Sex-Specific Alterations in Placental Proteomics Induced by Intrauterine Hyperglycemia

Gestational diabetes mellitus (GDM) with intrauterine hyperglycemia induces a series of changes in the placenta, which have adverse effects on both the mother and the fetus. The aim of this study was to investigate the changes in the placenta in GDM and its gender differences. In this study, we established an intrauterine hyperglycemia model using ICR mice. We collected placental specimens from mice before birth for histological observation, along with tandem mass tag (TMT)-labeled proteomic analysis, which was stratified by sex. When the analysis was not segregated by sex, the GDM group showed 208 upregulated and 225 downregulated proteins in the placenta, primarily within the extracellular matrix and mitochondria. Altered biological processes included cholesterol metabolism and oxidative stress responses. After stratification by sex, the male subgroup showed a heightened tendency for immune-related pathway alterations, whereas the female subgroup manifested changes in branched-chain amino acid metabolism. Our study suggests that the observed sex differences in placental protein expression may explain the differential impact of GDM on offspring.

Recent Advances in Folates and Autoantibodies against Folate Receptors in Early Pregnancy and Miscarriage

Though firstly identified in cerebral folate deficiency, autoantibodies against folate receptors (FRAbs) have been implicated in pregnancy complications such as miscarriage; however, the underlying mechanism needs to be further elaborated. FRAbs can be produced via sensitization mediated by folate-binding protein as well as gene mutation, aberrant modulation, or degradation of folate receptors (FRs). FRAbs may interfere with folate internalization and metabolism through blocking or binding with FRs. Interestingly, different types of FRs are expressed on trophoblast cells, decidual epithelium or stroma, and macrophages at the maternal-fetal interface, implying FRAbs may be involved in the critical events necessary for a successful pregnancy. Thus, we propose that FRAbs may disturb pregnancy establishment and maintenance by modulating trophoblastic biofunctions, placental development, decidualization, and decidua homeostasis as well as the functions of FOLR2+ macrophages. In light of these findings, FRAbs may be a critical factor in pathological pregnancy, and deserve careful consideration in therapies involving folic acid supplementation for pregnancy complications.

[Research on indicators of ideological and political resource database construction for curriculum of "Epidemiology"]

Objective: To construct indicators of the ideological and political resource database construction for the curriculum of "Epidemiology". Methods: Two rounds of expert consultation were conducted in 15 experts from 4 universities and 1 textbook publishing house using the Delphi method, and the importance and feasibility scores of the indicators were calculated with the degree of concentration and coordination of experts' opinions. Results: In the two rounds of consultation, the experts' positive coefficient of the two questionnaires were both 100.00% (15/15), the authoritative coefficients of experts were both 0.83, and the Kendall's W was 0.27 (P<0.05) and 0.33 (P<0.05), respectively. Consensus was reached on 4 primary indicators and 31 secondary indicators. Conclusion: The process of this study is scientific, and the indicators for the construction of ideological and political resource database for the curriculum of "Epidemiology" are authoritative, which can promote the establishment of ideological and political resource database for the curriculum of "Epidemiology".

[Metformin use and risk of ischemic stroke in patients with type 2 diabetes: A cohort study]

OBJECTIVE

To explore the association between the use of metformin and the risk of ischemic stroke in patients with type 2 diabetes.

METHODS

A prospective cohort study was designed from the Fangshan family cohort in Beijing. According to metformin use at baseline, 2 625 patients with type 2 diabetes in Fangshan, Beijing were divided into metformin group or non-metformin group and the incidence of ischemic stroke between the different groups during follow-up was estimated and compared by Cox proportional hazard regression model. The participants with metformin were first compared with all the parti-cipants who did not use metformin, and then were further compared with those who did not use hypoglycemic agents and those who used other hypoglycemic agents.

RESULTS

The patients with type 2 diabetes were with an average age of (59.5±8.7) years, and 41.9% of them were male. The median follow-up time was 4.5 years. A total of 84 patients developed ischemic stroke during follow-up, with a crude incidence of 6.4 (95%CI: 5.0-7.7) per 1 000 person-years. Among all the participants, 1 149 (43.8%) took metformin, 1 476 (56.2%) were metformin non-users, including 593 (22.6%) used other hypoglycemic agents, and 883 (33.6%) did not use any hypoglycemic agents. Compared with metformin non-users, the Hazard ratio (HR) for ischemic stroke in metformin users was 0.58 (95%CI: 0.36-0.93; P = 0.024). Compared with other hypoglycemic agents, HR was 0.48 (95%CI: 0.28-0.84; P < 0.01); Compared with the group without hypoglycemic agents, HR was 0.65 (95%CI: 0.37-1.13; P=0.13). The association between metformin and ischemic stroke was statistically significant in the patients ≥ 60 years old compared with all the metformin non-users and those who used other hypoglycemic agents (HR: 0.48, 95%CI: 0.25-0.92; P < 0.05). Metformin use was associated with a lower incidence of ischemic stroke in the patients with good glycemic control (0.32, 95%CI: 0.13-0.77; P < 0.05). In the patients with poor glycemic control, and the association was not statistically significant (HR: 0.97, 95%CI: 0.53-1.79; P>0.05). There was an interaction between glycemic control and metformin use on incidence of ischemic stroke (P_interaction < 0.05). The results of the sensitivity analysis were consistent with the results in the main analysis.

CONCLUSION

Among patients with type 2 diabetic in rural areas of northern China, metformin use was associated with lower incidence of ischemic stroke, especially in patients older than 60 years. There was an interaction between glycemic control and metformin use in the incidence of ischemic stroke.

[Genotype-environment interaction on arterial stiffness: A pedigree-based study]

OBJECTIVE

To utilized the baseline data of the Beijing Fangshan Family Cohort Study, and to estimate whether the association between a healthy lifestyle and arterial stiffness might be modified by genetic effects.

METHODS

Probands and their relatives from 9 rural areas in Fangshan district, Beijing were included in this study. We developed a healthy lifestyle score based on five lifestyle behaviors: smoking, alcohol consumption, body mass index (BMI), dietary pattern, and physical activity. The measurements of arterial stiffness were brachial-ankle pulse wave velocity (baPWV) and ankle-brachial index (ABI). A variance component model was used to determine the heritability of arterial stiffness. Genotype-environment interaction effects were performed by the maximum likelihood methods. Subsequently, 45 candidate single nucleotide polymorphisms (SNPs) located in the glycolipid metabolism pathway were selected, and generalized estimated equations were used to assess the gene-environment interaction effects between particular genetic loci and healthy lifestyles.

