Showing papers by "Stockholm University published in 1988"
TL;DR: It was concluded that the osseointegrated implant, if inserted according to the guidelines of Branemark, results in a very high degree of clinical success, thereby meeting any published oral implant success criteria.
Abstract: Fourteen Swedish teams outside the University of Gothenburg, each with minimally three years' experience in the Nobelpharma osseointegrated implant participated in a retrospective multiclinic study. The total number of consecutively inserted implants at the 14 clinics was 8139. The outcome of every implant was reported and all implant failures, irrespective of when they occurred, were published. The success criteria included absence of implant mobility, absence of radiolucent zones on x-rays, and an annual bone loss after the first year of less than 0.2 mm. In the mandible 334 implants were followed for five to eight years, with only three failures, for a success rate of 99.1%. In the maxilla 106 implants were followed for five to seven years, with a success rate of 84.9%. In irradiated and grafted mandibles, 56 implants were inserted and none was lost during a follow-up of up to five years. In the irradiated maxilla there were 16 implants inserted with three reported failures and in the grafted upper jaw 71 implants were inserted with 12 failures. The proportions of mandibular and maxillary sleeping implants were 0.8 and 0.3%, of patient drop-out implants 0.3 and 0.6%, and of patient death implants 0.9 and 1.2%, respectively. It was concluded that the osseointegrated implant, if inserted according to the guidelines of Branemark, results in a very high degree of clinical success, thereby meeting any published oral implant success criteria.
572 citations
456 citations
TL;DR: From the foregoing considerations, the energy-linked transhydrogenase reaction emerges as a powerful and flexible element in the network of redox and energy interrelationships that integrate mitochondrial and cytosolic metabolism.
Abstract: From the foregoing considerations, the energy-linked transhydrogenase reaction emerges as a powerful and flexible element in the network of redox and energy interrelationships that integrate mitochondrial and cytosolic metabolism. Its thermodynamic features make it possible for the reaction to respond readily to challenges, either on the side of NADPH utilization or on the side of energy depletion. Yet, the kinetic features are designed to prevent a wasteful input of energy when other sources of reducing equivalents to NADP are available, or to deplete the redox potential of NADPH in other than emergency conditions. By virtue of these characteristics, the energy-linked transhydrogenase can act as an effective buffer system, guarding against an excessive depletion of NADPH, preventing uncontrolled changes in key metabolites associated with NADP-dependent enzymes and calling on the supply of reducing equivalents from NAD-linked substrates only under conditions of high demand for NADPH. At the same time, it can provide an emergency protection against a depletion of energy, especially in situations of anoxia where a supply of reducing equivalents through NADP-linked substrates can be maintained. The flexibility of this design makes it possible that the functions of the energy-linked transhydrogenase vary from one tissue to another and are readily adjustable to different metabolic conditions.
333 citations
TL;DR: The stoichiometry of c Cecropin killing of bacteria suggests that amounts of cecropin sufficient to form a monolayer strongly modify the bacterial membrane.
297 citations
TL;DR: In this review, some important questions concerning the release of coexisting neurotransmitters are discussed and through these some insight is gained into the functional implications of coexistence.
Abstract: The joy of neurobiologists at the discovery of the coexistence of several neuroactive substances within the same neuron terminals can be compared with the delight of a man who has bought a radio he thought would only receive AM broadcasts, but who then discovers that it also gets all the FM stations. The discovery that the given neuronal network has the possibility of transmitting several different signals at the same time, at many of its syn apses, lends new dimensions to the workings of this network. The pace of morphological discovery of ever new examples of the coexistencel colocalization of two or more neuroactive substances in the same neuron is very high, producing several hundred new examples of coexistence phe nomena in the periphery and eNS (cf. 1-6). The work on the functional implications of the possibility of multiple signalling through the same syn apse-using several coexisting neurotransmitters-has been much slower. In this review, we discuss some important questions concerning the release of coexisting neurotransmitters and through these get some insight into the functional implications of coexistence. These questions are as follows: (a) Will a neuron at every one of its processes (dendrites and axon
284 citations
TL;DR: The mechanisms of action of inhibitors of mutagenesis and carcinogenesis are reviewed and the elucidation of the underlying mechanisms complements the results emerging from the monitoring of protective end-points in mutagenicity and carcinogenicity test systems.
