Bitter Taste Receptors as Regulators of Abdominal Muscles Contraction.

Bitter taste receptors (TAS2R) are expressed in many non-sensor tissues including skeletal muscles but their function remains unexplored. The aim of this study is to investigate the role of TAS2R in rat abdominal skeletal muscles contractions using denatonium, a TAS2R agonist. Low concentration of denatonium (0.01 mmol/l) caused a significant decrease of amplitudes of the electrical field stimulation (EFS)-induced contractions in abdominal skeletal muscles preparations in vitro. This inhibitory effect was significantly reduced when the preparations were pre-incubated with gentamicin (0.02 mmol/l) used as a non-specific inhibitor of IP3 formation or with BaCl(2) (0.03 mmol/l) applied to block the inward-rectifier potassium current. All experiments were performed in the presence of pipecuronium in order to block the nerve stimulation of the contractions. The data obtained suggest that denatonium decreases the force of rat abdominal muscles contractions mainly via activation of TAS2R, phosphatidylinositol 4,5-biphosphate and its downstream signal metabolites.

Cyclopiazonic acid-induced changes in contractile activity of smooth muscle strips isolated from cat and guinea-pig stomach.

The effects of cyclopiazonic acid (CPA), a specific inhibitor of sarcoplasmic reticulum Ca(2+)-ATPase, on contractile activity of circular smooth muscle strips isolated from the antrum, corpus and fundus regions of the cat and guinea-pig stomach were studied. Contractile activity was recorded under isometric conditions, in organ baths. CPA, concentration dependently (3 x 10(-7)-3 x 10(-5) M) increased the tone of the cat and guinea-pig gastric fundus and corpus as well as the amplitude of the phasic contractions of the cat corpus and antrum, affecting their frequency. CPA had a dual action on the phasic contractions of the guinea-pig antrum: an increase at low concentrations (up to 10(-6) M) and inhibition at high concentrations (10(-6)-3 x 10(-5) M). Tetrodotoxin (10(-6) M), atropine (10(-6) M) and N omega-nitro-L-arginine (10(-4) M) did not change significantly the effects of CPA. Nifedipine completely inhibited the CPA-induced phasic contractions and partly inhibited the CPA-induced tonic contractions. The nitric oxide-releasing agents, sodium nitroprusside (10(-3) M) and 3-morpholino-sydnonimine (10(-3) M), completely inhibited the CPA-induced tonic and phasic contractions. CPA induced tonic contractions in the cat and guinea-pig gastric fundus precontracted by acetylcholine (10(-5) M) and inhibited the acetylcholine (10(-6) M)-induced phasic contractions in the guinea-pig gastric antrum and corpus. The results suggest multiple roles for sarcoplasmic reticulum Ca2+ stores and sarcoplasmic reticulum Ca(2+)-ATPase in the shaping of spontaneous and evoked tonic and phasic contractions of the stomach, and highlight important species and tissue differences.

Control of the phasic and tonic contractions of guinea pig stomach by a ryanodine-sensitive Ca2+ store.

In some smooth muscle cells, the rise in intracellular Ca2+ as a result of a Ca2+ influx via plasma membrane Ca2+ channels can activate a further increase in intracellular Ca2+ as a result of Ca2+ release from intracellular stores. This study examined the role of the Ca2+-induced Ca2+ release from the ryanodine-sensitive intracellular Ca2+ stores in shaping the smooth muscle contractions of guinea pig stomach. The contractile activity of isolated muscle strips of the fundus, corpus and antrum region of the stomach was recorded under isometric conditions. Ryanodine, an activator of Ca2+-induced Ca2+ release, concentration dependently (10(-7)-3x10(-5) M) increased the tone of fundus and corpus strips. Ryanodine had a dual action on the phasic contractions of the antrum and corpus: increase by the low concentrations (up to 10(-6) M) and inhibition by the high concentrations (10(-6)-3x10(-5) M). Nifedipine (10(-5) M) completely inhibited the ryanodine (10(-6) M)-induced phasic contractions and only partly the ryanodine (3x10(-5) M)-induced tonic contractions. In the presence of 10(-5) M cyclopiazonic acid, a specific inhibitor of sarcoplasmic reticulum Ca2+-ATPase, ryanodine (3x10(-5) M) further increased the tone of the corpus and fundus strips. Ryanodine (3x10(-5) M) induced tonic contractions in the fundus and corpus precontracted by acetylcholine (10(-5) M), and inhibited the acetylcholine (10(-6) M)-induced phasic contractions in the antrum and corpus. Ruthenium red, an inhibitor of Ca2+-induced Ca2+ release, concentration dependently (10(-6)-10(-4) M) decreased the tone and amplitude of the phasic contractions. The data obtained provide evidence for the participation of a sarcoplasmic reticulum Ca2+-induced Ca2+ release mechanism in shaping the tonic and phasic contractions of guinea pig stomach, and highlight important tissue differences.

