Role of sodium bicarbonate on the initiation of sperm motility in the Japanese eel

ABSTRACT:   In order to find out the role of sodium bicarbonate (NaHCO₃) on the initiation of sperm motility in the Japanese eel Anguilla japonica , interactions were investigated between NaHCO₃ and various reagents (K⁺ channel blocker 4-aminopyridine [4-AP], ammonium chloride [NH₄Cl], sodium acetate and calcium chloride [CaCl₂]) that could regulate internal factors (intracellular K⁺, intracellular pH [[pH]_i] and intracellular Ca²⁺) in sperm motility. Contradictory effects of NaHCO₃ were observed (i.e. an inhibitory effect when 4-AP was absent and a promoting effect when 4-AP was present). Sodium bicarbonate inhibited the initiation of sperm motility in the Japanese eel. However, NaHCO₃ restored the motility of immotile sperm that 4-AP inhibited. The inhibitory effect of NaHCO₃ disappeared with the addition of NH₄Cl, which raised [pH]_i, but the promoting effect was not affected by [pH]_i. Although NaHCO₃ recovered motility in the presence of 4-AP, this recovery was also observed with the addition of CaCl₂ instead of NaHCO₃. In the initiation of sperm motility in the Japanese eel, two roles for NaHCO₃ are suggested: an inhibitory role relating to the regulation of [pH]_i and a promoting role relating to the uptake of another initiation factor, which could be Ca²⁺.     

Isolation of avian bornaviruses from psittacine birds using QT6 quail cells in Japan

Avian bornaviruses (ABVs) were recently discovered as the causative agents of proventricular dilatation disease (PDD). Although molecular epidemiological studies revealed that ABVs exist in Japan, no Japanese isolate has been reported thus far. In this study, we isolated four strains of Psittaciform 1 bornavirus from psittacine birds affected by PDD using QT6 quail cells. To our knowledge, this is the first report to isolate ABVs in Japan and to show that QT6 cells are available for ABV isolation. These isolates and QT6 cells would be powerful tools for elucidating the fundamental biology and pathogenicity of ABVs.     

Bacterial Leaf Spot of Ivy Caused by Xanthomonas campestris pv. hederae

A bacterial leaf spot disease was observed on Hedera helix (English ivy) and H. canariensis (Algerian ivy) in Japan. The causal agent was identified as Xanthomonas campestris pv. hederae (Arnaud 1920) Dye 1978. Received 13 May 2002/ Accepted in revised form 3 July 2002     

Oogenesis in the common Japanese conger Conger myriaster

ABSTRACT:    We investigated the process and characteristics of oogenesis in the common Japanese conger Conger myriaster . Young fish caught in November 1996 were reared for use in this experiment. Fish were sampled monthly from December 1997 to August 1998. Some were injected with human chorionic gonadotropin to stimulate ovarian maturation from May to August 1998. Oocytes from the chromatin nucleolus stage to the secondary yolk globule stage were obtained from non-hormone-treated fish; those of more advanced stages were obtained from hormone-treated ones. We divided oocyte development into eight stages from the chromatin nucleolus stage to the maturation stage. The yolk vesicle stage was not separated because yolk vesicles began to appear just after appearance of yolk globules. Oocyte, oil droplet, yolk globule and nucleus diameters all increased concomitant with oocyte development. Oil droplet and yolk globule diameters increased remarkably at the maturation stage. However, zona radiata thickness peaked at the secondary yolk globule stage, decreasing gradually thereafter. Increased gonadosomatic index was related to oocyte development as found in European and Japanese eels receiving hormone treatment to mature. The present study is the first report describing oogenesis characteristics in congrid eels. It indicates that oogenesis is almost identical to that of other anguillid eels.     

Urinary albumin and transferrin as early diagnostic markers of chronic kidney disease

Feline renal diseases are increasingly noted in veterinary practice. It is important to diagnose and identify the pathological basis of renal dysfunction accurately at an early stage, but there are only a few reports on this area in clinical veterinary medicine. We investigated the efficacy of measurement of urinary albumin (u-Alb) and urinary transferrin (u-Tf) for early diagnosis using 5-µl urine samples collected noninvasively by catheterization from normal (IRIS stage I) cats and cats with stage I chronic kidney disease (CKD). The u-Alb levels in normal and stage I CKD cats were 6.0 ± 4.5 and 11.2 ± 8.4 mg/dl, respectively, and the u-Tf levels were 0.09 ± 0.42 and 0.52 ± 0.79 mg/dl, respectively. Based on ROC curve analysis, the sensitivity and specificity of u-Alb and u-Tf were higher than those of the currently used biomarker, the plasma creatinine level. The sensitivity of u-Alb was higher than that of u-Tf, whereas the specificity of u-Tf was higher than that of u-Alb. The validity of the threshold albumin level (20 mg/dl) was confirmed by measurements using SDS-PAGE. Since leakage of u-Tf in urine precedes leakage of u-Alb, inclusion of u-Tf in biochemistry tests may be appropriate for IRIS staging as a diagnostic marker of early diagnosis of renal disorder in cats.     

Development of embryos and larvae in the common Japanese conger Conger myriaster

Development of embryos and larvae in the common Japanese conger Conger myriaster was observed after artificial fertilization. Eggs were obtained from females matured artificially by hormone injections and milt was obtained from males matured naturally. Fertilized eggs were kept in seawater at 12–14°C. The first cleavage occurred at 4 h, epiboly began at 24 h, the embryonic body was formed at 38 h and hatching occurred at 84 h after insemination. Newly hatched larvae were approximately 2.5 mm (total length) and similar to those of Anguilla japonica in terms of external features. The mouth and anus opened on the 7th day after hatching. Pigments began to appear at the tip of the tail on the 10th day. The total length of the larvae reached approximately 8 mm on the 11th day. Eye pigmentation began on the 14th day. One larva lived for 19 days without food.     

Cloning of estrogen receptor-β cDNA of common Japanese conger Conger myriaster and expression of the gene during oocyte development

ABSTRACT:   Estrogen receptor (ER) cDNA was cloned from the liver of common Japanese conger Conger myriaster . Common Japanese conger ER cDNA contains 2543 nucleotides including an open reading frame that encodes 596 amino acids, with a molecular weight of 66.1 kDa. The deduced amino-acid sequence of the common Japanese conger ER shares 85% identity with that of eel Anguilla japonica ER-β, and 39–46% and 53–59% identity with the deduced sequences of ER-α and ER-β of other species, respectively. In a phylogenetic analysis, the common Japanese conger ER was found to cluster with the ER-β of other species. The common Japanese conger ER-β also has six domains (A–F), which are conserved in the nuclear receptor superfamily. The amino-acid sequences in the C and E domains were highly conserved between common Japanese conger ER-β and other ER. However, the other domains showed low homology. In the female common Japanese conger, ER-β mRNA was highly expressed in the liver and pituitary gland. The expression levels of the ER-β gene increased from the oil droplet stage to the primary yolk globule stage and were maintained until the migratory nucleus stage.