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31.
Hyaluronic acid: a natural biopolymer with a broad range of biomedical and industrial applications 总被引:2,自引:0,他引:2
Hyaluronic acid (hyaluronan, HA) is a linear polysaccharide formed from disaccharide units containing N-acetyl-d-glucosamine and glucuronic acid. It has a high molecular mass, usually in the order of millions of Daltons, and interesting
viscoelastic properties influenced by its polymeric and polyelectrolyte characteristics. HA is present in almost all biological
fluids and tissues. In clinical medicine, it is used as a diagnostic marker for many diseases including cancer, rheumatoid
arthritis and liver pathologies, as well as for supplementation of impaired synovial fluid in arthritic patients by means
of intra-articular injections. It is also used in certain ophthalmological and otological surgeries and cosmetic regeneration
and reconstruction of soft tissue. Herein we present an overview of the occurrence and physiological properties of HA, as
well as of the recent advances in production biotechnology and preparation of the HA-based materials for medical application. 相似文献
32.
Singh R Kaur B Kalina I Popov TA Georgieva T Garte S Binkova B Sram RJ Taioli E Farmer PB 《Mutation research》2007,620(1-2):71-82
Epidemiological studies conducted in metropolitan areas have demonstrated that exposure to environmental air pollution is associated with increases in mortality. Carcinogenic polycyclic aromatic hydrocarbons (c-PAHs) are the major source of genotoxic activities of organic mixtures associated with respirable particulate matter, which is a constituent of environmental air pollution. In this study,we wanted to evaluate the relationship between exposure to these genotoxic compounds present in the air and endogenous oxidative DNA damage in three different human populations exposed to varying levels of environmental air pollution. As measures of oxidative DNA damage we have determined 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodG) by liquid chromatography–tandem mass spectrometry (LC–MS/MS) and cyclic pyrimidopurinone N-1,N2 malondialdehyde-2′-deoxyguanosine (M1dG) by the immunoslot blot assay from lymphocyte DNA of participating individuals. The level of endogenous oxidative DNA damage was significantly increased in individuals exposed to environmental air pollution compared to unexposed individuals from Kosice (8-oxodG adducts) and Sofia (M1dG adducts). However, there was no significant difference in the level of endogenous oxidative DNA and exposure to environmental air pollution in individuals from Prague (8-oxodG and M1dG adducts) and Kosice (M1dG adducts). The average level of M1dG adducts was significantly lower in unexposed and exposed individuals from Kosice compared to those from Prague and Sofia. The average level of 8-oxodG adducts was significantly higher in unexposed and exposed individuals from Kosice compared to those from Prague. A significant increasing trend according to the interaction of c-PAHs exposure and smoking status was observed in levels of 8-oxodG adducts in individuals from Kosice. However, no other relationship was observed for M1dG and 8-oxodG adduct levels with regard to the smoking status and c-PAH exposure status of the individuals. The conclusion that can be made from this study is that environmental air pollution may alter the endogenous oxidative DNA damage levels in humans but the effect appears to be related to the country where the individuals reside. Genetic polymorphisms of the genes involved in metabolism and detoxification and also differences in the DNA repair capacity and antioxidant status of the individuals could be possible explanations for the variation observed in the level of endogenous oxidative DNA damage for the different populations. 相似文献
33.
Glucuronoyl esterase is a novel carbohydrate esterase recently discovered in the cellulolytic system of the wood-rotting fungus
Schizophyllum commune on the basis of its ability to hydrolyze methyl ester of 4-O-methyl-d-glucuronic acid. This substrate was not fully corresponding to the anticipated function of the enzyme to hydrolyze esters
between xylan-bound 4-O-methyl-d-glucuronic acid and lignin alcohols occurring in plant cell walls. In this work we showed that the enzyme was capable of
hydrolyzing two synthetic compounds that mimic the ester linkages described in lignin-carbohydrate complexes, esters of 4-O-methyl-d-glucuronic and d-glucuronic acid with 3-(4-methoxyphenyl)propyl alcohol. A comparison of kinetics of hydrolysis of methyl and 3-(4-methoxyphenyl)propyl
esters indicated that the glucuronoyl esterase recognizes the uronic acid part of the substrates better than the alcohol type.
