| 1. |
- Aagaard, Sunniva M.D. 1977-, et al.
(författare)
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Homoploid hybridization in Central European Diphasiastrum (Lycopodiaceae).
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Three species of homoploid hybrid origin are commonly recognized among Central European Diphasiastrum, and reticulate evolutionary events have for a long time been acknowledged as an important factor contributing to the species count in the genus. Presented evidence obtained from molecular data has until recently been scarce and inconclusive. Recent studies have, however, documented reticulate phylogenetic patterns involving all putative parental combinations reported from Central Europe. Reciprocal crosses involving the same parental combinations have also been confirmed. In order to further explore these putative reticulate events, admixture analyses using a Bayesian approach as implemented in the program NewHybrids are conducted on an expanded dataset obtained from six Central European populations from where putative hybrid taxa are reported. A majority of the accessions included in the analyses were inferred to represent pure bred D. alpinum, D. complanatum, D. tristachyum, F1 hybrids, F2 hybrids or backcrosses with one of the parent species. Accessions displaying ambiguous classification were found in both allopatric parent populations as well as in Central European hybrid populations. Presented results indicate the presence of frequently occurring hybrid zones with first and second generation hybrids as well as backcrosses.
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| 2. |
- Aagaard, Sunniva M. D., 1977-, et al.
(författare)
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Occurrence and evolutionary origins of polyploids in the club moss genus Diphasiastrum (Lycopodiaceae)
- 2009
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Ingår i: Molecular Phylogenetics and Evolution. - : Elsevier BV. - 1055-7903 .- 1095-9513. ; 52:3, s. 746-754
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Tidskriftsartikel (refereegranskat)abstract
- Two polyploid taxa are commonly recognized in the genus Diphasiastrum, D. wightianum from Asia and D. zanclophyllum from South Africa and Madagascar. Here we present results from Feulgen DNA image densitometry analyses providing the first evidence for the polyploid origin of D. zanclophyllum. Reported for the first time is also data confirming that D. multispicatum and D. veitchii, representing putative parent lineages for D. wightianum, are diploids. Phylogenetic analyses of nuclear regions RPB2, LEAFY and LAMB4 reveal that putative tetraploid accessions are of allopolyploid origin. Diphasiastrum zanclophyllum shows close relationships to the North American taxon D. digitatum on the maternal side, but the paternal relationship is less clear. Two accessions from Asia, both found to be polyploid, have D. veitchii as maternal parent, whereas the paternal paralogs show relationships to D. multispicatum and D. tristachyum, respectively. None of these parental combinations have previously been hypothesized.
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| 3. |
- Aagaard, Sunniva M.D. 1977-, et al.
(författare)
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Resolving maternal relationships in the clubmoss genus Diphasiastrum (Lycopodiaceae)
- 2009
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Ingår i: Taxon. - 0040-0262 .- 1996-8175. ; 58:3, s. 835-848
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Tidskriftsartikel (refereegranskat)abstract
- Diphasiastrum comprises 20-30 species. In addition to a number of species with a circumboreal distribution, several island endemics and putative diploid hybrid species contribute to the diversity of the group. To assess the integrity and relationships of the recognized species, a global phylogeny of Diphasiastrum is constructed using five chloroplast regions comprising ~9000 bp. Six monophyletic groups are identified. Accessions identified as hybrid species cluster in all but one case together with one of its putative parents. Two microsatellite loci are identified, and allelic information combined with sequence information is found diagnostic for the three putative parental taxa in the Central Europe hybrid complexes. Haplotype screening is performed on six Central European populations, from where one or more putative diploid hybrid species have been reported to grow in sympatry with their parent species. The most common parental haplotypes are identified in all populations. Additional intraspecific variation, restricted to single populations, is identified in all sympatric populations at very low frequencies. Taking the low degree of sequence and microsatellite variation into consideration, the acknowledged morphological diversity in Central Europe is probably best explained by phenotypic plasticity, ancestral polymorphisms or relatively recent events of reticulate evolution.
