Koji Toyokawa

Changes in Distribution of Active Mitochondria during Oocyte Maturation and Fertilization in the Hamster

ABSTRACT The localization and activity of mitochondria in hamster oocytes during maturation and fertilization were monitored by using three different fluorescent probes: rhodamine 123 (Rh123), MitoTracker Red (MT-Red) and 3,3′-dihexyloxacarbocyanine iodide (DiOC6(3)). Oocytes aged in vivo were also examined. The germinal vesicle (GV) oocytes exhibited a range of mitochondrial organizations, from a uniform distribution to a more cortical restriction. Metaphase I (MI) and MII oocytes included numerous mitochondria, among which the fluorescence intensity increased two-fold over that of GV oocytes. About half (54.5%) of the MII oocytes exhibited a mitochondria free zone at the cortex. An approximately 10 % decline in the density of mitochondria was observed in the oocytes aged 10 h post-ovulation, despite no significant changes. After fertilization, mitochondria became progressively aggregated and localized in the perinuclear region of all eggs examined. These comparative studies show that the signals for Rh123 and MT-Red were virtually coincident, but that for DiOC6(3) displayed wider areas of bright organizations regardless of the very low concentration used in this study (5 ng/ml). In addition, transition from a relatively homogeneous distribution of active mitochondria to perinuclear clustering may reflect energy production and utilization during oocyte maturation and fertilization in hamsters, as reported in other species.

Silage preparation and nutritive value of Chinese yam by‐product

The objective of this experiment was to determine the ensiling characteristics, nutrient composition and nutritive value of Chinese yam by-product (CYBP) silage treated without additive (Control), with lactic acid bacteria (LY), with dried beet pulp (BY), or with mixtures of lactic acid bacteria and dried beet pulp (LBY) for a fermentation period of 150 days. The nutritive value of CYBP silage was studied in an in vivo digestibility trial using wethers in a 4 x 4 Latin square design. Addition of lactic acid bacteria and/or dried beet pulp greatly improved fermentation quality of CYBP silage. The pH was reduced to below 4.0 and lactic acid was produced at above 4.6% on dry matter basis. There were no statistical differences among treatments in the digestibilities of dry matter, organic matter, crude protein and energy in the silages, but neutral detergent fiber and acid detergent fiber digestibility were higher (P < 0.001) in wethers fed BY and LBY silages compared to the control and LY silages. It was estimated that total digestible nutrient and digestible energy in the CYBP silage averaged 79.1% and 14.3 MJ/kg on dry matter basis. The study suggests that CYBP can be well preserved by making a silage and it is a good potential energy source for ruminant diets.