[Long-term outcomes and failure patterns of definitive radiotherapy for cervical esophageal carcinoma]

Objective: To evaluate the long-term outcomes, failure patterns and prognostic factors of definitive radiotherapy in patients with cervical esophageal carcinoma (CEC). Methods: We retrospectively reviewed the clinical data of 148 CEC patients who treated with definitive radiotherapy in Cancer Hospital of Chinese Academy of Medical Sciences from January 2001 to December 2017. The median radiation dose was 66 Gy (59.4-70 Gy) and 33.1% of patients received concurrent chemotherapy. The Kaplan-Meier method was used to calculate survival rates. The log rank test was used for survival comparison and univariate prognostic analysis. The Cox model was used for multivariate prognostic analysis. Results: The median follow-up time was 102.6 months. The median survival time, 2- and 5-year overall survival (OS) were 22.7 months, 49.9% and 28.3%. The median, 2- and 5-year progression-free survival were 12.6 months, 35.8% and 25.8%. The 2- and 5-year locoregional recurrence-free survival were 59.1% and 50.8%. The 2- and 5-year distant metastases-free survival were 74.6% and 65.9%. Multivariate analysis showed that EQD(2)>66 Gy was the only independent prognostic indicator for OS (P=0.040). The median survival time and 5-year OS rate significantly improved in patients who received EQD(2)>66 Gy than those who received≤66 Gy (31.2 months vs. 19.2 months, 40.1% vs. 19.1%, P=0.027). A total of 87 patients (58.8%) developed tumor progression. There were 50 (33.8%), 23 (15.5%) and 39 (26.4%) patients developed local, regional recurrence and distant metastases, respectively. Eleven patients (7.4%) underwent salvage surgery, and the laryngeal preservation rate for entire group was 93.9%. Conclusions: Definitive radiotherapy is an effective treatment for cervical esophageal carcinoma with the advantage of larynx preservation. Local recurrence is the major failure pattern. EQD(2)>66 Gy is associated with the improved overall survival.

[Treatment and prognosis analysis of perineural invasion on sinonasal adenoid cystic carcinoma]

Objective: To analyze the efficacy of sinonasal adenoid cystic carcinoma (ACC) with perineural invasion (PNI), and explore the prognostic value of PNI on sinonasal adenoid cystic carcinoma. Methods: The clinical data of 105 patients with sinonasal ACC admitted to Cancer Hospital, Chinese Academy of Medical Sciences from January 2000 to December 2016 were retrospectively reviewed. All patients were restaged according to American Joint Committee on Cancer 8th edition. Follow-up visits were conducted to obtain information of treatment failure and survival outcome. The Log rank test was used for univariate analysis of prognostic factors, and Cox regression model was used for multivariate prognostic analysis. Results: The maxillary sinus (n=59) was the most common primary site, followed by the nasal cavity (n=38). There were 93 patients with stage Ⅲ-Ⅳ. The treatment modalities included surgery alone (n=14), radiotherapy alone (n=13), preoperative radiotherapy plus surgery (n=10), and surgery plus postoperative radiotherapy (n=68). The median follow-up time was 91.8 months, the 5-year local control (LC), distant metastasis-free survival (DMFS), progression-free survival (PFS), and overall survival (OS) rates were 72.6%, 73.0%, 52.9% and 78.0%, respectively. There were 33 patients (31.4%) with PNI-positive. The 5-year DMFS, PFS, and OS rates of PNI-positive group were 53.7%, 29.4% and 56.5%, respectively, which were significantly inferior to those of PNI-negative group (80.8%, 63.0% and 86.8%, respectively, P<0.05), while there was no significant difference in the 5-year LC rate between both groups (64.5% vs 76.5%, P=0.273). The multivariate Cox regression analysis showed PNI was one of the poor prognostic factors of DMFS (HR=3.514, 95%CI: 1.557-7.932), PFS (HR=2.562, 95%CI: 1.349-4.866) and OS (HR=2.605, 95%CI: 1.169-5.806). Among patients with PNI-positive, the 5-year LC, PFS and OS rates of patients received surgery combined with radiotherapy were 84.9%, 41.3% and 72.7%, respectively, which were significantly higher than 23.3%, 10.0% and 26.7% of patients receiving surgery or radiotherapy alone (P<0.05). Conclusion: The presence of PNI increases the risk of distant metastasis in patients with sinonasal ACC. Compared with patients with PNI-negative, the prognosis of patients with PNI-positive is relatively poor, and surgery combined with radiotherapy for PNI-positive sinonasal ACC results in good clinical outcomes.

