Onset of individual growth difference in larviculture of Pacific bluefin tuna <Emphasis Type="Italic">Thunnus orientalis</Emphasis> using fertilized eggs obtained from one female

We conducted a rearing experiment on Pacific bluefin tuna (PBT) larvae, which originated from one female broodstock, and determined the growth history of the larvae to clarify when the growth difference occurs. We investigated the otolith microstructure of the PBT larvae to examine the individual growth history and to predict the age and body size at the onset of individual growth difference. Since total length (TL) of fish can be back-calculated from otolith radius, we back-calculated TLs of 100 fish of 19 days post hatch (dph) divided into three size groups (small, intermediate, large). Growth difference was recognized from 3 dph (mouth opening), and the difference became larger thereafter. Growth of large-size fish was assumed to be promoted by the feeding conditions of PBT larvae.     

Effect of combination feeding of <Emphasis Type="Italic">Nannochloropsis</Emphasis> and freshwater <Emphasis Type="Italic">Chlorella</Emphasis> on the fatty acid composition of rotifer <Emphasis Type="Italic">Brachionus plicatilis</Emphasis> in a continuous culture

ABSTRACT:   A continuous culture of rotifer was conducted to investigate the effect of combination feeding of both a high density of Nannochloropsis oculata (N) and condensed freshwater Chlorella (FC) on the fatty acid composition of L-type rotifer Brachionus plicatilis in a continuous culture system. The algal feeding of the rotifers was carried out in three successive steps: N-feeding → N+FC-feeding → FC-feeding. The culture was conducted at 24°C and 25–27 psu in a 2000 mL bottle with 50% of water exchanged daily. The combination N+FC-feeding was effective in increasing rotifer density. The rotifers fed on N+FC (N+FC-R) had more non-polar lipids than polar ones, similar to those on N (N-R), opposite to the rotifers fed on FC (FC-R). N+FC-R contained higher levels of 16:2, 18:2n-6 (linoleic acid [LA]) and 20:2n-6, but lower levels of 18:1, 20:4n-6 (arachidonic acid), 20:5n-3 (eicosapentaenoic acid [EPA]) and 22:5n-3 (docosapentaenoic acid [DPA]) compared with N-R. Whereas N+FC-R contained higher levels of 16:1n-7, EPA and DPA, but lower levels of 16:2 and LA compared with FC-R. N+FC-R had more DPA in polar lipids than in non-polar ones. The Σn-6/Σn-3 ratio in N+FC-R was 0.9–1.0, significantly different from those in N-R (0.4) and FC-R (6.6–8.4). Therefore, it is inferred that the fatty acid profile of the N+FC-R cultured in a continuous culture system was affected by both N and FC. Also, the combination N+FC-feeding may be effective in manipulating the Σn-6/Σn-3 ratio in continuously cultured rotifers.     

Successive use of different habitats during the early life stages of Pacific herring <Emphasis Type="Italic">Clupea pallasii</Emphasis> in Akkeshi waters on the east coast of Hokkaido

Distributions of eggs, larvae and juveniles of Pacific herring Clupea pallasii were surveyed in Lake Akkeshi and the connecting Akkeshi Bay on the Pacific coast of eastern Hokkaido. Eggs were found attached to seagrasses and seaweeds in the densely vegetated eastern inner lake. Larvae (7.1–34.9 mm total length) were distributed in the less densely vegetated inner lake during April and June. Juveniles (35.0–89.6 mm) were collected in the central and western parts of the lake. The sites containing juveniles were less densely vegetated with water temperatures lower than 20 °C from June to August. When the water temperature of the entire lake rose to 20 °C in late summer, juveniles appeared to move from the lake to the bottom layer of Akkeshi Bay, which has lower temperatures. Thus, in Akkeshi waters, C. pallasii successively used different habitats during its egg, larval and juvenile stages. A comparison of the current limited distribution of eggs and larvae with the distribution over the entire lake and bay areas in the 1950s and 1960s (periods of large catch size) indicates that the spawning grounds and larval habitats of C. pallasii have contracted to the lake area due to low spawning stock biomass in recent years.     

