Source pool geometry and the assembly of continental avifaunas

Classical niche-assembly models propose that the composition of biotic communities in continental landscapes is determined chiefly by the autecology of species, interspecific competition, and the diversity of resources and habitats within a region. In contrast, stochastic models propose that simulation algorithms can replicate the macroecological patterns, if not the mechanisms, of community assembly. Despite fundamental differences in assumptions, both categories of models assume that species are drawn from regional source pools. We explored the implications of source pool geometry on the assembly of avian communities with an analysis of assemblage dispersion fields, which can be visualized by overlaying the geographic ranges of all species that occur in an assemblage. Contours of species richness surrounding focal quadrats illustrate the decay rate of assemblage similarity with distance and the probable geometry of assemblage source pools. We used a geographic database for 2,891 species of South American birds to characterize dispersion fields for assemblages sampled by 1 degrees latitude-longitude quadrats (n = 1,676). We show that the median range size of dispersion fields varies by an order of magnitude across the continent. Because abundance generally correlates with geographic range size within taxonomic groups, the number of individuals per species in avifaunal source pools must also vary by an order of magnitude. Most significantly, dispersion field geometry was surprisingly asymmetrical and exhibited complex geographical patterns that were associated with the distribution of biomes. These results are broadly consistent with the predictions of niche-assembly models but offer little support for stochastic assembly models.     

Limited (6-h) ambulatory blood pressure monitoring is a valid replacement for the office blood pressure by trained nurse clinician in the diagnosis of hypertension

OBJECTIVE: To assess the ability of limited ambulatory blood pressure monitoring as a valid replacement for office blood pressure measurement done to American Heart Association criteria in diagnosing hypertension. METHODS: In all, 105 adults, who had been referred for limited ambulatory blood pressure monitoring, participated in the study. Limited ambulatory blood pressure monitoring consisted of 6 h of blood pressure measurement while ambulatory at the Mayo Clinic, using a SpaceLabs 90207 (SpaceLabs Medical, Issaquah, Washington, USA) collecting six readings per hour for the period of observation. The study participants gave consent for three additional consecutive office blood pressure measurements, using a validated aneroid device, done to American Heart Association criteria, by a single hypertension nurse specialist. RESULTS: Mean systolic blood pressure by limited ambulatory blood pressure monitoring was 137.9+/-14.2 mmHg and for the nurse, 137.9+/-20.1 mmHg. Mean diastolic blood pressure by limited ambulatory blood pressure monitoring was 81.5+/-9.7 mmHg and for the nurse, 74.3+/-11.9 mmHg. The intermethod difference for systolic blood pressure was 0.03+/-12.5 mmHg and diastolic blood pressure, -7.2+/-8.0 mmHg. Using <140/90 as criteria factor, limited ambulatory blood pressure monitoring and the trained nurse agreed 77% of the time on whether the patient was hypertensive. This agreement increased to 81% if the participant's referral blood pressure was >or=140/90. CONCLUSIONS: Limited ambulatory blood pressure monitoring is an excellent replacement for office blood pressure, done to American Heart Association criteria, in diagnosing hypertension. This avoids issues of variability introduced by the observers, such as digit preference and bias, and increases reproducibility of blood pressure measurements. The appropriate normal value for limited ambulatory blood pressure monitoring is <140/90 mmHg compared with <135/85 mmHg used in 24-h ambulatory blood pressure monitoring.     

A mathematical model of optimized radioiodine-131 therapy of Graves' hyperthyroidism

Background

The current status of radioiodine-131 (RaI) dosimetry for Graves' hyperthyroidism is not clear. Recurrent hyperthyroidism and iatrogenic hypothyroidism are two problems which interact such that trying to solve one leads to exacerbation of the other. Optimized RaI therapy has therefore begun to be defined just in terms of early hypothyroidism (ablative therapy) as physicians have given up on reducing hypothyroidism.

