A Composite Polyelectrolytic Matrix for Controlled Oral Drug Delivery

The purpose of this study was to formulate drug-loaded polyelectrolyte matrices constituting blends of pectin, chitosan (CHT) and hydrolyzed polyacrylamide (HPAAm) for controlling the premature solvation of the polymers and modulating drug release. The model drug employed was the highly water-soluble antihistamine, diphenhydramine HCl (DPH). Polyelectrolyte complex formation was validated by infrared spectroscopy. Matrices were characterized by textural profiling, porositometry and SEM. Drug release studies were performed under simulated gastrointestinal conditions using USP apparatus 3. FTIR spectra revealed distinctive peaks indicating the presence of –COO⁻ symmetrical stretching (1,425–1,390 cm⁻¹) and -NH₃⁺ deformation (1,535 cm⁻¹) with evidence of electrostatic interaction between the cationic CHT and anionic HPAAm corroborated by molecular mechanics simulations of the complexes. Pectin–HPAAm matrices showed electrostatic attraction due to residual –NH₂ and –COO⁻ groups of HPAAm and pectin, respectively. Textural profiling demonstrated that CHT-HPAAm matrices were most resilient at 6.1% and pectin–CHT–HPAAm matrices were the least (3.9%). Matrix hardness and deformation energy followed similar behavior. Pectin–CHT–HPAAm and CHT–HPAAm matrices produced type IV isotherms with H3 hysteresis and mesopores (22.46 nm) while pectin–HPAAm matrices were atypical with hysteresis at a low P/P₀ and pore sizes of 5.15 nm and a large surface area. At t _2 h, no DPH was released from CHT–HPAAm matrices, whereas 28.2% and 82.2% was released from pectin–HPAAm and pectin–CHT–HPAAm matrices, respectively. At t _4 h, complete DPH release was achieved from pectin–CHT–HPAAm matrices in contrast to only 35% from CHT–HPAAm matrices. This revealed the release-modulating capability of each matrix signifying their applicability in controlled oral drug delivery applications.     

Release Behaviour of Propranolol HCl from Hydrophilic Matrix Tablets Containing Psyllium Powder in Combination with Hydrophilic Polymers

The objective of this study was to investigate the release behaviour of propranolol hydrochloride from psyllium matrices in the presence hydrophilic polymers. The dissolution test was carried out at pH 1.2 and pH 6.8. Binary mixtures of psyllium and hydroxypropyl methylcellulose (HPMC) used showed that an increase in the percentage of HPMC in the binary mixtures caused a significant decrease in the release rate of propranolol. Psyllium–alginate matrices produced lower drug release as compared to when the alginate was the matrix former alone. When sodium carboxy methyl cellulose (NaCMC) was incorporated into the psyllium, the results showed that matrices containing the ratio of psyllium–NaCMC in the 1:1 ratio are able to slow down the drug release significantly as compared to matrices made from only psyllium or NaCMC as retardant agent suggesting that there could be a synergistic effect between psyllium and NaCMC. The double-layered tablets showed that the psyllium and HPMC in the outer shell of an inner formulation of psyllium alone had the greatest effect of protecting the inner core and thus producing the lowest drug release (DE = 38%, MDT = 93 min). A significant decrease in the value of n in Q = kt ⁿ from 0.70 to 0.51 as the psyllium content was increased from 50 to 150 mg suggests that the presence of psyllium in HPMC matrices affected the release mechanism. Psyllium powder had the ability in the combination with other hydrophilic polymers to produce controlled release profiles. Care and consideration should as such be taken when formulating hydrophilic matrices in different combinations.     

Biotransformation of Acetamide to Acetohydroxamic Acid at Bench Scale Using Acyl Transferase Activity of Amidase of <Emphasis Type="Italic">Geobacillus pallidus</Emphasis> BTP-5x MTCC 9225

