Naturally segregating genetic variants contribute to thermal tolerance in a Drosophila melanogaster model system

Thermal tolerance is a fundamental physiological complex trait for survival in many species. For example, everyday tasks such as foraging, finding a mate, and avoiding predation are highly dependent on how well an organism can tolerate extreme temperatures. Understanding the general architecture of the natural variants within the genes that control this trait is of high importance if we want to better comprehend thermal physiology. Here, we take a multipronged approach to further dissect the genetic architecture that controls thermal tolerance in natural populations using the Drosophila Synthetic Population Resource as a model system. First, we used quantitative genetics and Quantitative Trait Loci mapping to identify major effect regions within the genome that influences thermal tolerance, then integrated RNA-sequencing to identify differences in gene expression, and lastly, we used the RNAi system to (1) alter tissue-specific gene expression and (2) functionally validate our findings. This powerful integration of approaches not only allows for the identification of the genetic basis of thermal tolerance but also the physiology of thermal tolerance in a natural population, which ultimately elucidates thermal tolerance through a fitness-associated lens.

Assessing Time to Removal of Tunneled Dialysis Catheters after Arteriovenous Access Creation

BACKGROUND

Tunneled dialysis catheters (TDCs) are a temporary bridge until definitive arteriovenous (AV) access is established. Our objective was to evaluate the time to TDC removal in patients who underwent AV access creations with TDCs already in place.

METHODS

A single-center analysis of all AV access creations in patients with TDCs was performed (2014-2020). Primary outcome was time to TDC removal after access creation.

RESULTS

There were 364 AV access creations with TDCs in place. The average age was 58 years, 44% of patients were female, and 64% were Black. The median time to TDC removal was 113 days (range, 22-931 days) with 71.4% having a TDC >90 days after access creation. Patients with TDC >90 days were often older (60 vs. 54.7), had hypertension (98.1% vs. 93.3%), were diabetic (65.4% vs. 47.1%), and had longer average time to maturation (107.1 vs. 55.4 days, P < 0.001) and first access (114 vs. 59.4 days, P < 0.001). Multivariable analysis showed that older age was associated with prolonged TDC placement (odds ratio [OR] 1.03, 95% confidence interval [CI] 1.01-1.05, P = 0.005) and prosthetic graft use was associated with shorter TDC indwelling time (OR 0.09, 95% CI 0.04-0.23, P ≤ 0.001). Kaplan-Meier analysis showed that 87% of TDCs were removed at 1 year.

CONCLUSIONS

The majority of patients with TDCs who underwent AV access creation had prolonged TDC placement. Prosthetic graft use was associated with shorter catheter times. Close follow-up after access placement, improving maturation times, and access type selection should be considered to shortened TDC times.

Alternative Conduits for Lower Extremity Bypass

While single-segment great saphenous vein (GSV) remains the gold-standard conduit for infrainguinal bypass, several alternative options are available for use when GSV is absent in patients with chronic limb threatening ischemia requiring infrainguinal revascularization including alternative autologous vein, prosthetic conduits, and cryopreserved vein grafts.

Identifying inconsistencies in exotic pet regulations that perpetuate trade in risky species

Regulatory inconsistencies at different jurisdictional levels have contributed to the global expansion of the exotic pet trade, with resultant increases in the spread of invasive species and pathogens. Researchers have enumerated multiple limitations and environmental risks posed by international and national rules that govern the exotic pet trade, yet little attention has focused on the regulation of the exotic pet trade within national borders. We reviewed state-level regulations that apply to the trade of vertebrate animal taxa in the United States. Definitions and classifications for regulating different vertebrate taxa varied greatly across states, and the terms pet and companion animal were poorly defined and inconsistent across states. States implemented regulations that permit trade in exotic vertebrate pets that are banned from import into the United States owing to public health and conservation concerns. Once species have been imported into the United States, inconsistent internal regulations facilitate the movement of animals that pose substantial invasion and disease risks. Violations of state laws were typically listed as misdemeanors, and the median fine for violating state wildlife trade laws was $1000. Inconsistent and incomplete regulation of exotic vertebrate pets across state borders, in conjunction with limited penalties for violating regulations, has facilitated continued possession of exotic pets in states where these animals are banned. Based on our review of regulatory weaknesses, we conclude that a transition to a federally enforced list of vertebrate species that may be traded as pets is needed, with all other vertebrate species banned from the exotic pet trade unless their potential invasion and disease risks have been assessed and demonstrated to be low or nonexistent.

Agave distribution and floral display influence foraging rates of an endangered pollinating bat and implications for conservation

Wildlife conservation involves making management decisions with incomplete knowledge of ecological relationships. Efforts to augment foraging resources for the endangered Mexican long-nosed bat (Leptonycteris nivalis) are progressing despite limited knowledge about the species' foraging behavior and requirements. This study aimed to understand L. nivalis responses to floral resource availability, focusing on individual agave- and local-scale characteristics influencing visitation rates to flowering agaves. We observed bat visitation at 62 flowering agaves around two roosts in northeast Mexico on 46 nights in the summers of 2017 and 2018. We found visitation rate had positive relationships with two agave-scale characteristics: the number of umbels with open flowers and the lower vertical position on the stalk of those umbels (i.e., earlier phenological stages of flowering). However, these factors exhibited strong negative interaction: with few umbels with open flowers, the position of flowering umbels had little effect on visitation rate, but when umbels with open flowers were abundant, visitation rate was more strongly related to the lower flowering umbel position. We also found relationships between visitation rate and two local-scale characteristics: negative for the density of flowering conspecifics within 30 m of the focal agave and positive for the density of dead standing agave stalks within 30 m. Our findings suggest opportunities to augment foraging resources for L. nivalis in ways that are consistent with their foraging behavior, including: increasing the supply of simultaneously blooming flowers by planting agave species that tend to have more umbels with simultaneously open flowers; planting multiple species of agaves with different flowering times to increase the availability of agaves with open flowers on lower-positioned umbels throughout the period when bats are present in the region; planting agaves in clusters; and keeping dead standing agave stalks on the landscape. Our study points to useful management strategies that can be implemented and monitored as part of an adaptive management approach to aid in conservation efforts.

Long-term functional outcomes of upper extremity civilian vascular trauma

OBJECTIVE

Civilian analyses of long-term outcomes of upper extremity vascular trauma (UEVT) are limited. Our goal was to evaluate the management of UEVT in the civilian trauma population and explore the long-term functional consequences.

METHODS

A retrospective review and analysis was performed of patients with UEVT at an urban Level 1 trauma center (2001-2022). Management and long-term functional outcomes were analyzed.

RESULTS

There were 150 patients with UEVT. Mean age was 34 years, and 85% were male. There were 42% Black and 27% White patients. Mechanism was penetrating in 79%, blunt in 20%, and multifactorial in 1%. Within penetrating trauma, mechanism was from firearms in 30% of cases. Of blunt injuries, 27% were secondary to falls, 13% motorcycle collisions, 13% motor vehicle collisions, and 3% crush injuries. Injuries were isolated arterial in 62%, isolated venous in 13%, and combined in 25% of cases. Isolated arterial injuries included brachial (34%), radial (27%), ulnar (27%), axillary (8%), and subclavian (4%). The majority of arterial injuries (92%) underwent open repair with autologous vein bypass (34%), followed by primary repair (32%), vein patch (6.6%), and prosthetic graft (3.3%). There were 23% that underwent fasciotomies, 68% of which were prophylactic. Two patients were managed with endovascular interventions; one underwent covered stent placement and the other embolization. Perioperative reintervention occurred in 12% of patients. Concomitant injuries included nerves (35%), bones (17%), and ligaments (16%). Intensive care unit admission was required in 45%, with mean intensive care unit length of stay 1.6 days. Mean hospital length of stay was 6.7 days. Major amputation and in-hospital mortality rates were 1.3% and 4.6% respectively. The majority (72%) had >6-month follow-up, with a median follow-up period of 197 days. Trauma readmissions occurred in 19%. Many patients experienced chronic pain (56%), as well as motor (54%) and sensory (61%) deficits. Additionally, 41% had difficulty with activities of daily living. Of previously employed patients (57%), 39% experienced a >6-month delay in returning to work. Most patients (82%) were discharged with opioids; of these, 16% were using opioids at 6 months.

