ABSTRACT
RATIONALE: Hemodialysis patients are at significant risk from COVID-19 due to their frequent interaction with the health care system and medical comorbidities. We followed up the trajectory of the first COVID-19-positive maintenance hemodialysis patient at Sunnybrook Health Sciences Centre in Toronto. We present the lessons learned and changes in practices that occurred to prevent an outbreak in our center. PRESENTING CONCERNS OF THE PATIENT: The patient, a 66-year-old woman on in-center hemodialysis, initially presented with a 2-day history of a productive cough. She subsequently developed a fever, was placed on contact and droplet isolation, and admitted to hospital. DIAGNOSES: On March 13, 2020, the patient tested positive for COVID-19. Within the next 48 hours, she developed hypoxia and acute respiratory distress syndrome as a complication of her illness requiring an extended critical care stay. This extended critical care stay resulted in critical illness-associated secondary sclerosing cholangitis. INTERVENTIONS: An interprofessional team was established, performing rapid Plan-Do-Study-Act quality improvement cycles to improve screening practices and promote the safety of patients and staff in the hemodialysis unit. OUTCOMES: We present here the lessons learned, the changes to our screening protocols, and the clinical course of our first in-center hemodialysis patient with SARS-CoV-2. TEACHING POINTS: Regular review of the infection screening processes is paramount in preventing outbreaks of COVID-19, particularly in hemodialysis units. Hospital admission should be arranged if a patient exhibits any clinical signs of hemodynamic compromise or hypoxia. Early education for health care practitioners caring for patients with COVID-19 and refresher information regarding personal protective equipment helped promote the safety of staff and prevent health care-associated outbreaks.
ABSTRACT
Sperm chemoattraction, where sperm locate unfertilized eggs by following a concentration gradient of egg-derived chemoattractants, has been widely documented across numerous taxa. While marine invertebrates are favoured models for understanding the underlying mechanisms of sperm chemoattraction, the evolutionary forces underpinning the process remain enigmatic. Here, we show that in mussels (Mytilus galloprovincialis), chemically moderated gamete preferences promote assortative fertilizations between genetically compatible gametes. When offered the choice of egg clutches from two females, sperm exhibited consistent but differential 'preferences' for chemical cues secreted from conspecific eggs. Critically, our data reveal that the preferences shown by sperm during the egg-choice trials are highly predictive of early embryonic viability when eggs and sperm from the same individuals are mixed during standard (no-choice) fertilization assays. Moreover, we demonstrate that by experimentally separating chemoattractants from eggs, sperm swimming behaviour is differentially regulated by egg-derived chemoattractants, and that these changes in sperm behaviour are highly consistent with observed patterns of gamete preferences, fertilization and larval survival. Together, this integrated series of experiments reveals that the behaviour of sperm is fine-tuned to respond differentially to the chemical signals emitted from different conspecific eggs, and that these choices have measurable fitness benefits.
