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PubMed2005

Community inertia of Quaternary small mammal assemblages in North America.

One of the longest running debates in ecology is whether chance or determinism structures biotic communities, and this question is often studied by looking for the presence or absence of community inertia (lack of change) over time or space. Results have been equivocal. We adopted three tactics for a fresh approach: (i) allowing the answer to vary with the geographic, temporal, and taxonomic scale of study, (ii) using appropriate reference points for the amount of inertia in random biological systems, and (iii) using a robust approach for measurement of inertia. We examined fossil assemblages of mammalian communities across almost 1,000,000 years and at sites spanning approximately 3,500 km. We showed that in general there is good evidence for inertia but that the results change in a quantifiable fashion with taxonomic, spatial, and temporal scales. By using neutral theory we place a reference point on the degree of inertia and demonstrate that empirical mammalian communities show greater inertia than neutral communities over time scales >3,000 year. Although our results do not specifically reveal mechanism, they emphasize that deterministic forces are at work in structuring communities over millennia.

Animals↗

PubMed2002

Prevalence and characterization of macrolide resistance in clinical isolates of Streptococcus pneumoniae and Streptococcus pyogenes from North America.

Resistance to macrolides is not a new phenomenon but it deserves attention because of the widespread use of these agents and their inclusion in many clinical guidelines for respiratory tract infections. The most common mechanisms by which Streptococcus pneumoniae and Streptococcus pyogenes develop resistance to macrolides is by target site modification (erythromycin ribosome methylase, erm) and efflux of the drug out of the organisms (macrolide efflux, mef). Target site modification may be of greater concern because it confers high-level resistance to all antimicrobials in the macrolide-lincosamide-streptograminB (MLSB) group. The genotype profiles of macrolide-resistant S. pneumoniae and S. pyogenes differ somewhat across regions in the US and between the US and Canada and other countries. There is some evidence for an association between macrolide resistance and treatment failure but this must be researched more fully. S. pneumoniae and S. pyogenes isolates resistant to macrolides are generally susceptible to ketolide antimicrobials because these agents bind more strongly to the relevant domain of the ribosomal subunit (withstanding erm resistance) and are less vulnerable to efflux compared to the macrolides.

Anti-Bacterial Agents↗

PubMed2002

Preoperative beta-blocker use and mortality and morbidity following CABG surgery in North America.

CONTEXT: beta-Blockade therapy has recently been shown to convey a survival benefit in preoperative noncardiac vascular surgical settings. The effect of preoperative beta-blocker therapy on coronary artery bypass graft surgery (CABG) outcomes has not been assessed. OBJECTIVES: To examine patterns of use of preoperative beta-blockers in patients undergoing isolated CABG and to determine whether use of beta-blockers is associated with lower operative mortality and morbidity. DESIGN, SETTING, AND PATIENTS: Observational study using the Society of Thoracic Surgeons National Adult Cardiac Surgery Database (NCD) to assess beta-blocker use and outcomes among 629 877 patients undergoing isolated CABG between 1996 and 1999 at 497 US and Canadian sites. MAIN OUTCOME MEASURE: Influence of beta-blockers on operative mortality, examined using both direct risk adjustment and a matched-pairs analysis based on propensity for preoperative beta-blocker therapy. RESULTS: From 1996 to 1999, overall use of preoperative beta-blockers increased from 50% to 60% in the NCD (P<.001 for time trend). Major predictors of use included recent myocardial infarction; hypertension; worse angina; younger age; better left ventricular systolic function; and absence of congestive heart failure, chronic lung disease, and diabetes. Patients who received beta-blockers had lower mortality than those who did not (unadjusted 30-day mortality, 2.8% vs 3.4%; odds ratio [OR], 0.80; 95% confidence interval [CI], 0.78-0.82). Preoperative beta-blocker use remained associated with slightly lower mortality after adjusting for patient risk and center effects using both risk adjustment (OR, 0.94; 95% CI, 0.91-0.97) and treatment propensity matching (OR, 0.97; 95% CI, 0.93-1.00). Procedural complications also tended to be lower among treated patients. This treatment advantage was seen among the majority of patient subgroups, including women; elderly persons; and those with chronic lung disease, diabetes, or moderately depressed ventricular function. Among patients with a left ventricular ejection fraction of less than 30%, however, preoperative beta-blocker therapy was associated with a trend toward a higher mortality rate (OR, 1.13; 95% CI, 0.96-1.33; P =.23). CONCLUSIONS: In this large North American observational analysis, preoperative beta-blocker therapy was associated with a small but consistent survival benefit for patients undergoing CABG, except among patients with a left ventricular ejection fraction of less than 30%. This analysis further suggests that preoperative beta-blocker therapy may be a useful process measure for CABG quality improvement assessment.

