[Detection of antibodies against pancreatic islet cells in clinical practice]

Development of diabetes mellitus caused by pancreatic beta-cell destruction of autoimmune origin is the result of a long lasting process. The most easily examinable feature of this stage is the occurrence of the islet cell antibodies. The sera which are positive for islet cell cytoplasmic antibodies (ICA), examined by indirect immunofluorescence, contain a mixture of antibodies. The glutamic acid decarbocylase (GAD), the tyrosin phosphatase (IA2), the insulin, and the GM2-1 glycolipid can be the targets of these antibodies. One can routinely examine the ICA, the GADA, the IA2 antibodies. The detection of antibodies against insulin (IAA) and GM-2-1 glycolipid is not invented in the routine laboratory work. The aim of the authors was the evaluation of clinical significance of occurrence of islet cell antibodies: one hundred and eighteen nondiabetic children an adult human being without known diabetic first degree relatives and 366 type 1 diabetic children and adult patients served as controls. The authors evaluated the predictive value of the different islet cell antibodies to the development of type 1 diabetes mellitus in 596 nondiabetic children with type 1 diabetic first degree relatives. The authors looked for markers of beta-cell destruction among sera of 320 diabetics manifested after 30 years of age with at least half a year of non-insulin-dependency and in the sera of 68 females suffered from gestational diabetes after 0-14 years of the index pregnancy. Finally the authors report 7 cases in which the examination of islet cell antibodies helped the diagnosis and classification of diabetes mellitus. Indirect immunofluorescence method was used for the detection of ICA, radioimmunoassay for that of GADA and IA2 antibodies. There was no positive reaction for ICA and GADA in the nondiabetic population without diabetic first degree relatives. Among the freshly diagnosed type 1 diabetic children 39% were positive for only ICA, 44% for only GADA and 80% for any antibodies. Among the freshly manifested type 1 diabetic adults ICA positivity only was observed in 21%, GADA positivity only in 7.1% and 93% for any antibodies. From the 595 nondiabetic children with type 1 diabetic first degree relatives 23 were positive for ICA, from whom 5 became diabetic during a two years observation period. These diabetic children had multiplex autoantibodies besides ICA. One child from this group, who was negative for ICA became diabetic, too. Among type 2 diabetic patients 13% were positive for ICA alone, 17% were positive for GADA alone and 27% were positive for any antibodies. The insulin dependency manifested in a short time was associated with antibody positivity. Among the gestational diabetics 10 were found positive for ICA. From them, 7 were type 1 diabetics, and 3 were type 2 diabetics at the time of the detection of antibodies. The authors suggest the need of determination of islet cell antibodies in the group of nondiabetic first degree relatives of type 1 diabetic patients (ICA, GADA, IA2 and IAA), in the group of non-insulin-dependent diabetics (ICA and GADA) as a screening for later insulin dependency, and in gestational diabetes after delivery (ICA) as screening for type 1 diabetes mellitus.

[Susceptibility to selected chemotherapeutics of Staphylococcus aureus strains resistant to methycyline isolated from clinical materials in the years 1991-1992 and 1997]

The susceptibility to selected chemotherapeutic agents was determined in 100 strains of Staphylococcus aureus methicillin-resistant (MRSA) isolated from clinical materials in 1991-1992 (50 strains) and in 1997 (50 strains). Two methods were used for the determination: disc method and antibiotic dilution in agar. The minimal inhibitory concentration (MIC) was determined for vancomycin, teicoplanin, furazolidone, nitrofurantoin, ofloxacin, gentamicin, netilmicin and trimethoprim. The concentrations of the chemotherapeutics in the substrate ranged from 0.125 to 512 mg/l. The obtained results served for drawing of the following conclusions: all studied MRSA strains isolated in 1991-1992 and in 1997 were sensitive to glycopeptide antibiotics: vancomycin and teicoplanin, to nitrofurans: nitrofurantoin and furazolidone, and to fusidic acid. MRSA strains isolated in 1991-1992 were sensitive to ofloxacin, but in 1997 about 80% of the strains were resistant to that antibiotic, and this resistance was noted in S. aureus strains with homogeneous resistance to methicillin. Increasing frequency of resistance to mupirocin was found, in 1991-1992 4% of the strains were resistant, and in 1997 the resistance of MRSA to that antibiotic was found in 12%. No changes occurred in the sensitivity of staphylococci to trimethoprim/sulfamethoxazole (cotrimoxazole). About 94% of strains in 1991-1992 and 1997 were sensitive to that drug. The sensitivity to cotrimoxazole is connected with one of its components (trimethoprim), with 94% of MRSA strains sensitive to it.

