Something in the wind: the influence of wind speed and direction on African lion movement behavior

Olfaction is a key sense, enabling animals to locate forage, select mates, navigate their environment, and avoid predation. Wind is an important abiotic factor that modulates the strength of olfactory information detected by animals. In theory, when airflow is unidirectional, an animal can increase odor detection probability and maximize the amount of olfactory information gained by moving crosswind. Given energetic costs inherent to activity and locomotion, behavioral search strategies that optimize the benefit-cost ratio should be advantageous. We tested whether African lions (Panthera leo) modify their movement directionality and distance according to wind speed and direction during hours of darkness when they are most active. We tracked 29 lions in southern Zimbabwe using GPS collars and deployed a weather station to collect detailed abiotic data. We found that when wind speeds increased lions were more likely to move crosswind. We also found that female lions, which tend to hunt more often than males, traveled farther when wind speeds were stronger. The results of our analysis suggest that lions adjust their movement behavior according to wind speed and direction. We inferred that this was a behavioral decision to maximize the amount of olfactory information gained per unit of energy spent. Our findings not only offer one of the first detailed insights on large carnivore anemotaxis (movement direction relative to wind) but also make an important contribution towards understanding the influence of wind on predator ecology in general which remains understudied to date.

Results of Two Cases of Pig-to-Human Kidney Xenotransplantation

BACKGROUND

Xenografts from genetically modified pigs have become one of the most promising solutions to the dearth of human organs available for transplantation. The challenge in this model has been hyperacute rejection. To avoid this, pigs have been bred with a knockout of the alpha-1,3-galactosyltransferase gene and with subcapsular autologous thymic tissue.

METHODS

We transplanted kidneys from these genetically modified pigs into two brain-dead human recipients whose circulatory and respiratory activity was maintained on ventilators for the duration of the study. We performed serial biopsies and monitored the urine output and kinetic estimated glomerular filtration rate (eGFR) to assess renal function and xenograft rejection.

RESULTS

The xenograft in both recipients began to make urine within moments after reperfusion. Over the 54-hour study, the kinetic eGFR increased from 23 ml per minute per 1.73 m² of body-surface area before transplantation to 62 ml per minute per 1.73 m² after transplantation in Recipient 1 and from 55 to 109 ml per minute per 1.73 m² in Recipient 2. In both recipients, the creatinine level, which had been at a steady state, decreased after implantation of the xenograft, from 1.97 to 0.82 mg per deciliter in Recipient 1 and from 1.10 to 0.57 mg per deciliter in Recipient 2. The transplanted kidneys remained pink and well-perfused, continuing to make urine throughout the study. Biopsies that were performed at 6, 24, 48, and 54 hours revealed no signs of hyperacute or antibody-mediated rejection. Hourly urine output with the xenograft was more than double the output with the native kidneys.

CONCLUSIONS

Genetically modified kidney xenografts from pigs remained viable and functioning in brain-dead human recipients for 54 hours, without signs of hyperacute rejection. (Funded by Lung Biotechnology.).

Response to American College of Physician's statement on the ethics of transplant after normothermic regional perfusion

This paper responds to the position statement released by the American College of Physicians (ACP) entitled "Ethics, Determination of Death, and Organ Transplantation in Normothermic Regional Perfusion (NRP) with Controlled Donation after Circulatory Determination of Death (cDCD): American College of Physicians Statement of Concern." The ACP's statement engages with critical ethical issues surrounding cDCD NRP, but several of their conclusions are flawed. Contrary to the statement, the practice respects the dead donor rule and the legal definition of death while honoring the wishes of the deceased and their loved ones to help save the lives of those in need of organ transplants. cDCD NRP is well established in many countries, it can enhance trust in medical practice and organ donation, and will increase the availability of optimal organs for life-saving transplants.