Adrenergic beta-Antagonists↗

PubMed1988

Epizootiology of skunk rabies in North America.

Public health surveillance data from the United States and Canada (1961 to 1982) were analyzed to determine if consistent temporal and spatial patterns in skunk rabies could be identified. Enzootic/epizootic rabies was recognized in 18 states (enzootic states) based on the criteria of greater than or equal to 20 yr of reported skunk rabies and at least 1 yr with a minimum of 50 reported rabid skunks. In other wildlife species, epizootics have been demonstrated to expand along a wave-like front. We hypothesized: if skunk rabies behaved in a similar fashion, states reporting rabid skunks would change over time. No such change was noted. During epizootics the number of counties reporting increased but not the number of states. Within Illinois certain counties were demonstrated to have persistent rabies histories and likely served as enzootic foci. Enzootic states combined prevalence indicated a 6 to 8 yr cycle for epizootics. Data on monthly percent rabies positive (number rabid/total number tested) were available from six states and Canada. Mean distributions were bimodal with winter and spring peaks. The patterns identified for skunk rabies differ from those of other major wildlife vectors and have significance for potential vaccination control regimes.

Animals↗

PubMed2002

[Report on the 86th Scientific Assembly and Annual Meeting of the Radiological Society of North America: motion artifact caused by heart pulsation observed on an electron beam and a multidetector-row CT].

UNLABELLED: Recently developed technologies in CT imaging have allowed higher temporal resolution and less motion artifacts caused by heart pulsation. However, complete deletion of motion artifacts has not altogether been accomplished. In interpreting images, differentiation of motion artifacts and true lesion is essential. In this exhibition, the ascending aorta, outer contour of the heart, valve, lung adjacent to the heart, and other structures in the mediastinum are demonstrated focusing on the characteristics of motion artifact. Images obtained with an electron beam CT (Imatron 150XL) and a MDCT (LightSpeed QX/i, GEMS) are comparatively demonstrated. In electron beam CT, the temporal resolution ranged from 50 msec to 2,000 msec. In multidetector-row CT, half reconstruction algorithm (500 msec) and newly developed algorithm (130 msec) can be applied to reduce temporal resolution, although temporal resolution (800msec) of a full scan is fixed. Degree, shape, and site at which motion artifacts arise are analyzed with respect to the temporal resolution on two different CT systems. LEARNING OBJECTIVES: Motion artifacts are correlated with the temporal resolution of the CT scanner. Electron beam and multidetector row CT provides different kinds of solutions to reduce motion artifacts.

Algorithms↗

PubMed1998

Epidemiologic transition theory and aging: Hispanic populations of North America and the Caribbean.

As the forces of social and economic development combine with epidemiological transitions, population aging will continue to impact world health status and the provision of health services. Epidemiology provides an interdisciplinary link to the traditional study of population change by enhancing the demographic parameters of fertility, life expectancy, and migration, with specific measures of mortality and morbidity in order better to predict the pace and concentration of aging within a population. In this article, the authors examine three theoretical models of epidemiological transition and offer historical (1950-1995) and projection (1995-2050) data for the development patterns in Cuba, Dominican Republic, Puerto Rico, and Mexico. They contrast trends in fertility, life expectancy ratios, and gender differences in these countries with the Hispanic population of the United States. Central to this study are the cause of death statistics presented to identify the model occurring in each country. Shifts in the gender mix at older ages are presented due to the decline in fertility and death associated with childbearing years and the timing of the transition from high mortality to infectious disease to high mortality from chronic and age-related disease.

