## 3 Results
### Lindane 100 \(\mu\)M (L100)  
Oocytes exposed to L100 showed significant ultrastructural alterations. By LM, the oocytes were seen to have a round shape, with an intact ZP and the presence of numerous vacuoles (Figure 4A, inset). TEM analysis revealed overall alterations, after comparison to the previous groups and especially to the controls, in the type of organelles present, their distribution, and their quantity (Figure 4A). The numerosity of mitochondria appeared drastically reduced; they were usually roundish or ovoid, with an inhomogeneous pattern distribution in the ooplasm, occasionally associated with vacuoles. Matrix density also appeared less intense (Figure 4A,B). Cytoplasmic lattices were identifiable by fibrillar structures; numerous vesicles attributable to SER dilation were present in the ooplasm, with electron-dense material in the lumen, suggesting ER stress leading to pronounced vacuolization (Figure 4B,C). Evident vacuolization was observed in this group (Figure 4A,B). Spherical vacuoles appeared generally empty, surrounded by a single membrane (Figure 4E). Swollen MVBs were mostly located in the cortex, near the plasma membrane, accompanied sometimes by autophagic-like vesicles (Figure 4C, inset). Dense lamellar bodies, sometimes containing flocculant material, were numerous. They were occasionally close to MVBs, forming organelle clusters. Notably, two dense lamellar bodies enclosed in a marked lumen bordered by a single membrane were frequently observed (Figure 4B, inset). Furthermore, TEM analysis showed structures compatible with mature autophagic vesicles, enclosed by a single membrane and containing membranous material of unrecognizable origin, dispersed in the ooplasm (Figure 4B,C, inset; Figure 4D). Some regions just beneath the oolemma showed organelle-free zones. CGs were almost absent in the cortical region of the oocytes. Although the oolemma was continuous, the microvillar coverage diminished, also with short and thick microvilli (Figure 4C,D). In the PVS, extracellular materials, such as debris, extracellular vesicles, and cell fragments, were found. Notably, dense lamellar bodies were observed in the PVS, likely originating from degenerating, altered microvilli (Figure 4D). The ZP appeared dense. Table 1 reports a summary of the morphological qualitative analysis. Figure 4: _The ultrastructure of mouse oocytes in the Lindane 100 \(\mu\)M group._ (**A**) A representative TEM micrograph of MII-stage mouse oocytes showing reduced organelle density. Few mitochondria (m) are visible, grouped mostly in the center of the oocyte; note the presence of moderate vacuolization. Cortical granules (CGs) are absent. v: vacuole; mv: microvilli; ZP: zona pellucida (TEM, bar: 4 \(\upmu\)m). Inset in A: A semithin section of mouse oocytes, with few organelles and vacuoles (LM, mag: 40\(\times\)). (**B**) A portion of the cortical region with an inhomogeneous organelle distribution. Mitochondria (m) are scarce and isolated, with few evident cristae; CGs are very rare. Dilated SER vesicles are detected; ZP: zona pellucida (TEM, bar: 4 \(\upmu\)m). Inset in B: A high-magnification image of an autophagic vesicle, with undistinguishable material, accompanied by double dense lamellar bodies enclosed in a single membrane (arrow) (TEM, bar: 800 nm). (**C**) A high-magnification image of a cortical area with a higher organelle density; dense lamellar bodies (dlbs), multivesicular bodies (MVBs), large vesicles of SER, and vacuoles (v) are visible. An isolated CG is visible. The microvilli (mv) are thick and irregularly distributed on the oolemma (TEM, bar: 1 \(\upmu\)m). Inset in C: Dilated MVAs in close association with dense lamellar bodies (dlbs), and autophagic-like vesicles (avs), at high magnification (TEM, bar: 400 nm). (**D**) An oocyte cortex showing few cell organelles present. The dense lamellar body (dlb) and MVB are close to autophagic-like vesicles (avs). Dilated SER is present, with unrecognizable electron-dense material in the lumen (arrow).