123,311 research outputs found
Monetary and Fiscal Policies in Bulgaria: Lessons from the Historical Record
No full textThere are two aspects through which an economic policy can influence the economic situation – monetary and fiscal. Monetary and fiscal policies have different and sometimes controversial goals to achieve by means of specific instruments. While the mission of central banks is generally price stability, governments usually set their goals in the realm of economic growth and employment. Fiscal institutions , however, often use inflation in order to derive revenues (seigniorage) and finance budget deficits. Hence, inflation is viewed as a public finance phenomenon (Barro, 1979; Mankiw, 1987; Grilli, 1989). The purpose of this paper is to present a historical perspective on the behaviour of the monetary and fiscal policies pursued in Bulgaria from 1879, when the Bulgarian National Bank was established (soon after the liberation from the Ottoman Empire). Furthermore, historical time series of monetary and fiscal indicators give us the chance to study the link between government budget problems, fluctuations of monetary variables and inflation dynamics in different monetary episodes.monetary and fiscal policy, inflation, exchange rate
Multiple Social Identities in Relation to Self-Esteem of Adolescents in Post-communist Albania, Bulgaria, the Czech Republic, Kosovo, and Romania
No full textWe test a model linking ethnic, familial, and religious identity to self-esteem among youth in Albania, Bulgaria, the Czech Republic, Kosovo, and Romania. All countries are post-communist nations in Europe, offering novel and underexplored settings to study identity. Participants were 880 adolescents (mean age, 15.93 years; SD, 1.40) with Albanian (n = 209), Bulgarian (n = 146), Czech (n = 306), Kosovan (n = 116), and Romanian (n = 103) background who filled in an Ethnic Identity Scale (Dimitrova et al., 2016), familial and religious identity scales adapted from the Utrecht Management of Identity Commitment Scales [U-MICS; Crocetti et al. Child and Youth Care Forum, 40, 7–23 (2011); Crocetti et al. Assessment, 1, 2–16 (2015)], and the Rosenberg’s Self-Esteem Scale [Rosenberg, Conceiving the self. Basic Books, New York (1979)]. A multigroup path model showed that ethnic, familial, and religious identities were significantly positively related to a single underlying construct of social identities. In all countries, youth with a stronger multiple identities reported higher self-esteem. These results are particularly valuable in addressing the scope of the proposed book by providing new knowledge on multiple social identities among under investigated samples from post-communist countries in Europe faced with dynamic societal changes. They also mirror increasing attention on multiple, inclusive, and intersectional identities as psychological assets for young generations
Citrilolepis Dimitrova & Georgiev & Mariaux & Vasileva 2019, n. g.
No full text<i>Citrilolepis</i> n. g. <i>Diagnosis</i> <p>Cyclophyllidea, Hymenolepididae. Body mediumsized. Scolex oval, covered by distinct microtriches. Rostellar apparatus musculo-glandular. Suckers round, muscular. Rostellum retractile, ovoid. Rostellar sheath oval, thick-walled, not reaching level of posterior margin of suckers. Rostellar hooks diorchoid, more than 10 in number, in single row. Neck long. Strobila with gradual maturation. Proglottides craspedote, much wider than long. Inner longitudinal muscle bundles numerous. Ventral osmoregulatory canals often with distinct irregular transverse anastomoses. Genital pores unilateral, sinistral. Genital ducts dorsal to osmoregulatory canals. Testes oval, usually three, rarely four or five per proglottis, arranged in transverse line, rarely in triangle; situated usually in two groups separated by female glands. Cirrus-sac elongate, thin-walled, situated near anterior proglottis margin, not reaching midline of proglottis. Cirrus cylindrical, armed. Female glands median. Ovary multilobate, median. Vitellarium median, with irregular shape, consisting of 3–4 compact, oval lobes, posterior to ovary. Seminal receptacle voluminous, convoluted. Vagina with thick-walled copulatory part, surrounded by thick cellular sleeve; ventral or posteroventral to cirrus-sac; lumen of copulatory part covered by hair-like microtriches. Young uterus narrow, tubular, transversely-elongated; with further development becoming labyrinthine, with numerous sacculations. Fully-developed uterus sacciform, thick-walled, occupying entire median field, not crossing lateral osmoregulatory canals. Eggs oval or elliptical, with thick embryophore. In Fringillidae (Passeriformes). <i>Type-species</i>: <i>Citrilolepis citrili</i> n. g., n. sp.</p> <p> <i>Etymology:</i> The name of the new genus is derived from the common English name (‘‘citril’’) of the typehost; ‘‘ <i>lepis</i> ’’ (Latin) - scale, a frequently used ending for names of cyclophyllidean cestode genera.</p>Published as part of <i>Dimitrova, Yana D., Georgiev, Boyko B., Mariaux, Jean & Vasileva, Gergana P., 2019, Two new cestode species of the family Hymenolepididae Perrier, 1897 (Cyclophyllidea) from passerine birds in Ethiopia, with the erection of Citrilolepis n. g., pp. 279-297 in Syst Parasitol 96</i> on page 286, DOI: 10.1007/s11230-019-09846-y, <a href="http://zenodo.org/record/2669972">http://zenodo.org/record/2669972</a>
Towards automated knowledge-based mapping between individual conceptualisations to empower personalisation of Geospatial Semantic Web
No full textGeospatial domain is characterised by vagueness, especially in the semantic disambiguation of the concepts in the domain, which makes defining universally accepted geo- ontology an onerous task. This is compounded by the lack of appropriate methods and techniques where the individual semantic conceptualisations can be captured and compared to each other. With multiple user conceptualisations, efforts towards a reliable Geospatial Semantic Web, therefore, require personalisation where user diversity can be incorporated. The work presented in this paper is part of our ongoing research on applying commonsense reasoning to elicit and maintain models that represent users' conceptualisations. Such user models will enable taking into account the users' perspective of the real world and will empower personalisation algorithms for the Semantic Web. Intelligent information processing over the Semantic Web can be achieved if different conceptualisations can be integrated in a semantic environment and mismatches between different conceptualisations can be outlined. In this paper, a formal approach for detecting mismatches between a user's and an expert's conceptual model is outlined. The formalisation is used as the basis to develop algorithms to compare models defined in OWL. The algorithms are illustrated in a geographical domain using concepts from the SPACE ontology developed as part of the SWEET suite of ontologies for the Semantic Web by NASA, and are evaluated by comparing test cases of possible user misconceptions
Passerilepis zimbebel Dimitrova & Georgiev & Mariaux & Vasileva 2019, n. sp.
