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21.
Astrid Löffler Justyna Wolinska Barbara Keller Karl-Otto Rothhaupt Piet Spaak 《Freshwater Biology》2004,49(10):1372-1380
1. We investigated whether Daphnia galeata × hyalina hybrids of Lake Constance and Lake Greifensee show the same pattern of life history parameters as previously reported for D. galeata × cucullata hybrids and whether such a pattern is consistent between Daphnia populations from those two lakes. 2. Hybrids in Lake Constance were intermediate in size compared with the parental species. Hybrids in Lake Greifensee were smaller than D. galeata. The intrinsic growth rate (r) of hybrids from Lake Constance was not significantly different from the faster growing parental taxon D. galeata. However, r of hybrids from Lake Greifensee was significantly lower than that of D. galeata. 3. The observed juvenile body length differences between the taxa varied with the clutch number. The first clutch juvenile lengths of the three taxa did not differ for Lake Constance. First clutch juveniles of Lake Greifensee D. galeata were smaller than hybrid first clutch juveniles. The third clutch juvenile length did not differ between taxa from Lake Greifensee, but D. galeata juveniles from Lake Constance were bigger than those of D. hyalina. 4. The life history pattern found in Lake Constance corresponds to previous findings from other studies. The hybrids in this lake combine the faster population growth of one parental species with a relatively small size. In the case of Lake Greifensee hybrids, the relatively large size of first clutch juveniles and the small size of the adults could be interpreted as dual adaptations to invertebrate and fish predation. We speculate that the lower population growth rate of the hybrids is a trade‐off for this twofold protection. 相似文献
22.
M. Atta Noële Debaecker K. K. Andersson Jean-Marc Latour Lars Thelander Astrid Gräslund 《Journal of biological inorganic chemistry》1996,1(3):210-220
Mouse ribonucleotide reductase is composed of a 1?:?1 complex of two homodimeric subunits and catalyses the first unique step on the biochemical pathway to DNA synthesis. The small subunit, protein R2, contains dinuclear iron-oxygen clusters and a tyrosyl free radical required for catalytic activity. We have studied the mixed valent and fully reduced forms of the diiron oxygen cluster from mouse R2 protein by low-temperature EPR. EPR signals of the mixed-valent states of proteins R2 reconstituted with ferrous iron and oxygen in normal and deuterated water, using the same buffers, show apparent g values of 1.92, 1.73, and 1.60 for the mixed-valent state in H2O and 1.93, 1.73, and 1.62 in D2O. These g values are typical for diiron-oxygen proteins, while the effect of D2O is unprecedented for this class of proteins. We estimate the coupling constant J for the Heisenberg exchange (H?=?2J*S1*S2) to be J?=?–7.5±1?cm–1 for the mixed-valent form. The diferrous R2 protein shows an integer spin EPR signal in the presence of azide or 20% glycerol. Variable temperature variable field saturation magnetisation measurements show that only in the azide-complexed R2 protein does a weak ferromagnetic coupling occur (J?=?0.26±0.05?cm–1), while R2 protein in the absence or presence of 20% glycerol contains non-coupled mononuclear ferrous iron (S?=?2) sites. 相似文献
23.
In potato tubers two starch phosphorylase isozymes, types L and H, have been described and are believed to be responsible for the complete starch breakdown in this tissue. Type L has been localized in amyloplasts, whereas type H is located within the cytosol. In order to investigate whether the same isozymes are also present in potato leaf tissue a cDNA expression library from potato leaves was screened using a monoclonal antibody recognizing both isozyme forms. Besides the already described tuber L-type isozyme a cDNA clone encoding a second L-type isozyme was isolated. The 3171 nucleotide long cDNA clone contains an uninterrupted open reading frame of 2922 nucleotides which encodes a polypeptide of 974 amino acids. Sequence comparison between both L-type isozymes on the amino acid level showed that the polypeptides are highly homologous to each other, reaching 81–84% identity over most parts of the polypeptide. However the regions containing the transit peptide (amino acids 1–81) and the insertion sequence (amino acids 463–570) are highly diverse, reaching identities of only 22.0% and 29.0% respectively.Northern analysis revealed that both forms are differentially expressed. The steady-state mRNA levels of the tuber L-type isozyme accumulates strongly in potato tubers and only weakly in leaf tissues, whereas the mRNA of the leaf L-type isozyme accumulates in both tissues to the same extent. Constitutive expression of an antisense RNA specific for the leaf L-type gene resulted in a strong reduction of starch phosphorylase L-type activity in leaf tissue, but had only sparse effects in potato tuber tissues. Determination of the leaf starch content revealed that antisense repression of the starch phosphorylase activity has no significant influence on starch accumulation in leaves of transgenic potato plants. This result indicated that different L-type genes are responsible for the starch phosphorylase activity in different tissues, but the function of the different enzymes remains unclear. 相似文献
24.
