Radioresistance of cancer stem‐like cell derived from canine tumours

Cancer stem‐like cells (CSCs)/cancer‐initiating cells (CICs) are a small subpopulation of cancer cells that are responsible for the initiation, recurrence and metastasis of cancer. We previously demonstrated that, using the Hoechst 33342 dye‐based side population technique, CSCs/CICs in canine lung adenocarcinoma cell line exist. In this study, as CSCs/CICs are known to form spheres in anchorage‐independent environment in vitro, we evaluated the stemness of spheroid cells derived from canine lung adenocarcinoma and osteosarcoma cells by expression of stemness markers, and investigated radioresistance. Spheroid cells showed greater expression of stemness markers Oct‐4 and CD133 gene than those of adherent‐cultured cells. In nude mouse xenograft models, spheroid cells showed higher tumourigenic ability than adherent‐cultured cells. In addition, spheroid cells showed significantly resistant against radioactivity as compared with adherent‐cultured cells. These results suggest that spheroid cells could possess stemness and provide a CSCs/CICs research tool to investigate CSCs/CICs of canine tumour cells.     

Effects of feeding calves genetically modified corn bt11: a clinico-biochemical study

Genetically modified corn Bt11 is insect-resistant and expresses Cry1Ab toxin, an insecticidal protein, in kernels. Although Bt11 corn is considered safe based on animal performance, there are no reports available on the clinico-biochemical effects of feeding it to cattle. In this study, we evaluated the effects of feeding Bt11 to calves, using blood and ruminal clinico-biochemical parameters. Our three-month-long feeding experiment demonstrated that calves (n=6), fed with a ration containing 43.3% of Bt11 corn kernels as dry matter, did not develop any discernible clinical, hematological, biochemical, or ruminal abnormalities as compared with control calves (n=6) fed non-Bt11 corn. The results suggest that the transgenic Bt11 has no negative clinico-biochemical effects on calves.     

Variation in floral scent compounds recognized by honeybees in Brassicaceae crop species

Floral scent attracts pollinators. We investigated the floral scent compounds recognized by pollinators in six Brassica crop species, including allogamous species with different genomes and autogamous species with two parental genomes and radish (Raphanus sativus). Biologically active compounds recognized by honeybees were screened from all floral compounds by combined gas chromatography–electroantennogram analysis and their profiles were determined by gas chromatography–mass spectrometry. Fourteen of the 52 compounds were active. All accessions had more than two active compounds, but the compounds greatly differed between the two genera. On the basis of similarities in whether active compounds were presence or absence, their amount and their composition ratio, we divided the Brassica accessions into three to five groups by cluster analyses. Most groups were composed of a mixture of allogamous and autogamous species sharing same genome, indicating that the variation depended on genome, not species. These results suggest that all species require pollinator visits for reproduction, despite their different reproductive systems. However, the inter-genus and intra-specific variations shown by the multiple groups within a species might cause different visitation frequencies by pollinators between genera and among accessions within a species, resulting in insufficient seed production in some accessions or species.     

Comparison of biomass estimates from multiple stratification approaches in a swept area method for Pacific saury Cololabis saira in the western North Pacific

Fishery-independent surveys using sea surface trawl nets for Pacific saury Cololabis saira in the western North Pacific since 2003 have enabled the investigation of their annual distribution patterns and total biomass during June and July, prior to the main fishing season in Japan. We compared biomass estimates and their associated variances derived based on five different post-stratification approaches in a swept area method, and then observed that these approaches have little effect on biomass estimates and their precision, owing to well-organized survey designs and homogeneously allocated sampling stations. We were able to utilize decreasing biomass estimates for 15 years as an essential abundance index in the ongoing stock assessment. Notably, examination based on stratification along with longitudinal survey lines indicated that the estimated biomass had decreased in the western survey area, resulting in an eastward shift in the gravity center of Pacific saury distribution after 2010. We recommend biomass estimation in an east–west direction based on longitudinal stratification as an effective measure to develop population dynamics models which reflect westward migration into the fishing grounds around Japanese coastal waters, and to forecast the expected catch during the subsequent fishing period.

