Physician-modified versus chimney endografting for pararenal aortic aneurysms: a systematic review and meta-analysis.

INTRODUCTION: We performed a systematic review and meta-analysis to assess the existing published evidence regarding the safety and efficacy of the endovascular aortic repair with chimney technique (ch-EVAR) and physician-modified stent-grafts (PMSGs) for the treatment of pararenal aortic aneurysm repair. EVIDENCE ACQUISITION: A systematic search of all relevant studies reported until October 2023 according to the PRISMA (preferred reporting items for systematic reviews and meta-analyses) guidelines was performed. The pooled 30-day mortality, peri- and postoperative complication rates were estimated using fixed or random effect methods. EVIDENCE SYNTHESIS: A total of 679 study titles were identified by the initial search strategy, of which 16 were considered eligible for inclusion in the meta-analysis. A total of 1094 patients (ch-EVAR N.=861 and PMSG N.=233) (90% male) were identified. The pooled 30-day mortality rate was 3.4% for ch-EVAR and 2.6% for PMSG. The major adverse events (MAE) in the early period was 14.7% for ch-EVAR and 18.5% PMSG, respectively. Higher occlusion rate was observed of the chimney stents grafts (8.2%) than the bridging stents (1.4%) during the follow-up period. CONCLUSIONS: Ch-EVAR and physician-modified technology are safe with low 30-day mortality in elective settings for pararenal aortic aneurysms repair. No significant differences were seen between the two surgical methods regarding the early major adverse events rate. However, higher occlusion rate for the chimneys can be expected over time.

Patient-specific risk factors for reintervention following primary endovascular treatment of iliac artery disease.

OBJECTIVE: Predictive models for reintervention may guide clinicians to optimize selection, education, and follow-up of patients undergoing endovascular iliac revascularization. Although the impact of lesion- and device-related characteristics on iliac restenosis and reintervention risk is well-defined, data on patient-specific risk factors are scarce and conflicting. This study aimed to explore the value of patient-related factors in predicting the need for clinically driven target-vessel revascularization (CD-TVR) in patients undergoing primary endovascular treatment of iliac artery disease. METHODS: Consecutively enrolled patients undergoing endovascular revascularization for symptomatic iliac artery disease at a tertiary vascular referral center between January 2008 and June 2020 were retrospectively analyzed. Primary and secondary outcomes were CD-TVR occurrence within 24 months and time to CD-TVR, respectively. Patients who died or did not require CD-TVR within 24 months were censored at the date of death or at 730 days, respectively. Multiple imputation was used to account for missing data in primary analyses. RESULTS: A total of 1538 iliac interventions were performed in 1113 patients (26% females; 68 years). CD-TVR occurred in 108 limbs (74 patients; 7.0%) with a median time to CD-TVR of 246 days. On multivariable analysis, increasing age was associated with lower likelihood of CD-TVR (odds ratio [OR], 0.64; 95% confidence interval [CI], 0.50-0.83; P = .001) and decreased risk of CD-TVR at any given time (hazard ratio [HR], 0.66; 95% CI, 0.52-0.84; P = .001). Similarly, a lower likelihood of CD-TVR (OR, 0.75; 95% CI, 0.59-0.95; P = .017) and decreased risk of CD-TVR at any given time (HR, 0.73; 95% CI, 0.58-0.93; P = .009) were observed with higher glomerular filtration rates. Lastly, revascularization of common vs external iliac artery disease was associated with lower likelihood of CD-TVR (OR, 0.48; 95% CI, 0.24-0.93; P = .030) and decreased risk of CD-TVR at any given time (HR, 0.48; 95% CI, 0.25-0.92; P = .027). No associations were observed between traditional cardiovascular risk factors (sex, hypertension, higher low-density lipoprotein cholesterol, higher hemoglobin A1c, smoking) and CD-TVR. CONCLUSIONS: In this retrospective cohort study, younger age, impaired kidney function, and external iliac artery disease were associated with CD-TVR. Traditional markers of cardiovascular risk were not seen to predict reintervention.