Role of sarcoplasmic reticulum in the myorelaxant activity of nitric oxide donors in guinea pig gastric fundus.

The relaxant effect of two nitric oxide (NO) donors: sodium nitroprusside and 3-morpholino-sydnonimine (SIN-1) on circular smooth muscle strips isolated from guinea pig gastric fundus was studied with the view to elucidating the mechanism, which underlies the NO-induced relaxation of this tissue. Both sodium nitroprusside (10(-9)-10(-5) M) and SIN-1 (10(-9)-10(-4) M) suppressed the spontaneous fundus tone and hyperpolarized the muscle cells by about 5 mV. They antagonized the acetylcholine (10(-6) M)-induced tone and exerted their relaxant effects even when Ca2+ influx into the cells was triggered through the Na+/Ca2+ exchanger. Sodium nitroprusside and SIN-1 antagonized the contraction induced by cyclopiazonic acid (10(-5) M), a specific inhibitor of the sarcoplasmic reticulum Ca2+-ATPase. In the presence of high concentrations of sodium nitroprusside or SIN-1, cyclopiazonic acid (10(-5) M) exerted only a slight if any contractile effect. After the complete relaxation induced by sodium nitroprusside or SIN-1, the K+-channel blockers, tetraethylammonium, apamin and charybdotoxin, as well as the Ca2+ ionophore, A 23187, induced high-amplitude contractions, suggesting that the Ca2+ sensitivity of the contractile myofilaments was not affected. The results suggest that NO, released from NO donors increases the sarcoplasmic reticulum Ca2+ uptake thereby enhancing the vectorial sarcoplasmic reticulum Ca2+ release toward the plasmalemma to elicit membrane hyperpolarization and relaxation in guinea pig gastric fundus.

Myorelaxant activity of 2-t-butyl-4-methoxyphenol (BHA) in guinea pig gastric fundus.

This study investigates the mechanism whereby the antioxidant 2-t-butyl-4-methoxyphenol (BHA) relaxes guinea pig gastric fundus smooth muscle. In circular smooth muscle strips, 10 microM cyclopiazonic acid, a specific inhibitor of sarcoplasmic reticulum Ca2+-ATPase, induced a prolonged rise in tension which depended on the presence of extracellular Ca2+. BHA (pIC50 = 5.83), sodium nitroprusside (6.85), isoproterenol (7.69) and nifedipine (8.02), but not 2,6-di-t-butyl-4-methoxyphenol (DTBHA) (up to 30 microM), relaxed muscle strips contracted with cyclopiazonic acid. Methyl-1,4-dihydro-2,6-dimethyl-3-nitro-4-(2-trifluoromethylphenyl)-pyri dine-5-carboxylate (Bay K 8644) (1 microM) antagonised the nifedipine- but not the BHA-induced relaxation. Nifedipine and isoproterenol (10 microM) caused a decrease in spontaneous tone, but did not counteract the subsequent rise in tension elicited by 10 microM cyclopiazonic acid. Conversely, 100 microM BHA and 100 microM sodium nitroprusside not only significantly reduced spontaneous tone but also markedly impaired the response of the muscles to cyclopiazonic acid. DTBHA failed to show either effect. When added to preparations completely relaxed by 100 microM BHA, 10 mM tetraethylammonium still elicited nifedipine-sensitive tonic and phasic contractions in the presence or absence of 10 microM cyclopiazonic acid. BHA and DTBHA inhibited, in a concentration-dependent manner, the Ca2+-promoted contraction of strips depolarised by 10 mM tetraethylammonium. The BHA antagonism showed a non-competitive profile while that of DTBHA was competitive. In muscle strips at rest, 10 microM BHA caused a significant increase in tissue cAMP concentration, leaving cGMP unmodified. To conclude, the myorelaxant action of BHA on gastric fundus smooth muscle appears to be mediated partly by an increase in cAMP levels and partly by inhibition of Ca2+ influx from the extracellular space.

The role of a ryanodine-sensitive Ca(2+)-store in the regulation of smooth muscle tone of the cat gastric fundus.

