Blood volume reduction due to rapid plasma loss after birth in preterm piglets.

BACKGROUND: Understanding changes in blood volume after preterm birth is critical to preventing cardiovascular deterioration in preterm infants. The aims were to determine if blood volume is higher in preterm than term piglets and if blood volume changes in the hours after birth. METHODS: Paired blood volume measurements were conducted in preterm piglets (98/115d gestation, ~28wk gestation infant) at 0.5-5 h (n = 12), 0.5-9 h (n = 44) and 5-11 h (n = 7) after birth, and in a term cohort at 0.5-9 h (n = 40) while under intensive care. RESULTS: At 30 min after birth, blood volume was significantly lower in preterm piglets compared to term piglets. By 9 h after birth, blood volume had reduced by 18% in preterm piglets and 13% in term piglets. By 5-9 h after birth, preterm piglets had significantly lower blood volumes than at term (61 ± 10 vs. 76 ± 11 mL/kg). CONCLUSIONS: In contrast to clinical resources, preterm piglets have a lower blood volume than at term. Substantial reductions in blood volume after birth leave some preterm piglets hypovolemic. If this also occurs in preterm infants, this may have important clinical consequences. Modern studies of blood volume changes after birth are essential for improving preterm outcomes. IMPACT: Preterm piglets do not have a higher blood volume than their term counterparts, in contrast to current clinical estimates. Rapid reduction in blood volume after birth leads to hypovolemia in some preterm piglets. There is a critical need to understand blood volume changes after birth in preterm infants in order to improve clinical management of blood volume.

Therapeutic potential of conduction system pacing as a method for improving cardiac output during ventricular tachycardia.

BACKGROUND: Ventricular tachycardia (VT) reduces cardiac output through high heart rates, loss of atrioventricular synchrony, and loss of ventricular synchrony. We studied the contribution of each mechanism and explored the potential therapeutic utility of His bundle pacing to improve cardiac output during VT. METHODS: Study 1 aimed to improve the understanding of mechanisms of harm during VT (using pacing simulated VT). In 23 patients with left ventricular impairment, we recorded continuous ECG and beat-by-beat blood pressure measurements. We assessed the hemodynamic impact of heart rate and restoration of atrial and biventricular synchrony. Study 2 investigated novel pacing interventions during clinical VT by evaluating the hemodynamic effects of His bundle pacing at 5 bpm above the VT rate in 10 patients. RESULTS: In Study 1, at progressively higher rates of simulated VT, systolic blood pressure declined: at rates of 125, 160, and 190 bpm, -22.2%, -42.0%, and -58.7%, respectively (ANOVA p < 0.0001). Restoring atrial synchrony alone had only a modest beneficial effect on systolic blood pressure (+ 3.6% at 160 bpm, p = 0.2117), restoring biventricular synchrony alone had a greater effect (+ 9.1% at 160 bpm, p = 0.242), and simultaneously restoring both significantly increased systolic blood pressure (+ 31.6% at 160 bpm, p = 0.0003). In Study 2, the mean rate of clinical VT was 143 ± 21 bpm. His bundle pacing increased systolic blood pressure by + 14.2% (p = 0.0023). In 6 of 10 patients, VT terminated with His bundle pacing. CONCLUSIONS: Restoring atrial and biventricular synchrony improved hemodynamic function in simulated and clinical VT. Conduction system pacing could improve VT tolerability and treatment.

Linking nematodes and ecosystem function: a trait-based framework.

Trait-based approaches are being increasingly adopted to understand species' ecological strategies and how organisms influence ecosystem function. Trait-based research on soil organisms, however, remains poorly developed compared with that for plants. The abundant and diverse soil nematodes are prime candidates to advance trait-based approaches belowground, but a unified trait framework to describe nematode ecological strategies and assess their linkages with ecosystem function is lacking. We categorized nematode traits as morphological, physiological, life history, and community clusters, and proposed the nematode economics spectrum (NES) to better understand nematode ecological strategies and their association with ecosystem function. We argue that bridging the NES and the plant economics spectrum will facilitate a more holistic understanding of ecosystem carbon and nutrient cycling under global change.

Machine learning-derived cycle length variability metrics predict spontaneously terminating ventricular tachycardia in implantable cardioverter defibrillator recipients.

