Differential growth rates related to initiation of piscivory by hatchery-reared larval Pacific bluefin tuna Thunnus orientalis

Fast growth plays an important role in survival processes during the early life stages of both field-captured and hatchery-reared Pacific bluefin tuna Thunnus orientalis. Marked growth variations in hatchery-reared tuna larvae are frequently observed even for the same age and within the same rearing tank after the onset of the piscivory. We hypothesized that these small growth variations in the growth of tuna larvae at the onset of piscivory lead subsequently to large growth variations and tested the hypothesis using three size groups (large, intermediate and small) of hatchery-reared fish by nitrogen stable isotope and otolith analyses. Stable isotope analysis revealed that the large group rapidly utilized prey fish larvae, but the smaller groups depended more on rotifers as the main prey item relative to the large group. The otolith radius from the core to the increment corresponding to the first feeding on yolk-sac larvae was compared among the three size groups. The results revealed that the large group had larger otolith radii than the small and intermediate groups. Our findings suggest that small growth variations apparent during the early larval stage of tuna could induce further large growth variations in the late-larval and juvenile stages through differences in the initial ability to utilize piscivory.     

Mapping the relative risk of surface water acidification based on cumulative acid deposition over the past 25 years in Japan

Sensitivity maps of atmospheric acid deposition in Japan have not been updated in 20 years. Here, we propose new relative risk maps of surface water acidification in forests based on a weighted overlay of cumulative potential acid deposition (CPAD) simulated for a 25-year period (1981–2005), including the sensitivities of soil and bedrock to acidification. We assumed that relative acidification risk is high in areas that exhibit high sensitivities of soil and bedrock to acid and have received a large amount of cumulative acid deposition over the past several decades. We aggregated fine soil and bedrock maps into a 20-km mesh for overlay onto an 80-km mesh map of CPAD by considering their spatial structures in Japan. Allocation of the weights among CPAD and soil and bedrock sensitivities was performed based on observational trends in river pH over the past 30 years. The resulting risk map for surface water acidification showed that large areas of western Japan, as well as smaller areas of Hokkaido, Tohoku, Kanto, and Kyushu, are at high risk of surface water acidification. Seventy-seven percent of all rivers for which a declining trend in pH was observed from 2001 to 2009 were also high-risk areas. Acid deposition might be one factor controlling surface water acidification in areas with high bedrock sensitivity, in addition to high CPAD and soil sensitivity, although the risk of soil acidification remains unclear.     

Characterization of the neurotoxin produced by isolates associated with avian botulism

Several varieties of birds are affected by type C botulism. We conducted neutralization tests of culture supernatants of isolates from cases of avian botulism. Whereas the toxin produced by isolates derived from mammalian botulism was neutralized only with type C antitoxin, the toxins of all isolates related to avian botulism were neutralized with both type C and D antitoxins. An analysis of nucleotide sequences with several strains revealed that the neurotoxin gene in the isolates from avian botulism comprises two thirds of the type C neurotoxin gene and one third of the type D neurotoxin gene. This indicates that the neurotoxin of avian isolates is a mosaic of type C and D neurotoxins. We prepared three sets of primers to differentiate the gene for the mosaic form from the conserved genes of type C and D neurotoxins. The results of polymerase chain reaction with these primers indicated that all avian botulism-related isolates and specimens possess the gene for the mosaic form of the neurotoxin. The toxins purified from avian and mammalian isolates exhibited the same degree of lethality in mice, but the former showed greater toxicity to chickens than the latter. These results indicate that the mosaic neurotoxin is probably a pathogenic agent causing some forms of avian botulism.     

Alleviative effects of gamma-aminobutyric acid (GABA) on behavioral abnormalities in aged dogs

gamma-aminobutyric acid (GABA, 30 mg/kg) was administered to aged dogs with recent history of veterinary clinic visits (mean age: 15.3 years old) once daily for 2 weeks by mixing with food. Their owners subjectively evaluated the effects of GABA on behavioral signs often associated with aging in the dogs. Improvement in some of behavioral signs was notable without any observable adverse effects. Dogs administered with GABA tended to exhibit improvement in emotional states and signs may be caused by neurovegetable dysfunction, though effects on cognitive dysfunction syndrome were not always observed. Thus, GABA administration may be one of the effective means of improving the quality of life of aged dogs.     

Foliar spray of validamycin a or validoxylamine a controls tomato fusarium wilt

ABSTRACT Tomato wilt, caused by the soilborne fungus Fusarium oxysporum f. sp. lycopersici, is effectively controlled by a foliar spray of validamycin A (VMA) or validoxylamine A (VAA) (>/=10 mug/ml); however, neither VMA nor VAA is antifungal in vitro. In pot tests, the effect of a foliar application of VMA or VAA at 100 mug/ml lasted for 64 days. Plants sprayed with VMA or VAA accumulated salicylic acid and had elevated expression of the systemic acquired resistance (SAR) marker genes P4 (PR-1), Tag (PR-2), and NP24 (PR-5). Foliar spray of VMA also controlled late blight and powdery mildew of tomato. The disease control by VMA and VAA lasted up to 64 days after treatment, was broad spectrum, and induced the expression of PR genes, all essential indicators of SAR, suggesting that VMA and VAA are plant activators. The foliar application of plant activators is a novel control method for soilborne diseases and may provide an economically feasible alternative to soil fumigants such as methyl bromide.     

