Showing papers by "University of Iceland published in 2000"

Incidence of skin cancer in 5356 patients following organ transplantation

Abstract: Background Skin cancer following solid organ transplantation is an important cause of morbidity in long-term survivors. This risk is well known but imprecisely quantified. Objectives We aimed to determine: (i) the skin cancer risks in transplant patients more precisely; (ii) whether the risk of malignant melanoma is altered; and (iii) whether the risk of epithelial cancers occurring at non-exposed sites is comparable with that seen in sun-exposed sites. Methods We linked a population-based cohort of 5356 patients who had received organ transplants in Sweden between 1970 and 1994 with the compulsory Swedish Cancer Registry, to identify all cancer cases except basal cell carcinomas, which are not registered. Results After a mean follow-up of 5.6 years post-transplantation, 172 of 5356 patients developed 325 non-melanoma skin cancers (excluding basal cell carcinomas) and six malignant melanomas. The relative risk of non-melanoma skin cancer was 108.6 [95% confidence interval (CI) 94.6-123.1 for men and 92.8 (95% CI 73.2-116.0) for women. The highest risks were noted for upper limbs, and the risk increased with time. No significant increase in malignant melanomas was noted: the relative risk was 1.6 (95% CI 0.5-3.7) for men and 0.5 (95% CI 0.0-2.6) for women. Except for the lip. which is also sun-exposed, other epithelial sites did not show comparable increases in cancer risk. Conclusions We conclude that organ transplant recipients are at a highly increased risk for non-melanoma skin cancer and must be closely followed throughout their lives. Cancer risk associated with transplantation is higher for sun-exposed than for non-sun-exposed epithelial tissues, even among populations living in regions with low solar insolation.

Discovering hidden time patterns in behavior: T-patterns and their detection

Abstract: This article deals with the definition and detection of particular kinds of temporal patterns in behavior, which are sometimes obvious or well known, but other times difficult to detect, either directly or with standard statistical methods. Characteristics of well-known behavior patterns were abstracted and combined in order to define a scale-independent, hierarchical time pattern type, called aT-pattern. A corresponding detection algorithm was developed and implemented in a computer program, called Theme. The proposed pattern typology and detection algorithm are based on the definition and detection of a particular relationship between pairs of events in a time series, called acritical interval relation. The proposed bottom-up, level-by-level (or breadth-first) search algorithm is based on a binary tree of such relations. The algorithm first detects simpler patterns. Then, more complex and complete patterns evolve through the connection of simpler ones, pattern completeness competition, and pattern selection. Interindividual T-patterns in a quarter-hour interaction between two children are presented, showing that complex hidden T-patterns may be found by Theme in such behavioral streams. Finally, implications for studies of complexity, self-organization, and dynamic patterns are discussed.

Influence of sulfide and temperature on species composition and community structure of hot spring microbial mats.

Abstract: In solfataric fields in southwestern Iceland, neutral and sulfide-rich hot springs are characterized by thick bacterial mats at 60 to 80°C that are white or yellow from precipitated sulfur (sulfur mats). In low-sulfide hot springs in the same area, grey or pink streamers are formed at 80 to 90°C, and a Chloroflexus mat is formed at 65 to 70°C. We have studied the microbial diversity of one sulfur mat (high-sulfide) hot spring and one Chloroflexus mat (low-sulfide) hot spring by cloning and sequencing of small-subunit rRNA genes obtained by PCR amplification from mat DNA. Using 98% sequence identity as a cutoff value, a total of 14 bacterial operational taxonomic units (OTUs) and 5 archaeal OTUs were detected in the sulfur mat; 18 bacterial OTUs were detected in the Chloroflexus mat. Although representatives of novel divisions were found, the majority of the sequences were >95% related to currently known sequences. The molecular diversity analysis showed that Chloroflexus was the dominant mat organism in the low-sulfide spring (1 mg liter−1) below 70°C, whereas Aquificales were dominant in the high-sulfide spring (12 mg liter−1) at the same temperature. Comparison of the present data to published data indicated that there is a relationship between mat type and composition of Aquificales on the one hand and temperature and sulfide concentration on the other hand.

