Showing papers by "University of Iceland published in 2006"

The antimicrobial peptide cathelicidin protects the urinary tract against invasive bacterial infection.

Abstract: The urinary tract functions in close proximity to the outside environment, yet must remain free of microbial colonization to avoid disease. The mechanisms for establishing an antimicrobial barrier in this area are not completely understood. Here, we describe the production and function of the cathelicidin antimicrobial peptides LL-37, its precursor hCAP-18 and its ortholog CRAMP in epithelial cells of human and mouse urinary tract, respectively. Bacterial contact with epithelial cells resulted in rapid production and secretion of the respective peptides, and in humans LL-37/hCAP-18 was released into urine. Epithelium-derived cathelicidin substantially contributed to the protection of the urinary tract against infection, as shown using CRAMP-deficient and neutrophil-depleted mice. In addition, clinical E. coli strains that were more resistant to LL-37 caused more severe urinary tract infections than did susceptible strains. Thus, cathelicidin seems to be a key factor in mucosal immunity of the urinary tract.

Natural Resources and Economic Growth: The Role of Investment

Abstract: This paper begins by a brief review of empirical evidence that seems to indicate that economic growth since 1965 has varied inversely with natural resource abundance or intensity across countries. The paper then proposes a new linkage between natural resources and economic growth, through saving and investment. When the share of output that accrues to the owners of natural resources rises, the demand for capital falls and this leads to lower real interest rates and less rapid growth. Moreover, the analysis shows that the discrepancy between the privately and socially optimal rates of growth increases with the natural capital share. Empirical evidence from 85 countries from 1965 to 1998 suggests that natural capital may on average crowd out physical as well as human capital, thereby inhibiting economic growth. The results also suggest that, across countries, heavy dependence on natural resources may hurt saving and investment indirectly by slowing down the development of the financial system.

The clinical value of somatic TP53 gene mutations in 1,794 patients with breast cancer.

Abstract: To investigate the clinical value of somatic TP53 mutations in breast cancer, we assembled clinical and molecular data on 1,794 women with primary breast cancer with long-term follow-up and whose tumor has been screened for mutation in exons 5 to 8 of TP53 by gene sequencing. TP53 mutations were more frequent in tumors of ductal and medullar types, aggressive phenotype (high grade, large size, node positive cases, and low hormone receptor content) and in women 10 years; P < 0.0001) compared with patients with no such mutation. The prognostic value of TP53 mutation was independent of tumor size, node status, and hormone receptor content, confirming and reconciling previous findings in smaller series. Moreover, an interaction between TP53 mutation and progesterone receptor (PR) status was revealed, TP53 mutation combined with the absence of progesterone receptor being associated with the worst prognosis. Whereas previous studies have emphasized the fact that missense mutations in the DNA-binding motifs have a worse prognosis than missense mutations outside these motifs, we show that non-missense mutations have prognostic value similar to missense mutations in DNA-binding motifs. Nonetheless, specific missense mutants (codon 179 and R248W) seem to be associated with an even worse prognosis. These results, obtained on the largest series analyzed thus far, show that TP53 mutations identified by gene sequencing have an independent prognostic value in breast cancer and could have potential uses in clinical practice.

Incentive-based approaches to sustainable fisheries

Abstract: The failures of traditional target-species management have led many to propose an ecosystem approach to fisheries to promote sustainability. The ecosystem approach is necessary, especially to account for fishery-ecosystem interactions, but by itself is not sufficient to address two important factors contributing to unsustainable fisheries: inappropriate incentives bearing on fishers and the ineffective governance that frequently exists in commercial, devel- oped fisheries managed primarily by total-harvest limits and input controls. We contend that much greater emphasis must be placed on fisher motivation when managing fisheries. Using evidence from more than a dozen natural experi- ments in commercial fisheries, we argue that incentive-based approaches that better specify community and individual harvest or territorial rights and price ecosystem services and that are coupled with public research, monitoring, and ef- fective oversight promote sustainable fisheries. 710 Resume : Les echecs des amenagements traditionnels centres sur les especes-cibles ont incite plusieurs chercheurs a proposer des approches halieutiques basees sur les ecosystemes pour favoriser les peches durables. L'approche ecosys- temique est necessaire, en particulier, pour tenir compte des interactions peche-ecosysteme; elle ne suffit pas,

