A new inbred rat strain (TS) with suprainguinal ectopic testes: a model for human cryptorchidism

A mutant rat (TS) has been described with so-called ectopic scrotum, but the published photograph suggested that only the testes were ectopic. We established a colony of these inbred rats as a possible model for cryptorchidism. Five breeding pairs were obtained from the Imamichi Institute, Japan. Immature male offspring (0–21 days) were examined macro- and microscopically to document inguinoscrotal anatomy and gubernacular development. Uni- or bilateral, suprainguinal ectopic testes occurred in 39/46 males. Abnormal gubernacular position was visible microscopically by 3 days and macroscopically by 3–7 days of age. The processus vaginalis, cremaster muscle, and epididymis developed normally. The scrotum was hypoplastic but in the normal position. The TS rat is a new animal model for superficial inguinal ectopic testes, and will be invaluable for elucidating the cause of cryptorchidism and studying the effects of treatment. Our preliminary morphological studies suggest that the gubernaculum develops properly, but appears to migrate in the wrong direction. Offprint requests to: J. M. Hutson     

Low oxygen exposure does not cause pulmonary injury in the newborn rat

BACKGROUND: Two recent studies have suggested that low levels of supplemental inspired oxygen may cause lung injury in preterm infants. AIMS: To assess lung injury of newborn rats exposed to 14 days of low-level variation of oxygen. STUDY DESIGN: Four groups were compared with 12 animals per group and 4 lung sections per animal. These were, a control group raised in room air and three groups raised in levels of inspired oxygen fluctuating around the following mean values: group Lo (mean FiO(2) 0.179), group N (mean FiO(2) 0.213), and group Hi (mean FiO(2) 0.247). The degree of oxygen variability was identical for each group. Lungs were inflated at 20 cm H(2)O, fixed and stained with H and E and Millers Elastin. SUBJECTS: Sprague Dawley albino newborn rats. OUTCOME MEASURES: Random alveolar areas were studied and analysed using imaging software to assess total amount of tissue and elastin, number of secondary septa, and mean linear intercept. RESULTS: There were no significant differences between the three experimental oxygen groups and the control group in terms of lung/body weight ratio and the measured markers of lung development. CONCLUSION: We conclude that low-level oxygen supplementation during early lung development does not affect alveolar development in the newborn rat.     

Bacteria ascend to liver from the bilioenteric conduit after choledochojejunostomy in the cholestatic rat

The high incidence of postoperative cholangitis in children with clinical restoration of bile flow after Roux-Y choledochojejunostomy (RYCJ) assumed the concept of a direct ascending cholangitis caused by pathogens in the intestine, into the intrahepatic bile duct via the porta hepatis. It is also well known that jaundiced animals (patients) are more susceptible to infections of the bile ducts following the procedure of bilioenteric anastomosis. An animal experiment was conducted to compare quantitative bacterial cultures of the choledochojejunostomy area and the liver 24 hours after Escherichia coli (ATCC 25922) or sterile normal saline was injected into the bilioenteric conduit (BEC), following RYCJ in rats with or without the proceeding bile duct ligation. A significant increase of E. coli of the same strain (ATCC 25922), that we injected into the BEC, was proved with pulse-field gel electrophoresis (PFGE) and shown in the liver of the jaundiced rats receiving E. coli (ATCC 25922), compared to that in the nonjaundiced rats with normal saline treatment. It is concluded that bacteria often ascend early to the liver from the BEC following RYCJ. This ascending cholangitis model might be produced for further studies.     

Abnormal lung development in congenital diaphragmatic hernia

The outcomes of patients diagnosed with congenital diaphragmatic hernia (CDH) have recently improved. However, mortality and morbidity remain high, and this is primarily caused by the abnormal lung development resulting in pulmonary hypoplasia and persistent pulmonary hypertension. The pathogenesis of CDH is poorly understood, despite the identification of certain candidate genes disrupting normal diaphragm and lung morphogenesis in animal models of CDH. Defects within the lung mesenchyme and interstitium contribute to disturbed distal lung development. Frequently, a disturbance in the development of the pleuroperitoneal folds (PPFs) leads to the incomplete formation of the diaphragm and subsequent herniation. Most candidate genes identified in animal models have so far revealed relatively few strong associations in human CDH cases. CDH is likely a highly polygenic disease, and future studies will need to reconcile how disturbances in the expression of multiple genes cause the disease. Herein, we summarize the available literature on abnormal lung development associated with CDH.     

