Effects of TAK-044, a nonselective endothelin receptor antagonist, on the spontaneous and indomethacin- or methylene blue-induced constriction of the ductus arteriosus in rats

We studied the effects of TAK-044, a nonselective endothelin (ET) receptor antagonist, on the indomethacin- or methylene blue-induced constriction of the ductus arteriosus (DA) in rats and compared them with the effects on spontaneous DA constriction. Injection of TAK-044 into 21-day-old fetuses in utero was performed through the uterine wall of laparotomized mother rats under light ether anesthesia. The fetuses were autopsied 3 hr after treatment with TAK-044 (10 mg/kg) in utero and simultaneous administration to the laparotomized mother rats of indomethacin (3 mg/kg, p.o.) or methylene blue (100 mg/kg, i.p.). In the second experiment, pregnant rats were decapitated on day 21 of gestation to obtain newborn rats by cesarean delivery. Newborn rats which were given TAK-044 (2, 10 mg/kg) immediately after or 1 hr before cesarean delivery were autopsied at various times after birth. In both experiments, pups were rapidly frozen in an acetone-dry ice mixture at autopsy to evaluate the DA constriction by the whole-body freezing and shaving method. TAK-044 injection into the fetus 3 hr before autopsy completely inhibited the DA constriction induced by maternal treatment with indomethacin or methylene blue. TAK-044 caused dose-dependent inhibition of the spontaneous closure of the DA after birth. The inhibitory effect was more pronounced in pups which were given TAK-044 in utero 1 hr before birth; however, the inhibitory effect was incomplete in newborn pups. These results, together with the previous finding that BQ-123, an ETA-specific receptor antagonist, inhibits the ductal constriction induced by oxygen in vitro [Coceani et al., 1992], indicate that the ETA receptor plays a significant role in the indomethacin- or methylene blue-induced DA constriction as well as in the spontaneous DA constriction after birth, and also indicate that the inhibition of ETA receptor by TAK-044 was more easily achieved in fetuses than in neonates.     

Different development of pine wilt disease in artificially infectedPinus thunbergii seedlings potted together with different tree species

To evaluate the effect of adjacent tree species on the susceptibility of Japanese black pine (Pinus thunbergii) to pine wilt disease, an inoculation experiment was conducted usingP. thunbergii seedlings potted with seedlings of six tree species,i. e. Alnus sieboldiana, Eurya japonica, Lespedeza bicolor formacutifolia, Pinus thumbergii, Robinia pseudo-acacia andSarothamus scoparius. About ten months after planting, they were inoculated with the pinewood nematode (Bursaphelenchus xylophilus) in early July 1992. After that, the proportion of pine seedlings with completely discolored foliage increased more quickly when the seedlings were potted withR. pseudo-acacia, S. scoparius orA. sieboldiana than when potted withP. thunbergii, L. bicolor orE. japonica. At the end of the study period, 17 weeks after inoculation, it reached 90.6%, 90.0%, 87.5%, 72.7%, 63.3%, and 59.4% when the pine seedlings were potted withR. pseudo-acacia, S. scoparius, A. sieboldiana, P. thunbergii, L. bicolor andE. japonica, respectively. This indicated that the susceptibility ofP. thunbergii seedlings to pine wilt disease was influence by the species of adjacent trees.     

Estimation of the biomass of fine roots and mycorrhizal fungi: a case study in a Japanese red pine (Pinus densiflora) stand

As part of a study on soil carbon flow in forest ecosystems, the biomass of fine roots (2.0mm in diameter) and root-associated fungi, including ectomycorrhizal fungi, were estimated in the summer season in 1998 at a Pinus densiflora (Japanese red pine) stand in western Japan. Fine roots of pine were classified into three categories: class I roots (0.5–2.0mm in diameter), long class II roots (long roots with diameter 0.5mm; II_L), and short class II roots (short roots with diameter 0.5mm; II_S). Total biomass of fine roots (I + II_L + II_S) at this stand was estimated to be 91.0gm^–2, about 23% of which was class II roots (II_L + II_S). Ergosterol, which is a component of fungal membranes, was analyzed to estimate the biomass of root-associated fungi in roots. In the upper soil layers (from the surface to 13.4cm in depth), ergosterol contents in the class I, II_L and II_S roots were in the ranges 43.1–82.2, 126.1–196.3 and 271.2–321.0µgg^–1 root DW, respectively. The ergosterol content was converted to fungal biomass using the median (minimum–maximum) value of ergosterol concentration reported for ectomycorrhizal fungi. Root-associated fungal biomass in this stand was estimated to be 2.0 (0.5–9.6) gm^–2. The data suggest the biomass of ectomycorrhizal fungi in the P. densiflora stand is small compared with that in other forest ecosystems.