Risk factors for postpartum haemorrhage in women with histologically verified placenta accreta spectrum disorders: a retrospective single-centre cross-sectional study.

BACKGROUND: Placenta accreta spectrum (PAS) disorders have been reported with an increasing frequency of up to 3%. The increase in the incidence can be explained by the rising rate of Caesarean section (CS), assisted reproductive technology (ART) and previous uterine surgeries. PAS disorders are usually associated with postpartum haemorrhage (PPH). In our study, we investigated the risk factors for increased blood loss in women with histologically verified PAS disorders independent of delivery mode. METHODS: In a retrospective single-centre cross-sectional study, 2,223 pregnant women with histologically verified PAS disorders were included. Risk factors for PPH in women with PAS disorders were examined and compared between women with PPH (study group; n = 879) and women with normal blood loss (control group; n = 1150), independent of delivery mode. PAS disorders were diagnosed histologically from the following specimens: placenta, placental-bed specimens, uterine curettage, uterine resection and/or total/partial hysterectomy. Medical data were extracted from clinical records of pregnant women with PAS disorders delivering at the University Hospital Basel between 1986 and 2019. The placenta data of women with PAS disorders were obtained and identified through a search from the database of the Department of Pathology, University Hospital Basel. RESULTS: Between 1986 and 2019, there were 64,472 deliveries at the University Hospital Basel. PAS disorders were histologically verified in 2,223 women (2,223/64,472), and the prevalence of PAS disorders was 3.45%. A total of 879 women with PAS disorders showed PPH, independent of delivery mode (43.3%). Due to missing data for 194 women, the final analysis was conducted with the remaining 2,029 women. Placenta praevia (O.R. = 6.087; 95% CI, 3.813 to 9.778), previous endometritis (O.R. = 3.011; 95% CI, 1.060 to 9.018), previous manual placenta removal (O.R. = 2.530; 95% CI, 1.700 to 3.796), ART (O.R. = 2.169; 95% CI, 1.593 to 2.960) and vaginal operative birth (O.R. = 1.715; 95% CI, 1.225-2.428) can be considered important risk factors, and previous CS (O.R. = 1.408; 95% CI, 1.016 to 1.950) can be considered a moderate potential risk factor of PPH in women with PAS disorders. CONCLUSIONS: Placenta praevia, previous endometritis, previous placenta removal, ART and vaginal operative birth can be considered important risk factors of PPH in women with PAS disorders. STUDY REGISTRATION: The study was registered under http://www. CLINICALTRIALS: gov (NCT05542043) on 15 September 2022.

Identification of microorganisms by a rapid PCR panel from positive blood cultures leads to faster optimal antimicrobial therapy - a before-after study.

BACKGROUND: The BioFire® FilmArray® Blood Culture Identification Panel 1 (BF-FA-BCIP) detects microorganisms with high accuracy in positive blood cultures (BC) - a key step in the management of patients with suspected bacteraemia. We aimed to compare the time to optimal antimicrobial therapy (OAT) for the BF-FA-BCIP vs. standard culture-based identification. METHODS: In this retrospective single-centre study with a before-after design, 386 positive BC cases with identification by BF-FA-BCIP were compared to 414 controls with culture-based identification. The primary endpoint was the time from BC sampling to OAT. Secondary endpoints were time to effective therapy, length of stay, (re-)admission to ICU, in-hospital and 30-day mortality. Outcomes were assessed using Cox proportional hazard models and logistic regressions. RESULTS: Baseline characteristics of included adult inpatients were comparable. Main sources of bacteraemia were urinary tract and intra-abdominal infection (19.2% vs. 22.0% and 16.8% vs. 15.7%, for cases and controls, respectively). Median (95%CI) time to OAT was 25.5 (21.0-31.2) hours with BF-FA-BCIP compared to 45.7 (37.7-51.4) hours with culture-based identification. We observed no significant difference for secondary outcomes. CONCLUSIONS: Rapid microorganism identification by BF-FA-BCIP was associated with a median 20-h earlier initiation of OAT in patients with positive BC. No impact on length of stay and mortality was noted. TRIAL REGISTRATION: Clinicaltrials.gov, NCT04156633, registered on November 5, 2019.

