Measurement of shear stress-mediated intracellular calcium dynamics in human dermal lymphatic endothelial cells

The shear stress applied to lymphatic endothelial cells (LEC) by lymph flow changes dramatically under normal conditions as well as in response to disease conditions and immune reactions. In general, LEC are known to regulate the contraction frequency and strength of lymphatic pumping in response to shear stress. Intracellular calcium concentration ([Ca(2+)]i) is an important factor that regulates lymphatic contraction characteristics. In this study, we measured changes in the [Ca(2+)]i under different shear stress levels and determined the source of this calcium signal. Briefly, human dermal LEC were cultured in custom-made microchannels for 3 days before loading with 2 µM fura-2 AM, a ratiometric calcium dye to measure [Ca(2+)]i. Step changes in shear stress resulted in a rapid increase in [Ca(2+)]i followed by a gradual return to the basal level and sometimes below the initial baseline (45.2 ± 2.2 nM). The [Ca(2+)]i reached a peak at 126.2 ± 5.6 nM for 10 dyn/cm(2) stimulus, whereas the peak was only 71.8 ± 5.4 nM for 1 dyn/cm(2) stimulus, indicating that the calcium signal depends on the magnitude of shear stress. Removal of the extracellular calcium from the buffer or pharmocological blockade of calcium release-activated calcium (CRAC) channels significantly reduced the peak [Ca(2+)]i, demonstrating a role of extracellular calcium entry. Inhibition of endoplasmic reticulum (ER) calcium pumps showed the importance of intracellular calcium stores in the initiation of this signal. In conclusion, we demonstrated that the shear-mediated calcium signal is dependent on the magnitude of the shear and involves ER store calcium release and extracellular calcium entry.

Comparison of antibiotic susceptibility in viridans group streptococci in low and high antibiotic-prescribing General Practices

WHAT IS KNOWN AND OBJECTIVE

Antibiotic resistance has become a global public health issue. Most antibiotics are prescribed in the community, although there is less stewardship of such agents in the community compared to secondary and tertiary care. Few studies have attempted to examine the prescribing practices in General Practice and its impact on antibiotic resistance and, therefore, a study was performed in order to compare antibiotic susceptibilities of commensal viridans group streptococci (VGS) obtained from patient cohorts in General Practices (GP), who were high and low prescribers of oral antibiotics.

METHOD

Sixty-five patients (<1 month-81 years; 77% female: 23% male) were enrolled onto the study, and viridans group streptococci (n = 5/patient) were collected from each patient's nasal passages and oropharynx region and tested for antibiotic susceptibility against (i) tetracyclines (doxycycline); (ii) macrolides (erythromycin); (iii) β-lactams (penicillin G); and (iv) fluoroquinolones (ofloxacin & levofloxacin).

RESULTS AND DISCUSSION

There were no significant differences in MICs between high and low GP prescribers with doxycycline (P = 0·094), erythromycin (P = 0·122), ofloxacin (P = 0·193) and levofloxacin (P = 0·058). However, there was a significant difference between high and low GP practices with regard to penicillin G (P = 0·031). This finding is important as the β-lactams are the most commonly prescribed oral antibiotic in the community.

WHAT IS NEW AND CONCLUSION

This study demonstrates that high prescribing practices may lead to an altered (higher) level of resistance to these agents in the commensal VGS population, which may be important as reservoirs of antibiotic resistance determinants in subsequent horizontal gene transfer events, particularly with newly colonizing pathogens, including pneumococci. Primary care physicians should be aware that increased prescribing of antibiotics may led to increased level of penicillin resistance.

