Rapid discrimination of Shigella spp. and Escherichia coli via label-free surface enhanced Raman spectroscopy coupled with machine learning algorithms.

Shigella and enterotoxigenic Escherichia coli (ETEC) are major bacterial pathogens of diarrheal disease that is the second leading cause of childhood mortality globally. Currently, it is well known that Shigella spp., and E. coli are very closely related with many common characteristics. Evolutionarily speaking, Shigella spp., are positioned within the phylogenetic tree of E. coli. Therefore, discrimination of Shigella spp., from E. coli is very difficult. Many methods have been developed with the aim of differentiating the two species, which include but not limited to biochemical tests, nucleic acids amplification, and mass spectrometry, etc. However, these methods suffer from high false positive rates and complicated operation procedures, which requires the development of novel methods for accurate and rapid identification of Shigella spp., and E. coli. As a low-cost and non-invasive method, surface enhanced Raman spectroscopy (SERS) is currently under intensive study for its diagnostic potential in bacterial pathogens, which is worthy of further investigation for its application in bacterial discrimination. In this study, we focused on clinically isolated E. coli strains and Shigella species (spp.), that is, S. dysenteriae, S. boydii, S. flexneri, and S. sonnei, based on which SERS spectra were generated and characteristic peaks for Shigella spp., and E. coli were identified, revealing unique molecular components in the two bacterial groups. Further comparative analysis of machine learning algorithms showed that, the Convolutional Neural Network (CNN) achieved the best performance and robustness in bacterial discrimination capacity when compared with Random Forest (RF) and Support Vector Machine (SVM) algorithms. Taken together, this study confirmed that SERS paired with machine learning could achieve high accuracy in discriminating Shigella spp., from E. coli, which facilitated its application potential for diarrheal prevention and control in clinical settings. Graphical abstract.

Human PIH1 associates with histone H4 to mediate the glucose-dependent enhancement of pre-rRNA synthesis.

Ribosome biogenesis is critical in the growth of eukaryotic cells, in which the synthesis of precursor ribosomal RNA is the first and rate-limiting step. Here, we show that human PIH1 domain-containing protein 1 (PIH1) interacts directly with histone H4 and recruits the Brg1-SWI/SNF complex via SNF5 to human rRNA genes. This process is likely involved in PIH1-dependent DNase I-hypersensitive chromatin remodeling at the core promoter of the rRNA genes. PIH1 mediates the occupancy of not only the Brg1 complex but also the Pol I complex at the core promoter and enhances transcription initiation of rRNA genes. Additionally, the interaction between PIH1 and H4K16 expels TIP5, a component of the silencing nucleolar remodeling complex (NoRC), from the core region, suggesting that PIH1 is involved in the derepression of NoRC-silenced rRNA genes. These data indicate that PIH1 is a positive regulator of human rRNA genes and is of great importance for the recovery of human cells from nutrient starvation and the transition to glucose-induced exponential growth in vivo.

[Prenatal diagnosis of ß-thalassaemia using cell-free fetal DNA in maternal plasma].

OBJECTIVE: To investigate the clinical feasibility of cell-free fetal DNA (cffDNA)-based noninvasive prenatal diagnosis of ß-thalassemia. METHODS: Nine samples of amniotic fluid were obtained to detect the 8 common and 9 relatively rare mutation sites of ß-thalassaemia in Guangdong Province. The maternal blood samples were also collected for extracting and purification of the cffDNA, and a duplex PCR was performed using 3 pairs of primers and the fetal ß-globin genotype was analyzed by reverse dot-blot hybridization. RESULTS: Among the 9 cases, 5 showed fetal genotypes of ß-thalassemia inherited from the father by examination of the amniotic fluid, and 2 fetuses were identified to have ß-thalassemia genes inherited from the father determined based on the cffDNA in the maternal blood. CONCLUSIONS: The cffDNA-based noninvasive prenatal diagnosis is feasible for ß-thalassemia, but the contamination of the maternal background DNA results in a low detection rate.

High-fat feeding reduces endothelium-dependent vasodilation in rats: differential mechanisms for saturated and unsaturated fatty acids?

1. Chronic feeding with a high-fat diet can cause metabolic syndrome in rodents similar to humans, but the role of saturated versus unsaturated fats in vascular tension remains unclear. 2. The present study shows that rats on a diet rich in either saturated or unsaturated fat had higher blood pressure compared with chow-fed rats (approximately 130 vs 100 mmHg, respectively), along with hyperlipidaemia and insulin resistance. Compared with responses of phenylephrine-preconstricted artery segments from chow-fed rats, vasorelaxation of isolated renal arteries from high-fat fed rats was reduced substantially (> 50%) in response to acetylcholine (0.01-10 micromol/L) and moderately to nitroprusside (>or=1 micromol/L) at low concentrations. Acetylcholine-induced vasorelaxation of arteries from high-fat fed rats was also more sensitive to inhibition by the nitric oxide (NO) synthase inhibitors NG-nitro-L-arginine and methylene blue. 3. In human umbilical vein endothelial cells, the production of NO and endothelin-1 was significantly inhibited by unsaturated fatty acids. In comparison, saturated fatty acids stimulated endothelin-1 production without altering NO production. 4. The data indicate that both saturated and unsaturated high-fat feeding may result in an increase in blood pressure owing to reduced endothelium-dependent vasorelaxation in the arterial system. The impaired endothelium-dependent vasorelaxation induced by saturated and unsaturated fatty acids may involve different mechanisms.