Allosteric modulation of neurotoxin binding to voltage-sensitive sodium channels by Ptychodiscus brevis toxin 2

The effects of Ptychodiscus brevis toxin 2 (PbTx-2) on the binding of neurotoxins at four different neurotoxin receptor sites on voltage-sensitive sodium channels in rat brain synaptosomes were examined. Binding of saxitoxin at neurotoxin receptor site 1 and Leiurus quinquestriatus alpha-scorpion toxin (LqTx) at neurotoxin receptor site 3 was unaffected. PbTx-2 enhanced binding of batrachotoxinin A 20-alpha-benzoate (BTX-B) to neurotoxin receptor site 2 and Centruroides suffusus suffusus beta-scorpion toxin (CsTx II) to site 4 on sodium channels. These results support the proposal that PbTx-2 and related toxins act at a new receptor site (site 5) that has not been previously analyzed in binding experiments. Half-maximal effects of PbTx-2 were observed in the range of 20-50 nM PbTx-2. The enhancement of BTX-B binding was reduced by depolarization. Saturating concentrations of PbTx-2 reduced KD values for binding of BTX-B and CsTx-II 2.9-fold and 2.6-fold, respectively. The effects of PbTx-2 and LqTx in enhancing BTX-B binding were synergistic. A model involving both preferential binding of BTX-B, PbTx-2, LqTx, and CsTx II to active states of sodium channels and allosteric interactions among the four receptor sites at which these toxins act accommodates these and previous results.     

Ptychodiscus brevis toxin enhances the frequency-dependent depression of the monosynaptic reflex in neonatal rat spinal cord in vitro

The involvement of frequency-dependent depression (FDD) of synaptic transmission for the depressant action of the Ptychodiscus brevis toxin (PbTx) was investigated in neonatal rat spinal cord in vitro. The stimulation of a dorsal root by train of pulses (five stimuli) at different frequencies evoked potentials in the ventral root (monosynaptic reflex, MSR). Amplitude of the fifth response as percent of first response at 0.1, 0.2, 0.5, 1.0 and 2.0 Hz were 90, 80, 75, 70 and 50%, respectively. In Mg2+-free medium, PbTx depressed the MSR and also enhanced the FDD in a concentration-dependent manner. Further, the PbTx-induced depression can well be correlated with the enhancement of FDD (r=0.98). In the presence of Mg2+ (1.3 mM), the FDD was greater than that in the absence of Mg2+. But in the presence of Mg2+ PbTx did not alter FDD, even though there was 25% depression at 28 microM (significantly lesser than in Mg2+-free medium). The results indicate that the Mg2+-sensitive component of PbTx-induced depression of MSR is mediated via the neuronal systems involving FDD.     

Relative potency of synthetic analogs of Ptychodiscus brevis toxin in depressing synaptic transmission evoked in neonatal rat spinal cord in vitro

Effects of Ptychodiscus brevis toxin (PbTx) analogs on the spinal synaptic transmission in neonatal rats in vitro were evaluated. PbTx1/PbTx2 had aromatic groups and PbTx3/PbTx4 had aliphatic groups. All the analogs depressed monosynaptic reflex (MSR) and polysynaptic reflex (PSR) in a concentration-dependent manner. The maximal depression of MSR (75% from initial) and PSR (96%) was at 84 microM for PbTx1. Concentration to produce 25% inhibition from initial (IC25) by PbTx1 for MSR and PSR was < or =2.8 microM. The maximal depression of MSR (80%) was at 96 microM and PSR (100%) was at 32 microM by PbTx2. IC25 for MSR and PSR were 5.5 microM and <3.2 microM, respectively. PbTx3 decreased MSR by 25% maximally (=IC25) at 36 microM. The depression of PSR fluctuated and was maximal (75%) at 108 microM and IC25 was 6.2 microM. PbTx4 depressed MSR and PSR at the maximum of 35% at 32 microM and IC25 for MSR was 8.3 microM and for PSR was 35 microM. Rank order of potency of toxins for depressing MSR was PbTx1>PbTx2>PbTx4>PbTx3; and for PSR it was PbTx2>PbTx1>PbTx3>PbTx4. Results indicate that the toxins having aromatic groups exhibited greater neurotoxicity.     

