[Phenotypic and genotypic characteristics of Escherichia coli causing bloodstream and abdominal co-infection].

Objective: To analyze the phenotypic and genotypic characteristics of Escherichia coli causing bloodstream and abdominal co-infection (CoECO), and provide clues for empirical antibiotics treatment. Methods: The strains of Escherichia coli isolated from blood and abdominal samples in the Department of Laboratory Medicine of the First Medical Center of the PLA General Hospital from 2010 to 2020 were retrospectively analyzed. Mass spectrometer was used to identify all of the strains and the minimum inhibitory concentration (MIC) were detected by VITEK 2 Compact. All isolates were sequenced by 2×150 bp double terminal sequencing strategy on the HiSeq X Ten sequencer (Illumina). After the genome sequence was spliced, the single nucleotide polymorphism (SNP) analysis of the strain sequence was performed using kSNP3 software to clarify the homologous relationship between strains. If the strains isolated from two different parts had high homology, they were regarded as the same strain and the case was with CoECO infection. Meanwhile, the multilocus sequence type (MLST) was determined using PubMLST website and resistant genes were screened by CARD website. Results: A total of 70 cases of CoECO infection were screened, including 45 males and 25 females, and aged (59.2±16.3) years old. The 70 CoECO isolates belonged to 35 sequence types (STs). The most prevalent STs included ST38 (n=6), ST 405 (n=6), ST 1193 (n=6) and ST131 (n=5), and other ST types contained less than 5 strains. The homologous relationship among strains was relatively scattered, presenting a sporadic trend as a whole, and only a few strains had a small-scale outbreak. The CoECO isolates showed significantly resistance to ampicillin (91.4%, 64/70), ampicillin/sulbactam (74.3%, 5 2/70), ceftriaxone (72.9%, 51/70), ciprofloxacin (71.4%, 50/70) and levofloxacin (71.4%, 50/70), and high-sensitivity to piperacillin/tazobactam, carbapenems and amikacin. The most prevalent resistant gene was tet (A/B) (70%, 49/70), followed by blaTEM (58.6%, 41/70), sul1 (55.7%, 40/70), sul2 (54.3%, 38/70), blaCTX-M-14(25.7%, 18/70), blaCTX-M-15(17.1%, 13/70), blaCTX-M-55(15.7%, 11/70), blaCTX-M-64/65(5.7%, 4/70), blaCTX-M-27(4.3%, 3/70), mcr-1 (4.3%, 3/70), blaNDM-5(2.9%, 2/70). Conclusions: CoECO is distributed dispersedly and has no obvious advantage clone. No genotype with obvious advantages was found. Although the strain has a high resistance rate to some antibacterial drugs, the proportion of carrying resistant genes is low, and it has a high sensitivity to some first-line antibacterial drugs.

[Progress in research of etiology of childhood obesity based on interaction between genes and environment].

Childhood obesity is a global public health problem, which can not only endangers children's health, but also might be an important cause of chronic diseases in adulthood. In recent years, with the in-depth development of precision medicine research, more and more research evidences have shown that there are interactions between environmental factors, such as early intrauterine environment, children's diet, physical activity and children's gene factor on the incidence of childhood obesity, which can result in or inhibit the incidence and development of childhood obesity. This paper summarizes the progress in research in this field to reveal the effects and potential mechanisms of genetic factors and environmental factors on the incidence of childhood obesity in order to provide reference for the precise prevention and control of childhood obesity under different genetic backgrounds.

[The study of mitochondrial disorder pedigree associated with FASTKD2 variants and uniparental disomy].