The impact of competing stroke etiologies in patients with atrial fibrillation.

BACKGROUND: Data on the impact of competing stroke etiologies in stroke patients with atrial fibrillation (AF) are scarce. METHODS: We used prospectively obtained data from an observational registry (Novel-Oral-Anticoagulants-in-Ischemic-Stroke-Patients-(NOACISP)-LONGTERM) of consecutive AF-stroke patients treated with oral anticoagulants. We compared the frequency of (i) the composite outcome of recurrent ischemic stroke (IS), intracerebral hemorrhage (ICH) or all-cause death as well as (ii) recurrent IS alone among AF-stroke patients with versus without competing stroke etiologies according to the TOAST classification. We performed cox proportional hazards regression modeling adjusted for potential confounders. Furthermore, the etiology of recurrent IS was assessed. RESULTS: Among 907 patients (median age 81, 45.6% female), 184 patients (20.3%) had competing etiologies, while 723 (79.7%) had cardioembolism as the only plausible etiology. During 1587 patient-years of follow-up, patients with additional large-artery atherosclerosis had higher rates of the composite outcome (adjusted HR [95% CI] 1.64 [1.11, 2.40], p = 0.017) and recurrent IS (aHR 2.96 [1.65, 5.35 ], p < 0.001), compared to patients with cardioembolism as the only plausible etiology. Overall 71 patients had recurrent IS (7.8%) of whom 26.7% had a different etiology than the index IS with large-artery-atherosclerosis (19.7%) being the most common non-cardioembolic cause. CONCLUSION: In stroke patients with AF, causes other than cardioembolism as competing etiologies were common in index or recurrent IS. Concomitant presence of large-artery-atherosclerosis seems to indicate an increased risk for recurrences suggesting that stroke preventive means might be more effective if they also address competing stroke etiologies in AF-stroke patients. CLINICAL TRIAL REGISTRATION: NCT03826927.

Renal Function and Body Mass Index Contribute to Serum Neurofilament Light Chain Levels in Elderly Patients With Atrial Fibrillation.

Objective: Serum neurofilament light chain (sNfL) is increasingly used as a neuroaxonal injury biomarker in the elderly. Besides age, little is known about how other physiological factors like renal function and body mass index (BMI) alter its levels. Here, we investigated the association of estimated glomerular filtration rate (eGFR) and BMI with sNfL in a large sample of elderly patients with atrial fibrillation (AF). Methods: This is a cross-sectional analysis from the Swiss-AF Cohort (NCT02105844). We measured sNfL using an ultrasensitive single-molecule array assay. We calculated eGFR using the chronic kidney disease epidemiology collaboration (CKD-EPI) creatinine (eGFRcrea) and creatinine-cystatin C (eGFRcrea-cys) formulas, and BMI from weight and height measurements. We evaluated the role of eGFR and BMI as determinants of sNfL levels using multivariable linear regression and the adjusted R2 (R2adj). Results: Among 2,277 Swiss-AF participants (mean age 73.3 years), eGFRcrea showed an inverse curvilinear association with sNfL after adjustment for age and cardiovascular comorbidities. BMI also showed an independent, inverse linear association with sNfL. The R2adj of models with age, eGFRcrea, and BMI alone was 0.26, 0.35, and 0.02, respectively. A model with age and eGFRcrea combined explained 45% of the sNfL variance. Sensitivity analyses (i) further adjusting for vascular brain lesions (N = 1,402 participants with MRI) and (ii) using eGFRcrea-cys yielded consistent results. Interpretation: In an elderly AF cohort, both renal function and BMI were associated with sNfL, but only renal function explained a substantial proportion of the sNfL variance. This should be taken into account when using sNfL in elderly patients or patients with cardiovascular disease.

SARS-CoV-2 Vaccine Alpha and Delta Variant Breakthrough Infections Are Rare and Mild but Can Happen Relatively Early after Vaccination.

