Flavonoids protect neuronal cells from oxidative stress by three distinct mechanisms

Flavonoids are a family of antioxidants found in fruits and vegetables as well as in popular beverages such as red wine and tea. Although the physiological benefits of flavonoids have been largely attributed to their antioxidant properties in plasma, flavonoids may also protect cells from various insults. Nerve cell death from oxidative stress has been implicated in a variety of pathologies, including stroke, trauma, and diseases such as Alzheimer's and Parkinson's. To determine the potential protective mechanisms of flavonoids in cell death, the mouse hippocampal cell line HT-22, a model system for oxidative stress, was used. In this system, exogenous glutamate inhibits cystine uptake and depletes intracellular glutathione (GSH), leading to the accumulation of reactive oxygen species (ROS) and an increase in Ca(2+) influx, which ultimately causes neuronal death. Many, but not all, flavonoids protect HT-22 cells and rat primary neurons from glutamate toxicity as well as from five other oxidative injuries. Three structural requirements of flavonoids for protection from glutamate are the hydroxylated C3, an unsaturated C ring, and hydrophobicity. We also found three distinct mechanisms of protection. These include increasing intracellular GSH, directly lowering levels of ROS, and preventing the influx of Ca(2+) despite high levels of ROS. These data show that the mechanism of protection from oxidative insults by flavonoids is highly specific for each compound.     

Relationships between the extent of apnea-induced bradycardia and the vascular response in the arm and leg during dynamic two-legged knee extension exercise

Our aim was to test the hypothesis that apnea-induced hemodynamic responses during dynamic exercise in humans differ between those who show strong bradycardia and those who show only mild bradycardia. After apnea-induced changes in heart rate (HR) were evaluated during dynamic exercise, 23 healthy subjects were selected and divided into a large response group (L group; n = 11) and a small response group (S group; n = 12). While subjects performed a two-legged dynamic knee extension exercise at a work load that increased HR by 30 beats/min, apnea-induced changes in HR, cardiac output (CO), mean arterial pressure (MAP), arterial O(2) saturation (Sa(O(2))), forearm blood flow (FBF), and leg blood flow (LBF) were measured. During apnea, HR in the L group (54 ± 2 beats/min) was lower than in the S group (92 ± 3 beats/min, P < 0.05). CO, Sa(O(2)), FBF, LBF, forearm vascular conductance (FVC), leg vascular conductance (LVC), and total vascular conductance (TVC) were all reduced, and MAP was increased in both groups, although the changes in CO, TVC, LBF, LVC, and MAP were larger in the L group than in the S group (P < 0.05). Moreover, there were significant positive linear relationships between the reduction in HR and the reductions in TVC, LVC, and FVC. We conclude that individuals who show greater apnea-induced bradycardia during exercise also show greater vasoconstriction in both active and inactive muscle regions.     

Extended-gate FET-based enzyme sensor with ferrocenyl-alkanethiol modified gold sensing electrode

We developed a field-effect transistor (FET)-based enzyme sensor that detects an enzyme-catalyzed redox-reaction event as an interfacial potential change on an 11-ferrocenyl-1-undecanethiol (11-FUT) modified gold electrode. While the sensitivity of ion-sensitive FET (ISFET)-based enzyme sensors that detect an enzyme-catalyzed reaction as a local pH change are strongly affected by the buffer conditions such as pH and buffer capacity, the sensitivity of the proposed FET-based enzyme sensor is not affected by them in principle. The FET-based enzyme sensor consists of a detection part, which is an extended-gate FET sensor with an 11-FUT immobilized gold electrode, and an enzyme reaction part. The FET sensor detected the redox reaction of hexacyanoferrate ions, which are standard redox reagents of an enzymatic assay in blood tests, as a change in the interfacial potential of the 11-FUT modified gold electrode in accordance with the Nernstian response at a slope of 59 mV/decade at 25 degrees C. Also, the FET sensor had a dynamic range of more than five orders and showed no sensitivity to pH. A FET-based enzyme sensor for measuring cholesterol level was constructed by adding an enzyme reaction part, which contained cholesterol dehydrogenase and hexacyanoferrate (II)/(III) ions, on the 11-FUT modified gold electrode. Since the sensitivity of the FET sensor based on potentiometric detection was independent of the sample volume, the sample volume was easily reduced to 2.5 microL while maintaining the sensitivity. The FET-based enzyme sensor successfully detected a serum cholesterol level from 33 to 233 mg/dL at the Nernstian slope of 57 mV/decade.     