CONCLUSIONS

UEVT is associated with long-term functional impairments and opioid use. It is imperative to counsel patients prior to discharge and ensure appropriate follow-up and therapy.

Recent evaluation by nephrologists is associated with decreased incidence of tunneled dialysis catheter being used at the time of first arteriovenous access creation

OBJECTIVE

Late primary care provider (PCP) or nephrologist evaluation of patients with progressive kidney disease may be associated with increased morbidity and mortality. Among patients undergoing initial arteriovenous (AV) access creation, we aimed to study the relationship of recent PCP and nephrologist evaluations with perioperative morbidity and mortality.

METHODS

We performed a retrospective review of patients from 2014 to 2022 who underwent initial AV access creation at an urban, safety-net hospital. Univariable and multivariable analyses identified associations of PCP and nephrologist evaluations <1 year and <3 months before surgery, respectively, with hemodialysis initiation via tunneled dialysis catheters (TDCs), 90-day readmission, and 90-day mortality.

RESULTS

Among 558 patients receiving initial AV access, mean age was 59.7 ± 14 years, 59% were female gender, and 60.6% were Black race. Recent PCP and nephrology evaluations occurred in 386 (69%) and 362 (65%) patients, respectively. On multivariable analysis, unemployed and uninsured statuses were associated with decreased likelihood of PCP evaluation (unemployment: odds ratio [OR], 0.51; 95% confidence interval [CI], 0.34-0.77; uninsured status: OR, 0.05; 95% CI, 0.01-0.45) and nephrologist evaluation (unemployment: OR, 0.63; 95% CI, 0.43-0.91; uninsured status: OR, 0.22; 95% CI, 0.06-0.83) (all P < .05). Social support was associated with increased likelihood of PCP evaluation (OR, 1.81; 95% CI, 1.07-3.08) (all P < .05). Hemodialysis was initiated with TDCs in 304 patients (55%). Older age (OR, 0.98; 95% CI, 0.96-0.99), obesity (OR, 0.38; 95% CI, 0.25-0.58), and nephrologist evaluation (OR, 0.12; 95% CI, 0.08-0.19) were independently associated with decreased hemodialysis initiation with TDCs in patients receiving an initial AV access (all P < .05). Ninety-day readmission occurred in 270 cases (48%). Cirrhosis (OR, 2.5; 95% CI, 1.03-6.03; P = .04), coronary artery disease (OR, 2.31; 95% CI, 1.5-3.57), prosthetic AV access (OR, 1.84; 95% CI, 1.04-3.26), and impaired ambulation (OR, 1.75; 95% CI, 1.15-2.66) were independently associated with increased readmission (all P < .05). Older age (OR, 0.98; 95% CI, 0.97-0.99), prior TDC (OR, 0.65; 95% CI, 0.45-0.94), and unemployment (OR, 0.58; 95% CI, 0.39-0.86) were associated with decreased readmission (all P < .05). Ninety-day mortality occurred in 1.6% of patients. Neither PCP nor nephrologist evaluation was associated with readmission or mortality.

CONCLUSIONS

Recent nephrology evaluation was associated with reduced hemodialysis initiation with TDCs among patients undergoing initial AV access creation. Unemployed and uninsured statuses posed barriers to accessing nephrology care.

Outcomes of lower extremity revascularization in octogenarians and nonagenarians for intermittent claudication

OBJECTIVE

Revascularization for intermittent claudication (IC) due to infrainguinal peripheral arterial disease (PAD) is dependent on durability and expected benefit. We aimed to assess outcomes for IC interventions in octogenarians and nonagenarians (age ≥80 years) and those younger than 80 years (age <80 years).

METHODS

The Vascular Quality Initiative was queried (2010-2020) for peripheral vascular interventions (PVIs) and infrainguinal bypasses (IIBs) performed to treat IC. Baseline characteristics, procedural details, and outcomes were analyzed (comparing age ≥80 years and age <80 years).

RESULTS

There were 84,210 PVIs (12.1% age ≥80 years and 87.9% age <80 years) and 10,980 IIBs (7.4% age ≥80 years and 92.6% age <80 years) for IC. For PVI, patients aged ≥80 years more often underwent femoropopliteal (70.7% vs 58.1%) and infrapopliteal (19% vs 9.3%) interventions, and less often iliac interventions (32.1% vs 48%) (P < .001 for all). Patients aged ≥80 years had more perioperative hematomas (3.5% vs 2.4%) and 30-day mortality (0.9% vs 0.4%) (P < .001). At 1-year post-intervention, the age ≥80 years cohort had fewer independently ambulatory patients (80% vs 91.5%; P < .001). Kaplan-Meier analysis showed patients aged ≥80 years had lower reintervention/amputation-free survival (81.4% vs 86.8%), amputation-free survival (87.1% vs 94.1%), and survival (92.3% vs 96.8%) (P < .001) at 1-year after PVI. Risk adjusted analysis showed that age ≥80 years was associated with higher reintervention/amputation/death (hazard ratio [HR], 1.22; 95% confidence interval [CI], 1.1-1.35), amputation/death (HR, 1.85; 95% CI, 1.61-2.13), and mortality (HR, 1.92; 95% CI, 1.66-2.23) (P < .001 for all) for PVI. For IIB, patients aged ≥80 years more often had an infrapopliteal target (28.4% vs 19.4%) and had higher 30-day mortality (1.3% vs 0.5%), renal failure (4.1% vs 2.2%), and cardiac complications (5.4% vs 3.1%) (P < .001). At 1 year, the age ≥80 years group had fewer independently ambulatory patients (81.7% vs 88.8%; P = .02). Kaplan-Meier analysis showed that the age ≥80 years cohort had lower reintervention/amputation-free survival (75.7% vs 81.5%), amputation-free survival (86.9% vs 93.9%), and survival (90.4% vs 96.5%) (P < .001 for all). Risk-adjusted analysis showed age ≥80 years was associated with higher amputation/death (HR, 1.68; 95% CI, 1.1-2.54; P = .015) and mortality (HR, 1.85; 95% CI, 1.16-2.93; P = .009), but not reintervention/amputation/death (HR, 1.1; 95% CI, 0.85-1.44; P = .47) after IIB.

CONCLUSIONS

Octogenarians and nonagenarians have greater perioperative morbidity and long-term ambulatory impairment, limb loss, and mortality after PVI and IIB for claudication. Risks of intervention on elderly patients with claudication should be carefully weighed against the perceived benefits of revascularization. Medical and exercise therapy efforts should be maximized in this population.

Functional Impairment is Associated with Poor Long-Term Outcomes after Arteriovenous Access Creation

BACKGROUND

Functional impairment affects outcomes after a variety of procedures. However, the impact of functional impairment on outcomes of arteriovenous (AV) access creation is unclear. We aimed to evaluate the association of patients' ability to ambulate and perform activities of daily living (ADL) with AV access outcomes.

METHODS

We retrospectively reviewed patients undergoing AV access creation at an urban, safety-net hospital from 2014 to 2022. We evaluated associations of impaired ambulatory and assisted ADL status with 90-day readmission, 1-year primary patency, and 5-year mortality.

