Inhibitory effect of 2,4-dibromophenol and 2,4,6-tribromophenol on larval survival and metamorphosis of the sea urchin <Emphasis Type="Italic">Strongylocentrotus nudus</Emphasis>

ABSTRACT:   As a possible factor leading to the low recruitment level of sea urchins in kelp forests, the inhibitory effect of 2,4-dibromophenol (DBP) and 2,4,6-tribromophenol (TBP) released from the large perennial brown algae Ecklonia kurome and Eisenia bicyclis on survival and metamorphosis of eight-armed larvae of the sea urchin Strongylocentrotus nudus was examined. The percentage of larvae that underwent metamorphosis in filtered sea water after 1 h exposure to one-half dilution of saturated dibromomethane solution (∼60 ppm) as a chemical inducer reached approximately 100% after 1 h, while that in filtered sea water containing 1 ppm TBP was reduced to 73%. This was further reduced to less than 40% in the presence of 10 and 20 ppm TBP after 2 h. In filtered sea water containing 1 and 10 ppm DBP, the proportion of metamorphosed larvae was reduced markedly to 43 and 5% after 2 h, respectively. All larvae exposed to 50 ppm TBP and to 20 and 50 ppm DBP died after 1 h. These findings suggest that DBP is more toxic than TBP for sea urchin larvae, strongly inhibiting their metamorphosis.     

Diel timing of molting and metamorphosis of Panulirus japonicus phyllosoma larvae under laboratory conditions

ABSTRACT:   The timing of molting and metamorphosis was monitored for Panulirus japonicus phyllosoma larvae cultured in the laboratory. Larvae cultured under natural light–dark cycle molted synchronously within approximately 1.0 h before and after sunrise, except for a short period after hatching; the timing of molting changed with time of sunrise. When three artificial light–dark cycles were introduced, larvae molted around the start of lighting, irrespective of the light–dark cycles. In the event of a sudden change in the start or end of lighting, molting was regulated by an endogenous rhythm. The start of lighting had a greater impact on the timing of molting than the end of lighting, suggesting that sunrise is probably the critical signal for phase-setting in molting rhythm. Metamorphosis to the puerulus stage occurred within 0.4 h before and 1.2 h after sunset under a natural light–dark cycle, and the timing of metamorphosis was also changed artificially by regulating the end of lighting.     

Activated Vitamin D3 and Pro-activated Vitamin D3 Attenuate Induction of Permanent Changes Caused by Neonatal Estrogen Exposure in the Mouse Vagina

Exposure of mice to a high dose of estrogens including diethylstilbestrol (DES) during the neonatal period modifies the developmental plan of the genital tract, which leads to various permanent changes in physiology, morphology and gene expression. These changes include development of an abnormal vaginal epithelium lined with hyperplastic mucinous cells accompanied by Tff1 gene expression in mice. Here, the influence of vitamin D on the direct effect of estrogen on the developing mouse vagina was examined. The mid-vagina of neonatal mice was cultured in a serum-free medium containing estradiol-17β (E₂) and various concentrations of 1,25-dihydroxyvitamin D₃ (1,25(OH)₂D) ex vivo and then was transplanted under the renal capsule of ovariectomized host mice for 35 days. Exposure to E₂ alone caused the vaginal tissue to develop estrogen-independent epithelial hyperplasia and to express TFF1 mRNA, while addition of a low nanomolar amount of 1,25(OH)₂D added at the same time as E₂ to the culture medium attenuated the effects of estrogen. Expression of vitamin D receptor was also evident in the neonatal mouse vagina. Interestingly, addition of 25-hydroxyvitamin D₃, a pro-activated form of vitamin D, at the micromolar level was found to be potent in disrupting the developmental effects of E₂, while cholecalciferol was not at least at the dose examined. Correspondingly, expression of Cyp27B1, a kidney-specific 25-hydroxyvitamin D hydroxylase, was evident in the neonatal mouse vagina when examined by RT-PCR. In addition, simultaneous administration of 1,25(OH)₂D successfully attenuated DES-induced ovary-independent hyperplasia in the vagina in neonatal mice in vivo. Thus, manipulation of vitamin D influenced the harmful effects of estrogens on mouse vaginal development.     