25.
Dicotyledon plants adapt to iron (Fe) deficiency through a seriesof reactions that increase the ability of the plant to assimilateFe and to increase the efficiency of Fe utilization. In an attemptto gain an insight into these adaptive processes, the specificchanges in protein synthesis associated with the onset of theFe deficiency response in tomato roots (Lycopersicon esculentumMill cv. Rutgers) have been investigated. Roots were grown underFesufficient and deficient conditions, and thepattern of protein synthesis was analysed by in vitro translationof root mRNA and by in vivo labelling of root proteins. Polypeptideswere resolved by twodimensional polyacrylamide gel electrophoresis.Seven polypeptides were identified by in vitro translation,whose synthesis was significantly increased during Fe deficiency.The increase was probably specific to Fe deficiency in thatthe polypeptide synthesis was not increased during phosphatedeficiency stress, was less prominent following prolonged Fedeficiency and was decreased following resupply of Feto the hydroponic medium. The pattern of in vitro translation of mRNA isolated from Fedeficientroots was compared to the results obtainedin vivo followingradiolabelling of proteins. In these analyses, eight polypeptideswere identified, tentatively including the seven polypeptidespreviously identified by in vitro translation. All polypeptideswere characterized with regard to molecular mass and pl andtheir localization in the cell, whether being membrane boundor soluble. It is suggested that members of this group of polypeptidesare involved in the response of the root to Fe deficiency: althoughtheir functions remain to be identified. Key words: In vitro protein synthesis, iron, iron deficiency, root, 2-dimensional PAGE 相似文献
26.
Astrid Schön 《Molecular biology reports》1995,22(2-3):139-145
RNase P consists of both protein and RNA subunits in all organisms and organelles investigated so far, with the exception of chloroplasts and plant nuclei where no enzyme-associated RNA has been detected to date. Studies on substrate specificity revealed that cleavage by plant nuclear RNase P is critically dependent on a complete and intact structure of the substrate. No clearcut answer is yet possible regarding the order of processing events at the 5 or 3 end of tRNAs in the case of nuclear or chloroplast processing enzymes. RNase P from a phylogenetically ancient photosynthetic organelle will be discussed in greater detail: The enzyme from theCyanophora paradoxa cyanelle is the first RNase P from a photosynthetic organelle which has been shown to contain an essential RNA subunit. This RNA is strikingly similar to its counterpart from cyanobacteria, yet it lacks catalytic activity. Properties of the holoenzyme suggest an intermediate position in RNA enzyme evolution, with an eukaryotic-type, inactive RNA and a prokaryotic-type small protein subunit. The possible presence of an RNA component in RNase P from plant nuclei and modern chloroplasts will be discussed, including a critical evaluation of some criteria that have been frequently applied to elucidate the subunit composition of RNase P from different organisms.Abbreviations RNase P
Ribonuclease P
- (pre-)tRNA
transfer ribonucleic acid (precursor)
- tRNA
Ser
(-
Tyr
, -
Phe
)
transfer ribonucleic acid specific for serine (tyrosine, phenylalanine)
- CyRP RNA
RNA component of cyanelle RNase P 相似文献
27.
