Reexamination of Damping in Sliding Friction.

Friction is responsible for about one-third of the primary energy consumption in the world. So far, a thorough atomistic understanding of the frictional energy dissipation mechanisms is still lacking. The Amontons' law states that kinetic friction is independent of the sliding velocity while the Prandtl-Tomlinson model suggests that damping is proportional to the relative sliding velocity between two contacting objects. Through careful analysis of the energy dissipation process in atomic force microscopy measurements, here we propose that damping force is proportional to the tip oscillation speed induced by friction. It is shown that a physically well-founded damping term can better reproduce the multiple peaks in the velocity-dependent friction force observed in both experiments and molecular dynamics simulations. Importantly, the analysis gives a clear physical picture of the dynamics of energy dissipation in different friction phases, which provides insight into long-standing puzzles in sliding friction, such as velocity weakening and spring-stiffness-dependent friction.

Modulating Friction by the Phase of the Vertical Vibrational Excitation at Washboard Frequency.

Applying external vibrations at the resonant frequencies of the frictional system has been a highly effective approach to suppress friction but usually requires additional energy consumption. In this study, we find that in addition to exerting the vibration at the resonant frequency of the frictional system, the friction force on the atomically flat silicon surface can also present a local minimum when the oscillation frequency of the vertical vibrational excitation equals the washboard frequency with respect to the sliding velocity. Moreover, compared with the additional energy consumption at the resonant frequency, applying vertical vibrational excitation at the washboard frequency requires much less energy consumption. The study further shows that the friction force under the washboard frequency can be effectively mediated depending on how the initial phase angle of the vertical vibrational excitation affects the effective substrate potential barrier at the slip moment of the tip. We have also extended the proposed friction modulation technique on atomically flat surfaces to periodic textured surfaces and confirmed its practicality and great potential for controlling friction.

Hsa_circ_0017956 Acts as miR-758-3p Sponge to Facilitate the Progression of Non-small-Cell Lung Cancer by Regulating FOXP4 Expression.

Accumulating studies have demonstrated the important role of circular RNAs (circRNAs) in the progression of different human tumors, including non-small-cell lung cancer (NSCLC). The purpose of this study was to deeply study the function and mechanism of circ_0017956 in NSCLC. Real-time quantitative polymerase chain reaction (RT-qPCR) was applied to detect the expression of circ_0017956, microRNA-758-3p (miR-758-3p), and Forkhead Box P4 (FOXP4). Western blot was performed to determine the protein levels. Cell proliferation was examined by cell counting kit-8 (CCK-8) assay and 5-ethynyl-2'-deoxyuridine (EdU) assay. Flow cytometry was used to evaluate the apoptosis of NSCLC cells. Transwell assay was applied to detect cell migratory and invasive capacities. The angiogenesis ability was evaluated by tube formation experiment. The target relationship between miR-758-3p and circ_0017956 or FOXP4 was confirmed by dual-luciferase reporter assay. Animal experiment was conducted to assess the effect of circ_0017956 in vivo. Circ_0017956 and FOXP4 were upregulated, while miR-758-3p was downregulated in NSCLC tissues and cells. Silencing of circ_0017956 significantly suppressed cell proliferation, migration, invasion, and angiogenesis, but promoted cell apoptosis in NSCLC cells. Mechanically, circ_0017956 functioned as a sponge for miR-758-3p and miR-758-3p could directly interact with FOXP4. Moreover, silencing of miR-758-3p or overexpression of FOXP4 could overturn the anticancer influence of circ_0017956 interference on NSCLC cells. Besides that, circ_0017956 knockdown hindered tumor growth in vivo. Altogether, circ_0017956 promoted the progression of NSCLC by regulating FOXP4 through sponging miR-758-3p.

NLRC4 Gene Single Nucleotide Polymorphisms Are Associated with the Prognosis of Hemophagocytic Lymphohistiocytosis.

