High parasite virulence necessary for the maintenance of host outcrossing via parasite-mediated selection.

Biparental sex is widespread in nature, yet costly relative to uniparental reproduction. It is generally unclear why self-fertilizing or asexual lineages do not readily invade outcrossing populations. The Red Queen hypothesis predicts that coevolving parasites can prevent self-fertilizing or asexual lineages from invading outcrossing host populations. However, only highly virulent parasites are predicted to maintain outcrossing, which may limit the general applicability of the Red Queen hypothesis. Here, we tested whether the ability of coevolving parasites to prevent invasion of self-fertilization within outcrossing host populations was dependent on parasite virulence. We introduced wild-type Caenorhabditis elegans hermaphrodites, capable of both self-fertilization and outcrossing, into C. elegans populations fixed for a mutant allele conferring obligate outcrossing. Replicate C. elegans populations were exposed for 24 host generations to one of four strains of Serratia marcescens parasites that varied in virulence, under three treatments: a heat-killed (control, noninfectious) parasite treatment, a fixed-genotype (nonevolving) parasite treatment, and a copassaged (potentially coevolving) parasite treatment. As predicted, self-fertilization invaded C. elegans host populations in the control and fixed-parasite treatments, regardless of parasite virulence. In the copassaged treatment, selfing invaded host populations coevolving with low- to mid-virulence strains, but remained rare in hosts coevolving with highly virulent bacterial strains. Therefore, we found that only highly virulent coevolving parasites can impede the invasion of selfing.

Colorectal Cancer Screening Knowledge and Practices Among Practicing Obstetrician-Gynecologists and Residents.

Background: Colorectal cancer (CRC) is the second leading cause of cancer death in the US, the third most diagnosed cancer in women, and the second leading cause of cancer death in women. The aims of our study are to (1) investigate knowledge of and adherence to CRC screening guidelines by obstetrician-gynecologists (Ob/Gyns) and (2) assess whether this knowledge/adherence vary by demographic and practice characteristics. Methods: An anonymous cross-sectional survey was distributed to a convenience sample of 142 practicing Obs/Gyns drawn from National Medical Association section members/conference attendees and hospital Ob/Gyn department members. Results: Most respondents (80.3%) viewed colorectal screening within the scope of Ob/Gyn practice, and 71.8% used the American College of Obstetricians and Gynecologists guidelines for screening. Most respondents were knowledgeable regarding CRC screening but not in all areas. On average they only identified half of the 10 risk factors listed and only one-quarter correctly identified the age when screening can stop. Residents were somewhat more knowledgeable about screening guidelines and risk factors than attendings. More than half of respondents (57.8%) reported always initiating CRC screening for the appropriate age and risk factors. Respondents identified education and awareness (56.3%) and patients' unwillingness to undergo an invasive procedure (75.4%) as barriers to screening. Conclusions: Knowledge regarding CRC screening was less than optimal and differed by attending/resident status. Greater emphasis should be placed on CRC screening and guidelines training for primary care providers like Ob/Gyns. Some of this could be accomplished through maintenance of certification and continued integration into residency education.

Cardiovascular and Cerebrovascular Complications With COVID-19.

The coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus-2 has affected the health of people across the globe. Cardiovascular diseases (CVDs) have a significant relationship with COVID-19, both as a risk factor and prognostic indicator, and as a complication of the disease itself. In addition to predisposing to CVD complications, the ongoing pandemic has severely affected the delivery of timely and appropriate care for cardiovascular conditions resulting in increased mortality. The etiology behind the cardiac injury associated with severe acute respiratory syndrome coronavirus-2 is likely varied, including coronary artery disease, microvascular thrombosis, myocarditis, and stress cardiomyopathy. Further large-scale investigations are needed to better determine the underlying mechanism of myocardial infarction and other cardiac injury in COVID-19 patients and to determine the incidence of each type of cardiac injury in this patient population. Telemedicine and remote monitoring technologies can play an important role in optimizing outcomes in patients with established CVD. In this article, we summarize the various impacts that COVID-19 has on the cardiovascular system, including myocardial infarction, myocarditis, stress cardiomyopathy, thrombosis, and stroke.

No measurable fitness cost to experimentally evolved host defence in the Caenorhabditis elegans-Serratia marcescens host-parasite system.

Host susceptibility to parasites can vary over space and time. Costs associated with the maintenance of host defence are thought to account for a portion of this variation. Specifically, trade-offs wherein elevated defence is maintained at the cost of fitness in the absence of the parasite may cause levels of host defence to change over time and differ between populations. In previous studies, we found that populations of the host nematode, Caenorhabditis elegans, evolved greater levels of parasite avoidance and resistance against the bacterial parasite, Serratia marcescens. Here, we passaged these host populations either in the presence or absence of the parasite to test for a cost of elevated host defences. After 16 generations, we found that elevated levels of host defence were maintained during evolution in both the presence and absence of the parasite. Further, this maintenance of defence was not the result of limited standing genetic variation, but rather the absence of a measurable cost associated with defence. Therefore, costs associated with host defence may not broadly account for differences in host susceptibility across space and time.