Investigation of serum concentrations and immunohistochemical localization of α1-acid glycoprotein in tumor dogs

The purpose of this study was to measure the dynamics of serum α1-acid glycoprotein (AGP) concentration in dogs with various tumors, and to investigate the localization of AGP in some tissues using immunohistochemical staining. Sera were obtained from 171 dogs bearing tumors of various types. Serum AGP concentration was measured by single radial immunodiffusion. Tumors occurring in the liver and spleen were also investigated immunohistochemically using anti-canine AGP antibody. Mean serum AGP levels were 749 ± 602 mg/L in dogs with carcinoma (n = 39), 1,014 ± 971 mg/L with sarcoma (n = 18), and 887 ± 935 mg/L with round cell tumors (n = 46), all significantly higher than serum AGP level in healthy dogs (n = 137, 364 ± 106 mg/L). Mean serum AGP levels were significantly higher than in healthy dogs in complex mammary gland carcinoma (n = 5, 876 ± 721 mg/L), malignant melanoma (n = 7, 1,010 ± 821 mg/L), and hepatocellular carcinoma (n = 5, 936 ± 741 mg/L) among carcinomas, hemangiosarcoma (n = 5, 1,740 ± 1,323 mg/L) among sarcomas, and lymphoma (n = 19, 1,072 ± 965 mg/L) and histiocytic tumor (n = 6, 1,800 ± 1,387 mg/L) among round cell tumors. In an immunohistochemical investigation of AGP localization, both weak and strong staining for anti-AGP antibody were seen in hepatic tissue in dogs with primary non-tumorous lesions originating in the spleen (hematoma) and elevated serum AGP, but all tumor tissue in the spleen was negative. Among dogs with primary tumor lesions of the spleen (hemangiosarcoma) and elevated serum AGP levels, both weak, moderate and strong staining for anti-AGP antibody were seen in hepatic tissue, while strong positive staining was apparent in all tumorous tissue from the spleen. In primary tumor lesions in the liver (hepatocellular carcinoma), both moderate and strong staining for anti-AGP antibody were seen in normal hepatic tissue, and both weak, moderate and strong staining were seen in tumor tissues of the liver. AGP levels thus appear to be elevated in dogs with carcinomas, sarcomas, and round cell tumors. With some of these malignant tumors, localization of AGP in tumor tissue was seen.     

Prognosis of canine patients with nasal tumors according to modified clinical stages based on computed tomography: a retrospective study

To evaluate the efficacy of clinical staging based on computed tomography (CT) imaging over the World Health Organization (WHO) staging system based on radiography for nasal tumors in dogs, a retrospective study was conducted. This study used 112 dogs that had nasal tumors; they had undergone radiography and CT and had been histologically confirmed as having nasal tumors. Among 112 dogs, 85 (75.9%) were diagnosed as adenocarcinoma. Then they were analyzed for survival time according to each staging system. More than 70% of the patients with adenocarcinoma were classified as having WHO stage III. The patients classified under WHO stage II tended to survive longer than those classified under WHO stage III. Dogs classified under WHO stage III were further grouped into CT stages III and IV, and CT stage III patients had a significantly longer survival time than CT stage IV patients. In addition, patients treated with a combination of surgery and radiation had a significantly longer survival time than the patients who did not receive any treatment in CT stage III. On the other hand, different treatment modalities did not show a significant difference in the survival time of CT stage IV dogs. The results suggest that WHO stage III dogs may have various levels of tumor progression, indicating that the CT staging system may be more accurate than the WHO staging system.     

Rapid visualization of mammary gland tumor lesions of dogs using the enzyme-activated fluorogenic probe; γ-glutamyl hydroxymethyl rhodamine green

Since gamma-glutamyl transpeptidase (GGT) is highly and locally expressed in human breast cancer, a GGT-enzymatically activatable fluorescent probe, gamma-glutamyl hydroxymethyl rhodamine green (gGlu-HMRG), has been developed to detect the human breast cancer area with high performance. In this study, GGT expression and the efficacy of gGlu-HMRG on visualization were investigated in canine mammary gland tumors (MGT). Seventeen non-fixed fresh-frozen MGT specimens and each peritumoral control tissue were utilized. The GGT mRNA levels were highly observed in the tumor specimens compared with the control. GGT immunostaining was mostly observed on the cell membrane and cytosol of the alveolar and duct mammary epithelium of MGT tissues. These signals were strongly positive in several cases while they were mild to not observed in other cases. When gGlu-HMRG solution was dropped to the non-fixed tissue pieces of MGT or control tissues, the fluorescence intensities (FIs) were measured using Maestro in-vivo imaging device. FIs in MGT tissues were significantly higher than each control tissue 20 min after treatment. Based on Youden index method said that the maximum sensitivity and specificity of FI was 82.4% and 82.4%. These findings suggest that GGT is highly expressed in several MGTs in dogs and gGlu-HMRG could visualize at least a part of MGT tissues in dogs. Nevertheless, it should be needed to assess the false-negative areas more carefully in canine than human cases.