Japanese Society for Animal Reproduction: award for outstanding research 2002. Mechanisms controlling neurohypophysial hormone release in the rat

To explore mechanisms of osmotic control of neurohypophysial hormone release, electrical activity of magnocellular neurons (MCNs) in the hypothalamus, related neurons and efferent renal sympathetic nerve activity (RSNA) were recorded from urethane-anesthetized rats. Local osmotic stimulation applied to organum vasculosum of the lamina terminalis (OVLT) or median preoptic nucleus (MnPO) excited MCNs. Although OVLT neurons projected to MCNs were unresponsive to hyperosmotic stimulation, those projected to MnPO and also receiving excitatory inputs from MCNs, were excited by it. MnPO neurons, which were driven by OVLT stimulation and projected to MCNs, were also osmosensitive. Excitatory connections thus exist from MCNs to OVLT, from OVLT to MnPO and from MnPO to MCNs. Neurons in each of these connections were osmosensitive. This circuit thus appears to constitute an osmoreceptor complex essential for the osmoreception of MCNs. MnPO neurons constituting a part of the osmosensitive circuit were also sensitive to hemodynamic change. Thus this circuit may integrate hemodynamic and osmotic information. Local anesthesia of MnPO diminished activation of RSNA and pressor response induced by third cerebroventricular injection of hypertonic saline. The results suggest that the osmosensitive circuit is involved in body fluid regulation not only by controlling vasopressin secretion but also by modulating sympathetic outflow.     

Isolation of Encephalitozoon cuniculi using primary tissue culture techniques from a rabbit in a colony showing encephalitozoonosis

Encephalitozoon spores were isolated in a primary tissue culture of the kidneys from an encephalitozoonosis-suspected rabbit in a municipal zoo in Hokkaido. The isolated spores were morphologically characteristic of microsporidial ones in chromotrope stain, and proven to be E. cuniculi by a polymerase chain reaction (PCR) with a species-specific primer set and by direct DNA sequencing of the PCR products.     

Maternal exposure of low dose of TCDD modulates the expression of estrogen receptor subunits of male gonads in offspring

We have analyzed the effects of low-dose transplacental and lactational exposure of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on gene expression relating to the dioxin and sexual hormone cascade, and demonstrated the effects on testicular growth and sexual maturation in male offspring rats. TCDD (10 ng/kg) was administered to dams on Days 7 and 14 of gestation, and on Days 0, 7 and 14 after delivery. Gene expression of cytochrome P450 family 1 subfamily A polypeptide 1 (CYP1A1) in the liver of 17-day-old rats was significantly increased compared with controls. Furthermore, expression of estrogen receptors (ER)alpha and ERbeta was significantly increased at 17 and 42 days old, respectively in the testis of TCDD-administered rats compared with controls. Although testicular weight and the seminiferous tubule diameter were increased in 17-day-old rats, there was no difference in the number of germ cells between TCDD-treated and control animals. The expressions of androgen receptor and inhibin subunit genes were not significantly changed. These findings suggest that low-dose exposure of TCDD leads to unusual development of the testis by perturbation of steroid hormone homeostasis.     

Survival time of juvenile pen shell Atrina pectinata (Bivalvia: Pinnidae) in hyposaline water

International Aquatic Research - Survival time of juvenile pen shell Atrina pectinata (shell length ≈ 34 mm) exposed to hyposaline water without sediments was...     

Effective combinations of functional groups in chemically modified kraft lignins for reduction of aluminum toxicity

Plant growth tests were performed with radish (Raphanus sativa var. radicula Pers.) in culture solutions containing low molecular weight compounds in the presence of aluminum to determine the types of functional groups in kraft lignin (KL) modified with ozone and alkali that contributed to reducing aluminum toxicity. The low molecular weight compounds used in this study contained carboxyl, formyl, methoxyl, alcohol hydroxyl, and phenolic hydroxyl groups. The compounds that had adjacent two carboxyl groups (oxalic acid), carboxyl/alcohol hydroxyl groups (glycolic acid), or carboxyl/formyl groups (glyoxylic acid) were effective in reducing aluminum toxicity. Malonic acid, having two carboxyl groups, also reduced aluminum toxicity. The ability of ozone-treated KLs to reduce aluminum toxicity was considered to be partly due to these chemical structures. Protocatechuic acid, having two adjacent phenolic hydroxyl groups, was also effective in reducing aluminum toxicity. This indicated that the effectiveness of the alkaline-treated KL was partly due to its catechol structure. This report was presented in part at the 58th Annual Meeting of the Japan Wood Research Society, Tsukuba, Japan, March 2008     

