1.Repeated gonadotropin stimulations lower the developmental potential of mouse oocytes.
Yu-Hong PENG ; Shou-Zhen XIE ; Xiao-Kun WANG ; Bo DIAO ; Meng-Lin ZHANG ; Yan WANG
Journal of Southern Medical University 2009;29(6):1232-1234
OBJECTIVETo assess the effect of repeated gonadotropic stimulations on the developmental potential and growth differentiation factor-9 (GDF-9) expression of mouse oocytes.
METHODSFemale Kunming mice were treated with pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotropin (HCG) for 3 times, and the control mice were treated with normal saline. The two groups of mice were both stimulated subsequently to obtain the mature oocytes. Immunocytochemical staining was employed to evaluate GDF-9 expression in the oocytes. The oocytes were then inseminated and cultured till the formation of blastocysts to compare the cleavage rate and blastocyst formation rate between the groups.
RESULTSA total of 253 mature oocytes were obtained in the repeated stimulation group, with a mean of 11.5 oocytes from each mouse; 521 mature oocytes were obtained in the control group with a significantly greater mean number of 32.6 from each mouse (P<0.05). The average optical density and integrated optical density for GDF-9 expression were significantly lower in the oocytes in repeated stimulation group than in the control group (P<0.05 and 0.01, respectively). After insemination, the cleavage rate were comparable between repeated stimulation group and the control group (85.6% vs 88.8%), but the blastocyst formation rate was significantly lower in repeated stimulation group (20.8% vs 35.2%, P<0.01).
CONCLUSIONRepeated gonadal stimulation decreases the developmental potential of mouse oocytes possibly due to reduced GDF-9 expression.
Animals ; Cells, Cultured ; Female ; Gonadotropins ; pharmacology ; Growth Differentiation Factor 9 ; metabolism ; Mice ; Oocytes ; cytology ; growth & development ; metabolism ; Ovulation Induction ; adverse effects ; methods
2.Study on hepatitis C virus genotyping in Yixing area, Jiangsu province.
Ke XU ; Xiao-zhao DENG ; Wei-liang DING ; Jian GAO ; Rong-bin YU ; Zhen-yu DIAO ; Yong-fei TAN ; Yun ZHANG
Chinese Journal of Epidemiology 2005;26(11):901-903
OBJECTIVETo investigate the distribution of hepatitis C virus (HCV) genotypes in Yixing, Jiangsu province.
METHODSGenotypes identification on sera samples were obtained from 158 donors who had already been anti-HCV positive through PCR method with type specific primer designed according to the sequence of 5'non-coding region (5'NCR). 5'NCR was also sequenced and compared with published date. Genotypes distribution was investigated in patients with different sex and clinical types of hepatitis C.
RESULTSOf the total 158 patients, 95 were HCV RNA positive in which 80 patients having genotype 1b (80/95; 84.4%), 5 patients having genotype 2(5/95; 5.3%), 5 patients with 1b/2 mixed genotypes (5/ 95; 5.3%) and another 5 patients whose genotype undetermined. The difference on the distribution of HCV genotypes was significant between female and male patients (P < 0.05) but not in different kinds of hepatitis C patients.
CONCLUSIONType 1b was the predominant HCV genotype in Yixing area.
Base Sequence ; Blood Donors ; China ; epidemiology ; Female ; Genotype ; Hepacivirus ; genetics ; isolation & purification ; Hepatitis C ; epidemiology ; prevention & control ; therapy ; virology ; Humans ; Male ; Middle Aged ; Sequence Analysis, DNA ; Sex Factors
3.Study on the coinfection of Hantavirus and Orientia tsutsugamushi in tissue cell culture.
Xiao-zhao DENG ; Ke XU ; Jing KONG ; Zhen-yu DIAO ; Jun-ying QIAN ; Yong-fei TAN ; Mao ZHANG ; Guang-wen CAO ; Yun ZHANG
Chinese Journal of Epidemiology 2006;27(6):518-521
OBJECTIVETo investigate the possibility of Hantavirus (HV) and Orientia tsutsugamushi (Ot) coinfection in their hosts.