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| 4. |
- Aagaard, Sunniva Margrethe Due
(författare)
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Reticulate Evolution in Diphasiastrum (Lycopodiaceae)
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis relationships and the occurrence of reticulate evolutionary events in the club moss genus Diphasiastrum are investigated. Diphasiastrum is initially established as a monophyletic group within Lycopodiaceae using non recombinant chloroplast sequence data. Support is obtained for eight distinct parental lineages in Diphasiastrum, and relationships among the putative parent taxa in the hypothesized hybrid complexes; D. alpinum, D. complanatum, D. digitatum, D. multispicatum, D. sitchense, D. tristachyum and D. veitchii are presented. Feulgen DNA image densitometry data and sequence data obtained from three nuclear regions, RPB2, LEAFY and LAMB4, were used to infer the origins of three different taxa confirmed to be allopolyploid; D. zanclophyllum from South Africa, D. wightianum from Malaysia and an undescribed taxon from China. The two Asian polyploids have originated from two different hybrid combinations, D. multispicatum x D. veitchii and D. tristachyum x D. veitchii. Diphasiastrum zanclophyllum originates from a cross between D. digitatum and an unidentified diploid taxon. The occurrence of three homoploid hybrid combinations commonly recognized in Europe, D. alpinum x D. complanatum, D. alpinum x D. tristachyum and D. complanatum x D. tristachyum, are verified using the same three nuclear regions. Two of the three hybrid combinations are also shown to have originated from reciprocal crosses. Admixture analyses performed on an extended, dataset similarly identified predominately F1 hybrids and backcrosses. The observations and common recognition of hybrid species in the included populations are hence most likely due to frequent observations of neohybrids in hybrid zones. Reticulate patterns are, however, prominent in the presented dataset. Hence future studies addressing evolutionary and ecological questions in Diphasiastrum should emphasize the impact of gene flow between parent lineages rather than speciation as the result of hybridization.
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| 5. |
- Aagaard, Sunniva M.D. 1977-, et al.
(författare)
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Reticulate phylogenetic patterns in diploid European Diphasiastrum (Lycopodiaceae).
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- In Central Europe, three species belonging to Diphasiastrum are considered to be of homoploid hybrid origin. Diphasiastrum issleri is suggested to have originated from a cross between D. alpinum and D. complanatum, D. oellgaardii from D. alpinum and D. tristachyum, and D. zeilleri from D. complanatum and D. tristachyum. Variation at three nuclear regions and two chloroplast microsatellites verify the presence of all three putative parental combinations in Europe. Data obtained with Feulgen DNA image densitometry confirms that all specimens displaying such pattern are diploid. Also, two of three parental combinations have probably arisen repeatedly, implied by the occurrence of chloroplast haplotypes associated with different parents. The presented dataset cannot be used as argument for the existence of independent evolutionary entities hybrid origin. This is nonetheless an important first step in order to address the influence of reticulate evolutionary events in European Diphasiastrum.
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| 6. |
- Abu Hamdeh, Sami, et al.
(författare)
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Extended anatomical grading in diffuse axonal injury using MRI : Hemorrhagic lesions in the substantia nigra and mesencephalic tegmentum indicate poor long-term outcome
- 2017
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Ingår i: Journal of Neurotrauma. - : Mary Ann Liebert Inc. - 0897-7151 .- 1557-9042. ; 5:34, s. 341-352
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Tidskriftsartikel (refereegranskat)abstract
- Clinical outcome after traumatic diffuse axonal injury (DAI) is difficult to predict. In this study, three magnetic resonance imaging (MRI) sequences were used to quantify the anatomical distribution of lesions, to grade DAI according to the Adams grading system, and to evaluate the value of lesion localization in combination with clinical prognostic factors to improve outcome prediction. Thirty patients (mean 31.2 years ±14.3 standard deviation) with severe DAI (Glasgow Motor Score [GMS] <6) examined with MRI within 1 week post-injury were included. Diffusion-weighted (DW), T2*-weighted gradient echo and susceptibility-weighted (SWI) sequences were used. Extended Glasgow outcome score was assessed after 6 months. Number of DW lesions in the thalamus, basal ganglia, and internal capsule and number of SWI lesions in the mesencephalon correlated significantly with outcome in univariate analysis. Age, GMS at admission, GMS at discharge, and low proportion of good monitoring time with cerebral perfusion pressure <60 mm Hg correlated significantly with outcome in univariate analysis. Multivariate analysis revealed an independent relation with poor outcome for age (p = 0.005) and lesions in the mesencephalic region corresponding to substantia nigra and tegmentum on SWI (p = 0.008). We conclude that higher age and lesions in substantia nigra and mesencephalic tegmentum indicate poor long-term outcome in DAI. We propose an extended MRI classification system based on four stages (stage I—hemispheric lesions, stage II—corpus callosum lesions, stage III—brainstem lesions, and stage IV—substantia nigra or mesencephalic tegmentum lesions); all are subdivided by age (≥/<30 years).
