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1.
Anaerobe ; 67: 102295, 2021 Feb.
Article in English | MEDLINE | ID: mdl-33246096

ABSTRACT

OBJECTIVE: Clostridioides difficile may colonize healthy infants and young children asymptomatically and for the long-term. C. difficile genotypes and the rate and determinants of colonization differ substantially and vary among countries and regions. A 1-year follow-up study was performed to determine the incidence, kinetics and influencing factors of C. difficile intestinal colonization. METHODS: Twenty-nine healthy infants (14 girls and 15 boys) living at home with their parents in Handan City were followed by survey from birth to 1 year of age, specifically from October 2014 through December 2015. C. difficile isolates were typed by PCR ribotyping and analyzed for the presence of toxin genes. RESULTS: During the follow-up study period in the first year of life, 20 of the 29 total enrolled infants acquired C. difficile. A total of 437 fecal samples were obtained, and 111 (25.4%) samples contained C. difficile, including 79 (71.2%) toxigenic strains. The toxigenic isolates comprised six PCR ribotypes, and two PCR ribotypes were identified as nontoxigenic strains. CONCLUSION: Our study showed that C. difficile colonization increase with age during the 12-month period, and the dominant toxigenic types of C. difficile isolates in infants were those involved in long-term colonization. Feeding patterns may affect the dynamic progress of C. difficile colonization.


Subject(s)
Carrier State/epidemiology , Clostridioides difficile/classification , Clostridioides difficile/genetics , Clostridium Infections/epidemiology , Biodiversity , China/epidemiology , Clostridioides difficile/isolation & purification , DNA, Bacterial , Feces/microbiology , Feeding Behavior , Female , Follow-Up Studies , Genotype , Humans , Incidence , Infant , Infant, Newborn , Intestines/microbiology , Male , Polymerase Chain Reaction , RNA, Ribosomal, 16S , Ribotyping
2.
Anaerobe ; 56: 116-123, 2019 Apr.
Article in English | MEDLINE | ID: mdl-30849459

ABSTRACT

Clostridioides difficile is a colonizer of the human gut; asymptomatic colonization has been reported to be more common in infants and is highly variable across regions even with no symptoms of diarrhea or death. Antibiotic treatment strategies might increase the antibiotic resistance of C. difficile. We performed a one-point study involving 1098 healthy infants (0-36 months) to address the deficiency of reports on C. difficile colonization in Chinese community infants. The C. difficile colonization rate was 22.8% (250/1098), and more than half of the strains (55.2%) were toxigenic isolates. Among the 138 toxigenic isolates, 111 were of the A+B+CDT- genotype, 26 strains were A-B+CDT-, and one strain was A+B+CDT+. Fifteen different PCR ribotypes were found among the 250 isolates, and PCR-ribotype HB03 appeared to be dominant type, accounting for 19.6% (49/250). High levels of resistance to antimicrobial agents were observed. Our study showed that age and hospitalization before stool collection were positively correlated with the C. difficile colonization rate, whereas the delivery term was negatively related to the colonization rate. Particular attention should be paid to the increasing resistance of C. difficile to rifamycin.


Subject(s)
Carrier State/epidemiology , Clostridioides difficile/isolation & purification , Clostridium Infections/epidemiology , Asian People , Bacterial Toxins/genetics , Carrier State/microbiology , China/epidemiology , Clostridium Infections/microbiology , Genotype , Healthy Volunteers , Humans , Infant , Molecular Epidemiology , Polymerase Chain Reaction , Prevalence , Ribotyping
3.
Opt Lett ; 43(4): 667-670, 2018 Feb 15.
Article in English | MEDLINE | ID: mdl-29444048

ABSTRACT

We produce extremely bright mid-infrared (mid-IR) pulses with a tunable wavelength of 7 µm to 15 µm through difference frequency generation. Optimization of beam quality and beam focusing results in an intense mid-IR field spatiotemporally confined in the lambda-cubic volume. A near planar wavefront is achieved through manipulating the wavefront curvature of the pumping pulse in the frequency downconversion process. Coherent mid-IR pulses are produced with the peak field of 280 MV/cm at 10 µm, and its intensity exceeds 100 TW/cm2, estimated from measured pulse energy, and spatial and temporal pulse profiles. Interaction of such an intense mid-IR field with Xe and Kr gas forms plasma and generates a supercontinuum in the visible range.

