Sugammadex Versus Neostigmine for Reversal of Neuromuscular Blockade in Patients With Severe Renal Impairment: A Randomized, Double-Blinded Study.

BACKGROUND: Sugammadex is not advised for patients with severe renal impairment, but has been shown in a variety of other populations to be superior to neostigmine for reversal of neuromuscular blockade. The objective of this study was to determine if reversal of rocuronium-induced neuromuscular blockade with sugammadex versus reversal of cisatracurium-induced neuromuscular blockade with neostigmine results in a faster return to a train-of-four ratio (TOFR) ≥90% in patients with severe renal impairment. METHODS: We conducted a prospective, randomized, blinded, controlled trial at a large county hospital. A total of 49 patients were enrolled. Inclusion criteria included patients age ≥18, American Society of Anesthesiologists (ASA) physical status III and IV, with a creatinine clearance <30 mL/min, undergoing general anesthesia with expected surgical duration ≥2 hours and necessitating neuromuscular blockade. Subjects received either cisatracurium 0.2 mg/kg or rocuronium 0.6 mg/kg for induction of anesthesia to facilitate tracheal intubation. Subjects were kept at moderate neuromuscular blockade during surgery and received either 2 mg/kg sugammadex or 50 µg/kg neostigmine with 10 µg/kg glycopyrrolate for reversal of neuromuscular blockade. Neuromuscular monitoring was performed with electromyography (TwitchView), and the TOFR was recorded every minute after administration of the reversal agent. The time from administration of neuromuscular reversal until the patient reached a TOFR ≥90% was recorded as the primary outcome. RESULTS: The mean time to recovery of TOFR ≥90% was significantly faster with sugammadex at 3.5 (±1.6) min compared with neostigmine at 14.8 (±6.1) min ( P < .0001; mean difference, 11.3 minutes; 95% confidence interval [CI], 9.0-13.5 minutes). There were no major adverse events in either group. CONCLUSIONS: In patients with severe renal impairment, neuromuscular blockade with rocuronium followed by reversal with sugammadex provides a significantly faster return of neuromuscular function compared to cisatracurium and neostigmine, without any major adverse effects.

Neutrophil Lymphocyte Ratio as a predictor of systemic inflammation - A cross-sectional study in a pre-admission setting.

BACKGROUND: Neutrophil:lymphocyte ratio (NLR)  is an emerging biomarker that is used to predict postoperative mortality and morbidity in cardiac and cancer surgeries. The association of this biomarker with systemic illness and its usefulness in risk assessment of preoperative patients has not been fully elucidated. OBJECTIVES: To determine the prevalence of elevated NLR in preoperative patients and to examine the relationship between elevated NLR and the presence of systemic illnesses as well as anaesthesia risk indices such as American Society of Anesthesia (ASA) and the revised cardiac risk index (RCRI) scores.   DESIGN: Cross-sectional study Setting: Anaesthesia pre-admission clinic, Toronto Western Hospital, Toronto, Canada Patients: We evaluated 1117 pre-operative patients seen at an anesthesia preadmission clinic. RESULTS: NLR was elevated (>3.3) in 26.6% of target population. In multivariate analysis, congestive cardiac failure, diabetes mellitus and malignancy were independent risk factors predicting raised NLR. After regression analysis, a relationship between NLR and ASA score (Odds Ratio 1.78; 95% CI: 1.42-2.24) and revised cardiac risk index (RCRI, odds ratio 1.33; 95% CI: 1.09-1.64, p-value: 0.0063) was observed. CONCLUSIONS:  NLR was elevated (> 3.3) in 26.6% of patients. Congestive cardiac failure and malignancy were two constant predictors of elevated NLR at >3.3 and > 4.5. There was a strong association between NLR and anesthesia risk scoring tools of ASA and RCRI.

Free flap reconstruction experience and outcomes at a low-volume institution over 20 years.