OBJECTIVE: To analyze and study the correlation between NLR family CARD domain-containing 4 (NLRC4) gene single nucleotide polymorphisms and the prognosis of patients with hemophagocytic lymphohistiocytosis (HLH). METHODS: In this study, we retrospectively studied the clinical data of 62 HLH patients, including 40 males and 22 females. The genomic DNA was extracted, and the genotypes at rs385076 locus and rs479333 locus of the NLRC4 gene were analyzed. The level of blood interleukin-18 (IL-18) was analyzed by enzyme-linked immunosorbent assay (ELISA). RESULTS: Compared with the TT genotype at the NLRC4 gene rs385076 locus, the mortality of HLH patients with TC genotype and CC genotype was higher (RR = 3.205, 95% CI: 1.277-4.788, p = 0.012; RR = 3.052, 95% CI: 1.098-4.753, p = 0.031). Taking the CC genotype at rs479333 of the NLRC4 gene as a reference, HLH patients with CG genotype and GG genotype had a higher risk of death (RR = 3.475, 95% CI: 1.488-5.775, p = 0.003; RR = 2.986, 95% CI: 1.014-5.570, p = 0.047). NLRC4 gene rs385076 T>C and rs479333 C>G were significantly related to the poor prognosis of HLH patients. The area under the curve (AUC) of the receiver operating curve (ROC) for the prognostic outcome of HLH with serum IL-18 level was 0.6813 (95% CI: 0.5365-0.8260, p = 0.0189). NLRC4 gene rs385076 T>C and rs479333 C>G were related to higher serum IL-18 levels. CONCLUSION: NLRC4 gene rs385076 T>C and rs479333 C>G are related to the poor prognosis of HLH patients.

Resonance in Atomic-Scale Sliding Friction.

Friction represents a major energy dissipation mode, yet the atomistic mechanism of how friction converts mechanical motion into heat remains elusive. It has been suggested that excess phonons are mainly excited at the washboard frequency, the fundamental frequency at which relative motion excites the interface atoms, and the subsequent thermalization of these nonequilibrium phonons completes the energy dissipation process. Through combined atomic force microscopy measurements and atomistic modeling, here we show that the nonlinear interactions between a sliding tip and the substrate can generate excess phonons at not only the washboard frequency but also its harmonics. These nonequilibrium phonons can induce resonant vibration of the tip and lead to multiple peaks in the friction force as the tip sliding velocity ramps up. These observations disclose previously unrecognized energy dissipation channels associated with tip vibration and provide insights into engineering friction force through adjusting the resonant frequency of the tip-substrate system.

Preferential insertion of a Ty1 LTR-retrotransposon into the A sub-genome's HD1 gene significantly correlated with the reduction in stem trichomes of tetraploid cotton.

Stem trichomes and seed fibers originate from epidermal cells and partially share a regulatory pathway at the molecular level. In Gossypium barbadense, two insertions of a Ty1 long-terminal repeat-retrotransposon [transposable element TE1 and TE2] in a homeodomain-leucine zipper gene (HD1) result in glabrous stems. The primers used to identify the TE insertions in G. barbadense were applied to screen for the same events in 81 modern G. hirsutum varieties and 31 wild races. Three wild races were found carrying the same TEs as G. barbadense. However, the TE insertions in two of these wild races occurred at different sites (4th exon), therefore, named TE3, while the TE in the other wild race occurred at the same site as TE2. An RNA sequencing and qRT-PCR analysis indicated that the loss of HD1 function was caused by the TE insertion. Genetic mapping revealed a strong association between glabrous stems and TE3 insertions, confirming that HD1 is a critical gene for stem trichome initiation in G. hirsutum, as in G. barbadense. Using the long-terminal repeat sequence as a query to search against the Texas Marker-1 reference genome sequence, we found that the TE occurred after tetraploid cotton formation and evolved at different rates in G. hirsutum and G. barbadense. Interestingly, at least three independent insertion events of the same retrotransposon occurred preferentially in the A sub-genome's HD1 gene, but not in the D sub-genome of G. hirsutum or G. barbadense, suggesting that an unknown TE insertion mechanism and resultant gene function changes may have hastened cotton speciation.

