Application of some droplet sedimentation theories to layered erythrocyte suspensions

The applicability of some existing droplet sedimentation theories to erythrocyte suspensions was investigated using glutaraldehyde-fixed erythrocytes from horse, canine, pig, chicken, and human. The Svensson criteria were shown to underestimate the load supportable by a density gradient. The available theories on droplet formation times could not predict each other, and the data on erythrocyte suspensions, especially at high suspension concentrations. It was finally argued that, since the behavior of erythrocytes was not controlled by the diffusion process, the erythrocyte suspensions were not expected to exhibit lasting or absolute stability even when the particle load was small.     

Application of gravitational sedimentation to efficient cellular recycling in continuous alcoholic fermentation

A mathematical model for the sedimentation velocity in an inclined parallel plate sedimenter is proposed. The parameters of the alcoholic fermentation broth (cell density of Saccharomyces cerevisiae, density of the fermentation medium, viscosity of the broth at various alcohol and biomass contents) were determined experimentally. The sedimentation velocities were predicted under the various operational conditions and parameters, both of the broth (the alcohol concentration and cell content) and the sedimenter prototype (length, distance between the plates, and slope). The proposed model for the sedimentation velocity presented a good correlation with the experimental results of continuous sedimentation. These sedimenter prototypes were assembled and tested for efficiency of separation of yeast cell under conditions considered for interest for continuous alcoholic fermentation. A selective filter for the overflow composed of calcium alginate gel improved operation. A high operational stability, high separation efficiency (over 98%), and adequate settler residence times (about 20 min) were attained. The operational results permitted the operation of continuous alcoholic fermentation with cellular recycling effected exclusively by gravitational sedimentation, this characterizing a process of enormous industrial interest because of the operational simplicity and low operational and maintenance costs. (c) 1993 John Wiley & Sons, Inc.     

Effects of estuarine infauna on sediment stability and particle sedimentation

Secretions produced by the two estuarine benthic invertebrates Corophium volutator and Nereis diversicolor stabilise sediments by increasing their shear strength, and reduce sedimentation of previously resuspended particles. The secretions consist of 1 to 2 m threads which bind the particles together. They are used by both species in the production of complex burrow systems in the top 15 cm of sediment. The burrow systems have been demonstrated by a new resin impregnation technique. These results have widespread implications for the stability and erosion of estuarine sediments.     

Identical reactivity of brain and erythrocyte cholinesterases of some mammals

The paper deals with a comparative study of various aspects of reactivity (substrate and inhibitor specificity, sensitivity to action of hydrophobic organophosphorus inhibitors, capability for reactivation) of cholinesterase preparations from brain, erythrocytes, and serum of a group of mammals (human, rabbit, rat, cattle, dog, and cat). It has turned out that at preservation of the species and tissue specificity, catalytic properties of the brain and erythrocyte cholinesterases of the same animal species are very close to each other.     

Cryopreservation of shoot-tips by droplet vitrification applicable to all taro (Colocasia esculenta var. esculenta) accessions

The application of the droplet vitrification cryopreservation technique to taro accessions from a range of Asia Pacific countries is presented. The optimum protocol involves excision of about 0.8 mm shoot-tips from in vitro plants, 20–40 min PVS2 exposure at 0°C followed by rapid plunge into liquid nitrogen. Thawing was done at room temperature (25°C) and shoot-tips inoculated on MS medium with 0.1 M sucrose regenerated into plantlets 4–6 weeks later. This new droplet vitrification protocol improved the mean post-thaw regeneration rates to 73–100% from 21–30% obtained with the previous cryo-vial vitrification protocol.     

Comparison of droplet digital PCR to real-time PCR for quantification of hepatitis B virus DNA

Quantitative real-time PCR (qPCR) has been widely implemented for clinical hepatitis B viral load testing, but a lack of standardization and relatively poor precision hinder its usefulness. Droplet digital PCR (ddPCR) is a promising tool that offers high precision and direct quantification. In this study, we compared the ddPCR QX100 platform by Bio-Rad with the CFX384 Touch Real-Time PCR Detection System (Bio-Rad, USA) to detect serial plasmid DNA dilutions of known concentrations as well as HBV DNA extracted from patient serum samples. Both methods showed a high degree of linearity and quantitative correlation. However, ddPCR assays generated more reproducible results and detected lower copy numbers than qPCR assays. Patient sample quantifications by ddPCR and qPCR were highly agreeable based on the Bland–Altman analysis. Collectively, our findings demonstrate that ddPCR offers improved analytical sensitivity and specificity for HBV measurements and is suitable for clinical HBV detection.     

