Time-frequency representations of Lamb waves

The objective of this study is to establish the effectiveness of four different time-frequency representations (TFRs)--the reassigned spectrogram, the reassigned scalogram, the smoothed Wigner-Ville distribution, and the Hilbert spectrum--by comparing their ability to resolve the dispersion relationships for Lamb waves generated and detected with optical techniques. This paper illustrates the utility of using TFRs to quantitatively resolve changes in the frequency content of these nonstationary signals, as a function of time. While each technique has certain strengths and weaknesses, the reassigned spectrogram appears to be the best choice to characterize multimode Lamb waves.

Core-shell polymeric nanoparticles co-loaded with photosensitizer and organic dye for photodynamic therapy guided by fluorescence imaging in near and short-wave infrared spectral regions

BACKGROUND

Biodistribution of photosensitizer (PS) in photodynamic therapy (PDT) can be assessed by fluorescence imaging that visualizes the accumulation of PS in malignant tissue prior to PDT. At the same time, excitation of the PS during an assessment of its biodistribution results in premature photobleaching and can cause toxicity to healthy tissues. Combination of PS with a separate fluorescent moiety, which can be excited apart from PS activation, provides a possibility for fluorescence imaging (FI) guided delivery of PS to cancer site, followed by PDT.

RESULTS

In this work, we report nanoformulations (NFs) of core-shell polymeric nanoparticles (NPs) co-loaded with PS [2-(1-hexyloxyethyl)-2-devinyl pyropheophorbide-a, HPPH] and near infrared fluorescent organic dyes (NIRFDs) that can be excited in the first or second near-infrared windows of tissue optical transparency (NIR-I, ~ 700-950 nm and NIR-II, ~ 1000-1350 nm), where HPPH does not absorb and emit. After addition to nanoparticle suspensions, PS and NIRFDs are entrapped by the nanoparticle shell of co-polymer of N-isopropylacrylamide and acrylamide [poly(NIPAM-co-AA)], while do not bind with the polystyrene (polySt) core alone. Loading of the NIRFD and PS to the NPs shell precludes aggregation of these hydrophobic molecules in water, preventing fluorescence quenching and reduction of singlet oxygen generation. Moreover, shift of the absorption of NIRFD to longer wavelengths was found to strongly reduce an efficiency of the electronic excitation energy transfer between PS and NIRFD, increasing the efficacy of PDT with PS-NIRFD combination. As a result, use of the NFs of PS and NIR-II NIRFD enables fluorescence imaging guided PDT, as it was shown by confocal microscopy and PDT of the cancer cells in vitro. In vivo studies with subcutaneously tumored mice demonstrated a possibility to image biodistribution of tumor targeted NFs both using HPPH fluorescence with conventional imaging camera sensitive in visible and NIR-I ranges (~ 400-750 nm) and imaging camera for short-wave infrared (SWIR) region (~ 1000-1700 nm), which was recently shown to be beneficial for in vivo optical imaging.

CONCLUSIONS

A combination of PS with fluorescence in visible and NIR-I spectral ranges and, NIR-II fluorescent dye allowed us to obtain PS nanoformulation promising for see-and-treat PDT guided with visible-NIR-SWIR fluorescence imaging.

Endotoxin tlerance inhibits lipopolysaccharide-initiated acute pulmonary inflammation and lung injury in rats by the mechanism of nuclear factor-kappaB

