| 1. |
- Balatsouka, Dimitra, et al.
(author)
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The impact of nicotine on bone healing and osseointegration.
- 2005
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In: Clinical oral implants research. - : Wiley. - 0905-7161 .- 1600-0501. ; 16:3, s. 268-76
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Journal article (peer-reviewed)abstract
- OBJECTIVES: To examine the short-term effect of nicotine on bone healing and osseointegration. MATERIAL AND METHODS: Sixteen female rabbits were divided into two groups. The test group was exposed to nicotine tartrate for 8 weeks and the control group was exposed to placebo. Nicotine or placebo was administered via a miniosmotic pump and plasma cotinine levels were measured weekly. The pump delivered 15 mg of nicotine/day for the animals in the test group. All rabbits had three tibial bone preparations. In the proximal and distal bone bed, implants were placed after 4 weeks (right tibia) and after 6 weeks (left tibia). Thus, 2- and 4-week healing groups were created. Removal torque test (RMT) was performed at the distal implants. Ground sections were made from the proximal and the central bone beds. The fraction of mineralized bone in contact to the implant (BIC) and the bone density within the implant threads (BD-i) were determined for the bone-implant specimens. For the central bone beds without implants the bone density (BD-c) in the bone defects was determined. RESULTS: No significant difference in RMT values was found between the test and the control group. Histomorphometric measurements of the BIC and the peri-implant BD-i showed no significant differences between the test and the control group after 2 or 4 weeks. Significant differences were, however, found between the 2- and 4-week samples. In the central bone beds, there was no significant difference in BD-c between the test and the control group. CONCLUSION: Nicotine exposure in a short period of time did not have a significant impact on bone healing or implant osseointegration in rabbits.
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| 2. |
- Fayad, B. R., et al.
(author)
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Non-standard smooth realizations of Liouville rotations
- 2007
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In: Ergodic Theory and Dynamical Systems. - 0143-3857 .- 1469-4417. ; 27, s. 1803-1818
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Journal article (peer-reviewed)abstract
- We augment the C-infinity conjugation approximation method with explicit estimates on the conjugacy map. This allows us to construct ergodic volume-preserving diffeomorphisms measure-theoretically isomorphic to any a priori given Liouville rotation on a variety of manifolds. In the special case of tori the maps can be made uniquely ergodic.
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| 3. |
- Giese, Jochen, et al.
(author)
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Space-time code design for unknown frequency-selective channels
- 2002
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In: 2002 IEEE INTERNATIONAL CONFERENCE ON ACOUSTICS, SPEECH, AND SIGNAL PROCESSING. ; , s. 2413-2416
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Conference paper (peer-reviewed)abstract
- The design of space-time codes has so far mostly focused on one-tap channel models while in this paper code design for multi-tap (frequency-selective) channels is discussed when joint channel estimation and data detection is used at the receiver. A transmission model using multiple transmitter and receiver antennas for multi-path propagation through unknown channels is presented and shown to be closely linked to a single-antenna model which has been investigated earlier. Using a randomized search strategy, codes of arbitrary rates for combined channel estimation and error protection over these channels can be designed. Simulations demonstrate the performance of codes designed with the proposed scheme. An example code outperforms an approach based on an extension of the Alamouti scheme.
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| 4. |
- Arnoldsson, Kristina, 1961-
(author)
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Polybrominated dibenzo-p-dioxins : Natural formation mechanisms and biota retention, maternal transfer, and effects
- 2012
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Doctoral thesis (other academic/artistic)abstract
- Polybrominated dibenzo-p-dioxins (PBDD) and dibenzofurans (PBDF) are a group of compounds of emerging interest as potential environmental stressors. Their structures as well as toxic responses are similar to the highly characterized toxicants polychlorinated dibenzo-p-dioxins. High levels of PBDDs have been found in algae, shellfish, and fish, also from remote areas in theBaltic Sea. This thesis presents studies on PBDD behavior in fish and offspring, and natural formation of PBDDs from naturally abundant phenolic precursors.The uptake, elimination, and maternal transfer of mono- to tetraBDD/Fs were investigated in an exposure study reported in Paper I. The effects of PBDDs in fish were examined in a dose-response study (Paper II). It was shown that fish can assimilate PBDD/Fs from their feed, although non-laterally substituted congeners were rapidly eliminated. Laterally substituted congeners were retained as was congeners without vicinal hydrogens to some extent. PBDD/Fs were transferred to eggs, and congeners that were rapidly eliminated in fish showed a higher transfer ratio to eggs. Exposure to the laterally substituted 2,3,7,8-TeBDD had significant effects on the health, gene expression and several reproduction end-points of zebrafish, even at the lowest dose applied.The geographical and temporal variations of PBDD in biota samples from the Baltic Seasuggest biogenic rather than anthropogenic origin. In Paper III, bromoperoxidase-mediated coupling of 2,4,6-tribromophenol yielded several PBDD congeners, some formed after rearrangement. The overall yield was low, but significantly higher at low temperature, and the product profile obtained was similar to congener profiles found in biota from the Swedish West Coast. In Paper IV, photochemically induced cyclization of hydroxylated polybrominated diphenyl ethers under natural conditions produced PBDDs at percentage yield. Rearranged products were not detected, and some abundant congeners do not seem to be formed this way. However, the product profile obtained was similar to congener profiles found in biota from the Baltic Proper.Since the PBDD congeners found in biota have a high turn-over in fish, the exposure must be high and continuous to yield the PBDD levels measured in wild fish. Thus, PBDDs must presumably be formed by common precursors in general processes, such as via enzymatic oxidations, UV-initiated reactions or a combination of both. The presented pathways for formation of PBDDs are both likely sensitive to changes in climatic conditions.
