Diurnal rhythm of serum steroid hormone levels in the Japanese whiting,Sillago japonica,a daily-spawning teleost

Ovarian developmental stages and serum steroid hormone levels were examined at six different times of day (0100, 0600, 1000, 1300, 1600, 2000 h) in a marine teleost, the Japanese whiting Sillago japonica, which has an asynchronous-type ovary containing oocytes at various stages of development and spawns every day during a period ranging up to three months. The largest oocytes in the ovaries at the active vitellogenic or post-vitellogenic stages were found between 0100 and 1300 h. Oocyte maturation indicated by germinal vesicle breakdown (GVBD) occurred at 1600 h, and ovulated oocytes were observed in the ovaries collected at 2000 h. These processes were accompanied by a significant daily change in serum steroid hormone levels. The serum level of estradiol-17β showed a peak in fish with mature oocytes sampled at 1600 h. In these fish, the second-largest oocytes in the ovaries were at the initial stage of vigorous vitellogenesis, the secondary yolk stage. Therefore the highest level of serum estradiol-17β was considered to be due to the second-largest oocytes. Testosterone levels remained low and constant throughout the experimental period. The serum levels of 17α,20β-dihydroxy-4-pregnen-3-one (17α,20β-diOHprog) peaked at 1600 h at which time all fish had mature oocytes. These results indicate that the Japanese whiting possesses a diurnal rhythm of oocyte development including vitellogenesis, oocyte maturation and ovulation, and further suggest that daily cycles in oocyte growth and maturation which simultaneously take place in an ovary are regulated by diurnal secretions of estradiol-17β and the maturation-inducing steroid, 17α,20β-diOHprog.     

Species-specific PCRs differentiate <Emphasis Type="Italic">Rosellinia necatrix</Emphasis> from <Emphasis Type="Italic">R. compacta</Emphasis> as the prevalent cause of white root rot in Japan

Rosellinia compacta, described recently, resembles R. necatrix and also causes white root rot. Here a species-specific PCR was developed for R. compacta, and the two R. necatrix-specific primer sets already available were validated in terms of species specificity. PCRs using the primer sets for R. necatrix amplified specific products exclusively from R. necatrix isolates. The R. compacta-specific primer set exclusively detected R. compacta, which appears to be a rare but widely distributed species. We conclude that R. necatrix is the major cause of the disease in Japan but that the involvement of R. compacta should be studied further.     

A cytogenetic study of bilateral sexual polyploidization in cassava (Manihot esculenta Crantz)

Microsporogenesis and megasporogenesis were cytogenetically and histologically analysed in three cassava clones:‘Rayong 1′,‘Rayong 60′,‘M. mga’ and two hybrid lines,‘OMR 3641‐1’ and ‘OMR 3641‐1’ to elucidate the evolution of sexual polyploids in cassava. At telophase II, formation of 17‐21 micronuclei per pollen cell plate was observed in 16 out of 351 cell plates in ‘M. mga’. Micronuclei were observed at low (0.3‐2.3%) frequencies, at the sporad stage in all clones. Monads, dyads, triads and tetrads, which are established sources of high ploidy levels were observed at low (2.6%) and high (22.2%) frequencies. Megasporogenesis in ‘Rayong 1’ and ‘Rayong 60’ showed a lack of second meiotic divisions after a successful first division that resulted in partly unreduced embryo sacs with 2n eggs, suggesting another unrecognized and, as yet, unreported source of sexual polyploid formation in cassava. Meiotic abnormalities during microsporogenesis and megasporogenesis are implicated as being responsible for the formation of mixoploids (triploids and tetraploids) in cassava breeding programmes. A cytogenetic mechanism resulting in bilateral sexual polyploids through different gametic fertilization pathways in cassava is suggested and its role in breeding is briefly discussed.     