No full text<i>Passerilepis zimbebel</i> n. sp. <p> <i>Type-host</i>: <i>Terpsiphone viridis</i> (Passeriformes: Monarchidae), African paradise flycatcher.</p> <p> <i>Type-locality</i>: Wondo Genet (7.08°N, 38.63°E), Ethiopia.</p> <p> <i>Type-material</i>: A total of 14 specimens (coll. 23.xi.2012) and fragments of strobila (in total 21 slides. Holotype: MHNG-PLAT- 121392, a complete gravid specimen, stained and mounted in Canada balsam. Paratypes: MHNG-PLAT- 121393 (in total 16 slides), 7 specimens and fragments of strobila, stained whole-mounts; one slide with a scolex mounted in Berlese’s medium; IBER-BAS-C0159.1.1–1.3 (3 slides), two specimens, stained whole-mounts; one scolex in Berlese’s medium. Hologenophore (paratype): MHNG-PLAT- 121394, stained whole-mount.</p> <p> <i>Site in host</i>: Small intestine.</p> <p> <i>Prevalence and intensity</i>: 14 individuals; in 1 out of 1 bird studied.</p> <p> <i>Representative DNA sequence</i>: <i>cox</i> 1 mtDNA, one sequence (GenBank: MK463854).</p> <p> <i>Etymology</i>: The species name is after the Amharic name of the host, <i>zimbe-bel</i>; it is a noun in apposition.</p> Description (Figs. 1, 2) <p>[Based on 14 specimens.] Body long, slender, ribbonshaped, when fully-developed with maximum length 21–28 mm (26, n = 3); maximum width at pregravid proglottides, 446–641 (559, n = 14); width at gravid proglottides 366–624 (542, n = 18); width at mature proglottides 391–495 (424, n = 20). Strobila consisting of 191–228 (215, n = 3) proglottides: 95–102 (98, n = 3) juvenile; 33–41 (38, n = 3) premature; 17–24 (21, n = 3) mature; 32–47 (41, n = 3) postmature; 3–4 (3, n = 3) pregravid; 5–14 (10, n = 3) gravid. Fully developed strobila (before starting apolysis) may contain 3–5 (n = 3) sterile terminal proglottides. Scolex oval, with conically protruded anterior part; 96–148 (125, n = 14) long and 141–210 (180, n = 14) wide at middle of suckers (Fig. 1A). Suckers oval, unarmed, directed antero-laterally, with moderately developed musculature; diameter of suckers 59–92 (78, n = 50). Rhynchus thin-walled, forming short, conical apical protrusion anterior to crown of rostellar hooks when rostellum invaginated. Rostellum sac-like, retractile, 119–145 (127, n = 11) long, 42–77 (60, n = 11) wide at middle, thick-walled, with muscular apical enlargement; intensely-stained glandular cells and retractor muscles present within its cavity. Rostellar sheath elliptical, thick-walled, passing beyond level of posterior margins of suckers, 121–162 (139, n = 10) long and 62–96 (78, n = 11) wide at middle; intensely-stained glandular cells present in its cavity, more densely distributed near bottom. Rostellar hooks 10 in number, in single row; hooks diorchoid, with very long handle with tapering and slightly curved and flattened end, short sickle-shaped blade and well-developed guard, shorter that blade (Fig. 1B). Measurements of hooks: total length 37–38 (38, n = 10); length of blade 9–10 (9, n = 10); length of base 28–30 (29, n = 10); distance between tip of blade and tip of handle 9–11 (10, n = 10). Neck 77–119 (93, n = 10) wide. Proglottides with well-developed velum. Inner longitudinal muscle bundles numerous. Genital pores unilateral, dextral, opening at anterior half of lateral proglottis margin (Fig. 1C, D, 2A, B). Genital atrium surrounded by intensely stained glandular cells, funnel-shaped, thickwalled, 22–27 (24, n = 10) deep, 2–7 (4, n = 10) wide at base, 7–17 (13, n = 10) wide at orifice (Fig. 2C); atrium eversible in mature proglottides, sometimes forming short genital papilla. Genital ducts dorsal to dorsal and ventral poral osmoregulatory canals in majority of proglottides. In some proglottides, genital ducts passing between dorsal and ventral poral osmoregulatory canal; number of proglottides with genital ducts passing between osmoregulatory canals varying in different specimens between 1 and 13% of all proglottides with well-developed genital ducts (mean = 4%; n = 438). Dorsal canal 2–10 (5, n = 41) wide, ventral canal 7–25 (13, n = 37) wide (Fig. 2C); no transverse anastomoses of both dorsal and ventral canals.</p> <p>Strobila protandrous with gradual maturation. Testes 3, oval, with diameter 67–96 (83, n = 32), dorsal to female glands; situated in triangle, 2 antiporal and 1 poral to primordia of female gonads (Fig. 1C, D, 2A); their degeneration starting at postmature proglottides. External seminal vesicle elongate-oval, situated near to anterior proglottis margin, dorsal to female glands and antero-dorsal to seminal receptacle; connecting to cirrus-sac by distinct canal, 49–59 (53, n = 5) long and 7–17 (11, n = 11) wide in mature proglottides (Fig. 2C). Cirrus-sac lemon-shaped, thin-walled, 91–136 (117, n = 37) long, 45–62 (52, n = 37) wide, slightly oblique to anterior proglottis margin, crossing poral osmoregulatory canals, never reaching midline of proglottis (Fig. 1D, 2 A–C). Ejaculatory duct surrounded by intenselystained cells. Internal seminal vesicle oval, occupying half of cirrus-sac when fully-developed, 49–94 (71, n = 41) long, 42–57 (47, n = 41) wide, surrounded by intensely stained glandular cells. Evaginated cirrus not available in material studied; armament in <i>ductus cirri</i> not observed (Fig. 2C).