Objective: To analyse the genetic cause of a proband with mitochondrial disease caused by FASTKD2 gene variation and uniparental disomy. Methods: Detailed medical history of a child suspected "mitochondrial disease" were inquired in Peking University First Hospital on November 23, 2017. c.810_820dup homozygous variation in FASTKD2 gene was found by high-throughput sequencing, and her mother had heterozygous variation, but her father didn't have such variation, which didn't conform to the genetic law of variation. Further clinical examinations and molecular genetic tests were carried out. The venous blood of the child and her parents was drawn, and genomic DNA was extracted. Sanger sequencing, polymerase chain reaction (PCR) testing, short tandem repeat (STR) analysis, chromosome microarray analysis and loss of heterozygosity (LOH) genetic relationship analysis were performed on the proband and the parents to determine the variation. Results: The clinical manifestations, physical examination and laboratory examination of the child supported the diagnosis of mitochondrial disease. c.810_820dup(p.Ser274Phefs*8) homozygous variant in FASTKD2 gene was identified. Sanger sequencing indicated that the mother was a heterozygote of the variant, while the father had no such variation, which did not conform to the genetic law. PCR testing and Sanger sequencing review to eliminate sampling errors, PCR amplification and sequencing errors. Non-biological father was excluded by STR analysis. Three large segmental LOH of FASTKD2 gene were found by chromosome microarray analysis, then the LOH relative analysis verified the child was a mixed maternal uniparental disomy of chromosome 2. The child was diagnosed as mitochondrial disease caused by oxidative phosphorylation coupling defect of type 44. Conclusions: In this study, an autosomal recessive mitochondrial disease which does not conform to the genetic law was found, and it was confirmed that this mitochondrial disease family had both pathogenic variation and uniparental disomy phenomenon. It was diagnosed as mitochondrial disease caused by type 44 oxidative phosphorylation coupling defect.

[Exploration of cystathionine ß-synthase and cystathionine γ-lyase gene expression poor prognostic predictive value with the application of bioinformatics data mining in liver cancer].

Objective: To study the relationship between cystathionine ß-synthase (CBS) and cystathionine γ-lyase (CTH) genes-related signaling pathways in liver cancer cells. Methods: We conducted a correlation analysis between the clinical features of CBS and CTH gene expression by mining the GEO (Gene Expression Omnibus) and TCGA (The Cancer Genome Atlas) databases of liver cancer. Additionally, liver cancer cell lines were verified by immunoblotting. Results: CBS and CTH expressions were significantly lower in tumors than in non-tumors (P < 0.05). COX regression result showed that CBS was an independent risk factor for the poor prognosis of liver cancer cells (HR=0.65, P = 0.02). A univariate logistic regression analysis was performed on the different tumor stages focusing on the CBS gene, which showed that TNM stage II verses I (P = 0.01, OR=0.50), stage III verses I (P = 0.03, OR=0.56), T stage T2 verses T1 (P < 0.01, OR=0.43), and T3 stage verses T1 (P = 0.02, OR=0.54) were significantly lower in liver cancer. TNM stage III verses I (P = 0.01, OR=0.50), Edmondson stage II verses I (P = 0.03, OR=0.48), stage III verses stage I (P < 0.01, OR=0.30), stage IV verses I (P = 0.03, OR=0.22), and T stage T3 verses T1(P = 0.03, OR=0.22) of the CTH gene expressions were significantly lower in liver cancer. GSEA enrichment analysis result revealed that the signaling pathway most correlated with the expression of CTH and CBS genes in liver cancer cells was cytochrome P450 (CYP450) (FDR Q < 0.01, FWER P < 0.01). Western blot results showed that the expression of the CTH downstream protein CSE was reduced in HCC cell lines such as HLE and Hep3B cells compared with the human immortalized liver cell line HL-7702. Conclusion: CBS and CTH gene expressions are lower in tumor tissue than in normal tissue groups. The CBS gene is an independent risk factor for poor prognosis in stem cell carcinoma. The cytochrome P450 is the signaling pathway most closely related to the CBS and CTH genes.

[Progress in application of deep learning in orthodontic diagnosis and treatment].

