Regulated endocytosis of G-protein-coupled receptors by a biochemically and functionally distinct subpopulation of clathrin-coated pits

beta-2 Adrenergic receptors (B2ARs) are endocytosed by clathrin-coated pits. This process serves specialized functions in signal transduction and receptor regulation, raising the question of whether B2ARs are associated with biochemically specialized membrane vesicles during their endocytic trafficking. Here we show that B2ARs are endocytosed by a distinct subpopulation of clathrin-coated pits, which represent a limited subset of coated pits present in the plasma membrane, even in cells overexpressing both B2ARs and beta-arrestin. Coated pits mediating agonist-induced endocytosis of B2ARs differ from other coated pits mediating constitutive endocytosis of transferrin receptors in their temperature dependence for fission from the plasma membrane and in the association of their membrane coats with beta-arrestin. Endocytosis of these coated pits generates endocytic vesicles selectively enriched in B2ARs, which fuse within approximately 10 min after their formation with a common population of endosomes containing both B2ARs and transferrin receptors. These observations demonstrate, for the first time, the existence of a functionally and biochemically distinct subpopulation of clathrin-coated pits that mediate the agonist-regulated endocytosis of G-protein-coupled receptors, and they suggest a new model for the formation of compositionally specialized membrane vesicles at the earliest stage of the endocytic pathway.     

Comparative pharmacodynamics of CYP2B induction by DDT, DDE, and DDD in male rat liver and cultured rat hepatocytes

In this study the pharmacodynamics were characterized of rat hepatic cytochrome P-450 2B (CYP2B) induction by the pesticide DDT [1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane] and its metabolites DDE [1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene], which is bioretained, and DDD [1,1-dichloro-2,2-bis(p-chlorophenyl)ethane], which is metabolized further and therefore less prone to bioaccumulate. DDT, DDE, and DDD were each found to be pure phenobarbital-type cytochrome P-450 inducers in the male F344/NCr rat, causing induction of hepatic CYP2B and CYP3A, but not CYP1A. The ED50 values for CYP2B induction (benzyloxyresorufin O-dealkylation) by DDT, DDE, and DDD were, respectively, 103, 88, and > or = 620 ppm in diet (14 d of exposure). The efficacies (Emax values) for induction of benzyloxyresorufin O-dealkylation by DDT, DDE, and DDD were 24-, 22-, and > or = 1-fold, respectively, compared to control values. The potencies of the three congeners for CYP2B induction appeared also to be similar, with EC50 values (based on total serum DDT equivalents) of 1.5, 1.8, and > or = 0.51 microM, respectively. The EC50 values based on DDT equivalents in hepatic tissue were 15, 16, and > or = 5.9 micromol/kg liver tissue, respectively. In primary cultures of adult rat hepatocytes, DDT, DDE, and DDD each displayed ability to induce total cellular RNA coding for CYP2B (ED50 values of 0.98, 0.83, and > or = 2.7 microM, respectively). These results suggest that DDT, DDE, and DDD each possess a high degree of intrinsic CYP2B-inducing ability for rat liver, despite marked differences in bioretention among the congeners.     

Kappa-opioids produce significantly greater analgesia in women than in men

Sex differences in human responses to nociceptive stimuli and painful pathological conditions have generally indicated that women report higher pain levels or exhibit less tolerance than men for given stimulus intensities (reviewed in ref. 1 and 2). However, studies have not evaluated sex differences in analgesic responses. We recently reported that the opioid agonist-antagonist pentazocine, which acts predominantly at kappa-receptors, produced significantly better postoperative analgesia in females than in males in patients who underwent surgery for the removal of their third molars (wisdom teeth). In the current study, we evaluated the hypothesis that this sex difference is a characteristic of kappa-opioid agonism. In order to determine whether there are sex differences associated with kappa-opioid agonism, the analgesic efficacy of two other predominantly kappa-opioid analgesics, nalbuphine and butorphanol; was compared in males and females who underwent surgery for the removal of third molar teeth. We found that both nalbuphine and butorphanol produced significantly greater analgesia in females as compared with males. Considering our earlier findings, we conclude that kappa-opioid analgesia is greater in females than in males, probably reflecting a difference in kappa-opioid-activated endogenous pain modulating circuits.     

Coincident DiGeorge anomaly and renal agenesis and its relation to maternal diabetes

We describe 2 cases of DiGeorge anomaly with bilateral renal agenesis-one, who also had hemivertebrae, in an infant of an insulin-dependent diabetic mother (IDDM). In a review we identified 2 other instances of this combination, both in IDDMs. The currently accepted notion that DiGeorge anomaly and renal agenesis are developmental field defects, coupled with their coincidence in IDDM, suggests that this combination is an association.     

Interposition grafting for reoperation on the common femoral artery

PURPOSE: This report details our experience with common femoral artery resection and Dacron interposition grafting in the management of vascular reoperations involving the common femoral artery. DESIGN: Retrospective review. SETTING: University teaching hospital. SUBJECTS: Consecutive reoperative patients who had common femoral artery interposition grafting for arteriosclerotic occlusive disease from 1986 to 1997. INTERVENTIONS: Common femoral artery resection and interposition grafting. MAIN OUTCOME MEASURES: Operative morbidity and mortality rates and long-term patency, limb salvage, patient survival, freedom-from-graft-infection, and freedom-from-reoperation rates. RESULTS: Ninety-nine common femoral arteries (16 bilateral) were resected and replaced with Dacron interposition grafts in 83 patients (50 male, 33 female; mean age, 65 years) who had had 237 previous ipsilateral common femoral artery operations (mean, 2.4 operations; range, 1-9 operations). Simultaneous infrainguinal bypass grafts were performed in 52 operations (53%), and 60 operations (61%) were performed in patients who had had previous ipsilateral proximal bypass grafts. Operative mortality was 2%, with a 14% rate of perioperative wound complications. Mean follow-up time was 22 months. One- and 3-year assisted primary patency rates for the interposition grafts were 90% and 77%, respectively. Both 1- and 3-year life-table-determined limb salvage rates were 95%. One- and 3-year life-table-determined freedom-from-reoperation rates were 74% and 43%, respectively. One- and 3-year life-table-determined freedom-from-infection rates were 99% and 92%, respectively. One- and 3-year life-table-determined survival rates were 82% and 73%, respectively. CONCLUSIONS: Common femoral artery resection and Dacron interposition grafting are safe, and they obviate many difficulties associated with reoperative common femoral artery surgery with satisfactory long-term results.