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PubMed2003

Molecular and serological aspects of HBsAg-negative hepatitis B virus infections in North America.

A few hepatitis B virus (HBV) infections are characterized by the presence of HBV DNA in serum or liver tissue, or both, in the absence of detectable hepatitis B surface antigen (HBsAg) in serum. However, such infections have rarely been described previously in North American patients. In the present study, 31 hepatocellular carcinoma (HCC) patients from the United States and Canada who had no detectable HBsAg in their serum were studied. In these 31 HBsAg-negative HCC patients, HBV DNA was detected in HCC and/or in adjacent nontumorous liver tissue using nested polymerase chain reaction (PCR) in 5/9 (56%) patients from the United States and in 12/22 (55%) from Canada. The 17 HBV DNA-positive/HBsAg-negative patients from the United States and Canada included 9 without any serological markers for HBV and 8 with detectable antibodies to hepatitis B core antigen. In these patients, HBV genotype C was the most prevalent genotype (11/17; 64%). HBV genotypes have not been previously reported in HCC patients from North America. Replicative intermediate forms of HBV (covalently closed circular HBV DNA) were detected in 2/17 (12%) HBV DNA-positive/HBsAg-negative patients, indicating that at least two of these patients had actively replicating HBV infections. The use of tests to detect HBV DNA permitted the identification of HBV infections in HBsAg-negative HCC patients from North America. Among these patients, those with antibody to hepatitis C virus (HCV) would otherwise have been designated "HCV-associated HCCs" based on serological tests alone. These findings provide a new perspective on determining the possible viral etiologies of HCCs in North America.

Amino Acid Sequence↗
PubMed1994

Brazilian immigration to North America.

"This article is a comparative study of Brazilian immigration to Canada and the United States. Analysis of recently collected data in Toronto, Ontario and in a medium-size U.S. community facilitated the examination of the adaptation and adjustment experiences of a new group of immigrants to North America. This article begins with a discussion of the origins of this recent immigrant group and its rapid expansion. Next, it focuses on the labor force activities of Brazilian immigrants and compares and contrasts their experiences in the United States and Canada. A final section examines social adaptation in North America by exploring linguistic and cultural dimensions. This article closes with a section on the future aspirations of these immigrants."

Acculturation↗
PubMed2005

Mercury in northeastern North America: a synthesis of existing databases.

A large number of datasets representing mercury (Hg) levels in northeastern North America were assembled in a standardized format between 2000 and 2003. Based on support from the Northeastern States Research Cooperative, scientists annually gathered and developed an operational template to collaboratively analyze and interpret these data for a series of peer-reviewed publications. The diverse group covered Hg policy connections, Hg in air, sediment and surface water, Hg in biota, and Hg collection, assessment and monitoring tools. A site-specific application of these Hg data is provided to demonstrate the importance of well-placed air monitoring stations, the need for integrative multimedia data sets, and the complexity of linking abiotic and biotic Hg compartments. Demonstrated is the ubiquitous nature of Hg and methylmercury availability and how its heterogeneous distribution is now relatively well understood for northeastern North America.

Animals↗
PubMed2001

Acupuncture in an outpatient clinic in China: a comparison with the use of acupuncture in North America.

BACKGROUND: The National Institutes of Health Consensus Panel on Acupuncture has listed as a priority the study comparing indications and patterns of use of acupuncture in different countries. METHODS: I visited an outpatient acupuncture clinic in China and reviewed the clinical files. A MEDLINE search was done to compare the use of acupuncture in North America and China. RESULTS: The most common disorder treated in the clinic was musculoskeletal pain. Less common indications included stroke rehabilitation, Bell's palsy, cholelithiasis, tinnitus, insomnia, migraine, and visceral pain. In North America, acupuncture is primarily for pain relief. Other uses include stroke rehabilitation, various emetic problems, migraine, and various addictions. CONCLUSIONS: Acupuncture is most frequently used in China and North America for pain relief. Other common indications include peripheral nerve palsy, peripheral nerve neuralgia, stroke rehabilitation, psychoemotional disorders, migraine, visceral pain, emesis, asthma, and tinnitus. Acupuncture for cholelithiasis in China but not in the United States suggests a novel use of this modality.

