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21.
Summary In a geographically wide distribution the life cycles of different populations of the cabbage moth Mamestra brossicae are adapted to a remarkable diversity of climatic conditions. This is undoubtedly a proof of its success in adaptation. Some populations living in regions characterized by a drought period interrupting the growth season are capable of distinguishing between one critical day length signalling the onset of the drought period and another signalling the end of the growth season. This study, therefore, is primarily concerned with the geographical patterns in the variability of the adaptional responses of populations exposed to environmental conditions requiring different strategies and tactics in, synchronizing individual, life cycles. It is also a contribution to our understanding of evolutionary mechanisms maintaining median responses to photoperiodically inductive day lengths in geographically different populations. The populations investigated originated from regions differing in predictability of the incidence, onset and duration of a drought period: Freiburg (48.0°N, Southern Germany), Avignon (44.0°N, Southern France), and Argelès (42.5°N, Southern France). Geographical variation with respect to both onset and duration of a drought period consequently results in clinal variation of the variability of innate day length thresholds triggering aestival dormancy and of innate duration of aestivation. In this paper we considered the influence of geographically changing temperatures on aestival dormancy induction. Even in southern populations of M. brassicae a temperature dependent switch off-mechanism exists which prevents aestival dormancy under certain environmental conditions. The effective temperatures vary geographically, too. What the geographical patterns in adaptive responses really are, is discussed.This research was supported by the Deutsche Forschungsgemeinschaft (Sa 259/3-1) 相似文献
22.
We isolated hybridomas that produced monoclonal antibodies specific for the UDP-galactose: sn -glycerol-3-phosphate α-D-galactosyltransferase (IFP synthase, EC 2.4.1.96), an enzyme involved in the volume regulation of Poterioochromonas malhamensis Peterfi. Western blotting of native gradient gels with the most reactive antibody S 162 revealed several immunoreactive proteins in crude homogenates suggesting the occurrence of multiple molecular mass species of the galactosyltransferase. The amount of the presumed enzyme monomer (64 kDa under native conditions) was strongly increased by a pH shift of crude homogenates from pH 8 to 6. During activation of the galactosyltransferase in the cell homogenate and also by shrinking the cells, the presumed enzyme monomer appeared to be proteolytically degraded generating stepwise products of 52 and 40 kDa. We assume that the proteolytically processed enzyme becomes highly active, but is very susceptible to further proteolytic degradation. 相似文献
23.
A model is presented describing the relationship between chlorophyll fluorescence quenching and photoinhibition of Photosystem (PS) II-dependent electron transport in chloroplasts. The model is based on the hypothesis that excess light creates a population of inhibited PS II units in the thylakoids. Those units are supposed to posses photochemically inactive reaction centers which convert excitation energy to heat and thereby quench variable fluorescence. If predominant photoinhibition of PS II and cooperativity in energy transfer between inhibited and active units are presumed, a quasi-linear correlation between PS II activity and the ratio of variable to maximum fluorescence, FVFM, is obtained. However, the simulation does not result in an inherent linearity of the relationship between quantum yield of PS II and FVFM ratio. The model is used to fit experimental data on photoinhibited isolated chloroplasts. Results are discussed in view of current hypotheses of photoinhibition.Abbreviations FM
maximum total fluorescence
- F0
initial fluorescence
- FV
maximum variable fluorescence
- PS
Photosystem
- QA, QB
primary and secondary electron acceptors of Photosystem II 相似文献
24.
25.
