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Concept: Serial dilution


Influenza is a highly infectious viral disease that is particularly common in the winter months. Oscillococcinum(®) is a patented homeopathic medicine that is made from a 1% solution of wild duck heart and liver extract, which is then serially diluted 200 times with water and alcohol.

Concepts: Medicine, Infectious disease, Alternative medicine, Evolutionary medicine, Serial dilution


Abstract A solute aspirated into a prefilled tube of diluent undergoes a dilution effect known as dispersion. Traditionally the effects of dispersion have been considered a negative consequence of using liquid-filled fixed-tip liquid handlers. We present a novel device and technique that utilizes the effects of dispersion to the benefit of making dilutions. The device known as the Gradient Diluter extends the dilution range of practical serial dilutions to six orders of magnitude in final volumes as low as 10 μL. Presented are the device, dispersion methods, and validation tests using fluorescence detection of sulforhodamine and the high-performance liquid chromatography/ultraviolet detection of furosemide. In addition, a T-cell inhibition assay of a relevant downstream protein is used to demonstrate IC(50) curves made with the Gradient Diluter compare favorably with those generated by hand.

Concepts: Fluorescence, Effect, Volume, Colloid, Effects unit, Laboratory techniques, Dilution, Serial dilution


The debate between those who believe homeopathy and hormesis derive from the same root and those who believe the two are different phenomena is as old as hormesis. It is an emotionally loaded discussion, with both sides fielding arguments which are far from scientific. Careful analysis of the basic paradigms of the two systems questions the claim of the homeopaths, who find similarities between them. The authors discuss these paradigms, indicating the differences between the claims of homeopathy and hormesis. It is time for thorough and serious research to lay this question to rest. One possible approach is to compare the activity of a hormetic agent, prepared in the usual way, with that of the same agent in the same concentration prepared homeopathically by serial dilution and succussion.

Concepts: Debate, English-language films, Question, Difference, Argumentation theory, Homeopathy, Serial dilution, Patent infringement


Extreme dilutions, especially homeopathic remedies of 30c, 200c, and higher potencies, are prepared by a process of serial dilution of 1:100 per step. As a result, dilution factors of 10(60), 10(400), or even greater are achieved. Therefore, both the presence of any active ingredient and the therapeutic efficacy of these medicines have been contentious because the existence of even traces of the starting raw materials in them is inconceivable. However, physicochemical studies of these solutions have unequivocally established the presence of the starting raw materials in nanoparticulate form even in these extreme (super-Avogadro, >10(23)) dilutions. In this article, we propose and validate a hypothesis to explain how nanoparticles are retained even at such enormous dilution levels. We show that once the bulk concentration is below a threshold level of a few nanograms/milliliter (ng/mL), at the end of each dilution step, all of the nanoparticles levitate to the surface and are accommodated as a monolayer at the top. This dominant population at the air-liquid interface is preserved and carried to the subsequent step, thereby forming an asymptotic concentration. Thus, all dilutions are only apparent and not real in terms of the concentrations of the starting raw materials.

Concepts: Electrochemistry, Concentration, Colloid, Physical chemistry, Solution, Dilution, Serial dilution, Froth flotation


With rapid emergence of multi-drug resistant bacteria, there is often need to perform susceptibility testing for less commonly used or newer antimicrobial agents. Such testing can often only be performed using labor-intensive, manual dilution methods and lies outside the capacity of most clinical labs, necessitating reference laboratory testing, and thereby delaying availability of susceptibility data. To address the compelling clinical need for microbiology laboratories to perform such testing in house, we explored a novel, automated, at-will broth microdilution susceptibility testing platform. Specifically we used the modified inkjet printer technology in the HP D300 digital dispensing system to dispense, directly from stock solutions into a 384-well plate, the two-fold serial dilution series required for broth microdilution testing. This technology was combined with automated absorbance readings and data analysis to determine minimal inhibitory concentrations. Performance was verified by testing Enterobacteriaceae for susceptibility to ampicillin, cefazolin, ciprofloxacin, colistin, gentamicin, meropenem, and tetracycline in comparison to a broth microdilution reference standard. In precision studies, essential and categorical agreement were 96.8% and 98.3%, respectively. Furthermore, significantly fewer D300-based measurements were outside ±1 dilution from the modal MIC, suggesting enhanced reproducibility. In accuracy studies performed using a panel of 80 curated clinical isolates, essential and categorical agreement; and very major, major, and minor errors were 94%, 96.6%, 0%, 0%, and 3.4%, respectively. Based on these promising initial results, it is anticipated that the D300-based methodology will enable hospital-based clinical microbiology laboratories to perform at-will broth microdilution testing of antimicrobials and address a critical testing gap.