(1) Background: Some COVID-19 vaccine recipients show breakthrough infection. It remains unknown, which factors contribute to risks and severe outcomes. Our aim was to identify risk factors for SCoV2 breakthrough infections in fully vaccinated individuals. (2) Methods: We conducted a retrospective case-control study from 28 December 2020 to 25 October 2021. Data of all patients with breakthrough infection was compared to data of all vaccine recipients in the Canton of Basel-City, Switzerland. Further, breakthrough infections by Alpha- and Delta-variants were compared. (3) Results: Only 0.39% (488/126,586) of all vaccine recipients suffered from a breakthrough infection during the observational period, whereof most cases were asymptomatic or mild (97.2%). Breakthrough infections after full vaccination occurred in the median after 78 days (IQR 47-123.5). Factors with lower odds for breakthrough infection were age (OR 0.987) and previous COVID-19 infection prior to vaccination (OR 0.296). Factors with higher odds for breakthrough infection included vaccination with Pfizer/BioNTech instead of Moderna (OR 1.459), chronic disease (OR 2.109), and healthcare workers (OR 1.404). (4) Conclusions: Breakthrough infections are rare and mild but can occur early after vaccination. This implies that booster vaccination might be initiated earlier, especially for risk groups. Due to new variants emerging repeatedly, continuous monitoring of breakthrough infections is crucial.

Birds of different morphs use slightly different strategies to achieve similar reproductive performance following heatwave exposure.

Responses to extreme climatic events may differ between individuals of distinct morphs which differ in life-history strategies, resulting in climate change 'winners' and 'losers' within species. We examined the reproductive performance and carry-over effects on offspring of black- and red-headed Gouldian finches Erythrura gouldiae after exposure to simulated heatwaves of moderate or severe intensity. We expected black-headed pairs' reproductive performance to decline after the severe heatwave because only the condition of black-headed females deteriorates during such a heatwave. Supporting the fact that Gouldian finches of different morphs use alternative reproductive strategies, we found that black-headed females initiated egg-laying a month earlier than red-headed females after experiencing a severe heatwave. We also found that this severe heatwave resulted in shorter spermatozoa in males irrespective of their morph. Despite these effects associated with heatwave intensity, the overall reproductive performance of both morphs was not affected by this factor, which was possibly due to an increased nestling provisioning rate by parents after exposure to the severe heatwave. However, offspring still bore the cost of parental exposure to the severe heatwave, as they showed a reduced condition (lower plasma antioxidant capacity and transient lower breathing rate) and higher oxidative damage (at least in fledglings with black-headed parents). These results suggest that inter-morph phenotypic variability in the Gouldian finch does not result in clear differences in reproductive performance following heatwave exposure, despite basal phenotypic differences between morphs. Whether animals using alternative reproductive strategies are, in the end, differently affected by climate changes will likely depend on the capacity of their offspring to recover from altered developmental conditions.

Oxidative costs of cooperation in cooperatively breeding Damaraland mole-rats.

Within cooperatively breeding societies, individuals adjust cooperative contributions to maximize indirect fitness and minimize direct fitness costs. Yet, little is known about the physiological costs of cooperation, which may be detrimental to direct fitness. Oxidative stress, the imbalance between reactive oxygen species (by-products of energy production) and antioxidant protection, may represent such a cost when cooperative behaviours are energetically demanding. Oxidative stress can lead to the accumulation of cellular damage, compromising survival and reproduction, thus mediating the trade-off between these competing life-history traits. Here, we experimentally increased energetically demanding cooperative contributions in captive Damaraland mole-rats (Fukomys damarensis). We quantified oxidative stress-related effects of increased cooperation on somatic and germline tissues, and the trade-off between them. Increased cooperative contributions induced oxidative stress in females and males, without increasing somatic damage. Males accumulated oxidative damage in their germline despite an increase in antioxidant defences. Finally, oxidative damage accumulation became biased towards the germline, while antioxidant protection remained biased towards the soma, suggesting that males favour the maintenance of somatic tissues (i.e. survival over reproduction). Our results show that heightened cooperative contributions can ultimately affect direct fitness through oxidative stress costs, which may represent a key selective pressure for the evolution of cooperation.

