Impaired hippocampal long-term potentiation and failure of learning in β1,4-N-acetylgalactosaminyltransferase gene transgenic mice

Gangliosides (sialic acid-containing glycosphingolipids) play important roles in many physiological functions, including synaptic plasticity in the hippocampus, which is considered as a cellular mechanism of learning and memory. In the present study, three types of synaptic plasticity, long-term potentiation (LTP), long-term depression (LTD) and reversal of LTP (depotentiation, DP), in the field excitatory post-synaptic potential in CA1 hippocampal neurons and learning behavior were examined in β1,4-N-acetylgalactosaminyltransferase (β1,4 GalNAc-T; GM2/GD2 synthase) gene transgenic (TG) mice, which showed a marked decrease in b-pathway gangliosides (GQ1b, GT1b and GD1b) in the brain and isolated hippocampus compared with wild-type (WT) mice. The magnitude of the LTP induced by tetanus (100 pulses at 100?Hz) in TG mice was significantly smaller than that in control WT mice, whereas there was no difference in the magnitude of the LTD induced by three short trains of low-frequency stimulation (LFS) (200 pulses at 1?Hz) at 20?min intervals between the two groups of mice. The reduction in the LTP produced by delivering three trains of LFS (200 pulses at 1?Hz, 20?min intervals) was significantly greater in the TG mice than in the WT mice. Learning was impaired in the four-pellet taking test (4PTT) in TG mice, with no significant difference in daily activity or activity during the 4PTT between TG and WT mice. These results suggest that the overexpression of β1,4 GalNAc-T resulted in altered synaptic plasticity of LTP and DP in hippocampal CA1 neurons and learning in the 4PTT, and this is attributable to the shift from b-pathway gangliosides to a-pathway gangliosides.     

Preparation and immunological characterization of β-lactoglobulin-amylose conjugate

β-Lactoglobulin (BLG), a major allergen of cow's milk, was conjugated with the N-hydroxysuccinimide ester of the amylose-glycylglycine adduct (AG-ONSu) to reduce its immunogenicity, and the biochemical and immunological properties of the resulting conjugate (AG-BLG) were studied. The conjugate was prepared by modifying BLG with AG-ONSu, and was purified in a Sephadex G-100 column. The analytical data for AG-BLG indicated that 10.5 moles of AG-ONSu, with a mean molecular weight of 2,800, was covalently attached to the amino groups of the BLG molecule. Conjugation with AG-ONSu greatly decreased the reactivity of BLG with anti-BLG polyclonal antibodies owing to its shielding action for epitopes on the protein's surface. These findings suggest that AG-ONSu can be used advantageously to suppress the hypersensitivity mediated by IgG antibodies in milk allergy.     

High molecular weight lectin isolated from the mucus of the giant African snail Achatina fulica

To understand better the host defense mechanisms of mollusks against pathogens, we examined the anti-microbial activity of mucus from the giant African snail Achatina fulica. Hemagglutination activity of the mucus secreted by the integument of snails inoculated with Escherichia coli was observed to increase and to cause hemagglutination of rabbit red blood cells. Purification of the snail mucus lectin by sequential column chromatography revealed that the relative molecular mass of the lectin was 350 kDa. The hemagglutination activity of the lectin was Ca(2+)-dependent and was inhibited by galactose. Growth arrest tests showed that the lectin did not inhibit bacterial growth, but did induce agglutination of gram-positive and gram-negative bacteria. Tissue distribution analyses using a polyclonal antibody revealed that the lectin was expressed in the tissues of the mantle collar. The lectin isolated from the mucus of the snail appeared to contribute to its innate immunity.     

Effects of struvite formation and nitratation promotion on nitrogenous emissions such as NH3, N2O and NO during swine manure composting

To reduce nitrogenous emissions from composting, two different countermeasures were applied simultaneously in swine manure composting. One was forming struvite by adding Mg and P at the start of composting, and the other was to promote nitratation (nitrite being oxidized nitrate) by adding nitrite-oxidizing bacteria after the thermophilic phase of composting. In the laboratory- and mid-scale composting experiments, 25-43% of NH3, 52-80% of N2O and 96-99% of NO emissions were reduced. From the nitrogen balance, it was revealed that the struvite formation reduced not only NH3, but also other nitrogenous emissions except N2O. The amount of total nitrogen losses was reduced by 60% by the two combined countermeasures, against 51% by the struvite formation alone. However, the nitratation promotion dissolved struvite crystals due to the pH decline, diminishing the effect of struvite as a slow-release fertilizer.     