Pulmonary oxygen toxicity: Demonstration of abnormal capillary permeability using contrast-enhanced MRI

An animal model of oxygen-induced pulmonary injury was used to assess the potential of contrastenhanced MRI to identify and quantify abnormal capillary permeability. Sprague-Dawley rats were exposed to 100% oxygen for 48 h (n=5) or 60 h (n=9). Axial spinecho MR images were acquired in intubated, anesthetized rats with ECG-gating (TR 400; TE 6) immediately or 7 days after the cessation of oxygen exposure. Polylysine-Gd-DTPA, a macromolecular paramagnetic blood-pool marker, was then given intravenously and the lungs were serially imaged for 42 to 47 min to monitor changes in signal intensity. Pulmonary enhancement was stable in rats exposed to 48 h of oxygen, and in rats exposed to 60 h of oxygen and given 7 days to recover. However, animals exposed to 100% oxygen for 60 h without a period of recovery showed a progressive increase in lung signal intensity for 15 min after polylysine-Gd-DTPA. Pleural effusions also showed progressively increasing signal, reflecting a capillary endothelial leak. A two compartment model describing the kinetics of polylysine-Gd-DTPA in the plasma and interstitial water of the lung was consistent with the dynamic MRI data and allowed estimation of the fractional leak rate (0.235 min^–1) of the contrast agent from plasma to interstitial water. Given the assumption of our kinetic model, MRI following intravenous administration of polylysine-Gd-DTPA can be used to quantitate changes in capillary integrity induced by hyperoxia, including acute capillary leakiness and return to normal endothelial integrity with recovery from hyperoxic injury.This study was supported in part by CA 49786 from the National Cancer Institute. Y.B. was supported in part by Bourse de Recherche Scientifique et Technique du Traite de l'Atlantique Nord (O.T.A.N.)Presented at the 1992 Annual Meeting of the Society for Pediatric Radiology in Orlando, Florida; recipient of the Caffey Award     

Lung development in the streptozotocin rat fetus: antioxidant enzymes and survival in high oxygen

Offspring of experimentally induced diabetic animals demonstrate delays in functional, biochemical, and morphological aspects of lung maturation, dealing mainly with the surfactant system. To investigate whether the development of the lung antioxidant enzyme system would be similarly delayed, and thus compromise their tolerance to high O2 exposure, we did the following: 1) produced the diabetic state in rats with streptozotocin injection 24 h after the onset of pregnancy; 2) examined fetal animals from streptozotocin and control rats at gestational days 19, 20, and 21, and newborn animals at day 22 for whole lung disaturated phosphatidylcholine and total phospholipid and for the three antioxidant enzymes: superoxide dismutase, catalase, glutathione peroxidase; and 3) exposed newborn offspring from streptozotocin-treated and control rats to greater than 95% O2 for several days and their survival, changes in antioxidant enzymes and disaturated phosphatidylcholine and light microscopic findings in response to hyperoxic challenge were compared. Streptozotocin offspring demonstrated essentially no developmental differences in whole lung disaturated phosphatidylcholine, total phospholipid, or antioxidant enzymes activity at the 4 gestational days studied. However, newborns of streptozotocin mothers had consistently superior tolerance to hyperoxic exposure, consisting of increased survival [23/34 (68%) versus 8/26 (31%) in controls, after O2-exposure for 13 days, p less than 0.001], microscopic evidence of reduced inhibition of alveolarization (p less than 0.05), and a trend toward greater antioxidant enzymes response. Thus, in this animal model of experimental diabetes, neither the development of the antioxidant enzymes system nor the development of the surfactant system (as assessed by whole lung disaturated phosphatidylcholine and total phospholipid) appear delayed.(ABSTRACT TRUNCATED AT 250 WORDS)     

Psychosocial predictors of medication adherence in pediatric heart and lung organ transplantation

