A multichannel automated chamber system for continuous measurement of forest soil CO2 efflux

We developed a fast-response multi-chamber system for measuring soil-surface CO2 efflux (Fc). The chambers (90 x 90 x 50 cm, L x W x H) had lids that opened and closed automatically, and were connected in parallel to a single CO2 analyzer equipped with a 16-channel gas sampler. Between measurements the chamber lids were raised to allow precipitation and leaf litter to reach the enclosed soil surface. When a chamber was closed, it was ventilated with well-buffered ambient air (125 l min-1) that entered by an inlet on one chamber sidewall and exited through a large vent on the opposite sidewall. The pressure difference between the inside and outside of the chamber was less than 0.22 Pa. Two additional mixing fans maintained an air speed of 0.3 +/- 0.1 m s-1 at 20 cm above the soil surface. Air was withdrawn continuously from the inlets and outlets of each chamber, and fed sequentially to an infrared CO2 analyzer. With this system, we measured Fc in a 40-year-old temperate Pinus densiflora Sieb. & Zucc. forest from February 8 to May 30, 2001. Mean Fc increased steadily from 0.9 micro mol m-2 s-1 at the beginning of February to 4.6 micro mol m-2 s-1 by the end of May. There was a statistically significant correlation between Fc and surface soil temperature (r = 0.896; P < 0.0001), and the Q10 value was 2.8. Spatial variation of Fc was higher in the non-growing season than in the growing season. Measurements were not interrupted by either rain or snow.     

Long-term growth analyses of Japanese cedar trees in a plantation: neighborhood competition and persistence of initial growth deviations

The individual growth of tree diameter at breast height (dbh) is analyzed in an even-aged plantation of Cryptomeria japonica from stand age of 45 to 94 years, to examine how the growth of individual trees has been affected by the changes in spacing resulting from thinning operations. At any age, a significant proportion (0.37–0.46) of the variation in dbh growth during a 5–11-year period was explained by dbh at the beginning of the period, probably due to greater leaf mass of larger trees. Next, either one-sided or two-sided competition was added to the model, by calculating the basal area (BA) of neighboring trees around each tree within a given radius or BA for trees having larger dbh than the focal tree within the radius. After preliminary analyses, a radius of 8 m was selected as the critical range for tree competition. Although both types of competition explained a significant proportion (0.09–0.43) of growth variation, one-sided competition was not significant at ages greater than 54 years. Based on the model at 45 years of age, the initial deviation of growth rate for each tree from the predicted rate was calculated and added to the models as a third variable. This raised the coefficient of determination up to 0.50–0.74. These findings have practical significance for forest plantation management, particularly for controlling the growth of standing trees via thinning, to produce high-quality timber in the future.     

Effect of a single injection of gonadotropin-releasing hormone (GnRH) and human chorionic gonadotropin (hCG) on testicular blood flow measured by color doppler ultrasonography in male Shiba goats

Although color Doppler ultrasonography has been used to evaluate testicular blood flow in many species, very little has been done in goat. Eight male Shiba goats were exposed to a single intramuscular injection of either gonadotropin-releasing hormone (GnRH group; 1 µg/kg BW) or human chorionic gonadotropin (hCG group; 25 IU/kg BW). Plasma testosterone (T), estradiol (E2) and inhibin (INH) were measured just before (0 hr) and at different intervals post injection by radioimmunoassay. Testis volume (TV) and Doppler indices, such as resistive index (RI) and pulsatility index (PI) of the supratesticular artery, were measured by B-mode and color Doppler ultrasonography, respectively. The results indicated an increase in testicular blood flow in both groups, as RI and PI decreased significantly (P<0.05), but this increase was significant higher and earlier in hCG group (1 hr) than in the GnRH group (2 hr). A high correlation was found for RI and PI with both T (RI, r= −0.862; PI, r= −0.707) and INH in the GnRH group (RI, r=0.661; PI, r=0.701). However, a significant (P<0.05) correlation was found between E2 and both RI (r= −0.610) and PI (r= −0.763) in hCG group. In addition, TV significantly increased and was highly correlated with RI in both groups (GnRH, r= −0.718; hCG, r= −0.779). In conclusion, hCG and GnRH may improve testicular blood flow and TV in Shiba goats.     

Accessory corpora lutea formation in pregnant Hokkaido sika deer (Cervus nippon yesoensis) investigated by examination of ovarian dynamics and steroid hormone concentrations

Generally, sika deer conceive a single fetus, but approximately 80% of pregnant females have two corpora lutea (CLs). The function of the accessory CL (ACL) is unknown; moreover, the process of ACL formation is unclear, and understanding this is necessary to know its role. To elucidate the process of ACL formation, the ovarian dynamics of six adult Hokkaido sika deer females were examined ultrasonographically together with peripheral estradiol-17β and progesterone concentrations. ACLs formed in three females that conceived at the first estrus of the breeding season, but not in those females that conceived at the second estrus. After copulation, postconception ovulation of the dominant follicle of the first wave is induced by an increase in estradiol-17β, which leads to formation of an ACL. A relatively low concentration of progesterone after the first estrus of the breeding season is considered to be responsible for the increase in estradiol-17β after copulation.     

Estrogen suppresses melatonin-enhanced hyperactivation of hamster spermatozoa

Hamster sperm hyperactivation is enhanced by progesterone, and this progesterone-enhanced hyperactivation is suppressed by 17β-estradiol (17βE₂) and γ-aminobutyric acid (GABA). Although it has been indicated that melatonin also enhances hyperactivation, it is unknown whether melatonin-enhanced hyperactivation is also suppressed by 17βE₂ and GABA. In the present study, melatonin-enhanced hyperactivation was significantly suppressed by 17βE₂ but not by GABA. Moreover, suppression of melatonin-enhanced hyperactivation by 17βE₂ occurred through non-genomic regulation via the estrogen receptor (ER). These results suggest that enhancement of hyperactivation is regulated by melatonin and 17βE₂ through non-genomic regulation.     

Regulation of gonadotropin subunit genes expression by 11-ketotestosterone during early spermatogenesis in male red seabream, Pagrus major

To examine the roles of gonadal steroids in the regulation of expression of gonadotropin subunit genes, male red seabream were gonadectomized and a sub-group was treated with 11-ketotestosterone (11-KT). Castration of males during the early stage of spermatogenesis elicited a significant increase in FSHβ mRNA levels, which was prevented by 11-KT replacement. By contrast, LHβ mRNA levels were not changed by castration or 11-KT replacement. In addition, administration of 11-KT to sham-operated males suppressed the steady-state FSHβ and LHβ mRNA levels. These results indicate that 11-KT may function as a negative feedback regulator of FSHβ gene expression, and may act through the testis to down-regulate LHβ mRNA levels in male red seabream during this period.