Inhibiting geranylgeranyltransferase I activity decreases spine density in central nervous system.

Geranylgeranyltransferase I (GGT), a protein prenyltransferase, is responsible for the posttranslational lipidation of Rho GTPases, such as Rac, Rho and Cdc42, all of which play an important role in neuronal synaptogenesis. We previously demonstrated that GGT promotes dendritic morphogenesis in cultured hippocampal neurons and cerebellar slices. We report here that inhibiting GGT activity decreases basal- and activity-dependent changes in spine density as well as in learning and memory ability of mice in vivo. We found that KCl- or bicuculline-induced dendritic spine density increases was abolished by specific GGT inhibitor GGTi-2147 treatment in cultured hippocampal neurons. GGTi-2147 lateral ventricular injection reduced GGT activity and membrane association of Rac and decreased the density of dendritic spines in the mouse hippocampus, frontal cortex and cerebellum. GGTi-2147 administration also impaired learning and memory ability of mice. More importantly, mice exposed to environmental enrichment (EE) showed increased spine density and learning and memory ability, which were significantly reversed by GGTi-2147 administration. These data demonstrate that inhibiting GGT activity prevents both basal- and activity-dependent changes in spine density in central nervous system both in vitro and in vivo. Manipulating GGT activity may be a promising strategy for the therapies of neurodevelopmental disorders, such as autism, depression, and schizophrenia.

[Drug resistance analysis of pan-drug-resistant Acinetobacter baumannii in hospital].

OBJECTIVE: To investigate current situation of pan-drug-resistant Acinetobacter baumannii in hospital and its drug-resistance , then provide reference for rational use of antibiotics in clinic. METHODS: All kinds of microbial test specimens from January 2009 to December 2012 of hospitalized patients were cultured and separated. VITEK 2-Compact fully automatic microorganism analyzer was used to identify and analyze drug sensitivity. RESULTS: Three hundred and seven strains pan-drug-resistant Acinetobacter baumannii were isolated in 4 years, the primarily source were sputum, accounted for 69.4%, followed by the wound secretion 14.7%. The highest three places of samples separation of extensive drug-resistant Acinetobacter baumannii positive was intensive care unit (ICU, accounted for 26.4%), department of respiratory medicine (accounted for 26.1%) and department of geriatrics (accounted for 23.1%). Extensive drug-resistant Acinetobacter baumannii almost completely resisted to clinical commonly used antimicrobial agents, drug resistant rate could be as high as 100% such as cefotaxime, meropenem, piperacillin, imipenem, ciprofloxacin, and tetracycline except for cefoperazone-sulbactam and polymyxin, and the rate of other drugs were all above 90%. Drug-resistant of cefoperazone-sulbactam was nearly 30% in our hospital, and sensitive rate was 100% to polymyxin. CONCLUSIONS: Pan-drug-resistant Acinetobacter baumannii is resistant for most clinical commonly used antimicrobial drug, antimicrobial agents were chosen according to drug susceptibility testing. Antibacterial drugs such as polymyxin and cefoperazone-sulbactam or sulbactam contained drugs can be selected for pan-drug-resistant.

Geranylgeranyltransferase I mediates BDNF-induced synaptogenesis.

Geranylgeranyltransferase I (GGT) is a prenyltransferase that mediates lipid modification of Rho small GTPases, such as Rho, Rac, and Cdc42, which are important for neuronal synaptogenesis. Although GGT is expressed in brain extensively, the function of GGT in central nerves system is largely unknown so far. We have previously demonstrated that GGT promotes the basal and neuronal activity and brain-derived neurotrophic factor (BDNF)-induced dendritic morphogenesis of cultured hippocampal neurons and cerebellar slices. This study is to explore the function and mechanism of GGT in neuronal synaptogenesis. We found that the protein level and activity of GGT gradually increased in rat hippocampus from P7 to P28 and subcellular located at synapse of neurons. The linear density of Synapsin 1 and post-synaptic density protein 95 increased by over-expression of GGT ß, while reduced by inhibition or down-regulation of GGT. In addition, GGT and its known substrate Rac was activated by BDNF, which promotes synaptogenesis in cultured hippocampal neurons. Furthermore, BDNF-induced synaptogenesis was eliminated by GGT inhibition or down-regulation, as well as by non-prenylated Rac1 over-expression. Together, our data suggested that GGT mediates BDNF-induced neuronal synaptogenesis through Rac1 activation.

