ObjectiveUsing multi-omics technology， we conducted the present study to determine whether dexamethasone has therapeutic effect on pneumonia rats through the regulation of intestinal flora and metabolites. MethodsTotally 18 Sprague-Dawley rats were randomly divided into 3 groups （n = 6 each）： Control group， Model group and Dexamethasone （Dex） group. Lipopolysaccharide （LPS） was continuously injected intraperitoneally into rats at a dose of 4 mg/kg for 7 days to induce pneumonia except the Control group. Then the Dex group was given Dex at a dose of 2 mg/kg via oral gavage for 12 days， and both the other two groups received continuously equal volume of sterile PBS buffer for 12 days. On the 19th day， lung， plasma， feces and intestinal contents of rat were collected. Hematoxylin-eosin （H&E） staining and Bio-plex suspension chip system were applied to evaluate the effect of Dex on pneumonia. Furthermore， metagenomic sequencing and UPLC-Q-TOF-MS/MS technology were employed to determine the intestinal flora and metabolites of rats， respectively. ResultsH&E staining results showed that the lung tissue of the Model group was infiltrated with inflammatory cells， the alveolar septum was increased， alveolar hemorrhage， and histological lesions were less severe in Dex group than in the model group. The levels of 3 inflammatory cytokines including TNF-α （P < 0.000 1）， IL-1α （P = 0.009 6） and IL-6 （P < 0.000 1） in the Model group were increased compared with the Control group， while Dex treatment reduced the levels of the three inflammatory factors. Taken together， Dex treatment effectively reversed the features of pneumonia in rats. Metagenomic analysis revealed that the intestinal flora structure of the three groups of rats was changed. In contrast with the Model group， an increasing level of the Firmicutes and an elevated proportion of Firmicutes/Bacteroidetes were observed after Dex treatment. Dex-treated rats possessed notably enrichment of Bifidobacterium， Lachnospiraceae and Lactobacillus. Multivariate statistical analysis showed a great separation between Model group and Dex group， indicating metabolic profile changes. In addition， 69 metabolites （P < 0.05） were screened， including 38 up-regulated in the Model group and 31 elevated in the Dex group， all of which were mainly involved in 3 metabolic pathways： linoleic acid metabolism， tryptophan metabolism and primary bile acid biosynthesis. ConclusionsIn summary， we demonstrate the beneficial effects of Dex on the symptoms of pneumonia. Meanwhile， integrated microbiome-metabolome analysis reveals that Dex improves LPS-induced pneumonia in rats through regulating intestinal flora and host metabolites. This study may provide new insights into the mechanism of Dex treatment of pneumonia in rats.

OBJECTIVE: To explore characteristics of contrast-enhanced ultrasound (CEUS) images features and diagnostic value of rotator cuff tear subtypes. METHODS: From January 2019 to March 2022, percutaneous ultrasound-guided subacromial bursography (PUSB) with persutaneous ultrasound-guide tendon lesionography (PUTL) was performed on 114 patients with suspected rotator cuff injury were evaluated, including 54 males and 60 females ranged in age from 35 to 75 years old with an average of (58.8±8.7 ) years old;76 patients on the right side and 38 patients on the left side;the course of disease ranged from 0.13 to 111 months with an average of (10.2±9.8) months. GE LOGIQ E9 color doppler ultrasound diagnostic high frequency(6 to 12 MHz) was used to CEUS Using arthroscopy as gold standard, receiver operating characteristic (ROC) curve was used to evaluate diagnostic efficacy of US, MRI and CEUS for rotator cuff injury, also sensitivity, specificity, positive predictive value, negative predictive value and accuracy were calculated. RESULTS: The sensitivity of US in diagnosing full-thickness tears was 72.1%, specificity was 93.0%, and accuracy was 85.1%. The sensitivity, specificity and accuracy of MRI diagnosis of full-thickness tear were 90.9%, 92.6% and 92.1% respectively. The sensitivity, specificity and accuracy of CEUS in diagnosis of full-thickness tear were 100%. The sensitivity, specificity and accuracy of US in the diagnosis of partial tear were 85.7%, 77.2% and 79.8% respectively. The sensitivity, specificity and accuracy of MRI diagnosis of partial tear were 83.7%, 81.7% and 82.5% respectively. The sensitivity, specificity and accuracy of CEUS in diagnosis of partial tear were 95.7%, 92.6% and 93.9% respectively. There were significant differences in diagnosis results of US, MRI and CEUS for rotator cuff bursa tear (P<0.001). Kapp test showed good consistency between CEUS and arthroscopy in diagnosing rotator cuff tear subtypes (full-thickness and partial tears). CONCLUSION Using PUSB/PUTL to observe distribution of contrast media in bursa, tendon and joint cavity to evaluate the type of rotator cuff tear, its diagnostic performance is significantly better than US and MRI. Therefore, percutaneous contrast-enhanced ultrasound can be a reliable method for diagnosing subtypes of rotator cuff tears.
