Rescue of vitrified-warmed bovine mature oocytes by short-term recovery culture with resveratrol

Resveratrol, a well-known antioxidant, has been reported to protect mouse metaphase-II (M − II) stage oocytes from vitrification injuries when used as a treatment during a series of vitrification processes. The present study was conducted to investigate whether short-term treatment of post-warm bovine mature oocytes with resveratrol can increase blastocyst formation rate following in vitro fertilization and culture. Bovine denuded M − II oocytes were vitrified-warmed using Cryotop® or nylon mesh (pore size = 37 μm) as a cryodevice. The post-warm oocytes were treated for 2 h with 1 μM resveratrol in recovery culture medium. The resveratrol treatment had no harmful influence on morphological survival and cleavage rate of the oocytes vitrified-warmed with Cryotop® or nylon mesh. In the Cryotop® vitrification series, blastocyst formation rate of resveratrol-treated post-warm oocytes (39.0%) was not significantly different from that of non-treated post-warm oocytes (31.7%). However in the nylon mesh vitrification series, there was a significant increase in the blastocyst yield (42.4% vs. 31.3%, P < 0.05) when post-warm oocytes were treated with resveratrol. Blastocyst yield from fresh control oocytes was 49%. Levels of reactive oxygen species were comparable between post-warm and fresh control M − II oocytes, and decreased in oocytes after recovery culture with resveratrol. Mitochondrial activity of post-warm oocytes was restored to the pre-vitrification level during the recovery culture regardless of resveratrol supplementation. Thus, short-term recovery culture with resveratrol can rescue bovine M − II oocytes vitrified-warmed on a nylon mesh cryodevice.     

Ovarian development and modes of apoptosis during oogenesis in various castes of the termite Reticulitermes aculabialis

Reproductive division in termites is the most significant biological process that leads to the formation of caste‐specific differences in tasks and status. However, little is known about the mechanism of reproductive division that underlies caste differentiation. In the present study, ovarian development and stage‐specific apoptotic patterns are investigated during oogenesis in reproductive, worker and soldier termites Reticulitermes aculabialis Tsai & Hwang. The results show that the mean lengths of the ovaries of reproductives are two‐fold longer compared with those of workers and six‐fold longer compared with soldiers. By contrast to the reproductives, the process of oogenesis in the workers includes only the oogonium differentiation stage (stage I) and oocyte growth stage (stage II), and oogenesis in the soldiers stops at stage I. Vitelogenic oocytes (stage III) are absent from workers and soldiers. During stage II in the reproductives and workers, the layer of follicle cells has a thickness of 7.56 ± 0.52 and 2.81 ± 0.34 µm, respectively. In addition, there are significant differences in the number and size of the germ cells at the same stage in the various castes. The existence of two apoptotic patterns during oogenesis is demonstrated by the terminal deoxynucleotidyl transferase‐mediated dUTP nick end labelling (TUNEL) assay. First, the majority of the cells showing apoptosis occur at stage I of oogenesis in reproductives, workers and soldiers. Second, DNA fragmentation is demonstrated by TUNEL staining of the follicle cell layers and oocytes at stage II in reproductives. Finally, the proliferation activity of follicle cells in the reproductives is observed by 5‐bromo‐2′‐deoxy‐uridine labelling. The level of oogenesis may explain the significant discrepancies in the reproductive capacity among the reproductives, soldiers and workers. These large discrepancies are controlled by apoptosis during early oogenesis.     

Habitat, reproductive biology and size composition of Parequula melbournensis, a gerreid with a temperate distribution

Trawling was carried out over sandy substrates in the shallow (5–15m) and deeper (20–35m) waters of four regions along 250 km of the lower west coast of Australia, during seven consecutive seasons. This yielded 32 752 individuals of the gerreid Parequula melbournensis , which constituted c. 42% of the total number of fish. Densities of P. melbournensis were greatest in the most southern region, reaching a seasonal maximum of 835 fish ha⁻¹: at one site in that region. Since P. melbournensis is restricted largely to the southern coastline of Australia, it has a temperate rather than subtropical or tropical distribution and thus is not a typical gerreid. Furthermore, unlike most other gerreids, it does not spend part of its life cycle in either estuaries or nearshore marine waters. The maximum total length of P. melbournensis was 175 mm, with the length at maturity ( L ₅₀) being 115 mm in females and 121 mm in males. No clear monthly trends were exhibited by gonadosomatic indices, the prevalence of mature ovaries and the oocyte size-frequency distributions of female P. melbournensis , and no clear and consistent modes were observed in length-frequency data for this species. These strong indications that spawning occurs throughout the year were substantiated by the occurrence of post-ovulatory follicles in the ovaries of large fish in all months but August, and by the presence in that month of advanced yolk granule oocytes in some ovaries, which implies that spawning was imminent. The spawning of P. melbournensis throughout the year contrasts with the far more restricted spawning periods recorded for other teleosts in the same temperate Australian waters. In this respect, P. melbournensis exhibits the characteristics of the essentially tropical family to which it belongs. Annuli, which could be detected on the otoliths of c . 40% of fish, suggest that the majority of P. melbournensis Were <3 years old.