In vitro synthesis of the unit that links teichoic acid to peptidoglycan

The role of cytidine diphosphate (CDP)-glycerol in gram-positive bacteria whose walls lack poly(glycerol phosphate) was investigated. Membrane preparations from Staphylococcus aureus H, Bacillus subtilis W23, and Micrococcus sp. 2102 catalyzed the incorporation of glycerol phosphate residues from radioactive CDP-glycerol into a water-soluble polymer. In toluenized cells of Micrococcus sp. 2102, some of this product became linked to the wall. In each case, maximum incorporation of glycerol phosphate residues required the presence of the nucleotide precursors of wall teichoic acid and of uridine diphosphate-N-acetylglucosamine. In membrane preparations capable of synthesizing peptidoglycan, vancomycin caused a decrease in the incorporation of isotope from CDP-glycerol into polymer. Synthesis of the poly (glycerol phosphate) unit thus depended at an early stage on the concomitant synthesis of wall teichoic acid and later on the synthesis of peptidoglycan. It is concluded that CDP-glycerol is the biosynthetic precursor of the tri(glycerol phosphate) linkage unit between teichoic acid and peptidoglycan that has recently been characterized in S. aureus H.     

Sarcoidosis and thyrotoxicosis: A study of five patients

Regional blood flow of the gastrointestinal (GI) tract and cardiac output have been determined in male Sprague-Dawley rats weighing from 30-726 g. The cardiac output (ml/min per kg) was highest in rats weighing 80-100 g. In heavier rats the cardiac output decreased proportionally with the body weight. The gradient of blood flow to the different parts of the GI tract develops step by step. In the weaning period the blood flow (ml/min per g tissue) through the stomach was less than that through the distal parts of the GI tract. However, the blood flow through the small intestine, cecum and large intestine was uniform at this age. In rats weighing 80-100 g the blood flow through both the cecum and large intestine was less than that through the small intestine. The gradient in blood flow through the various segments of small intestine developed last.     

Microbiological results from milk samples obtained premilking and postmilking for the diagnosis of bovine intramammary infections.

Bacteriological culture results were compared between 336 pairs of quarter milk samples collected premilking and postmilking. Using a positive result on either premilking or postmilking samples as the definitive diagnosis, premilking sampling sensitivity was 91% for Staphylococcus aureus, 91% for coagulase-negative staphylococci, and 97% for Streptococcus other than agalactiae. Postmilking sampling sensitivities were 81, 45, and 58%, respectively, for the same pathogens. Requiring both premilking and postmilking samples for the definitive diagnosis, specificities were 92, 86, and 95% for premilking sampling alone and 96, 98, and 99% for postmilking sampling alone. Such differences in specificity would result in major differences in predictive value of a positive culture for herds with a low prevalence. Multiple isolates were significantly more common from premilking samples.     

Lysine‐241 Has a Role in Coupling 2OG Turnover with Substrate Oxidation During KDM4‐Catalysed Histone Demethylation

The JmjC histone lysyl demethylases (KDMs) play important roles in modulating histone methylation states and have the potential to be regulated by oxygen availability. Lys241 of the KDM4 subfamily is proposed to be important in oxygen binding by KDM4A. We report evidence that, although Lys241 is unlikely to be directly involved in oxygen binding, it has an important role in coupling 2‐oxoglutarate cosubstrate oxidation with lysine demethylase activity. The results suggest that compounds promoting the uncoupling of substrate oxidation are of interest as JmjC‐KDM inhibitors.     

Numerical simulation of dilute turbulent gas‐particle flow with turbulence modulation

A numerical study of a dilute turbulent gas‐particle flow with inelastic collisions and turbulence modulation in an Eulerian framework is described. A new interpretation is provided for the interaction/coupling terms, based on a fluctuating energy transfer mechanism. This interpretation provides for a new robust closure model for the interaction terms with the ability to predict the turbulence dampening as well as the turbulence enhancement phenomenon. Further, the model developed herein is investigated along with a variety of other published closure models used for the interaction/coupling terms, particle drag, and solid stress. The models are evaluated against several sets of benchmark experiments for fully‐developed, turbulent gas‐solid flow in a vertical pipe. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Influence of normal contact force model on simulations of spherocylindrical particles

