Breeding of Saccharomyces cerevisiae with a High-Throughput Screening Strategy for Improvement of S-Adenosyl-L-Methionine Production

S-adenosyl-l-methionine (SAM), a vital physiologically active substance in living organisms, is produced by fermentation over Saccharomyces cerevisiae. The main limitation in SAM production was the low biosynthesis ability of SAM in S. cerevisiae. The aim of this work is to breed an SAM-overproducing mutant through UV mutagenesis coupled with high-throughput selection. Firstly, a high-throughput screening method by rapid identification of positive colonies was conducted. White colonies on YND medium were selected as positive strains. Then, nystatin/sinefungin was chosen as a resistant agent in directed mutagenesis. After several cycles of mutagenesis, a stable mutant 616-19-5 was successfully obtained and exhibited higher SAM production (0.41 g/L vs 1.39 g/L). Furthermore, the transcript levels of the genes SAM2, ADO1, and CHO2 involved in SAM biosynthesis increased, while ergosterol biosynthesis genes in mutant 616-19-5 significantly decreased. Finally, building on the above work, S. cerevisiae 616-19-5 could produce 10.92 ± 0.2 g/L SAM in a 5-L fermenter after 96 h of fermentation, showing a 2.02-fold increase in the product yield compared with the parent strain. Paving the way of breeding SAM-overproducing strain has improved the good basis for SAM industrial production.

Improving ATP availability by sod1 deletion with a strategy of precursor feeding enhanced S-adenosyl-L-methionine accumulation in Saccharomyces cerevisiae

S-adenosyl-L-methionine (SAM), used in diverse pharmaceutical applications, was biosynthesized from L-methionine (L-met) and adenosine triphosphate (ATP). This study aims to increase the accumulation of SAM in Saccharomyces cerevisiae by promoting ATP availability. Strain ΔSOD1 was obtained from the parent strain WT15-33 (CCTCC M 2021915) by deleting gene sod1, which improved the supply of ATP. The SAM content in strain ΔSOD1 exhibited a 22.3% improvement compared to the parent strain, which reached 93.6 mg g^-1. The transformation of NADH (reduced nicotinamide adenine dinucleotide) and the relative expression of ATPase essential genes were investigated, respectively. The results showed that the lack of gene sod1 benefited the generation of ATP, which positively regulated the synthesis of SAM. Besides that, the production of SAM was further enhanced by improving substrate assimilation. With the infusion of 1.44 g L^-1L-met and 0.60 g L^-1 adenosine at 24 h (h) and 0 h following fermentation, the optimum medium could produce 1.54 g L^-1 SAM. Based on the regulations mentioned above, the SAM concentration of strain ΔSOD1 enhanced from 7.3 g L^-1 to 10.1 g L^-1 in a 5-L fermenter in 118 h. This work introduces a novel idea for the biosynthesis of ATP and SAM, and the strain ΔSOD1 has the potential for industrial production.

Deletion of Schizophrenia Susceptibility Gene Ulk4 Leads to Abnormal Cognitive Behaviors via Akt-GSK-3 Signaling Pathway in Mice

OBJECTIVES

Despite of strenuous research in the past decades, the etiology of schizophrenia (SCZ) still remains incredibly controversial. Previous genetic analysis has uncovered a close association of Unc-51 like kinase 4 (ULK4), a family member of Unc-51-like serine/threonine kinase, with SCZ. However, animal behavior data which may connect Ulk4 deficiency with psychiatric disorders, particularly SCZ are still missing.

METHODS

We generated Emx1-Cre:Ulk4flox/flox conditional knockout (CKO) mice, in which Ulk4 was deleted in the excitatory neurons of cerebral cortex and hippocampus.

RESULTS

The cerebral cellular architecture was maintained but the spine density of pyramidal neurons was reduced in Ulk4 CKO mice. CKO mice showed deficits in the spatial and working memories and sensorimotor gating. Levels of p-Akt and p-GSK-3α/β were markedly reduced in the CKO mice indicating an elevation of GSK-3 signaling. Mechanistically, Ulk4 may regulate the GSK-3 signaling via putative protein complex comprising of two phosphatases, protein phosphatase 2A (PP2A) and 1α (PP1α). Indeed, the reduction of p-Akt and p-GSK-3α/β was rescued by administration of inhibitor acting on PP2A and PP1α in CKO mice.