L-type calcium current in catecholamine-induced cardiac hypertrophy in the rat

This study investigates whether an increase in L-type calcium current (ICa) could explain the prolongation of the action potential associated with the cardiac hypertrophy produced by repeated administration of isoprenaline. Hypertrophy was induced by daily injection of isoprenaline (5 mg/kg i.p.) for 7 days in male Wistar rats. Under whole-cell voltage-clamp conditions, ICa was evoked in Na(+)- and K(+)-free solution, by step depolarizations from a holding potential of -45 mV in single left ventricular myocytes isolated from control and hypertrophied rat hearts. In the test group, heart weight to body weight ratio and cell membrane capacitance were increased by 30 and 34%, respectively. Peak ICa was increased by 26% (control, -1.46 +/- 0.06 nA, n = 17; hypertrophy, -1.85 +/- 0.13 nA, n = 19; P < 0.02). However, when normalized for cell capacitance, there was no significant difference in peak current density (control, -12.1 +/- 0.5 pA/pF; hypertrophy, -11.5 +/- 0.6 pA/pF). The voltage dependence of ICa was similar in both cell types. No change was observed either in the steady-state activation or inactivation kinetics, or in the time course of inactivation. The recovery from inactivation of ICa, when fitted with monoexponential function with time constant tau rec, was not changed significantly by hypertrophy (control, tau rec = 115 +/- 23 ms, n = 9; hypertrophy, tau rec = 120 +/- 12 ms, n = 15). The increased calcium current occurs in parallel with the increase in cell size. The prolonged action potential duration seen in this model must be explained by changes in currents other than L-type calcium current.

Transient outward current in catecholamine-induced cardiac hypertrophy in the rat

We have demonstrated that a daily injection of isoproterenol (5 mg/kg ip) for 7 days induces a 30% increment in heart weight-to-body weight ratio and prolongs the action potential duration (APD) in male Wistar rats. The underlying mechanism of the prolonged APD was investigated in this model of hypertrophy by measuring the transient outward potassium current (Ito) in left ventricular myocytes of the rat with whole cell voltage-clamp techniques. Cell membrane capacitance was increased by 39%: 122 +/- 3 (n = 23) and 171 +/- 5 (SE) pF (n = 20) in control and hypertrophy, respectively (P < 0.001). Ito was evoked in sodium-free solutions containing 0.5 mM Ca2+ and 2 mM Co2+ by step depolarizations from a holding potential of -80 mV. The amplitude of the 4-aminopyridine-sensitive Ito (at 70 mV) was reduced by 28% in hypertrophy: 3.2 +/- 0.3 (n = 23) and 2.3 +/- 0.4 (SE) nA (n = 20) in control and hypertrophy, respectively (P < 0.05). When normalized for cell capacitance, the reduction was much larger: 26.4 +/- 2.5 and 13.1 +/- 1.8 pA/pF in control and hypertrophy, respectively (P < 0.001). The voltage dependence of Ito was similar in both cell types. No change was observed in the steady-state activation and inactivation kinetics in the two groups, nor was there a change in the time dependence of inactivation. The recovery from inactivation of Ito when fitted with a monoexponential function was not changed significantly in hypertrophy: time constants = 8.2 +/- 0.4 (n = 13) and 8.3 +/- 0.3 ms (n = 12) in control and hypertrophy, respectively. These results show that Ito density is decreased in catecholamine-induced cardiac hypertrophy, but current kinetics are not affected. The reduced Ito density may underlie the prolongation of APD in this model of hypertrophy.

[Intrauterine management of Rh-alloimmunization]

The authors report the strategy of invasive management of Rh alloimmunisation in pregnancy. From the 34 pregnancies 6 were monitored by amniocenteses, 11 by fetal blood sampling, and 4 with combination of the two above mentioned diagnostic procedures. In 13 cases the fetuses were treated with intrauterine intravascular blood transfusions. All the procedures were ultrasound guided. The fetal blood sampling and the transfusions were carried out by puncturing the umbilical vein or artery. For transfusions, maternal blood was used in case of identical blood type, otherwise adult Rh negative, filtered, washed, irradiated blood was transfused. They report the complications as well, giving the cause of their fetal losses in details. There were no maternal complications observed. Out of the 34 pregnant women 25 had healthy newborns, which number is acceptable in this disease with a very high mortality rate. The authors underline that the technique of fetal blood sampling and intrauterine transfusion if needed is necessary in the management of Rh alloimmunised pregnancies.

