UV screening by plant surfaces can be determined by exposing plant organs to UV radiation and measuring the chlorophyll (Chl) fluorescence elicited. From this fluorescence, the UV transmittance can be derived: the more intense the screening the lower the reporter Chl fluorescence and the lower the UV transmittance. The relationships between UV screening at 375 nm, as determined in the field by a portable UV-A-PAM fluorimeter, and UV screening at 314 and 360 nm, measured in the laboratory with the non-portable XE-PAM fluorimeter, were investigated in leaves of grapevine (Vitis vinifera L. cv. Bacchus) and barley (Hordeum vulgare cv. Ricarda), as well as in white grape berries. With leaves, linear trends were observed between XE-PAM measurements at 314 nm and UV-A-PAM measurements at 375 nm but the relationship between transmittance at 360 and 375 nm in barley was curved: a simple model calculation suggests that this curvi-linearity arises from particularly weak absorbance of barley flavonoids at 375 nm relative to absorbance at 360 nm. Transmittance values at 314 nm plotted against 375 nm yielded a much smaller slope in grapevine leaves than in barley leaves, which was attributed to screening in the short-wavelength UV by hydroxycinnamic acids in the former but not in the latter species. With grape berries, a poor correlation was detected between transmittances at 314 and 375 nm which might arise from high scattering of UV radiation at the berry surface. Such artefacts appear to be confined to the UV-B region, as berry transmittance at 360 nm correlated very well with that at 375 nm. Thus, assessment of UV screening in the field at short UV wavelengths using 375 nm readings from a UV-A-PAM fluorimeter is possible provided that information is available on the relationship between the transmittance at the UV wavelength of interest and at 375 nm for the sample tissue being investigated. and C. A. Kolb ... [et al.].
Seedlings of Rhizophora apiculata were exposed to UV-B radiation at four doses equivalent to 10, 20, 30, and 40 % ozone depletion. The seedlings irradiated with high doses of UV-B had characteristic decline in contents of specific proteins with molecular masses of 33, 23, and 17 kDa. On the contrary, proteins of 55, 33, 25, 23, and 17 kDa were accumulated in the seedlings exposed to low doses of UV-B. The UV-B, in general, enhanced formation of saturated fatty acids and reduced unsaturated fatty acids, to a maximum extent of 88 and 26 %, respectively. The low dose of UV-B increased content of oleic acid by 9 %, and the high dose reduced it by 34 %. The high dose of UV-B enhanced the lipid peroxidation by 48 %, whereas the low dose of UV-B did not show any significant effect. The contents of amino acids such as aspartate, glutamate, asparagine, serine, glutamine, threonine, and histidine were increased in low UV-B doses by 53, 86, 142, 72, 3, 119, and 32 %, respectively; while in high doses they were reduced significantly. and P. Moorthy, K. Kathiresan.
The purpose of this study was to determine the production of metalloproteinases (MMP) 2 and 9 following UV-B irradiation in human corneal epithelial cells and fibroblasts. Epithelial cells and fibroblasts were separated from human donor corneas and exposed to UV-B lamp irradiation for 20, 40, 80 and 120 s. Media samples were collected at 8, 24, 48 and 72 h and gelatinase A and B production was assayed by the ELISA test. Statistical significance of production was assessed by the paired t-test. Increased production of MMP-2 was found in human corneal fibroblasts in response to UV-B irradiation. A statistically significant production of MMP-2 was not observed in human corneal epithelial cells following UV-B exposure. We did not detect any increase in MMP-9 after irradiation in either epithelial cells or fibroblasts. MMP-2 is produced by the corneal fibroblasts in the acute phase after UV-B irradiation. MMP-9 is not released in vitro following UV-B irradiation damage and therefore does not directly participate in the pathophysiology of acute photokeratitis., I. Kozák, D. Klisenbauer, T. Juhás., and Obsahuje bibliografii
The review deals with the comprehensive analysis of ultraviolet-B (UV-B) induced alterations in photosynthetic processes of higher plants and possible protection mechanisms. Between two photosystems, photosystem 2 (PS2) is main target for UV- B radiation stress. Depending on the mode of treatment, the oxidising side of PS2 and reaction centres are mainly affected by UV-B treatment. As response to UV-B stress plants develop some inherent adaptive mechanisms which decide the extent of the overall damage.
The kinetics and other characteristics of nitrate reductase (NR, EC 1.6.6.1) in cowpea [Vigna unguiculata (L.) Walp.] seedlings irradiated with biologically effective UV-B radiation (280-320 nm, 3.2 W m-2 s-1) were recorded. The in vivo and in vitro NR activities were inhibited by 34 and 41 % under UV-B treatment, respectively. Both Vmax and Km for the substrate were enhanced by UV-B radiation. The Km for nitrate increased from 1.2 to 1.7 mM after the UV-B irradiation. The change in Km for NADH was from 0.12 to 0.17 mM. The increases in Km indicate that UV-B radiation seriously changes the topology of NR, particularly with respect to the nitrate and NADH binding sites. The rate of NR turnover indicates the extent of damage inflicted by UV-B radiation on the nitrate metabolism. The half-life (t1/2) of NR was reduced from 7 to 4 h in the UV-B treated seedlings. UV-B also inhibited the kinetics of nitrate uptake by plants: its Km increased from 0.08 to 0.12 mM. and T. Balakumar ... [et al.].
