DEVELOPMENT OF A TEXTURE PROFILE PANEL FOR EVALUATING RESTRUCTURED BEEF STEAKS VARYING IN MEAT PARTICLE SIZE

A texture profile panel was developed for measuring textural properties of restructured beef steaks differing in meat particle size. For steaks of different particle sizes, considerable differences existed in the type of sample breakdown and shape of chewed pieces after just two chews. Panelists also found restructured steaks made from large meat particle sizes to be visually more distorted and to contain more gristle than steaks made from small meat particle sizes. Several characteristics (chunkiness after two chews, coarseness of chewed mass at 15 chews) were dropped from the profile over time, while several characteristics (type of sample breakdown and shape of chewed pieces at two chews, size of chewed pieces at 10 chews) not used initially, were added. The texture profile panel approach appears suitable for discerning the textural differences in restructured steaks that can arise from using different meat particle sizes during processing.     

Particle deposition onto a human head: Influence of electrostatic and wind fields

This study investigates electrostatic fields surrounding the human head and particle deposition onto facial skin and eyes caused by the combined effect of electrostatic and wind fields. The electrostatic fields are calculated by a three-dimensional numerical model calculating the field strength between a field source and a human head. The deposition velocity can be viewed as determined by the sum of two contributions: that of an electrostatic field and that of a wind field. Deposition velocities are calculated by a semiempirical particle deposition model that considers particle transport from the free stream to the human face. The particle deposition model uses the electrostatic field model results as input parameters and is applied to the forehead and eyes of two facial shapes for two different turbulence conditions and aerosol charge distributions. The results of different practical working conditions, under which the potential difference between head (person) and source ranges from 5.6 to 15.0 kV, indicates that the presence of electrostatic fields always increases particle deposition for industrial aerosols. For aged aerosols an effect is only present for submicron particles. Bioelectromagnetics 19:246–258, 1998. © 1998 Wiley-Liss, Inc.     

Deep learning image analysis models pretrained on daily objects are useful for the preliminary characterization of particulate pharmaceutical samples

Visible and subvisible particles are a quality attribute in sterile pharmaceutical samples. A common method for characterizing and quantifying pharmaceutical samples containing particulates is imaging many individual particles using high-throughput instrumentation and analyzing the populations data. The analysis includes conventional metrics such as the particle size distribution but can be more sophisticated by interpreting other visual/morphological features. To avoid the hurdles of building new image analysis models capable of extracting such relevant features from scratch, we propose using well-established pretrained deep learning image analysis models such as EfficientNet. We demonstrate that such models are useful as a prescreening tool for high-level characterization of biopharmaceutical particle image data. We show that although these models are originally trained for completely different tasks (such as the classification of daily objects in the ImageNet database), the visual feature vectors extracted by such models can be useful for studying different types of subvisible particles. This applicability is illustrated through multiple case studies: (i) particle risk assessment in prefilled syringe formulations containing different particle types such as silicone oil, (ii) method comparability with the example of accelerated forced degradation, and (iii) excipient influence on particle morphology with the example of Polysorbate 80 (PS80). As examples of agnostic applicability of pretrained models, we also elucidate the application to two high-throughput microscopy methods: microflow and background membrane imaging. We show that different particle populations with different morphological and visual features can be identified in different samples by leveraging out-of-the-box pretrained models to analyze images from each sample.     

Sizing particles with a Coulter counter

A theorem is presented which permits a determination of the amplitude of the signal generated by the passage of a particle of arbitrary shape through a Coulter counter. The theorem is applied to particles of two shapes, a sphere and a prolate spheroid. For the sphere the signal is directly proportional to the volume of the particle. For the spheroid the result is a complicated function of the shape. Two spheroids of the same volume but different shapes will give different signals.     

Ascidian suspension feeding

Ascidians are a diverse group of benthic suspension feeders. This review presents and discusses the current literature on ascidian suspension feeding including the different structures involved in feeding as well as how feeding responds to variation in environmental parameters like water temperature and particle concentration. It is concluded that clearance rates in different species at identical conditions will not vary more than within the same species of different sizes, and that variation in clearance rate in ascidians in relation to temperature and particle concentration involves different regulatory mechanisms. Finally ascidian and mussel suspension feeding is compared. It is concluded that the two pumps are very alike with regard to pump performance and specific clearance rate, but whereas ascidian suspension feeding is characterised by high efficiency in terms of particle range and costs of pumping, mussel suspension feeding is more adapted to turbid conditions.     

Replication of double-stranded RNA in particles of Penicillium stoloniferum virus S.