Blood pressure and heart rate reactivity to mental strain in adolescent judo athletes

This exploratory investigation examined the association between maximal aerobic power (VO2max) and blood pressure (BP) and heart rate (HR) reactivity to mental challenge. Adolescent male judo athletes (n = 20) performed a 2-min mental arithmetic. Heart rate was recorded before, during, and after the arithmetic, and BP was recorded before and after the mental challenge. Blood pressure in the immediate stress-recovery period was not related to VO2max, but subjects having a higher maximal aerobic power showed faster HR recovery from mental stress than those having a lower VO2max. Subjects who showed earlier peak HR responses, during the stress episode, demonstrated lower average HR reactivity than subjects who attained the maximal HR response later in the stress period. The relationship between the interval to reach peak HR and the magnitude of reactivity deserves further attention. However, at present these findings should be viewed as tentative because of the uniqueness and size of the sample.

[Surgical treatment of bacterial endocarditis of the tricuspid valve]

We present a rare case of bacterial endocarditis of tricuspid valve caused by temporary intracardiac pacing. The 48-year old male patient developed complete a-v block during the 1st day of acute inferior myocardial infarction. Intracardiac electrode was inserted for temporary pacing. After 4 days signs of bacterial endocarditis developed. Patient was markedly febrile, moderate tachycardia with gallop rhythm and systolic murmur of tricuspid valve insufficiency were present. Dullness to percussion was audible at the base of right lung. Hepato- and splenomegaly appeared during the second month of hospitalization. Laboratory tests revealed: elevated ESR, leukocytosis with a shift to the left, several blood cultures were positive to Staphylococcus aureus. On repeated chest X-ray patchy infiltrates with thin-walled translucent pools were visible. Transthoracic and transoesophageal++ echocardiography provided more precise informations. Bacterial vegetations were visualised on the tricuspid valve. Coronary angiography revealed proximal occlusion of the right coronary artery and 75-80% stenosis of the left circumflex artery. Antibacterial treatment guided by blood cultures was begun: vancomycin combined with netilmycin, then tienamycin and diflucan--after 10 weeks treatment was decided to be unsuccessful and the decision about surgical treatment was made. In extracorporeal circulation posterior left leaflet together with granular bacterial growths was excised. Septal and anterior leaflets were found normal. Cultures made of excised tissue were positive for Staphylococcus aureus and subsequent treatment with fluoroquinolones gave satisfactory result. Postoperative echocardiography revealed only small tricuspid valve insufficiency. Coronary by-pass surgery was performed later because of the high risk of simultaneous operation.(ABSTRACT TRUNCATED AT 250 WORDS)

Developmental changes in long-opening behavior of L-type Ca2+ channels in embryonic chick heart cells

In the early (3-day) stage of development, long-lasting openings of the L-type Ca2+ channels (mode 2) occur in embryonic chick heart cells. Since mode-2 behavior is infrequently observed in adult heart cells of other species, in the present study, developmental change in behavior of the Ca2+ channel was examined in young (3-day) and old (17-day) embryonic chick heart cells. In the whole-cell voltage clamp, the L-type Ca2+ current carried by Ca2+ ions was smaller in amplitude and had a faster inactivation in 17-day cells than in 3-day cells. The peak current density was 8.1 +/- 0.2 microA/cm2 (mean +/- SEM, n = 5) and 5.1 +/- 0.3 microA/cm2 (n = 5) in 3-day and 17-day cells, respectively. When the charge carrier was Ba2+, the L-type Ca2+ channel current density was also smaller in 17-day cells (22.7 +/- 1.8 microA/cm2) than in 3-day cells (28.3 +/- 2.1 microA/cm2). In single-channel recordings, the mode-2 behavior was infrequent in 17-day cells compared with 3-day cells. High-open probability sweeps (with an open probability of greater than 0.25), reflecting mode-2 behavior, accounted for 20.2% and 3.7% in 3-day and 17-day cells, respectively. The ensemble-averaged currents in 17-day cells was 37% of that current in 3-day cells. In addition, decay of the averaged current appeared to be faster in 17-day cells than in 3-day cells. All data from the single-channel analysis agreed with the data from the whole-cell voltage clamp.(ABSTRACT TRUNCATED AT 250 WORDS)

Sodium-pump injury and arrhythmogenic transient depolarizations in catecholamine-induced cardiac hypertrophy