Natural Resources, Education, and Economic Development

Abstract: Economic growth since 1965 has varied inversely with the share of natural capital in national wealth across countries. Four main channels of transmission from abundant natural resources to stunted economic development are discussed: (a) the Dutch disease, (b) rent seeking, (c) overconfidence, and (d) neglect of education. Public expenditure on education relative to national income, expected years of schooling for girls, and gross secondary-school enrolment are all shown to be inversely related to the share of natural capital in national wealth across countries. Natural capital appears to crowd out human capital, thereby slowing down the pace of economic development.

The tephrochronology of Iceland and the North Atlantic region during the Middle and Late Quaternary: a review

Abstract: The tephrochronology of Iceland and the North Atlantic region is reviewed in order to construct a unified framework for the last 400 kyr BP. Nearly all of the tephra layers described are also characterised geochemically. A number of new tephra layers are analysed for the first time for their geochemical signature and a number of pre-Holocene tephra layers have been given an informal denotation. The tephrostratigraphy of Ash Zone II is highlighted. Where possible the rhyolitic tephra layers found outside Iceland have been correlated to known Icelandic tephra layers or to the volcanic source area. The application of tephra fallout in various depositional environments is described and discussed. Copyright © 2000 John Wiley & Sons, Ltd.

Screening and prevention of diabetic blindness.

Abstract: Diabetic eye disease remains a major cause of blindness in the world. Laser treatment for proliferative diabetic retinopathy and diabetic macular edema became available more than two decades ago. The outcome of treatment depends on the timing of laser treatment. The laser treatment is optimally delivered when high-risk characteristics have developed in proliferative retinopathy or diabetic macular edema and before this has significantly affected vision. Laser treatment is usually successful if applied during this optimal period whereas the treatment benefit falls sharply if the treatment is applied too late. In order to optimize the timing of laser treatment in diabetic eye disease screening programs have been established. The oldest screening program is 20 years old and several programs have been established during the last decade. In this paper the organisation and methods of screening programs are described including direct and photographic screening. The incidence and prevalence of blindness is much lower in populations where screening for diabetic eye disease has been established compared to diabetic populations without screening. Technical advantages may allow increased efficiency and telescreening. From a public health standpoint screening for diabetic eye disease is one of the most cost effective health procedures available. Diabetic eye disease can be prevented using existing technology and the cost involved is many times less than the cost of diabetic blindness.

Late‐glacial and Holocene palaeoceanography of the North Icelandic shelf

Abstract: High-resolution gravity cores and box cores from the North Icelandic shelf have been studied for palaeoceanographic history based on lithological and biostratigraphical foramin- iferal data. Results from two outer shelf cores covering the last 13.6 k 14 C yr BP are presented in this paper. The sediments accumulated in north-south trending basins on each side of the Kolbeinsey Ridge at water depths of ca. 400 m. Sedimentation rates up to 1.5 m kyr -1 are observed during the Late-glacial and Holocene. The Vedde and Saksunarvatn tephras are present in the cores as well as the Hekla 1104. A new tephra, KOL-GS-2, has been identified and dated to 13.4 k 14 C yr BP, and another tephra, geochemically identical to the Borrobol Tephra, has been found at the same level. At present, the oceanographic Polar Front is located on the North Icelandic shelf, which experiences sharp oceanographic surface boundaries between the cold East Icelandic Current and the warmer Irminger Current. Past changes in sedimentological and biological processes in the study area are assumed to be related to fluctuations of the Polar Front. The area was deglaciated before ca. 14 kyr BP, but there is evidence of ice rafting up to the end of the GS-1 (Greenland Stadial 1, Younger Dryas) period, increasing again towards the end of the Holocene. Foraminiferal studies show a relatively strong GS-2 (pre-13 kyr BP) palaeo-Irminger Current, followed by severe cooling and then by unstable conditions during the remainder of the GI-1 (Greenland Interstadial 1, Bolling-Allerod) and GS-1 (Younger Dryas). Another cooling event occurred during the Preboreal before the Holocene current system was established at about 9 kyr BP. After a climatic optimum between 9 and 6 kyr BP the climate began to deteriorate and fluctuate. Copyright © 2000 John Wiley & Sons, Ltd.

