Modified Simiaowan prevents and treats gouty arthritis via the Nrf2/NLRP3 inflammasome signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Modified Simiaowan (MSM) is a six-herb formula that has been shown to be effective in gouty arthritis (GA) has been proven, but its regulatory mechanism has not been fully elucidated.

AIM OF THE STUDY

To investigate the therapeutic effects and mechanism of MSM on gouty arthritis.

MATERIALS AND METHODS

Mouse J774A.1 macrophages were induced with Lipopolysaccharide (LPS) and then stimulated with Adenosine 5'-triphosphate (ATP) or Nigericin (Nig.) in presence or absence of MSM. Expression of key indicators of pro-inflammatory cytokines and the NLRP3 inflammasome signaling pathway were investigated by western blot, ELISA and qRT-PCR. Fluorescence staining and flow cytometry were performed to detect intracellular reactive oxygen species (ROS) production. Another study, the anti-inflammatory and antioxidant activities of MSM were evaluated in rats with monosodium urate (MSU) -induced gouty arthritis using ELISA, hematoxylin-eosin staining (HE) staining, immunohistochemistry, and oxidative stress kits to measure relevant inflammatory markers and oxidative stress-related biomarkers.

RESULTS

ELISA and qRT-PCR results demonstrated that MSM effectively reduced the secretion and the mRNA expression levels of pro-inflammatory cytokines. Western blot results indicated that MSM can suppress the expression of NLRP3, an inflamasomes-related protein. In addition, MSM regulated the transition from M1 to M2 macrophages and upregulated the protein expression of Nrf2 and HO-1. The flow cytometry results and the fluorescence staining result were consistent with hypothesis that a large amount of ROS could be effectively cleared by MSM. However, the anti-inflammatory effect of MSM was attenuated after the use of ML385. In vivo experiments demonstrated that joint swelling was significantly attenuated and knee neutrophil infiltration was alleviated in rats given MSM. SOD and GSH-px levels were elevated significantly, while COX-2 and MDA levels decreased. The immunohistochemical results suggested that MSM could effectively inhibit the activation of the NLRP3 inflammasome and the regulation of macrophage polarization in rat synovial tissue, and remarkably enhance the expression of Nrf2 and HO-1.

CONCLUSION

MSM has potent anti-inflammatory and antioxidant effects on MSU-induced gouty arthritis. MSM alleviates GA through Nrf2/HO-1/ROS/NLRP3 signaling pathway.

[Effect of acupuncture on analgesia and sedation in elderly patients with severe pneumonia during invasive mechanical ventilation]

OBJECTIVE

To observe the analgesic and sedative effects of acupuncture in elderly patients with severe pneumonia during invasive mechanical ventilation.

METHODS

A total of 188 elderly patients with severe pneumonia were randomly divided into an observation group and a control group, 94 cases in each group. Both groups were treated with routine nursing and treatment of severe pneumonia such as invasive mechanical ventilation, analgesia and sedation. Based on these, the observation group was treated with acupuncture at Neiguan (PC 6), Hegu (LI 4), Yintang (GV 29) and Baihui (GV 20), twice a day until the mechanical ventilation was offline. The critical care pain observation tool (CPOT) score and Richmond agitation-sedation score (RASS) were observed before treatment and 0.5 h after analgesia and sedation; the average time of reaching the standard, the reaching standard rate of shallow sedation and analgesia within 0.5 h and 72 h as well as the dosage of analgesic and sedative drugs and compilations were compared between the two groups. The mean arterial pressure (MAP), heart rate (HR), respiratory rate (RR) and blood oxygen saturation (SpO₂) were observed before treatment and 0.5 h, 1 h and 2 h after analgesia and sedation. The levels of partial pressure of blood oxygen (PaO₂), partial pressure of carbon dioxide (PaCO₂) and lactic acid (Lac) were observed before treatment and 12 h, 24 h, 48 h, 72 h, 96 h, 120 h and 144 h after analgesia and sedation. The white blood cell (WBC), neutrophil percentage (NEUT%), high-sensitivity C-reactive protein (hs-CRP), aspartate aminotransferase (AST), alanine aminotransferase (ALT) and creatinine (Cr) were observed before treatment and 72 h after analgesia and sedation. The tracheal intubation time and ICU hospitalization time were compared between two groups.

