Effect of histamine-sensitizing factor of Bordetella pertussis on pharmacologic response of rat atria

The effects of sensitization with the histamine-sensitizing factor (HSF) of Bordetella pertussis as well as Bordetella vaccines on a pharmacologic response in rat heart preparations were determined. In normal rats the spontaneous beating of atria in vitro through the positive inotropic action produced by the addition of epinephrine was inhibited immediately by addition of acetylcholine, whereas in the B. pertussis vaccine-treated rats the exciting atria were scarcely inhibited by acetylcholine. Neither B. parapertussis nor B. bronchiseptica vaccines induced such an altered atrial response in rats. Of the B. pertussis cell components purified HSF induced the altered response at the minimal dose of 0.1 microgram per rat, and a dose of 1 microgram or more produced the maximal change. This altered atrial-inducing activity of HSF was inactivated by heating at 63 C for 30 min, and was neutralized by anti-HSF rabbit serum. The altered response rose quickly in 1 day after i.v. injection of 1 microgram of HSF, reached a plateau in 3 to 5 days, which lasted at least 14 days, and disappeared completely 56 days later. HSF failed to produce directly any functional damage to the beating atria in vitro, and to induce the altered response of the normal rat atria by incubation with as much as 10 microgram of HSF per bath (50 ml) for 4 hr. A trace stimulation was found in the normal rat atria as well as in perfused frog hearts, if HSF was given directly at a dose of 20 microgram per bath.     

Glycerol-Releasing Activity of Histamine-Sensitizing Factor of Bordetella pertussis for Rat Adipocytes In Vitro

Histamine-sensitizing factor (HSF) purified from Bordetella pertussis induced specifically the release of glycerol from rat epididymal adipocytes in vitro. The most sensitive and reproducible results were obtained by using 1 to 2 × 10⁵ adipocytes/tube from rats weighing 150 to 200 g, and by incubation at 37 C for 180 min. After a lag period of about 60 min, HSF-treated adipocytes released glycerol in increasing amounts between 60 and 240 min, depending on the dose of HSF. A close correlation between the glycerol-releasing (GR) activity of HSF for adipocytes and histamine-sensitizing or leukocytosis-promoting activity in mice was observed. The GR activity was inactivated by heating at 56 C for 60 min, 63 C for 30 min or 96 C for 10 min. The adipocytes washed out with a Krebs-Ringer bicarbonate buffer immediately after being exposed to HSF for 1 to 3 min manifested about 75% of the total GR activity induced by HSF, and those washed out after being exposed for 30 min or longer had full activity. Anti-HSF serum neutralized the activity when it was added to adipocytes simultaneously with HSF, but did not when it was added 30 min after being exposed to HSF. By using both native and ¹²⁵I-labeled HSF, the ratio of binding of HSF to adipocytes was estimated to be 10 to 15% of the total HSF per 2 × 10⁵ cells/tube, and to be about 1,000 molecules of HSF per cell to induce the release of glycerol. The GR activity induced with 10 ng of HSF was inhibited by addition of insulin at a dose of over 1 μIU/tube, but not by concanavalin A.     

Species differences in the negative inotropic effect of acetylcholine and soman in rat,guinea pig,and rabbit hearts

1. Acetylcholine reduced atrial contractions by 82.5% in guinea pig, 50.8% in rat, and 41.5% in rabbit.2. The EC₅₀ values for the negative inotropic effect of acetylcholine were 3.3 × 10⁻⁷ M in rat and guinea pig atria and 4.1 × 10⁻⁶ M in rabbit atria.3. There was no correlation between the species differences in the negative inotropic effect of acetylcholine in atria and the density or affinity of acetylcholinesterase or muscarinic receptors.4. Inhibition of atrial acetylcholinesterase with soman reduced the ec₅₀of acetylcholine three-fold in all species, but did not change the maximal inotropic effect of acetylcholine.5. Species differences in the negative inotropic effect of acetylcholine may be caused by differences in the coupling between myocardial muscarinic receptors and the ion channels that mediate negative inotropy.     

