Showing papers by "University of Iceland published in 1999"

A MIXED BLESSING: Natural Resources and Economic Growth

Abstract: This paper diagnoses the symptoms of the Dutch disease in a two-sector stochastic endogenous growth model. A productive, low-skill-intensive primary sector causes the currency to appreciate in real terms, thus hampering the development of a high-skill-intensive secondary sector and thereby reducing growth. Moreover, the volatility of the primary sector generates real-exchange-rate uncertainty and may thus reduce investment and learning in the secondary sector and hence also growth. Cross-sectional and panel regressions based on data for 125 countries in the period 1960–1992 confirm a statistically significant inverse relationship between the size of the primary sector and economic growth, but not between the volatility of the real exchange rate and growth.

Retrotransposon BARE-1 and Its Role in Genome Evolution in the Genus Hordeum.

Abstract: The replicative retrotransposon life cycle offers the potential for explosive increases in copy number and consequent inflation of genome size. The BARE-1 retrotransposon family of barley is conserved, disperse, and transcriptionally active. To assess the role of BARE-1 in genome evolution, we determined the copy number of its integrase, its reverse transcriptase, and its long terminal repeat (LTR) domains throughout the genus Hordeum. On average, BARE-1 contributes 13.7 x 10(3) full-length copies, amounting to 2.9% of the genome. The number increases with genome size. Two LTRs are associated with each internal domain in intact retrotransposons, but surprisingly, BARE-1 LTRs were considerably more prevalent than would be expected from the numbers of intact elements. The excess in LTRs increases as both genome size and BARE-1 genomic fraction decrease. Intrachromosomal homologous recombination between LTRs could explain the excess, removing BARE-1 elements and leaving behind solo LTRs, thereby reducing the complement of functional retrotransposons in the genome and providing at least a partial "return ticket from genomic obesity."

Change of Diet of the Greenland Vikings Determined from Stable Carbon Isotope Analysis and 14C Dating of Their Bones

Abstract: Bone samples from the Greenland Viking colony provide us with a unique opportunity to test and use (super 14) C dating of remains of humans who depended upon food of mixed marine and terrestrial origin. We investigated the skeletons of 27 Greenland Norse people excavated from churchyard burials from the late 10th to the middle 15th century. The stable carbon isotopic composition (delta (super 13) C) of the bone collagen reveals that the diet of the Greenland Norse changed dramatically from predominantly terrestrial food at the time of Eric the Red around AD 1000 to predominantly marine food toward the end of the settlement period around AD 1450. We find that it is possible to (super 14) C-date these bones of mixed marine and terrestrial origin precisely when proper correction for the marine reservoir effect (the (super 14) C age difference between terrestrial and marine organisms) is taken into account. From the dietary information obtained via the delta (super 13) C values of the bones we have calculated individual reservoir age corrections for the measured (super 14) C ages of each skeleton. The reservoir age corrections were calibrated by comparing the (super 14) C dates of 3 highly marine skeletons with the (super 14) C dates of their terrestrial grave clothes. The calibrated ages of all 27 skeletons from different parts of the Norse settlement obtained by this method are found to be consistent with available historical and archaeological chronology. The evidence for a change in subsistence from terrestrial to marine food is an important clue to the old puzzle of the disappearance of the Greenland Norse, obtained here for the first time by measurements on the remains of the people themselves instead of by more indirect methods like kitchen-midden analysis.

Geochemistry of historical-age silicic tephras in Iceland:

Abstract: The major element chemistry of nine silicic tephras of historical age from Iceland is assessed as a key step in the development of the recent tephrochronology of the North Atlantic region. The tephras include the largest such layers produced by each of the five central volcanoes Hekla, O raefajokull, Eyjafjallajokull, Torfajokull and Askja since the ninth century ad (H 1104, O1362, E 1821, Landnam tephra c. 870, A 1875) and four other tephras (H 1158, H 1510, H 1947, O1727). The determination of grain discrete major element chemistry of the glass fraction is a fundamental stage in the identification and correlation of tephra, and allows links to be made between Icelandic source areas (with precise dating evidence) and distal deposits elsewhere in the North Atlantic region. Although major element data can be used to discriminate between tephra layers produced by the different central volcanoes, on its own it cannot be used to identify all the Holocene layers produc...