OBJECTIVE: Assess the efficacy of free flap reconstruction performed at a low-volume program and evaluate how volume and outcomes have changed over 20 years. STUDY DESIGN: Case series with chart review. SETTING: Tertiary academic medical center. SUBJECTS AND METHODS: A retrospective chart review was performed at a tertiary care academic program on all free tissue flaps from the primary reconstructive surgeon over 20 years (1993-2013). In total, 136 procedures were obtained from operative notes, billing codes, and chart databases. Outcome variables included procedure success and complications. Patients stayed in general intensive care unit and hospital floor units. RESULTS: Flap success was 92.6% of all cases. In the past 13 years, 70 flaps were performed with 3 failures (96% success rate). Take-back rate was 16% of total cases with a flap recovery rate of 60%. Postoperative failure occurred after 72 hours in 60% of cases. Nearly 60% of patients experienced a complication of any type or severity. Twenty percent had a flap complication while maintaining viability, with half of these being partial dehiscence. Systemic complications affected 20% of all cases. The average hospital stay for noncomplicated patients was 13 days. There was 1 postoperative mortality. Fibula and radial forearm were the most common flaps at 44% and 26%, respectively. CONCLUSION: Free flap reconstruction of the head and neck can be performed by appropriately skilled surgeons with acceptable outcomes in low-volume settings. Success rate appears to increase as clinical experience is gained.

Pharmacokinetic and pharmacodynamics studies of nicotine after oral administration in mice: effects of methoxsalen, a CYP2A5/6 inhibitor.

INTRODUCTION: The use of novel oral nicotine delivery devices and compositions for human consumption and for animal research studies has been increasing in the last several years. METHODS: Studies were undertaken to examine whether the systemic administration of methoxsalen, an inhibitor of human CYP2A6 and mouse CYP2A5, would modulate nicotine pharmacokinetics and pharmacological effects (antinociception in the tail-flick, and hot-plate tests, and hypothermia) in male ICR mouse after acute oral nicotine administration. RESULTS: Administration of intra peritoneal (ip) methoxsalen significantly increased nicotine's Cmax, prolonged the plasma half-life (fourfold decrease) of nicotine, and increased its area under the curve (AUC) compared with ip vehicle treatment. Methoxsalen pretreatment prolonged the duration of nicotine-induced antinociception and hypothermia (15mg/kg, po) for periods up to 6- and 24-hr postnicotine administration, respectively. Additionally, methoxsalen potentiated nicotine-induced antinociception and hypothermia as evidenced by leftward shifts in nicotine's dose-response curve. Furthermore, this prolongation of nicotine's effects after methoxsalen was associated with a parallel prolongation of nicotine plasma levels in mice. These data strongly suggest that variation in the rates of nicotine metabolic inactivation substantially alter pharmacological effects of nicotine given orally. CONCLUSION: We have shown that the pharmacological effects of inhibiting nicotine's metabolism after oral administration in mice are profound. Our results suggest that inhibiting nicotine metabolism can be used to dramatically enhance nicotine's bioavailability and its resulting pharmacology, which further supports this inhibitory approach for clinical development of an oral nicotine replacement therapy.

NK4 antagonizes Tbx1/10 to promote cardiac versus pharyngeal muscle fate in the ascidian second heart field.

