Although central to evolution, the causes of hybrid inviability that drive reproductive isolation are poorly understood. Embryonic lethality occurs when eggs of the frog
X. tropicalis
are fertilized ...with either
X. laevis
or
X. borealis
sperm. We observed that distinct subsets of paternal chromosomes failed to assemble functional centromeres, causing their mis-segregation during embryonic cell divisions. Core centromere DNA sequence analysis revealed little conservation among the three species, indicating that epigenetic mechanisms that normally operate to maintain centromere integrity are disrupted on specific paternal chromosomes in hybrids. In vitro reactions combining
X. tropicalis
egg extract with either
X. laevis
or
X. borealis
sperm chromosomes revealed that paternally matched or over-expressed centromeric histone CENP-A and its chaperone HJURP could rescue centromere assembly on affected chromosomes in interphase nuclei. However, whereas the
X. laevis
chromosomes maintained centromeric CENP-A in metaphase,
X. borealis
chromosomes did not, and also displayed ultra-thin regions containing ribosomal DNA. Both centromere assembly and morphology of
X. borealis
mitotic chromosomes could be rescued by inhibiting RNA Polymerase I or by preventing collapse of stalled DNA replication forks. These results indicate that specific paternal centromeres are inactivated in hybrids due to disruption of associated chromatin regions that interfere with CENP-A incorporation, at least in some cases due to conflicts between replication and transcription machineries. Thus, our findings highlight the dynamic nature of centromere maintenance and its susceptibility to disruption in vertebrate interspecies hybrids.
Centromere incompatibilities in inviable
Xenopus
hybrids are sequence-independent and result from disruption of epigenetic pathways required for centromere maintenance.
Summary Microparticles (MP) derived from vascular endothelium or circulating blood cells circulate in the peripheral blood. They originate from blebbing and shedding from cell membrane surfaces in ...physiological and pathological conditions and are present in low concentrations in normal plasma. Increased levels are generated by a number of mechanisms including platelet activation, direct vascular endothelial damage, thrombin activity on the cell surface, C5b-9 activation, and PF4-heparin-antibody interaction. Several techniques are currently used to study the generation and nature of circulating microparticles. In particular, the genesis and role of microparticles, derived from platelets, endothelial cells and monocytes, in sepsis (especially meningococcal-induced), heparin-induced thrombocytopenia (HIT), thrombotic thrombocytopenic purpura (TTP), aplastic anaemia, paroxysmal nocturnal haemoglobinuria (PNH) and sickle cell disease (SCD) have been well studied, and provide important insights into the underlying diseases. A defect in the ability to form microparticles leads to the severe bleeding disorder of Scott syndrome, which in turn provides a revealing insight into the physiology of coagulation. In addition the complex role of microparticles in vascular and cardiovascular diseases is an area of immense interest, that promises to yield important advances into diagnosis and therapy.
In The Contemplative Mind in the Scholarship of Teaching and Learning, Patricia Owen-Smith considers how contemplative practices may find a place in higher education. By creating a bridge between ...contemplative practices and the Scholarship of Teaching and Learning (SoTL), Owen-Smith brings awareness of contemplative pedagogy to a larger audience of college instructors, while also offering classroom models and outlining the ongoing challenges of both defining these practices and assessing their impact in education. Ultimately, Owen-Smith asserts that such practices have the potential to deepen a student's development and understanding of the self as a learner, knower, and citizen of the world.
ABSTRACT
Predation and scavenging have been classically understood as independent processes, with predator–prey interactions and scavenger–carrion relationships occurring separately. However, the ...mere recognition that most predators also scavenge at variable rates, which has been traditionally ignored in food‐web and community ecology, leads to a number of emergent interaction routes linking predation and scavenging. The general goal of this review is to draw attention to the main inter‐specific interactions connecting predators (particularly, large mammalian carnivores), their live prey (mainly ungulates), vultures and carrion production in terrestrial assemblages of vertebrates. Overall, we report an intricate network of both direct (competition, facilitation) and indirect (hyperpredation, hypopredation) processes, and provide a conceptual framework for the future development of this promising topic in ecological, evolutionary and biodiversity conservation research. The classic view that scavenging does not affect the population dynamics of consumed organisms is questioned, as multiple indirect top‐down effects emerge when considering carrion and its facultative consumption by predators as fundamental and dynamic components of food webs. Stimulating although challenging research opportunities arise from the study of the interactions among living and detrital or non‐living resource pools in food webs.