Acupuncture Therapy↗
PubMed2002

Reports of presumptive brown recluse spider bites reinforce improbable diagnosis in regions of North America where the spider is not endemic.

Envenomations by the brown recluse spider have been reported throughout North America, despite the fact that the spider's range is limited to the South and central Midwest of the United States. Several of these medical reports have originated from regions of nonendemicity where the spider has never or rarely been documented and brown recluse spider populations are unknown. In most of these reports, no spider is positively identified in association with the dermonecrotic wound, and diagnosis has been based on clinical examination findings. Considering the extreme rarity of brown recluse spiders in areas of nonendemicity, the diagnosis of a presumptive bite is a misdiagnosis that reinforces the assumption that brown recluse spiders are common local etiologic agents of necrosis. There are many medical conditions of diverse origin that have been misdiagnosed as brown recluse spider bites, some of which can be fatal or debilitating. Physicians' awareness of these conditions will increase diagnostic accuracy in areas of North America where bites from brown recluse spiders are improbable.

Diagnostic Errors↗
PubMed1991

Mammalian extinctions in the late Pleistocene of northern Eurasia and North America.

The 'mass extinctions' at the end of the Pleistocene were unique, both in the Pleistocene and earlier in the geological record, in that the species lost were nearly all large terrestrial mammals. Although a global phenomenon, late Pleistocene extinctions were most severe in North America, South America and Australia, and moderate in northern Eurasia (Europe plus Soviet Asia). In Africa, where nearly all of the late Pleistocene 'megafauna' survives to the present day, losses were slight. Ruling out epidemic disease or cosmic catastrophe, the contending hypotheses to explain late Pleistocene extinctions are: (a) failure to adapt to climatic/environmental change; and (b) extermination by human hunters ('prehistoric overkill'). This review focuses on extinctions in northern Eurasia (mainly Europe) in comparison with North America. In addition to reviewing the faunal evidence, the highly relevant environmental and archaeological backgrounds are summarized. The latest survival dates of extinct species are estimated from stratigraphic occurrences of fossil remains, radiocarbon dates, or association with archaeological industries. The Middle and Upper Pleistocene (ca. 700,000-10,000 BP) in northern Eurasia and North America was a time of constantly changing climate, ranging from phases of extensive glaciation in cold stages, to temperate periods (interglacials). In the Lateglacial (ca. 15,000-10,000 BP), during which most extinctions occurred, there was a major reorganization of vegetation, mainly involving the replacement of open vegetation by forests. These changes were more profound than earlier in the Last Cold Stage, but similar in nature to vegetational changes that took place at previous cold stage/interglacial transitions. The archaeological record shows that humans have been present in Europe since the early Middle Pleistocene. The arrival in Europe ca. 35,000 BP of 'anatomically modern humans', with their technologically more advanced upper palaeolithic industries, was a 'quantum leap' in human history. Extinctions occurred throughout the European Pleistocene, but until the late Pleistocene most losses were replaced by the evolution or immigration of new species, and most of those lost without replacement were small mammals. In marked contrast, extinctions without replacement in the late Pleistocene were almost entirely confined to the largest mammals (greater than 1000 kg) and some medium-large species (100-1000 kg).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1986

Peptide mapping of the group-specific antigens from the Australian bluetongue virus (BTV-20) and serotypes from southern Africa and North America.