Smoking, rheumatoid factor isotypes and severity of rheumatoid arthritis

Abstract: Objectives. Smokers have an increased incidence of rheumatoid factor (RF ) and rheumatoid arthritis (RA) and one report has also indicated that smoking may also adversely influence the severity of RA. Methods. Sixty-three women with advanced RA answered a structured questionnaire that included detailed information about their smoking history. The women were also evaluated clinically and radiologically. Results. Heavy smoking (≥ 20 pack-yr) was associated with rheumatoid nodules (P = 0.01), a higher HAQ score (P = 0.002) and a lower grip strength (P = 0.01). Smoking was also associated with more radiological joint damage (P = 0.02). A positive correlation was observed between smoking and RF levels, in particular IgA RF and a combined elevation of IgM and IgA RF. Conclusions. Smoking has an adverse effect on disease progression in patients with RA. An association was also observed between smoking and those RF types that predispose to RA and have the highest diagnostic specificity for this disease. K : Smoking, Rheumatoid arthritis, Rheumatoid factor, Prognosis.

Laser treatment and the mechanism of edema reduction in branch retinal vein occlusion

Abstract: PURPOSE To test a hypothesis on the physiological mechanism of the disappearance of macular edema after laser treatment The hypothesis is based on the effect grid laser treatment has on retinal oxygenation and hemodynamics It predicts that laser-induced reduction of macular edema is associated with shortening and narrowing of retinal vessels in patients with branch retinal vein occlusion (BRVO) METHODS The study included 12 subjects, treated with argon laser photocoagulation for BRVO and macular edema Fundus photographs taken at the time of diagnosis and again after laser treatment, were digitized, and diameter and segment length of retinal vessels was measured using NIH-Image program RESULTS Macular edema disappeared or was dramatically reduced in all cases after laser treatment The diameter of occluded venules constricted to 081 6 002 (mean 6 SD, P 5 0019) of the prelaser diameter and adjacent arterioles constricted to 078 6 001 (P 5 0008) The laser treatment also led to shortening of the affected vessels The final segment length of the occluded venules was 095 6 017 (P 5 0005) of the length before treatment The corresponding value for the adjacent arterioles is 095 6 014 (P 5 0008) Control arterioles and venules in the same fundus did not change in either length or width CONCLUSIONS These results do not reject the authors’ hypothesis that the disappearance of macular edema in BRVO can be explained by the effect the laser photocoagulation has on retinal oxygenation Increased oxygenation causes vessel constriction and shortening and lower intravascular pressure, which reduces edema formation according to Starling’s law (Invest Ophthalmol Vis Sci 2000;41:877‐ 879)

Incidence of cancer among commercial airline pilots

Abstract: OBJECTIVES—To describe the cancer pattern in a cohort of commercial pilots by follow up through the Icelandic Cancer Registry. METHODS—This is a retrospective cohort study of 458 pilots with emphasis on subcohort working for an airline operating on international routes. A computerised file of the cohort was record linked to the Cancer Registry by making use of personal identification numbers. Expected numbers of cancer cases were calculated on the basis of number of person-years and incidences of cancer at specific sites for men provided by the Cancer Registry. Numbers of separate analyses were made according to different exposure variables. RESULTS—The standardised incidence ratio (SIR) for all cancers was 0.97 (95% confidence interval (95% CI) 0.62 to 1.46) in the total cohort and 1.16 (95% CI 0.70 to 1.81) among those operating on international routes. The SIR for malignant melanoma of the skin was 10.20, 95% CI 3.29 to 23.81 in the total cohort and 15.63, 95% CI 5.04 to 36.46 in the restricted cohort. Analyses according to number of block-hours and radiation dose showed that malignant melanomas were found in the subgroups with highest exposure estimates, the SIRs were 13.04 and 28.57 respectively. The SIR was 25.00 for malignant melanoma among those who had been flying over five time zones. CONCLUSIONS—The study shows a high occurrence of malignant melanoma among pilots. It is open to discussion what role exposure of cosmic radiation, numbers of block-hours flown, or lifestyle factors—such as possible excessive sunbathing—play in the aetiology of cancer among pilots. This calls for further and more powerful studies. The excess of malignant melanoma among those flying over five time zones suggests that the importance of disturbance of the circadian rhythm should be taken into consideration in future studies. Keywords: cancer registry; malignant melanoma of the skin; cosmic radiation; block-hours; time zones

Chronology of late Holocene climatic events in the northern North Atlantic based on AMS 14C dates and tephra markers from the volcano Hekla, Iceland