Experimental manipulation of reproductive tactics in Seba's short-tailed bats: consequences on sperm quality and oxidative status.

To reproduce, males have to fertilize the female's eggs, sometimes in competition with ejaculates of other males. In species where males display alternative reproductive tactics, whereby territorial males secure mating and non-territorial males have to sneak copulations, the latter might be expected to invest relatively more resources towards sperm quality compared with the territorial males. Sperm cells are especially vulnerable to oxidative stress, which reduces male fertility. Therefore, antioxidant resources are expected to modulate sperm quality, and might be allocated differently between reproductive tactics. To test the link between reproductive tactics, redox profile and sperm quality, we experimentally induced changes in the reproductive tactics of 39 captive males Seba's short-tailed bats Carollia perspicillata. We monitored the blood and ejaculate oxidative balance, and the sperm quality before, 7 days and 21 days after the manipulation of reproductive tactic. Although ejaculates' oxidative damage was negatively related to sperm velocity, males exhibited similar blood and ejaculates redox profiles and similar sperm quality, regardless of their reproductive tactic. Possibly, these results arise as a consequence of some constraints having been lifted during the experiment. Our results also suggest that, in Seba's short-tailed bats, the expression of alternative reproductive tactics is not subjected to strong oxidative constraints. Furthermore, our results could reflect an absence of trade-off between pre- and post-copulatory traits in harem males, as they could be selected to invest both in female attraction and sperm quality, as a consequence of their inability to fully monopolize females.

Social dominance, but not parasite load, affects sperm quality and sperm redox status in house sparrows.

Sperm performance is an important component of male reproductive success. However, sperm production is costly and males need to optimize their investment in sperm quality versus the somatic traits involved in mating success, e.g. their social status. As oxidative stress affects both sperm performance and somatic functions, it has been hypothesized to mediate such a trade-off. According to the oxidation-based soma/germline trade-off hypothesis, dominant males should favour the antioxidant protection of their somatic tissues, and subordinate males should favour the antioxidant protection of their sperm. We tested this hypothesis by experimentally infecting wild-caught house sparrows Passer domesticus with Coccidia Isopora sp., an internal parasite known to deplete antioxidant resources. We predicted that (i) increased parasite load affects sperm oxidative status and sperm performance and that (ii) males with experimentally high parasite load adjust the antioxidant protection of their soma versus their sperm according to their social status. Despite a 5400% increase in parasite load, sperm performance and somatic and spermatic oxidative status remained unaffected, irrespective of male social status. Nevertheless, males increased their sperm performance over time, a pattern mirrored by an increase in the antioxidant protection of their sperm. Moreover, males at the lower end of the hierarchy always produced sperm of lower velocity, suggesting that they were constrained and privileged their soma over their germline. To conclude, high parasite loads do not necessarily affect sperm performance and oxidative status. In contrast, social hierarchy and the relative investment in soma versus sperm antioxidant protection are determinants of sperm performance.

A large-scale survey of house sparrows feathers reveals ubiquitous presence of neonicotinoids in farmlands.

The massive use of neonicotinoid insecticides has been repeatedly incriminated for their impacts to avian populations. Some studies have reported contamination of granivorous birds by neonicotinoids but very little is known about exposure to neonicotinoids in other bird species. To fill this lack of knowledge, we trapped house sparrows Passer domesticus, an omnivorous bird whose diet is composed of both grains and insects, and we collected 617 feathers from individuals living on 47 conventional, integrated-production (IP-Suisse) and organic farms distributed all over the Swiss plateau, the country's main agricultural area. We then assessed the concentration of five neonicotinoids in 146 pools of feathers. We found that all feather samples were contaminated by at least one neonicotinoid at measurable concentration (>LOQ), with thiacloprid accounting for most of the prevalence (99%), while clothianidin was found at highest concentrations (with averages ranging from 1.68 to 9.2 ppb). Additionally, house sparrows living on conventional farms showed higher concentrations of neonicotinoids (15.26 ±â€¯3.58 ppb) than individuals living on IP-Suisse (3.38 ±â€¯0.86 ppb), and organic farms (2.59 ±â€¯0.56 ppb). Our large-scale survey highlights how ubiquitous neonicotinoid insecticides have become in agricultural habitats, and reveals generalized exposure of house sparrows, and potentially other species inhabiting farmlands, to neonicotinoids.