A Genome-Wide Scan Reveals a Maternal Susceptibility Locus for Pre-Eclampsia on Chromosome 2p13

Abstract: Pre-eclampsia is a common and serious disease and a major cause of maternal and infant mortality. Antenatal care systems world-wide screen for signs of the disease such as hypertension and proteinuria. Unlike most other human disorders it impacts two individuals, the mother and the child, both of whom can be severely affected. The pathophysiology of the disorder is incompletely understood, but familial clustering of the disease is apparent. Here we report the results of a genome-wide screen of Icelandic families representing 343 affected women. Including those patients with non-proteinuric pre-eclampsia (gestational hypertension), proteinuric pre-eclampsia and eclampsia, we detected a significant locus on 2p13 with a lod score of 4.70 (single point P < 3.49 x 10(-6)). This is the first reported locus for pre-eclampsia meeting the criteria for genome-wide significance.

Humoral immune parameters in Atlantic cod (Gadus morhua L.) I. The effects of environmental temperature.

Abstract: The effects of environmental temperature on certain humoral immune parameters in Atlantic cod (Gadus morhua L.) were studied. Serum samples were collected from captive cod, of wild origin, kept at different temperatures for 12 months. It was found that immunoglobulin and natural antibody levels increased with increasing temperature whereas the total serum protein concentration, anti-protease activity, iron concentration, unsaturated and total iron binding capacity decreased with increasing temperature. Haemolytic activity and percentage iron saturation also tended to decrease with increasing temperature although this was not statistically significant.

International variation in the incidence of hip fractures: Cross-national project on osteoporosis for the world health organization program for research on aging

Abstract: A cross-national study of hip fracture incidence was carried out in five geographic areas – Beijing, China; Budapest, Hungary; Hong Kong; Porto Alegre, Brazil; and Reykjavik, Iceland – during the years 1990–1992 Cases of hip fracture among women and men of age 20 years and older were identified using hospital discharge data in conjunction with medical records, operating room logs, and radiology logs Estimated incidence rates varied widely, with Beijing reporting the lowest rates (age-adjusted rate per 100 000 population for men 20 years and older = 454; women = 396) and Reykjavik the highest rates (men = 1413; women = 2741) Rates were higher for women than for men in every area except Beijing In every area except Budapest, review of the operating room or radiology logs identified additional cases that were not reported in the discharge list, increasing the estimated number of hip fractures by 11% to 62%, depending on the area Review of medical records identified miscoding of hip fractures (ICD9 820) as ‘shaft of femur and other femur fractures’ (ICD9 821) in the discharge lists of every area except Budapest, increasing the estimated number of hip fractures by 1% to 30% The final estimates of hip fracture incidence taking into account all investigated sources of undercount and overcount ranged from 15% lower to 89% higher than an estimate based on the discharge diagnoses alone Although these results indicate substantial limitations in relying on hospital discharge data alone to estimate hip fracture incidence rates, the extent of errors found in the discharge lists is smaller than the large international variation found here and previously reported in incidence rates The findings support the conclusion that the differences reported among countries mainly reflect genuine variation in the hip fracture incidence rates

16°C Rapid Temperature Variation in Central Greenland 70,000 Years Ago

Abstract: Variations in the29N2/28N2 ratio of air bubbles trapped in polar ice cores and their relation to variations of the 18O/16O of the ice allow past surface temperature variations and ice age–gas age differences to be determined. High-resolution measurements of29N2/28N2 in Dansgaard-Oeschger event 19 (around 70,000 years before the present) in ice from Central Greenland show that at the beginning of the event, the ice age–gas age difference was 1090 ± 100 years. With the use of a combined firn densification, temperature, and gas diffusion model, the δ18Oice-temperature coefficient α was determined to be 0.42 ± 0.05 per mil per kelvin. This coefficient implies a mean surface temperature change of 16.0 kelvin (between 14.3 and 18.1 kelvin), which differs substantially from values derived from borehole temperatures and modern spatial δ18Oice–surface temperature correlations.