The smooth muscle of the gastric fundus maintains spontaneous tone, but the mechanism underlying this activity is not fully understood. The aim of the present study was to examine whether Ca2+ release from the sarcoplasmic reticulum (SR) could play a role in the maintenance of the spontaneous smooth muscle tone of the cat gastric fundus. The effects on the contractile activity of SR Ca2+ release activators ryanodine and caffeine and of the inhibitor ruthenium red were studied. The contractile activity of isolated muscle strips was recorded under isometric conditions using organ baths. Ryanodine concentration-dependently (10(-7)-3.10(-5) mol/l) increased the tone of the fundus strips. In the presence of nifedipine (10(-5) mol/l), ryanodine induced a nifedipine-resistant tonic contraction. The tonic contraction induced after inhibition of the SR Ca(2+)-pump by cyclopiazonic acid was potentiated by ryanodine (10(-5) mol/l). In strips precontracted with supramaximal concentration of acetylcholine (10(-5) mol/l), ryanodine (3.10(-5) mol/l) further potentiated the tone. Caffeine (10(-4)-10(-2) mol/l) decreased and even completely inhibited the tone, suggesting some other effects of caffeine. Ruthenium red concentration-dependently (10(-6)-10(-4) mol/l) decreased the tone. The present data provide evidence for the role of Ca2+ release from a SR ryanodine-sensitive Ca2+ store in the maintenance of the muscle tone of the cat gastric fundus.

Cyclic GMP-induced activation of potassium currents by sarcoplasmic reticulum Ca2+ pump-dependent mechanism.

In voltage-clamped single smooth muscle cells from the circular layer of the guinea-pig gastric fundus NO-liberating substance or an analogue of cyclic 3, 5'-guanosine monophosphate (cGMP) increased or decreased the outward K+ current amplitudes depending on the Ca2+ buffering capacity of the intracellular medium. In a high EGTA-containing pipette solution dibutyryl-cGMP or sodium nitroprusside (SNP) attenuated both the fast and the late K+ current components. In pipette solution with lower Ca2+ -buffering capacity these drugs caused a sustained increase of K+ current amplitudes, which was effectively antagonized by thapsigargin, an inhibitor of Ca2+ -ATPase in the sarcoplasmic reticulum (SR). Our data suggest that, in gastric fundus smooth muscles, NO-liberating substances and cGMP analogues contribute to the activation of a Ca2+ -release mechanism from the cell bulk, i.e. the myoplasm surrounding the contractile filaments, towards the plasma membrane, crossing the SR Ca2+ -stores. Thus, a decreased intracellular free calcium concentration ([Ca2+]) is coupled with an elevation of subplasmalemmal calcium, which in turn causes cell membrane hyperpolarization. The latter is a consequence of the opening of tetraethylammonium-sensitive Ca2+ -activated K+ channels and leads to sustained smooth muscle relaxation, most characteristic for gastric fundus preparations.

Safety investigation of team performance in accidents.

The paper presents the capacities of the performance evaluation of teamwork (PET) method. Its practicability and efficiency are illustrated by retrospective human reliability analyse of the famous nuclear and maritime accidents. A quantitative assessment of operators' performance on the base of thermo-hydraulic (T/H) calculations and full-scope simulator data for set of NPP design basic accidents with WWER is demonstrated. The last data are obtained on the 'WWER-1000' full-scope simulator of Kozloduy NPP during the regular practical training of the operators' teams. An outlook on the "evaluation system of main control room (MCR) operators' reliability" project, based on simulator data of operators' training is given.

Hb Jambol: a new hyperunstable hemoglobin causing severe hemolytic anemia.

We describe a new hyperunstable beta-chain variant due to a complex genomic rearrangement. The abnormal hemoglobin (Hb) was found as a de novo mutation in a 2-year-old Bulgarian girl with severe hemolytic anemia. The mutation was detected through RNA/DNA analysis. It represents a complex genomic rearrangement involving an insertion of 23 nts after IVS-II-535 (derived by triplication of the 12-nts adjacent sequence and subsequent deletion of 1 nt), a deletion of 310 nts extending from IVS-II-550 to the first nt of Cd 108 and an insertion of 28 nts at the deletion junctions (derived from the inverted sequence between nts +3,707 and +3,734 3' to the beta-globin gene termination codon). At the protein level this mutation leads to a deletion of 4 amino acid residues (Leu-Leu-Glu-Asn) at positions 105-108 and an insertion of 9 residues (Val-Pro-Ser-Val-Thr-Leu-Phe-Phe-Asp) at the same location, creating an abnormal elongated beta-chain of 151 amino acid residues. This highly unstable variant was named 'Hb Jambol' after the geographic location in which the patient resides.

[Effect of high temperatures in the housing on some indices of carbohydrate metabolism in layers]. / Vliianie na visokite temperaturi v pomeshteniiata vurkhu niakoi pokazateli na vuglekhidratnata obmiana na kokoshki nosachki

Experiments were carried out with a total of 60 layers of the White Plymouth Rock breed at the age of one year, acclimiatized to a temperature of 15 degrees C and relative humidity of 60 per cent. The following temperature and moisture regimes were tested: I--20 degrees C and 70 per cent; II--24 degrees C and 70 per cent; III--28 degrees C and 50 per cent; and IV--33 degrees C and 50 per cent. The birds of the control group were raised at 15 degrees C and relative moisture capacity of the air of 60-70 per cent. At the 24th hour and by the end of the seventh 24-hour period temperature vales of more than 28 degrees C led to dependable activization of the glucose-6-phosphatase enzyme in the liver and lower concentration of blood glucose and liver glycogen.

