In eubacteria and mitochondria, Hsp70 chaperone activity is controlled by the nucleotide exchange factor GrpE. We have identified the chloroplastic GrpE homolog of Chlamydomonas, CGE1, as an ∼26-kD ...protein coimmunoprecipitating with the stromal HSP70B protein. When expressed in Escherichia coli, CGE1 can functionally replace GrpE and interacts physically with DnaK. CGE1 is encoded by a single-copy gene that is induced strongly by heat shock and slightly by light. Alternative splicing generates two isoforms that differ only by two residues in the N-terminal part. The larger form is synthesized preferentially during heat shock, whereas the smaller one dominates at lower temperatures. Fractions of both HSP70B and CGE1 associate with chloroplast membranes in an ATP-sensitive manner. By colorless native PAGE and pulse labeling, CGE1 monomers were found to assemble rapidly into dimers and tetramers. In addition, CGE1 was found to form ATP-sensitive complexes with HSP70B of ∼230 and ∼120 kD, the latter increasing dramatically after heat shock.
ABSTRACT
The aim of this study is to quantify changes of atmospheric circulation over Europe using a large number of classifications of circulation types that were collected and developed within the ...COST733 Action ‘Harmonisation and Applications of Weather Types Classifications for European Regions’. Circulation changes over Europe are studied in terms of changing seasonal frequency and persistence of daily circulation types in the period September 1957–August 2002. The extensive collection of both subjective and objective (computer‐assisted) catalogues of circulation types in 12 European domains serves as a platform for comparison of different classification methods, varying numbers of circulation types, sequencing of input sea‐level pressure data, and spatial scale of circulation processes. The overall picture of frequency and persistence trends is consistent with two large‐scale tendencies: strengthening and eastward shift of the North Atlantic Oscillation, and a northwestward shift of storm tracks. There is, however, a limited consistency in the trends between individual classifications. This inconsistency leads us to the recommendation that results of climatological analyses based on a single classification should not be generalized and overinterpreted; it is highly advisable to simultaneously use multiple, and as many as possible, classifications in climatological studies.
Mutants with defects in the cytochrome (cyt) b₆/f complex were analyzed for their effect on the expression of a subgroup of nuclear genes encoding plastid-localized enzymes participating in ...chlorophyll biosynthesis. Their defects ranged from complete loss of the cytb₆/f complex to point mutations affecting specifically the quinone-binding $\text{Q}_{\text{O}}$ site. In these seven mutants, light induction of the tetrapyrrole biosynthetic genes was either abolished or strongly reduced. In contrast, a normal induction of chlorophyll biosynthesis genes was observed in mutants with defects in photosystem II, photosystem I, or plastocyanin, or in wild-type cells treated with 3-(3′4′-dichlorophenyl)-1,1-dimethylurea or 2,5-dibromo-3-methyl-6-isopropyl benzoquinone. We conclude that the redox state of the plastoquinone pool does not control light induction of these chlorophyll biosynthetic genes. The signal that affects expression of the nuclear genes appears to solely depend on the integrity of the cytb₆/f complex $\text{Q}_{\text{O}}$ site. Since light induction of these genes in Chlamydomonas has recently been shown to involve the blue light receptor phototropin, the results suggest that cytb₆/f activity regulates a plastid-derived factor required for their expression. This signaling pathway differs from that which regulates state transitions, since mutant stt7, lacking a protein kinase involved in phosphorylation of the light-harvesting complex II, was not altered in the expression of the chlorophyll biosynthetic genes.
Carotid artery stenting (CAS) is associated with the risk of periprocedural embolic events. The procedural risk may vary with plaque characteristics. We aimed at determining the impact of carotid ...plaque surface irregularity on the risk of cerebral embolism during CAS.
Solid microembolic signals (MES) during CAS for symptomatic carotid stenosis were assessed by means of dual-frequency transcranial Doppler ultrasound. Study endpoint was the number of solid MES during CAS in 12 patients with irregular carotid stenosis compared to 12 matched patients with smooth carotid stenosis.
A total of 438 solid MES were detected. The cumulative number of solid MES was 329 in patients with irregular plaques and 109 in those with smooth plaques. The proportion of subjects in whom solid MES were detected was higher in the irregular plaque group (11/12) than in the smooth plaque group (5/12) (p = 0.030). The numbers of solid MES per CAS procedure and per hour of CAS procedure were both higher in patients with irregular plaques than in those with smooth plaques (p = 0.008 and 0.015, respectively).
Carotid plaque surface irregularity predicts solid cerebral embolism during stenting of symptomatic carotid artery stenosis.
