Nestling Physiology Is Independent of Somatic Development in a Common Raptor, the American Kestrel (Falco sparverius).

AbstractAlthough many studies have documented the developmental trajectory of somatic traits in birds, few measure physiological traits, and even fewer document individual variation in developmental trajectory across ecological context. Hematological traits underlying aerobic capacity can be predictive of nestling survival, fledgling flight ability, and ultimately recruitment. This study aimed to assess individual variation in the developmental trajectory of two physiological traits that underlie aerobic capacity, hematocrit and hemoglobin concentration, in relation to somatic development and ecological context. Our study species, the American kestrel (Falco sparverius), is sexually dimorphic and therefore likely to show sexual variation in developmental trajectory and nestling maturity. We used lay date, year, brood size, nestling sex ratio, and parental nest visit rate to assess ecological context. Although somatic traits showed similar trajectories across nestlings, developmental trajectory for hematocrit and hemoglobin concentration showed individual variation not previously documented. This individual variation in developmental change, or trajectory, for physiological traits could not be explained by somatic development, sex, parental nest visit rate, lay date, year, brood size, or nestling sex ratio. However, we did find higher final hemoglobin concentration in 2018 and in nests with earlier lay dates. These findings demonstrate the importance of assessing physiological traits that capture aspects of individual quality distinct from somatic traits. Future studies are needed to understand the causes of individual variation in developmental trajectory, which cannot be explained by the ecological variables presented here, and the potential fitness consequences of this variation.

Synthesis and comparison of nickel, palladium, and platinum bis(N-heterocyclic carbene) pincer complexes for electrocatalytic CO2 reduction.

A valence isoelectronic and isostructural series of charged bis(N-heterocyclic carbene) pincer complexes [M(bC^N^bC)X]OTf and [M(bC^N^bC)CH3CN](OTf)2 (where M = Ni, Pd, and Pt, bC^N^bC = 1,1'-(pyridine-2,6-diylbis(methylene))bis(3-butylbenzo[d]imidazol-2-ylidene)) were synthesized, characterized, modelled by density functional theory calculations, and compared for their electrochemical properties and reactivity with CO2. Although the electrochemical response of each complex is altered by the presence of CO2, controlled potential electrolysis experiments demonstrated the superior ability of [Pd] to reduce CO2 to CO in faradaic efficiencies up to 58% in the presence of trifluoroacetic acid, compared to [Pt] and [Ni] which showed only marginal production of CO, giving the trend [Pd] ≫ [Pt] > [Ni] for this series.

Mesenchymal-like stem cells in canine ovary show high differentiation potential.

OBJECTIVES: Recent studies have reported the existence of stem cells in ovarian tissue that show enhanced proliferative and differentiation potential compared to other adult tissues. Based on this evidence, we hypothesized that ovarian tissue contained mesenchymal-like stem cells (MSC) that could be isolated using a novel rapid plastic adhesion technique. MATERIALS AND METHODS: We established MSC lines derived from ovarian and adipose tissue based on their ability to rapidly adhere to plastic culture dishes in the first 3 hours after plating and studied their potentiality in terms of molecular markers and differentiation capacity. RESULTS: Morphological and kinetic properties of in vitro cultured ovarian MSC were similar to adipose-derived MSC, and both reached senescence after similar passage numbers. Ovarian-derived MSC expressed mesenchymal (CD90 and CD44) but not haematopoietic markers (CD34 and CD45), indicating similarity to adipose-derived MSC. Moreover, ovarian-derived MSC expressed NANOG, TERT, SOX2, OCT4 and showed extensive capacity to differentiate not only into adipogenic, osteogenic and chondrogenic tissue but also towards neurogenic and endodermal lineages and even precursors of primordial germ cells. CONCLUSION: These results show for the first time the derivation of ovarian cells with the molecular properties of MSC as well as wide differentiation potential. Canine ovarian tissue is accessible, expandable, multipotent and has high plasticity, holding promise for applications in regenerative medicine.

Pulsed resources at tundra breeding sites affect winter irruptions at temperate latitudes of a top predator, the snowy owl.

