Maria Lazarova

Aminoderivatives of cycloalkanespirohydantoins: synthesis and biological activity

3-Aminocycloalkanespiro-5-hydantoins were synthesized and their biological activity was studied. In contrast to hydantoins, these compounds failed to induce either anticonvulsive effects in the central nervous system or inhibitory effects on cholinergic contractions in the enteric nervous system. However, they exerted well pronounced, atropinsensitive, contractile effects on the guinea-pig ileum longitudinal muscle preparations. Structure-activity relationships established allow the assumption that: (i) the reduction of the ring size in the molecule of the spirohydantoins leads to an increase in the potency of the respective analogue to induce contractile effect; (ii) the introduction of -NH2 in position 3 increases the ability of all the compounds studied to exert contractions; (iii) the enlargement of the ring leads to: (1) an increase of the degree of desensitization of the preparations; and (2) a decrease (except 1a) of the potency of the analogues to exert contractile effects.

Disjunct Occurrences of Plant Species in the Refugial Mires of Bulgaria

Many mire vascular plant and bryophyte species have disjunct occurrences in Bulgaria despite that most of south-eastern Europe is not suitable for the occurrence of permanently waterlogged and nutrient-limited wetlands due to the current and glacial dry climate conditions as well as prevailing limestone bedrock. Unfortunately, such important distributional data are scattered throughout numerous papers and reports, and are not adequately provided even by national checklists and floras. No attempt to summarize them has been done yet. Therefore, the main aim of this paper is to review and enlarge such data, and to use the resulting data set to address the question whether the disjunctly occurring rare species are concentrated in certain mire complexes or even in particular vegetation plots and if they do characterize such localities. Our current research shows that the phenomenon of isolated occurrences of mire plants in Bulgaria is even more widespread than previously thought. Seventeen species were found as new for Bulgaria with their distribution range limits there, and distributional data of many other species, including some previously considered extinct, were enlarged. Fifty-four mire species were found at only three or fewer sites. Our analyses showed a conspicuous concentration of rare, disjunctly occurring species at a few sites, which are, however, largely unexplored in terms of palaeoecology or ecology, not legally protected and currently threatened by human activities. The distributions of target rare species within Bulgarian mires were significantly nested, which means that more species-poor assemblages were subsets of richer ones. Nestedness was significantly related to the estimated area of mire complex, but not all high-diversity mires were large. Disjunctly occurring rare species were more concentrated in particular vegetation plots at lower altitudes and in mineral-rich fens. Fragmentary data about the ecology and history of Bulgarian refugial mires suggest that these mires harbour specific ecotypes and genotypes, contain specifically distributed biogeographic groups of species, provide an opportunity to test biogeographical hypotheses and shelter crucial information about the history of European mires. Thus, these sites have a potential to become a source of very important information for biogeographical, palaeoecological, and phylogeographical analyses.

Somatostatin stimulates striatal acetylcholine release by glutamatergic receptors: an in vivo microdialysis study.

The modulation of striatal cholinergic neurons by somatostatin (SOM) was studied by measuring the release of acetylcholine (ACh) in the striatum of freely moving rats. The samples were collected via a transversal microdialysis probe. ACh level in the dialysate was measured by the high performance liquid chromatography method with an electrochemical detector. Local administration of SOM (0.1, 0.5 and 1 microM) produced a long-lasting and concentration-dependent increase in the basal striatal ACh output. The stimulant effect of SOM was antagonized by the SOM receptor antagonist cyclo(7-aminopentanoyl-Phe-D-Trp-Lys-Thr[BZL]) (1 microM). In a series of experiments, we studied the effect of 6,7-dinitroquinoxaline-2, 3-dione (DNQX), a selective non-NMDA (N-methyl-D-aspartate) glutamatergic antagonist, on the basal and SOM-induced ACh release from the striatum. DNQX, 2 microM, perfused through the striatum had no effect on the basal ACh output but inhibited the SOM (1 microM)-induced ACh release. The non-NMDA glutamatergic receptor antagonist 1-(4-aminophenyl)-4-methyl-7,8-methylendioxy-5H-2,3- benzodiazepine (GYKI-52466), 10 microM, antagonized the SOM (1 microM)-induced release of ACh in the striatum. Local administration of the NMDA glutamatergic receptor antagonist, 2-amino-5-phosphonopentanoic acid (APV), 100 microM, blocked SOM (1 microM)-evoked ACh release. Local infusion of tetrodotoxin (1 microM) decreased the basal release of ACh and abolished the 1 microM SOM-induced increase in ACh output suggesting that the stimulated release of ACh depends on neuronal firing. The present results are the first to demonstrate a neuromodulatory role of SOM in the regulation of cholinergic neuronal activity of the striatum of freely moving rats. The potentiating effect of SOM on ACh release in the striatum is mediated (i) by SOM receptor located on glutamatergic nerve terminals, and (ii) by NMDA and non-NMDA glutamatergic receptors located on dendrites of cholinergic interneurones of the striatum.