Abstract: The mechanisms of action of inhibitors of mutagenesis and carcinogenesis are reviewed in the light of our present knowledge. The identified mechanisms are classified into several categories and sub-categories, depending on the stage of intervention in the mutagenesis and carcinogenesis processes, and on the patterns of modulation of the host defense devices. Although a number of the known mechanisms fit into the proposed scheme, the available information on these problems is still fragmentary, and often inhibitors act through multiple mechanisms or can interact with other inhibitors. Moreover, due to the double-edged nature of many protective factors of the organism, and to the wide array of biological properties displayed by several inhibitors, the beneficial effects are in many instances counter-balanced by adverse reactions. Nevertheless, the present data-base on mechanisms of inhibitors, which is expected to grow rapidly in the near future, provides an extremely useful scientific premise for the primary prevention of mutation-related diseases. In this prospect, the elucidation of the underlying mechanisms complements the results emerging from the monitoring of protective end-points in mutagenicity and carcinogenicity test systems.
280 citations
TL;DR: In this article, a three party bargaining model is developed in which one distinguished party, the firm, has to reac h agreements with the other two parties, each of which is a group of workers.
Abstract: A strategic three party bargaining model is developed in which one distinguished party, the firm, has to reac h agreements with the other two, each of which is a group of workers. In the prebargaining stage, the two worker groups decide whether to organize jointly or separately. The main observation relates the equi librium pattern of unionization to the substitutability in production between the two groups: the outcome is joint or separate unions acco rding to whether the two groups are substitute or complementary facto rs of production. The analysis also considers possibilities for firm' s strategic intervention in the unionization process. Copyright 1988 by Royal Economic Society.
230 citations
TL;DR: It is concluded that unpalatability is an important predisposing factor for the evolution of egg clustering and larval gregariousness in butterflies and kin selection is of minor importance for the development of both unpal atability and warning coloration.
Abstract: Gregariousness ought to be disadvantageous for palatable organisms that live exposed and are relatively immobile and small in comparison to potential predators. Therefore, the idea that unpalatability generally evolves before egg clustering/larval gregariousness in butterflies was tested. Aposematic coloration in the larva was used as the criterion of unpalatability (it is argued that Batesian mimicry is rare in butterfly larvae), and the relative order of evolution of aposematism and gregariousness was inferred through phylogenetic analysis. Here, existing phylogenies were used, and the analysis was based on an assumption of a minimum number of evolutionary changes (parsimony). A total of 23 cases of independent evolution of gregariousness and 12 cases of independent evolution of aposematic coloration were found. In five cases, gregariousness evolved in cryptic species, the palatability of which is unknown. For lineages in which both unpalatability, as evidenced by aposematic coloration, and gregariousness were found and the two evolutionary events could be separated, unpalatability always preceded gregariousness: five cases of independent evolution of warning coloration were followed by a total of 15 cases of independent evolution of gregariousness. In no lineage did gregariousness evolve before warning coloration. It is thus concluded that unpalatability is an important predisposing factor for the evolution of egg clustering and larval gregariousness in butterflies. Insofar as kin selection is related to larval gregariousness, this study indicates that kin selection is of minor importance for the evolution of both unpalatability and warning coloration.
227 citations
TL;DR: An intriguing lateral migration of certain proteins and protein complexes between the appressed and nonappressed regions of the membrane maintains a lateral heterogeneity of function between these two regions to optimize photosynthesis and minimize damage to the photosystems.
222 citations
220 citations
TL;DR: The plausibility of the notion that there is a separate T cell subpopulation with a suppressor function, which exists to control other cells of the immune system is questioned, but the notion of suppressor Tcells as a separate subpopulation of T cells is sceptical.