RESULTS

Among the 689 patients receiving AV access, mean age was 59.6 ± 13.9 years, 59% were male, and 60% were Black. Access types included brachiocephalic (42%), brachiobasilic (26%), radiocephalic (14%), other autogenous (5%) fistulas, and prosthetic grafts (13%). Impaired ambulatory status was identified in 35% and assisted ADL status, when assessed, was identified in 21% of patients. Ninety-day readmission was more likely in patients with impaired ambulatory (58% vs. 39%, P < 0.001) and assisted ADL (56% vs. 41%, P = 0.004) status. On Kaplan-Meier analysis, 1-year primary patency was lower for patients with impaired ambulatory status (44% ± 3% vs. 29% ± 3%, P = 0.001), but was not significantly different for patients with assisted ADL status (41% ± 3% vs. 32% ± 5%, P = 0.12). Five-year survival was lower for patients with impaired ambulatory status (53% ± 5% vs. 74% ± 4%, P < 0.001), but was not significantly different for patients with assisted ADL status (45% ± 9% vs. 71% ± 4%, P = 0.1). On multivariable analysis, increased likelihood of 90-day readmission was significantly associated with impaired ambulatory status (odds ratio (OR) 2.03, 95% confidence interval (CI) 1.4-2.94, P < 0.001) and assisted ADL status (OR 1.66, 95% CI 1.07-2.57, P = 0.02). One-year primary patency was not significantly associated with impaired ambulatory (hazard ratio (HR) 1.25, 95% CI 0.98-1.6, P = 0.07) or assisted ADL status (HR 1.13, 95% CI 0.87-1.48, P = 0.36). Increased likelihood of 5-year mortality was associated with impaired ambulatory (HR 1.65, 95% CI 1.04-2.62, P = 0.04) and assisted ADL status (HR 2.63, 95% CI 1.35-5.11, P = 0.004).

CONCLUSIONS

Impaired ambulatory and assisted ADL statuses were associated with increased readmissions and long-term mortality after AV access creation. Approximately half of patients with functional impairment were not alive at 5 years. Setting outcome expectations as well as prospectively examining the impact of physical therapy and visiting nursing services for functionally impaired patients undergoing AV access creation are warranted.

Analysis of Early Death after Elective Open Abdominal Aortic Aneurysm Repair

BACKGROUND

Mortality after open abdominal aortic aneurysm repair is a quality measure and early death may represent a technical complication or poor patient selection. Our objective was to analyze patients who died in the hospital within postoperative day (POD) 0-2 after elective abdominal aortic aneurysm repair.

METHODS

The Vascular Quality Initiative was queried from 2003-2019 for elective open abdominal aortic aneurysm repairs. Operations were categorized as in-hospital death on POD 0-2 (POD 0-2 Death), in-hospital death beyond POD 2 (POD ≥3 Death), and those alive at discharge. Univariable and multivariable analyses were performed.

RESULTS

There were 7,592 elective open abdominal aortic aneurysm repairs with 61 (0.8%) POD 0-2 Death, 156 (2.1%) POD ≥3 Death, and 7,375 (97.1%) alive at discharge. Overall, median age was 70 years and 73.6% were male. Iliac aneurysm repair and surgical approach (anterior/retroperitoneal) were similar among groups. POD 0-2 Death, compared to POD ≥3 Death and those alive at discharge, had the longest renal/visceral ischemia time, more commonly had proximal clamp placement above both renal arteries, an aortic distal anastomosis, longest operative time, and largest estimated blood loss (all P < 0.05). Postoperative vasopressor usage, myocardial infarction, stroke, and return to the operating room were most frequent in POD 0-2 Death and extubation in the operating room was least frequent (all P < 0.001). Postoperative bowel ischemia and renal failure occurred most commonly among POD ≥3 Death (all P < 0.001).On multivariable analysis, POD 0-2 Death was associated with congestive heart failure, prior peripheral vascular intervention, female sex, preoperative aspirin use, lower center volume quartile, renal/visceral ischemia time, estimated blood loss, and older age (all P < 0.05).

CONCLUSIONS

POD 0-2 Death was associated with comorbidities, center volume, renal/visceral ischemia time, and estimated blood loss. Referral to high-volume aortic centers could improve outcomes.

Brachiocephalic and Radiocephalic Arteriovenous Fistulas in Patients with Tunneled Dialysis Catheters Have Similar Outcomes

BACKGROUND

Patients with tunneled dialysis catheters (TDCs) have a time-sensitive need for a functional permanent access due to high risk of catheter-associated morbidity. Brachiocephalic arteriovenous fistulas (BCF) have been reported to have higher maturation and patency compared to radiocephalic arteriovenous fistulas (RCF), although more distal creation is encouraged when possible. However, this may lead to a delay in establishing permanent vascular access and, ultimately, TDC removal. Our goal was to assess short-term outcomes after BCF and RCF creation for patients with concurrent TDCs to see if these patients would potentially benefit more from an initial brachiocephalic access to minimize TDC dependence.

METHODS

The Vascular Quality Initiative hemodialysis registry was analyzed from 2011 to 2018. Patient demographics, comorbidities, access type, and short-term outcomes including occlusion, reinterventions, and access being used for dialysis, were assessed.

RESULTS

There were 2,359 patients with TDC, of whom 1,389 (58.9%) underwent BCF creation and 970 (41.1%) underwent RCF creation. Average patient age was 59 years, and 62.8% were male. Compared with RCF, those with BCF were more often older, of female sex, obese, nonindependently ambulatory, have commercial insurance, diabetes, coronary artery disease, chronic obstructive pulmonary disease, be on anticoagulation, and have a cephalic vein diameter of ≥3 mm (all P < 0.05). Kaplan-Meier analysis for 1-year outcomes for BCF and RCF, respectively, showed that primary patency was 45% vs. 41.3% (P = 0.88), primary assisted patency was 86.7% vs. 86.9% (P = 0.64), freedom from reintervention was 51.1% vs. 46.3% (P = 0.44), and survival was 81.3% vs. 84.9% (P = 0.02). Multivariable analysis showed that BCF was comparable to RCF with respect to primary patency loss (hazard ratio [HR] 1.11, 95% confidence interval [CI] 0.91-1.36, P = 0.316), primary assisted patency loss (HR 1.11, 95% CI 0.72-1.29, P = 0.66), and reintervention (HR 1.01, 95% CI 0.81-1.27, P = 0.92). Access being used at 3 months was similar but trending towards RCF being used more often (odds ratio 0.7, 95% CI 0.49-1, P = 0.05).

CONCLUSIONS

BCFs do not have superior fistula maturation and patency compared to RCFs in patients with concurrent TDCs. Creation of radial access, when possible, does not prolong TDC dependence.

Five Year Survival in Medicare Patients Undergoing Interventions for Peripheral Arterial Disease: a Retrospective Cohort Analysis of Linked Registry Claims Data

OBJECTIVE

To justify the up front risks of offering elective interventions for intermittent claudication (IC), patients should have reasonable life expectancy to derive durable clinical benefits. Open surgery for chronic limb threatening ischaemia (CLTI) is maximally beneficial in patients surviving ≥ 2 years. The aim was to assess long term survival after IC and CLTI interventions.

METHODS

In a retrospective cohort analysis, the Vascular Quality Initiative (VQI) registry from 1 January 2010 to 31 May 2021 was queried for peripheral vascular intervention (PVI), infra-inguinal bypasses (IIB), and supra-inguinal bypasses (SIB) for IC and CLTI across 286 US centres. VQI linkage to Medicare insurance claims provided five year survival data. Multivariable analysis identified factors associated with five year mortality.