牛磺酸对H2O2诱导的红细胞溶血率的影响

研究牛磺酸对H2O2诱导的红细胞溶血的抵抗作用的影响。实验设对照组(H2O2 生理盐水)和给药组(H2O2 牛磺酸的生理盐水溶液),将绵羊血、小鼠血、家鸡血、家兔血及人血红细胞悬液分别加入对照组和给药组,37℃水浴1h,测定吸光度,计算溶血率。结果显示,给药组的溶血率均明显低于对照组溶血率(p<0,05或p<0.01)。实验证明牛磺酸对H2O2诱导的红细胞溶血有明显的抵抗作用。     

高原低氧习服大鼠红细胞变形性的变化规律及其分子机制

目的：探讨高原低氧习服大鼠红细胞变形性的变化规律及其分子机制。方法：将健康雄性大鼠随机分为3组（n=10）：常氧对照组、急性低氧组和低氧习服组。模拟高原低氧环境对大鼠分别进行急性低氧和间断低氧习服,麻醉后心脏采血,分别测定大鼠红细胞变形性、膜流动性、膜胆固醇和总磷脂含量、膜磷脂成分的含量、红细胞ATP酶活性、红细胞内Na＋和Ca2＋浓度及建立红细胞膜蛋白质双向电泳图谱,寻找差异蛋白质点,对其进行质谱鉴定。结果：①急性低氧大鼠红细胞变形性、膜流动性、膜胆固醇和总磷脂含量、红细胞ATP酶活性均降低;红细胞内Na＋和Ca2＋浓度均增高;红细胞膜磷脂酰丝氨酸（PS）、鞘磷脂（SM）含量增加,磷脂酰胆碱（PC）含量降低;建立了红细胞膜蛋白质双向电泳图谱,选取7个差异蛋白质点,其中4个在急性低氧后表达降低。②低氧习服大鼠红细胞变形性、膜流动性、膜胆固醇和总磷脂含量、红细胞ATP酶活性明显均增高;红细胞内Na＋和Ca2＋浓度均降低;红细胞膜PS、SM含量降低,PC含量增加;上述7个差异蛋白质点中4个在低氧习服后表达增高,3个表达降低,质谱技术鉴定结果为补体结合蛋白、水通道蛋白、膜攻击复合物抑制因子、葡萄糖运载体、脂质移行酶、氨基磷脂转移酶、依赖ATP的翻转酶,其中后三个酶与红细胞膜磷脂翻转有关。结论：急性低氧引起红细胞变形性、膜流动性、膜蛋白质表达、红细胞ATP酶活性及胞内Na＋和Ca2＋浓度方面相应的改变;经低氧习服后,上述指标有所改善,低氧习服对急性低氧引起红细胞的影响具有一定的保护作用;红细胞膜上的3种蛋白质,包括脂质移行酶、氨基磷脂转移酶和依赖ATP的翻转酶在低氧习服改善红细胞变形性的机制中可能发挥重要的作用。     

Possibilities and limitations of sediment traps to measure sedimentation and resuspension

Settling flux of particulate matter measured by sediment traps in shallow and turbulent waters considerably exceeds settling flux calculated from mass balances. Theoretical consideration on sinking distance and particle settling leads to the conclusion that traps overtrap particles in even moderately turbulent waters. The disappearance of turbulent diffusion and bottom shear stress within the traps causes the high rates of trapping, whereas their presence in natural water bodies hampers sedimentation.The use of sediment traps may be restricted to the identification of rapidly sinking particles, measurement of sinking velocities of well defined types of particles, and estimation of resuspension.     

Binding of vanadate to human erythrocyte ghosts and subsequent events

Spectroscopic techniques were used to investigate the interaction between vanadate and human erythrocyte ghosts. Direct evidence from ⁵¹V nuclear magnetic resonance (NMR) studies suggested that the monomeric and polymeric vanadate species may bind to the anion binding sites of band 3 protein of the erythrocyte membrane. The results of ⁵¹V NMR studies and the quenching effect of vanadate on the intrinsic fluorescence of the membrane proteins indicated that in the low concentration range of vanadate (<0.6 mm), monomeric vanadate binds mostly to the anion sites of band 3 protein with the dissociation constant close to 0.23 mm. The experiments of sulfhydryl content titration by the method of Ellman and residue sulfhydryl-labeled fluorescence spectroscopies clearly displayed that vanadate reacts directly with sulfhydryl groups. The appearance of the anisotropic election spin resonance (ESR) signal of vanadyl suggests that a small (c. 3%) amount of vanadate was reduced by sulfhydryl groups of membrane proteins. The fluidity and order of intact ghost membrane were reduced by the reaction with vanadate, as shown by the ESR studies employing the protein- and lipid-specific spin labels. It was concluded that although vanadates mainly bind to band 3 protein, a minor part of vanadate may oxidize the residue sulfhydryl groups of membrane proteins, and thus decrease the fluidity of erythrocyte membrane.     

