A comparative study of cellular diversity between the Xenopus pronephric and mouse metanephric nephron.

The kidney is an essential organ that ensures bodily fluid homeostasis and removes soluble waste products from the organism. Nephrons, the functional units of the kidney, comprise a blood filter, the glomerulus or glomus, and an epithelial tubule that processes the filtrate from the blood or coelom and selectively reabsorbs solutes, such as sugars, proteins, ions, and water, leaving waste products to be eliminated in the urine. Genes coding for transporters are segmentally expressed, enabling the nephron to sequentially process the filtrate. The Xenopus embryonic kidney, the pronephros, which consists of a single large nephron, has served as a valuable model to identify genes involved in nephron formation and patterning. Therefore, the developmental patterning program that generates these segments is of great interest. Prior work has defined the gene expression profiles of Xenopus nephron segments via in situ hybridization strategies, but a comprehensive understanding of the cellular makeup of the pronephric kidney remains incomplete. Here, we carried out single-cell mRNA sequencing of the functional Xenopus pronephric nephron and evaluated its cellular composition through comparative analyses with previous Xenopus studies and single-cell mRNA sequencing of the adult mouse kidney. This study reconstructs the cellular makeup of the pronephric kidney and identifies conserved cells, segments, and associated gene expression profiles. Thus, our data highlight significant conservation in podocytes, proximal and distal tubule cells, and divergence in cellular composition underlying the capacity of each nephron to remove wastes in the form of urine, while emphasizing the Xenopus pronephros as a model for physiology and disease.

Combined assessment of myocardial perfusion and diastolic function enhances risk stratification in patients with anterior wall myocardial infarction.

OBJECTIVE: Evaluate the utility of a combined risk stratification scheme including diastolic dysfunction and "no-reflow," to identify high-risk patients following acute myocardial infarction (AMI). BACKGROUND: Recent studies have demonstrated that the "no-reflow" phenomenon (defined by myocardial contrast echocardiography) and severe diastolic dysfunction (identified by Doppler echocardiography) identify patients at high risk for mortality following AMI. METHODS: We evaluated 111 patients with recent anterior acute myocardial infarction from July 2000 to June 2004. Diastolic function and myocardial perfusion was evaluated by echocardiography. Patients were placed into 1 of 3 groups based on diastolic function and myocardial perfusion: Group 1 (normal perfusion and normal diastolic function), Group 2 (abnormal perfusion or abnormal diastolic function), and Group 3 (abnormal perfusion and abnormal diastolic function). We compared the long term all-cause mortality within these groups. RESULTS: Patients in each group were similar with respect to myocardial infarction size as defined by biomarkers, extent and severity of coronary artery disease, and medical and interventional therapy. Mortality was much higher in Group 3 (26.9%) compared to Group 1 (0%) and Group 2 (15.2%) (p = 0.048). CONCLUSION: Combined assessment of diastolic function and myocardial perfusion enhances risk stratification post myocardial infarction.