The pathogenesis of arrhythmogenic transient depolarizations (TDs) was studied by means of electrophysiological and cytochemical methods in normal and hypertrophied left ventricular myocardium of the rat. In hypertrophy induced by administration of 5 mg/kg isoprenaline once daily for 7 days, the myocardial membrane was depolarized, the action potential duration was prolonged and the Vmax was decreased, as compared with those of age-matched normal controls. TDs induced by a train of action potentials could be observed in hypertrophied myocardium, but not in normal control myocardium. Ryanodine completely abolished TDs, but the beta-adrenoceptor agonist noradrenaline and the adenylate cyclase activator forskolin were without effect. In cytochemical studies, the Na+,K(+)-ATPase activity was localized in the sarcolemma, and three times as much reaction product, which appeared on the inner side of the cell membrane, was found in the normal myocardium than in the hypertrophied myocardium. The results suggest that catecholamine-induced cardiac hypertrophy damages the membrane-bound Na+,K(+)-ATPase and causes a cAMP-independent intracellular Ca overload and TDs, thereby permitting abnormal impulse formation, which predisposes the diseased myocardium to develop arrhythmias.

Catecholamine-induced cardiac hypertrophy uncouples beta-adrenoceptors from slow calcium channels

Changes in the parameters of Ca(2+)-dependent slow action potentials (APs) and in their sensitivity to noradrenaline, forskolin, dibutyryl-cAMP and extracellular Ca2+ concentration were studied and compared in left ventricular trabeculae from normal control rats and rats with cardiac hypertrophy. Cytochemical studies were also carried out to determine changes in the activity of membrane-bound adenylate cyclase. Hypertrophy was induced by administration of 5 mg/kg isoproterenol once daily for 7 days. In hypertrophied cardiac muscle, the overshoot of the slow APs was increased by 75%, the maximum rate of rise (Vmax) increased by 76% and the AP duration at 50% repolarization (APD50) prolonged by 56%. The Vmax, an indicator of the slow inward Ca2+ current, increased, in a dose-dependent manner, in response to the beta-adrenoceptor agonist noradrenaline, the adenylate cyclase activator forskolin, the protein kinase activator cAMP and elevated Ca2+ concentration in normal control preparations, whereas in hypertrophied myocardium, the beta-agonist noradrenaline and the adenylate cyclase activator forskolin had no effect. In cytochemical studies with ATP as substrate, adenylate cyclase activity was localized in the sarcolemma, and significantly fewer reaction products appeared on the outer side of the cell membrane in hypertrophied myocytes than in control myocytes. The results suggest that catecholamine-induced cardiac hypertrophy damages the catalytic subunit of membrane-bound adenylate cyclase, thus uncoupling beta-adrenoceptors from slow Ca2+ channels in the transmembrane signalling process.

The synthesis and pharmacological activity of two new derivatives of benzazocine

Two new derivatives of benzazocine of anticipated analgesic action were synthesized. Pharmacological investigations were carried out to confirm their analgesic activity, affinity to the opiate receptor and potential antagonistic properties.

[Use of isolated myocytes and the patch clamp technic in pharmacological studies]

Effects of palmitylcarnitine, a toxic metabolite of ischaemia, on the electrophysiological properties of single ventricular myocytes of guinea pig were studied by means of patch clamp technique. Cells were enzymatically isolated by perfusing the heart with Ca-free Tyrode solution containing collagenase enzyme. Before experimentation, cells were allowed to recover in a regenerating solution for at least one hour at room temperature. An aliquot of the cell suspension was placed in a small (0.5 ml volume) chamber mounted on the stage of an inverted microscope. After a settling period of 10 minutes, the cells were superfused with Tyrode solution at a rate of 2 to 4 ml/min. Bath temperature was maintained at 35 degrees C. Patch electrodes were fabricated from glass capillary tubes. The electrodes having resistances of 2 to 4 M were connected to a LIST EPC-7 voltage clamp amplifier. The passive parameters (membrane resistance, time constant, capacitance), and resting and action potentials of the cells were recorded in current clamp mode, while the ionic currents (inward calcium, outward potassium) were recorded in voltage clamp mode. Palmitylcarnitine at 10(-6) M concentration increased the membrane resistance, time constant, and depolarized the cell membrane which was accompanied by a marked prolongation of the action potential duration. Under the effect of the drug, the outward potassium current responsible for the repolarization was decreased, while the inward calcium current responsible for the plateau phase was significantly increased mainly at positive membrane potentials. The steady-state activation and inactivation curves were shifted to less negative potentials. The results indicate that the changes in the membrane electrical properties play an important role in the development of the well-known arrhythmogenic effect of palmitylcarnitine.