</p> <p>Ovary with maximum width 161–222 (186, n = 10), median, ventral to testes and genital ducts, consisting of 3 compact lobes with oval or irregular shape (Fig. 1D). Vitellarium compact, sometimes with lobed margins, posterior and dorsal to ovary, ventral to testes and Mehlis’ gland; 62–106 (78, n = 15) wide, 32–57 (40, n = 15) long (Fig. 1D). Seminal receptacle thin-</p> <p>walled, voluminous, 87–168 (128, n = 18) long, 57–101 (80, n = 18) wide, posterior and ventral to cirrus-sac and external seminal vesicle, dorsal to ovary and uterus, connected with oötype by distinct duct, 24–29 (27, n = 5) long, 10–12 (12, n = 5) wide (Fig. 2A). Vagina opening ventrally to cirrus-sac, usually passing laterally and sometimes posteriorly to it, surrounded by thick sleeve of intensely stained cells. Vagina consisting of well-defined copulatory part and conductive part; copulatory part tubular, 62–99 (79, n = 30) long, 7–23 (12, n = 34) wide, with thick walls consisting of strong circular musculature; conductive part thin, tubular, 10–17 (13, n = 13) long, 2–5 (3, n = 13) wide (Fig. 2C).</p> <p>Young uterus appearing as thick-walled, transversely-elongate narrow sac, with ends slightly curved in posterior direction; situated in median field, anterior to vitellarium, dorsal to ovary and ventral to seminal receptacle, Mehlis’ gland and testes (Fig. 1D), not crossing lateral osmoregulatory canals; uterine walls containing large intensely stained cells. With further development, uterus enlarging laterally but its middle part remaining slightly narrower than lateral parts in postmature proglottides (Fig. 2 A). Gravid uterus sacciform, filling entire median field of proglottis, slightly overlapping but not crossing lateral osmoregulatory canals (Fig. 2 B). Eggs 42–67 (52, n = 25) in diameter, with thin outer coat; embryophore elliptical, thickwalled, 35–47 (40, n = 25) long, 32–37 (35, n = 14) wide, with thickness of walls 2–7 (3, n = 30); no polar filaments observed on embryophore; oncosphere elliptical, 29–37 (33, n = 30) long and 22–27 (25, n = 14) wide. Embryonic hooks differing in shape and length: median pair 20–21 (20, n = 13) long; internal lateral pair more robust, 17 (17, n = 26) long; external lateral pair 16–17 (17, n = 26) long (Fig. 2D).</p> Remarks <p>The present material corresponds to the original diagnosis of the genus <i>Passerilepis</i> as defined by Spasskii & Spasskaya (1954). The specimens from <i>Terpsiphone viridis</i> are characterised by a rostellum armed with a single row of ten hooks, the diorchoid shape of the rostellar hooks (with a long handle, shorter blade and small but well-developed guard), unarmed suckers, three testes situated in a triangle (one poral and two antiporal), the cirrus-sac not reaching the midline of the proglottis, the absence of accessory sacs in the genital atrium, the median female gonads and the sacciform uterus. Initially, the genus <i>Passerilepis</i> incorporated fifteen cestode species parasitising mainly passerine birds (Spasskii & Spasskaya, 1954). The analysis of the previous records revealed 23 valid species of this genus parasitising mostly terrestrial birds of the orders Passeriformes, Coraciiformes and Trogoniformes in the Holarctic, Neotropical, Nearctic, Afrotropical and Oriental Regions (Spasskii & Spasskaya, 1954, 1964; Yamaguti, 1956, 1959; Spasskaya, 1966; Schmidt, 1986) (see Table 1).</p> <p>The most frequently used characters for the identification of <i>Passerilepis</i> spp. are the length and the shape of the rostellar hooks (Spasskii & Spasskaya, 1954, 1964). The specimens of the present material possess rostellar hooks 37–38 µm long, thus resembling four described species of <i>Passerilepis</i> having rostellar hook with lengths 34–40 µm (Table 1). These are <i>P. septemsororum</i> (Burt, 1944), <i>P. dahurica</i> (von Linstow, 1903), <i>P. pellucida</i> (Fuhrmann, 1906) and <i>P. brevis</i> (Fuhrmann, 1906). According to the classification of the rostellar hooks of hymenolepidids from birds (Skrjabin & Mathevosian, 1945), two of these species (<i>P. dahurica</i> and <i>P. brevis</i>) are characterised with arcuatoid type of hooks, i.e. a hook with a long handle, a weakly-developed small blade and a guard almost as long as the blade (see also the definition in Khalil et al., 1994). In contrast, the specimens from Ethiopia are characterised by the diorchoid shape of the hooks. The hooks of <i>P. pellucida</i> have a longer blade compared to the arcuatoid type of hooks of the above-mentioned species. However, its guard is thicker, and the shape of this hook is rather fraternoid (Fuhrmann, 1906a). The hooks of <i>P. septemsororum</i> have an intermediate shape between diorchoid and arcuatoid, i.e. with a very long handle and much shorter claw-like blade, the guard is prominent and thick (Burt, 1944).