Toward the improvement of total nitrogen deposition budgets in the United States.

Frameworks for limiting ecosystem exposure to excess nutrients and acidity require accurate and complete deposition budgets of reactive nitrogen (Nr). While much progress has been made in developing total Nr deposition budgets for the U.S., current budgets remain limited by key data and knowledge gaps. Analysis of National Atmospheric Deposition Program Total Deposition (NADP/TDep) data illustrates several aspects of current Nr deposition that motivate additional research. Averaged across the continental U.S., dry deposition contributes slightly more (55%) to total deposition than wet deposition and is the dominant process (>90%) over broad areas of the Southwest and other arid regions of the West. Lack of dry deposition measurements imposes a reliance on models, resulting in a much higher degree of uncertainty relative to wet deposition which is routinely measured. As nitrogen oxide (NOx) emissions continue to decline, reduced forms of inorganic nitrogen (NHx = NH3 + NH4+) now contribute >50% of total Nr deposition over large areas of the U.S. Expanded monitoring and additional process-level research are needed to better understand NHx deposition, its contribution to total Nr deposition budgets, and the processes by which reduced N deposits to ecosystems. Urban and suburban areas are hotspots where routine monitoring of oxidized and reduced Nr deposition is needed. Finally, deposition budgets have incomplete information about the speciation of atmospheric nitrogen; monitoring networks do not capture important forms of Nr such as organic nitrogen. Building on these themes, we detail the state of the science of Nr deposition budgets in the U.S. and highlight research priorities to improve deposition budgets in terms of monitoring and flux measurements, leaf- to regional-scale modeling, source apportionment, and characterization of deposition trends and patterns.

Prevalence and behavioural risk factors of Staphylococcus aureus nasal colonization in community-based injection drug users.

The aims of this study were to identify Staphylococcus aureus nasal colonization prevalence, behavioural risk factors, and to determine staphylococcal protein A (spa) types in community-based injection drug users (IDUs). Nasal swabs were collected and methicillin susceptibility testing and spa/SCCmec typing were performed on S. aureus isolates. Generalized estimating equations were used to report adjusted odds ratios and 95% confidence intervals. Of the 440 participants, 24·1% were colonized and 5·7% had methicillin-resistant S. aureus (MRSA). Colonization was associated with age, employment/marital status, and the presence of scabs but not with sexually transmitted disease co-infection, HIV status, antibiotic use, hospitalization, or drug treatment programme participation. The USA300 MRSA clone spa types were most common, but 15/49 spa types were new to one of the international databases. Community-based IDUs appear to have different risk factors compared to IDUs from clinical studies. In addition, the number of newly identified spa types indicates a diverse, understudied population.

Physiological responses of lichens to factorial fumigations with nitric acid and ozone.

This paper addresses the effects of gaseous nitric acid (HNO(3)) and ozone (O(3)), two important air pollutants, on six lichen species with different morphological, ecological, and biological characteristics. The treatment chambers were set up in a factorial design consisting of control chambers, chambers fumigated with HNO(3), with O(3), and with HNO(3) and O(3), together. Each species showed a different sensitivity to the fumigations, reflecting the physiological variation among species. Our results clearly indicate that HNO(3) is a strong phytotoxin to many lichens, and that O(3) alone has little effect on the measured parameters. The combined fumigation effects of HNO(3) and O(3) were not significantly different from HNO(3) alone.

Relationship between heterosexual anal sex, injection drug use and HIV infection among black men and women.

US blacks carry a disproportionate risk of heterosexually transmitted HIV. This study aimed to evaluate the association between self-reported heterosexual anal intercourse and HIV. Using respondent-driven sampling (RDS), we recruited and interviewed 909 blacks from areas of high poverty and HIV prevalence in Houston, Texas, and who reported heterosexual sex in the last year. All individuals were tested for HIV. Weighted prevalence values were calculated to account for non-random recruitment associated with RDS. The weighted population prevalence of HIV infection was 2.4% and 2.5% among men and women, respectively. Education, employment status, income and crack cocaine use were not associated with HIV infection. Lifetime injection drug use (odds ratio [OR] 3.31, 95% confidence interval [CI] 1.31-8.33%) and heterosexual anal intercourse (OR 2.41, 95% CI 1.02-5.73%) were associated with HIV infection. Individuals who reported both injection drug use and heterosexual anal intercourse had 6.21 increased odds of HIV (95% CI 2.47-15.61%). Our results suggest that heterosexual anal sex may be a vector for HIV transmission, especially in the context of injection drug use. Prevention strategies directed at curbing the HIV epidemic among black heterosexuals require that we correctly identify the risks so that appropriate interventions can be developed.