Peter Allard Jüri Jarvet Anders Ehrenberg Astrid Gräslund 《Journal of biomolecular NMR》1995,5(2):133-146
Summary The peptide hormone motilin was synthesised with a 13C-enriched -carbon in the leucine at position 10. In aqueous solution, six different relaxation rates were measured for the 13C–H fragment as a function of temperature and with and without the addition of 30% (v/v) of the cosolvent d
2-1,1,1,3,3,3-hexafluoro-2-propanol (HFP). The relaxation rates were analysed employing the spectral density mapping technique introduced by Peng and Wagner [(1992) J. Magn. Reson., 98, 308–322] and using the model-free approach by Lipari and Szabo [(1982) J. Am. Chem. Soc., 104, 4546–4570]. The fit to various models of dynamics was also considered. Different procedures to evaluate the overall rotational correlation time were compared. A single exponential time correlation function was found to give a good fit to the measured spectral densities only for motilin in 30% (v/v) HFP at low temperatures, whereas at high temperatures in this solvent, and in D2O at all temperatures, none of the considered models gave an acceptable fit. A new empirical spectral density function was tested and found to accurately fit the experimental spectral density mapping points. The application of spectral density mapping based on NMR relaxation data for specific 13C–1H vector is shown to be a highly useful method to study biomolecular dynamics. Advantages are high sensitivity, high precision and uniform sampling of the spectral density function over the frequency range.Abbreviations CD
circular dichroism
- NOE
nuclear Overhauser enhancement
- NOESY
two-dimensional NOE spectroscopy
- INEPT
insensitive nuclei enhanced by polarisation transfer
- DANTE
delays alternating with nutations for tailored excitation
- WALTZ-16
wideband, alternating phase, low-power technique for zero residual splitting
- FID
Free induction decay
- ppm
parts per million
- TSPA
3-trimethylsilyl-(3,3,2,2-d)-propionic acid
- HFP
d
2-1,1,1,3,3,3-hexafluoro-2-propanol
- CPMG
Carr-Purcell-Meiboom-Gill
- TFD
time-resolved fluorescence depolarisation
- CSA
chemical shift anisotropy
Partly presented at the symposium Dynamics and Function of Biomolecules, Szeged, Hungary, July 31–August 2, 1993. 相似文献
28.
Astrid Zimmermann Anke Haina Ute Gröschel-Stewart 《Development genes and evolution》1995,204(4):271-275
The development of the autonomic ganglia of Auerbach's plexus and gizzard smooth muscle was studied in chicken embryos. Nervous system and smooth-muscle-specific antibodies were employed in immunofluorescence stainings on tissue sections to investigate the temporal and spatial frame of neural and muscular differentiation in relation to each other. Subserosal clusters of neural cells were clearly demonstrable at embryonic day 5 (ED5), the earliest stage analysed, with the monoclonal antibody El (SGIII-1). Fine nerve fibres (ED6) and, later, large axon bundles projecting from subserosal neuron clusters towards the lumen were followed and found to reach the luminal border by ED11. Already in early development the area of the future laminar tendons on the ventral and dorsal surface of the gizzard was devoid of neuroblasts, and nerve fibres were not extending to the muscle-tendon borderline until ED16. Double stainings with antibodies to smooth muscle myosin (SMM) and El revealed that SMM expression, taken as an indicator for muscle differentiation, followed neural growth. It was first detectable in close apposition to the differentiating neuroblasts in the caudal and cranial portion of the gizzard at ED6. With further development, myosin expression proceeded inward towards the lumen in a wave which followed the ingrowth of E1-positive nerve fibres from the prospective Auerbach plexus. Neuromuscular differentiation deviated from this pattern in the lateral tendon area where nerve growth was delayed and myosin expression preceeded the arrival of E1-positive nerve fibres. The findings suggest that the gizzard could serve as a model system for the analysis of potential early nervous system imprints on smooth premuscle mesenchyme differentiation. 相似文献
29.
30.
Abstract— The convulsant action of allylglycine (2-amino-4-pentenoic acid) is due to the metabolic conversion of allylglycine to 2-keto-4-pentenoic acid, a more potent glutamic acid decarboxylase inhibitor and more potent convulsant than the parent compound. We report regional changes in cerebral GABA concentration in rats after administration of d - and l -allylglycine. d -Allylglycine (3.75 mmol/kg) induced convulsions in 95–115 min, characterised by repeated clonic limb movements and rapid rotation around the head to tail axis. GABA concentrations were only reduced in cerebellum and ponsmedulla during the pre and post-convulsive periods. The localised reduction of GABA concentration is consistent with the enzymic conversion of d -allylglycine to 2-keto-4-pentenoic acid catalysed by cerebral d -amino acid oxidase, an enzyme known to be localised to the hind brain and spinal cord. l -allylglycine (1.2mmol/kg i.p.) induced convulsions in 65 -90 min, characterised by violent running followed by tonic flexion and extension. During the pre-convulsive period, GABA concentrations were reduced in all brain areas studied except the globus pallidus and ventral midbrain. The widespread decreases in GABA concentration suggest that the enzyme(s) which catalyse the conversion of l -allylglycine to 2-keto-4-pentenoic acid are widely distributed within the brain. 相似文献