Studies on the Holocene history of vegetation in the region of lake Srebarna (northeast Bulgaria)

Abstract. The results of pollen analysis of two sediment cores from lake Srebarna (northeast Bulgaria) are presented. On the basis of the palynological data and the radiocarbon dates a reconstruction of the past flora and vegetation is made. For the first time a continuous palaeosuccession is established for the area of the Danubian Dobrudza and the Ludogorie district of northeast Bulgaria: a dominance of mixed xero- and mesophilous oak woods with Carpinus betulus, Ulmus, Tilia, Corylus during the Atlantic period; mixed oak woods with increasing importance of Tilia, Ulmus, Acer and a considerable presence of Carpinus betulus and Fagus during the Sub-boreal period; degradation of the woodland vegetation and transition to secondary plant communities with Carpinus orientalis and herbs during the Sub-atlantic period.

6. Peat-bog Begbunar (Osogovo Mountains, south-west Bulgaria): Four millennia of vegetation history

The peat-bog Begbunar (42°09¢ N, 22° 33¢ E; 1750 m a.s.l.) is located in the central treeless zone of the Osogovo mountains, which are situated at the border between south-western Bulgaria and the north-eastern former Yugoslav Republic of Macedonia. This bog was formed near a freshwater spring on a north-western slope, which continues into a steep, deep ravine where isolated stands of beech (Fagus sylvatica L.) exist. The modern mountain vegetation consists of several vegetation belts: the oak-hornbeam belt (up to 1000 m), the compact beech belt (1000 – 1900 m) with fragments of conifers (Pinus nigra J. F. Arnold and Abies alba Mill.) and the subalpine belt, which is occupied by plant communities of Juniperus sibirica Burgsd., Vaccinium myrtillus L., Bruckenthalia spiculifolia (Salisb.) Rchb., Chamaecytisus absinthioides Janka (Kuzm.), Nardus stricta L., and scattered groups of Pinus sylvestris L., etc. The present-day vegetation composition has been strongly influenced by the long-lasting anthropogenic impact, including ore-mining industry and erosion caused by deforestation (Velcev & Tonkov, 1986; Tonkov, 2003). Geologically, the massif is composed mainly of Palaeozoic metamorphic and intrusive rocks, while geomorphological evidence suggests that small valley glaciers existed in the highest parts during Quaternary glaciations. The climate above 1000 m is typical montane with a mean annual precipitation of 700–900 mm. The basic soil types are cinnamomic-forest, brown forest and mountainous-meadow (Velcev et al., 1994).

Characteristics of Honey from Serpentine Area in the Eastern Rhodopes Mt., Bulgaria

Honey samples collected during 2007–2010 from serpentine and non-serpentine localities in the Eastern Rhodopes Mt. (Bulgaria) were characterized on the basis of their pollen content by qualitative melissopalynological analysis and physicochemical composition. Water content, pH, electrical conductivity, macroelements—K, Ca, Mg, P, and microelements—As, Cd, Co, Cr, Cu, Fe, Mn, Na, Ni, Pb, and Zn were determined after the Harmonised Methods of the International Honey Commission and ICP-AES method. The results from serpentine honey samples were compared with data from bee pollen collected from the same serpentine area. Different elements have different concentrations in honey from the same botanical type even collected from the same geographical region, same locality, and same beehive but in different vegetation season. The elements Mg, Mn, Ni, and P contribute mostly for separation of the serpentine honey samples based on measured elemental concentrations and performed principal component analysis. The element concentrations were higher in bee pollen and above the permissible limits for the toxic metals Cd and Pb. No specific indicator plant species was found for identification of the geographical origin of serpentine honey in relation to the forage of bees.