In this study, the effect of endotoxin tolerance on lipopolysaccharide (LPS)-initiated pulmonary inflammation, the local production of tumour necrosis factor-alpha (TNF-alpha) and the cytokine-induced neutrophil attractant (CINC), as well as the activation of nuclear factor-kappaB (NF-kappaB) and its subunit composition, were examined in vivo. Endotoxin tolerance was reproduced by four consecutive daily intraperitoneal injections of 0.6 mg/kg of Escherichia coli 055:B5 LPS. Compared with control rats, endotoxin-tolerant rats failed to increase the permeability of pulmonary microvascular or recruit neutrophil to lung tissue upon restimulation with 6 mg/kg of LPSs. Pretreatment with LPSs inhibited the protein level of TNF-alpha in bronchoalveolar lavage fluid (BALF) and mRNA expression of CINC in lung tissue in response to subsequent LPS stimulation. These changes were accompanied by the suppression of activation of NF-kappaB, including the low level of total amount of DNA-binding activity and high percentage of non-transactive p50 homodimers. These data demonstrate that endotoxin tolerance can alleviate the LPS-induced acute neutrophilic pulmonary inflammation in rats and can inhibit the proinflammatory cytokines in lung and suggest that endotoxin tolerance might result from the unresponsiveness of NF-kappaB and persistent high percentage of p50 homodimers. Therefore, the phenomenon of endotoxin tolerance might be used as a strategy for the prevention or treatment of LPS-associated acute respiratory distress syndrome in which excessive or dysregulated inflammation leads to acute lung injury.

Quantitative FRET measurement using emission-spectral unmixing with independent excitation crosstalk correction

Quantification of fluorescence resonance energy transfer (FRET) needs at least two external samples, an acceptor-only reference and a linked FRET reference, to calibrate fluorescence signal. Furthermore, all measurements for references and FRET samples must be performed under the same instrumental conditions. Based on a novel notion to predetermine the molar extinction coefficient ratio (RC ) of acceptor-to-donor for the correction of acceptor excitation crosstalk, we present here a robust and independent emission-spectral unmixing FRET methodology, Iem-spFRET, which can simultaneously measure the E and RC of FRET sample without any external references, such that Iem-spFRET circumvents the rigorous restriction of keeping the same imaging conditions for all FRET experiments and thus can be used for the direct measurement of FRET sample. We validate Iem-spFRET by measuring the absolute E and RC values of standard constructs with different acceptor-to-donor stoichiometry expressed in living cells. Our results demonstrate that Iem-spFRET is a simple and powerful tool for real-time monitoring the dynamic intermolecular interaction within single living cells.

Clinical and etiological analysis of co-infections and secondary infections in COVID-19 patients: An observational study

Background

Co‐infections, secondary bacterial or fungal infections, are important risk factors for poor outcomes in viral infections. The prevalence of co‐infection and secondary infection in patients infected with SARS‐CoV‐2 is not well understood.

Aims

To investigate the role of co‐infections and secondary infections in disease severity of hospitalized individuals with COVID‐19.

Materials and Methods

A retrospective study was carried out between 11 January 2020 and 1 March 2020 among 408 laboratory confirmed COVID‐19 patients in China. These patients were divided into three groups based on disease severity: mild or moderate, severe, or critically ill. Microbiological pathogens in blood, urine, and respiratory tract specimens were detected by the combination of culture, serology, polymerase chain reaction, and metagenomic next‐generation sequencing (mNGS).

Results

The median age of participants was 48 years (IQR 34–60 years). Fifty‐two patients (12.7%) had at least one additional pathogen, 8.1% were co‐infected, and 5.1% had a secondary infection. There were 13 Mycoplasma pneumoniae cases, 8 Haemophilus influenzae cases, 8 respiratory viruses, and 3 Streptococcus pneumoniae cases, primarily detected in mild and moderate COVID‐19 patients. Hospital‐acquired infection pathogens were more common in critically ill patients. Compared to those without additional pathogens, patients with co‐infections and/or secondary infections were more likely to receive antibiotics (p < 0.001) and have elevated levels of d‐dimer (p = 0.0012), interleukin‐6 (p = 0.0027), and procalcitonin (p = 0.0002). The performance of conventional culture was comparable with that of mNGS in diagnosis of secondary infections.

Conclusion

Co‐infections and secondary infections existed in hospitalized COVID‐19 patients and were relevant to the disease severity. Screening of common respiratory pathogens and hospital infection control should be strengthened.