In recent years, the application of artificial intelligence technology in the field of orthodontics has gradually increased, and deep learning, as a hot direction, has also been rapidly applied in the detection, evaluation, diagnosis, prediction and effect evaluation. At present, deep learning research has the advantages of high efficiency and accuracy, but it also has limitations such as weak interpretability and insufficient data volume. This paper reviewed the proposal and development of deep learning, the application in orthodontic diagnosis and treatment, as well as the limitations and countermeasures of the popularization, and prospect of the future research.

[The diagnostic value of chromosome microarray analysis technique in the genetic causes of children with intellectual disability or global developmental delay].

Objective: To study the value of chromosome microarray analysis (CMA) application in children with developmental delay (DD), intellectual disability (ID), autistic spectrum disorder (ASD) and multiple congenital anomalies (MCA). Methods: Genomic DNA was extracted from peripheral blood samples. Array-based comparative genomic hybridization (array-CGH) analysis and single nucleotide polymorphism array (SNP-array) were performed in 1 320 children with DD/ID, ASD, with or without epilepsy and MCA who were admitted to Peking University First Hospital from 2014 to 2019. The results of genetic etiology test of CMA in children with mental retardation or global DD was summarized. Results: Of 1 320 samples, there were 10 cases of aneuploid abnormality, 6 cases of uniparental disomy and one case of mosaicism, respectively. Pathogenic copy number variations (CNVs) were found in 320 cases and pathogenic CNVs were detected in 23 cases, with a combined detection rate of 26% (343/1 320). CNVs of uncertain clinical significance occurred in 107 cases, accounting for 8.1% (107/1 320). There were 25 cases of possible benign CNVs, accounting for 2% (25/1 320), while benign CNVs were reported in 20 cases, accounting for 1.5% (20/1 320). The detection rate of MCA with DD/ID was 39.8% (130/327). Conclusions: CMA has the advantages of high resolution and covering the whole genome. It can detect the chromosomal abnormalities, microdeletions and duplications seen under the microscope, thus the genetic etiology of children with mental retardation or global DD can be diagnosed.

Correction: Protein kinase Mζ in medial prefrontal cortex mediates depressive-like behavior and antidepressant response.

Following publication of this article, the authors noted that the bands of Na-K ATPase in Figure S1B were mislabelled when selecting representative blots, and were erroneously duplicated from GluA2. However, the data analysis was still made with the correct immunoblots. The Supplementary Information file has now been updated to include the corrected Figure S1 with the correct western blot bands of Na-K ATPase.The authors would like to apologise for this error and the inconvenience this may have caused. This has been corrected in both the PDF and HTML versions of the article.

LncRNA SNHG8 participates in the development of endometrial carcinoma through regulating c-MET expression by miR-152.

OBJECTIVE: To investigate the possible function and mechanism of lncRNA SNHG8 in the pathogenesis of endometrial carcinoma. PATIENTS AND METHODS: We utilized qRT-PCR to detect the expression of SNHG8 in 60 cases of endometrial carcinoma and 25 cases of normal endometrium; after that, the endometrial carcinoma cell lines were screened. SNHG8 was transfected into endometrial carcinoma cells by Lipofectamine and the proliferative activity of cells was detected by cell counting kit-8 (CCK-8) assay. Bioinformatics methods were used to detect the target microRNA. miR-152 is predicted to bind to SNHG8 and target genes of c-MET. Luciferase reporter assay was performed to detect the relative luciferase activity between miR-152 and c-MET, SNHG8. The interactions between SNHG8, miR-152, and c-MET were further verified by transfection of miR-152 mimics, miR-152 mimics + OE-SNHG8, SNHG8 siRNA, and SNHG8 siRNA + miR-152 inhibitor. RESULTS: SNHG8 expression in endometrial carcinoma tissue was significantly higher than that in normal endometrium. After transfection with SNHG8 siRNA, the cell viability of AN3CA cells decreased, whereas the activity of Ishikawa was increased after transfection with SNHG8 overexpression plasmid. Bioinformatics predictions and dual luciferase reporter assay illustrated that SNHG8 was bound to miR-152 and miR-152 targeted on c-MET. In addition, miR-152 mimics inhibited the expression of c-MET, and the inhibitory effect was reversed after SNHG8 overexpression. Silencing SNHG8 reduced c-MET expression, and c-MET expression was reversed after addition of miR-152 inhibitor. CONCLUSIONS: SNHG8 is highly expressed in endometrial carcinoma, and SNHG8 targets c-MET through miR-152 to regulate the proliferation of endometrial cancer cells.

