ExcStr_Dept.gif (1864 bytes)                 BG 
blue_but.gif (1076 bytes)Head
blue_but.gif (1076 bytes)Staff
blue_but.gif (1076 bytes)Research Topics
blue_but.gif (1076 bytes)Experimental Methods
blue_but.gif (1076 bytes)Selected Publications
blue_but.gif (1076 bytes)Books
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blue_but.gif (1076 bytes)Head:   Andon Kossev

Phone: +359-2-9793702
Fax: +359-2-9712493
E-mail: kossev@iph.bio.bas.bg
1950   Born February 5, Sofia
1972   MS, Technical University, Sofia
1978   MS, Sofia University, Faculty of Mathematics
1978   PhD in Physiology
1988   Associate Professor in Biophysics
1993   DSc in Physiology
1999   Professor
2008   Corresponding Member
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blue_but.gif (1076 bytes)Staff:

Diana Stephanova, Professor, PhD, DSc

Lilia Christova, Associate Professor, PhD

Nicolina Radicheva, Associate Professor, MD, PhD

Alexander Alexandrov, Associate Professor, PhD

Mariya Daskalova, Research Associate, PhD

Ivan Kristev, Research Associate

Teodora Vukova, Research Associate

Vladimir Dimitrov, Research Associate

Krassimir Gatev, BS, Mathematician

Monika Christova, Research Associate, PhD

Neno Pondev, PhD Student

Radoslava Nedialkova, Technical Assistant

Laboratory Ion Channels:

Hristo Gagov, Associate Professor, PhD

Polina Petkova-Kirova, Research Associate, PhD

Kiril Hristov, Research Associate, PhD

Daniela Dimitrova, Research Associate

Emil Dimitrov, Computer Engineer

Veska Subeva, Specialist

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blue_but.gif (1076 bytes)Research Topics

Relationship between intra- and extracellular action potentials of excitable cells: isolated muscle fibres, axons and neurons and estimation of their functional state (electrical, mechanical and enzyme activity) under physical and chemical influences. Experimental and model investigations of the peculiarities of the extracellular potential field generated by single muscle fibres, motor units and synchronized compound muscle action potentials. Association between the muscle structure and the generated myoelectric activity. Single motor unit activity in health and disease and their relevance to the function of the whole muscle. Fatigue of muscle fibres, motor units and whole muscle. Electromyographic assessment of the muscle functional state. Integrative of the neuromuscular system: sensory-motor integration, motor control in health and disease. Numerical simulations giving an objective interpretation of the membrane property abnormalities of hereditary, chronic and acquired demyelinating neuropathies and neuronopathies in the peripheral nerve system.

Laboratory Ion Channels:

Our scientific interests are focused on the mechanisms of electro-mechanical and pharmaco-mechanical coupling in smooth muscles. Our studies implement registration of contractile activity of smooth muscle preparations, observing and recording the changes in the membrane potential and biophysical properties of transmembrane ionic currents, expressed by single smooth muscle cells under various experimental conditions. Thus, we expose cells to different biologically active substances in order to observe their effects on cellular excitability and tissue contractility, and then we try to figure out how and why did it happen. In search of the most plausible explanations we sometimes benefit from the help of our foreign collaborators, who possess some resources facilitating the monitoring of the dynamics of intracellular calcium movements, or assessing the molecular changes in intracellular proteins and second messengers.

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blue_but.gif (1076 bytes)Experimental Methods

Recording of intra- (microelectrode technique) and extracellular action potentials and muscle fibre contractions, spectro photometry, selective intramuscular recording of single muscle fibers and motor unit potentials, selective surface motor unit action potential measurements, invasive and surface electromyography during isometric contractions and movements, transcranial magnetic stimulation.

Laboratory Ion Channels:

Whole-cell and single-channel voltage clamp, registration of contractions in native and skinned smooth muscles, contraction measurements in resistant vessels (Mulvany’s myography), fluorescent imaging of living cells, intracellular perfusion (Kostyuk’s method).