Aims: Implantable cardioverter defibrillator (ICD) therapies have been associated with increased mortality and should be minimized when safe to do so. We hypothesized that machine learning-derived ventricular tachycardia (VT) cycle length (CL) variability metrics could be used to discriminate between sustained and spontaneously terminating VT. Methods and results: In this single-centre retrospective study, we analysed data from 69 VT episodes stored on ICDs from 27 patients (36 spontaneously terminating VT, 33 sustained VT). Several VT CL parameters including heart rate variability metrics were calculated. Additionally, a first order auto-regression model was fitted using the first 10 CLs. Using features derived from the first 10 CLs, a random forest classifier was used to predict VT termination. Sustained VT episodes had more stable CLs. Using data from the first 10 CLs only, there was greater CL variability in the spontaneously terminating episodes (mean of standard deviation of first 10 CLs: 20.1 ± 8.9 vs. 11.5 ± 7.8 ms, P < 0.0001). The auto-regression coefficient was significantly greater in spontaneously terminating episodes (mean auto-regression coefficient 0.39 ± 0.32 vs. 0.14 ± 0.39, P < 0.005). A random forest classifier with six features yielded an accuracy of 0.77 (95% confidence interval 0.67 to 0.87) for prediction of VT termination. Conclusion: Ventricular tachycardia CL variability and instability are associated with spontaneously terminating VT and can be used to predict spontaneous VT termination. Given the harmful effects of unnecessary ICD shocks, this machine learning model could be incorporated into ICD algorithms to defer therapies for episodes of VT that are likely to self-terminate.

Leaf phosphorus fractions vary with leaf economic traits among 35 Australian woody species.

Adaptations of plants to phosphorus (P) deficiency include reduced investment of leaf P in storage (orthophosphates in vacuoles), nucleic acids and membrane lipids. Yet, it is unclear how these adaptations are associated with plant ecological strategies. Five leaf P fractions (orthophosphate P, Pi ; metabolite P, PM ; nucleic acid P, PN ; lipid P, PL ; and residual P, PR ) were analysed alongside leaf economic traits among 35 Australian woody species from three habitats: one a high-P basalt-derived soil and two low-P sandstone-derived soils, one undisturbed and one disturbed by human activities with artificial P inputs. Species at the undisturbed low-P site generally exhibited lower concentrations of total leaf P ([Ptotal ]), primarily associated with lower concentrations of Pi , and PN . The relative allocation of P to each fraction varied little among sites, except that higher PL per [Ptotal ] (rPL ) was recorded at the undisturbed low-P site than at the high-P site. This higher rPL , reflecting relative allocation to membranes, was primarily associated with lower concentrations of leaf nitrogen at the undisturbed low-P site than at the high-P site. Associations between leaf P fractions and leaf nitrogen may provide a basis for understanding the variation in plant ecological strategies dependent on soil P availability.

Fractures in Thoroughbred racing and the potential for pre-race identification of horses at risk.

Risk rates for and predisposing factors to fractures occurring in Thoroughbred racing that have been published in peer reviewed journals are documented. The potential for currently available techniques to identify horses at increased risk for fracture is discussed on the bases of principles, practicalities, advantages, disadvantages and current data. All are reviewed in light of justifiable decision making and importance of fractures to horseracing's social license.

Arthroscopically guided lag screw fixation of subchondral bone cysts in the medial femoral condyle in Thoroughbred racehorses: description of technique and comparative results.

OBJECTIVE: To describe an arthroscopically guided technique for lag screw placement across subchondral bone cyst (SBC) in the medial femoral condyle (MFC) and to compare postoperative racing performance with corticosteroid injection and cyst debridement. STUDY DESIGN: Retrospective cohort study. ANIMALS: One hundred twenty-three horses with 134 MFC SBCs undergoing treatment at a single referral hospital in the UK between January, 2009, and December, 2020. METHODS: Sex, age, limb affected, radiographic cyst dimensions, preoperative and postoperative lameness, surgical technique (lag screw placement, cyst debridement, intralesional corticosteroid injection), and, where applicable, screw positioning were recorded retrospectively. A ratio was calculated using measurements from preoperative and postoperative radiographs. Outcome was assessed by resolution or improvement in lameness, reduction in cyst size, and starting one race after treatment. Outcome data was compared between treatment groups. RESULTS: Twenty-six of 45 (57.8%) horses that underwent transcondylar screw placement raced postoperatively, at a median of 403 days between surgery and first postoperative race. There was no difference between treatment groups with regard to racing or preoperative and postoperative lameness. Cysts treated with transcondylar screw placement had a greater reduction in cyst size and a reduced period of convalescence in comparison with those that underwent debridement; the results were similar to those treated by intralesional corticosteroid injection. CONCLUSION: Postoperative racing rates were similar for all techniques. Convalescence was reduced for lag screw placement and corticosteroid injection compared to debridement. CLINICAL SIGNIFICANCE: The arthroscopically guided technique results in radiographically consistent screw placement and cyst engagement and offers a viable alternative to other treatments.