The Australian bluetongue virus (BTV-20) was compared with six serotypes isolated in southern Africa and North America by peptide mapping of the virus proteins with group antigen properties. The p7 group antigens from each of the seven serotypes analysed did not have identical primary structures and a comparison of shared and unique tryptic peptides has been used as a means of estimating virus relationships. Whereas serological studies have suggested that BTV-20 is closely related to BTV serotypes 4 and 17, comparative peptide mapping of p7 indicates a different set of relationships with viruses from both southern Africa and North America. In contrast with cross-immune precipitation results, peptide mapping of p3 suggest that this protein is not a group specific antigen.

Antigens, Viral↗
PubMedDate not supplied

[Brazilian migration to North America].

"This article is a comparative study of Brazilian immigration to Canada and the United States. Analyses of recently collected data, in Toronto, Ontario, as well as in a medium sized U.S. community permit this study to examine the adaptation and adjustment experiences of a new group of immigrants to North America. This article begins with a discussion of the origins of this recent immigrant group, and its rapid expansion. Next, this study focuses on the labor force activities of Brazilian immigrants and compares and contrasts their experiences in the U.S. and Canada. A final section examines social adaptation in North America by exploring linguistic and cultural dimensions." (SUMMARY IN ENG)

Acculturation↗
PubMed1997

Wood dust and nasal cancer risk. A review of the evidence from North America.

In this article, biomedical literature assessing risks of nasal cancer and nonmalignant nasal pathology among woodworkers in North America is reviewed in detail and contrasted with experience from Europe and elsewhere. Exceptionally high rates of nasal adenocarcinoma have occurred among European hardwood furniture workers, but the epidemiologic evidence documents a disparity in findings between North America and Europe. Cohort studies of American wood-dust-exposed groups do not reveal excesses of nasal cancer, and wood-dust associations from US and Canadian case-control studies of nasal cancer tend not to be strong and differ across studies. Quantitative wood-dust exposure data are generally unavailable, but general dose information in European studies suggests that the excess risk of nasal cancer is associated with high levels of exposure. There is also an inconsistent association between wood-dust exposure per se and mucostasis or nasal histologic changes, and the mucostasis/metaplasia/dysplasia route to nasal cancer is still an unverified hypothesis. Considering the totality of evidence on the risk of cancer in exposed workers, it appears that wood-dust-related nasal adenocarcinoma essentially can be eliminated in Europe and its occurrence prevented in the United States if wood-dust exposures do not exceed an 8-hour time-weighted average 5 mg/m3 standard.

Adenocarcinoma↗
PubMedDate not supplied

Costs and health effects of breast cancer interventions in epidemiologically different regions of Africa, North America, and Asia.

We estimated the costs and health effects of treating stage I, II, III, and IV breast cancer individually, of treating all stages, and of introducing an extensive cancer control program (treating all stages plus early stage diagnosis) in three epidemiologically different world regions--Africa, North America, and Asia. We developed a mathematical simulation model of breast cancer using the stage distribution and case fatality rates in the presence and absence of treatment as predictors of survival. Outcome measures were life-years adjusted for disability (DALYs), costs (in 2000 U.S. dollars) of treatment and follow-up, and cost-effectiveness ratios (CERs; in dollars per DALY averted). Sensitivity analyses were performed to determine the robustness of the results. Treating patients with stage I breast cancer resulted in 23.41, 12.25, and 19.25 DALYs averted per patient in Africa, North America, and Asia, respectively. The corresponding average CERs compared with no intervention were 78 U.S. dollars , 1,960 U.S. dollars, and 62 U.S. dollars per DALY averted. The number of DALYs averted per patient decreased with stage; the value was lowest for stage IV treatment (0.18-0.19), with average CERs of 4,986 U.S. dollars in Africa, 70,380 U.S. dollars in North America, and 3,510 U.S. dollars per DALY averted in Asia. An extensive breast cancer program resulted in 16.14, 12.91, and 12.58 DALYs averted per patient and average CERs of 75 U.S. dollars, 915 U.S. dollars, and 75 U.S. dollars per DALY averted. Outcomes were most sensitive to case fatality rates for untreated patients, but varying model assumptions did not change the conclusions. These findings suggest that treating stage I disease and introducing an extensive breast cancer program are the most cost-effective breast cancer interventions.