Molecular characterisation of a type III restriction-modification system in Campylobacter upsaliensis

Two examples of Campylobacter upsaliensis RM3195 and JV21 strains are shown to carry putative type III restriction (res)-modification (mod) enzyme gene clusters, following genome sequence analyses. It is suggested that the cluster is composed of at least three structural genes, res, internal methylase gene and mod, in the strains, based on the nucleotide sequence information. A ribosome binding site, a putative promoter consisting of a consensus sequence at the -10-like structure and a semiconserved T-rich region and a putative intrinsic p-independent transcriptional terminator were identified for the gene cluster in the two strains. Using two primer pairs, f-/r-res and f-/r-mod, 34 of 41 C. upsaliensis isolates generated two expected amplicons of the res and mod gene segments, and using another primer pair, the same number of isolates also generated an amplicon of the res and mod gene segments cluster, including the third internal methylase gene. Thus, C. upsaliensis isolates frequently carried putative type III R-M gene clusters, encoding the three enzymes. Interestingly, two possible overlaps were identified within the three tandem structural genes. In addition, the type III R-M gene cluster loci appear to be very similar among the C. upsaliensis isolates and very different from other thermophilic campylobacters.

Construction and expression of a recombinant urease gene cluster from Campylobacter sputorum biovar paraureolyticus

Recombinant full-length urease gene cluster and seven 100% deletion recombinant variants of urease subunits genes, (ureG, ureH, ureA, ureB, ureC, ureE and ureF) were constructed in vitro from the Campylobacter sputorum biovar paraureolyticus LMG17591 strain and expressed in Escherichia coli JM109 cells. A urease-positive reaction (1.885 micromol/min/mg protein) in the log-phase cultured E. coli cells transformed with pGEM-T vector carrying the recombinant full-length urease genes cluster was detected. Among the seven 100% deletion recombinant variants, each of the ureG-, ureH(D)-, ureA-, ureB-, ureC-, ureE- and ureF-deletion variants showed no change in assay of the urease reaction, and similarly as in the E. coli cell lysate with pGEM-T vector only. Recombinant full-length urease gene cluster and 100% deletion recombinants of the ureE gene in the transformed and log-phase cultured E. coli cells from the C. sputorum showed positively accelerated urease activities when cultured in the medium containing NiCl2 (750 micromol/L), but no activity was accelerated in the C. sputorum cultured in NiCl2. In addition, thiourea (20 mmol/L) completely inhibited urease activities from all C. sputorum examined. The putative recombinant urease subunits A and C were immunologically identified by Western blot analysis with polyclonal anti-urease alpha (A) and beta (B), raised against Helicobacter pylori.

Reliability of self-reporting of antibiotic consumption in the community - Index of Reliability

WHAT IS KNOWN AND OBJECTIVE

To date, there is no evidence to indicate the reliability of how patients self-report their own antibiotic usage in the community. Such data are fundamental in supporting antimicrobial stewardship practices, and so there is a need to determine its accuracy and reliability.

COMMENT

Patients in the community (n = 476) were required to recollect their antibiotic usage in the past three months. Simultaneously, similar information was obtained by careful extraction from their respective medical notes, which was qualitatively compared with the patient's recollection. Overall, concordance was high (88·1%), but age (<20 and >80 years) and sex (female) were significant factors of reliability.

WHAT IS NEW AND CONCLUSION

This study suggests that basic self-reporting of antibiotic usage amongst patients is relatively reliable, with increasing accuracy with years until 80 years. Where such information is critical, the current study can help decide who to interview and whose notes to interrogate, in the quest to obtain reliable and accurate information.

Eradication of Pseudomonas aeruginosa in adults with cystic fibrosis

BACKGROUND

Eradication of new infection of Pseudomonas aeruginosa is an important intervention in managing cystic fibrosis (CF). Previous trials, studying predominantly under 18-year-olds, indicate that antibiotic eradication therapy (AET) has success rates of 62.8-93.0%. In this retrospective cohort study, we report the outcomes of AET in an adult population.

METHODS

Adults with a confirmed diagnosis of CF and a first isolation of P aeruginosa were studied between 1999 and 2012. Choice of therapy, time to eradication and reinfection, and lung function (forced expiratory volume in 1 s (FEV1)) were determined.