Abstract: The notion of suppressor T cells has had a great impact in immunology and clinical medicine, A number of diseases, such as allergy and autoimmunity, are now considered to be caused by a relative lack of suppressor T cells, while other conditions, such as immunodeficiencies, are thought to be due to too many suppressor cells. Even fundamental immunological concepts, like immunological tolerance and the distinction between self and non-self, are often thought to be regulated by a delicate balance between suppressor cells and potentially autoreactive T and B cells. The concept of suppressor T cells has markedly affected the way immunologists interpret their findings. A depressed response is generally considered to be caused by suppression and implicitly by suppressor T cells. It is quite interesting to observe the changes that have occurred during the last 15 years: suppressor eells are now considered to be not only the essential, but also the only regulating elements of the immune system. The previous concept of powerful and specific regulating mechanisms, such as antibody feed-back inhibition ofthe immune response that efficiently regulates both T and B cells, now appears to be of little interest, I should like to analyse in general terms the plausibility of the eoneept that there is a separate T cell subpopulation with a suppressor function, which exists to control other cells of the immune system, I am not questioning the existence of suppressive phenomena or findings that T cells can mediate suppressive effects, but I am sceptical ofthe notion of suppressor Tcells as a separate subpopulation of T cells.
TL;DR: The finding of a differential response of macro-and meiofauna to severe hypoxia confirms previous studies which indicate that macrofauna in general is more sensitive than meioFauna to low oxygen concentrations.
Abstract: The response of benthic macro-and meiofauna to severe hypoxia was studied in the deep basis (115 m) of Gullmar Fjord, western Sweden. Abundances and bionasses of the faunal taxa, the redox-potential of the sediment, and the temperature, salinity and dissolved oxygen in the bottom water were recorded over the period 1977 to 1981. In the winter of 1979/80, when a depressed oxygen level of 0.21 ml l-1 was recorded, the macrofaunal component of the fauna disappeared. The ensuing recolonization, with an initial peak of opportunistic capitellid polychaetes, proceeded slowly and the pre-collapse community was not reestablished within 1 1/2 yr after the hypoxia. In contrast, the permanent meiofauna exhibited no clear signs of being affected by the hypoxia. In the temporary meiofauna, polychaetes seemed to be negatively affected. The finding of a differential response of macro-and meiofauna confirms previous studies which indicate that macrofauna in general is more sensitive than meiofauna to low oxygen concentrations.
TL;DR: It is suggested that female preference for loud, rapidly repeated calls may be adaptive in the sense of minimizing the costs of locating conspecific males, rather than maximizing the probability of obtaining a high quality mate.
Abstract: Variation in seasonal mating success among male natterjack toads (Bufo calamita) was influenced by the number of nights that males spent at the pond and by male body size. Large males produced louder and lower frequency calls than small males, and maintained larger acoustic territories. After arriving at the pond, one half of all observed females mated with the first male they encountered. The remainder visited several males before initiating amplexus, but no criteria could be identified that females might have used when deciding whether to accept or reject a male. Movements between several males seem to be best explained by low female responsiveness to male advertisement calls on cold nights which were nonoptimal for oviposition. Females attempted to reject non-calling males both before and after amplexus, but this may be a mechanism to avoid mismating with males of the common toad (Bufo bufo), an explosive breeder that utilised the same pond. In two-choice playback experiments using synthetic advertisement calls, females showed no preference for calls based on their frequency. Females preferred calls of intermediate pulse repetition rate equivalent to those produced by a male at the same body temperature. Pulse rate is thus potentially subject to stabilishing selection and may be an important character for species-recognition. Females preferred fast rather than slow call rates, but only when the alternative rates were extreme. They also preferred calls which they perceived at the highest sound pressure level, but did not discriminate between absolute sound pressure levels of alternative stimuli at different distances. Since females that delay mating and oviposition may suffer predation, it is suggested that female preference for loud, rapidly repeated calls may be adaptive in the sense of minimizing the costs of locating conspecific males, rather than maximizing the probability of obtaining a high quality mate. Competition between males to maintain large acoustic territories and produce calls that can be easily detected by females would seem to be a sufficient mechanism to explain the evolution of the striking calls produced by male natterjacks.
TL;DR: Internal structures in the field can be created, controlled solely by steering the collimator leaves, and the opening density determined by the algorithm never gives rise to underdosage: this is important from a radiobiological point of view.