The heart and head muscles share common developmental origins and genetic underpinnings in vertebrates, including humans. Parts of the heart and cranio-facial musculature derive from common mesodermal progenitors that express NKX2-5, ISL1, and TBX1. This ontogenetic kinship is dramatically reflected in the DiGeorge/Cardio-Velo-Facial syndrome (DGS/CVFS), where mutations of TBX1 cause malformations in the pharyngeal apparatus and cardiac outflow tract. Cardiac progenitors of the first heart field (FHF) do not require TBX1 and segregate precociously from common progenitors of the second heart field (SHF) and pharyngeal muscles. However, the cellular and molecular mechanisms that govern heart versus pharyngeal muscle specification within this lineage remain elusive. Here, we harness the simplicity of the ascidian larva to show that, following asymmetric cell division of common progenitors, NK4/NKX2-5 promotes GATAa/GATA4/5/6 expression and cardiac specification in the second heart precursors by antagonizing Tbx1/10-mediated inhibition of GATAa and activation of Collier/Olf/EBF (COE), the determinant of atrial siphon muscle (ASM) specification. Our results uncover essential regulatory connections between the conserved cardio-pharyngeal factor Tbx1/10 and muscle determinant COE, as well as a mutual antagonism between NK4 and Tbx1/10 activities upstream of GATAa and COE. The latter cross-antagonism underlies a fundamental heart versus pharyngeal muscle fate choice that occurs in a conserved lineage of cardio-pharyngeal progenitors. We propose that this basic ontogenetic motif underlies cardiac and pharyngeal muscle development and evolution in chordates.

eLearning among Canadian anesthesia residents: a survey of podcast use and content needs.

BACKGROUND: Podcasts are increasingly being used in medical education. In this study, we conducted a survey of Canadian anesthesia residents to better delineate the content needs, format preferences, and usage patterns among anesthesia residents. METHODS: 10/16 Canadian anesthesia program directors, representing 443/659 Canadian anesthesia residents, allowed their residents to be included in the study. 169/659 (24%) residents responded to our survey. A 17-item survey tool developed by the investigators was distributed by email eliciting information on patterns of podcast use, preferred content, preferred format, and podcast adjuncts perceived to increase knowledge retention. RESULTS: 60% (91/151) had used medical podcasts with 67% of these users spending up to 1 hour per week on podcasts. 72.3% of respondents selected 'ability to review materials whenever I want' was selected by the majority of respondents (72%) as the reason they found podcasts to be valuable. No clear preference was shown for audio, video, or slidecast podcasts. Physiology (88%) and pharmacology (87%) were the most requested basic science topics while regional anesthesia (84%), intensive care (79%) and crisis resource management (86%) were the most requested for procedural, clinical and professional topics respectively. Respondents stated they would most likely view podcasts that contained procedural skills, journal article summaries and case presentations and that were between 5-15 minutes in duration A significantly greater proportion of senior residents (81%) requested podcasts on 'pediatric anesthesia' compared to junior residents 57% (P = 0.007). CONCLUSIONS: The majority of respondents are using podcasts. Anesthesia residents have preferred podcast content, types, length and format that educators should be cognizant of when developing and providing podcasts.

Physical activity and influenza-coded outpatient visits, a population-based cohort study.

BACKGROUND: Although the benefits of physical activity in preventing chronic medical conditions are well established, its impacts on infectious diseases, and seasonal influenza in particular, are less clearly defined. We examined the association between physical activity and influenza-coded outpatient visits, as a proxy for influenza infection. METHODOLOGY/PRINCIPAL FINDINGS: We conducted a cohort study of Ontario respondents to Statistics Canada's population health surveys over 12 influenza seasons. We assessed physical activity levels through survey responses, and influenza-coded physician office and emergency department visits through physician billing claims. We used logistic regression to estimate the risk of influenza-coded outpatient visits during influenza seasons. The cohort comprised 114,364 survey respondents who contributed 357,466 person-influenza seasons of observation. Compared to inactive individuals, moderately active (OR 0.83; 95% CI 0.74-0.94) and active (OR 0.87; 95% CI 0.77-0.98) individuals were less likely to experience an influenza-coded visit. Stratifying by age, the protective effect of physical activity remained significant for individuals <65 years (active OR 0.86; 95% CI 0.75-0.98, moderately active: OR 0.85; 95% CI 0.74-0.97) but not for individuals ≥ 65 years. The main limitations of this study were the use of influenza-coded outpatient visits rather than laboratory-confirmed influenza as the outcome measure, the reliance on self-report for assessing physical activity and various covariates, and the observational study design. CONCLUSION/SIGNIFICANCE: Moderate to high amounts of physical activity may be associated with reduced risk of influenza for individuals <65 years. Future research should use laboratory-confirmed influenza outcomes to confirm the association between physical activity and influenza.