RESULTS

At the time point of 0.5 h after treatment, the CPOT and RASS scores in the two groups were lower than those before treatment (P<0.05); the average time of reaching the standard in the observation group was shorter than that in the control group (P<0.01); the 30 min reaching standard rates of CPOT and RASS scores as well as the rate of reaching the shallow sedation and analgesia within 72 h in the observation group were higher than those in the control group (P<0.01, P<0.05). The dosage and duration of dexmedetomidine, propofol and butorphanol in the observation group were less than those in the control group (P<0.05), and the occurrence times of hypotension, respiratory depression, bradycardia, constipation as well as average tracheal intubation time and average ICU hospitalization time in the observation group were less than those in the control group (P<0.05). After 0.5 h, 1 h and 2 h of treatment, the HR and RR were lower than those before treatment in the two groups (P<0.05), MAP and SpO₂ were higher than those before treatment in the two groups (P<0.05); the MAP 0.5 h after treatment in the observation group was higher than that in the control group (P<0.05); the HR after 1 h and 2 h of treatment in the observation group was lower than that in the control group (P<0.05). Compared before treatment, the levels of PaCO₂ and Lac were reduced and the levels of PaO₂ were increased 12 h, 24 h, 48 h, 72 h, 96 h, 120 h and 144 h after treatment in both groups (P<0.05); compared before treatment, the WBC, NEUT%, hs-CPR, ALT and Cr were reduced 72 h after treatment in the two groups (P<0.05), and the hs-CRP in the observation group was lower than that in the control group (P<0.05).

CONCLUSION

Acupuncture has analgesic and sedative effect in elderly patients with severe pneumonia during invasive mechanical ventilation, which could reduce the dosage of sedative and analgesic drugs and the occurrence of complications, improve blood oxygen, and has good safety.

[Effect of acupuncture on diaphragmatic function in patients with AECOPD typeⅡ respiratory failure evaluated by ultrasound detection]

OBJECTIVE

To observe the therapeutic effect of acupuncture combined with western conventional therapy on type Ⅱ respiratory failure of acute exacerbation of chronic obstructive pulmonary disease (AECOPD) and evaluate the effect of acupuncture on diaphragmatic function and prognosis by bedside ultrasound.

METHODS

A total of 111 patients with AECOPD type Ⅱ respiratory failure were randomized into an acupuncture group, a conventional treatment group and a non-acupoint acupuncture group, 37 cases in each one. The routine AECOPD nursing care and treatment with western medicine were provided in the 3 groups. Additionally, in the acupuncture group, acupuncture was applied at Dingchuan (EX-B 1), Feishu (BL 13), Taiyuan (LU 9), Danzhong (CV 17) and Zhongwan (CV 12), etc. In the non-acupoint acupuncture group, acupuncture was given at the points 5 to 10 mm lateral to each of the acupoints selected in the acupuncture group. Acupuncture was given once every day, 30 min each time, consecutively for 10 days in the above two groups. Separately, before treatment, on day 3, 7 and 10 of treatment, arterial partial pressure of oxygen (PaO₂), partial pressure of carbon dioxide (PaCO₂) and diaphragm thickening fraction (TFdi) were observed in each group. Before and after treatment, the inflammatory and immune indexes (levels of white blood cell [WBC], procalcitonin [PCT], hypersensitive C-reactive protein [hs-CRP] and T lymphocyte percentage [ %]), auxiliary respiratory muscle movement score, the score of chronic obstructive pulmonary disease (COPD) assessment test (CAT), the score of the modified British Medical Research Council dyspnea scale (mMRC) and the TCM syndrome score were compared in each group. The duration of mechanical ventilation, relative complications, 14-day clinical controlled discharge rate and the therapeutic effect were observed in each group.

RESULTS

On day 3, 7 and 10 of treatment, PaO₂ and TFdi were all increased as compared with those before treatment (P<0.01) and PaCO₂ was reduced as compared with that before treatment in each group (P<0.01). After treatment, % was increased as compared with that before treatment in each group (P<0.01), WBC, PCT, hs-CRP, auxiliary respiratory muscle movement score, CAT score, mMRC score and TCM syndrome score were all reduced as compared with those before treatment in each group (P<0.01). After treatment, PaCO₂, WBC, PCT, hs-CRP, auxiliary respiratory muscle movement score, CAT score and mMRC score in the acupuncture group were all lower than the other two groups (P<0.01), PaO₂ and TFdi were higher than the other two groups (P<0.01); % was higher and TCM syndrome score was lower in the acupuncture group compared with those in the non-acupoint acupuncture group (P<0.01). The duration of mechanical ventilation and the total incidence of complications in the acupuncture group were all lower than the other two groups (P<0.01), and the 14-day clinical controlled discharge rate and total clinical effective rate were higher than the other two groups (P<0.01).

