Hypoxia/reoxygenation-induced myocardial lesions in newborn piglets are related to interindividual variability and not to oxygen concentration

Skeletal Deformities in Osterix-Cre;Tgfbr2f/f Mice May Cause Postnatal Death

Transforming growth factor β (TGFβ) signaling plays an important role in skeletal development. We previously demonstrated that the loss of TGFβ receptor II (Tgfbr2) in Osterix-Cre-expressing mesenchyme results in defects in bones and teeth due to reduced proliferation and differentiation in pre-osteoblasts and pre-odontoblasts. These Osterix-Cre;Tgfbr2^f/f mice typically die within approximately four weeks for unknown reasons. To investigate the cause of death, we performed extensive pathological analysis on Osterix-Cre- (Cre-), Osterix-Cre+;Tgfbr2^f/wt (HET), and Osterix-Cre+;Tgfbr2^f/f (CKO) mice. We also crossed Osterix-Cre mice with the ROSA26mTmG reporter line to identify potential off-target Cre expression. The findings recapitulated published skeletal and tooth abnormalities and revealed previously unreported osteochondral dysplasia throughout both the appendicular and axial skeletons in the CKO mice, including the calvaria. Alterations to the nasal area and teeth suggest a potentially reduced capacity to sense and process food, while off-target Cre expression in the gastrointestinal tract may indicate an inability to absorb nutrients. Additionally, altered nasal passages and unexplained changes in diaphragmatic muscle support the possibility of hypoxia. We conclude that these mice likely died due to a combination of breathing difficulties, malnutrition, and starvation resulting primarily from skeletal deformities that decreased their ability to sense, gather, and process food.

Histological study on the heart ventricle of Egyptian bovines (Bos aegyptiacus)

Background:

The heart ventricles have thicker walls than atrium as they pump blood through blood vessels into all body organs.

Aim:

This study aimed to describe the histological changes of the heart ventricles in Egyptian bovine (Bos aegyptiacus) with special reference to Purkinje fibers.

Methods:

A total of 10 male Egyptian bovines of 1–10 years old were divided into three groups according to age; immature, mature, and adult animals.

Results:

The histological sections from all examined animals’ groups revealed three different layers of the wall of both right and left ventricles; endocardium, myocardium, and epicardium. The endocardium was lined with endothelium and filled with fibrous connective tissue. The endocardium of adult bovine was the thickest. Purkinje fibers appeared of pale cytoplasm with few myofibrils. They were present in the deep layer of the endocardium and in the myocardium. The size of Purkinje fibers and the amount of their myofibrils appeared to be increased with advanced age. Bundles of cardiac muscles were the main constituent of the myocardium. The myocardial bundles were separated by fine connective tissue in immature animals that showed an increased amount in the adult animals. The hypereosinophilic cardiac muscle cells were observed in the ventricles of both mature and adult animals suggesting hypercontraction during rigor mortis. An external layer of the ventricles was the epicardium which consisted of connective tissue and covered with mesothelium.

Conclusion:

Overall, this study revealed histological changes in the wall of the ventricle and Purkinje fibers of Egyptian bovines (B. aegyptiacus) in relation to age. Additionally, the hypereosinophilia of the cardiac muscle cells was recorded in the ventricles of mature and adult bovines.

Prolonged second stage labour and consequences of hypoxia in the neonate: A review

Hypoxia due to dystocia and its repercussions are serious issues concerning the health of neonates. In order to gain a better understanding of the cause and especially the effects and potential long-term disorders, a critical analysis of peer-reviewed literature was made. As shown by many authors, initially the most devastating peripartal cause of ill health in neonates is associated with the serious effects of prolonged and severe acidosis. Other life threatening complications are related to disorders such as meconium aspiration syndrome (MAS), neonatal respiratory distress syndrome, hypoxic ischaemic encephalopathy and necrotising enterocolitis. Despite the astonishing ability of neonates to compensate mixed metabolic and respiratory acidosis with breathing onset directly postpartum, the longer second stage labour takes and the more extreme the acidosis is, the more detrimental its consequences. Lungs are especially vulnerable in this phase of life, aspired meconium can result in increased expression of pro-inflammatory chemotactic cytokines, phospholipase A2 and PGE2 levels , exacerbating inflammatory reactions of lung tissue and exerting a deleterious effect on alveolar cells. Neonates experiencing dystocia could greatly benefit from administration of buffering substances and non-steroidal anti-inflammatory drugs.

Intravenous nanosomes of quercetin improve brain function and hemodynamic instability after severe hypoxia in newborn piglets

Perinatal asphyxia is a major cause of death and neurological morbidity in newborns and oxidative stress is one of the critical mechanisms leading to permanent brain lesions in this pathology. In this context we have chosen quercetin, a natural antioxidant, known also by its brain protective effects to study its potential as a therapy for brain pathology provoked by severe hypoxia in the brain. To overcame the difficulties of quercetin to access the brain, we have developed lecithin/cholesterol/cyclodextrin nanosomes as a safe and protective vehicle. We have applied the nanosomal preparation intravenously to newborn piglets submitted to a severe hypoxic or ischemic/hypoxic episode and followed them for 8 or 72 h, respectively. Either towards the end of 8 h after hypoxia or up to 72 h after, electroencephalographic amplitude records in animals that received the nanosomes improved significantly. Animals receiving quercetin also stabilized blood pressure and recovered spontaneous breathing. In this experimental group mechanical ventilation assistance was withdrawn in the first 24 h while the hypoxic and vehicle groups required more than 24 h of mechanical ventilation. Three days after the hypoxia the suckling and walking capacity in the group that received quercetin recovered significantly compared with the hypoxic groups. Pathological studies did not show significant differences in the brain of newborn piglets treated with nanosomes compared with hypoxic groups. The beneficial effects of quercetin nanosomal preparation after experimental perinatal asphyxia show it as a promising putative treatment for the damaged brain in development.