Official Labeling, Criminal Embeddedness, and Subsequent Delinquency: A Longitudinal Test of Labeling Theory

Abstract: This article examines the short-term impact of formal criminal labeling on involvement in deviant social networks and increased likelihood of subsequent delinquency. According to labeling theory, formal criminal intervention should affect the individual’s immediate social networks. In many cases, the stigma of the criminal status may increase the probability that the individual becomes involved in deviant social groups. The formal label may thus ultimately increase involvement in subsequent deviance. We use panel data of a sample of urban adolescents to examine whether involvement in deviant social groups mediates the relationship between juvenile justice intervention and subsequent delinquent behavior. Using measures from three successive points in time, the authors find that juvenile justice intervention positively affects subsequent involvement in serious delinquency through the medium of involvement in deviant social groups, namely, street gangs and delinquent peers.

Improved outcome in shigellosis associated with butyrate induction of an endogenous peptide antibiotic.

Abstract: Shigella is a major cause of morbidity, mortality, and growth retardation for children in developing countries. Emergence of antibiotic resistance among Shigellae demands the development of effective medicines. Previous studies found that the endogenous antimicrobial peptide LL-37 is down-regulated in the rectal epithelium of patients during shigellosis and that butyrate up-regulates the expression of LL-37 in colonic epithelial cells in vitro and decreases severity of inflammation in experimental shigellosis. In this study, Shigella-infected dysenteric rabbits were treated with butyrate (0.14 mmol/kg of body weight) twice daily for 3 days, and the expression levels of the rabbit homologue to LL-37, CAP-18, were monitored in the colon. Butyrate treatment resulted in (i) reduced clinical illness, severity of inflammation in the colon, and bacterial load in the stool, (ii) significant up-regulation of CAP-18 in the surface epithelium, and (iii) disappearance of CAP-18-positive cells in lamina propria. The active CAP-18 peptide was released in stool from its proform by butyrate treatment. In healthy controls, CAP-18 expression was localized predominantly to the epithelial surface of the colon. In infected rabbits, CAP-18 expression was localized to immune and inflammatory cells in the colon, whereas the ulcerated epithelium was devoid of CAP-18 expression. The combination of CAP-18 and butyrate was more efficient in killing Shigella in vitro than CAP-18 alone. Our findings indicate that oral butyrate treatment in shigellosis may be of clinical value because of induction of the endogenous cathelicidin CAP-18 in the colonic epithelium, stimulation of the release of the active peptide CAP-18, and promoting elimination of Shigella.

Epidermal T lymphocytes and HLA-DR expression in psoriasis.

Abstract: Publisher Summary This chapter discusses a study analyzing epidermal T lymphocytes and human leukocyte antigen-DR expression in psoriasis. Twenty patients were studied. None of the patients had been on systemic treatment, including PUVA, for at least 3 months, and all local treatments were stopped at least 2 weeks before biopsy. For analysis, the guttate lesions were divided into early guttate lesions, which were 2 mm or less in diameter and less than 1-week-old, while late guttate lesions were more than l cm in diameter and mostly 3–8 weeks old. Uninvolved skin l cm away was also biopsied. Biopsies were also taken from normal controls. Punch biopsies (2 mm) were frozen immediately in liquid nitrogen and stored at −80°C. DR+ dendritic cells significantly increased in number in early guttate and late guttate lesions compared with normal skin. However, double labeling with OKT6 showed that only approximately 50% of OKT6+ dendritic cells in normal and uninvolved psoriatic skin also expressed DR antigen. In contrast, this proportion increased to 80% in lesions of early and late guttate psoriasis.

Automatic retinal oximetry.

