Influence of estradiol-17β, testosterone, and 11-ketotestosterone on testicular development, serum steroid hormone, and gonadotropin secretion in male red sea bream Pagrus major

ABSTRACT:   In order to investigate the influence of estrogen and androgen on reproductive activities of male teleosts, male red sea bream were implanted with silicone capsules containing estradiol-17β (E2), testosterone (T) or 11-ketotestosterone (11-KT) in immature and early spermatogenic stages. One month after implantation of either E2 or T, the gonadosomatic index decreased in accordance with testicular regression in both stages. Implantation of E2 decreased circulating 11-KT levels but did not affect gonadotropin (GTH) subunits, follicle stimulating hormone-β (FSHβ), luteinizing hormone-β (LHβ), α glycoprotein subunit (αGSU) gene expression, and serum LH levels in both stages. Alternatively, T decreased serum 11-KT and LH levels, and FSHβ and LHβ mRNA levels in the early spermatogenic stage but not in the immature stage. These results suggest E2 may directly inhibit testicular development through the suppression of 11-KT production. Meanwhile, T may decrease serum 11-KT levels through the suppression of FSH and LH secretion, resulting to inhibition of testicular development in the early spermatogenic stage. Treatment with 11-KT did not affect the testis in either stage, whereas 11-KT increased LHβ and αGSU mRNA levels in immature, and decreased FSHβ mRNA levels in the early spermatogenic stage. These results suggest that 11-KT may have different effects on GTH subunit gene expression in each reproductive stage.     

Bacterial community in plant residues in a Japanese paddy field estimated by RFLP and DGGE analyses

Plant residues (PRs) are “hot spots” of microbial activities in soil. PRs with the size more than 0.5 mm were collected from a Japanese paddy field during rice cultivation period (from May to September) and fractionated into four categories by size (>4, 2-4, 1-2, and 0.5-1 mm) using sieves. Restriction fragment length polymorphism (RFLP) and denaturing gradient gel electrophoresis (DGGE) patterns were compared among the fractions after DNA extraction from the PRs and PCR amplification. The total amount of PRs with the size over 0.5 mm decreased in the field with the first-order kinetics (r²=0.810, p<0.01) with time from rice transplanting to harvest. RFLP analysis showed that the bacterial community structure in PRs with the 0.5-2 mm fraction was different from that in PRs with the >2 mm fraction and the latter community structure changed after the midseason drainage. In contrast, the DGGE patterns of the bacterial community in the PRs indicated the succession from June to September during rice cultivation forming three major groups irrespective of the fraction size. Sequence analysis of DGGE bands showed that Firmicutes (clostridia), α-, γ-, δ-Proteobacteria (myxobacteria), Nitrospira, Acidobacteria, Bacteroidetes, Verrucomicrobia and Spirochaetes were predominant members in the PRs irrespective of fraction size.     

人工合成甘蓝型油菜的繁育特性与试管繁殖

通过甘蓝品种(2n=18，CC)与白菜品种(2n=20，AA)杂交并借助胚珠培养和染色体加倍，获得一系列人工甘蓝型油菜新品系。对18个人工合成甘蓝型油菜新品系的花粉育性、自交结实性、异交结实性等研究表明，人工油菜品系花期自交不结实或结实率很低。蕾期自交一朵花平均获3．6粒种子，平均结角率为19．7％。但是，人工甘蓝型油菜无论作父本还是作母本与天然甘蓝型油菜杂交的结实率都较高。以人工油菜作父本与天然油菜杂交。42个组合平均杂交一朵花获得10．3粒杂交种子；以人工油菜作母本与天然油菜杂交，15个组合平均杂交一朵花获得8．5粒杂交种子。分析结果表明。本试验的人工油菜品系具有很强的自交不亲和性，蕾期自交结实率也较低，但对异交结实影响不大，因此可以直接用于杂种生产。试验对自交结实特别困难的5个人工甘蓝型油菜新品系进行了试管繁殖，采取子叶、下胚轴和茎尖联合培养方式。22株无菌苗经过2个月快繁，获得260株苗。平均繁殖系数为12．4。不同基因型繁殖系数差异较大。变幅为3．3～21．0。     

Suspected spontaneous hyperadrenocorticism in a young experimental beagle dog

A 6-month-old female beagle dog, assigned to the low-dose group in a toxicity study, was evaluated for compound toxicity, and spontaneous hyperadrenocorticism was suspected. The animal had an externally apparent distended abdomen on clinical examination upon arrival. Pre-dose clinical pathology showed slightly higher erythroid parameters and stress leukogram on hematology; plasma biochemistry showed higher total protein, gamma-glutamyl transferase, total cholesterol, and triglyceride levels than the reference data. On necropsy, a prominent increase in adipose tissues of the subcutis and abdomen and increased weight of the adrenal gland and liver were observed. Histopathology revealed diffuse hyperplasia of adrenocortical cells in the zona fasciculata and reticularis, cortical atrophy of the thymus, and abundant glycogen accumulation in the hepatocytes. These findings were incidental and not test-substance-related. Electron microscopy of the adrenocortical cells in the zona fasciculata revealed decreased typical translucent lipid droplets, increased electron-dense lipid droplets, and abundant smooth endoplasmic reticulum and lysosomes. Additionally, increased numbers of various sizes and forms of mitochondria with tubular, vesicular, or lamellar cristae compared to that of normal animals were observed. These ultrastructural characteristics of the adrenocortical cells suggested hyperfunction. The pre-dose plasma cortisol levels were slightly higher than those of other females assigned to the toxicity study, while plasma adrenocorticotropic hormone levels were within the normal range. These findings indicate that hyperadrenocorticism is a possible cause of the systemic changes in this case.     

