Interaction of batrachotoxin with the local anesthetic receptor site in transmembrane segment IVS6 of the voltage-gated sodium channel

The voltage-gated sodium channel is the site of action of more than six classes of neurotoxins and drugs that alter its function by interaction with distinct, allosterically coupled receptor sites. Batrachotoxin (BTX) is a steroidal alkaloid that binds to neurotoxin receptor site 2 and causes persistent activation. BTX binding is inhibited allosterically by local anesthetics. We have investigated the interaction of BTX with amino acid residues I1760, F1764, and Y1771, which form part of local anesthetic receptor site in transmembrane segment IVS6 of type IIA sodium channels. Alanine substitution for F1764 (mutant F1764A) reduces tritiated BTX-A-20-α-benzoate binding affinity, causing a 60-fold increase in Kd. Alanine substitution for I1760, which is adjacent to F1764 in the predicted IVS6 transmembrane alpha helix, causes only a 4-fold increase in Kd. In contrast, mutant Y1771A shows no change in BTX binding affinity. For wild-type and mutant Y1771A, BTX shifted the voltage for half-maximal activation ≈40 mV in the hyperpolarizing direction and increased the percentage of noninactivating sodium current to ≈60%. In contrast, these BTX effects were eliminated completely for the F1764A mutant and were reduced substantially for mutant I1760A. Our data suggest that the BTX receptor site shares overlapping but nonidentical molecular determinants with the local anesthetic receptor site in transmembrane segment IVS6 as well as having unique molecular determinants in transmembrane segment IS6, as demonstrated in previous work. Evidently, BTX conforms to a domain–interface allosteric model of ligand binding and action, as previously proposed for calcium agonist and antagonist drugs acting on l-type calcium channels.

Critical relationship between sodium valproate dose and human teratogenicity: results of the Australian register of anti-epileptic drugs in pregnancy

To compare the incidence of foetal malformations (FMs) in pregnant women with epilepsy treated with different anti-epileptic drugs (AED) and doses, and the influence of seizures, family and personal history, and environmental factors. A prospective, observational, community-based cohort study. Methods. A voluntary, Australia-wide, telephone-interview-based register prospectively enrolling three groups of pregnant women: taking AEDs for epilepsy; with epilepsy not taking AEDs; taking AEDs for a non-epileptic indication. Four hundred and fifty eligible women were enrolled over 40 months. Three hundred and ninety six pregnancies had been completed, with 7 sets of twins, for a total of 403 pregnancy outcomes. Results. 354 (87.8%) pregnancy outcomes resulted in a healthy live birth, 26 (6.5%) had a FM, 4 (1%) a death in utero, 1 (0.2%) a premature labour with stillbirth, 14 (3.5%) a spontaneous abortion and 4 lost to follow-up. The FM rate was greater in pregnancies exposed to sodium valproate (VPA) in the first trimester (116.0%) compared with those exposed to all other AEDs (16.0% vs. 2.4%, P < 0.01) or no AEDs (16.0% vs. 3.1 %, P < 0.01). The mean daily dose of VPA taken in pregnancy with FMs was significantly greater than in those without (11975 vs: 1128 mg, P < 0.01). The incidence of FM with VPA doses greater than or equal to 1100 mg was 30.2% vs. 3.2% with doses < 1100 mg (P < 0.01). Conclusions. There is a dose-effect relationship for FM and exposure to VPA during the first trimester of pregnancy, with higher doses of VPA associated with a significantly greater risk than with lower doses or with other AEDs. These results highlight the need to limit, where possible, the dose of VPA in pregnancy. (C) 2004 Elsevier Ltd. All rights reserved.

The use of sodium carboxymethylcellulose in the preparation of spray-dried proteins for pulmonary drug delivery

The use of sodium carboxymethylcellulose (NaCMC) as a spray-drying excipient in the preparation of inhalable formulations of proteins was investigated, using alkaline phosphatase as a model functional protein. Two spray-dried powders were investigated: a control powder comprising 100% (w/w) alkaline phosphatase and a test powder comprising 67% (w/w) NaCMC and 33% (w/w) alkaline phosphatase. Following physicochemical characterisation, the powders were prepared as both dry powder inhaler (DPI) and pressurised metered dose inhaler (pMDI) formulations. The aerosolisation performance of the formulations was assessed using a Multi-Stage Liquid Impinger, both immediately after preparation and over a 16-week storage period. Formulating the control powder as a DPI resulted in a poor fine particle fraction (FPF: 10%), whereas the FPF of the NaCMC-modified DPI formulation was significantly greater (47%). When the powders were formulated as pMDI systems, the control and NaCMC-modified powders demonstrated FPFs of 52% and 55%, respectively. Following storage, reduced FPF was observed for all formulations except the NaCMC-modified pMDI system; the performance of this formulation following storage was statistically equivalent to that immediately following preparation. Co-spray-drying proteins and peptides with NaCMC may therefore offer an alternative method for the preparation of stable and respirable pMDI formulations for pulmonary delivery. © 2010 Elsevier B.V.

