Morphology of bakers' yeast and dissolved oxygen saturation during fed-batch growth

By complementary use of freeze-etching and scanning electron microscopy techniques, the morphology of cytoplasmic membrane and mitochondria of bakers' yeast ( Saccharomyces cerevisiae ) was shown to be sensitive to momentary lack of dissolved oxygen in fed-batch growth medium. Cells grown under constant excess oxygenation had more invaginations on their cytoplasmic membranes and showed larger mitochondria as assessed from the dimensions of their giant mitochondria.     

Protection of Recombinant Mammalian Antibodies from Development-Dependent Proteolysis in Leaves of Nicotiana benthamiana

The expression of clinically useful proteins in plants has been bolstered by the development of high-yielding systems for transient protein expression using agroinfiltration. There is a need now to know more about how host plant development and metabolism influence the quantity and quality of recombinant proteins. Endogenous proteolysis is a key determinant of the stability and yield of recombinant proteins in plants. Here we characterised cysteine (C1A) and aspartate (A1) protease profiles in leaves of the widely used expression host Nicotiana benthamiana, in relation with the production of a murine IgG, C5-1, targeted to the cell secretory pathway. Agroinfiltration significantly altered the distribution of C1A and A1 proteases along the leaf age gradient, with a correlation between leaf age and the level of proteolysis in whole-cell and apoplast protein extracts. The co-expression of tomato cystatin SlCYS8, an inhibitor of C1A proteases, alongside C5-1 increased antibody yield by nearly 40% after the usual 6-days incubation period, up to ∼3 mg per plant. No positive effect of SlCYS8 was observed in oldest leaves, in line with an increased level of C1A protease activity and a very low expression rate of the inhibitor. By contrast, C5-1 yield was greater by an additional 40% following 8- to 10-days incubations in younger leaves, where high SlCYS8 expression was maintained. These findings confirm that the co-expression of recombinant protease inhibitors is a promising strategy for increasing recombinant protein yields in plants, but that further opportunity exists to improve this approach by addressing the influence of leaf age and proteases of other classes.     

Species traits dictate seasonal-dependent responses of octocoral–algal symbioses to elevated temperature and ultraviolet radiation

Coral Reefs - Ultraviolet radiation (UVR) can exacerbate the effects of elevated seawater temperatures concomitant with climate change. Such stressors can collapse the mutualism of scleractinian...     

Spaceflight suppresses exercise-induced release of bioassayable growth hormone.

We have reported that bed rest suppressed the release of bioassayable growth hormone (BGH) that normally occurs after an acute bout of unilateral plantar flexor exercise (G. E. McCall, C. Goulet, R. E. Grindeland, J. A. Hodgson, A. J. Bigbee, and V. R. Edgerton. J. Appl. Physiol. 83: 2086-2090, 1997). In the present study, the effects of spaceflight on the hormonal responses to this exercise protocol were examined. Four male astronauts on the National Aeronautics and Space Administration Shuttle Transport System (STS-78) mission completed the exercise protocol before, during, and after a 17-day spaceflight. The maximal voluntary contraction torque output at the onset of exercise was similar on all test days. Before spaceflight, plasma BGH increased 114-168% from pre- to postexercise. During spaceflight and after 2 days recovery at normal gravity (1 G), the BGH response to exercise was absent. After 4 days of recovery, this response was restored. Plasma concentrations of immunoassayable growth hormone were similar at all time points. The preexercise plasma immunoassayable insulin-like growth factor I (IGF-I) levels were elevated after 12 or 13 days of microgravity, and a approximately 7% postexercise IGF-I increase was independent of this spaceflight effect. The suppression of the BGH response to exercise during spaceflight indicates that some minimum level of chronic neuromuscular activity and/or loading is necessary to maintain a normal exercise-induced BGH release. Moreover, these results suggest that there is a muscle afferent-pituitary axis that can modulate BGH release.     

Repeatability and correlation of physiological traits: Do ectotherms have a “thermal type”?

Across a range of taxa, individuals within a species differ in suites of correlated traits. These trait complexes, known as syndromes, can have dramatic evolutionary consequences as they do not evolve independently but rather as a unit. Current research focuses primarily on syndromes relating to aspects of behavior and life history. What is less clear is whether physiological traits also form a syndrome. We measured 10 thermal traits in the delicate skink, Lampropholis delicata, to test this idea. Repeatability was calculated and their across‐context correlations evaluated. Our results were in alignment with our predictions in that individual thermal traits varied consistently and were structured into a physiological syndrome, which we are referring to as the thermal behavior syndrome (TBS). Within this syndrome, lizards exhibited a “thermal type” with each being ranked along a cold–hot continuum. Hot types had faster sprint speeds and higher preferred body temperatures, whereas the opposite was true for cold types. We conclude that physiological traits may evolve as a single unit driven by the need to maintain optimal temperatures that enable fitness‐related behaviors to be maximized.     