RESULTS

There were 31 457 PVIs (44.7% IC, 55.3% CLTI), 7 978 IIBs (26.9% IC, 73.1% CLTI), and 2 149 SIBs (50.1% IC, 49.9% CLTI) recorded in the VQI. Among the PVI, IIB, and SIB cohorts, average ages were 75, 73, and 72 years, respectively. Respective five year mortality after PVI for IC and CLTI was 37.2% and 71.1%; after IIB for IC and CLTI it was 37.8% and 60%; and after SIB for IC and CLTI it was 33.8% and 53.8%. On multivariable analysis, across all procedures, end stage renal disease, CLTI, congestive heart failure, anaemia, chronic obstructive pulmonary disease, and prior amputation were independently associated with increased mortality. Pre-admission home living and pre-operative aspirin use were independently associated with decreased mortality.

CONCLUSION

Long term survival in Medicare patients undergoing interventions in VQI centres for peripheral arterial disease is poor. Two thirds of CLTI patients and over one third of IC patients were not alive at five years. Intervening for IC in patients with high mortality risk should be avoided. For CLTI patients identified with decreased survival likelihood, intervention durability may be less important than invasiveness. Pre-operative medical optimisation should always be undertaken.

Naturally segregating genetic variants contribute to thermal tolerance in a D. melanogaster model system

Thermal tolerance is a fundamental physiological complex trait for survival in many species. For example, everyday tasks such as foraging, finding a mate, and avoiding predation, are highly dependent on how well an organism can tolerate extreme temperatures. Understanding the general architecture of the natural variants of the genes that control this trait is of high importance if we want to better comprehend how this trait evolves in natural populations. Here, we take a multipronged approach to further dissect the genetic architecture that controls thermal tolerance in natural populations using the Drosophila Synthetic Population Resource (DSPR) as a model system. First, we used quantitative genetics and Quantitative Trait Loci (QTL) mapping to identify major effect regions within the genome that influences thermal tolerance, then integrated RNA-sequencing to identify differences in gene expression, and lastly, we used the RNAi system to 1) alter tissue-specific gene expression and 2) functionally validate our findings. This powerful integration of approaches not only allows for the identification of the genetic basis of thermal tolerance but also the physiology of thermal tolerance in a natural population, which ultimately elucidates thermal tolerance through a fitness-associated lens.

The Effect of Chronic and End Stage Renal Disease on Long-term Outcomes after Infrainguinal Bypass

OBJECTIVES

Patients undergoing infrainguinal bypass for chronic limb threatening ischemia (CLTI) with renal dysfunction are at an increased risk for perioperative and long-term morbidity and mortality. Our goal was to examine perioperative and 3-year outcomes after lower extremity bypass for CLTI stratified by kidney function.

METHODS

A retrospective, single-center analysis of lower extremity bypass for CLTI was performed between 2008 and 2019. Kidney function was categorized as normal (estimated glomerular filtration rate (eGFR) ≥60ml/min/1.73m²), chronic kidney disease (CKD) (eGFR15-59ml/min/1.73m²), and end stage renal disease (ESRD) (eGFR<15ml/min/1.73m²). Kaplan-Meier and multivariable analysis were performed.

RESULTS

There were 221 infrainguinal bypasses performed for CLTI. Patients were classified by renal function as normal (59.7%), CKD (24.4%), and ESRD (15.8%). Average age was 66 years and 65% were male. Overall, 77% had tissue loss with 9%, 45%, 24%, and 22% being Wound, Ischemia, and foot Infection (WIfI) stages 1-4, respectively. The majority (58%) of bypass targets were infrapopliteal and 58% used ipsilateral greater saphenous vein. The 90-day mortality and readmission rates were 2.7% and 49.8%, respectively. ESRD, compared to CKD and normal renal function, respectively, had the highest 90-day mortality (11.4% vs. 1.9% vs. .8%, P=.002) and 90-day readmission (69% vs. 55% vs. 43%, P=.017). On multivariable analysis, ESRD, but not CKD, was associated with higher 90-day mortality (OR 16.9, 95% CI 1.83-156.6, P=.013) and 90-day readmission (OR 3.02, 95% CI 1.2-7.58, P=.019). Kaplan Meier 3-year analysis showed no difference between groups for primary patency or major amputation, however ESRD, compared to CKD and normal renal function, respectively, had worse primary-assisted patency (60% vs. 76% vs. 84%, P=.03) and survival (72% vs. 96% vs. 94%, P=.001). On multivariable analysis, ESRD and CKD were not associated with 3-year primary patency loss/death, but ESRD was associated with higher primary-assisted patency loss (HR 2.61, 95% CI 1.23-5.53, P=.012). ESRD and CKD were not associated with 3-year major amputation/death. ESRD was associated with higher 3-year mortality (HR 4.95, 95% CI 1.52-16.2, P=.008) while CKD was not.

CONCLUSION

ESRD, but not CKD, was associated with higher perioperative and long-term mortality after lower extremity bypass for CLTI. Although ESRD was associated with lower long-term primary-assisted patency, there were no differences in loss of primary patency or major amputation.

Postoperative Disability and One-Year Outcomes for Patients Suffering a Stroke after Carotid Endarterectomy

OBJECTIVES

Although post-carotid endarterectomy (CEA) strokes are rare, they can be devastating. The degree of disability that patients develop after such events and its effects on long-term outcomes are unclear. Our goal was to assess the extent of postoperative disability in patients suffering strokes after CEA and evaluate its association with long-term outcomes.

METHODS

The Vascular Quality Initiative CEA registry (2016-2020) was queried for CEAs performed for asymptomatic or symptomatic indications in patients with preoperative modified Rankin Scale (mRS) scores of 0-1. The mRS grades stroke-related disability as 0 (none), 1 (not significant), 2-3 (moderate), 4-5 (severe), and 6 (dead). Patients suffering postoperative strokes with recorded mRS scores were included. Postoperative stroke-related disability based on mRS and its association with long-term outcomes were analyzed.

RESULTS

Among 149,285 patients undergoing CEA, there were 1,178 patients without preoperative disability who had postoperative strokes and reported mRS scores. Mean age was 71 ± 9.2 years and 59.6% of patients were male. Regarding ipsilateral cortical symptoms within six months preoperatively, 83.5% of patients were asymptomatic, 7.3% had transient ischemic attacks, and 9.2% had strokes. Postoperative stroke-related disability was classified as mRS 0 (11.6%), 1 (19.5%), 2-3 (29.4%), 4-5 (31.5%), and 6 (8%). One-year survival stratified by postoperative stroke-related disability was 91.4% for mRS 0, 95.6% for mRS 1, 92.1% for mRS 2-3, and 81.5% for mRS 4-5 (P<.001). Multivariable analysis demonstrated that while severe postoperative disability was associated with increased death at one year (HR 2.97, 95% CI 1.5-5.89, P=.002), moderate postoperative disability had no such association (HR .95, 95% CI .45-2, P=.88). One-year freedom from subsequent ipsilateral neurological events or death stratified by postoperative stroke-related disability was 87.8% for mRS 0, 93.3% for mRS 1, 88.5% for mRS 2-3, and 77.9% for mRS 4-5 (P<.001). Severe postoperative disability was independently associated with increased ipsilateral neurological events or death at one year (HR 2.34, 95% CI 1.25-4.38, P=.01). However, moderate postoperative disability exhibited no such association (HR .92, 95% CI .46-1.82, P=.8).

CONCLUSIONS

The majority of patients without preoperative disability who suffered strokes after CEA developed significant disability. Severe stroke-related disability was associated with higher one-year mortality and subsequent neurological events. These data can improve informed consent for CEA and guide prognostication after postoperative strokes.

Qualitative Analysis of Length of Stay and Readmission after Carotid Endarterectomy

BACKGROUND

Length of stay (LOS) and readmissions are common measures to evaluate quality of health care. The objective of this study was to evaluate factors related to hospital LOS and readmission within 90 days following carotid endarterectomy (CEA) in patients who have not had a stroke.