Male ; Female ; Humans ; Infant, Newborn ; Infant ; Child, Preschool ; Child ; Rotator Cuff Injuries/diagnostic imaging* ; Rotator Cuff/diagnostic imaging* ; Sensitivity and Specificity ; Ultrasonography ; Magnetic Resonance Imaging/methods* ; Rupture ; Arthroscopy

OBJECTIVE: To compare the clinical efficacy of acupuncture with different frequencies in the treatment of patients with functional dyspepsia (FD). METHODS: A total of 90 patients with FD were randomly divided into a 3-time acupuncture treatment per week group (3-A group, 31 cases, 2 cases dropped off), a 1-time acupuncture treatment per week group (1-A group, 30 cases, 2 cases dropped off) and a control group (29 cases, 2 cases dropped off). In the two acupuncture groups, the acupoints were Zhongwan (CV 12) and bilateral Tianshu (ST 25), Neiguan (PC 6), Liangqiu (ST 34), Yanglingquan (GB 34), Zusanli (ST 36) and Taichong (LR 3), stimulated 3 times a week and once a week, respectively; and the treatment was given consecutively for 4 weeks. In the control group, no intervention was adopted, but the compensatory therapy was provided after the end of follow-up. The scores of the symptom index of dyspepsia (SID), self-rating anxiety scale (SAS) and self-rating depression scale (SDS) were compared among the 3 groups before treatment, after 4 weeks of treatment and in 4 and 8 weeks after treatment completion separately. The score of Nepean dyspepsia life quality index (NDLQI) was evaluated before treatment, after 2 and 4 weeks of treatment and in 4 and 8 weeks after treatment completion. RESULTS: After 4 weeks of treatment and in 4 and 8 weeks after treatment completion, the scores of SID, SAS and SDS were all reduced in the 3-A group and the 1-A group when compared with the scores before treatment (P<0.000 1, P<0.05). After 4 weeks of treatment, the scores of SID, SAS and SDS in the two acupuncture groups were lower than those in the control group (P<0.000 1). After 2 and 4 weeks of treatment, the increased values of NDLQI score in the two acupuncture groups were all higher than those in the control group (P<0.05). In 4 and 8 weeks after treatment completion, the scores of SID, SAS and SDS in the 3-A group were lower than those in the 1-A group (P<0.001, P<0.05), and the increased values of NDLQI score in the 3-A group were higher than those in the 1-A group (P<0.000 1). CONCLUSION Acupuncture given 3 times per week is superior to the treatment given once per week in the aspects of relieving the clinical symptoms, improving the quality of life and regulating the emotional state in patients with FD. This efficacy is persistent for 8 weeks after treatment completion.