[Risk factors related to HIV new infections among men who have sex with men in a cohort study]

Objectives: To analyze and understand the risk factors related to HIV new infections among men who have sex with men (MSM). Methods: A longitudinal observational study among MSM was conducted to collect information on HIV related behaviors and sero-conversion. Univariate and multivariate generalized estimating equations (GEE) were used to discuss the risk factors for HIV new infection. Results: A total number of 4 305 MSM were followed during 2013-2015. Among those self-reported MSM who are seeking partners on the Interner tended to have higher proportion on receptive anal intercourse and consistent condom use during anal intercourse than the subgroups seeking their partners in gay bars or bathrooms. HIV incidence among followed MSM during the study period appeared as 4.3/100 person years, with adjusted RR (aRR) of HIV infection for receptive anal intercourse as group 2.20 (95% CI: 1.49-3.24) times than that of insertion anal intercourse group. Those who used rush-poppers (aRR=1.55, 95% CI: 1.10-2.17), unprotected anal intercourse (aRR=2.24, 95%CI: 1.62-3.08), and those with syphilis infection (aRR=2.95, 95%CI: 2.00-4.35) were also risk factors for HIV new infections. After controlling other factors, the relationship between the ways of seeking partners and HIV new infection was not statistical significant. Conclusion: Risk factors for HIV new infection among MSM appeared complex and interactive, suggesting that further studies are needed to generate tailored strategies for the prevention of HIV epidemic among MSM population.

Molecular Weight, Protein Binding Affinity and Methane Mitigation of Condensed Tannins from Mangosteen-peel (Garcinia mangostana L)

The objectives of this study were to determine the molecular weight of condensed tannins (CT) extracted from mangosteen (Garcinia mangostana L) peel, its protein binding affinity and effects on fermentation parameters including total gas, methane (CH₄) and volatile fatty acids (VFA) production. The average molecular weight (M_w) of the purified CT was 2,081 Da with a protein binding affinity of 0.69 (the amount needed to bind half the maximum bovine serum albumin). In vitro gas production declined by 0.409, 0.121, and 0.311, respectively, while CH₄ production decreased by 0.211, 0.353, and 0.549, respectively, with addition of 10, 20, and 30 mg CT/500 mg dry matter (DM) compared to the control (p<0.05). The effects of CT from mangosteen-peel on in vitro DM degradability (IVDMD) and in vitro N degradability was negative and linear (p<0.01). Total VFA, concentrations of acetic, propionic, butyric and isovaleric acids decreased linearly with increasing amount of CT. The aforementioned results show that protein binding affinity of CT from mangosteen-peel is lower than those reported for Leucaena forages, however, the former has stronger negative effect on IVDMD. Therefore, the use of mangosteen-peel as protein source and CH₄ mitigating agent in ruminant feed requires further investigations.

Application of HPLC–ESI–ITMS in the quality control of carboxyterminal sequence confirmation for the recombinant DNA product Hirudin Variant 3

In the present study, HPLC-ESI-IT (ion-trap) MS was used for carboxyterminal (C-terminal) amino acid sequence confirmation of intact recombinant Hirudin Variant 3 (HV3) and alkylated HV3. The C-terminal amino acid sequence of HV3 was determined by the use of carboxypeptidase P (CPP), and by the combined use of carboxypeptidase P and carboxypeptidase Y (CPY). The C-terminal amino acid sequence of alkylated HV3 with 1,4-dithiothreitol (DTT) reduction was also confirmed by the combined use of CPP and CPY (abbreviated to CPP-CPY). Up to 19 amino acid residues were confirmed in the nanomolar concentration range by analyzing the molecular weights of the truncated peptides of HV3. Another five amino acids were confirmed in the nanomolar concentration range of alkylated HV3 with DTT reduction. For sequencing alkylated HV3 with DTT reduction, HV3 reduced with DTT followed by alkylation with iodoacetamide. The reaction mixture, which included alkylated HV3, DTT, and iodoacetamide, was then directly sequenced without any further pre-treatment. The reaction was designed in a time-, and concentration-dependent manner to obtain the maximum sequence information. The results showed that HPLC-ESI-ITMS cannot only determine the C-terminal amino acid sequence of HV3, but also gives important information about the enzymatic degradation and subsequent release of the C-terminal amino acids of HV3.

