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T Altmann

Publications and source records attributed to T Altmann.

27 records · Page 2Linked to original sources
PubMed1998

Use of the IGF BAC library for physical mapping of the Arabidopsis thaliana genome.

In order to generate a physical map of the Arabidopsis thaliana genome based on bacterial artificial chromosome clones (BACs), an iterative high throughput hybridisation strategy was applied and its efficiency was evaluated. Thus, probes generated from both ends of 500 BAC clones selected from the Arabidopsis-IGF-BAC library were hybridised to the entire library gridded on high density filters. The 1000 hybridisation reactions identified 4496 clones (41.8% of the complete library, or 50.3% if organellar, centromeric, and ribosomal DNA carrying clones are excluded) which were assembled into a minimum of 220 contigs. These results demonstrate the viability of the applied 'double-end clone-limited/sampling without replacement' hybridisation strategy for the generation of a high resolution physical map, and provide a highly useful resource for map-based gene cloning approaches and further genome analysis.

Arabidopsis↗
PubMed1998

Inactivation of a glycyl-tRNA synthetase leads to an arrest in plant embryo development.

Embryo formation is the first patterning process during vegetative plant growth. Using transposons as insertional mutagens in Arabidopsis, we identified the mutant edd1 that shows embryo-defective development. The insertion mutation is lethal, arresting embryo growth between the globular and heart stages of embryonic development. The mutant phenotype cosegregates with a transposed Dissociation element. Sequences flanking the transposed element were isolated and used to isolate a full-length cDNA clone representing the wild-type EDD1 gene. Complementation of the mutant through Agrobacterium-mediated gene transfer of an EDD1 wild-type copy as well as loss of the transposon concomitant with phenotypic reversion demonstrated that the transposon had caused the mutation. Based on homology to Escherichia coli, the EDD1 gene is predicted to encode a novel glycyl-tRNA synthetase (GlyRS) that has not been identified previously in higher plants. An N-terminal portion of the plant protein is able to direct a marker protein into pea chloroplasts. Thus, the gene identified by the embryo-defective insertion mutation encodes a GlyRS homolog, probably acting within the plastidic compartment.

Amino Acid Sequence↗
PubMed1997

Brassinosteroids from seeds of Arabidopsis thaliana.

Extracts of seeds of Arabidopsis thaliana (ecotype 24) were analysed for the presence of free and conjugated brassinosteroids. 24-epi-Brassinolide (ca 220 ng kg-1) and castasterone (ca 360 ng kg-1) could be isolated and unambiguously identified as native brassinosteroids by GC/MS.

Arabidopsis↗
PubMed1996

Brassinosteroids rescue the deficiency of CYP90, a cytochrome P450, controlling cell elongation and de-etiolation in Arabidopsis.

The cpd mutation localized by T-DNA tagging on Arabidopsis chromosome 5-14.3 inhibits cell elongation controlled by the ecdysone-like brassinosteroid hormone brassinolide. The cpd mutant displays de-etiolation and derepression of light-induced genes in the dark, as well as dwarfism, male sterility, and activation of stress-regulated genes in the light. The CPD gene encodes a cytochrome P450 (CYP90) sharing homologous domains with steroid hydroxylases. The phenotype of the cpd mutant is restored to wild type both by feeding with C23-hydroxylated brassinolide precursors and by ectopic overexpression of the CPD cDNA. Brassinosteroids also compensate for different cell elongation defects of Arabidopsis det, cop, fus, and axr2 mutants, indicating that these steroids play an essential role in the regulation of plant development.

Arabidopsis↗
PubMed1996

Elevated potassium enhances glutamate vulnerability of dopaminergic neurons developing in mesencephalic cell cultures.

This study examines the effects of high K+ concentration on the growth and development of mesencephalic cells and their glutamate vulnerability. Mesencephalic cell cultures obtained from Wistar rat embryos on the 14th gestational day were maintained for 14 days in medium with either normal (4.2 mM) or elevated (24.2 mM) potassium concentration. There was no significant difference due to various K+ concentration in cell growth and survival up to day in vitro (DIV) 13-14. In order to test the glutamate (Glu) vulnerability, cultures were treated with 100 mu M Glu for 15 min in salt solution on the DIV 3,6,8 and 13. Glu-induced neuronal damage was estimated 24 h later by measuring the neuron-specific enolase (NSE) content in the culture medium and by counting the number of tyrosine hydroxylase-immunoreactive (TH-IR) neurons. Glu had no damaging effect on the cells on DIV 3, but became pronounced beyond DIV 6. Elevated potassium concentration 24.2 mM) in the culture medium during development significantly increased neuronal vulnerability to Glu treatment, indicated by a higher increase of NSE content in the medium and by a more pronounced Glu-induced decrease of the number of TH-IR cells. The Glu-induced decrease of the number of TH-IR cells and of NSE-IR cells let us conclude that dopaminergic neurons are more vulnerable to glutamate than other neurons from mesencephalic culture.

Animals↗
PubMed1996

Glutamate-induced efflux of protein, neuron-specific enolase and lactate dehydrogenase from a mesencephalic cell culture.