Condom use among high-risk heterosexual women with concurrent sexual partnerships, Houston, Texas, USA.

Concurrent sexual partnerships allow for enhanced transmission of sexually transmitted infections (STIs). Condom use dynamics in this context may be an important factor for transmission of HIV. We conducted a cross-sectional study to describe the frequency of concurrency among high-risk heterosexual women in Houston, Texas and determine the factors associated with condom use. A total of 553 participants were recruited using respondent-driven sampling and completed an anonymous questionnaire; 256 (49%) were identified as having a concurrent partnership. The prevalence of condom use at last sexual encounter was 26%. Women were significantly more likely to use condoms if their sexual encounter was with a casual partner and if alcohol and/or drugs were not used. The high prevalence of concurrent partnerships suggests the presence of a dense sexual network which may enable the rapid spread of STIs and HIV. The risk of transmission may be additionally increased due to the low prevalence of condom use.

The prevalence of suicidal behaviours in a group of HIV-positive men.

We studied a convenience sample of 54 HIV-positive men, recruited from HIV/AIDS community based service organizations. Data were collected on HIV risk factors and suicidal behaviours. Fifty-nine percent of the sample reported ever thinking about suicide, and 50% of those individuals reported attempting suicide at some point in their lives. Suicide ideation and attempts were more common among white participants. Suicidal behaviours were prevalent in this sample suggesting a need for mental health and suicide interventions targeted for this population.

The prevalence of partner violence in a group of HIV-infected men.

There is a paucity of literature regarding partner violence among males that identifies the sex and relationship of their partner(s). We studied a convenience sample of 54 HIV-infected men, recruited from HIV/AIDS service organizations. Using a standard questionnaire, we collected data on HIV risk behaviours and self-reports of acts of partner violence and forced sex. Physical violence perpetrated by a primary or a casual partner was reported by 39% and 17% of the sample, respectively. Life-time forced sex by a primary or casual partner was reported by 32% and 15% of the sample, respectively. Forced sex was more commonly reported by participants who were non-white and reported a higher number of primary partners in the previous 12 months. We recommend that health care providers be aware of the high rates of intimate partner violence among men infected or at risk of infection with HIV.

Passive sampler for measurements of atmospheric nitric acid vapor (HNO3) concentrations.

Nitric acid (HNO3) vapor is an important nitrogenous air pollutant responsible for increasing saturation of forests with nitrogen and direct injury to plants. The USDA Forest Service and University of California researchers have developed a simple and inexpensive passive sampler for monitoring air concentrations of HNO3. Nitric acid is selectively absorbed on 47-mm Nylasorb nylon filters with no interference from particulate NO3-. Concentrations determined with the passive samplers closely corresponded with those measured with the co-located honeycomb annular denuder systems. The PVC protective caps of standardized dimensions protect nylon filters from rain and wind and allow for reliable measurements of ambient HNO3 concentrations. The described samplers have been successfully used in Sequoia National Park, the San Bernardino Mountains, and on Mammoth Mountain in California.

Concentrations, deposition, and effects of nitrogenous pollutants in selected California ecosystems.