RESULTS

20 patients (median age 27 years) isolated P aeruginosa during the study period. 10 patients were treated with oral ciprofloxacin (median duration 6 weeks) and nebulised colomycin (median duration 3 months). 7 patients were treated with intravenous antipseudomonal antibiotics (median duration 14 days). 2 patients received other combinations of oral and inhaled antipseudomonal therapy and one patient received no therapy. AET was successful in 15 cases who received antipseudomonal therapy (79%). The median time to eradication was 1 month. The median time to reinfection with P aeruginosa was 43 months. There was no significant change in FEV1 after 12 months.

CONCLUSIONS

Aggressive AET of new infection of P aeruginosa in adults is successful in the majority of patients and has similar efficacy to the reported efficacy in paediatric populations.

Molecular cloning and characterisation of the methionine sulphoxide reductase A (msrA) gene locus in Campylobacter lari organisms

The methionine sulphoxide reductase A (msrA) gene and its adjacent genetic loci from urease-negative (UN) Campylobacter lari RM2100 and urease-positive thermophilic Campylobacter (UPTC)CF89-12 strains appear to be composed of a msrA structure gene (507 base pairs [bp]) and another five-gene cluster (approximately 6300 bp) in the same strand and direction. A primer pair (F1/R4-msrA) for polymerase chain reaction (PCR) amplification was designed to generate a product of approximately 900 bp of the msrA gene, including its adjacent genetic loci for the thermophilic Campylobacter organisms and generate an amplicon with 16 C. lari isolates (n = 4 for UN C. lari; n = 12 for UPTC). Following direct nucleotide sequencing, sequence analysis and nucleotide sequence alignment analysis, the putative full-length msrA gene from the 16 C. lari isolates showed high nucleotide sequence similarities (91.8-100%) to each other and relatively low similarity (69.3-71.8%) to three reference C. jejuni and C. coli strains. In addition, the msrA gene was transcribed in both the UPTC CF89-12 and NCTC12893 cells using reverse transcription PCR. An immunoreactively positive signal was identified in the UPTC CF89-12 and NCTC12893 cells with anti-UPTC MsrA synthetic peptide antibodies.

Differential orientation of 10T1/2 mesenchymal cells on non-uniform stretch environments

Non-uniform stress and strain fields are prevalent in many tissues in vivo, and often exacerbated by disease or injury. These mechanical gradients potentially play a role in contributing to pathological conditions, presenting a need for experimental tools to allow investigation of cell behavior within non-uniformly stimulated environments. Herein, we employ two in vitro cell-stretching devices (one previously published; one newly presented) capable of subjecting cells to cyclic, non-uniform stretches upon the surface of either a circular elastomeric membrane or a cylindrical PDMS tube. After 24 hours of cyclic stretch, 10T1/2 cells on both devices showed marked changes in long-axis orientation, with tendencies to align parallel to the direction of minimal deformation. The degree of this response varied depending on location within the stretch gradients. These results demonstrated the feasibility of conducting cell mechanobiology investigations with the two novel devices, while also highlighting the experimental capabilities of non-uniform mechanical environments for these types of studies. Such capabilities include robust data collection for developing mechanobiological dose-response curves, signal threshold identification, and potential spatial targeting for drug delivery.

Development of a model of a multi-lymphangion lymphatic vessel incorporating realistic and measured parameter values