METHODSHV and Ot were used to infect Vero E6 cells cultured in vitro singly, simultaneously or successively. Genes of HV and Ot were identified in different generation cells with RT-PCR.
RESULTSFive experiment groups of infected Vero E6 cells were tested, the results were as follows: HV and Ot were both positive in infected Vero E6 cells passaged 2 times and the positive rate increased following the passaged times in HV and Ot infection groups, simultaneously or successively. However, in the groups which were infected with HV and Ot separately, the gene of HV or Ot could be detected in infected Vero E6 cells passaged only once and the positive rate increased following the times of the passaged. The positive rate was higher in the singly infected groups than in those infected simultaneously or successively.
CONCLUSIONCoinfection of HV and Ot did exist in the hosts while HV and Ot could inhibit each other in the initial infection stage.
Animals ; Cell Division ; Cercopithecus aethiops ; Hantavirus ; pathogenicity ; Hantavirus Infections ; Orientia tsutsugamushi ; pathogenicity ; Reverse Transcriptase Polymerase Chain Reaction ; Scrub Typhus ; Vero Cells
4.AntiEGFRnano inhibites proliferation and migration of estrogen-dependent Ishikawa cells of human endometrial cancer cell line.
Zhen-yu DIAO ; Wu-guang LU ; Peng CAO ; Yun-long HU ; Xing ZHOU ; Ping-ping XUE ; Li SHEN ; Hai-xiang SUN
Acta Pharmaceutica Sinica 2012;47(10):1341-1346
Nanobody is a kind of antibody from camel, which misses light chain. Nanobody has the same antigen binding specificity and affinity as mAb. Moreover, because of its small molecular weight, high stability and easy preparation, nanobody has great value of biomedical applications. In this study, we successfully prepared highly pure antiEGFR nanobody in E.coli using genetic engineering techniques. Cell proliferation assay (CCK-8 assay) and migration experiments (cell scratch test and Transwell assay) indicated that the recombinant antiEGFRnano can significantly inhibit the proliferation and migration of endometrial cancer cells. These results provide a new way of thinking and methods for EGFR-targeted therapy of endometrial cancer.
Adenocarcinoma
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metabolism
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pathology
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Amino Acid Sequence
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Base Sequence
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Cell Line, Tumor
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Cell Movement
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drug effects
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Cell Proliferation
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drug effects
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Endometrial Neoplasms
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metabolism
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pathology
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Escherichia coli
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metabolism
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Estrogens
;
metabolism
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Female
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Genetic Vectors
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Humans
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Plasmids
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Receptor, Epidermal Growth Factor
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genetics
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immunology
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Recombinant Proteins
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metabolism
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Single-Domain Antibodies
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genetics
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pharmacology
5.Detection the coinfection of Hantavirus and Orientia tsutsugamushi in primary cultured mite cells.
Xiao-zhao DENG ; Ke XU ; Chun-mei JIANG ; Zhong-can WANG ; Jing KONG ; Zhen-yu DIAO ; Jun-ying QIAN ; Yun ZHANG ; Guang-wen CAO
Chinese Journal of Experimental and Clinical Virology 2007;21(4):307-309
OBJECTIVETo investigate whether HV and Ot can coexist in their host (Leptotrombidium scutellare).
METHODSCollecting the separate Leptotrombidium scutellare and the ones from mice in epidemic area. The cells of mites at larva, nymph, and adult stages were cultured and made into smear. In situ RT-PCR and PCR were used to detect and locate HV RNA and Ot DNA in the primary cultured cells.
RESULTSPositive signals of HV RNA and Ot DNA distributed mostly in epithelial cells of digestive system and ovary cells of larva and nymph. The positive rate increased by the generation of passages.
CONCLUSIONCoinfection of HV and Ot did exist in wild Leptotrombidium scutellare.
