Gábor Fekete

Static and dynamic approaches to landscape heterogeneity in the Hungarian forest‐steppe zone

. This paper describes the successional status of the vegetation in a clear-felled dry oak woodland at the edge of the Hungarian forest-steppe zone on the basis of a vegetation map. Due to a varied geomorphology of the colline landscape several so-called landscape units can be distinguished. The patchwork on the vegetation map is evaluated using several, morphology-based attributes (static morphological indices) traditionally applied in landscape ecology. In the ca. 100 years that elapsed since forest clear-cut, xeric grassland species and steppe elements became more abundant and the former xeromesophilous vegetation – containing even some woodland components – is slowly turning into xeric grassland communities. The vegetation units mapped can be arranged into a hypothetical succession scheme in which successional distances (the number of steps between two stages) are determined. Based on the distances thus obtained, a new dynamic morphological index is introduced. This is applied to each landscape unit for the dynamic evaluation of successional vegetation, its results being compared with those obtained by static morphological indices.

Polarized light and oviposition site selection in the yellow fever mosquito: no evidence for positive polarotaxis in Aedes aegypti.

Aquatic insects and insects associated with water use horizontally polarized light (i.e., positive polarotaxis) to detect potential aquatic or moist oviposition sites. Mosquitoes lay their eggs onto wet substrata, in water, water-filled tree/rock holes, or man-made small containers/bottles/old tyres containing water. Until now it has remained unknown whether mosquitoes are polarotactic or not. The knowledge how mosquitoes locate water would be important to develop new control measures against them. Thus, we studied in dual-choice laboratory experiments the role of horizontally polarized light in the selection of oviposition sites in blood-fed, gravid females of the yellow fever mosquito, Aedes aegypti. On the basis of our results we propose that Ae. aegypti is not polarotactic. Thus the yellow fever mosquito is the first known water-associated insect species that does not detect water by means of the horizontally polarized water-reflected light. This can be explained by the reflection-polarization characteristics of small-volume water-filled cavities/containers preferred by Ae. aegypti as oviposition sites.

Development of a small-animal focal brain irradiation model to study radiation injury and radiation-injury modifiers.

Abstract Purpose: Our aim was to establish an effective small-animal focal brain radiation model for research on brain injuries. Material and methods: Groups of up to six rats were exposed to a range of doses from 120–40 Gy, at 10 intervals of a 6 MeV electron beam. Open-field motor functions and water maze learning-memory tests were performed after the irradiation at two-week intervals. Morphological changes were detected through repeated magnetic resonance imaging (MRI) monthly and were compared with the histopathological findings to determine if they predicted late microscopic changes. Results: The development of necrosis proved to be dose-dependent. 120 Gy resulted in serious deterioration within 4 weeks in all rats. Localized necrosis in one hemisphere was detected 2 months after the irradiation with ≥ 70 Gy, and 3 months after 40–60 Gy consistent for all animals. The Morris water maze (MWM) tests proved to be the most sensitive tool for the early detection of a brain functional impairment. MRI screening provided useful information on the development of radiation necrosis, which defined the time point for histological examinations. Conclusions: The described method permits accurate dose delivery to a definite part in one hemisphere of the brain for six rats at a time. Following complex examinations, a dose of 40 Gy and a follow-up time of 4 months are proposed for investigations on neuroradiation modifiers.

Winter photosynthetic activity of twenty temperate semi-desert sand grassland species

