Performance of batch membrane reactor: Glycerol-3-phosphate synthesis coupled with adenosine triphosphate regeneration.

Glycerol-3-phosphate (G3P) was synthesized from glycerol using glycerol kinase (GK). This reaction requires adenosine triphosphate (ATP) and was coupled with the ATP regeneration reaction using acetate kinase (AK) in a batch-operated ultrafiltration hollow-fiber reactor. By taking into consideration the dynamic nature of the bioreactor performance under non-steady-state conditions, a model for the performance of a batch membrane reactor for G3P synthesis coupled with ATP regeneration was developed and studied. The simulation results showed good agreement with the experimental results. The simulation studies have provided some insight into the process dynamics of the coupled reactions in the reactor system studied. For the reactor operational model used, in which the enzymes are retained in the shell side and the substrates are also initially placed in the shell side, it was found that the substrate concentration in the lumen side increased to a level higher than that in the shell side, and a backdiffusion occurred from the lumen side to the shell side during reactor operation. The ratio of the reaction rate to diffusion rate goes through a sharp peak during the time that the direction of diffusion is reversed. For another reactor operational model, in which the substrates were initially placed in the lumen side and enzymes were retained in the shell side, it was found that the rate-controlling step between the reaction and diffusion was switched during the reactor operation. Initially, the reaction rate increased while the diffusion rate was high and the substrate concentrations increased in the shell side. The ratio of reaction rate to diffusion rate increased to a maximum and remained at a constant level as the diffusion rate decreased to a low level due to the nonlinear characteristics of mass transfer process. This study provides information that is useful for optimization of batch membrane enzyme reactor operation and for a fed-batch-type process with an intermittent feeding strategy for efficient use of substrates.     

Changes in various plasma lipid components, glucose, and insulin in Spermophilus lateralis during hibernation

This study evaluated fat mobilization as related to gluconeogenesis in two age groups of hibernating golden-mantled ground squirrels (Spermophilus lateralis). Our experimental group consisted of a total of 16 male and 15 female squirrels. Plasma samples were collected from selected animals being killed weekly from January to March, and the concentration of triglycerides, glycerol (GY), free fatty acids (FFA), total cholesterol, lipase activity, glucose, and insulin, were determined by biochemical assays and radioimmunoassay. Our results showed a mean FFA/GY ratio of five, which was higher than the predicted value of three, suggesting a significant depletion of GY and an enhanced rate of gluconeogenesis via GY to maintain glucose homeostasis in the hibernating animals. The factor of age did not significantly affect plasma lipid components. However, in the male group, plasma glucose levels were significantly higher for adults than for juveniles. Overall, females had significantly higher plasma glucose levels than males (150 ± 11 vs. 110 ± 8 mg%, P < 0.05). In the adult group, a gender influence was also seen on plasma insulin levels, with females' being higher than males' (66 ± 13 vs. 25 ± 3 μIU/ml, P < 0.01). We suggest that during hibernation, female squirrels may have a higher rate of lipolysis and gluconeogenesis along with a lower glucose utilization than their male counterparts. Additionally, adult females may exhibit a higher peripheral insulin resistance during hibernation than adult males, a possibility which merits further study.     

The ionic basis of electrical activity in embryonic cardiac muscle

The intracellular sodium concentration reported for young, embryonic chick hearts is extremely high and decreases progressively throughout the embryonic period, reaching a value of 43 mM immediately before hatching. This observation suggested that the ionic basis for excitation in embryonic chick heart may differ from that responsible for electrical activity of the adult organ. This hypothesis was tested by recording transmembrane resting and action potentials on hearts isolated from 6-day and 19-day chick embryos and varying the extracellular sodium and potassium concentrations. The results show that for both young and old embryonic cardiac cells the resting potential depends primarily on the extracellular potassium concentration and the amplitude and rate of rise of the action potential depend primarily on the extracellular sodium concentration.     

Selective single cell isolation for genomics using microraft arrays

Genomic methods are used increasingly to interrogate the individual cells that compose specific tissues. However, current methods for single cell isolation struggle to phenotypically differentiate specific cells in a heterogeneous population and rely primarily on the use of fluorescent markers. Many cellular phenotypes of interest are too complex to be measured by this approach, making it difficult to connect genotype and phenotype at the level of individual cells. Here we demonstrate that microraft arrays, which are arrays containing thousands of individual cell culture sites, can be used to select single cells based on a variety of phenotypes, such as cell surface markers, cell proliferation and drug response. We then show that a common genomic procedure, RNA-seq, can be readily adapted to the single cells isolated from these rafts. We show that data generated using microrafts and our modified RNA-seq protocol compared favorably with the Fluidigm C1. We then used microraft arrays to select pancreatic cancer cells that proliferate in spite of cytotoxic drug treatment. Our single cell RNA-seq data identified several expected and novel gene expression changes associated with early drug resistance.     

Molecular Characterization of Ethylene Response Sensor 1 (BoERS1) in <Emphasis Type="Italic">Bambusa oldhamii</Emphasis>

An ethylene receptor gene named BoERS1 was cloned from a bamboo (Bambusa oldhamii) cDNA library. The open reading frame of BoERS1 was 1,899 bp and encoded a 632-amino acid protein, which contains the five conserved motifs (H, N, G1, F, and G2 boxes) of the bacterial two-component system histidine kinases and shows high sequence similarity with other ethylene receptors in plants, such as rice and maize. Expression of BoERS1 in bamboo shoots increased with the growth of the emerging shoots. In an in vitro kinase assay, the expressed histidine kinase domain of BoERS1 (BHK) was phosphorylated in the presence of Mn²⁺, and LC-ESI-MS/MS analysis showed that four amino acids, namely T442, S444, S489, and S503, were phosphorylated. It is interesting to note that S489 and S503 are located in a loop region (L1) that is found only in plant histidine kinase-containing enzymes. The identification of multiple phosphorylation sites on BoERS1 provides a new avenue for future structure–function studies of the ethylene receptor protein family.     

SH3‐like motif‐containing C‐terminal domain of staphylococcal teichoic acid transporter suggests possible function

The negatively charged bacterial polysaccharides—wall teichoic acids (WTAs) are synthesized intracellularly and exported by a two‐component transporter, TagGH, comprising a transmembrane subunit TagG and an ATPase subunit TagH. We determined the crystal structure of the C‐terminal domain of TagH (TagH‐C) to investigate its function. The structure shows an N‐terminal SH3‐like subdomain wrapped by a C‐terminal subdomain with an anti‐parallel β‐sheet and an outer shell of α‐helices. A stretch of positively charged surface across the subdomain interface is flanked by two negatively charged regions, suggesting a potential binding site for negatively charged polymers, such as WTAs or acidic peptide chains. Proteins 2016; 84:1328–1332. © 2016 Wiley Periodicals, Inc.     

In Vivo Neurochemical Characterization of Developing Guinea Pigs and the Effect of Chronic Fetal Hypoxia

Neurochemical Research - The guinea pig is a frequently used animal model for human pregnancy complications, such as oxygen deprivation or hypoxia, which result in altered brain development. To...