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| 7. |
- Abu Hamdeh, Sami, et al.
(författare)
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Intracranial pressure elevations in diffuse axonal injury : association with nonhemorrhagic MR lesions in central mesencephalic structures
- 2019
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Ingår i: Journal of Neurosurgery. - 0022-3085 .- 1933-0693. ; 131:2, s. 604-611
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Increased intracranial pressure (ICP) in patients with severe traumatic brain injury (TBI) with diffuse axonal injury (DAI) is not well defined. This study investigated the occurrence of increased ICP and whether clinical factors and lesion localization on MRI were associated with increased ICP in patients with DAI.Methods: Fifty-two patients with severe TBI (median age 24 years, range 9–61 years), who had undergone ICP monitoring and had DAI on MRI, as determined using T2*-weighted gradient echo, susceptibility-weighted imaging, and diffusion-weighted imaging (DWI) sequences, were enrolled. The proportion of good monitoring time (GMT) with ICP > 20 mm Hg during the first 120 hours postinjury was calculated and associations with clinical and MRI-related factors were evaluated using linear regression.Results: All patients had episodes of ICP > 20 mm Hg. The mean proportion of GMT with ICP > 20 mm Hg was 5%, and 27% of the patients (14/52) spent more than 5% of GMT with ICP > 20 mm Hg. The Glasgow Coma Scale motor score at admission (p = 0.04) and lesions on DWI sequences in the substantia nigra and mesencephalic tegmentum (SN-T, p = 0.001) were associated with the proportion of GMT with ICP > 20 mm Hg. In multivariable linear regression, lesions on DWI sequences in SN-T (8% of GMT with ICP > 20 mm Hg, 95% CI 3%–13%, p = 0.004) and young age (−0.2% of GMT with ICP > 20 mm Hg, 95% CI −0.07% to −0.3%, p = 0.002) were associated with increased ICP.Conclusions: Increased ICP occurs in approximately one-third of patients with severe TBI who have DAI. Age and lesions on DWI sequences in the central mesencephalon (i.e., SN-T) are associated with elevated ICP. These findings suggest that MR lesion localization may aid prediction of increased ICP in patients with DAI.Abbreviations: ADC = apparent diffusion coefficient; CPP = cerebral perfusion pressure; DAI = diffuse axonal injury; DWI = diffusion-weighted imaging; EVD = external ventricular drain; GCS = Glasgow Coma Scale; GMT = good monitoring time; GOSE = Glasgow Outcome Scale–Extended; ICC = intraclass correlation coefficient; ICP = intracranial pressure; MAP = mean arterial blood pressure; NICU = neurointensive care unit; SN-T = substantia nigra and mesencephalic tegmentum; SWI = susceptibility-weighted imaging; TBI = traumatic brain injury; T2*GRE = T2*-weighted gradient echo.
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| 8. |
- Abu Hamdeh, Sami, et al.
(författare)
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Intracranial pressure elevations in diffuse axonal injury are associated with non-hemorrhagic MR lesions in central mesencephalic structures
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Objective: Increased intracranial pressure (ICP) in severe traumatic brain injury (TBI) patients with diffuse axonal injury (DAI) is not well defined. This study investigated the occurrence of increased ICP and whether clinical factors and lesion localization on MRI were associated with increased ICP in DAI patients.Methods: Fifty-two severe TBI patients (median 24, range 9-61 years), with ICP-monitoring and DAI on MRI, using T2*-weighted gradient echo, susceptibility-weighted and diffusion-weighted (DW) sequences, were enrolled. Proportion of good monitoring time (GMT) with ICP>20 mmHg during the first 120 hours post-injury was calculated and associations with clinical and MRI-related factors were evaluated using linear regression. Results: All patients had episodes of ICP>20 mmHg. The mean proportion of GMT with ICP>20 mmHg was 5% and 27% of the patients (14/52) had more than 5% of GMT with ICP>20 mmHg. Glasgow Coma Scale motor score at admission (P=0.04) and lesions on DW images in the substantia nigra and mesencephalic tegmentum (SN-T, P=0.001) were associated with the proportion of GMT with ICP>20 mmHg. In multivariate linear regression, lesions on DW images in SN-T (8% of GMT with ICP>20 mmHg, 95% CI 3–13%, P=0.004) and young age (-0.2% of GMT with ICP>20 mmHg, 95% CI -0.07–-0.3%, P=0.0008) were associated with increased ICP. Conclusions: Increased ICP occurs in ~1/3 of severe TBI patients with DAI. Age and lesions on DW images in the central mesencephalon (SN-T) associate with elevated ICP. These findings suggest that MR lesion localization may aid prediction of increased ICP in DAI patients.
