Intermittent Short-Duration Re-oxygenation Attenuates Cardiac Changes in Response to Hypoxia: Histological, Ultrastructural and Oxidant/Antioxidant Parameters

Figures

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  FIGURE 1. The effect of intermittent re-oxygenation on oxidative stress biomarkers in rats. Heart homogenates levels of MDA (A) and SOD (B) were assessed in different groups of rats at the end of the experiment; Normoxia group, hypoxia group, and re-oxygenation group. Results were represented as mean (±SD); n = 6 for each group. Experiments were performed in triplicate. *p < 0.05 versus normoxia, **p < 0.05 versus hypoxia.

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  FIGURE 2. The effect of intermittent re-oxygenation on proinflammatory biomarkers in rats. TNF-a (A) and IL-6 (B) levels in the heart tissue were assessed at the end of the experiment in the different groups of rats; Normoxia group, hypoxia group, and re-oxygenation group. Results represent the mean (±SD); n = 6 for each group. Experiments were performed in triplicate. *p < 0.05 versus normoxia, **p < 0.05 versus hypoxia.

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  FIGURE 3. Histopathological evaluation from all groups of rats (400X). (A) Contol (Normoxia) group: The rat’s cardiac muscle structure shows centrally located nuclei (N), branching cytoplasmic network with striations (S), and delicate connective tissue between the muscle fibres (arrow) with few capillaries (C). (B) Hypoxia group: Rats in the hypoxia showed more apparent alterations, where most of the cardiac muscle fibre striations (S) have disorganization and fragmentation, increment of nuclear peripheralization and pyknosis (N) together with sarcoplasmic vacuolation. Increased interstitial space (arrow) with congestion (V) and dilation of the blood capillaries (C) are displayed. (C) Hypoxia group: The rats of this group showed disruption of cardiac myocyte, degeneration of muscle fibres (S), pyknotic nuclei (N), congestion and dilation of the myocardial capillaries (C) are displayed. A marked increase of the interstitial space (arrow) is also noticed. (D) Intermittent short-duration reoxygenated group: The rat’s cardiac muscle after recovery showed the approximately normal histological appearance of cardiac myocyte striations (S), minimal interstitial space (arrow), decreased congestion…

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  FIGURE 4. Transmission electron micrographs obtained from all groups (100,00X). (A) Normoxia group rats showed a normal myocardial striations architecture with well preserved mitochondrial (m) integrity. Dense cytoplasm filled with healthy myofibrils and its striated pattern with clear bands (Z and H), intact nucleus with a normal distribution of chromatin (Chr), and nuclear envelope (ne). (B) Hypoxia group rats showing slightly disrupted myofibrils with minimal disarrangement of muscle bands (Z and H) and swollen mitochondria (m) with disoriented and dissolution cristae, flocculent density deposition and breaks in the outer mitochondrial membrane. Disassembly of the nuclear envelope (ne), clumped chromatin (Chr) randomly dispersed in the nuclei (N), and a few vacuoles (V) are also observed. (C) Hypoxia group rats showed marked myofibrils disruption with disarrangement of muscle bands (Z and H) and swollen mitochondria (m) with disoriented and dissolute cristae, flocculent density deposition, and breaks in the outer mitochondrial membrane. Disassembly of the nuclear envelope (ne), clumped heterochromatin randomly dispersed in the disrupted nuclei (N), few vacuoles (V) and marked spaces…

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  FIGURE 5. Transmission electron micrographs of the rats attained from all groups of rats (Intercalated disc with fascia adherent) (100,00X). (A) Normoxia group rats showed normal cardiocyte structure with dense cytoplasm comprising healthy myofibrils and its striated pattern with clear bands (Z and H) and intact mitochondria (m). Intercalated disc with characteristic fascia adherent (FA), desmosomes (D) and gap junction (N) are also seen. (B) Hypoxia group rats showed disrupted cytoplasm of myofibrils with the fragmentation of muscle bands (Z and H) and pleomorphic mitochondria (m). Damaged intercalated discs with fascia adherent (FA), desmosomes (D) and gap junction (N) are also seen. (C) Hypoxia group rats showed marked degeneration of the cytoplasm of myofibrils with the fragmentation of muscle bands (Z and H) and pleomorphic mitochondria (m). Damaged intercalated discs with fascia adherent (FA), desmosomes (D) and gap junction (N) are also seen. (D) Intermittent short-duration reoxygenated group rats: showing normal myofibrils with a striated pattern of clear bands (Z and H), mitochondria (m) and intercalated discs with fascia adherent (FA), desmosomes (D) and gap junction (N) are also…

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  FIGURE 6. Transmission electron micrographs of the rats obtained from all groups (300,00X). (A) Normoxia group rats showing normal cardiocyte structure with dense cytoplasm filled with normal myofibrils with striated pattern and clear bands (Z and H) and evenly distributed mitochondria (m) as chain-like structures closely related to the length of sarcomeres. Mitochondria are usually oval, containing outer and inner membrane (mm) transversally oriented cristae (mc) within a moderately electron-dense mitochondrial matrix (mx). (B) Hypoxia group rats showing disruption of contractile elements with multifocal lysis of myofibrils (Z and H) and severe mitochondrial (m) degenerative alterations compared with the normal ultrastructure in control rats. The mitochondrial inner membrane (mm) is destroyed into the distended matrix (mx) and the cristae (mc) fragmentation or central effacement (*). (C) Intermittent short-duration reoxygenated group rats: showing almost normal cardiac muscle fibres with a striated pattern of clear bands (Z and H). Mitochondria (m) retained their intact cristae (mc) and dense matrix (mx), while few appeared swollen (*) with an irregular shape, size, and partially…