METHODS

Using a single institution database, patients who underwent CEA for carotid stenosis between 2014 and 2019 were identified. Asymptomatic carotid stenosis (no history of any stroke or transient ischemic attack (TIA) within 6 months prior to CEA), and patients who had a TIA without stroke were included. Demographic and perioperative factors were collected. Primary outcomes analyzed were increased LOS (>1 day) and readmission within 90 days after surgery.

RESULTS

There were 125 patients identified who underwent CEA for 133 carotid stenosis, and 8 patients had bilateral CEA; of which 36.8% were asymptomatic carotid stenosis with the remaining being operated on for TIA without any stroke. The mean age was 68 years old and 36.1% of cases were female. The median postoperative LOS was 2 days. Increased LOS occurred in 81 cases (60.9%). Increased LOS, compared to no increased LOS, occurred more often in patients with diabetes (48.1% vs. 30.8%, P = 0.047), in those with operations starting after 12:00 pm (45.7% vs. 21.2%, P = 0.004) and those with any minor complications such as neck swelling, neck pain, and urinary retention (30.9% vs. 15.4%, P = 0.044). Readmission within 90 days after CEA occurred in 24 (18%) of cases. Readmission within 90 days, compared to no readmission within 90 days, occurred more often in patients with a history of coronary artery disease (58.3% vs. 27.5%, P = 0.004), congestive heart failure (37.5% vs. 11%, P = 0.001), and atrial fibrillation (29.2% vs. 8.3%, P = 0.004).

CONCLUSIONS

More than half of patients undergoing CEA for carotid stenosis were discharged after postoperative day 1. Interventions on modifiable clinical risk factors, such as morning CEA scheduling and management of comorbidities, may decrease LOS and 90-day readmission rates.

Variations in Practice Patterns for Peripheral Vascular Interventions Across Clinical Settings

BACKGROUND

Peripheral vascular interventions (PVIs) for lower extremity peripheral artery disease have been increasing, particularly in the office-based setting. Our goal was to evaluate practice patterns for PVI by site of service using a contemporary real-world dataset.

METHODS

The Vascular Quality Initiative PVI registry was queried from 2010-2021. Site of service was classified as hospital/inpatient, hospital/outpatient, and ambulatory/office-based center. Patient demographics, comorbidities, procedural details, and periprocedural outcomes were analyzed.

RESULTS

There were 54,897 hospital/inpatient (43.2%), 64,105 hospital/outpatient (50.4%), and 8,179 ambulatory/office-based center (6.4%) PVI. When comparing the 2 outpatient settings, ambulatory/office-based center patients were older than hospital/outpatient (mean age 70.7 vs. 68.7 years), more often female sex (41.4% vs. 39.1%), never smokers (27.5% vs. 18.5%), primary Medicare (61.6% vs. 55.9%), nonambulatory (6.5% vs. 4.7%), less often with coronary artery disease (30.2% vs. 34.1%), chronic obstructive pulmonary disease (18.1% vs. 26.9%), congestive heart failure (13% vs. 17.2%), obesity (30.9% vs. 33.6%), and less often on a statin (71.4% vs. 76.1%) (P < 0.001). Ambulatory/office-based center procedures were more likely for claudication (60.1% vs. 55.8%), more often involved femoro-popliteal (73.1% vs. 64.6%) and infrapopliteal (36.7% vs. 24.3%), and less often iliac interventions (24.1% vs. 33.6%) (P < 0.001).Overall, atherectomy was used in 14.2% of hospital/inpatient, 19.4% of hospital/outpatient, and 63.4% of ambulatory/office-based center procedures. Stents were used in 41.8% of hospital/inpatient, 45.1% of hospital/outpatient, and 48.8% of ambulatory/office-based center procedures. However, stent grafts were used in 12.5% of hospital/inpatient, 8.8% of hospital/outpatient, and only 1.3% of ambulatory/office-based center procedures. On multivariable analysis, compared with hospital/inpatient, atherectomy use was associated with ambulatory/office-based center setting (Odds ratio 10.9, 95% confidence interval 10.3-11.5, P < 0.001) and hospital/outpatient setting (Odds ratio 1.57, 95% confidence interval 1.51-1.62, P < 0.001). Periprocedure complications including hematoma requiring intervention (0.3%), any stenosis/occlusion (0.2%), and distal embolization (0.6%) were quite low across all settings.

CONCLUSIONS

There are substantial variations in patient populations, procedural indications, and types of interventions undertaken during PVI across different locations. Ambulatory/office-based procedures more commonly treat claudicants, use atherectomy, and less often use stent grafts. Further research is warranted to investigate long-term trends in practice patterns and long-term outcomes, for PVI in the ever-expanding ambulatory/office-based setting.

A systematic review of routine post operative screening duplex ultrasound after thermal and non-thermal endovenous ablation

OBJECTIVE

The Society of Vascular Surgery and the American Venous Forum recommend duplex ultrasound (DUS) following endovenous ablation. However, this screening may not be cost-effective or clinically indicated. The most common abnormal finding, endovenous heat-induced thrombosis (EHIT level 1-2), represents extension of thrombus from the saphenous <50% across the femoral or popliteal vein, which is thought to have a benign course regardless of intervention. The likelihood of venous thromboembolism (VTE) after thermal and non-thermal ablations was explored to determine the utility of routine postoperative DUS.

METHODS

This is an updated and expanded systematic review including data from randomized trials and large observational studies (≥150 patients) of thermal and non-thermal ablations, examining the incidence of VTE. Using PubMed and EMBASE, 4584 publications were screened from 2000 through 2020. After applying inclusion and exclusion criteria, 72 studies were included. Random effects DerSimonian-Laird method was conducted to obtain the pooled incidence. We calculated the number of tests needed to detect one VTE, and the cost was derived from Center for Medicare Services tables.

RESULTS

A total of 31,663 patients were included. The pooled incidence of EHIT II-IV, deep venous thrombosis (DVT), and pulmonary embolism (PE) was 1.32% (95% confidence interval [CI], 0.75%-2.02%); DVT (excluding EHIT), 0.20% (95% CI, 0.0%-0.2%); EHIT (I-IV), 2.51% (95% CI, 1.54%-3.68%); and EHIT (II-IV), 1.00% (95% CI, 0.51%-1.61%). There was no mortality. There was a lower DVT rate in thermal vs non-thermal ablations (0.23% vs 0.43%; P = .02); however, for all VTE (EHIT I-IV + DVT + PE), thermal techniques had more thrombosis (2.5% vs 0.5%; P <.001). When clinical significance is defined as DVT + EHIT (II-IV), 175 studies are needed to identify one VTE, costing $21,813 per "significant VTE." Patients receiving pharmacological prophylaxis had less EHIT I-IV compared with those who did not (3.04% vs 1.63%; P < .001); those who received DUS during the first post-op week had three times higher EHIT incidence compared with those whose first DUS was >7 days postoperative (6.6% vs 2.4%; P < .001).

CONCLUSIONS

For thermal and non-thermal endovenous ablations, the incidence of VTE diagnosed with routine DUS is small and without clear clinical significance but caries a high cost. The Society of Vascular Surgery and the American Venous Forum recommendation to perform DUS within 72 hours is not justified by these data. We recommend a more targeted post-ablation scanning protocol including symptomatic patients and those at high risk.

Female Sex is Associated with More Reinterventions after Endovascular and Open Interventions for Intermittent Claudication

BACKGROUND

Intermittent claudication (IC) is a commonly treated vascular condition. Patient sex has been shown to influence outcomes of interventions for other vascular disorders; however, whether outcomes of interventions for IC vary by sex is unclear. We sought to assess the association of patient sex with outcomes after IC interventions.

METHODS

The Vascular Quality Initiative was queried from 2010-2020 for all peripheral endovascular interventions (PVI), infra-inguinal bypasses (IIB), and supra-inguinal bypasses (SIB) for any degree IC. Univariable and multivariable analyses compared peri-operative and long-term outcomes by patient sex.