Early prediction of fetal macrosomia in diabetes mellitus

We studied 374 pregnant diabetic women to determine the value of various ultrasound parameters in the prediction of fetal macrosomia. The correlation between ultrasonographic signs and maternal glycaemia in the development of fetal macrosomia was also studied. Significant correlation was observed between the accurence of hydramnios and future macrosomia during the second-trimester (p less than 0.001). Serum fructosamine levels as an index of maternal glycaemia in patients of macrosomic fetuses were significantly higher throughout the pregnancy as compared with mothers of infants with normal birth weight (p less than 0.001). These data suggest: 1. The presence of hydramnios in the second trimester is a useful predictor of macrosomia in diabetic patients (specificity: 86%, negative predictive value: 88%). 2. Maternal diabetic control during pregnancy has a significant influence on fetal growth and contributes to the development of fetal macrosomia. 3. The lack of correlation between the frequency of hydramnios and fructosamine levels suggests that a mechanism other than carbohydrate metabolism also plays an important role in the development of fetal macrosomia.

Calcium ions and 1-palmitoyl carnitine reduce erythrocyte electrophoretic mobility: test of a surface charge hypothesis

In ventricular muscle, 1-palmitoyl carnitine (1-PC) acted like calcium ions to shift the voltage-dependent inactivation of excitatory ion currents to less negative potentials. We proposed that 1-PC affected ion current kinetics by reducing surface negative charge. This hypothesis was tested in cell electrophoresis experiments where the electrophoretic mobility (EPM) of erythrocytes was measured in the absence and presence of test ligands. Calcium (0.18 to 3.6 mM) or 1-PC (10(-7) to 10(-6) M) reduced erythrocyte EPM in a concentration-dependent manner; the maximum reduction of EPM by either ligand was approximately 40%. In the presence of calcium, 1-PC produced a smaller decrement of EPM as expected from an occlusive interaction. Treatment of erythrocytes to remove sialic acids not only predictably reduced EPM but also diminished the ability of 1-PC and calcium to do so. These results indicate that the surface negative charge of sialic acid carboxyl groups is an important determinant both of erythrocyte EPM and of erythrocyte interaction with either 1-PC or calcium. The findings are consistent with the surface charge hypothesis for 1-PC action. We propose that 1-PC is not a neutral molecule at the cell surface but is able to neutralize surface negative charge by electrostatic interaction between the sialic acid carboxyl groups and the 1-PC quaternary ammonium moiety on the one hand and between the 1-PC carboxyl group and counterions near the membrane surface.

ECoG spectral analysis of apamin effects on the rat brain with pretrigeminal or high spinal transection of the central nervous system

Rats were injected into one lateral ventricle (icv) with apamin (50 and 100 ng per animal). The resulting desynchronization pattern in the electro-corticogram (ECoG) and the symptoms of apaminism (uncoordinated hypermotility and jerks) were monitored. The results of presented experiments contributed additional data concerning the topography of apamin effects. When injected into the ventricle of intact rats, generalized apaminism and massive desynchronization (reduction of total power and increase in beta waves band) of the cortical ECoG emerged. Transection of the spinal cord at the C1-C2 level (encéphalé isolé preparation) displayed apaminism of the head together with significant decrease in the total and relative power connected with a significant decrease in both beta and theta waves. Pretrigeminal transsection of the brain stem abolished the desynchronization in ECoG, whereas the generalized apaminism persisted, however it occurred after a longer latency than in intact animals. Morphine (10 mg/kg, sc) reversed the ECoG effects of apamin in intact rats but remained without effect on the motility changes. Our data indicate that apamin acts primarily on the brain stem and spinal cord, i.e. the structures possessing a sensory input, and by that way indirectly on the higher integrating systems.

Blockage of the fast sodium current by dimethindene in frog auricular fibres

The effect of dimethindene (DMI) on action potential and fast inward Na current (INa) of frog atrial fibres was studied using double sucrose gap voltage-clamp technique. DMI reduced the amplitude and maximum rate of rise of the action potentials without altering the resting membrane potential. The drug inhibited the fast Na conductance in a concentration-dependent manner, without changing the reversal potential. The shape of the current-voltage curve along the voltage axis remained unchanged in the presence of DMI. The time to peak of the INa was not significantly altered by the drug whereas the rate of the INa inactivation (tau h) was slowed. DMI shifted the steady-state inactivation curve of INa (h infinity) to more negative potentials, and increased the reactivation time constant of the sodium system (tau r). The inhibition of INa was use-dependent. The results suggest that DMI interacts with the inactivation mechanism of the sodium channel of the frog myocardium, and explain its favourable antiarrhythmic activity.