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| 5. |
- Heathfield, Terrence
(author)
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The collagen fibrillar network: Sequential degradation of its constituents by tissue metalloproteinases.
- 2003
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Doctoral thesis (other academic/artistic)abstract
- The cartilage matrix is made up of a fibrillar meshwork comprising type II collagen and other associated proteins. One main function of this network is to retain the large aggregating proteoglycan, aggrecan, a vital component in the regulation of fluid flux in cartilage. In disease such as osteoarthritis, the breakdown of the collagen network appears to be the final step in destruction of cartilage. The aim of the work described in this thesis was to develop specific tools for the detection of extracellular matrix degradation products as a means to monitor cartilage disease. In the first instance we elaborated an ELISA assay specific for denatured type II collagen. Application of this assay to the detection of collagen denaturation in osteoarthritic versus normal cartilage showed that nearly four times greater percentage unwound collagen could be detected in diseased tissue (denatured/total). The focus was then placed on the fate of some of the fibril associated proteins. Indeed we demonstrated that fibromodulin, a member of the leucine rich repeat proteins, was degraded prior to significant loss of type II collagen in a degradative cartilage explant culture system. Only one major product of degraded fibromodulin could be isolated and this was characterised in order to determine its neo N-terminus. This revealed that this product was lacking the entire tyrosine sulphate rich N-terminus and had an intact C-terminus. Cleavage at the same site could also be performed in vitro with purified MMP-13 (not with MMPs 2, 8 or 9). An antibody directed to the neo-N-terminus of this fragment reacted specifically with degraded fibromodulin in Western blotting, but showed poor reactivity with the natural cleavage product in ELISA assay. Prior to further attempts at raising functional antibodies to the cleavage product we opted to characterise the domains surrounding the site of processing. This work showed that the N-terminal cystine double loop has a cruciform structure. This may cause shielding of the epitope by steric hindrance. We also determined experimentally the presence of sulphation on nearly all of the tyrosine residues found in the N-terminus of fibromodulin including those neighbouring the cleavage site. An error in the sequence was also noted and corrected. The information gained from these characterisation studies will be vital in the choice and composition of immunising peptides used to generate neo-epitope antibodies.
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| 6. |
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| 7. |
- Knorpp, Carina, et al.
(author)
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Tissue-specific differences of the mitochondrial protein import machinery : in vitro import, processing and degradation of the pre-F1β subunit of the ATP synthase in spinach leaf and root mitochondria
- 1994
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In: Plant Molecular Biology. - 0167-4412 .- 1573-5028. ; 26:2, s. 571-579
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Journal article (peer-reviewed)abstract
- In this study we report the first comparison of the mitochondrial protein import and processing events in two different tissues from the same organism. Both spinach leaf and root mitochondria were able to import and process the in vitro transcribed and translated Neurospora crassa F1 subunit of ATP synthase to the mature size product. Temperature optimum for protein import, 20 °C, was considerably lower than that found in other systems. In spinach leaf mitochondria, the processing peptidase has been shown to constitute an integral part of the bc1 complex of the respiratory chain. In accordance with these results, the majority of the processing activity in root mitochondria was also localized in the membrane. However, although the same amount of the processing peptidase was present per mg of membrane protein in both leaf and root mitochondria, as determined immunologically, the specific processing activity was several-fold higher in roots. Furthermore, in contrast to the processing enzyme in leaf, a portion of the processing activity could be disassociated from the root membrane with relatively weak salt treatment. The processing event in both the leaf and root membranes was always accompanied by a degradation of the F1 precursor. The degradation activity was found to be several-fold higher in roots than in leaves and was also partially dissociated from the membrane after salt treatment. Both the processing and degradation activities were inhibited by orthophenanthroline, a known metalloprotease inhibitor. These results show tissue-specific differencies of the processing event catalyzed by the bc1 complex and indicate the presence of two populations of the processing peptidase in root mitochondria.