     

Backward spreading of memory-retrieval signal in the primate temporal cortex

Bidirectional signaling between neocortex and limbic cortex has been hypothesized to contribute to the retrieval of long-term memory. We tested this hypothesis by comparing the time courses of perceptual and memory-retrieval signals in two neighboring areas in temporal cortex, area TE (TE) and perirhinal cortex (PRh), while monkeys were performing a visual pair-association task. Perceptual signal reached TE before PRh, confirming its forward propagation. In contrast, memory-retrieval signal appeared earlier in PRh, and TE neurons were then gradually recruited to represent the sought target. A reasonable interpretation of this finding is that the rich backward fiber projections from PRh to TE may underlie the activation of TE neurons that represent a visual object retrieved from long-term memory.     

Oceanographic factors affecting interannual recruitment variability of Pacific saury (Cololabis saira) in the central and western North Pacific

Pacific saury (Cololabis saira) has a short life span of 2 years and tends to exhibit marked population fluctuations. To examine the importance of sea surface temperature (SST) and mixed layer depth (MLD) as oceanographic factors for interannual variability of saury recruitment in early life history, we analyzed the relationship between abundance index (survey CPUE (catch per unit of effort)) of age‐1 fish and the oceanographic factors in the spawning and nursery grounds of the previous year when they were born, for the period of 1979–2006, in the central and western North Pacific. Applying the mixture of two linear regression models, the variability in the survey CPUE was positively correlated with previous year's winter SST in the Kuroshio Recirculation region (KR) throughout the survey period except 1994–2002. In contrast, the survey CPUE was positively correlated with the previous year's spring MLD (a proxy of spring chlorophyll a (Chl‐a) concentration) in the Kuroshio‐Oyashio Transition and Kuroshio Extension (TKE) during 1994–2002. This period is characterized by unusually deep spring MLD during 1994–1997 and anomalous climate conditions during 1998–2002. We suggest that saury recruitment variability was generally driven by the winter SST in the KR (winter spawning/nursery ground), or by the spring Chl‐a concentration (a proxy of prey for saury larvae) in the TKE (spring spawning/nursery ground). These oceanographic factors could be potentially useful to predict abundance trends of age‐1 saury in the future if the conditions leading to the switch between SST and MLD as the key input variable are elucidated further.     

Direct estimation of stock abundance of Pacific saury <Emphasis Type="Italic">Cololabis saira</Emphasis> in the northwestern Pacific Ocean using a mid-water trawl

Drifting gill-nets were for a long time the main research gear for investigating the distribution of Pacific saury Cololabis saira. However, it has proven to be difficult to estimate the absolute abundance of saury using drifting gill-nets due to a lack of knowledge on the survey areas swept by these gill-nets. A mid-water trawl stock abundance estimation has the advantage of being able to estimate the absolute stock abundance before the commercial fishing season begins, whereas the conventional stock abundance estimation based on catch per unit efforts of commercial fisheries must be done after the commercial fishing season has ended. To confirm the practicality of a mid-water trawl to estimate the stock abundance of saury, we conducted a comparative survey in the northwestern Pacific Ocean using both a mid-water trawl and drifting gill-nets. We found that the geographic distribution pattern of catch per unit effort for both the mid-water trawl and driftnets was similar. Using the area-swept method and data on the fishing efficiency of the mid-water trawl obtained in a previous study, we were able to estimate the stock abundance plus confidence limits within the research areas. Our results suggest that the size composition of saury sampled by the mid-water trawl can be considered to approximate the actual size composition of saury.     

Characterization of compounds that induce symbiosis between sea anemone and anemone fish

The species-specific partnership between the sea anemone and anemone fish in many parts of the Indo-Pacific region is a well-known phenomenon. Chemicals secreted by the sea anemone to elicit symbiotic behavior of the fish have been studied for two host-guest pairs, Radianthus kuekenthali (sea anemone)-Amphiprion perideraion (anemone fish) and Stoichactis kenti-A. ocellaris. A new pyridinium compound, amphikuemin, which induces characteristic attracted swimming (toward the chemical stimulus) in A. perideraion, has been isolated from R. kuekenthali and characterized. Several other chemicals that elicit characteristic symbiotic movements have also been identified.