| 1. |
- Abul-Kasim, Kasim, et al.
(författare)
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Advanced radiological work-up as an adjunct to decision in early reconstructive surgery in brachial plexus injuries
- 2010
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Ingår i: Journal of Brachial Plexus and Peripheral Nerve Injury. - : BioMed Central. - 1749-7221. ; 5, s. 14-
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundAs neurophysiologic tests may not reveal the extent of brachial plexus injury at the early stage, the role of early radiological work-up has become increasingly important. The aim of the study was to evaluate the concordance between the radiological and clinical findings with the intraoperative findings in adult patients with brachial plexus injuries.MethodsSeven consecutive male patients (median age 33; range 15-61) with brachial plexus injuries, caused by motor cycle accidents in 5/7 patients, who underwent extensive radiological work-up with magnetic resonance imaging (MRI), computed tomography myelography (CT-M) or both were included in this retrospective study. A total of 34 spinal nerve roots were evaluated by neuroradiologists at two different occasions. The degree of agreement between the radiological findings of every individual nerve root and the intraoperative findings was estimated by calculation of kappa coefficient (К-value). Using the operative findings as a gold standard, the accuracy, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the clinical findings and the radiological findings were estimated.ResultsThe diagnostic accuracy of radiological findings was 88% compared with 65% for the clinical findings. The concordance between the radiological findings and the intraoperative findings was substantial (К = 0.76) compared with only fair (К = 0.34) for the clinical findings. There were two false positive and two false negative radiological findings (sensitivity and PPV of 0.90; specificity and NPV of 0.87).ConclusionsThe advanced optimized radiological work-up used showed high reliability and substantial agreement with the intraoperative findings in adult patients with brachial plexus injury.
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| 2. |
- Aronsson, Henrik, et al.
(författare)
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Characterisation of the assembly pathway of the pea NADPH:protochlorophyllide (Pchlide) oxidoreductase (POR), with emphasis on the role of its substrate, Pchlide
- 2001
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Ingår i: Physiologia Plantarum. - Hoboken, NJ : Wiley-Blackwell Publishing Inc.. - 0031-9317 .- 1399-3054. ; 111:2, s. 239-244
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Tidskriftsartikel (refereegranskat)abstract
- The homologous import and membrane association of a key enzyme for chlorophyll biosynthesis, the NADPH:protochlorophyllide (Pchlide) oxidoreductase (PAR, EC 1.6.99.1) into pea chloroplasts was investigated in vitro. The co-factor, NADPH, decreased binding of the precursor protein (pPOR) to the envelope membranes in the presence of ATP. The decrease of the binding reaction with NADPH was not observed with the precursor of the small subunit of Rubisco (pSS). To investigate possible substrate-dependency for the import reaction, internal Pchlide concentrations in the plastids were raised by either an addition of ÎŽ-aminolevulinic acid to isolated plastids or etiolation of the seedlings prior to plastid isolation. Increased amounts of plastid-bound Pchlide gave no observable differences in POR import. The capacity of POR and 11 different POR mutants, carrying charged-to-alanine scanning substitutions, to form a catalytically active POR-Pchlide-NADPH complex and to associate with the thylakoid membranes in a protease-resistant way were tested. Wild-type POR, as well as the mutants with charge substitutions in the N-terminal region of the protein, exhibited higher catalytic activity than the POR mutants carrying substitutions in the C-terminal region. Formation of a catalytically active complex did not, however, increase the association efficiency onto the thylakoids. We can, therefore, postulate that the import of pea POR into pea chloroplasts was not substrate-dependent, nor did formation of catalytically active complexes stimulate or inhibit the membrane association reaction of POR.
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| 3. |
- Aronsson, H., et al.
(författare)
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Characterization of the plastid import reaction of the pea NADPH-protochlorophyllide oxidoreductase (POR)
- 1998
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Ingår i: The Chloroplast. - New York : Springer-Verlag. - 9780792355779 - 0792355776 ; , s. 167-170
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Konferensbidrag (refereegranskat)abstract
- NADPH: protochlorophyllide (POR) is a vital enzyme in the biosynthesis of chlorophyl where it catalyzes the reduction of Pchlide into Chlide in a light-dependent manner. POR is nucleus-encoded and imported into the plastids where it is found at the inner membranes. Together with its substrate and the co-factor NADPH it forms a ternary complex which is needed for catalytical activity. The anomaly of a decreasing POR level during active chlorophyll synthesis was cleared with the discovery of two different POR proteins, POR-A and POR-B, in barley and Arabidopsis thaliana. During greening, POR-A is negatively regulated by light both at transcriptional and proteolytical levels. In addition, the import of POR-A, but not POR-B, has been suggestedto require Pchlide in order to be translocated into the plastid. In this respect, POR-A differs from other known nucleus-encoded plastid proteins, and as it appears, this requirements represents a novel and exclusive import characteristic. In pea, only one POR gene has been found indicating that the situation for the regulation of POR import and accumulation is far from clear. We here present a characterization of the import conditions of the pea POR, including the potentional role of Pchlide inthe translocation step.