The winter photosynthetic activity (quantified by net CO(2) assimilation rates and chlorophyll (Chl) a fluorescence parameters) of 20 plant species (including two lichens and two mosses) of a Hungarian temperate semi-desert sand grassland was determined on one occasion per year in 1984, 1989 and 1994. Throughout winter, the overwintering green shoots, leaves or thalli were regularly exposed to below zero temperatures at night and daytime temperatures of 0-5 degrees C. In situ tissue temperature varied between -2.1 and +6.9 degrees C and the photosynthetic photon flux density (PPFD) between 137 and 351 micromol m(-2)s(-1). Under these conditions 18 of the grassland species exhibited photosynthetic CO(2) uptake (range: vascular plants ca. 0.2-3.8 micromol m(-2)s(-1), cryptogams 0.3-2.79 micromol kg(-1)s(-1)) and values of 0.9-5.1 of the Chl fluorescence decrease ratio R(Fd). In 1984, Festuca vaginata and Sedum sexangulare had net CO(2) assimilation at leaf temperatures of -0.85 to -1.2 degrees C. In 1989, all species except Cladonia furcata showed net CO(2) assimilation at tissue temperatures of 0 to +3.3 degrees C, with the highest rates observed in Poa bulbosa and F. vaginata. The latter showed a net CO(2) assimilation saturation at a PPFD of 600 micromol m(-2)s(-1) and a temperature optimum between +5 and +18 degrees C. At the 1994 measurements, the photosynthetic rates were higher at higher tissue water contents. The two mosses and lichens had a net photosynthesis (range: 1.1-2.79 micromol CO(2)kg(-1)s(-1)) at 2 degrees C tissue temperature and at 4-5 degrees C air temperature. Ca. 80% of the vascular grassland plant species maintained a positive C-balance during the coldest periods of winter, with photosynthetic rates of 1.5-3.8 micromol CO(2)m(-2)s(-1). In an extremely warm beginning March of the relatively warm winter of 2006/2007, the dicotyledonous plants had much higher CO(2) assimilation rates on a Chl (range 6-14.9 micromol g(-1)Chl s(-1)) and on a dry weight basis (9-48 micromol kg(-1)dw s(-1)) than in the cold winter of 1994. However, the assimilation rates of the three investigated cryptogams (Tortula and two Cladonia) and the two grasses Festuca and Poa were not affected by this increase. The results indicate that the photosynthetic activity of temperate semi-desert sand grassland species can help somewhat in slowing the general CO(2) rise in winter and function as a potential carbon sink of the investigated semi-desert Hungarian grassland species.

Peripheral inflammatory activation after hippocampus irradiation in the rat

Abstract Purpose: To detect the possible biochemical signs of inflammatory activation in the peripheral circulation in a rodent model of hippocampus irradiation, and to examine the effects of L-alpha-glycerylphosphorylcholine (GPC) in this experimental protocol. Materials and methods: Anesthetized Sprague-Dawley rats were subjected to 40 Gy cobalt irradiation of both hemispheres of the hippocampus, with or without GPC treatment (50 mg/kg intravenously (i.v.), 5 min before the irradiation, n = 6, each). A third group (n = 6) served as saline-treated control. Blood samples were obtained 3 h after the end of irradiation in order to examine the changes in plasma histamine, tumor necrosis factor-alpha (TNF-α), interleukin 1-beta, interleukin 6 (IL-6) and interleukin 10 (IL-10); liver tissue samples were taken to determine adenosine triphosphate (ATP) concentrations. Results: The hepatic ATP levels were significantly declined, while plasma concentrations of circulating TNF-α, IL-6, IL-10 and histamine were significantly increased after hippocampus irradiation. GPC treatment significantly reduced the irradiation-induced release of cytokines and histamine, and the liver ATP level was maintained at the control value. Conclusions: Targeted brain irradiation produced measurable pro- and anti-inflammatory cytokine changes in the systemic circulation. GPC supplementation provides significant protection against irradiation-induced peripheral pro-inflammatory activation and ATP depletion.