[The changes in subgroup of helper T lymphocyte and calcitonin and their correlation in patients with severe hospital acquired pneumonia].

OBJECTIVE: To observe the changes in subgroups of helper T cells and serum calcitonin (PCT) levels in patients with hospital acquired pneumonia (HAP) and their correlation. METHODS: Eighty-nine patients with diagnosis of HAP (severe in 59 patients, mild in 30 cases) were included, with 20 healthy adults as control. Percentage of CD4(+), Th1 and Th2 cells, and Th1/Th2 ratio were determined, and sandwich immune luminescence was used to detect the level of serum PCT. RESULTS: The percentage of Th1 cells [(8.40 ± 3.01)%] was significantly lower in patients with severe HAP compared with that of mild pneumonia group [(13.90 ± 2.37)%, P < 0.05] and healthy controls [(17.40 ± 4.20)%, P < 0.01]. Percentage of Th2 cells was obviously higher in patients with severe HAP [(17.30 ± 5.74)%] than mild pneumonia group [(7.70 ± 2.35)%, P < 0.05] and healthy controls [(7.90 ± 1.92)%, P < 0.01]. Th1/Th2 ratio was also obviously lower in severe pneumonia group (0.57 ± 0.15) than that of mild pneumonia group (2.80 ± 0.46, P < 0.01) and healthy controls (3.11 ± 0.87, P < 0.01). Compared with healthy controls, Th1 cells in mild pneumonia patients were reduced significantly (P < 0.05), but there was no significant difference in Th2 cells and Th1/Th2 ratio (both P > 0.05). There was no difference in CD4(+) among severe, mild pneumonia and healthy controls [(30.20 ± 10.83)%, (34.70 ± 13.57)%, (28.80 ± 9.61)%, respectively, all P >0.05]. The level of PCT (µg/L) was significantly elevated in mild and severe pneumonia patients compared with that of healthy controls (1.73 ± 0.88, 3.51 ± 2.66 vs. 0.30 ± 0.10, both P < 0.01), and the level of PCT in severe pneumonia was significantly higher than that of mild pneumonia (P < 0.05). Regression analysis of Th1/Th2 and PCT revealed a significant negative correlation, with regression equation Y = -0.937x (F=236.23,P = 0.0000). CONCLUSIONS: Patients with severe HAP had obvious imbalance of Th1/Th2. The suppression of cellular immune function, reduction in Th2 cells and exacerbation of anti-inflammatory reaction intensify the infection leading to multiple organ dysfunction syndrome. There is obvious negative correlation between Th1/Th2 and PCT. PCT could be used as an indicator of immune response in reflecting cellular and humoral immunity of the patient.

An unprecedented strategy for selective and sensitive fluorescence detection of nitric oxide based on its reaction with a selenide.

A new strategy that utilizes the interaction between NO and a selenide is reported for fluorescence detection of NO, in which rhodamine B selenolactone serves as a model selenide.

Determination of non-protein cysteine in human serum by a designed BODIPY-based fluorescent probe.

A novel fluorescent probe is designed and synthesized for the determination of cysteine in biological samples by incorporating 2,4-dinitrobenzenesulfonyl (DBS) group as a quencher into the BODIPY skeleton. The BODIPY-based probe itself shows weak fluorescence due to the strong intramolecular charge transfer process. Upon reaction with cysteine, however, the probe produces a rapid and large fluorescence enhancement through the removal of the DBS unit by nucleophilic aromatic substitution. This valuable property leads to the development of a new and simple method for cysteine assay. Under the optimized conditions, the fluorescence enhancement value is directly proportional to the concentration of cysteine in the range 2-12 µM, with a detection limit of 30 nM (S/N=3). The applicability of the developed method has been successfully demonstrated on the determination of non-protein cysteine in human serum. Compared to most of the existing fluorescent probes proposed for cysteine, the BODIPY-based one exhibits an excellent overall performance in terms of selectivity, sensitivity and simplicity.

