Comparison perception of singular transcranial magnetic stimuli by subjectively electrosensitive subjects and general population controls

Transcranial magnetic stimulation of the dorsolateral prefrontal cortex by single pulses of varying field intensities was used to measure thresholds of individual perception and motor response in three groups of subjects: subjectively electrosensitive people, general population controls with a high burden of complaints related to electromagnetic field (EMF) exposure in the literature (highest decile in complaint burden), and general population controls with a low burden of complaints (lowest decile in complaint burden). The major study endpoint was the ability of the subjects to differentiate between real magnetic stimulation and a sham condition. There were no significant differences between groups in the thresholds, neither of detecting the real magnetic stimulus nor in motor response. But the three groups differed significantly in differentiating between stimulation and sham condition, with the subjectively electrosensitive people having the lowest ability to differentiate and the control group with high level of EMF-related complaints having the best ability to differentiate. Differences between groups were mostly due to false alarm reactions in the sham condition reported by subjectively electrosensitives (SES). We found no objective correlate of the self perception of being "electrosensitive." Overall, our experiment does not support the hypothesis that subjectively electrosensitive patients suffer from a physiological hypersensitivity to EMFs or stimuli. Further research should focus on disposing factors explaining the unspecific sensory hyperresponsiveness of subjectively electrosensitive subjects.     

Changes in Electrogenesis in the Motor Nerve Terminal with Long-Lasting High-Frequency Activation as a Factor of the Control of Transmitter Release

Using the technique of extracellular recording from the region of the neuromuscular junction in the cutaneous-sternal muscle in the frog under conditions of a reduced concentration of Ca²⁺ in the surrounding milieu, we demonstrated that long-lasting (10 min) rhythmic stimulation of the motor nerve with a frequency of 10 sec^{− 1} leads to a gradual increase in the evoked transmitter release. These changes are accompanied by a decrease in the amplitude of electrical responses of the nerve terminal (NT) and by a retardation of its second phase, as well as by a diminution of the third phase. Under conditions of long-lasting (5 min) stimulation with a frequency of 50 sec⁻¹, we observed a two-phase change in the intensity of transmitter release: on the 2nd min, the initial rise was replaced by inhibition. Modifications of the response of the NT with different stimulation frequencies were qualitatively similar, but with a frequency of 10 sec⁻¹ they were clearly expressed. Mathematical simulation of ion currents in the NT demonstrated that voltage-dependent potassium and sodium channels are inactivated in the course of long-lasting high-frequency excitation; the shape of the action potential is modified with changes in the rate of such inactivation. This leads to either an increase or a decrease of the inward calcium current. We conclude that the change in electrogenesis in the NT with long-lasting high-frequency activation of neuromuscular junctions exerts a significant influence on the dynamics of transmitter release. Neirofiziologiya/Neurophysiology, Vol. 37, No. 2, pp. 108–115, March–April, 2005.     

Life-history traits of the acarophagous lady beetle,<Emphasis Type="Italic">Stethorus japonicus</Emphasis> at three constant temperatures

Stethorus japonicusKamiya (Coleoptera: Coccinellidae) is an indigenous ladybird beetle in Japan, which feeds on many spider mite species. We evaluated the development, survivorship and life-history parameters of this lady beetle on a diet of eggs of the two-spotted spider mite, Tetranychus urticae Koch (red form) (Acari: Tetranychidae). In addition, the effect of short photoperiod on its reproduction was assessed. Survival rates from egg to adult were more than 71% at temperatures between 17.5 and 30 °C. The highest immature mortality was 100% at 35 °C followed by 76% at 15 °C and 52% at 32.5 °C. The lower threshold temperature for development from egg to egg-laying adult was 13.0 °C and the thermal constant was calculated as 238.7° days. Based on these data, the maximum number of generations that could complete development in a year under field conditions in Ibaraki, central Japan, would be between five and seven. The intrinsic rates of natural increase (r_m) were 0.093 at 20 °C, 0.156 at 25 °C and 0.241 at 30 °C. Reproductive diapause was induced at photoperiods with light phases shorter than 13 h at 18 °C.     

Purification and characterization of an extracellular alpha-amylase from Bacillus subtilis AX20

A Bacillus subtilis AX20 from soil with ability to produce extracellular alpha-amylases was isolated. The characterization of microorganism was performed by biochemical tests as well as 16S rDNA sequencing. Maximum amylase activity (38 U/ml) was obtained at stationery phase when the culture was grown at 37 degrees C. The enzyme was purified to homogeneity with an overall recovery of 24.2% and specific activity of 4133 U/mg. The native protein showed a molecular mass of 149 kDa composed of a homodimer of 78 kDa polypeptide by SDS-PAGE. The optimum pH and temperature of the amylase were 6 and 55 degrees C, respectively. The enzyme was inhibited by Hg(2+), Ag(2+), and Cu(2+) and it did not show an obligate requirement of metal ions. The enzyme was not inhibited by EDTA or EGTA, suggesting that this enzyme is not a metalloenzyme. The end products of corn starch and soluble starch were glucose (70-75%) and maltose (20-25%). Rapid reduction of blue value and the end products suggest an endo mode of action for the amylase. The purified amylase shows interesting properties useful for industrial applications.     

