Objective: To investigate the impact of mandibular retrognathism on brain function in rats and its potential mechanisms． Methods : Male SD rats aged 3 to 4 weeks ( w) were randomly divided into control group ( n = 10) and mandible retrusion ( MR) group ( n = 30) ，with the MR group further divided into three subgroups: 1，2， or 4 weeks，with 10 rats in each subgroup．The MR group used modified metal tubes，which were bonded to the lingual side of the maxillary incisors in rats，forcing the mandible to retract by 2－2. 5 mm，thereby achieving the goal of constructing a mandibular retrognathism model; the control group received no interventions．The effects of mandibular retraction on the spatial learning ability and memory ability of rats were explored by behavioral experi- ments such as Morris water maze，Y maze and new object recognition 1，2，and 4 weeks after modeling，respective- ly．Hematoxylin-eosin ( HE) and Nissl staining were employed to observe the histomorphological changes in CA1， CA3，and DG regions of hippocampal tissues．Immunohistochemistry was employed to detect the protein expression levels of tropomyosin receptor kinase B ( TrkB) in the CA1，CA3，and dentate gyrus ( DG) regions of the hippo- campus．Western blot was used to assess the expression changes in the TrkB / phosphoinositide 3-kinase ( PI3K) / protein kinase B ( AKT) pathway in hippocampal tissue．Quantitative analysis of apoptosis-related proteins in the hippocampus，including Bcl-2-associated X protein ( Bax) ，B-cell lymphoma-2 protein ( Bcl-2) ，and Caspase-3， was conducted using qRT-PCR and Western blot． Results: Behavioral experiments showed that rats in the MR group，especially the MR 4 w group，were significantly weaker in learning and spatial memory than the control group，MR 1 w，and MR 2 w( P＜0. 05) ．HE staining showed that pyramidal cells in the control group were ar- ranged orderly with regular morphology．In contrast，the MR group exhibited a reduction in the number of cells in the hippocampal CA1，CA3，and dentate gyrus ( DG) regions．The cells were sparsely and irregularly arranged， with nuclear condensation and enlarged cellular spaces． Nissl staining further demonstrated damage to the Nissl bodies in the MR group．Meanwhile，the TrkB / PI3K / AKT signaling pathway was activated in the MR group，and the expression of p-TrkB，PI3K，and p-AKT proteins was up-regulated ( P ＜0. 05) ．Western blot and qRT-PCR indicated that MR up-regulated the expression of pro-apoptotic protein Bax，apoptotic effector protein Caspase-3 ( P＜0. 05) ，and inhibited the expression of anti-apoptotic protein Bcl-2 ( P ＜0. 05) ． Conclusion Mandibular retraction impairs brain function and affects cognition and learning memory in rats．This may be achieved by regula- ting the TrkB / PI3K / AKT signaling pathway to induce apoptosis in hippocampal neurons．

Objective To explore the changes in cerebral blood flow caused by mandibular retrusion,as well as the impact and potential mechanisms on stroke recovery.Methods 6-week-old SD male rats were selected as experi-mental subjects.The metal cannula was bonded to the rat maxillary incisor for one week,forcing mandibular retru-sion(MR).Cerebral blood flow was detected by laser speckle imaging.Cognitive function was detected by the Morris water.Then,the stroke model was constructed in MR rats by using the middle cerebral artery occlusion(MCAO)method for one week.Meanwhile,metal cannulae were then removed in rats to restore the lower jaw's position(MCAO RO),serving as a positive control group.Consequently,rats were randomly divided into the fol-lowing groups:Sham groups,MCAO groups,MCAO MR groups,and MCAO RO groups.Neurological recovery was assessed through the modified neurological severity score(mNSS).The area of cerebral infarction was evalua-ted by using triphenyltetrazolium(TTC)staining.The changes in nerve cells were observed by using hematoxylin eosin(HE)staining.The protein expression level of vascular endothelial growth factor(VEGF)was detected by immunohistochemistry.The protein expression levels of platelet-endothelial cell adhesion molecule(CD31),sirtuin 6(SIRT6),and thioredoxin interaction protein(TXNIP)were detected by Western blot.The mRNA expression levels of SIRT6,TXNIP,and VEGF were determined by qRT-PCR.Microglia activation marker molecule 1(IBA-1)was detected by immunofluorescence.Resluts Because of mandibular retrusion,laser speckle showed de-creased cerebral blood flow,and the water maze showed decreased cognitive function.Compared to other groups,MCAO MR showed a larger ischemic area in TTC staining,while HE staining and neurological scoring showed poo-rer neurological function recovery.Western blot and qRT-PCR showed that the MCAO MR group inhibited the mR-NA and protein expression levels of SIRT6,upregulated the mRNA and protein expression levels of TXNIP,and in-creased the activation of microglia.Conclusion Mandibular retrusion reduces cerebral blood flow and alters cogni-tive function in rats.Mandibular retrusion inhibits recovery in stroke through the SIRT6/TXNIP axis.