RESULTS

There were 24,701 female and 40,051 male patients undergoing PVI, 2,789 female and 6,525 male patients undergoing IIB, and 1,695 female and 2,370 male patients undergoing SIB for IC. Guideline-recommended pre-operative medical therapy differed with female patients less often prescribed aspirin for PVI (73.4% vs. 77.3%), IIB (71.5% vs. 74.8%), and SIB (70.9% vs. 74.3%) or statins for PVI (71.8% vs. 76.7%) and IIB (73.1% vs. 76.0%) (all P < 0.05). Female compared with male patients had lower 1-year reintervention-free survival after PVI (84.4% ± 0.3% vs. 86.3% ± 0.2%, P < 0.001), IIB (79.0% ± 0.9% vs. 81.2% ± 0.6%, P = 0.04), and SIB (89.4% ± 0.9% vs. 92.6% ± 0.7%, P = 0.005), but similar amputation-free survival and survival across all procedures. Multivariable analysis confirmed that female sex was associated with increased 1-year reintervention for PVI (HR 1.16, 95% CI 1.09-1.24, P < 0.001), IIB, (HR 1.16, 95% CI 1.03-1.31, P = 0.02), and SIB (HR 1.60, 95% CI 1.20-2.13, P = 0.001).

CONCLUSIONS

Female patients undergoing interventions for IC were less often pre-operatively medically optimized than male patients, though the difference was small. Furthermore, female sex was associated with more reinterventions after interventions. Interventionists treating female patients should increase their efforts to maximize medical therapy. Future research should clarify reasons for poorer intervention durability in female patients.

What Is the Best Treatment for Acute Limb Ischemia?

Acute limb ischemia (ALI) is a vascular emergency associated with high rates of limb loss and mortality. Management of these patients is challenging given the severe systemic illness resulting from tissue ischemia and the high incidence of preexisting comorbid conditions and underlying peripheral arterial disease. Expeditious diagnosis, anticoagulation, and revascularization are of utmost importance in reducing morbidity. Revascularization may be accomplished using open, endovascular, or hybrid techniques. Approach to revascularization depends on the severity of ischemia, location of occlusion, cause, chance of recovery, comorbidities, and available resources.

Unplanned Shunting Is Associated with Higher Stroke Risk after Eversion Carotid Endarterectomy

BACKGROUND

Shunting during eversion carotid endarterectomy (eCEA) may be technically challenging. Whether shunting practice patterns modify perioperative stroke risk after eCEA is unclear. We aimed to compare eCEA outcomes based on shunting practice.

METHODS

The Vascular Quality Initiative (2011-2019) was queried for eCEAs performed for symptomatic and asymptomatic carotid stenosis. Univariable and multivariable analyses compared outcomes based on whether shunting was routine practice, preoperatively-indicated, intraoperatively-indicated, or not performed.

RESULTS

There were 13,207 eCEAs identified. Average age was 71.4 years and 59.4% of patients were male sex. Ipsilateral carotid stenosis was >80% in 45.6% and there was severe contralateral carotid stenosis in 8.6%. Early ipsilateral symptoms within 14 days of eCEA were transient ischemic attack in 5.6% and stroke in 7%. The majority of cases were performed under general anesthesia (82.7%). Electroencephalogram monitoring and stump pressures were utilized in 30.9% and 14.7%, respectively. Shunting was routine (25.4%), preoperatively-indicated (1.9%), intraoperatively-indicated (4.7%), or not implemented (68%). Preoperatively-indicated shunting was more often performed in patients with early symptomatic carotid stenosis or severe contralateral carotid stenosis. After routine shunting, preoperatively-indicated shunting, intraoperatively-indicated shunting, and no shunting, median operative duration was 110, 101, 112, and 97 min, respectively (P < 0.001), and ipsilateral perioperative stroke prevalence was 0.6%, 1.2%, 1.9%, and 0.7%, respectively (P = 0.004). On multivariable analysis, longer operative time was associated with routine shunting (MR 1.17, 95% CI 1.15-1.19, P < 0.001), preoperatively-indicated shunting (MR 1.09, 95% CI 1.04-1.15, P < 0.001), and intraoperatively-indicated shunting (MR 1.12, 95% CI 1.09-1.16, P < 0.001) compared with no shunting. Compared with no shunting, routine shunting (OR 0.91, 95% CI 0.54-1.54, P = 0.74) and preoperatively-indicated shunting (OR 1.53, 95% CI 0.47-4.99, P = 0.48) were not associated with stroke; however, intraoperatively-indicated shunting was associated with increased stroke (OR 2.74, 95% CI 1.41-5.3, P = 0.003). Shunting type was not associated with perioperative mortality.

CONCLUSIONS

Intraoperatively-indicated shunting during eCEA was associated with longest operative duration and increased perioperative stroke risk. Surgeon familiarity with shunting and planning to shunt in advance may permit more expeditious shunting and prevent stroke.

Access Site Complications Are Uncommon with Vascular Closure Devices or Manual Compression after Lower Extremity Revascularization

OBJECTIVE

Vascular closure devices (VCD) and manual compression (MC) are used to achieve hemostasis following peripheral vascular interventions (PVI). We sought to compare perioperative outcomes between MC and four VCDs following PVI in a multicenter setting.

METHODS

The Vascular Quality Initiative was queried for all lower extremity (LE) PVIs with common femoral artery access performed from 2010-2020. VCDs included were MynxGrip® (Cordis, Santa Clara, CA, USA), StarClose SE™ (Abbott, Redwood City, CA, USA), Angio-Seal® (Terumo, Somerset, NJ, USA), and Perclose ProGlide™ (Abbott, Redwood City, CA, USA). In a blinded fashion, these four VCDs (A, B, C, D) were compared to MC for baseline characteristics, procedural details, and outcomes (access site hematoma and stenosis/occlusion). Sheath size >8 Fr were excluded. Propensity score matching (1:1) was performed. Univariable and multivariable analyses were completed for unmatched and matched data.

RESULTS

There were 84,172 LE PVIs identified: 32,013 (38%) used MC and 52,159 (62%) used VCDs (A-12,675;B-6,224;C-19,872;D-13,388). Overall, average age was 68.7 years and 60.4% were male; indications for intervention were most commonly claudication (43.8%) and tissue loss (40.1%). When compared to MC, VCDs were utilized more often in patients with obesity, diabetes, and end stage renal disease (all P<.001). VCDs were used less often in patients with hypertension, chronic obstructive pulmonary disease, coronary artery disease, prior percutaneous coronary and extremity interventions, and major amputation (all P<.001). VCD use was more common, compared to MC, during femoral-popliteal (73% vs. 63.8%) and tibial interventions (33.8% vs. 22.3%), but less common with iliac interventions (20.6% vs. 34.7%) (all P<.001). Protamine was used less often after VCDs (19.1% vs. 25.6%, P<.001). Overall, there were 2,003 (2.4%) hematomas of which 278 (13.9%) required thrombin/surgical intervention. When compared to MC, any VCD use had fewer hematomas (1.7% vs. 3.6%, P<.001) and hematomas requiring intervention (.2% vs. .5%, P<.001). When divided by hemostatic technique, any hematoma were MC-3.6%; A-1.4%; B-1.2%; C-2.3%; D-1.1%, P<.001. Hematomas requiring intervention were MC-.5%; A-.2%; B-.2%; C-.3%; D-.1%, P<.001. Access site stenosis/occlusion was similar between MC and any VCDs (.2% vs. .2%, P=.12). Multivariable analysis demonstrated that any VCDs and individual VCDs, vs. MC, were independently associated with fewer hematomas. Access site stenosis/occlusion was similar between any VCDs and MC. Matched analysis revealed similar findings.

CONCLUSIONS

Although overall rates of hematomas requiring intervention were low regardless of hemostatic technique, VCD use, irrespective of type, compared favorably to MC with significantly fewer access site complications after PVI.

