Mammalian Response Research Articles

Skeletal Muscle and the Effects of Ammonia Toxicity in Fish, Mammalian, and Avian Species: A Comparative Review Based on Molecular Research.

Typically, mammalian and avian models have been used to examine the effects of ammonia on skeletal muscle. Hyperammonemia causes sarcopenia or muscle wasting, in mammals and has been linked to sarcopenia in liver disease patients. Avian models of skeletal muscle have responded positively to hyperammonemia, differing from the mammalian response. Fish skeletal muscle has not been examined as extensively as mammalian and avian muscle. Fish skeletal muscle shares similarities with avian and mammalian muscle but has notable differences in growth, fiber distribution, and response to the environment. The wide array of body sizes and locomotion needs of fish also leads to greater diversity in muscle fiber distribution and growth between different fish species. The response of fish muscle to high levels of ammonia is important for aquaculture and quality food production but has not been extensively studied to date. Understanding the differences between fish, mammalian and avian species’ myogenic response to hyperammonemia could lead to new therapies for muscle wasting due to a greater understanding of the mechanisms behind skeletal muscle regulation and how ammonia effects these mechanisms. This paper provides an overview of fish skeletal muscle and ammonia excretion and toxicity in fish, as well as a comparison to avian and mammalian species.

The Viral Defense Gene RNaseL Acts as a Regeneration Repressor

Mammalian injury responses are characterized by fibrosis and scarring rather than functional regeneration. Limited regenerative capacity in mammals could reflect a loss of pro-regeneration programs or active suppression by genes functioning akin to tumor suppressors. To uncover programs governing regeneration in mammals, we performed comprehensive transcript screening in human subjects after laser rejuvenation treatment. We searched for overlapping transcripts also associated with Wound Induced Hair Neogenesis (WIHN), a rare example of regeneration in mice. We found the anti-viral endoribonuclease RNase L to be a powerful suppressor of regeneration. Rnasel-/- mice exhibit remarkable regenerative capacity and accelerated wound healing following injury, through the production of IL-36α. Consistent with the known role of RNase L to stimulate caspase-1 signaling, we find that pharmacologic inhibition of caspases promotes regeneration in a novel IL-36-dependent manner. We also find a gene set of inner root sheath keratins, such as KRT71, that is associated with poor wound healing in mouse and man, and decreases with caspase inhibition. Finally, these responses are not limited to skin, but occur following intestinal injury as well, suggesting that suppression of regeneration is a general characteristic of epithelial wound healing. In all, this work suggests that RNaseL functions as a regeneration repressor gene in a functional tradeoff that prioritizes host antiviral abilities and is a target to enhance healing in multiple epithelial organs, perhaps even during viral infection.

Gut microbiome, diet, and conservation of endangered langurs in Sri Lanka

AbstractUnderstanding the mechanisms by which organisms respond to environmental change is critical to conservation biology. Recent research indicates that the gut microbiome may mediate mammalian responses to the environment and can be used as a biomarker to understand host ecological strategies. Here, we explore the relationship between the gut microbiome, host dietary niche, and potential resilience to habitat alteration using two closely related, sympatric non‐human primate species: the tufted gray langur (Semnopithecus priam) and the purple‐faced langur (Semnopithecus vetulus). The gray langur is suspected to be a habitat generalist less perturbed by anthropogenic disturbance, while the purple‐faced langur is suspected to be a specialist more sensitive to disturbance. To test these characterizations, we assessed the gut microbiome using 16S rRNA gene amplicon sequencing of fecal samples collected from Kaludiyapokuna Forest Reserve, Sri Lanka (gray langur n = 50 samples, purple‐faced langur n = 7 samples). Our results demonstrate that despite strong gut microbial similarities, gray langurs had a more diverse gut microbiome that harbored Prevotella and Akkermansia, taxa involved in starch degradation, while the purple‐faced langur gut microbiome harbored Roseburia, Clostridium, and Ruminococcus, taxa involved in processing plant structural carbohydrates. Compared to related species in other locations, both Sri Lankan langurs harbored more pathogenic bacteria. These differences suggest that gray langurs have more generalist diets, making them more resilient to anthropogenic change, but also indicate that they are not impervious to human encroachment. Our findings suggest that microbiome analyses are an important tool for langur ecology and conservation, and should be integrated into ongoing studies.

