CONTENTS & ABSTRACTS

In English. Summaries in Estonian

Proceedings of the Estonian Academy of Sciences.

Biology. Ecology

 

Volume 52 No. 1 March 2003

 

A comparison between 1928 and 2000 indicates major changes in the macrozoobenthos species composition and abundance on the SW coast of Finland (Baltic Sea); 3–16

Ari O. Laine, Kaisa Luodekari, Minna Poikonen, and Markku Viitasalo

Abstract. In 1928, Sven G. Segerstråle made detailed analyses of benthic communities in the Tvärminne region (SW coast of Finland). In addition to traditional presentation, he included illustrative photographs where the collected macroinvertebrates were laid on black background, in natural density, and reproduced in their natural size. This approach was replicated in the present study. The photographs highlight changes that have taken place during the past century in the benthic communities. In the deeper area there has been a change from an amphipod (Monoporeia affinis) dominated community to one dominated by the Baltic clam Macoma baltica. In the shallower study area the diverse Corophium volutator–M. baltica–chironomid community has been replaced by a community dominated by Macoma and a North American invader, the polychaete Marenzelleria viridis. Furthermore, the density of macroinvertebrates has declined considerably. The causes for these changes remain unclear, but are most likely connected to eutrophication related factors in the coastal ecosystem and concurrent interspecific interactions.

Key words: macrozoobenthos, long-term change, Baltic Sea.

 

Chronology of embryonic development in Baltic herring Clupea harengus membras; 17–25

Aune Veersalu and Toomas Saat

Abstract. Thirty stages were distinguished in the development of the Baltic herring embryo during the period from insemination to hatching. The age of embryos at these stages was expressed in relative time units (t₀) and the timing of herring embryo development was compared with data for other teleosts. The chronology of Baltic herring’s embryonic development was rather similar to that of salmonid fishes and differed from that of cyprinid fishes.

Key words: Clupea harengus membras, development chronology, temperature, heterochrony.

Autumn numbers and distribution of the staging greylag goose Anser anser in Estonia in 1990–98; 26–39

Aivar Leito, Tõnu Möls, Eve Mägi, and Taivo Kastepõld

Abstract. We analysed the results of mid-September counts of staging greylag geese in Estonia in 1990–98. Each year 9800 to 15 700 greylags were counted in western Estonia during this period. The analysis provides no evidence of an overall linear trend, but differences between linear trends in certain site clusters are statistically significant proving that the preferences in halting sites have changed in the study years. Principal Component Analysis suggests that the first principal component, characterizing the total number of birds and defined as the Abundance Factor, explains about 56% of the variability of square-root transformed counts. The second principal component, Matsalu Preference Factor, indicates whether birds prefer Matsalu and South Saaremaa to Hiiumaa, West Saaremaa and East Saaremaa. It explains about 24% of the total variability. A significant increase of Matsalu Preference Factor suggests that the importance of Matsalu Bay has increased considerably among geese staging areas in recent years. Two structural indices describe stable proportions of the distribution of birds over the study area characterizing their possible relocation patterns.

Key words: Estonia, distribution, numbers, staging, relocation, Anser anser.

 

Photodynamic therapy of tumours with chlorin-e₆ is pH dependent; 40–54

Lyudmila Chekulayeva, Igor Shevchuk, and Vladimir Chekulayev

Abstract. Ehrlich ascites carcinoma (EAC) cells were used to investigate the effect of pH and glucose on the antitumour efficiency of photodynamic therapy (PDT) with chlorin-e₆ trimethyl ester (E6). For in vitro experiments, the cells were pre-incubated with E6 in a serum-free medium at pH 7.2 or 6.2 and were then irradiated with red light at 665 nm. It was found that their photosensitivity increased with decreasing pH value, although the cellular uptake of the sensitizer was slightly (by about 25%) depressed. As the pH value in malignant tumours tends to be lower than that of normal tissue and can be suppressed selectively by glucose administration, experiments were performed on mice bearing EAC cells grafted subcutaneously. An apparent delay in the tumour growth was obtained by combining E6–PDT with a single injection of glucose (2 g/kg body weight). This administration of glucose (2 h before the PDT) caused a substantial decrease in the tumour pH from an initial value of ~ 7.2 to ~ 6.3, as measured by a needle pH electrode. Studies on the mechanism suggest that under acidification the impairment of the mitochondrial function and the inhibition of E6 photobleaching in the cells are probably the main factors as to the revealed effect of pH on the antitumour efficiency of PDT with the sensitizer. It was also demonstrated that during E6–PDT along with singlet molecular oxygen hydroxyl free radicals are involved in the cell death.

Key words: chlorin-e₆, glucose, photobleaching, succinate dehydrogenase, superoxide, hydroxyl radical.

 

On the mechanism of cellular death under photoexcitation of haematoporphyrin derivative; 55–72

Vladimir Chekulayev, Igor Shevchuk, and Lyudmila Chekulayeva

Abstract. The goal of this study was to estimate the importance of damage of lipids compared to proteins in the deterioration of plasma membrane integrity, the mitochondrial function, and cell killing by photodynamic therapy (PDT) with haematoporphyrin derivative (HPD). It was found that photoirradiation of Ehrlich ascites carcinoma (EAC) cells pre-incubated with HPD resulted in a considerable inhibition of their glycolytic and respiratory activity, decreasing substantially the adenosine triphosphate (ATP) content. The obtained results indicate a close relationship between the HPD–PDT induced disturbances of the energy metabolism of irradiated cells and their ability to survive, e.g. 20 min of light exposure caused an 80% decrease in the ATP level and inactivation of approximately 98% of the cells (as measured by MTT-assay). Other effects of HPD–PDT, such as an increased permeability of the outer membrane to trypan blue and the alterations in cell morpho­logy (swelling, appearance of large protrusions on the cell surface), were observed at much larger light doses. Our studies showed that there is a very low probability that the phototoxic effects of HPD toward EAC cells, including mitochondrial, were mediated by the peroxidation of membrane lipids since only negligible amounts of oxidation products of unsaturated fatty acids were detected. Furthermore, the photosensitization of EAC cells by HPD had a minor effect on the intracellular content of cholesterol. However, we found that cellular proteins are very sensitive to the damaging influence of HPD–PDT; a clearly expressed decrease in the content of tryptophan, cysteine and, especially, histidine was registered. The HPD-photosensitized oxidation of proteins was associated with disruption of the cytoplasmic membrane and an inhibition of the mitochondrial function. Our data suggest that cellular proteins are the most critical targets upon photoexcitation of HPD.

Key words: photodynamic therapy, tumour, lipid peroxidation, proteins, blebbing, adenosine triphosphate, MTT-assay.

 

Effect of green manuring on Globodera rostochiensis and Pratylenchus spp. (Nematoda); 73–78

Zlatka Trifonova

Abstract. Concomitant effect of Globodera rostochiensis and Pratylenchus spp. on potato was investigated under glasshouse conditions. G. rostochiensis alone or with Pratylenchus spp. reduced significantly the weight and number of size 3 (> 100 g) tubers. Experiments with various green manure crops showed that growing Brassica nigra L. and Tagetes patula L. prior to potato resulted in a decline of G. rostochiensis and Pratylenchus spp. population densities and a tuber yield increase compared to control. Hordeum vulgare L. increased the density of Pratylenchus spp. in soil.

Key words: Nematoda, population density, intercropping, green manure.

Instructions to authors; 79