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...     

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.     

Flow cytometric analysis of thymocyte subpopulations in mice after whole-body X-irradiation.

To determined the cellular kinetics of thymocyte subpopulations in DBA1 mice after whole-body 6.8 Gy X-irradiation, they were analyzed for the expression of several cell surface antigens using flow cytometry. The results show that i) The majority of thymocytes rapidly depleted by irradiation was CD4+8+ cells. ii) radioresistant CD4+8- and CD4-8+ survived 18-48 hr after X-irradiation were considered to be relatively mature type, since they expressed high levels of CD3 and LECAM-1. iii) CD3-positive cells were detected in CD4-8- cells at 72 hr after irradiation.     

B220 is expressed on apoptotic thymocytes induced by X-irradiation.

CD45 is cell surface glycoprotein and expressed on all haematopoietic cells except mature erythrocytes and platelets. Eight isoforms of CD45 are generated by alternative splicing of exons 4-6. B220 including all three exons is expressed specifically on pan-B cell lineage. Recently, it was reported that B220 was expressed on apoptotic T cells induced by staphylococcal enterotoxin B (SEB). In the present study, we investigated the expression of B220 on murine thymocytes after whole-body X-irradiation. We used the forward light scattering of flow cytometry as a parameter of cell size, and defined two populations; FSChigh (normal cell size) and FSClow (correspond to apoptotic cell in size) fraction. B220+ cells in FSChigh fraction reached a maximum value (35%) at 18 hr after irradiation. In FSClow fraction, 40-60% cells were positive for B220 at any time points. These results suggest that B220 is expressed on thymocytes in the pre-apoptotic stage, because B220 was expressed on not only FSClow cells but also FSChigh cells.     

Immunoreactive changes in pituitary FSH and LH cells during seasonal reproductive and spawning cycles of female chub mackerel <Emphasis Type="Italic">Scomber japonicus</Emphasis>

The physiological functions of pituitary gonadotropins (GtHs) are well established in higher vertebrates, whereas those in teleosts are still poorly understood. To describe the role of GtHs during gonadal development of female chub mackerel Scomber japonicus, changes in follicle-stimulating hormone (FSH) and luteinizing hormone (LH) cells were investigated immunohistochemically during the seasonal reproductive and spawning cycles. FSH and LH cells were identified in the different cell types of the proximal pars distalis (PPD); FSH cells were located in the central PPD, whereas LH cells were localized along the border of the pars intermedia. To examine changes in FSH and LH cells, the percentage of FSH or LH cell-occupying area in the PPD was evaluated and represented as FSHβ-immunoreactive (ir) or LHβ-ir levels, respectively. FSHβ-ir levels increased significantly from immature to the completion of vitellogenesis, whereas LHβ-ir levels were maintained at high levels from early vitellogenesis to post-spawning. During the spawning cycle, which consisted of four stages from just after spawning to the next oocyte maturation, both FSHβ-ir and LHβ-ir levels showed no significant changes among different stages; however, LHβ-ir levels remained relatively high, and FSHβ-ir levels were constantly low. These results suggest that both FSH and LH may be involved in vitellogenesis and LH may act at final oocyte maturation in female chub mackerel, although the role of FSH during the spawning cycle is still unclear.     

Age validation,growth and annual reproductive cycle of chub mackerel <Emphasis Type="Italic">Scomber japonicus</Emphasis> off the waters of northern Kyushu and in the East China Sea

The age and growth of chub mackerel Scomber japonicus collected from the East China Sea and the northern waters off Kyushu between June 2000 and June 2001 were determined by observing the otolith surface after dipping it in xylene. The translucent and opaque zones on the otolith surface were identified, and the number of translucent zones was counted. Monthly changes in the frequency of fish with translucent zones on the otolith margin, and in the marginal increments, indicated that the translucent zones were formed between April and June. The seasonal pattern of annulus formation on the otolith became clear by observing the otoliths of fish with known ages, and the otolith formation in wild fish was consistent with that of fish with known ages. The mean gonadosomatic index of male and female fish was high from March to May, and spawning females were observed from mid-March to mid-May. The estimated ages were 1–5 years for males and 1–6 years for females. The von Bertalanffy growth parameters did not significantly differ between male and female. The model was obtained as FL _t=406×{1−exp[−0.372×(t+1.68)]     

A simulation study for a linear measurement error model when error variances vary between measurements

When predicting scores in the Draize eye irritation test based on measurements of in vitro alternative tests, we are often faced with estimating parameters in a linear measurement error model with heterogeneous error variances. This article proposes a new statistical method for parameter estimation to address this issue. The proposed method is an extension of an earlier proposal that applied a linear measurement error model with homogeneous error variances, to cases with heterogeneous error variances. A simulation study to examine the performance of the proposed method was conducted in a framework that was adaptable to the data, which was obtained in a validation study of alternative methods to animal experiments conducted in Japan. The proposed method reduced the biases of estimates in comparison with an ordinary regression analysis method and three other methods under the assumption of homogeneous error variances. Although the proposed method did not fit the real data well, the resulting prediction formula was far better than those obtained by other methods.