Our published model of a lymphatic vessel consisting of multiple actively contracting segments between non-return valves has been further developed by the incorporation of properties derived from observations and measurements of rat mesenteric vessels. These included (1) a refractory period between contractions, (2) a highly nonlinear form for the passive part of the pressure-diameter relationship, (3) hysteretic and transmural-pressure-dependent valve opening and closing pressure thresholds and (4) dependence of active tension on muscle length as reflected in local diameter. Experimentally, lymphatic valves are known to be biased to stay open. In consequence, in the improved model, vessel pumping of fluid suffers losses by regurgitation, and valve closure is dependent on backflow first causing an adverse valve pressure drop sufficient to reach the closure threshold. The assumed resistance of an open valve therefore becomes a critical parameter, and experiments to measure this quantity are reported here. However, incorporating this parameter value, along with other parameter values based on existing measurements, led to ineffective pumping. It is argued that the published measurements of valve-closing pressure threshold overestimate this quantity owing to neglect of micro-pipette resistance. An estimate is made of the extent of the possible resulting error. Correcting by this amount, the pumping performance is improved, but still very inefficient unless the open-valve resistance is also increased beyond the measured level. Arguments are given as to why this is justified, and other areas where experimental data are lacking are identified. The model is capable of future adaptation as new experimental data appear.

Altered phenotypic gene expression of 10T1/2 mesenchymal cells in nonuniformly stretched PEGDA hydrogels

Disease-related phenotype modulation of many cell types has been shown to be closely related to mechanical loading conditions; for example, vascular smooth muscle cell (SMC) phenotype shift from a mature, contractile state to a proliferative, synthetic state contributes to the formation of neointimal tissue during atherosclerosis and restenosis development and is related to SMC mechanical loading in vivo. The majority of past in vitro cell-stretching experiments have employed simplistic (uniform, uniaxial or biaxial) stretching environments to elucidate mechanobiological pathways involved in phenotypic shifts. However, the in vivo mechanics of the vascular wall consists of highly nonuniform stretch. Here we subjected 10T1/2 murine mesenchymal cells (an SMC precursor) to two- and three-dimensional nonuniform stretch environments. After 24 h of stretch, cells on an elastomeric membrane demonstrated varied proliferation [assessed by 5-bromo-2'-deoxyuridine (BrdU) incorporation] depending on location upon the membrane, with maximal proliferation occurring in a region of high, uniaxial stretch. Cells subjected to a nonuniform stretching regimen within three-dimensional polyethylene glycol diacrylate (PEGDA) hydrogel constructs demonstrated marked changes in mRNA expression of several phenotype-related proteins, indicating a sort of "hybrid" phenotype with contractile and synthetic markers being both upregulated and downregulated. Furthermore, expression levels of mRNAs were significantly different between various locations within the stretched gel. With the proliferation results, these data exhibit the capability of nonuniform stretching devices to induce heterogeneous cell responses, potentially indicative of spatial distributions of disease-related behaviors in vivo.

Construction, expression and characterisation of recombinant molecules of the urease gene operon from a urease-positive thermophilic Campylobacter (UPTC) isolate

A recombinant molecule of the full-length urease gene operon was constructed in vitro from the Japanese urease-positive thermophilic Campylobacter (UPTC) CF89-12 isolate and expressed in Escherichia coli cells. Several large deletion recombinant variants of urease subunit genes were also constructed and expressed in E. coli cells. A positive urease reaction with the log-phase cultured E. coli JM109 cells in the NiCl2-containing medium transformed with pGEM-T vector carrying the recombinant molecule of the full-length operon was detected with isopropyl-beta-D-thiogalactoside. Among the several deletion recombinant variants, each ureA-, ureB-, ureE-, ureF-, ureG- and ureH-large deficient, only ureE-large deletion variant (63% deficient) showed a positive urease reaction (approximately 15-fold). In addition, a ureE-complete deletion recombinant variant (100% deficient) constructed also showed a positive reaction of urease (approximately 18-fold). Recombinant urease subunits A and B were immunologically identified by Western blot analysis with anti-urease alpha (A) and beta (B) raised against Helicobacter pylori.