Methods

Optimized therapy is evaluated both in terms of the greatest separation of cure rate from hypothyroidism rate (non-ablative therapy) or in terms of early hypothyroidism (ablative therapy) by mathematical modeling of outcome after radioiodine and critically discussing the three common methods of RaI dosing for Graves' disease.

Results

Cure follows a logarithmic relationship to activity administered or absorbed dose, while hypothyroidism follows a linear relationship. The effect of including or omitting factors in the calculation of the administered I–131 activity such as the measured thyroid uptake and effective half-life of RaI or giving extra compensation for gland size is discussed.

Conclusions

Very little benefit can be gained by employing complicated methods of RaI dose selection for non-ablative therapy since the standard activity model shows the best potential for cure and prolonged euthyroidism. For ablative therapy, a standard MBq/g dosing provides the best outcome in terms of cure and early hypothyroidism.     

The potential for Cerenkov luminescence imaging of alpha-emitting radionuclides

Targeted α-emitting drugs are promising for cancer therapy, but cannot be effectively imaged by conventional techniques. Cerenkov luminescence imaging (CLI) has previously been shown capable of imaging β(+)- and β(-)-emitting radionuclides in vivo and could have the potential to image α-emitters. Cerenkov light production from α-emitters is through Compton scattering and from farther down the decay chain. This causes the Cerenkov production to vary in time and depend on sample geometry, complicating the interpretation of CLI images. We used the simulation toolkit Geant4 to predict the Cerenkov light output from five α-emitting radionuclides that have therapeutic potential: (225)Ac, (230)U, (213)Bi, (212)Bi and (212)At. We found that (225)Ac, (213)Bi and (212)Bi produced an order of magnitude more Cerenkov light than (18)F. However, the light from (225)Ac is delayed from the initial decay, possibly decreasing the correlation of the drug and light source. This indicates that CLI will not be helpful in the development of some α-emitting drugs.     

Rickettsial Infections in Southeast Asia: Implications for Local Populace and Febrile Returned Travelers

Rickettsial infections represent a major cause of non-malarial febrile illnesses among the residents of Southeast Asia and returned travelers from that region. There are several challenges in recognition, diagnosis, and management of rickettsioses endemic to Southeast Asia. This review focuses on the prevalent rickettsial infections, namely, murine typhus (Rickettsia typhi), scrub typhus (Orientia tsutsugamushi), and members of spotted fever group rickettsiae. Information on epidemiology and regional variance in the prevalence of rickettsial infections is analyzed. Clinical characteristics of main groups of rickettsioses, unusual presentations, and common pitfalls in diagnosis are further discussed. In particular, relevant epidemiologic and clinical aspects on emerging spotted fever group rickettsiae in the region, such as Rickettsia honei, R. felis, R. japonica, and R. helvetica, are presented. Furthermore, challenges in laboratory diagnosis and management aspects of rickettsial infections unique to Southeast Asia are discussed, and data on emerging resistance to antimicrobial drugs and treatment/prevention options are also reviewed.     

The prevalence of headache with emphasis on tension-type headache in rural Tanzania: a community-based study

The aim of the study was to assess the prevalence of headache with special attention to tension-type headache (TTH) in a rural area in northern Tanzania. A door-to-door study was performed using a standardized and validated questionnaire. A total of 7412 participants were screened. The total headache prevalence during the past year was 12.1%; the overall 1-year prevalence of TTH was 7%; 5% reported episodic TTH and 0.4% chronic TTH. Borderline cases (International Headache Society code 2.3) were described in 1.6%. The prevalence of headache was highest in the 41–50-year-old group in women and in the 61+ age group in men. This is the first account of the prevalence of TTH in a rural Tanzanian population, and shows that headache in general and, more specifically, TTH are prevalent disorders that deserve attention. However, the prevalence of primary headache seems to be lower than in Western countries.     

Monocyte chemoattractant protein 1 and interleukin-8 production in mononuclear cells stimulated by oral microorganisms.

