Neonatal hypoxic-ischemic encephalopathy (HIE) occurs when the brain receives insufficient oxygen and blood supply before or during childbirth. HIE is a leading cause of neonatal mortality and morbidity that may also affect later brain development, specifically gyrification - folding of the cerebral cortex creating gyri and sulci. The nonhuman primate (NHP) brain is gyrified, similar to humans, making NHPs a highly translatable model to examine brain development after injury, which has not been well-studied in HIE. In our nonhuman primate (NHP) model of neonatal HIE, we induced injury through in utero umbilical cord occlusion (UCO) for 20 minutes, mimicking the cause of HIE in humans. Twenty-two term-equivalent pigtailed macaques (Macaca nemestrina) underwent UCO and were randomized to no treatment (n = 11) or treatment with therapeutic hypothermia and erythropoietin (TH + Epo [5x1000 U/kg]; n = 11), while non-UCO animals served as controls (n = 7). All animals were delivered via cesarian section. Injury severity was determined by physiological parameters (Apgar score), lactate, and pH levels after resuscitation. To evaluate the impact of injury on gyrification, we will utilize magnetic resonance imaging (MRI) taken 6-months post-injury to measure the gyrification index (GI). GI will be calculated by taking brain’s inner-to-outer hemispheric ratio; the inner trace following the contours of the gyri and sulci, and the outer trace following the circumference of the cerebral cortex. We hypothesize that global and regional GI will be altered in animals exposed to UCO, corresponding with decreased brain volume and greater injury. We also hypothesize that treatment will mitigate some of these changes, leading to a GI closer to control. These results will help determine whether hypoxia-ischemia alters the trajectory of cortical development, as well as the association between injury severity, brain volume, and gyrification.

Traumatic brain injury (TBI), characterized by a physical impact to the skull, is a significant health concern among veterans, athletes, and the elderly, with over 200,000 TBI-related hospitalizations in 2020. TBI causes shearing forces and physical damage to the brain, resulting in increased risk of neurodegeneration and mental health problems. When they expect an impact, humans brace, exhaling against a closed airway in what is known as a Valsalva maneuver. This prevents venous return from the head, pressurizes the vascular network in the brain, and increases intracranial pressure (ICP) in a way that may protect the brain from TBI. We aim to mimic a Valsalva-like response (VLR) through external abdominal stimulation and measure corresponding ICP changes. First, we performed a 3mm-wide craniotomy in anesthetized ferrets and implanted a pressure transducer inside the brain to collect baseline pressure readings. After skull closure, VLR was performed both supine and upright (body at 45°), either physically (pVLR, 80-120mmHg by abdominal compression using a blood pressure cuff, n=4) or electrically (eVLR, bilateral 25-30mA stimulus of the rectus muscles, n=4). pVLR resulted in a 2-4mmHg increase in ICP over 2-5 sec. By comparison eVLR resulted in a larger and faster ICP increase - 3-7mmHg with an onset of 250-750ms. Consequently, we will utilize eVLR to modulate ICP in a TBI model to determine whether it is neuroprotective. Ferrets will be assigned to control or randomized to receive a TBI impact with either sham eVLR or eVLR. Animals will be subjected to baseline (pre-TBI), acute, and long-term behavioral testing. Additionally, we will perform brain cell specific histological staining. Results from behavioral testing and histology will inform us of the potential neuroprotective effects of eVLR against TBI and provide future direction towards translating the findings into a wearable device for at-risk individuals.

Bacteria can shuttle pieces of DNA between unrelated cells via a process called horizontal gene transfer (HGT). Genes that undergo HGT (i.e. mobile genes) evolve in different host bacteria with different genomic backgrounds, which can influence the types of mutations the mobile gene acquires. Studying the effect of HGT on mobile gene evolution is important as many clinically relevant antibiotic resistance genes are mobile. In a prior study, we used a simple model to simulate mobile gene evolution as they engage in HGT. Under the simple model, the mobile gene evolves in only one species at a time. With this model, we found that fitness landscape similarity between two host species engaging in HGT is highly indicative of the effect HGT has on mobile gene fitness outcomes (i.e. whether performing HGT has a positive, negative, or neutral effect on fitness). We expanded the simple model into a more ecologically realistic consumer-resource model (CRM), in which the mobile gene continuously transfers between species. We observed similar outcomes between the two models; however, in the CRM there was an increase in cases in which performing HGT had a positive fitness effect. We hypothesize that the CRM highlights features like the continuous existence of host species, resulting in constant gene flow between the two species. To further probe how gene flow influences the effect HGT has on mobile gene evolution, I tested how varying the HGT rate with the CRM (effectively allowing us to control the amount of gene flow) affects mobile gene fitness outcomes. I used the same host landscape pairs used in our pilot study while varying the HGT rate along a biologically relevant range. I expect to find a positive correlation between HGT rate and the magnitude of positive fitness effects conferred by a mobile gene that has undergone HGT.

