Painful inflammation-induced increase in mu-opioid receptor binding and G-protein coupling in primary afferent neurons

Opioids mediate their analgesic effects by activating mu-opioid receptors (MOR) not only within the central nervous system but also on peripheral sensory neurons. The peripheral analgesic effects of opioids are best described under inflammatory conditions (e.g., arthritis). The present study investigated the effects of inflammation on MOR binding and G-protein coupling of full versus partial MOR agonists in dorsal root ganglia (DRG) of primary afferent neurons. Our results show that Freund's complete adjuvant (FCA) unilateral hindpaw inflammation induces a significant up-regulation of MOR binding sites (25 to 47 fmol/mg of protein) on DRG membranes without affecting the affinity of either full or partial MOR agonists. In our immunohistochemical studies, the number of MOR-immunoreactive neurons consistently increased. This increase was mostly caused by small-diameter nociceptive DRG neurons. The full agonist DAMGO induced MOR G-protein coupling in DRG of animals without FCA inflammation (EC50 = 56 nM; relative Emax = 100%). FCA inflammation resulted in significant increases in DAMGO-induced MOR G-protein coupling (EC50 = 29 nM; relative Emax = 145%). The partial agonist buprenorphine hydrochloride (BUP) showed no detectable G-protein coupling in DRG of animals without FCA inflammation; however, partial agonist activity of BUP-induced MOR G-protein coupling was detectable in animals with FCA inflammation (EC50 = 1.6 nM; relative Emax = 82%). In behavioral studies, administration of BUP produced significant antinociception only in inflamed but not in noninflamed paws. These findings show that inflammation causes changes in MOR binding and G-protein coupling in primary afferent neurons. They further underscore the important differences in clinical studies testing peripherally active opioids in inflammatory painful conditions.     

On the performance of random-coefficient pattern-mixture models for non-ignorable drop-out

Random-coefficient pattern-mixture models (RCPMMs) have been proposed for longitudinal data when drop-out is thought to be non-ignorable. An RCPMM is a random-effects model with summaries of drop-out time included among the regressors. The basis of every RCPMM is extrapolation. We review RCPMMs, describe various extrapolation strategies, and show how analyses may be simplified through multiple imputation. Using simulated and real data, we show that alternative RCPMMs that fit equally well may lead to very different estimates for parameters of interest. We also show that minor model misspecification can introduce biases that are quite large relative to standard errors, even in fairly small samples. For many scientific applications, where the form of the population model and nature of the drop-out are unknown, interval estimates from any single RCPMM may suffer from undercoverage because uncertainty about model specification is not taken into account.     

Saline,mannitol, and furosemide hydration in acute cisplatin nephrotoxicity: a randomized trial

OBJECTIVE: To determine which hydration (saline, saline + mannitol, or saline + furosemide) is associated with least cisplatin nephrotoxicity. METHODS: We randomized 49 women who received cisplatin (75 mg/m(2) every 3 weeks) into one of the three hydration arms. The 24-h creatinine clearance was measured before and on day 6 after cisplatin infusion. The patients of each arm received 2 l of saline hydration. In the saline + furosemide arm, 40 mg of furosemide was given after hydration. In the saline + mannitol arm, 50 g of mannitol was mixed with the cisplatin. RESULTS: For the first cycle of chemotherapy, 15 women were randomized to saline, 17 to saline + furosemide, and 17 to saline + mannitol. For each group, the creatinine clearances before cisplatin infusion were (means+/-SD, milliliters per minute) 84.5+/-26.8, 82.5+/-24.0 and 87.4+/-25.6, and after cisplatin infusion were 79.1+/-31.9, 68.7+/-21.5, and 56.4+/-22.9, respectively. The decreases in creatinine clearance were similar between the saline group and the saline + furosemide group ( P=0.66), but different between the saline + mannitol group and the saline group ( P=0.02) or the saline + furosemide group ( P=0.02). As each woman received multiple courses of cisplatin, 15 who received saline contributed 41 paired datasets, 17 who received saline + furosemide contributed 49 paired datasets, and 17 who received saline + mannitol contributed 36 paired datasets showed similar patterns. CONCLUSIONS: Hydration with saline or saline + furosemide appears to be associated with less cisplatin nephrotoxicity than saline + mannitol.     