The bioprocess employing acyl transferase activity of intracellular amidase of Geobacillus pallidus BTP-5x MTCC 9225 was harnessed for the synthesis of pharmaceutically important acetohydroxamic acid. G. pallidus BTP-5x exhibited highest acyl transferase activity with acetamide: hydroxylamine in ratio of 1:5 in 0.1 M NaH₂PO₄/Na₂HPO₄ buffer (pH 7.5) at 65°C. In one liter fed-batch reaction containing 1:5 ratio of two substrates total of eight feedings of 0.05 M/20 min of acetamide were made and it was found that maximum acetohydroxamic production was achieved at 3:5 ratios of substrate and cosubstrate. In 1 l bench scale batch reaction containing 0.3 M acetamide, 0.5 M hydroxylamine in 0.1 M NaH₂PO₄/Na₂HPO₄ buffer (pH 7.5, 50°C, 400 rpm) and 0.5 mg/ml (dry cell weight) of whole cells of G. pallidus BTP-5x (as biocatalyst) resulted in an yield of 0.28 M of acetohydroxamic acid after 20 min reaction time at 50°C. The acetamide bioconversion rate was 90–95% (mol mol⁻¹) and 51 g powder containing 40% (w/w) acetohydroxamic acid was recovered after lyophilization.     

Scutellarin Blocks Sodium Current in Freshly Isolated Mouse Hippocampal CA1 Neurons

Scutellarin (Scu), the main bioactive component of Erilgeron breviscapus, protects the brain against ischemic damages. To explore the therapeutic mechanism of Scu, we investigated the impact of Scu on sodium current (I _Na) of freshly isolated mouse hippocampal CA1 neurons using the whole-cell patch clamp technique. Results showed that Scu inhibited I _Na in concentration- and holding potential-dependent manners. At 50 μM, Scu markedly shifted the steady state inactivation curve of I _Na towards a more negative potential, slowed down the recovery of I _Na from inactivation state, and elicited a frequency-dependent block of I _Na. The shape of the current–voltage (I–V) curve and the steady state activation curve of I _Na were unaffected by Scu treatment. These findings suggest that Scu is capable of inhibiting I _Na in neurons through predominantly affecting the inactivated state of I _Na. Inhibition of Na⁺ channels provides a novel pharmacological basis for the anti-ischemic application of Scu.     

Acaricidal effects of <Emphasis Type="Italic">Corymbia citriodora</Emphasis> oil containing <Emphasis Type="Italic">para</Emphasis>-menthane-3,8-diol against nymphs of <Emphasis Type="Italic">Ixodes ricinus</Emphasis> (Acari: Ixodidae)

The toxicity of para-menthane-3,8-diol (PMD), the main arthropod-repellent compound in the oil of the lemon eucalyptus, Corymbia citriodora, was evaluated against nymphs of Ixodes ricinus using five methods (A–E) of a contact toxicity bioassay. Mortality rates were estimated by recording numbers of dead nymphs at 30 min intervals during the first 5 h after the start of exposure and at longer intervals thereafter. The mortality rate increased with increasing concentration of PMD and duration of exposure with a distinct effect after 3.5 h. From the results obtained by methods A, C and E, the LC₅₀ range was 0.035–0.037 mg PMD/cm² and the LC₉₅ range was 0.095–0.097 mg PMD/cm² at 4 h of exposure; the LT₅₀ range was 2.1–2.8 h and the LT₉₅ range was 3.9–4.2 h at 0.1 mg PMD/cm². To determine the duration of toxic activity of PMD, different concentrations (0.002, 0.01, 0.1 mg PMD/cm²) were tested and mortality was recorded at each concentration after 1 h; thereafter new ticks were tested. This test revealed that the lethal activity of PMD remained for 24 h but appeared absent after 48 h. The overall results show that PMD is toxic to nymphs of I. ricinus and may be useful for tick control.     

Combined arene ruthenium porphyrins as chemotherapeutics and photosensitizers for cancer therapy

