Increased diet viscosity by oat β-glucans decreases the passage rate of liquids in the stomach and affects digesta physicochemical properties in growing pigs

Rheological properties of digesta play a role in digesta passage kinetics through the gastrointestinal tract, in turn affecting nutrient absorption kinetics. Therefore, we studied the effects of diet viscosity on digesta passage and physicochemical properties in pigs. Twenty male growing pigs (35 kg body weight at the start) were assigned to one of five diets with increasing dietary concentrations of β-glucans (BG; from 0 % to 10 %), in exchange for maize starch. After a 17-day adaptation period, pigs were euthanised and the mean retention time (MRT) of digesta solids (TiO₂) and liquids (Cr-EDTA) in the stomach, and proximal and distal half of the small intestine was quantified. In the stomach, the MRT of liquids, but not of solids, increased when dietary BG level increased (6 min per % dietary BG, P = 0.008 and R² = 0.35). Concomitantly, stomach DM content (5 g/kg per % dietary BG, P < 0.001 and R² = 0.53) and apparent digesta viscosity (56 Pa × s at 1/s shear rate per % dietary BG, P = 0.003 and R² = 0.41) decreased. In the proximal half of the small intestine, no effects of dietary BG level were observed. In the distal half of the small intestine, water-binding capacity (WBC) of digesta increased (0.11 g/g digesta DM per % dietary BG, P = 0.028 and R² = 0.24) and starch digestibility decreased (0.3% per % dietary BG, P = 0.034 and R² = 0.23) when dietary BG level increased. In the colon, apparent digesta viscosity at 45/s shear rate increased (0.1 Pa × s per % dietary BG, P = 0.03 and R² = 0.24) in the proximal half of the colon, and digesta WBC increased (0.06 g/g digesta DM per % dietary BG, P = 0.024 and R² = 0.26) in the distal half of the colon when dietary BG level increased. To conclude, increasing dietary BG level caused the MRT of liquids, but not that of solids, to increase in the stomach, resulting in reduced separation of the solid and liquid digesta fractions. This caused dilution of the stomach content and reduction in digesta viscosity when dietary BG levels increased. Effects of dietary BG level on physicochemical properties in the proximal small intestine were absent and may have been due to a low DM content. The WBC of digesta in the distal small intestine and colon increased when dietary BG level increased, as did apparent digesta viscosity in the proximal colon. This likely reflects the concentration of BG in digesta when moving through the gastrointestinal tract.     

The Rheology of Liquid Pentane Isomers by Non-Equilibrium Molecular Dynamics Simulations

Abstract

In this paper, non-equilibrium molecular dynamics (NEMD) simulations of planar Couette flow are reported for an expanded collapsed atom model for liquid pentane isomers at 273.15 K. The strain rate dependent viscosity for liquid pentane isomers exhibits shear-thinning and a linear dependence on γ^1/2. Newtonian viscosities for liquid pentane isomers obtained by a linear extrapolation to zero strain rate are: 0.256cP for normal pentane, 0.219cP for isopentane, and 0.168cP for neopentane. The strain rate dependent pressure difference and normal stress difference vary nearly linearly with the γ^3/2 law and the γ law, respectively, for all three liquid pentane isomers. The overall trend of the square of radius of gyration and end-to-end distance for normal pentane is a linear increase with strain rate. For isopentane, the trend hardly changes for the range of shear rate in this study. The alignment angle decreases with increasing strain rate and the alignment angle of the straight chain alkane is less than that of the branched chain alkane. The average percentage of C?C?C?C trans for normal pentane as a function of strain rate is in excellent correlation with the square of the radius of gyration and the average end-to-end distance. Applying the strain rate in the x-direction, the alignment angle is forced to decrease and the percentage of C?C?C?C trans increases with increasing strain rate.     

Visualizing Cytoplasmic Flow During Single-cell Wound Healing in Stentor coeruleus

Although wound-healing is often addressed at the level of whole tissues, in many cases individual cells are able to heal wounds within themselves, repairing broken cell membrane before the cellular contents leak out. The giant unicellular organism Stentor coeruleus, in which cells can be more than one millimeter in size, have been a classical model organism for studying wound healing in single cells. Stentor cells can be cut in half without loss of viability, and can even be cut and grafted together. But this high tolerance to cutting raises the question of why the cytoplasm does not simply flow out from the size of the cut. Here we present a method for cutting Stentor cells while simultaneously imaging the movement of cytoplasm in the vicinity of the cut at high spatial and temporal resolution. The key to our method is to use a "double decker" microscope configuration in which the surgery is performed under a dissecting microscope focused on a chamber that is simultaneously viewed from below at high resolution using an inverted microscope with a high NA lens. This setup allows a high level of control over the surgical procedure while still permitting high resolution tracking of cytoplasm.     