Luminescent nanoparticles for rapid monitoring of endogenous acetylcholine release in mice atria

The present work introduces for the first time a nanoparticulate approach for ex vivo monitoring of acetylcholinesterase‐catalyzed hydrolysis of endogenous acetylcholine released from nerve varicosities in mice atria. Amino‐modified 20‐nm size silica nanoparticles (SNs) doped by luminescent Tb(III) complexes were applied as the nanosensors. Their sensing capacity results from the decreased intensity of Tb(III)‐centred luminescence due to the quenching effect of acetic acid derived from acetylcholinesterase‐catalyzed hydrolysis of acetylcholine. Sensitivity of the SNs in monitoring acetylcholine hydrolysis was confirmed by in vitro experiments. Isolated atria were exposed to the nanosensors for 10 min to stain cell membranes. Acetylcholine hydrolysis was monitored optically in the atria samples by measuring quenching of Tb(III)‐centred luminescence by acetic acid derived from endogenous acetylcholine due to its acetylcholinesterase‐catalyzed hydrolysis. The reliability of the sensing was demonstrated by the quenching effect of exogenous acetylcholine added to the bath solution. Additionally, no luminescence quenching occurred when the atria were pre‐treated with the acetylcholinesterase inhibitor paraoxon.     

Choline Modulates Cardiac Membrane Repolarization by Activating an M3 Muscarinic Receptor and its Coupled K+ Channel

Choline is a necessary substrate of the lipid membrane and for acetylcholine synthesis. Accumulating evidence indicates that besides being a structural component, choline is also a functional modulator of the membrane. It has been shown to be a muscarinic acetylcholine receptor (mAChR) agonist and can induce a novel K⁺ current in cardiac cells. However, the potential role of choline in modulating cardiac functions remained unstudied despite that mAChRs are known to be important in regulating heart functions. With microelectrode techniques, we found that choline produced concentration-dependent (0.1∼10 mm) decreases in sinus rhythm and action potential duration in isolated guinea pig atria. The effects were reversed by 2 nm 4DAMP (an M₃-selective antagonist). Whole-cell patch-clamp recordings in dispersed myocytes from guinea pig and canine atria revealed that choline is able to induce a K⁺ current with delayed rectifying properties. The choline-induced current was suppressed by low concentrations of 4DAMP (2∼10 nm). Antagonists toward other subtypes (M₁, M₂ or M₄) all failed to alter the current. The affinity of choline (K _d ) at mAChRs derived from displacement binding of [³H]-NMS in the homogenates from dog atria was 0.9 mm, consistent with the concentration needed for the current induction and for the HR and APD modulation. Our data indicate that choline modulates the cellular electrical properties of the hearts, likely by activating a K⁺ current via stimulation of M₃ receptors. Received: 1 December 1998/Revised: 12 February 1999     

Reentrant tachyarrhythmias in right atria of cardiomyopathic versus healthy Syrian hamster

We studied the role of acetylcholine (ACh) and calcium overload in the induction of atrial flutter or atrial fibrillation (AF) in right atria from 34 normal male Syrian hamsters (F1B) and 33 cardiomyopathic Syrian hamsters (BIO 14.6) associated with focal myocardial necrosis. Action potential (AP) was recorded with conventional microelectrode techniques and twitch force by a transducer. ACh (0.1, 1 and 10 µM) induced high-frequency AF (around 33 Hz) along with tension oscillations and contracture in 7 of 12 normal hamster atria. These effects of ACh were abolished by tetrodotoxin or quinidine as well as by atropine. In contrast, ACh induced AF only in 1 of 12 myopathic atria. In both normal and myopathic atria, ACh induced similar changes in AP duration, spontaneous rate and force. The effects of calcium overload were tested by means of a high [Ca²⁺]_o (8.1 mM) low [K⁺]_o (1 mM) solution in another series of experiments. This solution also induced incidence of AF higher in normal (10/12) than in myopathic atria (4/12). The calcium load was also increased by high-frequency pacing (32 Hz for 3 or 30 s): AF occurred in normal atria (5/8), but not in myopathic atria (0/8). Measurement of the refractory period revealed a longer refractory period in myopathic than in control atria. We concluded that the lower incidence of AF in myopathic atria was probably due to their longer refractory period and the associated focal myocardial necrosis which then hindered the establishment of such a reentrant rhythm.     