Abstract: Traditionally, the shaping of non-uniform dose distributions has been performed by using wedges or compensating filters. The advent of high resolution multileaf collimators may largely eliminate the need for material attenuators for modification of the beam. This is achieved by a new technique for the shaping of arbitrary dose distributions by dynamic motion of the collimator leaves. By employing narrow elementary slit beams that correspond to the smallest possible opening of the multileaf collimator, the optimal density of such slit beams, i.e. opening density, can be determined automatically using a newly developed inversion algorithm. The present method has two major advantages (1) internal structures in the field can be created, controlled solely by steering the collimator leaves, (2) the opening density determined by the algorithm never gives rise to underdosage: this is important from a radiobiological point of view.
TL;DR: In this paper, a new rule for calculating chemisorption energies using the cluster model was proposed, based on the realization that relatively large clusters (50 atoms and more) often need to be prepared for bonding by making an excitation to a proper bonding state (such a state will always be easily accessible in an infinite cluster).
TL;DR: The behaviour of profilactin and profilin in the presence of different types of phospholipids and neutral lipids under different conditions is described.
Abstract: Profilactin, the profilin:actin complex, which is present in large amounts in extracts of many types of eukaryotic cells, appears to serve as the precursor of microfilaments. It was reported recently that profilactin interacts specifically with phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) (Lassing and Lindberg: Nature 314:472-474, 1985.) The present paper describes in detail the behaviour of profilactin and profilin in the presence of different types of phospholipids and neutral lipids under different conditions. PtdIns(4,5)P2 is the only phospholipid found so far which in the presence of 80 mM KCl and at Ca2+ concentrations below 10(-5) M effectively dissociates profilactin with the resulting polymerization of the actin. Phosphatidylinositol 4-monophosphate exhibits some activity but phosphatidylinositol is inactive. Both calf spleen profilin and profilin from human platelets form stable complexes with PtdIns(4,5)P2 micelles. PtdIns(4,5)P2 is active also when incorporated together with other phospholipids in mixed vesicles.
TL;DR: The hypothesis that endogenous cytokinins are involved in the regulation of adventitious root formation is supported after stem cuttings were rooted in nutrient solution.
TL;DR: A recent suggestion that the observations of monochromatic photons from annihilation of photinos into quarkonium plus a photon could be a signature of dark-matter photinos is extended to include all S- and P-wave bound quarksonium states for a general interaction Lagrangian and an estimate of the cross sections is given.
Abstract: A recent suggestion that the observations of monochromatic photons from annihilation of photinos into quarkonium plus a photon could be a signature of dark-matter photinos is extended to include all S- and P-wave bound quarkonium states for a general interaction Lagrangian and an estimate of the cross sections is given. We also propose the process \ensuremath{\lambda}\ensuremath{\lambda}\ifmmode\bar\else\textasciimacron\fi{}\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma} as a potentially rich source of monochromatic photons and estimate its strength.
TL;DR: It is concluded that male toads adopt a conditional strategy which depends on their attractiveness to females, and the model offers insights into the behaviour of other species in which males display in groups to attract females.
TL;DR: In this paper, the authors present a legal opinion on the applicability of commercial or impression systématiques in the context of the agreement of publication mathématique de l'I.H.É.S.
Abstract: © Publications mathématiques de l’I.H.É.S., 1988, tous droits réservés. L’accès aux archives de la revue « Publications mathématiques de l’I.H.É.S. » (http:// www.ihes.fr/IHES/Publications/Publications.html) implique l’accord avec les conditions générales d’utilisation (http://www.numdam.org/legal.php). Toute utilisation commerciale ou impression systématique est constitutive d’une infraction pénale. Toute copie ou impression de ce fichier doit contenir la présente mention de copyright.
TL;DR: The use of energy-conversion factors based on AFDW is preferable due to their lower dispersion, and a general conversion factor of 23 J · mg−1 AFDW can be used for aquatic macrobenthic invertebrates.
TL;DR: In this article, it was shown that if M contains a compact subset of category k (in M), then each function f ∈ C 1 (M, ℝ ) which is bounded below and satisfies the Palais-Smale condition must necessarily have k critical points.