4.
PLoS One ; 11(3): e0151964, 2016.
Article in English | MEDLINE | ID: mdl-27011211

ABSTRACT

Clostridium difficile is a spore-forming, gram-positive, anaerobic bacillus that can cause C. difficile infection (CDI). However, only a few studies on the prevalence and antibiotic resistance of C. difficile in healthy individuals in China have been reported. We employed a spore enrichment culture to screen for C. difficile in the stool samples of 3699 healthy Chinese individuals who were divided into 4 groups: infants younger than 2 years of age and living at home with their parents; children aged 1 to 8 years of age and attending three different kindergarten schools; community-dwelling healthy adult aged 23-60 years old; and healthcare workers aged 28-80 years old. The C. difficile isolates were analyzed for the presence of toxin genes and typed by PCR ribotyping and multilocus sequence typing (MLST). The minimum inhibitory concentration of 8 antimicrobial agents was determined for all of the isolates using the agar dilution method. The intestinal carriage rate in the healthy children was 13.6% and ranged from 0% to 21% depending on age. The carriage rates in the 1654 community-dwelling healthy adults and 348 healthcare workers were 5.5% and 6.3%, respectively. Among the isolates, 226 were toxigenic (225 tcdA+/tcdB+ and 1 tcdA+/tcdB+ ctdA+/ctdB+). Twenty-four ribotypes were found, with the dominant type accounting for 29.7% of the isolates. The toxigenic isolates were typed into 27 MLST genotypes. All of the strains were susceptible to vancomycin, metronidazole, fidaxomicin, and rifaximin. High resistance to levofloxacin and ciprofloxacin at rates of 39.8% and 98.3%, respectively, were observed. ST37 isolates were more resistant to levofloxacin than the other STs. The PCR ribotypes and sequence types from the healthy populations were similar to those from the adult patients.


Subject(s)
Anti-Bacterial Agents/pharmacology , Clostridioides difficile/drug effects , Clostridioides difficile/isolation & purification , Drug Resistance, Bacterial , Enterocolitis, Pseudomembranous/drug therapy , Enterocolitis, Pseudomembranous/microbiology , Intestines/microbiology , Adult , Aged , Aged, 80 and over , Anti-Bacterial Agents/therapeutic use , Child , Child, Preschool , China/epidemiology , Clostridioides difficile/genetics , Enterocolitis, Pseudomembranous/epidemiology , Female , Humans , Infant , Male , Microbial Sensitivity Tests , Middle Aged , Multilocus Sequence Typing , Prevalence , Ribotyping , Young Adult
5.
Neurosci Lett ; 441(1): 50-5, 2008 Aug 15.
Article in English | MEDLINE | ID: mdl-18586400

ABSTRACT

The atypical serine/threonine protein kinase, a mammalian target of rapamycin (mTOR), is believed to be essential to the regulation of cell growth and the functions of the central nervous system. By using calcium imaging and patch-clamping techniques to study the role of this signaling pathway in the activity of cultured hippocampal neurons, we found that rapamycin significantly reduces the spontaneous activities of network neurons as well as the efficacy of synaptic transmission through insulin-mTOR signaling pathway. Our study sheds light on understanding the role of mTOR signaling pathway in controlling the information processing of network neurons.


Subject(s)
Action Potentials/drug effects , Calcium Signaling/drug effects , Calcium/metabolism , Enzyme Inhibitors/pharmacology , Hippocampus/cytology , Neurons/drug effects , Sirolimus/pharmacology , Action Potentials/physiology , Animals , Calcium Signaling/physiology , Cells, Cultured , Dose-Response Relationship, Drug , Dose-Response Relationship, Radiation , Electric Stimulation , Embryo, Mammalian , Neurons/physiology , Patch-Clamp Techniques , Rats , Time Factors
6.
Biochem Pharmacol ; 75(11): 2147-56, 2008 Jun 01.
Article in English | MEDLINE | ID: mdl-18439986

ABSTRACT

The present study established a model of RyR(2) knockdown cardiomyocytes and elucidated the role of RyR(2) in aconitine-induced arrhythmia. Cardiomyocytes were obtained from hearts of neonatal Sprague-Dawley rats. siRNAs were used to down-regulate RyR(2) expression. Reduction of RyR(2) expression was documented by RT-PCR, western blot, and immunofluorescence. Ca(2+) signals were investigated by measuring the relative intracellular Ca(2+) concentration, spontaneous Ca(2+) oscillations, caffeine-induced Ca(2+) release, and L-type Ca(2+) currents. In normal cardiomyocytes, steady and periodic spontaneous Ca(2+) oscillations were observed, and the baseline [Ca(2+)](i) remained at the low level. Exposure to 3 microM aconitine increased the frequency and decreased the amplitude of Ca(2+) oscillations; the baseline [Ca(2+)](i) and the level of caffeine-induced Ca(2+) release were increased but the L-type Ca(2+) currents were inhibited after application of 3 microM aconitine for 5 min. In RyR(2) knockdown cardiomyocytes, the steady and periodic spontaneous Ca(2+) oscillations almost disappeared, but were re-induced by aconitine without affecting the baseline [Ca(2+)](i) level; the level of caffeine-induced Ca(2+) release was increased but L-type Ca(2+) currents were inhibited. Alterations of RyR(2) are important consequences of aconitine-stimulation and activation of RyR(2) appear to have a direct relationship with aconitine-induced arrhythmias. The present study demonstrates a potential method for preventing aconitine-induced arrhythmias by inhibiting Ca(2+) leakage through the sarcoplasmic reticulum RyR(2) channel.


