Showing papers by "Stockholm University published in 1994"
01 Nov 1994-Comparative Biochemistry and Physiology Part C: Pharmacology, Toxicology and Endocrinology
TL;DR: 11-Oxygenated androgens are generally more effective than T in stimulating secondary sexual characters, reproductive behaviour and spermatogenesis in teleost fishes but receptor-like binding has only reported for T and not for 11KT.
802 citations
TL;DR: In this paper, the authors present a presentation of 30 relationships, the 30Rs, as a way of making the relationship marketing philosophy more operational and generally applicable, providing a basis for companies to work out their own specific relationship portfolio as part of their marketing planning process.
Abstract: Based on a research project with the purpose of defining the essence and scope of relationship marketing (RM). The marketing mix theory, which constitutes the prevailing approach to marketing, is made operational through the definition of the 4Ps and extensions of these. The core is a presentation of 30 relationships, the 30Rs, as a way of making the RM philosophy more operational and generally applicable. The 30Rs provide a basis for companies to work out their own specific relationship portfolio as part of their marketing planning process.
797 citations
TL;DR: It is shown that symmetry preferences may arise as a by-product of the need to recognize objects irrespective of their position and orientation in the visual field as well as by natural selection acting on biological signals and human artistic innovation.
Abstract: Humans and certain other species find symmetrical patterns more attractive than asymmetrical ones. These preferences may appear in response to biological signals, or in situations where there is no obvious signalling context, such as exploratory behaviour and human aesthetic response to pattern. It has been proposed that preferences for symmetry have evolved in animals because the degree of symmetry in signals indicates the signaller's quality. By contrast, we show here that symmetry preferences may arise as a by-product of the need to recognize objects irrespective of their position and orientation in the visual field. The existence of sensory biases for symmetry may have been exploited independently by natural selection acting on biological signals and by human artistic innovation. This may account for the observed convergence on symmetrical forms in nature and decorative art.
396 citations
TL;DR: In this paper, the authors report evidence for steep declines in the atmospheric concentrations of base cations (sum of non-sea-salt Ca2+, Mg2+, K+ and Na+) over the past 10 to 26 years from high-quality precipitation chemistry records in Europe and North America.
Abstract: HUMAN activities have caused marked changes in atmospheric chemistry over large regions of Europe and North America. Although considerable attention has been paid to the effects of changes in the deposition of acid anions (such as sulphate and nitrate) on terrestrial and aquatic ecosystems1–7, little is known about whether the concentrations of basic components of the atmosphere have changed over time8,9 and what the biogeochemical consequences of such potential changes might be. In particular, there has been some controversy8–12 as to whether declines in base-cation deposition have countered effects of recent reductions in SO2emission. Here we report evidence for steep declines in the atmospheric concentrations of base cations (sum of non-sea-salt Ca2+, Mg2+, K+ and Na+) over the past 10 to 26 years from high-quality precipitation chemistry records in Europe and North America. To varying but generally significant degrees, these base-cation trends have offset recent reductions in sulphate deposition in the regions examined. The observed trends seem to be ecologically important on decadal timescales, and support earlier contentions8–10 that declines in the deposition of base cations may have contributed to increased sensitivity of poorly buffered ecosystems.
389 citations
TL;DR: The results are consistent with the assumption that psychological stress plays a role in musculoskeletal disorders by increasing muscular tension both in low-load work situations and in the absence of physical load.
Abstract: Although it is generally assumed that mental stress induces muscular tension, the experimental data have, so far, been inconclusive. Likely explanations for these inconsistent findings are (a) too small subject samples in some experiments, (b) the use of only one type of stress stimulation, and (c) the lack of objective (physiological) measurements documenting the stress-inducing properties of the experimental treatment. Furthermore, the effect of mental stress and physical load separately, versus the combined influence of physical and mental load on muscular tension, has not been investigated earlier. Therefore. the aim of the present experiment was to examine the effects of mental stress as well as of physical load, separately and in combination, on perceived stress, physiological stress responses, and on muscular tension as reflected in electromyographical (EMG) activity of the trapezius muscle. Sixty two female subjects were individually exposed to mental arithmetic, the Stroop color word test (CWT), the cold pressor test, standardized test contractions (TCs), and the CWT combined with a TC. Compared to baseline, the stress session induced significant increases in systolic and diastolic blood pressure, heart rate, urinary catecholamines, salivary Cortisol, and self-reported stress. Each of the two mental stress tests induced a significant increase in EMG activity, The CWT caused a rise in EMG activity also during the TC, which was significantly more pronounced than the increase induced by the CWT alone. Blood pressure responses and self-reported stress followed the same pattern as the EMG activity. The results are consistent with the assumption that psychological stress plays a role in musculoskeletal disorders by increasing muscular tension both in low-load work situations and in the absence of physical load. It is also indicated that the stress-induced increase in muscular tension is accentuated on top of a physical load.