Diagnosis, treatment, response monitoring, and outcome of pediatric acute myeloid leukemia (AML) have made enormous progress during the past decades. Because AML is a rare type of childhood cancer, ...with an incidence of approximately seven occurrences per 1 million children annually, national and international collaborative efforts have evolved. This overview describes these efforts and includes a summary of the history and contributions of each of the main collaborative pediatric AML groups worldwide. The focus is on translational and clinical research, which includes past, current, and future clinical trials. Separate sections concern acute promyelocytic leukemia, myeloid leukemia of Down syndrome, and relapsed AML. A plethora of novel antileukemic agents that have emerged, including new classes of drugs, are summarized as well. Finally, an important aspect of the treatment of pediatric AML--supportive care--and late effects are discussed. The future is bright, with a wide range of emerging innovative therapies and with more and more international collaboration that ultimately aim to cure all children with AML, with fewer adverse effects and without late effects.
Perilla mint (
(L.) Britt.) is an annual plant native to Asia and considered invasive in North America where it has escaped cultivation as an ornamental (Miller 1947; Swearingen et al. 2010). In ...August 2021, an anthracnose disease was observed on invasive perilla found along the disturbed margins of a forest in Frederick County, Maryland, United States. Symptoms included necrotic lesions with chlorotic halos, were concentrated in the lower canopy, and caused premature defoliation of lower leaves (Figure S1). Leaves from four plants were surface sterilized by rinsing for 30 s in 70% ethanol, 60 s in 0.8% NaClO, and 60 s in sterile water and then incubated on 2% water agar under ambient laboratory conditions to permit sporulation. After three days, spores that exuded from individual lesions were streaked onto acidified potato dextrose agar. Two single-conidium isolates were recovered from each plant. All eight isolates were identified to species using DNA sequences. A single isolate (21-067) was selected at random for morphological characterization and completion of Koch's postulates. Morphological features were recorded after seven days of growth on synthetic low-nutrient agar (SNA) and potato dextrose agar (PDA) incubated at 22°C under 12 hr UV-B and white fluorescent lighting. Measurements were based on a minimum of 20 observations per structure. Cultures on SNA were flat, hyaline to pale salmon, lacked sporodochia and grew at a rate of 1.3 mm day
(n = 3). Vegetative hyphal width was (minimum-maximum) 1.5-4.0 μm, (average ± standard deviation) 2.7 ± 0.9 μm. Conidiophores arose directly from hyphae, were hyaline, smooth, unbranched and measured 40.0-180.0 x 1.5-4.5 μm, 102.3 ± 33.9 x 2.7 ± 0.8 μm. Conidia were single celled, straight, hyaline, glabrous, rounded at both ends and measured 10.0-20.0 x 3.8-6.3 μm, 15.4 ± 2.5 x 4.9 ± 0.7 μm. Setae, observed only on PDA, were pale brown, 1-2 septate, straight, blunt tipped and measured 42.5-97.5 μm, 70.8 ± 13.4 μm. Appressoria formed on PDA were single-celled, pigmented, smooth, and obovoid with entire margins, measuring 5.2-7.7 x 8.6-13.8 μm, 6.8 ± 0.6 x 10.8 ± 1.4 μm. These characteristics were consistent with members of the
species complex. Partial DNA sequences from five loci were amplified following the procedures of Damm et al. 2014: internal transcribed spacer region of rDNA (ITS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), chitin synthase 1 (CHS-1), actin (ACT), and beta-tubulin (TUB2). Pairwise sequence comparisons to references using the Blastn algorithm found 99.8% similarity between isolate 21-067 and ex-type
isolate JCM 31818: MH660930 (ITS, 545/546 bp), MH660931 (GAPDH,192/192 bp), MH660929 (CHS-1, 278/280 bp), MH660928 (ACT, 262/262 bp), and MH660932 (TUB2, 511/511 bp) (Altschul et al. 1990; Gan et al. 2019). Subsequently, sequences from all eight isolates were aligned with Clustal Omega (Sievers and Higgins 2018), concatenated, and used in a Bayesian phylogenetic reconstruction (Huelsenbeck and Ronquist 2001) of the
species complex (Figure S2), confirming the species identity as
. Sequences were deposited in NCBI GenBank under accession numbers OM865277-OM865284 and OM885059-OM885090. Koch's postulates were fulfilled using perilla grown in a greenhouse until second true leaves emerged. Inoculum washed from two-week-old fungal cultures grown on potato dextrose agar was adjusted to 4 x 10
conidia mL
and applied to three replicate plants with an aspirator until runoff. Three plants were sprayed with sterile water as a negative control. Plants were covered with plastic bags for 72 hrs and maintained in a growth chamber at 20°C and 80% RH for 14 days. Inoculated plants displayed disease symptoms similar to those observed under field conditions, and control plants did not develop symptoms.
was reisolated from symptomatic tissue and reidentified based on morphology. The experiment was completed twice. To the authors' knowledge, this is the first report of
on
in the United States.
has not been reported as a pathogen on other plants in the United States and may have potential use as a biological control agent for invasive perilla.