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| 9. |
- Abu Hamdeh, Sami, et al.
(författare)
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MRI analysis of diffuse axonal injury - Hemorrhagic lesions in the mesencephalon idicate poor long-term outcome
- 2016
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Ingår i: MRI analysis of diffuse axonal injury - Hemorrhagic lesions in the mesencephalon idicate poor long-term outcome. - : Springer.
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Konferensbidrag (refereegranskat)abstract
- Purpose: Clinical outcome after traumatic diffuse axonal injury (DAI) is difficult to predict. Three MRI techniques were compared in demonstrating acute brain lesions. Relationship of the anatomical distribution of the lesions in combination with clinical prognostic factors to outcome after 6 months was evaluated. Methods and Materials: Thirty patients, aged 16-60 years (mean 31.2 years) with severe DAI (Glasgow Motor Score = GMS < 6) were examined with MRI at 1.5T within one week after the injury. A diffusion-weighted (DW) sequence (SE-EPI, b value 1000 s/mm2), a T2*-weighted gradient echo (T2*GRE) sequence and a susceptibility-weighted (SWI) sequence were evaluated by two independent reviewers with short and long neuroradiological experiences. Clinical outcome was assessed with Extended Glasgow Outcome Score (GOSE) after ≥ 6 months.Results: Interreviewer agreement for DAI classification was very good (ҡ 0.82 – 0.91) with all three sequences. SWI visualized more lesions than the T2*GRE or DW sequence. In univariate analysis, number of DW lesions in the deep gray matter area including the internal capsules, number of SWI lesions in the mesencephalon, age, and GMS at admission and discharge correlated significantly with poor outcome. Multivariate analysis only revealed an independent relation with poor outcome for age (p = 0.011) and lesions in the mesencephalic region including crura cerebri, substantia nigra and tegmentum on SWI (p = 0.032).Conclusion: SWI is the most sensitive technique to visualize lesions in DAI. Age over 30 years and hemorrhagic mesencephalic lesions anterior to the tectum are indicators of poor long-term outcome in DAI.
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| 10. |
- Ali, Zafar, et al.
(författare)
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Homozygous GRID2 missense mutation predicts a shift in the D-serine binding domain of GluD2 in a case with generalized brain atrophy and unusual clinical features
- 2017
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Ingår i: BMC Medical Genetics. - : Springer Science and Business Media LLC. - 1471-2350. ; 18:1
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Spinocerebellar ataxias comprise a large and heterogeneous group of disorders that may present with isolated ataxia, or ataxia in combination with other neurologic or non-neurologic symptoms. Monoallelic or biallelic GRID2 mutations were recently reported in rare cases with cerebellar syndrome and variable degree of ataxia, ocular symptoms, hypotonia and developmental delay.CASE PRESENTATION: We report on a consanguineous family with autosomal recessive childhood onset of slowly progressive cerebellar ataxia and delayed psychomotor development in three siblings. MRI of an adult and affected family member revealed slightly widened cerebral and cerebellar sulci, suggesting generalized brain atrophy, and mild cerebellar atrophy. Using whole exome sequencing we identified a novel homozygous missense variant [c.2128C > T, p.(Arg710Trp)] in GRID2 that segregates with the disease. The missense variant is located in a conserved region encoding the extracellular serine-binding domain of the GluD2 protein and predicts a change in conformation of the protein.CONCLUSION: The widespread supratentorial brain abnormalities, absence of oculomotor symptoms, increased peripheral muscle tone and the novel missense mutation add to the clinical and genetic variability in GRID2 associated cerebellar syndrome. The neuroradiological findings in our family indicate a generalized neurodegenerative process to be taken into account in other families segregating complex clinical features and GRID2 mutations.
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