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The present study was done to investigate Slit2 expression in neural stem cell differentiation and maturation and its inhibitory effect on axon growth. Neural stem cells were extracted from newborn SD rats. After neurospheres were formed, immunofluorescence staining was performed to observe cell morphology and to identify cell types after differentiation and maturation of NSCs. NSCs were then induced by culturing into a differentiation culture medium. Western blotting was performed to detect Slit2 protein expressions. Slit2 siRNA was prepared and transfected into NSCs. Transwell chamber assay was used to observe cell migration and CCK-8 assay was performed to detect cell proliferation. Our results show that NSCs have the potential to differentiate into a variety of neural cells and Slit2 expression is significantly increased during differentiation of NSCs. Slit2 siRNA transfection efficiency showed that Slit2 siRNA was successfully transfected into NSCs, and Slit2 siRNA transfection inhibited NSCs migration and proliferation together with axonal growth of NSCs. Therefore, we conclude that Slit2 can promote NSCs migration and proliferation, and can inhibit nerve cell axon growth, which is favorable for neural network reconstruction.

BackgroundAt birth, the release of surfactant from alveolar type II cells (ATIIs) is stimulated by increased activity of the beta-adrenergic/adenylyl cyclase/cyclic 3′-5′ adenosine monophosphate-signaling cascade. Atrial natriuretic peptide (ANP) stimulates surfactant secretion through natriuretic peptide receptor A (NPR-A). ANP inhibits adenylyl cyclase activity through its binding to NPR-C. We wished to further understand the role of the NPR-C in perinatal transition.MethodsWe studied ATII expression of NPR-C in fetal and newborn sheep using immunohistochemistry, and surfactant secretion in isolated ATIIs by measuring 3[H] choline release into the media.ResultsANP induced surfactant secretion, and, at higher doses, it inhibits the stimulatory effect of the secretagogue terbutaline. ATII NPR-C expression decreased significantly after birth. Premature delivery also markedly decreased ANP and NPR-C in ATIIs. Co-incubation of terbutaline (10−4M) with ANP (10−6M) significantly decreased 3[H] choline release from isolated newborn ATII cells when compared with terbutaline alone; this inhibitory effect was mimicked by the specific NPR-C agonist, C-ANP (10−10M).ConclusionANP may act as an important epithelial-derived inhibitor of surfactant release in the fetal lung, and downregulation of ANP and NPR-C following birth may sensitize ATII cells to the effects of circulating catecholamines, thus facilitating surfactant secretion.

The optimal oxygen concentration for the resuscitation of term infants remains controversial. We studied the effects of 21 versus 100% oxygen immediately after birth, and also exposure for 24 h to 100% oxygen, on oxidant lung injury and lung antioxidant enzyme (AOE) activities in term newborn lambs. Lambs at 139 d gestation were delivered and ventilated with 21% (RAR) or 100% (OXR) for 30 min. A third group of newborn lambs were ventilated with 100% O2for 24 h (OX24). Oxidized glutathione levels in whole blood were significantly different among the groups with lower values in the RAR group, and these values correlated highly with partial pressure of arterial oxygen (Pao2). The reduced to oxidized glutathione ratio was significantly different among the groups, the ratio decreasing with increasing oxygen exposure. Lipid hydroperoxide (LPO) activity was significantly higher in the OXR and OX24 groups. AOE activity was higher in the whole lung and in red cell lysate in the OX24 group. Increased myeloperoxidase (MPO) activity, percent neutrophils, and proteins in lung lavage suggested inflammation in the OX24 group after maximal oxygen exposure. We conclude that even relatively brief exposure of the lung to 100% oxygen increases systemic oxidative stress and lung oxidant injury in ventilated term newborn lambs.

The optimal oxygen concentration for the resuscitation of term infants remains controversial. We studied the effects of 21 versus100% oxygen immediately after birth, and also exposure for 24 h to 100% oxygen, on oxidant lung injury and lung antioxidant enzyme (AOE) activities in term newborn lambs. Lambs at 139 d gestation were delivered and ventilated with 21% (RAR) or 100% (OXR) for 30 min. A third group of newborn lambs were ventilated with 100% O2for 24 h (OX24). Oxidized glutathione levels in whole blood were significantly different among the groups with lower values in the RAR group, and these values correlated highly with partial pressure of arterial oxygen (Pao2). The reduced to oxidized glutathione ratio was significantly different among the groups, the ratio decreasing with increasing oxygen exposure. Lipid hydroperoxide (LPO) activity was significantly higher in the OXR and OX24 groups. AOE activity was higher in the whole lung and in red cell lysate in the OX24 group. Increased myeloperoxidase (MPO) activity, percent neutrophils, and proteins in lung lavage suggested inflammation in the OX24 group after maximal oxygen exposure. We conclude that even relatively brief exposure of the lung to 100% oxygen increases systemic oxidative stress and lung oxidant injury in ventilated term newborn lambs.