Thioacetamide-induced Hepatocellular Necrosis Is Attenuated in Diet-induced Obese Mice

To assess modification of thioacetamide-induced hepatotoxicity in mice fed a high-fat diet, male C57BL/6J mice were fed a normal rodent diet or a high-fat diet for 8 weeks and then treated once intraperitoneally with thioacetamide at 50 mg/kg body weight. At 24 and 48 hours after administration, massive centrilobular hepatocellular necrosis was observed in mice fed the normal rodent diet, while the necrosis was less severe in mice fed the high-fat diet. In contrast, severe swelling of hepatocytes was observed in mice fed the high-fat diet. In addition, mice fed the high-fat diet displayed more than a 4-fold higher number of BrdU-positive hepatocytes compared with mice fed the normal rodent diet at 48 hours after thioacetamide treatment. To clarify the mechanisms by which the hepatic necrosis was attenuated, we investigated exposure to thioacetamide and one of its metabolites, the expression of CYP2E1, which converts thioacetamide to reactive metabolites, and the content of glutathione S-transferases in the liver. However, the reduced hepatocellular necrosis noted in mice fed the high-fat diet could not be explained by the differences in exposure to thioacetamide or thioacetamide sulfoxide or by differences in the expression of drug-metabolizing enzymes. On the other hand, at 8 hours after thioacetamide administration, hepatic total glutathione in mice fed the high-fat diet was significantly lower than that in mice fed the normal diet. Hence, decreased hepatic glutathione amount is a candidate for the mechanism of the attenuated necrosis. In conclusion, this study revealed that thioacetamide-induced hepatic necrosis was attenuated in mice fed the high-fat diet.     

Female preference did not evolve under laboratory conditions in the solanaceous fruit fly Bactrocera latifrons

Sterile insect technique (SIT) is widely used to eradicate target pest species. Its effectiveness depends on the ability of released sterile males to mate with wild females. In pest species with a female choice mating system, there is potential for female preference to evolve in the wild population in view of the resulting zero-fitness in females that mate with sterile males. The evolution of female preference against sterile males can, therefore, reduce the efficiency of the SIT as the likelihood decreases that sterile males will mate with wild females. We examined this experimentally by using the solanaceous fruit fly Bactrocera latifrons, a serious pest of solanaceous crops, by allowing female preference in mass-reared fruit flies to select between fertile and sterile males over 12 generations. However, this did not generate a rapid evolutionary response. Also the remating rate of females did not increase, even when the first mating partner was a sterile male. We discuss the implication of the results for the eradication project by the SIT program.     

Predicting soil water movement in converted soybean fields under high moisture condition

Paddy and Water Environment - Crops adapt to variable soil moisture by varying the distribution of their roots and patterns of water absorption. Meanwhile, proper numerical model for predicting...     

Digestibility of common reed (Pharagmites communis Trin.) silage as ruminant feed and effects of inclusion levels in the diet of breeding cows on feed intake,ruminal fermentation and blood metabolites

To examine the digestibility of common reed (Pharagmites communis Trin.) silage and effects of inclusion levels in the diet of breeding cows on nutrient intakes, ruminal fermentation and nutrient status, two digestion trials using four sheep and cows, respectively, at the maintenance stage were conducted. In the trial using sheep, common reed silage contained 20% crude protein (CP) and 50% total digestible nutrients (TDN) on a dry matter basis. In the trial using cows, treatments were the control (92.4% Sudangrass hay and 7.6% soybean meal) and CS25, CS50 and CS80 (replacing 25%, 50%, and 80% of the control with silage, respectively). The intake and sufficiency rate of CP increased by increasing the silage level in the diet (P < 0.05), and the CP requirements of cows at maintenance was satisfied in CS80. In contrast, the sufficiency rate of TDN decreased in CS80, although it was 99.8%. Ruminal pH and NH₃‐N concentration changed among the treatments (P < 0.05); however, the blood metabolites were not affected by silage. The results indicated that including common reed silage of up to 80% in the diet of breeding cows was possible and did not have adverse effects on the blood metabolites.     

Effects of synthetic kisspeptin peptides and GnRH analogue on oocyte growth and circulating sex steroids in prepubertal female chub mackerel (Scomber japonicus)

In recent years, kisspeptin peptides, encoded by kiss genes have been used to manipulate reproductive processes in farmed animals, including fish. Our previous studies demonstrated that the chub mackerel brain expresses kiss1 and kiss2 and intramuscular injection of synthetic Kiss1 pentadecapeptide (Kiss1‐15) but not Kiss2 dodecapeptide (Kiss2‐12) accelerates spermatogenesis in prepubertal male chub mackerel (Scomber japonicus). In the present study, we evaluated their effects in prepubertal female chub mackerel. The gonadosomatic index (GSI) values of experimental fish did not show any significant changes. Condition factor (CF) values increased significantly in Kiss1‐15 treated fish, in comparison with control and GnRH analogue (GnRHa) injected fish. Histologically, only perinucleolar oocytes were found in all experimental fish. However, Kiss and GnRHa treated fish showed a significant increase in the perinucleolar oocyte diameter, in comparison with the control fish. Gene expression analyses revealed decreased expression of gnrh1 in the telencephalon‐preoptic region of the brain of Kiss2‐12 and GnRHa injected fish, in comparison with control fish. In contrast, GnRHa injected fish exhibited higher levels of fshβ in the pituitary, with no changes in the levels of lhβ among different treatments. Levels of circulating sex steroids, testosterone, and estradiol‐17β were significantly higher in Kiss1‐15 injected fish, in comparison with control fish. These results indicate that synthetic kisspeptin peptides and GnRHa can induce oocyte growth in prepubertal female chub mackerel.