Biomedical subjects

M Lukaszewicz

Publications and source records attributed to M Lukaszewicz.

16 recordsLinked to original sources

PubMed2003

Regeneration of flax ( Linum usitatissimum L.) plants from anther culture and somatic tissue with increased resistance to Fusarium oxysporum.

The aim of this study was to establish a protocol for the efficient production of flax plants of microspore origin. The results were compared to those obtained for plants regenerated from somatic explants from hypocotyls, cotyledons, leaves, stems and roots. All the plants obtained during the experiments were regenerated from callus that was grown for periods from a few weeks to a few months before the regeneration was achieved. Anther cultures were less effective in plant regeneration than somatic cell cultures. However, regenerants derived from anther cells showed valuable breeding features, including increased resistance to fungal wilt. The age of the donor plants and the season they grew in had a noticeable effect on their anther callusing and subsequent plant regeneration. Low temperature had a negative effect and dark pre-treatment a positive effect on callusing and plant regeneration. Different media were most effective for callus induction, shoot induction and rooting. For callus induction two carbon sources (2.5% sucrose and 2.5% glucose) were most effective; for shoots, only sucrose at lower concentration (2%) was effective. Rooting was most efficient in 1% sucrose and reduced (50%) mineral concentration in the medium. It was found that the length of in vitro cultivation significantly increases the ploidy and affects such features as regenerant morphological characteristics, petal colour, and resistance to Fusarium oxysporum-induced fungal wilt. The established plant regeneration system provides a basis for the creation of transgenic flax.

Culture Techniques↗

PubMed2002

Functional dissection of the ParB homologue (KorB) from IncP-1 plasmid RK2.

Active partitioning of low-copy number plasmids requires two proteins belonging to the ParA and ParB families and a cis-acting site which ParB acts upon. Active separation of clusters of plasmid molecules to the defined locations in the cell before cell division ensures stable inheritance of the plasmids. The central control operon of IncP-1 plasmids codes for regulatory proteins involved in the global transcriptional control of operons for vegetative replication, stable maintenance and conjugative transfer. Two of these proteins, IncC and KorB, also play a role in active partitioning, as the ParA and ParB homologues, respectively. Here we describe mapping the regions in KorB responsible for four of its different functions: dimerisation, DNA binding, repression of transcription and interaction with IncC. For DNA binding, amino acids E151 to T218 are essential, while repression depends not only on DNA binding but, additionally, on the adjacent region amino acids T218 to R255. The C-terminus of KorB is the main dimerisation domain but a secondary oligomerisation region is located centrally in the region from amino acid I174 to T218. Using three different methods (potentiation of transcriptional repression, potentiation of DNA binding and activation in the yeast two-hybrid system) we identify this region as also responsible for interactions with IncC. This IncC-KorB contact differs in location from the ParA-ParB/SopA-SopB interactions in P1/F but is similar to these systems in lying close to a masked oligomerisation determinant.

Amino Acid Sequence↗

PubMed2001

The antioxidant activity of BHT and new phenolic compounds PYA and PPA measured by chemiluminescence.

The antioxidative properties of two series of new phenolic, amphiphilic compounds were evaluated using the chemiluminescence (CL) method. 2,2'-Azobis (2-amidinopropane) dihydrochloride (AAPH) was used as a source of free radicals, to obtain high and prolonged CL. Three different kinds of buffers (organic and inorganic) were tested. The CL level varied only slightly depending on the buffer but increased significantly with the pH. Twelve newly synthesised compounds were compared with butylated hydroxytoluene (BHT), a commercially used antioxidant. The new antioxidants included two classes of quaternary ammonium salts with a phenol substituent functioning as an antioxidant. The salts were synthesised by quaternarization of pyrrolidine ethyl esters of dihydrocinnamic acid by n-alkoxymethyl bromides (PYA-n) or quaternarization of 2-dimethylaminoethyl esters by n-alkyl bromides (PPA-n). All the tested compounds quenched CL proportionally to their concentrations. In our experimental conditions 8.5 microM BHT quenched 50% of the CL. The PYA and PPA compounds had IC50 two to six times lower than BHT. CL inhibition was proportional to the pH for all antioxidants. The relationships between the structure and activity of the tested compounds are discussed.

Amidines↗

PubMed2000

In vivo evaluation of the context sequence of the translation initiation codon in plants.

Statistical analysis of the AUG initiation codon context in several plant organisms identified a nucleotide preference in some positions around the AUG. Sixteen AUG contexts were studied using transient expression in tobacco, maize and Norway spruce. Besides the importance of A or G at position -3, we revealed the role of positions -2, -1 for which AA or CC were found to be the best for tobacco and maize, respectively. GC (positions +4, +5) were also found to be important in both tobacco and maize. Finally, we identified a variation in context efficiency according to cell type, since A was better than G at position -3 in tobacco leaf protoplasts, while both nucleotides were equally efficient in tobacco suspension cells.

Journal Article↗

PubMed2000

Spontaneous and radical-induced plasma membrane lipid peroxidation in differently oxidant-sensitive yeast species and its suppression by antioxidants.