A mixed mesencephalic cell culture damaged by glutamate was used as a model to study the efflux of lactate dehydrogenase and neuron-specific enolase from neuronal cells into the culture medium. Glutamate toxicity was induced in sister cultures by 15 min exposure to 100 mumol/l glutamate in a Ca2+ containing salt solution. Cell injury was monitored 24 h later by measuring the lactate dehydrogenase activity and the neuron-specific enolase content in the cells and in the culture medium. The neuronal cell damage is reflected by an efflux of neuron-specific enolase and lactate dehydrogenase from the cells and an increase of lactate dehydrogenase catalytic activity concentration and neuron-specific enolase mass concentration in the culture medium. It was found that the efflux fraction calculated from estimations of the cells was clearly higher than the efflux fraction calculated from estimations of the amount of enzymes found in the culture medium. Calculations of the recovery of lactate dehydrogenase and neuron-specific enolase and experiments designed to study the efflux of lactate dehydrogenase and neuron-specific enolase during incubation and washing showed that higher amounts of neuron-specific enolase are released than lactate dehydrogenase. A close correlation was found between the glutamate-induced changes of the neuron-specific enolase efflux fraction, based on enzyme determinations of the cells, and the change of the microscopically counted neuron-specific enolase immunoreactive cell numbers. This indicates that the determination of the neuron-specific enolase efflux fraction (cells) is an accurate and sensitive marker of damaged neurons. The lactate dehydrogenase efflux fraction seems to be less sensitive for the quantitation of neuronal cell damage; in addition, it depends not only on the neuronal damage but also on the proportion of neurons in the cell culture.

Animals↗
PubMed1995

Ac/Ds transposon mutagenesis in Arabidopsis thaliana: mutant spectrum and frequency of Ds insertion mutants.

Using a two-component Ac/Ds system consisting of a stabilized Ac element (Acc1) and a non-autonomous element (DsA), 650 families of plants carrying independent germinal DsA excisions/transpositions were isolated. Progenies of 559 of these Acc1/DsA families, together with 43 families of plants selected for excision/transposition of wild-type (wt) Ac, were subjected to a broad screening program for mutants exhibiting visible alterations. This resulted in the identification of 48 mutants showing a wide variety of mutant phenotypes, including embryo lethality (24 mutants), chlorophyll defects (5 mutants), defective seedlings (2 mutants), reduced fertility (5 mutants), reduced size (3 mutants), altered leaf morphology (2 mutants), dark green, unexpanded rosette leaves (3 mutants), and aberrant flower or shoot morphology (4 mutants). To whether these mutants were due to transposon insertions, a series of Southern blot experiments was performed on 28 families, comparing in each case several mutant plants with others showing the wild-type phenotype. A preliminary analysis revealed in 4 of the 28 families analyzed a common, novel DsA fragment in all mutant plants, which was present only in heterozygous plants with wt phenotype, as expected for DsA insertion mutations. These four mutants included two showing embryo lethality, one with dark green, unexpanded rosette leaves and stunted inflorescences, and one with curly growth of stems, leaves and siliques. Further evidence for DsA insertion mutations was obtained for one embryo lethal mutant and for the stunted mutant, while in case of the second embryo lethal mutant, the DsA insertion could be separated from the mutant locus by genetic recombination.

Arabidopsis↗
PubMedDate not supplied

[The effects of hook plates on the subacromial space--a clinical and MRT study].

AIM: The analysis of middle- and long-term results after treatment of acromioclavicular joint injuries with a hook plate as a temporary implant and a comparison of the results with those described in literature have been made. METHOD: In a retrospective study we were able to conduct follow-up examinations on 28 out of 39 Tossy III patients (72 %) who received surgical treatment using a hook plate according to Dreithaler. Examinations took place on average 3.0 (1.2-5.6) years after surgery. A special focus of attention was the effect of the hook plate on the subacromial space. Accordingly, physical examination was supplemented by sonography of the shoulder as well as comparative bilateral shoulder MRI. RESULTS: 86 % of our patients expressed satisfaction with the functional outcome of surgery as opposed to 54 % concerning its cosmetic result. In shoulder sonography no patient turned out to have suffered a higher grade rotator cuff lesion, whereas age-related degenerative alterations were found in 46 % of the patients. Instability under load was found in 7 patients (25 %). Among these were 3 with severe instability (11 %). 2 patients (7 %) were found to have a permanent subluxation of the acromioclavicular joint with partial range of motion impairment. All scores monitored (DASH, Taft, Constant-Murley) on average returned good to excellent results. MRI scans displayed no case of higher grade rotator cuff lesion. In accordance with the findings of ultrasound imaging a higher incidence of extraarticular ossification was found as well as, in some cases, arthrosis of the acromioclavicular joint. CONCLUSION: In our opinion, the hook plate designed by Dreithaler is easy to handle and serves as a qualified implant for temporary stabilisation of the acromioclavicular joint with middle- and long-term good to excellent results.

Acromion↗