CONCLUSION

Acupuncture as adjunctive therapy achieves significant therapeutic effect on AECOPD type Ⅱ respiratory failure. It improves diaphragmatic function, promotes oxygenation and relieves carbon dioxide retention of artery, alleviates clinical symptoms and reduces the time of mechanic ventilation and hospitalization. Besides, the bedside ultrasound detection can objectively reflect the effect of acupuncture on diaphragmatic function in the patients with AECOPD complicated with typeⅡrespiratory failure.

Ryanodine- and thapsigargin-insensitive Ca2+-induced Ca2+ release is primed by lowering external Ca2+ in rabbit autonomic neurons

Rises in cytosolic Ca2+ induced by a high K+ concentration (30 or 60 mM) (K+-induced Ca2+ transient) were recorded by fluorimetry of Ca2+ indicators in cultured rabbit otic ganglion cells. When external Ca2+ ([Ca2+]o) was reduced to a micromolar (10-40 microM) or nanomolar (<10 nM) level prior to high-K+ treatment, K+-induced Ca2+ transients of considerable amplitude (50% of control) were generated in most cells, although those initiated at normal [Ca2+]o were reduced markedly or abolished by reducing [Ca2+]o during exposure to a high K+ concentration. Lowering [Ca2+]o alone occasionally caused a transient rise in cytosolic Ca2+. K+-induced Ca2+ transients at micromolar [Ca2+]o were repeatedly generated and propagated inwardly at a speed slower than that at normal [Ca2+]o, while those at nanomolar [Ca2+]o occurred only once. K+-induced Ca2+ transients at micromolar [Ca2+]o were not blocked by ryanodine (10 microM), carbonyl cyanide p-(trifluoromethoxy) phenylhydrazone (FCCP, 5 microM: at 20-22 degrees C but blocked at 31-34 degrees C) or thapsigargin (1-2 microM), but were blocked by Ni2+ (1 mM) or nicardipine (10 microM). Thus, there is a ryanodine-insensitive Ca2+-release mechanism in FCCP- and thapsigargin-insensitive Ca2+ stores in rabbit otic ganglion cells, which is primed by lowering [Ca2+]o and then activated by depolarization-induced Ca2+ entry. This Ca2+-induced Ca2+ release may operate when [Ca2+]o is decreased by intense neuronal activity.

Modes of propagation of Ca(2+)-induced Ca2+ release in bullfrog sympathetic ganglion cells

How depolarization-induced Ca2+ entry or caffeine activates Ca(2+)-induced Ca2+ release (CICR) in the cytoplasm and nucleoplasm was studied by recording intracellular Ca2+ ([Ca2+]i) with a confocal microscope in cultured bullfrog sympathetic ganglion cells. The amplitude and propagation speed of voltage pulse-induced rises in [Ca2+]i were greater in the submembrane (< 5 microns depth) region than in the core region, and delayed and smaller, but significant, in the nucleus. Ryanodine and dantrolene reduced the rises in [Ca2+]i in both the cytoplasm and nucleus. A rapid application of high K+ solution induced global rises in [Ca2+]i in both the cytoplasm and nucleoplasm, which were decreased by dantrolene. Caffeine produced a slow, small rise in [Ca2+]i which grew into a global, regenerative rise both in the cytoplasm and nucleoplasm with some inward gradient in the cytoplasm. Each of the high [Ca2+]i phases during caffeine-induced [Ca2+]i oscillation began in the submembrane region, while low [Ca2+]i phases started in the core region. These results suggest that CICR activated by Ca2+ entry or caffeine occurs predominantly in the submembrane region causing an inwardly spreading Ca2+ wave or [Ca2+]i oscillations, and that the nuclear envelope can cause CICR in the nucleoplasm, which is delayed due to Ca2+ diffusion barrier at the nuclear pores.