Concepts: Microbiology, Inkjet printer, Antimicrobial, Antimicrobials, Serial dilution, Hewlett-Packard


Classical homeopathy is based on the therapeutic application of highly diluted homeopathic stocks. The indications of such medicines are determined by proving, i.e. by applying the remedies in healthy subjects. However, there are several complex homeopathic medicinal products on the market with approved therapeutic indications. The efficacy of these medicines has been assessed in clinical trials on patients. There is no upper limit of dosing for such homeopathic remedies, and these products often contain undiluted mother tincture. The aim of our study was to compare an allopathic herbal medicine and a homeopathic product containing undiluted mother tincture based on the same plant. Two products (an allopathic herbal medicine and a homeopathic product) containing Vitex agnus-castus extract were analyzed by HPLC-DAD for their agnuside and casticin contents. The agnuside content of the allopathic product was approximately four times higher, while the amount of casticin was in the same order of magnitude. Our experiments revealed the presence of active ingredients in allopathic quantity in a homeopathic preparation, highlighting the controversy between the principles of classical and practice of contemporary homeopathy. According to the principles of classical homeopathy these remedies cannot be considered as homeopathic remedies but rather as (allopathic) herbal ones. This phenomenon necessitates a case-by-case approach towards the possible adverse effects and drug interactions of homeopathics in the daily medical practice. Homeopathic products containing active agents in allopathic doses should be treated the same way as allopathic medicines from the point of view of quality assurance and pharmacovigilance.

Concepts: Pharmacology, Medicine, Placebo, Alternative medicine, Homeopathy, Vitex agnus-castus, Serial dilution, George Vithoulkas


The scale-up of rapid drug resistance testing for TB is a global priority. MTBDRplus is a WHO-endorsed multidrug-resistant (MDR)-TB PCR assay with suboptimal sensitivities and high indeterminate rates on smear-negative specimens. We hypothesised that widespread use of incorrect thermocycler ramp rate (speed of temperature change between cycles) impacts performance. A global sample of 72 laboratories was surveyed. We tested 107 sputa from Xpert MTB/RIF-positive patients and, separately, dilution series of bacilli, both at the manufacturer-recommended ramp rate (2.2 °C/s) and the most frequently reported incorrect ramp rate (4.0 °C/s). Mycobacterium tuberculosis-complex DNA (TUB-band)-detection, indeterminate results, accuracy, and inter-reader variability (dilution series only) were compared. 32 respondents did a median (IQR) of 41 (20-150) assays monthly. 78% used an incorrect ramp rate. On smear-negative sputa, 2.2 °C/s vs. 4.0 °C/s improved TUB-band positivity (42/55 vs. 32/55; p = 0.042) and indeterminate rates (1/42 vs. 5/32; p = 0.039). The actionable results (not TUB-negative or indeterminate; 41/55 vs. 28/55) hence improved by 21% (95% CI: 9-35%). Widespread use of incorrect ramp rate contributes to suboptimal MTBDRplus performance on smear-negative specimens and hence limits clinical utility. The number of diagnoses (and thus the number of smear-negative patients in whom DST is possible) will improve substantially after ramp rate correction.