Mononuclear 5-(4-pyridyl)-10,15,20-triphenylporphyrin and 5-(3-pyridyl)-10,15,20-triphenylporphyrin as well as tetranuclear 5,10,15,20-tetra(4-pyridyl)porphyrin (tetra-4-pp) and 5,10,15,20-tetra(3-pyridyl)porphyrin) (tetra-3-pp) arene ruthenium(II) derivatives (arene is C₆H₅Me or p-Pr ⁱ C₆H₄Me) were prepared and evaluated as potential dual photosensitizers and chemotherapeutics in human Me300 melanoma cells. In the absence of light, all tetranuclear complexes were cytotoxic (IC₅₀ ≤ 20 μM), while the mononuclear derivatives were not (IC₅₀ ≥ 100 μM). Kinetic studies of tritiated thymidine and tritiated leucine incorporations in cells exposed to a low concentration (5 μM) of tetranuclear p-cymene derivatives demonstrated a rapid inhibition of DNA synthesis, while protein synthesis was inhibited only later, suggesting arene ruthenium–DNA interactions as the initial cytotoxic process. All complexes exhibited phototoxicities toward melanoma cells when exposed to laser light of 652 nm. At low concentration (5 μM), LD₅₀ of the mononuclear derivatives was between 5 and 10 J/cm², while for the tetranuclear derivatives LD₅₀ was approximately 2.5 J/cm² for the [Ru₄(η⁶-arene)₄(tetra-4-pp)Cl₈] complexes and less than 0.5 J/cm² for the [Ru₄(η⁶-arene)₄(tetra-3-pp)Cl₈] complexes. Examination of cells under a fluorescence microscope revealed the [Ru₄(η⁶-arene)₄(tetra-4-pp)Cl₈] complexes as cytoplasmic aggregates, whereas the [Ru₄(η⁶-arene)₄(tetra-3-pp)Cl₈] complexes were homogenously dispersed in the cytoplasm. Thus, these complexes present a dual synergistic effect with good properties of both the arene ruthenium chemotherapeutics and the porphyrin photosensitizer.     

Type 1 copper site synthetic model complexes with increased redox potentials

Reactions of NaSCPh₃ with (R₃tacn)Cu(OTf)₂ (R is Me, iPr; tacn is 1,4,7-triazacyclononane; OTf is CF₃SO₃ ⁻) yield blue complexes identified as ((R₃tacn)CuSCPh₃)(OTf) on the basis of UV–vis, resonance Raman, and electron paramagnetic resonance (EPR) spectroscopy and electrospray ionization mass spectrometry. These complexes exhibit spectroscopic properties typical of type 1 copper sites in proteins, including diagnostic Sπ → Cu(d_{x² - y²} ) (d_{{x^{2} - y^{2} }} ) ligand-to-metal charge transfer transitions at approximately 610–630 nm and small A _|| values in EPR spectra of less than 100 × 10⁻⁴ cm⁻¹. Cyclic voltammetry experiments revealed redox potentials for the complexes similar to those of several low-potential type 1 copper proteins (e.g., azurin, stellacyanin) and approximately 0.5 V higher than those of previously reported model compounds. Thus, the new complexes mimic key aspects of both the structure and the function of type 1 copper sites.     

Comparative Tolerances of Various <Emphasis Type="Italic">Beauveria bassiana</Emphasis> Isolates to UV-B Irradiation with a Description of a Modeling Method to Assess Lethal Dose

The tolerances of 20 Beauveria bassiana isolates derived from host insects worldwide to UV-B irradiation were assessed quantitatively in multi-dose bioassays. Conidial suspensions of the isolates smeared on glass slides were exposed to the gradient UV-B doses of 0.1–1.6 J cm⁻² (D), which generated from 0.75 to 10.17 min irradiation of weighted 312-nm wavelength at 2.0–2.61 mW cm⁻². Irradiated conidia were then incubated for 24 h at 25°C under saturated humidity. The ratio of germination at each dose over that in the blank control was defined as survival index (I _s). For all isolates, the I _s − D observations fit well with the survival model I _s = 1/[1 + exp(a + bD)] (0.94 ≤ r ² ≤ 0.99) generated widely spanned lethal doses of 0.154–0.928, 0.240–1.139, and 0.383–1.493 J cm⁻² for their losses of 50%, 75%, and 95% viabilities, respectively. These were far below the solar UV-B dose of 2.439 J cm⁻² measured in a sunny day during the summer. The large variation of UV-B tolerance among the isolates indicates a necessity to select UV-tolerant candidates for formulations applied to insect control during summer. The highly efficient bioassay method was developed to measure accurately the UV-B tolerances of fungal biocontrol agents as lethal doses.     

