Urinary citrate is an important endogenous inhibitor of calcium nephrolithiasis. Systemic acidosis increases renal citrate reabsorption (decreases urinary excretion) and hence is associated with nephrolithiasis; systemic alkali administration increases citrate excretion. We studied the mechanism by which acidosis and alkalosis alter citrate reabsorption in the proximal convoluted tubule, the predominant nephron segment reabsorbing citrate. Tubules were perfused in vitro and citrate reabsorption was measured by use of luminal [14C]citrate. Changes in solution pH were accomplished by changes in bicarbonate concentration with constant PCO2. Decreasing peritubular pH acutely from 7.4 to 7.2 caused an increase in citrate reabsorption. However, the change seen with an acid peritubular pH was abolished by additional buffering of the luminal solution. Increasing peritubular pH from 7.4 to 7.6 resulted in a fall in citrate reabsorption that was not significantly greater than a time-dependent fall in citrate reabsorption in this preparation. The effect of luminal pH on proximal citrate reabsorption was also examined directly. Decreasing perfusate (luminal) pH from 7.4 to 7.2 with constant peritubular pH increased citrate reabsorption. Increasing perfusate pH to 7.6 decreased citrate reabsorption insignificantly (0.1 less than P less than 0.2). These data suggest that luminal pH in the proximal tubule is an important determinant of alterations in citrate reabsorption with acid-base disorders. The effect of luminal pH on citrate reabsorption is probably due to a change in concentration of the transported ionic species, citrate2-.

Implementation of a PICU asthma de-escalation pathway demonstrated statistical decrease in the reported measures for children with status asthmaticus. Although the clinical significance of these changes may be debatable, the results demonstrate that efforts to standardize asthma care in the PICU setting is an area in need of further study.

Primary ciliary dyskinesia (PCD) is a rare inherited condition affecting motile cilia and leading to organ laterality defects, recurrent sino-pulmonary infections, bronchiectasis, and severe lung disease. Research over the past twenty years has revealed variability in clinical presentations, ranging from mild to more severe phenotypes. Genotype and phenotype relationships have emerged. The increasing availability of genetic panels for PCD continue to redefine these genotype-phenotype relationships and reveal milder forms of disease that had previously gone unrecognized.

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DNAAF5 is a dynein motor assembly factor associated with the autosomal heterogenic recessive condition of motile cilia, primary ciliary dyskinesia (PCD). The effects of allele heterozygosity on motile cilia function are unknown. We used CRISPR-Cas9 genome editing in mice to recreate a human missense variant identified in patients with mild PCD and a second, frameshift-null deletion in Dnaaf5 . Litters with Dnaaf5 heteroallelic variants showed distinct missense and null gene dosage effects. Homozygosity for the null Dnaaf5 alleles was embryonic lethal. Compound heterozygous animals with the missense and null alleles showed severe disease manifesting as hydrocephalus and early lethality. However, animals homozygous for the missense mutation had improved survival, with partially preserved cilia function and motor assembly observed by ultrastructure analysis. Notably, the same variant alleles exhibited divergent cilia function across different multiciliated tissues. Proteomic analysis of isolated airway cilia from mutant mice revealed reduction in some axonemal regulatory and structural proteins not previously reported in DNAAF5 variants. Transcriptional analysis of mouse and human mutant cells showed increased expression of genes coding for axonemal proteins. These findings suggest allele-specific and tissue-specific molecular requirements for cilia motor assembly that may affect disease phenotypes and clinical trajectory in motile ciliopathies.