RNA polymerase activity was assayed in different particle classes of Penicillium stoloniferum virus S. RNA polymerase activity was found to be associated with H particles, which contain double-stranded RNA and single-stranded RNA, but not with L particles, which contain only double-stranded RNA and not with M particles, which contain only single-stranded RNA. In H particles the reaction occurred with the formation of one new molecule of double-stranded RNA (or two complementary single strands of RNA) per virus particle and the production of product particles (P particles), which contained two molecules of double-stranded RNA (or its equivalent). This RNA polymerase is therefore a replicase, which catalyses the synthesis of the two complementary strands of double-stranded RNA in a single virus particle. This is the first report of this type of RNA polymerase system.     

Coloidal gold, ferritin and peroxidase as markers for electron microscopic double labeling lectin techniques

Three markers, colloidal gold, ferritin and peroxidase, were checked for usefulness in double labeling of lectin-binding sites. The amount of various lectins for the stabilization of good sols of a different particle size was evaluated. Several lectin-gold complexes were prepared for electron microscopic labeling purposes, and the optimal amount of various lectins needed for stabilization of gold solutions of a different particle size was determined. The following combinations were investigated for their usefulness in labeling two different lectin-binding sites: lectin-gold and lectin-gold (different particle size), lectin-gold and lectin-ferritin, as well as lectin-ferritin and lectin-peroxidase. Of these combinations the latter did not give satisfactory results for double labeling. In all single and double labeling techniques with the above mentioned markers the quantitative evaluation of the number of lectin-binding sites is not feasible, but these techniques will be of considerable value for the investigation of the dynamics of different lectin-binding sites on the cell surface.     

Mathematical Modeling of Size Exclusion Chromatography

A mathematical model of the size exclusion chromatography (SEC) process in chromatographic columns has been developed. It considers the following three mass transfer processes in the SEC column: axial dispersion in the bulk‐fluid phase, interfacial film mass‐transfer between the stationary and mobile phases, and diffusion of solutes within the macro pores of the packing particles. Differential equations of the process model were solved by the finite difference method. Characteristics of the column and the packing particles (bed void volume fraction, particle porosity, accessible particle porosity) were obtained experimentally, as well as retention times of different molecules with known molecular weights. Experiments were performed with two different columns containing two different packing materials, Superdex 75 HR 10/30 and BioSep SEC S2000, respectively. The model has been validated by comparing theoretical and experimental retention times for the different columns.     

Model-based particle picking for cryo-electron microscopy

We describe an algorithm for finding particle images in cryo-EM micrographs. The algorithm starts from a crude 3D map of the target particle, computed from a relatively small number of manually picked images, and then projects the map in many different directions to give synthetic 2D templates. The templates are clustered and averaged and then cross-correlated with the micrographs. A probabilistic model of the imaging process then scores cross-correlation peaks to produce the final picks. We give quantitative results on two quite different target particles: keyhole limpet hemocyanin and p97 AAA ATPase. On these particles our automatic particle picker shows human performance level, as measured by the Fourier shell correlations of 3D reconstructions.     

Vaccinia virus morphogenesis and dissemination

Vaccinia virus is the smallpox vaccine. It is the most intensively studied poxvirus, and its study has provided important insights about virus replication in general and the interactions of viruses with the host cell and immune system. Here, the entry, morphogenesis and dissemination of vaccinia virus are considered. These processes are complicated by the existence of two infectious vaccinia virus particles, called intracellular mature virus (IMV) and extracellular enveloped virus (EEV). The IMV particle is surrounded by one membrane, and the EEV particle comprises an IMV particle enclosed within a second lipid membrane containing several viral antigens. Consequently, these virions have different biological properties and play different roles in the virus life cycle.     

Localization of carotenoids in plasma low-density lipoproteins studied by surface-enhanced resonance Raman spectroscopy

Surface-enhanced resonance Raman scattering (SERRS) spectra were measured for the beta-carotene and lycopene carotenoids present in low-density lipoproteins (LDLs), which were isolated from human plasma and adsorbed on roughened silver surfaces. The silver surface was modified by formation of a self-assembled monolayer (SAM) of carboxylate-terminated linear alkanethiols in order to simulate the LDL binding region of the cellular LDL receptor. Thiols of different chain length were used to produce SAMs of varying thicknesses. It was shown that carotenoids are not released from the LDL particle upon adsorption onto the bare and thiol modified silver surfaces. The SERRS studies indicated that beta-carotene and lycopene were present in the shell of the LDL particle. The dependence of SERRS on the distance from the silver surface was different for beta-carotene and lycopene in LDL. This observation suggests that the two carotenoids are located in different places of the LDL particle.     

