Mutations in a Cl- channel (cystic fibrosis transmembrane conductance regulator or CFTR) are responsible for the cystic fibrosis (CF) phenotype. Increased Na+ transport rates are observed in CF airway epithelium, and recent studies suggest that this is due to an increase in Na+ channel open probability (Po). The Xenopus renal epithelial cell line, A6, expresses both cAMP-activated 8-picosiemen (pS) Cl- channels and amiloride-sensitive 4-pS Na+ channels, and provides a model system for examining the interactions of CFTR and epithelial Na+ channels. A6 cells express CFTR mRNA, as demonstrated by reverse transcriptase-polymerase chain reaction and partial sequence analysis. A phosphorothioate antisense oligonucleotide, complementary to the 5' end of the open reading frame of Xenopus CFTR, was used to inhibit functional expression of CFTR in A6 cells. Parallel studies utilized the corresponding sense oligonucleotide as a control. CFTR protein expression was markedly reduced in cells incubated with the antisense oligonucleotide. Incubation of A6 cells with the antisense oligonucleotide led to inhibition of forskolin-activated amiloride-insensitive short circuit current (Isc). After a 30-min exposure to 10 microM forskolin, 8-pS Cl- channel activity was detected in only 1 of 31 (3%) cell-attached patches on cells treated with antisense oligonucleotide, compared to 5 of 19 (26%) patches from control cells. A shift in the single-channel current-voltage relationship derived from antisense-treated cells was also consistent with a reduction in Cl- reabsorption. Both amiloride-sensitive Isc and Na+ channel Po were significantly increased in antisense-treated, forskolin-stimulated A6 cells, when compared with forskolin-stimulated controls. These data suggest that the regulation of Na+ channels by CFTR is not limited to respiratory epithelia and to epithelial cells in culture overexpressing CFTR and epithelial Na+ channels.

Objective: To evaluate leptin values in placental cord blood of newborns with normal intrauterine growth after 30–42 weeks of gestation. Design: Leptin, a protein encoded by the ob gene, plays an important role in the regulation of feeding behaviour and energy balance in rodents, primates and humans. The presence of leptin in human amniotic fluid and cord blood has recently been reported in human gestations at term and the possible role of leptin in human fetal growth suggested. However, little is known of leptin synthesis during human foetal development. Thus, the aim of our work was to measure leptin (RIA, Linco Research, Inc.) in placental cord blood of human newborns at different fetal ages. Patients: One hundred and twenty-six healthy newborns with normal intrauterine growth were studied. Twenty-nine were preterm (15 males and 14 females; gestational age: 30–36 weeks) and 99 were at term (49 males and 48 females; gestational age: 37–42 weeks). Results: Leptin values increase progressively throughout gestation from 1.30 ± 0.53 ng/ml at 30 weeks of gestation to 7.98 ± 4.96 ng/ml (mean ± SD) at term, and correlate positively with birth weight (r = 0.56, p < 0.005, n = 126), length (r = 0.37, p < 0.005, n = 126), BMI (r = 0.57, p < 0.005, n = 126), head circumference (r = 0.37, p < 0.005, n = 126), gestational age (r = 0.48, p < 0.005, n = 126) and placental weight (r = 0.38, p < 0.003, n = 59). Leptin values are statistically significantly lower (p < 0.005) preterm (median: 2.05 ng/ml; range: 0.7–8.3 ng/ml) than at term (median: 7.0 ng/ml; range: 1.1–28.1 ng/ml). Leptin values are also significantly (p < 0.005) higher in females (median: 7.2 ng/ml; range: 0.9–23.6 ng/ml, n = 62) than in males (median: 4.8 ng/ml; range: 0.7–28.1 ng/ml, n = 64), although there are no differences in weight (2,864 ± 536 g in females vs. 2,937 ± 744 g in males). Multiple regression analysis shows weight to be a positive sex-independent predictor of serum leptin values (p < 0.0005). Sex also proves to be a predictor of leptin, independently of weight and is higher in females than in males (p < 0.003). Conclusion: Leptin is present in placental human cord blood after 30–42 weeks of gestation. Newborn weight and sex are independent predictors of leptin values.

Abnormal cellular ion homeostasis is a well-recognized component of diabetic glomerular disease. In cultured rat glomerular mesangial cells, we have previously shown that insulin regulates Ca(2+)-dependent activation of 4-pS Cl- channels and 27-pS nonselective cation channels (NSCC) by angiotensin II (ANG II). To assess whether extracellular glucose also affects mesangial ion channels, we applied patch-clamp techniques to cells incubated in constant insulin (100 mU/ml) and either "normal" (5 mM) or "high" (30 mM) glucose for 1 wk. In normal glucose, 100 nM ANG II increased Cl- and NSCC activity by > 16-fold and > 60-fold, respectivley. Direct release of intracellular Ca2+ ([Ca2+]i) stores (0.25 microM thapsigargin) mimicked ANG II-induced channel stimulation. In high glucose, Cl- and NSCC stimulation by ANG II was attenuated (< 7-fold), whereas channel activation by thapsigargin was unaffected. Protein kinase C (PKC) inhibition (30-min exposure to 0.5 microM calphostin) or downregulation (24-h exposure to 0.1 microM 4 beta-phorbol 12-myristate 13-acetate), but not aldose reductase inhibition (0.5 mM sorbinil), restored channel responsiveness to ANG II despite high glucose. Channel responsiveness was also restored if mesangial cells were coincubated in both high glucose and 500 microM myo-inositol. Acute exposure to a synthetic diacylglycerol (100 microM 1-oleoyl-2-acetyl glycerol) reestablished channel unresponsiveness to ANG II. We conclude the following in rat mesangial cell cultures: 1) Activation of Ca(2+)-dependent Cl- and NSCCs by ANG II is reduced by high extracellular glucose.(ABSTRACT TRUNCATED AT 250 WORDS)

COVID-19 has circled the globe, rapidly expanding into a pandemic within a matter of weeks. While early studies revealed important features of SARS-CoV-2 transmission, the role of variation in free-living virus survival in modulating the dynamics of outbreaks remains unclear. Using an empirically determined understanding of SARS-CoV-2 natural history and detailed, country-level case data, we elucidate how variation in freeliving virus survival influences key features of COVID-19 epidemics. Our findings suggest that COVID-19's basic reproductive number (ℛ 0 ) and other key signatures of outbreak intensity are defined by transmission between infected individuals and the environment. Summarizing, we propose that variation in environmental transmission may explain observed differences in disease dynamics from setting to setting, and can inform public health interventions.