The Mammalian Diving Response: Inroads to Its Neural Control.

The mammalian diving response (DR) is a remarkable behavior that was first formally studied by Laurence Irving and Per Scholander in the late 1930s. The DR is called such because it is most prominent in marine mammals such as seals, whales, and dolphins, but nevertheless is found in all mammals studied. It consists generally of breathing cessation (apnea), a dramatic slowing of heart rate (bradycardia), and an increase in peripheral vasoconstriction. The DR is thought to conserve vital oxygen stores and thus maintain life by directing perfusion to the two organs most essential for life—the heart and the brain. The DR is important, not only for its dramatic power over autonomic function, but also because it alters normal homeostatic reflexes such as the baroreceptor reflex and respiratory chemoreceptor reflex. The neurons driving the reflex circuits for the DR are contained within the medulla and spinal cord since the response remains after the brainstem transection at the pontomedullary junction. Neuroanatomical and physiological data suggesting brainstem areas important for the apnea, bradycardia, and peripheral vasoconstriction induced by underwater submersion are reviewed. Defining the brainstem circuit for the DR may open broad avenues for understanding the mechanisms of suprabulbar control of autonomic function in general, as well as implicate its role in some clinical states. Knowledge of the proposed diving circuit should facilitate studies on elite human divers performing breath-holding dives as well as investigations on sudden infant death syndrome (SIDS), stroke, migraine headache, and arrhythmias. We have speculated that the DR is the most powerful autonomic reflex known.

Elucidation of the Metabolic Pathways of Methylarginines in Saccharomyces cerevisiae

BACKGROUNDThe methylation of arginine residues in proteins is a ubiquitous post‐translational modification that is predominantly metabolized during protein catabolism. It has been postulated that methylarginines play a functional role in the mammalian stress response due to their presence in stress granules, although this has not been largely explored. Saccharomyces cerevisiae is a suitable model organism to study the role of methylarginines in the eukaryotic stress response due to the high degree of similarity between the yeast and mammalian stress pathways and methyltransferasomes. Free methylarginines need to be tightly regulated because they inhibit the production of nitric oxide, a cell signalling molecule that is crucial in eukaryotic stress responses. Mammals metabolize free methylarginine into citrulline and methylamine by dimethylarginine dimethylaminohydrolase (DDAH) to circumvent nitric oxide synthase inhibition. Conversely, yeast lack classical DDAH activity and therefore cannot counteract this inhibition in the same way. The purpose of this research is to explore how yeast cope with free methylarginine in response to stress.METHODSWe applied different stress conditions to yeast cells, including heat shock, osmotic shock, rapamycin treatment, nutrient deprivation, and stationary phase and observed the effect on methylarginine concentration in proteins and in spent culture media. Methylarginine species were quantified using a tandem mass spectrometry assay. To explore possible metabolic pathways of yeast methylarginines, we also monitored the expression levels and subcellular localization of a constitutively expressed autophagy marker GFP‐Atg8, a key component in the formation of the phagophore assembly site, via Western Blot and fluorescence microscopy. We also observed the effect of gene deletions involved in autophagy and the proteasome on methylarginine processing.RESULTSThe condition that elicited the most significant change in methylarginine concentration response was stationary phase, a nutrient‐depriving growth condition. Specifically, we observed a substantial release of free methylarginine species into the culture media, accompanied by cleavage of GFP‐Atg8 and localization of GFP‐Atg8 to the vacuole, consistent with functional autophagy. In yeast mutants lacking functional autophagy, we fail to see the expelled free methylarginine species. However, in proteasome‐deficient yeast, methylarginine efflux is still observed.CONCLUSIONSWe postulate that autophagy serves as the major metabolic pathway for degradation of methylarginine‐containing proteins in yeast. We predict that methylarginine efflux is a crucial coping mechanism to avoid methylarginine‐mediated cell toxicity due to inhibition of nitric oxide synthesis. This work examines yeast methylarginines under stress for the first time and reveals new effects of methylarginine. This will contribute to the knowledge of how cells respond to stress and impacts what we know about autophagy and amino acid metabolism.Support or Funding InformationWe thank the Natural Sciences and Engineering Research Council of Canada (NSERC) for support (RGPIN‐2015–04450 Discovery Grant to A.F., USRA to E.Z., and Alexander Graham Bell CGS‐D to J.I.B.).