Abstract: A combination of AMS14C dating and tephrochronology has been used to date late Holocene oceanographic events in a 335 cm marine record, covering about 4600 cal. yr with sedimentation rates exceeding 80 cm 1000 yr−1. The core site is located 50 km offshore on the northern Icelandic shelf. Tephra markers from Iceland serve to correlate the marine and terrestrial records. Especially notable is the presence of three geochemically correlated tephra markers from the Icelandic volcano Hekla (Hekla 4, Hekla 3 and Hekla 1104). Benthic and planktonic foraminiferal abundance and distribution as well as the petrography of the sand fraction of the muddy shelf sediments are used as palaeoceanographic proxies. The foraminiferal assemblages reflect a general cooling trend during the last 4600 yr. A marked drop in sea-surface temperatures is registered at about 3000 cal. yr BP, corresponding to the level of the Hekla 3 tephra. There is faunal indication of temperature amelioration during the Medieval Warm Period and a cooling again during the Little Ice Age. Periods of ice rafting events are indicated by ice rafted debris (IRD) concentrations, e.g. at around 3000 cal. yr BP and during the Little Ice Age. The former event occurred just prior to the deposition of the Hekla 3 tephra marker, the largest Holocene Hekla eruption. A correlation with terrestrial climatic events in Iceland is presented. A standard marine reservoir correction of 400 14C yr appears to be reasonable, at least during periods with high influence of water masses from the Irminger Current on the northern Icelandic shelf. An increase to ca. 530 14C yr may have occurred, however, when water masses derived from the East Greenland Current were dominant in the area. Copyright © 2000 John Wiley & Sons, Ltd.

Prevalence of menstrual cycle symptom cyclicity and premenstrual dysphoric disorder in a random sample of women using and not using oral contraceptives

Abstract: Background. The prevalence of symptom cyclicity and premenstrual dysphoric disorder in randomly recruited samples of women has not been ascertained. We assessed this prospectively in 83 Icelandic women, aged 20-40 years, using and not using oral contraceptives (OCs). Methods. A check list of 57 symptoms, divided into 7 symptom groups, was used to assess experiences. All symptoms and summarized symptom scores within symptom groups were tested for significant change between the follicular and the luteal phase of each menstrual cycle. When a symptom or a summarized symptom score was higher during the luteal phase compared to the follicular phase the cyclicity is labelled 'expected' cyclicity and the opposite 'unexpected' cyclicity. Results. The women charted from 1-7 menstrual cycles each, with 66 of them charting 3-4 cycles. Cyclicity was never displayed by 9.6% of participants; 80.7% displayed expected cyclicity and 72.3% unexpected cyclicity at least once. Cyclicity in somatic symptoms was most often demo...

“With the rule” astigmatism is not the rule in the elderly

Abstract: . Purpose: To study refractive state and visual acuity in citizens of Reykjavik 50 years and older. Methods: 1700 persons were randomly selected from the national population census. 1379 could be located and qualified whereof 1045 participated. Evaluation of refraction was performed using Nidek ARK 900 autorefracto-keratometer. Visual acuity was tested on a Snellen chart. Results: The prevalence of hypermetropia increases with age by 0.3 D in five years. The prevalence of “against the rule” astigmatism increased on average 5.3% and oblique 3.9% in five years. Analysis of corneal astigmatism measured by keratometer shows an “against the rule” change with age. Conclusions: Hypermetropia increases by age. The prevalence of astigmatism increases and the axis turns to “against the rule”. The changes in total astigmatism and corneal astigmatism is almost parallel which might indicate that the “against the rule” change is related to changes in the cornea.

Genomic, transcriptional and mutational analysis of the mouse microphthalmia locus.

