| 1. |
- Bendazzoli, Simone, et al.
(författare)
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Automatic rat brain segmentation from MRI using statistical shape models and random forest
- 2019
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Ingår i: MEDICAL IMAGING 2019. - : SPIE-INT SOC OPTICAL ENGINEERING. - 9781510625464 - 9781510625457
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Konferensbidrag (refereegranskat)abstract
- In MRI neuroimaging, the shimming procedure is used before image acquisition to correct for inhomogeneity of the static magnetic field within the brain. To correctly adjust the field, the brain's location and edges must first be identified from quickly-acquired low resolution data. This process is currently carried out manually by an operator, which can be time-consuming and not always accurate. In this work, we implement a quick and automatic technique for brain segmentation to be potentially used during the shimming. Our method is based on two main steps. First, a random forest classifier is used to get a preliminary segmentation from an input MRI image. Subsequently, a statistical shape model of the brain, which was previously generated from ground-truth segmentations, is fitted to the output of the classifier to obtain a model-based segmentation mask. In this way, a-priori knowledge on the brain's shape is included in the segmentation pipeline. The proposed methodology was tested on low resolution images of rat brains and further validated on rabbit brain images of higher resolution. Our results suggest that the present method is promising for the desired purpose in terms of time efficiency, segmentation accuracy and repeatability. Moreover, the use of shape modeling was shown to be particularly useful when handling low-resolution data, which could lead to erroneous classifications when using only machine learning-based methods.
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| 2. |
- Brusini, Irene, et al.
(författare)
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Changes in brain architecture are consistent with altered fear processing in domestic rabbits
- 2018
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 115:28, s. 7380-7385
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Tidskriftsartikel (refereegranskat)abstract
- The most characteristic feature of domestic animals is their change in behavior associated with selection for tameness. Here we show, using high-resolution brain magnetic resonance imaging in wild and domestic rabbits, that domestication reduced amygdala volume and enlarged medial prefrontal cortex volume, supporting that areas driving fear have lost volume while areas modulating negative affect have gained volume during domestication. In contrast to the localized gray matter alterations, white matter anisotropy was reduced in the corona radiata, corpus callosum, and the subcortical white matter. This suggests a compromised white matter structural integrity in projection and association fibers affecting both afferent and efferent neural flow, consistent with reduced neural processing. We propose that compared with their wild ancestors, domestic rabbits are less fearful and have an attenuated flight response because of these changes in brain architecture.
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| 3. |
- Counter, S Allen, et al.
(författare)
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Experimental Fusion of Contrast Enhanced High-Field Magnetic Resonance Imaging and High-Resolution Micro-Computed Tomography in Imaging the Mouse Inner Ear
- 2015
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Ingår i: The Open Neuroimaging Journal. - : Bentham Science Publishers Ltd.. - 1874-4400. ; 9, s. 7-12
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: Imaging cochlear, vestibular, and 8th cranial nerve abnormalities remains a challenge. In this study, the membranous and osseous labyrinths of the wild type mouse inner ear were examined using volumetric data from ultra high-field magnetic resonance imaging (MRI) with gadolinium contrast at 9.4 Tesla and high-resolution micro-computed tomography (µCT) to visualize the scalae and vestibular apparatus, and to establish imaging protocols and parameters for comparative analysis of the normal and mutant mouse inner ear.METHODS: For in vivo MRI acquisition, animals were placed in a Milleped coil situated in the isocenter of a horizontal 9.4 T Varian magnet. For µCT examination, cone beam scans were performed ex vivo following MRI using the µCT component of a nanoScan PET/CT in vivo scanner.RESULTS: The fusion of Gd enhanced high field MRI and high-resolution µCT scans revealed the dynamic membranous labyrinth of the perilymphatic fluid filled scala tympani and scala vestibule of the cochlea, and semicircular canals of the vestibular apparatus, within the µCT visualized contours of the contiguous osseous labyrinth. The ex vivo µCT segmentation revealed the surface contours and structural morphology of each cochlea turn and the semicircular canals in 3 planes.CONCLUSIONS: The fusion of ultra high-field MRI and high-resolution µCT imaging techniques were complementary, and provided high-resolution dynamic and static visualization of the complex morphological features of the normal mouse inner ear structures, which may offer a valuable approach for the investigation of cochlear and vestibular abnormalities that are associated with birth defects related to genetic inner ear disorders in humans.