Reentrant wetting transition on surfactant solution surfaces

The wetting of polydimethylsiloxane oil drops on the surfaces of anionic surfactant sodium dodecylsulfate solutions is studied systematically by changing the bulk surfactant concentration. The wetting state changes from complete wetting to pseudopartial wetting at 0.3 cmc (critical micelle concentration) surfactant concentration and there is a reentrant transition back to complete wetting at 1.4 cmc. The measured free energy is consistent with the prediction of the wetting theory. The interaction potential minimum of the two surfaces of the oil film disappears at the reentrant point, which is speculated to be an effect of micelle formation in the solution.

Effects of berberine on intracellular free calcium in smooth muscle cells of Guinea pig colon

AIM

To investigate the effects and mechanism of berberine (Ber) on the intracellular free calcium concentration ([Ca(2+)](i)) in the smooth muscle cells of guinea pig colon.

METHODS

The changes of [Ca(2+)](i) were assayed by the biwavelength spectrophotometry with Fura 2-AM in the cell suspension of the smooth muscle cells, which were freshly isolated from guinea pig colon.

RESULTS

In the resting state, [Ca(2+)](i) in the HEPES-Ringer solution (CaCl(2) 1.5 mmol.l(-1)) was (108 +/- 9.4) nmol.l(-1) (n = 7). Ber had no significant effects on the resting [Ca(2+)](i), but markedly inhibited the increase in [Ca(2+)](i )induced by 60 mmol.l(-1) KCl in a concentration-dependent manner. The value of IC(50 )was 34.09 micromol.l(-1). 30 and 100 micromol.l(-1) Ber also inhibited the elevation of [Ca(2+)](i) evoked by 10 micromol.l(-1) Ach in a dose-dependent fashion in the presence or absence of extracellular Ca(2+). In addition, Ber inhibited the elevation of [Ca(2+)](i) stimulated by cyclopiazonic acid (CPA) in a dose-dependent manner. This effect was more potent in the HEPES-Ringer solution (IC(50) = 37.79 micromol.l(-1)) than Ca(2+)-free medium (IC(50) = 49.70 micromol.l(-1)).

CONCLUSIONS

Ber possessed an inhibitory effect on the influx of extracellular Ca(2+) and Ca(2+)-release from intracellular stores in the smooth muscle cells of colon. That is to say Ber may be a blocker of Ca(2+) channels.

Biotransformation of hydroxylaminobenzene and aminophenol by Pseudomonas putida 2NP8 cells grown in the presence of 3-nitrophenol

Biotransformation products of hydroxylaminobenzene and aminophenol produced by 3-nitrophenol-grown cells of Pseudomonas putida 2NP8, a strain grown on 2- and 3-nitrophenol, were characterized. Ammonia, 2-aminophenol, 4-aminophenol, 4-benzoquinone, N-acetyl-4-aminophenol, N-acetyl-2-aminophenol, 2-aminophenoxazine-3-one, 4-hydroquinone, and catechol were produced from hydroxylaminobenzene. Ammonia, N-acetyl-2-aminophenol, and 2-aminophenoxazine-3-one were produced from 2-aminophenol. All of these metabolites were also found in the nitrobenzene transformation medium, and this demonstrated that they were metabolites of nitrobenzene transformation via hydroxylaminobenzene. Production of 2-aminophenoxazine-3-one indicated that oxidation of 2-aminophenol via imine occurred. Rapid release of ammonia from 2-aminophenol transformation indicated that hydrolysis of the imine intermediate was the dominant reaction. The low level of 2-aminophenoxazine-3-one indicated that formation of this compound was probably due to a spontaneous reaction accompanying oxidation of 2-aminophenol via imine. 4-Hydroquinone and catechol were reduction products of 2- and 4-benzoquinones. Based on these transformation products, we propose a new ammonia release pathway via oxidation of aminophenol to benzoquinone monoimine and subsequent hydrolysis for transformation of nitroaromatic compounds by 3-nitrophenol-grown cells of P. putida 2NP8. We propose a parallel mechanism for 3-nitrophenol degradation in P. putida 2NP8, in which all of the possible intermediates are postulated.