Three-dimensional spheroid culture of adipose stromal vascular cells for studying adipogenesis in beef cattle.

Protocols designed for the adipogenic differentiation of human and mouse cells are commonly used for inducing the adipogenesis of bovine stromal vascular cells. However, likely due to metabolic differences between ruminant and non-ruminant animals, these methods result in only few cells undergoing complete adipogenesis with minimal lipid droplet accumulation. Here, we discuss the development of an adipogenic differentiation protocol for bovine primary cells through a three-dimensional spheroid culture. Stromal vascular cells derived from bovine intramuscular fat were isolated and stored in liquid nitrogen before culturing. Cells were cultured in hanging drops for 3 days to allow for the formation of spherical structures. The spheroids were then transferred to cell culture plates with endothelial basal medium-2 for 3 days and in Dulbecco's Modified Eagle's Medium (DMEM) supplemented with a standard adipogenic cocktail for 3 additional days, which were then allowed to fully differentiate for 3 days in DMEM supplemented with insulin. Compared with conventional two-dimensional culture, cells in a three-dimensional spheroid culture system had higher adipogenic gene expression and consequently contained more adipocytes with larger lipid droplets. In addition, endothelial induction of spheroids prior to adipogenic differentiation is essential for efficient induction of adipogenesis of bovine stromal vascular cells, mimicking in vivo adipose development. In summary, the newly developed three-dimensional spheroid culture method is an efficient way to induce adipogenic differentiation and study adipose development of cells derived from ruminant animals, which also can be used for studying the role of angiogenesis in adipose development.

Protein kinase Mζ in medial prefrontal cortex mediates depressive-like behavior and antidepressant response.

Neuronal atrophy and alterations of synaptic structure and function in the medial prefrontal cortex (mPFC) have been implicated in the pathogenesis of depression, but the underlying molecular mechanisms are largely unknown. The protein kinase Mζ (PKMζ), a brain-specific atypical protein kinase C isoform, is important for maintaining long-term potentiation and storing memory. In the present study, we explored the role of PKMζ in mPFC in two rat models of depression, chronic unpredictable stress (CUS) and learned helplessness. The involvement of PKMζ in the antidepressant effects of conventional antidepressants and ketamine were also investigated. We found that chronic stress decreased the expression of PKMζ in the mPFC and hippocampus but not in the orbitofrontal cortex. Overexpression of PKMζ in mPFC prevented the depressive-like and anxiety-like behaviors induced by CUS, and reversed helplessness behaviors. Inhibition of PKMζ in mPFC by expressing a PKMζ dominant-negative mutant induced depressive-like behaviors after subthreshold unpredictable stress and increased learned helplessness behavior. Furthermore, stress-induced deficits in synaptic proteins and decreases in dendritic density and the frequency of miniature excitatory postsynaptic currents in the mPFC were prevented by PKMζ overexpression and potentiated by PKMζ inhibition in subthreshold stress rats. The antidepressants fluoxetine, desipramine and ketamine increased PKMζ expression in mPFC and PKMζ mediated the antidepressant effects of ketamine. These findings identify PKMζ in mPFC as a critical mediator of depressive-like behavior and antidepressant response, providing a potential therapeutic target in developing novel antidepressants.

Population genetic structure and its implication in the conservation of Schizopygopsis pylzovi in Yellow River as inferred from mitochondrial DNA sequence analysis.