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| 4. |
- Aronsson, Henrik, et al.
(författare)
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POR hits the road : import and assembly of a plastid protein
- 2003
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Ingår i: Plant Molecular Biology. - Berlin : Springer-Verlag. - 0167-4412 .- 1573-5028. ; 51:1, s. 1-7
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Tidskriftsartikel (refereegranskat)abstract
- The biosynthesis of chlorophyll is a strictly light-dependent multistep process in higher plants. The light-dependent step is catalysed by NADPH:protochlorophyllide oxidoreductase (POR, EC.1.6.99.1), which reduces protochlorophyllide (Pchlide) to chlorophyllide (Chlide). POR is nucleus-encoded and post-translationally imported into plastids. It has been proposed that the import of a POR protein isozyme (PORA) is totally dependent on Pchlide and uses a novel import pathway. This proposal is based on findings that PORA import only occurs in the presence of Pchlide and that the presence of overexpressed precursor of Rubisco small subunit (pSS), a protein which is known to use the general import pathway, does not outcompete PORA import. Another study demonstrated that POR precursor protein (pPOR) can be cross-linked to one of the components in the translocation machinery, Toc75, in the absence of Pchlide, and that its import can be outcompeted by the addition of the pSS. This indicates that pSS and pPOR may use the same translocation mechanism. Thus, POR does not necessarily need Pchlide for import – which is in contrast to earlier observations – and the exact POR import mechanism remains unresolved. Once in the stroma, the POR transit peptide is cleaved off and the mature POR protein is associated to the plastid inner membranes. Formation of the correct membrane–associated, thermolysin-protected assembly is strictly dependent of NADPH. As a final step, the formation of the NADPH-Pchlide-POR complex occurs. When POR accumulates in the membranes of proplastids, an attraction of monogalactosyl diacylglycerol (MGDG) can occur, leading to the formation of prolamellar bodies (PLBs) and the development of etioplasts in darkness.
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| 5. |
- Aronsson, Henrik, et al.
(författare)
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POR – import and membrane association of a key element in chloroplast development
- 2003
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Ingår i: Physiologia Plantarum. - : Blackwell Publishing. - 0031-9317 .- 1399-3054. ; 118:1, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- The development of proplastids or etioplasts to chloroplast is visualized by the accumulation of chlorophyll in leaves of higher plants. The biosynthesis of chlorophyll includes a light-dependent reduction of protochlorophyllide (Pchlide) to chlorophyllide (Chlide). This light-dependent step is catalysed by the nucleus-encoded NADPH:Pchlide oxidoreductase (POR, EC 1.6.99.1). POR is active within plastids and therefore has to be translocated over the plastid envelope membranes. The import of chloroplast proteins seems to follow a general import pathway using translocons at the outer and inner envelope membrane. POR cross-linking to Toc75, one of the major translocon components at the outer envelope membrane, indicates its use of the general import pathway. However, since variations exist within the so-called general import pathway one has to consider previous data suggesting a novel totally Pchlide-dependent import pathway of one POR isoform, PORA. The suggested Pchlide dependency of POR import is discussed since recent observations contradict this idea. In the stroma the POR transit peptide is cleaved off and the mature POR protein is targeted to the plastid inner membranes. The correct and stable association of POR to the membrane requires the cofactor NADPH. Functional activity of POR calls for formation of an NADPH–Pchlide–POR complex, a formation that probably takes place after the membrane association and is dependent on a phosphorylation reaction.
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| 6. |
- Dahlin, Clas
(författare)
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Surface charge densities and membrane fluidities in thylakoids with different degrees of thylakoid appression after Norflurazon treatment
- 2003
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Ingår i: Photosynthetica (Praha). - : Springer-Verlag. - 0300-3604 .- 1573-9058. ; 41:4, s. 635-639
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Tidskriftsartikel (refereegranskat)abstract
- Wheat seedlings (Triticum aestivum L.) develop plastids (etioplasts and chloroplasts) which exhibit alterations in inner membrane organisation after treatment with Norflurazon (NF), an inhibitor of carotenoid biosynthesis. In dark-grown plants, results in a decreased amount of partitions (contact zones) between prothylakoids. In weak red light, the results in plants containing chloroplasts devoid of grana. Assays have been performed to investigate the membrane surface charge density in these membranes, and relate possible differences to the absence of (pro-)thylakoid overlap after NF teatment. Using the fluorescent probe 9- amino acridine (9-AA), the average surface charge density of isolated PTs was -21.8±3.2 mC m-2 and - 27.4±2.6 mC m-2 in the control and after, respectively. Thylakoid membranes isolated from plants grown in weak red light exhibited slightly more negative values, -23.5±2.9 mC m-2 and -29.0±2.1 mC m-2, in control and after, respectively. The surface charge density of destacked thylakoids from greenhouse-grown untreated plants, containing extensive grana stacking, was -34.3±2.5 mC m-2. Assays using the fluorescent probe of DPH (1,6- diphenyl- 1,3,5- hexatriene) showed that this probe exhibits a higher polarisation value when incorporated into thylakoids from NF- treated plants compared to untreated plants grown in weak red light. The highest polarisation value was found in untreated plants grown in the greenhouse. This indicates a lower rotation transition of the probe in the lipid environment of thylakoids after NF treatment, which can be interpreted as more rigid membranes. These results suggest that the surface charge density and the mobility of membrane components may play a major role for the formation of partitions in dark-grown plants and in the formation of grana in plants grown in weak red light. 23 Additional key words: chloroplasts; etioplasts; (pro-)thylakoids; Triticum; stacking; wheat; 9- amino acridine.