Mga, a dual-specificity transcription factor that interacts with Max and contains a T-domain DNA-binding motif.

Abstract: The basic-helix-loop-helix-leucine zipper (bHLHZip) proteins Myc, Mad and Mnt are part of a transcription activation/repression system involved in the regulation of cell proliferation. The function of these proteins as transcription factors is mediated by heterodimerization with the small bHLHZip protein Max, which is required for their specific DNA binding to E-box sequences. We have identified a novel Max-interacting protein, Mga, which contains a Myc-like bHLHZip motif, but otherwise shows no relationship with Myc or other Max-interacting proteins. Like Myc, Mad and Mnt proteins, Mga requires heterodimerization with Max for binding to the preferred Myc-Max-binding site CACGTG. In addition to the bHLHZip domain, Mga contains a second DNA-binding domain: the T-box or T-domain. The T-domain is a highly conserved DNA-binding motif originally defined in Brachyury and characteristic of the Tbx family of transcription factors. Mga binds the preferred Brachyury-binding sequence and represses transcription of reporter genes containing promoter-proximal Brachyury-binding sites. Surprisingly, Mga is converted to a transcription activator of both Myc-Max and Brachyury site-containing reporters in a Max-dependent manner. Our results suggest that Mga functions as a dual-specificity transcription factor that regulates the expression of both Max-network and T-box family target genes.

Greedy local improvement and weighted set packing approximation

Abstract: Given a collection of weighted sets, each containing at most k elements drawn from a finite base set, the k-set packing problem is to find a maximum weight sub-collection of disjoint sets. A greedy algorithm for this problem approximates it to within a factor of k, and a natural local search has been shown to approximate it to within a factor of roughly k?1. However, neither paradigm can yield approximations that improve on this.We present an approximation algorithm for the weighted k-set packing problem that combines the two paradigms by starting with an initial greedy solution and then repeatedly choosing the best possible local improvement. The algorithm has a performance ratio of 2(k+1)/3, which we show is asymptotically tight. This is the first asymptotic improvement over the straightforward ratio of k.

PrP gene polymorphism and natural scrapie in Icelandic sheep.

Abstract: The association between scrapie and polymorphism of the prion protein (PrP) gene was studied in the Icelandic sheep breed Polymorphism of the three codons, 136, 154 and 171, that are important for scrapie susceptibility was determined A BspHI restriction analysis was used to study the alleles of codons 136 and 154, while density gradient gel electrophoresis (DGGE) was used to analyse codon 171 and detect new polymorphisms The PrP allelic variant, VRQ (amino acids at codons 136, 154 and 171), was found to be highly statistically associated with scrapie, whereas the allelic variant, AHQ, was never found in scrapie-affected animals, a finding that is statistically significant Iceland has a few scrapie-free regions, which are a part of a quarantine network Homozygotes for the VRQ variant were found there at a low frequency, indicating that genetic susceptibility is not enough for scrapie to develop and further evidence for the infectious nature of the disease A comparison of PrP genotypes between sheep outside and within the scrapie-free zones revealed an increase in the AHQ allelic variant in the latter No polymorphism was found at codon 171 in a total of 932 sheep studied, all individuals having the glutamine allele Two novel, rare PrP alleles were found using DGGE at codons 138 and 151, ie S138N and R151C Their relevance to scrapie is still unclear, but the former was found in scrapie-affected sheep as well as healthy sheep, whereas the latter was only found in healthy sheep

Iceland: the case of a national human genome project.

Abstract: L'Islande a ete le lieu d'evenements complexes et controverses entre 1996 et 1999 : DeCode Genetics, une institution de recherche genetique a eu le projet de dresser une carte des genomes des populations et de mettre en place une base de donnees medicale afin de relever les maladies, les avancees cliniques depuis 1915 et d'enregistrer les donnees genealogiques. Les AA. ont etudie le developpement et l'expansion de cette institution, la construction de la base de donnees et les debats publics autour de ce projet. Cet article se veut une reflexion relative a la position de l'anthropologie vis-a-vis de la biotechnologie, de l'industrie du genome humain et du monde des medias. Quelles sont les relations entre ce type d'anthropologie appliquee et la pratique ethnographique ? Quelle position ethique faut-il adopter ?

