The efficacy of natural selection in producing optimal sex ratio adjustments in a fig wasp species.

Ever since Darwin's discovery of natural selection, we expect traits to evolve to increase organisms' fitness. As a result, we can use optimization models to make a priori predictions of phenotypic variation, even when selection is frequency-dependent. A notable example is the prediction of female-biased sex ratios resulting from local mate competition (LMC) and inbreeding. LMC models incorporate the effects of LMC and inbreeding. Fig wasp sex ratio adjustments fit LMC predictions well. However, the appropriateness of LMC models to fig wasps has been questioned, and the role that a coincidental by-product plays in creating the apparent fit has been clearly illustrated. Here, we show that the sex ratio adjustments of a fig wasp are the result of a dual mechanism. It consists of a standard facultative LMC response favoured by natural selection, as well as a mechanism that may be the result of selection, but that could also be a coincidental by-product. If it is a by-product, the fitness increase is coincidental and natural selection's role was limited to fine-tuning it for higher fitness returns. We further document a case of an apparent fitness-reducing sex ratio adjustment. We conclude that the use of the adaptationist approach demands that our understanding of traits must be remodelled continually to rectify spurious assumptions.

Effect of feeding a daily oral care chew on the composition of plaque microbiota in dogs.

The objective of this study was to investigate the influence of daily feeding of an oral care chew on the composition of canine supragingival plaque microbiota. Twelve beagle dogs were recruited to the randomized cross-over study. The dogs were fed one of two dietary regimes, both consisting of a commercially available wet and dry diet mix, either with or without daily supplementation with an oral care chew. After each 28-day test phase, supragingival plaque samples were collected and processed via Illumina sequencing to determine the microbiota composition. A comparative analysis of bacterial species associated with health and periodontal disease, identified from prior clinical studies, revealed differences between the dietary regimes. Consumption of the daily oral care chew, resulted in a significant increase in proportion of 6 health associated taxa but only 3 disease associated taxa compared to no chew. In contrast, 8 disease and 1 health associated taxa showed increased proportions for no chew versus the oral care chew. Daily feeding of the oral care chew tested in this study has therefore been shown to increase the proportion of health associated bacteria, over bacteria associated with periodontal disease, in supragingival plaque compared to no chew. By influencing plaque microbiota towards a bias for health associated bacteria, feeding of the oral care chew provides a means to reduce the prevalence of bacterial species shown to be associated with periodontal disease in dogs.

MicroRNA-34a (miR-34a) Mediates Retinal Endothelial Cell Premature Senescence through Mitochondrial Dysfunction and Loss of Antioxidant Activities.

Stress-associated premature senescence (SAPS) is involved in retinal microvascular injury and diabetic retinopathy. We have investigated the role and mode of action of miR-34a in retinal endothelial cells senescence in response to glucidic stress. Human retinal microvascular endothelial cells (HuREC) were exposed to glucidic stress (high glucose (HG) = 25 mM d-glucose) and compared to cells exposed to normal glucose (NG = 5 mM) or the osmotic control l-glucose (LG = 25 mM). HG stimulation of HuREC increased the expression of miR-34a and induced cellular senescence. HG also increased the expression of p16ink4a and p21waf1, while decreasing the histone deacetylase SIRT1. These effects were associated with diminished mitochondrial function and loss of mitochondrial biogenesis factors (i.e., PGC-1α, NRF1, and TFAM). Transfection of the cells with miR-34a inhibitor (IB) halted HG-induced mitochondrial dysfunction and up-regulation of senescence-associated markers, whereas miR-34a mimic promoted cellular senescence and mitochondrial dysfunction. Moreover, HG lowered levels of the mitochondrial antioxidants TrxR2 and SOD2, an effect blunted by miR-34a IB, and promoted by miR-34a mimic. 3'-UTR (3'-untranslated region) reporter assay of both genes validated TrxR2 as a direct target of miR-34a, but not SOD2. Our results show that miR-34a is a key player of HG-induced SAPS in retinal endothelial cells via multiple pathways involved in mitochondrial function and biogenesis.

Deficiency of metabolite sensing receptor HCA2 impairs the salutary effect of niacin in hemorrhagic shock.

Inflammation and cellular energetics play critical roles in organ dysfunction following hemorrhagic shock. Recent studies suggest a putative role for sirtuin 1 (SIRT1) in potentiating mitochondrial function and improving organ function following hemorrhagic shock in animal models. SIRT1 is an NAD+ dependent protein deacetylase and increased availability of NAD+ has been shown to augment SIRT1 activity. As niacin is a precursor of NAD+, in this study, we tested whether niacin can improve survival following hemorrhagic shock. However niacin also mediates its biological action by binding to its receptor, hydroxyl-carboxylic acid receptor 2 (HCA2 or Gpr109a); so we examined whether the effect of niacin is mediated by binding to Gpr109a or by increasing NAD+ availability. We found that niacin administered intravenously to rats subjected to hemorrhagic injury (HI) in the absence of fluid resuscitation resulted in a significantly prolonged duration of survival. However, treatment of rats with similar doses of nicotinamide mononucleotide (NMN), a precursor to NAD+ that does not bind Gpr109a, did not extend survival following HI. The duration of survival due to niacin treatment was significantly reduced in Gpr109a-/- mice subjected to HI. These experiments demonstrated that the Gpr109a receptor-mediated pathway contributed significantly to niacin mediated salutary effect. Further studies showed improvement in markers of cellular energetics and attenuation of inflammatory response with niacin treatment. In conclusion, we report that Gpr109a-dependent signalling is important in restoring cellular energetics and immunometabolism following hemorrhagic shock.

