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71.
Chlorophyll fluorescence measurements have a wide range of applications from basic understanding of photosynthesis functioning
to plant environmental stress responses and direct assessments of plant health. The measured signal is the fluorescence intensity
(expressed in relative units) and the most meaningful data are derived from the time dependent increase in fluorescence intensity
achieved upon application of continuous bright light to a previously dark adapted sample. The fluorescence response changes
over time and is termed the Kautsky curve or chlorophyll fluorescence transient. Recently, Strasser and Strasser (1995) formulated
a group of fluorescence parameters, called the JIP-test, that quantify the stepwise flow of energy through Photosystem II,
using input data from the fluorescence transient. The purpose of this study was to establish relationships between the biochemical
reactions occurring in PS II and specific JIP-test parameters. This was approached using isolated systems that facilitated
the addition of modifying agents, a PS II electron transport inhibitor, an electron acceptor and an uncoupler, whose effects
on PS II activity are well documented in the literature. The alteration to PS II activity caused by each of these compounds
could then be monitored through the JIP-test parameters and compared and contrasted with the literature. The known alteration
in PS II activity of Chenopodium album atrazine resistant and sensitive biotypes was also used to gauge the effectiveness and sensitivity of the JIP-test. The information
gained from the in vitro study was successfully applied to an in situ study. This is the first in a series of four papers. It shows that the trapping parameters of the JIP-test were most affected
by illumination and that the reduction in trapping had a run-on effect to inhibit electron transport. When irradiance exposure
proceeded to photoinhibition, the electron transport probability parameter was greatly reduced and dissipation significantly
increased. These results illustrate the advantage of monitoring a number of fluorescence parameters over the use of just one,
which is often the case when the FV/FM ratio is used.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
72.
Effects of physioball and conventional floor exercises on early phase adaptations in back and abdominal core stability and balance in women 总被引:1,自引:0,他引:1
Cosio-Lima LM Reynolds KL Winter C Paolone V Jones MT 《Journal of strength and conditioning research / National Strength & Conditioning Association》2003,17(4):721-725
The purpose of this study was to compare the effects of 5 weeks of physioball core stability and balance exercises with conventional floor exercises in women. The experimental group (n = 15) performed curl-ups and back extensions on the physioball while the control group (n = 15) performed the same exercises on the floor. Baseline and post-training tests included electromyography (EMG) recordings of the rectus abdominus and erector spinae muscles; abdominal, back, and knee strength measurements with the Cybex Norm System; and 2 unilateral stance balance tests. The physioball group was found to have significantly greater mean change in EMG flexion and extension activity (p = 0.04 and p = 0.01, respectively) and greater balance scores (p < 0.01) than the floor exercise group. No significant changes (p > 0.05) were observed for heart rate or Cybex strength measurements. Early adaptations in a short-term core exercise program using the physioball resulted in greater gains in torso balance and EMG neuronal activity in previously untrained women when compared to performing exercises on the floor. 相似文献
73.
The histone gene H1t is expressed exclusively in pachytene spermatocytes of the testis. In this report we have eliminated the single copy H1t gene by homologous recombination from the mouse genome to analyse the function of the H1t protein during spermatogenesis. Mice homozygous for the mutated H1t gene locus developed normally and showed no anatomic abnormalities until the adult stage. In addition, H1t-deficient mice were fertile and reproduced as wild-type mice. The process of spermatogenesis and the testicular morphology remained unchanged in the absence of H1t. RNase protection analysis demonstrated that H1.1, H1.2 and H1.4 histone gene expression is enhanced during spermatogenesis in H1t-deficient mice. 相似文献
74.
Sister chromatid cohesion and recombination in meiosis 总被引:10,自引:0,他引:10
Sister chromatids are associated from their formation until their disjunction. Cohesion between sister chromatids is provided
by protein complexes, of which some components are conserved across the kingdoms and between the mitotic and meiotic cell
cycles. Sister chromatid cohesion is intimately linked to other aspects of chromosome behaviour and metabolism, in particular
chromosome condensation, recombination and segregation. Recombination, sister chromatid cohesion and the relation between
the two processes must be regulated differently in mitosis and meiosis. In meiosis, cohesion and recombination are modified
in such a way that reciprocal exchange and reductional segregation of homologous chromosomes are ensured.
Received: 11 October 1999; in revised form: 3 December 1999 / Accepted: 6 December 1999 相似文献
75.
