Complete nucleotide sequence and variation of mitochondrial DNA from 10 individuals of walleye pollock, Theragra chalcogramma

ABSTRACT:   The complete mitochondrial genome sequence of 10 walleye pollocks, Theragra chalcogramma , from the Japan Sea and Bering Sea was determined. The 16 568–16 571 bp genome contains the same 37 mitochondrial structural genes (two ribosomal RNA, 22 transfer RNA, and 13 protein-coding genes) as found in all other vertebrates analyzed, in an organization identical to that of other bony fish. The major non-coding region had several conserved sequence features. Nucleotide variations of ND1, ND5, and control region were high, and these regions appear to be good candidates for high-resolution markers in population studies.     

Plasma vitellogenin levels in male common carp Cyprinus carpio and crucian carp Carassius cuvieri of Lake Kasumigaura

In order to investigate the possible influence of estrogenic environmental endocrine disruptors on the reproductive activity of fish in Lake Kasumigaura, plasma levels of vitellogenin (VTG), a biomarker of estrogen exposure, were measured in wild and cultured male common carp Cyprinus carpio and wild crucian carp Carassius cuvieri . Testicular histology and plasma steroid hormone levels were also examined. Fish were collected from June 1998 to August 1999. Plasma VTG levels in most fish examined were below a detection limit (40 ng/mL) throughout the sampling period, and a small amount of VTG (43.5 ng/mL–1680 ng/mL) compared to that in females was detected in some fish. Active spermatogenesis in the testis and increased levels of plasma sex steroids were observed in most of the fish examined. Thus, no marked influence of estrogenic chemicals was detected in the reproductive activity of male common carp and crucian carp in Lake Kasumigaura collected from the sampling sites in the present investigation.     

Oxazolone-induced gastrointestinal disorders enhance the oral transmission of AA amyloidosis in mice

Amyloid A (AA) amyloidosis is a lethal disease characterized by systemic AA amyloid deposition, and is reported in many animal species. Despite experiments have shown that AA amyloidosis can be transmitted orally, horizontal transmission and cross-species transmission are concerns, the transmission mechanism has been unknown. In this study, we examined the oral transmission efficiency of AA amyloidosis using oxazolone-induced gastrointestinal disorder mice. As a result, the upper or lower gastrointestinal disorder groups developed more severe amyloid deposition in systemic tissues than the group without gastrointestinal disorders. The results of this study suggest that gastrointestinal damage promotes the oral transmission of AA amyloidosis.     

Production of asexual and sexual offspring in the triploid sexual planarian Dugesia ryukyuensis

Certain freshwater planarians reproduce asexually as well as sexually, and their chromosomal ploidies include polyploidy, aneuploidy and mixoploidy. Previously, we successfully performed an experiment in which a clonal population produced by asexual reproduction of the Dugesia ryukyuensis (OH strain) switched to the sexual mode of reproduction. Worms of this strain are triploid with a pericentric inversion on Chromosome 4. The worms were switched to sexual reproduction after being fed with sexually mature Bdellocephala brunnea, which is a sexually reproducing species. The resulting sexualized OH strain produced cocoons filled with several eggs. Two putative factors, Mendelian factor(s) and chromosomal control(s), have been proposed as determining the reproductive mode. The present study demonstrated that inbreeding of the resultant sexualized worms produced the following four types of offspring through sexual reproduction: diploid asexual worms, triploid asexual worms, diploid sexual worms and triploid sexual worms. The chromosomal mutation on Chromosome 4 was inherited by these offspring independent of their reproductive mode. These results provide two important pieces of information: (i) the putative genetic factor was not necessarily inherited in a Mendelian fashion; and (ii) the reproductive mode is not regulated by chromosomal changes such as polyploidy or chromosomal mutations. This suggests that asexuality in D. ryukyuensis is regulated by an unknown factor(s) other than a Mendelian factor or a chromosomal control.     

Effects of 5'-uridylic acid feeding on postprandial plasma concentrations of metabolites and metabolic hormones in pre-weaning goats

5'-Uridylic acid (UMP), which is present at high concentrations in cow's colostrum, has been shown to cause a reduction in increased plasma levels of insulin and glucose after ingestion of milk replacer in pre-weaning calves. However, the precise mechanisms of UMP action have not been investigated, and its action has not been investigated in other pre-weaning ruminants. In order to demonstrate whether UMP causes changes in postprandial metabolic and hormonal parameters in pre-weaning goats, 11 Saanen kids were given milk replacer (twice a day) without ( n  = 5) or with ( n  = 6) UMP (1 g for each meal, 2 g/day for each head) for 14 days. Analysis of blood samples taken in the morning of day 14 demonstrated that the feeding of milk replacer with UMP abolished the significant changes in postprandial plasma glucose, NEFA, GH and insulin concentrations induced by feeding of milk replacer alone, and demonstrated a tendency to increase IGF-I levels. However, there was no significant difference between the two groups at any sampling time. We conclude that UMP feeding with milk replacer showed a tendency to blunt the postprandial changes in levels of some plasma metabolites and hormones that are induced by replacer alone in pre-weaning goats.     

Effects of central administration of glucagon on feed intake and endocrine responses in sheep

This study was conducted to investigate effects of glucagon intracerebroventricularly administered on feed intake and endocrine changes in sheep. Four male sheep (48–55 kg BW) were used. The animals were acclimatized to be fed alfalfa hay cubes at 12.00 hour. Human glucagon (40 and 80 µg/0.5 mL) was injected into the lateral ventricle at 12.00 hour. Blood samples were taken every 10 min from 30 min before to 180 min after the glucagon injection. Soon after the injection, the animals were given alfalfa hay cubes, and the amounts of the feed eaten within 2 h were measured. Feed intakes were significantly (P < 0.05) suppressed by 80 µg of glucagon. Plasma glucose levels in control animals were gradually decreased after the feeding, whilst those in glucagon‐treated animals were temporarily elevated just after the feeding and then kept higher than control levels. Plasma insulin was abruptly elevated after the feeding and was maintained at higher levels than before the feeding in all treatments. Plasma NEFA concentrations were decreased after the feeding in all treatments. A tendency of increase in plasma cortisol levels occurred in glucagon‐injected animals. The present study provides the first evidence that glucagon directly acts on the brain, then inhibiting feeding behavior and inducing endocrine responses in ruminants.