Development of acid soil conditioning agent from lignin by ozone treatment II

Kraft lignins (KLs) modified with ozone were saponified with 0.1 M NaOH at room temperature overnight and the abilities of the modified KLs in reducing aluminum toxicity in acidic soil were assayed by planting experiments with radish (Raphanus sativa var. radicula Pers.). The abilities of ozone-treated KLs in reducing aluminum toxicity and accelerating root elongation increased markedly by saponification. Furthermore, KL treated with 0.1 M NaOH at room temperature overnight also effectively reduced aluminum toxicity and accelerated root elongation. These results suggest that KL contains chemical structures that contribute toward these favorable effects. Saponified ozone-treated KLs reduced aluminum toxicity at lower dosages than the alkaline-treated KL. This report was presented in part at the 57th Annual Meeting of the Japan Wood Research Society, Hiroshima, Japan, August 2007, and at the 52nd Lignin Symposium, Utsunomiya, Japan, November 2007     

Genetic dissection of black grain rice by the development of a near isogenic line

Rice (Oryza sativa L.) can produce black grains as well as white. In black rice, the pericarp of the grain accumulates anthocyanin, which has antioxidant activity and is beneficial to human health. We developed a black rice introgression line in the genetic background of Oryza sativa L. ‘Koshihikari’, which is a leading variety in Japan. We used Oryza sativa L. ‘Hong Xie Nuo’ as the donor parent and backcrossed with ‘Koshihikari’ four times, resulting in a near isogenic line (NIL) for black grains. A whole genome survey of the introgression line using DNA markers suggested that three regions, on chromosomes 1, 3 and 4 are associated with black pigmentation. The locus on chromosome 3 has not been identified previously. A mapping analysis with 546 F₂ plants derived from a cross between the black rice NIL and ‘Koshihikari’ was evaluated. The results indicated that all three loci are essential for black pigmentation. We named these loci Kala1, Kala3 and Kala4. The black rice NIL was evaluated for eating quality and general agronomic traits. The eating quality was greatly superior to that of ‘Okunomurasaki’, an existing black rice variety. The isogenicity of the black rice NIL to ‘Koshihikari’ was very high.     

GnRH systems in masu salmon and barfin flounder

Multiple forms of the gonadotropin-releasing hormone (GnRH) exist in teleost fish. A salmonid fish, masu salmon Oncorhynchus masou has salmon GnRH (sGnRH) and chicken GnRH-II (cGnRH-II). sGnRH neurons were scattered from the olfactory nerve through the ventral telencephalon (VT) and the preoptic area (POA). sGnRH but not cGnRH-II was detected in the pituitary. sGnRH mRNA levels in the VT and the POA increased during gonadal maturation, suggesting that sGnRH neurons in these areas are involved in gonadal maturation. sGnRH neurons were first detected in a cluster near the olfactory epithelium 40 days after fertilization. sGnRH neurons were not detected in the brain by the olfactory epithelia lesion, suggesting that sGnRH neurons are derived from the olfactory epithelium. A pleuronectiform fish, barfin flounder Verasper moseri has sGnRH, cGnRH-II and seabream GnRH (sbGnRH). sGnRH and cGnRH-II-immunoreactive fibers were observed throughout the brain, but not in the pituitary. sbGnRH neurons were located in the POA and sent fibers to the pituitary, indicating that sbGnRH is involved in GTH secretion. Judging from the location of neuronal somata and their projections, it is indicated that three GnRH systems exist in the barfin flounder; the TN-, the MT- and the POA-GnRH system. However, in masu salmon, clear anatomical identification of the TN- and the POA-GnRH system is difficult, because the GnRH neurons located in the ventral forebrain are consecutive and the GnRH form produced in these neurons is the same (sGnRH). Thus, it is suggested in masu salmon that sGnRH neurons are derived from the olfactory epithelium, migrate into the brain and play different roles according to the location in the brain.