Irruptive migration is mostly observed in species specialized on pulsed resources and is thought to be a response to unpredictable changes in food supply. We assessed two alternative hypotheses to explain the periodic winter irruptions of snowy owls Bubo scandiacus every 3-5 years in temperate North America: (a) the lack-of-food hypothesis, which states that a crash in small mammal abundance on the Arctic breeding grounds forces owls to move out of the tundra massively to search for food in winter; (b) the breeding-success hypothesis, which states that high abundance of tundra small mammals during the summer allows for high production of young, thus increasing the pool of migrants moving south the following winter. We modeled winter irruptions of snowy owls in relation to summer food resources and geographic location. Winter abundance of owls was obtained from citizen-based surveys from 1994 to 2011 and summer abundance of small mammals was collected in summer at two distant sites in Canada: Bylot Island, NU (eastern High Arctic) and Daring Lake, NWT (central Low Arctic). Winter owl abundance was positively related to prey abundance during the previous summer at both sites and tended to decrease from western to eastern temperate North America. Irruptive migration of snowy owls was therefore best explained by the breeding success hypothesis and was apparently caused by large-scale summer variations in food. Our results, combined with previous findings, suggest that the main determinants of irruptive migration may be species specific even in a guild of apparently similar species.

Differentiation of equine induced pluripotent stem cells into a keratinocyte lineage.

REASONS FOR PERFORMING STUDY: Skin trauma in horses often leads to the development of chronic nonhealing wounds that lack a keratinocyte cover, vital for healing. Reports in mouse and man confirm the possibility of generating functional keratinocytes from induced pluripotent stem cells (iPSC), thus presenting myriad potential applications for wound management or treatment of skin disease. Similarly, differentiation of equine iPSC (eiPSC) into a keratinocyte lineage should provide opportunities for the advancement of veterinary regenerative medicine. OBJECTIVES: The purpose of this study was to develop an efficient method for the differentiation of eiPSC into a keratinocyte lineage. It was hypothesised that eiPSC can form differentiated keratinocytes (eiPSC-KC) comparable with primary equine keratinocytes (PEK) in their morphological and functional characteristics. STUDY DESIGN: Experimental in vitro study. METHODS: Equine iPSC established using a nonviral system were treated for 30 days with retinoic acid and bone morphogenetic protein-4 to induce directed differentiation into iPSC-KC. Temporospatial gene and protein expression by eiPSC-KC was measured at weekly intervals of differentiation and in response to calcium switch. Proliferative and migratory capacities of eiPSC-KC were compared with those of PEK. RESULTS: Equine iPSC, upon directed differentiation, showed loss of pluripotency genes and progressive increase in pancytokeratin expression indicating ectodermal specification into keratinocytes. High differentiation efficiency was achieved, with 82.5% of eiPSC expressing keratin 14, a marker of epidermal-specific basal stem cells, after 30 days of directed differentiation. Moreover, the proliferative capacity of eiPSC-KC was superior, while the migratory capacity (measured as the ability to epithelise in vitro wounds) was comparable with that of PEK. CONCLUSIONS: This proof of concept study suggests that eiPSC can successfully be differentiated into equine keratinocytes (eiPSC-KC) with features that are promising to the development of a stem cell-based skin construct, with the potential to regenerate lost or damaged skin.

Predation pressure by avian predators suggests summer limitation of small-mammal populations in the Canadian Arctic.

