Deriving theoretical phase locking values of a coupled cortico-thalamic neural mass model using center manifold reduction

Cognitive functions such as sensory processing and memory processes lead to phase synchronization in the electroencephalogram or local field potential between different brain regions. There are a lot of computational researches deriving phase locking values (PLVs), which are an index of phase synchronization intensity, from neural models. However, these researches derive PLVs numerically. To the best of our knowledge, there have been no reports on the derivation of a theoretical PLV. In this study, we propose an analytical method for deriving theoretical PLVs from a cortico-thalamic neural mass model described by a delay differential equation. First, the model for generating neural signals is transformed into a normal form of the Hopf bifurcation using center manifold reduction. Second, the normal form is transformed into a phase model that is suitable for analyzing synchronization phenomena. Third, the Fokker–Planck equation of the phase model is derived and the phase difference distribution is obtained. Finally, the PLVs are calculated from the stationary distribution of the phase difference. The validity of the proposed method is confirmed via numerical simulations. Furthermore, we apply the proposed method to a working memory process, and discuss the neurophysiological basis behind the phase synchronization phenomenon. The results demonstrate the importance of decreasing the intensity of independent noise during the working memory process. The proposed method will be of great use in various experimental studies and simulations relevant to phase synchronization, because it enables the effect of neurophysiological changes on PLVs to be analyzed from a mathematical perspective.     

Purification, characterization, and cDNA cloning of lipoate-activating enzyme from bovine liver

In mammals, lipoate-activating enzyme (LAE) catalyzes the activation of lipoate to lipoyl-nucleoside monophosphate. The lipoyl moiety is then transferred to the specific lysine residue of lipoate-dependent enzymes by the action of lipoyltransferase. We purified LAE from bovine liver mitochondria to apparent homogeneity. LAE activated lipoate with GTP at a 1000-fold higher rate than with ATP. The reaction absolutely required lipoate, GTP, and Mg(2+) ion, and the reaction product was lipoyl-GMP. LAE activated both (R)- and (S)-lipoate to the respective lipoyl-GMP, although a preference for (R)-lipoate was observed. Similarly, lipoyltransferase equally transferred both the (R)- and (S)-lipoyl moieties from the respectively activated lipoates to apoH-protein. Interestingly, however, only H-protein carrying (R)-lipoate was active in the glycine cleavage reaction. cDNA clones encoding a precursor LAE with a mitochondrial presequence were isolated. The predicted amino acid sequence of LAE is identical with that of xenobiotic-metabolizing/medium-chain fatty acid:CoA ligase-III, but an amino acid substitution due to a single nucleotide polymorphism was found. These results indicate that the medium-chain acyl-CoA synthetase in mitochondria has a novel function, the activation of lipoate with GTP.     

Comparison of the structural changes in two cellobiohydrolases, CcCel6A and CcCel6C, from Coprinopsis cinerea--a tweezer-like motion in the structure of CcCel6C

The basidiomycete Coprinopsis cinerea produces five cellobiohydrolases belonging to glycoside hydrolase family 6 (GH6). Among these enzymes, C. cinerea cellulase 6C (CcCel6C), but not C. cinerea cellulase 6A (CcCel6A), can efficiently hydrolyze carboxymethyl cellulose and is constitutively expressed in C. cinerea. In contrast, CcCel6A possesses a cellulose-binding domain, and is strongly induced by cellobiose. Here, we determined the crystal structures of the CcCel6A catalytic domain complexed with a Hepes buffer molecule, with cellobiose, and with p-nitrophenyl β-D-cellotrioside (pNPG3). A notable feature of the GH6 cellobiohydrolases is that the active site is enclosed by two loops to form a tunnel, and the loops have been demonstrated to open and close in response to ligand binding. The enclosed tunnel of CcCel6A-Hepes is seen as the open form, whereas the tunnels of CcCel6A-cellobiose and CcCel6A-pNPG3 adopt the closed form. pNPG3 was not hydrolyzed by CcCel6A, and bound in subsites +1 to +4. On the basis of this observation, we constructed two mutants, CcCel6A D164A and CcCel6C D102A. Neither CcCel6A D164A nor CcCel6C D102A hydrolyze phosphoric acid-swollen cellulose. We have previously determined the crystal structures of CcCel6C unbound and in complex with ligand, both of which adopt the open form. In the present study, both CcCel6A and CcCel6C mutants were identified as the closed form. However, the motion angle of CcCel6C was more than 10-fold greater than that of CcCel6A. The width of the active site cleft of CcCel6C was narrowed, owing to a tweezer-like motion.     