The Integral Nature of Encounter Rate in Predicting Livestock Depredation Risk

Carnivore depredation of livestock is one of the primary drivers of human-carnivore conflict globally, threatening the well-being of livestock owners, and fueling large carnivore population declines. Interventions designed to reduce carnivore depredation typically center around predictions of depredation risk. However, these spatial risk models tend to be informed by data depicting the number of livestock attacked by carnivores. Importantly, such models omit key stages in the predation sequence which are required to predict predation risk, or in this case depredation risk. Applying the classic predation risk model defined by Lima and Dill demonstrates that depredation risk is dependent upon quantifying the rates at which carnivores encounter livestock before attacking. However, encounter rate is challenging to estimate, necessitating novel data collection systems. We developed and applied such a system to quantify carnivore-livestock encounters at livestock corrals (i.e., bomas) across a 9-month period in Central Kenya. Concurrently, we monitored the number of livestock attacked by carnivores at these bomas. We calculated carnivore-livestock encounter rates, attack rates, and depredation risk at the boma. We detected 1,383 instances in which carnivores encountered livestock at the bomas. However, we only recorded seven attacks. We found that the encounter rate and attack rate for spotted hyenas were almost six and three times higher than that for any other species, respectively. Consequently, spotted hyenas posed the greatest depredation risk for livestock at the boma. We argue that better understanding of carnivore-livestock encounter rates is necessary for effective prediction and mitigation of carnivore depredation of livestock.

The efficacy of interventions to protect crops from raiding elephants

Both African elephants (Loxodonta spp.) and the Asian elephant (Elephas maximus) across their range come into conflict with people because of their crop-raiding behavior, which presents profound impediments to farmer livelihoods. In response, a series of interventions, designed to reduce elephant crop raiding have been applied. Based on an extensive review of elephant crop-raiding studies published over a 31-year period, we identified four primary categories of interventions including: (i) detection efforts; (ii) preemptive measures; (iii) fencing and trenches; and (iv) deterrent techniques. The interventions reported to be most effective involved chili peppers (i.e., fences, spray, and briquettes) and crop guarding coupled with deterrents. The extent to which these interventions can be applied more widely is unclear as only two studies examined efficacy across sites in more than one country. Thus, future inquiry should evaluate the ability of effective interventions, or indeed a combination of interventions, to be applied across the range of elephants to reduce crop raiding at scale.

OUP accepted manuscript

Because biodiversity loss has largely been attributed to human actions, people, particularly those in the Global South, are regularly depicted as threats to conservation. This context has facilitated rapid growth in green militarization, with fierce crackdowns against real or perceived environmental offenders. We designed an undergraduate course to assess student perspectives on biodiversity conservation and social justice and positioned those students to contribute to a human heritage-centered conservation (HHCC) initiative situated in Uganda. We evaluated changes in perspectives using pre- and postcourse surveys and reflection instruments. Although the students started the course prioritizing biodiversity conservation, even when it was costly to human well-being, by the end of the course, they were recognizing and remarking on the central importance of social justice within conservation. We present a framework for further integration of HHCC approaches into higher education courses so as to conserve the integrity of coupled human and natural systems globally.

Phylogeny is a stronger predictor of activity than allometry in an African mammal community

In promoting coexistence, sympatric species often partition shared resources along spatio-temporal domains. Similarly sized and phylogenetically close species, for instance, partition the times of day in which they are active to limit interference competition. Given that variation in species body mass has evolutionary underpinnings, species activity levels (time spent active in a 24-h daily cycle) within animal communities might be structured by phylogeny. However, few studies have tested this hypothesis across animal communities, and none among medium-sized to large mammals. We quantified the relative contributions of phylogeny and body mass in predicting activity levels in a community of 22 sympatric mammal species in Murchison Falls National Park, Uganda. We show that phylogeny is a stronger predictor of species activity levels than body mass. Our findings provide empirical evidence for the phylogenetic structuring of mammal activity in diverse communities. More broadly, our results suggest that evolutionary relationships mask allometry in predicting species traits in diverse animal communities.

First Measurement of Timelike Compton Scattering

We present the first measurement of the timelike Compton scattering process, γp→p^{'}γ^{*}(γ^{*}→e^{+}e^{-}), obtained with the CLAS12 detector at Jefferson Lab. The photon beam polarization and the decay lepton angular asymmetries are reported in the range of timelike photon virtualities 2.25<Q^{'2}<9  GeV^{2}, squared momentum transferred 0.1<-t<0.8  GeV^{2}, and average total center-of-mass energy squared s=14.5  GeV^{2}. The photon beam polarization asymmetry, similar to the beam-spin asymmetry in deep virtual Compton scattering, is sensitive to the imaginary part of the Compton form factors and provides a way to test the universality of the generalized parton distributions. The angular asymmetry of the decay leptons accesses the real part of the Compton form factors and thus the D-term in the parametrization of the generalized parton distributions.