A novel four base-pair deletion within the Agamma-GLOBin gene promoter associated with slight increase of Agamma expression in adult

We studied a Chinese family and revealed 5.4% and 3.2% fetal hemoglobin (HbF) with advantageously Agamma type in the mother and the daughter, respectively, using alkali denaturation assay and urea-Triton-acrylamide gel electrophoresis and high-performance liquid chromatography. The father's HbF was less than 0.5%. Large deletion was not observed within the beta-globin gene cluster by restriction endonuclease mapping. Characterization by the polymerase chain reaction (PCR) and DNA sequencing demonstrated the mother is a homozygote with a novel four base-pair "AAGC" (-226 to -223) deletion within the Agamma-globin gene promoter and the daughter is a heterozygote with this deletion. The deletion was not detected in the father. No any mutations were identified in the Ggamma promoter of all the subjects studied. We propose that the small deletion is associated with the slight increase of Agamma gene expression in adult.

Removal of known, abundant cDNA species by specific double-stranded cDNA synthesis-based subtraction

An efficient and simple method for removing known, abundant cDNA species from the cDNA pool of highly differentiated cells is reported. The method involves preparation of sscDNA, followed by dscDNA-synthesis of known, abundant cDNA species led by specific primers and removal of the synthesized dscDNA with hydroxyapatite. By using this method, the globin cDNAs were reduced to less than 10(-5) of their original abundance. The results suggest that this method may facilitate the isolation of new genes from specific cells or tissues.

Heterogeneous loss of connexin43 protein in ischemic dog hearts

INTRODUCTION

Ischemia causes cell decoupling in the myocardium. Prolonged ischemia activates proteases and causes degradation of structural proteins as well as gap junctions. There is little information about the degradation of gap junction protein during the early time period after acute ischemia. The purpose of the present study was to investigate connexin43 (Cx43) protein degradation and distribution patterns in the canine left ventricular wall during 1 to 6 hours of ischemia.

METHODS AND RESULTS

Ischemia of canine left ventricular myocardium was induced by ligation of the left anterior descending coronary artery. Following a period of in situ ischemia of up to 6 hours, samples were harvested, and standard paraffin slides were prepared for Cx43 and wheat germ agglutinin double labeling. Cx43 distribution was visualized by confocal microscopy. In controls, homogeneous distribution of Cx43 staining was determined. Ischemia caused a loss of Cx43 with a heterogeneous pattern by mixing foci of infarcted cells among normal cardiac myocytes. To determine if the changes were induced by heterogeneous reduction in the blood supply, an in vitro ischemic model was studied to induce more homogeneous ischemia. Western blot analysis of these in vitro ischemic tissue samples revealed a reduction of Cx43 protein concentration with a 50% decay time of 4.8 hours. Cx43 dephosphorylation was detected after 1 hour of in vitro ischemia. Heterogeneous loss of Cx43 was found in the in vitro ischemic tissue. There were no significant changes in Cx43 staining density during the first hour of ischemia at a time when dephosphorylation of the protein was observed. After 1 hour of ischemia, Cx43 was reduced at intercalated disk areas, and, after 6 hours, most Cx43 disappeared at intercalated disk areas, while small amounts of Cx43 remained at side-to-side junctions.

CONCLUSION

Cx43 undergoes both distribution and concentration changes following acute cardiac ischemia. The loss of Cx43 protein is heterogeneous. Cx43 dephosphorylation occurred within 1 hour following ischemia.

Radiofrequency catheter ablation of the atria eliminates pacing-induced sustained atrial fibrillation and reduces connexin 43 in dogs

BACKGROUND

We assessed the effects of radiofrequency catheter ablation (RFCA) of the atrial epicardium on pacing-induced sustained atrial fibrillation (AF) and the expression and distribution of the intercellular gap junction protein connexin 43 (Cx43) in dogs.