Prostacyclin (PGI2) stimulates adenyl cyclase to synthesize cAMP within the vascular smooth muscle resulting in vasodilatation. Milrinone inhibits cAMP clearance by phosphodiesterase type III. We studied the dose response of pulmonary and systemic hemodynamics to intratracheal (IT) PGI2in newborn lambs with pulmonary hypertension (PH) and whether intravenous milrinone potentiate these effects. IT-PGI2at varying doses was administered to lambs with PH induced by prenatal ductal ligation. IT-PGI2doses were repeated in the presence of intravenous milrinone (bolus—100 µg/kg followed by infusion at 1 µg/kg/min). Increasing doses of IT-PGI2significantly decreased mean pulmonary arterial pressures (PAP) and pulmonary vascular resistance (PVR) and increased pulmonary blood flow (PBF). Intravenous milrinone by itself produced a significant reduction in PVR and a significant increase in PBF. Intravenous milrinone significantly shortened the onset, prolonged the duration and degree of pulmonary vasodilation produced by PGI2. We conclude that intravenous milrinone potentiates the pulmonary vasodilator effects of PGI2at lower doses.

Prostacyclin (PGI2) stimulates adenyl cyclase to synthesize cAMP within the vascular smooth muscle resulting in vasodilatation. Milrinone inhibits cAMP clearance by phosphodiesterase type III. We studied the dose response of pulmonary and systemic hemodynamics to intratracheal (IT) PGI2in newborn lambs with pulmonary hypertension (PH) and whether intravenous milrinone potentiate these effects. IT-PGI2at varying doses was administered to lambs with PH induced by prenatal ductal ligation. IT-PGI2doses were repeated in the presence of intravenous milrinone (bolus—100 g/kg followed by infusion at 1 g/kg/min). Increasing doses of IT-PGI2significantly decreased mean pulmonary arterial pressures (PAP) and pulmonary vascular resistance (PVR) and increased pulmonary blood flow (PBF). Intravenous milrinone by itself produced a significant reduction in PVR and a significant increase in PBF. Intravenous milrinone significantly shortened the onset, prolonged the duration and degree of pulmonary vasodilation produced by PGI2. We conclude that intravenous milrinone potentiates the pulmonary vasodilator effects of PGI2at lower doses.

The aim of the present study was to assess with ultrasound the ductus venosus flow velocity in newborn lambs with increasing pulmonary artery pressures and to evaluate whether this is a useful method to detect elevated pulmonary artery pressure. The ductus venosus flow velocity was studied with pulsed-wave Doppler echocardiography in nine newborn lambs =30 h old. The lambs were anesthetized, mechanically ventilated, and instrumented to measure mean airway pressure and pulmonary artery and arterial blood pressures. A vascular occluder was placed around the main pulmonary artery. With mean pressures ranging from 20 to 50 mm Hg in the pulmonary artery, the ductus venosus flow velocity was examined. In seven lambs, the mean portal pressure and central venous pressure were also measured. With a stepwise increase in the pulmonary artery pressure, the minimum ductus venosus flow velocity during atrial systole decreased to a reversed flow, and the duration of this reversed flow component increased. The systolic forward peak flow velocity signal also gradually decreased. No changes were detected in the mean central venous or in the portal pressure with increasing pulmonary artery pressure or changes in ductus venosus flow. The flow velocity in the ductus venosus, which is higher than in other precordial veins, shows a reduction and even reversal of the nadir and an increase of the duration of reversed flow during atrial systole as a response to increased pulmonary artery pressure. Thus, Doppler ultrasound of the ductus venosus flow velocity may be a useful noninvasive diagnostic supplement to detect pulmonary hypertension of the newborn.

The aim of the present study was to assess with ultrasound the ductus venosus flow velocity in newborn lambs with increasing pulmonary artery pressures and to evaluate whether this is a useful method to detect elevated pulmonary artery pressure. The ductus venosus flow velocity was studied with pulsed-wave Doppler echocardiography in nine newborn lambs ≤30 h old. The lambs were anesthetized, mechanically ventilated, and instrumented to measure mean airway pressure and pulmonary artery and arterial blood pressures. A vascular occluder was placed around the main pulmonary artery. With mean pressures ranging from 20 to 50 mm Hg in the pulmonary artery, the ductus venosus flow velocity was examined. In seven lambs, the mean portal pressure and central venous pressure were also measured. With a stepwise increase in the pulmonary artery pressure, the minimum ductus venosus flow velocity during atrial systole decreased to a reversed flow, and the duration of this reversed flow component increased. The systolic forward peak flow velocity signal also gradually decreased. No changes were detected in the mean central venous or in the portal pressure with increasing pulmonary artery pressure or changes in ductus venosus flow. The flow velocity in the ductus venosus, which is higher than in other precordial veins, shows a reduction and even reversal of the nadir and an increase of the duration of reversed flow during atrial systole as a response to increased pulmonary artery pressure. Thus, Doppler ultrasound of the ductus venosus flow velocity may be a useful noninvasive diagnostic supplement to detect pulmonary hypertension of the newborn.