and published data on toxicity in mice and Drosophila. It appears that the CHO cell cloning assay may be useful in preliminary screening of metallic compounds as an indicator of their predicted toxicity in higher organisms.

The organic aerosols of Titan

A dark reddish organic solid, called tholin, is synthesized from simulated Titanian atmospheres by irradiation with high energy electrons in a plasma discharge. The visible reflection spectrum of this tholin is found to be similar to that of high altitude aerosols responsible for the albedo and reddish color of Titan. The real (n) and imaginary (k) parts of the complex refractive index of thin films of Titan tholin prepared by continuous D.C. discharge through a 0.9 N2/0.1 CH4 gas mixture at 0.2 mb is determined from x-ray to microwave frequencies. Values of n (approximately equal to 1.65) and k (approximately equal to 0.004 to 0.08) in the visible are consistent with deductions made by ground-based and spaceborne observations of Titan. Many infrared absorption features are present in k (lambda), including the 4.6 micrometers nitrile band. Molecular analysis of the volatile component of this tholin was performed by sequential and non-sequential pyrolytic gas chromatography/mass spectrometry. More than one hundred organic compounds are released; tentative identifications include saturated and unsaturated aliphatic hydrocarbons, substituted polycyclic aromatics, nitriles, amines, pyrroles, pyrazines, pyridines, pyrimidines, and the purine, adenine. In addition, acid hydrolysis produces a racemic mixture of biological and non-biological amino acids. Many of these molecules are implicated in the origin of life on Earth, suggesting Titan as a contemporary laboratory environment for prebiological organic chemistry on a planetary scale.

Investigation of correlations between chemical parameters of metal ions and acute toxicity in mice and Drosophila

We are studying correlations between physicochemical properties associated with metal ions and observed toxicity. In order to test correlations, we obtained, under uniform conditions, LD50 values for acute toxicity in mice for 24 metal ions. The new data show a better correlation between LD50 and Pearson and Mawby's softness parameter sigma p, defined using chemical concepts of hard and soft acids and bases, than had been obtained by others. From a wide range of physicochemical parameters, the electrode potential can give almost as good a correlation as sigma p. Better correlations might exist for parameters more relevant to biological systems.