Decay of the GRB 990123 Optical Afterglow: Implications for the Fireball Model

Abstract: Broad-band (ultraviolet to near-infrared) observations of the intense gamma ray burst GRB 990123 started ∼8.5 hours after the event and continued until 18 February 1999. When combined with other data, in particular from the Robotic Telescope and Transient Source Experiment (ROTSE) and the Hubble Space Telescope (HST), evidence emerges for a smoothly declining light curve, suggesting some color dependence that could be related to a cooling break passing the ultraviolet-optical band at about 1 day after the high-energy event. The steeper decline rate seen after 1.5 to 2 days may be evidence for a collimated jet pointing toward the observer.

In Vitro Susceptibilities of Neisseria gonorrhoeae to Fatty Acids and Monoglycerides

Abstract: The susceptibility of Neisseria gonorrhoeae to several medium-chain fatty acids and their 1-monoglycerides was tested at a short inactivation time of 1 min. The results indicate that monocaprin, a monoglyceride of capric acid (10 carbon atoms, no double bonds), causes the fastest and most effective killing of all strains of N. gonorrhoeae tested.

Coordinated Ground Forces Exerted by Buttocks and Feet are Adequately Programmed for Weight Transfer During Sit-to-Stand

Abstract: The purpose of this study was to test the hypothesis whether weight transfer during sit-to-stand (STS) is the result of coordinated ground forces exerted by buttocks and feet before seat-off. Whole-body kinematics and three-dimensional ground forces from left and right buttock as well as from left and right foot were recorded for seven adults during STS. We defined a preparatory phase from onset of the first detectable anterior/posterior (A/P) force to seat-off (buttock forces fell to 0) and a rising phase from seat-off to the decrease of center of mass (CoM) vertical velocity to zero. STS was induced by an increase of vertical and backward directed ground forces exerted by the buttocks that significantly preceded the onset of any trunk movement. All ground forces peaked before or around the moment of seat-off, whereas all kinematic variables, except trunk forward rotation and hip flexion, peaked after seat-off, during or after the rising phase. The present study suggests that the weight transfer from sit to stand is induced by ground forces exerted by buttocks and feet before seat-off, i.e., during the preparatory phase. The buttocks generate the isometric "rising forces," e.g., the propulsive impulse for the forward acceleration of the body, while the feet apply adequate damping control before seat-off. This indicates that the rising movement is a result of these coordinated forces, targeted to match the subject's weight and support base distance between buttocks and feet. The single peaked, bell-shaped profiles peaking before seat-off, were seen beneath buttocks for the "rising drive," i.e., between the time of peak backward directed force and seat-off, as well as beneath the feet for the "damping drive," i.e., from onset to the peak of forward-directed force and for CoM A/P velocity. This suggests that both beginning and end of the weight transfer process are programmed before seat-off. The peak deceleration of A/P CoM took place shortly ( approximately 100 ms) after CoM peak velocity, resulting in a well controlled CoM deceleration before seat-off. In contrast to the view of other authors, this suggests that body equilibrium is controlled during weight transfer.

The genetic element pSSVx of the extremely thermophilic crenarchaeon Sulfolobus is a hybrid between a plasmid and a virus