To assess the genetic diversity, structure, and population dynamics of Schizopygopsis pylzovi, we examined the changes in mitochondrial DNA sequences (the mtDNA control region and the Cyt b gene; 1835 bp) in 304 individuals from nine populations. The samples were segregated into 112 haplotypes, with high haplotype diversity and low nucleotide diversity. The haplotype diversity was highest in the Minhe (HS) range of Huangshui River and lowest in the Weiyuan (WY) range of Weihe River. Analysis of molecular variance showed that 69.64% of the total genetic variance was contributed by within-the-group variation and 30.36% was contributed by among-the-group variation. Pairwise FST revealed significant divergence between the populations. The FST between the MT and WY was highest, and that between the YZ and YJ was lowest. The neighbor-joining phylogenetic tree demonstrated that all geographic populations were not monophyletic, but overlapped each other, indicating that the duration of geographical isolation was not long enough or the populations had not yet reached significant genetic isolation or differentiation at the monophyletic level. Tajima's D and Fu's Fs were negative and statistically significant, indicating that S. pylzovi had experienced certain population expansion events, which is consistent with the hypothesis that the headwater area of the Yellow River was dramatically affected by the geological and climatic upheaval during the Quaternary ice age. Our analysis indicated that the management units corresponding to the WY population should be managed and conserved first. In situ conservation is first recommended to protect the original habitat from further destruction.

Effects of LeY glycan expression on embryo implantation.

OBJECTIVE: To investigate the correlation between LeY glycan expression and embryo implantation. MATERIALS AND METHODS: Uterine epithelial cells before implantation were transfected with FUT1siRNA to inhibit FUT1 (the gene encoding the key enzyme of LeY synthesis) expression and treated with 10 ng/ml leukemia inhibitory factor (LIF). Murine embryo implantation model in vitro was prepared by late blastocysts with identical morphology and treated uterine epithelial cells co-culture. Using RT-PCR, dot blot and observation of embryo attachment to analyze FUT1 gene expression and LeY synthesis of uterine epithelial cells and studied further the correlation of LeY expression level and embryo implantation. RESULTS: FUT1 gene expression and LeY synthesis declined after cells were transfected with FUT1siRNA, and LIF promoted FUT1 expression and LeY synthesis. After expression of FUT1 gene was inhibited, attachment rate of embryos lowered, but LIF up-regulated FUT1 expression and increased the attachment rate of embryos. CONCLUSIONS: These results indicated regulating FUT1 expression affected LeY synthesis, and then LeY regulated the recognition and attachment of uterus-embryo and participates in embryo implantation further.

Environmental tobacco smoke exposure, urine CC-16 levels, and asthma outcomes among Chinese children.

BACKGROUND: Previous studies have shown the relationship between club cell secretory protein (Clara) (CC-16) and respiratory diseases. However, few studies have explored the associations between urine CC-16 levels and environmental tobacco smoke (ETS) exposure in children. The objective of this study was to evaluate whether ETS exposure is associated with CC-16 when stratified by asthma status. METHODS: In our study, CC-16 was measured on 537 children aged 9-15 from northeast China in 2011-2012 using the Human Clara Cell Protein ELISA kits. Doctor-diagnosed asthma was defined as having ever been diagnosed with asthma by a physician. The relationship between ETS exposure and urine CC-16 level was assessed using linear regression. RESULTS: When stratified by asthma status, a negative association between ETS exposure and urine CC-16 was observed after adjusting for the effects of the related covariates, with an adjusted ß coefficient [P value] = -0.31 [0.006] in the first 2 years of life and with an adjusted ß coefficient [P value] = -0.68 [0.004] in the first 2 years of life and current. CONCLUSIONS: Our study shows long-term exposure to ETS was associated with urinary CC-16 among children without asthma.

MiR-181 family: regulators of myeloid differentiation and acute myeloid leukemia as well as potential therapeutic targets.