Few studies have identified the psychosocial characteristics of those children and their families associated with future non‐adherence to immunosuppressive medications following a heart or lung transplant. UNOS data and medical records information were used to test the association between patient and family psychosocial characteristics and medication adherence. Medication adherence outcomes were obtained using the physician assessments in the UNOS data and measured through patient‐level standard deviation scores of immunosuppressive medication blood levels. Complete data were collected on 105 pediatric heart and lung transplant recipients and their families. Multivariate, stepwise analyses were conducted with each adherence outcome. Physician reports of adherence were associated with age of the child at transplantation, parental education, two‐parent families, significant psychosocial problems, and the pretransplant life support status of the child. The resulting model (χ²=28.146, df=5, P<.001) explained approximately 39.5% of the variance in physician reports of adherence (Nagelkerke r²=.395). Blood level standard deviation scores were predicted by age at transplant (F=5.624, P=.02, r²=.05). Results point to the difficulties experienced by children and families when undergoing a heart or lung transplantation. Efforts to develop standardized and evidence‐based pretransplant psychosocial assessments in pediatric populations are suggested, especially those surrounding familial risk factors.     

Elastase and cell matrix interactions in the pathobiology of vascular disease

Ultrastructural observations in lung tissue implicated an endogenous vascular elastase (EVE), in the pathobiology of pulmonary vascular disease. In experimental rats, increased activity of a 20 kDa serine proteinase related to adipsin precedes the development of sustained pulmonary hypertension and vascular abnormalities. A further increase in activity is related to malignant progression of the disease. A cause and effect relationship was suggested by studies in which elastase inhibitors successfully prevented or retarded progression of pulmonary hypertension. In vitro studies have shown that both serum and endothelial factors induce EVE via tyrosine kinase intracellular signalling. Induction of EVE can release basic fibroblast growth factor from the extracellular matrix in an active form stimulating smooth muscle cell proliferation. Elastase activity was also observed in the process of smooth muscle cell migration and neointimal formation in coronary arteries following experimental cardiac transplantation. An immune/inflammatory response is observed with increased production of cytokines, tumor necrosis factor-α and interleukin (IL)-1β, reciprocally up-regulating production of fibronectin, a glycoprotein which mediated smooth muscle cell migration. The action of IL-1β in inducing fibronectin is facilitated by the production of elastin peptides generated by increased activity of an elastase in the coronary arteries. Our studies suggest that ligation of the elastin binding protein by elastin peptides unmasks IL-1 receptors. Fibronectin also stimulates transendothelial migration of lymphocytes which perpetuates the inflammatory response leading to neointimal formation in this model. Masking integrins on T cells with a decoy synthetic CS-1 (fibronectin) peptide largely prevented transendothelial migration and coronary neointimal formation following cardiac transplant.     

Timing of surfactant administration determines its physiologic response in a rabbit model of airway lavage

Surfactant response depends on timing of surfactant administration in infants with respiratory distress syndrome (RDS). We performed lung function studies in an animal model to describe the underlying differences in response related to gas exchange, lung volume and lung mechanics comparing early and late surfactant administration protocols. Young New Zealand rabbits were made surfactant deficient by repeated airway lavage with warm saline until the a/A O(2) ratio decreased to 相似文献   

维生素D缺乏与新生儿肺发育

维生素D对新生儿肺发育有重要作用。目前研究多采用美国AAP和IOM的标准定义维生素D不足(血清25-OH-D<50 nmol/L),国内研究显示新生儿维生素D缺乏的比例较高。动物实验显示1,25(OH)2D3通过影响肺泡数量、肺泡隔厚度、气道阻力、肺容量以及免疫细胞聚集,从而影响肺发育。人群研究提示维生素D缺乏新生儿需要辅助通气、呼吸窘迫综合征的比例较高,需氧时间更长。     

Physiological consequences of intrauterine insults

Fetal lung development occurs as a complicated series of interactions between the different cell types in the lung in response to different growth factors and hormones. At birth, the human lung is in the stage of alveolar development in which the gas exchange units (alveoli) are being actively formed. The alveolar growth continues into postnatal life. Different intrauterine insults perturb this sequence of lung development in different ways. The ultimate result of aberrant lung development depends on the type of intrauterine insult, the severity, the duration of the insult and the developmental stage at which the insult occurs. This review article focuses on the common intrauterine insults encountered in clinical practice, such as infections, disorders of amniotic fluid volume, nutrition and maternal smoking. The information derived from clinical studies is juxtaposed with data from animal experiments to discuss the physiological consequences of intrauterine insults on fetal lung growth.     

