Enhanced trehalose production improves growth of Escherichia coli under osmotic stress

The biosynthesis of trehalose has been previously shown to serve as an important osmoprotectant and stress protectant in Escherichia coli. Our results indicate that overproduction of trehalose (integrated lacI-Ptac-otsBA) above the level produced by the native regulatory system can be used to increase the growth of E. coli in M9-2% glucose medium at 37 degrees C to 41 degrees C and to increase growth at 37 degrees C in the presence of a variety of osmotic-stress agents (hexose sugars, inorganic salts, and pyruvate). Smaller improvements were noted with xylose and some fermentation products (ethanol and pyruvate). Based on these results, overproduction of trehalose may be a useful trait to include in biocatalysts engineered for commodity chemicals.     

Classification of the extracellular fields produced by activated neural structures

Background  

Classifying the types of extracellular potentials recorded when neural structures are activated is an important component in understanding nerve pathophysiology. Varying definitions and approaches to understanding the factors that influence the potentials recorded during neural activity have made this issue complex.     

Ovarian aging and menopause: current theories, hypotheses, and research models

Aging of the reproductive system has been studied in numerous vertebrate species. Although there are wide variations in reproductive strategies and hormone cycle components, many of the fundamental changes that occur during aging are similar. Evolutionary hypotheses attempt to explain why menopause occurs, whereas cellular hypotheses attempt to explain how it occurs. It is commonly believed that a disruption in the hypothalamic-pituitary-gonadal axis is responsible for the onset of menopause. Data exist to demonstrate that the first signs of menopause occur at the level of the brain or the ovary. Thus, finding an appropriate and representative animal model is especially important for the advancement of menopause research. In primates, there is a gradual decline in the function of the hypothalamic-pituitary-gonadal (HPG) axis ultimately resulting in irregularities in menstrual cycles and increasingly sporadic incidence of ovulation. Rodents also exhibit a progressive deterioration in HPG axis function; however, they also experience a period of constant estrus accompanied by intermittent ovulations, reduced progesterone levels, and elevated circulating estradiol levels. It is remarkable to observe that females of other classes also demonstrate deterioration in HPG axis function and ovarian failure. Comparisons of aging in various taxa provide insight into fundamental biological mechanisms of aging that could underlie reproductive decline.     

Gastric and thymic assay of acute oral treatment of rats with nitric oxide esters of ibuprofen or indomethacin

Two common non-steroidal anti-inflammatory drugs (NSAIDs) and their nitric oxide (NO) adducts were evaluated for effects on stomach and thymus. Following 4-h duration (acute) oral dosing of fasted male Wistar rats, 1.33 x 10(-4)mol/kg of ibuprofen caused significant visual irritation score and microscopic thinning, although an ulceration assay proved insensitive. Ibuprofen esterified with NO abolished irritation and significantly reduced thinning. Gastro-protective effects of NO-linked ibuprofen were associated with higher levels of diaphorase by optical density, an enzymatic marker of local synthesis of nitric oxide. Both indomethacin and its congener at 2 x 10(-5)mol/kg produced microscopic signs of thinning only, not visible irritation or alteration of diaphorase staining. Results suggest that NO-linked ibuprofen can promote resistance to mucosal injury, possibly via local synthesis of NO. All NO-congeners and parent NSAIDs produced comparable reductions in the abundance of medullary nitrergic cells, those synthesising NO in thymus, without significantly lowering T-cellularity, the relative size of cortex wherein T-cells are produced. Findings indicate disturbance of T-cell tolerance, consistent with increased risk of autoimmune susceptibility.     

A novel anti-oxidant and anti-cancer strategy: a peptoid anti-inflammatory drug conjugate with SOD mimic activity

Activation of reactive oxygen and nitrogen species (RONS) by redox-active metal ions has been proposed to contribute to oxidative damage in inflamed tissues. Here, we report a dual-function anti-oxidant conjugate comprising an anti-inflammatory agent (5-aminosalicylic acid) and a chelator with potential as a superoxide dismutase mimic. The conjugate ethylenediaminetetraacetic acid bis-(5-aminosalicylic acid methyl ester) [EBAME] chelates Cu(II) ions in a 1:1 ratio, as assessed spectrophotometrically using Job's method. Superoxide dismutase (SOD) activity was determined for the Mn(II)-conjugate as 0.758+/-0.130 U at a concentration of 0.99 microM. In inflamed tissues, peptidase mediated release of active 5-ASA would also release the EDTA chelator which has significant SOD mimic activity when complexed to Cu(II) ions. Thus, EBAME has potential as a dual-function anti-inflammatory agent with reduced gastric irritability.     

Isolation of recombinant proteins from culture broth by co‐precipitation with an amino acid carrier to form stable dry powders

Protein‐coated microcrystals can be generated by co‐precipitation of protein and a water‐soluble crystalline carrier by addition to excess water miscible organic solvent. We have investigated this novel process for its utility in the concentration and partial purification of a recombinant protein exported into the culture broth during expression by Pichia pastoris. Co‐precipitation with a L ‐glutamine carrier selectively isolated the protein content of the culture broth, with a minimal number of steps, and simultaneously removed contaminants including a novel yeast metabolite. This pigment co‐elutes during aqueous chromatography but its elucidation as a benzoylated glycosamine suggested a simple route of removal by partition during the co‐precipitation process. Scale‐up of the process was readily achieved through in‐line mixing and subsequent reconstitution of the dried protein‐coated microcrystals yielded natively folded, bioactive protein. Additional washing of the crystals with saturated L ‐glutamine facilitated further purification of the recombinant protein immobilized on the L ‐glutamine carrier. Thus, we present a novel method for the harvesting of recombinant protein from culture broth as a dry powder, which may be of general applicability to bioprocessing. Biotechnol. Bioeng. 2010;106: 764–773. © 2010 Wiley Periodicals, Inc.     

Engineering Escherichia coli for xylitol production from glucose-xylose mixtures

The range of value-added chemicals produced by Escherichia coli from simple sugars has been expanded to include xylitol. This was accomplished by screening the in vivo activity of a number of heterologous xylitol-producing enzymes. Xylose reductases from Candida boidinii (CbXR), Candida tenuis (CtXR), Pichia stipitis (PsXR), and Saccharmoyces cerivisiae (ScXR), and xylitol dehydrogenases from Gluconobacter oxydans (GoXDH) and Pichia stipitis (PsXDH) were all functional in E. coli to varying extents. Replacement of E. coli's native cyclic AMP receptor protein (CRP) with a cyclic AMP-independent mutant (CRP*) facilitated xylose uptake and xylitol production from mixtures of glucose and xylose, with glucose serving as the growth substrate and source of reducing equivalents. Of the enzymes tested, overexpression of NADPH-dependent CbXR produced the highest concentrations of xylitol in shake-flask cultures (approximately 275 mM in LB cultures, approximately 180 mM using minimal medium). Expression of CbXR in strain PC09 (crp*, DeltaxylB) in a 10-L controlled fermentation containing minimal medium resulted in production of approximately 250 mM xylitol (38 g/L), with concomitant utilization of approximately 150 mM glucose. The ratio of moles xylitol produced (from xylose) per mole glucose consumed was improved to > 3.7:1 using metabolically active "resting" cells.