Mitochondrial permeability transition pore opening induces the initial process of renal calcium crystallization

Renal tubular cell injury induced by oxidative stress via mitochondrial collapse is thought to be the initial process of renal calcium crystallization. Mitochondrial collapse is generally caused by mitochondrial permeability transition pore (mPTP) opening, which can be blocked by cyclosporine A (CsA). Definitive evidence for the involvement of mPTP opening in the initial process of renal calcium crystallization, however, is lacking. In this study, we examined the physiological role of mPTP opening in renal calcium crystallization in vitro and in vivo. In the in vitro study, cultured renal tubular cells were exposed to calcium oxalate monohydrate (COM) crystals and treated with CsA (2 μM). COM crystals induced depolarization of the mitochondrial membrane potential and generated oxidative stress as evaluated by Cu-Zn SOD and 4-HNE. Furthermore, the expression of cytochrome c and cleaved caspase 3 was increased and these effects were prevented by CsA. In the in vivo study, Sprague-Dawley rats were administered 1% ethylene glycol (EG) to generate a rat kidney stone model and then treated with CsA (2.5, 5.0, and 10.0 mg/kg/day) for 14 days. EG administration induced renal calcium crystallization, which was prevented by CsA. Mitochondrial collapse was demonstrated by transmission electron microscopy, and oxidative stress was evaluated by measuring Cu-Zn SOD, MDA, and 8-OHdG generated by EG administration, all of which were prevented by CsA. Collectively, our results provide compelling evidence for a role of mPTP opening and its associated mitochondrial collapse, oxidative stress, and activation of the apoptotic pathway in the initial process of renal calcium crystallization.     

Morphometric variation in the pusillus group of the genus Rhinolophus (Mammalia: Chiroptera: Rhinolophidae) in East Asia

Based on 203 specimens belonging to the Rhinolophus "pusillus group" (Mammalia: Chiroptera: Rhinolophidae), univariate and multivariate morphometric analyses using 19 characters were performed to assess the confused species taxonomy. The results indicated that R. pusillus (including calidus, parcus, and szechuanus) in the continental region and Hainan Island of China and "R. cornutus" in Japan are morphologically divergent species. Rhinolophus cornutus should be further split into R. cornutus (including orii, pumilus, and miyakonis) in the main islands of Japan, the Amami and Okinawa Group of the central Ryukyu Archipelago, and Miyako Group of the southern Ryukyus; and R. perditus and R. imaizumii from the Yaeyama Group in the southern Ryukyus. Rhinolophus monoceros from Taiwan is morphologically more similar to species in Japan than to R. pusillus. In addition to R. pusillus, another form that is morphologically similar to species in Japan was recognized from Langzhong in Sichuan Province; this may represent an undescribed species, and further examination is necessary to determine its taxonomic status. Specimens from Guang'an in Sichuan Province, China, are also different from the others, and are characterized by the smallest skull size. Although further studies are required, these specimens were tentatively identified as R. subbadius.     

West Nile virus noncoding subgenomic RNA contributes to viral evasion of the type I interferon-mediated antiviral response

We previously showed that a noncoding subgenomic flavivirus RNA (sfRNA) is required for viral pathogenicity, as a mutant West Nile virus (WNV) deficient in sfRNA production replicated poorly in wild-type mice. To investigate the possible immunomodulatory or immune evasive functions of sfRNA, we utilized mice and cells deficient in elements of the type I interferon (IFN) response. Replication of the sfRNA mutant WNV was rescued in mice and cells lacking interferon regulatory factor 3 (IRF-3) and IRF-7 and in mice lacking the type I alpha/beta interferon receptor (IFNAR), suggesting a contribution for sfRNA in overcoming the antiviral response mediated by type I IFN. This was confirmed by demonstrating rescue of mutant virus replication in the presence of IFNAR neutralizing antibodies, greater sensitivity of mutant virus replication to IFN-α pretreatment, partial rescue of its infectivity in cells deficient in RNase L, and direct effects of transfected sfRNA on rescuing replication of unrelated Semliki Forest virus in cells pretreated with IFN-α. The results define a novel function of sfRNA in flavivirus pathogenesis via its contribution to viral evasion of the type I interferon response.     