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| 4. |
- Counter, S Allen, et al.
(författare)
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MRI evidence of endolymphatic impermeability to the gadolinium molecule in the in vivo mouse inner ear at 9.4 tesla
- 2013
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Ingår i: The Open Neuroimaging Journal. - : Bentham Science Publishers Ltd.. - 1874-4400. ; 7, s. 27-31
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE:Previous in vivo experimental magnetic resonance imaging (MRI) investigations of the mammalian inner ear at 4.7 Tesla have indicated that intravenously injected gadolinium (Gd) penetrates the perilymphatic labyrinth, but not the endolymphatic membranous labyrinth. In the present study, high field MRI at 9.4T was used to visualize the in vivo mouse vestibulo-cochlea system, and to determine whether the endolymphatic system is permeable to a Gd complex.METHODS:A 9.4 T Varian magnet equipped with a 12 cm inner diameter gradient system with maximum gradient strength of 600 mT/m, a millipede coil (Varian design) and a Gd contrast agent were used for image acquisition in the normal C57 BL-6 mouse.RESULTS:High-resolution 2D and 3D images of the mouse cochlea were acquired within 80 minutes following intravenous injection of Gd. Gd initially permeated the perilymphatic scala tympani and scala vestibuli, and permitted visualization of both cochlear turns from base to apex. The superior, inferior and lateral semicircular canals were subsequently visualized in 3 planes. The membranous endolymphatic labyrinth was impermeable to intravenously injected Gd, and thus showed no apparent uptake of Gd at 9.4T.CONCLUSION:The 9.4T field strength MRI permitted acquisition of high resolution images of anatomical and physiological features of the normal, wild type mouse perilymphatic inner ear in vivo, and provided further evidence that the endolymphatic system is impermeable to intravenously injected Gd.
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| 5. |
- Counter, S. Allen, et al.
(författare)
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Ultra-high-field (9.4 T) MRI Analysis of Contrast Agent Transport Across the Blood-Perilymph Barrier and Intrastrial Fluid-Blood Barrier in the Mouse Inner Ear
- 2017
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Ingår i: Otology and Neurotology. - 1531-7129 .- 1537-4505. ; 38:7, s. 1052-1059
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Tidskriftsartikel (refereegranskat)abstract
- Hypothesis: Effective paramagnetic contrast agent for the penetration of the perilymphatic spaces of the scala tympani, scala vestibuli, and scala media of the mouse inner ear can be determined using intravenous injection of various gadolinium (Gd) complexes and ultra-high-field magnetic resonance imaging (MRI) at 9.4 Tesla.Background: A number of contrast agents have been explored in experimental high-field MRI to determine the most effective Gd complex for ideal signal-to-noise ratio and maximal visualization of the in vivo mammalian inner ear in analyzing the temporal and spatial parameters involved in drug penetration of the blood-perilymph barrier and intrastrial fluid-blood barrier in the mouse model using MRI.Methods: Gadoteric acid (Dotarem), Gadobutrol (Gadovist), Gadodiamide (Omniscan), Gadopent acid (Magnevist), and Mangafodipir (Teslascan) were administered intravenously using the tail vein of 60 Balb/C mice. High-resolution T1 images of drug penetration were acquired with a horizontal 9.4 T Agilent magnet after intravenously injection. Signal intensity was used as a metric of temporal and spatial parameters of drug delivery and penetration of the perilymphatic and endolymphatic spaces.Results: ANOVA analysis of the area under the curve of intensity enhancement in perilymph revealed a significant difference (p < 0.05) in the scalae uptake using different contrast agents (F (3,25) = 3.54, p = 0.029). The Gadoteric acid complex Dotarem was found to be the most effective Gd compound in terms of rapid, morphological enhancement for analysis of the temporal, and spatial distribution in the perilymphatic space of the inner ear.Conclusion: Gadoteric acid (Dotarem) demonstrated efficacy as a contrast agent for enhanced visualization of the perilymphatic spaces of the inner ear labyrinthine in the mouse, including the scala tympani and scala vestibuli of the cochlea, and the semicircular canals of the vestibular apparatus. These findings may inform the clinical application of Gd compounds in patients with inner ear fluid disorders and vertigo.