Quality Control of Portal Imaging with PTW EPID QC PHANTOM

Purpose:Quality assurance (QA) and quality control (QC) of different electronic portal imaging devices (EPID) and portal images with the PTW EPID QC PHANTOM®.Material and Methods:Characteristic properties of images of different file formats were measured on Siemens OptiVue500aSi®, Siemens BeamView Plus®, Elekta iView®, and Varian PortalVision™ and analyzed with the epidSoft® 2.0 program in four radiation therapy centers. The portal images were taken with Kodak X-OMAT V® and the Kodak Portal Localisation ReadyPack® films and evaluated with the same program.Results:The optimal exposition both for EPIDs and portal films of different kind was determined. For double exposition, the 2+1 MU values can be recommended in the case of Siemens OptiVue500aSi®, Elekta iView® and Kodak Portal Localisation ReadyPack® films, while for Siemens BeamView Plus®, Varian PortalVision™ and Kodak X-OMAT V® film 7+7 MU is recommended.Conclusion:The PTW EPID QC PHANTOM® can be used not only for amorphous silicon EPIDs but also for images taken with a video-based system or by using an ionization chamber matrix or for portal film. For analysis of QC tests, a standardized format (used at the acceptance test) should be applied, as the results are dependent on the file format used.Ziel:Qualitätssicherung (QA) und Qualitätskontrolle (QC) verschiedener elektronischer Feldkontrollaufnahmegeräte (EPID) und Portfilme mit einem PTW EPID QC PHANTOM®.Material und Methodik:Charakteristische Eigenschaften von Bildern unterschiedlicher Datenformate wurden bestimmt. Die Bilder wurden mit Siemens OptiVue500aSi®, Siemens BeamView Plus®, Elekta iView® und Varian PortalVision™ erzeugt und mit dem Programm epidSoft® 2.0 in vier Strahlentherapieabteilungen analysiert. Für Feldkontrollaufnahmen wurden Kodak X-OMAT V®- und Kodak Portal Localisation ReadyPack®-Filme verwendet und mit demselben Programm analysiert.Ergebnisse:Die optimalen Expositionswerte der EPID-Systeme und der Filmkombinationen wurden bestimmt. Für eine Doppelexposition empfehlen sich bei Verwendung von Siemens OptiVue500aSi®, Elekta iView® oder Kodak Portal Localisation ReadyPack®-Film 2+1 MU und bei Verwendung von Siemens BeamView Plus®, Varian PortalVision™ oder Kodak X-OMAT V®-Film 7+7 MU.Schlussfolgerung:Das PTW EPID QC PHANTOM® eignet sich nicht nur zur Kontrolle amorpher Siliciumsysteme, sondern auch für mit Hilfe eines Videosystems oder einer Ionisationskammermatrix angefertigte Bilder oder eine Film-Folien-Kombination als Detektor. Da die Resultate vom Dateiformat abhängig sind, sollte zur Analyse des QC-Tests ein konstantes Format gewählt werden.

Novel real‑time cell analysis platform for the dynamic monitoring of ionizing radiation effects on human tumor cell lines and primary fibroblasts

Translational research in radiation oncology is important for the detection of adverse radiation effects, cellular responses, and radiation modifications, and may help to improve the outcome of radiation therapy in patients with cancer. The present study aimed to optimize and validate a real‑time label‑free assay for the dynamic monitoring of cellular responses to ionizing radiation. The xCELLigence system is an impedance‑based platform that provides continuous information on alterations in cell size, shape, adhesion, proliferation, and survival. In the present study, various malignant human primary fibroblast cells (U251, GBM2, MCF7, A549, HT‑29) were exposed to 0, 5 and 10 Gy of Cobalt60 radiation. As well as the xCELLigence system, cell survival and proliferation was evaluated using the following conventional end‑point cell‑based methods: Clonogenic, MTS, and lactate dehydrogenase assays, and apoptosis was detected by fluorescence‑activated cell sorting. The effects of ionizing radiation were detected for each cell line using impedance monitoring. The real‑time data correlated with the colony forming assay results. At low cell densities (1,000‑2,000 cells/well) the impedance‑based method was more accurate at monitoring dose‑dependent changes in the malignant human primary fibroblast cell lines, as compared with the end‑point assays. The results of the present study demonstrated that the xCELLigence system may be a reliable and rapid diagnostic method for the monitoring of dynamic cell behavior following radiation. In addition, the xCELLigence system may be used to investigate the cellular mechanisms underlying the radiation response, as well as the time‑dependent effects of radiation on cell proliferation and viability.