Ambient temperature affects glabrous skin vasculature and sweating responses to mental task in humans

We compared responses in heart rate (HR), mean blood pressure (MAP), sweating rate (SR), sweating expulsion (SwE), and skin vascular conductance (VC) to mental task among different ambient temperature (Ta) conditions, i.e., 12, 16, 20, and 24 degrees C. Seven subjects (27+/-5 yrs, 64+/-14 kg) underwent a 2-min color word conflict test (CWT) after 2 mins of baseline data acquisition following a 20-min resting period. All subjects wore long sleeve shirts and long pants. The skin blood flow was measured with a laser Doppler probe on the left index finger pulp to calculate skin VC, and the SR and sweating expulsion (SwE) were measured with a ventilated capsule on the left thenar. CWT significantly increased the HR and MAP, while there was no significant effect of Ta on the magnitudes of these responses. CWT significantly decreased the skin VC when the Ta was 24 degrees C, whereas it significantly increased the skin VC when the Ta was 12 or 16 degrees C. CWT significantly increased SR and SwE in all Ta conditions, and the SwE was greater in warmer conditions. These findings suggest that different ambient temperatures induce different responses in finger skin vasculature to mental task, implying the independent response of cutaneous vasomotor tone and sweat glands in glabrous skin to mental task.     

Differential arterial blood flow response of splanchnic and renal organs during low-intensity cycling exercise in women

To investigate the regional hemodynamic responses of abdominal arteries at the onset of exercise and to focus on their transient responses, eight female subjects (21-30 yr) performed ergometer cycling exercise at 40 W for 4 min in a semi-supine position. Mean blood velocities (MBVs) in the right renal (RA), superior mesenteric (SMA), and splenic (SA) arteries were measured by pulsed echo-Doppler ultrasonography, with beat-by-beat measurements of heart rate (HR) and mean arterial pressure (MAP). The vascular resistance index (RI) of each artery was calculated from MBV/MAP. MAP (76 +/- 9 to 83 +/- 8 mmHg at 4 min) and HR (60 +/- 7 to 101 +/- 9 beats/min at 4 min) increased during exercise (P < 0.05). The MBV of RA and SA rapidly decreased after the onset of exercise (30 s; -19 +/- 5% and -19 +/- 12%, respectively), reaching -27 +/- 7% and -27 +/- 15% at the end of exercise (P < 0.05). RI did not change during the initial 30 s of exercise, reflecting a reduction in MAP, and increased toward the end of the exercise (+55 +/- 21% and +59 +/- 39%, respectively). In contrast, both the MBV and RI in the SMA remained constant throughout the exercise. The results indicate that, whereas the responses of renal and splenic vessels changed similarly throughout the protocol, the vascular response of SMA that mainly supplies blood to the intestinal tract was unchanged during exercise. We, therefore, conclude that low-intensity cycling exercise resulted in differential blood flow responses in arteries supplying the abdominal organs.     

Enzymatic activities of novel mutant endoglucanases carrying sequential active sites

Novel mutant enzymes of endoglucanase II (EGII) from fungus Trichoderma viride were prepared and their hydrolysis and enzymatic polymerization activities were studied. EGII((core)2) and EGII((core)2-His), which possess sequential two active sites of EGII with a His-tag probe at the N-terminal and with His-tag probes at the N and C terminals, respectively, showed higher hydrolysis activities than EGII(core) with a single active site even in comparison on the active-site concentration basis. These mutant enzymes were applied to the enzymatic polymerization to afford artificial cellulose. The polymerization rates with using EGII((core)2) and EGII((core)2-His) were also higher than that with using EGII(core). The polymerization products were identified as highly crystalline cellulose of type II. The mutant enzymes were also effective to prepare spherulites. EGII((core)2) and EGII((core)2-His) are considered to possess higher hydrolysis and polymerization activities than EGII(core) mainly due to the suitably stabilized conformation with the sequential arrangement.     