CONCLUSIONS

Our data identified potential downstream signaling pathway of Ulk4, which plays important roles in the cognitive functions and when defective, may promote SCZ-like pathogenesis and behavioral phenotypes in mice.

[A study of the effectiveness of nucleos(t)ide analogues in the treatment of HBeAg- positive chronic hepatitis B with normal alanine aminotransferase and high level of HBV DNA]

Objective: To investigate the effectiveness of nucleos(t)ide analogues in the treatment of HBeAg-positive chronic hepatitis B with normal alanine aminotransferase and high level of HBV DNA. Methods: Treatment-naïve chronic hepatitis B patients who were followed up at the Center of Infectious Diseases, West China Hospital of Sichuan University from January 2019 to January 2020 were selected as subjects. Demographic characteristics, the results of laboratory examination before treatment and one year after treatment were retrospectively collected. Patients were divided into tenofovir dipivoxil (TDF) and propofol fumurate tenofovir (TAF) treatment group according to different types of medication. The changes of serum HBV DNA level, HBeAg serological conversion and HBsAg quantitative level were analyzed and compared between the two groups. Results: A total of 38 cases were enrolled. Among them, there were 16 and 22 cases in the TDF and TAF group, respectively. There was no statistically significant difference in demographic characteristics, baseline HBV DNA levels and HBsAg quantitative levels between the two groups. Virological response was achieved in 60.5% (23/38) of patients after one year of antiviral therapy. Serum HBV DNA levels below the lower limit of detection [68.2% (15/22) vs. 50.0% (8/16), P=0.258] and higher HBeAg seroconversion rate [18.2%] (4/22) vs. 6.3% (1/16), P=0.374] was obtained in TAF than TDF group; however, there was no statistically significant differences between the two. Serum HBsAg quantitative level was significantly reduced with TDF and TAF treatment. In addition, alanine aminotransferase elevation was reduced in TAF than TDF treated group. Multivariate logistic regression analysis showed that patient age was an independent predictor of a virological response to antiviral therapy. Conclusion: HBeAg-positive CHB patients with normal alanine aminotransferase, and high HBV DNA level can obtain better curative effect after TDF and TAF treatment.

Anomalous Josephson current through a topological noncoplanar ferromagnetic trilayer

We present an anomalous Josephson effect in a TI-based Josephson junction with a ferromagnetic insulator (FI) trilayer which has noncoplanar magnetizations. It is shown that there exist equal fractional spin-singlet and -triplet correlations due to the magnetism-tuning chiral Dirac energy band structure. The consequent anomalous Josephson supercurrent is exhibited, in which a 0-πor similar 0-πstate transition through phase shift is induced only by exchange field strength of the first FI region, while theϕ₀supercurrent and the maximum one gradually drop with the increase of exchange field strengths of the second and third FI regions without relative state transitions. With the increase of the FI region length, theϕ₀supercurrent and the maximum one are also both decreased, are found, which is different from the situation for increasing the exchange filed strength. In addition, the corresponding free energies are presented and discussed.

[The mediating role of psychological resilience to childhood abuse and binge eating among middle school students]

To explore the mediating role of psychological resilience to childhood abuse and binge eating. This study assessed the childhood abuse, binge eating and psychological resilience of 3 453 middle school students in Harbin city, Heilongjiang Province. SPSS PROCESS macro program, combined with Bootstrap method, was employed to explore the mediating effect of psychological resilience. The incidence of middle school students experiencing at least one type of abuse in their childhood was 81.3% (2 807/3 453). Childhood abuse, psychological resilience and binge eating were all significantly different in terms of gender, household registration and whether they were only child (all P values<0.05). There was a significant positive correlation between childhood abuse and binge eating. Psychological resilience was negatively associated with childhood abuse and binge eating. Childhood abuse could not only directly predict the binge eating behavior of adolescents, but also could indirectly affect it via psychological resilience.