Humans ; Dyspepsia/therapy* ; Quality of Life ; Acupuncture Therapy ; Acupuncture Points ; Emotions

Objective To explore whether metformin preconditioning can protect brain injury after cardiac arrest/cardiopulmonary resuscitation(CA/CPR)and its possible mechanisms and signaling pathways.Methods Constructed a CA model by using electrical stimulation.Rats were randomly divided into the sham group(0.9％NaCl gavage daily for 14 days,without inducing CA),model group(CA model was induced after 0.9％NaCl gavage daily for 14 days),experimental group(CA model was induced after 200 mg·kg-1 Met+0.9％NaCl gavage daily for 14 days),Cc group[200 mg·kg-1 Met+0.9％NaCl gavage daily for 14 days,adenosine 5'-monophosphate kinase-activated protein(AMPK)inhibitor Compoud C(Cc)was injected intraperitoneally at 1 hour before modeling],chloroquine(CQ)group(daily 200 mg·kg-1 Met+0.9％NaCl gavage for 14 days,intraperitoneal injection of autophagy inhibitor CQ at 1 hour before modeling)and AICAR group(continuous daily 200 mg·kg-1 Met+0.9％NaCl gavage for 14 days,intraperitoneal injection of AMPK agonist AICAR at 1 hour before modeling).The 7-day survival rate after CA/CPR via using survival curves was recorded;the neurological function 7-days after CA/CPR was scored by using the neurological disability scale;the protein malondialdehyde(MDA)level were measured using the Coomassie Brilliant Blue method;detection of reactive oxygen species(ROS)levels in brain tissue by using ROS fluorescent probe DHE;Western blotting was used to determine the expression levels of related proteins such as AMPK,p-AMPK,microtubule associated protein 1 light chain 3 Ⅰ(LC3 Ⅰ),LC3 Ⅱ,and p62 in brain tissue.Results The 7-day survival rates of sham,model,experimental,Cc,CQ and AICAR groups rats were 100％,40％,70％,40％,40％and 65％,respectively;the 7-day neurological function scores were 78.35±1.65,46.50±4.41,67.93±4.64,49.50±3.53,52.00±2.83 and 68.33±1.53,respectively;the ROS levels were(417.60±8.37),(748.60±36.05),(575.80±10.73),(713.80±18.85),(668.20±9.58)and(566.00±24.48)U·mg-1,respectively;the MDA levels were(4.38±0.33),(8.06±0.76),(5.50±0.48),(7.18±0.29),(6.82±0.31)and(5.20±0.34)nmol·mg-1,respectively;the brain tissue p-AMPK/AMPK were 0.74±0.04,0.87±0.01,1.61±0.01,0.55±0.05,1.09±0.09 and 1.27±0.07,respectively;the p62 values were 0.42±0.02,0.86±0.05,0.61±0.04,0.98±0.04 and 0.78±0.03,respectively;the LC3 Ⅱ/LC3 1 were 0.29±0.32,0.37±0.26,0.96±0.78,0.58±0.26,0.43±0.03 and 1.40±0.10,respectively.Compared with the model group,the differences of above indexes in the experimental group,AICAR group were statistically significant(all P＜0.05);compared with the experimental group,the differences of above indexes in the Cc group,CQ group were statistically significant(all P＜0.05).Conclusion Metformin preconditioning can play a protective role in brain injury after cardiac arrest/cardiopulmonary resuscitationin in rats by activating the AMPK signaling pathway,regulating mitochondrial energy metabolism and promoting autophagy.

This study aimed to provide scientific evidence for predicting quality markers(Q-markers) of Elephantopus scaber by establishing UPLC fingerprint of E. scaber from different geographical origins and determining the content of 13 major components, as well as conducting in vitro anti-cancer activity investigation of the main components. The chromatographic column used was Waters CORTECS UPLC C_(18)(2.1 mm×150 mm, 1.6 μm), and the mobile phase consisted of acetonitrile and 0.1% formic acid solution(gradient elution). The column temperature was set at 30 ℃, and the flow rate was 0.2 mL·min~(-1). The injection volume was 1 μL, and the detection wavelength was 240 nm. The UPLC fingerprint of E. scaber was fitted using the Similarity Evaluation System for Chromatographic Fingerprint of Traditional Chinese Medicine(2012 edition) to determine common peaks, evaluate similarity, identify and determine the content of major components. The CCK-8 assay was used to explore the inhibitory effect of the main components on the proliferation of lung cancer cells. The results showed that in the established UPLC fingerprint of E. scaber, 35 common peaks were identified. Thirteen major components, including neochlorogenic acid(peak 1), chlorogenic acid(peak 2), cryptochlorogenic acid(peak 3), caffeic acid(peak 4), schaftoside(peak 6), galuteolin(peak 9), isochlorogenic acid B(peak 10), isochlorogenic acid A(peak 12), isochlorogenic acid C(peak 18), deoxyelephantopin(peak 28), isodeoxyelephantopin(peak 29), isoscabertopin(peak 31), and scabertopin(peak 32) were identified and quantified, and a quantitative analysis method was established. The results of the in vitro anti-cancer activity study showed that deoxyelephantopin, isodeoxyelephantopin, isoscabertopin, and scabertopin in E. scaber exhibited inhibition rates of lung cancer cell proliferation exceeding 80% at a concentration of 10 μmol·L~(-1), higher than the positive drug paclitaxel. These results indicate that the fingerprint of E. scaber is highly characteristic, and the quantitative analysis method is accurate and stable, providing references for the research on quality standards of E. scaber. Four sesquiterpene lactones in E. scaber show significant anti-cancer activity and can serve as Q-markers for E. scaber.