The catalytic efficiency of the enzyme was much higher with the ester of 4-O-methyl-d-glucuronic acid than with that of d-glucuronic acid. Examination of the action of glucuronoyl esterase on a series of methyl esters of 4-O-methyl-d-glucopyranuronosyl residues α-1,2-linked to xylose and several xylooligosaccharides suggested that the rate of deesterification
is independent of the character of the carbohydrate part glycosylated by the 4-O-methyl-d-glucuronic acid. 相似文献
34.
Drivers of temporal changes in temperate forest plant diversity vary across spatial scales 下载免费PDF全文
Markus Bernhardt‐Römermann Lander Baeten Dylan Craven Pieter De Frenne Radim Hédl Jonathan Lenoir Didier Bert Jörg Brunet Markéta Chudomelová Guillaume Decocq Hartmut Dierschke Thomas Dirnböck Inken Dörfler Thilo Heinken Martin Hermy Patrick Hommel Bogdan Jaroszewicz Andrzej Keczyński Daniel L. Kelly Keith J. Kirby Martin Kopecký Martin Macek František Máliš Michael Mirtl Fraser J.G. Mitchell Tobias Naaf Miles Newman George Peterken Petr Petřík Wolfgang Schmidt Tibor Standovár Zoltán Tóth Hans Van Calster Gorik Verstraeten Jozef Vladovič Ondřej Vild Monika Wulf Kris Verheyen 《Global Change Biology》2015,21(10):3726-3737
Global biodiversity is affected by numerous environmental drivers. Yet, the extent to which global environmental changes contribute to changes in local diversity is poorly understood. We investigated biodiversity changes in a meta‐analysis of 39 resurvey studies in European temperate forests (3988 vegetation records in total, 17–75 years between the two surveys) by assessing the importance of (i) coarse‐resolution (i.e., among sites) vs. fine‐resolution (i.e., within sites) environmental differences and (ii) changing environmental conditions between surveys. Our results clarify the mechanisms underlying the direction and magnitude of local‐scale biodiversity changes. While not detecting any net local diversity loss, we observed considerable among‐site variation, partly explained by temporal changes in light availability (a local driver) and density of large herbivores (a regional driver). Furthermore, strong evidence was found that presurvey levels of nitrogen deposition determined subsequent diversity changes. We conclude that models forecasting future biodiversity changes should consider coarse‐resolution environmental changes, account for differences in baseline environmental conditions and for local changes in fine‐resolution environmental conditions. 相似文献
35.
Jaroslav Červinka Martin Šálek Petr Pavluvčík Jakub Kreisinger 《Biodiversity and Conservation》2011,20(14):3459-3475
The marked negative impact of habitat fragmentation and the edge effect on many populations of bird species is a recent major
concern in conservation biology. Here, we focus on the edge effect in different sized forest patches in Central European farmland. In particular, we tested
whether the distribution of mammalian mesopredators is related to fragment size and distance to habitat edge, and whether
the contribution of these factors is additive or interactive. To assess fine-scale utilization of forest edges, we established
transects of four scent stations at different distances from forest edges into the interior (0, 25, 50, 100 m) in 146 forest
fragments of variable patch size (3.2–5099.6 ha) from May to June, 2008–2009. This large sample size allowed us to perform
detailed analyses separately for all detected species. Our findings confirm that mammalian mesopredators strongly prefer habitat
edges and small forest fragments. The probability of occurrence tended to decrease with increasing distance from the edge
for all seven carnivore species detected. The carnivores’ occurrence was also negatively correlated with forest fragment area.
All detected species tended to prefer small fragments, with the exception of the Eurasian badger (showing the reverse but
non-significant pattern) and the red fox (no effect of fragment size). In addition, the non-significant interaction between
fragment size and distance to edge suggests that both of these factors contribute independently and additively to mesopredator-mediated
effects on biota in a fragmented landscape. 相似文献
36.
The structural chirality is an inherent feature of fully synthetic boron cluster compounds that sometimes exhibit unique biochemical effects. HPLC studies with zwitter-ionic cluster boron compounds and electrophoretic studies with boron cluster anions reveal that the chiral separability of these species is remarkably dissimilar to that of organic species, if uncharged cyclodextrins are used as chiral selectors. Furthermore, marked differences were found between the analytical characteristics of the chiral separations of the boron cluster species and those of the organic species with uncharged cyclodextrins. The present-day experimental database indicates that the rules valid for the chiral separations of the organic species cannot be applied to the chiral separations of the boron cluster species without experimental verification. The current extent of research work devoted to the investigation of chirality and chiral separations of boron cluster species is negligibly small in comparison with that devoted to the investigation of chirality and chiral separations of organic species. This makes difficult a reliable explanation of both the particularities observed in chiral separations of boron cluster species with cyclodextrins as chiral selectors and the strange effects related to these separations at the moment. 相似文献
37.