Aged↗

PubMed1994

New morphological characters for identifying individual specimens of Haemonchus spp. (Nematoda: Trichostrongyloidea) and a key to species in ruminants of North America.

The large stomach worms Haemonchus contortus, Haemonchus placei, and Haemonchus similis are important pathogens of cattle and sheep. This paper describes characteristics of surface cuticular ridges (synlophe), which for the first time provide morphological criteria for identifying individual adult specimens of either sex. The diagnostic patterns of the synlophe on the anterior half of specimens can be observed at 400x in temporary mounts on glass slides. The synlophe can be studied in cleared preserved specimens or in living or freshly thawed frozen specimens mounted in water. The synlophe of H. contortus has 30 ridges in the region of the posterior half of the esophagus, 4 fewer than H. placei and H. similis. The 4 extra ridges of H. placei and H. similis are consistently located bilaterally to the 3 ventralmost and the 3 dorsalmost ridges. The 4 extra ridges of H. similis extend to the end of the synlophe posterior to midbody, but in H. placei they extend posteriorly only to the end of the anterior quarter of the nematode. A key is included to the 3 species of Haemonchus parasitic in domestic sheep and cattle using characteristics of spicules, female reproductive system, female tail, and the synlophe.

Animals↗

PubMed2005

Management of infants with bronchopulmonary dysplasia in North America.

The in-hospital management of infants with BPD includes minimizing the duration of mechanical ventilation and avoiding the use of high inspired oxygen concentrations while maintaining adequate oxygenation. Fluid restriction, bronchodilators, and diuretic therapy can improve lung function and reduce the need for supplemental oxygen and high ventilator settings, but do not change the ultimate course of these infants. Corticosteroids also improve lung function and accelerate weaning from oxygen and mechanical ventilation, but their use during the first weeks of life is associated with worse neurological outcome. Adequate nutrition plays an important role in lung injury protection and recovery. Infants with severe BPD frequently develop pulmonary hypertension and may benefit from the use of pulmonary vasodilators. Outpatient management must be carefully planned and carried out by experienced multidisciplinary teams. Social and financial issues must be addressed with the family and caregivers. Home oxygen and mechanical ventilation therapy are used frequently after discharge and require specialized staff and equipment. Maintenance of oxygenation and proper nutritional support are critical aspects in the post-discharge management of these infants. Immunizations and RSV prevention are also important to prevent infections in these vulnerable immunocompromised patients.

Adrenal Cortex Hormones↗

PubMed2002

Cuticular hydrocarbons suggest three lineages in Reticulitermes (Isoptera: Rhinotermitidae) from North America.

Cuticular hydrocarbon mixtures can be used to discriminate insect taxa. They have utility for determining phylogenetic relationships where they are independent characters with discrete states and represent a hierarchical distribution of shared, derived characters. We report inferred degrees of relatedness among the chemical phenotypes of Reticulitermes from PAUP (phylogenetic analysis using parsimony) analyses of cuticular hydrocarbon characters. One hundred and forty-one Reticulitermes colonies collected from California, Georgia, New Mexico, Arizona and Nevada were used. Initial maximum parsimony analyses sorted the 141 colonies into 26 chemical phenotypes. Subsequent analyses, using the ancestral species Coptotermes formosanus and Heterotermes sp. as outgroups, sorted Reticulitermes taxa into three major lineages, each characterized by a different set of dominant methyl-branched or unsaturated hydrocarbon components. Reticulitermes in lineage I have cuticular hydrocarbon mixtures with a preponderance of internally branched monomethylalkanes and 11,15-dimethylalkanes. Those in lineage II are defined by a preponderance of 5-methylalkanes and 5,17-dimethylalkanes. Taxa in lineage III are characterized by the predominance of olefins and a relative paucity of n-alkanes and methyl-branched alkanes. Bootstrap analyses and decay indices provided statistical support and robustness for these chemical-based relationships.