Leaf-level coordination principles propagate to the ecosystem scale.

Fundamental axes of variation in plant traits result from trade-offs between costs and benefits of resource-use strategies at the leaf scale. However, it is unclear whether similar trade-offs propagate to the ecosystem level. Here, we test whether trait correlation patterns predicted by three well-known leaf- and plant-level coordination theories - the leaf economics spectrum, the global spectrum of plant form and function, and the least-cost hypothesis - are also observed between community mean traits and ecosystem processes. We combined ecosystem functional properties from FLUXNET sites, vegetation properties, and community mean plant traits into three corresponding principal component analyses. We find that the leaf economics spectrum (90 sites), the global spectrum of plant form and function (89 sites), and the least-cost hypothesis (82 sites) all propagate at the ecosystem level. However, we also find evidence of additional scale-emergent properties. Evaluating the coordination of ecosystem functional properties may aid the development of more realistic global dynamic vegetation models with critical empirical data, reducing the uncertainty of climate change projections.

Comparison of radiography and CT for the evaluation of third carpal bone slab fractures in Thoroughbred racehorses.

Slab fractures of the third carpal bone (C3) are a common cause of lameness in Thoroughbred racehorses. Information on fracture morphology is commonly obtained from radiographs or CT. This retrospective, methods comparison aimed to explore the agreement between radiography and CT for imaging C3 slab fractures and discuss the contribution of the latter to clinical case management. Thoroughbred racehorses with a slab or incomplete slab fracture of C3 identified on radiographs that subsequently underwent CT examination were included. Fracture characteristics (location, plane, classification, displacement, comminution) and fracture length as a percentage of the proximodistal length of the bone, termed the proximodistal fracture percentage (PFP) were recorded independently from both modalities and then compared. Across all fractures (n = 82) radiographs and CT showed slight agreement on the presence of comminution (Cohen's Kappa (κ) 0.108, P 0.031) and moderate agreement on fracture displacement (K 0.683, P < 0.001). Computed tomography identified comminution in 49 (59.8%) and displacement in nine (11.0%) fractures that were not detected by radiographs. Half of the fractures were only seen on flexed dorsoproximal-dorsodistal oblique (DPr-DDiO) radiographs and therefore were of unknown length without additional CT imaging. Incomplete fractures that could be measured on radiographs (n = 12) had a median (IQR) PFP of 40% (30%-52%) on radiographs and 53% (38%-59%) on CT, a statistically significant difference (P = 0.026). Radiography and CT showed the poorest agreement when determining the presence of comminution. Additionally, radiography often underestimated the incidence of displacement, and fracture length, and resulted in more fractures being classified as incomplete when compared to CT.

Analysis of exotic pathogens found in a large group of imported dogs following an animal welfare investigation.

BACKGROUND: Increased dog relocation can cause dissemination of pathogen and vector populations, and this is being recognised in countries across Northern Europe, including the UK. Data regarding the prevalence of exotic infections in dogs entering the UK would be beneficial to veterinarians to help assess pets entering the UK from abroad and to help calculate the risk of establishment of novel pathogens. This study reports the findings from a group of imported dogs that was seized as part of a Royal Society for the Prevention of Cruelty to Animals (RSPCA)-led animal welfare investigation and subsequently blood tested for exotic pathogens. METHODS: As part of the RSPCA investigation, 151 dogs were removed from the site. Blood tests were performed for Babesia canis, Ehrlichia canis, Hepatozoon canis and Leishmania infantum by PCR, Brucella canis by antibody serology and Dirofilaria immitis by blood antigen. In addition to pathogen screening, a serology titre for rabies was measured for each dog. A clinical examination was performed by a veterinary surgeon, and clinical signs were recorded. RESULTS: Overall, 24% (32/133) of the dogs tested positive for an infection with one or more exotic pathogens. Two dogs were positive for Br. canis antibodies and had no clinical signs indicative of infection. Leishmania was identified in 10.5% (14/133) of dogs, and all but two of these were implanted with microchips of Romanian origin. H. canis was identified in 9.6% (10/104) of dogs, all of whom had a Romanian microchip. D. immitis was identified in 4.1% (5/121) of dogs, B. canis in 2.3% (3/129) of dogs and E. canis in only 1.5% (2/131) of dogs tested. Only four dogs were found to have co-infections. No significant association was found between the pathogens detected and presenting clinical signs. LIMITATIONS: This was a group of rescued dogs that were tested for a range of pathogens. They were not randomly selected and as such do not represent the true prevalence of these pathogens in dogs imported into the UK. CONCLUSIONS: This study demonstrates a range of exotic pathogens entering the UK, including Br. canis, and demonstrates the importance of screening imported dogs. The emphasis on early recognition of exotic pathogens in imported dogs has relied on screening based on relevant clinical signs and the country of origin. While these factors are useful, this study demonstrated no significant association between presenting clinical signs and the pathogens carried.