Humans ; Chromatography, High Pressure Liquid ; Drugs, Chinese Herbal/chemistry* ; Asteraceae/chemistry* ; Lung Neoplasms/drug therapy*

ObjectiveSepsis associated acute kidney injury （SA-AKI） is a critical clinical disease. The purpose of this study was to investigate the role and molecular mechanism of miR-4321 in the HK2 cellular damage induced by lipopolysaccharides （LPS）. MethodsRT-qPCR was conducted to detect the expression of miR-3165， miR-4270 and miR-4321 in LPS-induced HK2 cell model and cecal ligation and puncture （CLP）-induced renal injury model. In LPS-induced HK2 cell model， miR-4321-inhibitor was used to inhibit the miR-4321 expression. The effects of miR-4321 on cell proliferation， cell viability， cytokines and apoptosis-related protein levels were evaluated by CCK-8 analysis， EdU staining analysis and western blotting analysis， respectively. In CLP-induced renal injury model， miR-4321-Antago was used to intervene the miR-4321 expression. The changes of renal tissue structure were examined by H&E staining. The levels of serum creatinine and blood urea nitrogen （BUN） were measured by colorimetric method. ELISA was employed to assess the expression of interleukin-6 （IL-6）， interleukin-1β （IL-1β） and tumor necrosis factor-α （TNF-α） in serum. IHC staining and western blotting were performed to determine the mTOR level and apoptosis-related protein expression in kidney tissues. Target genes of miR-4321 were predicted by Targetscan software and verified by dual-luciferase reporter assay. ResultsCompared with the control group， the miR-4321 expression was increased in LPS-induced HK2 cell model （n=3， t=7.154， P=0.001 3）. miR-4321 inhibitor promoted the proliferation and viability of HK2 cells， decreased the expression of LPS-induced IL-6， IL-1β and TNF-α and apoptosis-related proteins. In vivo experiments showed that miR-4321-Antago inhibited serum creatinine and BUN levels in CLP mice， improved renal injury， reduced levels of IL-1β， IL-6 and TNF-α， promoted the mTOR expression in renal tissues and inhibited the apoptosis-related protein expression. mTOR signaling pathway was believed the target gene of miR-4321. ConclusionInhibition of miR-4321 significantly alleviates SA-AKI， which may be achieved by increasing the expression of mTOR.

Objective: To examine the outcomes of Slide tracheoplasty for the children with severe congenital tracheal stenosis received previous repeated balloon dilatation or metal stent placement under endoscopy. Methods: A retrospective study was conducted in 9 children with congenital tracheal stenosis undergoing previous interventional therapy under tracheoscopy and later received Slide tracheoplasty due to obvious respiratory symptoms at Department of Cardiac Surgery, Qilu Children's Hospital of Shandong University between February 2017 and July 2021. There were 7 males and 2 females with a median age at operation of 72.4 months (range: 13.3 to 98.9 months), and the median weight was 19.0 kg (range: 9.0 to 33.0 kg). Among the 9 patients, 2 patients began to receive repeated balloon dilatation (more than 3 times) 17.8 and 51.8 months ago respectively. One patient received metal stents placement into the trachea for 4 days and the other 6 children for median 56.8 months (range: 21.6 to 74.2 months). Complete tracheal cartilage rings and long segmental stenosis were present. in all 9 children. Operative details and outcome measures, including the need for endoscopic airway intervention and mortality, were collected. Results: Slide tracheoplasty was performed in all cases. Two patients with repeated balloon dilatation had different thickness of tracheal wall, local scar hyperplasia and irregular lumen. Among them, 1 case had obvious local calcification of tracheal wall, which was difficult to suture. The metal stent in one patient with short time of placement was completely removed. However, only part of the metal stents could be removed due to the long placement time in the other 6 cases. There was no operative death in the 9 children. The median postoperative tracheal intubation time was 25.3 hours (range: 17.4 to 74.5 hours). A silicone stent was placed in the trachea of 1 child due to obvious respiratory symptoms. Follow-up of median 11 months (range: 1 to 23 months) showed that no death occurred after discharge and all children had basically normal activity tolerance with no obvious respiratory symptoms. Conclusions: Slide tracheoplasty is feasible for children undergoing prior balloon dilatation or metal stents placement. Previously repeated balloon dilatation or metal stent placement under endoscopy increased the difficulty of slide tracheoplasty, the metal stent could not be completely removed after a long time.