Mechanistic characterization of gastric copper transport in rainbow trout

An in vitro gut-sac technique and ⁶⁴Cu as a radiotracer were used to characterize gastric copper (Cu) transport. Cu transport was stimulated by low luminal pH (4.0 vs. 7.4), to a greater extent than explained by the increased availability of the free Cu²⁺ ion. At pH = 4.0, uptake kinetics were indicative of a low affinity (K _m = 525 μmol L⁻¹), saturable carrier-mediated component superimposed on a large linear (diffusive and/or convective) component, with about 50% occurring by each pathway at Cu = 50 μmol L⁻¹. Osmotic gradient experiments showed that solvent drag via fluid transport may play a role in Cu uptake via the stomach, in contrast to the intestine. Also unlike the intestine, neither the Na⁺ gradient, high Ag, nor phenamil had any influence on gastric Cu transport, and a tenfold excess of Fe and Zn failed to inhibit Cu uptake. These findings indicate that neither Na⁺-dependent pathways nor DMT1 are likely candidates for carrier-mediated Cu transport in the stomach. We have cloned a partial cDNA sequence for the copper transporter Ctr1, and show its mRNA expression in all segments of the trout gastrointestinal tract, including the stomach. Based on the fact that this transporter is functional at low pH conventionally found in the stomach lumen, we suggest Ctr1 is a pathway for gastric Cu transport in trout. Extreme hypoxia inhibited Cu uptake. High P_\textCO2 P_{{{\text{CO}}_{2} }} levels (7.5 torr) increased Cu uptake and acetazolamide (100 μmol L⁻¹) significantly inhibited Cu uptake, indicating carbonic anhydrase activity was involved in gastric Cu transport. Transport of Cu was insensitive to bafilomycin (10 μmol L⁻¹) suggesting a V-ATPase did not play a direct role in the process. Expression (mRNA) of H ⁺ , K ⁺-ATPase, carbonic anhydrase 2, and the α-3 isoform of Na ⁺–K ⁺-ATPase were observed in the stomach. We suggest these enzymes facilitate Cu transport in the stomach indirectly as part of a physiological mechanism exporting H⁺ to the cell exterior. However, pre-treatment with the H ⁺ , K ⁺-ATPase proton pump blocker omeprazole did not affect gastric Cu transport, suggesting that other mechanisms must also be involved.     

In vitro and in vivo responses of fungal biocontrol agents to gradient doses of UV-B and UV-A irradiation

Conidia of Beauveria bassiana and Metarhizium spp. smeared on glass slides were assayed for their responses to irradiation with weighted 312-nm UV-B and 365-nm UV-A at gradient doses of 0.005–1.1 and 1.0–18.0 J cm⁻², respectively. All inverted, sigmoid dose–survival trends showed good fit to a survival model (r ² ≥ 0.97), yielding respective UV-B LD₅₀s of 0.23–0.59 and 0.05–0.65 J cm⁻² for 24 B. bassiana and 36 Metarhizium isolates, and UV-A LD₅₀s of 2.78–10.46 J cm⁻² for 24 Metarhizium isolates. Myzus persicae apterae on detached leaves were sprayed with a concentrated spore suspension of B. bassiana or M. anisopliae, followed by exposure to the UV-B doses to cause 10–90% viability losses. These doses caused aphid mortality reductions as expected but affected neither spray-to-death period nor fungal growth on cadavers. The results highlight the merits of using UV-tolerant candidates and photoprotection measures in fungal formulations for pest control.     

Oxygen consumption rate and Na<Superscript>+</Superscript>/K<Superscript>+</Superscript>-ATPase activity in early developmental stages of the sea urchin <Emphasis Type="Italic">Paracentrotus lividus</Emphasis> Lam.

Changes in oxygen consumption rate and Na⁺/K⁺-ATPase activity during early development were studied in the sea urchin Paracentrotus lividus Lam. The oxygen consumption rate increased from 0.12 μmol O₂ mg protein⁻¹ h⁻¹ in unfertilized eggs to 0.38 μmol O₂ mg protein⁻¹ h⁻¹ 25 min after fertilization. Specific activity of the Na⁺/K⁺-ATPase was significantly stimulated after fertilization, ranging up to 1.07 μmol P_i h⁻¹ mg protein⁻¹ in the late blastula stage and slightly lower values in the early and late pluteus stages.     

Enhancement of Lanthanum (III) on Sodium Currents in Acutely Isolated Hippocampal CA1 Neurons of Rat

The effects of lanthanum (III) (La³⁺) on voltage-gated sodium channel currents (I _Na) in freshly dissociated rat hippocampal CA1 neurons were studied using the whole-cell patch clamp techniques. La³⁺ reversibly enhanced I _Na in a concentration- and voltage-dependent manner. The 50% enhancement concentration (EC₅₀) of La³⁺ on I _Na was 9.93 μM. In addition, 10 μM La³⁺ shifted the steady state activation curve of I _Na towards positive potential and the steady state inactivation curve towards negative potential without changing the slope factor. These results indicated that La³⁺ could increase the amplitudes of I _Na and change the activation and inactivation courses of I _Na even in very low concentration.     