METHODS AND RESULTS

In 12 mongrel dogs, after creation of complete AV block and implantation of a ventricular inhibited pacemaker, a high-rate pulse generator (20 to 30 Hz to induce AF) was implanted in the neck, connected to a right atrial endocardial pacing lead, and used to pace the atrium for 10 to 14 weeks. In group 1 (n=9 dogs), corrected sinus node recovery time (CSNRT), P-wave duration, 24-hour Holter ECG, maximal heart rate (MHR) in response to isoproterenol, and intrinsic heart rate (IHR) after atropine (0.04 mg/kg) and propranolol were measured before and after atrial pacing and RFCA. Group 2 dogs were used to assess the effect of chronic AF alone on Cx43 expression and distribution. All group 1 dogs developed sustained (>24 hours) AF. Right-sided RFCA of the atria eliminated the sustained AF in 5 dogs, but both right and left atrial RFCA was required to abolish sustained AF in the other 4 dogs. After RFCA restored sinus rhythm, CSNRT and P-wave duration were prolonged and MHR and IHR were decreased. Chronic rapid atrial pacing (group 2) increased the expression of Cx43, which was absent in ablated areas and markedly depressed in viable atrial myocytes near the ablation zones (group 1).

CONCLUSIONS

Rapid atrial pacing for long time periods induced sustained AF that can be eliminated by linear right and left atrial lesions created with RFCA, with preservation of sinus rhythm and atrial contractile function. Chronic AF increased the expression and distribution of gap junction protein Cx43, which became reduced in ablated and nearby nonablated areas.

Photoinduced toxicity of PAHs to the foliar regions of Brassica napus (canola) and Cucumbis sativus (cucumber) in simulated solar radiation

Simulated solar radiation and natural sunlight can enhance polycyclic aromatic hydrocarbon (PAH) toxicity, previously reported in terms of inhibited production of Lemna gibba leaves and diminished growth of Brassica napus seedling roots. This work has been extended to examine the photoinduced impact of PAHs on the foliar regions of terrestrial plants. To carry out these experiments two crop species, B. napus (canola) and Cucumbis sativus (cucumber), were chosen to test the photoinduced toxicity of six PAHs (anthracene, phenanthrene, benzo(a)anthracene, benzo(a)pyrene, flouranthene, and pyrene). Aqueous solutions containing PAHs were sprayed on the foliage of the plants. It was found that all the PAHs tested had negative impacts on the foliage of the plants and the concentrations that induced toxicity were consistent with those observed for inhibition of growth of L. gibba. The impacts were observed as diminished biomass accumulation, induction of chlorosis, and inhibition of photosynthesis. It may be concluded from this work that PAHs in rain and surface waters could be harmful to photosynthetic tissues of terrestrial plants.

Changes in the expression and distribution of connexin 43 in isolated cultured adult guinea pig cardiomyocytes

In the present study, we have investigated the changes in the expression and distribution of the principal gap-junction channel protein in ventricular muscle, connexin 43 (Cx43), during the first 2 weeks of culturing adult guinea pig cardiomyocytes at low density to prevent formation of cellular contacts. In freshly isolated cardiomyocytes, immunoreactive Cx43 occupied 6.5 +/- 0.4% of the pixel area of the cell, with 85% being localized to dense particles at the step-like end projections of the myocytes (intercalated disk regions) and 15% being within the sarcoplasm or along the lateral surface of the myocytes ("nondisk" distribution). During the myocytes' first 48 h in culture, immunoreactive Cx43 decreased by 27.5% from control values, to 4.7 +/- 0.5% of the cells' pixel area (P < 0.01). Cx43 particles also redistributed: after 48 h in culture approximately 90% of the immunoreactive Cx43 was localized in the sarcoplasm and nondisk regions of the myocyte. After 7 days, immunoreactive Cx43 only occupied 50% of the cells' control pixel area (P < 0.01) and was nearly uniform in its punctate pattern throughout the sarcoplasm. This distribution remained the same during the 2nd week in culture. Changes in myosin light chain staining during 8 days in culture largely paralleled those in Cx43 staining. Laser confocal microscopic analysis of double-immunolabeled myocytes that had been in culture for 24-48 h showed colocalization of Cx43 with clathrin in approximately 30% of the sarcoplasmic Cx43 particles. Thus it is demonstrated that the expression of Cx43 decreases significantly during the first 48 h in culture after myocyte isolation and that Cx43 also undergoes substantial redistribution but for the next 2 weeks remains more or less unchanged and at relatively high levels (approximately 50%). These data indicate that cardiomyocytes in isolation maintain their ability to reconnect with each other for up to at least 2 weeks. This is the first time that this property has been investigated in cultured adult ventricular cardiomyocytes.