A rapid bacterial pathogen and antimicrobial resistance diagnosis workflow using Oxford nanopore adaptive sequencing method

Metagenomic sequencing analysis (mNGS) has been implemented as an alternative approach for pathogen diagnosis in recent years, which is independent of cultivation and is able to identify all potential antibiotic resistance genes (ARGs). However, current mNGS methods have to deal with low amounts of prokaryotic deoxyribonucleic acid (DNA) and high amounts of host DNA in clinical samples, which significantly decrease the overall microbial detection resolution. The recently released nanopore adaptive sampling (NAS) technology facilitates immediate mapping of individual nucleotides to a given reference as each molecule is sequenced. User-defined thresholds allow for the retention or rejection of specific molecules, informed by the real-time reference mapping results, as they are physically passing through a given sequencing nanopore. We developed a metagenomics workflow for ultra-sensitive diagnosis of bacterial pathogens and ARGs from clinical samples, which is based on the efficient selective 'human host depletion' NAS sequencing, real-time species identification and species-specific resistance gene prediction. Our method increased the microbial sequence yield at least 8-fold in all 21 sequenced clinical Bronchoalveolar Lavage Fluid (BALF) samples (4.5 h from sample to result) and accurately detected the ARGs at species level. The species-level positive percent agreement between metagenomic sequencing and laboratory culturing was 100% (16/16) and negative percent agreement was 100% (5/5) in our approach. Further work is required for a more robust validation of our approach with large sample size to allow its application to other infection types.

Epidemiological characterization of respiratory tract infections caused by Mycoplasma pneumoniae during epidemic and post-epidemic periods in North China, from 2011 to 2016

BACKGROUND

Mycoplasma pneumoniae (M. pneumoniae) is a commonly causative pathogen for respiratory tract infections (RTIs) in humans. The epidemiological features of M. pneumoniae infections during post-epidemic, including age distribution and the seasonality of the patients, are not well investigated.

METHODS

We retrospectively analyzed the clinical data of 7835 consecutive RTIs patients (3852 adults and 3983 children) who visited a teaching hospital, and defined an epidemic (2011-2013) and a post-epidemic period (2014-2016). M. pneumoniae was detected by fluorescence-quantatitive PCR in respiratory samples. Informed consent was obtained by all adults and the legal representatives of patients aged < 18 years, and the study was approved by Institutional Review Board of Beijing Chao-Yang Hospital (project approval number 10-KE-49).

RESULTS

The median (IQR) age was 16 (53) years (range < 0-105 years). The M. pneumoniae positive rate was 14.4% (21.2%, epidemic; 6.7%, post-epidemic), with seasonal peaks from late summer to autumn during epidemic, and from fall to winter during post-epidemic period, which was highest in children aged 7-17 years. In epidemic, no statistical difference was found in the positive rates between children and adults among most months (except February, July and August), neither for the positive rates among age groups (P = 0.801). However, in post-epidemic period, significant differences were observed in the positive rates between children and adults in nearly every month (P< 0.05 or P< 0.001, except May), as well as in the positive rates among age groups (P< 0.001). Most of the older patient admissions and all of ICU admissions occurred during the epidemic.

CONCLUSIONS

Different patterns of age distribution and seasonality of M. pneumoniae RTIs between epidemic and post-epidemic periods were reported. Our results suggest that M. pneumoniae should be considered as a possible pathogen in pneumonia patients admitted to the ICU in the setting of an epidemic.