The purpose of this study was to examine the extent to which the presence of chronic noncancer pain (CNCP) impacts the likelihood that patients with diagnoses of depression will initiate depression ...treatment compared with those without CNCP.
We performed a retrospective cohort study of Kaiser Permanente of Georgia members older than 18 years who received a diagnosis of depression. Demographics and medical history were extracted from the electronic health record database. Members were further classified by the presence or absence of a CNCP diagnosis. Outcomes of interest were treated as time dependent and included ( 1 ) time to fulfillment of a new antidepressant medication and ( 2 ) time to a follow-up mental health encounter. Outcomes were compared between members with and without a CNCP diagnosis using Kaplan-Meier survival curves and Cox proportional hazard regression models.
During the study period, 22,996 members met the inclusion criteria and 27.4% had a diagnosis of CNCP. In the matched sample, there was no difference in the time to a new antidepressant fill among members with and without CNCP (hazard ratio = 0.96; 95% confidence interval = 0.90-1.02; p = .18). In contrast, members with CNCP were significantly less likely to have a new mental health encounter after diagnosis (hazard ratio = 0.87; 95% confidence interval = 0.81-0.94; p < .001).
Patients with CNCP were significantly less likely to have a new mental health encounter after a depression diagnosis compared with patients without CNCP. Additional outreach and consideration may be needed to improve initiation of depression treatment for newly diagnosed patients with comorbid depression and CNCP.
Climate and land use change modify surface water availability in African savannas. Surface water is a key resource for both wildlife and livestock and its spatial and temporal distribution is ...important for understanding the composition of large herbivore assemblages in savannas. Yet, the extent to which ungulate species differ in their water requirements remains poorly quantified. Here, we infer the water requirements of 48 African ungulates by combining six different functional traits related to physiological adaptations to reduce water loss, namely minimum dung moisture, relative dung pellet size, relative surface area of the distal colon, urine osmolality, relative medullary thickness, and evaporation rate. In addition, we investigated how these differences in water requirements relate to differences in dietary water intake. We observed strong correlations between traits related to water loss through dung, urine and evaporation, suggesting that ungulates minimize water loss through multiple pathways simultaneously, which suggests that each trait can thus be used independently to predict water requirements. Furthermore, we found that browsers and grazers had similar water requirements, but browsers are expected to be less dependent on surface water because they acquire more water through their diet. We conclude that these key functional traits are a useful way to determine differences in water requirements and an important tool for predicting changes in herbivore community assembly resulting from changes in surface water availability.
Aim: Africa is renowned for the current abundance and diversity of its large mammals. The aim of this study was to assess distinctions evident in the functional composition of continental large ...herbivore faunas during the late Pleistocene before extinctions depleted the megafauna outside Africa. Location: The African large herbivore fauna was compared with that formerly inhabiting South America, Australia, North America, Eurasia and tropical Asia during the late Pleistocene. Methods: Pleistocene faunas were reconstructed from the literature in terms of their relative body size composition, grazer/browser contributions and taxonomic representations, omitting forest and island species. Results: Although the three southern continents were closely similar in the overall species richness of large herbivores that they supported during the late Pleistocene, South America had a predominance of very large herbivores, while most of Australia's mammalian herbivores were relatively small and those of Africa were intermediate. Africa had many more grazers, especially in the size range 100—1000 kg, than other continents. The South American pattern resembled that in North America and Eurasia, while Africa and Australia diverged in different ways. Main conclusions: Neither the total extent of savannas in each continent nor the morphological features enabling bovid radiation seemed adequate on their own to explain the greater richness of macrograzers in Africa. Africa is characterized by the widespread occurrence of arid/eutrophic savannas, which are unrepresented in other continents. The prevalence of savanna is partly attributable to the high elevation of interior eastern and southern Africa, associated with relatively low rainfall, and to the comparatively high soil fertility, related to volcanic influences. This promoted an abundance and diversity of medium-sized grazing ruminants unrivalled elsewhere. Indigenous grasses in South America and Australia are less well adapted to withstand severe grazing than the African grasses introduced to support livestock. The locally high abundance of African ungulates presented conditions that facilitated the adaptive transition by early hominins from plant-gatherers to meat-scavengers.
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