Animals ; Cells, Cultured ; DNA, Bacterial ; analysis ; Female ; Hantavirus ; isolation & purification ; Mice ; Mites ; microbiology ; virology ; Orientia tsutsugamushi ; isolation & purification ; RNA, Viral ; analysis ; Reverse Transcriptase Polymerase Chain Reaction
6.MLST typing of Streptococcus suis isolated from clinical patients in Guangdong Province in 2005.
Hong-min WANG ; Chang-wen KE ; Wu-bin PAN ; Bi-xia KE ; Jing-diao CHEN ; Xiao-ling DENG ; Mei-zhen LIU ; Guo-ren CHEN ; Xing-fen YANG ; Zhen-yu ZHU
Journal of Southern Medical University 2008;28(8):1438-1441
Intensive surveillance of human S.suis infection was carried out in July and August of 2005 in Guangdong Province, which coincided with the Sichuan outbreak. Five isolated cases of human infections were identified during this period, from which 5 S. suis serotype 2 isolates were recovered. MLST analysis showed that these 5 isolates shared identical sequences of 6 MLST housekeeping genes except for one point mutation found within the thrA gene fragment, a neutral mutation (TTA to TTG) in the third nucleotide (360 nt) of the codon for leucine. MLST analysis identified 2 sequence types in the Guangdong sporadic infection. Three Guangdong isolates L-SS002, L-SS003 and L-SS005 belonged to ST7, while the other two isolates L-SS004 and L-SS006 belonged to ST1, but they all belonged to ST1 clonal complex. This finding represents a striking feature that differs from the Sichuan outbreak caused by a single ST7 SS2 clone. The 3 isolates of ST7 were probably imported from Sichuan Province, while the origin of the other 2 isolates of ST1 still remain to be clarified.
Animals
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Bacterial Typing Techniques
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methods
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China
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DNA, Bacterial
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genetics
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Humans
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Sequence Analysis, DNA
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Streptococcal Infections
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microbiology
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Streptococcus suis
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classification
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genetics
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pathogenicity
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Swine
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Swine Diseases
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microbiology
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Zoonoses
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microbiology
7.ICSI with testicular or epididymal sperm for patients with obstructive azoospermia: A systematic review.
Xu-Xin ZHAN ; Chang-Chun WAN ; Hai-Bo LI ; Jiang GOU ; Hong-Cai CAI ; Jing ZHAO ; Chun-Fang YAN ; Zhen-Yu DIAO ; Xue-Jun SHANG
National Journal of Andrology 2016;22(12):1122-1130
ObjectiveTo assess the effects of testicular sperm and epididymal sperm on the outcomes of ICSI for patients with obstructive azoospermia.
METHODSWe searched PubMed, MEDLINE, EMBASE, Cochrane, CNKI, VIP, CBM, and Wanfang Database up to December 2015 for published literature relevant to ICSI with testicular or epididymal sperm for obstructive azoospermia patients. According to the inclusion and exclusion criteria, two reviewers independently conducted literature screening, data extraction and quality assessment of the included trials, followed by meta-analysis with the RevMan 5.3 software.
RESULTSA total of 14 studies were identified, involving 1 278 patients and 1 553 ICSI cycles. ICSI with epididymal sperm exhibited a significantly higher fertilization rate than that with testicular sperm (RR = 1.08, 95% CI 1.05-1.11, P<0.01). No statistically significant differences were observed between the epididymal and testicular sperm groups in the rates of cleavage (RR = 1.04, 95% CI 0.99-1.10, P = 0.13), good-quality embryo (RR = 1.01, 95% CI 0.93-1.09,P = 0.85), implantation (RR = 1.14, 95% CI 0.75-1.73, P = 0.55), clinical pregnancy (RR = 1.14, 95% CI 0.98-1.31, P = 0.08), and miscarriage (RR = 0.86, 95% CI 0.53-1.39,P = 0.54).
CONCLUSIONSICSI with epididymal sperm yields a markedly higher fertilization rate than that with testicular sperm, but has no statistically significant differences from the latter in the rates of cleavage, good-quality embryo, implantation, clinical pregnancy, and miscarriage in the treatment of obstructive azoospermia.