Animals↗

PubMed2006

Antimicrobial activity and spectrum of cefovecin, a new extended- spectrum cephalosporin, against pathogens collected from dogs and cats in Europe and North America.

Cefovecin is a new extended-spectrum semisynthetic cephalosporin indicated for the treatment of bacterial infections in dogs and cats. This study evaluated the in vitro activity and spectrum of cefovecin against 2,641 recent clinical isolates (1,660 canine and 981 feline isolates) from Europe and the United States. MIC determinations against cefovecin and other reference antimicrobials were performed by broth microdilution methods recommended by the Clinical and Laboratory Standards Institute (CLSI, formerly NCCLS). Cefovecin demonstrated bactericidal activity against both gram-positive and gram-negative pathogens. Cefovecin exhibited in vitro activity against all major aerobic and anaerobic bacterial pathogens associated with skin, urinary tract, and periodontal infections in dogs and cats. The MIC90 values of cefovecin against Staphylococcus intermedius, Escherichia coli, and Pasteurella multocida were 0.25 microg/ml, 1.0 microg/ml, and 0.06 microg/ml, respectively. No significant differences were observed in terms of the activities of cefovecin against pathogens from different European countries and against pathogens of European and U.S. origin.

Animals↗

PubMed2006

The neurosurgical workforce in North America: a critical review of gender issues.

OBJECTIVE: The role of women in Western society has changed dramatically in the past several decades. Despite this, many gender disparities still exist for professionals in the health care sector. In neurosurgery, a disproportionately small percentage of the workforce in the United States and Canada is female. These figures are lower than most reported in other medical specialties. This review critically examines factors that may be influencing women's ability to advance in demanding subspecialties such as neurosurgery. METHODS: The literature on women in medicine, and surgery in particular, were reviewed to identify different issues facing women currently in practice in neurosurgery. In addition, the concerns of prospective trainees were examined. RESULTS: There remain many challenges for women entering neurosurgery, including unique lifestyle concerns, limited mentorship, out-dated career programs, and deep-seeded societal beliefs. Discrimination and harassment are also contributing factors. CONCLUSION: If neurosurgery is to continue to progress as a subspecialty, the issue of gender inequality needs to be scrutinized more closely. Innovative programs must be developed to meet the needs of current female faculty members and to ensure attracting the brightest individuals of both genders into a career in neurosurgery.

Career Mobility↗

PubMed2003

Prehospital management of acute ST-elevation myocardial infarction: a time for reappraisal in North America.

Although the medical and technologic revolution in the last 3 decades has improved clinical outcome in patients sustaining acute ST-elevation myocardial infarction (STEMI), residual morbidity and mortality remain major health concerns. The critical roles of temporal delay and optimal sustained patency as modulators of successful reperfusion have been repeatedly demonstrated, and investigation into the ideal interface between pharmacologic and mechanical reperfusion continues. Despite physician awareness and patient education programs, time from symptom onset to treatment in STEMI remains stalled at approximately 3 hours for pharmacologic reperfusion, as documented in major clinical trials. Multifaceted improvements with advanced paramedic training, transmittable 12-lead electrocardiograms, and bolus fibrinolytics facilitate potential prehospital diagnosis and treatment. Thus, as we proceed into the 21st century, it is essential to reexamine strategies for addressing these and other issues relating to the process of delivering optimal care to most patients with STEMI. Especially notable are the opportunities provided through prehospital management with initiation of therapy, triage to appropriate hospitals, or both as major potential avenues to further enhance patient outcomes. We review past research in prehospital therapy for STEMI and practical impediments to implementation to establish a framework for interpretation of future developments.

Clinical Trials as Topic↗

PubMed2005

Patterns of mercury deposition and concentration in northeastern North America (1996-2002).