Tubers from potato lines expressing a tomato Kunitz protease inhibitor are substantially equivalent to parental and transgenic controls

Recombinant protease inhibitors represent useful tools for the development of insect‐resistant transgenic crops, but questions have been raised in recent years about the impact of these proteins on endogenous proteases and chemical composition of derived food products. In this study, we performed a detailed compositional analysis of tubers from potato lines expressing the broad‐spectrum inhibitor of Ser and Asp proteases, tomato cathepsin D inhibitor (SlCDI), to detect possible unintended effects on tuber composition. A compositional analysis of key nutrients and toxic chemicals was carried out with tubers of SlCDI‐expressing and control (comparator) lines, followed by a two‐dimensional gel electrophoresis (2‐DE) proteomic profiling of total and allergenic proteins to detect eventual effects at the proteome level. No significant differences were observed among control and SlCDI‐expressing lines for most chemicals assayed, in line with the very low abundance of SlCDI in tubers. Likewise, proteins detected after 2‐DE showed no quantitative variation among the lines, except for a few proteins in some control and test lines, independent of slcdi transgene expression. Components of the patatin storage protein complex and Kunitz protease inhibitors immunodetected after 2‐DE showed unaltered deposition patterns in SlCDI‐expressing lines, clearly suggesting a null impact of slcdi on the intrinsic allergenic potential of potato tubers. These data suggest, overall, a null impact of slcdi expression on tuber composition and substantial equivalence between comparator and SlCDI‐expressing tubers despite reported effects on leaf protein catabolism. They also illustrate the usefulness of proteomics as a tool to assess the authenticity of foods derived from novel‐generation transgenic plants.     

DMF inhibits PDGF-BB induced airway smooth muscle cell proliferation through induction of heme-oxygenase-1

Background

Airway wall remodelling is an important pathology of asthma. Growth factor induced airway smooth muscle cell (ASMC) proliferation is thought to be the major cause of airway wall thickening in asthma. Earlier we reported that Dimethylfumarate (DMF) inhibits platelet-derived growth factor (PDGF)-BB induced mitogen and stress activated kinase (MSK)-1 and CREB activity as well as IL-6 secretion by ASMC. In addition, DMF altered intracellular glutathione levels and thereby reduced proliferation of other cell types.

Methods

We investigated the effect of DMF on PDGF-BB induced ASMC proliferation, on mitogen activated protein kinase (MAPK) activation; and on heme oxygenase (HO)-1 expression. ASMC were pre-incubated for 1 hour with DMF and/or glutathione ethylester (GSH-OEt), SB203580, hemin, cobalt-protoporphyrin (CoPP), or siRNA specific to HO-1 before stimulation with PDGF-BB (10 ng/ml).

Results

PDGF-BB induced ASMC proliferation was inhibited in a dose-dependant manner by DMF. PDGF-BB induced the phosphorylation of ERK1/2 and p38 MAPK, but not of JNK. DMF enhanced the PDGF-BB induced phosphorylation of p38 MAPK and there by up-regulated the expression of HO-1. HO-1 induction inhibited the proliferative effect of PDGF-BB. HO-1 expression was reversed by GSH-OEt, or p38 MAPK inhibition, or HO-1 siRNA, which all reversed the anti-proliferative effect of DMF.

Conclusion

Our data indicate that DMF inhibits ASMC proliferation by reducing the intracellular GSH level with subsequent activation of p38 MAPK and induction of HO-1. Thus, DMF might reduce ASMC and airway remodelling processes in asthma.     

The mechanisms for compression and reflection of cortical waves

Waves are common in cortical networks and may be important for carrying information about a stimulus from one local circuit to another. In a recent study of visually evoked waves in rat cortex, compression and reflection of waves are observed as the activation passes from visual areas V1 to V2. The authors of this study apply bicuculline (BMI) and demonstrate that the reflection disappears. They conclude that inhibition plays a major role in compression and reflection. We present several models for propagating waves in heterogeneous media and show that the velocity and thus compression depends weakly on inhibition. We propose that the main site of action of BMI with respect to wave propagation is on the threshold for firing which we suggest is related to action on potassium channels. We combine numerical and analytic methods to explore both compression and reflection in an excitable system with synaptic coupling.