A bolus infusion of xylitol solution in the treatment of cow ketosis does not cause a surge in insulin secretion

When a solution of xylitol was rapidly administered intravenously (bolus infusion) to healthy cattle or those with ketosis, different results were obtained. In healthy cattle, a temporary surge in insulin secretion was observed, whereas in ketotic cattle no such surge was found, but instead a moderate level of secretion continued for a lengthy period. No significant difference in the areas under the insulin curve (AUC) was found between healthy cattle and ketotic cattle up to 120 min after xylitol infusion. These results clearly demonstrated that a bolus infusion of xylitol solution in ketotic cattle does not cause a temporary surge in insulin secretion unlike in healthy animals, but rather results in a continuous, gradual rise in secretion.     

Heifers express G‐protein coupled receptor 153 in anterior pituitary gonadotrophs in stage‐dependent manner

We recently found that orphan G‐protein‐coupled receptor (GPR)153 is expressed in the anterior pituitary (AP) of heifers, leading us to speculate that GPR153 colocalizes with gonadotropin‐releasing hormone receptor (GnRHR) in the plasma membrane of gonadotrophs and is expressed at specific times of the reproductive cycle. To test this hypothesis, we examined the coexpression of GnRHR, GPR153, and either luteinizing hormone or follicle‐stimulating hormone in AP tissue and cultured AP cells by immunofluorescence microscopy. GPR153 was detected in the gonadotrophs, and was colocalized with GnRHR in the plasma membrane. GPR153 was also detected in the cytoplasm of cultured gonadotrophs. Real‐time PCR and western blot analyses found that expression was lower (P < 0.05) in AP tissues during early luteal phase as compared to pre‐ovulation or late luteal phases. The 5′‐flanking region of the GPR153 gene contained a consensus response element sequence for estrogen, but not for progesterone. These data suggest that some, but not all GPR153 colocalizes with GnRHR in the plasma membrane of gonadotrophs, and its expression changes stage‐dependently in the bovine AP.     

Perspectives on improvement of reproduction in cattle during heat stress in a future Japan

Heat stress (HS) causes hyperthermia, and at its most severe form, can lead to death. More commonly, HS reduces feed intake, milk yield, growth rate and reproductive function in many mammals and birds, including the important cattle breeds in Japan. Rectal temperatures greater than 39.0°C and respiration rates greater than 60/min indicate cows are undergoing HS sufficient to affect milk yield and fertility. HS compromises oocyte quality and embryonic development, reduces expression of estrus and changes secretion of several reproductive hormones. One of the most effective ways to reduce the magnitude of HS is embryo transfer, which bypasses the inhibitory effects of HS on the oocyte and early embryo. It may also be possible to select for genetic resistance to HS. Cooling can also improve reproductive performance in cows and heifers, and probably, the most effective cooling systems currently in use are those that couple evaporative cooling with tunnel ventilation or cross ventilation. Its effect on improving reproductive performance in Japan remains to be evaluated.     

Imposex in Thais gradata as a Biomarker for TBT Contamination on the Southern Coast of Peninsular Malaysia

Thais gradata samples were collected from six locations along the southern shores of Peninsular Malaysia and analyzed for imposex incidence and organotin (butyltins (BTs), including tributyltin, dibutyltin, and monobutyltin, and phenyltins (PTs), including triphenyltin, diphenyltin, and monophenyltin concentrations), in tissue burden. On average, the BT levels were found to be higher than the levels reported a year before for other biota. In contrast, the PT compounds were found to be lower than in the previous report. The present study also classified the morphological expressions of the imposex scheme for this species into seven stages (stage 0 to stage 6) by observing the development of vas deference sequence (VDS) and penis bulk. This latest imposex scheme clearly indicates the mechanism of VDS growth, the structural changes from penis bulk to a penis with flagellum, and from a normal vaginal opening to a swollen vaginal opening. The degree of imposex was assessed using the vas deference sequence index and the percentage of females possessing the imposex characteristics. It was found that locations possessing high imposex levels also tended to show high BT levels in the snail tissue samples. However, correlation analysis did not show a significant relationship among the two parameters. A better result could be obtained if more samples and sampling locations were added in order to prove the hypothesis. The nonsignificant correlation between the shell height and any of the organotin compounds, along with no significant differences between BT levels in female and lower imposex stage samples, suggests that the BT concentration detected was a recent contamination.     

Northerly shift of warm‐water copepods in the western subarctic North Pacific: Continuous Plankton Recorder samples (2001–2013)

Spatial and temporal variation in copepod community structure, abundance, distribution and biodiversity were examined in the western subarctic North Pacific (40–53°N, 144–173°E) during 2001–2013. Continuous Plankton Recorder (CPR) observational data during the summer season (June and July) were analyzed. The latitudinal distribution of warm‐water species in June shifted northward after 2011 while no apparent latitudinal shift of cold‐water and other species was observed. Species number and the Shannon–Wiener biodiversity index (H′) in June tended to increase in the northern area after 2011. The warm‐water species abundance and center latitude of warm‐water distribution were positively correlated with sea surface temperature (SST) across sampling locations, whereas no significant correlations with SST were observed for cold‐water species or other species. Warm SSTs in June after 2011 appeared to cause the northward shift of warm‐water species distribution, which in turn contributed to the higher biodiversity in the northern area. This study demonstrated the rapid response of warm‐water species to warm SST variation, whereas cold‐water and other species did not exhibit such clear responses. These findings indicate that the response of copepods to environmental changes differs among copepod species, highlighting the importance of investigating lower trophic levels to the species level to evaluate individual species’ responses to climate change.     

Links between de novo fatty acid synthesis and leptin secretion in bovine adipocytes

Leptin secretion by adipose tissue is involved in many physiological control systems, including those that determine growth, development, body composition, milk production, and reproductive function. In the adipocyte of monogastric animals, malonyl CoA (coenzyme A) seems to link the flux of energy substrates to the control of leptin production. In this study, we tested this for ruminants by examining the effect of cerulenin, an inhibitor of de novo fatty acid synthesis at the step from malonyl CoA to palmitate, on leptin production by cultured bovine adipocytes derived from intermuscular fat. Purified preadipocytes were obtained by the ceiling culture method, and adipogenic media were used to induce their differentiation into adipocytes. We found that leptin concentrations increased significantly with time in culture, and with increases in glucose concentration. Addition of 2-deoxy-D-glucose to the medium, a competitive inhibitor of glucose transport and metabolism, suppressed leptin secretion. In media with high glucose concentrations, cerulenin enhanced leptin secretion. We conclude that, as in monogastrics, malonyl CoA may play a key role in the control of leptin secretion in ruminants.     

Association between the planktonic larval and benthic stages of Manila clam <Emphasis Type="Italic">Ruditapes philippinarum</Emphasis> in eastern Hokkaido,Japan

The association between planktonic larval and benthic stages of Manila clam Ruditapes philippinarum and factors determining successful recruitment were studied in Akkeshi-ko estuary and Akkeshi Bay, Hokkaido, northern Japan. The field study showed that planktonic larvae were localized mainly in the bay after dispersal from the estuary and recruitment to the estuarine fishing grounds was not always successful. A numerical analysis suggested that estuarine circulation transported tracers, used to simulate planktonic larva, from the estuary to the bay but the number of returning tracers varied depending on the river discharge and wind direction. The planktonic larvae were affected by unsuitable conditions for survival in the estuary, such as high turbidity. We conclude that most larvae develop within the bay, where conditions are more saline and less turbid, and that although return to the estuary is essential for recruitment, it is not necessarily related to the abundance of larvae.