Extracellular Cysteine in Connexins: Role as Redox Sensors

Connexin-based channels comprise hemichannels and gap junction channels. The opening of hemichannels allow for the flux of ions and molecules from the extracellular space into the cell and vice versa. Similarly, the opening of gap junction channels permits the diffusional exchange of ions and molecules between the cytoplasm and contacting cells. The controlled opening of hemichannels has been associated with several physiological cellular processes; thereby unregulated hemichannel activity may induce loss of cellular homeostasis and cell death. Hemichannel activity can be regulated through several mechanisms, such as phosphorylation, divalent cations and changes in membrane potential. Additionally, it was recently postulated that redox molecules could modify hemichannels properties in vitro. However, the molecular mechanism by which redox molecules interact with hemichannels is poorly understood. In this work, we discuss the current knowledge on connexin redox regulation and we propose the hypothesis that extracellular cysteines could be important for sensing changes in redox potential. Future studies on this topic will offer new insight into hemichannel function, thereby expanding the understanding of the contribution of hemichannels to disease progression.

[Ureteroscopy. Our results and complications]

From November, 1987 to December, 1990, 399 cases of ureteral calculi were treated by rigid ureteroscopy (URS). Our success and complication rates are presented. Of these, 99 (25%) had a calculus in the pelvis (78/99), iliac (15/99) or lumbar (6/99) ureter, and 300 (75%) had Sandstrasse in the distal ureter. The cases with Sandstrasse were submitted to ureteroscopy within the first 48-72 hours to remove the ureteral obstruction, prevent hydronephrosis or sepsis and to expedite treatment. If symptomatic, obstructive and/or 7 mm or more in diameter, a nephrostomy tube was placed first whenever there was sepsis [23/300 (7%) of those with Sandstrasse and 3/99 (3%) of those with a ureteral calculus] or marked dilatation of the renal cavities [29/300 (9%) and 6/99 (6%), respectively]. The success rate was 93% for the cases with Sandstrasse versus 85% for those with a ureteral calculus, and the complication rates were 5.7% versus 9%, respectively. The foregoing results confirm the high success rate and scant morbidity of ureteroscopy in the treatment of ureteral calculus and Sandstrasse.