PD-1-expressing MAIT cells from patients with tuberculosis exhibit elevated production of CXCL13

To understand functional role of PD-1-expressing MAIT cells during tuberculosis infection in humans, sorted PD-1⁺ and PD-1^- MAIT cells from pleural effusions of patients with pleural tuberculosis were subjected to transcriptome sequencing. PD-1-expressing MAIT cells were analysed by flow cytometry and their phenotypic and functional features were investigated. Transcriptome sequencing identified 144 genes that were differentially expressed between PD-1⁺ and PD-1^- MAIT cells from tuberculous pleural effusions and CXCL13 was the gene with highest fold difference. The level of PD-1-expressing MAIT cells was associated with extent of TB infection in humans. PD-1-expressing MAIT cells had increased production of CXCL13 and IL-21 as determined by flow cytometry. PD-1^high CXCR5^- MAIT cells were significantly expanded in pleural effusions from patients with pleural tuberculosis as compared with those from peripheral blood of both patients with tuberculosis and healthy controls. Although PD-1^high CXCR5^- MAIT cells from tuberculous pleural effusions had reduced IFN-γ level and increased expression of Tim-3 and GITR, they showed activated phenotype and had higher glucose uptake and lipid content. It is concluded that PD-1-expressing MAIT cells had reduced IFN-γ level but increased production of both CXCL13 and IL-21.

An Integrated Amplification-Free Digital CRISPR/Cas-Assisted Assay for Single Molecule Detection of RNA

Conventional nucleic acid detection technologies usually rely on amplification to improve sensitivity, which has drawbacks, such as amplification bias, complicated operation, high requirements for complex instruments, and aerosol pollution. To address these concerns, we developed an integrated assay for the enrichment and single molecule digital detection of nucleic acid based on a CRISPR/Cas13a and microwell array. In our design, magnetic beads capture and concentrate the target from a large volume of sample, which is 100 times larger than reported earlier. The target-induced CRISPR/Cas13a cutting reaction was then dispersed and limited to a million individual femtoliter-sized microwells, thereby enhancing the local signal intensity to achieve single-molecule detection. The limit of this assay for amplification-free detection of SARS-CoV-2 is 2 aM. The implementation of this study will establish a "sample-in-answer-out" single-RNA detection technology without amplification and improve the sensitivity and specificity while shortening the detection time. This research has broad prospects in clinical application.

Non-walled spherical Acinetobacter baumannii is an important type of persister upon β-lactam antibiotic treatment

Bacterial persistence is one of the major causes of antibiotic treatment failure and the step stone for antibiotic resistance. However, the mechanism by which persisters arise has not been well understood. Maintaining a dormant state to prevent antibiotics from taking effect is believed to be the fundamental mechanistic basis, and persisters normally maintain an intact cellular structure. Here we examined the morphologies of persisters in Acinetobacter baumannii survived from the treatment by three major classes of antibiotics (i.e. β-lactam, aminoglycoside, and fluoroquinolone) with microcopy and found that a fraction of enlarged spherical bacteria constitutes a major sub-population of bacterial survivors from β-lactam antibiotic treatment, whereas survivors from the treatment of aminoglycoside and fluoroquinolone were less changed morphologically. Further studies showed that these spherical bacteria had completely lost their cell wall structures but could survive without any osmoprotective reagent. The spherical bacteria were not the viable-but-non-culturable cells and they could revive upon the removal of β-lactam antibiotics. Importantly, these non-walled spherical bacteria also persisted during antibiotic therapy in vivo using Galleria mellonella as the infection model. Additionally, the combinational treatment on A. baumannii by β-lactam and membrane-targeting antibiotic significantly enhanced the killing efficacy. Our results indicate that in addition to the dormant, structure intact persisters, the non-wall spherical bacterium is another important type of persister in A. baumannii. The finding suggests that targeting the bacterial cell membrane during β-lactam chemotherapy could enhance therapeutic efficacy on A. baumannii infection, which might also help to reduce the resistance development of A. baumannii.

3D Black-Blood Luminal Angiography Derived from High-Resolution MR Vessel Wall Imaging in Detecting MCA Stenosis: A Preliminary Study

BACKGROUND AND PURPOSE

3D high-resolution vessel wall imaging is increasingly used for intracranial arterial diseases. This study compared the diagnostic performance of black-blood luminal angiography derived from 3D vessel wall imaging with source images of vessel wall imaging and TOF-MRA in detecting middle cerebral artery stenosis.