Abstract: PURPOSE To measure hemoglobin oxygen saturation (SO(2)) in retinal vessels and to test the reproducibility and sensitivity of an automatic spectrophotometric oximeter. METHODS Specialized software automatically identifies the retinal blood vessels on fundus images, which are obtained with four different wavelengths of light. The software calculates optical density ratios (ODRs) for each vessel. The reproducibility was evaluated by analyzing five repeated measurements of the same vessels. A linear relationship between SO(2) and ODR was assumed and a linear model derived. After calibration, reproducibility and sensitivity were calculated in terms of SO(2). Systemic hyperoxia (n = 16) was induced in healthy volunteers by changing the O(2) concentration in inhaled air from 21% to 100%. RESULTS The automatic software enhanced reproducibility, and the mean SD for repeated measurements was 3.7% for arterioles and 5.3% venules, in terms of percentage of SO(2) (five repeats, 10 individuals). The model derived for calibration was SO(2) = 125 - 142 . ODR. The arterial SO(2) measured 96% +/- 9% (mean +/- SD) during normoxia and 101% +/- 8% during hyperoxia (n = 16). The difference between normoxia and hyperoxia was significant (P = 0.0027, paired t-test). Corresponding numbers for venules were 55% +/- 14% and 78% +/- 15% (P < 0.0001). SO(2) is displayed as a pseudocolor map drawn on fundus images. CONCLUSIONS The retinal oximeter is reliable, easy to use, and sensitive to changes in SO(2) when concentration of O(2) in inhaled air is changed.

Decision Fusion for the Classification of Urban Remote Sensing Images

Abstract: The classification of very high resolution remote sensing images from urban areas is addressed by considering the fusion of multiple classifiers which provide redundant or complementary results. The proposed fusion approach is in two steps. In a first step, data are processed by each classifier separately, and the algorithms provide for each pixel membership degrees for the considered classes. Then, in a second step, a fuzzy decision rule is used to aggregate the results provided by the algorithms according to the classifiers' capabilities. In this paper, a general framework for combining information from several individual classifiers in multiclass classification is proposed. It is based on the definition of two measures of accuracy. The first one is a pointwise measure which estimates for each pixel the reliability of the information provided by each classifier. By modeling the output of a classifier as a fuzzy set, this pointwise reliability is defined as the degree of uncertainty of the fuzzy set. The second measure estimates the global accuracy of each classifier. It is defined a priori by the user. Finally, the results are aggregated with an adaptive fuzzy operator ruled by these two accuracy measures. The method is tested and validated with two classifiers on IKONOS images from urban areas. The proposed method improves the classification results when compared with the separate use of the different classifiers. The approach is also compared with several other fuzzy fusion schemes

Epigenetic silencing and deletion of the BRCA1 gene in sporadic breast cancer

Abstract: Introduction BRCA1 or BRCA2 germline mutations increase the risk of developing breast cancer Tumour cells from germline mutation carriers have frequently lost the wild-type allele This is predicted to result in genomic instability where cell survival depends upon dysfunctional checkpoint mechanisms Tumorigenic potential could then be acquired through further genomic alterations Surprisingly, somatic BRCA mutations are not found in sporadic breast tumours BRCA1 methylation has been shown to occur in sporadic breast tumours and to be associated with reduced gene expression We examined the frequency of BRCA1 methylation in 143 primary sporadic breast tumours along with BRCA1 copy number alterations and tumour phenotype

Tectonic stress and magma chamber size as controls on dike propagation : Constraints from the 1975-1984 Krafla rifting episode

Abstract: [1] The best-studied dike intrusion events on a divergent plate boundary occurred along the Krafla segment of the northern rift zone in Iceland from 1975–1984. Seismic and geodetic measurements there showed that a central magma chamber fed dikes that propagated laterally many times the thickness of the lithosphere. The patterns of dike length, dike width, caldera subsidence, and lava extrusion strongly suggest that dike propagation is affected by tectonic stresses that change with each dike intrusion event and that magma pressures are linked to the dike opening. These observations have inspired us to develop a quantitative model for the lateral propagation of basaltic dikes away from a magma chamber. We assume dikes propagate as long as there is sufficient driving pressure, defined as the difference between magma pressure and tectonic stress at the dike tip. The opening dike and the magma chamber are treated as a closed system for a given dike intrusion event. During an event, magma pressure is reduced linearly with the magma volume withdrawn from the chamber. Relative tectonic tension in the lithosphere is reduced linearly as the dike width increases. A dike begins propagation when the driving pressure equals the “breakout” pressure needed to force the magma out of the chamber. It stops when the driving pressure reaches a minimum value. Generally, the dike width is proportional to this “stopping” pressure, and a reasonable value gives a width of 1 m. Besides the breakout and stopping pressures, the propagation distance depends on the initial distribution of tectonic stress and the thickness of the lithosphere cut by a dike. The intrusion of a dike changes the tectonic stress distribution so that subsequent dikes may propagate different distances and directions than the first dike. After a period of magma chamber refilling, a new dike can initiate if the breakout pressure is reached. For an idealized spreading segment the tectonic stress field evolves to produce a sequence of dikes propagating in one direction followed by a sequence of dikes propagating in the opposite direction. The first dike in each sequence should be the longest followed by successively shorter dikes. When tectonic stresses close to a magma chamber have been largely relieved, then extrusion of magma may start. The model pattern of dike propagation and extrusion is consistent with data from the Krafla episode. Magma chamber size should have a major effect on magmatic systems in other tectonic settings with larger magma chambers producing longer characteristic dikes.