Atmospheric deposition of nitrogen (N) in California ecosystems is ecologically significant and highly variable, ranging from about 1 to 45 kg/ha/year. The lowest ambient concentrations and deposition values are found in the eastern and northern parts of the Sierra Nevada Mountains and the highest in parts of the San Bernardino and San Gabriel Mountains that are most exposed to the Los Angeles air pollution plume. In the Sierra Nevada Mountains, N is deposited mostly in precipitation, although dry deposition may also provide substantial amounts of N. On the western slopes of the Sierra Nevada, the majority of airborne N is in reduced forms as ammonia (NH3) and particulate ammonium (NH4+) from agricultural activities in the California Central Valley. In southern California, most of the N air pollution is in oxidized forms as nitrogen oxides (NOx), nitric acid (HNO3), and particulate nitrate (NO3-) resulting from fossil fuel combustion and subsequent complex photochemical reactions. In southern California, dry deposition of gases and particles provides most (up to 95%) of the atmospheric N to forests and other ecosystems. In the mixed-conifer forest zone, elevated deposition of N may initially benefit growth of vegetation, but chronic effects may be expressed as deterioration of forest health and sustainability. HNO3 vapor alone has a potential for toxic effects causing damage of foliar surfaces of pines and oaks. In addition, dry deposition of predominantly HNO3 has lead to changes in vegetation composition and contamination of ground- and stream water where terrestrial N loading is high. Long-term, complex interactions between N deposition and other environmental stresses such as elevated ozone (O3), drought, insect infestations, fire suppression, or intensive land management practices may affect water quality and sustainability of California forests and other ecosystems.

A longitudinal evaluation of dipyridamole drug use in an ambulatory elderly population.

STUDY OBJECTIVE: To determine the pattern of dipyridamole use over the past 14 years. DESIGN: A longitudinal health screening program of ambulatory elderly participants was used to study changes in dipyridamole drug use. Participants included all subjects screened in the Florida Geriatric Research Program since 1978. The main outcome measure in this study was self-reported dipyridamole use at every visit to the program since August 1, 1978. RESULTS: A total of 3.6% of men (mean age, 82.6 years) and 3.4% of women (mean age, 80.8 years) reported the use of dipyridamole in the 1991-1992 period. The prevalence of dipyridamole use ranged from a low of 1.6% in 1978-1979 to a high of 7.3% in 1986-1987. There was a significant increase in the use of this drug from 1978-1979 to 1991-1992 (p < 0.038). Over the 14-year period of study, the percent of subjects using dipyridamole concurrently with coumarin anticoagulants ranged from a low of 5.8% to a high of 17.9%. CONCLUSIONS: The level of dipyridamole use in this elderly population has increased since 1978-1979. The only FDA indication for this drug is in combination with coumarin anticoagulants to prevent postoperative thromboembolic complications of cardiac valve replacement. Less than 20% of patients in this study used the drug in combination with coumarin anticoagulants. Educational programs are needed to improve the prescribing of dipyridamole.

Treatment of subjects with refractory periodontal disease.

The aim of the present study was to evaluate the effect of non-surgical periodontal therapy with the adjunct of a selected antibiotic in subjects diagnosed with refractory periodontal disease. 21 subjects were selected for the study; all had a history of periodontal surgery, tetracycline therapy, and regular maintenance by a periodontist. When disease activity was detected, a bacterial sample was taken and a whole plaque susceptibility test was performed. Before the outcome of the susceptibility test the subjects were assigned to either antibiotic or placebo therapy. All subjects received scaling and rootplaning prior to antibiotic or placebo therapy. Based on the susceptibility test, subjects in the antibiotic group were treated either with Augmentin or clindamycin. The results demonstrated that in subjects with refractory periodontal disease there was no significant difference (N.S.) in the proportion of sites losing attachment before and after treatment (11.3% and 12.4%, respectively) over a 2-year post therapy observation period. However, the proportion of sites showing gain of attachment increased from 0.9% before therapy to 5.1% (p = 0.029) following selective antibiotic therapy when combined with scaling and rootplaning. The remainder of sites showed no change between pre- and post-therapy monitoring periods. The progression of attachment loss in the active sites could not be completely stopped over the entire 2-year period. After 12-15 months following therapy, there was a tendency towards new loss of attachment and an increase of pocket depth. However, all 4 subjects treated with placebo drug demonstrated continuous deterioration and had to be retreated. Although the proportion of sites losing attachment decreased from 5.1% to 2.3% (N.S.), the proportion of sites gaining attachment also decreased from 2.0% to 1.0% (N.S.). The results suggest that scaling and rootplaning together with selected antibiotic therapy repeated every 12-15 months may be beneficial for these subjects although it may not completely stop progressive attachment loss.

Benzodiazepine use in an ambulatory elderly population: a 14-year overview.