Interaction between adenosine and antiarrhythmic agents in atrial myocardium of guinea-pig

The effect of quinidine (class 1 agent) and verapamil (class 4 agent) on the adenosine-induced changes in the electrical and mechanical activity of the left atrial myocardium of guinea-pig was studied. Adenosine alone shortened the action potential duration, slightly hyperpolarized the membrane and increased the Vmax as well as induced a negative inotropic effect. Quinidine, a membrane-stabilizing drug, prolonged the action potential duration, decreased the Vmax, and increased the contractile force, i.e. diminished the electrical and mechanical changes in the atria treated with adenosine. These effects became more pronounced in the presence of aminophylline, a P1-purinoceptor blocker. In contrast, verapamil, a Ca-channel blocker, enhanced the adenosine-induced shortening in the early repolarization phase of the action potential, and the negative inotropic effect. This action of verapamil could be attenuated with aminophylline. The results suggest that adenosine can influence the effect of antiarrhythmics compounds and vice versa, and that the action of adenosine is possibly mediated via interaction with an extracellular P1-purinoceptor.

Mechanism of the antifibrillatory action of Chinoin-103, a new antiarrhythmic drug

The studies deal with the relationship between antifibrillatory and electrophysiological effects of Chinoin-103 (CH-103) on right ventricular myocardium of cats. In experiments carried out on right ventricles of open-chested cats, CH-103 markedly increased the fibrillation threshold in a dose-dependent manner. In electrophysiological experiments performed on isolated, electrically driven right ventricular papillary muscles of cats, the drug, at the concentrations needed to increase the fibrillation threshold, decreased the maximum rate of rise of action potential (Vmax) without changing the resting membrane potential. The reduction of Vmax was found to be voltage- and use-dependent. Steady state inactivation of Vmax, an index of the fast inward Na current, was shifted to more negative potentials by CH-103. During a train of stimuli applied after a long resting period, the amplitude of Vmax decreased gradually and reached a new steady state within 8-10 action potentials, thus suggesting that CH-103 inhibited the rate of recovery from inactivation of the fast inward Na+ current. It is concluded that the antifibrillatory effect of CH-103 may be due to a use-dependent block of fast inward Na+ current, which can suppress extrasystoles and tachycardias.

Habenulo-interpeduncular lesions: the effects on pain sensitivity, morphine analgesia and open-field behavior in rats

The lesions of medial habenular nuclei increased the pain sensitivity, enhanced the analgesic activity of morphine and slightly activated the behavior. The lesion of fasciculus retroflexus, a pathway connecting habenular nuclei with interpeduncular nucleus enhanced the pain sensitivity less markedly, did not change the efficacy of morphine analgesia, but significantly increased the activity of animals. The lesion of interpeduncular nucleus influenced the pain sensitivity to a smallest degree, did not change the analgesic activity of morphine, but dramatically increased the activity of animals. The activation did not resemble the aimless excitation of amphetamine-treated or raphe-lesioned rats, and no signs of increased emotionality or irritability were noted. The results are interpreted as an evidence of habenulo-interpenduncular complex being a part of a system, involved in the regulation of behavioral activity and the sensitivity to the aversive stimuli. These functions are in all probability mediated partly through substance P and met-enkephalin containing neurons, present in these structures.

Eradication of some infectious pig diseases by perinatal tiamulin treatment and early weaning