RESULTS

A total of 6 302 study subjects across 3 225 pedigrees were enrolled in this study, with a mean age of 56.9 years and 45.1% male. Heritability of baPWV and ABI was 0.360 (95%CI: 0.302-0.418) and 0.243 (95%CI: 0.175-0.311), respectively. Significant genotype-healthy diet interaction on baPWV and genotype-BMI interaction on ABI were observed. Following the findings of genotype-environment interaction analysis, we further identified two SNPs located in ADAMTS9-AS2 and CDH13 might modify the association between healthy dietary pattern and arterial stiffness, indicating that adherence to a healthy dietary pattern might attenuate the genetic risk on arterial stiffness. Three SNPs in CDKAL1, ATP8B2 and SLC30A8 were shown to interact with BMI, implying that maintaining BMI within a healthy range might decrease the genetic risk of arterial stiffness.

CONCLUSION

The current study discovered that genotype-healthy dietary pattern and genotype-BMI interactions might affect the risk of arterial stiffness. Furthermore, we identified five genetic loci that might modify the relationship between healthy dietary pattern and BMI with arterial stiffness. Our findings suggested that a healthy lifestyle may reduce the genetic risk of arterial stiffness. This study has laid the groundwork for future research exploring mechanisms of arterial stiffness.

Hypoxia-mediated chemotaxis and residence of macrophage in decidua by secreting VEGFA and CCL2 during normal pregnancy

Infiltration and residence of decidual macrophage (dM) are of great significance to pregnancy maintenance for its role in angiogenesis, placental development and inducing immune tolerance. Besides, hypoxia has now been acknowledged as an important biological event at maternal-fetal interface in the first trimester. However, whether and how hypoxia regulates biofunctions of dM remains elusive. Herein, we observed increased expression of C-C motif chemokine ligand 2 (CCL2) and residence of macrophages in decidua when comparing to secretory-phase endometrium. Moreover, hypoxia treatment on stromal cells improved migration and adhesion of dM. Mechanistically, these effects might be mediated by upregulated CCL2 and adhesion molecules (especially ICAM2 and ICAM5) on stromal cells in the presence of endogenous vascular endothelial growth factor-A (VEGFA) in hypoxia. These findings were also verified by recombinant VEGFA and indirect coculture, indicating the interaction between stromal cells and dM in hypoxia condition may facilitate dM recruitment and residence. In conclusion, VEGFA derived from hypoxic environment may manipulate CCL2/CCR2 and adhesion molecules to enhance the interactions between dM and stromal cells and thus contribute to the enrichment of macrophages in decidua during early normal pregnancy.

IL-27 deficiency inhibits proliferation and invasion of trophoblasts via the SFRP2/Wnt/β-catenin pathway in fetal growth restriction

Background: Fetal growth restriction (FGR) is characterized by restricted fetal growth and dysregulated placental development. The etiology and pathogenesis still remain elusive. IL-27 shows multiple roles in regulating various biological processes, however, how IL-27 involves in placentation in FGR pregnancy hasn't been demonstrated. Methods: The levels of IL-27 and IL-27RA in FGR and normal placentae were determined by immunohistochemistry, western blot and RT-PCR. HTR-8/SVneo cells and Il27ra^-/- murine models have been adopted to evaluate the effects of IL-27 on the bio-functions of trophoblast cells. GO enrichment and GSEA analysis were performed to explore the underlying mechanism. Findings: IL-27 and IL-27RA was lowly expressed in FGR placentae and administration of IL-27 on HTR-8/SVneo could promote its proliferation, migration and invasion. Comparing with wildtypes, Il27ra^-/- embryos were smaller and lighter, and the placentae from which were poorly developed. In mechanism, the molecules of canonical Wnt/β-catenin pathway (CCND1, CMYC, SOX9) were downregulated in Il27ra^-/- placentae. In contrast, the expression of SFRP2 (negative regulator of Wnt) was increased. Overexpression of SFRP2 in vitro could impair trophoblast migration and invasion capacity. Interpretation: IL-27/IL-27RA negatively regulates SFRP2 to activate Wnt/β-catenin, and thus promotes migration and invasion of trophoblasts during pregnancy. However, IL-27 deficiency may contribute to the development of FGR by restricting the Wnt activity.

[Family-based association tests for rare variants]

Next-generation sequencing has revolutionized family-based association tests for rare variants. As the lower power of genome wide association study for detecting casual rare variants, methods aggregating effects of multiple variants have been proposed, such as burden tests and variance component tests. This paper summarizes the methods of rare variants association test that can be applied for family data, introduces their principles, characteristics and applicable conditions and discusses the shortcomings and the improvement of the present methods.

The metabolic characteristic of decidual immune cells and their unique properties in pregnancy loss

Maternal tolerance to semi- or fully allograft conceptus is a prerequisite for the maintenance of pregnancy. Once this homeostasis is disrupted, it may result in pregnancy loss. As a potential approach to prevent pregnancy loss, targeting decidual immune cells (DICs) at the maternal-fetal interface has been suggested. Although the phenotypic features and functions of DIC have been extensively profiled, the regulatory pathways for this unique immunological adaption have yet to be elucidated. In recent years, a pivotal mechanism has been highlighted in the area of immunometabolism, by which the changes in intracellular metabolic pathways in DIC and interaction with the adjacent metabolites in the microenvironment can alter their phenotypes and function. More inspiringly, the manipulation of metabolic profiling in DIC provides a novel avenue for the prevention and treatment of pregnancy loss. Herein, this review highlights the major metabolic programs (specifically, glycolysis, ATP-adenosine metabolism, lysophosphatidic acid metabolism, and amino acid metabolism) in multiple immune cells (including decidual NK cells, macrophages, and T cells) and their integrations with the metabolic microenvironment in normal pregnancy. Importantly, this perspective may help to provide a potential therapeutic strategy for reducing pregnancy loss via targeting this interplay.