A survey on use of benzodiazepines was conducted among participants in the Florida Geriatric Research Program. In 1978-79, benzodiazepine use was reported by 14.4% of 1448 women and 9.7% of 855 men; in 1984-85, by 12.0% of 1429 women and 5.9% of 784 men; and in 1991-92, by 13.4% of 1124 women and 6.6% of 497 men. The changes were not significant. During this period the mean ages of the women increased from 74.6 to 78.1 years and the men from 75.0 to 80.2 years. Chlordiazepoxide, diazepam, and flurazepam accounted for 98.1% of all benzodiazepines used in 1978-79 and for 35.5% in 1991-92, when alprazolam, lorazepam, and temazepam accounted for 47.1% of benzodiazepines used.

An amino-acid-grown maize cell line for use in investigating nitrate assimilation.

Studies on uptake and assimilation of nitrate in plants are confounded by differences in cell function associated with anatomical features of roots as well as by problems inherent with growing plants without nitrate. To circumvent these problems, a Zea mays L. embryo cell line was grown in suspension culture using an amino-acid-based medium consisting of a Murashige and Skoog medium in which ammonium and nitrate were replaced by aspartic acid (100 mg/l), glycine (100 mg/l), arginine (150 mg/l), and glutamine (1 g/l). The growth, cellular characteristics, and physical appearance of the amino-acid-grown cells were similar to cells grown in the presence of nitrate. The amino-acid-grown cells exhibited the expected induction pattern and inhibitor sensitivity of nitrate uptake. This cell line should facilitate research on the induction of nitrate uptake and the regulation of nitrate assimilation into proteins.

Contamination of Ammonium-Based Nutrient Solutions by Nitrifying Organisms and the Conversion of Ammonium to Nitrate.

Conversion of ammonium to nitrate and contamination by nitrifying organisms are often assumed not to be significant in ammonium-based nutrient solutions. To assess this assumption, maize (Zea mays) and pea (Pisum sativum) were grown under greenhouse conditions in aeroponic, hydroponic, and sand-culture systems containing 2 mM ammonium chloride as the sole nitrogen source and evaluated for the activity of contaminating nitrifying organisms. In all three culture systems, root colonization by nitrifying organisms was detected within 5 d, and nitrate was detected in the nutrient solution within 10 d after seedling transfer. In sand culture, solution nitrate concentration reached 0.35 mM by the end of the 17-d experiment. Consistent with the microbial ammonium oxidation sequence, nitrite was detected earlier than nitrate and remained at lower levels throughout the experiment. Nitrate was found in significant quantities in root and shoot tissues from seedlings grown in ammonium-based nutrient solutions in all of the solution culture systems. Maize seedlings grown in an ammonium-based hydroponic system contained nitrate concentrations at 40% of that found in plants grown in nitrate-based solution. Determination of nitrate (or nitrite) levels in the nutrient solution was the weakest indicator of the activity of nitrifying organisms. A bioassay for the presence of nitrifying organisms in combination with tissue analysis for nitrate was a better indicator of microbial conversion of ammonium to nitrate in nutrient solution culture. The results have implications for the use of ammonium-based nutrient solutions to obtain plants suitable for research on induction of nitrate uptake and reduction or for research using solution culture to compare ammonium versus nitrate fertilization.

Canine exposure to Borrelia burgdorferi and prevalence of Ixodes dammini (Acari: Ixodidae) on deer as a measure of Lyme disease risk in the northeastern United States.

Surveillance programs that identify areas where both the vector (Ixodes dammini) and etiologic agent (Borrelia burgdorferi) are present may identify the risk of Lyme disease and its spread earlier and more accurately than do programs relying on any single method, particularly human case reports. Hunter-killed deer (n = 1,204) from 22 counties in Maryland, Massachusetts, New Hampshire, New York, and Pennsylvania were examined in fall 1989 and all ectoparasites were identified. The following spring, canine sera (n = 884) were obtained from these sites, which included known endemic areas and those where Lyme disease is uncommon, and tested by enzyme-linked immunosorbent assay. Regression analysis of canine seroprevalence versus tick prevalence on deer from the same counties demonstrate a significant positive linear relationship. Sites were designated as low-, moderate-, or high-risk counties based upon their position on the regression curve. The geographic distribution of the sites correlated well with the distribution of known Lyme disease endemic and nonendemic areas. Locations were also identified where Lyme disease may be emerging. The positive relationship between measures of vector and pathogen abundance determined in this study permits public health workers to identify endemic and potentially endemic areas independently of human case reports.