Africa↗
PubMed2001

Barley yellow rust in North America.

Yellow rust of barley is an invasive disease that was found in the past 10 years in North America. The causal agent, Puccinia striiformis f. sp. hordei, was introduced into Colombia, South America, from Europe in 1975. It spread to all major barley-producing areas in South America by 1982. In 1988 it was found in Mexico and in 1991 in Texas. Since then it has been found in all major barley-producing areas of the American West. Originally described as race (R) 24, barley yellow rust in North America is now known to be a very heterogeneous population. Resistance has been identified, evaluated, and is being introduced into commercial malting and other barley cultivars. Cultural and chemical controls are effective and available. An integrated approach using general field resistance and other tactics is described for sustainable management of barley yellow rust.

Agriculture↗
PubMed2006

Seroprevalence of feline leukemia virus and feline immunodeficiency virus infection among cats in North America and risk factors for seropositivity.

OBJECTIVE: To determine seroprevalence of FeLV and FIV infection among cats in North America and risk factors for seropositivity. DESIGN: Prospective cross-sectional survey. ANIMALS: 18,038 cats tested at 345 veterinary clinics (n=9,970) and 145 animal shelters (8,068) between August and November 2004. PROCEDURE: Cats were tested with a point-of-care ELISA for FeLV antigen and FIV antibody. A multivariable random effects logistic regression model was used to identify risk factors significantly associated with seropositivity while accounting for clinic-to-clinic (or shelter) variability. RESULTS: 409 (2.3%) cats were seropositive for FeLV antigen, and 446 (2.5%) cats were seropositive for FIV antibody; 58 (0.3%) cats were seropositive for infection with both viruses. Multivariable analysis indicated that age, sex, health status, and cat lifestyle and source were significantly associated with risk of seropositivity, with adults more likely to be seropositive than juveniles (adjusted odds ratios [ORs], 2.5 and 2.05 for FeLV and FIV seropositivity, respectively), sexually intact adult males more likely to be seropositive than sexually intact adult females (adjusted ORs, 2.4 and 4.66), and outdoor cats that were sick at the time of testing more likely to be seropositive than healthy indoor cats (adjusted ORs, 8.89 and 11.3). CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that certain characteristics, such as age, sex, health status, and lifestyle, are associated with risk of FeLV and FIV seropositivity among cats in North America. However, cats in all categories were found to be at risk for infection, and current guidelines to test all cats at the time of acquisition and again during illness should be followed.

Age Factors↗
PubMed2004

West Nile virus and North America: an unfolding story.

Before the introduction of the West Nile virus (WNV) into the United States of America (USA) in 1999, conditions in North America were ideal for an arboviral epidemic. Such factors as the large, susceptible and non-immune animal and human populations, the presence of competent vectors, increasing international travel and commerce, existing methods for rapid dissemination and an ill-prepared animal and public health infrastructure all combined to create the essential elements for a severe animal and public health crisis--the 'perfect microbial storm'. The introduction of WNV into New York City was the final factor, serving as the catalyst to initiate one of the most significant epidemics in the USA. The spread of WNV across the country resulted in very large populations of wildlife, equines and people being exposed and infected. The epidemic is still not fully understood and its character continues to change and adapt. The recent recognition of a number of non-vector modes of transmission has revealed the disease as a greater threat and more difficult to control than first thought. West Nile virus gives every indication that it will become a permanent part of the 'medical landscape' of the USA, continuing to threaten wildlife, domestic animals and humans as a now endemic disease. This paper discusses the features of this extraordinary epidemic, and emphasises the need for an integrated surveillance system, greater diagnostic capacity and improved control strategies.

Animals↗
PubMed2002

Molecular phylogeography of common garter snakes (Thamnophis sirtalis) in western North America: implications for regional historical forces.