Insight of Autophagy in Spontaneous Miscarriage

In some cases of spontaneous miscarriage (SM), the exact etiology cannot be determined. Autophagy, which is responsible for cellular survival under stress conditions, has also been implicated in many diseases. Recently, it is also surmised to be correlated with SM. However, the detailed mechanism remains elusive. In fact, there are several essential steps during pregnancy establishment and maintenance: trophoblasts invasion, placentation, decidualization, enrichment and infiltration of decidua immune cells (e.g., natural killer, macrophage and T cells). Accordingly, upstream molecules and downstream effects of autophagy are discussed in these processes, respectively. Of note, autophagy regulates the crosstalk between these cells at the maternal-fetal interface as well. Aberrant autophagy is found in villi, decidual stromal cells, peripheral blood mononuclear cells in SM patients, although the findings are inconsistent among different studies. Furthermore, potential treatments targeting autophagy are included, during which rapamycin and vitamin D are hot-spots in recent literatures. To conclude, a moderately activated autophagy is deeply involved in pregnancy, suggesting that autophagy should be a regulator and promising target for treating SM.

[Venous thromboembolism risk and prophylaxis status of cancer inpatient]

Objective: To determine the risk profile of venous thromboembolism (VTE) and evaluate VTE prophylaxis implementation of the hospitalized cancer patients in the DissolVE 2 study. Methods: The data of hospitalized cancer patients in the DissolVE 2 study were analyzed. The risk distribution of VTE, preventive measures and in-hospital VTE events of hospitalized patients with tumors were described by percentage and 95% confident interval (CI). Results: A total of 1 535 cancer patients were included. According to the Padua score, 826 (53.8%) patients were at low risk of VTE, while 709 (46.2%) patients were at high VTE risk. VTE events occurred in 4 low-risk patients (0.5%; 95%CI: 0.1%, 1.2%) and 5 high-risk patients (0.7%; 95%CI: 0.2%, 1.6%). The overall incidence was 0.6% (9/1 535, 95%CI: 0.3%, 1.1%). Among patients with high VTE risk, 666 (93.9%) did not receive any VTE prophylaxis, and only 11 (1.6%) patients received appropriate VTE prophylaxis. Among patients who received VTE prevention, no VTE event was observed. Conclusions: Nearly half of the hospitalized cancer patients are at high risk of VTE, but most of them don't receive VTE prophylaxis. The results reflect the insufficient management of VTE risk for hospitalized cancer patients in China, and improvement of awareness and practice of VTE prophylaxis is urgently needed.

WISP2/IGF1 promotes the survival of DSCs and impairs the cytotoxicity of decidual NK cells

The survival and development of a semi-allogeneic fetus during pregnancy require the involvement of decidual stromal cells (DSCs), a series of cytokines and immune cells. Insulin-like growth factor 1 (IGF1) is a low molecular weight peptide hormone with similar metabolic activity and structural characteristics of proinsulin, which exerts its biological effects by binding with its receptor. Emerging evidence has shown that IGF1 is expressed at the maternal-fetal interface, but its special role in establishment and maintenance of pregnancy is largely unknown. Here, we found that the expression of IGF1 in the decidua was significantly higher than that in the endometrium. Additionally, decidua from women with normal pregnancy had high levels of IGF1 compared with that from women with unexplained recurrent spontaneous miscarriage. Estrogen and progesterone led to the increase of IGF1 in DSCs through upregulating the expression of WISP2. Recombinant IGF1 or DSCs-derived IGF1 increased the survival, reduced the apoptosis of DSCs, and downregulated the cytotoxicity of decidual NK cells (dNK) through interaction with IGF1R. These data suggest that estrogen and progesterone stimulate the growth of DSCs and impair the cytotoxicity of dNK possibly by the WISP2/IGF1 signaling pathway.

Development and validation of nomograms to intraoperatively predict metastatic patterns in regional lymph nodes in patients diagnosed with esophageal cancer

BACKGROUND

An accurate intraoperative prediction of lymph node metastatic risk can help surgeons in choosing precise surgical procedures. We aimed to develop and validate nomograms to intraoperatively predict patterns of regional lymph node (LN) metastasis in patients with esophageal cancer.

METHODS

The prediction model was developed in a training cohort consisting of 487 patients diagnosed with esophageal cancer who underwent esophagectomy with complete LN dissection from January 2016 to December 2016. Univariate and multivariable logistic regression were used to identify independent risk factors that were incorporated into a prediction model and used to construct a nomogram. Contrast-enhanced computed tomography reported LN status and was an important comparative factor of clinical usefulness in a validation cohort. Nomogram performance was assessed in terms of calibration, discrimination, and clinical usefulness. An independent validation cohort comprised 206 consecutive patients from January 2017 to December 2017.

RESULTS

Univariate analysis and multivariable logistic regression revealed three independent predictors of metastatic regional LNs, three independent predictors of continuous regional LNs, and two independent predictors of skipping regional LNs. Independent predictors were used to build three individualized prediction nomograms. The models showed good calibration and discrimination, with area under the curve (AUC) values of 0.737, 0.738, and 0.707. Application of the nomogram in the validation cohort yielded good calibration and discrimination, with AUC values of 0.728, 0.668, and 0.657. Decision curve analysis demonstrated that the three nomograms were clinically useful in the validation cohort.

CONCLUSION

This study presents three nomograms that incorporate clinicopathologic factors, which can be used to facilitate the intraoperative prediction of metastatic regional LN patterns in patients with esophageal cancer.

[Clinicopathological features and prognosis of 59 patients with platelet-derived growth factor α-mutant gastrointestinal stromal tumor]

