| 1. |
- Abul-Kasim, Kasim, et al.
(författare)
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Vertebral Hemangiomas : Prevalence, New Classification and Natural History. Magnetic Resonance Imaging-Based Retrospective Longitudinal Study
- 2023
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Ingår i: Neuroradiology Journal. - : SAGE Publications. - 1971-4009 .- 2385-1996. ; 36:1, s. 23-30
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Tidskriftsartikel (refereegranskat)abstract
- Background and purpose: To determine the prevalence of vertebral hemangiomas (VHs), establish a new classification of VHs based on their MRI-signal pattern, and study their natural history. Methods: MRI of 1000 consecutive patients who underwent at least two MRI with an interval of at least 3 years. Growth rate and change of MRI-signal pattern during the follow-up period were the parameters included in studying the natural history of VHs. Results: The prevalence of VHs was 41%. VHs were classified as type I–IV with fat-rich VHs (type I), constituted 79% of all VHs. VHs were more common among females 43% versus males 39%, p =.22. The most affected vertebra was L1. Occurrence rates for cervical (1%), thoracic (7%), and lumbar spine (10%) differed significantly (p <.001). The prevalence of VHs increased with age regardless of gender or spinal part involved (p <.001). Only 26% of VHs changed their size and 4% changed their signal during the average follow-up of 7 years. All VHs were slowly growing lesions (average expected growth of <3 mm/10 years). No significant difference between growth rate of VHs type I (0.25 mm/year) and other types of VHs. None of the VHs that were initially reported as “metastases cannot be rule out” showed alarming change in signal or size. Conclusions: VH can be classified into four types based on their MRI-signal pattern. Regardless of their type, VHs are slowly growing lesions. The presence of typical morphological pattern should enable radiologists to confidently differentiate them from vertebral metastases.
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| 2. |
- Garwicz, Martin, et al.
(författare)
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Common principles of sensory encoding in spinal reflex modules and cerebellar climbing fibres.
- 2002
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Ingår i: Journal of Physiology. - : Wiley. - 1469-7793 .- 0022-3751. ; 540:Pt 3, s. 1061-1069
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Tidskriftsartikel (refereegranskat)abstract
- An important step towards understanding the function of olivo-cerebellar climbing fibres must be to clarify what they signal. We suggest that climbing fibres projecting to paravermal cerebellum mediate highly integrated sensorimotor information derived from activity in spinal withdrawal reflex modules acting on single forelimb muscles. To test this hypothesis, cutaneous nociceptive receptive fields of spinal reflex modules were mapped and compared to those of climbing fibres. Quantitative methods were used both for mapping and for comparing receptive fields. The organization of muscle afferent input converging on individual climbing fibres was analysed in the light of results from receptive field comparisons. Individual cutaneous receptive fields in the two systems were readily matched. Matched pairs were highly similar with regard to detailed distributions of sensitivity: correlation coefficient r = 0.85; overlap of receptive field foci 72 % (average values). The olivary targets of muscle afferents from a given muscle were mainly climbing fibres with cutaneous receptive fields similar to that of the muscle itself, but to a lesser extent also other climbing fibres. In conclusion, paravermal climbing fibres apparently convey information integrating (i) cutaneous input to an individual spinal withdrawal reflex module, (ii) muscle afferent input from the output muscle of that module and (iii) muscle afferent input from muscles that constitute the output of functionally related modules. This suggests that an individual climbing fibre signals cutaneous sensory events reflecting activity of a single muscle conditional upon the functional state of the muscle itself and that of functionally related muscles.
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| 3. |
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| 4. |
- Johnson, Toby, et al.
(författare)
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Blood Pressure Loci Identified with a Gene-Centric Array.