</p> <p>The specimens from Ethiopia can also be distinguished from the remaining valid <i>Passerilepis</i> spp. by some features of the strobilar morphology, i.e. the position of the genital ducts in relation to the osmoregulatory canals and the shape of the female gonads. Similarly to the majority of the avian hymenolepidids (Czaplinski & Vaucher, 1994), the species of <i>Passerilepis</i> have genital ducts passing dorsally to the poral osmoregulatory canals and this character remains constant in all proglottides of the strobila. The majority of the studied specimens from <i>T. viridis</i> have strobila consisting of proglottides with the same position of the genital ducts. There are exceptions in several specimens where the genital ducts pass between the dorsal and ventral poral osmoregulatory canals (in 4% of proglottides on average). This variation in the position of the genital ducts has not been observed in other <i>Passerilepis</i> spp. Since the frequency of occurrence of this configuration is not high, we think it can be considered as anomalous. The specimens from Ethiopia are also characterised by a median ovary consisting of three compact lobes of oval or irregular shape as well as by the compact median vitellarium. In contrast, the female gonads of <i>P. stylosa</i> (Rudolphi, 1809) and <i>P. crenata</i> (Goeze, 1782) are multilobate.</p> <p>*Species known from the original record only</p> <p>Four species of <i>Passerilepis</i> have been recorded in the Afrotropical Region. These are <i>P. stylosa</i>, <i>P. passeris</i> (Gmelin, 1790), <i>P. passerina</i> (Fuhrmann, 1907) and <i>P. crenata. Passerilepis passerina</i> is known only from its original description from ‘‘ <i>Turdus parochus</i> ’’ (most probably, a mislabelled sample, see Kuchta et al., 2012) from Egypt (Fuhrmann, 1907). It differs from the present specimens from Ethiopia by its arcuatoid hooks (see figure 30 in Fuhrmann, 1907) which are of considerably smaller size (20 <i>vs</i> 37–38 µm in specimens from Wondo Genet). In addition, the cirrus-sac in <i>P. passerina</i> is much longer, i.e. 200 <i>vs</i> 91–136 µm in <i>P. zimbebel</i> n. sp. The remaining three species, i.e. <i>P. passeris</i>, <i>P. stylosa</i> and <i>P. crenata</i>, are among the most frequently recorded <i>Passerilepis</i> spp. worldwide. The only Afrotropical record of <i>P. passeris</i> is from <i>Dicrurus modestus</i> Hartlaub (Dicruridae) from the Democratic Republic of the Congo (Southwell & Lake, 1939). <i>Passerilepis passeris</i> is characterised by its almost diorchoid hooks but they are considerably shorter than the hooks of <i>P. zimbebel</i> n. sp. (Table 1). In addition, <i>P. passeris</i> has a multilobate ovary (Spasskaya, 1966), whereas the ovary of the new species has three almost oval and compact lobes. The African record of <i>P. crenata</i> is from <i>Corvus cornix</i> (L.) (Corvidae) in Egypt (Krabbe, 1869). This species differs significantly from our material by its rostellar hooks, which are 20–26 µm long and their shape is similar to fraternoid. The African record of <i>P. stylosa</i> is from <i>Baeopogon indicator</i> (Verreaux & Verreaux) (Pycnonotidae) from the Democratic Republic of the Congo (Southwell & Lake, 1939). This species differs from the specimens from Ethiopia by the arcuatoid shape of its hooks. As was mentioned above, <i>P. stylosa</i> differs from the specimens from Ethiopia by its multilobate ovary.</p> <p>The specimens studied differ from the remaining <i>Passerilepis</i> spp. by the length of the rostellar hooks (Table 1).</p> <p>Based on the above-mentioned differences, we recognise the specimens from <i>Terpsiphone viridis</i> in Ethiopia as a new species, <i>P. zimbebel</i> n. sp.</p>Published as part of <i>Dimitrova, Yana D., Georgiev, Boyko B., Mariaux, Jean & Vasileva, Gergana P., 2019, Two new cestode species of the family Hymenolepididae Perrier, 1897 (Cyclophyllidea) from passerine birds in Ethiopia, with the erection of Citrilolepis n. g., pp. 279-297 in Syst Parasitol 96</i> on pages 280-286, DOI: 10.1007/s11230-019-09846-y, <a href="http://zenodo.org/record/2669972">http://zenodo.org/record/2669972</a>
Inhibition of Candida albicans extracellular enzyme activity by selected natural substances and their application in Candida infection
No full textExtracellular enzymes secreted by Candida albicans are claimed to be virulence factors responsible for penetration of the yeast into host cells. Substances able to inhibit lipolytic and proteinase activities of the fungus might be of therapeutic use in some pathologic conditions caused by C. albicans. In the present work, we have tested the influence of the flavonoid compounds apigenin and kaempferol, the indole alkaloid ibogaine, and the protoberberine alkaloid berberine on the in vitro enzyme activity of C. albicans. The substances showed complex suppressive effects concerning the processes of adherence to epithelial cells, secreted aspartyl proteinase activity, and the rate of cell wall protein glycosylation. Apigenin and kaempferol were administered in systemic C. albicans infection, demonstrating an increased number of survivors by kaempferol. The application of apigenin, kaempferol, ibogaine, and berberine in cutaneous infection suppressed the symptoms and accelerated elimination of the yeast from the site of inoculation
