Short and long loop nephrons

The purpose of this article is to consider the question: what is the importance to the urinary concentrating mechanism of having nephrons with two different configurations? The question is important, since of the two types of nephron, only one has loops of Henle in the inner renal medulla, the region with the highest osmotic pressure. While a definitive answer is not yet available, several features are described which lay the basis for a speculative conclusion

Potassium secretion by the descending limb or pars recta of the juxtamedullary nephron in vivo

Potassium secretion by the descending limb or pars recta of the juxtamedullary nephron in vivo. Potassium reabsorption by the juxtamedullary nephron up to the hairpin turn was studied by the micropuncture technique in the exposed renal papilla of rats. In 18 nondiuretic rats, the fraction of filtered potassium remaining at the end of the desdending limb averaged 113 ± 9%, indicating either that potassium is not reabsorbed by the juxtamedullary proximal tubule and descending limb or that potassium is reabsorbed and secreted in those segments. Furosemide, a drug which inhibits NaCl reabsorption in the ascending limb downstream from the descending limb, significantly decreased the potassium remaining at the end of the descending limb from 106 ± 12 to 72 ± 11% in seven rats. Benzolamide, a drug which inhibits reabsorption of NaHCO3 and water in the proximal tubule upstream from the descending limb, significantly increased the potassium remaining from 103 ± 13 to 177 ± 32% in eight rats. These findings support the hypothesis that in the rat, potassium is normally reabsorbed by the proximal convoluted tubule and secreted in the pars recta or descending limb of the juxtamedullary nephron

Effects of folic acid supplementation on overall and site-specific cancer incidence during the randomised trials: meta-analyses of data on 50 000 individuals

Some countries fortify flour with folic acid to prevent neural tube defects but others do not, partly because of concerns about cancer risks. We aimed to assess the effects of folic acid supplementation on site-specific cancer rates in the randomised trials

Teaching the History of Civil Rights at A Predominantly White Institution

Building on a 2003 pilgrimage to a dozen sites important in the Civil Rights Movement of the 1950\u27s and 1960\u27s, and conversations with movement leaders of then and now, the authors created an initiative at their 93% white campus to educate today\u27s students about the heritage the civil rights struggl