Risk of second cancer among women with breast cancer.

Abstract: A large number of women survive a diagnosis of breast cancer. Knowledge of their risk of developing a new primary cancer is important not only in relation to potential side effects of their cancer treatment, but also in relation to the possibility of shared etiology with other types of cancer. A cohort of 525,527 women with primary breast cancer was identified from 13 population-based cancer registries in Europe, Canada, Australia and Singapore, and followed for second primary cancers within the period 1943-2000. We used cancer incidence rates of first primary cancer for the calculation of standardized incidence ratios (SIRs) of second primary cancer. Risk of second primary breast cancer after various types of nonbreast cancer was also computed. For all second cancer sites combined, except contralateral breast cancer, we found a SIR of 1.25 (95% CI = 1.24-1.26) on the basis of 31,399 observed cases after first primary breast cancer. The overall risk increased with increasing time since breast cancer diagnosis and decreased by increasing age at breast cancer diagnosis. There were significant excesses of many different cancer sites; among these the excess was larger than 150 cases for stomach (SIR = 1.35), colorectal (SIR = 1.22), lung (SIR = 1.24), soft tissue sarcoma (SIR = 2.25), melanoma (SIR = 1.29), non-melanoma skin (SIR = 1.58), endometrium (SIR = 1.52), ovary (SIR = 1.48), kidney (SIR = 1.27), thyroid gland (SIR = 1.62) and leukaemia (SIR = 1.52). The excess of cancer after a breast cancer diagnosis is likely to be explained by treatment for breast cancer and by shared genetic or environmental risk factors, although the general excess of cancer suggests that there may be additional explanations such as increased surveillance and general cancer susceptibility.

Probing cosmic chemical evolution with gamma-ray bursts: GRB 060206 at z = 4.048

Abstract: Aims.We present early optical spectroscopy of the afterglow of the gamma-ray burst GRB 060206 with the aim of determining the metallicity of the GRB absorber and the physical conditions in the circumburst medium. We also discuss how GRBs may be important complementary probes of cosmic chemical evolution. Methods.Absorption line study of the GRB afterglow spectrum. Results.We determine the redshift of the GRB to be z=4.04795±0.00020. Based on the measurement of the neutral hydrogen column density from the damped Lyman-alpha line and the metal content from weak, unsaturated S II lines we derive a metallicity of [S/H]=-0.84±0.10. This is one of the highest metallicities measured from absorption lines at z~4. From the very high column densities for the forbidden Si II*, O I*, and O I** lines we infer very high densities and low temperatures in the system. There is evidence for the presence of H2 molecules with log N(H_2)~17.0, translating into a molecular fraction of log{f}≈ -3.5 with f=2N(H2)/(2N(H2) + N(H I)). Even if GRBs are only formed by single massive stars with metallicities below ~0.3 Zo, they could still be fairly unbiased tracers of the bulk of the star formation at z>2. Hence, metallicities as derived for GRB 060206 here for a complete sample of GRB afterglows will directly show the distribution of metallicities for representative star-forming galaxies at these redshifts.