Outcomes of Axillofemoral Bypass for Intermittent Claudication

OBJECTIVE

While endovascular therapy is often first-line treatment for medically refractory intermittent claudication (IC) caused by aorto-femoral disease, suprainguinal bypass is commonly performed. Although this is often aorto-femoral bypass (AoFB), axillo-femoral bypass (AxFB) is still sometimes performed despite limited data evaluating its utility in the management of IC. Our goal was to assess the safety and durability of AxFB performed for IC.

METHODS

The Vascular Quality Initiative (2009-2019) was queried for suprainguinal bypass performed for IC. Univariable and multivariable analyses were used to compare perioperative and one-year outcomes between AxFB and a comparison cohort of AoFB.

RESULTS

We identified 3,261 suprainguinal bypasses performed for IC: 436 AxFB and 2,825 AoFB. Overall, mean age was 61.4 ± 9.1 years, 58.8% of patients were male sex, and 59.7% currently smoked. Patients undergoing AxFB, compared with AoFB, were more often older, male, never-smokers, and ambulated with assistance (all P<.001). They more often had hypertension, diabetes, coronary artery disease, congestive heart failure, chronic obstructive pulmonary disease, end-stage renal disease, previous outflow peripheral endovascular interventions, and previous inflow or outflow bypass. AxFB, compared with AoFB, were more often uni-femoral (all P<.05). Patients undergoing AxFB, compared with AoFB, had shorter postoperative length of stay (median 4 vs. 6 days) and fewer perioperative pulmonary (3% vs. 7.9%) and renal complications (5.5% vs. 9.9%), but more perioperative ipsilateral major amputations (.9% vs. 0.04%) (all P<.05). There were no significant differences in perioperative myocardial infarction (2.8% vs. 2.7%), stroke (.7% vs. 1.1%), and death (1.8% vs. 1.7%) rates, respectively. At one year, Kaplan-Meier analysis demonstrated that the AxFB, compared with AoFB cohort, exhibited higher rates of death (7.3% vs. 3.6%, P=.002); graft occlusion or death (14.3% vs. 7.2%, P=.001); ipsilateral major amputation or death (12.5% vs. 5.6%, P<.001); and reintervention, amputation, or death (19% vs. 8.6%, P<.001). On multivariable analysis, AxFB was independently associated with increased risk of one-year reintervention, amputation, or death (HR 1.6, 95% CI 1.03-2.4, P=.04).

CONCLUSIONS

This retrospective analysis suggests that long-term complications were more frequent in patients who underwent AxFB as compared to AoFB, although patients treated with AxFB were at higher risk with more comorbidities. Since AxFB is associated with significant perioperative morbidity, mortality, and long-term complications, serious consideration should be given prior to its use for IC.

Diverse biological processes coordinate the transcriptional response to nutritional changes in a Drosophila melanogaster multiparent population

Background

Environmental variation in the amount of resources available to populations challenge individuals to optimize the allocation of those resources to key fitness functions. This coordination of resource allocation relative to resource availability is commonly attributed to key nutrient sensing gene pathways in laboratory model organisms, chiefly the insulin/TOR signaling pathway. However, the genetic basis of diet-induced variation in gene expression is less clear.

Results

To describe the natural genetic variation underlying nutrient-dependent differences, we used an outbred panel derived from a multiparental population, the Drosophila Synthetic Population Resource. We analyzed RNA sequence data from multiple female tissue samples dissected from flies reared in three nutritional conditions: high sugar (HS), dietary restriction (DR), and control (C) diets. A large proportion of genes in the experiment (19.6% or 2471 genes) were significantly differentially expressed for the effect of diet, and 7.8% (978 genes) for the effect of the interaction between diet and tissue type (LRT, P_adj. < 0.05). Interestingly, we observed similar patterns of gene expression relative to the C diet, in the DR and HS treated flies, a response likely reflecting diet component ratios. Hierarchical clustering identified 21 robust gene modules showing intra-modularly similar patterns of expression across diets, all of which were highly significant for diet or diet-tissue interaction effects (FDR P_adj. < 0.05). Gene set enrichment analysis for different diet-tissue combinations revealed a diverse set of pathways and gene ontology (GO) terms (two-sample t-test, FDR < 0.05). GO analysis on individual co-expressed modules likewise showed a large number of terms encompassing many cellular and nuclear processes (Fisher exact test, P_adj. < 0.01). Although a handful of genes in the IIS/TOR pathway including Ilp5, Rheb, and Sirt2 showed significant elevation in expression, many key genes such as InR, chico, most insulin peptide genes, and the nutrient-sensing pathways were not observed.

Conclusions

Our results suggest that a more diverse network of pathways and gene networks mediate the diet response in our population. These results have important implications for future studies focusing on diet responses in natural populations.

Learning to collaborate: bringing together behavior and quantitative genomics

The genetic basis of complex trait like learning and memory have been well studied over the decades. Through those groundbreaking findings, we now have a better understanding about some of the genes and pathways that are involved in learning and/or memory. However, few of these findings identified the naturally segregating variants that are influencing learning and/or memory within populations. In this special issue honoring the legacy of Troy Zars, we review some of the traditional approaches that have been used to elucidate the genetic basis of learning and/or memory, specifically in fruit flies. We highlight some of his contributions to the field, and specifically describe his vision to bring together behavior and quantitative genomics with the aim of expanding our knowledge of the genetic basis of both learning and memory. Finally, we present some of our recent work in this area using a multiparental population (MPP) as a case study and describe the potential of this approach to advance our understanding of neurogenetics.

Multiple genetic loci affect place learning and memory performance in Drosophila melanogaster

Learning and memory are critical functions for all animals, giving individuals the ability to respond to changes in their environment. Within populations, individuals vary, however the mechanisms underlying this variation in performance are largely unknown. Thus, it remains to be determined what genetic factors cause an individual to have high learning ability and what factors determine how well an individual will remember what they have learned. To genetically dissect learning and memory performance, we used the Drosophila synthetic population resource (DSPR), a multiparent mapping resource in the model system Drosophila melanogaster, consisting of a large set of recombinant inbred lines (RILs) that naturally vary in these and other traits. Fruit flies can be trained in a "heat box" to learn to remain on one side of a chamber (place learning) and can remember this (place memory) over short timescales. Using this paradigm, we measured place learning and memory for ~49 000 individual flies from over 700 DSPR RILs. We identified 16 different loci across the genome that significantly affect place learning and/or memory performance, with 5 of these loci affecting both traits. To identify transcriptomic differences associated with performance, we performed RNA-Seq on pooled samples of seven high performing and seven low performing RILs for both learning and memory and identified hundreds of genes with differences in expression in the two sets. Integrating our transcriptomic results with the mapping results allowed us to identify nine promising candidate genes, advancing our understanding of the genetic basis underlying natural variation in learning and memory performance.

The evolutionary potential of diet-dependent effects on lifespan and fecundity in a multi-parental population of Drosophila melanogaster

The nutritional conditions experienced by a population have a major role in shaping trait evolution in many taxa. Constraints exerted by nutrient limitation or nutrient imbalance can influence the maximal value that fitness components such as reproduction and lifespan attains, and organisms may shift how resources are allocated to different structures and functions in response to changes in nutrition. Whether the phenotypic changes associated with changes in nutrition represent an adaptive response is largely unknown. Further, it is unclear whether the response of fitness components to diet even has the potential to evolve in most systems. In this study, we use an admixed multi-parental population of Drosophila melanogaster reared in three different diet conditions to estimate quantitative genetic parameters for lifespan and fecundity. We find significant genetic variation for both traits in our population and show that lifespan has moderate to high heritabilities within diets. Genetic correlations for lifespan between diets were significantly less than one, demonstrating a strong genotype by diet interaction. These findings demonstrate substantial standing genetic variation in our population that is comparable to natural populations and highlights the potential for adaptation to changing nutritional environments.