Purification and characterization of the α-glucosidase produced by thermophilic fungus <Emphasis Type="Italic">Thermoascus aurantiacus</Emphasis> CBMAI 756

An α-glucosidase enzyme produced by the fungus Thermoascus aurantiacus CBMAI 756 was purified by ultra filtration, ammonium sulphate precipitation, and chromatography using Q Sepharose, Sephacryl S-200, and Superose 12 columns. The apparent molecular mass of the enzyme was 83 kDa as determined in gel electrophoresis. Maximum activity was observed at pH 4.5 at 70°C. Enzyme showed stability stable in the pH range of 3.0–9.0 and lost 40% of its initial activity at the temperatures of 40, 50, and 60°C. In the presence of ions Na⁺, Ba²⁺, Co²⁺, Ni²⁺, Mg²⁺, Mn²⁺, Al³⁺, Zn²⁺, Ca²⁺ this enzyme maintained 90–105% of its maximum activity and was inhibited by Cr³⁺, Ag⁺, and Hg²⁺. The enzyme showed a transglycosylation property, by the release of oligosaccharides after 3 h of incubation with maltose, and specificity for short maltooligosaccharides and α-PNPG. The K_m measured for the α-glucosidase was 0.07 μM, with a V_max of 318.0 μmol/min/mg.     

Resonance Scattering Spectral Detection of Trace Pb<Superscript>2+</Superscript> Using Aptamer-Modified AuPd Nanoalloy as Probe

The resonance scattering spectral probe for Pb²⁺ was obtained using aptamer-modified AuPd Nanoalloy. In the pH 7.0 Na₂HPO₄–NaH₂PO₄ buffer solution, the aptamer interacted with AuPd nanoalloy particles to form stable aptamer-AuPd nanoalloy probe for Pb²⁺ that is stable in high concentration of salt. The probe combined with Pb²⁺ ions to form a G-quadruplex and to release AuPd nanoalloy particles that aggregate to form big particles which led the resonance scattering (RS) intensity enhancing. The reaction solution was filtered by 0.15 μm membrane to obtain the filtration containing aptamer-AuPd nanoalloy probe that has strong catalytic effect on the electrodeless nickel particle plating reaction between Ni(II) and PO₂³⁻ that exhibited a strong RS peak at 508 nm. The RS intensity at 508 nm decreased when the Pb²⁺ concentration increased. The decreased intensity (ΔI _508nm) is linear to the concentration of 0.08–42 nM Pb²⁺, with regress equation of DI_508nm = 16.3 c + 1.5 \Delta {I_{{5}0{\rm{8nm}}}} = {16}.{3}\,c + {1}.{5} , correlation coefficient of 0.9965, and detection limit of 0.04 nM Pb²⁺. The RS assay was applied to the analysis of Pb²⁺ in wastewater, with satisfactory results.     

Transmembrane Transport and Release of GABA in the Brain of Rats Subjected to Postnatal Hypoxia

We studied the effects of early postnatal hypoxia on the efficiency of active GABA transport through the plasma membrane of synaptic terminals (synaptosomes) isolated from the cerebral cortex, hippocampus, and thalamus of rats and on non-stimulated and Ca²⁺-stimulated GABA release. The state of hypoxia was induced by exposure of 10- to 12-day-old rats to a respiratory medium with low O₂ content (4% О₂ and 96% N₂) for 12 min (up to the initiation of clonico-tonic seizures). Animals were taken in the experiment 8 to 9 weeks after an episode of hypoxic stress. The intensity of transmembrane transport of GABA was estimated according to accumulation of [³Н]GABA in a coarse synaptosomal fraction. The process was characterized by calculation of the Michaelis constant K _m and also of the initial (within the 1st min) and maximum rates of accumulation of [³Н]GABA. The means of the initial rate of [³Н]GABA accumulation in preparations from the thalamus, cortex, and hippocampus were 205.5 ± 8.8, 266.2 ± 29.6, and 302.3 ± 31.2 pmol/min⋅mg protein, respectively. Hypoxic stress influenced the rates of accumulation of [³Н]GABA in synaptic terminals from the cortex and hippocampus but not in those from the thalamus. According to the characteristics of the response to hypoxic stress, all experimental animals could be classified into two groups. In some rats, accumulation of [³Н]GABA in both cortical and hippocampal synaptosomes decreased insignificantly (by about 15%), while in other animals this parameter increased significantly (by nearly 50%) for the cortex and decreased by 21.5%, on average, for the hippocampus. The affinity of the transporter with respect to [³Н]GABA in the cortex and hippocampus was nearly the same and showed no changes under the influence of hypoxia. The non-stimulated release of [³Н]GABA after the influence of hypoxia increased in all structures, while the depolarization-induced Ca²⁺-dependent release of [³Н]GABA was intensified only in synaptosomes from the cerebral cortex. The mechanisms of development of modifications of GABA-ergic processes under the influence of hypoxic stress in the course of the perinatal period are discussed. Neirofiziologiya/Neurophysiology, Vol. 40, No. 4, pp. 293–302, July–August, 2008.     