19. Mire Kupena, Western Rhodopes Mountains (South Bulgaria)

Site details Mire Kupena is a former lake (41◦ 59′ 07.5′′ N, 24◦ 19′ 05.1′′ E; 1356 m above sea level (a.s.l.)) located on the territory of the Biosphere Reserve Kupena, Western Rhodopes Mountains, Bulgaria. The reserve is located between 600 and 1400 m a.s.l. on a north-facing slope and its vegetation is rather diverse. In the lower parts, the most common plant communities are those of Quercus dalechampii Ten. mixed in some places with Carpinus betulus L., Fagus sylvatica L., Pinus nigra Arn. and Pinus sylvestris L. At higher altitudes, plant communities of F. sylvatica dominate, followed by those of Pinus sylvestris with some Abies alba Mill. and Picea abies (L.) Karst. The mire is formed in a depression on an area of 6 ha, surrounded by an almost pure forest of Pinus sylvestris with an admixture of Picea abies, A. alba, F. sylvatica, Betula pendula Roth., Sorbus aucuparia L., Q. dalechampii and an undergrowth of Juniperus communis L., Vaccinium myrtillus L. and V. vitis-idaea L. The mire vegetation is represented by sparse moss cover (Sphagnum spp.) and includes various species of Carex, Juncus, Potentilla, Ranunculus, Galium. The basin is fed by rainfall and water from melting snow. During the last two decades most of the mire surface on the hummocks has been overgrown by pine trees (Huttunen et al., 1992; Bozilova et al., 2011). The climate in the area is montane with a mean annual temperature of 5–10 ◦S and a mean annual precipitation of 600–800 mm with a maximum in May–June. The basic soil types are brown forest (60%), humic-carbonate and cinnamomic-forest.

Significant parameters of Bulgarian honeydew honey

Three main physico-chemical parameters (moisture content, pH, and electrical conductivity), 19 elements contents (K, Ca, Mg, P, S, Al, As, Cd, Co, Cr, Cu, Fe, Mn, Na, Ni, Pb, Sr, V, and Zn) and microscopic characteristics of 30 honeydew honey samples from Bulgaria were evaluated. The most abundant elements were K, P, Ca and Mg in the honeydew honey investigated and low concentrations of toxic elements and heavy metals were established. The electrical conductivity – one of the most important parameters for honeydew honey, exceeded 0.8 mS*cmˉ¹. The honeydew index in Bulgarian honeydew honey varied widely and its values were often below 3.

17. Lake Skakavitsa (Bulgaria): Late Holocene vegetation dynamics in north-western Rila Mountains

The lake Skakavitsa (Skakavishko ezero) is located in the lower part of the subalpine vegetation belt of the north-western part of the Rila Mountains [42◦ 12′ 52′′ N, 23◦ 18′ 18′′ E, 2170 m above sea level (a.s.l.)]. It has an elongated shape narrowing in its northern part and is about 250 m long and 60 m wide. The western shores are rocky and abrupt, the other are flattened. The inflow lies to the south and the outflow to the north, which forms the beginning of the river Skakavitsa (Stoyneva & Michev, 2007). The lake lies in a shallow cirque and is of glacial origin. The core was taken from a marginal peat land in the shallow south-eastern part of the basin. The major peat land plants are Sphagnum capillifolium (Ehrh.) Hedw. and Polytrichum commune Hedw. The lake is surrounded by dense Juniperus sibirica Burgsd., Pinus mugo Turra and Vaccinium uliginosum L. scrubs with herbaceous communities on open areas. The most common taxa in the herbaceous vegetation are Bistorta vivipara (L.) Delarbre, Empetrum nigrum L., Bruckenthalia spiculifolia Rchb., Homogyne alpine Cass., Carex rostrata Michx., Alopecurus gerardii Vill., Avenula versicolor (Vill.) M. Laínz, Potentilla erecta Raeusch., Eriophorum, Pseudorchis albida (L.) Á. Löve & D. Löve, Euphrasia, Agrostis, Carex, Nardus stricta L., Plantago media L., Festuca, Luzula, Deschampsia, Juncus, Geum coccineum Sibth. & Sm., Allium, Gentianella bulgarica (Velen.) Holub, Primula farinosa L. and Antennaria dioica Gaertn. Below the subalpine belt, a coniferous belt is developed. It is composed mainly of Pinus sylvestris L.,