8.Effect of intestinal obstruction stent combined with neoadjuvant chemotherapy on the pathological characteristics of surgical specimens in patients with complete obstructive colorectal cancer.
Ke CAO ; Xiao Li DIAO ; Jian Feng YU ; Gan Bin LI ; Zhi Wei ZHAI ; Bao Cheng ZHAO ; Zhen Jun WANG ; Jia Gang HAN
Chinese Journal of Gastrointestinal Surgery 2022;25(11):1012-1019
Objective: To compare the effects of three treatment options: emergency surgery, stent-surgery, and stent-neoadjuvant chemotherapy-surgery, on the pathological characteris- tics of surgically-resected specimens from patients with completely obstructive colorectal cancer. Methods: This was a retrospective cohort study analyzing clinicopathological data of patients with complete obstructive colorectal cancer who were admitted to the General Surgery Department of Beijing Chaoyang Hospital, Capital Medical University, between May 2012 and August 2020. The inclusion criteria were diagnosed with complete colorectal obstruction, pathologically confirmed as adenocarcinoma, resectable on imaging assessment, and without distant metastasis, combined with the patients' clinical manifestations and imaging examination findings. Patients with multiple colorectal cancers, refusal to undergo surgery, and concurrent peritonitis or intestinal perforation before stenting of the intestinal obstruction were excluded. Eighty-nine patients with completely obstructive colorectal cancer were enrolled in the study and were divided into emergency surgery group (n=30), stent-surgery group (n=34), and stent-neoadjuvant chemotherapy- surgery group (n=25) according to the treatment strategy. Differences in the pathological features (namely perineural infiltration, lymphovascular infiltration, tumor deposits, specimen intravascular necrosis, inflammatory infiltration, abscesses, mucus lake formation, foreign body giant cells, calcification, and tumor cell ratio) and biomolecular markers (namely cluster of differentiation (CD)34, Ki67, Bcl-2, matrix metalloproteinase-9, and hypoxia-inducible factor alpha) were recorded. Pathological evaluation was based on the presence or absence of qualitative evaluation of pathological features, such as peripheral nerve infiltration, vascular infiltration, and cancer nodules within the specimens. The evaluation criteria for the pathological features of the specimens were as follows: Semi-quantitative graded evaluation based on the proportion of tissue necrosis, inflammatory infiltrates, abscesses, mucus lake formation, foreign body giant cells, calcification, and tumor cells in the field of view within the specimen were classified as: grade 0: not seen within the specimen; grade 1: 0-25%; grade 2: 25%-50%; grade 3: 50%-75%; and grade 4: 75%-100%. The intensity of cellular immunity was classified as none (0 points), weak (1 point), moderate (2 points), and strong (3 points). The two evaluation scores were then multiplied to obtain a total score of 0-12. The immunohistochemical results were also evaluated comprehensively, and the results were defined as: negative (grade 0): 0 points; weakly positive (grade 1): 1-3 points; moderately positive (grade 2): 4-6 points; strongly positive (grade 3): 7-9 points; and very strong positive (grade 4): 10-12 points. Normally-distributed values were expressed as mean±standard deviation, and one-way analysis of variance was used to analyze the differences between the groups. Non-normally-distributed values were expressed as median (interquartile range: Q1, Q3). A nonparametric test (Kruskal-Wallis H test) was used for comparisons between groups. Results: The differences were not statistically significant when comparing the baseline data for age, gender, tumor site, American Society of Anesthesiologists score, tumor T-stage, N-stage, and degree of differentiation among the three groups (all P>0.05). The differences were not statistically significant when comparing the pathological characteristics of the resected tumor specimens, such as foreign body giant cells, inflammatory infiltration, and mucus lake formation among the three groups (all P>0.05). The rates of vascular infiltration