Hypoxic-ischemic encephalopathy (HIE) is a leading cause of neonatal morbidity and mortality worldwide. The ferret provides a highly translational model to investigate HIE; the gyrified ferret brain has a similar grey-to-white matter ratio to humans, allowing for better assessment of white matter injury and impairment of cortical development compared to rodents. Our previous work has suggested that ferret brains also show greater resilience to hypoxia-ischemia (HI) than rats. Ferrets tolerate exposure to much longer and more significant HI, and 100-fold larger doses of inflammatory stimuli, than rats do. We seek to identify signatures of the ferret's protective mechanisms by comparing differentially regulated genetic pathways in the ferret versus the rat when exposed to identical insults. Whole-hemisphere organotypic brain slices were obtained from term-equivalent ferrets and rats and cultured for 72 hours. Slices were randomly assigned to control or oxygen-glucose deprivation (OGD), an in-vitro model of HIE. Cytotoxicity was assessed by lactate dehydrogenase (LDH) release, while global transcriptomics were analyzed via a 770-gene digital transcriptomics panel. Preliminary results show significantly lower LDH release in ferrets compared to rats, reaffirming the ferrets' resilience to OGD. We identified 90 differentially expressed genes in ferrets following OGD, and 11 genes in the rat. Ferrets upregulated CCL2 and LGALS, genes associated with inflammatory responses, and downregulated ADRB1 and NOS2, suggesting reduced oxidative stress. Rats downregulated KIR3DL1/2 and TGM1, which suppress natural killer cells and form the cell envelope, respectively. The experiment will be repeated with double the sample size and region-specific analysis of gene regulation. We hypothesize the ferret will display lower injury markers globally, which will be associated with regional differences in gene expression compared to the rat. We hope this will enable us to identify potential treatment targets for infants with HIE that can increase resilience and repair after injury. 

Hypoxic Ischemic Encephalopathy (HIE) is a brain injury caused by a lack of oxygen and blood flow in the peripartum period. Cardiac dysfunction occurs in up to 80% of infants with HIE and is associated with worse neurodevelopmental outcomes. The current standard of care for HIE is whole body therapeutic hypothermia (TH). The expected physiologic response to TH is a decrease in cardiac output by 10%, and heartrate (HR) by 10bpm, per 1-degree Celsius decrease in body temperature. However, neonates with cardiac dysfunction tend to have normal or elevated HR to compensate for decreased cardiac output. Therefore, normal or elevated HR during TH may indicate compromised cardiac function. We hypothesize that in neonates with HIE, HR trends during TH reflect cardiac function, and a sustained HR above 100bpm is indicative of cardiac dysfunction. Using echocardiograms performed within the first 2 days after birth in babies with HIE treated with TH at the Seattle Children's neonatal intensive care unit (NICU; n=19), we categorized neonates by cardiac function: normal, right ventricular (RV) dysfunction, and RV plus left ventricular (LV) dysfunction. We then extracted continuous HR data and compared median HR during TH across groups using linear regression during specific periods: 12-24h, 24-36h, and 36-48h after birth. Results showed that infants with RV+LV dysfunction had a higher HR than those with RV dysfunction only or normal function. Across all time periods, infants with any kind of cardiac dysfunction had an average HR above 100bpm, while those without dysfunction had average HRs less than 100bpm. Therefore, it appears that HR can be utilized as a proxy for cardiac dysfunction in neonates with HIE. Utilizing HR as screening biomarker for cardiac dysfunction may allow improve optimal resource utilization of echocardiograms as well as real-time, cost-effective monitoring and targeted treatment initiation. 

Using temperature reconstruction to understand how the Earth’s climate responded to external forcing from factors such as CO2 in the past can inform predictions about future climate change due to global warming. This project aims to examine a recent paleoclimate data assimilation study of the past 24,000 years from the Last Glacial Maximum (LGM) to the present day. Paleoclimate data assimilation combines both proxy data and climate model simulations to address the discrepancies in climate reconstructions produced by each. For the LGM to present, discrepancies between model simulations and proxy data include the timing and characteristics of climate events like deglaciation. While data assimilation helps to resolve some of these discrepancies, it also makes assumptions about the uncertainty of the proxy data used. Processes that introduce proxy uncertainty such as bioturbation–sediment mixing by marine organisms–and calibration errors are often not characterized as time scale-dependent which could potentially introduce bias and affect the accuracy of these data assimilation studies. We examine the proxy uncertainty within this data assimilation to identify timescale-dependent errors and measure their impact on the accuracy of the temperature reconstruction. We do this by producing a set of pseudoproxies, which are synthetic datasets of different sediment proxies such as δ¹⁸O, to create hypothetical systems of past climate. By isolating and controlling different uncertainty characteristics, we are able to measure their overall impact on the climate reconstructions.