Block of Persistent Late Na+ Currents by Antidepressant Sertraline and Paroxetine

Antidepressants, such as traditional tricyclic antidepressants (TCAs), are the first-line treatment for various pain syndromes. Available evidence indicates that TCAs may target Na⁺ channels for their analgesic action. In this report, we examined the effects of contemporary antidepressants sertraline and paroxetine on (1) neuronal Na⁺ channels expressed in GH₃ cells and (2) muscle rNav1.4 Na⁺ channels heterologously expressed in Hek293t cells. Our results showed that both antidepressants blocked Na⁺ channels in a highly state-dependent manner. The 50% inhibitory concentrations (IC₅₀) for sertraline and paroxetine ranged ∼18–28 μm for resting block and ∼2–8 μm for inactivated block of neuronal and rNav1.4 Na⁺ channels. Surprisingly, the IC₅₀ values for both drugs were about 0.6–0.7 μm for the open channel block of persistent late Na⁺ currents generated through inactivation-deficient rNav1.4 mutant Na⁺ channels. For comparison, the open channel block in neuronal hNav1.7 counterparts yielded IC₅₀ values around 0.3–0.4 μm for both drugs. Receptor mapping using fast inactivation-deficient rNav1.4-F1579A/K mutants with reduced affinities toward local anesthetics (LAs) and TCAs indicated that the F1579 residue is not involved in the binding of sertraline and paroxetine. Thus, sertraline and paroxetine are potent open channel blockers that target persistent late Na⁺ currents preferentially, but their block is not mediated via the phenylalanine residue at the known LA/TCA receptor site.     

Ultraviolet Photoalteration of Late Na+ Current in Guinea-pig Ventricular Myocytes

UV irradiation has multiple effects on mammalian cells, including modification of ion channel function. The present study was undertaken to investigate the response of membrane currents in guinea-pig ventricular myocytes to the type A (355, 380 nm) irradiation commonly used in Ca²⁺ imaging studies. Myocytes configured for whole-cell voltage clamp were generally held at −80 mV, dialyzed with K⁺-, Na⁺-free pipette solution, and bathed with K⁺-free Tyrode’s solution at 22°C. During experiments that lasted for ≈ 35 min, UVA irradiation caused a progressive increase in slowly-inactivating inward current elicited by 200-ms depolarizations from −80 to −40 mV, but had little effect on background current or on L-type Ca²⁺ current. Trials with depolarized holding potential, Ca²⁺ channel blockers, and tetrodotoxin (TTX) established that the current induced by irradiation was late (slowly-inactivating) Na⁺ current (I_Na). The amplitude of the late inward current sensitive to 100 μM TTX was increased by 3.5-fold after 20–30 min of irradiation. UVA modulation of late I_Na may (i) interfere with imaging studies, and (ii) provide a paradigm for investigation of intracellular factors likely to influence slow inactivation of cardiac I_Na.     

Interfacial Tension of the Lipid Membrane Formed from Phosphatidylcholine–Decanoic Acid and Phosphatidylcholine–Decylamine Systems

Interfacial tension has been determined for phosphatidylcholine (PC)–decanoic acid (DA) and PC–decylamine (DE) membranes. PC (lecithin), DA and DE were used in the experiments; the interfacial tension values of the pure components are 1.62 × 10⁻³, −2.38 × 10⁻² and −3.88 × 10⁻² N/m (hypothetical values for DA and DE), respectively. The 1:1 complexes were formed during formation of PC–DA and PC–DE membranes. The following parameters describing the complexes were determined: the surface concentrations of the lipid membranes formed from these complexes, A₃ ^{- 1} A_{3}^{ - 1} ; the interfacial tensions of such membranes, γ ₃; and the stability constants of these complexes, K.     