were 56.6% (17/30), 41.2% (15/34), and 20.0% (5/25) in the emergency surgery, stent-surgery, and stent- neoadjuvant chemotherapy-surgery groups, respectively, with statistically significant differences between the groups (χ2=7.142, P=0.028). Additionally, the rate of vascular infiltration was significantly lower in the stent-neoadjuvant chemotherapy-surgery group than that in the emergency surgery group (P=0.038). Peripheral nerve infiltration rates were 55.3% (16/30), 41.2% (14/34), and 16.0% (4/25), in the emergency surgery, stent-surgery, and stent-neoadjuvant chemotherapy-surgery groups, respectively, with statistically significant differences (χ2=7.735, P=0.021). The infiltration peripheral nerve rates in the stent-neoadjuvant chemotherapy-surgery group were significantly lower than those in the emergency surgery group (P=0.032). The necrosis grade was 2 (1, 2), 2 (1, 3), and 2 (2, 3) in the emergency surgery, stent- surgery, and stent-neoadjuvant chemotherapy-surgery groups, respectively, with statistically significant differences (H=10.090, P=0.006). Post hoc comparison revealed that the necrosis grade was higher in the stent-surgery and stent-neoadjuvant chemotherapy-surgery groups compared with the emergency surgery group (both P<0.05). The abscess grade was 2 (1, 2), 3 (1, 3), and 2 (2, 3) in the emergency surgery, stent-surgery, and stent-neoadjuvant chemotherapy-surgery groups, respectively, with statistically significant differences (H=6.584, P=0.037). Post hoc comparison revealed that the abscess grade in the emergency surgery group was significantly lower than that in the stent-surgery group (P=0.037). The fibrosis grade was 2 (1, 3), 3 (2, 3), and 3 (2, 3), in the emergency surgery, stent-surgery, and stent-neoadjuvant chemotherapy-surgery groups, respectively, with statistically significant differences (H=11.078, P=0.004). Post hoc analysis revealed that the fibrosis degree was higher in both the stent-surgery group and the stent- neoadjuvant chemotherapy-surgery group compared with the emergency surgery group (both, P<0.05). The tumor cell ratio grades were 4 (3, 4), 4 (3, 4), and 3 (2, 4), in the emergency surgery, stent-surgery, and stent-neoadjuvant chemotherapy-surgery groups, respectively, with statistically significant differences (H=8.594, P=0.014). Post hoc analysis showed that the tumor cell ratio in the stent-neoadjuvant chemotherapy-surgery group was significantly lower than that in the emergency surgery group (P=0.012). The CD34 grades were 2 (2, 3), 3 (2, 4), and 3 (2, 3) in the emergency surgery, stent-surgery, and stent-neoadjuvant chemotherapy-surgery groups, respectively, and the difference was statistically significant (H=9.786, P=0.007). Post hoc analysis showed that the CD34 grades in the emergency surgery, stent-surgery, and stent-neoadjuvant chemotherapy-surgery groups were 2 (2, 3), 3 (2, 4), and 3 (2,3), respectively. Post hoc analysis revealed that the CD34 concentration was higher in the stent-surgery group than that in the emergency surgery group (P=0.005). Conclusion: Stenting may increase the risk of distant metastases in obstructive colorectal cancer. The stent-neoadjuvant chemotherapy-surgery treatment model promotes tumor cell necrosis and fibrosis and reduces the proportion of tumor cells, vascular infiltration, and peripheral nerve infiltration, which may help decrease local tumor infiltration and distant metastasis in completely obstructive colorectal cancer after stent placement.
Humans
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Neoadjuvant Therapy/methods*
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Abscess
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Retrospective Studies
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Intestinal Obstruction/etiology*
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Stents
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Colorectal Neoplasms/therapy*
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Necrosis
9.Clinical treatment outcomes and their changes in extremely preterm twins: a multicenter retrospective study in Guangdong Province, China.