[Changes in the biochemical and hematological indices of chickens raised under high temperature and humidity]. / Vurkhu promenite v niakoi biokhimichni i khematologichni pokazateli pri pileta, otglezhdani pri visoka temperatura i vlazhnost.

Biochemical and hematological investigations were carried out with broilers raised at extreme temperature and humidity regimes-high temperature in combination with high relative humidity. Under the effect of high temperature (30-35 degrees C) and high relative humidity of the air (85-95 per cent) there was noted a rise of the lymphocytes and monocytes and a drop of the basophile, eosinophile, and pseudoeosinophile leukocytes in the white blood picture. After vaccination of the birds of the test groups with the vaccinal La Sota strain the blood serum showed negative titers. It was found that the Ca and P content in the blood serum of such broilers was higher as compared with that of the control group.

[Comparative study of microbial and mold pollution of the air in locations for poultry-keeping in various technologies]. / Sravnitelni izsledvaniia na mikrobnata zam'rsenost na v'zdukha v pomeshteniia za otglezhdane na ptitsi pri razlichni tekhnologii

Experiments were carried out to establish the microbial and mold contamination of the air on premises where birds were raised following varying patterns of tending and feeding. It was found that on premises for layers, raised in cages, the microbial contamination of the air was 2-3 times lower. The results obtained showed that the main source of air contamination in places where birds are kept is the litter (the other alternative being the floor type of raising). Differences were established in the egg laying, on the one hand, and the forage intake per 'market' egg, on the other, comparing the two types of raising. As all other factors of microclimate were within the normal range of zoohygiene standards, the basic factor which was incriminated to affect both productivity and forage intake per egg was the amount of the microbial flora of the air. Studies have shown that the number of birds per unit of area is an important factor determining the microbial contamination of the air and the health condition of birds.

[Veterinary health examination of the microclimate of the cow complex in the Vidin district]. / Veterinarnokhigienna otsenka na mikroklimata v kravekompleksite na Vidinski okrug.

Studied was the dynamics of the microclimate at the cow complexes in the district of Vidin, where cows are raised of the Dutch Black Pied, Bulgarian Simmental, and Bulgarian Red cattle breeds. The temperature and relative humidity dynamics of the air was followed up as well as the values of ammonia gas and carbon dioxide, the microbial contamination, the coefficient of natural illumination, and the level of noise. The effectiveness of the ventilation system was assessed by direct and indirect criteria as suggested by the authors. The veterinary and sanitary evaluation by individual elements of the microclimate is carried out on the basis of normative documents in the People's Republic of Bulgaria, USSR, and GDR.

[Contamination of the air with microorganisms at various distances from the poultry house]. / Zam'rsenost na v'zdukha s mikroorganizmi na razlichni razstoianiia ot pticharnitsite

Experiments were carried out to establish the microbial contamination of air (including moulds) at various distances from the buildings for raising birds. Results showed that the presence of organisms in the outer air is directly dependent on the microbial contamination of the air in the poultry houses. It was found that the distances between the buildings are too short and the air driven into the premises is of a high bacterial count. Comparative investigations have revealed that the contamination of the air out of the buildings is likewise dependent on the technologic design of the ventilation system. It is concluded that the low contamination of outdoor air is substantiated by an effective system of forced ventilation on the premises coupled with measures lowering the microbial count indoors.

[Effect of population density on the raising of broiler chickens]. / Prouchvaniia vurkhu vliianieto na gustotata pri otglezhdane na pileta broileri.

Experiments were carried out to study the influence of density in industrial broiler-raising. They took place during different seasons of the year and with a different density of habitation (12, 14, 16, 18, 20 and 22 pieces on m2) and through an optimization of technological indices in broiler-raising. The dynamism of microclimatic indices was traced out (temperature, humidity, gas composition, dust and microbe contamination of air in the buildings having a different density of habitation. Hematological and biochemical studies were carried out concerning total protein, protein fractions, contents of hemoglobin and number of erythrocytes, as well as the contents of alkaline reserves of blood. The experiments were also devoted to the growth and development, the consumption of fodder for a single unit of production, the morbidity rate and the death rate with chickens raised in different density. It was proved that the density of habitation exerts an influence over microclimatic indices. If the density is greater the contents of ammonia in the buildings is by 1.5 times over the zoohygienic requirements. Under the influence of the density of habitation certain changes occurred concerning the hematological and biochemical indices of blood. A correlation was observed between the density of habitation and the development of some diseases. Certain changes occurred also in the growth and in the development of broilers. By virtue of the results obtained, suggestions are put forward to optimize the density of habitation in industrial broiler-raising.