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blue_but.gif (1076 bytes)Selected Publications

Stephanova DI, Alexandrov AS, Kossev A, Christova L (2007) Simulating focal demyelinating neuropathies: membrane property abnormalities. Biol. Cybern. 96:195-208.  

Christova L, Stephanova D, Kossev A (2007) Branched EMG electrodes for stable and selective recording of single motor unit potentials in humans. Biomed. Tech.52:117-121.  

Vydevska-Chichova M, Mileva K, Radicheva N (2007) Differential changes in myeloelectric characteristics of slow and fast fatigable frog muscle fibres during long-lasting activity J. Electromyogr. Kinesiol. 17:131-141.  

Stephanova DI, Daskalova M, Alexandrov AS (2006) Differences in membrane properties in simulated cases of demyelinating neuropathies. Internodal focal demyelination with conduction block. Journal of Biological Physics 32:129-144.  

Stephanova DI, Alexndrov AS (2006) Simulating mild systematic and focal demyelinating neuropathies: membrane property abnormalities. Journal of Integrative Neuroscience 5:595-623.  

Stephanova DI (2006) Excitability and potentials of human fibres in amyotrophic lateral sclerosis: model investigations, In Amyotrophic Lateral Sclerosis: New Research, Editor: Murray CA, Nova Science Publishers Inc, New York, pp.155-178.  

Nikolova M, Pondev N, Christova L, Wolf W, Kossev A (2006) Motor cortex excitability changes preceding voluntary muscle activity in simple reaction time task. Eur. J. Appl. Physiol. 98:212-219.    

Christova MI, Pondev NG, Christova LG, Wolf W, Dengler R, Kossev AR (2006) Motor cortex excitability during unilateral muscle activity. J. Electromyogr. Kinesiol. 16:477-484.  

Mohammadi B, Krampfl K, Petri S, Bogdanova D, Kossev A, Bufler J, Dengler R (2006) Selective and nonselective benzodiazepine agonists have different effects on motor cortex excitability. Muscle & Nerve 33: 778-784.  

Ishpekova BA, Christova LG, Alexandrov AS, Thomas PK (2005) The electrophysiological profile of hereditary motor and sensory neuropathy – Lom. J. Neurology Neurosurgery and Psychiatry 76:875-878.  

Vydevska-Chichova M, Mileva K, Todorova R, Dimitrova M, Radicheva N (2005) Slow and fast fatigable frog muscle fibres: electrophysiological and histochemical characteristics. Gen. Physiol. Biophys. 24:381-396.  

Stephanova DI, Daskalova M (2005) Differences in potentials and excitability properties in simulated cases of demyelinating neuropathies. Part III. Paranodal internodal demyelination. Clin. Neurophysiol. 116:2334-2341.      

Stephanova DI, Daskalova M (2005) Differences in potentials and excitability properties in simulated cases of demyelinating neuropathies. Part II. Paranodal demyelination. Clin. Neurophysiol. 116:1159-1166.

Stephanova DI, Daskalova M, Alexandrov AS (2005) Differences in potentials and excitability properties in simulated cases of demyelinating neuropathies. Part I. Clin. Neurophysiol. 116:1153-1158.   

Rollnik JD, Kommisarov L, Bogdanova D, Krampfl K, Khabirov FA, Kossev A, Dengler R, Bufler J (2004) Triple stimulation technique (TST) in Amyotrophic Lateral Sclerosis. Clin. Neurophysiol. 115:356-360.  

Mileva K, Georgieva B, Radicheva N (2003) About the biological effects of high- and extremely high frequency electromagnetic fields (Review article). Acta Physiol. Pharmacol. Bulg. 27:89-100.  

Kirilov G, Tomova A, Dakovska K, Kumanov Ph, Shinkov A, Aleksandrov A (2003) Elevated plasma endothelin as an additional cardiovascular risk factor in patients with Cushin's syndrome. European Journal of Endocrinology 149(6):549-553.

