[Machine learning and its epidemiological applications].

As an important branch of artificial intelligence, machine learning is widely used in various fields. Machine learning has similarity to classical statistical methods, but can solve many problems which are difficult for traditional statistics, so it is one of the important tools in epidemiological research. This paper introduced 9 common algorithms of machine learning and summarized their characteristics and applications in epidemiological research. Readers could choose appropriate machine learning method according to the research purpose for the better application of machine learning in epidemiological research.

[Effect of Echinococcus multilocularis infections on mitochondrial functions of macrophages].

OBJECTIVE: To investigate the changes of mitochondrial metabolic functions of macrophages following Echinococcus multilocularis infections, so as to provide insights into the pathogenesis of alveolar echinococcosis. METHODS: Two groups were assigned according to different treatment methods. In the culture group, mouse leukemic monocyte macrophage RAW264.7 cells were cultured with 2 000 E. multilocularis at a ratio of 500∶1, while RAW264.7 cells in the control group were given no treatment. Then, both the culture and control groups were further divided into the 24 h and 72 h subgroups. Mitochondria were stained with MitoTracker® Deep Red FM and the mean fluorescence intensity of macrophage mitochondria was measured with the Cytation 5 Cell Imaging Multi-Mode Reader. The mitochondrial DNA copy number was quantified using the quantitative real-time PCR (qPCR) assay, and the mitochondrial energy metabolism was monitored using the Seahorse XF assay. In addition, the mitochondrial reactive oxygen species and mitochondrial membrane potential were detected using flow cytometry. RESULTS: The mean fluorescence intensities of macrophage mitochondria were significantly lower in the 24 h (15 341 ± 2 532 vs. 17 823 ± 3 429; t = 6.379, P < 0.01) and 72 h (18 102 ± 3 505 vs. 21 511 ± 5 144; t = 17.680, P < 0.01) culture subgroups than in the corresponding control subgroups, and lower mitochondrial DNA copy numbers were measured in the 72 h culture subgroup than in the 72 h control group [(3.23 × 109 ± 1.78 × 107) vs. (4.39 × 109 ± 3.70 × 107); t = 8.85, P < 0.001]. The oxygen consumption rates were significantly greater in the 24 h [(241.70 ± 73.13) pmol/min vs. (69.05 ± 52.30) pmol/min; t = 7.89, P < 0.01] and 48 h culture groups [(249.50 ± 42.06) pmol/min vs. (60.28 ± 40.66) pmol/min; t = 8.64, P < 0.01] than in the corresponding control groups, and a higher extracellular acidification rate was seen in the 48 h culture group than in the 48 h control group ([ 111.6 ± 17.49) mpH/min vs. (35.05 ± 7.57) mpH/min; t = 16.90, P < 0.01]. In addition, flow cytometry detected higher mean fluorescence intensity of mitochondrial reactive oxygen species (58 264 ± 10 087 vs. 4 307 ± 97; t = 12.930, P < 0.01) and lower mitochondrial membrane potential (9.833% ± 2.285% vs. 2.667% ± 0.208%; t = 6.645, P < 0.01) in the 72 h culture group than in the control group. CONCLUSIONS: E. multilocularis infection may impair mitochondrial functions and inhibit oxidative phosphorylation of macrophages, resulting in increased macrophage glycolysis. It is speculated that the alteration of macrophage metabolic states may contribute to the mechanisms underlying the development and progression of alveolar echinococcosis.

[A sequential conditional mean model for assessing total effects of exposure in longitudinal data].

In prospective cohort study, multi follow up is often necessary for study subjects, and the observed values are correlated with each other, usually resulting in time-dependent confounding. In this case, the data generally do not meet the application conditions of traditional multivariate regression analysis. Sequential conditional mean model (SCMM) is a new approach that can deal with time-dependent confounding. This paper mainly summarizes the basic theory, steps and characteristics of SCMM.

Biosynthesis and fate of proteoglycans in cartilage and bone during development and mineralization.

Subcutaneous implantation of demineralized bone matrix in rats induces migration of host cells into the site and results in the sequential development of cartilage and bone. The biosynthesis and metabolic fate of proteoglycans in the plaques at the bone matrix implantation site were investigated by [35S]sulfate labeling in vivo. 35S-Labeled proteoglycans were extracted with 4 M guanidine HCl and purified by DEAE-Sephacel chromatography. Analysis of proteoglycans on Sepharose CL-2B chromatography showed two major peaks at Kd = 0.28 and 0.68 (peaks I and II, respectively). Peak I proteoglycan has a high buoyant density and contains chondroitin sulfate chains of average Mr = 20,000. Peak II proteoglycan has a lower average buoyant density and contains dermatan sulfate chains of average Mr = 33,000. Throughout the endochondral bone development sequence, peak II proteoglycan predominates. Peak I was low on Day 3, became prominent on Day 7 (approximately 30% of the total radioactivity), and declined after Day 9. The calculated half-lives of peak I and II proteoglycans labeled on Day 7 were about 1.8 and 2.8 days, respectively. After the initiation of osteogenesis, a species of mineral-associated proteoglycan was extracted with a 4 M guanidine HCl solvent containing 0.5 M EDTA. This proteoglycan has a small hydrodynamic size (Kd = 0.38 on Sepharose CL-6B chromatography) and shows a long half-life, about 6 days.