Iodine intake as a possible cause of discontinuous decline in sperm counts: a re-evaluation of historical and geographic variation in semen quality

In order to examine whether iodine supplements may have caused a global decline in sperm concentrations during the past several decades, the synchronicity of the decline in mean sperm counts and the introduction of iodine supplements was analyzed statistically. A positive correlation between the incidence of thyroid disease and sperm counts has been detected in Europe. In addition, it has been shown that sperm counts began falling around 1965 in the United States, 40 years after iodine supplements were introduced. Mean sperm counts before and after 1965 were 111 x 10(6)/ml and 70 x 10(6)/ml, respectively, in calculations weighted by the number of subjects included in each individual publication. The timing of the declines coincided with the introduction of iodine supplements in the United States, France, and the United Kingdom. The implications are that the global decline in sperm concentrations may be caused by iodine intake. Geographical variation in the types of sperm count decline also appears to be present.     

Microscopic structure of the large intestinal mucosa in piglets during an antibiotic-associated diarrhea

Antibiotic-associated diarrhea (AAD) is caused by the treatments of broad-spectrum antimicrobials that seriously affect the activity and composition of the large intestinal microflora. The pathogenic bacteria or low concentration of short-chain fatty acids (SCFAs) has been repeatedly discussed in relation to AAD. Recently, we reported the detection of a large amount of succinate and lactate in the diarrheal feces in AAD-induced piglets. In this study, we investigated histologically the large intestinal mucosa in AAD-induced piglets, in which succinate and lactate were accumulated. AAD was induced in the piglets by an oral dose of polymyxin B sulfate (PL) or by an intra-muscular injection of enrofloxacin (ERFX). When the piglets were defecating diarrheal feces with a high concentration of succinate and/or lactate, the large intestine was removed and separated into four segments (cecum, gyri centripetales, gyri centrifugales, and rectum). Healthy piglets were used as the control. In the AAD-induced piglets, the lamina propria was edematous in the gyri centripetales. Piglets treated with ERFX were also edematous in gyri centrifugales. These edematous lamina propria contained larger amounts of inflammatory cells than observed in control tissues. ERFX-treated piglets had a more shallow crypt than PL-treated and control piglets. The mucosal tissue of the large intestine was more seriously damaged in the ERFX- than in the PL-treated piglets, which might have been caused by the high succinate and low SCFAs concentration in the digesta.     

Distribution of glutamic acid decarboxylase, neurotensin, enkephalin, neuropeptide Y, and cholecystokinin neurons in the septo-preoptic region of male rats

Neurons in the lateral septum (LS) and preoptic area (POA) are known to play an inhibitory role in feminine sexual behavior regulation in male rats. In this study, the distribution of neurons containing glutamic acid decarboxylase (GAD) and of the peptidergic neurotransmitters neurotensin (NT), enkephalin (ENK), neuropeptide Y (NPY), and cholecystokinin (CCK), was examined immunohistochemically in the LS and POA of castrated male rats subcutaneously implanted with estrogen-containing Silastic tubes. Colchicine was injected into the lateral ventricle of the animals. The forebrain sections were immunostained for each substance. A large number of GAD-immunoreactive (ir) cells were found in the LS. Many NT-ir cells were seen in the intermediate and ventral parts of the LS at the rostral and middle levels. A considerable number of ENK-ir cells were scattered over the LS at the rostral and middle levels and were observed in the ventral part of the caudal LS. There were only a few NPY-ir cells in the LS. No CCK-ir cells were observed in the LS. In the POA, GAD-ir cells were observed in abundance. Many NT-ir cells were seen, especially in the medial preoptic nucleus. Some ENK-ir cells and a few NPY-ir cells were found in the medial POA. CCK-ir cells of the POA were restricted to the periventricular and paraventricular hypothalamic nuclei.     

A new ENU-induced mutant mouse with defective spermatogenesis caused by a nonsense mutation of the syntaxin 2/epimorphin (Stx2/Epim) gene

Repro34 is an N-ethyl-N-nitrosourea (ENU)-induced mutation in mice showing male-specific infertility caused by defective spermatogenesis. In the present study, we investigated pathogenesis and molecular lesions in relation to spermatogenesis in the repro34/repro34 homozygous mouse. Histological examination of the testis showed that the seminiferous epithelium of the repro34/repro34 mouse contained spermatogonia and spermatocytes but no round and elongating spermatids. Instead of these haploid cells, multinucleated giant cells occupied the niche of the seminiferous tubules. Immunohistochemical staining for Hsc70t, an elongating spermatid specific protein, confirmed the absence of elongating spermatids. Furthermore, RT-PCR showed that there were significantly reduced expressions of the marker genes specifically expressed in the spermatid and that there was no difference in the expressions of the spermatocyte specific marker genes. These findings indicated interruption of the spermatogenesis during transition from the spermatocyte to spermatid in the repro34/repro34 mouse. The repro34 locus has been mapped on a 7.0-Mb region of mouse chromosome 5 containing the Syntaxin 2/Epimorphin (Stx2/Epim) gene, and targeted disruption of this gene has been reported to cause defective spermatogenesis. We therefore sequenced the entire coding region of the Stx2/Epim gene and found a nucleotide substitution that results in a nonsense mutation of this gene. The expression pattern of the Stx2/Epim gene during the first wave of spermatogenesis, increased expression at later stages of spermatogenesis, was in agreement with the affected phase of spermatogenesis in the adult repro34/repro34 testis. We therefore concluded that the male infertility of the repro34/repro34 mouse is caused by the interruption of spermatogenesis during transition from the spermatocyte to spermatid and that the nonsense mutation of the Stx2/Epim gene is responsible for the interruption of spermatogenesis.