Interaction of the inotropic effect of norepinephrine and acetylcholine on the guinea pig's myocardium]

The experiments on guinea pig myocardium slices have been carried out to study the interaction of inotropic effects of different doses of norepinephrine (NE, from 10(-7) to 10(-5) mol/l) and acetylcholine (AC, from 10(-8) to 10(-6) mol/l). With an increase of NE concentration the negative influence of AC on the inotropic action is replaced by positive one. It is shown that there are optimal concentrations of NE and AC to exert a negative influence of AC on adrenergic inotropic effect (in these experiments--3 x 10(-7) mol/l for both influences). A decrease in frequency of contractions of AC on NE effect and positive influence of adrenergic myocardium stimulation on inotropic effect of AC, respectively. Such a type of relation of cardial effects of choline- and adrenergic influences is suggested to be designated by term "negatively accentuative antagonism" unlike the opposite type of choline-adrenergic interaction--"positive accentuative antagonism", under which AC increases inotropic effect of adrenergic myocardium stimulation, while adrenergic positive inotropic influences decrease AC effect.     

乙酰胆碱对豚鼠心房肌和心室肌的动作电位和收缩力的不同作用

实验采用标准玻璃微电极细胞内记录技术记录心肌细胞动作电位（action potential,AP）、肌力换能器记录心肌收缩力（force contraction,Fc）,研究乙酰胆碱（acetylcholine,ACh）对离体豚鼠心房肌、心室肌的作用。结果表明,10μmol/L ACh可缩短心房肌、心室肌动作电位的时程（action potential duration,APD）。心房肌APD在给药前后分别为208.57±36.05ms及101.78±14.41ms（n=6,P<0.01）,心室肌APD在给药前后分别为286.73±36.11ms及265.16±30.06 ms（n=6,P<0.01）。心房肌动作电位的幅度（action potential amplitude,APA）也降低,给药前后分别为88.00±9.35 mV及62.62±20.50 mV（n=6,P<0.01）,而心室肌APA无明显变化。ACh还降低心房肌、心室肌的收缩力,心房肌、心室肌Fc的抑制率分别为100％（n=6,P<0.01）和37.57±2.58％（n=6,P<0.01）。ACh对心房肌、心室肌APD和Fc的抑制作用在一定范围内（1nmol/L～100μmol/L）随ACh浓度的增高而增强。用Scott法求出ACh对心房肌、心室肌APD缩短作用的KD值,分别为0.275和0.575μmol/L,对Fc抑制作用的KD值分别为0.135和0.676μmol/L。各浓度下ACh对心房肌效应与心室肌效应作组间t检验,从10nmol/L到0.1mmol/L均有显著的统计学差异。此外,10μmol/L阿托品及20mmol/L     

Age-related changes in albumin and actin of human myocardium

Proteomic technologies revealed products of 2 genes (α-actin and albumin) in a human myocardium tissue. They exist as fragments and their appearance and increased content correlated with age. The age-related variants differ from the mature forms of these proteins by the absence of N-terminal fragments of the amino acid sequences. In the chronic ischemic heart disease (CIHD), these age-related proteins were found in 50% of cases (in the age group 31–40 years), whereas in the control group such combination was detected only in 10% of the examined individuals. Subsequent studies in this field would probably reveal molecular mechanisms responsible for impairment and/or ageing of the myocardium and also of adaptation/disadaptation mechanisms in the CIHD.     

Comparative studies on the positive inotropic effect of isoproterenol and bromobenzoyl-methyladamantylamine in guinea pig ventricular myocardium

The effects of bromobenzoyl-methyladamantylamine (BMA) on the transmembrane potentials, contractile force, and 42K efflux were investigated and compared to that of isoproterenol (IPR) in guinea pig ventricular myocardium. Both drugs exerted positive inotropic effect. BMA lengthened the action potential duration, depolarized the membrane, and decreased the Vmax. IPR increased the height of the plateau, accelerated repolarization, slightly increased the resting potential. In preparations depolarized partially by 26 mmol/l K+, both BMA (10(-4) mol/l) and IPR (10(-7) mol/l) induced slow response action potentials, but the duration of BMA-induced ones was twice longer than that of IPR-induced ones. BMA markedly reduced the 42K efflux from ventricular myocardium, whereas IPR had no effect on it. Moreover, BMA also decreased the 26 mmol/l K+-induced increment in 42K efflux, while IPR did not. It is concluded that BMA and IPR exert their positive inotropic effects on different ways. IPR increases the slow inward Ca2+ current directly by activating a phosphorylation process, whereas BMA enhances it indirectly by reducing the K+ conductance, lengthening the repolarization and consequently prolonging the time during which the slow inward Ca2+ current can be operative.     

