ABSTRACT
Objective To explore the effects of endoplasmic reticulum (ER) stress in the hyperoxia-induced lung injury in premature rats. Methods Forty-eight premature Wistar rats were randomized into two groups 12 hours after birth:hyperoxia group (n=24) inhaled 95%oxygen and control group (n=24) inhaled air. Eight rats were sacriifced in each group on day 1, 3, 7 after the treatment and the left lungs were embedded. The pathological changes in the HE stained sections of lung tissues were observed. The expressions of ER related protein ERp57 and c/EBP homologous protein CHOP were detected by immuno histo-chemistry and the apoptosis of lung cells was detected by TUNEL analysis. Results The typical pathological characteristics of acute lung injury were observed in hyperoxia group. The expressions of ERp57 and CHOP were increased with the exposure time in hyperoxia group, and were signiifcantly higher than in control group (P<0.05). The apoptosis rate of lung cells in hyperoxia group was signiifcantly higher than in control group (P<0.01). There was signiifcant positive correlation between cell apoptosis index and expressions of Erp57 and c/EBP homogeneous protein. Conclusions ER stress initiated apoptosis participates and plays an important role in the process of hyperoxia-induced lung injury in premature rats.
ABSTRACT
Objective To discover the influence of thiomersalate exposure on the behavior and humoral immunity of premature rats.Methods According to common thiomersalate dose of vaccine used in human,the surface conversation method was used to change the dose to 1,2,3,4 times for rats(32.8,65.6,98.4 and 131.2 μg/kg),and the thiomersalate was separately injected to the gluteus maximus of premature rats respectively,which were delivered on the 20th day of gestation by cesarean for the injection on day 1 (premature).Simultaneously,saline was injected to the control group.On day 44 to 48 after injection,the Morris water maze test was used to evaluate the spatial learning and memory abilities of rats and on the post-injection day 49,immunoglobulin content in rat blood and cerebrospinal fluid was measured.Results The spatial learning abilities of rats in 131.2 μg/kg group and the memory abilities in 65.6 μg/kg,98.4 μg/kg and 131.2 μg/kg group were significantly weaker than those in 9 g/L saline group(all P ＜0.001).The immunoglobulin content in blood and cerebrospinal fluid changed in different groups exposed to thiomersalate.The levels of IgG,IgA,IgE,IgM in 98.4 μg/kg group and 131.2 μg/kg group rose significantly higher than those in 9 g/L saline group(all P ＜ 0.01).Analysis of rectilinear correlation between the immunoglobulin and learning abilities of rats revealed that IgG,IgA,IgE levels in the blood were correlated with the spatial learning abilities (r =0.36,0.47,0.50,all P ＜ 0.05) and the levels of IgG,IgA,IgE,IgM in blood were rectilinear correlated with the memory abilities of rats (r =-0.39,-0.43,-0.49,-0.38,all P ＜ 0.05).In rats'cerebrospinal fluid,IgG,IgA,IgE,IgM levels were rectilinear correlative with both the spatial learning and memory abilities (r =0.48,0.59,0.54,0.41,all P＜0.05;r=-0.39,-0.61,-0.57,-0.44,all P＜0.05).Conclusion With the dose ofthiomersalate increased,the learning and memory and humoral immunity are sustained damaged for premature rats.
ABSTRACT
Objective To study the influence of postnatal high protein feeding on learning and memory abilities of preterm rats.Methods After weaning,the SD offspring were divided into 6 groups randomly according random digits table:preterm standard protein group (group A),term standard protein group (group B),preterm low protein group (group C),term low protein group (group D),preterm high protein group (group E),and term high protein group (group F),with 34 rats in each group.Starting from 22 days of age,the standard protein group,low-protein group and the high-protein group were respectively fed with a standard protein diet (containing 18％ protein),low-protein diet (containing 8％ protein) and a high-protein diet (containing 30％ protein) until the end of experiment.Within each group,the rats were respectively tested in 6 weeks and 8 weeks.Morris water maze task was performed to assess the learning and memory abilities of the premature rats.Results 1.Directional navigation experiments:(1) At the age of 6 weeks,the escape latencies to find the platform were shortened with increased training times for full-term rats.The escape latencies of the premature rats did not change significantly on the third and fourth day of the experiment.(2) At the age of 8 weeks,the escape latencies to find the platform were shortened with increased training time for all of the rats.2.Probe trial test:(1)At the age of 6 weeks,premature rats spent significantly less time in target quadrant than full-time rats.And the percent age of traveled distance in target quadrant of premature rats was significantly less than full term rats (P ＜ 0.05).(2) At the age of 8 weeks,group E [(68.48 ± 20.65) s] spent significantly greater time in target quadrant than group A and group C [group A(52.41 ± 11.24) s,group C (49.54 ± 11.04) s].And the percent age of traveled distance in target quadrant of group E [(36.56 ± 10.44) ％] were significantly higher than group A and group C [group A (29.83 ± 8.33) ％,group C (26.97 ± 5.41) ％] (P ＜ 0.05).(3) At the age of 8 weeks,group E spent time in target quadrant and the percent of traveled distance in target quadrant [(68.48 ± 20.65) s,(36.56 ±10.44)％] were higher than group F [(61.29 ± 16.27) s,(35.71 ±6.61)％],but there was no significant difference (P ＞ 0.05).Conclusions In the early growth and development process of the brain,premature birth may seriously affect early brain functions in rats,and the learning and cognitive abilities of the premature rats are worse than full-term rats.In the subsequent process of growth and development,after a long time of high protein nutritional intake,the learning and cognitive abilities of the premature rats can be restored and they can catch up with full-term rats.