Polyphosphate:AMP phosphotransferase and polyphosphate:ADP phosphotransferase activities of Pseudomonas aeruginosa

In Pseudomonas aeruginosa PAO1, we have found massive polyphosphate:AMP phosphotransferase activity and polyphosphate:ADP phosphotransferase activity known as the reverse catalytic activity of polyphosphate kinase which participates in polyphosphate synthesis in the bacterium. Biochemical analysis using the partially purified polyphosphate:ADP phosphotransferase has revealed that it is independent of polyphosphate kinase and can function as polyphosphate-dependent nucleoside diphosphate kinase which most prefers GDP to the other three nucleoside diphosphates as a phospho-acceptor. It has been also demonstrated that polyphosphate:AMP phosphotransferase activity marked in the bacterium mainly originates from the combined action of the polyphosphate:ADP phosphotransferase described above and adenylate kinase. Both of the polyphosphate-utilizing activities require short polyP as a phospho-donor whose chain length is <75.     

Saiko-ka-ryukotsu-borei-to,an herbal medicine,prevents chronic stress-induced disruption of glucocorticoid negative feedback in rats

Exposure to stress is known to precipitate or exacerbate many neuropsychiatric disorders such as depression. Abnormality of the neuroendocrine system, as shown by increased adrenal weight and attenuated glucocorticoid negative feedback, is frequently seen in depression. The aim of the present study is to clarify the usefulness of saiko-ka-ryukotsu-borei-to, an herbal medicine, in the treatment of abnormality of the neuroendocrine system using an experimental stress-depression model. Rats were subjected to water immersion and restraint for 2 h daily for 4 weeks (chronic stress), followed by recovery for 10 days. Saiko-ka-ryukotsu-borei-to was administered during the stress and recovery periods (100, 300, or 1000 mg/kg daily, p.o.) or only during the recovery period (1000 mg/kg). After the recovery period, the adrenal weight was measured, and glucocorticoid feedback ability was evaluated by a dexamethasone suppression test using 30 microg/kg dexamethasone. The administration of saiko-ka-ryukotsu-borei-to during the stress and recovery periods prevented the stress-induced increase in adrenal weight or the attenuated negative feedback in a dose-dependent manner. The administration of saiko-ka-ryukotsu-borei-to during the recovery period alone also ameliorated the abnormality of the neuroendocrine system. These results indicate that saiko-ka-ryukotsu-borei-to is effective against chronic stress-induced abnormality of the neuroendocrine system. Because some symptoms and symptomatic relapses in depressives are attributed to dysfunction of the hypothalamo-pituitary-adrenal axis, the present findings provide information important for prevention and treatment of depression.     

Enhancement of metabolizing herbicides in young tubers of transgenic potato plants with the rat CYP1A1 gene

A rat P450 monooxygenase gene (CYP1A1) was introduced into potato plants to enhance the metabolism of the environmental contaminants in subterranean organs. The CYP1A1 gene was kept under the control of the potato patatin promoter to enhance tuber-specific expression. A total of 106 transgenic plants (PAT1A1 plants) were obtained following selection by a resistance test to kanamycin and PCR analysis. PAT1A1 plants treated with 10% exogenous sucrose showed a higher activity of monooxgenase in the leaves than the non-transgenic plants. This indicated that the activity enhanced by 10% sucrose was due to the patatin promoter containing the sucrose-inducted elements. One representative transgenic plant, Ag2197, was selected on the basis of monooxgenase activity in the leaves and Western blot analysis. Ag2197 was found to accumulate a large amount of CYP1A1 mRNA and protein in the developing tuber but not in the mature tuber. The residual herbicides, atrazine and chlortoluron, were analyzed in the micro-tubers of Ag2197 and non-transgenic plants. The amount of residual herbicides in Ag2197 was much lower than that in the non-transgenic plant, indicating that the transgenic plant metabolized the herbicides to a detoxified form. The transgenic plants produced in this study might be useful for the phytoremediation of chemical pollution in the soil.