From 10 days before the expected date of farrowing onwards, 97 sows infected by Mycoplasma hyopneumoniae and Treponema hyodysenteriae were given tiamulin daily at a dosage of 20 mg/kg bodyweight via the feed. Three days before farrowing the sows were washed with a disinfectant and transferred to an isolated farrowing house. The sucking piglets remained with their dams for five days, during which time the sows continued to receive the tiamulin-containing feed. The sucking piglets also received tiamulin daily at a dosage of 30 mg/kg bodyweight. At six days old the weaker piglets of the litter were returned to the original herd, together with their dams. A total of 574 piglets of about 1.5 kg bodyweight each were transferred to an isolated and previously disinfected pig farm and reared there. A total of 13.8 per cent of these pigs died by 50 days old. On the isolated farm, 10.9 per cent of the 829 second generation piglets born to the 101 first generation sows, died up to the age of 50 days. On the isolated farm about 2000 pigs were subjected to repeated clinical, pathological and laboratory examinations for M hyopneumoniae, T hyodysenteriae, Aujeszky's disease virus and Leptospira species during the three year period of study. No evidence of infection with any of these agents was found in the 2000 pigs of the isolation herd, although the original sow herd had been latently infected by these pathogens. No maternally derived antibodies against these pathogens were detectable in sera of three-day-old sucking piglets of the second and third generations.

Antagonism between adenosine and bromobenzoyl-methyladamantylamine, a K+-channel blocker, in atrial myocardium of guinea pig

The effect of bromobenzoyl-methyladamantylamine (BMA) on the adenosine-induced changes in the electrical and mechanical activity of the atrial muscle, and the effect of adenosine on the slow action potentials induced by BMA in K+-depolarized atrial myocardium of guinea pig were studied. BMA was able to antagonize the adenosine-induced shortening of the action potential duration and negative inotropic effect. This action of BMA was potentiated by theophylline, and reduced by dipyridamole. Adenosine depressed the BMA-induced slow action potentials. The results suggest that there may be an antagonism between BMA and adenosine.

Action of dimethindene on the electrophysiological and mechanical properties of atrial and ventricular myocardium of guinea-pig

The effect of dimethindene (DMI) on transmembrane potentials and contractile force was studied in atrial and ventricular myocardium of guinea-pigs. DMI reduced the maximum rate of depolarization (Vmax) without changing the resting potential in both preparations. In ventricular myocardium, DMI shortened the action potential duration and exerted a negative inotropic effect. In atrial muscle, the drug prolonged the action potential duration and induced a positive inotropic effect which could be antagonized with neither the alpha-blocker phentolamine, nor the beta-blocker pindolol, H1-blocker mepyramine and H2-blocker cimetidine. DMI had no effect on the slow action potentials induced by caffeine in K+-depolarized myocardial preparations. The drug consistently shifted the sodium inactivation curve to more negative membrane potentials. The results suggest that DMI has a quinidine-like membrane-stabilizing property, which may be due to its fast Na+ channel blocking activity. The differential inotropic action of the drug in atrial and ventricular myocardium is discussed.

Effect of dimethindene, an antihistaminic drug, on the transmembrane potentials of mammalian myocardium

Dimethindene (DMI) decreased the maximum rate of rise of action potential (AP) without changing the resting potential in cat ventricular myocardium. DMI abolished the histamine-induced slow APs in left atria but not in right ventricular papillary muscles of guinea-pig, suggesting that DMI blocked the histamine H1-receptors.

Effect of Chinoin-103, a new antiarrhythmic drug, on the transmembrane potentials, ionic currents and contractile force in heart muscle

The effect of Chinoin-103 (CH-103) was examined on the electrophysiological and mechanical properties of the isolated guinea-pig atrial and ventricular myocardium and on membrane ionic currents of the frog atrial trabeculae using glass-microelectrode and voltage clamp techniques. In the guinea-pig atrial and ventricular myocardium, CH-103 had no effect on the resting membrane potential, but decreased the action potential overshoot and maximum rate of depolarization (Vmax). CH-103 exerted a negative inotropic effect on both preparations. The drug (10(-5) M) consistently shifted the membrane responsiveness curve to more negative potentials. CH-103 rapidly abolished the membrane electrogenesis in myocardial preparations pretreated with 5 mM MnCl2. The slow action potentials induced in K+-depolarized preparations by caffeine were slightly reduced, whereas the isoproterenol-induced ones were markedly depressed by the drug. In voltage clamp experiments, CH-103 strongly reduced the fast inward Na+ current, but hardly decreased the slow inward Ca2+ current and the delayed outward K+ current. These results suggest that CH-103 has both membrane stabilizing and beta-blocking effects, and can explain the antiarrhythmic action of CH-103.