Incorporating measured valve properties into a numerical model of a lymphatic vessel

An existing lumped-parameter model of multiple lymphangions (lymphatic vascular segments) in series is adapted for the incorporation of recent physiological measurements of lymphatic vascular properties. The new data show very marked nonlinearity of the passive pressure-diameter relation during distension, relative to comparable blood vessels, and complex valve behaviour. Since lymph is transported as a result of either the active contraction or the passive squeezing of vascular segments situated between two one-way valves, the performance of these valves is of primary importance. The valves display hysteresis (the opening and closing pressure drop thresholds differ), a bias to staying open (both state changes occur when the trans-valve pressure drop is adverse) and pressure-drop threshold dependence on transmural pressure. These properties, in combination with the strong nonlinearity that valve operation represents, have in turn caused intriguing numerical problems in the model, and we describe numerical stratagems by which we have overcome the problems. The principal problem is also generalised into a relatively simple mathematical example, for which solution detail is provided using two different solvers.

Molecular identification of an arsenic four-gene operon in Campylobacter lari

An arsenic (ars) four-gene operon, containing genes encoding a putative membrane permease (ArsP), a transcriptional repressor (ArsR), an arsenate reductase (ArsC) and an arsenical-resistance membrane transporter (Acr3) was first identified in urease-positive thermophilic Campylobacter (UPTC) isolate, CF89-12. UPTC CF89-12 and some other Campylobacter lari isolates contained their ars four-genes, similarly, differing from that in the reference C. lari RM2100 strain. Two putative promoters and a putative terminator were identified for the operon in UPTC CF89-12. In vivo transcription of the operon was confirmed in the UPTC cells. PCR experiments using two primer pairs designed in silico to amplify two arsR and arsC-acr3 segments, respectively, generated two amplicons, approximately 200 and 350 base pairs, with all 31 of 31 and 19 of 31 C. lari isolates (n = 17 for UPTC; n = 14 for UN C. lari), respectively. An inverted repeat forming a dyad structure, a potential binding site for a transcriptional repressor, was identified in the promoter region. Within the deduced 61 amino acids sequence of the putative arsR open reading frame from the UPTC CF89-12, a metal binding box and a DNA-binding helix-turn-helix motif were identified. The UPTC CF89-12 and some other UPTC isolates isolated from natural environment were resistant to arsenate.

Finite-temperature dynamical density matrix renormalization group and the Drude weight of spin-1/2 chains

We propose an easily implemented approach to study time-dependent correlation functions of one-dimensional systems at finite-temperature T using the density matrix renormalization group. The entanglement growth inherent to any time-dependent calculation is significantly reduced if the auxiliary degrees of freedom which purify the statistical operator are time evolved with the physical Hamiltonian but reversed time. We exploit this to investigate the long-time behavior of current correlation functions of the XXZ spin-1/2 Heisenberg chain. This allows a direct extraction of the Drude weight D at intermediate to large T. We find that D is nonzero--and thus transport is dissipationless--everywhere in the gapless phase. At low temperatures we establish an upper bound to D by comparing with bosonization.

Comparative analysis of Campylobacter lari cytolethal distending toxin (CDT) effect on HeLa cells

We aimed to clarify if Campylobacter lari exerts a cytolethal distending toxin (CDT) effect on HeLa cells. Campylobacter cell lysates (CCLys) from C. jejuni 81-176 and urease-positive thermophilic Campylobacter (UPTC) CF89-12 and UPTC NCTC12893 isolates were shown to exert a CDT effect on HeLa cells with morphological changes examined by Giemsa staining and microscopy. However, Campylobacter lari JCM2530(T) isolate showed no effect. In addition, Campylobacter cell culture supernatant wash gave low or absent toxic effects with both C. jejuni and C. lari organisms. When western blot analysis was carried out to clarify if there was a CDTB effect in the CCLys and soluble fractions from Campylobacter isolates, which had a CDT effect on HeLa cells or did not have any effect, anti-recombinant CjCDTB antibodies identified an immunoreactively positive signal at around approximately 25 kDa on all the C. lari isolates examined, as well as the C. jejuni 81116 strain. Thus, all the Campylobacter isolates including those without any CDT effect were shown to express CDTB at the translational level.