Why do female migratory birds arrive later than males

Abstract: 1. In migratory birds males tend to arrive first on breeding grounds, except in sex-role reversed species. The two most common explanations are the rank advantage hypothesis, in which male-male competition for breeding sites drives stronger selection for early arrival in males than females, and the mate opportunity hypothesis, which relies on sexual selection, as early arrival improves prospects of mate acquisition more for males than for females. 2. To date, theoretical work has focused on selection for early arrival within a single sex, usually male. However, if fitness depends on territory quality, selection for early arrival should operate on both sexes. Here we use two independent modelling approaches to explore the evolution of protandry (male-first arrival) and protogyny (female-first arrival) under the rank advantage and mate opportunity hypotheses. 3. The rank advantage hypothesis, when operating alone, fails to produce consistent patterns of protandry, despite our assumption that males must occupy territories before females. This is because an individual of either sex benefits if it out-competes same-sex competitors. Rather than promoting protandry, the rank advantage mechanism can sometimes result in protogyny. Female-female competition is stronger than male-male competition early in the season, if females compete for a resource (territories occupied by males) that is initially less common than the resource of interest to males (unoccupied territories). 4. Our results support the mate opportunity hypothesis as an explanation of why protandry is the norm in migratory systems. Male-biased adult sex ratios and high levels of sperm competition (modelled as extra-pair young: EPY) both produce protandry as a result of sexual selection. Protogyny is only observed in our models with female-biased sex ratios and low EPY production. 5. We also show that the effects of sex ratio biases are much stronger than those of EPY production, explore the evidence for sex ratio biases and extra-pair paternity in migratory species and suggest future research directions.

Second Primary Cancers in Thyroid Cancer Patients: A Multinational Record Linkage Study

Abstract: Context: Increasing incidence and improved prognosis of thyroid cancer have led to concern about the development of second primary cancers, especially after radioiodine treatment. Thyroid cancer can also arise as a second primary neoplasm after other cancers. Objective: The objective of the study was to assess the risk of second primary cancer after thyroid cancer and vice versa. Design: This was a multinational record linkage study. Setting: The study was conducted at 13 population-based cancer registries in Europe, Canada, Australia, and Singapore. Patients or Other Participants: A cohort of 39,002 people (356,035 person-yr of follow-up) with primary thyroid cancer were followed up for SPN for up to 25 yr, and 1,990 cases of thyroid cancer were diagnosed after another primary cancer. Main Outcome Measures: To assess any possible excess of second primary neoplasms after thyroid cancer, the observed numbers of neoplasms were compared with expected numbers derived from age-, sex-, and calendar period-speci...

Infectious agent of sheep scrapie may persist in the environment for at least 16 years.

Abstract: In 1978, a rigorous programme was implemented to stop the spread of, and subsequently eradicate, sheep scrapie in Iceland. Affected flocks were culled, premises were disinfected and, after 2-3 years, restocked with lambs from scrapie-free areas. Between 1978 and 2004, scrapie recurred on 33 farms. Nine of these recurrences occurred 14-21 years after culling, apparently as the result of environmental contamination, but outside entry could not always be absolutely excluded. Of special interest was one farm with a small, completely self-contained flock where scrapie recurred 18 years after culling, 2 years after some lambs had been housed in an old sheep-house that had never been disinfected. Epidemiological investigation established with near certitude that the disease had not been introduced from the outside and it is concluded that the agent may have persisted in the old sheep-house for at least 16 years.

Natural Resources and Economic Growth: From Dependence to Diversification

Abstract: This Paper reviews the relationship between natural resource dependence and economic growth, and stresses how natural capital intensity tends to crowd out foreign capital, social capital, human capital, physical capital, and financial capital, thereby impeding economic growth across countries. Specifically, the Paper presents empirical cross-country evidence to the effect that nations that depend heavily on their natural resources tend to have (a) less trade and foreign investment, (b) more corruption, (c) less equality, (d) less political liberty, (e) less education, (f) less domestic investment, and (g) less financial depth than other nations that are less well endowed with, or less dependent on, natural resources. This matters for long-run growth because empirical evidence also suggests that trade, honesty, equality, liberty, education, investment, and financial maturity are all positively and significantly related to economic growth across countries. Before concluding, the Paper briefly compares and contrasts the experience of the OPEC countries with that of Norway, a singularly successful oil producer.