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| 6. |
- Damberg, Peter, 1973-
(författare)
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Development of NMR methods for studies of dynamics and structure : applications to motilin, Alzheimer β-peptide and ubiquitin
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- NMR spin relaxation was used to study structure and dynamics of two biologically important peptides.The first case concerns the three-dimensional structure of the 22 amino acid residue peptide hormone motilin in the presence of SDS micelles, which mimic a biomembrane environment. Motilin was found to have a well-defined structure when associated with the micelle, with a central amphiphatic helix and two turns in the biologically active N-terminal end. Residues 3-5 are buried in the interior of the micelle as evident from experiments where spin-labels were inserted into the micelles at certain depths. 13C NMR relaxation on a selectively isotope labeled motilin sample showed that the rotational correlation time is in agreement with the peptide being associated with a spherical micelle.The peptide corresponding to residues 12-28 of the Alzheimer related peptide Ab was studied in solution by NMR spectroscopy, circular dichroism spectroscopy, molecular weight cut-off filtering and NMR diffusion measurements. Both increased salt concentration and increased temperature induced reversible random-coil to b-sheet transitions and aggregation, but with certain differences between the structures induced by salt and temperature.Development of NMR methods used for studying molecular motions, such as diffusion and local dynamics is discussed. The methodology for estimation of translational diffusion coefficients by NMR was improved by taking into account the inhomogeneity of the magnetic field gradient pulses. A practical way to correct for the inhomogeniety was suggested.Parameters describing the chemical shift anisotropies of 13C and 15N nuclei have been estimated from the relaxation rates of the nuclear spins measured at several magnetic field strengths. New NMR methodology was developed where only longitudinal rates need to be measured. The site-specific chemical shift anisotropies for 15N nuclei in the backbone of ubiquitin were estimated. It was found that the variations in the effective shift anisotropy along the polypeptide backbone for 15N nuclei in ubiquitin are of the same order as the variations in isotropic chemical shift, i.e. a 90% confidence region for the site-to-site variability spans from 3.7 ppm to 10.5 ppm. The average orientation parameter for the CSA tensors was found to be -0.84, which corresponds to an angle between the symmetry axis of the CSA tensor and the N-H bond vector of 19° in the approximation of an axially symmetric CSA tensor. Significant variations between the orientation parameters of different sites were observed with a 90% confidence interval spanning from 0.027 to 0.066.Fluorescence polarization anisotropy decay data and NMR relaxation data to describe the dynamics of a 13C-labeled tyrosine ring in motilin were compared. The two methods showed very similar results in terms of correlation times and order parameters. This study indicates that the previously observed differences between the results of the two methods applied to the same protein are mainly due to either influences of internal probe dynamics or varying sample conditions, in particular peptide or protein concentrations.
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| 7. |
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| 8. |
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| 9. |
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| 11. |
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| 12. |
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| 13. |
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| 14. |
- Kitambi, Satish Srinivas, et al.
(författare)
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Vulnerability of Glioblastoma Cells to Catastrophic Vacuolization and Death Induced by a Small Molecule
- 2014
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Ingår i: Cell. - : Elsevier BV. - 0092-8674 .- 1097-4172. ; 157:2, s. 313-328
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Tidskriftsartikel (refereegranskat)abstract
- Glioblastoma multiforme (GBM) is the most aggressive form of brain cancer with marginal life expectancy. Based on the assumption that GBM cells gain functions not necessarily involved in the cancerous process, patient-derived glioblastoma cells (GCs) were screened to identify cellular processes amenable for development of targeted treatments. The quinine-derivative NSC13316 reliably and selectively compromised viability. Synthetic chemical expansion reveals delicate structure-activity relationship and analogs with increased potency, termed Vacquinols. Vacquinols stimulate death by membrane ruffling, cell rounding, massive macropinocytic vacuole accumulation, ATP depletion, and cytoplasmic membrane rupture of GCs. The MAP kinase MKK4, identified by a shRNA screen, represents a critical signaling node. Vacquinol-1 displays excellent in vivo pharmacokinetics and brain exposure, attenuates disease progression, and prolongs survival in a GBM animal model. These results identify a vulnerability to massive vacuolization that can be targeted by small molecules and point to the possible exploitation of this process in the design of anticancer therapies.
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| 15. |
- Krishnamurthy, Akilan, et al.
