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Microbial eukaryotes, critical links in aquatic food webs, are unicellular, but some, such as choanoflagellates, form multicellular colonies. Are there consequences to predator avoidance of being unicellular vs. forming larger colonies? Choanoflagellates share a common ancestor with animals and are used as model organisms to study the evolution of multicellularity. Escape in size from protozoan predators is suggested as a selective factor favoring evolution of multicellularity. Heterotrophic protozoans are categorized as suspension feeders, motile raptors, or passive predators that eat swimming prey which bump into them. We focused on passive predation and measured the mechanisms responsible for the susceptibility of unicellular vs. multicellular choanoflagellates, Salpingoeca helianthica, to capture by passive heliozoan predators, Actinosphaerium nucleofilum, which trap prey on axopodia radiating from the cell body. Microvideography showed that unicellular and colonial choanoflagellates entered the predator's capture zone at similar frequencies, but a greater proportion of colonies contacted axopodia. However, more colonies than single cells were lost during transport by axopodia to the cell body. Thus, feeding efficiency (proportion of prey entering the capture zone that were engulfed in phagosomes) was the same for unicellular and multicellular prey, suggesting that colony formation is not an effective defense against such passive predators.

Early on in the COVID-19 pandemic it was reported that angiotensin converting enzyme 2 inhibitors (ACE2i) could be associated with worse disease course due to potential increase in ACE2 receptors which SARS-CoV2 virus uses for cellular entry. Subsequent studies refuted such concerns, reporting that the continued use of ACEis and angiotensin receptor blockers (ARBs) in hypertensive individuals is in fact protective. Moreover, certain comorbidities, such as hypertension and heart disease, have been linked to an increased risk of disease severity. However, there is still paucity of data evaluating the effects of the use of different antihypertensive medications, steroids and beta blockers in chronic kidney disease (CKD) populations and in individuals with normal kidney function. This study was designed to evaluate the potential risk associated with renin angiotensin system inhibitors, calcium channel blocker, mineralocorticoid receptor blocker, steroids and beta blockers in a cohort of mostly African Americans and Caucasians. We conducted a retrospective study on patients who were admitted to the Detroit Medical Center, Detroit, MI during March and April of 2020. The data were collected through the medical chart reviews. We assessed 330 patients using inclusion criteria of age > 18 years and a positive SARS-CoV2 PCR test. We used the mean, standard deviation/standard error of mean, and percentages when appropriate for the description of patient characteristics. Group differences (CKD vs. non-CKD) were compared using the Pearson χ2 test. P-values of <0.05 were regarded as significant. We conducted binary logistic regression analysis to determine the effect of biological sex and CKD status on death due to COVID-19 during hospitalization. We conducted multivariate regression analysis for factors contributing to death during hospitalization due to COVID-19 and ICU admission, evaluating the contribution of different medications, comorbidities, and clinical course of the disease. On regression analyses, the odds of death in the hospital due to COVID-19 infection was not significantly associated with either biological sex or CKD status in our sample population. The odds of dying in the hospital were higher in patients who were on calcium channel blockers (OR 2.99, 95% CI 1.29-6.93, P = 0.01) and steroids (OR 4.23, 95% CI 1.17-15.31, P = 0.03). The only significance for ICU admission was obtained for steroid use (OR 1.872, 95% CI 1.059-3.311, P = 0.03). Likewise, COPD was the only comorbidity found to be associated with ICU admission (OR 2.38, 95% CI 1.282 - 4.426, P = 0.006), Significant associations were not observed for patients taking ACEis, ARBs, mineralocorticoid receptor inhibitors, diuretics, beta blockers and sympatholytics. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

(1) Background: Data on COVID-19 outcomes and disease course as a function of different medications used to treat cardiovascular disease and chronic kidney disease (CKD), as well as the presence of different comorbidities in primarily Black cohorts, are lacking. (2) Methods: We conducted a retrospective medical chart review on 327 patients (62.6% Black race) who were admitted to the Detroit Medical Center, Detroit, MI. Group differences (CKD vs. non-CKD) were compared using the Pearson χ2 test. We conducted univariate and multivariate regression analyses for factors contributing to death during hospitalization due to COVID-19 (primary outcome) and ICU admission (secondary outcome), adjusting for age, sex, different medications, and comorbidities. A sub-analysis was also completed for CKD patients. (3) Results: In the fully adjusted model, a protective effect of ACEi alone, but not in combination with ARB or CCB, for ICU admission was found (OR = 0.400, 95% CI [0.183–0.874]). Heart failure was significantly associated with the primary outcome (OR = 4.088, 95% CI [1.1661–14.387]), as was COPD (OR = 3.747, 95% CI [1.591–8.828]). (4) Conclusions: Therapeutic strategies for cardiovascular disease and CKD in the milieu of different comorbidities may need to be tailored more prudently for individuals with COVID-19, especially Black individuals.

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