[Mechanism of cleft palate in C57BL/6N mice induced by retinoic acid]

Objective: To investigate the mechanism of cleft palate in mice induced by excessive all-trans retinoic acid (atRA). Methods: The pregnant mice were randomly divided into atRA-treated group (n=27) and control group (n=27). atRA-treated group was given by gavage a single dose of atRA (100 mg/kg) at 8: 00 AM on gestation day 10 (GD10) and the control group was given by gavage the isopyknic corn oil. At GD13-GD15, the fetal mice palate development was observed by HE staining. The mouse embryonic palatal mesenchymal cell proliferation was detected by 5-bromo-2-deoxyuridine (BrdU) immunohistochemistry. The expressions of Smad2, phospho-Smad2 (p-Smad2), Smad4 and Smad7 in mouse embryonic palatal mesenchyme were analyzed by Western blotting. Results: At GD13-GD15, compared with the control, the ratio of BrdU-positive cells in the palatal mesenchyme of atRA-treated fetuses decreased significantly (P<0.05), especially at GD14, atRA inhibition rate was (65.4±1.7)%. Moreover, atRA decreased the levels of p-Smad2 and Smad4 in embryonic palate mesenchymal cells, whereas the expression of Smad7 was significantly increased at GD14 and GD15. Conclusions: atRA may lead to cleft palate by inhibiting the activation of Smad signaling pathway and affecting the proliferation of palatal mesenchymal cells.

Superconductivity switch from spin-singlet to -triplet pairing in a topological superconducting junction

The interedge coupling is the cardinal characteristic of the narrow quantum spin Hall (QSH) insulator, and thus could bring about exotic transport phenomena. Herein, we present a theoretical investigation of the spin-resolved Andreev reflection (AR) in a QSH insulator strip touching on two neighbouring ferromagnetic insulators and one s-wave superconductor. It is demonstrated that, due to the interplay of the interedge coupling and ferromagnetic configuration, there could be not only usual local ARs leading to the spin-singlet pairing with the incident electron and Andreev-reflected hole from different spin subbands, but also novel local ARs giving rise to the spin-triplet pairing from the same spin subband. However, only the latter exists in the absence of the interedge coupling, and therefore the two pairings in turn testify the helical spin texture of the edge states. By proper tuning of the band structures of the ferromagnetic layers, under the resonance bias voltage, the usual and novel local ARs of [Formula: see text] can be all exhibited, resulting in fully spin-polarized pure spin-singlet superconductivity and pure spin-triplet superconductivity, respectively, which suggests a superconductivity switch from spin-singlet to -triplet pairing by electrical control. The results can be experimentally confirmed by the tunneling conductance and the noise power.

Supercurrent switch in π topological junctions based upon a narrow quantum spin Hall insulator

The narrow quantum spin Hall (QSH) insulator is characterized by interedge coupling, which could feature exotic transport phenomena, and thus serves as the key element for topological superconducting electronic devices. Herein, we theoretically explore possible Josephson π states in a QSH insulator strip touching on two s-wave superconductors in the presence of the interedge coupling. It is shown that the interedge coupling could give rise to a 0 - π transition modulated by the gate voltage, originating from an additional π phase difference caused by the interedge backscattering. The 0 - π transition in turn can manifest the helical spin texture of the edge states. A considerable residual value of the supercurrent at the 0 - π transition point is always exhibited, suggesting a very efficient performance of the device as a supercurrent switch. Moreover, the region of coexisting 0 and π states is found fairly large, which can be used to improve accuracy in the design of a π superconducting quantum interference device.

Coexistence of perfect spin filtering for entangled electron pairs and high magnetic storage efficiency in one setup

For Entangled electron pairs superconducting spintronics, there exist two drawbacks in existing proposals of generating entangled electron pairs. One is that the two kinds of different spin entangled electron pairs mix with each other. And the other is a low efficiency of entanglement production. Herein, we report the spin entanglement state of the ferromagnetic insulator (FI)/s-wave superconductor/FI structure on a narrow quantum spin Hall insulator strip. It is shown that not only the high production of entangled electron pairs in wider energy range, but also the perfect spin filtering of entangled electron pairs in the context of no highly spin-polarized electrons, can be obtained. Moreover, the currents for the left and right leads in the antiferromagnetic alignment both can be zero, indicating 100% tunnelling magnetoresistance with highly magnetic storage efficiency. Therefore, the spin filtering for entangled electron pairs and magnetic storage with high efficiencies coexist in one setup. The results may be experimentally demonstrated by measuring the tunnelling conductance and the noise power.

Prevalence and patterns of multimorbidity in northeastern China: a cross-sectional study

OBJECTIVES

Information on multimorbidity in the general populations of developing countries is lacking. We examine the prevalence and patterns of multimorbidity in northeastern China.

STUDY DESIGN

A cross-sectional study was conducted on adult residents in Jilin Province, northeastern China from June 2012 to August 2012.