Partial breast radiotherapy with simple teletherapy techniques

A prospective pilot study of partial breast irradiation (PBI) with conventional vs hypofractionated schedules was set out. The study aimed to determine efficacy, acute and late side effects, and the preference of photon vs electron irradiation based on individual features. Patients were enrolled according to internationally accepted guidelines on PBI. Conformal radiotherapy plans were generated with both photon and electron beams, and the preferred technique based on dose homogeneity and the radiation exposure of healthy tissues was applied. For electron dose verification, a special phantom was constructed. Patients were randomized for fractionation schedules of 25 × 2 vs 13 × 3Gy. Skin and breast changes were registered at the time of and ≥1 year after the completion of radiotherapy. Dose homogeneity was better with photons. If the tumor bed was located in the inner quadrants, electron beam gave superior results regarding conformity and sparing of organ at risk (OAR). If the tumor was situated in the lateral quadrants, conformity was better with photons. A depth of the tumor bed ≥3.0cm predicted the superiority of photon irradiation (odds ratio [OR] = 23.6, 95% CI: 5.2 to 107.5, p < 0.001) with >90% sensitivity and specificity. After a median follow-up of 39 months, among 72 irradiated cases, 1 local relapse out of the tumor bed was detected. Acute radiodermatitis of grade I to II, hyperpigmentation, and telangiectasia developed ≥1 year after radiotherapy, exclusively after electron beam radiotherapy. The choice of electrons or photons for PBI should be based on tumor bed location; the used methods are efficient and feasible.

Aquatic effect duration study of Cry4 toxin with immunoassay and Aedes aegypti larval biotest

Bacillus thuringiensis subsp. israelensis (Bti) preparations are widely used for culicid larvae. There is no suitable commercially available analytical method for Cry4 toxin as active ingredient in Bti preparations. To overcome this limitation, an enzyme-linked immunosorbent assay (ELISA) was developed for quantitative determination of Cry4 toxin allowing a limit of detection (LOD) of ∼2 ng ml−1 in water. Preconcentration of aqueous samples by lyophilisation resulted in low but reproducible recoveries (25.7±6.8%), and the practical LODs for Bti preparations VECTOBAC WDG granulate and VECTOBAC 12 AS suspension were found to be ∼170 ng ml−1 and ∼900 ng ml−1, respectively. ELISA determinations indicated a rapid decay in detectable concentrations of VECTOBAC WDG applied at 400 ng ml−1 concentration in surface water: detected concentrations decreased by 18% and 44% in 4 days in water collected from two locations, and dropped below LOD afterwards. Larval mortality of Aedes aegypti indicated a continuous decrease even thereafter. Thus, quantitative Cry4 toxin detection facilitates proper timing and frequency of treatments to achieve optimal efficacy.

Dolomite versus Limestone Habitats: a Study of Ionic Accumulation on a Broader Floristic Basis)

Summary Limestone and dolomite are widely distributed substrates in Hungarian Middle Mountain-Range. The paper deals with differences in ionic accumulation of plants growing on the rocks mentioned. The 20 species (belonging to 17 families) growing on both kind of rocks differ significantly respecting Ca, Mg concentration and Ca/Mg ratio. The similarity of the same were expressed also on the basis of 11 element content. Displaying the results on a dendrogram, a group of “conservative” species (so: all the monocotyledonous ones) could be identified. In this case the concentration of components were not essentially modified by the difference in rock-type. Opposed to them are the plastic ones (Melittis grandiflora, Chrysanthemum corymbosum, Viola cyanea, Stachys recta, Geum urbanum) . Almost for all the species analysed a marked increase was found in values of concentration of both calcium and magnesium in autumn, compared to those obtained in spring. The obligate dolomite-plants did not prove to be “magnesium accumulators”.