In vitro antioxidant and immunomodulatory activity of transglutaminase-treated sodium caseinate hydrolysates

Sodium caseinate (NaCN) was incubated prior to and after hydrolysis with a microbial transglutaminase (TGase) and hydrolysed with Prolyve 1000. The resultant hydrolysates were tested for their immunomodulatory and antioxidant activity. TGase-treated hydrolysates significantly reduced (p < 0.05) the production of IL-6 at 0.5 and 1 mg mL−1 and the non-TGase treated hydrolysate reduced the production of IL-6 at 1 mg mL−1 in concanavalin (ConA) stimulated Jurkat T cells. None of the samples had an effect on IL-2. The hydrolysates showed higher oxygen radical absorbance capacity assay and ferric reducing antioxidant power activity than unhydrolysed NaCN, but no significant (p > 0.05) differences were found between the TGase-treated and non-TGase-treated samples. In the presence of hydrogen peroxide, the non-TGase-treated sample exhibited the highest DNA protective effect in U937 cells. These findings suggest that NaCN derived hydrolysates with and without treatment with TGase may exert specific antioxidant, genoprotective and anti-inflammatory effects.

Biodistribution of the Radiopharmaceutical Technetium- 99m-Sodium Phytate in Rats After Splenectomy

Drugs and surgery can interfere with the biodistribution of radiopharmaceuticals and data about the effect of splenectomy on the metabolism of phytate-Tc-99m are scarce. This study aimed at evaluating the interference of splenectomy on phytate-Tc-99m biodistribution and liver function in rats. The SP group rats (n=6) underwent splenectomy. In group C (control) the animals were not operated on. After 15 days, all rats were injected with 0.1mL of Tc-99m-phytate via orbital plexus (0.66MBq). After 30 minutes, liver samples were harvested, weighed and the percentage of radioactivity per gram (%ATI-g) was determined by a Wizard Perkin-Elme gama counter. The ATI%-g in splenectomized rats (0.99±0.02) was significantly higher than in controls (0.4±0.02), (p=0.034). ALT, AST and HDL were significantly lower in SP rats (p= 0.001) and leukocytosis was observed in SP rats. In conclusion, splenectomy in rats changed the hepatic biodistribution of Tc-99m-phytate and liver enzimatic activity

Biodistribution of the Radiopharmaceutical Technetium- 99m-Sodium Phytate in Rats After Splenectomy

Drugs and surgery can interfere with the biodistribution of radiopharmaceuticals and data about the effect of splenectomy on the metabolism of phytate-Tc-99m are scarce. This study aimed at evaluating the interference of splenectomy on phytate-Tc-99m biodistribution and liver function in rats. The SP group rats (n=6) underwent splenectomy. In group C (control) the animals were not operated on. After 15 days, all rats were injected with 0.1mL of Tc-99m-phytate via orbital plexus (0.66MBq). After 30 minutes, liver samples were harvested, weighed and the percentage of radioactivity per gram (%ATI-g) was determined by a Wizard Perkin-Elme gama counter. The ATI%-g in splenectomized rats (0.99±0.02) was significantly higher than in controls (0.4±0.02), (p=0.034). ALT, AST and HDL were significantly lower in SP rats (p= 0.001) and leukocytosis was observed in SP rats. In conclusion, splenectomy in rats changed the hepatic biodistribution of Tc-99m-phytate and liver enzimatic activity

Stability of micafungin sodium solutions at different concentrations in glass bottles and syringes

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Determination of potassium and sodium in an ash sample by gamma-ray spectroscopy

Neutron activation analysis and gamma-ray spectroscopy were used to determine the quantity of potassium and sodium in an ash sample of Tabebuia sp bombarded with thermal neutrons. These techniques, widely applied in nuclear physics, can be used in the context of wood science as an alternative for the usual physical chemistry methods applied in this area. The quantity of K and Na in an 8.60 +/- 0.10 mg of ash was determined as being 1.3 +/- 0.3 mg and 11.0 +/- 1.8 mu g, respectively. The ratio of Tabebuia sp converted into ash was also determined as 0.758 +/- 0.004%.