Activity-dependent changes in partial VAMP complexes during neurotransmitter release

The temporal sequence of SNARE protein interactions that cause exocytosis is unknown. Blockade of synaptic neurotransmitter release through cleavage of VAMP/synaptobrevin by tetanus toxin light chain (TeNT-LC) was accelerated by nerve stimulation. Botulinum/B neurotoxin light chain (BoNT/B-LC), which cleaves VAMP at the same site as TeNT-LC, did not require stimulation. Because TeNT-LC requires the N-terminal coil domain of VAMP for binding but BoNT/B-LC requires the C-terminal coil domain, it seems that, before nerve activity, the N-terminal domain is shielded in a protein complex, but the C-terminal domain is exposed. This N-terminal complex lasts until nerve activity occurs and may serve to cock synaptic vesicles for immediate exocytosis upon Ca2+ entry.

Different VAMP/synaptobrevin complexes for spontaneous and evoked transmitter release at the crayfish neuromuscular junction

Different VAMP/synaptobrevin complexes for spontaneous and evoked transmitter release at the crayfish neuromuscular junction. J. Neurophysiol. 80: 3233-3246, 1998. Although vesicle-associated membrane protein (VAMP/synaptobrevin) is essential for evoked neurotransmitter release, its role in spontaneous transmitter release remains uncertain. For instance, many studies show that tetanus toxin (TeNT), which cleaves VAMP, blocks evoked transmitter release but leaves some spontaneous transmitter release. We used recombinant tetanus and botulinum neurotoxin catalytic light chains (TeNT-LC, BoNT/B-LC, and BoNT/D-LC) to examine the role of VAMP in spontaneous transmitter release at neuromuscular junctions (nmj) of crayfish. Injection of TeNT-LC into presynaptic axons removed most of the VAMP immunoreactivity and blocked evoked transmitter release without affecting nerve action potentials or Ca2+ influx. The frequency of spontaneous transmitter release was little affected by the TeNT-LC when the evoked transmitter release had been blocked by >95%. The spontaneous transmitter release left after TeNT-LC treatment was insensitive to increases in intracellular Ca2+. BoNT/B-LC, which cleaves VAMP at the same site as TeNT-LC but uses a different binding site, also blocked evoked release but had minimal effect on spontaneous release. However, BoNT/D-LC, which cleaves VAMP at a different site from the other two toxins but binds to the same position on VAMP as TeNT, blocked both evoked and spontaneous transmitter release at similar rates. The data indicate that different VAMP complexes are employed for evoked and spontaneous transmitter release; the VAMP used in spontaneous release is not readily cleaved by TeNT or BoNT/B. Because the exocytosis that occurs after the action of TeNT cannot be increased by increased intracellular Ca2+, the final steps in neurotransmitter release are Ca2+ independent.

Electrical injuries from graphite fishing rods

High tension electrical injuries have a high morbidity and mortality. Carbon fibre and graphite used in the manufacture of fishing rods gives them superconductor qualities. The resistance of a fishing rod with a carbon content of more than 70 per cent is very low, ranging from 0.9 to 10.5 k omega. Nine cases are reported, which teach an important lesson not only in the management of those severe injuries, but also in their prevention.

Different responses of insulin, C-peptide, and testosterone to an oral glucose tolerance test in two groups of women with polycystic ovarian syndrome

BACKGROUND

To further investigate the relationship between inappropriate gonadotropin, hyperinsulinemia and androgen excess.

METHODS

We divided women with polycystic ovarian syndrome (PCOS) into two groups on the basis of LH/FSH (LH/FSH > or = 3, Group 1, n=30; LH/FSH<3, Group 2, n=25) and measured the responses of insulin, C-peptide (C-P), C-P/insulin (C-I) and testosterone concentrations to an oral glucose tolerance test (OGTT) in these patients and 15 control subjects.

RESULTS

Significant positive correlations were found between basal LH and T (r=O.58, p<0.05) in Group 1, and between fasting serum insulin and T (r=0.48, p<0.05) in Group 2. Although these patients had higher, delayed insulin and C-P responses to OGTT than the control group, much greater insulin and C-P levels and lower C/I values were found in Group 2. T concentrations decreased mildly during OGTT in Group 1 and the control, while they increased slightly in Group 2.

CONCLUSION

Our data suggest that hyperinsulinemia in PCOS is due to a enhanced beta-cell secretion and an impaired hepatic clearance of this hormone, hyperandrogenism may be LH-dependent in Group 1 and insulin-dependent in Group 2.