Hepatitis E virus infection and rejection in kidney transplant recipients

BACKGROUND

Hepatitis E virus (HEV) infection has been associated with immune-mediated kidney diseases in developing countries. However, its relationship with kidney transplant outcomes has never been studied. We investigated the association between HEV infection and kidney graft rejection among kidney transplant recipients (KTRs).

METHODS

We conducted a matched cohort and longitudinal study utilizing banked sera following kidney transplantation during 1988-2012. Studies with evidence of post-transplantation HEV infection were identified by positive ELISA tests (anti-HEV IgM or anti-HEV IgG seroconversion) or positive HEV PCR and matched to KTR controls with negative HEV ELISA and PCR tests in a 1:5 ratio by age, sex, crossmatch status, immunosuppression era, and time of HEV testing. Outcome data collected included time to first kidney graft rejection, transaminases, and glomerular filtration rates. Log-ranked test was used to analyze survival.

RESULTS

Of 271 KTRs, 9 (3%) had evidence of post-transplantation HEV infection and were compared to 45 negative, matched controls. Median age at transplantation was 46 years. Kidney graft rejection was reported in 8 (89%) of cases and 21 (47%) of controls. Median time to first episode of kidney graft rejection was 17.4 months in cases and 30.8 months in controls (p = 0.029), with a higher hazard of developing kidney graft rejection in cases (HR = 3.23, 95% CI: 1.19-8.79). Lower mean glomerular filtration rates over time were observed in cases (35 mL/min/1.73m²) versus controls (42.4 mL/min/1.73m²) but did not reach significance (p = 0.24).

CONCLUSION

Subjects with evidence of post-transplantation HEV infection demonstrated earlier kidney graft rejection compared to controls.

Outcomes at 3 years posttransplant in imlifidase-desensitized kidney transplant patients

Imlifidase is a cysteine proteinase which specifically cleaves IgG, inhibiting Fc-mediated effector function within hours of administration. Imlifidase converts a positive crossmatch to a potential donor (T cell, B cell, or both), to negative, enabling transplantation to occur between previously HLA incompatible donor-recipient pairs. To date, 39 crossmatch positive patients received imlifidase prior to a kidney transplant in four single-arm, open-label, phase 2 studies. At 3 years, for patients who were AMR+ compared to AMR-, death-censored allograft survival was 93% vs 77%, patient survival was 85% vs 94%, and mean eGFR was 49 ml/min/1.73 m² vs 61 ml/min/1.73 m² , respectively. The incidence of AMR was 38% with most episodes occurring within the first month post-transplantation. Sub-analysis of patients deemed highly sensitized with cPRA ≥ 99.9%, and unlikely to be transplanted who received crossmatch-positive, deceased donor transplants had similar rates of patient survival, graft survival, and eGFR but a higher rate of AMR. These data demonstrate that outcomes and safety up to 3 years in recipients of imlifidase-enabled allografts is comparable to outcomes in other highly sensitized patients undergoing HLA-incompatible transplantation. Thus, imlifidase is a potent option to facilitate transplantation among patients who have a significant immunologic barrier to successful kidney transplantation. Clinical Trial: ClinicalTrials.gov (NCT02790437), EudraCT Number: 2016-002064-13.

Dynamic prediction of renal survival among deeply phenotyped kidney transplant recipients using artificial intelligence: an observational, international, multicohort study

BACKGROUND

Kidney allograft failure is a common cause of end-stage renal disease. We aimed to develop a dynamic artificial intelligence approach to enhance risk stratification for kidney transplant recipients by generating continuously refined predictions of survival using updates of clinical data.