Is sperm morphology functionally related to sperm swimming ability? A case study in a wild passerine bird with male hierarchies.

BACKGROUND: Sexual selection continues after copulation via either sperm competition or cryptic female choice, and favors sperm traits that maximize sperm competitiveness. Both sperm swimming velocity and longevity are important determinants of the outcome of sperm competition. Theoretically, sperm morphology can influence sperm velocity at least in three different non-exclusive ways: (i) longer sperm may generate more propelling thrust, (ii) bigger midpieces may produce more energy, and/or (iii) larger flagella or mid-pieces relative to the head size may compensate for the drag forces around the head. A growing number of studies have investigated the relationship of sperm morphology with sperm performance, which remains equivocal at both the inter- and intra-specific levels. Here, we used House Sparrows to test the functional relationship between sperm morphology with sperm velocity and longevity. Based on a previous study showing that sperm swimming ability covaries with social rank, we predicted that -if a functional relationship exists-1) sperm morphology should differ across social ranks, and 2) correlations between sperm morphology and sperm velocity and/or sperm longevity should be constant across social ranks. RESULTS: We found no differences in sperm morphology across social ranks. Moreover, we found that sperm morphology may be correlated with sperm velocity, but such relationship varied across social ranks. This result contradicts the hypothesis of a functional relationship between sperm morphology and sperm performance. Finally, after experimentally manipulating social ranks, we observed that relationships between sperm morphology and sperm velocity and/or sperm longevity disappeared or changed direction. CONCLUSIONS: We suggest that in species with internal fertilization, while sperm morphology is likely constrained by the morphology of the female sperm storage organs, selection may act upon physiological traits that enhance sperm performance. Hence, these two selection forces could decouple sperm performance from sperm morphology.

Effects of an early-life paraquat exposure on adult resistance to oxidative stress, plumage colour and sperm performance in a wild bird.

Early-life stressful conditions can shape individual phenotypes and ultimately influence fitness. Oxidative stress is a pervasive threat that affects many fitness-related traits and can modulate life-history trade-offs. Yet, the extent to which exposure to oxidative stress during early life can have long-lasting effects on key fitness-related traits remains to be elucidated, particularly in natural populations of vertebrates. Using a wild population of great tits Parus major, we experimentally dosed 11-day-old birds with paraquat, a pro-oxidant molecule, aiming at increasing oxidative stress. One year later, we recaptured 39 of them as adult recruiting breeders and quantified effects of the paraquat exposure on their resistance to oxidative stress, carotenoid-based plumage coloration and male sperm performance. Despite the absence of a short-term effect of paraquat on oxidative stress measured two days later, the pre-fledging exposure to paraquat induced a reduction in individual oxidative damage measured at adulthood. Paraquat-dosed individuals also had brighter plumage, but no effect was observed on male sperm performance. For the first time in a natural population of vertebrates, we experimentally show that an early-life acute exposure to a pro-oxidant has long-lasting effects on individual resistance to oxidative stress at adulthood. Our results are in line with the environmental matching and the hormesis hypotheses but may also reflect selective disappearance of individuals with lower resistance to oxidative stress.

Sensitive and selective quantification of free and total malondialdehyde in plasma using UHPLC-HRMS.

Quantification of malondialdehyde (MDA) as a marker of lipid peroxidation is relevant for many research fields. We describe a new sensitive and selective method to measure free and total plasmatic MDA using derivatization with 2,4-dinitrophenylhydrazine (DNPH) and ultra-HPLC-high-resolution MS. Free and total MDA were extracted from minute sample amounts (10 µl) using acidic precipitation and alkaline hydrolysis followed by acidic precipitation, respectively. Derivatization was completed within 10 min at room temperature, and the excess DNPH discarded by liquid-liquid extraction. Quantification was achieved by internal standardization using dideuterated MDA as internal standard. The method's lowest limit of quantification was 100 nM and linearity spanned greater than three orders of magnitude. Intra- and inter-day precisions for total MDA were 2.9% and 3.0%, respectively, and those for free MDA were 12.8% and 24.9%, respectively. Accuracy was 101% and 107% at low and high concentrations, respectively. In human plasma, free MDA levels were 120 nM (SD 36.26) and total MDA levels were 6.7 µM (SD 0.46). In addition, we show the applicability of this method to measure MDA plasma levels from a variety of animal species, making it invaluable to scientists in various fields.