355 citations
TL;DR: The classic murine muscular dystrophy strain, dy, was first described almost 40 years ago and the molecular basis of an allele of dy, called dy 2J, is identified by detecting a mutation in the laminin α2 chain gene — the first identified mutation in lamin in-2.
Abstract: The classic murine muscular dystrophy strain, dy, was first described almost 40 years ago. We have identified the molecular basis of an allele of dy, called dy2J, by detecting a mutation in the laminin α2 chain gene — the first identified mutation in laminin-2. The G to A mutation in a splice site consensus sequence causes abnormal splicing and expression of multiple mRNAs. One mRNA is translated into an α2 polypeptide with a deletion in domain VI. The truncated protein apparently lacks important qualities of the wild type protein and is unable to provide sufficient muscle stability.
345 citations
TL;DR: It is argued that for the understanding of life history variation it is necessary to consider not only the two dimensions of age and size, but also to take into full account the triangular nature of the relationship between size, time and growth rate.
Abstract: An important assumption made in most lifehistory theory is that there is a trade-off between age and size at reproduction. This trade-off may, however, disappear if growth rate varies adaptively. The fact that individuals do not always grow at the maximum rate can only be understood if high growth rates carry a cost. This study investigates the presence and nature of such costs inPararge aegeria. Five females from two populations with known differences in life history (south Sweden and Maderia) were allowed to oviposit in the laboratory and their offspring were reared in environmental chambers under conditions leading to direct development. We measured several aspects of life history, including development times, pupal and adult weights, growth rate, female fecundity, longevity and larval starvation endurance. In both populations there seemed to be genetic variation in growth rate. There was no evidence for a trade-off between age and size at pupation. As predicted, larvae with high growth rates also lost weight at a relatively higher rate during starvation. High weight-loss rates were furthermore associated with a lower probability of surviving when food became available again. This is apparently the first physiological trade-off with growth rate that has been experimentally demonstrated. In both populations there were significant differences in growth rate between the sexes, but the populations differed in which sex was growing at the highest rate. In Sweden males had higher growth rates than females, whereas the reverse was true for Madeira. These patterns most likely reflect differences in selection for protandry, in turn caused by differences in seasonality between Sweden and Madeira. Together with the finding that males had shorter average longevity than females in the Swedish, but not in the Maderiran, population, this indicates that a lower adult quality also may be a cost of high growth rate. We argue that for the understanding of life history variation it is necessary to consider not only the two dimensions of age and size, but also to take into full account the triangular nature of the relationship between size, time and growth rate.
310 citations
TL;DR: The concentrations of hydroxylated PCB in the blood were almost in the same range as the most persistent PCB congeners both for seals and humans.
Abstract: Polychlorinated biphenyls (PCBs) are important environmental contaminants, and their toxicity to wildlife and humans are of major concern. PCBs form persistent and abundant metabolites, PCB methyl sulfones, that accumulate in biota. We now report that certain hydroxylated PCB metabolites show a strong and selective accumulation in mammalian blood. Plasma from experimentally PCB-dosed rats and blood from environmentally exposed grey seals (Halichoerus grypus) and humans were analyzed. Among all possible hydroxylated metabolites of PCB that may be formed, only a few, dominated by 4-OH-2,3,5,3',4'-pentachlorobiphenyl and 4-OH-2,3,5,6,2',4',5'-heptachlorobiphenyl, were found in the blood samples. All identified compounds have a structure with the hydroxy group in a para or meta position, with chlorine atoms on vicinal carbon atoms. The concentrations of hydroxylated PCB in the blood were almost in the same range as the most persistent PCB congeners both for seals and humans.
308 citations
TL;DR: Traditional gender differences in terms of main responsibility for household duties, child care etc. are revealed, with women reported higher levels of work overload, stress and conflict than men, which increased significantly with the number of children at home.
Abstract: A questionnaire assessing various aspects of paid as well as unpaid forms of productive activity was mailed to stratified samples of male and female white collar workers, approximately matched for educational and occupational level. Data from 501 men and 679 women employed full time revealed traditional gender differences in terms of main responsibility for household duties, child care etc. In keeping with this, women reported higher levels of work overload, stress and conflict than men, which increased significantly with the number of children at home. The various stress indices reached a peak between the ages of 35 and 39. Men reported more autonomy in their paid work whereas women reported more control at home. Men and women at the upper managerial levels reported more control over their total work situation and less conflict between demands.