Involvement of various organs in the initial plasma clearance of differently glycosylated rat liver secretory proteins 总被引:2,自引:0,他引:2
V Gross P C Heinrich D vom Berg K Steube T Andus T A Tran-Thi K Decker W Gerok 《European journal of biochemistry》1988,173(3):653-659
The initial plasma clearance and organ distribution of alpha 1-acid glycoprotein and alpha 2-macroglobulin carrying different types of oligosaccharide, side chains was studied in rats. The differently glycosylated proteins were synthesized by rat hepatocytes in culture in the presence of tunicamycin (unglycosylated form), swainsonine (hybrid type), or 1-deoxymannojirimycin (high-mannose type). Deglycosylated glycoproteins (Asn-GlcNAc) were obtained by endoglucosaminidase H treatment of high-mannose-type glycoproteins. Ten minutes after intravenous injection 3% of complex type, 26% of hybrid type, 84% of high-mannose type. 64% of unglycosylated and 80% of deglycosylated alpha 1-acid glycoprotein disappeared from the plasma. The respective values for alpha 2-macroglobulin were 26%, 42%, 59% and 67%. When the clearance of total hepatic secretory proteins was examined, major differences between glycosylated and unglycosylated (glyco)proteins were found, particularly in the case of low-molecular-mass polypeptides. Whereas complex-type alpha 1-acid glycoprotein and alpha 2-macroglobulin showed no accumulation in various organs, hybrid-type alpha 1-acid glycoprotein and alpha 2-macroglobulin were present in spleen and liver. High-mannose-type alpha 1-acid glycoprotein and alpha 2-macroglobulin also accumulated mainly in spleen and liver. Spleen had the highest specific activity; liver, due to its larger organ mass, represented the major organ for the uptake of high-mannose-type glycoproteins. Competition experiments with mannan and GlcNAc-bovine-serum-albumin showed a mannose/GlcNAc receptor-mediated removal. Whereas unglycosylated alpha 1-acid glycoprotein was taken up by the kidney, unglycosylated alpha 2-macroglobulin was found in the spleen. Deglycosylated glycoproteins (Asn-GlcNAc) were removed from the plasma via two different mechanisms: firstly, clearance by the kidney similar to the unglycosylated glycoproteins; secondly, clearance by a mannose/GlcNAc receptor-mediated uptake mainly into the spleen. We conclude that N-linked oligosaccharide side chains are important for the plasma survival of hepatic secretory glycoproteins and that unphysiologically glycosylated forms are cleared by different mechanisms. 相似文献
26.
27.
One-carbon metabolism in lectin-activated human lymphocytes 总被引:1,自引:0,他引:1
P B Rowe D Sauer D Fahey G Craig E McCairns 《Archives of biochemistry and biophysics》1985,236(1):277-288
Serine is an essential amino acid for the lectin-mediated transformation of human peripheral blood lymphocytes due to the inability of this cell to synthesize sufficient quantities via either the phosphorylated pathway or by reversal of the serine hydroxymethyltransferase reaction to meet the metabolic demands. The level of intracellular serine is tightly regulated, and the culture medium concentration for optimum cellular transformation falls within a relatively narrow range. The three-carbon atom of serine is the major source of one-carbon units required for purine and pyrimidine nucleotide biosynthesis, but the key effect of both serine deprivation and of high medium serine levels would appear to be on protein synthesis. Although an alternative source of one-carbon units, as provided by high levels of formate in the culture medium, can partially reverse the effects of serine deprivation, the only other demonstrable source of one-carbon units, tryptophan, requires serine for its incorporation and subsequent metabolism. Methionine is also essential for lymphocyte transformation and is involved in the synthesis of a small amount of phosphatidylcholine, although most of this phospholipid is provided by choline and lysophosphatidylcholine from the serum-supplemented culture medium. 相似文献
28.
The bacteriophage P22 arc and mnt repressors. Overproduction, purification, and properties 总被引:13,自引:0,他引:13
A K Vershon P Youderian M M Susskind R T Sauer 《The Journal of biological chemistry》1985,260(22):12124-12129
The arc and mnt genes of bacteriophage P22 encode small repressor proteins. We have cloned these genes onto plasmids that overproduce Arc and Mnt to greater than 1% of the soluble cellular protein. Both proteins were purified to greater than 95% homogeneity, and N-terminal sequences and amino acid compositions were determined. These data, in combination with previously determined gene sequences, establish the complete protein sequences for Arc (53 residues) and Mnt (82 residues). Both proteins have melting temperatures between 45 and 55 degrees C and can be renatured to a fully active species. Arc is a dimer in solution and Mnt is a tetramer. 相似文献
29.
The effect of light on the metabolism of ammonia was studied by subjecting detached maize leaves to 150 or 1350 mol m–2 s–1 PAR during incubation with the leaf base in 2 mM 15NH4Cl. After up to 60 min, leaves were extracted. Ammonia, glutamine, glycine, serine, alanine, and aspartate were separated by isothermal distillation and ion exchange chromatography. 15N enrichments were analyzed by emission spectroscopy. The uptake of ammonium chloride did not influence CO2 assimilation (8.3 and 17.4 mol m–1 s–1 at 150 and 1350 mol m–2 s–1 PAR, respectively). Leaves kept at high light intensity contained more serine and less alanine than leaves from low light treatments. Within 1 h of incubation the enrichment of ammonia extracted from leaves rose to approximately 20% 15N. In the high light regime the amino acids contained up to 15% 15N, whereas in low light 15N enrichments were small (up to 6%). The kinetics of 15N incorporation indicated that NH3 was firstly assimilated into glutamine and then into glutamate. After 15 min 15N was also found in glycine, serine and alanine. At high light intensity nearly half of the 15N was incorporated in glycine. On the other hand, at low light intensity alanine was the predominant 15N sink. It is concluded that light influences ammonia assimilation at the glutamine synthetase reaction. 相似文献
30.