Showing papers by "Stockholm University published in 1983"

Assessment of chronic pain. I. Aspects of the reliability and validity of the visual analogue scale

Abstract: The visual analogue scale (VAS) is a simple and frequently used method for the assessment of variations in intensity of pain. In clinical practice the percentage of pain relief, assessed by VAS, is often considered as a measure of the efficacy of treatment. However, as illustrated in the present study, the validity of VAS estimates performed by patients with chronic pain may be unsatisfactory. Two types of VAS, an absolute and a comparative scale, were compared with respect to factors influencing the reliability and validity of pain estimates. As shown in this study the absolute type of VAS seems to be less sensitive to bias than the comparative one and is therefore preferable for general clinical use. Moreover, the patients appear to differ considerably in their ability to use the VAS reliably. When assessing efficacy of treatment attention should therefore be paid to several complementary indices of pain relief as well as to the individual's tendency to bias his estimates.

Characteristics of northern hemisphere blocking as determined from a long time series of observational data

Abstract: 30 years of observational 500 mb geopotential height data have been used to assess the characteristics of northern hemisphere blocking situations. A zonal index suitable for identification of blockings is defined and translated into a computer program. Characteristics of blocking situations have been computed and are presented as statistics. As expected, there are 2 preferred regions for blocking, the Atlantic region and the Pacific region. The results show that the number of days with blocked flow has a maximum over the eastern part of the Atlantic region, while the maximum is found over the western part of the Pacific region. The annual variation shows that there is an extended maximum from February through April in the Atlantic region, while there is a pronounced maximum in January in the Pacific region. The occurrence of simultaneous blocking in the 2 regions has also been investigated. The results show that there is no preference for a connection. Investigation of individual blocking situations reveals that the shortest ones are also formed in preferred geographical locations, and are not just random configurations in the changing pattern of waves in the Westerlies. There is a tendency for blocking episodes to seem to be concentrated in certain geographical locations, the longer the duration of the episode. The results also show that long-lasting episodes are notably more frequent in the Atlantic region than in the Pacific. DOI: 10.1111/j.1600-0870.1983.tb00210.x

On lexicographically shellable posets

Abstract: Lexicographically shellable partially ordered sets are studied. A new recursive formulation of CL-shellability is introduced and exploited. It is shown that face lattices of convex polytopes, totally semimodular posets, posets of injective and normal words and lattices of bilinear forms are CL-shellable. Finally, it is shown that several common operations on graded posets preserve shellability and CL-shellability.

Microsomal glutathione transferase. Purification in unactivated form and further characterization of the activation process, substrate specificity and amino acid composition.

Abstract: The procedure developed for purification of the N-ethylmaleimide-activated microsomal glutathione transferase was applied successfully to isolation of this same enzyme in unactivated form. The microsomal glutathione transferases, the unactivated and activated forms, were shown to be identical in terms of molecular weight, immunochemical properties, and amino acid composition. In addition the microsomal glutathione transferase purified in unactivated form could be activated 15-fold with N-ethylmaleimide to give the same specific activity with 1-chloro-2,4-dinitrobenzene as that observed for the enzyme isolated in activated form. This activation involved the binding of one molecule N-ethylmaleimide to the single cysteine residue present in each polypeptide chain of the enzyme, as shown by amino acid analysis, determination of sulfhydryl groups by 2,2'-dithiopyridyl and binding of radioactive N-ethylmaleimide. Except for the presence of only a single cysteine residue and the total absence of tryptophan, the amino acid composition of the microsomal glutathione transferase is not remarkable. The contents of aspartic acid/asparagine + glutamic acid/glutamine, of basic amino acids, and of hydrophobic amino acids are 15%, 12% and 54% respectively. The isoelectric point of the enzyme is 10.1. Microsomal glutathione transferase conjugates a wide range of substrates with glutathione and also demonstrates glutathione peroxidase activity with cumene hydroperoxide, suggesting that it may be involved in preventing lipid peroxidation. Of the nine substrates identified here, the enzymatic activity towards only two, 1-chloro-2,4-dinitrobenzene and cumene hydroperoxide, could be increased by treatment with N-ethylmaleimide. This treatment results in increases in both the apparent Km values and V values for 1-chloro-2,4-dinitrobenzene and cumene hydroperoxide. Thus, although clearly distinct from the cytosolic glutathione transferases, the microsomal enzyme shares certain properties with these soluble enzymes, including a relative abundance, a high isoelectric point and a broad substrate specificity. The exact role of the microsomal glutathione transferase in drug metabolism, as well as other possible functions, remains to be established.