(författare)
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Combination of Two Monoclonal Anti–Citrullinated Protein Antibodies Induced Tenosynovitis, Pain, and Bone Loss in Mice in a Peptidyl Arginine Deiminase-4–Dependent Manner
- 2023
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Ingår i: Arthritis & Rheumatology. - : Wiley. - 2326-5191 .- 2326-5205. ; 75:2, s. 164-170
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Tidskriftsartikel (refereegranskat)abstract
- Objective. The appearance of anti–citrullinated protein antibodies (ACPAs) in the circulation represents a major risk factor for developing rheumatoid arthritis (RA). Patient-derived ACPAs have been shown to induce pain and bone erosion in mice, suggesting an active role in the pathogenicity of RA. We undertook this study to investigate whether ACPAs can induce tenosynovitis, an early sign of RA, in addition to pain and bone loss and whether these symptoms are dependent on peptidyl arginine deiminase 4 (PAD4).Methods. Monoclonal ACPAs generated from plasma cells of RA patients were transferred to wild-type and PAD4-deficient mice. Pain-like behavior and macroscopic inflammation were monitored for a period of 4 weeks, followed by the analyses of tenosynovitis in the ankle joints using magnetic resonance imaging (MRI) and bone microarchitecture in the tibia using an X-ray microscope. Microscopic changes in the tendon sheath were analyzed in decalcified ankle joint sections.Results. The combination of 2 monoclonal ACPAs (1325:04C03 and 1325:01B09) induced long-lasting pain-like behavior and trabecular bone loss in mice. Although no synovitis was observed macroscopically, we detected tenosynovitis in the ACPA-injected mice by MRI. Microscopic analyses of the joints revealed a cellular hyperplasia and a consequent enlargement of the tendon sheath in the ACPA-treated group. In PAD4−/− mice, the effects of ACPAs on pain-like behavior, tenosynovitis, and bone loss were significantly reduced.Conclusion. Monoclonal ACPAs can induce tenosynovitis in addition to pain and bone loss via mechanisms dependent on PAD4-mediated citrullination.
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| 16. |
- Kvist, Ola, et al.
(författare)
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Magnetic resonance and diffusion tensor imaging of the adolescent rabbit growth plate of the knee
- 2023
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Ingår i: Magnetic Resonance in Medicine. - : John Wiley & Sons. - 0740-3194 .- 1522-2594. ; 89:1, s. 331-342
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To assess the ability of MRI-DTI to evaluate growth plate morphology and activity compared with that of histomorphometry and micro-CT in rabbits.METHODS: The hind limbs of female rabbits aged 16, 20, and 24 wk (n = 4 per age group) were studied using a 9.4T MRI scanner with a multi-gradient echo 3D sequence and DTI in 14 directions (b-value = 984 s/mm2 ). After MRI, the right and left hind limb were processed for histological analysis and micro-CT, respectively. The Wilcoxon signed-rank test was used to evaluate the height and volume of the growth plate. Intraclass correlation and Pearson correlation coefficient were used to evaluate the association between DTI metrics and age.RESULTS: The growth plate height and volume were similar for all modalities at each time point and age. Age was correlated with all tractography and DTI metrics in both the femur and tibia. A correlation was also observed between all the metrics at both sites. Tract number and volume declined with age; however, tract length did not show any changes. The fractional anisotropy color map showed lateral diffusion centrally in the growth plate and perpendicular diffusion in the hypertrophic zone, as verified by histology and micro-CT.CONCLUSION: MRI-DTI may be useful for evaluating the growth plates.
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| 17. |
- Lendel, Christofer, et al.
(författare)
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3D J-resolved NMR spectroscopy for unstructured polypeptides : fast measurement of 3J HNH alpha coupling constants with outstanding spectral resolution.