Predation has been suggested to be especially important in simple food webs and less productive ecosystems such as the arctic tundra, but very few data are available to evaluate this hypothesis. We examined the hypothesis that avian predators could drive the population dynamics of two cyclic lemming species in the Canadian Arctic. A dense and diverse suite of predatory birds, including the Snowy Owl (Bubo scandiacus), the Rough-legged Hawk (Buteo lagopus), and the Long-tailed Jaeger (Stercorarius longicaudus), inhabits the arctic tundra and prey on collared (Dicrostonyx groenlandicus) and brown (Lemmus trimucronatus) lemmings during the snow-free period. We evaluated the predation pressure exerted by these predators by combining their numerical (variation in breeding and fledgling numbers) and functional (variation in diet and daily consumption rates) responses to variations in lemming densities over the 2004-2010 period. Breeding density and number of fledglings produced by the three main avian predators increased sharply without delay in response to increasing lemming densities. The proportion of collared lemmings in the diet of those predators was high at low lemming density (both species) but decreased as lemming density increased. However, we found little evidence that their daily consumption rates vary in relation to changes in lemming density. Total consumption rate by avian predators initially increased more rapidly for collared lemming but eventually leveled off at a much higher value for brown lemmings, the most abundant species at our site. The combined daily predation rate of avian predators exceeded the maximum daily potential growth rates of both lemming species except at the highest recorded densities for brown lemmings. We thus show, for the first time, that predation pressure exerted without delay by avian predators can limit populations of coexisting lemming species during the snow-free period, and thus, that predation could play a role in the cyclic dynamic of these species in the tundra.

Disentangling trophic relationships in a High Arctic tundra ecosystem through food web modeling.

Determining the manner in which food webs will respond to environmental changes is difficult because the relative importance of top-down vs. bottom-up forces in controlling ecosystems is still debated. This is especially true in the Arctic tundra where, despite relatively simple food webs, it is still unclear which forces dominate in this ecosystem. Our primary goal was to assess the extent to which a tundra food web was dominated by plant-herbivore or predator-prey interactions. Based on a 17-year (1993-2009) study of terrestrial wildlife on Bylot Island, Nunavut, Canada, we developed trophic mass balance models to address this question. Snow Geese were the dominant herbivores in this ecosystem, followed by two sympatric lemming species (brown and collared lemmings). Arctic foxes, weasels, and several species of birds of prey were the dominant predators. Results of our trophic models encompassing 19 functional groups showed that <10% of the annual primary production was consumed by herbivores in most years despite the presence of a large Snow Goose colony, but that 20-100% of the annual herbivore production was consumed by predators. The impact of herbivores on vegetation has also weakened over time, probably due to an increase in primary production. The impact of predators was highest on lemmings, intermediate on passerines, and lowest on geese and shorebirds, but it varied with lemming abundance. Predation of collared lemmings exceeded production in most years and may explain why this species remained at low density. In contrast, the predation rate on brown lemmings varied with prey density and may have contributed to the high-amplitude, periodic fluctuations in the abundance of this species. Our analysis provided little evidence that herbivores are limited by primary production on Bylot Island. In contrast, we measured strong predator-prey interactions, which supports the hypothesis that this food web is primarily controlled by top-down forces. The presence of allochthonous resources subsidizing top predators and the absence of large herbivores may partly explain the predominant role of predation in this low-productivity ecosystem.

Developmental and epigenetic anomalies in cloned cattle.

Many of the developmental anomalies observed in cloned animals are related to foetal and placental overgrowth, a phenomenon known as the 'large offspring syndrome' (LOS) in ruminants. It has been hypothesized that the epigenetic control of imprinted genes, that is, genes that are expressed in a parental-specific manner, is at the root of LOS. Our recent research has focused on understanding epigenetic alterations to imprinted genes that are associated with assisted reproductive technologies (ART), such as early embryo in vitro culture (IVC) and somatic cell nuclear transfer (SCNT) in cattle. We have sought and identified single nucleotide polymorphisms in Bos indicus DNA useful for the analysis of parental-specific alleles and their respective transcripts in tissues from hybrid embryos derived by crossing Bos indicus and Bos taurus cattle. By analysing differentially methylated regions (DMRs) of imprinted genes SNRPN, H19 and the IGF2R in cattle, we demonstrated that there is a generalized hypomethylation of the imprinted allele and the biallelic expression of embryos produced by SCNT when compared to the methylation patterns observed in vivo (artificially inseminated). Together, these results indicate that imprinting marks are erased during the reprogramming of the somatic cell nucleus during early development, indicating that such epigenetic anomalies may play a key role in mortality and morbidity of cloned animals.

Loss of methylation at H19 DMD is associated with biallelic expression and reduced development in cattle derived by somatic cell nuclear transfer.