- 2011
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Ingår i: American Journal of Human Genetics. - : Elsevier BV. - 1537-6605 .- 0002-9297. ; 89:6, s. 688-700
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Tidskriftsartikel (refereegranskat)abstract
- Raised blood pressure (BP) is a major risk factor for cardiovascular disease. Previous studies have identified 47 distinct genetic variants robustly associated with BP, but collectively these explain only a few percent of the heritability for BP phenotypes. To find additional BP loci, we used a bespoke gene-centric array to genotype an independent discovery sample of 25,118 individuals that combined hypertensive case-control and general population samples. We followed up four SNPs associated with BP at our p < 8.56× 10(-7) study-specific significance threshold and six suggestively associated SNPs in a further 59,349 individuals. We identified and replicated a SNP at LSP1/TNNT3, a SNP at MTHFR-NPPB independent (r(2) = 0.33) of previous reports, and replicated SNPs at AGT and ATP2B1 reported previously. An analysis of combined discovery and follow-up data identified SNPs significantly associated with BP at p < 8.56× 10(-7) at four further loci (NPR3, HFE, NOS3, and SOX6). The high number of discoveries made with modest genotyping effort can be attributed to using a large-scale yet targeted genotyping array and to the development of a weighting scheme that maximized power when meta-analyzing results from samples ascertained with extreme phenotypes, in combination with results from nonascertained or population samples. Chromatin immunoprecipitation and transcript expression data highlight potential gene regulatory mechanisms at the MTHFR and NOS3 loci. These results provide candidates for further study to help dissect mechanisms affecting BP and highlight the utility of studying SNPs and samples that are independent of those studied previously even when the sample size is smaller than that in previous studies.
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| 5. |
- Levinsson, Anders, et al.
(författare)
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Developmental tuning in a spinal nociceptive system: effects of neonatal spinalization
- 1999
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Ingår i: JNeurosci. - 1529-2401. ; 19:23, s. 10397-10403
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Tidskriftsartikel (refereegranskat)abstract
- Recent studies indicate a modular organization of the nociceptive withdrawal reflex system. Each module has a characteristic receptive field, closely matching the withdrawal movement caused by its effector muscle. In the rat, the strength of the sensory input to each module is tuned during the first postnatal weeks, i.e., erroneous spinal connections are depressed, and adequate connections are strengthened. To clarify if this tuning is dependent on supraspinal structures, the effect of a complete neonatal spinal cord transection on the postnatal tuning of withdrawal reflexes was studied. The nociceptive receptive fields of single hindlimb muscles and compound withdrawal reflexes were examined in decerebrate unanesthetized and awake rats, respectively. Noxious thermal CO2 laser stimulation was used to evoke reflex responses. Neonatal spinal cord transection resulted in a disrupted reflex organization in the adult rat, resembling that previously found in neonatal rats. The receptive fields of single hindlimb muscles exhibited abnormal distribution of sensitivity not matching the withdrawal action of the effector muscles. Likewise, the composite nocifensive movements, as documented in the awake rat, often resulted in erroneous movements toward the stimulus. It is concluded that withdrawal reflexes do not become functionally adapted in rats spinalized at birth. These findings suggest a critical role for supraspinal systems in the postnatal tuning of spinal nociceptive systems.
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| 6. |
- Levinsson, Anders, et al.
(författare)
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Functional connections are established in the deafferented rat spinal cord by peripherally transplanted human embryonic sensory neurons
- 2000
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Ingår i: European Journal of Neuroscience. - : Wiley. - 0953-816X .- 1460-9568. ; 12:10, s. 3589-3595
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Tidskriftsartikel (refereegranskat)abstract
- Functionally useful repair of the mature spinal cord following injury requires axon growth and the re-establishment of specific synaptic connections. We have shown previously that axons from peripherally grafted human embryonic dorsal root ganglion cells grow for long distances in adult host rat dorsal roots, traverse the interface between the peripheral and central nervous system, and enter the spinal cord to arborize in the dorsal horn. Here we show that these transplants mediate synaptic activity in the host spinal cord. Dorsal root ganglia from human embryonic donors were transplanted in place of native adult rat ganglia. Two to three months after transplantation the recipient rats were examined anatomically and physiologically. Human fibres labelled with a human-specific axon marker were distributed in superficial as well as deep laminae of the recipient rat spinal cord. About 36% of the grafted neurons were double labelled following injections of the fluorescent tracers MiniRuby into the sciatic and Fluoro-Gold into the lower lumbar spinal cord, indicating that some of the grafted neurons had grown processes into the spinal cord as well as towards the denervated peripheral targets. Electrophysiological recordings demonstrated that the transplanted human dorsal roots conducted impulses that evoked postsynaptic activity in dorsal horn neurons and polysynaptic reflexes in ipsilateral ventral roots. The time course of the synaptic activation indicated that the human fibres were non-myelinated or thinly myelinated. Our findings show that growing human sensory nerve fibres which enter the adult deafferentated rat spinal cord become anatomically and physiologically integrated into functional spinal circuits.