Bi-Jun SHI ; Ying LI ; Fan WU ; Zhou-Shan FENG ; Qi-Liang CUI ; Chuan-Zhong YANG ; Xiao-Tong YE ; Yi-Heng DAI ; Wei-Yi LIANG ; Xiu-Zhen YE ; Jing MO ; Lu DING ; Ben-Qing WU ; Hong-Xiang CHEN ; Chi-Wang LI ; Zhe ZHANG ; Xiao RONG ; Wei SHEN ; Wei-Min HUANG ; Bing-Yan YANG ; Jun-Feng LYU ; Hui-Wen HUANG ; Le-Ying HUO ; Hong-Ping RAO ; Wen-Kang YAN ; Xue-Jun REN ; Yong YANG ; Fang-Fang WANG ; Dong LIU ; Shi-Guang DIAO ; Xiao-Yan LIU ; Qiong MENG ; Yu WANG ; Bin WANG ; Li-Juan ZHANG ; Yu-Ge HUANG ; Dang AO ; Wei-Zhong LI ; Jie-Ling CHEN ; Yan-Ling CHEN ; Wei LI ; Zhi-Feng CHEN ; Yue-Qin DING ; Xiao-Yu LI ; Yue-Fang HUANG ; Ni-Yang LIN ; Yang-Fan CAI ; Sha-Sha HAN ; Ya JIN ; Guo-Sheng LIU ; Zhong-He WAN ; Yi BAN ; Bo BAI ; Guang-Hong LI ; Yue-Xiu YAN
Chinese Journal of Contemporary Pediatrics 2022;24(1):33-40
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*
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Female
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Gestational Age
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Humans
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Infant
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Infant, Extremely Premature
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Infant, Newborn
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Pregnancy
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Respiratory Distress Syndrome, Newborn/epidemiology*
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Retrospective Studies
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Treatment Outcome
10.Neutralization against SARS-CoV-2 Delta/Omicron variants and B cell response after inactivated vaccination among COVID-19 convalescents.
Hao WANG ; Yu YUAN ; Bihao WU ; Mingzhong XIAO ; Zhen WANG ; Tingyue DIAO ; Rui ZENG ; Li CHEN ; Yanshou LEI ; Pinpin LONG ; Yi GUO ; Xuefeng LAI ; Yuying WEN ; Wenhui LI ; Hao CAI ; Lulu SONG ; Wei NI ; Youyun ZHAO ; Kani OUYANG ; Jingzhi WANG ; Qi WANG ; Li LIU ; Chaolong WANG ; An PAN ; Xiaodong LI ; Rui GONG ; Tangchun WU
Frontiers of Medicine 2023;17(4):747-757
Emerging SARS-CoV-2 variants have made COVID-19 convalescents susceptible to re-infection and have raised concern about the efficacy of inactivated vaccination in neutralization against emerging variants and antigen-specific B cell response. To this end, a study on a long-term cohort of 208 participants who have recovered from COVID-19 was conducted, and the participants were followed up at 3.3 (Visit 1), 9.2 (Visit 2), and 18.5 (Visit 3) months after SARS-CoV-2 infection. They were classified into three groups (no-vaccination (n = 54), one-dose (n = 62), and two-dose (n = 92) groups) on the basis of the administration of inactivated vaccination. The neutralizing antibody (NAb) titers against the wild-type virus continued to decrease in the no-vaccination group, but they rose significantly in the one-dose and two-dose groups, with the highest NAb titers being observed in the two-dose group at Visit 3. The NAb titers against the Delta variant for the no-vaccination, one-dose, and two-dose groups decreased by 3.3, 1.9, and 2.3 folds relative to the wild-type virus, respectively, and those against the Omicron variant decreased by 7.0, 4.0, and 3.8 folds, respectively. Similarly, the responses of SARS-CoV-2 RBD-specific B cells and memory B cells were boosted by the second vaccine dose. Results showed that the convalescents benefited from the administration of the inactivated vaccine (one or two doses), which enhanced neutralization against highly mutated SARS-CoV-2 variants and memory B cell responses. Two doses of inactivated vaccine among COVID-19 convalescents are therefore recommended for the prevention of the COVID-19 pandemic, and vaccination guidelines and policies need to be updated.