Assessment of cryogenic pretreatment for simulating environmental weathering in the formation of surrogate micro- and nanoplastics from agricultural mulch film.

Microplastics (MPs) and nanoplastics (NPs) from mulch films and other plastic materials employed in vegetable and small fruit production pose a major threat to agricultural ecosystems. For conducting controlled studies on MPs' and NPs' (MNPs') ecotoxicity to soil organisms and plants and fate and transport in soil, surrogate MNPs are required that mimic MNPs that form in agricultural fields. We have developed a procedure to prepare MPs from plastic films or pellets using mechanical milling and sieving, and conversion of the resultant MPs into NPs through wet grinding, both steps of which mimic the degradation and fragmentation of plastics in nature. The major goal of this study was to determine if cryogenic exposure of two biodegradable mulch films effectively mimics the embrittlement caused by environmental weathering in terms of the dimensional, thermal, chemical, and biodegradability properties of the formed MNPs. We found differences in size, surface charge, thermal and chemical properties, and biodegradability in soil between MNPs prepared from cryogenically treated vs. environmentally weathered films, related to the photochemical reactions occurring in the environment that were not mimicked by cryogenic treatment, such as depolymerization and cross-link formation. We also investigated the size reduction process for NPs and found that the size distribution was bimodal, with populations centered at 50 nm and 150-300 nm, and as the size reduction process progressed, the former subpopulation's proportion increased. The biodegradability of MPs in soil was greater than for NPs, a counter-intuitive trend since greater surface area exposure for NPs would increase biodegradability. The result isassociated with differences in surface and chemical properties and to minor components that are readily leached out during the formation of NPs. In summary, the use of weathered plastics as feedstock would likely produce MNPs that are more realistic than cryogenically-treated unweathered films for use in experimental studies.

Habitat and Vegetation Variables Are Not Enough When Predicting Tick Populations in the Southeastern United States.

Two tick-borne diseases with expanding case and vector distributions are ehrlichiosis (transmitted by Amblyomma americanum) and rickettiosis (transmitted by A. maculatum and Dermacentor variabilis). There is a critical need to identify the specific habitats where each of these species is likely to be encountered to classify and pinpoint risk areas. Consequently, an in-depth tick prevalence study was conducted on the dominant ticks in the southeast. Vegetation, soil, and remote sensing data were used to test the hypothesis that habitat and vegetation variables can predict tick abundances. No variables were significant predictors of A. americanum adult and nymph tick abundance, and no clustering was evident because this species was found throughout the study area. For A. maculatum adult tick abundance was predicted by NDVI and by the interaction between habitat type and plant diversity; two significant population clusters were identified in a heterogeneous area suitable for quail habitat. For D. variabilis no environmental variables were significant predictors of adult abundance; however, D. variabilis collections clustered in three significant areas best described as agriculture areas with defined edges. This study identified few landscape and vegetation variables associated with tick presence. While some variables were significantly associated with tick populations, the amount of explained variation was not useful for predicting reliably where ticks occur; consequently, additional research that includes multiple sampling seasons and locations throughout the southeast are warranted. This low amount of explained variation may also be due to the use of hosts for dispersal, and potentially to other abiotic and biotic variables. Host species play a large role in the establishment, maintenance, and dispersal of a tick species, as well as the maintenance of disease cycles, dispersal to new areas, and identification of risk areas.

DNA hypomethylation in 5-azacytidine-induced early-flowering lines of flax.

HPLC analysis was used to examine the cytosine methylation of total DNA extracted from four early-flowering lines that were induced by treating germinating seeds of flax (Linum usitatissimum) with the DNA demethylating agent 5-azacytidine. In the normal lines that gave rise to the induced early-flowering lines, flowering usually begins approximately 50 days after sowing. The early-flowering lines flower 7-13 days earlier than normal. The normal level of cytosine methylation was approximately 14% of the cytosines and 2.7% of the nucleosides. In the early-flowering lines, these levels were 6.2% lower than normal in DNA from the terminal leaf clusters of 14-day-old seedlings and 9.7% lower than normal in DNA from the cotyledons and immature shoot buds of 4-day-old seedlings. This hypomethylation was seen in lines that were five to nine generations beyond the treatment generation. The level of hypomethylation was similar in three of the four early-flowering lines, but was not as low in the fourth line, which flowers early but not quite as early as the other three lines. Unexpectedly, the degree of hypomethylation seen in segregant lines, derived by selecting for the early-flowering phenotype in the F(2) and F(3) generations of out-crosses, was similar to that seen in the early-flowering lines. Analysis of the methylation levels in segregating generations of out-crosses between early-flowering and normal lines demonstrated a decrease in methylation level during the selection of early-flowering segregants. The results suggest an association between hypomethylation and the early-flowering phenotype, and that the hypomethylated regions may not be randomly distributed throughout the genome of the early-flowering lines.