Zaprianova E, Majtenyi K, Deleva D, Mikova O, Filchev A, Sultanov B, Kolyovska V, Sultanov E, Christova L, Kmetska X, Georgiev D (2003) Serum IgG and IgM Ganglioside GM1 Antibodies in Patients with Multiple Sclerosis. J. Clinical Neuroscience 56:144-149.

Kossev A, Siggelkow S, Dengler R, Rollnik JD (2003) Intracortical inhibition and facilitation in paired-pulse transcranial magnetic stimulation: effect of conditioning stimulus intensity on sizes and latencies of motor evoked potentials. J. Clin. Neurophysiol. 20:54-58.  

Kossev AR, Schrader C, Dauper J, Dengler R, Rollnik JD (2002) Increased intracortical inhibition in middle-aged humans - a study using paired-pulse transcranial magnetic stimulation. Neurosci. Lett. 333:83-86.  

Siggelkow S, Kossev A, Moll C, Däuper J, Dengler R, Rollnik JD (2002) Impaired sensorimotor integration in cervical dystonia - a study using transcranial magnetic stimulation and muscle vibration. J. Clin. Neurophysiol. 19:232-239.  

Rollnik JD, Siggelkow S, Moll C, Däuper J, Kossev AR, Dengler R (2001) Die transkranielle magnetische Doppelstimulation zur Beurteilung kortikokortikaler Inhibiotion und Fazilitierung. Klin. Neurophysiol. 32:26-29.  

Zaprianova E, Deleva D, Ilinov P, Sultanov E, Filchev A, Christova L, Sultanov B (2001) Serum ganglioside patterns in multiple sclerosis. Neurochemical Research 26(2):95-100.  

Stephanova DI (2001) Myelin as longitudinal conductor: a multi-layered model of the myelinated human motor nerve fibre. Biol Cybern. 84:301-308.  

Christova P, Kossev A (2001) Human motor unit recruitment and derecruitment during long lasting intermittent contractions. J. Electromyogr. Kinesiol. 11:189-196.  

Kossev A, Siggelkow S, Dengler R, Rollnik JD (2001) Crossed effects of muscle vibration on motor-evoked potentials. Clin. Neurophysiol. 112:453-456.  

Kristev I, Christova P, Christova L, Kossev A (2000) Branched surface EMG electrodes and measurement of propagation velocity of excitation along muscle fibers. Biomed. Techn. 45 (Ergänzungsband 2):233-239  

Christova L, Wolf W, Dimitrova M, Christova P, Kossev A (2000) Modulation of single motor unit discharge pattern during the premovement period. Biomed. Techn. 45 (Ergänzungsband 2):223-227.  

Peshev R, Christova L (2000) Study of Bovine herpes virus 1 spreading among buffalo hears in Bulgaria. Acta virologica, 44:229-230.  

Stephanova DI, Mileva K (2000) Different effects of blocked potassium channels on action potential, accommodation, adaptation and anode break excitation in human motor and sensory myelinated nerve fibres: computer simulations. Biol. Cybern. 83:161-167.  

Aleksandrov AS, Christova LG (1999) Comparison between normal and Parkinsonian patern of motor unit firing. Electormyography and Clinical Neurophysiology 39(8):469-472.  

Christova LG, Alexandrov AS, Ishpekova BA (1999) Single motor units activity pattern in patients with Schwartz-Jampel syndrome. J. Neurol. Neurosurg. Psych. 66:252-253.  

Ivanov R, Georgieva B, Naumova P, Mileva K, Radicheva N (1999) Influence of a Protein Hydrolysate from Green Algae on the Activity of Some ATPase Systems in Frog Skeletal Muscle. Methods Find. Exp. Clin. Pharmacol. 21(5):339-343.  

Radicheva N, Mileva K, Stoyanova N, Georgieva B (1999) Further Studies on Nivalin P - Induced Changes in Muscle Fibre Membrane Processes. Methods Find. Exp. Clin. Pharmacol. 21(1) :5-10.  

Christova P, Kossev A, Kristev I, Chichov V (1999) Surface EMG recorded by branched electrodes during sustained activity. J. Electromyogr. Kinesiol. 9:263-276.