Histological analysis of embryo-sac formation and detection of meiotic diplospory in cassava (Manihot esculenta Crantz)

Summary Embryo-sac formation in six cultivated Asian cassava clones and one unknown wild type, was histologically investigated to determine apomictic potential in the genus Manihot. All the 6 clones were found to possess one single sexual embryo-sac containing 6–8 nuclei at maturity. However, one clone, Rayong 3 possessed two functional embryo-sacs at 12 hours after controlled pollination (HACP). The larger embryo-sac was 6-nucleate (all 3 nuclei of the egg apparatus, 1 polar and 2 antipodal cells) and located towards the false micropylar or the nucellar beak region. The smaller embryo-sac also contained a total of 6 nuclei and approximately 10 m³ or 1/2 the volume of the former and located towards the chalazal pole. Percentage sexuality estimates indicated a 100% sexual reproduction in embryo-sacs of all the clones analysed. However, apomeiotic relationships indicate a low (0.3%) degree of meiotic diplosporous embryo-sac formation, thus suggesting facultative apomixis in cv. Rayong 3. This is the first embryological identification and evidence of apomeiosis and apomictic potential in cassava.Contribution from Plant Breeding Laboratory, Applied Genetics & Biotechnology Division, Faculty of Agriculture, Miyazaki University, No. 91.     

In vitro propagation of Japanese garden iris,Iris ensata Thunb.

Summary Explants of young scapes of Iris ensata were cultured on MS medium with 1 mg/l NAA, 1 mg/l 6-BA, 30 g/l sucrose and 10 g/l agar, and this species was characterized by high variety specificity for callus, shoot and root induction. Among 23 varieties and one wild form tested, Okichidori, Miyukisudare and Meiji-l exhibited a considerable rate of shoot induction, although these induced poorly rooted shoots. In addition, two types of callus induction such as green and white calli were observed, and the induction of green-type calli was significantly correlated with that of shoots. Surprisingly, the only modification, half-strength MS inorganic salts, for the above medium proved to be very effective for shoot induction in the scape culture. For shoots obtained from the scape culture, effects of sucrose concentrations and activated charcoal on root induction were examined by using 1/2 MS with 1 mg/l NAA, 1 mg/l 6-BA, 30 g/l sucrose and 10 g/l agar as the basic medium. The addition of 1% activated charcoal to the media had a marked effect for root induction independent of sucrose concentrations and varieties tested. The in vitro propagation technique of I. ensata is discussed.     

Perfluorooctane Sulfonate (PFOS) and Perfluorooctanoic Acid (PFOA) in Water Environment of Singapore

Recently, there has been increasing concern about perfluorinated compounds, especially perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) due to their biotic and abiotic persistence and chronic toxicity. To characterize the spatial distribution and seasonal variation of PFOS and PFOA in the aquatic and oceanic environment of Singapore, more than 100 water samples from reservoirs, rivers/canals, coastal waters, and treated effluents of wastewater treatment plants (WWTPs) were collected and analyzed in this study. Solid-phase extraction followed by high-performance liquid chromatography (HPLC) coupled with tandem MS (HPLC/MS/MS) was applied to quantitatively identify PFOS and PFOA. PFOS concentrations in surface waters, wastewaters and coastal waters were in the range of 2.2?C87.3 ng/L, 5.8?C532 ng/L, and 1.9?C8.9 ng/L, respectively, while those of PFOA were 5.7?C91.5 ng/L, 7.9?C1,060 ng/L, 2.4?C17.8 ng/L, respectively. Compared with surface waters and wastewaters, coastal waters had lower concentrations of PFOS and PFOA. Highest concentration of PFOA (532 ng/L) and PFOA (1,060 ng/L) were observed in treated effluents of two WWTPs. Our results suggest that coastal waters in the western area of Singapore are more heavily contaminated than those in the middle and eastern areas. The release of effluents from WWTPs is an important pathway by which perfluorinated compounds enter the oceanic environment. Between dry season and wet season, significant seasonal differences (p?=?0.025) were observed in surface waters for PFOS only, while no discernable seasonal differences were found for both PFOS and PFOA in coastal waters and wastewaters.     