Responses of soil nitrogen dynamics in a Mojave Desert ecosystem to manipulations in soil carbon and nitrogen availability.

We investigated the effects of changes in soil C and N availability on N mineralization, nitrification, denitrification, NH(3) volatilization, and soil respiration in the Mojave Desert. Results indicate a C limitation to microbial N cycling. Soils from underneath the canopies of Larrea tridentata (DC.) Cov., Pleuraphis rigida Thurber, and Lycium spp. exhibited higher rates of CO(2 ) flux, lower rates of NH(3) volatilization, and a decrease in inorganic N (NH(4)(+)-N and NO(3)(-)-N) with C addition. In addition to C limitation, soils from plant interspaces also exhibited a N limitation. Soils from all locations had net immobilization of N over the course of a 15-day laboratory incubation. However, soils from interspaces had lower rates of net nitrification and potential denitrification compared to soils from under plant canopies. The response to changes in C availability appears to be a short-term increase in microbial immobilization of inorganic N. Under controlled conditions, and over a longer time period, the effects of C and N availability appear to give way to larger differences due to spatial location. These findings have implications for ecosystems undergoing changes in soil C and N availability due to such processes as desertification, exotic species invasions, or elevated atmospheric CO(2) concentration.

Dispatcher assistance and automated external defibrillator performance among elders.

OBJECTIVES: Automated external defibrillators (AEDs) provide an opportunity to improve survival in out-of-hospital, ventricular fibrillation (VF) cardiac arrest by enabling laypersons not trained in rhythm recognition to deliver lifesaving therapy. The potential role of emergency dispatchers in the layperson use of AEDs is uncertain. This study was performed to examine whether dispatcher telephone assistance affected AED skill performance during a simulated VF cardiac arrest among a cohort of older adults. The hypothesis was that dispatcher assistance would increase the proportion who were able to correctly deliver a shock, but might require additional time. METHODS: One hundred fifty community-dwelling persons aged 58-84 years were recruited from eight senior centers in King County, Washington. All participants had received AED training approximately six months previously. For this study, the participants were randomized to AED operation with or without dispatcher assistance during a simulated VF cardiac arrest. The proportions who successfully delivered a shock and the time intervals from collapse to shock were compared between the two groups. RESULTS: The participants who received dispatcher assistance were more likely to correctly deliver a shock with the AED during the simulated VF cardiac arrest (91% vs 68%, p = 0.001). Among those who were able to deliver a shock, the participants who received dispatcher assistance required a longer time interval from collapse to shock [median (25th, 75th percentile) = 193 seconds (165, 225) for dispatcher assistance, and 148 seconds (138, 166) for no dispatcher assistance, p = 0.001]. CONCLUSIONS: Among older laypersons previously trained in AED operation, dispatcher assistance may increase the proportion who can successfully deliver a shock during a VF cardiac arrest.

Training seniors in the operation of an automated external defibrillator: a randomized trial comparing two training methods.

STUDY OBJECTIVE: This study evaluated the differences in efficacy of 2 methods for training seniors in the use of an automated external defibrillator (AED). We tested the hypothesis that each training method (face-to-face instruction compared with video-based instruction) would result in similar AED performance on a manikin. METHODS: Two hundred ten seniors from various senior centers were randomized to receive face-to-face or video-based instruction on AED skills. Seniors were assessed individually and tested on the speed and quality of AED performance. We retested 177 of these initial trainees 3 months after initial training. Similar performance measures were assessed. RESULTS: Although there were statistically significant differences between the 2 training methods in terms of average time to shock at both evaluations, the results in general demonstrate that there were no clinically meaningful distinctions (time differences of <20 seconds) between the AED performance of seniors trained with a video and seniors trained in a face-to-face setting at the initial training or at the retention assessment. At the initial evaluation, overall performance was satisfactory, with greater than 98% trained with either method delivering a shock. However, at the 3-month follow-up, almost one fourth of trainees were not able to deliver a shock, and almost half were not able to correctly place the pads on the manikin. CONCLUSION: We believe that seniors can be trained equally well in AED performance with video-based self-instruction or face-to-face instruction. How to maintain acceptable AED performance skills over time remains a challenge.