Overexpression of vascular endothelial growth factor by MCF-7 breast cancer cells promotes estrogen-independent tumor growth in vivo

Alteration of the phenotype of breast cancers from estrogen-dependent to estrogen-independent growth often leads to the failure of antiestrogenic tumor therapies. We report that overexpression of vascular endothelial growth factor (VEGF) by estrogen-dependent MCF-7 breast cancer cells could abolish estrogen-dependent tumor growth in ovariectomized mice. In the absence of estrogen, MCF-7 VEGF-expressing tumors with increased vessel density showed growth kinetics similar to, or even greater than, that of parental MCF-7 tumors with estrogen supplementation. Overexpression of VEGF by MCF-7 cells or treatment on parental MCF-7 cells with recombinant VEGF also stimulated cell proliferation in culture. Our data suggest that VEGF stimulation of MCF-7 tumor angiogenesis and growth is mediated by both autocrine and paracrine mechanisms.     

Prescribing for seniors: it's a balancing act

PURPOSE: To present a rational approach to prescribing for seniors, balancing the need for and number of medications. DATA SOURCES: Selected evidence-based reviews and research articles and the author's own experience. CONCLUSIONS: Whenever possible, alternatives to medication therapy should be considered as the initial treatment of choice; however, medications should be prescribed when indicated and not withheld due to a patient's age. Reducing the number of medications reduces the risk for adverse drug reactions and drug-to-drug interactions. IMPLICATIONS FOR PRACTICE: Careful review of an older patient's medication list prior to initiating new therapy is necessary. Follow-up care to review the efficacy and monitor any potential side effects is crucial. Timely discontinuation of a drug when therapeutic usefulness is surpassed is equally important.     

fMRI evidence that the neural basis of response inhibition is task-dependent

Event-related fMRI was used to investigate the hypothesis that neural activity involved in response inhibition depends upon the nature of the response being inhibited. Two different Go/No-go tasks were compared-one with a high working memory load and one with low. The 'simple' Go/No-go task with low working memory load required subjects to push a button in response to green spaceships but not red spaceships. A 'counting' Go/No-go task (high working memory load) required subjects to respond to green spaceships as well as to those red spaceships preceded by an even number of green spaceships. In both tasks, stimuli were presented every 1.5 s with a 5:1 ratio of green-to-red spaceships. fMRI group data for each task were analyzed using random effects models to determine signal change patterns associated with Go events and No-go events (corrected P< or =0.05). For both tasks, Go responses were associated with signal change in the left primary sensorimotor cortex, supplementary motor area (SMA) proper, and anterior cerebellum (right>left). For the simple task, No-go events were associated with activation in the pre-SMA; the working memory-loaded 'counting' task elicited additional No-go activation in the right dorsolateral prefrontal cortex. The findings suggest that neural contributions to response inhibition may be task dependent; the pre-SMA appears necessary for inhibition of unwanted movements, while the dorsolateral prefrontal cortex is recruited for tasks involving increased working memory load.     

The serum protein alpha 2-Heremans-Schmid glycoprotein/fetuin-A is a systemically acting inhibitor of ectopic calcification

Ectopic calcification is a frequent complication of many degenerative diseases. Here we identify the serum protein alpha2-Heremans-Schmid glycoprotein (Ahsg, also known as fetuin-A) as an important inhibitor of ectopic calcification acting on the systemic level. Ahsg-deficient mice are phenotypically normal, but develop severe calcification of various organs on a mineral and vitamin D-rich diet and on a normal diet when the deficiency is combined with a DBA/2 genetic background. This phenotype is not associated with apparent changes in calcium and phosphate homeostasis, but with a decreased inhibitory activity of the Ahsg-deficient extracellular fluid on mineral formation. The same underlying principle may contribute to many calcifying disorders including calciphylaxis, a syndrome of severe systemic calcification in patients with chronic renal failure. Taken together, our data demonstrate a critical role of Ahsg as an inhibitor of unwanted mineralization and provide a novel therapeutic concept to prevent ectopic calcification accompanying various diseases.