Actions of Ptychodiscus brevis toxins on nerve and muscle membranes

Pharmacological actions of two brevetoxins isolated from Ptychodiscus brevis, T17 and T34, on nerve and muscle membranes were studied using vertebrate and invertebrate preparations. T17 (10 ng/ml) caused an increase in the frequency of miniature endplate potentials (MEPPs) in rat and frog neuromuscular junctions. Application of tetrodotoxin (TTX) completely abolished the increase in MEPP frequency. The results suggest that T17 depolarizes the nerve terminal through opening of the sodium channel. Application of either T17 or T34 to the crayfish and squid giant axons caused a dose-dependent depolarization of the axon membranes with a maximum depolarization of about 30 mV. The depolarizing action was antagonized by sodium-free external saline solution or TTX. Voltage clamp experiments demonstrated that the primary action of the toxins is to cause the sodium channels to open at the normal resting potential. The binding of toxin to a channel site could be prevented by procaine, but not by TTX. The binding site for T17 is presumably separate from the TTX receptor, but related or identical to the binding site for procaine. The brevetoxin-induced depolarization of the nerve terminal membrane with the subsequent enhanced transmitter release is the underlying mechanism for a number of pharmacological actions on various neuro-effector systems.     

Isolation and spectral characteristics of four toxins from the dinoflagellate Ptychodiscus brevis

Four ichthyotoxins were isolated from crude toxic extracts of Ptychodiscus brevis using a combination of solvent partitioning, thin layer chromatography and reversed phase high pressure liquid chromatography. The toxins were analyzed by mass, infrared, 1H- and 13C-NMR spectroscopy and were found to constitute two structural families of two toxins each: brevetoxins 1 and 2 and brevetoxins 3 and 4. Comparison with literature data indicates that brevetoxins 1 and 2 are identical to the previously described and characterized 11-ring polyether toxins brevetoxins C and B, respectively. The other two compounds (brevetoxins 3 and 4) also represent a structural pair (with chloroacetone and alpha-methylene-propanal side chains, respectively) which has a different, but related, basic ring-structure.     

Specific antibodies directed against toxins of Ptychodiscus brevis (Florida's red tide dinoflagellate)

Specific antibodies directed against Ptychodiscus brevis 'brevetoxins' have been produced in a goat. The haptenic toxin T34 was chemically reduced to toxin T17, covalently-linked to succinic acid via anhydride coupling, and coupled to bovine serum albumin using standard carbodiimide condensation procedures. The hapten coupling efficiency ranged from 10.4 to 13.5 moles of toxin bound per mole of protein. Antibody titers were directly related to the frequency of immunization, and weekly intervals appeared optimum for maintaining adequate titers. [3H]Brevetoxin T17 is displaced in a competitive manner from the antibody-antigen complexes by unlabeled toxin, but the antibodies do not distinguish between T17 and T34. The sensitivity achieved, using purified brevetoxins as competitive inhibitors of [3H]T17 binding, was 600 picograms. The assay linearity ranged from 1.5 to 48 ng.     

Toxicity of two toxins from the Florida red tide marine dinoflagellate, Ptychodiscus brevis

The purification and crystallization of T17, a toxin from Ptychodiscus brevis, is reported. The toxicity of this compound and a second toxin known as T34 are compared by i.v., i.p. and oral administration in mice. Both toxins produce symptoms characteristic of muscarnic stimulants; hypersalivation, rhinorrhea and excessive urination and defecation being the most commonly observed. T17, which is orally toxic, is believed to be the agent responsible for Neurotoxic Shellfish Poisoning.     