Abstract: Let M be a complete Finsler manifold of class C1. It is shown that if M contains a compact subset of category k (in M), then each function f ∈ C 1 ( M , ℝ ) which is bounded below and satisfies the Palais-Smale condition must necessarily have k critical points. This should be compared with the known result that f has at least cat(M) critical points provided M is of class C2. An application is given to an eigenvalue problem for a quasilinear differential equation involving the p-Laplacian −div(|∇u|p−2∇u), 1
TL;DR: The most reliable information is probably provided by studies of lacustrine sediments as discussed by the authors, which shows that the most significant pre-Little Ice Age glacier advances most likely occurred in 7.5, 5.1−4.1, 3.2−2.8, 2.9 and 1.5−1.1 radiocarbon ka BP.
TL;DR: In the analysis of biological bulk specimens, the ZAF-correction method appears to be less useful, primarily because of the uneven surface of biological specimens, and the peak-to-local background model may be a more adequate method for thick specimens that are not mounted on a thick substrate.
Abstract: Qualitative X-ray microanalysis of biological specimens requires an approach that is somewhat different from that used in the materials sciences. The first step is deconvolution and background subtraction on the obtained spectrum. The further treatment depends on the type of specimen: thin, thick, or semithick. For thin sections, the continuum method of quantitation is most often used, but it should be combined with an accurate correction for extraneous background. However, alternative methods to determine local mass should also be considered. In the analysis of biological bulk specimens, the ZAF-correction method appears to be less useful, primarily because of the uneven surface of biological specimens. The peak-to-local background model may be a more adequate method for thick specimens that are not mounted on a thick substrate. Quantitative X-ray microanalysis of biological specimens generally requires the use of standards that preferably should resemble the specimen in chemical and physical properties. Special problems in biological microanalysis include low count rates, specimen instability and mass loss, extraneous contributions to the spectrum, and preparative artifacts affecting quantitation. A relatively recent development in X-ray microanalysis of biological specimens is the quantitative determination of local water content.
TL;DR: An extensive search for elution conditions, avoiding poly(L-proline) as the desorbant, has found that active proteins can be recovered from the affinity column with a buffer containing 30% dimethyl sulphoxide.
TL;DR: A mini review of the genetic covariation in Drosophila populations and its relation to some models of mate choice and the cost ofchoice in sexual selection.
Abstract: 1985. Mini review. Sexual selection, handicaps, and true fitness. J. Theoret. BioI. 115:1-8. O'DONALD, P. 1983. Sexualselection by female choice, pp. 53-66. In P. Bateson (ed.), Mate Choice. Cambridge Univ. Press, N.Y. PARKER, G. A. 1983. Mate quality and mating decisions, pp. 141-166. In P. Bateson (ed.), Mate Choice. Cambridge Univ. Press, N.Y. PARTRIDGE, L. 1983. Non-random mating and offspring fitness, pp. 227-256. In P. Bateson (ed.), Mate Choice. Cambridge Univ. Press, N.Y. POMIANKOWSKI, A. 1987. The cost ofchoice in sexual selection. J. Theoret. BioI. 128:195-218. ROSE, M. R. 1984. Genetic covariation in Drosophila: Untangling the data. Amer. Natur. 123:565-569. ROSE, M. R., AND B. CHARLESWORTH. 1981. Genetics of life history in Drosophila melanogaster. I. Sib analysis of adult females. Genetics 97:173-186. SEGER, J. 1985. Unifying genetic models for the evolution offemale choice. Evolution 39:1185-1193. SIMMONS, M. J., AND J. F. CROW. 1977. Mutations affecting fitness in Drosophila populations. Ann. Rev. Genet. 11:49-78. SIMMONS, M. J., C. R. PRESTON, AND W. R. ENGLES. 1980. Pleiotropic effects on fitness of mutations affecting viability in Drosophila melanogaster. Genetics 94:467-475. THORNHILL, R. 1980. Mate choice in Hylobittacus apicalis(Insecta: Mecoptera) and its relation to some models of mate choice. Evolution 34:519-538. TURELLI, M. 1984. Heritable genetic variation via mutation-selection balance: Lerch's zeta meets the abdominal bristle. Theoret. Popul. BioI. 25:138193. WILLIAMS, G. C. 1978. Mysteries of sex and recombination. Quart. Rev. BioI. 53:287-289.