Polarization-based brightness discrimination in the foraging butterfly, Papilio xuthus

The human eye is insensitive to the angular direction of the light e-vector, but several animal species have the ability to discriminate differently polarized lights. How the polarization is detected is often unclear, however. Egg-laying Papilio butterflies have been shown to see false colours when presented with differently polarized lights. Here we asked whether this also holds in foraging butterflies. After training individuals to feed on nectar in front of an unpolarized spectral light, we carried out three dual-choice tests, where the discrimination of (i) the spectral content, (ii) the light intensity, and (iii) the e-vector orientation were investigated. In the first test, the butterflies selected the trained spectrum irrespective of its intensity, and in the second test they chose the light with the higher intensity. The result of the e-vector discrimination test was very similar to that of the second test, suggesting that foraging butterflies discriminate differently polarized lights as differing in brightness rather than as differing in colour. Papilio butterflies are clearly able to use at least two modes of polarization vision depending on the behavioural context.     

Enhancement of autophagy is a potential modality for tumors refractory to radiotherapy

Radiotherapy is a well-established treatment for cancer. However, the existence of radioresistant cells is one of the major obstacles in radiotherapy. In order to understand the mechanism of cellular radioresistance and develop more effective radiotherapy, we have established clinically relevant radioresistant (CRR) cell lines, which continue to proliferate under daily exposure to 2 Gray (Gy) of X-rays for >30 days. X-ray irradiation significantly induced autophagic cells in parental cells, which was exiguous in CRR cells, suggesting that autophagic cell death is involved in cellular radiosensitivity. An autophagy inducer, rapamycin sensitized CRR cells to the level of parental cells and suppressed cell growth. An autophagy inhibitor, 3-methyladenine induced radioresistance of parental cells. Furthermore, inhibition of autophagy by knockdown of Beclin-1 made parental cells radioresistant to acute radiation. These suggest that the suppression of autophagic cell death but not apoptosis is mainly involved in cellular radioresistance. Therefore, the enhancement of autophagy may have a considerable impact on the treatment of radioresistant tumor.     

Age-related decrease of miRNA-92a levels in human CD8+ T-cells correlates with a reduction of naïve T lymphocytes

MicroRNA (miR)-17-92a expression plays a crucial role in lymphocyte ontogeny. We therefore set out to determine miR-92a expression levels in peripheral blood lymphocytes from healthy subjects to ascertain any association between these levels and ageing. We found a positive correlation between the miR-92a expression level and the percentages of RO-CD8⁺CD27⁺ (P = 0.0046) and CD3⁺CD8⁺CD62L⁺ (P = 0.0011). This suggests that the majority of miR-92a of CD8⁺ T cells is derived from naïve cells, and the miR-92a expression level in CD8⁺ T cells declines progressively with age. These results indicate that the age-related attrition of naïve T cells is linked to a reduction of miR-92a in human T -lymphocytes. Therefore, we should careful attention when evaluating human miRNA levels in T lymphocytes to use normal control values.     

Different Impacts of Neck Circumference and Visceral Obesity on the Severity of Obstructive Sleep Apnea Syndrome

