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991.
Question: How do various plant functional groups and types are related to regeneration of limestone grasslands and to temporal changes in cover of trees and shrubs? Which mechanisms are responsible for changes in differently treated grasslands? Location: Southern Poland, 50° 01'N, 19° 50'E. Methods: A 12‐year restoration experiment after the clearing of a 35‐yr‐old secondary pine wood developed on limestone grassland, and a parallel observation of succession in neighbouring abandoned grassland were carried out. Changes in cover of species with different functional traits and established strategies in relation to time and cover of shrub layer were analysed using multiple linear regression. Results: Over 12 years the composition and cover of species changed in the studied grasslands, but significant differences still occurred between the old grassland and the grassland restored in former wood gaps and that developed in former closed wood. Despite the very close proximity of the old grassland, the composition of restored grasslands was still much determined by initial conditions. In these grasslands, the cover of Festuco‐Brometea species was significantly lower than in the old grassland. In all sites, the cover of species with large leaves and with leaves distributed regularly along the stem, and the cover of CS strategists increased. With increasing shrub cover in restored grasslands, the cover of annuals and biennials, tall species, and R and CS strategists decreased. Conclusions: Limited availability of seeds seems the principal reason for the weak regeneration of xerothermic limestone grasslands. Trees and shrubs inhibit the developed of both early successional species and perennials occurring in established communities. They significantly hinder regeneration of grasslands and should be cut every five or six years. 相似文献
992.
993.
The edeines analogs were tested in several in vitro and in vivo assays using the mouse model, with edeine B (peptide W1) and cyclosporine A as reference compounds. The peptides displayed
moderate, stimulatory effects on concanavalin A-induced (ConA-induced) splenocyte proliferation, whereas their effects on
pokeweed mitogen-induced (PWM-induced) splenocyte proliferation were inhibitory. The peptides inhibited lipopolysacharide-induced
(LPS-induced) tumor necrosis factor alpha production but had little effect on interleukin 6 production. In the model of the
humoral immune response in vitro to sheep red blood cells, peptide 1 was distinctly stimulatory in the investigated concentrations (1-100 μg/ml), whereas
peptides 3 and 4 only stimulated the number of antibody-forming cells at the highest concentration (100 μg/ml). In the model
of the delayed type hypersensitivity in vivo to ovalbumin, the peptides were moderately suppressive (3 being the most active). The reference peptide W1 stimulated ConA-induced
cell proliferation at 1–10 μg/ml but was inhibitory at 100 μg/ml. It also inhibited PWM-induced cell proliferation in a dose-dependent
manner. This peptide had no effect on the humoral immune response in vitro or on cytokine production, but inhibited DTH reaction in vivo. The relationship between structure and activity, and a possible mode of action of the peptides, is discussed in this paper. 相似文献
994.
Malgorzata Kajstura H Dorota Halicka Juliusz Pryjma Zbigniew Darzynkiewicz 《Cytometry. Part A》2007,71(3):125-131
BACKGROUND: Internucleosomal DNA fragmentation is one of the hallmarks of apoptosis. Because the low molecular weight DNA fragments are extracted during cell staining in aqueous solutions, apoptotic cells can be identified on DNA content frequency histograms as cells with fractional ("sub-G(1)") DNA content. The aim of the present study was to explore whether in situ DNA fragmentation during apoptosis is discontinuous or progresses incessantly and if it is discontinuous, to define the resistant to cleavage fraction of DNA that remains stainable with the fluorochrome. MATERIALS AND METHODS: The model of activation-induced apoptosis of human lymphocytes was chosen as it provides uniform cell population with identical DNA content (DI = 1.00) that undergo apoptosis. Their apoptosis was induced by multivalent mitogen phytohemagglutinin (PHA) in the absence and presence of geldanamycin (GA), the benzoquinone ansamycin antibiotic which binds to Hsp90 (Heat Shock Protein 90) and alters its function. The cells were stained with acridine orange, the metachromatic fluorochrome that differentially stains cellular DNA and RNA. RESULTS: A sharp, discrete peak representing the subpopulation of "sub-G(1)" cells with highly reproducible DI = 0.42 +/- 0.02 (CV = 5.5 +/- 1.2) was observed on DNA content histograms of lymphocytes whose apoptosis was induced by PHA alone. Two distinct peaks, one representing cell subpopulations with DI = 0.42 (as above) and another, with DI = 0.79 +/- 0.04 (CV = 5.8 +/- 0.4), respectively, were seen in apoptotic cells from cultures stimulated with PHA in the presence of GA. The frequency of cells represented by the sub-G(1) peaks varied depending on time of induction of apoptosis and GA concentration. CONCLUSIONS: Apoptosis-induced DNA fragmentation is discontinuous; approximately 42% of DNA is relatively stable and remains within the cell. The data suggest that the stable DNA is associated with nuclear matrix while the degradable fraction represents DNA in loop domains. A transient DNA stabilization is apparent in the presence of GA as evidenced by the presence of cell subpopulations with 79% of DNA retained in the cell. The observed discontinuity of DNA fragmentation appears to reflect sequential involvement of different nucleases and may also be modulated by chromatin structure. 相似文献
995.