Child ; Constriction, Pathologic ; Dilatation ; Endoscopy ; Female ; Humans ; Infant ; Male ; Reconstructive Surgical Procedures ; Retrospective Studies ; Stents ; Trachea/surgery* ; Tracheal Stenosis/surgery* ; Treatment Outcome

Objective: To compare the effect of direct surgery or surgery after second-line chemotherapy for colorectal cancer patients with liver metastases who did not achieve objective remission after neoadjuvant chemotherapy. Methods: A retrospective case cohort study was used. The clinical and pathological data of 107 patients with colorectal cancer liver metastases who did not achieve objective response to neoadjuvant chemotherapy at Department of Hepatobiliary Surgery,Cancer Hospital,Chinese Academy of Medical Sciences from December 2008 to December 2016 were retrospectively collected. There were 71 males and 36 females, median age was 57 years (range: 28 to 79 years). According to the different treatment regimens after neoadjuvant chemotherapy,107 cases were divided into a direct surgery group (direct group,n=65) and an operation after receiving second-line chemotherapy group (second-line group,n=42). The propensity score matching(PSM) of the Logistic regression model was used to match the bilobar distribution of liver metastases and the number of first-line chemotherapy cycles in the two groups of patients. The caliper value was set to 0.10 and the matching ratio was 1∶2. T test, Mann-Whitney U test, χ² test or Fisher's exat test was used to analyzed the data between the tuo groups, respectively. Survival analysis design was used to investigate the difference in prognosis between the two groups of patients. Results: The follow-up time(M(IQR)) was 56.3(34.3) months (range: 2.1 to 95.0 months),and all patients were followed up. After PSM,there were 28 cases in the direct group and 42 cases in the second-line group, there were no significant differences in whether R0 resection was feasible,blood loss,blood transfusion,postoperative complications and postoperative hospital stay between the two groups (all P>0.05). The 1,3,and 5-year progression-free survival(PFS) rates of the direct group were 40.0%,16.5%,and 11.0%,and the 1,3,and 5-year overall survival(OS) rates were 98.5%,61.2%,and 41.4%,respectively, the second-line group 1,3,5 years PFS rates were 35.7%,14.3%,14.3%,1,3,5-year OS rate were 95.2%,55.1%,44.4%,respectively. The median PFS time of the direct group and the second-line group was 8.5 months and 7.5 months,respectively,and the difference was not statistically significant (P=0.826). The median OS time of the direct group and the second-line group were 33.8 months and 46.9 months,respectively. The difference was not statistically significant(P=0.646).The median PFS time of the direct group and second-line chemotherapy complete remission and partial remission group(CR/PR group) was 10.2 months and 9.1 months,respectively,and the difference was not statistically significant(P=0.669). The median OS time of the direct group and the second-line CR/PR group was 51.0 months and 46.9 months,respectively,and the difference was not statistically significant(P=0.427). The results of survival analysis suggested that major liver resection was an independent prognosis factor for PFS (HR=1.809,95%CI: 1.067 to 3.067,P=0.028) and OS(HR=2.751,95%CI: 1.317 to 5.747,P=0.007). Second-line chemotherapy was not an independent prognostic factor for PFS (HR=0.945, 95%CI:0.570 to 1.567,P=0.828) and OS (HR=0.866,95%CI: 0.468 to 1.602,P=0.646). Conclusions: There is no significant difference in the short-term outcome and long-term prognosis between direct surgery patients and second-line chemotherapy followed by surgery. Second-line chemotherapy is not an independent prognostic factor for colorectal cancer liver metastases patients who fail to achieve objective response after neoadjuvant chemotherapy.