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| 7. |
- Dahlin, Lars, et al.
(författare)
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Axillary nerve injury in young adults-An overlooked diagnosis? : early results of nerve reconstruction and nerve transfers
- 2012
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Ingår i: Journal of Plastic Surgery and Hand Surgery. - 2000-656X .- 2000-6764. ; 46:3-4, s. 257-261
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Tidskriftsartikel (refereegranskat)abstract
- An injury to the axillary nerve from a shoulder trauma can easily be overlooked. Spontaneous functional recovery may occur, but occasionally reconstructive surgery is required. The time frame for nerve reconstruction procedures is from a neurobiological view crucial for a good functional outcome. This study presents a group of operatively and non-operatively treated young adults with axillary nerve injuries caused by motorcycle accidents, where the diagnosis was set late. Ten young men (median age at trauma 13 years, range 9-24) with an axillary nerve injury were diagnosed by examination of shoulder function and electromyography (EMG). The patients had either a nerve reconstruction procedure or were treated conservatively and their recovery was monitored. The axillary nerve was explored and reconstructed at a median of 8 months (range 1-22 months) after trauma in 8/10 patients. Two patients were treated non-operatively. In 4/8 cases, a reconstruction with sural nerve graft was performed and in 1/8 case only exploration of the nerve was made (minor neuroma). In 3/8 cases a radial nerve branch transfer to the axillary nerve was chosen as the procedure. The shoulder was mobilised after 3 weeks with physiotherapy and the patients were monitored regularly. Functional recovery was observed in 9/10 cases (median follow up 11 months, range 7-64) with EMG signs of reinnervation in seven patients. Axillary nerve function should not be overlooked in young patients with a minor shoulder trauma. Nerve reconstruction can successfully recreate function.
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| 8. |
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| 9. |
- Dahlin, Lars B., et al.
(författare)
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Rehabilitation, Using Guided Cerebral plasticity, of a Brachial plexus Injury treated with Intercostal and phrenic Nerve transfers
- 2017
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Ingår i: Frontiers in Neurology. - : Frontiers Media SA. - 1664-2295. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Recovery after surgical reconstruction of a brachial plexus injury using nerve grafting and nerve transfer procedures is a function of peripheral nerve regeneration and cerebral reorganization. A 15-year-old boy, with traumatic avulsion of nerve roots C5-C7 and a non-rupture of C8-T1, was operated 3 weeks after the injury with nerve transfers: ( a) terminal part of the accessory nerve to the suprascapular nerve, (b) the second and third intercostal nerves to the axillary nerve, and (c) the fourth to sixth intercostal nerves to the musculocutaneous nerve. A second operation-free contralateral gracilis muscle transfer directly innervated by the phrenic nerve-was done after 2 years due to insufficient recovery of the biceps muscle function. One year later, electromyography showed activation of the biceps muscle essentially with coughing through the intercostal nerves, and of the transferred gracilis muscle by deep breathing through the phrenic nerve. Voluntary flexion of the elbow elicited clear activity in the biceps/gracilis muscles with decreasing activity in intercostal muscles distal to the transferred intercostal nerves (i.e., corresponding to eighth intercostal), indicating cerebral plasticity, where neural control of elbow flexion is gradually separated from control of breathing. To restore voluntary elbow function after nerve transfers, the rehabilitation of patients operated with intercostal nerve transfers should concentrate on transferring coughing function, while patients with phrenic nerve transfers should focus on transferring deep breathing function.
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| 10. |
- Dahlin, Lars, et al.
(författare)
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Compression of the lower trunk of the brachial plexus by a cervical rib in two adolescent girls : case reports and surgical treatment.
- 2009
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Ingår i: Journal of Brachial Plexus and Peripheral Nerve Injury. - : BioMed Central. - 1749-7221. ; 4, s. 14-
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Tidskriftsartikel (refereegranskat)abstract
- Presence of a cervical rib in children is extremely rare, particularly when symptoms of compression of the lower trunk of the brachial plexus occur. We present two cases with such a condition, where two young girls, 11 and 16 years of age were treated by resection of the cervical rib after a supraclavicular exploration of the lower trunk of the brachial plexus. The procedure led to successful results, objectively verified with tests in a work simulator, at one year follow-up.
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