Objective: Platelet-derived growth factor α (PDGFRA)-mutant gastrointestinal stromal tumor (GIST) is a relatively rare disease, whose clinicopathological characteristics and prognosis have been poorly studied. In this paper, the clinicopathological features and prognostic factors of PDGFRA-mutant GIST are investigated to provide more data for its understanding and treatment. Methods: A retrospective case-control study was used to collect the medical records of patients with GIST who underwent surgical resection in Zhongshan Hospital of Fudan University from January 2015 to August 2019. Patients with PDGFRA-mutant GIST were enrolled, and those with synonymous PDGFRA mutations, non-tumor-related deaths, and lack of clinicopathological data were excluded. The clinicopathological data were collected and the risk factors associated with prognosis were analyzed. Results: Among the enrolled 59 patients, there were 41 males (69.5%) and 18 females (30.5%) with the median age of 60 (25-79) years. All tumors originated from the stomach. The tumor size was 5 (3-7) cm, and the mitotic count was 2 (1-4)/50 high-power fields (HPF). According to the modified NIH risk stratification, 8 cases were classified as very low risk (13.6%), 25 cases as low risk (42.4%), 14 cases as moderate risk (23.7%), and 12 cases as high risk (20.3%). There were 7 cases of exon 12 mutation and 52 cases of exon 18 mutation (including 36 cases of D842V mutation). A comparison of clinicopathological features between the D842V mutation group and the non-D842V mutation group showed no statistically significant difference (all P>0.05). During a median follow-up of 21 (0-59) months, the 1- and 3-year relapse-free survival (RFS) rates of all the patients were 96.6% and 91.5%, respectively. There were 8 cases of recurrence and 3 cases of death. Six GIST patients with D842V mutation had tumor recurrence after operation, of whom 4 cases achieved varying degrees of tumor remission after being treated with dasatinib or avapritinib. Log-rank analysis showed that the overall survival (OS) of male was better than that of female (100% vs. 83.3%, P=0.046), but there was no significant difference in OS among patients with different risk grades (P=0.057). The RFS and OS of patients with D842V mutation and non-D842V mutation, exon 12 and exon 18 mutation were similar (all P>0.05). Univariate Cox analysis showed that RFS was associated with gender (P=0.010), tumor size (P=0.042), mitotic count (P=0.003), and the modified NIH risk stratification (P=0.042), while multivariate analysis revealed that higher risk grade was an independent risk factor for recurrence of PDGFRA-mutant GIST (HR=12.796, 95%CI: 1.326-123.501, P=0.028). Gender was an independent factor for recurrence, and the risk of recurrence in males was lower than that in females (HR=0.154, 95%CI: 0.028-0.841, P=0.031). Conclusions: Gender and the modified NIH risk stratification are independent risk factors for recurrence of PDGFRA-mutant GIST, while patients with D842V and non-D842V mutation, and exon 12 and exon 18 mutation have a similar risk of recurrence and death.

Clinical outcomes of different therapeutic modalities for rectal gastrointestinal stromal tumor: Summary of 14-year clinical experience in a single center

OBJECTIVE

The optimal treatment for gastrointestinal stromal tumor (GIST) of the rectum is controversial due to the extremely low incidence of the disease. The aim of the present study was to compare the clinical outcomes of different treatment modalities for rectal GIST by reviewing the 14-year experience in our center.

METHOD

Medical records of rectal GIST patients who received surgical treatment in our center between January 2004 to December 2017 were reviewed retrospectively. Overall survival (OS) and recurrence-free survival (RFS) were used as the observation endpoints.

RESULTS

Included in this study were 71 GIST patients, including 42 patients who underwent local excision (LE) and 29 patients who underwent segmental resection (SR). There were differences in tumor size (P = 0.001) and malignant risk grade (P = 0.007). The LE approach achieved a lower rate of R0 resection than SR (29/42 vs.27/29, P = 0.015) and shorter hospital stay (P = 0.004). Preoperative imatinib mesylate (IM) therapy improved the rate of sphincter-sparing surgery for patients with tumors in the very low segment of the rectum (P = 0.012) and offered better R0 resection margins (P = 0.027). Multivariate analysis showed that the resection margin status (P = 0.014), risk stratification (P = 0.001) and IM therapy (P = 0.042) were independent factors affecting RFS of rectal GIST patients but not the surgical modalities (LE vs. SR, P = 0.802). Multivariate analysis showed no significant impact of these variables on OS.

CONCLUSION

Selection of surgical modalities has no significant impact on the prognosis. Local excision is the preferred surgical modality for resectable rectal GIST by virtue of less injury and shorter hospital stay. IM therapy has proved to be associated with improved RFS for rectal GIST patients.

[Retrospect of 2019: focus on the research progress of gastric neoplasm]

Gastric carcinoma, gastrointestinal stromal tumor and gastric neuroendocrine tumor are the most common gastric neoplasms. A series of researches in 2019 showed that the safety and efficacy of laparoscopic gastrectomy in the treatment of both early and advanced gastric cancer patients are similar to open surgeries, providing a high-level evidence-based medical basis for the promotion of laparoscopic surgery in the treatment for gastric cancer. In multidisciplinary treatment and perioperative chemoradiotherapy, major research results have also been published, and clinical researches in China are gradually gaining international recognition and attention. Although the application of targeted therapy and immunotherapy has made progress, the first-line therapy after gastric cancer surgery has not been established. In the field of gastrointestinal stromal tumors, laparoscopic surgery has gradually been recognized, and surgical treatment of patients with advanced drug resistance still has its value. In terms of gastric neuroendocrine tumors, the latest researches showed that surgical methods should be selected according to tumor characteristics, and gastric adenocarcinoma with neuroendocrine components may have a worse prognosis.

Ultralow Thermal Conductivity and Extraordinary Thermoelectric Performance Realized in Codoped Cu3SbSe4 by Plasma Spark Sintering

Cu₃SbSe₄-based materials have attracted much attention for thermoelectric power generation in the mid-temperature range due to their low cost, ecofriendliness, and abundant elements on the earth. However, the peak figure of merit (ZT) for the Cu₃SbSe₄-based system prepared by the fusion method is usually smaller than unity because of its high thermal conductivity. Here, we show that through a coprecipitation method combined with spark plasma sintering ultrafine-grained Cu₃Sb_0.94Sn_0.06Se_4-yS_y (y = 0, 0.5) embedded with Cu₃SbSe₃ nanoprecipitates can be prepared. Due to the ultralow thermal conductivity and enhanced Seebeck coefficient, a record-high ZT value of 1.32 is achieved for the sample Cu₃Sb_0.94Sn_0.06Se_3.5Se_0.5. The ultralow thermal conductivity is attributed to the enhanced phonon scattering caused by the nanoprecipitates and fine grains of the samples, and the improved Seebeck coefficient originates from the enhancement of electronic density-of-state effective mass. Present results demonstrate that excellent thermoelectric performance can be realized in dual-substituted and fine-grained Cu₃Sb_0.94Sn_0.06Se_4-yS_y with nanoprecipitates.

[The shift of the treatment strategy of gastrointestinal stromal tumor from the surgical perspective]

As tumors originated from mesenchymal tissue, gastrointestinal stromal tumors (GIST) has its own typical history. For the idea of treatment for GIST at different historical periods, the role and value of surgery for the treatment of GIST keep changing. Laparoscopy and endoscopy will have the role they deserved. With the understanding of pathogenesis of GIST, targeted chemotherapy will be more and more accurate and individualized. How to improve the overall therapeutic effect of GIST, especially for the patients with the high risk and drug-resistance, is the dilemma and challenges for the surgeons.