MATERIALS AND METHODS

Sixty-two patients with suspected MCA atherosclerosis underwent TOF-MRA, vessel wall imaging, and CTA. Intracranial black-blood luminal angiography was created from source images of vessel wall imaging using minimum intensity projection. The degree and length of MCA stenosis were measured on source images of vessel wall imaging, TOF-MRA, and black-blood luminal angiography and compared using CTA as a reference standard.

RESULTS

The image quality of black-blood luminal angiography was diagnostic in most patients. The intra- and interobserver agreement for both stenosis degree and length measurements was excellent for black-blood luminal angiography. It was comparable with that of source images of vessel wall imaging in grading stenosis. Compared with TOF-MRA, black-blood luminal angiography showed significantly higher sensitivity for the detection of severe stenosis (89.3% versus 64.3%, P = .039) and higher specificity for the detection of occlusion (95.4% versus 84.6%, P = .039). Lesion length estimated on source images of vessel wall imaging was significantly greater than that measured by CTA and black-blood luminal angiography (P < .001 and P = .010).

CONCLUSIONS

Black-blood luminal angiography is better than TOF-MRA in detecting severe stenosis and occlusion of the MCA. Compared with source images of vessel wall imaging, it is more accurate in evaluating stenosis length. Black-blood luminal angiography can be produced as a derivative from vessel wall imaging and implemented as an adjunct to vessel wall imaging and TOF-MRA without extra acquisition time.

Advance in the study of inhibin, activin and follistatin production in pregnant women

This review summarizes the new information on the studies of inhibin, activin, and follistatin production in the placenta during human pregnancy. Inhibin and activin exert suppressive and stimulatory effects, respectively, on the release of FSH in the pituitary. Follistatin is bound to inhibin and activin and indirectly modulates the FSH release. The placenta produces these three proteins. The serum levels of inhibin, activin, and follistatin are elevated in pregnant women and decrease after delivery. The trophoblast cells from term placenta secrete inhibin and activin in the primary cultures. The production and mRNA expression of inhibin and activin are regulated by several stimulatory and suppressive hormones and growth factors in placental tissues. cAMP, Ca2+, and protein kinase-C may be involved in intracellular signal transduction in trophoblasts. Activin receptors are present on placental cells. Follistatin inhibits the binding of activin to ActRII receptor. Abnormal levels of inhibin and activin in maternal serum are observed in problem pregnancies and gestational diseases. Inhibin, activin, and follistatin may play roles in the regulation of reproductive endocrinology in pregnant women and the embryo/fetal development.

NSs protein of severe fever with thrombocytopenia syndrome virus suppresses interferon production through different mechanism than Rift Valley fever virus

Severe fever with thrombocytopenia syndrome virus (SFTSV) is a newly identified Phlebovirus that causes severe fever with thrombocytopenia syndrome. Our study demonstrated that SFTSV NSs functioned as IFN antagonist mainly by suppressing TBK1/IKKε-IRF3 signaling pathway. NSs interacted with and relocalized TANK-binding kinase 1 (TBK1) into NSs-induced cytoplasmic structures and this interaction could effectively inhibit downstream phosphorylation and dimerization of interferon regulatory factor 3 (IRF3), resulting in the suppression of antiviral signaling and IFN induction. Functional sites of SFTSV NSs binding with TBK1 were then studied and results showed that NSs had lost their IFN-inhibiting activity after deleting the 25 amino acids in N-terminal. Furthermore, the mechanism of Rift Valley fever virus (RVFV) NSs blocking IFN-β response were also investigated. Preliminary results showed that RVFV NSs proteins could neither interact nor co-localize with TBK1 in cytoplasm, but suppressed its expression levels, phosphorylation and dimerization of IRF3 in the subsequent steps, resulting in inhibition of the IFN-β production. Altogether, our data demonstrated the probable mechanism used by SFTSV to inhibit IFN responses which was different from RVFV and pointed toward a novel mechanism for RVFV suppressing IFN responses.