Barriers and facilitators to the prescription of automated external defibrillators for home use in patients with heart disease: a survey of cardiologists.

OBJECTIVE: Because the majority of cardiac arrests occur at home, the use of automated external defibrillators (AEDs) in the home could potentially improve survival of out-of-hospital cardiac arrest. Currently, physicians must prescribe AEDs for home use by patients. The purpose of this study was to investigate the barriers and facilitators to prescription of home use of AEDs. DESIGN: Telephone interviews were conducted with 85 cardiologists and paper and pencil surveys (via fax) with 59 additional cardiologists in Washington State. OUTCOME MEASURES: Cardiologists were asked about their current practices and their perceived barriers and facilitators to prescription of AEDs for home use. RESULTS: Eighty-five percent of the sample believed that AEDs could be effective in preventing death, although only 7% of the cardiologists had ever prescribed an AED. Reasons for nonprescription included the use of implantable cardioverter defibrillators, perceived lack of a clear patient niche, and lack of knowledge about the device. The majority of respondents reported that they would be more likely to prescribe AEDs if they were the standard of care (71%), were covered by insurance (67%), and came with comprehensive training (58%). CONCLUSION: The results showed that cardiologists believe that home use of AEDs can be effective but that many issues regarding the prescription of AEDs remain.

Reasons patients with chest pain delay or do not call 911.

STUDY OBJECTIVE: To determine the reasons patients with suspected acute myocardial infarction (AMI) delay seeking medical care or do not call 911. DESIGN: Telephone interview of patients hospitalized with suspected AMI. SETTING: Nine hospitals in King County, Washington. PARTICIPANTS: Patients admitted to a CCU or ICU between October 1, 1986, and December 31, 1987, with suspected AMI occurring out-of-hospital. Spouses of patients who met criteria but died during the hospitalization also participated. INTERVENTIONS: Hospital records were reviewed, and a 20-minute telephone interview was conducted of patients who reside in King County but do not live in an extended care facility. MEASUREMENTS: Patient demographics, cardiac history, symptoms, time of acute symptom onset, time of emergency department arrival, method of transportation, discharge diagnosis, and hospital outcome were abstracted from hospital records. Circumstances leading to the hospitalization, reasons for delay in seeking care, and reasons for not calling 911 were determined in the telephone interview. RESULTS: In a 15-month period, 5,207 patients were hospitalized for suspected AMI in King County, Washington. Twenty-seven percent had AMI. Median patient delay between symptom onset and hospital arrival was 2 hours. Paramedics transported 45% of all patients. A representative subset of patients (2,316) were interviewed. The main reasons for delay were because the patient thought that the symptoms would go away, because the symptoms were not severe enough, and because the patient thought that the symptoms were caused by another illness. The main reasons for not calling 911 were because the symptoms were not severe enough, because the patient did not think of calling 911, and because the patient thought that self-transport would be faster because of his or her close location to the hospital. CONCLUSION: Maximal benefit from thrombolytic therapy is not realized in a substantial proportion of patients with AMI because of delays in seeking medical care. Knowledge of the reasons patients delay or do not call 911 can help focus efforts on achieving more rapid treatment of patients with AMI.

Utilization of emergency medical services for symptoms of acute myocardial infarction.

OBJECTIVE: To examine patient characteristics and situational and clinical factors that affect utilization of Emergency Medical Services (EMS) for symptoms of acute myocardial infarction (AMI). DESIGN: Telephone interview of patients hospitalized with suspected AMI. SETTING: Nine hospitals in King County, Washington. PATIENTS: Patients admitted to a coronary or intensive care unit between October 1, 1986, and December 31, 1987, with suspected AMI occurring out of hospital. Spouses of patients who met criteria but died during the hospitalization also participated. OUTCOME MEASURES: Patient demographics, coping strategies, situational factors, prior cardiac history, perceived symptom severity, belief about the nature of condition, and method of transportation. RESULTS: Descriptive statistics showed that although few patients called EMS as a "first thing" in response to symptoms, almost half of all patients called EMS before being hospitalized. Stepwise logistic regression analyses revealed that being older, the belief that one was experiencing a heart attack, the presence of other people (including the spouse), and the lack of physical activity at time of symptom onset, were related to both greater and quicker utilization of EMS. Additionally, education, medical history of angina, and severity of symptoms also were related to utilization of EMS. CONCLUSION: The findings are discussed in a theoretical context, using Leventhal's self-regulatory model to suggest avenues for future research and interventions.