Muscarinic acetylcholine responses in the early embryonic chic retina

The action of acetylcholine on cytoplasmic Ca²⁺ concentration ([Ca²⁺]_i) was studied in early embryonic chick retinae. Whole neural retinae were isolated from embryonic day 3 (E3) chicks and loaded with a Ca²⁺-sensitive fluorescent dye (Fura-2). Increases in [Ca²⁺]_i were evoked by the puff application of acetylcholine at concentration than 0.1 μM. The Ca²⁺ response became larger in dose–dependant manner up to 10 μM of acetylcholine applied. The rise in [Ca²⁺]_i was not due to the influx of Ca⁺² through calcium channels, but to the release of Ca²⁺ from internal stores. A calcium channel antagonist, nifedipine, which completely blocks the Ca²⁺ rise caused by depolarization with 100 mM K⁺, had no effects on the acetylcholine response and the Ca²⁺ response to acetylcholine occurred even in a Ca²⁺-free medium. The Ca²⁺ response to acetylcholine was mediated by muscarinic receptors. Atropine of 1 μM abolished the response to 10 μM acetylcholine, whereas d-tubocurarine of 100 μM had no effects. Two muscarinic agonists, muscarine and carbamylcholine (100 μM each), evoked comparable responses with that to 10 μM acetylcholine. The developmental change of the muscarinic response was examined from E3 to E13. The Ca2+ response to 100 μM carbamylcholine was intense at E3-E5, then rapidly declined until E8. The muscarinic Ca²⁺ mobilization we found in the early embryonic chick retina may be regarded as a part of the “embryonic muscarinic system” proposed by Drew's group, which appears transiently and ubiquitously at early embryonic stages in relation to organogenesis. 1994 John Wiley & Sons, Inc.     

Nicotine Tolerance in Chromaffin Cell Cultures: Acute and Chronic Exposure to Smoking-Related Nicotine Doses

Abstract: Nicotine tolerance and dependence are key aspects of tobacco addiction; however, the cellular mechanisms underlying these phenomena are poorly understood. Adrenal chromaffin cells release catecholamines upon exposure to nicotine and with repeated exposure this response exhibits nicotine tolerance. Using bovine adrenal chromaffin cells in culture, we have demonstrated acute and chronic nicotine tolerance at doses relevant to that in the blood and tissues of smokers (10–⁷M to 10–⁶M). Chromaffin cells are preexposed to low doses of nicotine for time periods ranging from 10 min to 7 days and then subsequently challenged with a maximally stimulating dose of nicotine (10–⁵M) for 10 min, all at 37°C. Preexposure to nicotine results in a depression of ⁴⁵Ca uptake and catecholamine release upon subsequent nicotine challenge. Acute tolerance or desensitization of nicotinestimulated catecholamine release begins to occur in minutes after preexposure to 10–⁶M nicotine at 37°C. The depression of catecholamine release upon preexposure to nicotine is both dose and temperature dependent and is not seen with potassium-evoked release. Chronic exposure to 10–⁷M nicotine for 3 days led to a depression of the secretory response to ～70% of control responses. There was a trend toward recovery of full response by days 5 and 7 of 10–⁷M nicotine preexposure. Nearly complete depression of the nicotine-evoked release occurs within the first day of exposure to 10–⁶M nicotine and persists for at least a week of nicotine exposure at 37°C. Nicotine tolerance in the catecholamine release response was reversible after nicotine washout. Cross-tolerance between nicotine, acetylcholine, and dimethylphenylpiperazinium was observed after 5 days’exposure to one agonist and subsequent challenge with a different agonist. Acute tolerance is likely to be related to nicotinic receptor desensitization. The mechanisms of chronic tolerance and potential adaptive cellular changes remain to be determined.     