How the choice of elastic normal contact force model affects predictions from discrete element method simulations of spherocylindrical particles is investigated in this article. Three force models were investigated: (1) a Hertzian force model (HFM) which assumes a circular contact area; (2) a linear force model (LFM) with a constant stiffness; and (3) a modified HFM (MFM) that accounts for various contact areas and contact transitions. With the MFM, transitions between contact area types must be accounted for otherwise discontinuities in the contact force can occur. It is found that simple force models (HFM, LFM) can be substituted for more accurate force models if only force data and bulk properties are of interest. However, if more detailed contact information, such as contact area, contact overlap, contact duration, or collision frequency, are needed, for example, in population balance models and transient liquid bridge modeling, then a more accurate force model should be used. © 2018 American Institute of Chemical Engineers AIChE J, 64: 1986–2001, 2018     

Analysis of dichotomous outcome data for community intervention studies

Community intervention trials are becoming increasingly popular as a tool for evaluating the effectiveness of health education and intervention strategies. Typically, units such as households, schools, towns, counties, are randomized to receive either intervention or control, then outcomes are measured on individuals within each of the units of randomization. It is well recognized that the design and analysis of such studies must account for the clustering of subjects within the units of randomization. Furthermore, there are usually both subject level and cluster level covariates that must be considered in the modelling process. While suitable methods are available for continuous outcomes, data analysis is more complicated when dichotomous outcomes are measured on each subject. This paper will compare and contrast several of the available methods that can be applied in such settings, including random effects models, generalized estimating equations and methods based on the calculation of 'design effects', as implemented in the computer package SUDAAN. For completeness, the paper will also compare these methods of analysis with more simplistic approaches based on the summary statistics. All the methods will be applied to a case study based on an adolescent anti-smoking intervention in Australia. The paper concludes with some general discussion and recommendations for routine design and analysis.     

Modeling granular segregation in flow from quasi-three-dimensional, wedge-shaped hoppers

Granular materials may segregate upon processing and handling based on differences in particle properties such as size, density, or shape. In most instances, this segregation is problematic in that product quality is usually dependent on maintaining homogeneity of the blend. The present work investigates the causes and extent of segregation of granular materials during discharge from a hopper using the discrete element method. A quasi-three-dimensional, wedge-shaped hopper is modeled using two parallel periodic boundary conditions. The effects of various particle properties, such as diameter ratio, mean size, and mass fraction of each species, as well as hopper geometries, such as the height, width, outlet width, and wall angle, on the segregation results are examined. Additionally, the effects of friction coefficient and hopper fill methods are investigated. Results show that many factors affect the extent of segregation during hopper discharge, but some of the key factors include the particle diameter ratio, mass fraction, and ratio of hopper outlet to mean particle diameter as well as the hopper wall angle and wall roughness. Additionally, the method used to fill the hopper is shown to play a significant role in determining the segregation upon discharge. Visualization of the internal hopper flow patterns gives insight into the causes of segregation, which then aids in the proposal of various recommendations for reducing the extent of segregation during hopper discharge.     

Action of lysozyme and nisin mixtures against lactic acid bacteria

Lysozyme was formulated together with nisin for usage against food spoilage lactobacilli. The mixtures demonstrated improved minimal inhibitory concentrations (MIC), compared to the parent compounds, for many of the bacteria and media tested, including high salt media in which lysozyme lost virtually all of its activity. Synergy was also observed through measurement of the kinetics of bacterial killing of L. curvatus 845, in which strain synergy had been observed in MIC assays. The combination of lysozyme and nisin caused more severe cell damage as viewed by scanning electron microscopy, and a consequent change in optical density at 600 nm, compared to the parent compounds, effects that were presumed to reflect the action of lysozyme. In addition, the combination caused more rapid permeabilization (depolarization) of the cytoplasmic membranes of Staphylococcus aureus, an effect that reflected the mechanism of action of nisin. Thus, nisin and lysozyme appear to demonstrate synergy against gram-positive bacteria because they reinforce each others mechanisms of bacterial killing.