Properties of DI particle resistant mutants of vesicular stomatitis virus isolated from persistent infections and from undiluted passages

We describe an assay procedure to quantitate relative DI resistance of a variety of DI particle resistant (Sdi^?) mutants of vesicular stomatitis virus (VSV). We show that numerous diverse Sdi^? mutants of VSV are selected continuously in a stepwise manner during persistent infections, and also during serial undiluted lytic passages initiated with cloned virus. Concurrently with the successive appearance and disappearance of different Sdi^? mutants of infectious VSV, new DI particle types with altered interference properites also appear and disappear, resulting in rapid “coevolution” of virus and DI particle populations. Complementation tests with Sdi^? mutants indicate that mutations in at least two different virus factors (presumably associated with replication-encapsidation) can give rise to Sdi^? mutants. Interference studies with chimeric DI particles indicate that DI particle template RNA rather than DI particle protein determines the interference properties of DI particles interacting with Sdi^? and Sdi⁺ mutants of helper virus.     

Structural organization of free and esterified cholesterol in human high density lipoproteins. A 100.6 MHz 13C NMR study.

The structural organization of free and esterified cholesterol in human high density lipoproteins has been studied by high-field 1H and 13C NMR. The measurements are consistent with free cholesterol being present in at least two different environments. Part of the free cholesterol is oriented in the outer surface layer of the high density lipoprotein particle in contact with phospholipid or apoprotein, or both. The rest is probably present in the liquid, hydrophobic core of the HDL particle.     

The effect of particle size on bioavailability in cyclosporine preparations based on submicron dispersions

The effect of particle size on bioavailability of 9 different formulations with cyclosporine A was studied. A common feature of all the formulations was the ability to form submicron dispersions under dilution. The composition of individual formulations was chosen in such a way that they were based on same or similar excipients. For each formulation, pharmacokinetic study was carried out in beagle dogs. On groups of 10 dogs, the average AUC was evaluated. Particle size of formulations under dilution in water was measured by laser scattering method. According to the results of particle size measurement, the formulations were sorted out into groups of similar particle size distribution by use of two methods of multivariate statistical analysis. The average AUC within groups and between-groups was compared, and the effect of particle size on bioavailability was evaluated.     

Aerodynamic and Electrostatic Properties of Model Dry Powder Aerosols: a Comprehensive Study of Formulation Factors

The impact of formulation variables on aerodynamic and electrostatic properties of dry powder aerosol particles is of great importance to the development of efficient and reproducible inhaler products. Systematic evaluation requires a well-designed series of experiments using appropriate methods. A factorial experimental design was employed. In broad terms, the conditions considered were two drugs, albuterol and budesonide, in combination with different excipients, drug concentrations, delivered doses, and metering system (capsule composition) and sampled under different flow conditions using standard entrainment tubes. Samples were collected in an electrical low-pressure impactor, to evaluate distribution of electrostatic properties, and an Andersen eight-stage nonviable cascade impactor, to estimate aerodynamic particle size distribution, concurrently. The deposition studies allowed calculation of approximate per particle charge levels for drug. The results showed very high particle charge levels, often in the 1,000–10,000 of elementary charges per particle range, orders of magnitude higher than charge levels predicted by the Boltzmann charge distribution. The charge levels are considerably higher than had previously been estimated (200e per particle).KEY WORDS: aerodynamics, aerosol(s), electrostatics, experimental design, formulation factors     

Optically induced flow cytometry for continuous microparticle counting and sorting

This paper reports a new microfluidic device capable of performing optically induced flow cytometry (OIFC). This enables it to continuously count and to sort microparticles based on optically induced dielectrophoretic (ODEP) forces. Gravity was used to drive the particles instead of using syringe pumps. The particles were then focused inside a sample channel by the ODEP forces and then passed through a detection region. A pair of optical fibers were embedded into fiber channels to count the number of particles and analyze the particle size in real time. Using 20.9 and 9.7 microm polystyrene microparticles, the average light intensity were about 63.67 and 8.80 units, with a coefficient-of-variation (CV) of 7.46 and 25.57%, respectively. This demonstrated that these two particle sizes could be successfully distinguished. After detecting the number and size of the microparticles, an optically induced dynamic switch (ODS) was used to sort microparticles to downstream fluidic outlets. The ODS used ODEP forces generated by different illumination intensities or optical line widths. The ODS was composed of two virtual electrodes which controlled particle movement in two dimensions. The ODS can successfully sort microparticles with different sizes continuously. The development of the OIFC device is a major advancement in the design of microparticle counting and sorting devices. Applications in future biomedical applications for cell counting and manipulation are envisioned.     