OBJECTIVETo study the CPS-II mechanism underlying the pathological process of elevated blood ammonia leading to liver injury.

METHODSAn in vitro hyperammonemia hepatocyte cell model was constructed by exposure to various concentrations of NH4Cl. The subsequent changes to cellular morphology were observed by microscopy. to cell apoptosis were determined by flow cytometry, and to mRNA and protein expression of CPS-II were examined by real-time PCR and western blotting, respectively.

RESULTSExposure to NH₄Cl led to dose-dependent morphological damage, apoptosis and necrosis of the hepatocytes. The apoptosis rate was significantly higher for the high-dose group than for the control (no exposure) group (24.7% ± 2.39% vs. 4.1% ± 0.78%, q =8.06, P less than 0.05). Expression of the CPS-II mRNA was significantly elevated in response to NH₄Cl exposure (vs. the control group; F=191.881, P < 0.05).The CPS-II mRNA expression level increased with increasing NH₄Cl concentration (grey values: 1.040 ± 0.045, 1.641 ± 0.123, 2.285 ± 0.167 and 3.347 ± 0.124, respectively). The CPS-II protein expression level was also significantly enhanced in response to the NH₄Cl exposures (CPS-II protein and internal GAPDH grey value ratios: 0.099 ± 0.0130, 0.143 ± 0.025, 0.161 ± 0.036 and 0.223 ± 0.042, respectively; t=3.825, 3.968 and 6.908, P less than 0.05).

CONCLUSIONCPS-II mRNA and protein expression levels become elevated with increase in the NH₄Cl concentrations, suggesting that in addition to the urea cycle, CPS-II may play an important role in the ammonia metabolism under the condition of hyperammonemia.

Ammonia ; Apoptosis ; Hepatocytes ; Humans ; Hyperammonemia ; Liver ; RNA, Messenger ; Real-Time Polymerase Chain Reaction ; Somatostatin

Objective To study the profiles and function of small RNA (sRNA)gene during chondrogenesis in rats so as to clarify the mechanisms of chondrocytes proliferation and differentiation.Methods All the sRNAs were identified from the female SD rats femoral head cartilages at three time points:at birth,ablactation and maturation,and three sRNA libraries were constructed.The Solexa sequencing and the bioinformatics analysis were employed to be blasted with the genomes of SD rats.Results The perfect match reads in the three libraries were screened out,which were correspondent to the 21 7 921 (41.23%),1 96 650 (38.74%)and 245 436 (41.54%)unique sRNA sequence,respectively.The percentages of 20-24 nt sRNA were 71.94% (d0),72.85% (d21),and 86.39%(d42).Half of clean sequences were 22 nt sRNA.The distribution characteristics of the reads were in line with the high-quality sRNA.More than 62% clean reads were from mature miRNA while the ratios in the three libraries were only 0.69%,0.78% and 0.63%.About 60% of the unique sRNA could not be matched with miRBase20.0 or Rfam9.1.Conclusion The distribution model of miRNA in the three libraries indicates that the miRNAs with different functions or from different sources are involved in the regulation of chondrocytes proliferation and differentiation in bone development and formation.