Prediction of outcome from the chest radiograph appearance on day 7 of very prematurely born infants

Our aim was to determine whether the chest radiograph appearance at 7 days predicted chronic lung disease development (oxygen dependency at 36 weeks post-menstrual age) or death before discharge and if it was a better predictor than readily available clinical data. Two consecutive studies were performed. In both, chest radiographs taken at 7 days for clinical purposes were assessed using a scoring system for the presence of fibrosis/interstitial shadows, cystic elements and hyperinflation and data were collected regarding gestational age, birth weight, use of antenatal steroids and post-natal surfactant and requirement for ventilation at 7 days. Oxygenation indices were calculated in the first study (study A) at 120 h and in the second (study B) at 168 h. In study A, there were 59 infants with a median gestational age of 26 weeks (range 24 to 28 weeks) and in study B, 40 infants with a median gestational age of 27 weeks (range 25–31 weeks). In both studies, infants who developed chronic lung disease had a significantly higher total chest radiograph score, with a higher score for fibrosis/interstitial shadowing than the rest of the cohort. Infants who died before discharge differed significantly from the rest with regard to significantly higher scores for cysts. In both studies, the areas under the receiver operator characteristic curves with regard to prediction of chronic lung disease were higher for the total chest radiograph score compared to those for readily available clinical data. Conclusion:in infants who require a chest radiograph for clinical purposes at 7 days, the chest radiograph appearance can facilitate prediction of outcome of infants born very prematurely.Abbreviations CLD chronic lung disease - CXR chest radiograph - CMV conventional mechanical ventilation - HFO high frequency oscillation - KCH Kings College Hospital - OI oxygenation index - PIE pulmonary intestinal emphysema - PMA post-menstrual age - ROC receiver operator characteristic curves - UKOS United Kingdom Oscillation Study     

Time Course of Myocardial Amiodarone Uptake in the Piglet Heart Using a Chronic Animal Model

This investigation sought to study single dose pharmacokinetics of amiodarone in a chronic animal model. We developed a new chronic animal model that allows serial direct access to the heart of the immature piglet via an implanted acrylic thoracic window. Following instrumentation and 72-hour recovery, amiodarone (5 mg/kg) was administered as a single intravenous bolus in immature piglets. Timed paired serum samples and myocardial biopsies for amiodarone level were obtained prior to, and up to 72 hours following, amiodarone administration. Peak concentrations of amiodarone in both serum (3.60 ± 1.02 μg/ml) and tissue (84.2 ± 6.50 ng/mg) occurred within 5 minutes of drug administration. As reported by others, this study demonstrated that the volume of distribution (V_D) of amiodarone was large (33.31 ± 35.21 L/kg), and the clearance (Cl) was low (13.6 ± 4.4 ml/min/kg). Marked prolongation of both the serum t _1/2 (29.98 ± 29.26 hours) and the myocardial t _1/2 (29.20 ± 29.49 hours) were noted as well. The early, rapid myocardial peak of amiodarone in the immature myocardium corresponds with recent clinical observations of onset of antiarrhythmic efficacy 5 to 10 minutes following intravenous amiodarone administration in young children.     