Ca(2+)-induced Ca2+ release and its activation in response to a single action potential in rabbit otic ganglion cells

1. Ryanodine-sensitive intracellular Ca2+ release activated by Ca2+ entry was studied with fura-2 fluorescence and intracellular voltage recording techniques in rabbit otic ganglion cells. 2. The removal of extracellular Ca2+ reduced sustained, transient or oscillatory rises in intracellular Ca2+ ([Ca2+]i) induced at high extracellular K+ and abolished the [Ca2+]i oscillation in cultured neurones. 3. Ryanodine (10 microM) transiently increased [Ca2+]i and reduced the amplitude and rate of rise of the high-K(+)-induced rise in [Ca2+]i, while caffeine (5 mM) produced a few transient rises in [Ca2+]i in most cultured cells and [Ca2+]i oscillation only in one cell. 4. The two components of the slow after-hyperpolarization (AHP) of an action potential in neurones of freshly isolated ganglia were dependent on extracellular Ca2+ and abolished by Ca2+ channel blockers, Cd2+ or Co2+. 5. The late component of AHP (LAHP), but not the initial component, in 'fresh' neurones increased in area with an increase in the preceding interval, was abolished by ryanodine (10 microM) and intracellularly injected EGTA, and mimicked by intracellular injection of Ca2+. 6. A ryanodine-sensitive Ca(2+)-induced Ca2+ release thus exists, operates in response to an action potential-induced Ca2+ entry and underlies LAHP in rabbit otic ganglion cells.

A UV laser-scanning confocal microscope for the measurement of intracellular Ca2+

Modifications to the optics of a conventional confocal laser-scanning microscope were made to allow imaging intracellular Ca(2+)-dependent fluorescence with a UV laser (351 or 364 nm). Modifications included: (1) a chromatic compensation lens in the laser path; (2) the design of a practically achromatic relay lens; (3) a longer tube length for the objective; and (4) highly reflective mirrors maximizing fluorescence measurement. This UV laser-scanning confocal microscope (UV-CLSM) yielded a lateral resolution of < 0.3 micron and an axial resolution of < 1.5 microns and a relevant field size of 100 microns in diameter for a 40X objective). The effects of varying the focal length of a compensation lens, the degree of the correction for the coverglass thickness of objective and the detector aperture size on the quality of image formation were examined. Finally, UV-CLSM revealed optical sections of fine and complex structures of bullfrog sympathetic neurones loaded with a Ca(2+)-sensitive fluorescent probe. Changes in intracellular free Ca2+ distribution in response to high [K+] or caffeine were demonstrated. In addition, an increase in the intracellular concentration of caffeine applied externally was clearly imaged in space and time and distinguished from a resultant rise in [Ca2+]i. Thus, the UV-CLSM developed is suitable for ratiometric intracellular Ca2+ measurements and other biological studies.

Cyclic ADP-ribose modulates Ca2+ release channels for activation by physiological Ca2+ entry in bullfrog sympathetic neurons

Although Ca(2+)-induced Ca2+ release (CICR) via ryanodine receptors has been found to occur in intact neurons, little is known about the physiological processes that regulate it. We studied the effects of cyclic ADP-ribose (cADPR) on CICR in cultured bullfrog sympathetic neurons by fura-2 fluorescence recording and patch-clamp techniques. cADPR applied through a patch pipette augmented action potential- or depolarizing pulse-induced rises in intracellular Ca2+ without a change in Ca2+ entry initiating the responses, but not in the presence of ryanodine. Likewise, cADPR enhanced a single or oscillatory rise(s) in intracellular Ca2+ induced by caffeine. These results strongly suggest that cADPR can be an endogenous modulator of ryanodine receptors in neurons.

Characteristics of Ca2+ release induced by Ca2+ influx in cultured bullfrog sympathetic neurones

