Ultrastructural Morphometry of Bovine Compact Morulae Produced In Vivo or In Vitro: RESULTS

Various cellular components found within bovine compact morulae are illustrated in Figure 1. Examples of lipid droplets (L), vacuoles (V), mitochondria (M), and nuclei (N) within the cytoplasm, as well as intercellular space (IS) and microvilli, are depicted. Mature (MM) and vacuolated mitochondria (VM) are depicted in Figure 2, A and B. Immature (IM) and hooded mitochondria (HM), both of which were classified as immature mitochondria, are illustrated in Figure 2, C and D. Apoptotic bodies (AB) and inclusion bodies (IB) were also evaluated and are depicted in Figure 3.

The volume density of lipid in compact morulae originating from the three in vitro culture treatments (IVPS, IVPSR, and mSOF) was increased (P < 0.05) compared with those produced in vivo (Fig. 4). Compact morulae produced in the IVPS treatment had an increased (P < 0.05) proportional volume of vacuoles compared with embryos produced either in vivo or in the IVPSR or mSOF treatments (Fig. 5).

The volume density of mature mitochondria was decreased approximately 8-fold (P < 0.05) in compact morulae from IVPS, IVPSR, and mSOF compared with those produced in vivo (Table 1). Compact morulae from the IVPS medium had a reduced (P < 0.05) density of immature mitochondria compared with those from the IVPSR and mSOF treatments. There was no effect of treatment on the proportional volume of vacuolated mitochondria. Finally, the volume density of total mitochondria was decreased (P < 0.05) in compact morulae produced in the IVPS medium compared with that for compact morulae produced either in vivo or in the IVPSR or mSOF treatments (Table 1).

The proportional volume of cytoplasm in compact mor-ulae from the IVPS, IVPSR, and mSOF treatments was increased (P < 0.05) compared with that for embryos produced in vivo (Table 2). For morulae produced in the IVPS medium, the volume density of nuclei was significantly reduced compared with that for morulae produced in vivo (P < 0.05). The concurrent increase in volume density for cytoplasm and decrease in density for nuclei for compact mor-ulae in the IVPS treatment resulted in a cytoplasmic-to-nuclear ratio that was significantly greater (P < 0.05) than that for compact morulae produced in vivo (Table 2). There was no effect of treatment on the volume densities for intercellular space, debris, inclusion bodies, or apoptotic bodies (Table 2).

FIG. 1. General overview of cellular ultrastructure of a bovine compact morula (X5280); lipid droplets (L), vacuoles (V), mitochondria (M), nuclei (N), intercellular space (IS), and microvilli.

FIG. 2. Mitochondrial types within bovine compact morulae. A) Mature mitochondria (MM, X24 000); B) vacuolated mitochondria (VM, X24 000); C) immature mitochondria (IM, X24 000); D) hooded mitochondria (HM, X24 000).

FIG. 3. Inclusion bodies and apoptotic bodies (IB and AB, X8000) in a bovine compact morula.

FIG. 4. Volume density of lipid for compact morulae from MO, IVPS, IVPSR, and mSOF treatments (a,b P < 0.05).

FIG. 5. Volume density of cytoplasmic vacuoles for compact morulae from MO, IVPS, IVPSR, and mSOF treatments (a,b P < 0.05).

TABLE 1. Effect of treatment on the volume density (%) of mitochondrial type in bovine compact morulae (least-squares means ± SEM).

^a,^b Within columns, values with different superscripts differ at P < 0.05.

TABLE 2.

* Represents debris between cells.
^a‘^b Within rows, values with different superscripts differ at P < 0.05.