Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Reforestation Based on Mono-Plantation of Fast-Growing Tree Species Make It Difficult to Maintain (High) Soil Water Content in Tropics, a Case Study in Hainan Island, China

Reforestation has been assumed as a natural solution to recover soil water content, thereby increasing freshwater supply. Mono-plantation of fast-growing species is the first step for performing reforestation to prevent frequent and heavy rain-induced landslide in tropics. However, fast-growing species may have negative hydraulic response to seasonal drought to maintain high growth rate and, thus, may make it difficult for reforestation in tropics to recover soil water content. We tested this hypothesis in a setting involving (a) a reforestation project, which mono-planted eight fast-growing tree species to successfully restore a 0.2-km2 extremely degraded tropical rainforest, and (b) its adjacent undisturbed tropical rainforest in Sanya City, Hainan, China. We found that, for maintaining invariably high growth rates across wet to dry seasons, the eight mono-planted fast-growing tree species had comparable transpiration rates and very high soil water uptake, which in turn led to a large (3 times) reduction in soil water content from the wet to dry seasons in this reforested area. Moreover, soil water content for the adjacent undisturbed tropical rainforest was much higher (1.5 to 5 times) than that for the reforested area in both wet and dry seasons. Thus, the invariably very high water demand from the wet to dry seasons for the mono-planted fast-growing species possesses difficulty in the recovery of soil water content. We suggest, in the next step, to mix many native-species along with the currently planted fast-growing nonnative species in this reforestation project to recover soil water content

Comprehensive Evaluation of Quality Traits of Hovenia acerba Germplasm Resources in Fujian Province

Hovenia acerba is a precious medicinal and edible tree. We assessed the genetic variation of H. acerba quality traits and conducted a comprehensive germplasm resource evaluation to provide a theoretical basis for breeding edible, medicinal, and edible/medicine combination varieties. We evaluated 31 H. acerba germplasm resources, including 12 infructescence and 8 fruit quality traits using correlation, principal component, and cluster analyses. The results showed that there were significant differences in all quality traits, with an average coefficient of variation greater than 0.20, an average genetic diversity greater than 1.80, and an average repeatability greater than 0.90. The average genetic variation and repeatability of quality traits in infructescence were higher than fruit. Infructescence K, Ca, Mn, Mg, and reducing sugar contents are important indicators in evaluating infructescence and fruit quality traits, and infructescence K, Mg, and reducing sugar contents are also quality innovation indices of H. acerba germplasms. Tannin, protein, and soluble sugar were the most suitable quality components for screening, followed by reducing sugar, starch, fat, total saponins, and total flavones. According to principal component factor scores and cluster analysis results, specific genotypes were selected as breeding materials for infructescence protein, tannin, flavone, reductive sugar, fruit tannin, fat, flavonoid, saponin, protein, and starch. The correlation analysis with environmental factors showed that the total amount of applied water could influence H. acerba infructescence and fruit quality. In conclusion, the variability of H. acerba germplasm resources was rich, and selection potential is large, which is beneficial to germplasm quality innovation and breeding

Improving the Forming Quality of Laser Dynamic Flexible Micropunching by Laser Pre-Shocking

Laser pre-shocking (LPS) was introduced into the laser dynamic flexible micropunching process to refine the grain size of a workpiece to improve the forming quality of punched parts. T2 copper foils with five different grain sizes and seven different laser power densities with and without LPS were used for the experiment. The results showed that the grains are refined and the average surface roughness Ra decreases after LPS. For copper foils annealed at 650 °C, the value of Ra decreases from 0.430 to 0.363 µm. The increase in laser energy density and grain size leads to the deterioration of the fracture surface. LPS can improve the quality of the fracture surface. Compared with punched holes without LPS, the dimensional accuracy and shape accuracy of punched holes can be improved by LPS. When grain size is close to the thickness of the copper foil, the forming quality of the punched parts becomes uncertain, owing to the difference in the orientation of the initial grains. The instability of laser dynamic flexible micropunching can be reduced by LPS. Especially, the improvement of forming quality of the punched part brought by LPS is significant for the copper foils with coarse grains