Radiation response and regulation of apoptosis induced by a combination of TRAIL and CHX in cells lacking mitochondrial DNA: a role for NF-κB-STAT3-directed gene expression

Mitochondrial DNA depleted (ρ⁰) human skin fibroblasts (HSF) with suppressed oxidative phosphorylation were characterized by significant changes in the expression of 2100 nuclear genes, encoding numerous protein classes, in NF-κB and STAT3 signaling pathways, and by decreased activity of mitochondrial death pathway, compared to the parental ρ⁺ HSF. In contrast, the extrinsic TRAIL/TRAIL-Receptor mediated death pathway remained highly active, and exogenous TRAIL in a combination with cycloheximide (CHX) induced higher levels of apoptosis in ρ⁰ cells compared to ρ⁺ HSF. Global gene expression analysis using microarray and qRT-PCR demonstrated that mRNA expression levels of many growth factors and their adaptor proteins (FGF13, HGF, IGFBP4, IGFBP6, and IGFL2), cytokines (IL6, ΙL17Β, ΙL18, ΙL19, and ΙL28Β) and cytokine receptors (IL1R1, IL21R, and IL31RA) were substantially decreased after mitochondrial DNA depletion. Some of these genes were targets of NF-κB and STAT3, and their protein products could regulate the STAT3 signaling pathway. Alpha-irradiation further induced expression of several NF-κB/STAT3 target genes, including IL1A, IL1B, IL6, PTGS2/COX2 and MMP12, in ρ⁺ HSF, but this response was substantially decreased in ρ⁰ HSF. Suppression of the IKK–NF-κB pathway by the small molecular inhibitor BMS-345541 and of the JAK2–STAT3 pathway by AG490 dramatically increased TRAIL-induced apoptosis in the control and irradiated ρ⁺ HSF. Inhibitory antibodies against IL6, the main activator of JAK2–STAT3 pathway, added into the cell media, also increased TRAIL-induced apoptosis in HSF, especially after alpha-irradiation. Collectively, our results indicated that NF-κB activation was partially lost in ρ⁰ HSF resulting in downregulation of the basal or radiation-induced expression of numerous NF-κB targets, further suppressing IL6–JAK2–STAT3 that in concert with NF-κB regulated protection against TRAIL-induced apoptosis.     

Production of acetylcholine in rat brain following thiamine deprivation and treatment with thiamine antagonists

Abstract— The effects of thiamine deprivation and of treatment with the thiamine antagonists, oxythiamine and pyrithiamine, on the storage and synthesis of acetylcholine were studied in rats. Rats treated with pyrithiamine always developed ataxia and convulsions, and they died in an average of 36 ± 5.0 hr after onset of convulsions. Injections of sublethal doses of eserine after onset of convulsions had no effect or shortened survival time. If injections were started before the onset of convulsions, the survival time was increased to 56 ± 3.3 hr. The content of total acetylcholine-like compounds, measured by bioassay, in the brain was decreased in all three types of thiamine deficiency. On the other hand, the amount of parenterally administered [¹⁴C]pyruvate converted to [¹⁴C]acetylcholine in vivo was affected only by treatment with pyrithiamine. The increase found was probably due to an increased permeability of the blood-brain barrier to the pyruvate. Conversion of [¹⁴C]pyruvate to [¹⁴C]acetylcholine in vitro was decreased significantly in homogenates of brains from both oxythiamine and pyrithiamine-treated animals.     