Zitko J Dolezal M Svobodova M Vejsova M Kunes J Kucera R Jilek P 《Bioorganic & medicinal chemistry》2011,19(4):1471-1476
A series of fifteen new compounds related to pyrazinamide (PZA) were synthesized, characterized with analytical data and screened for antimycobacterial, antifungal and antibacterial activity. The series consists of 6-chloro-5-cyanopyrazine-2-carboxamide and N-substituted 6-amino-5-cyanopyrazine-2-carboxamides, derived from the previous by nucleophilic substitution with various non-aromatic amines (alkylamines, cycloalkylamines, heterocyclic amines). Some of the compounds exerted antimycobacterial activity against Mycobacterium tuberculosis equal to pyrazinamide (12.5-25 μg/mL). More importantly, 6-chloro-5-cyanopyrazine-2-carboxamide and 5-cyano-6-(heptylamino)pyrazine-2-carboxamide were active against Mycobacterium kansasii and Mycobacterium avium, which are unsusceptible to PZA. Basic structure-activity relationships are presented. Only weak antifungal and no antibacterial activity was detected. 相似文献
38.
African mole-rats (Bathyergidae, Rodentia) contain several social, cooperatively breeding species with low extrinsic mortality and unusually high longevity. All social bathyergids live in multigenerational families where reproduction is skewed towards a few breeding individuals. Most of their offspring remain as reproductively inactive "helpers" in their natal families, often for several years. This "reproductive subdivision" of mole-rat societies might be of interest for ageing research, as in at least one social bathyergid (Ansell's mole-rats Fukomys anselli), breeders have been shown to age significantly slower than non-breeders. These animals thus provide excellent conditions for studying the epigenetics of senescence by comparing divergent longevities within the same genotypes without the inescapable short-comings of inter-species comparisons. It has been claimed that many if not all social mole-rat species may have evolved similar ageing patterns, too. However, this remains unclear on account of the scarcity of reliable datasets on the subject. We therefore analyzed a 20-year breeding record of Giant mole-rats Fukomys mechowii, another social bathyergid species. We found that breeders indeed lived significantly longer than helpers (ca. 1.5-2.2fold depending on the sex), irrespective of social rank or other potentially confounding factors. Considering the phylogenetic positions of F. mechowii and F. anselli and unpublished data on a third Fukomys-species (F. damarensis) showing essentially the same pattern, it seems probable that the reversal of the classic trade-off between somatic maintenance and sexual reproduction is characteristic of the whole genus and hence of the vast majority of social mole-rats. 相似文献
39.
In the course of season 2010 (May–September), three 2-day trappings of female mosquitoes were carried out at two sites in
order to determine the daily activity of the common mosquito species (e.g. species from genus Culex, Aedes, Ochlerotatus, Anopheles, etc.) in the area. CDC light traps filled with CO2 and placed at a height of 1 m were used to trap individuals, and were sampled every 2 h. A total of 19,604 female mosquitoes
from 20 identifiable species were trapped: 7,549 at Sedlec and 12,055 at Kančí obora. The activity of the major species of
mosquitoes in South Moravia differed throughout the course of the day. Calamity species of the genus Aedes and Ochlerotatus remained active throughout the day and night, but with different course. Aedes vexans, Ae. cinereus, and Ae. rossicus were most active in the late afternoon and highly active for most of the night. Ochlerotatus sticticus was captured most often in the afternoon, and its abundance decreased rapidly before sunset. The activity of Oc. cantans s.l. (Oc. cantans + Oc. annulipes) females varied little during the day and night. The daily activity for the main vectors of West Nile virus, Culex pipiens and Cx. modestus, were totally different from that of other species. Cx. pipiens females showed significant night activity, while Cx. modestus was most active in the evening. Nighttime activity was also observed in female mosquitoes of the genus Anopheles. 相似文献
40.