Increased polycyclic aromatic hydrocarbon toxicity following their photomodification in natural sunlight: impacts on the duckweed Lemna gibba L. G-3

The authors previously demonstrated that simulated solar radiation (SSR), with a fluence rate of only 40 mumol m-2 sec-1, increased polycyclic aromatic hydrocarbon (PAH) toxicity to the duckweed Lemna gibba and that PAHs photomodified in SSR (generally oxygenation of the ring system) are more toxic than the parent compounds (Huang et al., Environ. Toxicol. Chem., 1993, 12, 1067-1077). It is not known, however, to what extent toxicity of PAHs can increase due to photomodification. Thus, natural sunlight, which has a high fluence rate (approximately 2000 mumol m-2 sec-1), was used to photomodify anthracene, benzo[a]pyrene, fluoranthene, phenanthrene, and pyrene. Toxicity was based on growth inhibition of L. gibba, measured as the rate of production of new leaves over an 8-day period. Initially, the toxicity of the PAHs applied in intact form was probed, with the compounds demonstrating greater toxicity in sunlight than in SSR. Next the PAHs were photomodified in sunlight prior to incubation with the plants. The half-lives of the PAHs in sunlight ranged from 12 min to 30 hr. Although most of the products of PAH photomodification are not yet identified, the degree that PAH toxicity increased following photomodification in sunlight could still be probed. The mixtures of photomodified chemicals that were derived from each PAH in sunlight were applied of L. gibba and growth inhibition under 100 mumol m-2 sec-1 of SSR was determined. The LC50s for the PAH photoproducts generated in sunlight were an order of magnitude lower than the LC50s for the PAHs applied in intact form.

Photoinduced toxicity of three polycyclic aromatic hydrocarbons (fluoranthene, pyrene, and naphthalene) to the duckweed Lemna gibba L. G-3

The authors recently demonstrated that light dramatically enhances the hazards of three polycyclic aromatic hydrocarbons (PAHs), anthracene, phenanthrene, and benzo[a]pyrene, to the duckweed Lemna gibba L. G-3 (X.-D. Huang, D. G. Dixon, and B. M. Greenberg, 1993, Environ. Toxicol. Chem., 12, 1067-1077). To extend this research, growth and chlorosis were used as end points to assess the photoinduced toxicity of three additional PAHs, fluoranthene, pyrene, and naphthalene, to L. gibba in the presence of simulated solar radiation (a light source with a UV-B: UV-A:visible light ratio equivalent to that of sunlight). The phytotoxicity of these three PAHs was photoactivated, with ultraviolet radiation being the only spectral region that enhanced the harmful effects of the chemicals. Dose-response curves based on chemical concentration and light intensity revealed that the order of phytotoxic strength was fluoranthene > pyrene > naphthalene. To explore whether photomodification (in addition to photosensitization) of fluoranthene, pyrene, and naphthalene could contribute to photoinduced toxicity, the chemicals were irradiated prior to (as opposed to simultaneously with) application to the plans. The rates of photomodification of the three PAHs were rapid enough for the photooxidized compounds to contribute to toxicity, and the photomodified PAHs were more toxic than the parent compounds. As well, toxicity could be correlated to photomodification; impacts increased in parallel with the extent of photomodification.

Optical perfect-shuffle network implementation by use of an ordinary imaging system and holographic gratings

We describe an approach to achieve the optical perfect-shuffle interconnection network in an ordinary optical imaging system; a holographic grating is inserted in the proper position, and a corresponding spatial filter is inserted in its back focal plane. This approach is simple, and the space-bandwidth product of the optical system can be better utilized. As an experimental demonstration, the perfectshuffle interconnection network is shown in one and in two dimensions.