Fig. 4 Citrilolepis citrili n. g., n in Two new cestode species of the family Hymenolepididae Perrier, 1897 (Cyclophyllidea) from passerine birds in Ethiopia, with the erection of Citrilolepis n. g.
No full textFig. 4 Citrilolepis citrili n. g., n. sp. A, Hermaphroditic mature proglottides with young uterus; B, Postmature proglottis; C, Pregravid proglottides. Scale-bars: A–C, 200 µmPublished as part of Dimitrova, Yana D., Georgiev, Boyko B., Mariaux, Jean & Vasileva, Gergana P., 2019, Two new cestode species of the family Hymenolepididae Perrier, 1897 (Cyclophyllidea) from passerine birds in Ethiopia, with the erection of Citrilolepis n. g., pp. 279-297 in Syst Parasitol 96 on page 290, DOI: 10.1007/s11230-019-09846-y, http://zenodo.org/record/266997
dimitrova
No full textK e y w o r d s : grehlin signaling, hormone, orexigenic, prostaglaudin, smooth muscle, tromboxane Furthermore, hormones and local mediators often change the conductivity of ion channels in the cell membrane, which can be used as sensors for proper signaling. Our pilot study showed that ghrelin reduces the iberiotoxin-sensitive Ca 2+ -activated potassium current (I K(Ca) ) elicited in freshly isolated smooth muscle cells of human mesenteric arteries via PLD-and PKCdependent mechanism (15). The sarcoplasmic reticulum is also necessary for this signaling as the blockade of sarco-endoplasmic reticulum Ca 2+ ATPase or IP 3 -activated Ca 2+ channels of internal Ca 2+ stores inhibit the effect of ghrelin on I K(Ca) In the present study, we used pharmacological tools to identify the participants of ghrelin signaling and found a second mediator involved. MATERIALS AND METHODS The investigation conformed to the 'Declaration of Helsinki' 1975Helsinki' (revised 1983. Mesenteric arteries were isolated from extracted specimens of human mesentery taken during abdominal surgery on patients -63 men aged 64.6±1.5 years and 43 women aged 59.3±1.9 -and transported to the laboratory in ice-cold saline. Half of the patients were operated for malignant growths (carcinoma sigma) and the rest -for nonmalignant conditions. Contraction studies Segments of mesenteric arteries were dissected, carefully cleaned of adipose and connective tissues and kept in ice-cold low Ca 2+ solution containing (mmol): 118 NaCl, 5 KCl, 1.2 MgCl 2 , 0.16 CaCl 2 , 10 glucose, 1.2 Na 2 HPO 4 and 24 HEPES. Arterial rings (2 mm long) were mounted on a wire-myograph for isometric tension recording DMT, model 410A (Danish Myo Technology, Aarhus, Denmark) whose chamber was filled with the same ice-cold low Ca 2+ solution. After the mounting of the vessel rings, the organ bath solution was replaced with the same solution containing 2.5 mmol CaCl 2 . The bath was heated up to 37°C and continually bubbled with carbogen (95% O 2 and 5% CO 2 ). The isometric force of contraction was recorded using the program Myodaq (DMT, Aarhus, Denmark). The arterial segments were equilibrated for 1 hour at 37°C in a buffer, which was changed at least 3 times during this equilibration period. In most experiments, the endothelium was removed by careful rubbing with a rat whisker. Then vessels were stretched to their optimal lumen diameter, corresponding to 90% of the passive diameter of the vessel at 100 mm Hg. The viability of the preparations was tested twice by application of 10 µmol noradrenaline. The integrity of the endothelium was tested with 10 µmol acetylcholine added to 10 µmol noradrenaline contracted rings. After the viability tests, the strips were contracted with 1 nmol ET-1, which produced relatively stable isometric contractions allowing the study of the effect of the increasing concentrations of ghrelin. The tension reached a steady state in about 40 minutes after the application of ET-1. Then ghrelin was applied to the bath in increasing concentrations of 10, 30, 100, 300 and 1000 nmol, i.e. starting from a value that is about 10 times higher than its plasma level. It led to a significant effect on native artery preparations (with endothelium and in the absence of TTX) at a 30-100 times higher concentration than in human circulation (11). A possible explanation of this result is that ghrelin has a low diffusion rate through the adventitia, which decreases its interaction with receptors of smooth muscle cells when applied to the bath solution. Other researchers have also used higher ghrelin concentrations while studying the effect of ghrelin on vascular preparations (12), probably due to the same reason. It is also possible that ghrelin reaches such values in the smooth muscle layer of the arterial wall due to its paracrine release from human vascular endothelium (16). Additionally, guinea pigs may have a higher plasma level of ghrelin if compared to humans or rats. The ghrelin-induced changes in tension were expressed as a percentage of the maximum tension elicited by 1 nmol ET-1. The influence of different pharmacological agents (inhibitors) on ghrelin