Effect of plasma-derived extracellular vesicles on erythrocyte deformability in polymicrobial sepsis.

Sepsis affects microcirculation and tissue perfusion leading to tissue hypoxia and multiple organ dysfunction. Red blood cells (RBCs; erythrocytes) are typically biconcave in shape, transport hemoglobin-bound oxygen and are reversibly deformable facilitating trafficking through capillaries. Decreased deformability of RBCs adversely affects tissue oxygenation. The purpose of this project was to determine RBC deformability in a murine model of polymicrobial sepsis by a method that utilizes laser diffraction and microfluidics, and to identify the causative factors in the plasma that may contribute to loss in RBC deformability. Blood samples from mice subjected to cecal ligation and puncture (CLP) model of sepsis were used. RBC deformability was tested using Rheoscan-AnD 300 under shear stress range of 0-20 Pascal (Pa) that depicts the common rheological behavior of RBCs flowing through blood vessels ranging from major vessels to capillaries. Normal RBCs were treated with plasma-derived extracellular vesicles (EVs) and their effect on RBC deformability was also tested. The experiments demonstrated a significant decrease in RBC deformability following sepsis. RBC deformability recovered in sham-operated animals by the third day, whereas animals with sepsis continued to show decreased levels of deformability. EVs isolated from the plasma of animals from the sepsis group significantly decreased deformability of RBCs ex vivo. Analysis of miRNA cargo in EVs showed distinct molecular profiles for sham-operated and sepsis-induced mice. In summary, sepsis induced a decrease in RBC deformability and the acquired rigidity may have adverse effect on microcirculation, tissue perfusion, and organ function.

Kidney-targeted inhibition of protein kinase C-α ameliorates nephrotoxic nephritis with restoration of mitochondrial dysfunction.

To investigate the role of protein kinase C-α (PKC-α) in glomerulonephritis, the capacity of PKC-α inhibition to reverse the course of established nephrotoxic nephritis (NTN) was evaluated. Nephritis was induced by a single injection of nephrotoxic serum and after its onset, a PKC-α inhibitor was administered either systemically or by targeted glomerular delivery. By day seven, all mice with NTN had severe nephritis, whereas mice that received PKC-α inhibitors in either form had minimal evidence of disease. To further understand the underlying mechanism, label-free shotgun proteomic analysis of the kidney cortexes were performed, using quantitative mass spectrometry. Ingenuity pathway analysis revealed 157 differentially expressed proteins and mitochondrial dysfunction as the most modulated pathway. Functional protein groups most affected by NTN were mitochondrial proteins associated with respiratory processes. These proteins were down-regulated in the mice with NTN, while their expression was restored with PKC-α inhibition. This suggests a role for proteins that regulate oxidative phosphorylation in recovery. In cultured glomerular endothelial cells, nephrotoxic serum caused a decrease in mitochondrial respiration and membrane potential, mitochondrial morphologic changes and an increase in glycolytic lactic acid production; all normalized by PKC-α inhibition. Thus, PKC-α has a critical role in NTN progression, and the results implicate mitochondrial processes through restoring oxidative phosphorylation, as an essential mechanism underlying recovery. Importantly, our study provides additional support for targeted therapy to glomeruli to reverse the course of progressive disease.

Mitochondrial dysfunction in rat splenocytes following hemorrhagic shock.

The regulation of mitochondrial function is critical in cellular homeostasis following hemorrhagic shock. Hemorrhagic shock results in fluid loss and reduced availability of oxygen and nutrients to tissues. The spleen is a secondary lymphoid organ playing a key role in 'filtering the blood' and in the innate and adaptive immune responses. To understand the molecular basis of hemorrhagic shock, we investigated the changes in splenocyte mitochondrial respiration, and concomitant immune and metabolic alterations. The hemorrhagic injury (HI) in our rat model was induced by bleeding 60% of the total blood volume followed by resuscitation with Ringers lactate. Another group of animals was subjected to hemorrhage, but did not receive fluid resuscitation. Oxygen consumption rate of splenocytes were determined using a Seahorse analyzer. We found a significantly reduced oxygen consumption rate in splenocytes following HI compared to sham operated rats. The mitochondrial stress test revealed a decreased basal oxygen consumption rate, ATP production, maximal respiration and spare respiratory capacity. The mitochondrial membrane potential, and citrate synthase activity, were also reduced in the splenocytes following HI. Hypoxic response in the splenocyte was confirmed by increased gene expression of Hif1α. Elevated level of mitochondrial stress protein, hsp60 and induction of high mobility group box1 protein (HMGB1) were observed in splenocytes following HI. An increased inflammatory response was demonstrated by significantly increased expression of IL-6, IFN-ß, Mip-1α, IL-10 and NFκbp65. In summary, we conclude that splenocyte oxidative phosphorylation and metabolism were severely compromised following HI.