SPARC: Parameters of Electrical Excitation and Block of the Rat Vagus Nerve

There is growing interest in bioelectronic medicines, where diseases are treated through electrical stimulation and block of the peripheral autonomic nervous system. Given the widespread connections of the vagus nerve from the brainstem to most truncal organs, applications include treating epilepsy, depression, obesity, heart failure, and rheumatoid arthritis. However, designing and programming the parameters of bioelectronic medicines require understanding the biophysical responses of small myelinated and unmyelinated autonomic fibers. Using in vivo electrophysiology, we quantified strength‐duration properties, activity‐dependent slowing (ADS), and responses to kilohertz frequency (KHF) signals for rapidly conducting (>2 m/s) and slowly conducting (<2 m/s) fibers in the rat vagus nerve.We stimulated the cervical vagus nerve and recorded compound action potential (CAP) input‐output curves from the abdominal vagus nerve for pulse widths from 20 to 1000 μs. Thresholds were largest for the slowest fibres (0.5 to 1 m/s), especially at shorter pulse widths. Fits to the data using standard strength‐duration equations were qualitatively similar, but the estimates of chronaxie and rheobase varied substantially.ADS describes the slowed conduction in peripheral axons resulting from persistent low frequency activity. Using a novel cross‐correlation CAP‐based analysis method, we measured ADS of ~2.3% after 3 min of 2 Hz stimulation, approximately constant across fiber conduction speeds. This is comparable to that reported for sympathetic efferents in somatic nerves, but much smaller than ADS in cutaneous nociceptors. We found greater ADS with higher stimulation frequency and non‐monotonic changes in conduction speed in select cases.KHF signals can block neural conduction in peripheral axons, and we used CAP recordings to quantify the effects of KHF signals from 10 to 80 kHz on small autonomic fibers. Block thresholds were higher for more slowly conducting fibers, and block thresholds increased monotonically with frequency, in contrast to published findings indicating that block thresholds of unmyelinated axons vary non‐monotonically with frequency. Further, there are varied reports on the time for recovery of neural conduction after KHF block; we found that the carryover effect could last tens of seconds following 25 s of KHF signal.The quantification of mammalian autonomic nerve responses to conventional and kilohertz frequency signals provides essential information for development of bioelectronic medical devices and for understanding mechanisms of action.Support or Funding InformationThis work was supported by Fulbright Canada (15122811), the Natural Sciences and Engineering Research Council of Canada (PGS M‐425353‐2012 and PGS D3‐437918‐2013), and Duke University (University Scholars Program, James B. Duke Fellowship, and Pratt School of Engineering Faculty Discretionary Fund).

Mammalian community response to historic volcanic eruptions

It is clear that ecosystems are devastated after a volcanic eruption coats the landscape with a layer of ash; however, the ecological recovery of mammalian communities after eruptions is poorly understood. Volcanic eruptions vary with magnitude and type and only a fraction of them have been analysed for effects on mammalian communities. To better understand mammalian community recovery, I investigated how species richness, evenness, and similarity change across volcanic boundaries in the 1980 Mount Saint Helens (MSH), Washington, and 1914–1917 Mount Lassen, California, eruptions. I compared these eruptions to Mount Rainier, Washington and Mount Shasta, California as controls for regional changes in the fauna. Richness and evenness remain relatively unchanged in Lassen. MSH saw an immediate drop in richness, followed by an increase over 5 years to pre-eruptive levels. Chord distance analysis suggests no long-term change in the Lassen fauna. The pre- and post-MSH fauna are different from one another. The post-eruptive fauna was more similar to neighbouring regions. It is clear from my results that larger eruptions tend to have a greater impact on mammalian community recovery than smaller eruptions, but ultimately, mammalian populations are robust and the presence of neighbouring communities is important for recolonizing devastated areas.

