Seasonal fluctuations in the flux of particulate organic matter discharged from net pens for fish farming

ABSTRACT:   Fish farming using net pens consumes large amounts of food for the reared fish, resulting in organic enrichment of the sediment below the fish farm from organic discharge in the forms of fish feces and food residues. Sediment traps were set at a net pen within and outside a fish farm, and organic flux on the sea floor was compared. The year-mean organic flux to the sea floor caused by fish farming from September 2003 to September 2004 was estimated at 2.11 gC/m²/day in total organic carbon (TOC) and 0.26 gN/m²/day in total nitrogen (TN), which were 2.5 times (TOC flux) and 2.2 times (TN flux) larger than that for natural organic flux outside the fish farm. The seasonal fluctuation patterns of organic flux to the sea floor below the fish farm did not necessarily coincide with those for the amount of food spent for the fish farming. The largest organic flux to the sea floor occurred in the autumn, when the vertical mixing of the water had just started. Therefore, organic enrichment of the sediment on the sea floor of a fish farm proceeded during this season.     

Control of dissolved oxygen levels of water in net pens for fish farming by a microscopic bubble generating system

ABSTRACT:   A microscopic bubble generating system (MBGS) has been developed to control dissolved oxygen (DO) levels suitable for fish farming. The MBGS has been tested to confirm its capability in net pens. Water conditions in a fish farm were monitored every two hours from June to October 2004 by setting an online vertical profiling system (OVPS) close to the net pen. DO in the net pen water decreased to physiologically stressful levels for the fish during the night (4.84–5.51 mg/L), while the DO was kept in saturated conditions during the day, due to oxygen supply from phytoplankton. The MBGS was operated from the evening to the morning of the next day for 16 h, to successfully create DO-saturated conditions in the net pen water at night. By using microscopic bubbles during the warm seasons, DO levels in the net pen water could be improved to a level suitable for fish farming. However, the low DO levels (<5.0 mg/L) of the bottom water occasionally extended to the net pen layers, despite the supply of microscopic bubbles to the water. To maintain the DO of the net pen water at levels suitable for fish farming, DO supply to the net pen water and the bottom water needs to be increased, and the organically enriched sediment just below the net pens needs to be treated.     

Involvement of nitric oxide generation in hypersensitive cell death induced by elicitin in tobacco cell suspension culture

Recent studies suggest that nitric oxide (NO), an important signaling and defense molecule in mammals, plays a key role in activating disease resistance in plants. We characterized NO production by tobacco Bright Yellow-2 cells pharmacologically after treatment with INF1, the major elicitin secreted by the late blight pathogen Phytophthora infestans, prepared from Escherichia coli. NO production rapidly occurred within 1h and reached a maximum level 3–6h after the addition of INF1. Carboxy-PTIO, a NO-specific scavenger, abolished INF1-induced NO production in a dose-dependent manner. Pretreatment of protein synthesis inhibitor cycloheximide and protein kinase inhibitor K252a blocked NO production 3–12h after INF1 treatment, indicating that NO production requires de novo protein synthesis and protein phosphorylation. In an investigation of the relations between NO generation and several defense responses induced by INF1, carboxy-PTIO completely suppressed activation of a 41-kDa protein kinase and cell death by INF1. Carboxy-PTIO also suppressed the induction of hypersensitive-related (hsr) genes HSR515 and HSR203J, the expression of which is strongly correlated with the hypersensitive response in plants. The results suggest that NO plays a crucial role in the induction of hypersensitive cell death.     

Seasonal influence on testicular function of male raccoons, Procyon lotor

In order to clarify the breeding capability of male raccoons in Japan, the testes of raccoons, a nuisance animal, collected in Kanagawa Prefecture and Hokkaido were histologically inspected. Furthermore, testosterone concentrations in their blood were measured. The testosterone concentrations increased in winter and the diameter of seminiferous tubules and the spermatogenetic score decreased in summer for the animals captured in Kanagawa Prefecture. For the animals captured in Hokkaido, the diameter of seminiferous tubules did not change and the decrease of the spermatogenetic score in summer was slight. As the above results show, there is a breeding season in male raccoons in Japan, and the reduction of testicular function in summer was greater in animals captured in Kanagawa Prefecture than in animals captured in Hokkaido.     

