Nematocidal quassinoids and bicyclophosphorothionates: a possible common mode of action on the GABA receptor

The present study was undertaken to identify noncompetitive γ-aminobutyric acid receptor (GABAR) antagonists that are effective in nematodes, as well as to examine the hypothesis that the noncompetitive antagonism of the GABAR underlies the nematocidal activity of quassinoids against free-living nematodes of the Diplogastridae family. First, 14 known GABAR antagonists were screened for the effectiveness of their nematocidal activity in Diplogastridae. As a result, 3-isopropyl-1-phospha-2,6,7-trioxabicyclo[2.2.2]octane 1-sulfides (3-isopropyl-BPTs) were found to have high nematocidal activities, and 4-cyclohexyl-3-isopropyl-BPT (23) and 3-isopropyl-4-(2-propenyl)-BPT (27) were the two most potent analogues; these compounds are equipotent to samaderine B and more potent than the anthelmintic abamectin. 23-resistant nematodes, selected by challenge with 23, showed cross-resistance to samaderine B. 23 (10 μM) reduced [³H]23 binding to nematode membranes by 30.4%. Samaderine B (10 μM) resulted in a similar level of the inhibition, but had neither additive nor synergistic effects on the 23 inhibition of [³H]23 binding. These findings suggest that samaderine B shares a common binding site with the GABAR antagonist 23 in Diplogastridae. The results of comparative molecular field analysis, a method of three-dimensional quantitative structure-activity relationship analysis, supported this conclusion.     

Antioxidative and antigenotoxic effects of Japanese horse chestnut (Aesculus turbinata) seeds

Japanese horse chestnut seed extract (HCSE) dose-dependently inhibited the autooxidation of linoleic acid (IC(50): 0.2 mg/ml), and the inhibition was almost complete at a concentration of 1 mg/ml. The HCSE scavenged DPPH (1,1-diphenyl-2-picrylhydrazyl) radicals and superoxide anions with EC(50)s of 0.65 and 0.21 mg/ml, respectively. However, it had no effect on hydrogen peroxide. The HCSE inhibited the genotoxicities of furylfuramide, N-methyl-N-nitrosourea, methyl methanesulfonate, mitomycin C, 2-aminoanthracene and aflatoxin B1 at a concentration of 1 mg/ml or more. Total polyphenol content of the HCSE was 21 mg/g (13 mg/g-seeds). These results indicate that the Japanese horse chestnut seed is an antioxidative and antimutagenic botanical resource.     

Nitrogen acquisition and its relation to growth and yield in recent high-yielding cultivars of rice (Oryza sativa L.) in Japan

During the last two decades, high-yielding cultivars for multipurpose use of rice have been bred and released in Japan. Some of them have repeatedly recorded high yields of over 9?t?ha^?1 of brown rice (about 11.25?t?ha^?1 of rough rice). Here, characteristic features of nitrogen (N) acquisition and its relation to formation of yield components, dry matter production and grain yield at yield levels over 9?t?ha^?1 of brown rice in recent high-yielding cultivars, a large grain type of japonica variety, “Akita 63,” extra-panicle weight types of indica variety, “Takanari” and “Saikai 198,” and a panicle weight type of japonica variety, “Fukuhibiki,” are described as compared with those in the standard japonica cultivars, “Toyonishiki” and “Nipponbare.” The grain yield of the recent high-yielding cultivars was 9.4 to 11.6?t?ha^?1 of brown rice; that is 1.2?1.7 times greater than those of the standard cultivars. Sink capacity (1000-grain weight?×?spikelet number per unit land area) was 47?62% greater in the recent high-yielding cultivars, largely due to their 1.3?1.5 times greater N-use efficiency for sink formation (sink capacity per unit amount of total plant N in the aboveground part at maturity), although major component(s) responsible for their greater sink capacity differ among the cultivars. The ratio of grain yield to total dry matter was 1.1?1.4 times greater in the recent high-yielding cultivars than in the standard cultivars, indicating that the former efficiently translocate dry matter into spikelets during the grain-filling period. N-use efficiency for dry matter production (total dry matter per unit amount of total plant N) was comparable between “Akita 63,” “Fukuhibiki” and “Toyonishiki,” and slightly greater in “Takanari” and “Saikai 198” than in “Nipponbare.”

These results indicate that greater N-use efficiency for sink formation and efficient translocation of dry matter into spikelets contribute greatly to the high-yielding potential of the recent high-yielding cultivars.     

The effects of allopurinol on the ultrastructure of ischaemic and reperfused large intestine of sheep

Objective To test the possible inhibitory effect of allopurinol on reperfusion injury, caused by oxygen-derived free radicals, of sheep large intestine.
Design An ultrastructural study on caecal tissues from control and treated groups.  

Animals

Fifty sheep in four ischaemic and reperfused (treatment) groups and one control group. Three of the treatment groups were subdivided for half to be injected with allopurinol and the other half with its solvent, potassium hydroxide (KOH).
Procedure Ischaemia of the caecum was induced in the four treatment groups for 60 minutes by clamping the apex. Allopurinol and its KOH solvent were injected intravenously in three treatment groups prior to ischaemia. Samples were collected before and 1 hour after induction of ischaemia and 1 min, 1 h and 8 h after reperfusion. Tissues were processed and examined with an electron microscope.
Results Untreated and solvent injected sheep showed minor ultrastructural changes following ischaemia. With reperfusion, there was severe mitochondrial, goblet cell and basement membrane damage. Tissues from allopurinoltreated sheep were preserved and appeared similar to tissues from the control group.  

Conclusion:

Pre-treatment with allopurinol prevented damage to tissues whereas untreated or allopurinol solventtreated showed severe damage following reperfusion. It is believed that allopurinol, an analogue of hypoxanthine and xanthine, prevents reperfusion injury by competitively binding with xanthine oxidase. This reduces or inhibits the xanthine oxidase mediated conversion of hypoxanthine to xanthine thereby preventing the formation of oxygen-derived free radicals.     

Gigantic photoresponse in 1/4-filled-band organic salt (EDO-TTF)2PF6

We report that the organic salt (EDO-TTF)2PF6 with 3/4-filled-band (1/4-filled in terms of holes), which forms an organic metal with strong electron and lattice correlation, shows a highly sensitive response to photoexcitation. An ultrafast, photoinduced phase transition from the insulator phase to the metal phase can be induced with very weak excitation intensity at near room temperature. This response makes the material attractive for applications in switching devices with room-temperature operation. The observed photo-induced spectroscopic change shows that this photoinduced phase transition process is caused by the cooperative melting of charge ordering assisted by coherent phonon generation.