[Study on the current status of postgraduates training in public health and preventive medicine in China in 2016]

To investigate the current status of postgraduates training in public health and preventive medicine in China. In this study, a questionnaire survey was conducted among directors of enrollment and teaching in 22 universities with postgraduate admission qualifications in corresponding disciplines nationwide. In 2016, full-time postgraduates were mainly academic masters. In addition to the graduate entrance examination, the common enrollment mode in colleges was to enroll a high qualified student with recommendations from relevant experts or institutions and an exemption from entrance examination (20/22). The emphasis on training contents between academic and public health master was different. Currently, the scale of public health postgraduate enrollment in public health and preventive medicine in China is stable, and the training program is reasonable, but there is an issue of monotonous model and uneven distribution of enrollment.

[Investigation on the current status of the cultivation of the master of public health (MPH) in colleges in China]

In order to understand the status of the cultivation of the masters of public health (MPH) in colleges in China and improve the cultivation model, an electronic questionnaire survey were conducted among 22 schools of public health in colleges. The result showed that the size and the enrolment scale of Chinese MPH students were relatively small, and the training objectives were still unclear. There was no obvious difference between the curriculum setting for MPH and academic master degree. The practical skill-oriented courses and emergency response ability of public health practice were insufficient. The cultivation model of MPH should be improved in future.

[Analysis of the contradiction between the supply and demand of Chinese graduate students' emergency professional ability in public health and preventive medicine in China]

In order to underst and the status of health emergency personnel training development and raising coping measures, electronic questionnaire surveys were conducted among 22 colleges and universities in different region of China. The result showed that colleges universities in China invested less in the training of emergency personnel. It is different and emphasized particularly for the cultivation of emergency professional ability among different types of public health students. Universities and employer hold relative evaluation of students' emergency professional ability with distinct regional differences.

[Construction of 3β-HSD gene silencing cell line and its effects on apoptosis induced by DEHP]

Objective: To construct 3β-HSD gene shRNA lentivirus interference vecto, then transfect into human MCF-7 cells, and construct cell line with 3β-HSD gene silencing, finally to study the effects of 3β-HSD on apoptosis induced by di- (2-ethylhexyl) phthalate (DEHP) . Methods: According to the mRNA sequence of 3β-HSD gene provided by GenBank, three interference sequences were designed and connected to PLVX-shRNA2-puro after annealing. The recombinant lentivirus vector was transfected into 293FT cells, the virus supernatants were collected and infected with MCF-7 cells. After puromycin screening, MCF-7 cells with 3β-HSD gene silencing were constructed. The cells with 3β-HSD gene silencing were identified by real-time quantitative PCR and western blot. Then the 3β-HSD gene silencing cells and MCF-7 cells were treated at various doses of DEHP for 24 hours to detect the gene expression and protein expression of apoptosis genes including Bax, Caspase-3 and Caspase-8. Results: The interference sequence of 3β-HSD gene inserted into lentivirus vector PLVX-shRNA2-puro is consistent with the designed sequence. 3β-HSD gene expression level in MCF-7 cells with 3β-HSD gene silencing was 77% lower than than that of control MCF-7 cells. 3β-HSD protein level in MCF-7 cells with 3β-HSD gene silencing was 74% lower than that of control MCF-7 cells. After DEHP treatment in MCF-7 cells with 3β-HSD gene silencing and control MCF-7 cells, qRT-PCR results showed that Bax gene expression levels increased by 28%-54%, Caspase-3 gene increased by 13%-49%, Caspase-8 gene increased by 21%-70% in MCF-7 cells when compared with the control group. Additionally, in the 3β-HSD gene silencing cells, Bax gene expression level decreased by 11%-28%, Caspase-3 gene expression decreased by 12%-23%, Caspase-8 gene expression decreased by 11%-34%, compared with the same treatment group of MCF-7 cells. Western blot results showed that Bax protein expression level increased by 28%-61%, Caspase-3 protein expression level increased by 40%-48%, Caspase-8 protein increased by 31%-84% in MCF-7 cells when compared with the control group. In 3β-HSD gene silencing cells, Bax protein expression level increased by 11%-27%, Caspase-3 protein increased by 21%-40%, Caspase-8 protein increased by 12%-25%, compared with the same treatment group of MCF-7 cells. Conclusion: The stable 3β-HSD gene silencing cell line are successfully constructed in this study. DEHP can induce increased expression of apoptotic gene and protein. Silencing of 3β-HSD gene can inhibit the activation of apoptotic gene by DEHP in a certain degree.

Alpha1,2-fucosyl transferase gene, the key enzyme of Lewis y synthesis, promotes Taxol resistance of ovarian carcinoma through apoptosis-related proteins

We aimed to investigate the role of FUT1 gene in Taxol resistance and to explore its mechanism in epithelial ovarian cancer. Three ovarian cancer cell lines, ES-2, SK-OV-3 and OVCAR-3 were selected from epithelial ovarian cancer in this experiment. Western blot was used to validate the protein expression level of FUT1 and the apoptosis proteins. The expression level of the corresponding carrier was validated by RT-PCR. Transfection and isolation of stable transfectants were carried out to establish the cell line models. The different concentrations of Taxol on the inhibition of cell growth rate was measured by MTT, in which Taxol resistance profiling in ovarian cancer cells was determined by IC50 data. Flow cytometry was conducted to compare cell apoptosis ability. Caspase-3 activity and the apoptosis proteins were measured by colorimetry and western blot, respectively, to further compare the cell apoptosis ability in different groups. To demonstrate the inhibition of miR-FUT1 combined with Taxol therapy against ovarian cancer, xenograft assay was carried out for the in vivo effect. The western blot results indicate that FUT1 is expressed in all of the ovarian cancer cells with different expression level: ES-2 > SK-OV-3 > OVCAR-3. Besides, FUT1 siRNA was used in the maximum expression of FUT1 cell line ES-2, or over-expression plasmid was used in the minimum expression of FUT1 cell line OVCAR-3, to establish stable expression cell lines. After the treatment with Taxol, the inhibition rate of Taxol was obviously decreased with the established cell model above, and the IC50 level was significantly increased in the FUT1 over-expression + Taxol group (p Keywords: FUT1, Lewis y, Taxol resistance, ovarian cancer, apoptosis.

