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At least 631 records · Page 35Linked to original sources
PubMed1984

Tree pollen allergy. I. Features of plant geography and pollen counts.

The distribution of trees and bushes in Sweden (viz. lignoses) of possible allergic importance is presented and comments made on analyses of pollen counts of lignose taxa from different parts of the country. Based on these data, 20 lignose taxa were selected for an allergen panel and used in a multi-centre study covering Sweden with the aim of revealing the pattern of sensitization to these plants among sufferers of springtime hay fever.

Humans↗
PubMed2005

Population differentiation and hybrid success in Campanula americana: geography and genome size.

Populations within a species may diverge through genetic drift and natural selection. Few studies report on population differentiation in autopolyploids where multiple gene copies and the ratio of cytoplasmic to nuclear genes differ from diploids and may influence divergence. In autotetraploid Campanula americana we created hybrids between populations that differed in geographic proximity and genome size. Differences in genome size (up to 6.5%) did not influence hybrid performance. In contrast, hybrid performance was strongly influenced by population proximity. F1 hybrids between distant populations performed poorly relative to their parents while hybrids between proximate populations outperformed their parents. Outbreeding depression was strongest for juvenile traits. The expression of outbreeding depression often differed between reciprocal hybrids indicating interactions between nuclear and cytoplasmic genes contribute to population differentiation. Because plants were grown under greenhouse conditions, the outbreeding depression was likely due to genetic (underdominance or loss of additive-by-additive epistasis) rather than ecological factors.

Biological Evolution↗
PubMed1985

A personality theory of U.S. migration geography.

"Neoclassical models of migration fail to account adequately for individual differences in propensity to migrate, rates of emigration from states and cities, and the generally high rates of population circulation common in the United States. This article proposes that migration propensity is related to an individual's personality. Using the facts that personality traits are generationally regenerative, both through inheritance and culture, and that the United States was settled in a series of migration waves from east to west, this theory predicts a spatial structuring of emigration rates which closely correspond to actual rates for states and major cities."

Americas↗
PubMed1999

Helicobacter pylori virulence and genetic geography.

Isolated for the first time in 1982 from human gastric biopsy, Helicobacter pylori is responsible for gastritis, peptic ulcer, and gastric cancer. A pathogenicity island acquired by horizontal transfer, coding for a type IV secretion system, is a major determinant of virulence. The infection is now treated with antibiotics, and vaccines are in preparation. The geographic distribution suggests coevolution of man and Helicobacter pylori.

Adult↗
PubMed1999

Geography of intestinal permeability and absorption.

BACKGROUND: Intestinal morphology and function vary geographically. AIMS: These functions were assessed in asymptomatic volunteers in European, North American, Middle Eastern, Asian, African, and Caribbean countries. METHODS: Five hour urine collections were obtained from each subject following ingestion of a 100 ml iso-osmolar test solution containing 3-0-methyl-D-glucose, D-xylose, L-rhamnose, and lactulose after an overnight fast, to assess active (3-0-methyl-D-glucose) and passive (D-xylose) carrier mediated, and non-mediated (L-rhamnose) absorption capacity, as well as intestinal permeability (lactulose:rhamnose ratio). RESULTS: A comparison of results for subjects from tropical countries (n=218) with those resident in the combined temperate and subtropical region (Europe, United States, Qatar) (n=224) showed significant differences. Residents in tropical areas had a higher mean lactulose:rhamnose ratio and lower mean five hour recoveries of 3-0-methyl-D-glucose, D-xylose, and L-rhamnose, indicating higher intestinal permeability and lower absorptive capacity. Investigation of visiting residents suggested that differences in intestinal permeability and absorptive capacity were related to the area of residence. Subjects from Texas and Qatar, although comprised of several ethnic groups and resident in a subtropical area, showed no significant difference from European subjects. CONCLUSIONS: There are clearly demarcated variations in intestinal permeability and absorptive capacity affecting asymptomatic residents of different geographical areas which correspond with the condition described as tropical enteropathy. Results suggest the importance of environmental factors. The parameters investigated may be relevant to the predisposition of the indigenous population and travellers to diarrhoeal illness and malnutrition. Intestinal function in patients from the tropics may be difficult to interpret, but should take into account the range of values found in the asymptomatic normal population.

Adult↗
PubMed2004

The geography of the highest mortality areas in Spain: a striking cluster in the southwestern region of the country.

AIMS: To determine the areas of Spain with the most increased mortality risk. METHODS: Age adjusted relative risk of death by gender was estimated in each of 2218 small areas of the country using a non-parametric empirical Bayes method. To determine areas with "significantly increased risk" a Poisson based score test was used. RESULTS: Mapping of the highest risk areas showed a striking geographical clustering in the southwestern region of the country. This region, comprising 8% of the Spanish population, accounts for about one third (2884 deaths) of the total excess mortality.

Cluster Analysis↗