Presynaptic effects of neuropeptide Y on [3H]noradrenaline and [3H]acetylcholine release

The electrically evoked release of radioactivity from mouse vas deferens and rat hypothalamic slices preloaded with [3H]noradrenaline was measured. In addition the release of [3H]acetylcholine from longitudinal muscle strip of guinea-pig ileum was also measured. Neurochemical evidence has been obtained that neuropeptide Y (NPY), although it co-exists and is released with (-)-noradrenaline (NA), it behaves differently as far as its effect on presynaptic modulation of chemical neurotransmission is concerned. It exerts a frequency-dependent presynaptic inhibitory effect on noradrenaline release from mouse vas deferens but has no effect on the electrically evoked release of NA from rat hypothalamus. Unlike NA, NPY does not influence the release of [3H]acetylcholine from the longitudinal muscle strip of guinea-pig ileum and does not potentiate the presynaptic effect of NA. It seems very likely, that the inhibitory effect of NPY is mediated via receptors. Its action is concentration dependent. While exogenous noradrenaline inhibited the release of noradrenaline by 91%, the maximum inhibition reached with NPY was not higher than 60%, indicating that either the intrinsic activity of NPY is lower or much less axon terminals are equipped with NPY receptors. Peptide YY (PYY) also reduced the release of NA from mouse vas deferens.     

Morphological changes in experimental infection in guinea pigs under the influence of prodigiozan and S-methylmethionine]

The effect of prodigiozan and S-methylmethionine on the level of histomorphological changes in the organs and tissues of guinea pigs with experimental typhoid fever, dysentery and staphylococcal infections, as well as the effect of prednizolone with respect to dysentery and staphylococcal infections were studied. In the control animals the highest histomorphological changes were observed on the 4th day after the infection in the liver, kidneys and spleen. In the animals with staphylococcal infection such changes were also observed in the lung tissue. In the animals treated with prodigiozan or S-methylmethionine in a dose of 20 mg or 0.3 ml of a 5 per cent solution respectively simultaneously with or 2 days after the infection the changes in the organs were less pronounced than those in the control. Under the effect of prednizolone used in a dose of 10 mg according to the same schedule the inflammatory-dystrophic changes in the internal organs of the animals with dysentery and staphylococcal infections were much higher as compared to the control.     

Age-related changes in microtubules in the guinea pig organ of Corti

Biochemical and immunocytochemical analyses have been used to provide new insights into age-related changes in the sensory and supporting cells of the guinea pig organ of Corti. Quantitative densitometry of immunoblots showed that, while levels of alpha-tubulin remained relatively constant in guinea pigs from 3 weeks to 18 months old, there were progressive shifts in some tubulin isoforms. Levels of tyrosinated tubulin increased with age, nontyrosinatable tubulin (delta2-tubulin) showed a compensatory decrease, but detyrosinated tubulin did not change; acetylated, polyglutamylated, and glycylated tubulin levels also decreased. Immunolabeled tissue sections showed that cell type-specific distribution of tubulin seen in young guinea pigs (tyrosinated in the microtubules of the sensory cells, and post-translationally modified isoforms in the supporting cells) did not change as animals aged. However, there were age-related decreases in labeling for alpha-tubulin and all post-translationally modified isoforms. Biochemical and immunocytochemical results both support an age-related decrease in the number and/or length of microtubules as well as an increase in the pool of soluble tyrosinated and detyrosinated tubulin. They further suggest that microtubules containing nontyrosinatable tubulin from older animals are the sites for further modification of tubulin by acetylation, polyglutamylation, and glycylation. Changes in tubulin isoform levels and stability of microtubules in the organ of Corti may alter its micromechanical properties; the resulting changes in conduction of sound-induced vibration would provide one mechanism for age-related hearing loss.     

