| 1. |
- Carlsson, Georg, et al.
(author)
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N-2 fixation in three perennial Trifolium species in experimental grasslands of varied plant species richness and composition
- 2009
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In: Plant Ecology. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 205, s. 87-104
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Journal article (peer-reviewed)abstract
- This study is the first to investigate quantitative effects of plant community composition and diversity on N-2 fixation in legumes. N-2 fixation in three perennial Trifolium species grown in field plots with varied number of neighbouring species was evaluated with the N-15 natural abundance method (two field sites, several growing seasons, no N addition) and the isotope dilution method (one site, one growing season, 5 g N m(-2)). The proportion of plant N derived from N-2 fixation, pNdfa, was generally high, but the N addition decreased pNdfa, especially in species-poor communities. Also following N addition, the presence of grasses in species-rich communities increased pNdfa in T. hybridum and T. repens L., while legume abundance had the opposite effect. In T. repens, competition for light from grasses appeared to limit growth and thereby the amount of N-2 fixed at the plant level, expressed as mg N-2 fixed per sown seed. We conclude that the occurrence of diversity effects seems to be largely context dependent, with soil N availability being a major determinant, and that species composition and functional traits are more important than species richness regarding how neighbouring plant species influence N-2 fixation in legumes.
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| 2. |
- Klein, Christoph, et al.
(author)
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HAX1 deficiency causes autosomal recessive severe congenital neutropenia (Kostmann disease)
- 2007
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In: Nature Genetics. - : Springer Science and Business Media LLC. - 1061-4036 .- 1546-1718. ; 39:1, s. 86-92
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Journal article (peer-reviewed)abstract
- Autosomal recessive severe congenital neutropenia (SCN) constitutes a primary immunodeficiency syndrome associated with increased apoptosis in myeloid cells, yet the underlying genetic defect remains unknown. Using a positional cloning approach and candidate gene evaluation, we identified a recurrent homozygous germline mutation in HAX1 in three pedigrees. After further molecular screening of individuals with SCN, we identified 19 additional affected individuals with homozygous HAX1 mutations, including three belonging to the original pedigree described by Kostmann. HAX1 encodes the mitochondrial protein HAX1, which has been assigned functions in signal transduction and cytoskeletal control. Here, we show that HAX1 is critical for maintaining the inner mitochondrial membrane potential and protecting against apoptosis in myeloid cells. Our findings suggest that HAX1 is a major regulator of myeloid homeostasis and underline the significance of genetic control of apoptosis in neutrophil development.
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| 3. |
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| 4. |
- Stenberg, Georg, et al.
(author)
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Semantic Priming In Schizophrenia - The N400 In A Picture Verification Task
- 2005
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In: Society for Psychophysiological Research. - 0048-5772.
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Conference paper (other academic/artistic)abstract
- Semantic memory access has been characterized as abnormal in schizophrenia, but findings concerning automatic spreading activation at short stimulus onset asynchronies (SOA) have been inconsistent. Using the N400 as an indicator of semantic priming, a recent study (Mathalon, Faustman, & Ford, 2002) found evidence of hyperpriming in schizophrenic patients in a picture verification task. The present study replicates the Mathalon et al. study and extends the paradigm to a third stimulus condition. Pictures of common objects were shown, followed at short SOAs by words with three types of semantic relation to the picture: (a) matching, e.g. dog-dog, (b) related, e.g. dog-cat, or (c) unrelated, e.g. dog-bicycle. We expected patients to show a smaller N400 than controls in the related condition, indicating hyperpriming of semantic relations. Eighteen medicated patients and twenty-four controls participated. Behavioral results revealed slowed reaction times in patients, but no interaction with stimulus condition. The P300 in the matching condition was normal. The N400 in the related condition was, as predicted, reduced in patients. Unexpectedly, the unrelated condition showed the same difference between patients and controls, suggesting that reduced N400 was not caused by activation spreading along normal pathways. Subtraction waveforms (related - unrelated) were equivalent in amplitude between groups, but peak latency was longer in patients. The results indicate slowed processing, and an atypical pattern of semantic activation in schizophrenia.
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