Synthesis and preclinical evaluation of radioiodinated hypericin dicarboxylic acid as a necrosis avid agent in rat models of induced hepatic, muscular and myocardial necroses

Myocardial infarction (MI) leads to substantial morbidity and mortality around the world. Accurate assessment of myocardial viability is essential to assist therapies and improve patient outcomes. (131)I-hypericin dicarboxylic acid ((131)I-HDA) was synthesized and evaluated as a potential diagnostic agent for earlier assessment of myocardium viability compared to its preceding counterpart (131)I-hypericin ((131)I-Hyp) with strong hydrophobic property, long plasma half-life, and high uptake in mononuclear phagocyte system (MPS). Herein, HDA was synthesized and characterized, and self-aggregation constant Kα was analyzed by spectrophotometry. Plasma half-life was determined in healthy rats by γ-counting. (131)I-HDA and (131)I-Hyp were prepared with iodogen as oxidant. In vitro necrosis avidity of (131)I-HDA and (131)I-Hyp was evaluated in necrotic cells induced by hyperthermia. Biodistribution was determined in rat models of induced necrosis using γ-counting, autoradiography, and histopathology. Earlier imaging of necrotic myocardium to assess myocardial viability was performed in rat models of reperfused myocardium infarction using single photon emission computed tomography/computed tomography (SPECT/CT). As a result, the self-aggregation constant Kα of HDA was lower than that of Hyp (105602 vs 194644, p < 0.01). (131)I-HDA displayed a shorter blood half-life compared with (131)I-Hyp (9.21 vs 31.20 h, p < 0.01). The necrotic-viable ratio in cells was higher with (131)I-HDA relative to that with (131)I-Hyp (5.48 vs 4.63, p < 0.05). (131)I-HDA showed a higher necrotic-viable myocardium ratio (7.32 vs 3.20, p < 0.01), necrotic myocardium-blood ratio (3.34 vs 1.74, p < 0.05), and necrotic myocardium-lung ratio (3.09 vs 0.61, p < 0.01) compared with (131)I-Hyp. (131)I-HDA achieved imaging of necrotic myocardium at 6 h postinjection (p.i.) with SPECT/CT, earlier than what (131)I-Hyp did. Therefore, (131)I-HDA may serve as a promising necrosis-avid diagnostic agent for earlier imaging of necrotic myocardium compared with (131)I-Hyp. This may support further development of radiopharmaceuticals ((123)I and (99m)Tc) based on HDA for SPECT/CT of necrotic myocardium.status: publishe

Synthesis and evaluation of 131I‐Skyrin as a necrosis avid agent for potential targeted radionuclide therapy of solid tumors

An innovative anticancer approach targeted to necrotic tissues, which serves as a noncancerous and generic anchor, may present a breakthrough. Necrosis avid agents with a flat conjugate aromatic structure selectively accumulate in necrotic tissues, but they easily form aggregates that undesirably distribute to normal tissues. In this study, skyrin, a dianthraquinone compound with smaller and distorted π-cores and thus decreased aggregates as compared with hypericin (Hyp), was designed to target necrosis for tumor therapy. Aggregation studies of skyrin by UV/vis spectroscopy showed a smaller self-association constant with skyrin than with Hyp. Skyrin was labeled by iodine-131 with a radiochemical purity of 98% and exhibited good stability in rat serum for 72 h. In vitro cell uptake studies showed significant difference in the uptake of 131I-skyrin by necrotic cells compared to normal cells (P < 0.05). Compared in rats with liver and muscle necrosis, radiobiodistribution, whole-body autoradiography, and SPECT/CT studies revealed higher accumulation of 131I-skyrin in necrotic liver and muscle (p < 0.05), but lower uptake in normal organs, relative to that of 131I-Hyp. In mice bearing H22 tumor xenografts treated with combretastatin A4 disodium phosphate, the highest uptake of 131I-skyrin was found in necrotic tumor. In conclusion, 131I-skyrin appears a promising agent with reduced accumulation in nontarget organs for targeted radionuclide therapy of solid tumors.status: publishe