Phosphatidylserine-mediated adhesion of T-cells to endothelial cells

Phosphatidylserine was exposed on the surface of human umbilical endothelial cells (ECV304) a few minutes after adding thrombin in vitro, as monitored by prothrombinase assays with and without annexin V. Jurkat T cells adhered to the thrombin-treated cells. The adhesion was inhibited by annexin V, indicating that it was mediated by exposed phosphatidylserine on the endothelial cells.

Sympathetic innervation alters activation of pacemaker current (If) in rat ventricle

Pacemaker current (If) exists in both neonatal and adult ventricles, but activates at more negative voltages in the adult. This study uses whole-cell patch clamp to investigate the factors that may contribute to the maturational shift of If, comparing neonatal rat ventricular myocytes that were cultured for 4-6 days either alone, in co-culture with sympathetic nerves, or with neurotransmitters chronically present in culture. If recorded from nerve-muscle co-cultures had a significantly more negative and shallower activation-voltage relation than that from control muscle cultures, which was reflected in the midpoint potential (V50) and slope factor (K) of activation. This effect of innervation was prevented by the sustained presence in the culture of the alpha1-adrenergic antagonist prazosin (Pz) at 10(-7) M. In parallel experiments, myocytes treated with noradrenaline (NA) at 10(-7) M or neuropeptide Y (NPY) at 10(-7) M during culture had the same If activation as control cells, but cells treated with NA and NPY together had a significantly more negative and shallower activation curve. Maximum conductance and reversal potential were unchanged. The effect of chronic exposure to NA + NPY was prevented by the sustained presence of either Pz or the NPY Y2 selective antagonist T4-[NPY(33-36)]4 (3.5 x 10(-7) M) in the culture, indicating a requirement for both alpha1-adrenergic and NPY Y2 activation. Substituting NA with the alpha1A-adrenergic selective agonist A61603 (5(-10) x 10(-9) M), in the presence of NPY, did not alter If, suggesting the involvement of alpha1B- rather than alpha1A-adrenoceptors. Further, sequential exposure to NPY followed by NA was effective in reproducing the action of chronic simultaneous exposure to these agonists, but sequential exposure to NA followed by NPY was ineffective. The results are consistent with past studies indicating that NPY affects the functional expression of the alpha1B-adrenergic cascade and suggest that sympathetic innervation induces a negative shift of If in ventricle via a combined action at alpha1B-adrenergic and NPY Y2 receptors. This effect of innervation probably contributes to the developmental maturation of If activation.

A study on the diagnosis of drowning by examination of lung chlorophyll(a) of planktons with a spectrofluorophotometer

An investigation on the diagnosis of drowning by analysis of chlorophyll(a) (Chl.(a)) of planktons in the lung sample with a spectrofluorophotometer (SFPM) is reported. The diagnostic criteria or main points of death by drowning are suggested are according to our experimental studies. Meanwhile two cases of submersion in water were investigated and the causes of death were diagnosed correctly. It is concluded that examination of lung Chl.(a) of planktons could be used as a reliable diagnostic method in forensic practice.

The effects of process technology on the physicochemical properties of peony seed oil

Peony seed oils (PSOs) were prepared using supercritical CO2 (SC) and compared with soxhlet extraction (SE) and mechanical screw press extraction (SPE) methods. The fatty acid compositions of the oils were determined, and the physicochemical properties of the oils, including free radical-scavenging activity, α-amylase and α-glucosidase inhibition, thermal and rheological properties were evaluated. The unsaturated fatty acids in the SE oils were higher than SC and SPE oils due to the higher percentage of olefinic, allylic methylene and allylic methine protons in the SE oils. The SPE oils also displayed the highest DPPH and ABTS+ radical scavenging activity at the tested concentrations. However, the SE oils showed stronger inhibitory effects on α-amylase and α-glucosidase enzymes under in vitro conditions when compared with the other oil samples. The three oils had similar melting and crystalline point due to similar contents of fatty acids (FAs). The SC oils had a lower Ea than the others.