- 2009
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Ingår i: Journal of biomolecular NMR. - : Springer Science and Business Media LLC. - 1573-5001 .- 0925-2738. ; 44:1, s. 35-42
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Tidskriftsartikel (refereegranskat)abstract
- A powerful experiment for the investigation of conformational properties of unstructured states of proteins is presented. The method combines a phase sensitive J-resolved experiment with a (1)H-(15)N SOFAST-HMQC to provide a 3D spectrum with an E.COSY pattern originating from splittings due to (3)J(HNH alpha) and (2)J(NH alpha) couplings. Thereby an effectively homodecoupled (1)H-(15)N correlation spectrum is obtained with significantly improved resolution and greatly reduced spectral overlap compared to standard HSQC and HMQC experiments. The (3)J(HNH alpha) is revealed in three independent ways directly from the peak positions, allowing for internal consistency testing. In addition, the natural H(N) linewidths can easily be extracted from the lineshapes. Thanks to the SOFAST principle, the limited sweep width needed in the J-dimension and the short phase cycle, data accumulation is rapid with excellent sensitivity per time unit. The experiment is demonstrated for the intrinsically unstructured 14 kDa protein alpha-synuclein.
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| 18. |
- Madani, Fatemeh, et al.
(författare)
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Hairpin Structure of a Biarsenical−Tetracysteine Motif Determined by NMR Spectroscopy
- 2009
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 131:13, s. 4613-4615
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Tidskriftsartikel (refereegranskat)abstract
- The biarsenical−tetracysteine motif is a useful tag for genetic labeling of proteins with small molecules in living cells. The present study concerns the structure of a 12 amino acid peptide FLNCCPGCCMEP bound to the fluorophore ReAsH based on resorufin. 1H NMR spectroscopy was used to determine the solution structure of the complex formed between the peptide and the ReAsH moiety. Structure calculations based on the NMR results showed that the backbone structure of the peptide is fairly well defined, with a hairpinlike turn, similar to a type-II β-turn, formed by the central CPGC segment. The most stable complex was formed when As2 was bonded to C4 and C5 and As1 to C8 and C9. Two clear NOESY cross-peaks between the Phe1 side chain and ReAsH confirmed the close positioning of the phenyl ring of Phe1 and ReAsH. Phe1 was found to have an edge−face geometry relative to ReAsH. The close interaction between Phe1 and ReAsH may be highly significant for the fluorescence properties of the ReAsH complex.
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| 19. |
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| 20. |
- Massad, Tariq, et al.
(författare)
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Crystal structure of the P2 C-repressor : a binder of nonpalindromic direct DNA repeats
- 2010
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Ingår i: Nucleic Acids Research. - : Oxford University Press (OUP). - 0305-1048 .- 1362-4962. ; 38:21, s. 7778-7790
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Tidskriftsartikel (refereegranskat)abstract
- As opposed to the vast majority of prokaryoticrepressors, the immunity repressor of temperateEscherichia coli phage P2 (C) recognizes nonpalindromicdirect repeats of DNA rather thaninverted repeats. We have determined the crystalstructure of P2 C at 1.8A ° . This constitutes the firststructure solved from the family of C proteins fromP2-like bacteriophages. The structure reveals thatthe P2 C protein forms a symmetric dimer orientedto bind the major groove of two consecutive turns ofthe DNA. Surprisingly, P2 C has great similarities tobinders of palindromic sequences. Nevertheless, thetwo identical DNA-binding helixes of the symmetricP2 C dimer have to bind different DNA sequences.Helix 3 is identified as the DNA-recognition motif inP2 C by alanine scanning and the importance for theindividual residues in DNA recognition is defined.A truncation mutant shows that the disorderedC-terminus is dispensable for repressor function.The short distance between the DNA-bindinghelices together with a possible interaction betweentwo P2 C dimers are proposed to be responsible forextensive bending of the DNA. The structure providesinsight into the mechanisms behind the mutants ofP2 C causing dimer disruption, temperature sensitivityand insensitivity to the P4 antirepressor.
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| 21. |
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| 23. |
- Massad, Tariq, et al.
(författare)
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The C repressor of the P2 bacteriophage
- 2016
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Ingår i: Journal of Biomolecular NMR. - : Springer Science and Business Media LLC. - 0925-2738 .- 1573-5001. ; 64:2, s. 175-180
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Tidskriftsartikel (refereegranskat)
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| 24. |
- Milosavljević, Filip, et al.