Kossev A, Siggelkow S, Schubert M, Wohlfarth K, Dengler R (1999) Muscle vibration: different effects on transcranial magnetic and electrical stimulation. Muscle and Nerve 22:946-948.

Mileva K, Vydevska M, Radicheva N (1998) Stretch- and stimulation frequency-induced changes in extracellular action potentials of muscle fibres during continuous activity. J.  of  Muscle Physiol. and Cell Mot. 19:95-103.  

Christova P, Kossev A, Radicheva N (1998) Discharge rate of selected motor units in human biceps brachii at different muscle lengths. J. Electromyogr. Kinesiol. 8: 287-294.  

Mileva K, Vydevska M, Radicheva N (1998) Stretch and stimulation frequency-induced changes in extracellular action potentials of muscle fibres during continuous activity. J. Musc. Physiol. Cell Mot. 19:95-103.  

Radicheva N, Slavcheva G (1998) Spectral and time domain characteristics of single muscle fibre action potentials during continuous activity extracted from model considerations. Biol. Cybern. 79(5): 427-435.  

Kossev A, Christova P (1998) Discharge pattern of human motor units during dynamic concentric and eccentric contractions. Electroenceph. Clin. Neurophysiol. 109: 245-255.

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Laboratory Ion Channels:

Barry London, Linda C Baker, Polina Petkova-Kirova, Jeanne M Nerbonne, Bum-Rack Choi, Guy Salama (2007) Dispersion of Repolarization and Refractoriness are Determinants of Arrhythmia Phenotype in Transgenic Mice with long QT. J. Physiol (London) 578(Pt 1):115-29.

Petkova-Kirova PS, Gursoy E, Mehdi H, McTiernan CF, London B, Salama G (2006) Electrical Remodeling of cardiac Myocytes from Mice with Heart Failure due to the Over-expression of Tumor Necrosis Factor {alpha). Am. J. Physiol. Heart Circ. Physiol. 290(5): 2098-107. 

Duridanova DB, Gagov HS, Bolton TB (2005) HO-1 induction in the guinea-pig stomach: protection of smooth muscle functional performance during cobalt-induced oxidative stress. Cell. Mol. Biol. 51:495-506.

Hristov K, Gagov HS, Itzev D, Duridanova DB (2004) Heme oxygenase-2 products activate IKCa: role of CO and iron in guinea pig portal vein smooth muscle cells. J. Muscle Res. Cell Motil. 25: 411-421.

Hristov K, Altankova I, Gagov H, Boev K, Bolton T, Duridanova D (2004) Calcium-dependent changes in potassium currents of the guinea-pig coronary artery smooth muscle cells after acute cobalt loading in vivo. Pfluegers Arch. – Eur. J. Physiol. 449: 16-25.

Schubert R, Krien U, Wulfsen I, Schiemann D, Lehmann G, Ulfig N, Veh R, Schwarz J, Gagov  H (2004) Nitric oxide donor sodium nitroprusside dilates rat small arteries by activation of inward rectifier potassium channels. Hypertension 43(4): 891-896.

Ahdut-Hacohen R, Duridanova D, Meiri H, Rahamimoff R (2004) Hydrogen ions control synaptic vesicle ion channel activity in Torpedo electromotor neurons. J. Physiol. 556(2): 347-352.

Gagov H, Kadinov B, Hristov K, Boev K, Itzev D, Bolton T, Duridanova D (2003) Role of constitutively expressed heme oxygenase-2 in the regulation of guinea pig coronary artery tone. Pfluegers Archiv-Eur. J. Physiol. 446: 412-421.

Christova TY, Gorneva GA, Taxirov SI, Duridanova DB, Setchenska MS (2003) Effect of cisplatin and cobalt chloride on antioxidant enzymes in the livers of Lewis lung carcinoma-bearing mice: protective role of heme oxygenase. Toxicol. Lett. 138: 235-242.

Kadinov B, Itzev D, Gagov H, Christova T, Bolton TB, Duridanova D (2002) Induction of heme oxygenase in guinea-pig stomach: role in contraction and single smooth mucle cells ionic currents. Acta Physiol. Scand. 175(4): 297-313.

