Local Inflammation Exacerbates the Severity of Staphylococcus aureus Skin Infection

Staphylococcus aureus is the leading cause of skin infections. In a mouse model of S. aureus skin infection, we found that lesion size did not correlate with bacterial burden. Athymic nude mice had smaller skin lesions that contained lower levels of myeloperoxidase, IL-17A, and CXCL1, compared with wild type mice, although there was no difference in bacterial burden. T cell deficiency did not explain the difference in lesion size, because TCR βδ (-/-) mice did not have smaller lesions, and adoptive transfer of congenic T cells into athymic nude mice prior to infection did not alter lesion size. The differences observed were specific to the skin, because mortality in a pneumonia model was not different between wild type and athymic nude mice. Thus, the clinical severity of S. aureus skin infection is driven by the inflammatory response to the bacteria, rather than bacterial burden, in a T cell independent manner.     

Postmating barriers to hybridization between an island’s native eucalypts and an introduced congener

We evaluate postmating barriers to hybridization between an exotic eucalypt and a group of native congeners on the island of Tasmania. We aimed to better understand the basis of reproductive isolation between the species, glean insights into the evolution of isolating mechanisms, and inform genetic risk management. Compatibility between the exotic plantation species Eucalyptus nitens (pollen parent) and 18 native Tasmanian taxa was assayed using experimental crossing for 17 taxa (13,458 flowers pollinated to produce 1058 female × male cross combinations), and previous data for one species. Compatibility was assessed in terms of F₁ hybrid production, as well as F₁ hybrid survival and growth after 5 years. This data was combined with measurements of style length, and genetic distance from E. nitens to each maternal species, in order to determine the importance of a sequence of prezygotic and postzygotic barriers. We found that the early-acting barrier of style length (prezygotic) had the strongest isolating effect, while later-acting (postzygotic) barriers, affecting early-age growth and survival, contributed little to reproductive isolation. Style length alone explained 46 % of the variation in hybridization rate. Conversely, there was no significant relationship between genetic distance and prezygotic or postzygotic compatibility in these closely related species. This pattern is consistent with selection driving the rapid evolution of prezygotic barriers, while drift-like-processes lead to the more gradual evolution of intrinsic barriers. Although other premating and postmating barriers clearly contribute, our results highlight the important role of early-acting postmating barriers in preventing gene flow from exotic E. nitens plantations.     

A simple recipe for setting up the flux equations of cyclic and linear reaction schemes of ion transport with a high number of states: The arrow scheme

The calculation of flux equations or current-voltage relationships in reaction kinetic models with a high number of states can be very cumbersome. Here, a recipe based on an arrow scheme is presented, which yields a straightforward access to the minimum form of the flux equations and the occupation probability of the involved states in cyclic and linear reaction schemes. This is extremely simple for cyclic schemes without branches. If branches are involved, the effort of setting up the equations is a little bit higher. However, also here a straightforward recipe making use of so-called reserve factors is provided for implementing the branches into the cyclic scheme, thus enabling also a simple treatment of such cases.     

Trend in Pacific walrus (Odobenus rosmarus divergens) tusk asymmetry, 1990–2014

We used the basal circumference of Pacific walrus (Odobenus rosmarus divergens) tusks (upper canine teeth, n = 21,068 pairs) to estimate fluctuating asymmetry (FA1 index) from 1990 to 2014. The mean difference in circumference between paired tusks was ?0.006 (SEM = 0.002) cm and approximately normally distributed. Measurement error was 0.6 (0.02)%, similar between biologists and lay persons (P = 0.83), and ≤15% of FA1. Tusk FA1 was greatest in 1990 then declined by 56% (P = 0.0001) through 2014. Male and female trends differed (P = 0.0001) and male FA1 was 40% greater (P = 0.0001) and the rate of decline 28% steeper (P = 0.3) than females. A quartic polynomial model (r² = 0.66, w_i = 0.685) fit the trend for female data better than simpler forms, whereas a linear model (r² = 0.55, w_i = 0.693) was a better fit for male data. Walrus tusk FA1 reflected periods when the population was stressed due to food limitations and then recovered, and perhaps when females began to experience the loss of preferred sea ice habitat in summer and FA1 is an easily monitored indicator. More work is needed to confirm the link between FA1, individual fitness, and adaptive potential.     