TL;DR: It is shown that neomycin, a drug which has a high affinity for phosphoinositides and in vivo interferes with the PI cycle, inhibits the polymerization of actin in platelets induced either by thrombin or by ADP.
TL;DR: Current knowledge on the biochemistry of oxygen toxicity in general and the is-chemia-reoxygenation tissue injury in particular is summarized.
Abstract: This paper summarizes current knowledge on the biochemistry of oxygen toxicity in general and the ischemia-reoxygenation tissue injury in particular. The superoxide radical, hydrogen peroxide, and the hydroxyl radical in cells can be formed enzymically or nonenzymically. Primary effects of oxygen radicals result in lipid peroxidation, which is believed to be initiated by a perferryl radical. Secondary effects are believed to be due to a disturbance in cellular calcium homeostasis. Reactions and treatment potentials are highly complex and their effects on cells, tissues, and organism are difficult to predict. Treatment potentials include superoxide dismutase, catalase, calcium entry blockers, iron chelators, xanthine oxidase inhibitors, and agents to prevent leukocyte adhesion. Reoxygenation injury mechanisms during resuscitation from clinical death can be studied in animals by evaluating the effects of antireoxygenation injury therapies and by monitoring free radical reactions.
TL;DR: The high‐frequency Raman spectra of highly ordered and disordered films are compared to show that the extent of crystallinity controls the amount of A‐DNA formed when ethanol is used to dehydrate the films, and it is shown that rapid dehydration does not result in a B to A transition.
Abstract: We have studied the hydration of Na-DNA and Li-DNA fibers and films, measuring water contents, x-ray fiber diffraction patterns, low-frequency Raman spectra (below 100 cm−1), high-frequency Raman spectra (600–1000 cm−1), and swelling, as a function of relative humidity. Most samples gain weight equilibrium (though not conformational equilibrium) in one day. The volume occupied by a base pair as the DNA is hydrated (obtained from the x-ray and swelling data) shows anomalies for the case of Na-DNA in the region where the A-form occurs. Our Raman and x-ray data reproduce the well-known features of the established conformational transitions, but we find evidence in the Raman spectra and optical properties of a transition to what may be a disordered B-like conformation in Na-DNA below 40% relative humidity. We have studied the effects of crystallinity on the A to B transition. We find that the transition to the B-form is impeded in highly crystalline samples. In most samples, the transition occurs in three days (after putting the sample at 92% relative humidity) but in highly crystalline samples, the transition may take months. By comparing the high-frequency Raman spectra of highly ordered and disordered films, we show that the extent of crystallinity controls the amount of A-DNA formed when ethanol is used to dehydrate the films. We show that rapid dehydration (by laser heating) does not result in a B to A transition. A fiber that gives A-type x-ray reflections probably contains B-like material in noncrystalline regions. The low-frequency Raman spectrum is dominated by a band at about 25 cm−1 in both Na- and Li-DNA. Another band is seen near 35 cm−1 in Na-DNA at humidities where the sample is in the A-form. In contrast to earlier reports, we find that the Raman intensity does not depend on fiber orientation relative to the scattering vector. The “35-cm−1” band is largely depolarized (i.e. vertical polarization incident and horizontal polarization scattered, VH, or vice versa, HV) while the “25-cm−1” band appears in both VV, VH and HV polarizations. These bands are all weaker in HH polarization. The “25-cm−1” band may be due to a shearing motion of the phosphates and their associated counterions, while the “35-cm−1” band may be characteristic of A-DNA crystallites. We consider mass-loading, relaxational coupling to the hydration shell, and softening of interatomic potentials as possible explanations of the observed softening of the low-frequency Raman bands on hydration. Relaxation data suggest that the added water binds tightly (on these time scales) and a mass-loading model accounts for the observed softening rather well.
We conclude that the A to B transition is not driven by softening of the “25-cm−1” band. Rather, it is most probably a consequence of crystal-packing forces, with the more regular A-form favored in crystals when these forces are strong.
TL;DR: The activity, the protein content and the manganese properties of photosystem II have been compared after photoinhibition of isolated thylakoid membranes and the results show a concomitant disappearance of the oxygen evolving activity and the ability to form the S2‐state multiline EPR signal.