Antineoplastic Combined Chemotherapy Protocols/therapeutic use* ; Cohort Studies ; Colorectal Neoplasms/pathology* ; Female ; Follow-Up Studies ; Humans ; Liver Neoplasms/secondary* ; Male ; Middle Aged ; Neoadjuvant Therapy ; Prognosis ; Retrospective Studies

OBJECTIVES: To investigate the clinical treatment outcomes and the changes of the outcomes over time in extremely preterm twins in Guangdong Province, China. METHODS: A retrospective analysis was performed for 269 pairs of extremely preterm twins with a gestational age of <28 weeks who were admitted to the department of neonatology in 26 grade A tertiary hospitals in Guangdong Province from January 2008 to December 2017. According to the admission time, they were divided into two groups: 2008-2012 and 2013-2017. Besides, each pair of twins was divided into the heavier infant and the lighter infant subgroups according to birth weight. The perinatal data of mothers and hospitalization data of neonates were collected. The survival rate of twins and the incidence rate of complications were compared between the 2008-2012 and 2013-2017 groups. RESULTS: Compared with the 2008-2012 group, the 2013-2017 group (both the heavier infant and lighter infant subgroups) had lower incidence rates of severe asphyxia and smaller head circumference at birth (P<0.05). The mortality rates of both of the twins, the heavier infant of the twins, and the lighter infant of the twins were lower in the 2013-2017 group compared with the 2008-2012 group (P<0.05). Compared with the 2008-2012 group, the 2013-2017 group (both the heavier infant and lighter infant subgroups) had lower incidence rates of pulmonary hemorrhage, patent ductus arteriosus (PDA), periventricular-intraventricular hemorrhage (P-IVH), and neonatal respiratory distress syndrome (NRDS) and a higher incidence rate of bronchopulmonary dysplasia (P<0.05). CONCLUSIONS There is a significant increase in the survival rate over time in extremely preterm twins with a gestational age of <28 weeks in the 26 grade A tertiary hospitals in Guangdong Province. The incidences of severe asphyxia, pulmonary hemorrhage, PDA, P-IVH, and NRDS decrease in both the heavier and lighter infants of the twins, but the incidence of bronchopulmonary dysplasia increases. With the improvement of diagnosis and treatment, the multidisciplinary collaboration between different fields of fetal medicine including prenatal diagnosis, obstetrics, and neonatology is needed in the future to jointly develop management strategies for twin pregnancy.
Bronchopulmonary Dysplasia/epidemiology* ; Female ; Gestational Age ; Humans ; Infant ; Infant, Extremely Premature ; Infant, Newborn ; Pregnancy ; Respiratory Distress Syndrome, Newborn/epidemiology* ; Retrospective Studies ; Treatment Outcome

OBJECTIVES: To investigate the incidence of extrauterine growth retardation (EUGR) and its risk factors in very preterm infants (VPIs) during hospitalization in China. METHODS: A prospective multicenter study was performed on the medical data of 2 514 VPIs who were hospitalized in the department of neonatology in 28 hospitals from 7 areas of China between September 2019 and December 2020. According to the presence or absence of EUGR based on the evaluation of body weight at the corrected gestational age of 36 weeks or at discharge, the VPIs were classified to two groups: EUGR group (n=1 189) and non-EUGR (n=1 325). The clinical features were compared between the two groups, and the incidence of EUGR and risk factors for EUGR were examined. RESULTS: The incidence of EUGR was 47.30% (1 189/2 514) evaluated by weight. The multivariate logistic regression analysis showed that higher weight growth velocity after regaining birth weight and higher cumulative calorie intake during the first week of hospitalization were protective factors against EUGR (P<0.05), while small-for-gestational-age birth, prolonged time to the initiation of total enteral feeding, prolonged cumulative fasting time, lower breast milk intake before starting human milk fortifiers, prolonged time to the initiation of full fortified feeding, and moderate-to-severe bronchopulmonary dysplasia were risk factors for EUGR (P<0.05). CONCLUSIONS It is crucial to reduce the incidence of EUGR by achieving total enteral feeding as early as possible, strengthening breastfeeding, increasing calorie intake in the first week after birth, improving the velocity of weight gain, and preventing moderate-severe bronchopulmonary dysplasia in VPIs.
Female ; Fetal Growth Retardation ; Gestational Age ; Hospitalization ; Humans ; Incidence ; Infant ; Infant, Newborn ; Infant, Premature ; Infant, Very Low Birth Weight ; Prospective Studies ; Risk Factors