Biological effects of exposure to high frequency electromagnetics on rabbits and guinea pigs]

To investigate the biological effects of exposure to feeble high frequency electromagnetism, skin surface temperature, blood vessel (arterioles and venules) diameter were examined, using infrared thermography, a laser doppler flowmeter, and a video microscope, respectively, in the ear of rabbits. After exposing the ear of rabbits to high frequency electromagnetism value of 9 MHz for 15 minutes, continued rising of local temperature was demonstrated. Though dilatation of arterioles was not seen. In addition, venules tended to dilate and blood flow also to increase, and microcirculation was accelerated at the site where electromagnetism was exposed. Hazardous effects of long term exposures of high frequency electromagnetism (9 MHz for 30 days, 8 hours/day) on guinea pigs were not observed in their behavior, food consumption, body and organ weights, hematological and biochemical values, macroscopic and microscopic findings on autopsy.     

Choline metabolism in the cerebral cortex of guinea pigs. Stable-bound acetylcholine

1. The turnover of synaptosomal (vesicular-cytoplasmic) and stable-bound (vesicular) acetylcholine isolated from cortical tissue was investigated after the administration, under local anaesthesia, of [N-Me-(3)H]choline into the lateral ventricles of guinea pigs. 2. Radioactive acetylcholine and choline present in acid extracts of subcellular fractions were separated by a combination of liquid and column ion-exchange and thin-layer chromatography. 3. The specific radioactivity and pattern of labelling of acetylcholine present in a fraction of monodisperse synaptic vesicles was found to be essentially the same as that of synaptosomal acetylcholine. 4. The specific radioactivity of stable-bound acetylcholine present in partially disrupted synaptosomes (fraction H) at short times (10-20min) after the injection of [N-Me-(3)H]choline was very variable and inversely related to the yield of acetylcholine in that fraction. 5. Evidence was found for the existence of two small, but highly labelled pools of acetylcholine, one which could be isolated in fraction H and the other which was lost when synaptosomes, after isolation by gradient centrifugation, were left at 0 degrees C or pelleted. 6. It is concluded that the results are best explained by metabolic differences among the nerve-ending compartments (thought to be vesicles) which contain stable-bound acetylcholine. Computer simulation of our experiments supports this possibility and suggests that the highly labelled pool in fraction H is present in vesicles close to the external membrane.     

Biochemical changes in guinea pigs after the application of high doses of ascorbic acid]

The effect of high doses of ascorbic acid (AA) (200 mg/kg body weight, s. c.) on the values of some biochemical parameters has been studied in guinea pigs (glucose, lactic acid, SH substances and GSH in blood, proteins and urea, and the LDH, MDH, ASAT, ALAT, and gamma-GT activities in the serum, the acid phosphatase activity in the liver, the gamma-GT activities in the liver and the kidney, and on the levels of SH substances and GSH in various organs). Ascorbic acid was administered to the animals in a single dose or in dialy doses for different periods (4 days, 2 weeks, and 7 weeks). The majority of the studied parameters showed a transient increase or decrease of the values which, however, after long term AA administration mostly returned to normal values. After 7 weeks, the level of urea in the serum remained increased (by approximately 30%) contrary to the decreased level of lactic acid, the gamma-GT activity in the serum, and the GSH level in some organs. In the experimental series carried out in the different seasons of the year, the results differed in some cases especially after short term AA administration. However, in a few cases, even the values obtained from the control animals tended to differ. If similar changes are to be expected in man after AA administration, then on the basis of our results it can be assumed that in the indicated cases the therapeutic long-term application of large AA doses does not present any hazard to the patient.     

Bronchial reactivities in guinea pigs to acetylcholine or histamine exposure

The bronchial reactivities in Hartley guinea pigs to acetylcholine (ACh) or histamine (Hist) were investigated, and the following results obtained; 1. Eight-week-old animals were exposed to ACh and Hist. A significant relationship was observed between the concentrations of the chemicals and the time needed to produce falling down (TNPFD) due to the asthmatic reaction to ACh and Hist. 2. Eight-week-old animals were exposed to 0.1% ACh and 0.05% Hist, for which the mean TNPFD +/- standard error were 377 +/- 33 sec and 122 +/- 5 sec respectivity. However, no difference in reactivity between male and female animals was noted. 3. Eight- and 9-week-old animals were exposed to 0.01% ACh and 0.025% Hist. A positive correlation was observed (r = 0.736, p less than 0.01) between the TNPFD for ACh and that for Hist. 4. Growing animals from 2 weeks to 20 weeks old were exposed to 0.08% ACh and 0.025% Hist. After inhalation of both chemicals, 6-week-old animals showed the greatest prolongation of mean TNPFD (lowest sensitivity). 5. Eight-week-old animals were exposed to 0.08% ACh and 0.025% Hist. With both of these chemicals, a positive correlation was observed between TNPFD and dose threshold (ACh r = 0.886, p less than 0.001; Hist r = 0.891, p less than 0.001).     

