Primary culture of atrioventricular nodal cells in newborn rabbit / 西安交通大学学报(医学版)

polyhornal and round cells.Conclusion The AVN of rabbit was made up by different cells.The polyhornal and round cells may be pacemaker cells;the spindle cells might be transitional cells,and the triangle cells may be myocardial cells.

Effect of Maturation on Endothelium-Dependent Relaxation in Pulmonary Arteries of the Newborn Rabbit

PURPOSE: This study was done to determine whether maturatin alters endothelium- dependent responses in pulmonary arteries. METHODS: Vascular rings of pulmonary arteries, with and without endothelium, taken from rabbits of 3 and 30 days of age were suspended in organ chambers filled with Krebs-Henseleit solution, bubbled with 95% O2-5% CO2 and maintained at 37degrees C. Immediately after mounting, the rings were stretched progressively until a maximal response to KCl was achieved. The rings were incubated with indomethacin and allowed to equilibrate before contraction and relaxation study. RESULTS: When the endothelium was intact in arterial rings from 3-day-old rabbits, acetylcholine (ACH) (10-6 M) relaxed preconstricted rings with histamine (5x10-6 M) (98.1 4.7% relaxation, mean SD). In rings without endothelium, KCl (10-2 to 9x10-2 M) and histamine (5x10-8 to 10-5 M) caused concentration-dependent contractions. When normalized to maximal contractions achieved to each agonist, the concentration-effect curves to KCl and histamine in rings without endothelium were similar to both ages. Rings with endothelium showed a progressive shift to the right of the concentration- effect curve to histamine. Relaxation to sodium nitroprusside were unaffected by age. In preconstricted ring, ACH (10-8 to 5x10-6 M) caused relaxations in rings with endothelium which were greater at 30-day compared to 3-day-old rabbits. CONCLUSION: These study demonstrates that endothelium-dependent relaxation increase with age, possibly due to changes in the release and/or effect of endothelium-derived relaxing factor (EDRF or nitric oxide) from pulmonary arteries during the neonatal period.

The Effect of Erythromycin on Gastric Antrum and Low Esophageal Sphincter in the Newborn Rabbit

PURPOSE: We studied smooth muscle strips from rabbit gastric antrum and low esophageal sphincter (LES) to explore the difference between newborn and adult rabbit on erythromycin (EM)- induced contractions. Another aim of this study was to determine the mechanism of LES contractile activities induced by erythromycin (EM). METHODS: Muscle strips prepared from newborn and adult rabbits were stimulated with agonists such as KCl, motilin and EM, and the isometric tensions were measured. To study the underlying mechanism of EM-stimulated contraction of LES, the receptor antagonsts, including tetrodotoxin, hexamethonium, atropine, propranolol and phentholamine, were used. A high concentration of motilin (1 micrometer) was employed to provoke tachyphylaxis. RESULTS: Antral smooth muscle and LES from newborn rabbits developed less active force than those from adult rabbits when stimulated with KCl, motilin and erythromycin, however, the effective concentrations (EC50s) were similar in both age groups. Antral smooth muscle strips showed both tonic and phasic contractions but LES muscle strips showed only tonic contractions. These findings were observed in both newborn and adult rabbits. The contraction force of antral smooth muscle strips in response to agonists was greater than that of LES. The contractile response of LES to repeated motilin or EM administration was markedly decreased. EM- induced contractions of LES were markedly decreased by motilin tachyphylaxis but were unaffected by tetrodotoxin, hexamethonium, atropine or propranolol plus phentolamine. CONCLUSOIN: The data suggest that the contractilities of antrum and LES smooth muscle from newborn rabbit are less than those from adult ones, however, the effective concentratons of EM (EC50) are not different between the two age groups. The results also suggest that erythromycin induces the contraction of rabbit LES via motilin receptor in vitro.

Study on Mechanism of Hyperoxia Through Mechanical Ventilation Induced Lung Injury in Newborn Rabbit / 实用儿科临床杂志

Objective To explore the effect of hyperoxia through mechanical ventilation induced lung injury(VILI) in newborn rabbit.Methods One hundred newborn rabbits aged 1-5 days were randomly divided into 4 groups: with 900 mL/L O2 and mechanical ventilation(MV),group A received high peak inspiratory pressure(HPIP),group B received moderate peak inspiratory pressure(MPIP),group C received low peak inspiratory pressure(LPIP),and group D with no mechanical ventilation with room air.There were 30 rabbits in group A,B,C,10 rabbits in D group.All rabbits were killed at 1,3,6 h after trial respectively.Wet-to-dry weight ratio(W/D) of left lung,and white blood cell(WBC)counts in broncho alveolar lavage fluid(BALF) were measured.The changes of lung histopathology were assessed by hematoxylin-eosin(HE) staining and observed under light microscope.Results Compared with group B and C,the group A demonstrated more pulmonary hemorrhage and pulmonary bullae formation,and the WBC and neutrophils counts in BALF increased and the W/D was higher compared with group B and group C.Meanwhile,alveolar epithelial cellⅡ(AECⅡ) hyperplasy transformed to AECⅠ.In group C,AECⅡswelled and lung tissue edema showed obviously,after 6 hours collagen fibers hyperplasia appeared.Part pulmonary atelectasis was obvious in group C.Conclusions HPIP ventilation can increase lung injury induced by hyperoxia in newborn rabbits,but has minimal effects on MPIP and LPIP ventilation.Pulmonary histopathologic changes participate in the newborn rabbit machine ventilation induced lung injury.