The atrial proliferative response following partial ventricular amputation in the heart of the adult newt. A light and electron microscopic autoradiographic study

This investigation characterizes the atrial proliferative response following partial ventricular amputation in adult newts. Newts processed for light microscopic autoradiography were given either a single injection (SI) of ³H-thymidine 1 hr before fixation and killed at intervals up to 25 days after ventricular wounding or were given six injections (MU), one every 12 hr, and fixed at intervals up to 21 days. Atria processed for EM autoradiography (EMA) were removed 1 hr after injection and 15 days after wounding. Mitotic (MI) and thymidine-labeling indices (TI) were calculated for the epicardium, subepicardial CT and myocardium of both atria. Sham-operated and unoperated animals served as controls. There was no localization of labeled or mitotic cells within the atria of SI or MU animals (P > 0.16) for any cell type. MI and TI for the epicardial and CT cells did not differ from sham-operated controls (P > 0.35). A maximum TI of 6.4% and MI of 0.4% was observed in the atrial myocardium of SI animals on day 15. A maximum TI of 13.8 and 5.9% was observed for the left and right atrial myocardium, respectively, of MI animals on day 12. EMA confirmed that atrial myocytes were engaging in mitosis and DNA synthesis.     

Ca2+ responses to acetylcholine and adenosine triphosphate in the otocyst of chick embryo

The action of acetylcholine and adenosine triphosphate (ATP) on cytoplasmic Ca²⁺ concentration ([Ca²⁺]_i) was studied in the otocyst epithelium of embryonic day 3 chicks with Ca²⁺-sensitive fluorescence measurements. Increases in [Ca²⁺]_i were evoked by the bath application of acetylcholine (1 μM or higher). The rise in [Ca²⁺]_i was due to the release of Ca²⁺ from intracellular Ca²⁺ stores, since the Ca²⁺ response occurred even in a Ca²⁺-free medium. The Ca²⁺ response to acetylcholine was mediated by muscarinic receptors. Atropine of 1 μM abolisehd the response to 10 μM acetylcholine; muscarine and carbamylcholine (100 μM each) evoked Ca²⁺ rises. Increases in [Ca²⁺]_i were also evoked by the bath application of ATP (10 μM or higher). The Ca²⁺ rise by ATP was evoked even in a Ca²⁺-free medium. Adenosine (500 μM) did not cause any Ca²⁺ response. Suramin and reactive blue 2 (200 μM each) completely blocked the Ca²⁺ response to 500μM ATP. Uridine triphosphate (500 μM) caused comparable Ca²⁺ responses with those to 500 μM ATP. These results suggested the involvement of P_2U purinoceptors. The potentiation of Ca²⁺ rise was observed when acetylcholine and ATP were co-applied at submaximal concentrations (10 μM and 100 μM, respectively). We conclude that undifferentiated cells in the otocyst epithelium have CaCa²⁺ mobilizing systems activated by acetylcholine and ATP. © 1995 John Wiley & Sons, Inc.     

Toxicity of A Novel Neonicotinoid Insecticide Paichongding to Earthworm Eisenia fetida

Traditional neonicotinoid insecticides are used worldwide. Paichongding (IPP), as a novel neonicotinoid pesticide, has been widely used in China. However, the ecotoxicity of IPP to non-target invertebrates in soil ecosystem has not been reported yet. In this study, acute toxicity of IPP to earthworm Eisenia fetida, as well as the antioxidant response after IPP exposure, was evaluated. In the filter paper contact test, the LC₅₀ at 24 hr and 48 hr for IPP were 14.98 μg/cm² and 7.59 μg/cm², respectively. In artificial soil test, the LC₅₀ (lethal concentration) at 14 days and 28 days for IPP were 541.07 mg/kg and 238.51 mg/kg, respectively. The LC₅₀ of IPP is much higher than that of traditional neonicotinoid insecticides. However, earthworm body weight assessment demonstrated that the growth of earthworm was inhibited by extended exposure to IPP at sublethal doses. The activities of antioxidative enzymes superoxide dismutase and catalase in earthworms were significantly induced after IPP exposure. Malondialdehyde, a biomarker of lipid peroxidation, was also increased after IPP exposure. Although the results indicated that IPP had potentially adverse effect on earthworms, its toxicity was much lower than traditional neonicotinoids.     