Christova TY, Duridanova DB, Setchenska MS (2002) Enhanced heme oxygenase activity increases the antioxidant defense capacity of guinea pig liver upon acute cobalt chloride loading: comparison with rat liver. Comp. Biochem. Physiol. C. 131: 177-184.

Christova T, Duridanova D, Braykova A, Setchenska M, Bolton T (2001) Heme oxygenase is the main protective enzyme in rat liver upon 6-day administration of cobalt chloride. Arch. Toxicol. 75: 445-451.

Lubomirov L, Gagov H, Petkova-Kirova P, Duridanova D, Kalentchuk V, Schubert R (2001) Urocortin relaxes rat tail arteries by a PKA-mediated reduction of sensitivity of the contractile apparatus for calcium. Brit. J. Pharmacol. 134:1564-1570.

Petkov GV, Fusi F, Saponara S, Gagov HS, Sgaragli G-P, Boev KK (2001) Characterization of voltage-gated calcium currents in freshly isolated smooth muscle cells from rat tail main artery. Acta Physiol. Scand. 173 (3): 257-265.

Schubert R, Krien U, Gagov H (2001) Protons inhibit the BKCa channel of rat small artery smooth muscle cells. J. Vasc. Res. 38 (1): 30-38.

Fusi F, Saponara S, Gagov H, Sgaragli G (2001) 2,5-Di-t-butyl-1,4-benzohydroquinone (BHQ) inhibits vascular L-type Ca2+ channel via superoxide anion generation. Br. J. Pharmacol. 133: 988-996.

Fusi F, Saponara S, Gagov H, Sgaragli G(2001) Effects of some sterically hindered phenols on whole-cell Ca2+ current of guinea-pig gastric fundus smooth muscle cells. Br. J. Pharmacol. 132: 1326-1332.

Petkova-Kirova PS, Lubomirov LT, Gagov HS, Kolev VB, Duridanova DB (2001) Thyrotropin-releasing hormone activates K+ channels in smooth muscle via intracellular Ca2+ release. Gen. Physiol. Biophys. 20(1):43-60.

Petkova-Kirova PS, Lubomirov LT, Gagov HS, Duridanova DB (2000) Superficial Ca2+ stores are involved in the effect of thyrotropin-releasing hormone on the K-Ca channel activity in smooth muscle cells of the gastric fundus. Neurophysiology+ 32 (3): 196-197.

Petkova-Kirova P, Gagov H, Krien U, Duridanova D, Noack T, Schubert R(2000) 4-Aminopyridine affects rat arterial smooth muscle BKCa current by changing intracellular pH. Brit. J. Pharmacol. 131: 1643-1650.

Petkova-Kirova PS, Gagov HS, Duridanova DB (2000) Urocortin hyperpolarizes stomach smooth muscle via activation of Ca2+-sensitive K+ currents. J. Muscle Res. Cell Motil. 21: 639-645.

Duridanova DB, Petkova-Kirova PS, Lubomirov LT, Gagov H, Boev KK (1999) Corticotropin-releasing hormone acts on guinea-pig ileal smooth muscle via protein kinase A. Pflugers Arch. - Eur. J. Physiology 438: 205-212.

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blue_but.gif (1076 bytes)Books

Ishpekova B, Milanov I, Christova L (2003) Clinical Electromyography, UNISON ART Ltd., Sofia (in Bulgarian).

Dengler R, Kossev A (2001) Sensorimotor Control, NATO Science Series I: Life and Behavioral Sciences - Vol.32, IOS Press, Amsterdam/Berlin/Oxford/Tokyo/Washington, DC.

Gydikov A (1992) Biophysics of the skeletal muscle extracellular potentials. Publ. House BAS, Sofia and Kluwer Academic Publishers, Dordrecht/ Boston/London.

Kosarov D, Shapkov YT (1983) Motor units of human skeletal muscles. Nauka, Leningrad, (in Russian).

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