Congenital diaphragmatic hernia: the impact of embryological studies

In recent years, a substantial research effort within the specialty of pediatric surgery has been devoted to improving our knowledge of the natural history and pathophysiology of congenital diaphragmatic hernias (CDH) and pulmonary hypoplasia (PH). However, the embryological background has remained elusive because certain events of normal diaphragmatic development were still unclear and appropriate animal models were lacking. Most authors assume that delayed or inhibited closure of the diaphragm will result in a diaphragmatic defect that is wide enough to allow herniation of the gut into the fetal thoracic cavity. However, we feel that this assumption is not based on appropriate embryological observations. To clarify whether it was correct, we restudied the morphology of pleuroperitoneal openings in normal rat embryos. Shortly before, a model for CDH and PH had been established in rats using nitrofen (2,4-di-chloro-phenyl-p-nitrophenyl ether) as teratogen. We used this model in an attempt to answer the following questions: (1) When does the diaphragmatic defect appear? (2) Are the pleuroperitoneal canals the precursors of the diaphragmatic defect? (3) Why is the lung hypoplastic in babies and infants with CDH? In our study we made following observations: (1) The typical findings of CDH and PH cannot be explained by inhibited closure of the pleuroperitoneal “canals”. In normal development, the pleuroperitoneal openings are always too small to allow herniation of gut into the thoracic cavity. (2) The maldevelopment of the diaphragm starts rather early in the embryonic period (5th week). The lungs of CDH rats are significantly smaller than those of control rats at the end of the embryonic period (8th week). (3) The maldevelopment of the lungs in rats with CDH is “secondary” to the defect of the diaphragm. (4) The defect of the lungs is “structural” rather than “functional”. Complete spontaneous correction of these lung defects is unlikely even after fetal intervention. (5) The “fetal lamb model” does not completely mimic the full picture of CDH, because the onset of the defect lies clearly in the fetal period. We believe that our rat model is better. It is especially useful for describing the abnormal embryology of this lesion.     

Continuous positive airway pressure and surfactant; combined data from animal experiments and clinical trials

Bronchopulmonary dysplasia (BPD) remains a cause of considerable morbidity for the preterm infant. Ventilation is a primary risk factor. This review discusses the rationale for combining surfactant and nasal continuous positive airway pressure (nCPAP) using evidence from both clinical and animal studies. The early application of nCPAP with or without surfactant is safe and reduces the need for mechanical ventilation. Combining nCPAP with surfactant results in dramatically improved lung structure in a primate model of BPD, but still does not allow for normal alveolarization. BPD is a complex condition resulting from the interaction of many factors. Experimental evaluation of nCPAP in appropriate animal models will allow new strategies for prevention and treatment of BPD to be developed.     

Partial liquid ventilation with low-dose perfluorochemical and high-frequency oscillation improves oxygenation and lung compliance in a rabbit model of surfactant depletion

BACKGROUND: Partial liquid ventilation (PLV) with perfluorochemical (PFC) has been advocated as a new therapy for acute respiratory distress syndrome in both clinical and animal studies, meconium aspiration syndrome, and RDS. PFC is referred to as liquid PEEP because it gets distributed to the most gravity-dependent regions of the lung due to its density. High-frequency oscillation (HFO) has been shown to prevent both acute and chronic lung injury in the management of very low birth weight infants with RDS, with gentle ventilation approach. Specifically, HFO with aggressive and adequate lung volume recruitment has been shown to reduce the incidence of chronic lung disease in very low birth weight infants. We hypothesized that PLV along with HFO might be effective in ARDS in an adult rabbit model. OBJECTIVES: To examine the efficiency of low-dose PLV with with HFO on pulmonary gas exchange and lung compliance in a surfactant-depleted rabbit model. METHODS: After induction of severe lung injury by repeated saline lung lavage, 19 adult white Japanese rabbits were randomized into two groups that received PLV with HFO (n=9) or HFO gas ventilation (n=10). Physiological and blood gas data were compared between the two groups by analysis of variance. RESULTS: The HFO-PLV group showed improved total lung compliance with maintenance of significantly lower mean airway pressure as compared with the HFO-GAS group so as to keep SpO2>90%. CONCLUSIONS: The addition of a low dose of PFC with HFO was effective in achieving adequate oxygenation, with a reduction in further lung injury in neonates.     

Interleukin 8 and granulocyte elastase α1 proteinase inhibitor complex in the tracheobronchial aspirate of infants with chronic lung disease following respiratory distress syndrome

In order to elucidate the role of interleukin 8 (IL-8) on the development of chronic lung disease (CLD) in neonates following an episode of respiratory distress syndrome (RDS), serial and simultaneous measurements of the concentration of IL-8 and granulocyte elastase α₁ proteinase inhibitor complex (E-α₁ PI) in the tracheobronchial aspirate of very low birthweight infants with RDS were conducted. The concentration of IL-8 and E-α₁ PI in infants with CLD was low in the first 48 h of life, but dramatically increased after 48 h. The concentration of IL-8 between 48 h of life and day 5 was significantly correlated to the fraction of inspired oxygen concentration (F₁o₂) within 48 h of age, but not to the mean airway pressure. Interleukin 8 seemed to stimulate neutrophils to release granulocyte elastase which, in turn, caused lung tissue injury, resulting in the development of CLD. It is suggested that high F₁o₂ is an important factor causing IL-8 production in the lung.     