Targeting Janus Kinases and Signal Transducer and Activator of Transcription 3 to Treat Inflammation, Fibrosis, and Cancer: Rationale, Progress, and Caution.

Before it was molecularly cloned in 1994, acute-phase response factor or signal transducer and activator of transcription (STAT)3 was the focus of intense research into understanding the mammalian response to injury, particularly the acute-phase response. Although known to be essential for liver production of acute-phase reactant proteins, many of which augment innate immune responses, molecular cloning of acute-phase response factor or STAT3 and the research this enabled helped establish the central function of Janus kinase (JAK) family members in cytokine signaling and identified a multitude of cytokines and peptide hormones, beyond interleukin-6 and its family members, that activate JAKs and STAT3, as well as numerous new programs that their activation drives. Many, like the acute-phase response, are adaptive, whereas several are maladaptive and lead to chronic inflammation and adverse consequences, such as cachexia, fibrosis, organ dysfunction, and cancer. Molecular cloning of STAT3 also enabled the identification of other noncanonical roles for STAT3 in normal physiology, including its contribution to the function of the electron transport chain and oxidative phosphorylation, its basal and stress-related adaptive functions in mitochondria, its function as a scaffold in inflammation-enhanced platelet activation, and its contributions to endothelial permeability and calcium efflux from endoplasmic reticulum. In this review, we will summarize the molecular and cellular biology of JAK/STAT3 signaling and its functions under basal and stress conditions, which are adaptive, and then review maladaptive JAK/STAT3 signaling in animals and humans that lead to disease, as well as recent attempts to modulate them to treat these diseases. In addition, we will discuss how consideration of the noncanonical and stress-related functions of STAT3 cannot be ignored in efforts to target the canonical functions of STAT3, if the goal is to develop drugs that are not only effective but safe.Significance StatementKey biological functions of Janus kinase (JAK)/signal transducer and activator of transcription (STAT)3 signaling can be delineated into two broad categories: those essential for normal cell and organ development and those activated in response to stress that are adaptive. Persistent or dysregulated JAK/STAT3 signaling, however, is maladaptive and contributes to many diseases, including diseases characterized by chronic inflammation and fibrosis, and cancer. A comprehensive understanding of JAK/STAT3 signaling in normal development, and in adaptive and maladaptive responses to stress, is essential for the continued development of safe and effective therapies that target this signaling pathway.

In vivo quantification of excitation and kilohertz frequency block of the rat vagus nerve

Objective. There is growing interest in treating diseases by electrical stimulation and block of peripheral autonomic nerves, but a paucity of studies on the excitation and block of small-diameter autonomic axons. We conducted in vivo quantification of the strength-duration properties, activity-dependent slowing (ADS), and responses to kilohertz frequency (KHF) signals for the rat vagus nerve (VN). Approach. We conducted acute in vivo experiments in urethane-anaesthetized rats. We placed two cuff electrodes on the left cervical VN and one cuff electrode on the anterior subdiaphragmatic VN. The rostral cervical cuff was used to deliver pulses to quantify recruitment and ADS. The caudal cervical cuff was used to deliver KHF signals. The subdiaphragmatic cuff was used to record compound action potentials (CAPs). Main results. We quantified the input–output recruitment and strength-duration curves. Fits to the data using standard strength-duration equations were qualitatively similar, but the resulting chronaxie and rheobase estimates varied substantially. We measured larger thresholds for the slowest fibres (0.5–1 m s−1), especially at shorter pulse widths. Using a novel cross-correlation CAP-based analysis, we measured ADS of ~2.3% after 3 min of 2 Hz stimulation, which is comparable to the ADS reported for sympathetic efferents in somatic nerves, but much smaller than the ADS in cutaneous nociceptors. We found greater ADS with higher stimulation frequency and non-monotonic changes in CV in select cases. We found monotonically increasing block thresholds across frequencies from 10 to 80 kHz for both fast and slow fibres. Further, following 25 s of KHF signal, neural conduction could require tens of seconds to recover. Significance. The quantification of mammalian autonomic nerve responses to conventional and KHF signals provides essential information for the development of peripheral nerve stimulation therapies and for understanding their mechanisms of action.

The effects of sex, body length, and different habitats on the serum protein electrophoresis of the broad-snouted caiman (Caiman latirostris).

