Meson-Baryon Couplings from QCD Sum Rules

Coupling constants of the pseudoscalar mesons to the octet baryons are calculated in the QCD sum rule approach. Two-point correlation function of the baryons are evaluated in a single meson state and the vacuum, which yields the designated coupling. The emphasis is on the flavor SU(3) structure of the coupling constants and reliability in extracting the coupling constants from the two-point correlation functions. We first calculate the baryon-diagonal couplings and study the reliability of the sum rule. The F/D ratio of the coupling is determined in the SU(3) limit. We further formulate the baryon-off-diagonal couplings using the projected correlation functions and the vertex functions, so that the unwanted excited states do not contaminate the sum rule. As an example, the (\pi - \Lambda - \Sigma) coupling constant is calculated and the flavor SU(3) breaking effect is studied. We find that the effect of SU(3) breaking on the (\pi - \Lambda - \Sigma) coupling constant is small.Comment: 33 pages, REVTeX4, 6 figure

The F/D Ratio and Meson-Baryon Couplings from QCD Sum Rules

Coupling constants of the pseudoscalar mesons to the octet baryons are computed in the QCD sum rule approach. The pi-NN, eta-NN, pi-XiXi, eta-XiXi, pi-SigmaSigma, eta-SigmaSigma as well as pi-Lambda-Sigma couplings are studied. Determining the pertinent Dirac structure in the correlation function, we analyze the couplings in the SU(3) limit. We find the F/D ratio to be \sim 0.6-0.8 that is consistent with the SU(6) value. We also estimate the SU(3) breaking effect using a projected correlation function method.Comment: 4 pages, Talk given at XVI International Conference on Particles and Nuclei (PANIC02), Osaka, Japan, Sep.30 - Oct.4, 200

Motor Protein KIF1A Is Essential for Hippocampal Synaptogenesis and Learning Enhancement in an Enriched Environment

SummaryEnvironmental enrichment causes a variety of effects on brain structure and function. Brain-derived neurotrophic factor (BDNF) plays an important role in enrichment-induced neuronal changes; however, the precise mechanism underlying these effects remains uncertain. In this study, a specific upregulation of kinesin superfamily motor protein 1A (KIF1A) was observed in the hippocampi of mice kept in an enriched environment and, in hippocampal neurons in vitro, BDNF increased the levels of KIF1A and of KIF1A-mediated cargo transport. Analysis of Bdnf+/− and Kif1a+/− mice revealed that a lack of KIF1A upregulation resulted in a loss of enrichment-induced hippocampal synaptogenesis and learning enhancement. Meanwhile, KIF1A overexpression promoted synaptogenesis via the formation of presynaptic boutons. These findings demonstrate that KIF1A is indispensable for BDNF-mediated hippocampal synaptogenesis and learning enhancement induced by enrichment. This is a new molecular motor-mediated presynaptic mechanism underlying experience-dependent neuroplasticity

INFRARED SPECTROSCOPY OF HYDROGEN-BONDED CLUSTERS OF PROTONATED HISTIDINE

Histidine(His), one of the essential amino acids, is involved in active sites in many enzyme proteins, and known to play fundamental roles in human body. Thus, to gain detailed information about intermolecular interactions of His as well as its structure is very important. In the present study, we have recorded IR spectra of hydrogen-bonded clusters of protonated His (HisH$^+$) in the gas phase to discuss the relation between the molecular structure and intermolecular interaction of HisH$^+$. Clusters of HisH$^+$-(MeOH)$_n$ ($n = 1, 2$) were generated by an electrospray ionization of the MeOH solution of L-His hydrochloride monohydrate. IR photodissociation spectra of HisH$^+$-(MeOH)$_{1,2}$ were recorded. By comparing with the results of the DFT calculations, we determined the structures of these clusters. In the case of $n = 1$ cluster, MeOH is bonded to the imidazole ring as a proton acceptor. The most of vibrational bands observed were well explained by this isomer. However, a free NH stretch band of the imidazole ring was also observed in the spectrum. This indicates an existence of an isomer in which MeOH is bounded to the carboxyl group of HisH$^+$. Furthermore, it is found that a protonated position of His is influenced by a hydrogen bonding position of MeOH. In the case of $n = 2$ cluster, one MeOH molecule is bonded to the amino group, while the other MeOH molecule is separately bonded to the carboxyl group in the most stable isomer. However, there is a possibility that other conformers also exist in our experimental condition. The details of the experimental and theoretical results will be presented in the paper

High-grade Glioma Masquerading as a Small Cerebral Hemorrhage: A Case Report

We report a rare case of a high-grade glioma masquerading as a small subcortical hemorrhage. A 71-year-old woman came to a local hospital with sudden right upper extremity numbness. Computed tomography revealed a small subcortical hemorrhage with faint perifocal edema in the left postcentral gyrus. Conservative treatment was initiated, and she was discharged from the hospital with no neurological deficits. Six months later after discharge, she suffered an acute partial seizure of the right upper extremity. Magnetic resonance imaging with gadolinium demonstrated a ring-enhancing mass surrounded by severe perifocal edema in the hemorrhagic scar. We performed complete resection of the tumor, and the histological diagnosis was anaplastic oligodendroglioma. The diagnosis of a high-grade glioma was delayed due to intratumoral hemorrhages mimicking a small subcortical hemorrhage; consequently, we suspected the hemorrhage was induced by cerebral amyloid angiopathy. It may be important to repeat radiological follow up, if necessary, and to maintain clinical observance of possible intracranial neoplasm, even when the hemorrhage is small, particularly when the cause of bleeding is unknown

Response of sweet pepper autofluorescence against solar radiation

Shades are adjusted in sweet pepper cultivation, based on solar exposure levels. Pyranometers and photosensitive films have recently been introduced to smart agriculture. However, there are no means of observing biological responses to solar exposure. In this study, we hypothesized that solar exposure levels affect the visible autofluorescence of sweet pepper under 365 nm illumination. To test this hypothesis, we cultivated sweet pepper plants under two exposure conditions, low (half of the normal) and high (the normal). Fluorescence photography (365 nm illumination) revealed that dark-fluorescent peppers only arise when cultivated under high-exposure conditions (0.7-fold decline at emission of 390 nm for high-exposure conditions). Microscopic and spectroscopic observations showed that blue autofluorescence was accompanied by an accumulation of UVB pigments (1.2-factor increase in the absorbance at 300 nm) and epidermal development (1.3-fold thicker cell wall). This study suggests that the autofluorescence of sweet pepper can possibly be used to understand the response of crop to solar radiation at a fruit level in horticulture