A highly specific ferrocene-based fluorescent probe for hypochlorous acid and its application to cell imaging.

A highly specific ferrocene-based fluorescent probe, (9-anthryl)ethenylferrocene, has been designed, synthesized and characterized for fluorescence imaging of hypochlorous acid (HOCl) in live cells. The design strategy for the probe is based on the strong quenching effect of electron-donor ferrocene on anthracene fluorescence via an intramolecular charge transfer process, and is accomplished through constructing the conjugated molecule by using a cleavable double bond as a linker. The double bond in the probe reacts selectively with HOCl rather than the other reactive oxygen species (e.g., *OH, *O(2)(-), (1)O(2), and H(2)O(2)) in pH 7.4, accompanied by more than 100-fold fluorescence enhancement. Moreover, the probe is cell membrane permeable, and its applicability has been successfully demonstrated for fluorescence imaging of HOCl in HeLa cells.

Evaluation of poly(styrene-alt-maleic anhydride)-ethanol as enteric coating material.

This study aims at evaluating the potential of SMA-ethanol as enteric coating polymer for erythromycin tablets. SMA-ethanol was synthesized and characterized for physicochemical properties, molecular weight and thermal analysis. Free films were prepared by adding different kinds and amounts of plasticizers, the film surface topography was determined by a SEM, the tensile strength, water vapor transmission rate and moisture absorption were also tested to choose the most promising film. DBP was proved to be the most suitable plasticizer with a best using amount of 20%, such polymer films had low vapor transmission rate and low moisture absorption which were very important to an enteric coating material. The polymer was further characterized for film coating by evaluating the release of erythromycin tablets in vitro, tablets coated with SMA-ethanol can satisfy the drug release requests of USP when the film weight gains were between 4 and 6%; tablets coated with both a subcoat and the polymer showed excellent gastro-resistance, less than 0.2% drug release occurred even with weight gains as less as 2% after 2h exposure to acid (pH 1), while over 90% drug release occurred in pH 6.8 sodium phosphate buffer within 45 min, regardless of weight gains of coating material, moreover, we confirmed that the application of a subcoat could decrease the amount of required coating polymer. In conclusion, the potential use of SMA-ethanol as enteric coating material was demonstrated.

[Effect of treatment with Xuebijing injection on serum inflammatory mediators and Th1/2 of spleen in rats with sepsis].

OBJECTIVE: To study the effect of treatment with Xuebijing injection on pro- or anti-inflammatory response and pathologic changes in immune organs in rats with sepsis. METHODS: Sepsis was reproduced in rats by cecal ligation and puncture. Rats were divided into four groups i.e. sham operation, sepsis, sepsis with levofloxacin treatment, and Xuebijing treatment groups. Blood samples were collected at 3, 24 and 72 hours after model was reproduced. Enzyme linked immunoadsorbent assay (ELISA) was used to determine the levels of serum tumor necrosis factor-alpha (TNF-alpha) and interleukin-10 (IL-10), expression level of spleen Th1/Th2 was assessed by FACS flow cytometer, and the pathological changes in immunological organs were examined. RESULTS: The results showed that the levels of Th1/Th2 and TNF-alpha, IL-10 were elevated in early period of sepsis, but lowered in late period of sepsis. Xuebijing could decrease the level of Th1/Th2, which showed an increase at 72 hours. Xuebijing could lower the levels of TNF-alpha and IL-10, rendering a balance of pro- and anti-inflammatory response. CONCLUSION: There is a dissonance in immunological function in sepsis, showing a depression in specific immunological function, but an exaggeration in non-specific immunological function. Xuebijing can obviously ameliorate the immunological disturbance in sepsis of rat.