Differences in muscle contractile characteristics among bodybuilders, endurance trainers and control subjects

The purpose of this investigation was to compare the myosin heavy chain (MHC) isoform expression of the triceps brachii muscle and isoinertial, isometric and isokinetic strength indices in competitive bodybuilders (CB, n = 5), recreational resistance trainers (RT, n = 5), endurance-trained rowers (ER, n = 5) and control (C, n = 5) subjects. Muscle tissue samples were analysed for MHC isoform content using 6% sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The CB possessed significantly smaller (P < 0.05) percentage of MHC type IIb proteins [12.92 (SD 7.08)%] than RT [30.08 (SD 6.58)%] ER [31.20 (SD 2.74)%] and C [38.22 (SD 2.95)%] groups (i.e. CB < RT ≈ ER < C). While the content of MHC type IIa isoforms did not differ significantly between the two resistance-trained groups [CB = 55.76 (SD 5.38)%; RT = 45.72 (SD 7.8)%], CB presented significantly more type IIa MHC isoforms than ER [42.84 (SD 2.98)%] and C [34.72 (SD 1.57)%] subjects (i.e. CB ≈ RT > ER ≈ C). The MHC type I protein content did not differ significantly among RT [24.20 (SD 4.89)%] ER [25.38 (SD 1.67)%] and C [27.06 (SD 1.81)%] groups. The CB [31.32 (SD 2.67)%] presented significantly more type I MHC isoforms only in comparison with RT. However, when changes in the percentage of MHC type I isoforms were converted to effect sizes (ES), it appeared that low statistical power rather than the absence of an effect accounted for the nonsignificant differences between CB and other groups (i.e. CB > RT ≈ ER ≈ C). Significant differences existed in isoinertial strength among the trained athletes (i.e. CB > RT > ER ≈ C), while isometric and isokinetic strength were not significantly different among any of the trained groups. However, the ES transformation of data demonstrated that large differences existed between resistance-trained groups and ER for isometric and isokinetic strength (i.e. CB ≈ RT > ER ≈ C). A statistically significant negative correlation (P < 0.001) was found between MHC type IIb isoforms and isoinertial strength index (r = − 0.68). The MHC type IIa proteins were positively related to all the strength measures considered (r = 0.51 – 0.61; P < 0.001). These data demonstrated different patterns of MHC isoform expression among the different groups of athletes and it is suggested that these differences on occasion may affect the expression of strength. Accepted: 24 September 1996     

A new manganese superoxide dismutase identified from Beauveria bassiana enhances virulence and stress tolerance when overexpressed in the fungal pathogen

A superoxide dismutase (SOD) was characterized from Beauveria bassiana, a fungal entomopathogen widely applied to insect control. This 209-aa enzyme (BbSod2) showed no more than 71% sequence identity to other fungal Mn-SODs, sharing all conserved residues with the Mn-SOD family and lacking a mitochondrial signal. The SOD activity of purified BbSod2 was significantly elevated by Mn²⁺, suppressed by Cu²⁺ and Zn²⁺ but inhibited by Fe³⁺. Overexpressing the enzyme in a BbSod2-absent B. bassiana strain enhanced its SOD activity (107.2 ± 6.1 U mg⁻¹ protein) by 4–10-fold in different transformants analyzed. The best BbSod2-transformed strain with the SOD activity of 1,157.9 ± 74.7 U mg⁻¹ was 93% and 61% more tolerant to superoxide-generating menadione in both colony growth (EC₅₀ = 2.41 ± 0.03 versus 1.25 ± 0.01 mM) and conidial germination (EC₅₀ = 0.89 ± 0.06 versus 0.55 ± 0.07 mM), and 23% more tolerant to UV-B irradiation (LD₅₀ = 0.49 ± 0.02 versus 0.39 ± 0.01 J cm⁻²). Its virulence to Spodoptera litura larvae was enhanced by 26% [LT₅₀ = 4.5 (4.2–4.8) versus 5.7 (5.2–6.4) days]. Our study highlights for the first time that the Mn²⁺-cofactored, cytosolic BbSod2 contributes significantly to the virulence and stress tolerance of B. bassiana and reveals possible means to improving field persistence and efficacy of a fungal formulation by manipulating the antioxidant enzymes of a candidate strain.