## 3 Results
### Lindane 1 \(\mu\)M (L1)  
By LM, oocytes exposed to Lindane 1 \(\mu\)M had a rounded shape, an intact ZP, and a narrow PVS (Figure 2A, inset). By TEM, at low magnification, the organelle density and distribution seemed slightly reduced, compared to controls. The fibrillar structures of the cytoplasmic lattice were commonly dispersed throughout the ooplasm (Figure 2A). Mitochondria, usually spherical or ovoid, were the most numerous organelles in this experimental group; their cristae were recognizable on the periphery and parallel to the outer mitochondrial membrane. They appeared mostly organized in clusters, with a double-layered electron-dense mitochondrial membrane and a homogeneous matrix, as in the control group (Figure 2B). Frequently, mitochondria presented a vacuole or prominent electron-dense granules in their matrix (Figure 2B,D,E); however, the density of vacuolar mitochondria was almost unchanged compared to the control group (Figure 2B,D,E) (Table 1). MVA and MVBs were found located in the cortical region of the ooplasm, near the plasma membrane (Figure 2C,D); dense lamellar bodies were occasionally detected in the ooplasm (Figure 2C inset). Tubular and vesicular SER elements, sometimes dilated and adjacent to mitochondria, were widespread in the ooplasm (Figure 2C). However, some areas appeared with a lower organelle density with respect to the controls. Below the oolemma, the CGs had an electron-dense and rounded appearance. Overall, a reduced amount of irregularly distributed CGs were present in the L1 group compared to controls (Figure 2B-D) (Table 1). \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Control** & **Lindane 1 \(\mu\)M** & **Lindane 10 \(\mu\)M** & **Lindane 100 \(\mu\)M** \\ \hline \multirow{4}{*}{**Mitochondria**} & Abundant, & Numerous, & Less numerous, & Few, round-to-ovoid \\  & round-to-ovoid & round-to-ovoid & round-to-ovoid & shape, electron-pale \\  & electron-dense & shape, electron-pale & shape, electron-pale & cristae, electron-pale \\  & cristae & cristae & cristae & matrix \\ \hline \multirow{4}{*}{**Cortical Granules**} & Numerous, & Less numerous, & Less numerous, & \\  & uniformly & irregularly & irregularly & irregularly \\  & distributed, round, & distributed, round, & distributed, round, & \\  & electron-dense & electron-dense & electron-dense & \\ \hline \multirow{2}{*}{**Microvilli**} & Numerous, long and & Less numerous, short & & \\  & thin & and thick & Rare, short and thick & Rare, short and thick \\ \hline \multirow{2}{*}{**Zona Pellucida**} & Dense & Thin and dense & Thick and dense & Thick and dense \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Morphological qualitative characterization of MII-stage mouse oocytes after IVM with or without (controls) increasing concentrations of Lindane (1–100 \(\mu\)M). The PVS appeared narrow, with a different distribution of microvilli with respect to what was observed in the control group. Among areas of long and thin microvilli, clusters of thicker and shorter microvilli were often found (Figure 2B,C inset). Extracellular material, exocytic vesicles, and cell fragments were detected in the PVS (Figure 2C). The ZP was thin, dense, and continuous (Figure 2A-C) (Table 1). Figure 2: _The ultrastructure of mouse oocytes in the Lindane 1 \(\mu\)M group._ (**A**) Low-magnification TEM micrographs from MII-stage mouse oocytes. Clustered mitochondria (m), accompanied by SER vesicle and multivesicular aggregates (MVAs) are visible; note the presence of an exocytotic vesicle (arrow) in the perivitelline space (PVS); cpl: cytoplasmic lattice (TEM, bar: 2 \(\upmu\)m). Inset in A: A representative semithin section of a mouse oocyte (LM, Mag: 40\(\times\)). (**B**) A TEM micrograph of the cortical region in MII mouse oocytes. Clusters of mitochondria (m), with electron-dense cristae and matrix, are visible; MVA: multivesicular aggregates; CGs: cortical granules; mv: microvilli; ZP: zona pellucida (TEM, bar: 1 \(\upmu\)m). (**C**) At higher magnification, generally, the cortex has a reduced organelle density.