Spark Ignition - Searching for the Optimal Spark Profile

The impact of different spark designs on the ignition and combustion stability is studied using a 13-liter CNG fueled heavy duty spark ignited engine to search for the “optimal” spark design. Experimental results show that robust ignition can be achieved using a significantly shorter spark duration and lower energy than expected. A capacitive discharge ignition (CDI) system enabled to separately control the available spark voltage, current and duration (FlexiSpark®CDI) was compared to a standard CDI system without spark control and an inductive discharge (IDI) ignition system. Typically, a robust ignition can be provided using only 5% of the spark duration and 17% of the spark energy compared to that required by an IDI system to accomplish an equivalent ignition and combustion stability. By applying control of the spark, a robust ignition can be provided which is optimized for the fuel, the engine design, the engine operating condition, and the condition of the spark plugs. This offers a potential to significantly reduce the spark-plug wear and the total cost of ownership without compromising engine performance.The results are especially interesting in the view of Hydrogen fueled SI-ICE, where the required available spark voltage is high, but the required spark energy is low. It is desirable to use a spark design with just enough voltage and power to initiate a sustainable combustion, but with minimal energy not to excessively wear and heat the spark plug electrodes to avoid pre-ignition

Studies on the role of NGF in arthritis-induced pain transmission using gait and weight bearing as outcome measures

Pain is one of the most common reasons for seeking healthcare, with approximately forty percent of those suffering from chronic pain having joint pain. Osteoarthritis is the most common cause of joint pain, but currently there are few treatments available. The search for new, effective pain treatment has been mostly unsuccessful, in spite of the discovery of mechanisms that are involved in the transmission of nociceptive signals from the periphery to the central nervous system where pain is experienced. This work focuses on the evaluation of rodent joint pain models, the behavioural manifestations of the injuries, and the possibility to detect treatment effects in these models. Three models have been evaluated in rats; intra-articular injection of carrageenan, Freund´s complete adjuvant (CFA), and monoiodoacetate (MIA) into one hind leg. In mice, two models have been evaluated; intra-articular injection of CFA, and the surgical model of anterior cruciate ligament transection (ACLT). Carrageenan injection resulted in an acute, robust inflammation, CFA injection caused a more long-lasting strong joint inflammation, and MIA injection resulted in an almost complete loss of joint cartilage after a few weeks. The model more resembling osteoarthritis was the surgical model, ACLT, which gave severe cartilage degeneration, osteophytes, and pathophysiological changes in synovia and ligaments. Gait and weight bearing during locomotion have been tested in all models. The degree of weight bearing reduction in the affected limb was largest in the CFA- and carrageenan-induced model, followed by the MIA model and least effect was seen in the ACLT surgical model. Thus the ACLT model was not possible to use for pharmacological evaluation of drugs, whereas carrageenan- and CFA-induced monoarthritis resulted in a big enough difference between animals with monoarthritis and those without, to test drugs commonly used for pain as well as those under investigation for effects on pain. Conventional pain relieving drugs such as non-stereoidal anti-inflammatory drugs (NSAIDs) and opioids were able to normalize effects on weight bearing caused by both the carrageenan- and the CFA-induced monoarthritis, as were treatments based on inhibiting the NGF-TrkA pathway; an anti-NGF antibody and two pan-Trk compounds. However, an antagonist of the TRPV1 receptor lacked effect. We also investigated mice with a mutation in the R100 NGFß gene (hR100E), in comparison with mice possessing a human wild-type NGF (hWT), similar but not exactly like the one found in a hereditary sensory and autonomic neuropathy type V (HSAN V) disorder. This disorder leads to insensitivity to deep pain in homozygous patients, with sensory and autonomic functions remaining almost normal. In mice with the hR100E mutation, we found similar behavioural outcome; normal peripheral sensory functions but less pain-like behaviour when assessing joint pain with gait and weight bearing. In summary, this work shows that in order to detect translatable effects on joint pain, models need to be robust enough, especially for pharmacological testing, but more important, the methods of testing need to be relevant for the study aim

Little difference between minimum inhibitory concentrations of Mycobacterium tuberculosis wild-type organisms determined with BACTEC MGIT 960 and Middlebrook 7H10

AbstractThe MIC wild-type (WT) distribution for Mycobacterium tuberculosis in BACTEC 960 MGIT is not defined, which may result in poor reproducibility for drug susceptibility testing (DST), as several DST methods with different breakpoints are in use. In a comparison between MGIT and Middlebrook 7H10 medium of seven first- and second-line drugs, including 133 MIC determinations of 15 WT isolates, we found an agreement of 91.7% within ± one MIC dilution step. The results confirm the agreement in MIC testing between 7H10 and MGIT and indicate that breakpoints could be harmonized in order to avoid misclassification

Evaluation of bleach-sedimentation for sterilising and concentrating Mycobacterium tuberculosis in sputum specimens

RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are.Abstract Background Bleach-sedimentation may improve microscopy for diagnosing tuberculosis by sterilising sputum and concentrating Mycobacterium tuberculosis. We studied gravity bleach-sedimentation effects on safety, sensitivity, speed and reliability of smear-microscopy. Methods This blinded, controlled study used sputum specimens (n = 72) from tuberculosis patients. Bleach concentrations and exposure times required to sterilise sputum (n = 31) were determined. In the light of these results, the performance of 5 gravity bleach-sedimentation techniques that sterilise sputum specimens (n = 16) were compared. The best-performing of these bleach-sedimentation techniques involved adding 1 volume of 5% bleach to 1 volume of sputum, shaking for 10-minutes, diluting in 8 volumes distilled water and sedimenting overnight before microscopy. This technique was further evaluated by comparing numbers of visible acid-fast bacilli, slide-reading speed and reliability for triplicate smears before versus after bleach-sedimentation of sputum specimens (n = 25). Triplicate smears were made to increase precision and were stained using the Ziehl-Neelsen method. Results M. tuberculosis in sputum was successfully sterilised by adding equal volumes of 15% bleach for 1-minute, 6% for 5-minutes or 3% for 20-minutes. Bleach-sedimentation significantly decreased the number of acid-fast bacilli visualised compared with conventional smears (geometric mean of acid-fast bacilli per 100 microscopy fields 166, 95%CI 68-406, versus 346, 95%CI 139-862, respectively; p = 0.02). Bleach-sedimentation diluted paucibacillary specimens less than specimens with higher concentrations of visible acid-fast bacilli (p = 0.02). Smears made from bleach-sedimented sputum were read more rapidly than conventional smears (9.6 versus 11.2 minutes, respectively, p = 0.03). Counting conventional acid-fast bacilli had high reliability (inter-observer agreement, r = 0.991) that was significantly reduced (p = 0.03) by bleach-sedimentation (to r = 0.707) because occasional strongly positive bleach-sedimented smears were misread as negative. Conclusions Gravity bleach-sedimentation improved laboratory safety by sterilising sputum but decreased the concentration of acid-fast bacilli visible on microscopy, especially for sputum specimens containing high concentrations of M. tuberculosis. Bleach-sedimentation allowed examination of more of each specimen in the time available but decreased the inter-observer reliability with which slides were read. Thus bleach-sedimentation effects vary depending upon specimen characteristics and whether microscopy was done for a specified time, or until a specified number of microscopy fields had been read. These findings provide an explanation for the contradictory results of previous studies.Peer Reviewe

Rapid culture-based methods for drug-resistance detection in Mycobacterium tuberculosis.

Tuberculosis still represents a major public health problem, especially in low-resource countries where the burden of the disease is more important. Multidrug-resistant and extensively drug drug-resistant tuberculosis constitute serious problems for the efficient control of the disease stressing the need to investigate resistance to first- and second-line drugs. Conventional methods for detecting drug-resistance in Mycobacterium tuberculosis are slow and cumbersome. The most commonly used proportion method on Löwenstein-Jensen medium or Middlebrook agar requires a minimum of 3-4 weeks to produce results. Several new approaches have been proposed in the last years for the rapid and timely detection of drug-resistance in tuberculosis. This review will address phenotypic culture-based methods for rapid drug susceptibility testing in M. tuberculosis

Phylogenetically informative mutations in genes implicated in antibiotic resistance in Mycobacterium tuberculosis complex

Funder: Joachim Herz Stiftung; doi: http://dx.doi.org/10.13039/100008662Abstract: Background: A comprehensive understanding of the pre-existing genetic variation in genes associated with antibiotic resistance in the Mycobacterium tuberculosis complex (MTBC) is needed to accurately interpret whole-genome sequencing data for genotypic drug susceptibility testing (DST). Methods: We investigated mutations in 92 genes implicated in resistance to 21 anti-tuberculosis drugs using the genomes of 405 phylogenetically diverse MTBC strains. The role of phylogenetically informative mutations was assessed by routine phenotypic DST data for the first-line drugs isoniazid, rifampicin, ethambutol, and pyrazinamide from a separate collection of over 7000 clinical strains. Selected mutations/strains were further investigated by minimum inhibitory concentration (MIC) testing. Results: Out of 547 phylogenetically informative mutations identified, 138 were classified as not correlating with resistance to first-line drugs. MIC testing did not reveal a discernible impact of a Rv1979c deletion shared by M. africanum lineage 5 strains on resistance to clofazimine. Finally, we found molecular evidence that some MTBC subgroups may be hyper-susceptible to bedaquiline and clofazimine by different loss-of-function mutations affecting a drug efflux pump subunit (MmpL5). Conclusions: Our findings underline that the genetic diversity in MTBC has to be studied more systematically to inform the design of clinical trials and to define sound epidemiologic cut-off values (ECOFFs) for new and repurposed anti-tuberculosis drugs. In that regard, our comprehensive variant catalogue provides a solid basis for the interpretation of mutations in genotypic as well as in phenotypic DST assays

Resistance to First-Line Anti-TB Drugs Is Associated with Reduced Nitric Oxide Susceptibility in Mycobacterium tuberculosis