Microphthalmia-associated transcription factor/T-box factor-2 axis acts through Cyclin D1 to regulate melanocyte proliferation

OBJECTIVES

Control of cell proliferation is critical for accurate cell differentiation and tissue formation, during development and regeneration. Here, we have analysed the role of microphthalmia-associated transcription factor MITF and its direct target, T-box factor TBX2, in regulating proliferation of mammalian neural crest-derived melanocytes.

MATERIALS AND METHODS

Immunohistochemistry was used to examine spatial and temporal expression of TBX2 in melanocytes in vivo. RNAi and cell proliferation analysis were used to investigate functional roles of TBX2. Furthermore, quantitative RT-PCR, western blot analysis and flow cytometry were used to further scrutinize molecular mechanisms underlying TBX2-dependent cell proliferation.

RESULTS

TBX2 was found to be co-expressed with MITF in melanocytes of mouse hair follicles. Specific Tbx2 knockdown in primary neural crest cells led to inhibition MITF-positive melanoblast proliferation. Tbx2 knockdown in melan-a cells led to reduction in Cyclin D1 expression and G1-phase cell cycle arrest. TBX2 directly activated Ccnd1 transcription by binding to a specific sequence in the Ccnd1 promoter, and the defect in cell proliferation could be rescued partially by overexpression of Cyclin D1 in Tbx2 knockdown melanocytes.

CONCLUSIONS

Results suggest that the Mitf-Tbx2-Cyclin D1 pathway played an important role in regulation of melanocyte proliferation, and provided novel insights into the complex physiology of melanocytes.

Inactivation of monomeric sarcosine oxidase by reaction with N-(cyclopropyl)glycine

Monomeric sarcosine oxidase (MSOX) catalyzes the oxidative demethylation of sarcosine (N-methylglycine) and contains covalently bound flavin adenine dinucleotide (FAD). The present study demonstrates that N-(cyclopropyl)glycine (CPG) is a mechanism-based inhibitor. CPG forms a charge transfer complex with MSOX that reacts under aerobic conditions to yield a covalently modified, reduced flavin (lambda(max) = 422 nm, epsilon(422) = 3.9 mM(-1) cm(-1)), accompanied by a loss of enzyme activity. The CPG-modified flavin is converted at an 8-fold slower rate to 1,5-dihydro-FAD (EFADH(2)), which reacts rapidly with oxygen to regenerate unmodified, oxidized enzyme. As a result, CPG-modified MSOX reaches a CPG-dependent steady-state concentration under aerobic conditions and reverts back to unmodified enzyme upon removal of excess reagent. No loss of activity is observed under anaerobic conditions where EFADH(2) is formed in a reaction that goes to completion at low CPG concentrations. Aerobic denaturation of CPG-modified enzyme yields unmodified, oxidized flavin at a rate similar to the anaerobic denaturation reaction, which yields 1,5-dihydro-FAD. The CPG-modified flavin can be reduced with borohydride, a reaction that blocks conversion to unmodified flavin upon removal of excess CPG or enzyme denaturation. The possible chemical mechanism of inactivation and structure of the CPG-modified flavin are discussed.

Airway hyperresponsiveness induced by repetitive intraperitoneal injection of lipopolysacharide and the involvement of inflammation and nitric oxide in guinea pigs

OBJECTIVE

Airway hyperresponsiveness (AHR) is involved in bronchial asthma and chronic obstructive pulmonary disease (COPD) and produces respiratory symptoms. Lipopolysaccharide (LPS) has been found to be significantly related to the severity of asthma. However, its clinical mechanism still remains controversial. This study investigated the in vivo effect of repetitive intraperitoneal administration of lipopolysaccharide (LPS) on airway hyperresponsiveness (AHR) in guinea pigs and the possible involvement of inflammation, nitric oxide (NO) and nitric oxide synthase (NOS).