1. A rise in intracellular Ca2+ ([Ca2+]i) and a Ca2+ current (ICa) induced by a depolarizing pulse were simultaneously recorded by fura-2 or indo-1 fluorescence and whole-cell patch clamp techniques in cultured bullfrog sympathetic ganglion cells. 2. [Ca2+]i (calculated from the ratio of fura-2 fluorescences excited at 380 and 340 nm and recorded with a photomultiplier at > 492 nm) rose regeneratively (in most cells) during a command pulse (from -60 to 0 mV, 100 ms), continued to rise thereafter, peaked at 666 ms (on average) and decayed slowly with a half-decay time of 22.8 s. 3. Scanning a single horizontal line across the cytoplasm with an ultraviolet argon ion laser (351 nm) and recording indo-1 fluorescences at two wavelengths (peaked at 410 and 475 nm) with a confocal microscope demonstrated that [Ca2+]i beneath the cell membrane rose much faster than that in the deeper cytoplasm. The time course of the spatial integral of [Ca2+]i, however, corresponded well with that recorded with fura-2 fluorescence using a photomultiplier. 4. [Ca2+]i measured by fura-2 fluorescence ratio using a photomultiplier did not increase during a strong depolarizing pulse (-60 to +80 mV), but sometimes rose after the pulse. A depolarization-induced rise in [Ca2+]i ([Ca2+]i transient) was blocked in a Ca(2+)-free, EGTA solution, reduced by lowering the extracellular Ca2+ concentration ([Ca2+]o) to 0.45 or 0.9 mM and enhanced by raising [Ca2+]o to 7.2 or 14.4 nM. 5. The extracellular Ca2+ dependence was non-linear when long depolarizing pulses (up to 500 ms) were applied; the amplitude of [Ca2+]i transient/Ca2+ entry (unit [Ca2+]i transient) increased with an increase in Ca2+ entry. 6. Increasing the duration of depolarization (-50 or -60 to 0 mV) from 20 to 500 ms enhanced asymptotically the integral of ICa (due to inactivation), and progressively the magnitude of [Ca2+]i transients, leading to the apparent non-linear dependence of unit [Ca2+]i transient on Ca2+ entry as well as on the duration of membrane depolarization. The peak time of [Ca2+]i transient was unchanged for pulse durations up to 300 ms, but prolonged with an increase in pulse duration to 500 ms. 7. Inhibitors of Ca2+ release from intracellular Ca2+ reservoirs, dantrolene (10 microM) and ryanodine (50 microM), blocked the [Ca2+]i transient to 56 and 30%, respectively, of the control. 8. The higher the basal [Ca2+]i level, the greater was the magnitude of the [Ca2+]i transients.(ABSTRACT TRUNCATED AT 400 WORDS)

Intracellular calcium dynamics in response to action potentials in bullfrog sympathetic ganglion cells

1. Dynamic changes in the intracellular free Ca2+ concentration ([Ca2+]i) following electrical membrane activity, were recorded from the neurone soma of the excised bullfrog sympathetic ganglion, using Fura-2 fluorescence and compared with the accompanying Ca(2+)-dependent electrical membrane responses. 2. The resting [Ca2+]i was about 100 nM, a value little changed by penetration with an intracellular electrode. 3. A net rise in fluorescence at a wavelength of 340 nm (Ca2+ transient) induced by a single action potential in Ringer solution rose almost in parallel with the initial decay phase of a slow Ca(2+)-dependent after-hyperpolarization; decayed in parallel with the late phase; and increased in amplitude and duration in the presence of tetraethylammonium (20 mM). 4. A Ca2+ transient induced by repetitive action potentials was increased asymptotically in amplitude and progressively in duration by increasing the number of spikes, and was slower in time course than the associated Ca(2+)-dependent K+ current. 5. Scanning a single horizontal line across the cytoplasm with an ultraviolet argon ion laser (351 nm) and recording Indo-1 fluorescence with a confocal microscope demonstrated an inward spread of a rise in [Ca2+]i following a tetanus. 6. Both single spike- and tetanus-induced Ca2+ transients were abolished in a Ca(2+)-free solution, while single or repetitive transient rises in [Ca2+]i induced by caffeine (5-10 mM) were generated under the same conditions. 7. Ryanodine (10-50 microM) did not affect tetanus-induced Ca2+ transients, whereas it blocked completely the caffeine-induced oscillation of [Ca2+]i. 8. Ca2+ transients induced by a tetanus in Ringer solution were independent of the interval from the preceding tetanus. The amplitude of Ca2+ transients induced by a tetanus in the presence of caffeine (5 mM) was equal to, or greater than, that generated in Ringer solution in any of the phases of [Ca2+]i oscillation. 9. It is suggested that under the physiological conditions here, the induction of action potentials does not cause the release of Ca2+ in the cells of the freshly excised bullfrog sympathetic ganglion, and that Ca(2+)-buffering systems contribute not only to lowering a transient rise in [Ca2+]i but also to sustaining an increased [Ca2+]i after a large Ca2+ load into the cell.