(författare)
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The humanised CYP2C19 transgenic mouse exhibits cerebellar atrophy and movement impairment reminiscent of ataxia
- 2023
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Ingår i: Neuropathology and Applied Neurobiology. - : Wiley. - 0305-1846 .- 1365-2990. ; 49:1
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Tidskriftsartikel (refereegranskat)abstract
- Aims: CYP2C19 transgenic mouse expresses the human CYP2C19 gene in the liver and developing brain, and it exhibits altered neurodevelopment associated with impairments in emotionality and locomotion. Because the validation of new animal models is essential for the understanding of the aetiology and pathophysiology of movement disorders, the objective was to characterise motoric phenotype in CYP2C19 transgenic mice and to investigate its validity as a new animal model of ataxia. Methods: The rotarod, paw-print and beam-walking tests were utilised to characterise the motoric phenotype. The volumes of 20 brain regions in CYP2C19 transgenic and wild-type mice were quantified by 9.4T gadolinium-enhanced post-mortem structural neuroimaging. Antioxidative enzymatic activity was quantified biochemically. Dopaminergic alterations were characterised by chromatographic quantification of concentrations of dopamine and its metabolites and by subsequent immunohistochemical analyses. The beam-walking test was repeated after the treatment with dopamine receptor antagonists ecopipam and raclopride. Results: CYP2C19 transgenic mice exhibit abnormal, unilateral ataxia-like gait, clasping reflex and 5.6-fold more paw-slips in the beam-walking test; the motoric phenotype was more pronounced in youth. Transgenic mice exhibited a profound reduction of 12% in cerebellar volume and a moderate reduction of 4% in hippocampal volume; both regions exhibited an increased antioxidative enzyme activity. CYP2C19 mice were hyperdopaminergic; however, the motoric impairment was not ameliorated by dopamine receptor antagonists, and there was no alteration in the number of midbrain dopaminergic neurons in CYP2C19 mice. Conclusions: Humanised CYP2C19 transgenic mice exhibit altered gait and functional motoric impairments; this phenotype is likely caused by an aberrant cerebellar development.
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| 25. |
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| 26. |
- Pierre, Pernilla Videhult, et al.
(författare)
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High-Dose Furosemide Enhances the Magnetic Resonance Signal of Systemic Gadolinium in the Mammalian Cochlea
- 2020
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Ingår i: Otology and Neurotology. - : LIPPINCOTT WILLIAMS & WILKINS. - 1531-7129 .- 1537-4505. ; 41:4, s. 545-553
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Tidskriftsartikel (refereegranskat)abstract
- Hypothesis:Furosemide alters the permeability of the intrastrial fluid-blood barrier.Background:The cochlear sensory cells are protected by the blood-perilymph and intrastrial fluid-blood barriers, which hinder substances, including gadolinium-based contrast agents (GdCAs), to enter the endolymphatic space. High-dose furosemide causes transient shift of hearing thresholds and morphological changes in stria vascularis. Furosemide is also known to enhance drug-induced ototoxicity.Methods:Furosemide (400mg/kg b.w.) was injected i.v. in Balb/C mice (n=20). Twenty minutes later, the GdCA gadobutrol, gadopentetic acid, or gadoteric acid was injected i.v. The distribution of GdCA to the perilymphatic and endolymphatic spaces was studied with MRI (9.4T) for 250minutes.Results:The perilymphatic and endolymphatic spaces were signal-enhanced in all animals. Gadopentetic acid and gadoteric acid yielded similar signal enhancement in all three scalae, while gadobutrol yielded significantly higher enhancement in scala tympani than scala media (p=0.043) and scala vestibuli (p=0.043). The signal enhancement reached a plateau but did not decrease during the time of observation.Conclusion:Treatment with a high dose of furosemide before injection of a GdCA resulted in enhancement of the MRI signal in the endolymphatic space as well as the perilymphatic space, which supports our hypothesis that furosemide alters the permeability of the intrastrial fluid-blood barrier.
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| 27. |
- Säwén, Elin, et al.