Interaction of lanthanum chloride with human erythrocyte membrane in relation to acetylcholinesterase activity

Lanthanum chloride (1 mM) inhibits the activity of acetylcholinesterasein vitro in the human erythrocyte membrane. Lineweaver-Burk analysis indicates that lanthanum chloride induced inhibition of acetylcholinesterase activity is competitive in nature. The Arrhenius plot shows that the transition temperature of erythrocyte membrane-bound acetylcholinesterase is significantly reduced in the presence of lanthanum chloride. These results suggest that lanthanum chloride increases the fluidity of the erythrocyte membrane and this may be a cause of inhibition of membrane-bound acetylcholinesterase activity.     

Structure- and configuration-dependent effects of C18 unsaturated fatty acids on the chicken and sheep erythrocyte membrane

High concentrations of unsaturated fatty acids are known to cause hemolysis. At low concentrations, however, unsaturated cis fatty acids have been found to protect erythrocytes against hypotonic hemolysis. In the present experiments we examined the effect of oleic (18:1), linoleic (18:2), linolenic (18:3), and elaidic (18:1) acid on the osmotic fragility of chicken and sheep erythrocytes, which markedly differ in their resistance to osmotic rupture. The results are summarized as follows: (A) The phenomenon of stabilization was observed in both species alike. (B) Interaction of cells with the fatty acids under isotonic conditions led to a persistent stabilization, i.e., the cells remained more resistant against osmolysis even after several washings. (C) Oleic and elaidic acid protected against osmotic rupture with a high degree of specificity. Linoleic and linolenic acid were much less protective. Thus, this effect appears to be specific for one double bond. (D) Contrary to the unsaturated fatty acids with cis configuration, elaidic acid with the trans configuration showed no biphasic behaviour, and even at the highest concentrations applied no hemolysis was observed.     

Activity of radiation degradation products of vitamins A and E to haemolyse erythrocyte

Exposure of vitamin A acetate in freely dissolved state to γ-radiationin vitro caused a dose dependent degradation accompanied by the formation of new products. The radiation degradation products were separated by chromatography using step gradient elution. The parent molecule, vitamin A acetate, induced negligible haemolysis of erythrocytes. In contrast, the polar products formed by irradiation were found to be potent haemolysing agents. A highly polar product, eluted with methanol revealed maximum haemolytic activity. Acetylation of these products resulted in loss of their haemolytic properties. Similarly, vitamin E acetate, a known stabilizer of the biomembranes, after irradiation yielded products which caused haemolysis of erythrocytes. It was demonstrated that irradiation introduces hydroxyl groups which impart haemolytic properties to the radiation degradation products of vitamin A     

Cell volume dependence of 1H spin-echo NMR signals in human erythrocyte suspensions: The influence of in situ field gradients

The ¹H spin-echo NMR signal amplitudes and intensities of low molecular weight solutes in the cytoplasm and extracellular fluid of suspensions of human erythrocytes were shown to depend on the osmotic pressure of the media. At low osmotic pressure (220 mosM/kg) freeze-thaw lysis of the cells resulted in signal enhancement which was greatest for extracellular molecules, but both intra- and extracellular species were almost equally enhanced at 580 mosM/kg. This effect is due to field gradients formed at cell boundaries as a result of differences in magnetic susceptibility between the medium and the cytoplasm. T₂ values measured using the Carr-Purcell-Meiboom-Gill pulse sequence, with τ = 0.0003 s, depended little on cell volume and absolute changes in volume magnetic susceptibility were also small. The mean field gradients, calculated from data obtained on cell suspensions at different osmotic pressures, were in the range 0.25–1.98 G/cm and 0.89–2.09 G/cm for intra- and extracellular compartments, respectively. The maintenance of isotonicity of the extracellular fluid during metabolic studies of cell suspensions is important in order to avoid artefacts in the determination of metabolite concentrations when using the spin-echo technique. Conversely it may be possible to perform transport measurements using spin-echo NMR to monitor the cell volume changes which occur during the transmembrane migration of molecules.     