METHODS

There were two exposure groups for intraperitoneal LPS injection: (1) LPS was given at a dose of 1 mg x kg(-1), followed by sterile saline (NS) 1 ml x kg(-1) 8 h later every 24 h; (2) LPS was given at a dose of 0.5 mg x kg(-1) two times with an interval of 8 h every 24 h. Each exposure regime was repeated 4 times. Control animals were given NS and 6 naive guinea pigs were used as baseline control. Determinations were made 24 h after each exposure.

RESULTS

Persistent AHR occurred 24 h after the third and fourth exposures to LPS in the first exposure group (at one dose), but occurred earlier after the exposures to LPS in the second exposure group (at divided doses). The numbers of total cells and neutrophils were elevated initially but subsided subsequently in LPS-treated groups. No evidence of morphological changes in the small airways was found 24 h after any of the exposures. The Ca(2+)-dependent and Ca(2+)-independent NOS activities (mainly produced by iNOS) in the BALF, as well as the production of NO, were significantly elevated 24 h after any of third and fourth exposures in LPS-treated groups.

CONCLUSIONS

Our results demonstrate that repetitive intraperitoneal LPS can induce persistent AHR which occurs earlier when the frequency of injection increase, and an elevation of NO production and iNOS activity may be involved in is systemic-LPS-induced AHR.

Characterization of 236 novel alleles at the HLA-A, -B, -C, -DRB1, -DQB1 and -DPB1 loci from China Marrow Donor Program

Two hundred and thirty-six novel human leukocyte antigen (HLA) alleles are described from volunteer donors of the China Marrow Donor Program: 71 HLA-A alleles, 79 HLA-B alleles, 43 HLA-C, 16 HLA-DRB1 alleles, 26 HLA-DQB1 and 1 HLA-DPB1. Two hundred and thirteen (90.3%) of the 236 novel alleles are single nucleotide substitution variants when compared with their most homologous allele. Seventy-eight of these single nucleotide variants are silent substitutions. The remaining novel alleles differ from their most similar allele by two to four nucleotide substitutions. Some of the novel alleles encode amino acid changes at positions not previously reported to be polymorphic, such as codons 57, 62, 67, 41 and 52 in HLA-A alleles; codons 133, 156, 201 and 215 in HLA-B alleles; codons 74, 208 and 225 in HLA-C; codons 25, 32 and 72 in HLA-DRB1; codons 20, 39 and 77 in HLA-DQB1.

Hyperspectral Multiplexed Biological Imaging of Nanoprobes Emitting in the Short-Wave Infrared Region

Optical bioimaging with exogenous luminophores emitting in short-wave infrared spectral region (SWIR, ~ 1000-1700 nm) is a rapidly developing field, and the development of multiple SWIR-photoluminescent nanoprobes has recently been reported. In this regard, hyperspectral imaging (HSI), combined with unmixing algorithms, is a promising tool that can allow for efficient multiplexing of the SWIR-emitting nanoagents by their photoluminescence (PL) spectral profiles. The SWIR HSI technique reported here is developed to multiplex two types of nanoprobes: polymeric nanoparticles doped with organic dye (PNPs) and rare-earth doped fluoride nanoparticles (RENPs). Both types of nanoprobes exhibit PL in the same spectral range (~ 900-1200 nm), which hinders spectral separation of PL with optical filters and limits possibilities for their multiplexed imaging in biological tissues. By applying SWIR HSI, we exploited differences in the PL spectral profiles and achieved the spectrally selective and sensitive imaging of the PL signal from every type of nanoparticles. Unmixing of acquired data allowed for multiplexing of the spectrally overlapping nanoprobes by their PL profile. Both quantitative and spatial distribution for every type of nanoparticles were obtained from their mixed suspensions. Finally, the SWIR HSI technique with unmixing protocol was applied to in vivo imaging of mice subcutaneously injected with PNPs and RENPs. The applicability of hyperspectral techniques to multiplex nanoprobes in the in vivo imaging was successfully demonstrated.