Knowledge of mammalian inflammatory responses is vast; however, many aspects of the inflammatory response in non-mammalian vertebrates, such as reptiles, remain unclear, including those regarding acute-phase proteins (APPs). Recent studies have focused on the use of serum protein electrophoresis (SPE) to assess inflammatory responses in the broad-snouted caiman (Caiman latirostris) and other reptiles. The purpose of this study was to examine the effects of sex, body length, and different habitats on SPE patterns in Clatirostris using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). A total of 40 animals of both sexes and varying body lengths were collected; of these, 23 were free-living in an industrial complex (site 1), and 17 were captive on a rural property (site 2). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis was performed to fractionate different serum protein constituents. Sex affected protein levels, with females showing higher serum levels of total protein, as well as the 90-, 66-, and 58-kDa proteins compared with males. Similarly, body length affected protein levels, with male adults >1.70m in length showing the lowest serum levels of 152-, 58-, 54-, and 27-kDa proteins of all other animals. Finally, habitat affected protein levels, with animals at site 1 showing higher serum levels of 152- and 41-kDa proteins compared with those at site 2. This preliminary study was the first to evaluate the SPE of Clatirostris using SDS-PAGE. Further studies to identify the proteins in each band with more specific and sensitive techniques (eg, mass spectrometry) should be conducted to elucidate the standard of APPs in reptiles better.

Model systems for regeneration: the spiny mouse, Acomys cahirinus.

The spiny mouse, Acomys spp., is a recently described model organism for regeneration studies. For a mammal, it displays surprising powers of regeneration because it does not fibrose (i.e. scar) in response to tissue injury as most other mammals, including humans, do. In this Primer article, we review these regenerative abilities, highlighting the phylogenetic position of the spiny mouse relative to other rodents. We also briefly describe the Acomys tissues that have been used for regeneration studies and the common features of their regeneration compared with the typical mammalian response. Finally, we discuss the contribution that Acomys has made in understanding the general principles of regeneration and elaborate hypotheses as to why this mammal is successful at regenerating.

Quantitative Cross-Species Prediction of β-Adrenergic Response in Ventricular Myocytes

Despite the large body of research on neural control of the heart, our quantitative understanding of the role of β-adrenergic receptor (β-AR) stimulation in human cardiac electrophysiology and arrhythmogenesis remains poor. One possible reason is in the fact that our knowledge is mostly based on experimental animal models (e.g., mouse and rabbit) characterized by quite different cellular electrophysiology. Indeed, we have shown that well conserved mammalian responses to β-AR stimulation (fight or flight) are mediated by different sub-cellular processes in mouse vs.

The tight junction protein TJP1 regulates the feeding-modulated hepatic circadian clock

Circadian clocks in the suprachiasmatic nucleus and peripheral tissues orchestrate behavioral and physiological activities of mammals in response to environmental cues. In the liver, the circadian clock is also modulated by feeding. However, the molecular mechanisms involved are unclear. Here, we show that TJP1 (tight junction protein 1) functions as a mediator of mTOR (mechanistic target of rapamycin) to modulate the hepatic circadian clock. TJP1 interacts with PER1 (period circadian regulator 1) and prevents its nuclear translocation. During feeding, mTOR phosphorylates TJP1 and attenuates its association with PER1, thereby enhancing nuclear shuttling of PER1 to dampen circadian oscillation. Therefore, our results provide a previously uncharacterized mechanistic insight into how feeding modulates the hepatic circadian clock.

ROS-mediated PI3K activation drives mitochondrial transfer from stromal cells to hematopoietic stem cells in response to infection

Hematopoietic stem cells (HSCs) undergo rapid expansion in response to stress stimuli. Here we investigate the bioenergetic processes which facilitate the HSC expansion in response to infection. We find that infection by Gram-negative bacteria drives an increase in mitochondrial mass in mammalian HSCs, which results in a metabolic transition from glycolysis toward oxidative phosphorylation. The initial increase in mitochondrial mass occurs as a result of mitochondrial transfer from the bone marrow stromal cells (BMSCs) to HSCs through a reactive oxygen species (ROS)-dependent mechanism. Mechanistically, ROS-induced oxidative stress regulates the opening of connexin channels in a system mediated by phosphoinositide 3-kinase (PI3K) activation, which allows the mitochondria to transfer from BMSCs into HSCs. Moreover, mitochondria transfer from BMSCs into HSCs, in the response to bacterial infection, occurs before the HSCs activate their own transcriptional program for mitochondrial biogenesis. Our discovery demonstrates that mitochondrial transfer from the bone marrow microenvironment to HSCs is an early physiologic event in the mammalian response to acute bacterial infection and results in bioenergetic changes which underpin emergency granulopoiesis.