Defective Virions of Reovirus

When purified preparations of stock reovirus, type 3, were digested with chymotrypsin, the virions were converted into two different types of particle. These new particles could be separated from each other by isopycnic centrifugation in cesium chloride gradients. One particle banded at a buoyant density of 1.43 g/cm(3), the other at a density of 1.415 g/cm(3). The former particle is termed the heavy (H) particle, the latter is the light (L) particle. The ratio of H/L particles varied between 0.5 and 0.25 in various purified preparations of virus. In electron micrographs, both H and L particles had the appearance and dimensions of viral cores. H particles were infectious for L cells. When plaques formed by stock virus, or by H particles, were picked and propagated in L cells, the majority of the clones gave rise only to H particles on chymotrypsin digestion. On continued serial passage of the clones, virions containing L particles again appeared in the progeny. The simplest explanation of these results was that stock virus was comprised of two populations of virions. One type of virion which contained H particles was infectious, whereas the other, which contained L particles, was not itself infectious and could replicate only in cells coinfected with an H particle virion. Added weight was given to this hypothesis by two observations. First, a small but definite separation of H and L virions could be achieved by isopycnic centrifugation in a gradient of cesium chloride. Second, L particles and virions containing L particles were both shown to lack the largest of the ten segments of double-stranded ribonucleic acid genome. Thus, L particle virions have defective genomes.     

定容重条件下生物炭对半干旱区土壤水分入渗特征的影响

了解生物炭添加土壤后对水分入渗过程的影响,可为半干旱区生物炭还田对土壤水文过程的影响评价提供科学依据.本文采用室内土柱模拟方法,在定容重条件下研究了3种生物炭粒径(1～2 mm、0.25～1 mm和≤0.25 mm)和4种添加量(10、50、100和150 g·kg^-1)对两种不同质地土壤(塿土和风沙土)累积入渗量、吸渗率和稳定入渗率的影响.结果表明: 与对照相比,生物炭总体上能够明显增加塿土入渗能力,降低风沙土入渗能力.在入渗100 min时,塿土添加生物炭处理的平均累积入渗量比对照高25.1%;在入渗15 min时,风沙土添加生物炭处理的平均累积入渗量比对照低11.1%.相同生物炭添加量下,生物炭粒径均对塿土累积入渗量具有促进作用,但不同添加量处理的最大作用粒径不尽一致.对于风沙土累积入渗量,低添加量(10 g·kg^-1)时,除≤0.25 mm粒径促进作用不明显外,其他两种粒径均表现出明显的促进作用,而高添加量(50、100和150 g·kg^-1)则表现出抑制作用,且100和150 g·kg^-1粒径处理风沙土累积入渗量随生物炭粒径的减小呈递减趋势.相同生物炭粒径下,风沙土的累积入渗量随着生物炭添加量的增加而递减,塿土则规律不明显.利用Philip入渗模型拟合的决定系数在0.965～0.999,拟合效果较好,说明此模型适合对添加生物炭的土壤水分入渗过程进行模拟.生物炭粒径、生物炭添加量及两者的交互效应对两种土壤的吸渗率和稳渗率均有显著影响,且生物炭添加量对入渗的影响最显著.生物炭对土壤水分入渗特征的影响取决于土壤的质地类型,且该影响程度与添加量呈正相关关系.     

An Escherichia coli enterobactin cluster gene with sequence homology to trpE and pabB

Abstract Oxaloacetate decarboxylase from Klebsiella pneumoniae is a membrane bound sodium-pumping biotin enzyme. In electron microscopic samples, the enzyme particle appeared rod-like, with a length of about 12.9 nm and a width of about 7.4 nm, and with two submasses. Based on electron microscopic comparison of full-size enzyme molecules and free α-subunits, it is concluded that oxaloacetate decarboxylase contains only one α-subunit per enzyme particle. The α-subunit of the enzyme revealed a subdivision into two domains of different sizes forming a 'cleft'. Electron microscopic affinity labeling with avidin demonstrated that the biotin prosthetic group present on the α-subunit is located in this cleft, close to the complex formed by the β- and γ-subunits. The fact that 'pairs' but no higher specific aggregates could be observed after incubation with avidin, also indicates that only one copy of the α-subunit is present in an oxaloacetate decarboxylase particle.     

A structural model for the GroEL chaperonin

Abstract Individual particle analysis of end views from negatively stained specimensof purified GroEL from Escherichia coli showed the presence of two different particle populations, those with a six-fold symmetry and those with a seven-fold symmetry, when studied at pH 7.7 and 5.0. Image processing of particles from frozen-hydrated specimens revealed at both pH values a homogeneous population of particles with a strong seven-fold symmetry component and an average image with seven asymmetric units. Biochemical analysis of purified GroEL showed unequivocally the presence of a single polypeptide with the N-terminal sequence identical to that of GroEL. These results are compatible with a structural model of GroEL as an asymmetric aggregate built up by two rings of seven-fold and six-fold symmetries, respectively.