Abstract: A new Sulfolobus islandicus strain, REY15/4, harboured both a novel fusellovirus, SSV2, and a small plasmid, pSSVx. The plasmid spread in S. solfataricus P1 together with the virus after infection with either the supernatant of a culture of REY15/4 or purified virus. Spreading of the plasmid required co-transfection with either SSV2 or the related SSV1 as helpers. Virus purified from REY15/4 constituted a mixture of two sizes of particles, one with the dimensions of a normal fusellovirus and the other smaller. Cloned SSV2 produced only the larger particles and only SSV2 DNA, indicating that the smaller particles contained pSSVx packaged into capsids made up of SSV2 components. The 5.7 kb genome of pSSVx revealed regions of high sequence similarity to the cryptic Sulfolobales plasmids pRN1, pRN2 and pDL10. Thus, pSSVx belongs to the family of pRN plasmids that share a highly conserved region, which probably constitutes the minimal replicon. They also contain a variable region showing no sequence similarity. In pSSVx, this region contains three open reading frames (ORFs), two of which are juxtapositioned and show high sequence similarity to a tandem of ORFs in fusellovirus genomes. Neither pRN1 nor pRN2, which lack this tandem, spread in the presence of the fuselloviruses, which implies that the sequences of these ORFs enable pSSVx to use the packaging system of the viral helpers for spreading.

Destabilizing effect of cannibalism on a structured predator–prey system

Abstract: The dynamics of a predator-prey system, where the predator has two stages, a juvenile stage and a mature stage, are modelled by a system of three ordinary differential equations. The mature predators prey on the juvenile predators in addition to the prey. If the mortality rate of juveniles is low and/or the recruitment rate to the mature population is high, then there is a stable equilibrium with all three population sizes positive. On the other hand, if the mortality rate of juveniles is high and/or the recruitment rate to the mature population is low, then the equilibrium will be stable for low levels of cannibalism, but a loss of stability by a Hopf bifurcation will take place as the level of cannibalism increases. Numerical studies indicate that a stable limit cycle appears. Cannibalism can therefore be a destabilizing force in a predator-prey system.

Copper, ceruloplasmin, superoxide dismutase and iron parameters in Parkinson's disease.

Abstract: In a previous study we found copper dyshomeostasis in patients with Alzheimer's disease. In this study, levels of copper in plasma, of ceruloplasmin in serum and ceruloplasmin oxidative activity as well as superoxide dismutase (SOD) activity in erythrocytes were determined in 40 patients with Parkinson's disease and their healthy age- and gender-matched controls. Copper concentrations did not differ significantly in the two groups, whereas both ceruloplasmin concentrations and ceruloplasmin oxidative activity were significantly lower in the patients, also relative to ceruloplasmin mass. SOD activity was not significantly different in the two groups but decreased significantly with the duration of disease. The same was found for ceruloplasmin oxidative activity. Ceruloplasmin oxidative activity and SOD activity did not decrease with age. Levels of serum iron, serum ferritin and total iron binding capacity were determined in about 30 of the patients and an equal number of controls and were not found to differ. Transferrin levels were significantly lower in the patients than in their controls but, conversely, the transferrin saturation was significantly higher in the patients. The results indicate that patients with Alzheimer's disease and Parkinson's disease have defective ceruloplasmin and SOD activities in common and that these defects are not necessarily associated with major disturbances in iron homeostasis.

Humoral immune parameters in Atlantic cod (Gadus morhua L.) II. The effects of size and gender under different environmental conditions.

Abstract: The effects of size and gender on several humoral immune parameters in cod were examined under different environmental conditions. Serum samples were collected from wild cod of different sizes. Two samplings were undertaken: In the spring in relatively cold waters off the north west coast of Iceland and in the fall in relatively warm waters off the west coast of Iceland. Most of the parameters increased with increasing cod size, except the haemolytic activity which decreased. Higher serum protein levels were seen in cod sampled in the fall than in the spring. In cod sampled in the spring there was an apparent difference between specimens B 75 cm in length and the larger specimens with respect to haemolytic activity and iron concentration. None of the parameters were influenced by the gender of the cod. © 1999 Elsevier Science Inc. All rights reserved.

Glacio-meteorological investigations on Vatnajokull, Iceland, summer 1996: an overview.