effect was studied by means of their addition to the bath about 40 min after ET-1 application and incubated for about 30 min before the application of ghrelin. The effects of inhibitors were studied using several types in vitro preparations: i) native (untreated) preparations of small human mesenteric arteries; ii) endothelium-denuded preparations; iii) native preparations with tetrodotoxin (TTX, 300 nmol) and mainly iv) endotheliumdenuded and TTX-treated preparations. The time control preparations were equally treated, but instead of ghrelin, an equal volume of solvent (deionised water) was added at the same time intervals. The inhibitors and antagonist were applied to block (to switch off) the studied enzyme or receptor activity and not to induce a partial inhibition only. This forced us to use a higher concentration of these substances. On the other hand, the possibility of a non-specific effect of the pharmacological tools restricted us to using them in lower concentrations. Thus, the aim to choose the optimal concentration of each substance for our experiments was not easy. For almost all of the blockers, however, there are at least several studies on arterial preparations in vitro, in some cases with dose-response curves and/or tests for cross-reaction. Besides, the choice of each concentration was based on our earlier experience with a significant part of the substances used either in electrophysiological or functional studies of different vascular beds. Whole-cell patch-clamp experiments This method has been described in detail elsewhere (17). In brief, whole-cell voltage-clamp experiments were performed on single smooth muscle cells, freshly isolated from human mesenteric arteries. The arteries were cut into 3 mm long pieces and placed in 0.1 mmol Ca 2+ -containing physiological salt solution (PSS, for composition see below) warmed to 37°C and containing 1.5 mg ml -1 collagenase II, 1 mg ml -1 papain, 15 µl ml -1 elastase and 1 mg ml -1 albumin. After 30 to 35 min incubation at 37°C with continuous O 2 bubbling, the enzymes were washed away and the tissue pieces triturated 5 times in Ca 2+ -free PSS using a pipette with a small tip opening. The remainder of the tissue was put back into the enzyme-containing solution for another 5 min and then carefully washed with Ca 2+ -free PSS. Single smooth muscle cells were obtained by gentle trituration in 2 ml of the same Ca 2+ -free solution. Cells could be stored for up to 8 hours in this solution at 4-6°C. The external solution (PSS) for single-cell voltage experiments contained (in mmol): 126 NaCl, 5.6 KCl, 10 HEPES, 20 taurine, 20 glucose, 1.1 MgCl 2 , 0.8 CaCl 2 , 5 Napyruvate and pH was adjusted to 7.4 with NaOH. The same solution was used for the isolation of cells. The solutions in the recording pipette contained (in mmol): 125 KCl, 6 NaCl, 10 HEPES, 1 MgCl 2 , 3 EGTA, 0.1 ATP, 5 Na-pyruvate, 5 succinate, 5 oxalacetate, 5 glucose and 2.15 CaCl 2 to give a calculated free Ca 2+ of 200 nmol and pH was adjusted to 7.4 with KOH. Chemicals Most of the substances used for solution preparation were obtained from ICN (Irvine, CA, USA). NaOH, BSA, 2-nitro-4-carboxyphenyl-N,N-diphenylcarbamate (NCDC), pertussis toxin, indomethacin, O-(octahydro-4,7-methano-1H-inden-5-yl) carbonopotassium dithioate (D-609), collagenase type II, prostaglandine F 2α (PGF 2α ), (5Z,13E) -(9S,11S,15R)-384 9,15,dihydroxy-11-fluoro-15-(2-indanyl)- Data analysis Current densities were expressed in pA/pF and plotted as functions of the potential applied to obtain data suitable for statistical analysis. The significance of differences between means was assessed using Tukey-Kramer multiple comparison test with p<0.05 regarded significant. The force of contraction was evaluated as a difference in tension (N/m) measured before ET-1 application and the plateau reached afterwards. The contractile effect of ghrelin was expressed as a percentage of the maximal ET-1 induced contraction, taken as 100%. Values were expressed as means±S.E.M. From five to ten human mesenteric arterial preparations (n) were included in the construction of each concentration-response curve of ghrelin. Data were subjected to a comparative statistical analysis one-way ANOVA with Bonferroni correction (p<0.05). RESULTS Octanoyl ghrelin, herein referred to as ghrelin, dosedependently increased the force of contraction of isometric human mesenteric artery preparations constricted with ET-1 The application of increasing doses of ghrelin to external solution containing either NCDC (50 mol) ( The application of increasing concentrations of ghrelin to TTX-and ET-1-containing bath solution failed to influence significantly the force of contraction of endothelium-denuded human mesenteric arteries in the presence of PP2 (10 µmol) -a selective Src family kinase inhibitor The addition of ghrelin (100 nmol) almost entirely inhibited the iberiotoxin-sensitive I K(Ca) recorded during a 500 ms depolarizing pulse to +40 mV from a holding potential of -50 mV (12). Rp-cAMPS (200 µmol), a specific membranepermeable inhibitor of PKA, was