Effect of weak static and low-frequency alternating magnetic fields on the fission and regeneration of the planarian dugesia (Girardia) tigrina

The effect of weak static (DC) and alternating (AC) magnetic fields (MFs), as well as combined (AC/DC) collinear MFs on the intensity of morphogenesis processes in the planarian Dugesia (Girardia) tigrina has been studied. It was found that combined MFs produce a stimulating effect on the fission and regeneration of planarians. Both components of the combined MFs, the direct (DC) and the alternating (AC), are important in the realization of the effects of weak MFs. The practically complete absence of one of the components (DC) reverses the sign of the effect. It was shown that the presence of concomitant background MFs does not substantially influence the effects of combined MFs with a very small AC component (100 nT). The effect of the "zero" field is significant and comparable in magnitude with the effects of combined MFs at effective frequencies. Narrow zones of effective amplitudes (in the region of tens and hundreds of nT) of the AC component of the combined MFs, with the DC component close to the value of the geomagnetic field were found, which alternate with regions where the response of the biological object to the influence is absent.     

Massive light-driven translocation of transducin between the two major compartments of rod cells: a novel mechanism of light adaptation

We report a new cellular mechanism of rod photoreceptor adaptation in vivo, which is triggered by daylight levels of illumination. The mechanism involves a massive light-dependent translocation of the photoreceptor-specific G protein, transducin, between the functional compartments of rods. To characterize the mechanism, we developed a novel technique that combines serial tangential cryodissection of the rat retina with Western blot analysis of protein distribution in the sections. Up to 90% of transducin translocates from rod outer segments to other cellular compartments on the time scale of tens of minutes. The reduction in the transducin content of the rod outer segments is accompanied by a corresponding reduction in the amplification of the rod photoresponse, allowing rods to operate in illumination up to 10-fold higher than would otherwise be possible.     

Ecto-ATPase activity in the rat cardiac muscle: biochemical characteristics and histocytochemical localization

We used a combined biochemical and histocytochemical approach to study ecto-ATPase in the rat cardiac muscle. The reaction medium employed for histocytochemical detection was optimized in biochemical assays to achieve the highest enzyme activity and lowest inhibition by the capture agent used for visualization of the reaction product. Approximately 70% of the enzyme activity was retained in samples after the fixation procedure. Divalent cations stimulated ecto-ATPase. High activity was detectable within a wide pH range. Histocytochemical reaction was observed at sites at which extracellular ATP can potentially exert its actions on the cardiac muscle: nerve endings, plasma membranes of cardiac myocytes and capillary endothelial cells, and T-tubules. Product of the reaction was found exclusively at the outer surface of the cells. In controls, enzyme activity was abolished by diethyl pyrocarbonate and slightly stimulated by digitonin and concanavalin A, whereas sodium orthovanadate, N-ethylmaleimide, and sodium azide yielded no effect. Our results support the view that cardiac ecto-ATPase is involved in important physiological functions and suggest that its activity may be regulated by the release of ATP from nerve endings.     

Three-dimensional rearrangement of proteins in the tail of bacteriophage T4 on infection of its host

The contractile tail of bacteriophage T4 undergoes major structural transitions when the virus attaches to the host cell surface. The baseplate at the distal end of the tail changes from a hexagonal to a star shape. This causes the sheath around the tail tube to contract and the tail tube to protrude from the baseplate and pierce the outer cell membrane and the cell wall before reaching the inner cell membrane for subsequent viral DNA injection. Analogously, the T4 tail can be contracted by treatment with 3 M urea. The structure of the T4 contracted tail, including the head-tail joining region, has been determined by cryo-electron microscopy to 17 A resolution. This 1200 A-long, 20 MDa structure has been interpreted in terms of multiple copies of its approximately 20 component proteins. A comparison with the metastable hexagonal baseplate of the mature virus shows that the baseplate proteins move as rigid bodies relative to each other during the structural change.     

The prokaryotic selenoproteome

In the genetic code, the UGA codon has a dual function as it encodes selenocysteine (Sec) and serves as a stop signal. However, only the translation terminator function is used in gene annotation programs, resulting in misannotation of selenoprotein genes. Here, we applied two independent bioinformatics approaches to characterize a selenoprotein set in prokaryotic genomes. One method searched for selenoprotein genes by identifying RNA stem-loop structures, selenocysteine insertion sequence elements; the second approach identified Sec/Cys pairs in homologous sequences. These analyses identified all or almost all selenoproteins in completely sequenced bacterial and archaeal genomes and provided a view on the distribution and composition of prokaryotic selenoproteomes. In addition, lineage-specific and core selenoproteins were detected, which provided insights into the mechanisms of selenoprotein evolution. Characterization of selenoproteomes allows interpretation of other UGA codons in completed genomes of prokaryotes as terminators, addressing the UGA dual-function problem.     