MicroRNAs have been shown to play an important role in normal hematopoisis and leukemogenesis. Here, we report function and mechanisms of miR-181 family in myeloid differentiation and acute myeloid leukemia (AML). The aberrant overexpression of all the miR-181 family members (miR-181a/b/c/d) was detected in French-American-British M1, M2 and M3 subtypes of adult AML patients. By conducting gain- and loss-of-function experiments, we demonstrated that miR-181a inhibits granulocytic and macrophage-like differentiation of HL-60 cells and CD34+ hematopoietic stem/progenitor cells (HSPCs) by directly targeting and downregulating the expression of PRKCD (which then affected the PRKCD-P38-C/EBPα pathway), CTDSPL (which then affected the phosphorylation of retinoblastoma protein) and CAMKK1. The three genes were also demonstrated to be the targets of miR-181b, miR-181c and miR-181d, respectively. Significantly decreases in the expression levels of the target proteins were detected in AML patients. Inhibition of the expression of miR-181 family members owing to Lenti-miRZip-181a infection in bone marrow blasts of AML patients increased target protein expression levels and partially reversed myeloid differentiation blockage. In the mice implanted with AML CD34+ HSPCs, expression inhibition of the miR-181 family by Lenti-miRZip-181a injection improved myeloid differentiation, inhibited engraftment and infiltration of the leukemic CD34+ cells into the bone marrow and spleen, and released leukemic symptoms. In conclusion, our findings revealed new mechanism of miR-181 family in normal hematopoiesis and AML development, and suggested that expression inhibition of the miR-181 family could provide a new strategy for AML therapy.

The role, mechanism and potentially therapeutic application of microRNA-29 family in acute myeloid leukemia.

Abnormal proliferation, apoptosis repression and differentiation blockage of hematopoietic stem/progenitor cells have been characterized to be the main reasons leading to acute myeloid leukemia (AML). Previous studies showed that miR-29a and miR-29b could function as tumor suppressors in leukemogenesis. However, a comprehensive investigation of the function and mechanism of miR-29 family in AML development and their potentiality in AML therapy still need to be elucidated. Herein, we reported that the family members, miR-29a, -29b and -29c, were commonly downregulated in peripheral blood mononuclear cells and bone marrow (BM) CD34+ cells derived from AML patients as compared with the healthy donors. Overexpression of each miR-29 member in THP1 and NB4 cells markedly inhibited cell proliferation and promoted cell apoptosis. AKT2 and CCND2 mRNAs were demonstrated to be targets of the miR-29 members, and the role of miR-29 family was attributed to the decrease of Akt2 and CCND2, two key signaling molecules. Significantly increased Akt2, CCND2 and c-Myc levels in the AML cases were detected, which were correlated with the decreased miR-29 expression in AML blasts. Furthermore, a feed-back loop comprising of c-Myc, miR-29 family and Akt2 were found in myeloid leukemogenesis. Reintroduction of each miR-29 member partially corrected abnormal cell proliferation and apoptosis repression and myeloid differentiation arrest in AML BM blasts. An intravenous injection of miR-29a, -29b and -29c in the AML model mice relieved leukemic symptoms significantly. Taken together, our finding revealed a pivotal role of miR-29 family in AML development and rescue of miR-29 family expression in AML patients could provide a new therapeutic strategy.

Bandwidth improvement for slow light using amplification characteristics of cascaded vertical-cavity surface-emitting lasers.

A scheme to improve the bandwidth of slow light using cascaded vertical-cavity surface-emitting lasers (VCSELs) is proposed and experimentally demonstrated. In the scheme, a proper adjustment on the gain peaks of two cascaded VCSELs enables the generation of the desired composite gain spectrum, which has flat-top gain and delay profiles with enhanced peak values. By employing the improved gain and delay profiles in a slow light system, a large delay can be achieved within a wider bandwidth. In the experiment, by using two cascaded VCSELs, a tunable slow light up to 135 ps for a 5 Gbits/s pseudorandom binary sequence is demonstrated with relatively low signal distortion.

Pets keeping in home, parental atopy, asthma, and asthma-related symptoms in 12,910 elementary school children from northeast China.

