Enhanced thermal destruction of Listeria monocytogenes and Staphylococcus aureus by the lactoperoxidase system

The lactoperoxidase system (LPS) enhanced thermal destruction of Listeria monocytogenes and Staphylococcus aureus. After LPS activation, biphasic survival curves were observed for L. monocytogenes at 57.8 degrees C and for S. aureus at 55.2 degrees C. The data were consistent with a model that assumed two bacterial populations differing in heat sensitivity. The more heat-sensitive fractions (93% of the L. monocytogenes, 92% of the S. aureus) were killed almost instantly. For these biphasic survival curves, D values were based on the much smaller, less-heat-sensitive fractions. For L. monocytogenes, the D52.2 degrees C values were 30.2 min (untreated milk) and 10.7 min (LPS activated); corresponding D55.2 degrees C values were 8.2 and 1.6 min; corresponding D57.8 degrees C values were 2.3 and 0.5 min. For S. aureus, the D52.2 degrees C values were 33.3 min (untreated milk) and 2.2 min (LPS activated), and the corresponding D55.2 degrees C values were 7.6 and 1.1 min, respectively. The most rapid killing of L. monocytogenes occurred when samples were heated soon after activation of the LPS. Activation of the LPS followed by heating can increase the margin of safety with respect to milkborne pathogens.     

Similar hypotensive responses to resistance exercise with and without blood flow restriction

Low intensity resistance exercise (RE) with blood flow restriction (BFR) has gained attention in the literature due to the beneficial effects on functional and morphological variables, similar to those observed during traditional RE without BFR, while the effects of BFR on post-exercise hypotension remain unclear. The aim of the present study was to compare the blood pressure (BP) response of trained normotensive individuals to RE with and without BFR. In this cross-over randomized trial, eight male subjects (23.8 ± 4 years, 74 ± 3 kg, 174 ± 4 cm) completed two exercise protocols: traditional RE (3 x 10 repetitions at 70% one-repetition maximum [1-RM]) and low intensity RE (3 x 15 repetitions at 20% 1-RM) with BFR. Blood pressure measurements were performed after 15 min of seated rest (0), immediately after and 10 min, 20 min, 30 min, 40 min, 50 min and 60 min after the experimental sessions. Similar hypotensive effects for systolic BP (SBP) were observed for both protocols (P < 0.05) after exercise, with no differences between groups (P > 0.05) and no statistically significant difference for diastolic BP (P > 0.05). These results suggest that in normotensive trained individuals, both traditional RE and RE with BFR induce hypotension for SBP, which is important to prevent cardiovascular disturbances.     

Individuality in seaweeds and why we need to care

Documenting the causes and consequences of intraspecific variation forms the foundation of much of evolutionary ecology. In this Perspectives piece, we review the importance of individual variation in ecology and evolution, argue that contemporary phycology often overlooks this foundational biological unit, and highlight how this lack of attention has potentially constrained our understanding of seaweeds. We then provide some suggestions of promising but underrepresented approaches, for instance: conducting more studies and analyses at the level of the individual; designing studies to evaluate heritability and genetic regulation of traits; and measuring associations between individual variation in functional traits and ecological outcomes. We close by highlighting areas of phycological research (e.g., population biology, ecology, aquaculture, climate change management) that could benefit immediately from including a focus on individual variation. Algae, for their part, provide us with a powerful and diverse set of ecological and evolutionary traits to explore these topics. There is much to be discovered.     

Energetic requirements of green sturgeon (<Emphasis Type="Italic">Acipenser medirostris</Emphasis>) feeding on burrowing shrimp (<Emphasis Type="Italic">Neotrypaea californiensis</Emphasis>) in estuaries: importance of temperature,reproductive investment,and residence time

Habitat use can be complex, as tradeoffs among physiology, resource abundance, and predator avoidance affect the suitability of different environments for different species. Green sturgeon (Acipenser medirostris), an imperiled species along the west coast of North America, undertake extensive coastal migrations and occupy estuaries during the summer and early fall. Warm water and abundant prey in estuaries may afford a growth opportunity. We applied a bioenergetics model to investigate how variation in estuarine temperature, spawning frequency, and duration of estuarine residence affect consumption and growth potential for individual green sturgeon. We assumed that green sturgeon achieve observed annual growth by feeding solely in conditions represented by Willapa Bay, Washington, an estuary annually frequented by green sturgeon and containing extensive tidal flats that harbor a major prey source (burrowing shrimp, Neotrypaea californiensis). Modeled consumption rates increased little with reproductive investment (<0.4%), but responded strongly (10–50%) to water temperature and duration of residence, as higher temperatures and longer residence required greater consumption to achieve equivalent growth. Accordingly, although green sturgeon occupy Willapa Bay from May through September, acoustically-tagged individuals are observed over much shorter durations (34 d + 41 d SD, N = 89). Simulations of <34 d estuarine residence required unrealistically high consumption rates to achieve observed growth, whereas longer durations required sustained feeding, and therefore higher total intake, to compensate for prolonged exposure to warm temperatures. Model results provide a range of per capita consumption rates by green sturgeon feeding in estuaries to inform management decisions regarding resource and habitat protection for this protected species.     