METHODS

In this observational study, we used data from adult recipients of kidney transplants from 18 academic transplant centres in Europe, the USA, and South America, and a cohort of patients from six randomised controlled trials. The development cohort comprised patients from four centres in France, with all other patients included in external validation cohorts. To build deeply phenotyped cohorts of transplant recipients, the following data were collected in the development cohort: clinical, histological, immunological variables, and repeated measurements of estimated glomerular filtration rate (eGFR) and proteinuria (measured using the proteinuria to creatininuria ratio). To develop a dynamic prediction system based on these clinical assessments and repeated measurements, we used a Bayesian joint models-an artificial intelligence approach. The prediction performances of the model were assessed via discrimination, through calculation of the area under the receiver operator curve (AUC), and calibration. This study is registered with ClinicalTrials.gov, NCT04258891.

FINDINGS

13 608 patients were included (3774 in the development cohort and 9834 in the external validation cohorts) and contributed 89 328 patient-years of data, and 416 510 eGFR and proteinuria measurements. Bayesian joint models showed that recipient immunological profile, allograft interstitial fibrosis and tubular atrophy, allograft inflammation, and repeated measurements of eGFR and proteinuria were independent risk factors for allograft survival. The final model showed accurate calibration and very high discrimination in the development cohort (overall dynamic AUC 0·857 [95% CI 0·847-0·866]) with a persistent improvement in AUCs for each new repeated measurement (from 0·780 [0·768-0·794] to 0·926 [0·917-0·932]; p<0·0001). The predictive performance was confirmed in the external validation cohorts from Europe (overall AUC 0·845 [0·837-0·854]), the USA (overall AUC 0·820 [0·808-0·831]), South America (overall AUC 0·868 [0·856-0·880]), and the cohort of patients from randomised controlled trials (overall AUC 0·857 [0·840-0·875]).

INTERPRETATION

Because of its dynamic design, this model can be continuously updated and holds value as a bedside tool that could refine the prognostic judgements of clinicians in everyday practice, hence enhancing precision medicine in the transplant setting.

FUNDING

MSD Avenir, French National Institute for Health and Medical Research, and Bettencourt Schueller Foundation.

Early experience with donation after circulatory death heart transplantation using normothermic regional perfusion in the United States

OBJECTIVE

This pilot study sought to evaluate the feasibility of our donation after circulatory death (DCD) heart transplantation protocol using cardiopulmonary bypass (CPB) for normothermic regional reperfusion (NRP).

METHODS

Suitable local DCD candidates were transferred to our institution. Life support was withdrawn in the operating room (OR). On declaration of circulatory death, sternotomy was performed, and the aortic arch vessels were ligated. CPB was initiated with left ventricular venting. The heart was reperfused, with correction of any metabolic abnormalities. CPB was weaned, and cardiac function was assessed at 30-minute intervals. If accepted, the heart was procured with cold preservation and transplanted into recipients in a nearby OR.

RESULTS

Between January 2020 and January 2021, a total of 8 DCD heart transplants were performed: 6 isolated hearts, 1 heart-lung, and 1 combined heart and kidney. All donor hearts were successfully resuscitated and weaned from CPB without inotropic support. Average lactate and potassium levels decreased from 9.39 ± 1.47 mmol/L to 7.20 ± 0.13 mmol/L and 7.49 ± 1.32 mmol/L to 4.36 ± 0.67 mmol/L, respectively. Post-transplantation, the heart-lung transplant recipient required venoarterial extracorporeal membrane oxygenation for primary lung graft dysfunction but was decannulated on postoperative day 3 and recovered uneventfully. All other recipients required minimal inotropic support without mechanical circulatory support. Survival was 100% with a median follow-up of 304 days (interquartile range, 105-371 days).

CONCLUSIONS

DCD heart transplantation outcomes have been excellent. Our DCD protocol is adoptable for more widespread use and will increase donor heart availability in the United States.

Imlifidase Desensitization in Crossmatch-positive, Highly Sensitized Kidney Transplant Recipients: Results of an International Phase 2 Trial (Highdes)

BACKGROUND

Highly HLA sensitized patients have limited access to life-saving kidney transplantation because of a paucity of immunologically suitable donors. Imlifidase is a cysteine protease that cleaves IgG leading to a rapid decrease in antibody level and inhibition of IgG-mediated injury. This study investigates the efficacy and safety of imlifidase in converting a positive crossmatch test to negative, allowing highly sensitized patients to be transplanted with a living or deceased donor kidney.