Severe hypoplasia of the omasal laminae in a Japanese Black steer with chronic bloat--a case report

An 11-month-old Japanese Black steer with chronic bloat underwent clinical and histological analyses. During the observation period, it showed normal appetite and fecal volume but persistent chronic bloat symptoms. Compared to controls, the steer's feces contained undigested large straws. Necropsy revealed normal rumen, reticulum, and abomasum but a small omasum. The rumen, reticulum, and abomasum mucosa was normal, with well-developed ruminal papillae. However, severe hypoplasia of the omasal laminae was observed along with hypoplasia reticular groove and ruminoreticular fold. The contents of the reticulum, omasum, and abomasums comprised undigested large sized hay particles. The omasum papillae showed no pathological abnormalities. This is a rare case of a steer with chronic bloat probably caused by severe hypoplasia of the omasal laminae.     

In vitro development of equine oocytes from preserved ovaries after intracytoplasmic sperm injection

In this study, we evaluated the meiotic competence of equine oocytes from ovaries preserved for one day. We also investigated fertilization, cleavage rate, developmental competence and freezability of equine embryos after intracytoplasmic sperm injection (ICSI). After collection from ovaries, the oocytes were classified into two groups comprised of those having compact cumulus layers (Cp) or those having expanded cumulus layers (Ex). Oocytes with a first polar body were subjected to fertilization by ICSI using frozen-thawed stallion spermatozoa and were then cultured in CR1aa medium. The rates of metaphase II-stage oocytes, normal fertilization and cleavage were not significantly different between the two oocyte categories (38.5, 70.0 and 48.7% for CP and 43.5, 60.0 and 58.8% for Ex, respectively). However, the blastocyst development rate of Ex was significantly (P<0.05) higher than that of Cp (25.5 vs. 7.7%). Three Cp-derived and 12 Ex-derived early blastocysts were cryopreserved using the slow cooling protocol, and all of them developed to hatching blastocysts after thawing. These results suggest that equine oocytes fertilized by ICSI can develop to the preimplantation stage in culture conditions similar to those used in the bovine. Furthermore, the Ex oocytes had higher developmental competence than the Cp oocytes, and the in vitro-produced blastocysts had high viability after freezing and thawing.     

Phosphorus Stress-Induced Differential Growth,and Phosphorus Acquisition and Use Efficiency by Spring Wheat Cultivars

ABSTRACT

Phosphorus (P) is a finite, non-renewable, and natural resource and a vital major nutrient for plant metabolic and developmental processes. However, adverse soil biogeochemical characteristics of alkaline-calcareous soils (especially Aridisols) and highly weathered acid soils (i.e., Ultisols and Oxisols) render orthophosphate (Pi) as the least available major nutrient due to P complexation, sorption, and/or fixation. In such soil environments, plant bioavailable P is only a small fraction of total soil P, seriously limiting crop growth and production. Different plant species, and even cultivars of the same species, may display a suite of growth responses that enable them to solubilize and scavenge soil P either by enhancing external Pi acquisition or reprioritizing internal Pi use under P-stress soil environments. This paper reports relative growth responses, P acquisition and P-use efficiency characteristics by 14 cultivars of spring wheat (Triticum aestivum L.) grown in solution culture with high/low P supply induced by applying soluble NH₄H₂PO₄, sparingly soluble rock phosphate, and Ca₃(PO₄)₂. The wheat cultivars exhibited considerable genetic diversity in biomass accumulation, P concentrations, P contents, factor (PSF) and P efficiency characteristics [i.e., P utilization efficiency (PUE), P efficiency (PE), and PE ratio (PER)]. Plant growth and PE parameters were significantly correlated, while P uptake was linearly related with biomass increase and solution pH decrease. The wheat cultivars with high PUE, PER and P uptake, and low PSF, and plant P concentration were more efficient in utilizing P and, hence, more tolerant under P-stress environment. Biomass and P contents of “P efficient/low-P tolerant” wheat cultivars were superior to “P inefficient/low-P sensitive” cultivars at all P-stress levels. Hence, “P efficient/low-P tolerant” cultivars are the most desirable wheat genotypes for P-stress environments because they are able to scavenge more P from sparingly soluble P sources or soil-bound P forms.