Superoxide Drives PI3 Kinase Mediated Mitochondria Transfer from the Bone Marrow Microenvironment to Hematopoietic Stem Cells in Response to Salmonella Typhimurium

Hematopoietic stem cells (HSC) undergo rapid expansion in response to stress stimuli. Specifically, there is rapid expansion of leukocytes in response to pathogenic bacteria which underpins the mammalian response to infection. Presently, the mechanisms by which HSC metabolism is regulated in response to the challenges of pathogenic stress are not fully understood. Here we investigate the bioenergetic processes which facilitate the HSCs expansion in response to infection. We created 2 animal models to study mitochondrial transfer from bone marrow cells to HSCs. The first is a xenograft humanized mouse model in which human CD34+ cord blood (CB) were transplanted into NSG (huNSG) to study mouse mtDNA transfer into cell sorted humanhematopoietic stem cells (huHSC) (mCD45-, hCD34+, hCD38-, hCD45RA-, hCD90+, hCD49f+). The second took advantage of strain specific SNP in the COX3 and ND3 region between NSG (A/C) and C57BL/6 (G/T) mice. Here we transplanted C57BL/6 derived lineage negative hematopoietic progenitor cells into NSG recipient animals and then the chimeric NSG mice were treated with lipopolysaccharide (LPS). We then isolated the HSCs by cell sorting (LN-, CD117+, Sca1+, CD48-, CD150+ and CD34+) and performed mitochondria analysis on the hematopoietic progenitors. In both transplant models we detected recipient mtDNA in donor HSC post infection (11.2% +/-4.1% of total mtDNA from recipient after LPS treatment).HSC expansion and differentiation (as measured by colony forming cell assay and Ki-67 staining) was shown for Salmonella Typhimurium (S.typhimurium)and LPS treated animals. Seahorse mitochondrial stress analysis confirmed increased oxygen consumption levels in hematopoietic stem and progenitor cells (HSPC) from LPS (2 hours) and S.typhimurium(72 hours) treated C57BL/6. We confirmed that this was not due to mitochondrial biogenesis by showing that TFAM was not upregulated in HSPC in response to LPS at 2 hours. In previous work we have reported that transfer of functional mitochondria from the BM to AML is driven by AML derived NOX2 dependent ROS (Marlein, Blood 2017). To determine if ROS drives mitochondrial transfer from bone marrow cells to HSCs, we treated huNSG with with L-buthionine-sulfoximine (BSO), a GSH biosynthesis inhibitor, for 2 hours. Mouse mtDNA (12.3% +/-4.8) was detected in huHSC from BSO treated huNSG mice but not in the control huHSC. Moreover, the ROS scavenger N-acetyl-cysteine (NAC) was shown to reduce mtDNA transfer in LPS treated mice. We next investigated which cell of the BM donates their mitochondria during stress hematopoiesis. To do this we cultured bone marrow stromal cells (BMSC), osteoblast and macrophages with HSPC in the presence of H2O2. Transfer of mtDNA was observed from BMSC to HSPC, but we did not see mitochondria transfer from either macrophages or osteoblasts to HSPC. In addition, in vivo mitochondrial levels were reduced in the BMSCs (CD105+, CD140a+ CD31-, Ter119-, CD45-) of LPS treated C57BL/6 compared to control animals and this reduction was inhibited by the addition of NAC. Finally, ROS has been shown to drive PtdIns(3,4,5)P3 (PIP3) oxidation of PTEN and subsequent activation of PI3K (Covey, Oncogene 2007). We foundthat AKT phosphorylation was elevated in both the BMSC and the HSC of LPS treated animals when compared to the untreated controls, andin vivoadministration ofidelalisib (a PI3 Kinase delta inhibiting drug), decreased mitochondrial transfer from the BMSC to HSC. Our data indicates that infection induced ROS drives PI3 kinase mediated mitochondrial transfer from the BM microenvironment to HSCs. This process is an early physiologic event in the mammalian response to acute bacterial infection and results in bioenergetic changes which underpin emergency granulopoiesis. Disclosures Bowles: Janssen: Research Funding; Abbvie: Research Funding. Rushworth:Abbvie: Research Funding; Janssen: Research Funding.