Subject(s)
Aconitine/toxicity , Arrhythmias, Cardiac/chemically induced , Arrhythmias, Cardiac/metabolism , Myocytes, Cardiac/drug effects , Ryanodine Receptor Calcium Release Channel/metabolism , Sarcoplasmic Reticulum/metabolism , Animals , Caffeine/pharmacology , Calcium Channels, L-Type/metabolism , Calcium Signaling/drug effects , Calcium Signaling/physiology , Cells, Cultured , Gene Expression/drug effects , Gene Silencing , Membrane Potentials/physiology , Myocytes, Cardiac/metabolism , RNA, Messenger/drug effects , RNA, Messenger/metabolism , RNA, Small Interfering/metabolism , Rats , Rats, Sprague-Dawley , Ryanodine Receptor Calcium Release Channel/genetics , Sarcoplasmic Reticulum/drug effects , Transfection
7.
Acta Pharmacol Sin ; 29(1): 57-64, 2008 Jan.
Article in English | MEDLINE | ID: mdl-18158866

ABSTRACT

AIM: To investigate the changes in the spontaneous neuronal excitability induced by astragaloside IV (AGS-IV) in the cultured hippocampal network. METHODS: Hippocampal neurons in culture for 9-11 d were used for this study. The spontaneous synaptic activities of these hippocampal neurons were examined by Ca2+ imaging and whole-cell patch-clamp techniques. In total, 40 mg/L AGS-IV dissolved in DMSO and 2 mL/L DMSO were applied to the neurons under a microscope while the experiments were taking place. RESULTS: AGS-IV inhibited the frequencies of synchronized spontaneous Ca2+ oscillations to 59.39%+/- 3.25%(mean+/-SEM), the spontaneous postsynaptic currents to 43.78%+/- 7.72%(mean+/-SEM), and the spontaneous excitatory postsynaptic currents to 49.25%+/- 7.06%(mean+/-SEM) of those of the control periods, respectively, at 16 min after the AGSIV applications. AGS-IV also decreased the peak values of the voltage-gated K+ and Na+ channel currents at that time point. CONCLUSION: These results indicate that AGS-IV suppresses the spontaneous neuronal excitabilities effectively. Such a modulation of neuronal activity could represent new evidence for AGS-IV as a neuroprotector.


Subject(s)
Calcium Signaling/drug effects , Hippocampus/drug effects , Neurons/drug effects , Neuroprotective Agents/pharmacology , Saponins/pharmacology , Synaptic Transmission/drug effects , Triterpenes/pharmacology , Animals , Cells, Cultured , Electrophysiology , Hippocampus/cytology , Patch-Clamp Techniques , Rats , Rats, Sprague-Dawley
8.
Phys Rev E Stat Nonlin Soft Matter Phys ; 69(6 Pt 2): 066410, 2004 Jun.
Article in English | MEDLINE | ID: mdl-15244748

ABSTRACT

We try to understand the presence of a quasistatic magnetic field on the basis of the stability of the laser-plasma system. A general theoretical model of laser self-focusing in the absence of a quasistatic magnetic field (QMF) is extended to discuss self-focusing in the presence of a QMF. Various transverse intensity profiles under different axial collective electronic speeds V(z) are calculated. Numerical results indicate that for suitable laser power and plasma density, the increment in V(z) can lead to a further separation between the photon fluid and the electron fluid and hence a decrement in the energy of the laser-plasma system. This causes it to be possible for the system state without a QMF, or V(z) =0 state, to be not stable relative to some V(z) not equal 0 states.

9.
Opt Lett ; 27(13): 1135-7, 2002 Jul 01.
Article in English | MEDLINE | ID: mdl-18026385

ABSTRACT

A compact multiterawatt laser system based on optical parametric chirped pulse amplification is demonstrated. Chirped pulses are amplified from 20 pJ to 900 mJ by two lithium triborate optical parametric preamplifiers and a final KDP optical parametric power amplifier with a pump energy of 5 J at 532 nm from Nd:YAG-Nd:glass hybrid amplifiers. After compression, we obtained a final output of 570-mJ-155-fs pulses with a peak power of 3.67 TW, which is the highest output power from an optical parametric chirped pulse amplification laser, to the best of our knowledge.

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