Abstract: We give an overview of a glacio-meteorological experiment carried out in the summer (melt season) of 1996 on the largest European ice cap, Vatnajokull, Iceland (area 8000 km2; altitude range: from sea level to about 2000 m). The main goal was to understand how the energy used in the melting of snow and ice is delivered to the surface. Many meteorological stations were operated simultaneously on the ice cap, at almost all of which profile measurements were made. Cable balloons and radiosondes were used to probe the vertical structure of the boundary layer. It appears that the flow near the surface is katabatic most of the time, with the height of the wind maximum varying between a few metres and a few tens of metres. It is only during the passage of intense storms that the katabatic wind in the melt zone disappears. Global radiation increases significantly with altitude. Surface albedo varies enormously in space and time, with very low values (≈ 0.1) being found at many places because of the melt out of volcanic ash layers. If we consider the total melt in the period 22 May–31 August 1996, we conclude that radiation typically provides two-thirds of the melt energy, and turbulent exchange of heat one-third. At locations high on the glacier, turbulent exchange becomes less significant.

Lean mass and physical activity as predictors of bone mineral density in 16-20-year old women.

Abstract: . Valdimarsson O, Kristinsson JO, Stefansson SO, Valdimarsson S, Sigurdsson G (Reykjavik Hospital, University of Iceland, Reykjavik, Iceland). Lean mass and physical activity as predictors of bone mineral density in 16–20-year old women. J Intern Med;245: 489–496. Objective. The aim of the study was to quantify the inter-relationship between bone mineral density and physical activity, muscle strength, and body mass composition in a group of healthy 16–20-year-old women. Design. A cross-sectional study. Setting. Reykjavik area. Subjects. Two-hundred and fifty-four Icelandic Caucasian women aged 16, 18 and 20 years, randomly selected from the registry of Reykjavik. Main outcome measures. Bone mineral content (BMC) and density (BMD) in lumbar spine, hip, distal forearm and total skeleton and lean mass and fat mass were measured with dual energy X-ray absorptiometry (DEXA) and compared with grip strength measured with a dynamometer and physical activity as assessed by a questionnaire. Results. The lean mass had the strongest correlation with BMC and BMD, stronger than weight, height and fat mass, both in univariate analysis (r = 0.41–0.77; P < 0.001) and in linear regression analysis. The total skeletal BMD was logarithmically higher by hours of exercise per week (P < 0.001)). About 30% of variability in total skeletal BMD in this age group can be predicted by lean mass and physical exercise. Conclusions. Modifiable factors, such as exercise and adequate muscle seem to be significant predictors of the attainment of peak bone mass in women.

Opening of an eruptive fissure and seaward displacement at Piton De La Fournaise Volcano measured by RADARSAT satellite radar interferometry

Abstract: Interferometric analysis of Synthetic Aperture Radar images acquired by the RADARSAT-1 satellite of Piton de la Fournaise volcano, show that an eruptive fissure which opened on 9th of March 1998 caused asymmetric deformation, with displacement and bulging of the volcanic edifice on the seaward side of the fissure. Up to 50 cm ground-to-satellite range change occurred in a 3-km wide area, in response to a shallow (< 1-km-deep) inclined dike that opened by up to 60 cm. The erupted magma was transported from more than 7-km-depth below sea level, causing no observable volcano-wide co-eruptive deflation. A series of pre-eruption interferograms show also that no significant inflation occurred prior to the eruption. The dike injection slightly reduced the stability of the volcano seaward flank.

Age related macular degeneration in monozygotic twins and their spouses in Iceland

Abstract: Purpose: To examine the importance of genetic factors in age-related macular degeneration by using a twin study to compare the concordance of age-related macular degeneration in monozygotic twin pairs and their spouses. Methods: This was a prospective study that included 50 twin pairs and 47 spouses. Zygosity was determined by genetic laboratory testing. Macular findings were graded based on the grading system used by the Macular Photocoagulation Study Group and the International ARM Epidemiological Study Group. Results: The concordance of age-related macular degeneration was 90% in monozygotic twin pairs which significantly exceeded that of twin/spouse pairs (70.2%); p‰0.0279. In the nine pairs that were concordant, fundus appearance and visual impairment were similar. Environmental factors and medical history were essentially the same in the twin pairs. Conclusion: The statistically significant higher concordance of age-related macular degeneration in monozygotic twins compared to their spouses strongly suggests the importance of genetic factors.