Clinicopathologic predictors of metastasis of different regional lymph nodes in patients intraoperatively diagnosed with stage-I non-small cell lung cancer

Background

Selection of the best lymph node for dissection is a controversial topic in clinical stage-I non-small cell lung cancer (NSCLC). Here, we sought to identify the clinicopathologic predictors of regional lymph node metastasis in patients intraoperatively diagnosed with stage-I NSCLC.

Methods

A retrospective review of 595 patients intraoperatively diagnosed as stage I non-small-cell lung cancer who underwent lobectomy with complete lymph node dissection was performed. Univariate and multivariable logistic regression analysis was performed to determine the independent predictors of regional lymph node metastasis.

Results

Univariate logistic regression and multivariable analysis revealed three independent predictors of the presence of metastatic hilar lymph nodes, five independent predictors for lobe specific mediastinal lymph nodes, two independent predictors for lobe nonspecific mediastinal lymph nodes and two independent predictors for skipping mediastinal lymph nodes.

Conclusions

A complete mediastinal lymph node dissection may be considered for patients suspected of nerve invasion and albumin (> 43.1 g/L) or nerve and vascular invasions. Lobe-specific lymph node dissection should probably be performed for patients suspected of pulmonary membrane invasion, vascular invasion, CEA (> 2.21 ng/mL), and tumor (> 1.6 cm) in the right lower lobe or mixed lobes. Hilar lymph node dissection should probably be performed for patients suspected of having bronchial mucosa and cartilage invasion, vascular invasion, and CEA (> 2.21 ng/mL).

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5632-2) contains supplementary material, which is available to authorized users.

[Preparation and evaluation of blank and doxorubicin loaded poly (acrylic acid) microspheres for embolization]

OBJECTIVE

To prepare ion exchange doxorubicin-loaded poly (acrylic acid) microspheres (DPMs) and evaluate the properties of these chemoembolic agents.

METHODS

Poly (acrylic acid) microspheres (PMs) without drug were prepared by inverse suspension polymerization method and then doxorubicin was loaded by ion exchange mechanism to prepare DPMs. Optical microscope was used to investigate the morphology and particle size distribution of PMs and DPMs; fluorescence microscope and confocal microscope were used to observe the distribution of doxorubicin after drug loading. Elasticities of both the microspheres were evaluated by texture analyzer. High performance liquid chromatography (HPLC) method was established to determine the drug loading behavior of PMs and releasing behavior of DPMs. The in vivo embolic property was evaluated by embolizing the hepatic artery of a rabbit with 0.1 mL of DPMs.

RESULTS

PMs and DPMs were both spherical in shape, smooth in surface and dispersed well. Doxorubicin was mainly in the outer area inside of DPMs and distributed evenly. The average particle size of PMs and DPMs were (283±136) μm and (248±149) μm, respectively. PMs and DPMs both had good compression ability with the Young's modulus of (62.63±1.65) kPa and (93.94±1.10) kPa separately. PMs reached the drug loading balance at 12 h, and the entrapment efficiency was greater than 99%. Drug loading of PMs in doxorubicin solution at the concentration of 5.0 g/L and 12.5 g/L was (19.78±0.27) g/L and (49.45±0.37) g/L, respectively. Doxorubicin released slowly from DPMs in PBS and the accumulative release percentages of DPMs with corresponding drug loading were 6.82%±0.02% and 2.83%±0.10% after 24 h, respectively. Arterial angiograms showed that the hepatic artery of the rabbit was successfully embolized with DPMs.

CONCLUSION

DPMs with good performance of loading doxorubicin could be a potential embolic agent for transcatheter arterial chemoembolization.

[Preparation and characterization of citric acid-modified superparamagnetic iron oxide nanoparticles]

OBJECTIVE

To prepare and characterize citric acid (CA)-modified super paramagnetic iron oxide nanoparticles (SPIONs) for magnetic targeting, hyperthermia and magnetic resonance imaging (MRI).

METHODS

CA-modified SPIONs (CA-SPIONs) were prepared by co-precipitation method and then the magnetic responsiveness, morphology, particle size, infrared feature, weight percentage of CA, magnetic property and X-ray diffraction pattern of CA-SPIONs were respectively characterized by magnet, transmission electron microscope, laser particle size analyzer, Fourier transform infrared (FT-IR) spectroscopy, thermogravimetry-differential thermal analyzer, vibrating sample magnetometer and X-ray diffractometer (XRD). The heating efficiency of the CA-SPIONs was investigated by a high frequency induction heater. The transverse relaxivity (r2) of the CA-SPIONs was evaluated by a 3.0 T MRI scanner.

RESULTS

The CA-SPIONs prepared were dispersed well in water with a dark black color and had good magnetic responsiveness. The CA-SPIONs were spherical in shape and uniform in size with an average size around 12 nm. The hydrodynamic average size of the CA-SPIONs was (72.35±4.47) nm with a polydispersity index of 0.231 ± 0.029. The result of infrared spectrum indicated that CA was successfully modified to the surface of SPIONs. The result of thermogravimetric analysis showed that the weight percentage of CA modified on the CA-SPIONs was 9.0%. The result of magnetic property evaluation demonstrated that the CA-SPIONs exhibited excellent superparamagetism with a saturation magnetism of 63.58 emu/g. The XRD result indicated that the CA-SPIONs were in inverse spinel structure. The crystallite size of the CA-SPIONs was calculated to be 12.4 nm by Debye-Scherrer equation. Under the high frequency alternating electromagnetic field with electric current of 9 A and frequency ranging from 45 to 50 kHz, the CA-SPIONs exhibited excellent heating efficiency and the specific absorption rate (SAR) value was calculated to be 26 W/g. The r2 of the CA-SPIONs was assessed to be 338 (mmol/L)^-1×s^-1 by a 3.0 T MRI scanner, which suggested the excellent negative contrast enhancement effect of the CA-SPIONs.

CONCLUSION

The CA-SPIONs are expected to be used as a promising agent for magnetic targeting, hyperthermia and MRI detection.

[Progress in research of family-based cohort study on common chronic non-communicable diseases in rural population in northern China]

Family-based cohort study is a special type of study design, in which biological samples and environmental exposure information of the member in a family are collected and related follow up is conducted. Family-based cohort study can be applied to explore the effect of genetic factors, environmental factors, gene-gene interaction, and gene-environment interaction in the etiology of complex diseases. This paper summarizes the objectives, methods and results, as well as the opportunities and challenges of the family-based cohort study on common chronic non-communicable diseases in rural population in northern China.