Chemokines are a family of low-molecular-weight proinflammatory cytokines that stimulate recruitment of leukocytes. The chemokines interleukin-8 (IL-8) and monocyte chemoattractant protein 1 (MCP-1) are relatively specific chemoattractants for neutrophils and monocytes, respectively. Chemokine expression contributes to the presence of different leukocyte populations observed in normal and pathologic states. In the present studies, peripheral blood mononuclear cells (PBMC) were stimulated by microbes (Candida albicans, Streptococcus mutans, Porphyromonas gingivalis, and Actinobacillus actinomycetemcomitans) selected based upon their importance as oral pathogens. IL-8 and MCP-1 gene expression and protein release were determined by Northern blot (RNA blot) analysis and enzyme-linked immunosorbent assay. C. albicans, P. gingivalis, and A. actinomycetemcomitans induced high levels of production of both MCP-1 and IL-8. S. mutans was a strong inducer of MCP-1, but it did not stimulate significant production of IL-8. C. albicans, S. mutans, and A. actinomycetemcomitans were 500 to 5,000 times more potent than P. gingivalis in terms of MCP-1 production. In general, the microbe-to-PBMC ratios required for maximum gene expression of MCP-1 were lower than those for IL-8. However, for actual protein release of MCP-1 versus IL-8, differences in the effects of various microbe concentrations were observed only for A. actinomycetemcomitans. These results demonstrate that different oral pathogens induce specific dose-dependent patterns of chemokine gene expression and release. Such patterns may help explain the immunopathology of oral infections, particularly with regard to inflammatory leukocyte recruitment.     

Temperament as a potential predictor of mortality: Evidence from a 41-year prospective study

Psychological factors were hypothesized to influence mortality, in particular, early versus later mortality. To explore the relationship between temperament, a psychological factor, and mortality in a prospective study of 1337 medical students, we constructed a measure portraying three temperament types, using latent class analysis. Death occurred in 113 subjects over 25–41 years of follow-up. In univariate survival analysis, subjects tending to direct tension inward when under stress (Tension-In) had a higher risk of mortality than Tension-Out or Stable types. These associations persisted after adjustment for age, smoking, cholesterol level, and Quetelet Index. The relative risk (RR) of mortality for Tension-In was 1.56 (95% confidence interval, 1.00–2.44) compared with the Stable group. The risk was due entirely to the excess risk in persons under 55 years of age (RR, 2.59; 95% confidence interval, 1.46–4.62); the corresponding risk of death in older persons was 0.66 (0.30–1.48). Thus temperament is a significant risk factor for mortality, in particular, premature death.     

Assessment of carotid plaque vulnerability using structural and geometrical determinants

BACKGROUND: Because many acute cerebral ischemic events are caused by rupture of vulnerable carotid atheroma and subsequent thrombosis, the present study used both idealized and patient-specific carotid atheromatous plaque models to evaluate the effect of structural determinants on stress distributions within plaque. METHODS AND RESULTS: Using a finite element method, structural analysis was performed using models derived from in vivo high-resolution magnetic resonance imaging (MRI) of carotid atheroma in 40 non-consecutive patients (20 symptomatic, 20 asymptomatic). Plaque components were modeled as hyper-elastic materials. The effects of varying fibrous cap thickness, lipid core size and lumen curvature on plaque stress distributions were examined. Lumen curvature and fibrous cap thickness were found to be major determinants of plaque stress. The size of the lipid core did not alter plaque stress significantly when the fibrous cap was relatively thick. The correlation between plaque stress and lumen curvature was significant for both symptomatic (p=0.01; correlation coefficient: 0.689) and asymptomatic patients (p=0.01; correlation coefficient: 0.862). Lumen curvature in plaques of symptomatic patients was significantly larger than those of asymptomatic patients (1.50+/-1.0 mm(-1) vs 1.25+/-0.75 mm(-1); p=0.01). CONCLUSION: Specific plaque morphology (large lumen curvature and thin fibrous cap) is closely related to plaque vulnerability. Structural analysis using high-resolution MRI of carotid atheroma may help in detecting vulnerable atheromatous plaque and aid the risk stratification of patients with carotid disease.