ABSTRACT
This study evaluates the classifications of atmospheric circulation patterns collected in the COST733 database (COST733cat) in terms of their ability to stratify daily surface temperature ...and precipitation in 12 domains covering the whole of Europe. The classifications differ in the classification methods used, in the number of types, the variable(s) classified, the number of days in a sequence that are classified and in whether the classification is based on year‐round or seasonal data. Several classification methods that perform fairly well are identified; they include a simple k‐means clustering, a k‐means clustering preceded by hierarchical cluster analysis, Litynski's method, and a classification based on circulation prototypes. On the other hand, there are a couple of classification methods that do not provide a good stratification of temperature and precipitation: orthogonally and obliquely rotated principal component analysis in a T‐mode, Lund's correlation method, Kirchhofer's sums‐of‐squares method, and Erpicum's method. Some methods tend to perform better on large domains, while others tend to perform better on smaller domains; however, the sensitivity of most classification methods to the domain size appears to be small. Several methods exhibit a geographical dependence of their performance, e.g. the method based on circulation prototypes tends to perform better in the northern domains, while Jenkinson–Collison and Erpicum's methods perform better in the southern domains. Classifications of 4‐day sequences are usually better in stratifying surface temperature than ordinary instantaneous classifications; the opposite is true for precipitation. Adding a mid‐tropospheric variable (500 hPa heights or 1000/500 hPa thickness) to sea level pressure as a classified variable improves the skill of classifications in stratifying temperature.
The first step in sexual differentiation of the unicellular green alga Chlamydomonas reinhardtii is the formation of gametes. Three genes, GAS28, GAS30, and GAS31, encoding Hyp-rich glycoproteins ...that presumably are cell wall constituents, are expressed in the late phase of gametogenesis. These genes, in addition, are activated by zygote formation and cell wall removal and by the application of osmotic stress. The induction by zygote formation could be traced to cell wall shedding prior to gamete fusion since it was seen in mutants defective in cell fusion. However, it was absent in mutants defective in the initial steps of mating, i.e. in flagellar agglutination and in accumulation of adenosine 3′,5′-cyclic monophosphate in response to this agglutination. Induction of the three GAS genes was also observed when cultures were exposed to hypoosmotic or hyperosmotic stress. To address the question whether the induction seen upon cell wall removal from both gametes and vegetative cells was elicited by osmotic stress, cell wall removal was performed under isosmotic conditions. Also under such conditions an activation of the genes was observed, suggesting that the signaling pathway(s) is (are) activated by wall removal itself.
We review recent advances in classifications of circulation patterns as a specific research area within synoptic climatology. The review starts with a general description of goals of classification ...and the historical development in the field. We put circulation classifications into a broader context within climatology and systematize the varied methodologies and approaches. We characterize three basic groups of classifications: subjective (also called manual), mixed (hybrid), and objective (computer-assisted, automated). The roles of cluster analysis and principal component analysis in the classification process are clarified. Several recent methodological developments in circulation classifications are identified and briefly described: the introduction of nonlinear methods, objectivization of subjective catalogs, efforts to optimize classifications, the need for intercomparisons of classifications, and the progress toward an optimum, if possible unified, classification method. Among the recent tendencies in the applications of circulation classifications, we mention a more extensive use in climate studies, both of past, present, and future climates, innovative applications in the ensemble forecasting, increasing variety of synoptic-climatological investigations, and steps above from the troposphere. After introducing the international activity within the field of circulation classifications, the COST733 Action, we briefly describe outputs of the inventory of classifications in Europe, which was carried out within the Action. Approaches to the evaluation of classifications and their mutual comparisons are also reviewed. A considerable part of the review is devoted to three examples of applications of circulation classifications: in historical climatology, in analyses of recent climate variations, and in analyses of outputs from global climate models.
The first step in sexual differentiation of the unicellular green alga Chlamydomonas reinhardtii is the formation of gametes. Three genes, GAS28, GAS30, and GAS31, encoding Hyp-rich glycoproteins ...that presumably are cell wall constituents, are expressed in the late phase of gametogenesis. These genes, in addition, are activated by zygote formation and cell wall removal and by the application of osmotic stress. The induction by zygote formation could be traced to cell wall shedding prior to gamete fusion since it was seen in mutants defective in cell fusion. However, it was absent in mutants defective in the initial steps of mating, i.e. in flagellar agglutination and in accumulation of adenosine 3',5'-cyclic monophosphate in response to this agglutination. Induction of the three GAS genes was also observed when cultures were exposed to hypoosmotic or hyperosmotic stress. To address the question whether the induction seen upon cell wall removal from both gametes and vegetative cells was elicited by osmotic stress, cell wall removal was performed under isosmotic conditions. Also under such conditions an activation of the genes was observed, suggesting that the signaling pathway(s) is (are) activated by wall removal itself.
Non-stationarities are inherent characteristics of the climate system and can be observed on different temporal and spatial scales. Non-stationarities in large-scale modes of climate variability of ...the Northern Hemisphere and the associated changes in the surface climate like modifications of the temperature and precipitation patterns are analysed. As major modes of climate variability the El Niño–Southern Oscillation phenomenon, the Pacific–North American pattern and the North Atlantic Oscillation are selected. The North Atlantic–European area is taken as an example to highlight non-stationarities in the atmospheric circulation and their impact on regional climate. The mechanisms and consequences of circulation-climate non-stationarities are discussed.
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