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| 7. |
- Levinsson, Anders, et al.
(författare)
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Sensorimotor transformation in cat nociceptive withdrawal reflex system
- 1999
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Ingår i: European Journal of Neuroscience. - 1460-9568. ; 11:12, s. 4327-4332
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Tidskriftsartikel (refereegranskat)abstract
- The withdrawal reflex system of higher vertebrates has been extensively used as a model for spinal sensorimotor integration, nociceptive processing and plasticity. In the rat, the nociceptive withdrawal reflex system appears to have a modular organization. Each reflex module controls a single muscle or a few synergistic muscles, and its cutaneous receptive field corresponds to the skin area withdrawn upon contraction of the effector muscle(s) when the limb is in the standing position. This organization principle is at odds with the 'flexion reflex' concept postulated from cat studies. To assess the generality of the modular organization principle we have therefore re-examined the cutaneous input to the withdrawal reflex system of the cat. The cutaneous receptive fields of hindlimb and forelimb muscles were mapped using calibrated noxious pinch stimulation and electromyographic recording technique in barbiturate anaesthetized animals. The investigated muscles had specific cutaneous receptive fields that appeared to correspond to the area of the skin withdrawn upon contraction of the muscle when the limb is in the standing position. The spatial organization of receptive fields in the cat was similar to that in the rat. However, differences in gain properties of reflexes to some anatomically equivalent muscles in the two species were observed, possibly reflecting adaptations to the biomechanics characteristic of the digitigrade and plantigrade stance in cats and rats, respectively. Implications of the findings for the generality of the modular organization of the withdrawal reflex system and for its adaptive properties are discussed.
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| 8. |
- Levinsson, Anders
(författare)
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Spinal Cord Processing of Sensory Information: Spatial Organization and Adaptive Mechanisms.
- 2000
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Principles for sensorimotor transformation and plasticity in the spinal cord and functional repair in the root-avulsed spinal cord were studied. A comparative study confirmed that the nociceptive withdrawal reflex (NWR) system is composed of reflex modules, with each performing a finely tuned transformation of skin sensory input to activity in one muscle. This suggests that modularity of the NWR system is a general organizational principle. The sensorimotor transformation in the reflex modules was adapted to species-specific specializations of the biomechanics of the motor plant, such as digitigrade or plantigrade stance. During postnatal development, the NWR modules undergo profound experience dependent changes from an unadapted to a functionally well-tuned system. This tuning was abolished after neonatal spinal transection, which indicates that input from supraspinal systems is needed for the formation of spinal memory engrams that specify input-output relations of NWRs. To further clarify principles for spinal sensorimotor transformation, a comprehensive morphological and electrophysiological mapping of the nociceptive and tactile cutaneous inputs to the spinal cord and their relation to the NWR network was made. The cutaneous somatotopy in the dorsal horn was found to be complex, exhibiting a high degree of representational overlap. The weight distribution of the monosynaptic tactile input to laminae III–IV was similar to that of ‘reflex encoder’ neurons in the deep dorsal horn. Therefore, it is suggested that the organization of input to the spinal cord reflects the demands of spinal motor systems rather than being primarily a body representation used for sensory discriminative functions. Furthermore, because the weight distribution of the cutaneous tactile input is similar to that of the tuned cutaneous input to reflex networks in the adult, it is conceivable that it is subject to a significant tuning during development. In a parallel study, transplanted human embryonic sensory neurons were shown to grow into the spinal cord and form functional connections with the recipient rat dorsal horn neurons. Although only weak activity could be evoked in the dorsal horn, the transplants had the capacity to evoke large amplitude motor reflexes, indicating compensatory mechanisms further downstream in the reflex connections. The bearing of spinal plasticity on the normal function of the spinal cord and on repair strategies after cord injuries are discussed.