Complete upper airway collapse and apnoea during tethered swimming in horses.

There is limited knowledge of the breathing strategy and impact on the patency of the upper respiratory tract (URT) in swimming horses. To describe the respiratory responses and endoscopic appearance of the URT during tethered swimming in horses. Prospective descriptive study. Ten race-fit horses, with no history of URT obstruction, were examined during tethered swimming. Endoscopic examination, heart rate, sound recordings and above and below water video recordings were obtained. Plasma lactate concentration was measured before and 5min after swimming and tracheal endoscopy was performed 30min after exercise to assess for presence of blood or mucus. Four horses also underwent endoscopy during exercise on the track. Mean (±s.d.) breathing frequency was 28±5breaths/min during swimming, with a brief inspiration (mean±s.d. TI =0.51±0.08s), followed by a period of apnoea (1.59±0.53s) and then a short, forced expiration (TE =0.42±0.5s). During apnoea all horses exhibited complete collapse of the URT including closure of the external nares, nasopharynx and rima glottidis (with bilateral adduction of the arytenoid cartilages and vocal folds) and, in two horses, epiglottic retroversion. No horses had URT collapse during overground exercise. Locomotor-respiratory coupling was not observed during swimming. Median (IQR) plasma lactate post swim was 4.71mmol/L (2.08-8.09mmol/L) vs 0.68mmol/L (0.65-0.71mmol/L) preswim. Post swim endoscopy revealed grade 1 exercise-induced pulmonary haemorrhage (EIPH) in 2 horses. Median mucus grade was 1 (range 0-3). Overground endoscopy was not performed in all horses. Horses experienced complete URT collapse associated with post inspiratory apnoea when swimming. The reason for this is unknown but may be to aid buoyancy or associated with the mammalian dive response - a survival reflex to preserve oxygen stores and prevent water entering the lungs.

CRH Promotes the Neurogenic Activity of Neural Stem Cells in the Adult Hippocampus

Local cues in the adult neurogenic niches dynamically regulate homeostasis in neural stem cells, whereas their identity and associated molecular mechanisms remain poorly understood. Here, we show that corticotropin-releasing hormone (CRH), the major mediator of mammalian stress response and a key neuromodulator in the adult brain, is necessary for hippocampal neural stem cell (hiNSC) activity under physiological conditions. In particular, we demonstrate functionality of the CRH/CRH receptor (CRHR) system in mouse hiNSCs and conserved expression in humans. Most important, we show that genetic deficiency of CRH impairs hippocampal neurogenesis, affects spatial memory, and compromises hiNSCs' responsiveness to environmental stimuli. These deficits have been partially restored by virus-mediated CRH expression. Additionally, we provide evidence that local disruption of the CRH/CRHR system reduces neurogenesis, while exposure of adult hiNSCs to CRH promotes neurogenic activity via BMP4 suppression. Our findings suggest a critical role of CRH in adult neurogenesis, independently of its stress-related systemic function.

"What a Girl Wants": What Can We Learn From Animal Models of Female Sexual Motivation?