Pharmacokinetics and pharmacodynamic effects in koi carp (Cyprinus carpio) following immersion in propofol

Objective

To test the hypothesis that plasma propofol concentration (PPC) is associated with anesthetic effect in koi carp administered propofol by immersion.

Investigation of fellow eye of unilateral retinal detachment in Shih‐Tzu

Objective To investigate disease in the fellow eye, and consider the relation to rhegmatogenous retinal detachment (RRD) in Shih‐Tzus. Animals studied The fellow eyes of 49 Shih‐Tzus (27 male, 22 female; median age: 6.8 years) with unilateral RRD diagnosed by funduscopy or ultrasonography at Rakuno Gakuen University Teaching Animal Hospital were assessed in this study. Procedures Ophthalmic examinations (including menace response, pupillary light reflex, slit‐lamp biomicroscopy, and funduscopy) were performed in the subjects. Electroretinography was performed in 12 eyes that developed retinal degeneration. Maximum follow‐up period was 42 months. Results Cataracts and vitreous opacity were observed in 26 (53%) and 32 eyes (65%), respectively, by slit‐lamp biomicroscopy. Retinal degeneration with various degrees of hyper‐reflectivity of the tapetal fundus and/or attenuation of retinal vessels was observed in 35 eyes (71%) on funduscopy. A reduction of amplitude in rod, standard combined and 30 Hz flicker electroretingram was detected in 5 (42%), 10 (83%), and 6 eyes (50%), respectively. During the follow‐up period, RRD was detected in six eyes. Conclusion Retinal degeneration was frequently detected by funduscopy and electroretingrams in the fellow eye in Shih‐Tzus with RRD. In our subjects, vitreous degeneration was also observed frequently. It has been reported that peripheral retinal degeneration is one of the causes of RRD associated with vitreous degeneration in humans. We assume that primary retinal degeneration with secondary vitreous degeneration is one of the causes of RRD in Shih‐Tzus.     

Contrast harmonic imaging of canine hepatic tumors

Six adult healthy Beagles were used to investigate the hepatic perfusion dynamics of Levovist, a contrast agent used in contrast harmonic imaging (CHI). In addition, 8 dogs with hepatocellular carcinoma (HCC) and 2 dogs with metastatic hepatic hemangiosarcoma (HSA) were used to characterize both the CHI findings with Levovist. In the Beagles, the start of intravenously injected Levovist into the aorta between the cranial mesenteric and renal arteries and the portal vein at the hepatic hilum were 5.47 +/- 1.52 sec and 16.03 +/- 3.39 sec, respectively. As a characteristic CHI finding in the 8 dogs with HCC, the early arterial phase showed a fine network of blood flow enhanced at the surrounding region and within the tumor in all the 8 dogs (100%), and the post vascular phase demonstrated a defect in the whole tumor and an enhancement of the surrounding hepatic tissues in 7 dogs (87.5%). In the 2 dogs with HSA, characteristic finding in which the early arterial and late vascular phases showed a rim contrast enhancement pattern, and the post vascular phase revealed that the whole tumor lacked contrast enhancement and the surrounding hepatic tissues was clearly enhanced. In dogs, the start of the early arterial and late vascular phases, and the characterizations of the CHI findings in HCC and HSA were suggested to be similar to those in humans. Therefore, CHI is thought to be useful for the diagnosis of HCC and metastatic hepatic HSA in dogs as well as in humans.     

Lung toxicity of a vapor-grown carbon fiber in comparison with a multi-walled carbon nanotube in F344 rats