Oxidative stress affects sperm performance and ejaculate redox status in subordinate house sparrows.

Oxidative stress is the result of random cellular damage caused by reactive oxygen species that leads to cell death, ageing or illness. Most physiological processes can result in oxidative stress, which in turn has been identified as a major cause of infertility. In promiscuous species, the fertilizing ability of the ejaculate partly determines the male reproductive success. When dominance determines access to fertile females, theory predicts that lower ranking males should increase resource investment into enhancing ejaculate quality. We hypothesized that subordinate males should thus prioritize antioxidant protection of their ejaculates to protect them from oxidative stress. We put this hypothesis to the test by chronically dosing wild house sparrows with diquat (∼1 mg kg-1), a herbicide that increases pro-oxidant generation. We found that, although they increased their antioxidant levels in the ejaculate, diquat-treated males produced sperm with reduced velocity. Importantly, and contrary to our hypothesis, males at the bottom of the hierarchy suffered the largest reduction in sperm velocity. We suggest that resource access hinders individuals' ability to cope with environmental hazards. Our results point at oxidative stress as a likely physiological mechanism mediating ejaculate quality, while individual ability to access resources may play a role in constraining the extent to which such resources can be allocated into the ejaculate.

Antioxidant allocation modulates sperm quality across changing social environments.

In promiscuous species, male reproductive success depends on their ability to mate with fertile females and on the fertilizing ability of their sperm. In such species, theory predicts that, owing to a trade-off between pre- and post-copulatory reproductive traits, males with lesser access to females should increase resource investment into those sperm traits that enhance fertilization success-usually referred to as ejaculate quality. This prediction has been validated in several taxa, yet studies on the physiological mechanisms modulating ejaculate quality are lacking. Sperm cells are highly vulnerable to oxidative stress, which impairs male fertility. Therefore, males that better protect their sperm from oxidative stress are expected to achieve higher ejaculate quality. Based on theoretical expectations, and since social dominance is a major determinant of mating opportunity, we predicted that subordinate males should invest more into the antioxidant protection of their sperm in order to achieve higher ejaculate quality. We maintained 60 male and 60 female wild-caught house sparrows Passer domesticus in outdoor aviaries, where we experimentally manipulated male social status to test our predictions. We measured cellular oxidative stress and enzymatic antioxidant activity in blood and sperm both before and after manipulating social ranks. Before manipulating the social status, we found that ejaculate viability correlated with oxidative stress level in sperm, with dominant males producing more oxidized and less viable ejaculates. Further, males at the lower end of the hierarchy produced ejaculates of similar quality to those of dominant males, suggesting that restricted access to resources might limit male reproductive strategies. After experimentally manipulating the social status, males matched their ejaculate quality to their new rank, while increases in antioxidant investment into ejaculates paralleled increases in ejaculate viability. Oxidative stress has been proposed as a general constraint to the evolution of life histories. Our results highlight oxidative stress and strategic antioxidant allocation as important proximate physiological mechanisms underlying male reproductive strategies.

Social dominance explains within-ejaculate variation in sperm design in a passerine bird.