Our aim was to investigate the significance of neck circumference (NC) on the presence and severity of obstructive sleep apnea (OSA) syndrome independent of visceral fat (VF) obesity. A total of 219 subjects with suspected OSA underwent a complete polysomnography (PSG) study, along with the measurement of NC, and total body fat (TF) and VF levels (VFLs) measured by bioelectrical impedance analysis. We proposed NC divided by height (NC/H) as the simple index for height‐corrected NC in Japanese subjects. NC/H exhibited a significantly stronger correlation than NC per se with BMI (r = 0.781 vs. 0.675, P = 0.0178), TF (r = 0.531 vs. 0.156, P < 0.0001), and VF (r = 0.819 vs. 0.731, P = 0.0203), indicating that NC/H is a better indicator of visceral obesity than NC per se. Interestingly, despite the strong correlation between NC/H and VFL, VFL was significantly associated with the apnea‐hypopnea index (AHI) ≥5, ≥15, and ≥30, but not with ≥40 or ≥50, whereas NC/H was significantly associated with higher AHI values, i.e., AHI ≥50 but not with lower AHI value. Furthermore, multiple regression analyses revealed that VFL and NC/H were independently associated with the square root of AHI (AHI^0.5) levels in obese and nonobese patients, respectively. In conclusion, NC is associated with the severity of OSA independently of visceral obesity, especially in nonobese patients.     

Nitrite is an alternative source of NO in vivo

In this study, we investigated whether orally administered nitrite is changed to NO and whether nitrite attenuates hypertension in a dose-dependent manner. We utilized a stable isotope of [15N]nitrite (15NO2-) as a source of nitrite to distinguish between endogenous nitrite and that exogenously administered and measured hemoglobin (Hb)-NO as an index of circulating NO in whole blood using electron paramagnetic resonance (EPR) spectroscopy. When 1 mg/kg Na15NO2 was orally administered to rats, an apparent EPR signal derived from Hb15NO (A(Z) = 23.4 gauss) appeared in the blood. The peak blood HbNO concentration occurred at the first measurement after intake (5 min) for treatment with 1 and 3 mg/kg (HbNO: 4.93 +/- 0.52 and 10.58 +/- 0.40 microM, respectively) and at 15 min with 10 mg/kg (HbNO: 38.27 +/- 9.23 microM). In addition, coadministration of nitrite (100 mg/l drinking water) with N(omega)-nitro-L-arginine methyl ester (L-NAME; 1 g/l) for 3 wk significantly attenuated the L-NAME-induced hypertension (149 +/- 10 mmHg) compared with L-NAME alone (170 +/- 13 mmHg). Furthermore, this phenomenon was associated with an increase in circulating HbNO. Our findings clearly indicate that orally ingested nitrite can be an alternative to L-arginine as a source of NO in vivo and may explain, at least in part, the mechanism of the nitrite/nitrate-rich Dietary Approaches to Stop Hypertension diet-induced hypotensive effects.     

Perfusion of hearts with triglyceride-rich particles reproduces the metabolic abnormalities in lipotoxic cardiomyopathy

Hearts with overexpression of anchored lipoprotein lipase (LpL) by cardiomyocytes (hLpL(GPI) mice) develop a lipotoxic cardiomyopathy. To characterize cardiac fatty acid (FA) and triglyceride (TG) metabolism in these mice and to determine whether changes in lipid metabolism precede cardiac dysfunction, hearts from young mice were perfused in Langendorff mode with [14C]palmitate. In hLpL(GPI) hearts, FA uptake and oxidation were decreased by 59 and 82%, respectively. This suggests reliance on an alternative energy source, such as TG. Indeed, these hearts oxidized 88% more TG. Hearts from young hLpL(GPI) mice also had greater uptake of intravenously injected cholesteryl ester-labeled Intralipid and VLDL. To determine whether perfusion of normal hearts would mimic the metabolic alterations found in hLpL(GPI) mouse hearts, wild-type hearts were perfused with [14C]palmitate and either human VLDL or Intralipid (0.4 mM TG). Both sources of TG reduced [14C]palmitate uptake (48% with VLDL and 45% with Intralipid) and FA oxidation (71% with VLDL and 65% with Intralipid). Addition of either heparin or LpL inhibitor P407 to Intralipid-containing perfusate restored [14C]palmitate uptake and confirmed that Intralipid inhibition requires local LpL. Our data demonstrate that reduced FA uptake and oxidation occur before mechanical dysfunction in hLpL(GPI) lipotoxicity. This physiology is reproduced with perfusion of hearts with TG-containing particles. Together, the results demonstrate that cardiac uptake of TG-derived FA reduces utilization of albumin-FA.