Morphine and (D-Ala2, NMe-Phe4, Gly-ol)-enkephalin increase the intracellular free calcium in isolated rat myocytes--effect of naloxone or pretreatment with morphine

The purpose of the present study was firstly to determine whether morphine and (D-Ala2, NMe-Phe4, Gly-ol)-enkephalin (DAGO), a highly selective mu-agonist, increased intracellular free calcium of rat myocytes and secondly to determine whether opioid receptors were involved. Two series of experiments were performed. In the first, the effect of morphine and DAGO on intracellular free calcium (Cai) of cultured isolated myocytes was studied with a spectrophotometric method using fura2-AM as the fluorescent Ca2+ indicator. In the second, the effect of morphine on Cai of isolated ventricular myocytes from rats which had received chronic daily injection of morphine for two weeks or myocytes which had been incubated in a solution with morphine for 12 hr was studied. It was found that both morphine at 100-250 microM and DAGO at 23-75 microM increased Cai dose-dependently and that the effect was significantly antagonized by naloxone at a concentration of 50 microM, which itself did not cause any significant alteration in Cai. Pretreatment with morphine also abolished the morphine-induced increase in Cai of isolated myocytes. The results suggest that morphine increases Cai by directly activating the cardiac receptors (most likely micro-receptors) on the membrane of ventricular myocytes.

Arrhythmogenic effect of forskolin in the isolated perfused rat heart: influence of nifedipine or reduction of external calcium [corrected]

1. This study investigated first the effects of forskolin on cardiac rhythm, and second the roles of calcium in cardiac arrhythmogenesis by cAMP. 2. Two series of experiments were performed. In the first series, forskolin was administered into the isolated perfused rat heart. In the second series, forskolin administration was preceded by administration of nifedipine, a calcium channel blocker, or infusion of a low concentration calcium solution. In both experiments, the myocardial cAMP level and electrocardiogram were determined. 3. It was found that forskolin increased cAMP level as well as inducing arrhythmia. Pretreatment with nifedipine or a reduction of external calcium, that either maintained or further enhanced the forskolin-induced increase in the cAMP level, abolished the forskolin-induced arrhythmia. 4. The results of the present study support the hypothesis that myocardial cAMP mediates cardiac arrhythmia, and provide evidence that calcium is essential in arrhythmia mediated by cAMP.

Cholera toxin enhances ischemia-induced arrhythmias in the isolated rat heart--involvement of a guanine nucleotide binding protein (Gs)

Cholera toxin (CTX) at a dose, which disturbed the intestinal functions, was administered into the rat via the tail vein. At 3 hr after injection, the heart was removed and perfused or subject to global ischemia in the Langendorff isolated heart preparation. Electrocardiogram (ECG) was recorded throughout the experiment. The myocardial cAMP content was measured in the intact non-ischemic heart, and in the isolated ischemic heart at 2.5, 5 and 10 min after ischemia. It was found that the incidence and severity of malignant ventricular arrhythmias including ventricular tachycardia (VT) and ventricular fibrillation (VF) was significantly increased during ischemia in the CTX treated group. The cAMP content was also significantly increased in the CTX treated group in both intact non-ischemic and ischemic hearts, indicating an activation of the guanine nucleotide regulatory protein (Gs). The results of the present study provide evidence that activation of Gs during ischemia may also contribute to the genesis of arrhythmia.

Naloxone inhibits arrhythmias induced by coronary artery occlusion and reperfusion in anaesthetized dogs

The intravenous administration of naloxone 2 min before coronary artery occlusion in anaesthetized dogs reduced the incidence and severity of cardiac arrhythmias during coronary occlusion (20 min) and reperfusion (120 min) in a dose-related manner. It also reduced the mortality. At a dose of 1 mg kg-1 (the maximum dose used in this study) naloxone abolished the appearance of the life threatening ventricular fibrillation (VF) and ventricular tachycardia (VT) and as a consequence all dogs in this group survived. The results suggest a possible involvement of endogenous opioid peptides in arrhythmogenesis during coronary occlusion and reperfusion in the dog.