METHODS

Data were collected from a large cross-sectional study (n = 21,435) of adult community residents in Jilin Province in northeastern China. Multimorbidity, or co-morbidity, was defined as having two or more of 18 specified prevalent chronic diseases. A range of demographics, socio-economic factors, other risk factors and general mental health were used in describing the distribution of multimorbidity and in exploring the associations between them.

RESULTS

Almost a quarter (24.7%) of the adults were found to be multimorbid for chronic diseases. Multimorbidity was more common among older adults, women, rural residents and those with low income. Smoking, increasing BMI and psychological distress were independently associated with multimorbidity. Multimorbid patients were frequent users of primary care. Most dyads of chronic diseases co-occurred more frequently than would be expected on the basis of chance.

CONCLUSIONS

Researchers, clinicians and policy makers need to pay special attention to the health care challenges of multimorbidity and develop effective intervention strategies and programs to reduce the burden of multimorbidity.

Prevalence of obesity and associated risk factors in Northeastern China

AIM

To investigate the prevalence of obesity and associated risk factors in the Northeastern Chinese city of Dehui.

METHODS

A cross-sectional study involving random sampling methods generated 3598 completed questionnaires by permanent residents of Dehui. Binary multivariate logistic regression analysis was used to identify factors that were significantly associated with obesity.

RESULTS

Based on the 2000 WHO diagnostic criterion regarding populations in the Asia-Pacific region, the prevalence of obesity was 37.71% (34.77% of females; 41.11% of males). Elevated body mass index (BMI) was significantly associated with cardiovascular disease (CVD)-associated conditions (P<0.05), and increased prevalence of abnormally high transaminase levels (P<0.05). Binary logistic regression analysis demonstrated the following variables were associated with obesity: increased age (odds ratio [OR]: 1.01, 95% confidence interval [CI]: 1.0-1.02), high total cholesterol (TC) (OR: 1.26, 95% CI: 1.03-1.54), high triglycerides (TG) (OR: 1.38, 95% CI: 1.16-1.64), hypertension (OR: 1.62, 95% CI: 1.39-1.90), fatty liver (OR: 2.91, 95% CI: 2.41-3.49), living in an urban setting (OR: 2.84, 95% CI: 2.39-3.38), and advanced education (OR: 1.22, 95% CI: 1.06-1.40).

CONCLUSIONS

Obesity is prevalent among the adult population in Northeastern China and is significantly associated with CVD risk factors such as hypertension, dyslipidemia, as well as transaminase abnormalities.

Simulating the role of microtubules in depolymerization-driven transport: a Monte Carlo approach

In this paper we present a model that simulates the role of microtubules in depolymerization-driven transport. The model simulates a system that consists of a 13-protofilament microtubule with "five-start" helical structure and a motor protein-coated bead that moves along one of the protofilaments of the microtubule, as in in vitro experiments. The microtubule is simulated using the lateral cap model, with substantial generalizations. For the new terminal configurations in the presence of the bead, rate constants for association and dissociation events of tubulin molecules are calculated by exploring the geometric similarities between different patterns of terminal configurations and by decomposing complex patterns into simpler patterns whose corresponding rate constants are known. In comparison with a previous model, in which simplifications are made about the structure of the microtubule and in which the microtubule can only depolymerize, the detailed structure of the microtubule is taken into account in the present model. Furthermore, the microtubule can be either polymerizing or depolymerizing. Force-velocity curves are obtained for both zero and non-zero tubulin guanosine 5'-triphosphate (GTP) concentrations. By analyzing the trajectory of the bead under different parameters, the condition for "run and pause" is analyzed, and the time scale of "run" and "pause" is found to be different for different motor proteins. We also suggest experiments that can be used to examine the results predicted by the model.

[Prevention and factors inducing respiratory distress syndrome in prematures]

An analysis of 105 cases of prematures with respiratory distress syndrome, the idiopathic type were 9.5% (10/105). Fetal anoxia and ischemia, induced by pregnancy and during labour amounting to 87.6% (92/105), and of which 2.9% (3/105) was due to diabetes. It indicated that most cases of RDS are predominantly related with fetal anoxia and ischemia which results in pulmonary surfactant abnormality or impaired activity. It is important that in clinical diagnosis one should monitor cautiously the presence of premature birth with anoxia and ischemia, Thus, a preventive treatment must be given at least 24 hours prior to birth, and the earlier the least morbidity of RDS occurred.