Induction of protective immune responses against NXS2 neuroblastoma challenge in mice by immunotherapy with GD2 mimotope vaccine and IL-15 and IL-21 gene delivery

The GD2 ganglioside expressed on neuroectodermal tumor cells is weakly immunogenic in tumor-bearing patients and induces predominantly IgM antibody responses in the immunized host. Using a syngeneic mouse challenge model with GD2-expressing NXS2 neuroblastoma, we investigated novel strategies for augmenting the effector function of GD2-specific antibody responses induced by a mimotope vaccine. We demonstrated that immunization of A/J mice with DNA vaccine expressing the 47-LDA mimotope of GD2 in combination with IL-15 and IL-21 genes enhanced the induction of GD2 cross-reactive IgG2 antibody responses that exhibited cytolytic activity against NXS2 cells. The combined immunization regimen delivered 1 day after tumor challenge inhibited subcutaneous (s.c.) growth of NXS2 neuroblastoma in A/J mice. The vaccine efficacy was reduced after depletion of NK cells as well as CD4⁺ and CD8⁺ T lymphocytes suggesting involvement of innate and adaptive immune responses in mediating the antitumor activity in vivo. CD8⁺ T cells isolated from the immunized and cured mice were cytotoxic against syngeneic neuroblastoma cells but not against allogeneic EL4 lymphoma, and exhibited antitumor activity after adoptive transfer in NXS2-challenged mice. We also demonstrated that coimmunization of NXS2-challenged mice with the IL-15 and IL-21 gene combination resulted in enhanced CD8⁺ T cell function that was partially independent of CD4⁺ T cell help in inhibiting tumor growth. This study is the first demonstration that the mimotope vaccine of a weakly immunogenic carbohydrate antigen in combination with plasmid-derived IL-15 and IL-21 cytokines induces both innate and adaptive arms of the immune system leading to the generation of effective protection against neuroblastoma challenge. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. This work was supported by the Roswell Park Alliance Foundation, funds to commemorate Dr. Goro Chihara’s research activity, and by a research grant R21 AI060375 from the National Institutes of Health.     

Effect of Val92Met and Arg163Gln variants of the MC1R gene on freckles and solar lentigines in Japanese

Melanocortin-1 receptor (MC1R) is a highly polymorphic gene. The variety of the variants is dependent on the ethnic background of the individual. In Caucasians, specific variants, such as Arg151Cys, Arg160Trp, and Asp294His, are strongly associated with red hair, skin cancer and pigmented lesions. In Asians, there is no report so far indicating an association such as that observed in Caucasians. Here, we performed an association study on melanogenic phenotypes in 245 Japanese individuals. We focused on freckles and solar lentigines as melanogenic phenotypes. The 92Met allele and the 163Arg allele were positively associated with freckles and severe solar lentigines; the 163Gln allele showed a negative association. Those subjects who were homozygous for both the 92Met and 163Arg alleles had a highly elevated risk of developing freckles (OR: 7.92; 95% CI: 1.52-39.6) and severe solar lentigines (OR: 4.08; 95% CI: 1.34-13.1). Our study is the first report to show a clear association of MC1R variants on melanogenic phenotypes in Asians and also indicates the importance of Arg163Gln. In vitro studies by other groups demonstrated that Val92Met impaired MC1R function but Arg163Gln did not. Based on these in vitro studies, we believe that the result we observed for Val92Met could be attributed to impaired MC1R function, while, for Arg163Gln, other factors, e.g. effect of other loci, need to be considered.     

Overexpression of the JAZ factors with mutated jas domains causes pleiotropic defects in rice spikelet development

In a determinate meristem, such as a floral meristem, a genetically determined number of organs are produced before the meristem is terminated. In rice, iterative formation of organs during flower development with defects in meristem determinacy, classically called ‘proliferation’, is caused by several mutations and observed in dependence on environmental conditions. Here we report that overexpression of several JAZ proteins, key factors in jasmonate signaling, with mutations in the Jas domains causes an increase in the numbers of organs in florets, aberrant patterns of organ formation and repetitious organ production in spikelets. Our results imply that JAZ factors modulate mechanisms that regulate meristem functions during spikelet development.