Carbon fibers have excellent physicochemical and electrical properties. Vapor-grown carbon fibers are a type of carbon fibers that have a multi-walled carbon tube structure with a high aspect ratio. The representative vapor-grown carbon fiber, VGCF^TM-H, is extremely strong and stable and has superior thermal and electrical conductivity. Because some high-aspect-ratio multi-walled carbon nanotubes (MWCNTs) have been reported to have toxic and carcinogenic effects in the lungs of rodents, we performed a 13-week lung toxicity study using VGCF^TM-H in comparison with one of MWCNTs, MWNT-7, in rats. Male and female F344 rats were intratracheally administered VGCF^TM-H at doses of 0.2, 0.4, and 0.8 mg/kg bw or MWNT-7 at doses of 0.4 and 0.8 mg/kg bw once a week for 8 weeks and then up to week 13 without treatment. The lung burden was equivalent in the VGCF^TM-H and MWNT-7 groups; however, the lung weight had increased and the inflammatory and biochemical parameters in the broncho-alveolar lavage fluid and histopathological parameters, including inflammatory cell infiltration, alveolar type II cells proliferation, alveolar fibrosis, pleural fibrosis, lung mesothelium proliferation, and diaphragm fibrosis, were milder in the VGCF^TM-H group than in the MWNT-7 group. In addition, the proliferating cell nuclear antigen (PCNA)-positive index in the visceral and pleural mesothelium was significantly higher in the MWNT-7 group than in the controls, but not in the VGCF^TM-H group. Thus, the results of this study indicate that the lung and pleural toxicities of VGCF^TM-H were less than those of MWNT-7.     

Effect of water management on the vivianite content of paddy-rice roots

Abstract

Vivianite is a hydrated ferrous phosphate mineral that can form in reducing environments, and it was recently identified on aged paddy rice (Oryza sativa, L., cultivar Hitomebore) roots. However, the formation and dissolution of vivianite appear highly susceptible to the soil redox potential. We examined the effect of water management on the vivianite content of rice roots in three experimental micro (1 m²) paddy fields. The vivianite content of the roots was estimated using a method based on the alteration of vivianite after heating at 105°C for 48 h. This alteration steeply lowers the dissolution of phosphate from the roots in a mixed acid solution of 0.1 mol L^?1 of hydrochloric acid (HCl) and 1 mol L^?1 of acetic acid (CH₃COOH). Efficiency of the method was confirmed regarding heating temperature and duration of heating. Using this method, we found that water management significantly influenced the vivianite content of the rice roots. The vivianite content of the rice roots was highest, i.e., 2.3 g phosphorus (P) kg^?1 expressed by its estimated P content, when the paddy field was continuously flooded from May to until early September. After flooding stopped, the soil was gradually oxidized, leading to a decrease in vivianite content. In the micro plot exposed to midseason drainage, the vivianite content increased to the level of the continuously flooded plot after reflooding, and finally decreased after flooding was stopped in late August. The plots exposed to midseason drainage followed by intermittent irrigation presented the lowest vivianite contents among the three experimental paddy fields. These results confirm that increases and decreases in the vivianite contents of paddy-rice roots strongly depend on water management.     

Histopathological and Immunohistochemical Characterization of Spontaneously Occurring Uterine Deciduomas in Young Adult Rats

Uterine deciduomas were found in two female virgin rats, a 15-week-old Lewis rat and a 7-week-old Sprague-Dawley rat. The firm white nodules were located at the base of unilateral uterine horns and were approximately 6 mm and 4 mm in diameter. Histopathologically, the nodules were composed of three areas, each with a distinct type of proliferating cells: large epithelioid decidual cells with round nuclei, prominent nucleoli and abundant eosinophilic cytoplasm (antimesometrial region); compact spindle-shaped cells with oval nuclei and vacuolar cytoplasm (transitional region); and pleomorphic and spiny cells with round to oval nuclei and compact eosinophilic cytoplasm (mesometrial region). These cells proliferated in sheet-like arrangements and transformed into the other types of cells located in surrounding regions. Immunohistochemically, proliferating cells in all regions were strongly positive for proliferating cell nuclear antigen. The proliferating cells were positive for vimentin, and large decidual cells were positive for common acute lymphoblastic leukemia antigen 10, a marker of uterine interstitial cells. Large decidual cells were positive for α-smooth muscle actin and desmin, suggesting differentiation into muscular cells. Progesterone receptor was expressed in all cell types; however, estrogen receptor α was not expressed in the antimesometrial region. These extremely rare tumor-like nodules represent nonneoplastic lesions referred as decidual reactions of endometrial interstitial cells, and their biological behavior is that of a space-occupying benign tumor in young rats. Our cases might provide information as a historical control in toxicity and pharmacological studies in rats.