Inhibition of myocardial K+ channels by bromobenzoyl-methyladamantylamine, an adamantane derivative

The effect of bromobenzoyl-methyladamantylamine (BMA) on transmembrane potentials and contractility of atrial and ventricular myocardium of guinea-pig and cat, as well as on transmembrane ionic currents of the frog atrial trabeculae was studied using conventional glass microelectrode and double sucrose-gap voltage clamp techniques. BMA markedly prolonged the action potential duration, depolarized the cell membrane, reduced the rate of rise of the action potential and exerted a positive inotropic effect on non-clamped myocardial preparations. The drug-induced pacemaker activity in ventricular working muscle of cat. Moreover, BMA antagonized the effects of the K+ channel activator acetylcholine in a dose-dependent manner. BMA was found to induce slow response action potentials in K+ -depolarized ventricular myocardium of guinea-pig. In voltage clamp experiments, BMA reduced the outward K+ current but had no effect on either rapid inward Na+ or slow inward Ca2+ currents. The results suggest that BMA is capable of selectively blocking the myocardial K+ channels.

Effect of dantrolene sodium on the mechanical and electrical properties of guinea-pig ventricular myocardium

The effect of dantrolene sodium on transmembrane potential and contractile force was examined in electrically driven right ventricular papillary muscles of guinea-pigs. Dantrolene sodium (2 x 10(-4) M) shortened the action potential and increased overshoot and the maximum rate of depolarization (Vmax), without changing the resting potential. Contractile force was increased by the drug. The dantrolene sodium-induced changes could be antagonized with pindolol, a beta-adrenoceptor blocker. Dantrolene sodium exerted a negative inotropic effect in papillary muscles of guinea-pigs pretreated with reserpine. The drug increased the amplitude and Vmax of slow action potentials. Pindolol was able to abolish this action. The results suggest that the positive inotropic effect of dantrolene sodium may be due to catecholamine release, whereas the drug has a negative inotropic effect by itself.

Effect of dantrolene sodium on the transmembrane potentials and contractility of guinea pig atrial myocardium

Dantrolene sodium (3 X 10(-4) M) exerted a biphasic effect on the mechanical and electrical activity of the isolated guinea pig left atrium. In the first phase, the drug increased the contractile force by about 200%, and prolonged the action potential duration. This transient positive inotropic effect was antagonized by D-600, a slow Ca2+ channel inhibitor. In the later phase, the drug gradually decreased the amplitude of contractions, shortened the action potential duration and induced contracture. Dantrolene sodium increased the rate of depolarization and overshoot of Ca2+ -mediated slow action potentials. The results suggest that dantrolene sodium increases the slow inward Ca2+ current, causing a positive inotropic effect in the atrial myocardium. The late negative inotropic effect of the drug could be due to a secondary inhibition of the slow inward Ca2+ current due to an increased intracellular free Ca2+ concentration as a consequence of other actions of the drug.

Substance P, hexapeptide pGlu6(SP6-11), analgesia and serotonin depletion

Substance P caused marked analgesic activity in rats after intraventricular administration and in mice after intraperitoneal injection. The hexapeptide pGlu6(SP6-11) was active in mice, but not in rats. Depletion of serotonin with p-chlorophenylalanine abolished the antinociceptive activity in mice, but not in rats, whereas lesion of raphe nuclei blocked the activity of substance P in the latter animals. Although different routes of administration were used, the results seem to indicate different mechanisms of analgesic activity of both peptides in rats and mice, as well as the different role of serotonergic transmission in pain control mechanisms in both species.

A study of the enzyme inducing effect of physical exercise after partial hepatectomy in the rat

Relationships among muscular exercise, enzyme induction and liver regeneration were studied. Exercized and control groups of rats showed no appreciable difference in liver regeneration rate expressed in liver weight increase. The enzyme-inducing effect of muscular exercise manifested itself also in the regenerating liver. The shortening of hexobarbital sleeping time occurred earlier in the group which had been trained already before partial hepatectomy than in the other group in which exercise training started only after the intervention. This was explained by a higher physical working capacity achieved by previous training, which was retained also after partial hepatectomy. This finding provides further indirect support for the relationship between enhanced biotransformation rate and muscular exercise, the latter being the agent in the induction process.

The effects of lesion of mesolimbic dopamine neurons on pain threshold and morphine analgesia in rats

Lesions of ventral tegmental area, localised in the region of A 10 group of dopaminergic mesolimbic neurons decreased the pain threshold in rats. The absolute threshold values in morphine treated animals with the above lesion were lower than in sham-operated controls, however, the thresholds expressed as percentage of predrug threshold values did not differ in both lesioned and sham-operated animals. It is thought, that lesions of ventral tegmental dopamine neurons decrease the pain threshold due to the increase of general excitability of animals, and that there is no direct involvement of the lesioned structure in the primary mechanism of morphine analgesia.