The externally contracted CI method applied to N2

Abstract: An approximate multireference CI method is presented. By grouping together configurations with the same internal parts and freezing their relative weights by the use of perturbation theory, the number of variational parameters is drastically reduced. The loss of correlation energy is shown to be usually less than 2%, and the timing is less than one ordinary CI iteration. Examples from calculations on some states of the nitrogen atom and nitrogen molecule are given. The basis set convergence for the lowest excitation energy in the atom is very slow. Less than 50% of the correlation effect is obtained at the s, p, d limit. After the inclusion of ƒ functions this value is improved to 83%. The dissociation energies of the molecule also show slow basis set convergence with errors of 0.5 eV even after addition of ƒ functions. The bond distances are, howeever, accurately reproduced with errors of less than 0.005 A for all the states. A qualitative discussion of predissociation in the a1Πg and B3Πgstates caused by spin–orbit interaction with the 5Σg+ state, is finally presented. Rapidly oscillating lifetimes between the different vibrational states are predicted.

Elemental carbon in the atmosphere: cycle and lifetime

Abstract: Particulate elemental carbon is found in the atmosphere in both urban and remote regions and isoften responsible for much of the absorption of solar radiation by atmospheric aerosols. Itsatmospheric lifetime is controlled by four factors: the initial size distribution, the concentrationof ambient particles, the frequency and duration of precipitation, and the efficiencies of removalmechanisms. A model of the atmospheric cycle of particulate elemental carbon which includesthese factors has been used to estimate the range of atmospheric lifetimes expected under variousconditions. Calculated lifetimes range from under 40 hours in rainy climates to well over 1 weekin clean, dry regions. DOI: 10.1111/j.1600-0889.1983.tb00027.x

Respiratory activity of isolated rat brain mitochondria following in vitro exposure to oxygen radicals.

Abstract: Respiratory activity of isolated rat brain mitochondria was measured following in vitro exposure to oxygen radicals. The radicals were generated by hypoxanthine and xanthine oxidase in the presence of a suitable iron chelate and caused a severe inhibition of respiration stimulated by phosphate plus ADP (with malate + glutamate as substrate). The damage could be prevented by catalase or high concentrations of mannitol, but not by superoxide dismutase. A similar effect was observed when hypoxanthine and xanthine oxidase were replaced by glucose and glucose oxidase or by hydrogen peroxide. Most of the findings indicate that the hydroxyl radical is the damaging agent. It is concluded that brain mitochondria exposed to oxygen radicals in vitro show an inhibition of respiratory activity similar to that reported by other investigators as occurring in mitochondria in vivo following transient cerebral ischemia. Therefore, oxygen radicals may contribute to this type of cell damage.