Abstract: Mouse microphthalmia transcription factor ( Mitf ) mutations affect the development of four cell types: melanocytes, mast cells, osteoclasts, and pigmented epithelial cells of the eye. The mutations are phenotypically diverse and can be arranged in an allelic series. In humans, MITF mutations cause Waardenburg syndrome type 2A (WS2A) and Tietz syndrome, autosomal dominant disorders resulting in deafness and hypopigmentation. Mitf mice thus represent an important model system for the study of human disease. Here we report the complete exon/intron structure of the mouse Mitf gene and show it to be similar to the human gene. We also found that the mouse gene is transcriptionally complex and is capable of generating at least 13 different Mitf isoforms. Some of these isoforms are missing important functional domains of the protein, suggesting that they might play an inhibitory role in Mitf function and signal transduction. In addition, we determined the molecular basis for six microphthalmia mutations. Two of the mutations are reported for the first time here ( Mitf mi-enu198 and Mitf mi-x39 ), while the others ( Mitf mi-ws , Mitf mi-bws , Mitf mi-ew , and Mitf mi-di ) have been described but the molecular basis for the mutation not determined. When analyzed in terms of the genomic and transcriptional data presented here, it is apparent that these mutations result from RNA processing or transcriptional defects. Interestingly, three of the mutations ( Mitf mi-x39 , Mitf mi-bws , and Mitf mi-ws ) produce proteins that are missing important functional domains of the protein identified in in vitro studies, further confirming a biological role for these domains in the whole animal.

Tephrochronology, Environmental Change and the Norse Settlement of Iceland

Abstract: The first human impacts on the Icelandic environment came with the Norse colonisation or Landnam of the ninth century AD. The colonisation represents a fundamental environmental change that is both rapid and profound. In this paper we assess geomorphological dimensions of the initial settlement period using a tephrochronology that includes the Landnam Tephra, erupted ca. 870 AD, two tenth century AD tephras KR 920 and E 935, and 11 other well dated tephra layers. We report a new 14C age of 1676 ±12 14C yr BP (cal AD 345 (400) 419) for the tephra SILK-YN which forms a key prehistoric marker horizon that constrains rates of environmental change in the centuries before Norse Settlement. Aeolian sediment accumulation rates show five geomorphological responses to settlement that differ in the rate and trajectory of change. These distinct anthropogenic signals are the result of spatially variable sensitivity to grazing and deforestation, and reflect the extent of local soil erosion. This critical erosio...

Resources, Agriculture and Economic Growth in Economies in Transition

Abstract: This paper reviews some reasons why natural resource abundance and extensive agriculture appear to impede economic growth around the world. The paper presents empirical, cross-sectional evidence of various aspects of this relationship in the transition economies in Central and Eastern Europe and Central Asia since 1990. The essence of the argument is that heavy dependence on natural resources and agriculture may result in rent seeking (e.g., corruption) and policy failures (e.g., inflation) and may, moreover, discourage education, external trade, and genuine saving, thereby retarding economic growth. The paper concludes with a brief discussion of the policy implications of the analysis.

On the plasma parameters of a planar inductive oxygen discharge

Abstract: Langmuir probes and a quadrupole mass spectrometer were used to determine the plasma parameters of an oxygen plasma in a planar inductive discharge. The electron density, effective electron temperature, the dc plasma potential and the electron energy probability function (EEPF) in the discharge centre plane were investigated as functions of power, gas pressure and radial position. The ion energy distribution and relative density of positive ions at the radial sheath edge were investigated as functions of power and pressure. A volume-averaged global model of the electronegative oxygen discharge is developed. The model uses a power balance equation to account for energy deposited into the plasma and lost via collisions and particle flux. The particle densities are modelled via rate equations estimated from collision cross sections assuming Maxwellian electron energy distribution functions. The volume-averaged model is shown to predict the experimental trends over a range of process conditions.

Icelandic Norms for the Snodgrass and Vanderwart (1980) Pictures: Name and Image Agreement, Familiarity, and Aage of Acquisition

Abstract: This paper presents Icelandic norms for the widely used pictorial stimuli of Snodgrass and Vanderwart (1980). Norms are presented for name agreement, familiarity, imageability, rated and objective age-of-acquisition (AoA) of vocabulary, and word frequency. The ratings were collected from 103 adult participants while the objective AoA values were collected from 279 children, 2,5–11 years of age. The present norms are in many respects similar to those already collected for other language groups indicating that the stimuli will be useful for further psychological studies in Iceland. The rated AoA values show a high correlation with objective AoA (r = 0.718) thus confirming previous studies conducted with English speaking participants that rated AoA is a relatively valid measure of objective AoA. However, word frequency and familiarity are more closely correlated with rated AoA than with objective AoA indicating that these factors play some role in the ratings. Objective AoA norms are therefore to be preferred in studies of cognitive processes.