The history of scientific endeavors towards understanding hagfish embryology

Due to their curious phylogenetic position and anatomy, hagfishes have attracted the interest of zoologists, especially in the context of vertebrate evolution. Embryological information on these animals is now also needed in the field of evolutionary developmental biology (Evo-Devo), as it is expected to provide hints about the origin of vertebrate traits, whether the hagfishes are an in-or outgroup of vertebrates. This review summarizes the importance of hagfish embryology from a phylogenetic perspective, and the history of attempts to obtain hagfish eggs and embryos. Clearly, the main difficulty associated with these animals is their deep-sea habitat. To circumvent this problem, this review also discusses the future prospects for obtaining embryological material, both from the wild and in the laboratory.     

Activation of subfornical organ neurons in rats through pre- and postsynaptic alpha-adrenoceptors

The effects of noradrenaline (NA) and its analogs on subfornical organ (SFO) neurons in rat slice preparations were investigated by using whole cell patch-clamp recording. In the current-clamp mode, the application of NA at 10-100 microM produced membrane depolarization (63%, 17 responsive neurons/27 neurons tested) and hyperpolarization (22%, 6/27 neurons). In the voltage-clamp mode, NA application at 1-100 microM produced inward currents (69%, 42/61 neurons) and outward currents (23%, 14/61 neurons). These currents remained in the presence of TTX or both glutamate and GABA receptor antagonists. In most of the neurons (25/31 neurons) showing inward currents in the presence of NA, the membrane conductance was not changed by voltage ramps or hyperpolarizing pulse stimulation. Similar responses were obtained by the application of the alpha1-agonist phenylephrine. The phenylephrine-induced inward currents were inhibited by the alpha1-antagonist prazosin. The alpha2-agonist clonidine decreased the frequency of spontaneous GABAergic inhibitory postsynaptic currents (4/10 neurons). In addition, RT-PCR assay and immunohistochemical staining showed the existence of alpha1-adrenoceptors in the SFO. The results suggest that SFO neurons in rats are activated postsynaptically through alpha1-adrenoceptors and that the activation is enhanced by suppressing GABAergic inhibitory synaptic inputs through presynaptic alpha2-adrenoceptors.     

Oxidative stress provokes atherogenic changes in adipokine gene expression in 3T3-L1 adipocytes

Increased oxidative stress has been associated with obesity-related disorders. In this study, we investigated how oxidative stress, in different ways of exposure, regulates gene expression of various adipokines in 3T3-L1 adipocytes. Exposure to 100-500microM H(2)O(2) for 10min, as well as exposure to 5-25mU/ml glucose oxidase for 18h, similarly decreased adiponectin, leptin, and resistin mRNAs, and increased plasminogen activator inhibitor-1 mRNA. Secretion levels of adipokines were also changed by oxidative stress in parallel with mRNA expression levels. Although a peak increase in plasminogen activator inhibitor-1 mRNA was achieved between 4 and 8h after exposure to H(2)O(2) for 10min, significant decreases in adiponectin and resistin mRNA were observed after 16h, while leptin mRNA was decreased earlier. Our results suggest that oxidative stress, even of short duration, has a significant impact on the regulation of various adipokine gene expressions favoring atherosclerosis.     

Symbiotic Bacteria Associated with Stomach Discs of Human Lice

The symbiotic bacteria associated with the stomach disc, a large aggregate of bacteriocytes on the ventral side of the midgut, of human body and head lice were characterized. Molecular phylogenetic analysis of 16S rRNA gene sequences showed that the symbionts formed a distinct and well-defined clade in the Gammaproteobacteria. The sequences exhibited AT-biased nucleotide composition and accelerated molecular evolution. In situ hybridization revealed that in nymphs and adult males, the symbiont was localized in the stomach disc, while in adult females, the symbiont was not in the stomach disc but in the lateral oviducts and the posterior pole of the oocytes due to female-specific symbiont migration. We propose the designation “Candidatus Riesia pediculicola” for the louse symbionts.     

Light induced structural changes of a full-length protein and its BLUF domain in YcgF(Blrp), a blue-light sensing protein that uses FAD (BLUF)

Blue-light sensing proteins that use FAD (BLUF) are members of a blue-light receptor family that is widely distributed among microorganisms. The Escherichia coli YcgF protein is a BLUF protein consisting of the N-terminal FAD-binding hold (BLUF domain) and the C-terminal EAL domain. The EAL domain of YcgF is predicted to have cyclic-di-GMP phosphodiesterase activity. Light-induced structural changes for the signaling state formation were studied using the light-induced Fourier transform infrared (FTIR) difference spectroscopy of both the full-length YcgF protein (YcgF-Full) and its BLUF domain (YcgF-BLUF). YcgF-Full and YcgF-BLUF showed identical UV-visible absorption spectra of flavin in the dark state and a light-induced absorption red shift for the signaling state, which relaxed to the dark state showing identical kinetics. The light-induced FTIR difference spectrum of YcgF-Full, however, was markedly different from that of YcgF-BLUF. The spectrum of YcgF-BLUF lacked most of the IR bands that were induced in the YcgF-Full spectrum. These bands were assigned to the light-induced structural changes of the protein. However, the bands for the C4=O stretching of a FAD isoalloxazine ring were induced at the same frequency with the same band intensity in the spectra for YcgF-Full and YcgF-BLUF. Furthermore, the YcgF-Full spectrum resembled that of the YcgF-BLUF when illuminated at medium-low temperatures because of the selective suppression of protein bands. The possibility that full-length-specific protein bands are predominantly ascribed to structural changes of the C-terminal EAL domain in the signaling state as a consequence of light excitation of the N-terminal BLUF domain is discussed.     