Impact of direct mail intervention on knowledge, attitudes, and behavioral intentions regarding use of emergency medical services for symptoms of acute myocardial infarction.

This study evaluated a direct mail intervention called the "Call Fast, Call 911" campaign designed to increase use of emergency medical services for symptoms of acute myocardial infarction. The campaign was targeted at individuals over the age of 50. Persons over 50 years of age (N = 130,000) in King County, Washington, were randomly assigned to intervention or control groups. Individuals in the intervention groups received six direct mail pieces over a 1-year period encouraging them to call 911 quickly in response to chest pain. A postintervention telephone survey of a random sample of households (N = 434) assessed the impact of the campaign on knowledge, attitudes, and behavioral intentions regarding use of emergency medical services for symptoms of acute myocardial infarction. The results showed no significant differences between intervention and control groups in terms of knowledge of AMI. However, there were significant differences in beliefs and behavioral intentions to call 911 in a cardiac emergency.

Characteristics of black patients admitted to coronary care units in metropolitan Seattle: results from the Myocardial Infarction Triage and Intervention Registry (MITI).

Since 1988, 641 black and 11,892 white patients with chest pain of presumed cardiac origin have been admitted to coronary care units in 19 hospitals in metropolitan Seattle. Black men and women were younger (58 vs 66, p less than 0.0001), more often admitted to central city hospitals (p less than 0.0001), and developed evidence of acute myocardial infarction (AMI) less often (19 vs 23%, p = 0.01). In the subset of 2,870 AMI patients, blacks (n = 121) were younger (59 vs 67, p less than 0.0001) and had less prior coronary artery bypass graft surgery (2 vs 10%, p = 0.005) and more prior hypertension (67 vs 46%, p less than 0.0001). During hospitalization, whites (n = 2,749) had higher rates of coronary angioplasty (18 vs 10%, p = 0.03) and coronary artery bypass graft surgery (10 vs 4%, p = 0.04), although thrombolytic therapy and cardiac catheterization were used equally in the 2 groups. Hospital mortality was 7.4% for black and 13.1% for white patients (p = 0.07). However, after adjustment for key demographic and clinical variables by logistic regression, this difference was not as apparent (p = 0.38). Questions about the premature onset of coronary artery disease, excess systemic hypertension, and the differential use of interventions in black persons have been raised by other investigators. Despite differences in age, referral patterns and the use of coronary angioplasty and bypass surgery, black and white patients with AMI in metropolitan Seattle had similar outcomes.

Delay between onset of chest pain and seeking medical care: the effect of public education.

Thrombolytic therapy for acute myocardial infarction (AMI) is now routinely given in the emergency department and is being considered for pre-hospital care. Its effectiveness is dependent on how early it can be given after the onset of AMI. Maximal benefit, however, is not realized in many patients due to delay in seeking care. The effect of a public media education campaign (message) to shorten patient delay and increase use of emergency medical services (EMS) was evaluated prospectively in King County, Washington. We interviewed 401 patients admitted with possible AMI in the premessage period (4.5 months) and 489 in the postmessage period (4.5 months). The two groups were comparable in all factors except for discharge diagnosis of AMI (premessage, 34%; postmessage, 25%; P less than .01) and history of myocardial infarction or angina (premessage, 52%; postmessage, 43%; P less than .01). The proportion of patients who heard new information on AMI increased significantly in the postmessage period (premessage, 53%; postmessage, 74%; P less than .0001). The campaign, however, did not significantly shorten patient delay in seeking care (median delay: premessage, 2.6 hours; postmessage, 2.3 hours) or alter the distribution of patients in the less-than-two-hour, two-to-four-hour, and more-than-four-hour intervals. The rate of EMS use also was not significantly changed (premessage, 42%; postmessage, 44%). We conclude that a short-duration education campaign may increase AMI knowledge but does not seem to significantly alter patient behavior.