Background and objective: The relative contribution of nitric oxide (NO) to the killing of Mycobacterium tuberculosis in human tuberculosis (TB) is controversial, although this has been firmly established in rodents. Studies have demonstrated that clinical strains of M. tuberculosis differ in susceptibility to NO, but how this correlates to drug resistance and clinical outcome is not known. Methods: In this study, 50 sputum smear- and culture-positive patients with pulmonary TB in Gondar, Ethiopia were included. Clinical parameters were recorded and drug susceptibility profile and spoligotyping patterns were investigated. NO susceptibility was studied by exposing the strains to the NO donor DETA/NO. Results: Clinical isolates of M. tuberculosis showed a dose- and time-dependent response when exposed to NO. The most frequent spoligotypes found were CAS1-Delhi and T3_ETH in a total of nine known spoligotypes and four orphan patterns. There was a significant association between reduced susceptibility to NO (>10% survival after exposure to 1mM DETA/NO) and resistance against first-line anti-TB drugs, in particular isoniazid (INH). Patients infected with strains of M. tuberculosis with reduced susceptibility to NO showed no difference in cure rate or other clinical parameters, but a tendency towards lower rate of weight gain after two months of treatment. Conclusion: There is a correlation between resistance to first-line anti-TB drugs and reduced NO susceptibility in clinical strains of M. tuberculosis. Further studies including the mechanisms of reduced NO susceptibility are warranted and could identify targets for new therapeutic interventions

Rapid determination of anti-tuberculosis drug resistance from whole-genome sequences

Mycobacterium tuberculosis drug resistance (DR) challenges effective tuberculosis disease control. Current molecular tests examine limited numbers of mutations, and although whole genome sequencing approaches could fully characterise DR, data complexity has restricted their clinical application. A library (1,325 mutations) predictive of DR for 15 anti-tuberculosis drugs was compiled and validated for 11 of them using genomic-phenotypic data from 792 strains. A rapid online ‘TB-Profiler’ tool was developed to report DR and strain-type profiles directly from raw sequences. Using our DR mutation library, in silico diagnostic accuracy was superior to some commercial diagnostics and alternative databases. The library will facilitate sequence-based drug-susceptibility testing

The search for translational pain outcomes to refine analgesic development: Where did we come from and where are we going?

Pain measures traditionally used in rodents record mere reflexes evoked by sensory stimuli; the results thus may not fully reflect the human pain phenotype. Alterations in physical and emotional functioning, pain-depressed behaviors and facial pain expressions were recently proposed as additional pain outcomes to provide a more accurate measure of clinical pain in rodents, and hence to potentially enhance analgesic drug development. We aimed to review how preclinical pain assessment has evolved since the development of the tail flick test in 1941, with a particular focus on a critical analysis of some nonstandard pain outcomes, and a consideration of how sex differences may affect the performance of these pain surrogates. We tracked original research articles in Medline for the following periods: 1973-1977, 1983-1987, 1993-1997, 2003-2007, and 2014-2018. We identified 606 research articles about alternative surrogate pain measures, 473 of which were published between 2014 and 2018. This indicates that preclinical pain assessment is moving toward the use of these measures, which may soon become standard procedures in preclinical pain laboratories.FPU grant from the Spanish Ministry of Education, Culture and SportsSpanish Ministry of Economy and Competitiveness (MINECO, grant SAF2016-80540-R)Ramón Areces FoundationJunta de Andalucía (grant CTS 109)Esteve PharmaceuticalsEuropean Regional Development Fund (ERDF

Antioxidants Protect Keratinocytes against M. ulcerans Mycolactone Cytotoxicity

BACKGROUND: Mycobacterium ulcerans is the causative agent of necrotizing skin ulcerations in distinctive geographical areas. M. ulcerans produces a macrolide toxin, mycolactone, which has been identified as an important virulence factor in ulcer formation. Mycolactone is cytotoxic to fibroblasts and adipocytes in vitro and has modulating activity on immune cell functions. The effect of mycolactone on keratinocytes has not been reported previously and the mechanism of mycolactone toxicity is presently unknown. Many other macrolide substances have cytotoxic and immunosuppressive activities and mediate some of their effects via production of reactive oxygen species (ROS). We have studied the effect of mycolactone in vitro on human keratinocytes--key cells in wound healing--and tested the hypothesis that the cytotoxic effect of mycolactone is mediated by ROS. METHODOLOGY/PRINCIPAL FINDINGS: The effect of mycolactone on primary skin keratinocyte growth and cell numbers was investigated in serum free growth medium in the presence of different antioxidants. A concentration and time dependent reduction in keratinocyte cell numbers was observed after exposure to mycolactone. Several different antioxidants inhibited this effect partly. The ROS inhibiting substance deferoxamine, which acts via chelation of Fe(2+), completely prevented mycolactone mediated cytotoxicity. CONCLUSIONS/SIGNIFICANCE: This study demonstrates that mycolactone mediated cytotoxicity can be inhibited by deferoxamine, suggesting a role of iron and ROS in mycolactone induced cytotoxicity of keratinocytes. The data provide a basis for the understanding of Buruli ulcer pathology and the development of improved therapies for this disease