Complete ND2 and partial ND4 and cytochrome b mitochondrial DNA (mtDNA) sequences were analysed to evaluate the phylogeographic patterns of common garter snakes (Thamnophis sirtalis) in western North America. This species is widely distributed throughout North America, and exhibits extensive phenotypic variation in the westernmost part of its range. The overall phylogeographic pattern based on mtDNA sequences is concordant with results from studies of other species in this region, implicating historical vicariant processes during the Pleistocene and indicating bottleneck effects of recent dispersal into postglacial habitat. Indeed, the topology is statistically consistent with the hypothesis of both southern (Great Basin and California) and northern (Haida Gwaii) refugia. Specifically, we identified genetic breaks among three major clades: Northwest Coastal populations, Intermountain populations, and all California populations. The California clade contained the only other well-supported branching patterns detected; relationships among populations within the two northern clades were indistinguishable. These molecular splits contrast sharply with all prior geographical analyses of phenotypic variation in T. sirtalis in this region. Our results suggest that the extensive phenotypic variation in western T. sirtalis has been shaped more by local evolutionary forces than by shared common ancestry. Consequently, we consider all morphologically based subspecies designations of T. sirtalis in this region invalid because they do not reflect reciprocal monophyly of the mtDNA sequences.

Animals↗
PubMed2000

Stimulated influences of Lake Agassiz on the climate of central North America 11,000 years ago

Eleven thousand years ago, large lakes existed in central and eastern North America along the margin of the Laurentide Ice Sheet. The large-scale North American climate at this time has been simulated with atmospheric general circulation models, but these relatively coarse global models do not resolve potentially important features of the mesoscale circulation that arise from interactions among the atmosphere, ice sheet, and proglacial lakes. Here we present simulations of the climate of central and eastern North America 11,000 years ago with a high-resolution, regional climate model nested within a general circulation model. The simulated climate is in general agreement with that inferred from palaeoecological evidence. Our experiments indicate that through mesoscale atmospheric feedbacks, the annual delivery of moisture to the Laurentide Ice Sheet was diminished at times of a large, cold Lake Agassiz relative to periods of lower lake stands. The resulting changes in the mass balance of the ice sheet may have contributed to fluctuations of the ice margin, thus affecting the routing of fresh water to the North Atlantic Ocean. A retreating ice margin during periods of high lake level may have opened an outlet for discharge of Lake Agassiz into the North Atlantic. A subsequent advance of the ice margin due to greater moisture delivery associated with a low lake level could have dammed the outlet, thereby reducing discharge to the North Atlantic. These variations may have been decisive in causing the Younger Dryas cold event.

Journal Article↗
PubMedDate not supplied

Prevalence of primary breed-related cataracts in the dog in North America.

The objective of the study was to determine the prevalence of cataracts in dogs presented to veterinary medical teaching hospitals in North America between 1964 and 2003. A retrospective study of all dogs presented with cataracts to veterinary medical teaching hospitals in North America between 1964 and 2003 was conducted to determine cataract prevalence. The different decades, breeds, gender, and age at time of presentation with cataract were compared. The prevalence of dogs presented with cataract varied by decade and ranged from 0.95% (1964-73), 1.88% (1974-83), 2.42% (1994-2003), to 3.5% (1984-93). The total number of dogs presented with cataracts over the 40-year period was 39,229. From 1964 to 2003 the prevalence of cataract formation in this patient population increased by about 255%. Fifty-nine breeds of dogs were affected with cataracts above the baseline prevalence of 1.61% seen in mixed-breed/hybrid dogs. The breeds with the highest cataract prevalence included: Smooth Fox Terrier (11.70%), Havanese (11.57%), Bichon Frise (11.45%), Boston Terrier (11.11%), Miniature Poodle (10.79%), Silky Terrier (10.29%) and Toy Poodle (10.21%). The breeds with the largest number of cataractous dogs during the entire four decades were the Boston Terrier (11.11%), Miniature Poodle (10.79%), American Cocker Spaniel (8.77%), Standard Poodle (7.00%), and Miniature Schnauzer (4.98%). Gender ratios of cataractous dogs seemed to affect limited breeds. Age of presentation with cataract diagnosis varied among several breeds. In the mixed-breed/hybrid baseline population, cataract formation appeared to be age related with a higher frequency of cataract formation in dogs after 4-7 years. Cataract formation is one of the most prevalent eye diseases in the dog population, and in about 60 breeds of dogs the prevalence of cataract exceeds that of the baseline mixed-breed/hybrid group. The prevalence of cataract is also influenced by age in most purebred dogs and affects 16.80% of the 7-15+-year-old mixed-breed/hybrid dog population. Total and age-related cataract prevalence in dogs seems very similar to that in man.