296 citations
TL;DR: In this paper, the future of service management in specific service management terms but also in broader, societal terms, from both a practitioner and a scholarly perspective, is discussed, and a new era of management that will fight the battle for economic survival in the future service society is presented.
Abstract: Deals with the future of service management in specific service management terms but also in broader, societal terms, from both a practitioner and a scholarly perspective. Claims that service management concerns not only what is traditionally known as service organizations, but also constitutes a future paradigm for organizations in general. The goods‐services division in its traditional sense is outdated; it represents a myopic production view, while the service economy is an expression for customer‐oriented and citizen‐oriented, value‐enhancing offering. Although service management has taken a giant step since the late 1970s, we are just beginning to see a new era of management that will fight the battle for economic survival in the future service society.
271 citations
TL;DR: The authors argue that these models constrain rather than empower the inquiry and the interpretation of the learning processes occurring in the classroom, which results in an "opportunistic" differentiation among contexts of interpretation.
TL;DR: In this article, the nature of the reactions that underlie the conversion of solar energy into chemical energy by photosynthesis is revealed, and a blueprint for new technologies to exploit solar energy is emerging.
Abstract: Recent research has revealed the nature of the reactions that underlie the conversion of solar energy into chemical energy by photosynthesis. Armed with this knowledge, a blueprint for new technologies to exploit solar energy is emerging.
TL;DR: In this paper, the question of whether or not distinct glacial and non-glacial landforms can survive beneath ice sheets and ice caps with little or no morphological alteration is addressed.
TL;DR: Rather than being a component of the haemolymph, the Drosophila lysozymes are found mainly in the digestive tract where they are expressed at a high level, and all genes, except LysP, encode acidic proteins, in contrast to the strongly basic “typical” ly sozymes.
Abstract: Lysozyme has been studied in insects as part of the system of inducible antibacterial defence in the haemolymph. We recently found two Drosophila lysozyme genes that are constitutively expressed in the digestive tract, and are probably involved in the digestion of bacteria in the food. To obtain an overview of the lysozyme genes in this species and their possible roles in immunity and digestion, we have now characterized all six lysozyme genes in the cloned part of the lysozyme locus at 61F, and a seventh gene that maps to the same chromosomal location. The expression of the genes follows four different patterns: firstly, four closely related genes, LysB, C, D and E, are all strongly expressed in the midgut of larvae and adults; secondly, LysP is expressed in the adult salivary gland; thirdly, LysS is expressed mainly in the gastric caecae of larvae; and finally, LysX is primarily expressed in the metamorphosing midgut of late larvae and early pupae. The LysD-like genes and LysS are strongly repressed in artificially infected animals, possibly reflecting a malaise reaction in the digestive tract. None of the genes is expressed in the fat body or haemocytes. Thus rather than being a component of the haemolymph, the Drosophila lysozymes are found mainly in the digestive tract where they are expressed at a high level. Furthermore all genes, except LysP, encode acidic proteins, in contrast to the strongly basic “typical” lysozymes. This is highly reminiscent of the situation in ruminants, where the lysozymes have been recruited for the digestion of symbiotic bacteria in the stomach.
TL;DR: The structure of the low-molecular-weight PTPase supports a reaction mechanism involving the conserved Cys 12 as an attacking nucleophile in an in-line associative mechanism and suggests a catalytic role for Asp 129 in the reaction cycle.
Abstract: PROTEIN tyrosine phosphorylation and dephosphorylation are central reactions for control of cellular division, differentiation and development1. Here we describe the crystal structure of a low-molecular-weight phosphotyrosine protein phosphatase (PTPase)2, a cytosolic phosphatase present in many mammalian cells. The enzyme catalyses the dephosphorylation of phosphotyrosine-containing substrates3–6, and overexpression of the protein in normal and transformed cells inhibits cell proliferation7,8. The structure of the low-molecular-weight PTPase reveals an α/β protein containing a phosphate-binding loop motif at the amino end of helix αl. This motif includes the essential active-site residues Cys 12 and Arg 18 and bears striking similarities to the active-site motif recently described in the structure of human PTP1B9. The structure of the low-molecular-weight PTPase supports a reaction mechanism involving the conserved Cys 12 as an attacking nucleophile in an in-line associative mechanism. The structure also suggests a catalytic role for Asp 129 in the reaction cycle.
TL;DR: It is shown that almost any desired energy fluence distribution can be created even when the limitations on velocity and acceleration are considered, and the method developed here for multileaf collimators is also suitable for simple block collims since it can be used to deliver arbitrary regular or irregular 'dynamic wedge' profiles along the direction of motion of the collimator blocks.