Formation of thiobarbituric acid-reactive substances (TBRS; nmol/mg lipids) indicative of lipid peroxidation was measured in whole cells and in isolated plasma membrane lipids from three yeast species differing in oxidant sensitivity (Schizosaccharomyces pombe, Saccharomyces cerevisiae and Rhodotorula glutinis) after exposure to the Fenton reagent, FeII, H2O2, tert-butyl hydroperoxide (TBHP) and azo compounds (AAPH, ACHN). In whole cells, spontaneous TBRS formation rose in the sequence S. pombe < S. cerevisiae < R. glutinis (1:approximately 5:approximately 7). Oxidants increased the TBRS production 13-18 fold in the sequence FeII approximately TBHP > AAPH approximately ACHN approximately Fe-Fenton > H2O2. This increase need not be solely due to increased lipid peroxidation. In isolated plasma membrane lipids from all three species, the spontaneous TBRS production referred to 1 mg lipids was 9-13-fold higher than in whole cells. In S. pombe lipids, only TBHP increased the TBRS production. In lipids from S. cerevisiae and R. glutinis, all added oxidants increased the spontaneous TBRS production 2-3 times in the sequence TBHP > ACHN > AAPH > FeII > Fe-Fenton > H2O2. Oxidant-induced TBRS production in both whole cells and isolated membrane lipids was partially suppressed by the lipid peroxidation inhibitors 2,6-di-tert-butyl-4-methylphenol ("butylated hydroxytoluene"; BHT) and the newly synthesized PYA12 compound. Both agents were more effective in isolated lipids than in whole cells and against OH.-producing than against ROO.- or RO.-producing oxidants. Yeast membrane lipids, which are generally poor in polyunsaturated fatty acids, are thus subject to perceptible lipid peroxidation.

Antioxidants↗

PubMed1998

Signs of translational regulation within the transcript leader of a plant plasma membrane H(+)-ATPase gene.

Transcripts of most plant plasma membrane H(+)-ATPase genes possess a leader (5' untranslated region) that is unusually long and that contains a short upstream open reading frame (uORF), two features which suggest post-transcriptional regulation. To investigate the putative role of the transcript leader, we have placed the leader of pma3, one of the Nicotiana plumbaginifolia H(+)-ATPase genes, between the CaMV 35S promoter and the sequence coding for the beta-glucuronidase (GUS) reporter gene. Transient expression of this chimeric gene and of derived mutants was analysed in electroporated tobacco protoplasts. The whole leader had a positive effect on translation, since deletion of most of its sequence reduced GUS activity. Suppression of the uORF by point mutation of its initiating AUG increased GUS activity by about 55%. Analysis of various deletions and mutations suggested that the uORF is translated by at least two-thirds of scanning ribosomes, half of which subsequently reinitiate downstream translation under our experimental conditions. Reinitiation did not depend on the nucleotide sequence of the uORF, nor on that separating the uORF and the main open reading frame. We conclude that the pma3 transcript possesses features of translational regulation, whose mode of functioning has yet to be discovered.

Base Sequence↗

PubMed1997

[Recurrent pulmonary embolism in an athlete. Vena cava filter implantation as a effective alternative to medical treatment].

The case of 63 years old judo trainer, actively working and suffering from pulmonary embolism originating from deep vein thrombosis aggravated by sport traumas, is presented. Repeated episodes of pulmonary embolism, despite treatment with oral anticoagulants, have led to alternative method of treatment--vena cava filter insertion. Diagnosis achieving process, concerning the sportive lifestyle, and the effectiveness of pharmacological treatment, are discussed.

Anticoagulants↗

PubMed1994

A plant plasma membrane proton-ATPase gene is regulated by development and environment and shows signs of a translational regulation.

A proton-pumping ATPase is present in the plasma membrane of plant cells where it sustains transport-related functions. This enzyme is encoded by a family of genes that shows signs of both transcriptional and post-transcriptional regulation. The regulation of pma1, one of the Nicotiana plumbaginifolia H+-ATPase genes, was characterized with the help of the beta-glucuronidase (gusA) receptor gene in transgenic plants. pma1 is active in the root epidermis, the stem cortex, and guard cells. This activity depends on developmental and growth conditions. For instance, pma1 activity in guard cells was strongly enhanced when the plant material (young seedlings or mature leaves) was incubated in liquid growth medium. pma1 is also expressed in several tissues of the reproductive organs where active transport is thought to occur but where scarcely any ATPase activity has been identified, namely in the tapetum, the pollen, the transmitting tissue, and the ovules. Several pma genes have a long 5'untranslated region (leader sequence) containing an upstream open reading frame (URF). Analysis of translational and transcriptional fusions with gusA in transgenic plants suggests that the pma1 leader sequence might activate translation of the main open reading frame, even though the URF is translated by a large majority of the scanning ribosomes. As confirmation, transient expression experiments showed that the pma1 leader causes a fourfold post-transcriptional increase of main open reading frame expression. Deletion of the URF by site-directed mutagenesis stimulated the main open reading frame translation 2.7-fold in an in vitro translational assay. These results are consistent with a regulatory mechanism involving translation reinitiation. Altogether, they suggest a fine, multilevel regulation of H+-ATPase activity in the plant.

Base Sequence↗

PubMed1985