Animals↗
PubMed1998

Hepatocellular carcinoma in North America: a multiinstitutional study of appearance on T1-weighted, T2-weighted, and serial gadolinium-enhanced gradient-echo images.

OBJECTIVE: The purpose of this study was to define the common appearances of hepatocellular carcinoma (HCC) in patients in North America by analyzing T1-weighted, T2-weighted, and serial gadolinium-enhanced gradient-echo images interpreted by radiologists at multiple institutions in North America. MATERIALS AND METHODS: One hundred thirteen consecutive patients with HCC from eight institutions were included in this retrospective case series. Inclusion criteria included MR imaging examinations performed on 1.5-T MR imagers using T1-weighted breath-hold spoiled gradient-echo images, T2-weighted images, and serial gadolinium-enhanced spoiled gradient-echo images. Diagnosis was established by histology in all patients. Images were analyzed retrospectively for lesion count, lesion diameter as less than or equal to 1.5 cm and greater than 1.5 cm, and signal intensity, by individual experienced radiologists at each institution. RESULTS: We found 354 HCC lesions in the 113 patients. Tumors were solitary in 63 patients, multifocal in 45 patients, and diffuse in five patients. Lesion appearance on combined T1-weighted, T2-weighted, and immediate gadolinium-enhanced spoiled gradient-echo images was as follows: 102 lesions (29%) were hypointense on T1-weighted images, were hyperintense on T2-weighted images, and exhibited diffuse heterogeneous enhancement; 52 lesions (15%) were isointense on both T1- and T2-weighted images and exhibited diffuse homogeneous enhancement (all of these lesions measured < or = 1.5 cm in diameter); 50 lesions (14%) were hypointense on T1-weighted images, were hyperintense on T2-weighted images, and exhibited diffuse homogeneous enhancement; 33 lesions (9%) were hypointense on T1-weighted images, were hyperintense on T2-weighted images, and exhibited predominantly peripheral rim enhancement; and 27 lesions (8%) were hypointense on T1-weighted images, were isointense on T2-weighted images, and exhibited diffuse homogeneous enhancement. The remaining 90 lesions showed less common patterns. The appearance of HCCs greater than 1.5 cm and of HCCs less than or equal to 1.5 cm was significantly different (p = .001). The appearance of histologically proven HCCs is separately described. CONCLUSION: The combination of hypointensity on T1-weighted images, hyperintensity on T2-weighted images, and diffuse heterogeneous enhancement was the most common appearance of HCC on MR images in a multiinstitutional patient population in North America. Small HCCs measuring less than or equal to 1.5 cm were frequently isointense on both T1-weighted and T2-weighted images and may be detected on immediate gadolinium-enhanced images only as diffuse homogeneously enhancing lesions.

Adolescent↗
PubMed2004

Pediatric pulmonology: a developmental history in north america.

We describe the development of pediatric pulmonology in North America, from its rudimentary beginning in the early part of the 20th century. Milestones in the history of lung diseases affecting children, such as tuberculosis, cystic fibrosis, asthma, and neonatal lung disease, are discussed. Finally, maturation into a subspecialty recognized by the American Board of Pediatrics is described.

History, 19th Century↗