Abstract: All current optimization techniques in radiation therapy benefit from the use of strongly non-uniform radiation beams. The most flexible way of generating these fields under real time control is by elementary beam scanning and/or dynamic multileaf collimation. In this work general analytical expressions are derived for the required motion of the collimator leaves to achieve a desired energy fluence distribution or collimator opening density in the patient in the shortest possible time. By simplification of the general expressions the equations of motion have been derived for both the shrinking field and the curtain shutter techniques with the associated approximations clearly quantified. The mechanical limitations on leaf motion, caused by the finite velocity and acceleration, are taken into account. It is shown that almost any desired energy fluence distribution can be created even when the limitations on velocity and acceleration are considered. The basic rule with the curtain shutter technique is that when the energy fluence gradient along the direction of motion of the leaves is positive, the leading leaf should move at maximum speed and the lagging leaf should modulate the field. In regions where the gradient is negative the lagging leaf should instead move at full speed and the leading leaf should modulate the field. The overall treatment time is then proportional to the total increment in energy fluence or opening density between consecutive minima and maxima. For energy fluence profiles with numerous high peaks the treatment time may therefore increase considerably over that for conventional uniform dose delivery. However, in general the treatment time is prolonged by a factor of about two compared to a traditional uniform treatment. Obviously the method developed here for multileaf collimators is also suitable for simple block collimators since it can be used to deliver arbitrary regular or irregular 'dynamic wedge' profiles along the direction of motion of the collimator blocks.
TL;DR: In this article, a method for static exchange calculations of the photoabsorption spectra of large molecules and clusters, with particular attention to near-edge X-ray absorption fine structures, is presented.
TL;DR: In this article, an alternative classification of values is suggested; primary and secondary values are defined as the outputs, life-support functions and services, generated by wetlands and methods for measuring these values are discussed.
Abstract: Wetlands are continuously degraded in many parts of the world. One reason is the lack of the appropriate valuation of the multifunctionality of wetland. In an attempt to improve the understanding of the importance of this feature of wetlands an alternative classification of values is suggested; primary and secondary values. Primary value refers to the development and maintenance of ecosystems — their self-organizing capacity. Secondary values are defined as the outputs, life-support functions and services, generated by wetlands. Methods for measuring these values are discussed. Three case studies are presented which use different valuation methods and which to different degrees capture the primary and secondary values. It is concluded that only part of the total wetland value can be captured in monetary terms.
TL;DR: The paper mainly focusses on nutritional aspects of environmental load, which has greatly reduced overall environmental loads, which are presently calculated with 10 kg phosphorus and 60 kg nitrogen per tonne of fish produced.
Abstract: Summary
The extent of the environmental impact of an aquaculture development is mainly dependent on husbandry, feeding technique, feed composition and site selection. Feed composition, digestibility and feed conversion coefficient are of paramount importance for the level of discharge of wastes derived from fish farming. These determine the release of nutrients (e.g. phosphorus and nitrogen) and organic material. Excretion products (in particular waste feed and faeces) may cause changes in the ecosystem. However, the overall environmental load derived from aquaculture is comparatively small when compared to other waste loads from communities, industries, agriculture and forestry. The amount of phosphorus and nitrogen in feeds has decreased to 1 % and 7%, respectively, while feed conversion efficiency due to high energy feeds has improved to values around 1.2 in most salmon farming operations. This has greatly reduced overall environmental loads, which are presently calculated with 10 kg phosphorus and 60 kg nitrogen per tonne of fish produced. The organic wastes per tonne produced are presently estimated to reach 2500 kg wet weight per tonne live weight fish. System design and site selection are additional important considerations which influence greatly the level of environmental impact. The advantage of land-based systems over water-based systems is the fact that water treatment of effluents is possible in such systems, thereby greatly reduction total loads to receiving waters. The paper mainly focusses on nutritional aspects of environmental load.
TL;DR: The aim of this work has been to examine whether i.v.Ig may influence cytokine production as an additional mode of immunoregulatory influence during treatment of various conditions of unknown origin.