ABSTRACT
Objectives To investigate the effect and mechanism of terbutaline sulfate on pulmonary fluid transport in pre-mature rats. Methods Pregnant rats were randomly divided into 5 groups (control group, premature group, low-dose terbutaline group, high-dose terbutaline group and dexamethasone group). Drugs were administered by gavage after rats were fertilized for 16 days and continued for 3 days. Premature rats were taken out from the 19 days pregnant rats, and mature rats were delivered on the due day. Lungs were collected, and the ratio of pulmonary wet weight to dry weight (W/D), Na+, K+-ATP ase activity and concentration of cyclic adenosine monophosphate (cAMP) were measured in lungs. Results The W/D rate, Na+,K+-ATPase acti-vity and cAMP concentration in lungs had significant difference among different groups (P<0.01). The W/D rate was highest in premature group and lowest in the control group. It was lower in the high-dose terbutaline group than in the low-dose terbutaline group and the dexamethasone group (P<0.05). The Na+,K+-ATPase activity was lowest in premature group and highest in high-dose terbutaline group. It was higher in dexamethasone group, low-dose terbutaline group, and high-dose terbutaline group than in premature group, and it was higher in high-dsoe terbutaline group than in low-dose terbutaline group and dexamethasone group (P<0.05). The cAMP levle was lowest in premature group and highest in high-dose terbutaline group. It was higher in dexamethasone group, low-dose terbutaline group, high-dose terbutaline group than in premature group, and it was higher in high-dose terbutaline group than in low-dose terbutaline group and dexamethasone group (P<0.05). Conclusions Terbutaline sulfate facilitates lung fluid transport in premature rats, leading to reduce the W/D rate in terbutaline-treated group. We speculate that this effect is related to the increased cAMP level and Na+, K+-ATPase activity in lung tissue.
ABSTRACT
Objective By making models of premature animal,explores the effects of dexamethasone on the brain development of premature rats and its mechanisms.Methods Eighteen SD rats were randomly divided into high-dexamethasone(H-Dex) group,low-dexamethasone (L-Dex) group and normal saline(NS) control group,with 6 rats in each group.The pregnant rats in L-Dex group were injected with dexamethasone [0.1 mg/(kg·d)] from 16 to 18 days of pregnancy,while the pregnant rats in H-Dex group were injected with dexamethasone [0.5 mg/(kg· d)] ; the pregnant rats in NS control group were injected with 0.9％ NaCl of the same volume.All of the fetal rats were received after administrating caesarean operation on the day 19 of pregnancy.Rats were sacrificed at the directed time and brain tissue was prepared.Histological feature and the water content of the brains were observed.Level of apoptosis was measured by flow cytometry.The expressions of myelin basic protein (MBP) and interleukin(IL)-1β in brain tissue homogenate were detected by ELISA.Results (1) The brain water contents of rats in H-Dex group,L-Dex group and NS control group were (85.94 ± 0.54) ％,(86.08 ± 1.01) ％,(86.94 ± 0.82) ％.Compared with NS control group,the water contents of Dex group were lower (P ＜ 0.05).(2) Glial cells of brain cortex in L-Dex group and H-Dex group were more mature than in NS control group,and the changes in H-Dex group was more significant.(3) The expressions of MBP in brain tissue of H-Dex group,L-Dex group and NS control group were (5.73 ± 1.06) μg/mg,(5.46 ±0.77) μg/mg and (2.42 ±0.52) μg/mg.Compared with NS control group,Dex group was higher(P ＜0.05).While the expressions of IL-1β in brain tissue of H-Dex group,L-Dex group and NS control group were (249.05 ± 11.29) pg/g,(257.47 ± 9.33) and (292.66 ± 21.51) pg/g.Compared with NS control group,Dex group was lower(P ＜ 0.05).There was no significant difference between H-Dex group and L-Dex group(P ＞ 0.05).(4) The level of apoptosis in H-Dex group,L-Dex group and NS control group were (18.07 ± 1.63) ％,(6.88 ± 0.47) ％ and (2.00 ± 0.32) ％.Compared with NS control group,the level of apoptosis in Dex group was higher(P ＜0.05),and H-Dex group was higher than that in L-Dex group.Conclusion (1) Using dexamethasone prophylactic could promote the development of glial cells,reduce the water content,increase the expressions of MBP,and decrease the expressions of IL-1β in brain tissues.It indicates that dexamethasone may play a major role in maturation of fetal brain.(2) Using dexamethasone prophylactic could increase the amounts of the apoptosis cells,and this effect is dose-dependent.It indicates that dexamethasone may have a negative effect on the fetal brain and suggestes that using dexamethasone in premature infant should be cautious,and if it has to,using a lower dose.