without effect on the total outward potassium current (I K ) (n=5), while the subsequent addition of ghrelin (100 nmol) decreased I K to the same degree as in the absence of this PKA inhibitor in single smooth muscle cells from human mesenteric arteries (n=5; p<0.01) DISCUSSION Ghrelin and des-octanoyl ghrelin are equipotent antagonists of ET-1 induced vasoconstriction of human mammary artery (13) while in single smooth muscle cells isolated from human mesenteric arteries des-octanoyl ghrelin blocks the ghrelininduced inhibition of I K(Ca) . This difference supposes the operation of more than one ghrelin receptors in human vascular beds -the des-octanoyl ghrelin-blockable GHS-R1a in human mesenteric arteries and another type in human mammary artery (for a review of ghrelin receptors see 19). Kleinz et al. (13) routinely applied indomethacin to exclude the possibility of endothelium dependent vasodilatation. This treatment however blocks not only endothelial COX1/2 but also those in the tunica media of the artery and thus eliminates the influence of COX1/2 downstream products generated in smooth muscle cells, as suggested by our study. Indeed, such a mechanism is unexpected in blood vessels but is reported in non-vascular smooth muscle (lower esophageal sphincter) that maintains mainly tonic type of contraction similarly to arteries (20). Therefore, it is still difficult to summarize the mechanisms of ghrelin effects on human arteries due to their opposite influences -relaxation and contraction, the different experimental conditions applied and the need for more detailed studies of the intracellular participants. Most often GHS-R1a interacts with heterotrimeric G q/11 proteins and stimulates the G q/11 /PI-PLC/IP 3 +Ca 2+ +DAG/PKC signaling (2). It was reported that the application of a specific PKC inhibitor entirely abolished the effect of ghrelin on I K(Ca) , recorded in single smooth muscle cells of human mesenteric arteries (15). In our study the force of contraction of human mesenteric arteries did not respond to ghrelin application if iberiotoxin or GF109203x were present in the bath solution. Thus, ghrelin requires activation of PKC and suppresses K Ca channels with a large conductance (BK Ca channels) to increase the force of contraction. Ghrelin regulates cAMP/PKA (3-5) and cGMP/PKG signaling (6), which can further influence ion channels. Han et al. (6) reported a ghrelin-induced reduction of voltage-gated I K of rat anterior pituitary tumor (GH3) cells by a PKG-dependent mechanism and Kohno et al. (21) -a ghrelin-induced activation of N-type Ca 2+ channels that required PKA. BK Ca channels are involved in the formation of the spontaneous artery tone, counteract the elevation of the agonist-induced cytosolic free Ca 2+ and participate in the relaxation induced by cAMP/PKAand cGMP/PKG-coupled agonists (22). Therefore, we investigated the participation of both cyclic nucleotides using specific inhibitors Rp-cAMPS for PKA and ODQ for soluble guanylate cyclase. The presence of inhibitors of PKA or soluble guanylate cyclase in the bath solution did not prevent the effect of ghrelin on I K(Ca) . We concluded that the second messengers cAMP and cGMP are not involved in the observed ghrelininduced inhibition of I K(Ca) . On the other hand, in human mesenteric arteries the effect of ghrelin on the force of contraction is blocked by pertussis toxin, which suggests the participation of G i -proteins. In rat islet β-cells ghrelin decreases the insulin secretion by a G αi2 -protein sensitive activation of voltage-gated K + channels and this effect is blocked by D-Lys 3 -GHRP-6, a specific GHS-R1a inhibitor (23). Ghrelin inhibits BK Ca channels in the guinea pig femoral artery via a pertussis toxin and GHS-R1a sensitive pathway (17). Ghrelin also activates G i -protein in cell cultures Ca 2+ released from sarcoplasmic reticulum activates BK Ca channels of smooth muscles cells (24). In human mesenteric arteries IP 3 -sensitive Ca 2+ release is essential for the ghrelininduced decrease of I K(Ca) (15) and for the increase of the force of contraction. Additionally, IP 3 -induced Ca 2+ release from sarcoplasmic reticulum participates in the ET-1 evoked contraction of this vascular bed. Our pharmacological studies suggest that several DAG-producing phospholipases (PI-PLC and PC-PLC) are important in establishing the effect of ghrelin in human mesenteric arteries. We presume that PI-PLC is essential mainly for triggering the contraction (25) and for the IP 3 -induced Ca 2+ release-dependent translocation of PKC to the plasma membrane, while the sustained DAG producer PC-PLC (25) is responsible for the long lasting PKC activation. This suggestion is indirectly supported by the slowly developing inhibition (in 10-14 min) of I K(Ca) by ghrelin in this tissue (15). Using different inhibitors we reveal several new enzymes participating in the ghrelin effect in human mesenteric arteries. Thus, the selective inhibition of MEK or Src kinase entirely blocks the ghrelin-induced contractions in endothelium-denuded human mesenteric arteries