Met-enkephalin effects on histamine-induced bronchoconstriction in guinea pigs

We investigated the effects of the neuropeptide met-enkephalin on histamine-induced bronhoconstriction in an experimental model of asthma. Classic Konzett and R?ssler's method of whole body plethysmography modified by Gjuris, was applied in the study. This method represents a standard experimental model of bronchoconstriction, suitable for the evaluation of peptide effects on the histamine-induced bronchoconstriction. The results of the measurements implicate a dose-related modulatory effect of met-enkephalin on the bronchoconstrictor action of histamine. Met-enkephalin doses of 1 mg/kg and 10 mg/kg, respectively, caused statistically significant reduction of the histamine-induced bronchoconstriction. Estimated ED50 dose was 0.235 mg/kg. Further studies are needed to define practical and therapeutical use of the presented observations in respiratory pharmacology.     

The inotropic and chronotropic responses of the guinea pig and dog myocardium to isoprenaline and salbutamol.

The relative effects of isoprenaline and salbutamol on the inotropic and chronotropic responses of the denervated myocardium of the chloralose anesthetized dog and of the isolated guinea pig atrium, and the inotropic response of the isolated dog papillary muscle were studied. Both the in vivo dog heart and the in vitro guinea pig atrium displayed a similar relative response pattern to isoprenaline and salbutamol with regard to their inotropic and chronotropic responses. However, a comparison of the relative inotropic responses of the dog heart in vivo and in vitro showed that in vitro, salbutamol has a much lower affinity and efficacy for the adrenergic receptors than isoprenaline.     

Age-related changes of hypocretin in basal forebrain of guinea pig

Hypocretin-1 (hcrt-1) and hypocretin-2 (hcrt-2) have been implicated in a wide variety of functions including sleep and wakefulness as well as related behaviors. Many of these functions of the hypocretins involve the activation of cholinergic neurons in the basal forebrain (BF). These neurons have been shown to exhibit age-related changes in a variety of species. In the present experiment, in adult and aged guinea pigs, we compared hypocretin immunoreactivity in regions of the BF that include the medial septal nucleus (MS), the vertical and horizontal limbs of the diagonal band of Broca (VDB and HDB) and the magocellular preoptic nucleus (MCPO). In adult guinea pigs (3–5 months of age), all of the preceding BF regions contained dense hypocretin fibers with varicosities. On the contrary, in old guinea pigs (27–28 months), although the MS exhibited a similar intensity of hypocretin immunoreactivity compared with the adult guinea pig, there was a significant decrease in the intensity of immunoreactivity of hypocretinergic fibers in the VDB, HDB and MCPO. These data indicate that the hypocretinergic innervation of specific nuclei of the BF is compromised during the aging process. We suggest that the reduction in hypocretinergic innervation of the BF nuclei may contribute to the age-related changes in the states of sleep and wakefulness as well as deficits in related systems that occur in old age.     

Antiradiation effects of leucynferon on dogs and guinea pigs

In experiments with two species of animals (dogs, guinea pigs) irradiated with sublethal and lethal doses of gamma-rays, it was observed, that leucynferon had antiradiation effect. Course of injections: dogs--8 injections subcutaneus: 2.0 ml (1, 3, 5, 8, 12, 14, 21, 34 days after irradiation); guinea pigs--14 injections subcutaneus, 0.2 ml (1-14 days after irradiation). Therapeutical effect was explained by capacity of the preparation to defend the hemopoietic organs from the radiation and to stimulate hemopoiesis. Leucynferon hindered the development of acute radiation sickness symptoms. Immunoreactivity of dogs and guinea pigs in experimental group was more complete and restored faster. The growth of the automicroflora on the skin was restrained. Production of interferon-gamma (which is a function of T-lymphocytes) was restored faster.