UNLABELLED: The effects of pet exposure and parental atopy on respiratory symptoms were investigated in 12,910 children residing in twelve districts of northeast China. Responses to a self-administered questionnaire completed by parents of children were used to ascertain children with persistent cough, persistent phlegm, doctor-diagnosed asthma, current asthma and current wheeze. Exposure to animals during pregnancy was positively associated with doctor-diagnosed asthma [adjusted odds ratio (ORs), 1.86; 95% confidence interval (CI) 1.35-2.57], current asthma (adjusted OR, 3.06; 95% CI, 1.95-4.81) and asthma-related symptoms. Pet exposure in the first year of life and currently having animals in household were also related to a significantly higher prevalence of doctor-diagnosed asthma and asthma-related symptoms in these children. Associations with respiratory symptoms strengthened with higher levels of animal exposure. Parental atopy increased the risk of asthma diagnosis (OR, 3.49; 95%CI, 2.84-4.30), current asthma (OR, 3.94; 95%CI, 2.81-5.54) and asthma-related symptoms. There was an interaction between parental atopy and pet exposure in persistent phlegm, but not in doctor-diagnosed asthma. We conclude that pet keeping and parental atopy increased the risk of respiratory symptoms in children. Parental atopy did modify the effect of pet exposure on persistent phlegm but not on doctor-diagnosed asthma. PRACTICAL IMPLICATIONS: The relationship between exposure to animals and allergic respiratory diseases in childhood is controversial. Inconsistent with other cross-sectional studies mostly conducted in industrialized countries, our study indicates that exposure to animals may increase the occurrence of respiratory symptoms and diseases in children, and the associations with respiratory symptoms strengthened with higher levels of animal exposure parental atopy did modify the effect of pet exposure on persistent phlegm but not on doctor-diagnosed asthma. These findings support the view that measures should be taken to reduce animal exposure for children in China.

Effects of environmental tobacco smoke on respiratory health of boys and girls from kindergarten: results from 15 districts of northern China.

UNLABELLED: The effects of childhood environmental tobacco smoke (ETS) exposure on respiratory symptoms were investigated in 6053 kindergarten-aged children residing in 15 districts of northern China. Responses to a self-administered questionnaire completed by parents of children from 30 kindergartens were used to ascertain children with persistent cough, persistent phlegm, asthma symptom, current asthma, wheeze and wheeze without asthma. In first 2 years ETS exposure and current ETS exposure were associated with increased prevalence of persistent cough, persistent phlegm, wheeze and wheeze without asthma. Among boys, ETS exposure was associated with more respiratory symptoms and diseases than in girls. ETS exposure during pregnancy was associated with asthma symptom [odds ratio (OR), 3.00; 95% confidence interval (CI): 1.28-7.03], current asthma (OR, 3.38; 95% CI: 1.25-9.14), persistent cough (OR, 1.64; 95% CI: 1.13-2.37), persistent phlegm (OR, 1.74; 95% CI: 1.01-3.01), wheeze (OR, 1.75; 95% CI: 1.15-2.68), and wheeze without asthma (OR, 1.46; 95% CI: 1.01-2.37) only among boys. In boys, the adjusted ORs for increased risk of asthma symptom and current asthma for household exposures (> or =10 cigarettes smoked per day vs. none smoked) during workday were 2.04 (95% CI: 1.01-3.89) and 2.76 (95% CI: 1.06-9.58), respectively. We conclude that ETS exposure increases the occurrence of respiratory symptoms and diseases during childhood. Boys may be more susceptible to ETS than girls. PRACTICAL IMPLICATIONS: Environmental tobacco smoke (ETS) is a highly prevalent respiratory irritant. In agreement with previous cross-sectional studies, our study indicates that exposure to ETS may increase the occurrence of respiratory symptoms and diseases in children, and the association of ETS exposure and respiratory health of children increased in strength with number of cigarettes smoked inside the house per day during workday and day-off. Boys may be more susceptible to ETS than girls. These findings support the view that measures should be taken to reduce ETS exposure for children.