Calcium modulatory properties of O,O-diphenyl O-N-cyclooctyl phosphoramidate [corrected] isolated from Ptychodiscus brevis in rat atria and smooth muscle

Calcium modulatory activity of a marine toxin has been studied employing in vitro preparations. The toxin induced contracture in rat diaphragm was not modified by denervation, d-tubocurarine and tetrodotoxin (TTX). In contrast, varying concentrations of calcium, EGTA and ryanodine inhibited the contracture significantly. The toxin produced a series of repeating contractions in vas deferens. Experiments with TTX, adrenoceptor blockers and other agents exclude a release of neuromediators or direct stimulation of post synaptic receptors to account for the rhythmic effect in vas deferens. The dependence of rhythmicity on external Ca2+ concentration and inhibiting effect of Mn2+, ryanodine and nifedipine indicate a direct activation of voltage-sensitive calcium channel. The toxin also evoked a similar pattern of response in paced atria mediated through Ca2+ influx.     

Determination of six major flavonoid glycosides in Saussurea mongolica by capillary electrophoresis

A new capillary electrophoresis (CE) method was established for simultaneous assay of six flavonoid O-glycosides, asebotin (AS), kaempferol 3- O-beta- D-glucopyranoside (KG), kaempferol 3- O-alpha- L-rhamnopyranoside (KR), 7-methoxykaempferol 3- O-alpha- L-rhamnopyranoside (KMR), quercetin 3- O-beta- D-glucopyranoside (QG) and quercetin 3- O-alpha- L-rhamnopyranoside (QR) obtained from Chinese herbal plant extract of Saussurea mongolica. The optimum buffer system was 30 mmol/L borate buffer (Na2B4O7/HCl, pH 9.00) with 40 % (v/v) methanol. Voltage was 15 kV and detection at 270 nm. The application of this method for the separation and determination of the six flavonoid O-glycosides in S. mongolica is reported. The relative standard deviations of migration times and peak areas were < 2.61 and 4.41%, respectively. The contents of six natural products ranged from 0.043 to 0.60 mg/g and recoveries ranged from 92.4 to 104.4%. The effects of pH value, buffer concentration, surfactant, beta -cyclodextrin and organic modifier on the separation were investigated.     

Isolation of the major lethal toxin in the venom of Bungarus flaviceps.

The major lethal toxin in the venom of Bungarus flaviceps has been isolated by ion-exchange chromatography, absorption chromatography and RP-HPLC with a 14-fold purification and an overall yield of 16.5% of the lethal toxicity contained in crude venom. Its sublethal dose (LD(50)) determined in mice weighing 18-20 g was 0.25 (0.19-0.32) microg per mouse. The lethal toxin was pure according to disc- and SDS-PAGE as well as gel HPLC. Its apparent molecular weight determined by SDS-PAGE was 29 kDa. It is a basic protein consisting of two polypeptide chains having apparent molecular weights of 17 and 8 kDa, respectively. The toxin has PLA activity but is free of ACE activity.     

Optimization of ultrasound assisted extraction of six major compounds from Cimicifugae Rhizome

Cimicifugae Rhizome (RC) is one of many commonly used traditional Chinese medicines. This study used Box-Behnken Design (BBD), a widely used form of response surface methodology (RSM), to optimize the conditions of the ultrasound-assisted extraction (UAE) for the extraction of phenolic compounds from CimicifugaeRhizome. The influence of three independent variables,including ethanol concentration (%), extraction time (min) and solvent-to-material ratio (mL/g), on the extraction yields of phenolic compounds were examined. The results demonstrated that the optimal ultrasound-assisted extraction (UAE) conditions were as follows: ethanol concentration of 68%, an extraction time of 19 min, and solvent-to-material ratio of 30 mL/g for the extraction of caffeic acid, cimicifugoside, ferulic acid, isoferulicacid, cimifugin, 4'-O-β-glucopyranosyl-5-O-methylvisamminol. These results demonstrated the suitability of UAE for the extraction of phenolic compounds from CimicifugaeRhizome.     