Mitochondrial targeting by dichloroacetate improves outcome following hemorrhagic shock.

Hemorrhagic shock is a leading cause of death in people under the age of 45 and accounts for almost half of trauma-related deaths. In order to develop a treatment strategy based on potentiating mitochondrial function, we investigated the effect of the orphan drug dichloroacetate (DCA) on survival in an animal model of hemorrhagic shock in the absence of fluid resuscitation. Hemorrhagic shock was induced in rats by withdrawing 60% of the blood volume and maintaining a hypotensive state. The studies demonstrated prolonged survival of rats subjected to hemorrhagic injury (HI) when treated with DCA. In separate experiments, using a fluid resuscitation model we studied mitochondrial functional alterations and changes in metabolic networks connected to mitochondria following HI and treatment with DCA. DCA treatment restored cardiac mitochondrial membrane potential and tissue ATP in the rats following HI. Treatment with DCA resulted in normalization of several metabolic and molecular parameters including plasma lactate and p-AMPK/AMPK, as well as Ach-mediated vascular relaxation. In conclusion we demonstrate that DCA can be successfully used in the treatment of hemorrhagic shock in the absence of fluid resuscitation; therefore DCA may be a good candidate in prolonged field care following severe blood loss.

Dynamic contrast enhanced magnetic resonance imaging of an orthotopic pancreatic cancer mouse model.

Dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) has been limitedly used for orthotopic pancreatic tumor xenografts due to severe respiratory motion artifact in the abdominal area. Orthotopic tumor models offer advantages over subcutaneous ones, because those can reflect the primary tumor microenvironment affecting blood supply, neovascularization, and tumor cell invasion. We have recently established a protocol of DCE-MRI of orthotopic pancreatic tumor xenografts in mouse models by securing tumors with an orthogonally bent plastic board to prevent motion transfer from the chest region during imaging. The pressure by this board was localized on the abdominal area, and has not resulted in respiratory difficulty of the animals. This article demonstrates the detailed procedure of orthotopic pancreatic tumor modeling using small animals and DCE-MRI of the tumor xenografts. Quantification method of pharmacokinetic parameters in DCE-MRI is also introduced. The procedure described in this article will assist investigators to apply DCE-MRI for orthotopic gastrointestinal cancer mouse models.

A spatially explicit approach to estimating species occupancy and spatial correlation.

1. Understanding and predicting the form of species distributions, or occupancy patterns, is fundamental to macroecology and is dependent on the identification of scaling relationships that underlie the patterns observed. 2. Occupancy-abundance models based on the negative binomial distribution and Taylor's power law are spatially implicit, rather than explicit, as they include no information on the relative positions of individuals. Here we present a spatially explicit model, the spatial scaling occupancy (SSO) model, to estimate species occupancy and spatial correlation, based on join-count statistics, or a pair approximation, approach. This model provides a spatially explicit description of species range size and aspects of range structure. 3. Occupancy data from Drosophilidae species inhabiting a decaying fruit mesocosm were used to test the SSO model. Predictions from the spatially implicit and explicit models were largely equally accurate. The SSO model is thus more efficient as it is less data demanding, and more informative as it provides an estimation of spatial correlation. 4. The results also showed that species distribution patterns differ when examined with spatially implicit vs. explicit approaches; the scaling relationship between occupancy and local density identifies a focal grain for studying the scale-dependent nature of ecological relationships; and the longer the length of the sample edge, the higher the occupancy observed under conditions of spatial aggregation. 5. The SSO model presents a step towards a general scaling model for occupancy, and demonstrates that the inclusion of spatially explicit information in macroecological models warrants further attention.

Body size patterns in Drosophila inhabiting a mesocosm: interactive effects of spatial variation in temperature and abundance.

Body size is a major component of fitness. However, the relative contributions of different factors to optimal size, and the determinants of spatial and temporal variation in size, have not been fully established empirically. Here, we use a mesocosm of a Drosophilidae assemblage inhabiting decaying nectarines to investigate the influence of spatial variation in temperature on adult body size in Drosophila simulans Sturtevant. Two treatments were established; one in the sun where developing larvae were exposed to high temperatures and the other in the shade where temperature conditions were milder. The simple developmental effects of temperature differences (i.e. larger flies are likely to emerge from cooler environments), or the simple effects of stressful temperatures (i.e. high temperatures yield wing abnormalities and smaller flies), were overridden by interactive effects between temperature and larval density. Emergences were lower in the sun than shade, probably as a result of temperature-induced mortality. However, flies attained the same final sizes in the shade and sun. In addition, abnormally winged flies were clustered in the shaded treatments. In the shade treatments, where emergences were higher than in the sun, stressful conditions as a result of high larval density likely resulted in wing abnormalities and small size. Consequently, there was little spatial variation in size across the mesocosm, but substantial spatial variation in abundance. Under natural conditions both mortality and non-lethal effects of temperature and/or crowding are likely to play a role in the evolution of body size.