丹参多酚酮酸盐对老年急性缺血性脑卒中患者血清hs-CRP、血液流变学及神经功能的影响

目的:观察丹参多酚酮酸盐对老年急性缺血性脑卒中患者血清超敏C反应蛋白(hs-CRP)、血液流变学及神经功能的影响。方法:将98例老年急性缺血性脑卒中患者随机分观察组(n=49例)和对照组(n=49例),对照组给以西医常规治疗,观察组在常规治疗的基础上加用丹参多酚酮酸盐治疗,两组均治疗2周;记录两组治疗前后的血液流变学相关指标、血清hs-CRP、分析NIHSS评分与Barthel指数评分的变化。结果:治疗2周后,观察组血浆黏度、全血黏度高切、全血黏度低切、红细胞比积均低于对照组(P0.05),其降低的幅度亦低于对照组(P0.05);观察组治疗后1周、2周血清hs-CRP水平、白细胞计数(WBC)、NIHSS评分明显低于对照组,而Barthel指数评分高于对照组(P0.05)。结论:丹参多酚酮酸盐能够有效降低急性缺血性脑卒中患者炎症水平、调节患者血液流变学指标、从而改善神经功能,有利于卒中患者的预后。     

Actin Mechanics and Fragmentation

Cell physiological processes require the regulation and coordination of both mechanical and dynamical properties of the actin cytoskeleton. Here we review recent advances in understanding the mechanical properties and stability of actin filaments and how these properties are manifested at larger (network) length scales. We discuss how forces can influence local biochemical interactions, resulting in the formation of mechanically sensitive dynamic steady states. Understanding the regulation of such force-activated chemistries and dynamic steady states reflects an important challenge for future work that will provide valuable insights as to how the actin cytoskeleton engenders mechanoresponsiveness of living cells.     

Circular Dichroism of Trimethylsilyl Derivatives of Aldonic Acid-γ-lactones and the Influences of the Cα Substituent and Ring Conformations on the Sign and the Magnitude

Circular dichroism of trimethylsilyl (TMS) derivatives of seven aldonic acid-γ-lactones were studied. As well as original sugar-γ-lactones the sign of the Cotton effect was determined by the C–2 configuration. The magnitude of CD peak was found to be related with the ring geometry. It leads to a conclusion that the observed molecular elipticities may be the sum of two effects; one effect of configuration at C–2 and the other effect of ring geometry. If these two effects are of the same sign, they overlap each other and give a strong CD peak. When the sign of these effects are opposite, they cancel each other and hence give a weak CD peak. Between the two effects, when C–2 substituent is OH or OTMS, the effect of configuration at C–2 is stronger than that of ring geometry.     

Growth of Filamentous Fungi in Submerged Culture: Problems and Possible Solutions

ABSTRACT:?

Filamentous fungi are important organisms industrially and continue to attract research interest as microbiologists attempt to overcome the problems associated with their behavior in submerged culture. This review critically examines the literature describing these problems and where available suggests possible solutions to them. The influence of the chemical and physical environment on culture morphology, the process engineering challenges presented by different fungal morphologies, and the relationship between fungal morphology and metabolite production are all discussed.     

The Tetracycline Fermentation and Its Regulation

Abstract

The β-glucans different from cellulose are the most abundant class of polysaccharides. They are found in microorganisms and higher plants as structural entities of cell wall, as cytoplasmic and vacuolar reserve materials, and as extracellular substances. Enzyme systems capable to hydrolyze β-glucans are produced by different microorganisms. The occurrence and nature of β-glucanases and their substrates are reviewed. The regulation of biosynthesis of these enzymes, their properties, substrate and product specificities, mode of action and molecular cloning are described. The participation of β-glucanases in the morphogenetic events of yeast cell is presented. The role and synergism of different types of 1,3-β-glucanases in microbial cell wall lysis and the potential application for isolation of intracellular materials like proteins, carbohydrates, enzymes and as an analytical tool are discussed in the light of current knowledge.     

Assessment and significance of protein–protein interactions during development of protein biopharmaceuticals

Early development of protein biotherapeutics using recombinant DNA technology involved progress in the areas of cloning, screening, expression and recovery/purification. As the biotechnology industry matured, resulting in marketed products, a greater emphasis was placed on development of formulations and delivery systems requiring a better understanding of the chemical and physical properties of newly developed protein drugs. Biophysical techniques such as analytical ultracentrifugation, dynamic and static light scattering, and circular dichroism were used to study protein–protein interactions during various stages of development of protein therapeutics. These studies included investigation of protein self-association in many of the early development projects including analysis of highly glycosylated proteins expressed in mammalian CHO cell cultures. Assessment of protein–protein interactions during development of an IgG1 monoclonal antibody that binds to IgE were important in understanding the pharmacokinetics and dosing for this important biotherapeutic used to treat severe allergic IgE-mediated asthma. These studies were extended to the investigation of monoclonal antibody–antigen interactions in human serum using the fluorescent detection system of the analytical ultracentrifuge. Analysis by sedimentation velocity analytical ultracentrifugation was also used to investigate competitive binding to monoclonal antibody targets. Recent development of high concentration protein formulations for subcutaneous administration of therapeutics posed challenges, which resulted in the use of dynamic and static light scattering, and preparative analytical ultracentrifugation to understand the self-association and rheological properties of concentrated monoclonal antibody solutions.