Although cloning of mammals has been achieved successfully, the percentage of live offspring is very low because of reduced fetal size and fewer implantation sites. Recent studies have attributed such pathological conditions to abnormal reprogramming of the donor cell used for cloning. The inability of the oocyte to fully restore the differentiated status of a somatic cell to its pluripotent and undifferentiated state is normally evidenced by aberrant DNA methylation patterns established throughout the genome during development to blastocyst. These aberrant methylation patterns are associated with abnormal expression of imprinted genes, which among other genes are essential for normal embryo development and gestation. We hypothesized that embryo loss and low implantation rates in cattle derived by somatic cell nuclear transfer (SCNT) are caused by abnormal epigenetic reprogramming of imprinted genes. To verify our hypothesis, we analyzed the parental expression and the differentially methylated domain (DMD) methylation status of the H19 gene. Using a parental-specific analysis, we confirmed for the first time that H19 biallelic expression is tightly associated with a severe demethylation of the paternal H19 DMD in SCNT embryos, suggesting that these epigenetic anomalies to the H19 locus could be directly responsible for the reduced size and low implantation rates of cloned embryos in cattle.

Acute myocardial infarction late after Mustard procedure for dextrotransposition of the great arteries.

Systemic right ventricular dysfunction has been closely linked to late mortality and sudden cardiac death in patients with Mustard procedure for dextrotransposition of the great arteries. Two young patients with dextrotransposition of the great arteries late after Mustard procedure who presented with acute transmural myocardial infarction and sudden cardiac death (one patient) without prior exertional angina or causative coronary abnormalities are reported. It is surmised that acute coronary emboli originating from a severely dilated, hypocontractile systemic ventricle were the cause of transmural myocardial infarction. This phenomenon may be an important and as yet unrecognized factor in late morbidity and mortality in such patients.

Repeated exposures of human skin equivalent to low doses of ultraviolet-B radiation lead to changes in cellular functions and accumulation of cyclobutane pyrimidine dimers.

Chronic exposure to sunlight may induce skin damage such as photoaging and photocarcinogenesis. These harmful effects are mostly caused by ultraviolet-B (UVB) rays. Yet, less is known about the contribution of low UVB doses to skin damage. The aim of this study was to determine the tissue changes induced by repeated exposure to a suberythemal dose of UVB radiation. Human keratinocytes in monolayer cultures and in skin equivalent were irradiated daily with 8 mJ/cm2 of UVB. Then structural, ultrastructural, and biochemical alterations were evaluated. The results show that exposure to UVB led to a generalized destabilization of the epidermis structure. In irradiated skin equivalents, keratinocytes displayed differentiated morphology and a reduced capacity to proliferate. Ultrastructural analysis revealed, not only unusual aggregation of intermediate filaments, but also disorganized desmosomes and larger mitochondria in basal cells. UVB irradiation also induced the secretion of metalloproteinase-9, which may be responsible for degradation of type IV collagen at the basement membrane. DNA damage analysis showed that both single and repeated exposure to UVB led to formation of (6-4) photoproducts and cyclobutane pyrimidine dimers. Although the (6-4) photoproducts were repaired within 24 h after irradiation, cyclobutane pyrimidine dimers accumulated over the course of the experiment. These studies demonstrate that, even at a suberythemal dose, repeated exposure to UVB causes significant functional and molecular damage to keratinocytes, which might eventually predispose to skin cancer.

Impact of pulmonary valve replacement on arrhythmia propensity late after repair of tetralogy of Fallot.