A model-based high throughput method for fecundity estimation in fruit fly studies

The ability to quantify fecundity is critically important to a wide range of experimental applications, particularly in widely-used model organisms such as Drosophila melanogaster. However, the standard method of manually counting eggs is time consuming and limits the feasibility of large-scale experiments. We develop a predictive model to automate the counting of eggs from images of eggs removed from the media surface and washed onto dark filter paper. Our method uses the simple relationship between the white area in an image and the number of eggs present to create a predictive model that performs well even at high egg densities where clumping can complicate the individual identification of eggs. A cross-validation approach demonstrates our method performs well, with a correlation between predicted and manually counted values of 0.88. We show how this method can be applied to a large data set where egg densities vary widely.

How to get the most bang for your buck: the evolution and physiology of nutrition-dependent resource allocation strategies

All organisms use resources to grow, survive and reproduce. The supply of these resources varies widely across landscapes and time, imposing ultimate constraints on the maximal trait values for allocation-related traits. In this review, we address three key questions fundamental to our understanding of the evolution of allocation strategies and their underlying mechanisms. First, we ask: how diverse are flexible resource allocation strategies among different organisms? We find there are many, varied, examples of flexible strategies that depend on nutrition. However, this diversity is often ignored in some of the best-known cases of resource allocation shifts, such as the commonly observed pattern of lifespan extension under nutrient limitation. A greater appreciation of the wide variety of flexible allocation strategies leads directly to our second major question: what conditions select for different plastic allocation strategies? Here, we highlight the need for additional models that explicitly consider the evolution of phenotypically plastic allocation strategies and empirical tests of the predictions of those models in natural populations. Finally, we consider the question: what are the underlying mechanisms determining resource allocation strategies? Although evolutionary biologists assume differential allocation of resources is a major factor limiting trait evolution, few proximate mechanisms are known that specifically support the model. We argue that an integrated framework can reconcile evolutionary models with proximate mechanisms that appear at first glance to be in conflict with these models. Overall, we encourage future studies to: (i) mimic ecological conditions in which those patterns evolve, and (ii) take advantage of the 'omic' opportunities to produce multi-level data and analytical models that effectively integrate across physiological and evolutionary theory.

The Role of the Model of End-Stage Liver Disease Score in Predicting Outcomes of Carotid Endarterectomy

Objectives:

The Model of End-Stage Liver Disease (MELD) score has been traditionally utilized to prioritize for liver transplantation; however, recent literature has shown its value in predicting surgical outcomes for patients with hepatic dysfunction. The benefit of carotid endarterectomy in asymptomatic patients is dependent on low perioperative morbidity. Our objective was to use MELD score to predict outcomes in asymptomatic patients undergoing carotid endarterectomy.

Methods:

Patients undergoing carotid endarterectomy were identified in the National Surgical Quality Improvement Program data sets from 2005 to 2012. The Model of End-Stage Liver Disease score was calculated using serum bilirubin, creatinine, and the international normalized ratio (INR). Patients were grouped into low (<9), moderate (9-14), and high (15+) MELD classifications. The effect of the MELD score on postoperative morbidity and mortality was assessed by multivariable logistic and gamma regressions and propensity matching.

Results:

There were 7966 patients with asymptomatic carotid endarterectomy identified. The majority 5556 (70%) had a low MELD score, 1952 (25%) had a moderate MELD score, and 458 (5%) had a high MELD score. High MELD score was independently predictive of postoperative death, increased length of stay, need for transfusion, pulmonary complications, and a statistical trend toward increased cardiac arrest/myocardial infarction. The Model of End-Stage Liver Disease score did not affect postoperative stroke, wound complications, or operative time.

Conclusion:

High MELD score places asymptomatic patients undergoing carotid endarterectomy at a higher risk of adverse outcomes in the 30 days following surgery. This provides further empirical evidence for risk stratification when considering treatment for these patients. Outcomes of medical management or carotid stenting should be investigated in high-risk patients.

Identifying Loci Contributing to Natural Variation in Xenobiotic Resistance in Drosophila

Natural populations exhibit a great deal of interindividual genetic variation in the response to toxins, exemplified by the variable clinical efficacy of pharmaceutical drugs in humans, and the evolution of pesticide resistant insects. Such variation can result from several phenomena, including variable metabolic detoxification of the xenobiotic, and differential sensitivity of the molecular target of the toxin. Our goal is to genetically dissect variation in the response to xenobiotics, and characterize naturally-segregating polymorphisms that modulate toxicity. Here, we use the Drosophila Synthetic Population Resource (DSPR), a multiparent advanced intercross panel of recombinant inbred lines, to identify QTL (Quantitative Trait Loci) underlying xenobiotic resistance, and employ caffeine as a model toxic compound. Phenotyping over 1,700 genotypes led to the identification of ten QTL, each explaining 4.5-14.4% of the broad-sense heritability for caffeine resistance. Four QTL harbor members of the cytochrome P450 family of detoxification enzymes, which represent strong a priori candidate genes. The case is especially strong for Cyp12d1, with multiple lines of evidence indicating the gene causally impacts caffeine resistance. Cyp12d1 is implicated by QTL mapped in both panels of DSPR RILs, is significantly upregulated in the presence of caffeine, and RNAi knockdown robustly decreases caffeine tolerance. Furthermore, copy number variation at Cyp12d1 is strongly associated with phenotype in the DSPR, with a trend in the same direction observed in the DGRP (Drosophila Genetic Reference Panel). No additional plausible causative polymorphisms were observed in a full genomewide association study in the DGRP, or in analyses restricted to QTL regions mapped in the DSPR. Just as in human populations, replicating modest-effect, naturally-segregating causative variants in an association study framework in flies will likely require very large sample sizes.

Dissecting complex traits using the Drosophila Synthetic Population Resource

For most complex traits we have a poor understanding of the positions, phenotypic effects, and population frequencies of the underlying genetic variants contributing to their variation. Recently, several groups have developed multi-parent advanced intercross mapping panels in different model organisms in an attempt to improve our ability to characterize causative genetic variants. These panels are powerful and are particularly well suited to the dissection of phenotypic variation generated by rare alleles and loci segregating multiple functional alleles. We describe studies using one such panel, the Drosophila Synthetic Population Resource (DSPR), and the implications for our understanding of the genetic basis of complex traits. In particular, we note that many loci of large effect appear to be multiallelic. If multiallelism is a general rule, analytical approaches designed to identify multiallelic variants should be a priority for both genome-wide association studies (GWASs) and multi-parental panels.

Genome-wide association study of extreme longevity in Drosophila melanogaster

Human genome-wide association studies (GWAS) of longevity attempt to identify alleles at different frequencies in the extremely old, relative to a younger control sample. Here, we apply a GWAS approach to “synthetic” populations of Drosophila melanogaster derived from a small number of inbred founders. We used next-generation DNA sequencing to estimate allele and haplotype frequencies in the oldest surviving individuals of an age cohort and compared these frequencies with those of randomly sampled individuals from the same cohort. We used this case–control strategy in four independent cohorts and identified eight significantly differentiated regions of the genome potentially harboring genes with relevance for longevity. By modeling the effects of local haplotypes, we have more power to detect regions enriched for longevity genes than marker-based GWAS. Most significant regions occur near chromosome ends or centromeres where recombination is infrequent, consistent with these regions harboring unconditionally deleterious alleles impacting longevity. Genes in regions of normal recombination are enriched for those relevant to immune function and a gene family involved in oxidative stress response. Genetic differentiation between our experimental cohorts is comparable to that between human populations, suggesting in turn that our results may help explain heterogeneous signals in human association studies of extreme longevity when panels have diverse ancestry.