A real‐time eco‐evolutionary dead‐end strategy is mediated by the traits of lineage progenitors and interactions with colony invaders

Evolutionary dead‐end strategies are characterized by short‐term productivity benefits and long‐term evolutionary costs. Here, I detail a real‐time dead‐end strategy associated with the behavioural traits of lineage progenitors in the social spider Anelosimus studiosus. Specifically, colony lineages founded by docile spiders were eight times more likely to suffer extinction, despite their superior reproductive output. However, when inquilines were experimentally removed from progenitor colonies, differences in extinction probability among lineages vanished. Similarly, among lineages founded by purely docile or aggressive individuals, the descendants of lineages with the highest reproductive output suffered the lowest survivorship, whereas lineages founded by a mixture of docile/aggressive lacked such a trade‐off. Finally, lineages with shorter progenitor‐descendant distances gained more inquilines and their descendants had lower survivorship, relative to more diffuse lineages. Overall, this study demonstrates how the traits of lineage progenitors and species interactions can unite to determine the fates of entire lineages.     

Inside Cover: Generalized spectral light scatter models of diverse bacterial colony morphologies (J. Biophotonics 12/2019)

The forward elastic‐light‐scattering pattern of a bacterial colony reflects its morphological characteristics. Three bacteria genera whose colonies having convex, crateriform, or irregular elevation were investigated to study the correlation between the morphology and the scattering pattern of the colony. The difference in the colony elevation produced distinct shapes of light diffraction in the scattering pattern, resulting circular diffraction rings or scattered light. Further details can be found in the article by Iyll‐Joon Doh, Jennifer Sturgis, Diana V. Sarria Zuniga, et al. ( e201900149 ).

     

Spindle assembly checkpoint genes reveal distinct as well as overlapping expression that implicates MDF-2/Mad2 in postembryonic seam cell proliferation in Caenorhabditis elegans

Background

The spindle assembly checkpoint (SAC) delays anaphase onset by inhibiting the activity of the anaphase promoting complex/cyclosome (APC/C) until all of the kinetochores have properly attached to the spindle. The importance of SAC genes for genome stability is well established; however, the roles these genes play, during postembryonic development of a multicellular organism, remain largely unexplored.

Results

We have used GFP fusions of 5' upstream intergenic regulatory sequences to assay spatiotemporal expression patterns of eight conserved genes implicated in the spindle assembly checkpoint function in Caenorhabditis elegans. We have shown that regulatory sequences for all of the SAC genes drive ubiquitous GFP expression during early embryonic development. However, postembryonic spatial analysis revealed distinct, tissue-specific expression of SAC genes with striking co-expression in seam cells, as well as in the gut. Additionally, we show that the absence of MDF-2/Mad2 (one of the checkpoint genes) leads to aberrant number and alignment of seam cell nuclei, defects mainly attributed to abnormal postembryonic cell proliferation. Furthermore, we show that these defects are completely rescued by fzy-1(h1983)/CDC20, suggesting that regulation of the APC/C^CDC20 by the SAC component MDF-2 is important for proper postembryonic cell proliferation.

Conclusion

Our results indicate that SAC genes display different tissue-specific expression patterns during postembryonic development in C. elegans with significant co-expression in hypodermal seam cells and gut cells, suggesting that these genes have distinct as well as overlapping roles in postembryonic development that may or may not be related to their established roles in mitosis. Furthermore, we provide evidence, by monitoring seam cell lineage, that one of the checkpoint genes is required for proper postembryonic cell proliferation. Importantly, our research provides the first evidence that postembryonic cell division is more sensitive to SAC loss, in particular MDF-2 loss, than embryonic cell division.     

Novel surface expression of reticulocalbin 1 on bone endothelial cells and human prostate cancer cells is regulated by TNF-alpha

An unbiased cDNA expression phage library derived from bone-marrow endothelial cells was used to identify novel surface adhesion molecules that might participate in metastasis. Herein we report that reticulocalbin 1 (RCN1) is a cell surface-associated protein on both endothelial (EC) and prostate cancer (PCa) cell lines. RCN1 is an H/KDEL protein with six EF-hand, calcium-binding motifs, found in the endoplasmic reticulum. Our data indicate that RCN1 also is expressed on the cell surface of several endothelial cell lines, including human dermal microvascular endothelial cells (HDMVECs), bone marrow endothelial cells (BMEC), and transformed human bone marrow endothelial cells (TrHBMEC). While RCN1 protein levels were highest in lysates from HDMVEC, this difference was not statistically significant compared BMEC and TrHBMEC. Given preferential adhesion of PCa to bone-marrow EC, these data suggest that RCN1 is unlikely to account for the preferential metastasis of PCa to bone. In addition, there was not a statistically significant difference in total RCN1 protein expression among the PCa cell lines. RCN1 also was expressed on the surface of several PCa cell lines, including those of the LNCaP human PCa progression model and the highly metastatic PC-3 cell line. Interestingly, RCN1 expression on the cell surface was upregulated by tumor necrosis factor alpha treatment of bone-marrow endothelial cells. Taken together, we show cell surface localization of RCN1 that has not been described previously for either PCa or BMEC and that the surface expression on BMEC is regulated by pro-inflammatory TNF-alpha.     

Role of the pleckstrin homology domain in intersectin-L Dbl homology domain activation of Cdc42 and signaling

Intersectin-long (ITSN-L) contains the invariant Dbl homology (DH) and pleckstrin homology (PH) domain structure characteristic of the majority of Dbl family proteins. This strict domain topography suggests that the PH domain serves an essential, conserved function in the regulation of the intrinsic guanine nucleotide exchange activity of the DH domain. We evaluated the role of the PH domain in regulating the DH domain function of ITSN-L. Surprisingly, we found that the PH domain was dispensable for guanine nucleotide exchange activity on Cdc42 in vitro, yet the PH domain enhanced the ability of the DH domain to activate Cdc42 signaling in vivo. PH domains can interact with phosphoinositide substrates and products of phosphatidylinositol 3-kinase (PI3K). However, PI3K activation did not modulate ITSN-L DH domain function in vivo.