Genomic Analysis Reveals Chromosomal Variation in Natural Populations of the Uncultured Psychrophilic Archaeon Cenarchaeum symbiosum 总被引:3,自引:0,他引:3
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Christa Schleper Edward F. DeLong Christina M. Preston Robert A. Feldman Ke-Ying Wu Ronald V. Swanson 《Journal of bacteriology》1998,180(19):5003-5009
Molecular phylogenetic surveys have recently revealed an ecologically widespread crenarchaeal group that inhabits cold and temperate terrestrial and marine environments. To date these organisms have resisted isolation in pure culture, and so their phenotypic and genotypic characteristics remain largely unknown. To characterize these archaea, and to extend methodological approaches for characterizing uncultivated microorganisms, we initiated genomic analyses of the nonthermophilic crenarchaeote Cenarchaeum symbiosum found living in association with a marine sponge, Axinella mexicana. Complex DNA libraries derived from the host-symbiont population yielded several large clones containing the ribosomal operon from C. symbiosum. Unexpectedly, cloning and sequence analysis revealed the presence of two closely related variants that were consistently found in the majority of host individuals analyzed. Homologous regions from the two variants were sequenced and compared in detail. The variants exhibit >99.2% sequence identity in both small- and large-subunit rRNA genes and they contain homologous protein-encoding genes in identical order and orientation over a 28-kbp overlapping region. Our study not only indicates the potential for characterizing uncultivated prokaryotes by genome sequencing but also identifies the primary complication inherent in the approach: the widespread genomic microheterogeneity in naturally occurring prokaryotic populations. 相似文献
76.
Elena I. Mikhailova Tomás Naranjo Ken Shepherd Jannie Wennekes-van Eden Christa Heyting J. Hans de Jong 《Chromosoma》1998,107(5):339-350
The Ph1 locus in wheat influences homo(eo)logous chromosome pairing. We have analysed its effect on the behaviour and morphology
of two 5RL rye telosomes in a wheat background, by genomic in situ hybridisation (GISH), using rye genomic DNA as a probe.
Our main objective was to study the effect of different alleles of the Ph1 locus on the morphology and behaviour of the rye telosomes in interphase nuclei of tapetal cells and in pollen mother cells
at early stages of meiosis. The telosomes, easily detectable at all stages, showed a brightly fluorescing chromomere in the
distal region and a constriction in the proximal part. These diagnostic markers enabled us to define the centromere and telomere
regions of the rye telosomes. In the presence of functional copies of Ph1, the rye telosomes associated at pre-leptotene, disjoined and reorganised their shape at leptotene, and became fully homologously
paired at zygotene – pachytene. In plants without functional alleles (ph1bph1b), the rye telosomes displayed an aberrant morphology, their premeiotic associations were clearly disturbed and their pairing
during zygotene and pachytene was reduced and irregular. The Ph1 locus also influenced the behaviour of rye telosomes in the interphase nuclei of tapetal cells: in Ph1Ph1 plants, the rye telosomes occupied distinct, parallel-oriented domains, whereas in tapetal nuclei of ph1bph1b plants they were intermingled with wheat chromosomes and showed a heavily distorted morphology. The results shed new light
on the effect of Ph1, and suggest that this locus is involved in chromosome condensation and/or scaffold organisation. Our explanation might account
for various apparently contradictory and pleiotropic effects of this locus on both premeiotic associations of homologues,
the regulation of meiotic homo(eo)logous chromosome pairing and synapsis, the resolution of bivalent interlockings and centromere
behaviour.
Received: 27 April 1998; in revised form: 5 August 1998 / Accepted: 11 August 1998 相似文献
77.
Gabriele Anton Rory Wilson Zhong-hao Yu Cornelia Prehn Sven Zukunft Jerzy Adamski Margit Heier Christa Meisinger Werner R?misch-Margl Rui Wang-Sattler Kristian Hveem Bruce Wolfenbuttel Annette Peters Gabi Kastenmüller Melanie Waldenberger 《PloS one》2015,10(3)
Advances in the “omics” field bring about the need for a high number of good quality samples. Many omics studies take advantage of biobanked samples to meet this need. Most of the laboratory errors occur in the pre-analytical phase. Therefore evidence-based standard operating procedures for the pre-analytical phase as well as markers to distinguish between ‘good’ and ‘bad’ quality samples taking into account the desired downstream analysis are urgently needed. We studied concentration changes of metabolites in serum samples due to pre-storage handling conditions as well as due to repeated freeze-thaw cycles. We collected fasting serum samples and subjected aliquots to up to four freeze-thaw cycles and to pre-storage handling delays of 12, 24 and 36 hours at room temperature (RT) and on wet and dry ice. For each treated aliquot, we quantified 127 metabolites through a targeted metabolomics approach. We found a clear signature of degradation in samples kept at RT. Storage on wet ice led to less pronounced concentration changes. 24 metabolites showed significant concentration changes at RT. In 22 of these, changes were already visible after only 12 hours of storage delay. Especially pronounced were increases in lysophosphatidylcholines and decreases in phosphatidylcholines. We showed that the ratio between the concentrations of these molecule classes could serve as a measure to distinguish between ‘good’ and ‘bad’ quality samples in our study. In contrast, we found quite stable metabolite concentrations during up to four freeze-thaw cycles. We concluded that pre-analytical RT handling of serum samples should be strictly avoided and serum samples should always be handled on wet ice or in cooling devices after centrifugation. Moreover, serum samples should be frozen at or below -80°C as soon as possible after centrifugation. 相似文献
78.