Cowpea [Vigna unguiculata (L.) Walp. cv. Co 4] seedlings were subjected to a weighted irradiance of 3.2 W m-2 s-1 of biologically effective ultraviolet-B radiation (UV-B, 280-320 nm) and the changes in the kinetic and other characteristics of nitrite reductase (NiR) were recorded. The activity of NiR was hampered by 19 % under UV-B irradiation compared to the control. The UV-B treated plants required higher concentrations of nitrate for the induction of NiR synthesis than the controls. The NiR activity decay kinetics showed that the UV-B treatment significantly lowers the t1/2 of the enzyme, thereby indicating a reduced rate of enzyme turnover. The comparison of kinetic characteristics of nitrate reductase (NR) and NiR under UV-B treatment showed that NiR was not so sensitive to UV-B radiation as NR. As shown by enzyme turnover rates, NiR extracted from plants irradiated by UV-B in situ was less sensitive to UV-B radiation than the enzyme extract subjected to in vitro UV-B irradiation. Though NiR was less damaged by UV-B treatment than NR, subtle changes occurred in its kinetic characteristics. and T. Balakumar ... [et al.].
Cílem zprávy je především otevření diskuse o metodologickém odkazu Viktora Kotrby (7. 5. 1906 Günzburg – 3. 9. 1973 Praha), jenž je ve srovnání například se svým generačním vrstevníkem Václavem Menclem (1905–1978) opomíjen. Východiskem jsou materiály v části Kotrbovy pozůstalosti, uložené v Ústavu dějin umění AV ČR v Praze, včetně dosud neznámého rukopisu Kotrbovy disertace, jejíž definitivní podoba je ztracena. Práce je inspirativním přínosem ke středoevropskému bádání o pozdně gotické architektuře. Důležitou součástí práce je stať o architektuře z katalogu výstavy Jihočeská pozdní gotika 1450–1530 z roku 1965. Výpisky z literatury a poznámek z terénního výzkumu poskytují vhled do Kotrbovy každodenní badatelské praxe a umožňují rekonstrukci jeho záměrů a metod. Jedním z příkladů je zájem o učence a faráře Václava Fabriho, jenž na základě zkušeností ze saského prostředí podnítil na počátku 16. století ambiciózní přestavbu farního chrámu sv. Mikuláše v Českých Budějovicích. Kotrba v tomto případě nahlížel nezachovanou stavbu nikoliv z hlediska jejích forem, ale na základě rekonstruovatelné vizuální zkušenosti jejího objednavatele. Podobně Kotrba předznamenal určité trendy v současné uměleckohistorické medievistice zájmem o recepci středověkých uměleckých děl jejich současnými konzumenty, když se zaměřil na vybrané pasáže z Kroniky české Eneáše Silvia Piccolominiho. Převážná část disertace je s přehledem napsanou syntézou, jež vychází z tehdejšího zcela aktuálního stavu poznání o vývoji a klíčových osobnostech pozdně gotické architektury v relevantních oblastech Svaté říše římské. Důraz na problematiku konstrukcí a stavebních postupů oproti sledování stylových proměn umělecké stránky kleneb řadí jinak neznámý Kotrbův text mezi standardní středoevropské uměleckohistorické práce o pozdně gotické architektuře. Text navíc místy vyniká jak bohatostí detailních poznatků, tak předznamenáním výše naznačených progresivnějších tendencí. Knižní vydání Kotrbovy disertace s komentáři k dodnes diskutovaným otázkám by se mohlo po šestačtyřiceti letech stát důstojným českým protějškem slavné monografie o Benediktu Riedovi z pera Götze Fehra, v jistém smyslu Kotrbova protějšku v Německu. and The aim of this account is to stimulate discussion of the methodological legacy of Viktor Kotrba (7. 5. 1906 Günzburg – 3. 9. 1973 Prague), who has been neglected, for example, in comparison with his contemporary Václav Mencl (1905–1978). The article is based on materials in Kotrba’s papers, deposited at the Institute for Art History, Academy of Sciences of the Czech Republic, in Prague,
including a hitherto unknown manuscript of Kotrba’s dissertation. Although the final form of this work has been lost, the manuscript makes an inspiring contribution to Central European research on late Gothic architecture. An article on architecture, from the exhibition catalogue South Bohemian Late Gothic 1450–1530 (1965) is an important component of the work. Excerpts from the literature and notes on the field research offer insight into Kotrba’s standard research practices and help one to reconstruct his intentions and methods. One example is his interest in the scholar and priest Václav Fabri, who, inspired by his knowledge of the Saxon milieu, initiated
the ambitious renovation of the parish Church of St Nicholas in České Budějovice at the beginning of the 16th century. In this instance, rather than looking at form, Kotrba considered the building, no longer extant, from the perspective of the reconstructible visual experience of the patron. Similarly, Kotrba’s interest in the reception
of medieval artworks by their contemporary consumers—evident in his attention to selected passages from Silvio Piccolomini’s Historia Bohemica—prefigured certain trends in current art history studies of the medieval period. With a broad overview, the dissertation focuses on the contemporaneous body of knowledge of the development and key figures of late Gothic architecture in the relevant regions of the Holy Roman Empire. On account of the emphasis on the issue of construction and building approaches, as opposed to tracing stylistic transformations of the art of vaulting, Kotrba’s text can be included
among the standard Central European art history works on late Gothic architecture. In addition, in places the text provides a wealth of detailed observations, as well as prefiguring the abovementioned progressive trends. A book edition of Kotrba’s dissertation, with commentary on questions still relevant today, would be, after forty-six
years, a dignified Czech counterpart to the famous monograph on Benedikt Ried written by Götz Fehr, who was, in a certain sense, Kotrba’s counterpart in Germany.