Intracellular Ca2+ dynamics in response to Ca2+ influx and Ca2+ release in autonomic neurones

Spatial and temporal changes in the intracellular free Ca2+ concentration in response to Ca2+ influx at the cell membrane and to Ca2+ release from intracellular organelles were studied by recording fluorescence of Ca(2+)-sensitive probes, fura 2 or indo 1, with conventional epifluorescence or confocal laser-scanning microscopy combined with recordings of Ca(2+)-dependent membrane responses in bullfrog sympathetic ganglion cells. It was found that an increase in the intracellular Ca2+ induced by (an) action potential(s) in freshly ganglion cells bathed in Ringer's solution was solely a result of Ca2+ influx, while a rise in the intracellular Ca2+ by Ca2+ current in voltage-clamped cultured neurones was caused by not only Ca2+ influx but also Ca2+ release. This Ca2+ release was suggested to occur by a voltage-dependent (and graded) mode of activation of a Ca(2+)-induced Ca2+ release mechanism, explaining the lack of Ca2+ release by action potentials (because of their short-lasting depolarization) in freshly isolated neurons. In both cases, there was an inward spread of an increase in intracellular Ca2+. On the other hand, all or nothing activation of Ca(2+)-induced Ca2+ release occurred in the presence of caffeine, leading to the oscillation of Ca2+ in the cells. Characteristics of this mode of Ca2+ release and unique properties of drugs to block Ca2+ release were described. Finally, the physiological significance of different types of Ca2+ release was discussed.

Basal Ca2+ and the oscillation of Ca2+ in caffeine-treated bullfrog sympathetic neurones

1. Effects of caffeine on the intracellular free Ca2+ concentration ([Ca2+]i) in single bullfrog sympathetic neurones in excised tissue were studied by recording Fura-2 fluorescence excited at 340, 361 or 380 nm and taking their ratios (R340/380 or R361/380). 2. Caffeine (3-10 mM) produced oscillation of [Ca2+]i and an 'apparent' decrease in the basal level of [Ca2+]i during a period between phasic rises. The mechanism of the latter effect was analysed in relation to the mechanism of the former. 3. Caffeine (3-10 mM) increased Fura-2 fluorescence in a range of excitation wavelength from 330 to 390 nm. The ratios of fluorescences, R340/380 and R361/380, however, were not significantly affected by caffeine. These results suggest that the 'apparent' reduction in the basal [Ca2+]i seen as a decrease in R340/380 or R361/380 results from a true decrease in [Ca2+]i. 4. Caffeine-induced decrease in [Ca2+]i persisted for every period between phasic rises of [Ca2+]i during [Ca2+]i oscillation, and after the blockade of [Ca2+]i oscillation by ryanodine. The decrease in the latter condition lasted for more than 20 min. 5. The decrease in the basal [Ca2+]i depended on the external Ca2+ concentration and was not mimicked by the action of cyclic nucleotides. 6. Possible mechanisms underlying the decrease in the basal [Ca2+]i produced by caffeine (effects on Ca2+ transport at the cell or Ca(2+)-storing organelle membrane) and their significance in relation to the [Ca2+]i oscillation were discussed.

Ultraviolet light activates blocking actions of dantrolene on intracellular Ca2+ release in bullfrog sympathetic neurones

Effects of dantrolene, a blocker of intracellular Ca2+ release, on the oscillation of the intracellular Ca2+ ([Ca2+]i) induced by caffeine were studied in bullfrog sympathetic ganglion cells, using a Fura-2 fluorescence technique. Dantrolene blocked the Ca2+ oscillation only in the cell illuminated by ultraviolet light (335-385 nm). Likewise, the blocking effects on rhythmic Ca(2+)-dependent hyperpolarizations, representing Ca2+ oscillations via activation of Ca(2+)-dependent K+ channel, occurred only under the illumination with ultraviolet light (335-385 nm), but not with visible light (404-417 nm). This wavelength dependence differs from the absorbance spectrum of dantrolene. On the other hand, dantrolene preirradiated with ultraviolet light under dark condition or ultraviolet light itself did not affect the [Ca2+]i oscillation. The blocking action was not prevented by the pretreatment of the cells with reducing agents. These results indicate that illumination of the Ca2+ release channel or dantrolene itself with ultraviolet light (possibly the former) is necessary for the drug to exert its blocking effect. Furthermore, dantrolene was found to decrease Fura-2 fluorescence and to increase cell autofluorescence, leading sometimes to a false decrease in the basal [Ca2+]i.