Retinoic acid signaling in vascular development

Formation of the vasculature is an essential developmental process, delivering oxygen and nutrients to support cellular processes needed for tissue growth and maturation. Retinoic acid (RA) and its downstream signaling pathway is vital for normal pre‐ and post‐natal development, playing key roles in the specification and formation of many organs and tissues. Here, we review the role of RA in blood and lymph vascular development, beginning with embryonic yolk sac vasculogenesis and remodeling and discussing RA's organ‐specific roles in angiogenesis and vessel maturation. In particular, we highlight the multi‐faceted role of RA signaling in CNS vascular development and acquisition of blood–brain barrier properties.     

Genomic Basis of Circannual Rhythm in the European Corn Borer Moth

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Decadal plant composition changes in grazed native grassland

Most high value grasslands of south‐eastern Australia are restricted to small fragmented areas of public land. However, a significant proportion of native grassland is privately owned, managed with grazing rather than fire and is rarely monitored. Hence, a better understanding of grassland management and conservation on the private estate is required. Eco‐markets are policy instruments that incentivise private landholders to effectively manage and conserve native vegetation. However, short funding cycles restrict the capacity of monitoring programs to assess long‐term vegetation changes. In this study, 17 native grassland remnants on private land managed with livestock grazing were monitored before and during a 4‐year eco‐market and 6 years after it ended to determine how composition had changed over 10 years of monitoring. Numerous grassland attributes were either maintained or improved over the 10‐year period, which coincided with one of the most severe and long‐lasting droughts in recent history (i.e. the Millennium drought). In addition, several threatened species were identified as part of the program. A decline in exotic forb richness, native grass cover and native forb richness suggests there is also some impact of the Millennium drought on plant mortality as evidenced by altered litter dynamics. Inherent variability year‐to‐year for most measures of grassland attributes over the monitoring period indicates that climatic conditions have a strong influence on grassland dynamics. Our ability to determine the driver(s) of grassland composition was limited by monitoring program design. Future eco‐market monitoring programs should have adequate resources allocated to enable effective monitoring designs, that incorporate reference information and control sites, and should aim to be long‐term (i.e. >10 years). This will provide clearer insights into the drivers of grassland dynamics and allow for refinement of management options for conservation of this threatened community.     

Utilizing a regulated targeted integration cell line development approach to systematically investigate what makes an antibody difficult to express

Chinese hamster ovary (CHO) cells are conventionally used to generate therapeutic cell lines via random integration (RI), where desired transgenes are stably integrated into the genome. Targeted integration (TI) approaches, which involve integration of a transgene into a specific locus in the genome, are increasingly utilized for CHO cell line development (CLD) in recent years. None of these CLD approaches, however, are suitable for expression of toxic or difficult-to-express molecules, or for determining the underlying causes for poor expression of some molecules. Here we introduce a regulated target integration (RTI) system, where the desired transgene is integrated into a specific locus and transcribed under a regulated promoter. This system was used to determine the underlying causes of low protein expression for a difficult-to-express antibody (mAb-A). Interestingly, we observed that both antibody heavy chain (HC) and light chain (LC) subunits of mAb-A independently contributed to its low expression. Analysis of RTI cell lines also revealed that while mAb-A LC triggered accumulation of intracellular BiP, its HC displayed impaired degradation and clearance. RTI pools, generated by swapping the WT or point-mutant versions of difficult-to-express antibody HC and LC with that of an average antibody, were instrumental in understanding the contribution of HC and LC subunits to the overall antibody expression. The ability to selectively turn off the expression of a target transgene in an RTI system could help to directly link expression of a transgene to an observed adverse effect. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 35: e2772, 2019.