Visfatin in adipocytes is upregulated by hypoxia through HIF1alpha-dependent mechanism

Obesity is associated with metabolic disorders, such as insulin resistance. Visfatin is an adipose-derived secretory factor to exert insulin-mimetic effects. Plasma visfatin levels and mRNA levels of visfatin in adipose tissues are increased in obesity. However, the mechanism that mediates induction of visfatin mRNA in adipose tissue of obesity remains unknown. Recent studies have reported that fat tissue is hypoxia in obesity. In this study, we investigated the effects of hypoxia on mRNA expression of visfatin in adipocytes. Hypoxia increased visfatin mRNA expression. Desferoxamine and Cobaltous chloride, two hypoxia mimetic compounds, also increased visfatin mRNA levels. Dimethyloxallyl glycine, a stabilizer of hypoxia-inducible factor 1alpha (HIF1alpha), mimicked the hypoxia-mediated upregulation of visfatin, and YC1, an inhibitor of HIF1 cancelled the hypoxia-induced upregulation of visfatin mRNA. We identified two functional hypoxia responsive elements (HRE) in mouse visfatin promoter. Hypoxic treatment and overexpression of HIF1alpha increased the promoter activity, and mutation of the HRE blunted hypoxia-induced activation of visfatin promoter. Our results suggest that visfatin mRNA expression is upregulated in the fat tissue of obesity through the activation of HIF1alpha pathway due to hypoxia.     

Crystal structures of the Synechocystis photoreceptor Slr1694 reveal distinct structural states related to signaling

Crystal structures of the Synechocystis BLUF phototaxis photoreceptor Slr1694 have been determined in two crystal forms, a monoclinic form at 1.8 A resolution and an orthorhombic form at 2.1 A resolution. In both forms, the photoreceptor is comprised of two pentamer rings stacked face to face. Twenty total subunits in the two asymmetric units of these crystal forms display three distinct tertiary structures that differ in the length of the fifth beta-strand and in the orientation of Trp91, a conserved Trp residue near the FMN chromophore. Fluorescence spectroscopic analysis on Slr1694 in solution is consistent with motion of Trp91 from a hydrophobic environment in the dark state to a more hydrophilic environment in the light-excited state. Mutational analysis indicates that movement of Trp91 is dependent on the occupancy of the hydrophobic Trp binding pocket with a nearby Met. These different tertiary structures may be associated with absorption changes in the blue region of the spectrum.     

Substrate specificity of archaeon Sulfolobus tokodaii biotin protein ligase

Biotin protein ligase (BPL) is an enzyme mediating biotinylation of a specific lysine residue of the carboxyl carrier protein (BCCP) of biotin-dependent enzymes. We recently found that the substrate specificity of BPL from archaeon Sulfolobus tokodaii is totally different from those of many other organisms, in reflection of a difference in the local sequence of BCCP surrounding the canonical lysine residue. There is a conserved glycine residue in the biotin-binding site of Escherichia coli BPL, but this residue is replaced with alanine in S. tokodaii BPL. To test the notion that this substitution dictates the substrate specificity of the latter enzyme, this residue, Ala-43, was converted to glycine. The K(m) values of the resulting mutant, A43G, for substrates, were smaller than those of the wild type, suggesting that the residue in position 43 of BPL plays an important role in substrate binding.     

IL-18 gene polymorphisms affect IL-18 production capability by monocytes

We previously demonstrated a significant association between IL-18 gene polymorphism 105A/C and asthma. In this study, we investigated the relationship of IL-18 gene polymorphism to IL-18 production capability by monocytes. The frequency of gene polymorphisms including IL-18-105A/C and IL-18--137G/C was determined by PCR analyses. The IL-18 production by monocytes stimulated without or with LPS or A23187+PMA for 1day was measured by ELISA. The produced IL-18 spontaneously or in response to A23187+PMA by monocytes was significantly higher for volunteers with 105A/A genotype than with 105A/C genotype. Similarly, the production capability of IL-18 by monocytes from volunteers with -137G/G genotype was significantly higher than that with -137G/C genotype and significant linkage disequilibrium was observed between 105A/C and -137G/C polymorphism. Thus, the genetic capacity to produce more IL-18 in response to stimuli may affect the onset of asthma.