Structural equation model of intersectional microaggressions, discrimination, resilience, and mental health among black women with hiv.

OBJECTIVE: Compared to non-Black women, Black women in the United States are more likely to be diagnosed with HIV, living with HIV, and have suboptimal HIV outcomes, disparities largely linked to structural and psychosocial factors that may impact mental health. METHOD: 151 Black women living with HIV (BWLWH) enrolled in a longitudinal cohort study completed baseline assessments between October 2019 and January 2020 in the Southeastern United States. Measures captured microaggressions (gendered-racial, HIV, and Lesbian/Gay/Bisexual/Transgender/Queer), "macro" discrimination acts (gender, race, HIV, sexual orientation), resilience factors (self-efficacy, trait resilience, posttraumatic growth, positive religious coping, and social support), and mental health (depressive symptoms, posttraumatic stress disorder (PTSD) symptoms, and posttraumatic cognitions). Four structural equation models were estimated with latent discrimination (LD), latent microaggression (LM), and latent resilience (LR) as predictors and depressive symptoms, PTSD symptoms, posttraumatic cognitions, and latent mental health (LH) as outcomes. Indirect pathways from LD and LM via LR and LR as a moderator were estimated. RESULTS: Models fit well based on indices. There were significant direct pathways from LM and LR to depressive symptoms, posttraumatic cognitions, and LH and a significant direct pathway from LM to PTSD symptoms, but not from LD to any mental health outcome. Indirect pathways were not significant. However, LR moderated the relationships between both LM and LD with PTSD symptoms. CONCLUSION: Intersectional microaggressions and resilience factors may play key roles in BWLWH's mental health. Research is needed to examine these pathways overtime and provide opportunities to improve mental health and HIV outcomes among BWLWH. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Ecological strategies of (pl)ants: Towards a world-wide worker economic spectrum for ants.

Current global challenges call for a rigorously predictive ecology. Our understanding of ecological strategies, imputed through suites of measurable functional traits, comes from decades of work that largely focussed on plants. However, a key question is whether plant ecological strategies resemble those of other organisms.Among animals, ants have long been recognised to possess similarities with plants: as (largely) central place foragers. For example, individual ant workers play similar foraging roles to plant leaves and roots and are similarly expendable. Frameworks that aim to understand plant ecological strategies through key functional traits, such as the 'leaf economics spectrum', offer the potential for significant parallels with ant ecological strategies.Here, we explore these parallels across several proposed ecological strategy dimensions, including an 'economic spectrum', propagule size-number trade-offs, apparency-defence trade-offs, resource acquisition trade-offs and stress-tolerance trade-offs. We also highlight where ecological strategies may differ between plants and ants. Furthermore, we consider how these strategies play out among the different modules of eusocial organisms, where selective forces act on the worker and reproductive castes, as well as the colony.Finally, we suggest future directions for ecological strategy research, including highlighting the availability of data and traits that may be more difficult to measure, but should receive more attention in future to better understand the ecological strategies of ants. The unique biology of eusocial organisms provides an unrivalled opportunity to bridge the gap in our understanding of ecological strategies in plants and animals and we hope that this perspective will ignite further interest. Read the free Plain Language Summary for this article on the Journal blog.

Leaf economics fundamentals explained by optimality principles.

The life span of leaves increases with their mass per unit area (LMA). It is unclear why. Here, we show that this empirical generalization (the foundation of the worldwide leaf economics spectrum) is a consequence of natural selection, maximizing average net carbon gain over the leaf life cycle. Analyzing two large leaf trait datasets, we show that evergreen and deciduous species with diverse construction costs (assumed proportional to LMA) are selected by light, temperature, and growing-season length in different, but predictable, ways. We quantitatively explain the observed divergent latitudinal trends in evergreen and deciduous LMA and show how local distributions of LMA arise by selection under different environmental conditions acting on the species pool. These results illustrate how optimality principles can underpin a new theory for plant geography and terrestrial carbon dynamics.