Arnould JC Delouvrié B Boutron P Dossetter AG Foote KM Hamon A Hancox U Harris CS Hutton M Lamorlette M Matusiak Z 《Bioorganic & medicinal chemistry letters》2007,17(23):6448-6454
A new class of small-molecule GnRH antagonists, the thieno[2,3-b]pyrroles, was designed. Herein, the synthesis and structure-activity relationships are described. Substitution at the C4 position was investigated; during this study, it was observed that introducing piperazines and piperidines improved the physical properties of the compounds while retaining good in vitro potency. This exploration led to the discovery of amidopiperidines with improved pharmacokinetic properties. 相似文献
996.
Agnieszka Klink Malgorzata Dambiec Pawel Bienkowski Janusz Klink Zbigniew Salamacha 《International journal of phytoremediation》2019,21(3):246-250
It is known that both natural and artificial electric fields (EF) affect plants physiological parameters as well as germination, growth and yield. The present article describes results of a preliminary experiment on the impact of electric field on aquatic plants biogeochemistry. The objective of the present study was the assessment of the influence exerted by the electric field on growth and trace metals content of Elodea canadensis. In a laboratory experiment plants were exposed to the field intensity of 54?kV m?1 for 7?days. The plants length was measured and the content of Fe, Mn, Ni, Pb, and Zn was determined using atomic absorption spectrometry (AAS). Results showed that the application of electric field slightly enhanced the growth of E. canadensis shoots. The content of Mn and Ni was significantly lower, and Pb and Zn significantly higher in plants exposed to the electric filed, while Fe content did not differ between control and EF treatment. This provides a rationale for further studies on biological effects of electric field in trace metal contaminated waters and application of an electrically enhanced phytoremediation. 相似文献
997.
998.
Małgorzata Krasińska Zygmunt Gżejewski Elżbieta Czykier Zbigniew A. Krasiński Magdalena Matuszewska 《Acta theriologica》2009,54(2):111-126
The material for this study was obtained from culled European bison (Linnaeus, 1758) originating from both captive breeding
and free-ranging populations in Białowieża and Borecka Forests (north-east Poland), and was mostly collected from November
until April. Mass difference between the right and left testis of the same individual up to 30% was considered to be physiological
asymmetry, which proved typical of the species. Hypoplasia or atrophy of the testes exceeding 30% in size, were found in 37
males (13.6% of the examined animals;n=272). Cryptorchidism was recorded in 20 bison culled in Białowieża Forest at the age over 1 year (10.6% of individuals at
the same age;n=188). We registered the weight of testes of 259 males aged 2 months to 20 years. In the examined males, no distinct predominance
in size and weight between the right and left testes was observed. The weight of testes was significantly correlated with
age (r=0.85,p < 0.0001) and body weight (r=0.93,p < 0.0001). The heaviest testicles belonged to older and sexually mature bulls aged 6–12 years (mean 216 g) and to old ones
over 13 years (mean 242 g). Two testis measurements (length and width) were taken from 136 culled males, while two additional
measurements (total length with the cauda of epididymis and circumference) from 65 males. The length and width of the testes
were moderately correlated with age (r=0.31 andr=0.20,p < 0.01) and highly significantly correlated with testis (r=0.79,p < 0.001) and body weight (r=0.92,p < 0.001). 相似文献
999.
Zbigniew Adamski Daria Korolczuk Magdalena Purgiel Anna Grewling Marlena Ratajczak Micha? Bankiet Kazimierz Ziemnicki 《Biologia》2009,64(1):197-202
The effect of four sublethal concentrations (from 0.01165 to 0.3025 μg per insect, responding to LC10/10, LC10, LC30 and LC50) of the organophosphorus insecticide, fenitrothion, on Spodoptera exigua (Lepidoptera, Noctuidae) larval development and ultrastructure of follicular cells of adult female moths was tested. The
most prominent malformations were: breaks in the cuticle, increased mortality during larval/pupal molting, alterations of
nuclear envelope, changed heterochromatin pattern and abnormalities in mitochondrial ultrastructure. Some of the alterations
are dose-dependent, but the other ones, like organization of rough endoplasmic reticulum (RER), show non-linear response:
cells exposed to lower concentrations (LC10/10 and LC10) of the insecticide possessed clusters of accumulated RER, which were absent within the cells exposed to higher ones (LC30 and LC50). Formation of the eggshell was also markedly postponed within the groups exposed to lower doses. These findings prove that
even minute amounts of xenobiotics may cause significant changes within exposed populations. 相似文献
1000.
Koprowska-Ratajska M Kluczyk A Stefanowicz P Bartosz-Bechowski H Szewczuk Z 《Amino acids》2009,36(2):309-315
A direct solid-phase synthesis of a series of substituted benzimidazole-containing peptides is described. The method involves
on-resin formation of new amino acids containing benzimidazole derivatives in the side chain. The heterocycle conjugates were
obtained by reaction between aldehydes and peptides containing β-(3,4-diaminophenyl)alanine residue, immobilized on a polymeric
solid support. 相似文献