BACKGROUND: Chronic pulmonary regurgitation after repair of tetralogy of Fallot (TOF) may lead to right ventricular dilatation, which may be accompanied by ventricular tachycardia and sudden death. We aimed to examine the effects of pulmonary valve replacement (PVR) on (1) certain electrocardiographic markers predictive of monomorphic ventricular arrhythmia and sudden death and (2) sustained atrial flutter/fibrillation and monomorphic ventricular tachycardia. METHODS AND RESULTS: We studied 70 patients who underwent PVR for pulmonary regurgitation and/or right ventricular outflow tract obstruction late after repair of TOF. Maximum QRS duration and QT dispersion were measured from standard ECGs before PVR and at the latest follow-up. Arrhythmia was defined as sustained atrial flutter/fibrillation or sustained monomorphic ventricular tachycardia. Concomitant intraoperative electrophysiological mapping and/or cryoablation were performed in 9 patients (60%) with preexisting ventricular tachycardia and 6 patients (50%) with preexisting atrial flutter. QRS duration remained unchanged in the study group (P=0.46), but it was significantly prolonged (P<0.001) in a comparable group of patients with repaired TOF who did not undergo PVR. At a mean follow-up of 4.7 years, the incidence of ventricular tachycardia diminished from 22% to 9% (P<0.001), and atrial flutter/fibrillation decreased from 17% to 12% (P=0.32). Intraoperative ablation prevented recurrence of preexisting tachyarrhythmia (0 of 15 patients). CONCLUSIONS: PVR in patients with previous TOF repair and chronic pulmonary regurgitation leads to stabilization of QRS duration and, in conjunction with intraoperative cryoablation, to a decrease in the incidence of preexisting atrial and ventricular tachyarrhythmia. When applicable, this combined approach should be used in patients late after repair of TOF.

Ablation of p21waf1cip1 expression enhances the capacity of p53-deficient human tumor cells to repair UVB-induced DNA damage.

During periods of genotoxic stress, the cyclin-dependent kinase inhibitor p21waf1cip1 (hereafter referred to as p21) is transcriptionally up-regulated by the p53 tumor suppressor and subsequently plays a key role in cellular growth arrest. Investigations have also indicated that p21 may regulate nucleotide excision repair, a critical pathway that removes carcinogenic DNA damage induced by UV light and other mutagens. In this study, we examined whether low levels of endogenous p21 expression can modulate nucleotide excision repair in p53-deficient human tumor cells after UVB exposure. For this purpose, we used the well-characterized p53-/-p21+/+ adenocarcinoma cell strain DLD1 and its isogenic counterpart carrying a homozygous knockout for p21 (p53-/-p21-/- DLD1). Because p53-/-p21+/+ DLD1 expresses very low levels of endogenous p21 protein that are not up-regulated after mutagen exposure, this strain has been considered functionally p21-deficient in the cellular response to DNA damage. Nonetheless, the ligation-mediated PCR technology was used here to demonstrate, at nucleotide resolution, that p53-/-p21+/+ DLD1 excises UVB-induced cyclobutane pyrimidine dimers from the c-jun proto-oncogene at a significantly lower rate than the isogenic p53-/-p21-/- derivative. The higher efficiency of DNA repair in UVB-exposed p53-/-p21-/- DLD1 cells is accompanied by increased clonogenic survival and reduced levels of apoptosis, relative to the p53-/-p21+/+ counterpart. Our results show that ablation of p21 expression can significantly enhance the capacity of p53-deficient human tumor cells to repair UVB-induced DNA damage.

Synthesis and characterization of the colistin peptide polymyxin E1 and related antimicrobial peptides.

Two strategies were developed to synthesize the acylated cyclic peptides know as polymyxins. Synthesis of polymyxin E1 and several analogs enabled us to evaluate the minimum inhibitory concentration of individual compounds against Gram-negative bacteria. In this study we also report the first identification of two component peptides in the complex polymyxin fermentation product colistin, a Thr2Ser isoform and an acyl group isomer. Both of these peptides, as well as a known component peptide, Leu7Ile, were similar to polymyxin E1 in potency, suggesting that conservative mutations in the colistin family are functionally inconsequential. In contrast, the acyclic analogs of all of these peptides were inactive, indicating that the characteristic lariat structure of the polymyxins is necessary for antimicrobial activity.

Angiotensin-converting enzyme inhibitors in adults after the Mustard procedure.

Angiotensin-converting enzyme inhibitors had no significant effect on cardiopulmonary exercise function in 14 patients who had undergone a Mustard operation for transposition of the great arteries. In some patients aerobic capacity improved and maximum systolic blood pressure decreased.