[Trend of development and prospect of gastrointestinal surgery in era of minimally invasive]

The development and popularization of minimally invasive treatment is gradually evolving in the course of human fighting against disease. Minimally invasive surgery has been widely accepted and carried out because of the advantages of smaller trauma, less pain, little impact on the body and physiological metabolism of the body. The evidence-based medicine makes it important to conduct clinical trials to confirm the technical and oncological safety. With the development of minimally invasive technologies, including three-dimensional laparoscopic, natural orifice transluminal endoscopic surgery, robotic surgery system, minimally invasive surgery are providing more opportunities and challenges for gastrointestinal diseases. The standard conduction of minimally invasive surgery in gastroenterology disease makes it important to improve surgical procedure safety and treatment effects.

[Construction of the pIRES2-ZsGreen1 eukaryotic expression vector of Factor Ⅸ gene and expression in HEK-293 cells]

目的

以含有凝血因子Ⅸ（FⅨ）cDNA的pcDNA/FⅨ质粒为模板构建真核表达载体pIRES2-ZsGreen1/FⅨ并检测其在HEK-293细胞中的表达。

方法

以pcDNA/FⅨ质粒为模板，扩增出目的基因FⅨ的开放阅读框（ORF）区，使用Infusion酶对线性pIRES2-ZsGreen1双酶切产物及FⅨORF扩增产物进行连接，连接产物进行转化后筛选阳性克隆，对阳性克隆进行DNA测序及凝胶电泳鉴定。野生型pIRES2-ZsGreen1/FⅨ转染HEK-293细胞后，分别采用实时定量PCR、细胞免疫荧光法、一期法检测野生型FⅨ基因mRNA表达水平、蛋白的表达量及细胞裂解液、细胞培养液的FⅨ活性。

结果

成功构建pIRES2-ZsGreen1/FⅨ并转染HEK-293细胞，实时定量PCR证实HEK-293细胞表达FⅨ mRNA，激光共聚焦显微镜下观察到FⅨ蛋白在细胞质中合成，野生型质粒pIRES2-ZsGreen1/FⅨ转染HEK-293细胞裂解液和细胞培养液的FⅨ活性分别为（92.03±0.29）%、（86.89±8.78）%，无转染的HEK-293细胞裂解液和培养液中FⅨ活性均为0。

结论

成功构建FⅨ野生型pIRES2-ZsGreen1真核表达载体。

[Current status and prospect of perioperative thrombus management in gastrointestinal cancer]

Thanks to the progress of surgical theory and skills, as well as the application of modern medical devices in general surgery, both the occurrence of perioperative complications and mortality of gastrointestinal surgery have significantly reduced recently. However, it is still far from optimal in terms of the perioperative venous thromboembolism (VTE) management in gastrointestinal cancer, and what is responsible for that? This paper aims at finding out the reasons contributing to the current status, giving suggestions for how to make improvement at both disease level and hospital management level. At the same time, while paying attention for the prophylaxis of VTE, there have been more and more patients receiving antithrombotic treatment require elective or emergent surgery in clinical practice, due to aging and increased incidence of cardiovascular disease year by year. How to balance the bleeding and thrombosis risk for these patients during perioperative periods is also a question we are going to discuss. In conclusion, as to the issue of the management of perioperative thrombosis, there will be a long way for Chinese doctors to go. Our peers should pay more attention to this problem and take more efforts, so that the thrombotic complications in surgical patients can be reduced.

[Comparison study of subcutaneous immunotherapy and sublingual immunotherapy in patients with allergic rhinitis]

Objective: To observe the compliance, efficacy and safety of subcutaneous immunotherapy(SLIT) and sublingual immunotherapy(SCIT) in patients with allergic rhinitis(AR).Method:One hundred and fifteen patients sensitized to house dust mites were recruited in this study. The standardized extract of house dust mites was used for SLIT in 64 cases, and the standardized extract of dual house dust mites was used for SCIT in the other 51 cases. The compliance, nasal symptom scores, the medication scores, the quality of life and the adverse reaction were evaluated before and 2 years after immunotherapy. SPSS 19.0 was used for data analysis. Result:Forty patients out of 64 completed the 2 years-SLIT, and the compliance rate was 62.50%. Forty three patients out of 51 completed the 2 years-SCIT and the compliance rate was 84.31%.The compliance rate of SLIT was significantly lower than that of SCIT(P <0.05). The nasal symptom scores, the anti-allergic medication, the scores in quality of life decreased significantly after receiving SLIT or SCIT for 2 years（P <0.05）. However, the changed values of scores between the two groups had no significant differences（P >0.05）. There was no moderate or severe adverse reactions occurred in SLIT group but a total of 6 moderate or severe adverse reactions occurred in SCIT group.Conclusion:SLIT has same effect compared with SCIT with a lower compliance rate but a significantly higher safety.

[Evaluation of physical function for the end-stage osteoarthritis patient waiting for the total knee replacement]

OBJECTIVE

To collect comprehensive data of the physical function of the end-stage osteoarthritis (OA) patients, and compare it with patients with mild OA. To evaluate the correlations among pain, self-reported questionnaire, performance based physical function and actual daily life activity level.

METHODS

In this prospective study, the comprehensive physical function parameters of 87 end stage OA patients waiting for total knee replacement, and that of 60 patients with mild OA [Kellgren-Lawrence (K-L) grade 0-2] were collected. The comprehensive physical function parameters including: age, height, body weight, 30 s chair stand test (30-CST), 40 m fast-paced walk test (40-FPWT), 12 steps stair climb test (12-SCT), timed up & go test (TUG), 6 minutes walk test (6-MWT), the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), knee society score (KSS), visual analogue scale (VAS) pain scale, and everyday steps counts for continuous 7 days. The data were analyzed with the soft ware SPSS 22.0. The descriptive report of all the parameters was made. Because the Kolmogorv-Smirnov test results for all the parameters were negative for normal distribution, nonparative Mann-Whitney test was used to analysis the differences between the two groups, as well as the Spearman test for the correlations.

RESULTS

All the parameters of the mild OA group were better than those of the end stage group, and the differences were significant (P<0.05). In the mild OA group, there were no correlations or weak correlations between all the physical function test and questionnaire, however, in the end stage group, the correlations were weak, moderate, or strong.