with suppressed neurotransmission. The nonselective COX1/2 inhibitor indomethacin eliminates either the ghrelin-induced constriction of human mesenteric arteries or the ghrelin-induced decrease of I K in single smooth muscle cells isolated from the same tissue. All these data suggest the existence of a ghrelin-induced and pertussis toxin-sensitive mechanism, which increases the force of contraction by a consequent activation of Src kinase, MEK and ERK. Similar G iprotein initiated signaling was reported for non-vascular tissues (for review see 26). Next, the stimulated ERK may activate the cytosolic PLA 2 (27), which increases vascular arachidonic acid production -the rate-limiting step for prostaglandin synthesis (28). COX1/2 transform this arachidonic acid into PGE 2 , and then PGE 2 into PGH 2 , which may further yield contracting prostaglandin or thromboxane, as reported for non-vascular smooth muscle It was reported that ghrelin receptor type GHR-R1a has the ability to oligomerize with prostanoid receptors, when they are transiently over-expressed in human embryonic kidney 293 cells (32). The same authors stated that this co-transfection significantly influenced GHR-R1a activity without changes in its affinity for ghrelin. Similarly, as an alternative explanation of our data, it is suggested that ghrelin first binds to GHS-R1a and then activates prostanoid receptor via a direct interaction in the existing GHS-R1a/prostanoid receptor heteromeric complex. If this is the case, the enzymes necessary to demonstrate the effect of ghrelin on the contractile activity (Src kinase, MEK, COX-1 and thromboxane synthase) only support the steady-state thromboxane A 2 production and are not additionally activated by ghrelin. The second explanation of our data, however, seems to be less probable as several new articles report a direct activation of ERK1/2 (3, 7, 33) and Src kinase (34) by ghrelin signaling. Ghrelin decreases the mean arterial pressure of the rat by a COX-insensitive and NOS-sensitive mechanism (35). In rat mesenteric arteries both ghrelin and desacyl ghrelin evoke endothelium-dependent dilation by NOS-and COX-insensitive mechanism (36). Ghrelin inhibits the contraction of human aortic smooth muscle cells by cAMP/PKA pathway activation (4). Ghrelin and desacyl ghrelin antagonize the ET-1-induced contraction of human internal mammary artery (13). Ghrelin decreases the mean arterial pressure in humans as well (11). On the other hand, contractile effects of ghrelin were reported in guinea pig femoral (37) and renal (17) arteries and in rat coronary artery (38). Ghrelin increases the force of contraction of human mesenteric arteries partially constricted with ET-1. The effect is stronger in endothelium-denuded preparations and most pronounced in endothelium-denuded artery segments with blocked action potential propagation of perivascular neurons. These data point to a relaxing effect of ghrelin via endothelium and axonal projections in adventitia, which antagonize the direct and stronger contractile action of ghrelin on the smooth muscle layer of the vascular wall. Additionally, if compared to native preparations during the first half of the experiments, the higher force of contractions of endothelium-denuded human mesenteric arteries suggest that endothelium, as well as perivascular neurotransmission are functional, i.e. they are not badly damaged by the therapy before the surgical intervention or during the transportation. It can be concluded that ghrelin either increases or decreases the force of contraction of arteries depending on their type and the species. Thus, ghrelin and desacyl ghrelin may influence the artery resistance similarly to other regulators of the circulation with opposite effects on different vascular beds. For example, catecholamines redistribute the blood flow throughout the body, depending on the physiological needs, via different adrenergic receptors and intracellular mechanisms. In summary, ghrelin has been shown to increase the force of contraction of human mesenteric arteries by a novel mechanism that requires active Src kinase, MEK, COX-1 and thromboxane synthase and that depends on the release of a local mediator -a T prostanoid receptor agonist. Additionally, our data suggest a novel physiological regulation, in which an empty stomachinitiated increase of ghrelin secretion reduces the abdominal circulation in adult humans until next meal. Acknowledgement
A Multi-Language Comparison of Influences on Author Verification using Character N-Grams
No full textWe create a new multi-language corpus for author verification based on Wikipedia talkpages, and evaluate the influence that differences in topic and time have on character n-gram author profiles. Topic alignment between two texts is found to increase author verification precision, and an authors writing style is found to change over time, but not more significantly after 3 years than after 1 year.Information ArchitectureWISElectrical Engineering, Mathematics and Computer Scienc
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