Reoxygenation of asphyxiated newborn piglets: administration of 100% oxygen causes significantly higher apoptosis in cortical neurons, as compared to 21%

OBJECTIVE

Evaluation of neuronal changes in an animal experimental model of normocapnic hypoxia- reoxygenation.

MATERIALS AND METHODS

Fifty male piglets were the study subjects; normocapnic hypoxia was induced in 40 piglets and ten were sham-operated (controls). When bradycardia and/or severe hypotension occurred, reoxygenation was initiated. Animals were allocated in 4 groups according to the oxygen concentration, they were resuscitated with 18%, 21%, 40%, and 100% O2. Persisting asystole despite 10 minutes of cardiopulmonary resuscitation and return of spontaneous circulation were the endpoints of the experiment. Surviving animals were euthanized and brain cortex samples were collected, hematoxylin and eosin-stained, and examined for apoptotic bodies observing 10 consecutive high power fields.

RESULTS

Histological examination of the control group did not show any pathological change. On the contrary, apoptosis of neurons was found in 87.5% of treated animals. When specimens were examined according to the oxygen concentration used for resuscitation, we found marked intergroup variability; a higher percentage of apoptotic neurons was observed in piglets of group 4 (100% oxygen) compared to the others (P=0.001).

CONCLUSIONS

This preliminary data shows that normocapnic hypoxia and reoxygenation in Landrace/Large White piglets resulted in significant histological changes in the brain cortex. The degree of pathological changes in cortical neurons was significantly associated with the oxygen concentration used for reoxygenation, with a higher percentage of apoptotic neurons being observed in piglets reoxygenated with 100% compared to 18% O2 and to 21% O2.

Hypoxia-induced endothelial damage and microthrombosis in myocardial vessels of newborn landrace/large white piglets

Objective. Evaluating the presence of endothelial changes in myocardial vessels in an experimental model of hypoxia and resuscitation in newborn piglets. Methods. Fifty male Landrace/Large White neonatal piglets were studied: ten of them were allocated in group A (control group, SHAM-operated). In group B (forty animals, experimental group) normocapnic hypoxia was induced by decreasing inspired concentration of O₂ to 6%–8%. When the animals developed bradycardia or severe hypotension, reoxygenation was initiated. The animals of group B were allocated in 4 subgroups of 10, according to the concentration of O₂ they were resuscitated with (groups 1, 2, 3, and 4 received 18%, 21%, 40%, and 100% O₂, resp.). Results. Control group animals did not show any significant endothelial lesions. Contrarily, endothelial lesions were detected in all experimental group cases. When these lesions were analyzed in the different heart zones, no significant difference in their incidence was observed; analyzing the frequency in the animals of the 4 subgroups, only microthrombosis showed a higher frequency in animals in groups 4 and 3. Conclusions. Endothelial damage represents a diffuse pathological feature in the myocardial vessels of piglets subjected to normocapnic hypoxia and resuscitation suggesting a possible role of hyperoxygenation in aggravating endothelial damage.

S100B immunoreactivity: a new marker of hypoxia-related cardiac damage in newborn piglets

OBJECTIVE

The evaluation of the expression of S100B protein, in the swine heart in an experimental model of hypoxia - reoxygenation.

METHODS

Normocapnic hypoxia was induced in 40 male Landrace/Large White neonatal piglets by decreasing the inspired concentration of oxygen to 6-8%. When animals developed bradycardia or severe hypotension, reoxygenation was initiated. Piglets were allocated in four groups of 10, according to the oxygen concentration they were reoxygenated with: Group 1, 2, 3 and 4 resuscitated with 18%, 21%, 40% and 100% oxygen, respectively. The animals were further classified into 4 groups according with the time required for reoxygenation: group A (<15 min); group B (16-60 min); group C (>60 min); group D (deceased animals).

RESULTS

Immunostaining for S100B protein was detected in 14 out of the 40 heart samples (35%), both inside the cytoplasm of cardiomyocytes and as globular deposits in the interstitial spaces. Significant differences were observed among groups 1-4 regarding S100B expression. Reactivity for S100B in cardiac cells was detected in 50%, 50%, 10% and 33% of animals in groups 1 and 2, 3 and 4, respectively. Marked differences were also observed among groups A-D: 75%, 33%, 12% and 22% of the animals in group 1, 2, 3 and 4, respectively, showed reactivity for S100B in the heart.

CONCLUSIONS

Expression of S100B protein occurred in the heart of some of newborn piglets following severe hypoxia. S100B storage in cardiomyocytes correlates with the different oxygen concentration used during reoxygenation, being higher in piglets reoxygenated with 18% and 21%, and lower in animals reoxygenated with 40% oxygen. Intermediate levels of S100B expression were found in 100% O2-treated animals. The finding of a higher percentage of S100B-immunoreactive hearts in piglets with a fast recovery and the detection of a decreased reactivity in animals with a slow and a very slow recovery clearly indicates S100B protein as an early protective factor with a positive prognostic value in asphyxiated newborn piglets.