Sexual motivation is notably different than other motivations such as hunger and thirst, because it lacks homeostatic drive. Sexual motivation poses no threat to physical well-being; individual survival is not at stake. Nevertheless, sexual motivation is a powerful drive and is critical for species survival. Understanding the complexity of sexual motivation has the potential to advance our understanding of other motivations, even pathological motivations, such as those associated with substance abuse. The study of motivation that is unique to females has often been neglected. A number of paradigms have been developed to investigate female sexual motivation beyond measuring only the lordosis reflex. Lordosis is a reflexive posture displayed by female mammals in response to male sexual stimulation to facilitate intromission. The lordosis reflex is essential, but studying the drive to mate is compromised in the absence of robust lordosis. Therefore, appetitive measures of sexual behavior (e.g., preferences, solicitation behaviors) are more specific and more sensitive indicators of sexual motivation than lordosis alone. Paradigms designed to study female sexual motivation often provide a female subject with the choice to interact with a sexually vigorous male or either a non-sexual partner (i.e., female, castrated male) or to remain alone. The study of appetitive measures of sexual motivation has elucidated the role of hormones in female sexual motivation, as well as the underlying neural pathways. The present review describes methods for studying female rats to advance our understanding of sexual motivation and sexual dysfunction.

Trait-mediated indirect interactions: Moose browsing increases sawfly fecundity through plant-induced responses.

Induced responses in plants, initiated by herbivory, create potential for trait‐mediated indirect interactions among herbivores. Responses to an initial herbivore may change a number of plant traits that subsequently alter ecological processes with additional herbivores. Although common, indirect interactions between taxonomically distant herbivores, such as mammals and insects, are less studied than between taxonomically related species (i.e., insect–insect). In terms of mammal–insect interactions, effects on insect numbers (e.g., density) are relatively well studied, whereas effects on performance (e.g., fecundity) are rarely explored. Moreover, few studies have explored mammal–insect interactions on coniferous plants.The aim of this study was to investigate the effect of mammalian induced responses on insect performance. We specifically investigated the effect of moose (Alces alces) browsing on Scots pine (Pinus sylvestris) and subsequent effects on sawfly (Neodiprion sertifer) performance.Sawfly larvae were reared on browsed, clipped, and unbrowsed control pine trees in a controlled field experiment. Afterward, cocoon weight was measured. Needle C:N ratio and di‐terpene content were measured in response to browsing.Sawfly performance was enhanced on trees browsed by moose. Cocoon weight (proxy for fecundity) was 9 and 13% higher on browsed and clipped trees compared to unbrowsed trees. Cocoon weight was weakly related to needle C:N ratio, and browsed trees had lower a C:N ratio compared to unbrowsed trees. Needle di‐terpene content, known to affect sawfly performance, was neither affected by the browsing treatments nor did it correlate with sawfly weight.We conclude that mammalian herbivory can affect insect herbivore performance, with potential consequences for ecological communities and with particular importance for insect population dynamics. The measured plant variables could not fully explain the effect on sawfly performance providing a starting point for the consideration of additional plant responses induced by mammalian browsing affecting insect performance.

LncRNA expression profile during autophagy and Malat1 function in macrophages.

Long noncoding RNAs (lncRNAs) are a class of functional non-coding transcripts that are longer than 200 nt and regulate gene expression via diverse mechanisms in eukaryotes. In fact, they have emerged as critical epigenetic and transcriptional regulators of autophagy in mammals in response to various stressors. Autophagy not only plays a crucial role in maintaining cellular homeostasis, but it is also essential to immunity, targets intracellular pathogens for degradation, modulates inflammation, and participates in adaptive immune responses. However, the expression profile of lncRNA and its role in regulating autophagy in macrophages have been poorly defined. Here, we used transcriptomic and bioinformatics to analysis LncRNA expression profile during autophagy and functional studies to evaluate the function of the metastasis-associated lung adenocarcinoma transcript-1 (Malat1) lncRNA in macrophages. A total of 1112 putative lncRNAs (240 novel lncRNAs) were identified, including 831 large intergenic, 129 intronic, and 152 anti-sense lncRNA, of which 59 differentially expressed transcripts exhibited a greater than 1.5-fold change under different conditions. The interaction of Malat1 lncRNA with microRNA (mir)-23-3p and lysosomal-associated membrane protein 1 (Lamp1) was found, Malat1 releases inhibition of Lamp1 expression in macrophages through competitive adsorption of mir-23-3p. The results of this study provide a better understanding of lncRNA function in macrophages and a basis for further investigation into the roles and mechanisms of ncRNA in immunology, particularly the functions of Malat1 and mir-23-3p in the pathogenesis of macrophages.