Sertraline versus paroxetine in major depression: clinical outcome after six months of continuous therapy

reuptake inhibitors (SSRIs) during continuation therapy. This investigation reports the differential effect of 6 months of treatment with sertraline versus paroxetine for symptoms of depression, quality of life, and personality outcomes. Outpatients with unipolar major depression (DSM-III-R) were randomly assigned to receive 24 weeks of double-blind treatment with flexible doses of paroxetine (20-40 mg) or sertraline (50-150 mg). Assessments included the Montgomery-Asberg Depression Rating Scale (MADRS), the Clinical Global Impression Scale, the Battelle Quality of Life Questionnaire, and the Structured Clinical Interview for DSM-III-R Personality Disorders screen questionnaire. One hundred seventy-six patients (mean age, 43 years; 64% female; baseline MADRS, 30.3) were treated with sertraline and 177 patients (mean age, 42 years; 71% female; MADRS, 30.7) with paroxetine. Antidepressant efficacy during continuation therapy was sustained, with only 2% of patients receiving sertraline and 9% of patients receiving paroxetine suffering a relapse. Continuation therapy resulted in a substantial conversion of responders during short-term treatment to full remission: remitter rates increased from 52% to 80% for sertraline and from 57% to 74% for paroxetine. The improvements in quality of life were related to a reduced depression score. SSRI treatment had significant beneficial effects on both categorical and dimensional measures of personality. A logistic regression analysis identified early response (25% reduction in MADRS scores at week 2) as the most important predictor of treatment response, whereas high severity, chronicity, and poor baseline quality of life had no effect. Both treatments were well-tolerated, with sertraline having a somewhat lower side effect profile. Sertraline and paroxetine demonstrated comparable efficacy during short-term and continuation therapy. Treatment was associated with significant improvement in quality of life and with reductions in axis II personality psychopathology.     

Variations in circulating cytokine levels during 52 week course of treatment with SSRI for major depressive disorder

Major depressive disorder (MDD) is a psychiatric condition characterized by hypercortisolism and variations in circulatory cytokines. Previously it has been reported that administration of selective serotonin reuptake inhibitors (SSRI) in MDD patients modify cortisol and cytokine levels but these studies only evaluated changes over a short time period. This work reports the long-term effects of administration of SSRI on the cortisol levels and pro-/anti-inflammatory cytokine profile in a group of MDD patients treated for 52 weeks. A total of 31 patients diagnosed with MDD received anti depressant treatment with SSRI. HDRS and BDI were administered over a year, and levels of interleukin IL-1β, IL-10, IL-2, IFN-γ, IL-4, IL-13, and 24-h urine cortisol were determined at weeks (W) 0, 5, 20, 36 and 52 of treatment. Before treatment we found high levels of cortisol, IL-4, IL-13 (Th2) and IL-10 in MDD patients when compared with healthy volunteers. At W20 psychiatric scales indicated a remission of the depressive episode concomitantly with increments in IL-2 and IL-1β but without changes in cortisol. Towards the end of the treatment (W52) we observed a significant reduction (p < 0.01) in cortisol levels, with an increment in IL-1β and IFN-γ and a decrease in Th2 cytokines. Our results suggest that depressed patients only reach a partial reestablishment of HPA axis function after the long-term administration of SSRI.     

Evaluation of the cyclooxygenase inhibiting effects of six major cannabinoids isolated from Cannabis sativa

Cyclooxygenase enzymes (COX-1 and COX-2) catalyse the production of prostaglandins from arachidonic acid. Prostaglandins are important mediators in the inflammatory process and their production can be reduced by COX-inhibitors. Endocannabinoids, endogenous analogues of the plant derived cannabinoids, occur normally in the human body. The Endocannabinoids are structurally similar to arachidonic acid and have been suggested to interfere with the inflammatory process. They have also been shown to inhibit cancer cell proliferation. Anti-inflammatory effects of cannabinoids and endocannabinoids have been observed, however the mode of action is not yet clarified. Anti-inflammatory activity (i.e., inhibition of COX-2) is proposed to play an important role in the development of colon cancer, which makes this subject interesting to study further. In the present work, the six cannabinoids tetrahydrocannabinol (Δ?-THC), tetrahydrocannabinolic acid (Δ?-THC-A), cannabidiol (CBD), cannabidiolic acid (CBDA), cannabigerol (CBG) and cannabigerolic acid (CBGA), isolated from Cannabis sativa, were evaluated for their effects on prostaglandin production. For this purpose an in vitro enzyme based COX-1/COX-2 inhibition assay and a cell based prostaglandin production radioimmunoassay were used. Cannabinoids inhibited cyclooxygenase enzyme activity with IC?? values ranging from 1.7·10?3 to 2.0·10?? M.     