Concepts: Polymerase chain reaction, Tuberculosis, Rates, Assay, Enzyme assay, Reaction rate, Serial dilution, Tuberculosis diagnosis


The aim of this work was to study Golenkinia sp. and microbial fuel cells (MFCs) for the treatment of anaerobically digested effluent from kitchen waste (ADE-KW) with different dilution factors. A dual-chamber MFC was fabricated for treating ADE-KW in the two chambers of the MFC and harvesting Golenkinia sp. All the anodic TN was removed more than 80%. COD removal efficiency increased from 48.2% to 76% when the dilution factor increased from 1 to 4. Maximum COD and TN removal rates were 3.56 and 3.71mg·L(-1)·h(-1) when ADE-KW was treated without dilution in the anodic chamber. All the cathodic TN and TP removal efficiencies were approximately 90%. The highest open circuit voltage (OCV) and power density were approximately 400mV and 400mW when ADE-KW was treated directly (undiluted) in the MFC, with the highest biomass and total lipid content production of Golenkinia sp. in the cathodic chamber.

Concepts: Archaea, Anaerobic digestion, Waste management, Battery, Electrolysis, Microbial fuel cell, Hydrogen production, Serial dilution


Many regulatory screening level exposure assessments are based on simple large scale conceptual scenarios. However, exposure, and therefore risks associated with chemicals, are characterised by high spatial variability. The Scenario assembly tool (ScenAT) is a global screening level model to enable spatially resolved local predictions of environmental concentrations of home and personal care chemicals. It uses the European Union Technical Guidance Document (TGD) equation to predict local scale freshwater concentrations (predicted environmental concentrations - PECs) of chemicals discharged via wastewater. ScenAT uses Geographic Information System (GIS) layers for the underlying socio-economic (population) and environmental parameters (per capita water use, sewage treatment plant connectivity, dilution factor). Using a probabilistic approach, we incorporate sources of uncertainty in the input data (tonnage estimation, removal in sewage treatment plants and seasonal variability in dilution factors) for two case-study chemicals: the antimicrobial triclosan (TCS) and the anionic surfactant linear alkylbenzene sulphonate (LAS). We then compare model estimates of wastewater and freshwater concentrations of TCS and LAS to UK monitoring data. Comparison showed that modeled PECs were on average higher than mean measured data for TCS and LAS by a factor 1.8 and 1.4, respectively. Considering the uncertainty associated with both model and monitoring data, the use of a probabilistic approach using the ScenAT model for screening assessment is reasonable. The combination of modelled and monitoring data enables the contextualisation of monitoring data. Spatial PECs can be used to identify areas of elevated concentration for further refined assessment.

Concepts: Risk, Prediction, Geographic information system, Water pollution, Sewage treatment, Sewage, Wastewater, Serial dilution


A series of amides possessing phenoxy/benzyloxy/pyridinyl groups has been synthesized by benzoylation of respective amines in presence of base with moderate to encouraging yields. Upon confirmation of structure, compounds were subjected for p38 kinase inhibitory, anti-inflammatory, antimicrobial and antitubercular activities. Antiinflammatory activity was determined using carageenan induced rat paw edema model while p38 kinase inhibitory activity was studied using ELISA method and serial dilution method was employed to determine MICs. Two compounds 4g and 4n showed over 30% p38 kinase inhibitory activity at 10 μM and best antiinflammatory activity was found for compounds 4g, 4i, 4n and 4o which exhibited to reduce paw edema over 70%. Compound 4b observed to be most potent against gram +ve organisms with MIC value of 1.6 μG/mL and compound 4u displayed potent antibacterial activity against gram negative organisms. Most encourging antitubercular activity was noticed for compounds 4u, 4r and 4k with 6.25, 12.5 and 12.5 μG/mL Further, in order to know binding site interactions, a docking simulations of compounds was performed. These preliminary results will certainly show fruitful directions to improve the activities of compounds.

Concepts: Inflammation, DNA, ELISA, Amide, Synthesis, Activity, Serial dilution, Carrageenan