Spatial and dynamic changes in intracellular Ca2+ measured by confocal laser-scanning microscopy in bullfrog sympathetic ganglion cells

Confocal laser scanning microscopy (CLSM) was used to record spatial and dynamic changes in the intracellular Ca2+ [(Ca2+]i) of bullfrog sympathetic ganglion cells in excised tissue or in culture. A CLSM utilizing Ar ion laser (488 nm) and recording fluo-3 fluorescence yielded the sliced image of ganglion cells, while conventional epifluorescence microscopy provided the cell image of a convex structure. A high K+ (50 mM) solution, caffeine (3-10 mM) and electrical stimulation (10-20 Hz, 0.5-10 s) caused a homogeneous increase in fluo-3 fluorescence with or without regional differences, possibly due to intracellular organelles and other constituents. Scanning a single horizontal line across the cytoplasm with He-Cd laser (325 nm) and recording indo-1 fluorescence demonstrated that the rate of rise in [Ca2+]i following action potentials depends on the distance from the cell membrane and on the cytoplasmic constituents, showing an inward spread of 'Ca(2+)-wave' at variable speeds of 17-219 microns/s. These results suggest that heterogeneity of the cytoplasmic structures and constituents affects dynamic and spatial changes of [Ca2+]i in response to stimuli in neurones. Such heterogenic changes in [Ca2+]i would better be studied by CLSM.

An electrophysiological study on the membrane receptor-mediated action of glucocorticoids in mammalian neurons

The action of glucocorticoids (GC) on neuronal cell membrane was studied in isolated and superfused guinea pig coeliac ganglia by the intracellular recording technique. Cortisol succinate (F) hyperpolarized the membrane potential of 47 of 179 cells and changed the cell's input resistance with a latency of less than 2 min in vitro. The effect persisted under low Ca2+/high Mg2+ superfusing condition and could be blocked by RU 38486, a competitive antagonist of GC cytosolic receptor. Cortisol-21-bovine albumin conjugant exhibited the same effect. Corticosterone (B) elicited hyperpolarization in another 15 of 83 cells, but dexamethasone (Dex) did not. Dex, however, depolarized 2 of 18 cells. Aldosterone, cholesterol and vehicle (ethyl alcohol) caused no detectable change in membrane potential. In vivo studies by iontophoretic application of steroids to hypothalamic paraventricular (PVN) neurons showed that F inhibited the unit discharges in 68 of 97 PVN neurons, and the effect could be antagonized by RU 38486. Dex excited 30 of 100 neurons. Estradiol (E) also inhibited the discharges, but this inhibition was not antagonized by RU 38486. The effect of GC on PVN neurons was also examined in hypothalamic slices including the paraventricular nucleus. B inhibited 28 of 104 units and excited 7 of 104 cells, and both effects could be antagonized by RU 38486. The threshold of inhibitory response was about 10(-7) M, which is close to the physiological level of the hormone in plasma. The results suggest that GC can act non-genomically and specifically through its membrane receptor on the neuronal surface, and that there might be a chemical similarity between the membrane receptor and the traditional cytosolic GC receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

[A simple vibratome for brain slice]

A simple vibratome was fabricated using double-function electric shaver and microscopic platform. Spontaneous discharge of neurons in hippocampal and hypothalamic brain slices (in 300-400 microns thick) prepared by the vibratome could kept above 12 hours in artificial cerebro-spinal fluid.

Membrane receptor-mediated electrophysiological effects of glucocorticoid on mammalian neurons

The nongenomic membrane receptor-mediated mechanism is an important but not fully explored facet in the action of steroid hormones. In the present study the action of glucocorticoid on nerve cell membrane was studied using isolated and superfused coeliac ganglion preparations by an intracellular electrophysiological technique. Glucocorticoid hyperpolarized the membrane potential of guinea pig ganglion neurons in vitro with a latency of less than 2 min. The effect persisted under low Ca2+/high Mg2+ superfusion conditions and could be abolished by RU38486, a competitive antagonist of glucocorticoid cytosolic receptor. Bovine albumin glucocorticoid conjugant exhibited the same effect. In neurons with spontaneous discharges the glucocorticoid-caused hyperpolarization of membrane potential decreased or eliminated the discharges. The results strongly suggest that glucocorticoid can act nongenomically through its neuronal membrane receptor. The steroid-induced hyperpolarization was accompanied by a change in the input resistance of the cell, indicating an involvement of some kind(s) of ion channel(s) in the action of glucocorticoid.