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| 8. |
- Norén, Karin, et al.
(author)
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From monogamy to complexity : social organization of arctic foxes (Vulpes lagopus) in contrasting ecosystems
- 2012
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In: Canadian Journal of Zoology. - 0008-4301 .- 1480-3283. ; 90:9, s. 1102-1116
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Journal article (peer-reviewed)abstract
- Canids display pronounced intraspecific variation in social organization, ranging from single breeding females to large and complex groups. Despite several hypotheses in this matter, little is understood about the ecological factors underlying this flexibility. We have used the arctic fox (Vulpes lagopus (L., 1758)) to investigate how contrasting ecosystem conditions concerning resources and predation influence group formation. We predicted that complex groups are more common in resource-rich ecosystems with predators, whereas simple groups occur in more marginal ecosystems without predators. Samples from 54 groups were collected from four populations of arctic foxes with contrasting prey resources and predation and these samples were genotyped in 10 microsatellite loci. We found considerable variation between ecosystems and a significant relationship between resources and formation of complex groups. We conclude that sufficient amounts of food is a prerequisite for forming complex groups, but that defense against predation further increases the benefits of living in larger groups. We present a conceptual model suggesting that a trade-off between the cost of resource depletion and the benefits obtained for guarding against predators explain the differences in social organization. The variable ecology of the arctic foxes makes it is a plausible model species for understanding the connection between ecology and social organization also in other species.
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| 9. |
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| 10. |
- Tenghe, Amabel, et al.
(author)
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Improving accuracy of bulls' predicted genomic breeding values for fertility using daughters' milk progesterone profiles
- 2018
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In: Journal of Dairy Science. - : American Dairy Science Association. - 0022-0302 .- 1525-3198. ; 101, s. 5177-5193
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Journal article (peer-reviewed)abstract
- The main objective of this study was to investigate the benefit of accuracy of genomic prediction when combining records for an intermediate physiological phenotype in a training population with records for a traditional phenotype. Fertility was used as a case study, where commencement of luteal activity (C-LA) was the physiological phenotype, whereas the interval from calving to first service and calving interval were the traditional phenotypes. The potential accuracy of across-country genomic prediction and optimal recording strategies of C-LA were also investigated in terms of the number of farms and number of repeated records for C-LA. Predicted accuracy was obtained by estimating population parameters for the traits in a data set of 3,136 Holstein Friesian cows with 8,080 lactations and using a deterministic prediction equation. The effect of genetic correlation, heritability, and reliability of C-LA on the accuracy of genomic prediction were investigated. When the existing training population was 10,000 bulls with reliable estimated breeding value for the traditional trait, predicted accuracy for the physiological trait increased from 0.22 to 0.57 when 15,000 cows with C-LA records were added to the bull training population; but, when the interest was in predicting the traditional trait, we found no benefit from the additional recording. When the genetic correlation was higher between the physiological and traditional traits (0.7 instead of 0.3), accuracy increased less when adding the 15.000 cows with C-LA (from 0.51 to 0.63). In across-country predictions, we observed little to no increase in accuracy of the intermediate physiological phenotype when the training population from Sweden was large, but when accuracy increased the training population was small (200 cows), from 0.19 to 0.31 when 15,000 cows were added from the Netherlands (genetic correlation of 0.5 between countries), and from 0.19 to 0.48 for genetic correlation of 0.9. The predicted accuracy initially increased substantially when recording on the same farm was extended and multiple C-LA records per cow were used in prediction compared with single records; that is, accuracy increased from 0.33 with single records to 0.38 with multiple records (on average 1.6 records per cow) from 2 yr of recording C-LA. But, when the number C-LA per cow increased beyond 2 yr of recording, we noted no substantial benefit in accuracy from multiple records. For example, for 5 yr of recording (on average 2.5 records per cow), accuracy was 0.47; on doubling the recording period to 10 yr (on average 3.1 records per cow), accuracy increased by 0.07 units, whereas when C-LA was recorded for 15 yr (on average 3.3 records per cow) accuracy increased only by 0.05 units. Therefore, for genomic prediction using expensive equipment to record traits for training populations, it is important to optimize the recording strategy. The focus should be on recording more cows rather than continuous recording on the same cows.
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