The effects of ponazuril on development of apicomplexans in vitro

We examined the effects of 5 microg/ml ponazuril treatment on developing tachyzoites of Neospora caninum and merozoites of Sarcocystis neurona to better determine the mode of action of this anticoccidial drug. Both parasites develop asexually by endogenesis. Neospora caninum was selected for study because it develops by endodyogeny, which results in two tachyzoites being produced internally, and S. neurona was selected because it develops by endopolygeny which results in many merozoites being produced internally. Ponazuril inhibited development of N. caninum after approximately 48 h post-exposure. Treated tachyzoites of N. caninum developed vacuoles and underwent degeneration. Ponazuril also inhibited development of merozoites of S. neurona. Treated merozoites and maturing schizonts of S. neurona developed vacuoles and underwent degeneration. The ability of S. neurona schizonts to undergo cytokinesis was inhibited. Our results are discussed in relation to previous ultrastructural research on endogenesis of tachyzoites of Toxoplasma gondii undergoing endodyogeny which indicated that ponazuril induced multinucleate stage formation and inhibited cytokinesis. Ponazuril is believed to act on the apicoplast and our study demonstrates that this agent may express its inhibitory effects in different phenotypic manners on different apicomplexan parasites. The enzyme/enzyme systems that are the inhibitory target of ponazuril may be different in these apicomplexans, or the results of inhibition may affect different pathways downstream of its initial site of action in these parasites.     

The reinfection threshold

Thresholds in transmission are responsible for critical changes in infectious disease epidemiology. The epidemic threshold indicates whether infection invades a totally susceptible population. The reinfection threshold indicates whether self-sustained transmission occurs in a population that has developed a degree of partial immunity to the pathogen (by previous infection or vaccination). In models that combine susceptible and partially immune individuals, the reinfection threshold is technically not a bifurcation of equilibria as correctly pointed out by Breban and Blower. However, we show that a branch of equilibria to a reinfection submodel bifurcates from the disease-free equilibrium as transmission crosses this threshold. Consequently, the full model indicates that levels of infection increase by two orders of magnitude and the effect of mass vaccination becomes negligible as transmission increases across the reinfection threshold.     

Identification of Catalytically Active Groups of Penicillium canescens F-436 β-Galactosidase

The functional groups of Penicillium canescens F-436 b-galactosidase have been identified. The pK values and heats of ionization of these groups and photoinactivation of the enzyme with methylene blue indicate that the active site contains carboxyl and imidazole groups. A mechanism for the participation of these groups in the cleavage of the glycoside bond in lactose is proposed.     

3α-Hydroxysteroid Dehydrogenase in Animal and Human Tissues

This review analyzes data on the biological role of 3-hydroxysteroid dehydrogenase (3-HSD) in animal and human tissues and describes its main characteristics, mechanism of action, and regulation of activity. Based on published data, a scheme for the actions of androgen, progestin, and glucocorticoids involving the participation of 3-HSD is proposed. According to this scheme, in the mechanism of steroid action 3-HSD not only regulates the concentration of the main effector androgen, 5-dihydrotestosterone, in target cells, but also switches androgen, progestin, and glucocorticosteroid genomic activity to non-genomic activity.     

Processing of Cry1Ab delta-endotoxin from Bacillus thuringiensis by Manduca sexta and Spodoptera frugiperda midgut proteases: role in protoxin activation and toxin inactivation

Activation of Cry protoxins is carried out by midgut proteases. This process is important for toxicity and in some cases for specificity. Commercial proteases have been used for in vitro protoxin activation. In the case of Cry1A protoxins, trypsin digestion generates a toxic fragment of 60–65 kDa. Here, we have analyzed the in vitro and in vivo activation of Cry1Ab. We found differences in the processing of Cry1Ab protoxin by Manduca sexta and Spodoptera frugiperda midgut proteases as compared to trypsin. Midgut juice proteases produced two additional nicks at the N-terminal end removing helices 1 and 2a to produce a 58 kDa protein. A further cleavage within domain II splits the toxin into two fragments of 30 kDa. The resulting fragments were not separated, but instead coeluted with the 58 kDa monomer, in size-exclusion chromatography. To examine if this processing was involved in the activation or degradation of Cry1Ab toxin, binding, pore formation, and toxicity assays were performed. Pore formation assays showed that midgut juice treatment produced a more active toxin than trypsin treatment. In addition, it was determined that the 1 helix is dispensable for Cry1Ab activity. In contrast, the appearance of the 30 kDa fragments correlates with a decrease in pore formation and insecticidal activities. Our results suggest that the cleavage in domain II may be involved in toxin inactivation, and that the 30 kDa fragments are stable intermediates in the degradation pathway.