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| 9. |
- Levinsson, Anders, et al.
(författare)
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Spinal sensorimotor transformation: Relation between cutaneous somatotopy and a reflex network
- 2002
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Ingår i: The Journal of Neuroscience. - 1529-2401. ; 22:18, s. 8170-8182
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Tidskriftsartikel (refereegranskat)abstract
- The projection of primary afferents onto spinal interneurons constitutes the first step in sensorimotor transformations performed by spinal reflex systems. Despite extensive studies on spinal somatotopy, uncertainties remain concerning the extent and significance of representational overlap and relation to spinal reflex circuits. To address these issues, the cutaneous projection from the hindpaw and its relation to the topography of lamina V neurons encoding withdrawal reflex strength ("reflex encoders") was studied in rats. Thin and coarse primary afferent terminations in laminas II and III-IV, respectively, were mapped by wheat germ agglutinin-horseradish peroxidase and choleragenoid tracing. The functional weights of these projections were characterized by mapping nociceptive and tactile field potentials and compared with the topography of reflex encoders. Both anatomical and physiological data indicate that thin and coarse skin afferent input is spatially congruent in the horizontal plane. The representation of the hindpaw in the spinal cord was found to be intricate, with a high degree of convergence between the projections from different skin sites. "Somatotopic disruptions" such as the representation of central pads medial to that of the digits were common. The weight distribution of the cutaneous convergence patterns in laminas III-IV was similar to that of lamina V reflex encoders. This suggests that the cutaneous convergence and features such as somatotopic disruptions have specific relations to the sensorimotor transformations performed by reflex interneurons in the deep dorsal horn. Hence, the spinal somatotopic map may be better understood in light of the topography of such reflex systems.
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| 10. |
- Nilsson, Hans-Jörgen, et al.
(författare)
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Cutaneous field stimulation (CFS) : A new powerful method to combat itch
- 1997
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Ingår i: Pain. - 1872-6623. ; 71:1, s. 49-55
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Tidskriftsartikel (refereegranskat)abstract
- Scratching the skin, while instantly relieving itch, often aggravates itch over time due to skin injury. To relieve itch, without damaging the skin, a new technique termed cutaneous field stimulation (CFS) was developed and tested on 21 subjects. CFS uses a flexible plate with needle-like electrodes (n = 16) to electrically stimulate nerve fibres in the superficial skin. The electrodes were stimulated consecutively (4 Hz per electrode, pulse duration 1 ms, intensity 0.4-0.8 mA, 25 min). CFS resulted in a pricking and burning sensation that usually faded rather quickly. The burning sensation was still present during a selective block of impulse conduction in myelinated fibres indicating that nociceptive C-fibres are activated by CFS. Furthermore, a flare reaction developed around the CFS electrodes indicating activation of axon reflexes in nociceptive C-fibres. Itch, elicited by transdermal iontophoresis of histamine, was abolished within the skin area pre-treated with CFS, and was reduced to 14% of control 10 cm distally. Contralateral effects were small or non-existent. After 4 h, itch was reduced ipsilaterally to 32% of control. In comparison, 2 h after transcutaneous electrical nerve stimulation (TENS; 10-20 mA, 100 Hz, 25 min) ipsilateral itch was reduced to 56% of control. In conclusion, CFS offers a powerful new method for combating itch. It is suggested that CFS acts through endogenous central inhibitory mechanisms that are normally activated by scratching the skin.
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