Stable isotope analysis suggests the existence of multiple populations of streaked spinefoot (<Emphasis Type="Italic">Siganus javus</Emphasis> L.) in Bandon Bay,Southern Thailand

The stock unit used in fisheries resource assessment and management is generally based on the morphological and genetic characteristics of a particular population or species to avert problems caused by the treatment of multiple populations as one stock, which can lead to the overestimation of population sizes and genetic pollution. Furthermore, since the linkage of microhabitats is an important factor affecting the reproduction of marine organisms in coastal areas, an understanding of the food web in each microhabitat is essential to establish sustainable fisheries management practices. We investigated spatial variations in the food sources and feeding habits of immature stage of Siganus javus using genetic population analyses and stable isotope analyses (δ¹³C and δ¹⁵N). These species are commonly harvested by small-scale fisheries, and it inhabits Bandon Bay in the Surat Thani Province of Southern Thailand. Genetic variation within sampling sites was greater than that between sites. The δ¹³C values of S. javus differed between sites, which suggest that the different ecological habitats exhibit different rates and patterns of carbon flow even among sites located in the same bay. Our results suggest that studies combining genetic population analyses and stable isotope analyses are required to confirm the delineation of fine-scale management units intended for the development of coastal fishery resources.     

Nebulin and N-WASP cooperate to cause IGF-1-induced sarcomeric actin filament formation

Insulin-like growth factor 1 (IGF-1) induces skeletal muscle maturation and enlargement (hypertrophy). These responses require protein synthesis and myofibril formation (myofibrillogenesis). However, the signaling mechanisms of myofibrillogenesis remain obscure. We found that IGF-1-induced phosphatidylinositol 3-kinase-Akt signaling formed a complex of nebulin and N-WASP at the Z bands of myofibrils by interfering with glycogen synthase kinase-3β in mice. Although N-WASP is known to be an activator of the Arp2/3 complex to form branched actin filaments, the nebulin-N-WASP complex caused actin nucleation for unbranched actin filament formation from the Z bands without the Arp2/3 complex. Furthermore, N-WASP was required for IGF-1-induced muscle hypertrophy. These findings present the mechanisms of IGF-1-induced actin filament formation in myofibrillogenesis required for muscle maturation and hypertrophy and a mechanism of actin nucleation.     

Biological roles of monoterpene volatiles derived from rough lemon (<Emphasis Type="Italic">Citrus jambhiri</Emphasis> Lush) in citrus defense

Volatile compounds of plants, including monoterpenes, are a possible source of signal molecules that induce defense systems to protect plants from tissue damage. Volatile compounds from rough lemon leaves were trapped by solid-phase microextraction fibers in sealed vials, and subsequent gas chromatography–mass spectrometry and gas chromatography analyses identified the profile of the major components, mainly various monoterpenes. Among several monoterpenes examined, citral, citronellal, and linalool significantly inhibited the spore germination and hyphal growth of Alternaria alternata. The effect of linalool was fungistatic, while the effects of citral and citronellal were partially fungicidal. Wounding of rough lemon leaves induced a significant increase in release of monoterpenes. The release of linalool was the most abundant and was 14.5 times that of unwounded rough lemon leaves. Unlike the wounding treatment, microbe attack did not significantly change monoterpene releases, and there was statistically no difference found in the peak areas from microbe-treated and untreated leaves. Linalool, limonene, and β-pinene also had insect-repellant effects on wild-type Drosophila melanogaster. Expression patterns of defense-related genes in rough lemon and rice significantly changed after treatment with vapors of monoterpene volatiles. Taking these results together, monoterpene volatiles are likely to play roles in the defense of rough lemon against microbe and insect pathogens.     

Expression of monocarboxylate transporter 1 (MCT1) in the dog intestine

In this study, the expression and distribution of monocarboxyolate transporter 1 (MCT1) along the intestines (duodenum, jejunum, ileum, cecum, colon and rectum) of dogs were investigated at both the mRNA and protein levels. The expression of MCT1 protein and its distribution were confirmed by Western blotting and immunohistochemical staining using the antibody for MCT1. We identified mRNA coding for MCT1 and a 43-kDa band of MCT1 protein in all regions from the duodenum to the rectum. Immunoreactive staining for MCT1 was also observed in epithelial cells throughout the intestines. MCT1 immunoreactivity was greater in the large intestine than in the small intestine. MCT1 protein was predominantly expressed on the basolateral membranes along intestinal epithelial cells, suggesting that MCT1 may play an important role in lactate efflux and transport of short-chain fatty acids (SCFAs) to the bloodstream across the basolateral membranes of the dog intestine.     