ABSTRACT
Objective To establish the model for periventricular leukomalacia(PVL) by intracerebral injection of 3-nitropropionic acid (3-NPA) and explore realistic model for concerned studies and investigate the diagnostic method with magnetic resonance imaging (MRI) examination. MethodsSprague-Dawley rat pups of both sexes at the age of postnatal day 5 (P5) were randomized and divided into two groups: NPA group and PBS group , and they were injected the same volume of 3-NPA and PBS with a tip located at the corpus callosum above the left ventricle by stereotaxis instrument, respectively. One day (P6), two days (P7), three days (P8) and nine days (P14) after injection, the injections were transcardially perfused and brains were collected. Then sections of brains were undertaken HE staining; growth and the time of opening eyes of the rats in the two different groups were observed and compared. Neurobehaviorai activity and memory tests were performed on postnatal day 29 (P29) and day 30 (P30). MRI examination was performed on postnatal day 30 (P30). ResultsMore weight increase and slower opening eye time were found in the NPA group compared with PBS group (P < 0.05). In the NPA group, sub-cortical and periventricular white matter rarefaction were observed by HE staining on P6, P7 and P8, significant lateral ventricle enlargement was found on P14, while the same changes were not found in the PBS group, and no histological changes in gray matter were noted in both groups. The outcomes of neurobehavioral tests of NPA group were much more abnormal compared with the PBS group (P < 0.05). MRI examination disclosed the signal changes of brain tissue is worse in the NPA group than that of the PBS group in muscle strength of limbs, autocinesis, capability and white matter. ConclusionsThe model for PVL induced by intracerebral injection of 3-NPA is characterized by damage to the periventricular white matter. The model can stimulate the pathologic change factually in vivo. The neurobehavioral movement is consistent with.clinical symptom. It can be used as a model to investigate some related disease. MRI examination is a feasible diagnostic method to show anatomic changes of white matter injury of the brain.
ABSTRACT
Objective To observe the changes of intracerebral amino acid transmitters in the periventricular leukomalacia (PVL) of newborn rats with microdialysis and so as to explore the role of excitotoxicity in PVL.Methods Replicated the model for PVL at the age of postnatal day 5 (P5) by intracerebral injection of 3-nitropropionic acid (3-NPA).Before injection of 3-NPA,and 15 min,30 min,45 min,60 min,75 min,90 min after injection of 3-NPA,collected the sample of extracellular fluid (ECF) at the corpus callosum above the left ventricle through microdialysis,respectively.After microdialysis,the experimental rats were allowed to survive to P6-P14,and then they were killed and the brains were prepared for HE stain.The amino accids of dialysate were quantified through high performance liquid chromatography(HPLC),and then the excitotoxic index (EI) was calculated.Results Fifteen min to 45 min after injection of 3-NPA,the concentrations of glumate (Glu) and aspartic acid (Asp) of ECF elevated significantly,and then returned to the normal levels.Fifteen min to 75 min and 15 min to 30 min after injection of 3-NPA,the concentrations of glycine (Gly) and GABA significantly elevated,respectively,and returned to normal levels at 90 min and 45 min after injection of 3-NPA,respectively.But the EI,which indicated the balance of excitatory amino acids(EAAs) and inhibitory amno aciols(IAAs),significantly elevated 15 min to 75 min after injection of 3-NPA,then retured to normal level after 90 min.Sub-cortical and periventricular white matter rarefaction and significant lateral ventricle enlargement were observed in HE staining.Conclusions Changes of intracerebral amino acid transmitters in the PVL of newborn rats show regularity:EAAs,IAAs of ECF and EI elavate in the early stage,and then return to the normal level quickly.It indicates that excitotoxicity play a great role in PVL,especially at the early stage.Therefore,the preventions of PVL must be executed at the early stage.
ABSTRACT
Objective To investigate the dynamic change of expression of cyclin dependent kinase-4(CDK4)and cyclin dependent kinase inhibitor(p21)in premature rats with hyperoxia-induced chronic lung disease(CLD)and its role.Methods Eighty premature rats were randomly and equally divided into model group(hyperoxia group)and control group(room air group).CLD was induced by hypemxia exposure.The expression of CDK4 and p21 were observed with immunohistochemical method,and the levels of type I collagen were detected by enzyme-linked immunosorbent assay on days 1,3,7,14 and 21.Results Compared with control group,in model group,the expression of CDK4 protein and level of type I collagen statistically increased,but expression of p21 protein decreased significantly on days 14 and 21.The expression of CDK4 was positive correlated with the degree of fibrosis,and expression of p21 was negative correlated with the degree of fibrosis in model group.Conclusion The expression of CDK4 increases and expression of p21 decreases in premature rats exposed to hyperoxia,which may play an important role in the lung fibrosis.