Biology subjects

Steele, M. A.

Publications and source records attributed to Steele, M. A..

3 recordsLinked to original sources

bioRxiv2021

A live yeast supplementation to gestating ewes improves bioactive molecules composition in colostrum with no impact on its bacterial composition and beneficially affects immune status of the offspring

Colostrum quality is of paramount importance in the management of optimal ruminant growth and infectious disease prevention in early life. Live yeast supplementation effect during the last month of gestation was evaluated on ewes colostrum composition. Two groups of ewes (n=14) carrying twin lambs were constituted and twins were separated into groups (mothered or artificially-fed) 12h after birth. Nutrient, oligosaccharides (OS), IgG and lactoferrin concentrations were measured over 72h after lambing, and bacterial community was described in colostrum collected at parturition (T0). Immune passive transfer was evaluated through IgG measurement in lamb serum. In both groups, colostral nutrient, OS concentrations and IgG concentrations in colostrum and lamb serum decreased over time, (p < 0.01) except for lactose, which slightly increased (p < 0.001) and lactoferrin which remained stable. Bacterial population was stable over time with high relative abundances of Aerococcaceae, Corynebacteriaceae, Moraxellaceae and Staphylococcaceae in T0-colostrum. No effect of supplementation was observed in nutrient and lactoferrin concentrations. In supplemented ewes, colostral IgG level was higher at T0 and a higher level of serum IgG was observed in lambs born from supplemented mothers and artificially-fed, while no effect of supplementation was observed in the mothered lambs groups. Using a metabolomic approach, we showed that supplementation affected OS composition with significantly higher levels of colostral Neu-5Gc compounds up to 5h after birth. No effect of supplementation was observed on bacterial composition. Our data suggest that live yeast supplementation offsets the negative impact of early separation and incomplete colostrum feeding in neonate lambs. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=135 SRC="FIGDIR/small/464371v1_ufig1.gif" ALT="Figure 1"> View larger version (22K): org.highwire.dtl.DTLVardef@8c4e5borg.highwire.dtl.DTLVardef@16c6cf6org.highwire.dtl.DTLVardef@1658d42org.highwire.dtl.DTLVardef@1cf0fa_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗

bioRxiv2020

Comparison of methods for milk pre-processing, exosome isolation, and RNA extraction in bovine and human milk

Milk is a highly complex, heterogeneous biological fluid that contains bioactive, membrane-bound extracellular vesicles called exosomes. Characterization of milk-derived exosomes (MDEs) is challenging due to the lack of standardized methods that are currently being used for milk pre-processing, exosome isolation, and RNA extraction. In this study, we tested: 1) three pre-processing methods to remove cream, fat, and casein proteins from bovine milk to determine whether pre-processing of whole milk, prior to long-term storage, improves MDE isolations, 2) two commonly-used exosome isolation methods, and 3) four extraction protocols for obtaining high quality MDE RNA from bovine and human milk. MDEs were characterized via Transmission Electron Microscopy (TEM) and Nanoparticle Tracking Analysis (NTA). We also present an optimized method of TEM sample preparation and isolation of total soluble protein from MDEs. Our results indicated that: 1) pre-processing of bovine milk prior to storage does not affect the final exosome yield or the purity, 2) ExoQuick precipitation is better suited for MDE isolation than ultracentrifugation for bovine and human milk, and 3) TRIzol LS produced the highest RNA yield in bovine milk, whereas TRIzol LS, TRIzol+RNA Clean and Concentrator, and TRIzol LS+RNA Clean and Concentrator methods can be used for human milk.

molecular biology↗

bioRxiv2017

Correlated seed failure as an environmental veto to synchronize reproduction of masting plants

Highly variable, synchronized seed production, called masting, is a widespread reproductive strategy in plants. Resource dynamics, pollination success, and, as described here, environmental veto, are possible proximate mechanisms of masting. We extended the resource budget model of masting with correlated and uncorrelated reproductive failure, and ran this model across its parameters space. Next, we parametrized the model based on a 16-year seed production data for red (Quercus rubra) and white (Q. alba) oaks. Simulations showed that resource dynamics and reproduction failure produce masting even in the absence of pollen coupling. In concordance, in both species, among-year variation in resource gain and correlated reproductive failure were necessary and sufficient to produce masting. Environmental variation is a form of reproduction failure caused by environmental veto that may drive large-scale synchronization without density-dependent pollen limitation. Reproductive-inhibiting weather events are prevalent in ecosystems, suggesting that these described mechanisms likely operate in many masting systems.

ecology↗