The “Tsesis” oil spill: Acute and long-term impact on the benthos

Abstract: The “Tsesis” oil spill in October 1977 resulted in the release of over 1 000 tons of medium grade fuel oil in an archipelago in the brackish Baltic Sea. Considerable oil quantities reached the benthos by sedimentation. Within 16 d benthic amphipods of the genus Pontoporeia, as well as the polychaete Harmothoe sarsi Kinberg, showed reduction to less than 5% of pre-spill biomasses at the most impacted station. The clam Macoma balthica (L.) was more resistant, and showed little or no mortality, but was heavily contaminated by oil (about 2 000 μg g-1 dry wt total hydrocarbons). The meiofauna was strongly affected, with ostracods, harpacticoids, Turbellaria and kinorhynchs showing clear reductions in abundance, while nematodes, as a group, were more resistant. In the winter following the spill gravid Pontoporeia affinis Lindstrom females showed a statistically significant increase in the frequency of abnormal or undifferentiated eggs. Food-chain transfer of oil to flounder [Platichthys flesus (L.)] was indicated. Not until the second summer after the spill were the first signs of recovery noted at the most heavily impacted station: Amphipods, H. sarsi and harpacticoids increased and the oil concentrations in M. balthica decreased (to about 1 000 μg g-1). In the area where amphipods had been virtually eliminated, there was an unusually heavy recruitment of M. balthica, reaching 4 000 juveniles, of 1.5–2 mm length, per square metre, probably from settling in summer 1978. Three years after the spill Pontoporeia spp. biomass was still depressed in the most affected area, while H. sarsi showed normal biomass, and M. balthica abundance was inflated. Oil concentrations in M. balthica (about 250 μg g-1) and flounder were only slightly elevated and the oil could no longer be confidently ascribed to “Tsesis” origin, even using GC/MS-analysis. Recovery was thus underway, but the long lifespan of M. balthica implies that the disturbed community composition may persist for many years at this station. Full recovery is likely to require more than 5 yr and may take a decade or more. An effort to evaluate the accumulated monetary loss to fishery from the accident indicates that direct costs of shoreline cleanup and vessel damage were considerably greater.

Dosimetry of genotoxic agents and dose-response relationships of their effects☆

Abstract: Dose-response relationships and determination of dose of mutagens and carcinogens are summarized and discussed on the basis of conceptual and kinetic aspects Different dose definitions may be referred to steps in the chain of events from exposure (or emission) to observed effects A system is applied to show the influence of various processes on the kinetics of the transfers between consecutive steps The same system illustrates processes influenced by protraction and fractionation of dose, synergists, comutagens/cocarcinogens, heritable factors, etc The response at a given dose is expected to depend on the product of consecutive transfer functions An application of general rules of chemical kinetics shows that when a chemical is introduced at a sufficiently low level, all processes affecting the transfers and therefore the transfer functions themselves become first-order, provided the induction status of enzymes and the cell-division rate remain constant Under the same conditions, dose-response relationships are expected to be linear, ie without “safe” thresholds However, present knowledge of the kinetics of repair at low levels of DNA damage and of the kinetics of induction of repair functions is not enough complete to be decisive These considerations and the fact that observed dose-response data in some cases indicate the existence of thresholds but in others appear able to reject the threshold hypothesis lead to the conclusion that, generally, dose-response curves are most probably linear down to dose zero However, certain mutagens/carcinogens give rise to lesions repaired so effectively that quasi-thresholds appear in certain subpopulations or organs

The effect of platelet-derived growth factor on morphology and motility of human glial cells

Abstract: Platelet-derived growth factor (PDGF) is a mitogen for several cell types in culture. It is documented in this work that one of the earliest effects of PDGF on serum-starved glial cells is an induction of intensive motile activity. Within the first minute after the addition of PDGF thin membrane lamellae grow out around almost all of the cell circumference. Later, circular arrangements of small ruffles appear on the dorsal surface of the cells. These rings of ruffles vary in size and some encircle almost the whole cell. The organization of the peripheral weave of microfilaments in the PDGF-induced advancing lamellae was closely similar to that of normally growing cells. In the regions of the circular arrangements of ruffles there was an extensive reorganization of the surface actin with unusual arrangements of microfilament bundles and polygonal networks. There was also a general intensification of the translocation of membrane ruffles and spikes from the cell periphery towards the centre of the cell, increased micropinocytotic activity and shuttling of intracellular particles.