Spatial variations in nitrous oxide and nitric oxide emission potential on a slope of Japanese cedar (Cryptomeria japonica) forest

To quantify the spatial variation and spatial structure of nitrous oxide (N₂O) and nitric oxide (NO) emission from forest soils, we measured N₂O and NO emission rates from surface soil cores taken at 1 m intervals on a cross-line transect (65 m × 20 m) on a slope of Japanese cedar ( Cryptomeria japonica ) forest in a temperate region of central Japan and analyzed the spatial dependency of N oxide gas emissions using geostatistics. We divided N₂O emission into N₂O from denitrification and N₂O from nitrification using the acetylene inhibition method. According to the geostatistical analysis, N₂O emission rates on the slope had large spatial variation and weak spatial dependency. This weak spatial dependency was caused by the inordinately high N₂O emissions on the slope, which were derived mainly from denitrification. In contrast, NO emission rate on the slope had large spatial variation, but strong spatial dependency and a distinct spatial distribution related to slope position, that is, high in the middle of the slope and low in the shoulder and the foot of the slope. The CN ratio and water-filled pore space were the dominant factors controlling NO emission rate on a slope. Our results suggest that spatial information about topographic factors helps to improve the estimation of both N₂O emission and NO emission from forest soils.     

Relationship between N2O and NO emission potentials and soil properties in Japanese forest soils

To determine the relationship between nitrous oxide (N₂O) and nitric oxide (NO) emission rates and soil properties in forest soils, N₂O and NO emission rates in soils were measured in incubation experiments under standardized temperature and water conditions (water content at a water-holding capacity of 60%) using soils packed into a cylindrical core, and variations in the soil properties were also determined. The N₂O emission rates from nitrification and from denitrification were determined separately using a nitrification inhibitor (10 Pa acetylene). Soil samples were taken from 25 forest stands in a central temperate area of Japan. The N₂O and NO emission rates were highly variable, even under the standardized temperature and water-holding capacity (60%) conditions. According to a partial least squared regression model analysis, the C:N ratio and pH strongly affected the N₂O emission rate, whereas     , water-soluble Al and the C:N ratio strongly affected the NO emission rate. The C:N ratio negatively affected the emission rate of both N oxide gases, suggesting that N mineralization is an important factor in the rates of N oxide gas emission. The acetylene inhibition experiment showed that N₂O emission from denitrification was positively affected by pH, water-filled pore space and filling density, and negatively affected by the C:N ratio, total carbon and total nitrogen.     

Purification and characterization of polyphenol oxidase from cauliflower (Brassica oleracea L.)

Polyphenol oxidase (PPO) of cauliflower was purified to 282-fold with a recovery rate of 8.1%, using phloroglucinol as a substrate. The enzyme appeared as a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The estimated molecular weight of the enzyme was 60 and 54 kDa by SDS-PAGE and gel filtration, respectively. The purified enzyme, called phloroglucinol oxidase (PhO), oxidized phloroglucinol (K(m) = 3.3 mM) and phloroglucinolcarboxylic acid. The enzyme also had peroxidase (POD) activity. At the final step, the activity of purified cauliflower POD was 110-fold with a recovery rate of 3.2%. The PhO and POD showed the highest activity at pH 8.0 and 4.0 and were stable in the pH range of 3.0-11.0 and 5.0-8.0 at 5 °C for 20 h, respectively. The optimum temperature was 55 °C for PhO and 20 °C for POD. The most effective inhibitor for PhO was sodium diethyldithiocarbamate at 10 mM (IC(50) = 0.64 and K(i) = 0.15 mM), and the most effective inhibitor for POD was potassium cyanide at 1.0 mM (IC(50) = 0.03 and K(i) = 29 μM).