Mechanisms of heterosynaptic facilitation in molluscan neurons

This review is focused on the analysis of research data obtained in one of the models of conditioned reflex, heterosynaptic facilitation (HSF), in the molluscan nervous system. Our experiments were performed on identified giant command neurons LS1 and PS1 of the freshwater snail Planorbarius corneus. HSF was elicited during the electrical stimulation of two nerves: pallial (the analog of unconditioned stimulation — US) and one of the cerebral nerves (the analog of the conditioned stimulation — CS). The degree of HSF manifestation depended not on the intensity of the synaptic response of the giant neuron to US, but the efficacy of the connection between the pallial nerve and neurosecretory neurons surrounding the command neuron of the mesocerebrum. It is demonstrated that HSF develops due to the diffuse neurohumoral action of serotonin (5-hydroxytryptamine — 5-HT) on the postsynaptic structures, but not as a result of local synaptic action on the presynaptic mechanism. Approximately 70% of US cases of 5-HT application induced a four- to six-fold increase in amplitude of the excitatory postsynaptic potential (EPSP) and acetylcholine (ACh) response. Both responses are N-cholinergic and depend on the membrane permeability to Na⁺ and K⁺. In 30% of the cases, ACh response diminished simultaneously with EPSP increase. The 5-HT effect on EPSP and ACh responses were mimicked by the action of phosphodiersterase blockers and adenylate cyclase activators. Thus, the activation of the adenylate cyclase system following 5-HT action facilitates the postsynaptic mechanism underlying HSF formation in command neurons of Planorbarius corneus. Dopamine (DA) and noradrenaline (NA) blocked EPSP and simultaneously increased the amplitude of ACh response. These monoamines were also blocked HSF. The wash-out of catecholamines following HSF blockade enhanced the restoration and subsequent prolongation of synaptic facilitation. It is thus concluded that DA or NA may control the HSF intensity and duration under natural conditions of the nervous system in the molluscs.Neirofiziologiya/Neurophysiology, Vol. 25, No. 3, pp. 224–232, May–June, 1993.     

Growth Stimulation of Human Skin Fibroblasts by Elastin-Derived Peptides

Elastin-derived peptides (kappa-elastin: KE, mean molecular mass: 75 kDa), either coated onto plastic dishes or added to culture media (0.26 to 1.33 nM) stimulated the growth of human skin fibroblasts (HSF) strains obtained from different donors and tested at different cell passages (4 to 12). Coated 44.4 μg/cm²insoluble elastin (iE) exhibited the same action; coated iE or KE significantly modifies the HSF morphology: after 5-6 days of culture, HSF are more elongated, and at preconfluence state, formation of HSF clusters surrounding iE were observed. Increased ³H thymidine incorporation and proliferative effect of HSF by KE (1.3 to 2.2 fold as compared to control cells) was observed after a lag phase period which raised with initial HSF density. Optimal proliferative effect was obtained at KE 8.5 10^?10M, a value close to the dissociation constant (k_D= 2.7 10^?10M) of KE to HSF. Valine-glycine-valine-alanine-proline-glycine (VGVAPG), but not valine-glycine-valine (VGV) or Valine-glycine-valine-valine-glycine-alanine (VGWGA) also significantly stimulated, optimally at 7.0 10^?10M, HSF proliferation. It was concluded that the stimulatory influence of elastin derived peptides on HSF proliferation was mediated through a binding to plasmalemmal receptor of HSF.