Mohamad Wessam Alnouri Stephan Jepards Alessandro Casari Anke C. Schiedel Sonja Hinz Christa E. Müller 《Purinergic signalling》2015,11(3):389-407
Adenosine receptors (ARs) have emerged as new drug targets. The majority of data on affinity/potency and selectivity of AR ligands described in the literature has been obtained for the human species. However, preclinical studies are mostly performed in mouse or rat, and standard AR agonists and antagonists are frequently used for studies in rodents without knowing their selectivity in the investigated species. In the present study, we selected a set of frequently used standard AR ligands, 8 agonists and 16 antagonists, and investigated them in radioligand binding studies at all four AR subtypes, A1, A2A, A2B, and A3, of three species, human, rat, and mouse. Recommended, selective agonists include CCPA (for A1AR of rat and mouse), CGS-21680 (for A2A AR of rat), and Cl-IB-MECA (for A3AR of all three species). The functionally selective partial A2B agonist BAY60-6583 was found to additionally bind to A1 and A3AR and act as an antagonist at both receptor subtypes. The antagonists PSB-36 (A1), preladenant (A2A), and PSB-603 (A2B) displayed high selectivity in all three investigated species. MRS-1523 acts as a selective A3AR antagonist in human and rat, but is only moderately selective in mouse. The comprehensive data presented herein provide a solid basis for selecting suitable AR ligands for biological studies.
Electronic supplementary material
The online version of this article (doi:10.1007/s11302-015-9460-9) contains supplementary material, which is available to authorized users. 相似文献79.
Lesley Cottrell Carrie Rishel Christa Lilly Scott Cottrell Aaron Metzger Halima Ahmadi Bo Wang Xiaoming Li Bonita Stanton 《PloS one》2015,10(5)
In this study, we examined how adolescents compare monitoring efforts by their parents to those of a "good parent" standard and assessed the impact of these comparisons on adolescent self-disclosure and risk behavior and their perceptions of their parents'' monitoring knowledge. Survey responses from 519 adolescents (12–17 years) at baseline of a larger, longitudinal study examining parental monitoring and adolescent risk were examined. Adolescents’ “good parent comparisons” differed greatly by monitoring areas (e.g., telephone use, health, money); however, between 5.5% and 25.8% of adolescents believed their parents needed to monitor their activities more than they currently were monitoring. Alternatively, between 8.5% and 23.8% of adolescents believed their parents needed to monitor their activities less often. These perceptions significantly distinguished adolescents in terms of their level of disclosure, perceived monitoring knowledge, and risk involvement. Adolescents who viewed their parents as needing to monitor more were less likely to disclose information to their parents (p<.001), less likely to perceive their parents as having greater monitoring knowledge (p<.001), and more likely to be involved in a risk behaviors (p<.001) than adolescents who perceived their parents needed no change. Adolescent disclosure to a parent is a powerful predictor of adolescent risk and poor health outcomes. These findings demonstrate that adolescents'' comparisons of their parents'' monitoring efforts can predict differences in adolescent disclosure and future risk. Obtaining adolescent "good parent" comparisons may successfully identify intervention opportunities with the adolescent and parent by noting the areas of need and direction of monitoring improvement. 相似文献
80.
Jean Yves Le Reste Patrice Nabbe Charles Rivet Charilaos Lygidakis Christa Doerr Slawomir Czachowski Heidrun Lingner Stella Argyriadou Djurdjica Lazic Radost Assenova Melida Hasaganic Miquel Angel Munoz Hans Thulesius Bernard Le Floch Jeremy Derriennic Agnieska Sowinska Harm Van Marwijk Claire Lietard Paul Van Royen 《PloS one》2015,10(1)