Replicated Evolution in Plants.

Similar traits and functions commonly evolve in nature. Here, we explore patterns of replicated evolution across the plant kingdom and discuss the processes responsible for such patterns. We begin this review by defining replicated evolution and the theoretical, genetic, and ecological concepts that help explain it. We then focus our attention on empirical cases of replicated evolution at the phenotypic and genotypic levels. We find that replication at the ecotype level is common, but evidence for repeated ecological speciation is surprisingly sparse. On the other hand, the replicated evolution of ecological strategies and physiological mechanisms across similar biomes appears to be pervasive. We conclude by highlighting where future efforts can help us bridge the understanding of replicated evolution across different levels of biological organization. Earth's landscape is diverse but also repeats itself. Organisms seem to have followed suit.

Red cell infusion but not saline is effective for volume expansion in preterm piglets.

BACKGROUND: A common first-line treatment for supporting cardiovascular function in preterm infants is volume expansion using saline, but this does not improve outcomes. This study aimed to determine if volume expansion with saline increases blood volume, blood pressure and cerebral oxygenation; and if volume expansion with packed red blood cells (RBC) is more effective. We hypothesized that RBC infusion is more effective than saline for increasing blood volume and maintaining cardiovascular function and cerebral oxygenation. METHODS: Five groups of preterm piglets (98/115d gestation) were infused with saline (10 or 20 mL/kg) or RBC (10 or 20 mL/kg) or no treatment. Blood volume, blood pressure, central venous pressure, heart rate, carotid flow, cerebral oxygenation, arterial pH, base excess, and lactate levels were assessed for 6 h after treatment started. RESULTS: Both RBC groups had significant increases in blood volume, and improved measures of cardiovascular function, cerebral oxygenation and metabolic acidosis. Saline infusion did not increase blood volume or measures of cardiovascular function, cerebral oxygenation or metabolic acidosis. CONCLUSIONS: The results suggest that the deteriorating cardiovascular function in the hours after birth in preterm piglets, and possibly in premature babies, may be reversed or halted by more effective support of blood volume. IMPACT: Blood volume decreases after birth in preterm piglets and this decrease is associated with deteriorating cardiovascular function and cerebral oxygenation. Infusion of saline does not increase blood volume nor prevent deterioration in cardiovascular function. Infusion of packed red blood cells results in an increase in blood volume and improvements in cardiovascular function and cerebral oxygenation. Deteriorating cardiovascular function in the hours after birth in preterm piglets, and possibly in human preterm neonates, may be reversed or halted by more effective support of blood volume.

Coordination of photosynthetic traits across soil and climate gradients.

"Least-cost theory" posits that C3 plants should balance rates of photosynthetic water loss and carboxylation in relation to the relative acquisition and maintenance costs of resources required for these activities. Here we investigated the dependency of photosynthetic traits on climate and soil properties using a new Australia-wide trait dataset spanning 528 species from 67 sites. We tested the hypotheses that plants on relatively cold or dry sites, or on relatively more fertile sites, would typically operate at greater CO2 drawdown (lower ratio of leaf internal to ambient CO2 , Ci :Ca ) during light-saturated photosynthesis, and at higher leaf N per area (Narea ) and higher carboxylation capacity (Vcmax 25 ) for a given rate of stomatal conductance to water vapour, gsw . These results would be indicative of plants having relatively higher water costs than nutrient costs. In general, our hypotheses were supported. Soil total phosphorus (P) concentration and (more weakly) soil pH exerted positive effects on the Narea -gsw and Vcmax 25 -gsw slopes, and negative effects on Ci :Ca . The P effect strengthened when the effect of climate was removed via partial regression. We observed similar trends with increasing soil cation exchange capacity and clay content, which affect soil nutrient availability, and found that soil properties explained similar amounts of variation in the focal traits as climate did. Although climate typically explained more trait variation than soil did, together they explained up to 52% of variation in the slope relationships and soil properties explained up to 30% of the variation in individual traits. Soils influenced photosynthetic traits as well as their coordination. In particular, the influence of soil P likely reflects the Australia's geologically ancient low-relief landscapes with highly leached soils. Least-cost theory provides a valuable framework for understanding trade-offs between resource costs and use in plants, including limiting soil nutrients.