Simultaneous determination of six major stilbenes and flavonoids in Smilax china by high performance liquid chromatography

A simple, sensitive and specific HPLC method was developed for simultaneous determination of the six major active constituents in Smilax china, namely taxifolin-3-O-glycoside (1), piceid (2), oxyresveratrol (3), engeletin (4), resveratrol (5) and scirpusin A (6), respectively. The samples were separated on an Aglient Zorbax XDB-C18 column with gradient elution of acetonitrile and 0.02% phosphoric acid (v/v) at a flow rate of 1.0 ml/min and detected at 300 nm. The six target compounds were completely separated within 35 min. All calibration curves showed good linearity (r2>0.999) within test ranges. The reproducibility was evaluated by intra- and inter-day assays and R.S.D. values were less than 3.7%. The recoveries were between 93.7 and 103.0%. The method was successfully applied to the analysis of six constituents in 15 commercial samples of S. china. The results indicated that the developed HPLC assay was readily utilized as a quality control method for S. china.     

Variations in Loxosceles spider venom composition and toxicity contribute to the severity of envenomation

Envenomation by Loxosceles spiders causes two main clinical manifestations: cutaneous and systemic loxoscelism. The factors contributing to the severity of loxoscelism are not fully understood. We have analysed biochemical and toxicity variations in venom of L. laeta and L. intermedia, with the aim to find a correlation with the seriousness of loxoscelism. Differences in expression of proteins, glycoproteins and sphingomyelinase activity were observed between venom from male and female spiders and between venom from the two species. These differences were reflected in the toxicity of the venoms including the capacity to induce complement-dependent haemolysis, dermonecrosis and lethality. Comparative analysis of gender and species, showed that these biological activities were more prominent in venom from female spiders, especially from L. laeta. Antiserum raised against venom from females L. laeta spiders had the highest efficacy in neutralizing venoms of males and females of both species. These results indicate that the severity of loxoscelism depends, at least partially, on the species and sex of the spider and suggest that for accidents involving L. laeta an specific serum therapy is necessary. Furthermore, it emphasizes the efficacy of the antiserum produced against L. laeta female venom in neutralizing Loxosceles venoms from different species and gender.     

Simultaneous quantification of six major active saponins of Panax notoginseng by high-performance liquid chromatography-UV method

A simple, sensitive and specific high-performance liquid chromatography-UV (HPLC-UV) method has been developed for the first time to simultaneously quantify the six major active saponins of Panax notoginseng, namely notoginsenoside R1, ginsenoside Rg1, Rb1, Rg2, Rh1 and Rd. Astragaloside IV is used as the internal standard. This HPLC assay was performed on a reversed-phase C18 column with gradient elution of acetonitrile and 0.01% formic acid in 30 min. The method provided good reproducibility and sensitivity for the quantification of six saponins with overall intra- and inter-day precision and accuracy of less than 4.0% and higher than 90%, respectively. This assay is successfully applied to the determination of the six saponins in 23 notoginseng samples. The results indicated that the developed HPLC assay can be readily utilized as a quality control method for P. notoginseng.     

Purification and composition of a toxin from the posterior salivary gland of Octopus dofleini

The venom from the posterior salivary gland of the octopus, O. dofleini, was fractionated using gel filtration. A single peak toxic to Crustacea was identified. SDS polyacrylamide gel electrophoresis indicates that the toxin has a molecular weight of 23,000 ± 1000 daltons. It consists of a single subunit with an isoelectric point of 5·2–5·3. This is consistent with the amino acid analysis which indicates a content of 31 aspartic and 27 glutamic residues in contrast to 10 lysine and 7 arginine. The toxic activities are notably resistant to proteolytic destruction but can be destroyed by boiling for 10 min.