(författare)
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Population distribution of flexible molecules from maximum entropy analysisusing different priors as background information: application to the phi,psi-conformational space of the a-(1→2)-linked mannose disaccharide presentin N- and O-linked glycoproteins
- 2010
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Ingår i: Organic and biomolecular chemistry. - : Royal Society of Chemistry (RSC). - 1477-0520 .- 1477-0539. ; 8:16, s. 3684-3695
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Tidskriftsartikel (refereegranskat)abstract
- The conformational space available to the flexible molecule a-D-Manp-(1→2)-a-D-Manp-OMe, amodel for the a-(1→2)-linked mannose disaccharide in N- or O-linked glycoproteins, is determinedusing experimental data and molecular simulation combined with a maximum entropy approach thatleads to a converged population distribution utilizing different input information. A database survey ofthe Protein Data Bank where structures having the constituent disaccharide were retrieved resulted inan ensemble with >200 structures. Subsequent filtering removed erroneous structures and gave thedatabase (DB) ensemble having three classes of mannose-containing compounds, viz., N- and O-linkedstructures, and ligands to proteins. A molecular dynamics (MD) simulation of the disaccharide revealeda two-state equilibrium with a major and a minor conformational state, i.e., the MD ensemble. Thesetwo different conformation ensembles of the disaccharide were compared to measured experimentalspectroscopic data for the molecule in water solution. However, neither of the two populations werecompatible with experimental data from optical rotation, NMR 1H,1H cross-relaxation rates as well ashomo- and heteronuclear 3J couplings. The conformational distributions were subsequently used asbackground information to generate priors that were used in a maximum entropy analysis. Theresulting posteriors, i.e., the population distributions after the application of the maximum entropyanalysis, still showed notable deviations that were not anticipated based on the prior information.Therefore, reparameterization of homo- and heteronuclear Karplus relationships for the glycosidictorsion angles f and y were carried out in which the importance of electronegative substituents on thecoupling pathway was deemed essential resulting in four derived equations, two 3JCOCC and two 3JCOCHbeing different for the f and y torsions, respectively. These Karplus relationships are denotedJCX/SU09. Reapplication of the maximum entropy analysis gave excellent agreement between theMD- and DB-posteriors. The information entropies show that the current reparametrization of theKarplus relationships constitutes a significant improvement. The fH torsion angle of the disaccharide isgoverned by the exo-anomeric effect and for the dominating conformation fH = -40◦ and yH = 33◦.The minor conformational state has a negative yH torsion angle; the relative populations of the majorand the minor states are ~3 : 1. It is anticipated that application of the methodology will be useful toflexible molecules ranging from small organic molecules to large biomolecules.
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| 28. |
- Videhult Pierre, Pernilla, et al.
(författare)
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Middle Ear Administration of a Particulate Chitosan Gel in an in vivo Model of Cisplatin Ototoxicity
- 2019
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Ingår i: Frontiers in Cellular Neuroscience. - : Frontiers Media SA. - 1662-5102. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- Background: Middle ear (intratympanic, IT) administration is a promising therapeutic method as it offers the possibility of achieving high inner ear drug concentrations with low systemic levels, thus minimizing the risk of systemic side effects and drug-drug interactions. Premature elimination through the Eustachian tube may be reduced by stabilizing drug solutions with a hydrogel, but this raises the secondary issue of conductive hearing loss.Aim: This study aimed to investigate the properties of a chitosan-based particulate hydrogel formulation when used as a drug carrier for IT administration in an in vivo model of ototoxicity.Materials and Methods: Two particulate chitosan-based IT delivery systems, Thio-25 and Thio-40, were investigated in albino guinea pigs (n = 94). Both contained the hearing protecting drug candidate sodium thiosulfate with different concentrations of chitosan gel particles (25% vs. 40%). The safety of the two systems was explored in vivo. The most promising system was then tested in guinea pigs subjected to a single intravenous injection with the anticancer drug cisplatin (8 mg/kg b.w.), which has ototoxic side effects. Hearing status was evaluated with acoustically evoked frequency-specific auditory brainstem response (ABR) and hair cell counting. Finally, in vivo magnetic resonance imaging was used to study the distribution and elimination of the chitosan-based system from the middle ear cavity in comparison to a hyaluronan-based system.Results: Both chitosan-based IT delivery systems caused ABR threshold elevations (p < 0.05) that remained after 10 days (p < 0.05) without evidence of hair cell loss, although the elevation induced by Thio-25 was significantly lower than for Thio-40 (p < 0.05). Thio-25 significantly reduced cisplatin-induced ABR threshold elevations (p < 0.05) and outer hair cell loss (p < 0.05). IT injection of the chitosan- and hyaluronan-based systems filled up most of the middle ear space. There were no significant differences between the systems in terms of distribution and elimination.Conclusion: Particulate chitosan is a promising drug carrier for IT administration. Future studies should assess whether the physical properties of this technique allow for a smaller injection volume that would reduce conductive hearing loss.
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