A circular dichroism study of human erythrocyte ghost proteins during exposure to 2450 MHz microwave radiation

The effect of 2450 MHz microwave radiation on the proteins of human erythrocyte ghosts has been investigated using circular dichroism spectroscopy. A specially constructed waveguide inserted into the spectropolarimeter allowed the continuous recording of optical activity before, during and after microwave irradiation. The data indicate that high levels of microwave radiation (600 mW/g, specific absorption rate) induce decreases in α-helical conformation that may result from both thermal vibrations and increased strain on the intramolecular hydrogen bonds that maintain secondary structure. The latter effect may result from differential intramolecular interactions with the oscillating electric field. Spectrin (bands 1 and 2) isolated from the ghosts was more sensitive to microwave irradiation than intact ghosts, and spectrin-depleted vesicles were the least sensitive. The data, therefore, indicate that the α-helical conformation of spectrin is altered by high levels of microwave radiation.     

Use of a fluorescence assay to monitor the kinetics of fusion between erythrocyte ghosts,as induced by sendai virus

The kinetics of the fusion process between erythrocyte ghosts, as induced by Sendal virus, were readily revealed by a simple fluorescence procedure previously employed to characterize the fusion of viruses with biological membranes. The method relies on the relief of fluorescence selfquenching of the membrane-inserted probe octadecyl Rhodamine B chloride (R₁₈) as occurs when labeled membranes fuse with unlabeled counterparts. The kinetics of R₁₈ insertion into ghost membranes, the non-exchangeable properties of the fluorophore and the kinetics, and some characteristics of Sendai virus-induced fusion of ghosts, are described. We propose that the experimental approach may be particularly advantageous to obtain insight into the efficiency and mechanism of a wide range of fusogens, capable of inducing fusion of erythrocyte membranes.     

Net and gross sedimentation in relation to the phosphorus budget of Eau Galle Reservoir,Wisconsin

We compared P retention with direct measures of Psedimentation, estimated fromsediment cores (annual P sedimentation) and sedimenttraps (daily P sedimentation),to quantify P sedimentation in Eau Galle Reservoir,Wisconsin. Mean annual Pretention was similar to mean annual P sedimentation,as estimated from sediment corerates integrated over the entire lake basin,indicating that annual P mass balanceapproximated annual net P sedimentation in thisreservoir. However, sediment trap Prates, measured over the summer stratified period,overestimated P retention ratesdetermined over the same period, suggestingsubstantial deposition of internally-derived P.Inclusion of measured internal P loadings from avariety of sources in EauGalle Reservoir in a P mass balance only accounted foran additional 24% of thesummer sediment trap P rate, indicating substantialuncertainty in the overall P budget.Imbalances in the P budget may also suggest depositionof sediment from other as yetunquantified internal sources. Potential internalsources of P include sedimentresuspension and chemical release and direct uptake ofP from the sediment byphytoplankton.     

Binding to erythrocyte membrane glycoproteins and carbohydrate specificity of F41 fimbriae of enterotoxigenic Escherichia coli

Abstract Haemagglutination of enterotoxigenic Escherichia coli (ETEC) possessing F41 fimbriae was found to be inhibited by N -acetylgalactosamine. Other monosaccharides, such as N -acetylglucosamine, galactose and fucose were also inhibitors, although less effective than N -acetylgalactosamine. Purified F41 fimbriae bound to glycoproteins of human erythrocytes and glycophorin was found to act as an erythrocyte receptor for F41.     

Binding of fibrinogen to platelet integrin αIIbβ3 in solution as monitored by tracer sedimentation equilibrium

Fibrinogen showed essentially no binding (K_D>1 mM ) to platelet αIIbβ3 integrin in solution in the presence of Triton or octylglucoside above critical micellar concentrations. Under these conditions the integrin was an αβ monomer. After removal of the detergent from the Triton containing buffer (25 mM Tris/HCl;, 150 mM NaCl, 1 mM CaCl₂, 1 mM MgCl₂, pH 7.4) the integrin formed aggregates with hexamers as the most prominent species, as demonstrated by analytical ultracentrifugation and electron microscopy. Tracer sedimentation equilibrium experiments indicate that fibrinogen binds to the integrin aggregates, but with a surprisingly large K_D (at least 3 μM ). This value is 10- to 100-fold higher than values determined by solid phase assays or with integrins reconstituted onto lipid bilayers.