Abstract: Human immunoglobulin preparations for intravenous use (i.v.Ig) have been successfully used in controlled clinical trials as substitution therapy for hypogammaglobulinemia (Ammann et al. 1982), but also in treatment of various conditions of unknown origin such as idiopathic thrombocytopenic purpura (Imbach et al. 1981), Kawasaki disease (Newburger et al. 1986) and dermatomyositis (Dalakas et al. 1993). The mechanisms by which i.v.Ig act in these diseases, apart from the antibody deficiencies, are not fully understood. Immunomodulatory effects of i.v.Ig include, among others, antigen neutralization, Fc-receptor blockade and anti-idiotypic interactions, all of which will be discussed in other reports of this volume. The aim of this work has been to examine whether i.v.Ig may influence cytokine production as an additional mode of immunoregulatory influence. Most of this presentation will be based on results obtained with studies of i.v.Igmediated effects on cytokine production in human cell cultures. Not many publications in the literature have addressed the question of whether i.v.Ig exposure of cells in vivo or in vitro will influence cytokine synthesis. Some examples of such studies will be summarized below. IL-1 receptor-antagonist (ILlra) was originally discovered in the supernatant of human monocytes cultured on adherent IgG (Arend et al. 1985). It was later confirmed that the co-culture of human monocytes and low doses of i.v.Ig also led to IL-1 ra formation (Pouts-
TL;DR: In this article, the authors compare two political regimes: direct democracy and representative democracy, where voters vote directly on the policy and elect a representative who then chooses policy, and show that in both regimes some form of commitment by the voters is necessary to avoid excessive taxation of capital.
TL;DR: In this paper, the authors provided a research report on leadership styles studied in a range of countries, industry types and organization levels, and found that the results showed no evidence of contingency effects, i.e. variations in effectiveness across broad contexts such as branch, function or hierarchic level, although the clusters differed with regard to representation in different contexts.
Abstract: The paper provides a research report on leadership styles studied in a range of countries, industry types and organization levels. Unequivocal evidence has been found for a three factor model of style, incorporating the well-known, task-oriented/people-oriented factors, and a change-oriented factor. The new factor is presumed to be a consequence of more turbulent environments. Further analysis of the leader reports (supplied by 3,857 respondent ‘followers’) found ten clusters of ‘blends’ of style, of which three - labelled super-leaders, gardeners and MBO leaders - were consistently rated more effective and most liked by subordinates. A significant theoretical implication is that the results showed no evidence of contingency effects, i.e. variations in effectiveness, across broad contexts such as branch, function or hierarchic level, although the clusters differed with regard to representation in the different contexts.
14 Feb 1994
TL;DR: In this article, the authors present a method for translating a schema in the relational model into a conceptual model, where the conceptual model is a formalization of an extended ER model, which also includes the subtype concept.
Abstract: A major problem with currently existing database systems is that there often does not exist a conceptual understanding of the data. Such an understanding can be obtained by describing the data using a semantic data model, such as the ER model. Consequently, there is a need for methods that translate a schema in a traditional data model into a conceptual schema. We present a method for translating a schema in the relational model into a schema in a conceptual model. We also show that the schema produced has the same information capacity as the original schema. The conceptual model used is a formalization of an extended ER model, which also includes the subtype concept. >
TL;DR: It is suggested that postnatal influences may well be as important as prenatal influences in producing any effect on ischaemic heart disease mortality and that the type of growth retardation in utero experienced by twins may not constitute a risk for ischaemia heart disease in adulthood.
TL;DR: In this article, a modem pollen/land-use data set of 124 surface samples (moss polsters) from different vegetation and land-use types in south Sweden is presented, where patterns of modern local pollen variation in relation to these environmental variables are explored by canonical correspondence analysis and tested by associated statistical procedures.
TL;DR: In this article, the authors abstract completely from well-understood economic issues and focus instead on the political effects of centralization, and show that centralization changes the coalition of voters who favor a large program in a direction that depends on the nature of the redistributive instrument.
TL;DR: Fish from the Baltic Sea is a major source of exposure to these compounds in Swedes and PCB congeners investigated, as well as for DDT and DDE, there were statistically significant associations with fish intake.
Abstract: Fatty fish species, e.g., salmon and herring, in the Baltic Sea have high levels of polychlorinated biphenyls (PCBs) and 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (p,p'-DDT), and its main metabolite: 1,1-dichloro-2,2-bis(p-chlorophenyl)-ethylene (p,p'-DDE). We determined levels of 10 different PCB congeners, including non- and mono-ortho-PCBs, as well as DDT and DDE, in human blood plasma from 37 subjects with varying intake of fish (0-1 750 g/wk) from the Baltic Sea. With respect to all of the PCB congeners we investigated, as well as for DDT and DDE, there were statistically significant associations with fish intake. Thus, fish from the Baltic Sea is a major source of exposure to these compounds in Swedes. Polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) had been determined earlier in 29 of the subjects. The PCB contribution to "dioxin-like" effects among high consumers of fish (calculated as Nordic TCDD equivalents) was almost 80%, whereas that from PCDD and PCDF was only 20%.