Individual differences in perceived exertion assessed by two new methods

Abstract: Each of 30 male subjects judged, in a single session, the loudness of a 1000-Hz tone and the exertion perceived while pedaling a bicycle. Two psychophysical methods were used—one employing a combined category-ratio scale whose upper limit was defined as “maximum sensation” and the other a freer magnitude-estimation scale having no verbal labels. Both methods yielded data consistent with power functions, although the combined category-ratio scale gave slightly smaller exponents. The category-ratio estimates provided a measure of individual differences in perceived exertion: At any work level, the differences across subjects in judgment correlated with differences in heart rate (a physiological indicant of strain); this result is consistent with Borg’s hypothesis that in dynamic work, maximal sensation is at least roughly equivalent across subjects. When the magnitude and the category-ratio estimates were converted to equivalent loudness (Stevens and Marks’s method of magnitude matching), the derived loudness values also correlated with heart rate: This outcome provides evidence for the utility of the cross-modal procedure and provides further evidence consistent with Borg’s model of perceived exertion.

A simple calculation of inelastic mean free path and stopping power for 50 eV-50 keV electrons in solids

Abstract: Inelastic electron scattering is calculated by means of a simplified model of the generalised oscillator strength density distribution of an atomic or solid target. The parameters of the model are a limited set of resonance energies (partial mean ionisation potentials) and oscillator strengths. Methods to estimate these parameters, involving a fit of the partial mean ionisation potentials to the empirical atomic mean ionisation potential, are described. The valence electron partial mean ionisation potential may be determined from the dielectric energy loss function, the local plasma approximation, or empirically. Good agreement with experiment and with recent calculations of stopping power and inelastic mean free path is obtained in the electron energy range 50 eV-50 keV.

Analysis of Toxaphene (PCC) and Chlordane in Biological Samples by NCI Mass Spectrometry

Abstract: Several recent reports indicate that both toxaphene (polychlorocamphene, PCC) and chlordane are widespread pollutants in our environment. These insecticides, both complex mixtures of chlorinated hydrocarbons, are difficult to separate from each other. Thus the analyses of them in environmental samples are difficult and furthermore complicated by interferences from other chlorinated hydrocarbons such as PCB and DDT compounds. Mass fragmentography using the negative ions formed by chemical ionization proved to be useful to selectively detect the toxaphenes and the chlordanes without interferences from DDT. High concentrations of PCB still influence on the results and have to be removed in the clean-up procedure.

Genetic differentiation in four European subspecies of red deer (Cervus elaphus L.).

Abstract: Red deer representing the four different European subspecies Cervus elaphus atlanticus, C. e. elaphus, C. e. germanicus, and C. e. scoticus were examined for allozyme variability at 35 enzyme loci. The proportion of polymorphic loci within populations (P) ranged from 0 to 13.8 per cent and the average heterozygosity (H) from 0 to 3.6 per cent. These estimates are within the range previously observed among mammalian species. Significant allele frequency differences were found both within and between subspecies. The mean genetic distance between subspecies (D = 0.0164) was smaller than the differentiation at similar taxonomic levels among other ungulates, probably because of a shorter time since divergence. Within subspecies the genetic differences between populations were similar to those reported between populations within closely related species in the same geographic region. Cluster analysis based on genetic distances indicated a major genetic dichotomy between the British C. e. scoticus and the Norwegian C. e. atlanticus on one hand and the Swedish C. e. elaphus and the continental C. e. germanicus on the other. Populations of pure C. e. elaphus were not found to differ genetically in any substantial way from Swedish populations of possible heterogeneous subspecific origin. An allele unique to C. e. scoticus was found in a Swedish enclosed population where imports of British deer are known to have taken place. A population established to preserve the genetic characteristics of the C. e. elaphus subspecies appeared to have lost 36 per cent of the electrophoretically measurable heterozygosity.