Data from 13 National Atmospheric Deposition Program Mercury Monitor Network (NADP/ MDN) monitoring stations (1996-2002) and the Underhill (VT) event-based monitoring site (1993-2002) were evaluated for spatial and temporal trends. More precipitation and mercury deposition occurred in the southern and coastal MDN sites, except for the Underhill site, which received more mercury deposition than surrounding sites. Precipitation patterns varied. Regionally, higher concentrations of mercury were recorded during the late spring and summer months. Several sub-regional clusters of MDN sites were evident, based on mercury deposition patterns. In general, more mercury was deposited during the summer months. "Enhanced" weekly deposition (> 250 ng/m2) and distinct seasonal deposition patterns were evident at all MDN sites. Regionally, high depositional periods contributed significantly to annual loads (< 20%- approximately 60%). Southern and coastal sites measured more frequent periods of high deposition than inland sites. Spring and summer "enhanced" deposition may be important contributing factors to mercury bioaccumulation during the growing season. Recent regional reductions of mercury emissions were not reflected in the regional mercury concentration or deposition data. Few sites showed linear relations between the concentration of mercury in precipitation and acid rain co-contaminants (sulfates and nitrates).

Air Pollutants↗

PubMed2003

The prevalence and predictors of helmet use by skiers and snowboarders at ski areas in western North America in 2001.

BACKGROUND: Helmets may protect the heads of skiers and snowboarders. The prevalence of helmet use by these groups was estimated. METHODS: Helmet use was observed in face-to-face surveys (N = 2,978) on sun protection at 28 ski areas in Alaska, California, Colorado, Idaho, Montana, New Mexico, Nevada, Oregon, Utah, and British Columbia (0.7% refusal rate) from January to April 2001. RESULTS: Helmets were worn by 12.1% (95% confidence interval [CI], 11.0-13.3) of the sample. Use was highest among guests who skied or snowboarded more frequently (fourth quartile vs. first quartile, odds ratio [OR] = 11.998 [95% CI, 6.774-21.251]; third vs. first, OR = 5.556 [95% CI, 3.119-9.896]; second vs. first, OR = 2.186 [95% CI, 1.162-4.112]), were experts (OR = 3.326 [95% CI, 1.297-8.528]), used snowboards (OR = 2.301 [95% CI, 1.731-3.058]), and were more educated (college graduate, OR = 2.167 [95% CI, 1.271-3.695]; some college, OR = 1.969 [95% CI, 1.130-3.431]). CONCLUSION: Helmet use was generally low but may be high enough by experts, snowboarders, and in the central Rocky Mountains to produce a norm stimulating further adoption.

Adult↗

PubMed2004

Sources of toxaphene and other organochlorine pesticides in North America as determined by air measurements and potential source contribution function analyses.

A previous study from our laboratory suggested that the Gulf of Mexico might be a potential source of toxaphene to the United States. To investigate this hypothesis, we measured gas-phase toxaphene concentrations at sampling sites ranging from northern Michigan to southern Louisiana; the samples were collected every 12 days during 2002-2003. We also measured other organochlorine pesticides in these samples. We identified major source regions of each pesticide group using the potential source contribution function model with the Clausius-Clapeyron equation defining the criterion levels. These results indicate that southern cotton farms are major sources of both toxaphene and p,p'-DDE to the northern United States. In fact, there is a very strong correlation of toxaphene and DDE atmospheric concentrations at all sites, further indicating a common source. On the other hand, the Gulf of Mexico is not a major source of toxaphene or DDE. DDE's source region is similar to that of toxaphene but somewhat broader, reflecting DDT's historically more diversified use. The level of endosulfan in the atmosphere at all of the sites was similar, and PSCF modeling indicated that its sources were all toward the east of the sampling sites.

Air Movements↗

PubMed1998

Prevalence of antimicrobial resistance among respiratory tract isolates of Streptococcus pneumoniae in North America: 1997 results from the SENTRY antimicrobial surveillance program.