BACKGROUND: Comparative studies suggest that sperm competition exerts stabilizing selection towards an optimal sperm design - e.g., the relative size and covariation of different sperm sections or a quantitative measure of sperm shape - that maximizes male fertility, which results in reduced levels of within-male variation in sperm morphology. Yet, these studies also reveal substantial amounts of unexplained within-ejaculate variance, and the factors presiding to the maintenance of such within-male variation in sperm design at the population level still remain to be identified. Sperm competition models predict that males should progressively invest more resources in their germline as their mating costs increase, i.e., the soma/germline allocation trade-off hypothesis. When access to fertile females is determined by social dominance, the soma/germline allocation trade-off hypothesis predicts that dominant males should invest less in the control of spermatogenesis. Hence, dominance should positively correlate with within-male variance in sperm design. RESULTS: In support of this hypothesis, we found that dominant house sparrow males produce ejaculates with higher levels of within-ejaculate variation in sperm design compared to subordinate males. However, after experimentally manipulating male social status, this pattern was not maintained. CONCLUSIONS: Our results suggest that males might control variation in sperm design according to their social status to some extent. Yet, it seems that such within-ejaculate variation in sperm design cannot be rapidly adjusted to a new status. While variation in sperm design could result from various non-exclusive sources, we discuss how strategic allocation of resources to the somatic vs. the germline functions could be an important process shaping the relationship between within-male variation in sperm design and social status.

Modification of sperm quality after sexual abstinence in Seba's short-tailed bat, Carollia perspicillata.

In polygynous mating systems, few males have stable access to sexual mates. With an expected higher copulation rate, harem males may deplete seminal fluids or increase epididymal sperm maturation, generating poor sperm quality. In a first study, we reported a higher sperm quality in sneaker males of Carollia perspicillata To test whether the lower sperm quality observed in harem males was generated by an elevated copulation rate, we temporarily removed males of both social statuses from the colony. We thus assessed status-related changes of sperm quality resulting from sexual abstinence. Moreover, released from territory and female guarding, harem males were expected to show a reduction in somatic costs. On the basis of sperm competition models, we predicted a higher resource investment in the ejaculate with the reduction of pre-copulatory efforts. In line with our predictions, sperm quality of harem males improved significantly in contrast to sneaker males, whose sperm quality did not change. Without an increase in ejaculate lipid peroxidation, our results also provide evidence that the duration of sexual abstinence was not sufficient to generate sperm oxidative damage through senescence. Harem males did not show a reduction in blood lipid peroxidation or in the ratio of oxidized to reduced glutathione. In line with the maintenance of these somatic costs, harem males did not invest more superoxide dismutase to the ejaculate to maintain sperm quality. Our results suggest that a difference in copulation rate rather than an adaptation to sperm competition provides sneaker males with higher sperm quality in C. perspicillata.

Maternal effects as drivers of sibling competition in a parent-offspring conflict context? An experimental test.

Maternal effects occur when the mother's phenotype influences her offspring's phenotype. In birds, differential allocation in egg yolk components can allow mothers to compensate for the competitive disadvantage of junior chicks. We hypothesize that the parent-older chick conflict peaks at intermediate conditions: parents benefit from the younger chick(s) survival, but its death benefits the older chick in terms of growth and survival. We thus expect maternal compensation to follow a bell-shaped pattern in relation to environmental conditions. We studied a black-legged kittiwake (Rissa tridactyla) population where previous results revealed increased allocation of yolk testosterone in younger as compared to older chicks in intermediate conditions, in line with our theoretical framework. We therefore predicted a maternally induced increase in aggressiveness, growth, and survival for younger chicks born in intermediate environmental conditions. Controlling for parental effects and chick sex, we manipulated food availability before egg laying to create a situation with intermediate (Unfed group) and good (Fed group) environmental conditions. Within each feeding treatment, we further created experimental broods where the natural hatching order was reversed to maximize our chances to observe an effect of feeding treatment on the younger chicks' aggressiveness. As predicted, we found that chick aggressiveness was higher in younger chicks born from the Unfed group (i.e., in intermediate environmental conditions), but only when they were put in a senior position, in reversed broods. Predictions on growth and survival were not confirmed. Mothers thus seem to favor the competitiveness of their younger chick in intermediate conditions via egg yolk components, but our study also suggests that hatching asynchrony need to be small for maternal compensation to be efficient. We emphasize the need for further studies investigating other chick behaviors (e.g., begging) and focusing on the relative role of different yolk components in shaping parent-offspring conflict over sibling competition.