A transporter of<Emphasis Type="Italic"> Escherichia coli</Emphasis> specific for<Emphasis Type="SmallCaps"> l</Emphasis>- and<Emphasis Type="SmallCaps"> d</Emphasis>-methionine is the prototype for a new family within the ABC superfamily

An ABC-type transporter in Escherichia coli that transports both l- and d-methionine, but not other natural amino acids, was identified. This system is the first functionally characterized member of a novel family of bacterial permeases within the ABC superfamily. This family was designated the methionine uptake transporter (MUT) family (TC #3.A.1.23). The proteins that comprise the transporters of this family were analyzed phylogenetically, revealing the probable existence of several sequence-divergent primordial paralogues, no more than two of which have been transmitted to any currently sequenced organism. In addition, MetJ, the pleiotropic methionine repressor protein, was shown to negatively control expression of the operon encoding the ABC-type methionine uptake system. The identification of MetJ binding sites (in gram-negative bacteria) or S-boxes (in gram-positive bacteria) in the promoter regions of several MUT transporter-encoding operons suggests that many MUT family members transport organic sulfur compounds. Electronic Supplementary Material Supplementary material is available for this article if you access the article at . A link in the frame on the left on that page takes you directly to the supplementary material.     

HIF-1 alpha protein as a target for S-nitrosation

Hypoxia-inducible factor-1 alpha (HIF-1 alpha) is a master regulator to sense decreased oxygen partial pressure. HIF-1 alpha stability regulation initiates a complex biological response that allows cells to act appropriately to meet patho-physiological situations of decreased oxygen availability. Recently, nitric oxide emerged as a messenger with the ability to stabilize HIF-1 alpha and to transactivate HIF-1 under normoxia. Considering that reactive nitrogen species are recognized for post-translation protein modifications, among others S-nitrosation, we asked whether HIF-1 alpha is a target for S-nitrosation. In vitro NO+ donating NO donors such as GSNO and SNAP provoked massive S-nitrosation of purified HIF-1 alpha. All 15 free thiol groups found in human HIF-1 alpha are subjected to S-nitrosation. Thiol modification is not shared by spermine-NONOate, a NO radical donating compound. However, spermine-NONOate in the presence of O(2)(-), generated by xanthine/xanthine oxidase, regained S-nitrosation, most likely via formation of a N(2)O(3)-like species. In vitro, S-nitrosation of HIF-1 alpha was attenuated by the addition of GSH or ascorbate. In RCC4 and HEK293 cells GSNO or SNAP reproduced S-nitrosation of HIF-1 alpha, however with a significantly reduced potency that amounted to modification of three to four thiols, only. Importantly, endogenous formation of NO in RCC4 cells via inducible NO synthase elicited S-nitrosation of HIF-1 alpha that was sensitive to inhibition of inducible NO synthase activity with N-monomethyl-L-arginine. NO-stabilized HIF-1 alpha was susceptible to the addition of N-acetyl-cysteine that destabilized HIF-1 alpha in close correlation to the disappearance of S-nitrosated HIF-1 alpha. In conclusion, HIF-1 alpha is a target for S-nitrosation by exogenously and endogenously produced NO.     

Long-term circulation of vaccine-derived poliovirus that causes paralytic disease

Successful implementation of the global poliomyelitis eradication program raises the problem of vaccination against poliomyelitis in the posteradication era. One of the options under consideration envisions completely stopping worldwide the use of the Sabin vaccine. This strategy is based on the assumption that the natural circulation of attenuated strains and their derivatives is strictly limited. Here, we report the characterization of a highly evolved derivative of the Sabin vaccine strain isolated in a case of paralytic poliomyelitis from a 7-month-old immunocompetent baby in an apparently adequately immunized population. Analysis of the genome of this isolate showed that it is a double (type 1-type 2-type 1) vaccine-derived recombinant. The number of mutations accumulated in both the type 1-derived and type 2-derived portions of the recombinant genome suggests that both had diverged from their vaccine predecessors approximately 2 years before the onset of the illness. This fact, along with other recent observations, points to the possibility of long-term circulation of Sabin vaccine strain derivatives associated with an increase in their neurovirulence. Comparison of genomic sequences of this and other evolved vaccine-derived isolates reveals some general features of natural poliovirus evolution. They include a very high preponderance and nonrandom distribution of synonymous substitutions, conservation of secondary structures of important cis-acting elements of the genome, and an apparently adaptive character of most of the amino acid mutations, with only a few of them occurring in the antigenic determinants. Another interesting feature is a frequent occurrence of tripartite intertypic recombinants with either type 1 or type 3 homotypic genomic ends.