As part of the ongoing multinational SENTRY antimicrobial resistance surveillance program, a total of 1,047 respiratory tract isolates of Streptococcus pneumoniae, 845 from 27 United States medical centers and 202 from seven Canadian institutions, were collected between February and June 1997 and characterized in a central laboratory. In the United States, the overall percentages of penicillin-intermediate strains and strains with high-level resistance to penicillin were 27.8% and 16.0%, respectively. In Canada, these values were 21.8% and 8.4%, respectively. Among the 31 centers in the United States and Canada that contributed at least 19 isolates, the combined rate of intermediate plus resistant strains varied between 24.0% and 67.8%. The in vitro activity of 19 other antimicrobials was assessed against all study isolates. Overall rates of resistance among selected agents in the United States and Canada, respectively, were as follows: amoxicillin, 18.1% and 10.5%; cefaclor, 38.3% and 26.2%; cefuroxime, 19.5% and 12.9%; cefpodoxime, 18.6% and 11.4%; cefepime, 8.2% and 4.5%; cefotaxime, 4.0% and 3.0%; macrolides (i.e., erythromycin, azithromycin, and clarithromycin), 11.7%-14.3% and 5.0%-7.4%; clindamycin, 3.5% and 3.5%; chloramphenicol, 3.9% and 4.0%; tetracycline, 10.2% and 10.9%; and trimethoprim-sulfamethoxazole, 19.8% and 15.8%.

Drug Resistance, Microbial↗

PubMed1998

Species of Myxobolus (Myxozoa) from the bulbus arteriosus of centrarchid fishes in North America, with a description of two new species.

Three species of Myxobolus (Myxozoa, Myxosporea) occur in heart tissue of centrarchids. Myxobolus paralintoni Li and Desser, 1985 from Lepomis gibbosus in Algonquin Park and in Lake Erie, Ontario, has subcircular spores (in plane of spore length) in frontal view (11-13 microm long, 9-10 microm wide, and 5 microm thick) with a width-to-length ratio of 1:1.2. Myxobolus jollimorei n. sp. from Lepomis macrochirus in Lake Erie and in the Pascagoula River System, Mississippi, has subcircular spores (in plane of spore width) in frontal view (10.0-11.5 microm long, 12.0-14.5 microm wide, and 6.5-8.0 microm thick) with a width-to-length ratio of 1:0.8. Myxobolus manueli n. sp. from Pomoxis nigromaculatus in Lake Erie has spores (10-11 microm long, 8-10 microm wide, and 6.5-7.0 microm thick) that are nearly circular in frontal view but that have 2 distinct sublateral knobs along the sutural ridge and a width-to-length ratio of 1:1.2. All 3 species occur in the bulbus arteriosus of their hosts where they form small, saucer-shaped pseudocysts. Free spores were found free in the lumen of the heart and bulbus arteriosus, in bile, and in kidney tissue presses.

Animals↗

PubMed2000

Update on ISI survey: Europe, North America and South America.

It is well known that the diagnostic process in amyotrophic lateral sclerosis (ALS) may be excessively prolonged, with negative consequences for the patients and their families. The ISIS study assessed the diagnostic process in 201 patients affected by ALS from 6 different countries (Argentina, Brazil, Germany, Italy, Spain and USA). The median time from onset to diagnosis ranged from 12 months in Spain to 17 months in Italy. The median time for patients to have a first consultation with a physician was 2 months (range: 1-1.5 months) and with a neurologist was 6-9 months. The median time needed for the neurologist to confirm the diagnosis was 3-6 months. Electromyography was performed on more than 90% of patients in all countries, and was requested in most cases by the neurologist. False-negative diagnoses were quite frequent (45% of cases with at least one other diagnosis evoked at any time before the ALS diagnosis) and were made by neurologists in 28% of cases, by general practitioners in 29% of cases, by orthopaedic surgeons in 26% of cases and by other specialists in 18% of cases. The reasons for misdiagnoses were: presence of other diseases to which the symptomatology was attributed, misinterpretation of examinations, and lack of familiarity with ALS.

Cross-Cultural Comparison↗