METHODS

This open-label, single-arm, phase 2 trial conducted at 5 transplant centers, evaluated the ability of imlifidase to create a negative crossmatch test within 24 h. Secondary endpoints included postimlifidase donor-specific antibody levels compared with predose levels, renal function, and pharmacokinetic/pharmacodynamic profiles. Safety endpoints included adverse events and immunogenicity profile.

RESULTS

Of the transplanted patients, 89.5% demonstrated conversion of baseline positive crossmatch to negative within 24 h after imlifidase treatment. Donor-specific antibodies most often rebounded 3-14 d postimlifidase dose, with substantial interpatient variability. Patient survival was 100% with graft survival of 88.9% at 6 mo. With this, 38.9% had early biopsy proven antibody-mediated rejection with onset 2-19 d posttransplantation. Serum IgG levels began to normalize after ~3-7 d posttransplantation. Antidrug antibody levels were consistent with previous studies. Seven adverse events in 6 patients were classified as possibly or probably related to treatment and were mild-moderate in severity.

CONCLUSIONS

Imlifidase was well tolerated, converted positive crossmatches to negative, and enabled patients with a median calculated panel-reactive antibody of 99.83% to undergo kidney transplantation resulting in good kidney function and graft survival at 6 mo.

Landscape complexity persists as a critical source of bias in terrestrial animal home range estimation

Home ranges provide a conceptual and quantitative representation of animal-habitat associations over time. Methods to estimate home ranges have swiftly progressed by dynamically accounting for various sources of bias. Across that period of growth, one potentially influential source of bias has yet to be robustly scrutinized. Animals inhabiting the terrestrial spatial domain make movement decisions in environments with variable landscape complexity. Despite that reality, home range estimation methods tend to be informed by two-dimensional (2D) data (i.e., x and y coordinates), which analytically presume that these landscapes are flat. This analytical tendency potentially misrepresents the configuration and size of animal home range estimates. To examine the prevalence of this bias, we reviewed literature of terrestrial animal home range estimation published between 2000 and 2019. We recorded the proportion of studies that (1) recognized and (2) incorporated landscape complexity. Over 22.0% (n = 271) of the 1,203 studies recognized the importance of landscape complexity for animal movement. Interestingly, just 0.7% (n = 8) incorporated landscape complexity into the home range estimation. We infer then that landscape complexity represents an important source of bias resulting in the underestimation of terrestrial animal home range size. Given the influence of landscape complexity on terrestrial animal decision making, energetics, and fitness, our analysis highlights an important gap in current home range methodologies. We discuss the implications of our analysis for biased understandings of terrestrial animal spatial ecology with subsequent impacts on management and conservation practices built upon these estimates.

Impact of the 2014 kidney allocation system changes on trends in A2/A2B into B kidney transplantation and organ procurement organization reporting of donor subtyping

The current kidney allocation system (KAS) preferentially allocates kidneys from blood type A2 or A2B (A/A2B) donors to blood type B candidates. We used national data to evaluate center-level performance of A2/A2B to B transplants, and organ procurement organization (OPO) reporting of type A or AB donor subtyping, in 5-year time periods prior to (2009-2014) and following (2015-2019) KAS implementation. The number of centers performing A2/A2B to B transplants increased from 17 pre-KAS to 76 post-KAS, though this still represents only a minority of centers (7.3% pre-KAS and 32.6% post-KAS). For high-performing centers, the median net increase in A2/A2B to B transplants was 19 cases (range -2-72) per center in the 5 years post-KAS. The median net increase in total B recipient transplants was 21 cases (range -17-119) per center. Despite requirements for performance of subtyping, in 2019 subtyping was reported on only 56.4% of A/AB donors. This translates into potential missed opportunities for B recipients, and even post-KAS up to 2322 A2/A2B donor kidneys may have been allocated for transplantation as A/AB. Further progress must be made both at center and OPO levels to broaden implementation of A2/A2B to B transplants for the benefit of underserved recipients.