Nitrofen interferes with trophoblastic expression of retinol-binding protein and transthyretin during lung morphogenesis in the nitrofen-induced congenital diaphragmatic hernia model

Background  

Retinoids play a key role in lung development. Retinoid signaling pathway has been shown to be disrupted in the nitrofen model of congenital diaphragmatic hernia (CDH) but the exact mechanism is not clearly understood. Retinol-binding protein (RBP) and transthyretin (TTR) are transport proteins for delivery of retinol to the tissues via circulation. Previous studies have shown that pulmonary retinol levels are decreased during lung morphogenesis in the nitrofen CDH model. In human newborns with CDH, both retinol and RBP levels are decreased. It has been reported that maternal RBP does not cross the placenta and the fetus produces its own RBP by trophoblast. RBP and TTR synthesized in the fetus are essential for retinol transport to the developing organs including lung morphogenesis. We hypothesized that nitrofen interferes with the trophoblastic expression of RBP and TTR during lung morphogenesis and designed this study to examine the trophoblastic expression of RBP and TTR, and the total level of RBP and TTR in the lung in the nitrofen model of CDH.     

Site-specific induction of lymphatic malformations in a rat model for image-guided therapy

Background Lymphatic malformation is a common benign mass in children and adults and is representative of a derangement in lymphangiogenesis. These lesions have high recurrence rates and significant morbidity associated with surgery. Several sclerotherapy regimens have been developed clinically to treat lymphatic malformations; however, an animal model has not been developed that is adequate to test the efficacy of image-guided therapeutic interventions. Objective To develop an animal model suitable for evaluation of percutaneous treatments of lymphatic malformations. Materials and methods Male Harlan Sprague-Dawley rats (n = 9) received two US-guided injections of Incomplete Freund’s Adjuvant (IFA) over a 2-week period. All nine rats were injected twice into the peritoneum (IP); a subgroup (n = 3) received additional injections into the neck. Three animals that received IP injections of saline were used as controls. The injection sites were monitored for the development of lesions by high-resolution ultrasonography at 2-week intervals for 100 days. High-resolution (4.7 Tesla) magnetic resonance imaging was then performed on two animals noted to have developed masses. The rats were sacrificed and histologic examination of the identified lesions was performed, including immunohistochemical staining for vascular (CD31) and lymphatic (Flt-4 and Prox-1) endothelium. Results All animals injected with IFA developed cystic lesions. The three animals injected at dual sites were noted to have both microcystic and macrocystic malformations in the neck and microcystic plaque-like lesions in the peritoneum. The macrocystic malformations (≥5 mm) in the neck were detected by ultrasonography and grossly later during necropsy. Histopathologic analysis revealed the cystic spaces to be lined by lymphatic endothelium supported by a connective tissue stroma. Control animals did not exhibit detectable lesions with either ultrasonography or necropsy. Conclusion This model represents a promising tool for translational development of image-guided interventions for lymphatic malformations. It may also serve as a model for the study of lymphangiogenesis and the development of anti-lymphangiogenic therapies.     

Prenatal administration of retinoic acid upregulates connective tissue growth factor in the nitrofen CDH model

Purpose  

Recent studies have suggested that retinoids may be involved in the molecular mechanisms of pulmonary hypoplasia (PH) in congenital diaphragmatic hernia (CDH). Connective tissue growth factor (CTGF) plays a key role in foetal lung development and remodelling during later gestation. CTGF knockout mice exhibit PH with similar characteristics to the human and nitrofen-induced PH. Prenatal administration of retinoic acid (RA) has been shown to stimulate alveologenesis in nitrofen-induced PH. In vitro studies have revealed that RA can induce CTGF gene expression. We hypothesized that pulmonary gene expression of CTGF is downregulated during the later stages of lung development, and that prenatal administration of RA upregulates CTGF in the nitrofen CDH model.