CONCLUSION

The usage of lots of different physical parameters from Chinese OA patients were reported in this study. The results showed that there are no good correlations among performance based physical function test, actual daily activity level, self reported questionnaires, and the pain scales. More comprehensive evaluation for the OA patients needs to be made, in order to make better decision for arthroplasty.

[NELL-1: a novel highly efficient and specific growth factor]

Regeneration of bone tissue, as well as other tissues, requires involvement and interaction of cells, scaffolds and relevant growth factors, among which growth factors play a crucial role in maintaining the stability of microenvironment. Nel-like-type 1 molecule (NELL-1), a novel growth factor in tissue engineering, has been studied intensively in recent years. Researches mainly covered gene and protein structure and their expression profiling, biological function, molecular mechanisms and disease relevance. NELL-1 expressed in embryonic tissue is essential for growth and development of bone tissue. NELL-1 presents excellent abilities of inducing bone and cartilage regeneration,especially with high specificity to chondrocyte lineage. Compared with classic osteogenic growth factor bone morphogenetic protein 2 (BMP-2), the process of osteogenesis interacted with NELL-1 exhibits stronger specificity, higher bone density and fewerside effects. Furthermore, a recent study shows synergistic effects of NELL-1 and BMP-2. NELL-1 enhances the osteogenic reaction induced by BMP-2 of cells and notably declines inflammation response caused by BMP-2. This review evaluates the current research progress of the function and application of NELL-1 by the systematic method of evidence-based medicine.

Effects of beta 2 adrenergic agonists on axonal injury and mitochondrial metabolism in experimental autoimmune encephalomyelitis rats

The primary aims of this study were to investigate mitochondrial metabolism during experimental allergic encephalomyelitis (EAE) animal model axonal injury and to determine the correlation among neurological function scores, pathological changes, and the activities of the BB isoenzyme of creatine kinase (CK-BB), catalase (CAT), and calpain in the brain tissues of EAE rats. Another goal was to preliminarily define the mechanism of mitochondrial metabolism resulting from the effect of beta 2 adrenergic agonists in the process of EAE animal model axonal damage. EAE was induced in specific pathogen free Wistar rats by guinea pig spinal cord homogenate, complete Freund's adjuvant, and pertussis vaccine. We recorded the behavioral change in EAE rats, detected pathological changes in central nervous tissue, and observed the changes of the CK-BB, CAT, and calpain in the EAE rat brain and spinal cord. The results indicated that the average neurologic function score increased in the EAE group compared to that of the controls (P < 0.01). In addition, CAT and CK-BB activities significantly decreased and the calpain activity significantly increased compared with those of the control group (P < 0.05). The decrease of the activity of central nervous CK-BB and CAT content, as well as the increase of calpain activity at the highest time point were considered to be the consequences of EAE. Furthermore, the results revealed that use of salbutamol could alleviate disease symptoms and reduce the recurrence of the EAE disease.

Complete nucleotide sequence and genome organization of a Chinese isolate of tobacco bushy top virus

The complete nucleotide sequence of a Chinese isolate of tobacco bushy top virus (TBTV), designated TBTV-Ch, was determined from cDNA generated from double-stranded RNA extracted from diseased tobacco. The genome is 4152 nucleotides (nt) in size, contains four putative open reading frames (ORFs) and untranslated regions of 10 nt and 645 nt at the 5' and 3' ends, respectively. In genome organization and in the amino acid sequence of its potential products, the RNA of TBTV-Ch is similar to other umbraviruses sequenced to date. The results suggested that TBTV should be regarded as a definitive species of the genus Umbravirus.

Effects of cholinoceptor and 5-hydroxytryptamine3 receptor antagonism on erythromycin-induced canine intestinal motility disruption and emesis

1. Erythromycin administration is associated with gastrointestinal problems, disturbed gastrointestinal motility and emesis. This study in the dog investigates the underlying mechanisms. 2. Intestinal myoelectrical activity and the occurrence and latency of emesis were recorded in eight conscious dogs. All drugs were administered intravenously. 3. Erythromycin (7 mg kg-1) increased contractions of the proximal small intestine, and caused emesis in all fasted dogs and in 5 dogs after food. Atropine (50 mg kg-1 min-1) and hexamethonium (10 mg kg-1 h-1) partially inhibited the GI motility effects but did not significantly reduce emesis. 4. Metoclopramide at a high dose (2 mg kg-1 h-1) reduced the incidence of emesis in the presence of increased intestinal motility, but a low dose (150 micrograms kg-1 h-1) was ineffective. 5. A 5-hydroxytryptamine3 (5-HT3) receptor antagonist, MDL 72222 (1 mg kg-1), reduced emesis when given alone and combined with metoclopramide (low dose). The 5-HT4 receptor agonist BRL24924 (Renzapride, 1 mg kg-1) had no effect on emesis either alone in combination with metoclopramide. 6. In conclusion, erythromycin-induced GI motility disturbances and emesis are not causally related. Whereas the increase in intestinal smooth muscle activity is possibly cholinergically mediated, emesis occurs at least in part via a 5-hydroxytryptaminergic mechanism, but does not involve the dopamine system.

Macrolides and gastrointestinal motility

Erythromycin was the first macrolide used clinically, and it is still the most widely prescribed in spite of reports of gastrointestinal side-effects. Erythromycin was given iv or orally to fasted and fed dogs with sensors implanted on the gastrointestinal tract for the measurement of motility. There was a large increase in stomach and upper small bowel contractile activity, accompanied by nausea and vomiting, while the distal small bowel appeared inhibited. Similar effects were seen in man. By contrast, two 16-membered macrolides, spiramycin and josamycin, did not produce such side-effects when given either orally or intravenously to dogs.

Comparison of the side effects and gastrointestinal motility observed after administration of erythromycin and josamycin to dogs

The effects of intravenous erythromycin and josamycin on gastrointestinal motility in dogs have been compared. Erythromycin interrupted the basal motility pattern in the fasted state and induced irregular bursts of spikes in both the fasted and fed states. Emesis occurred in all the dogs in the fasted state experiments and in four out of six dogs in the fed state experiments. Josamycin did not disturb gastrointestinal motility and no dog showed signs of discomfort. The difference in the chemical structure of erythromycin and josamycin is the main reason for their differential effect on the gastrointestinal tract.