Cost-utility analysis of primary prophylaxis versus secondary prophylaxis with granulocyte colony-stimulating factor in elderly patients with diffuse aggressive lymphoma receiving curative-intent chemotherapy.

PURPOSE: The 2006 American Society of Clinical Oncology (ASCO) guideline recommended primary prophylaxis (PP) with granulocyte colony-stimulating factor (G-CSF) instead of secondary prophylaxis (SP) for elderly patients with diffuse aggressive lymphoma receiving chemotherapy. We examined the cost-effectiveness of PP when compared with SP. METHODS: We conducted a cost-utility analysis to compare PP to SP for diffuse aggressive lymphoma. We used a Markov model with an eight-cycle chemotherapy time horizon with a government-payer perspective and Ontario health, economic, and cost data. Data for efficacies of G-CSF, probabilities, and utilities were obtained from published literature. Probabilistic sensitivity analysis (PSA) was conducted. RESULTS: The incremental cost-effectiveness ratio of PP to SP was $700,500 per quality-adjusted life-year (QALY). One-way sensitivity analyses (willingness-to-pay threshold = $100,000/QALY) showed that if PP were to be cost-effective, the cost of hospitalization for febrile neutropenia (FN) had to be more than $31,138 (2.5 × > base case), the cost of G-CSF per cycle less than $960 (base case = $1,960), the risk of first-cycle FN more than 47% (base case = 24%), or the relative risk reduction of FN with G-CSF more than 91% (base case = 41%). Our result was robust to all variables. PSA revealed a 10% probability of PP being cost-effective over SP at a willingness-to-pay threshold of $100,000/QALY. CONCLUSION: PP is not cost-effective when compared with SP in this population. PP becomes attractive only if the cost of hospitalization for FN is significantly higher or the cost of G-CSF is significantly lower.

The effectiveness of cognitive forcing strategies to decrease diagnostic error: an exploratory study.

BACKGROUND: Cognitive forcing strategies, a form of metacognition, have been advocated as a strategy to prevent diagnostic error. Increasingly, curricula are being implemented in medical training to address this error. Yet there is no experimental evidence that these curricula are effective. DESCRIPTION: This was an exploratory, prospective study using consecutive enrollment of 56 senior medical students during their emergency medicine rotation. Students received interactive, standardized cognitive forcing strategy training. EVALUATION: Using a cross-over design to assess transfer between similar (to instructional cases) and novel diagnostic cases, students were evaluated on 6 test cases. Forty-seven students were immediately tested and 9 were tested 2 weeks later. Data were analyzed using descriptive statistics and a McNemar chi-square test. CONCLUSIONS: This is the first study to explore the impact of cognitive forcing strategy training on diagnostic error. Our preliminary findings suggest that application and retention is poor. Further large studies are required to determine if transfer across diagnostic formats occurs.

Dopaminergic signaling mediates the motivational response underlying the opponent process to chronic but not acute nicotine.

The mesolimbic dopamine (DA) system is implicated in the processing of the positive reinforcing effect of all drugs of abuse, including nicotine. It has been suggested that the dopaminergic system is also involved in the aversive motivational response to drug withdrawal, particularly for opiates, however, the role for dopaminergic signaling in the processing of the negative motivational properties of nicotine withdrawal is largely unknown. We hypothesized that signaling at dopaminergic receptors mediates chronic nicotine withdrawal aversions and that dopaminergic signaling would differentially mediate acute vs dependent nicotine motivation. We report that nicotine-dependent rats and mice showed conditioned place aversions to an environment paired with abstinence from chronic nicotine that were blocked by the DA receptor antagonist alpha-flupenthixol (alpha-flu) and in DA D(2) receptor knockout mice. Conversely, alpha-flu pretreatment had no effect on preferences for an environment paired with abstinence from acute nicotine. Taken together, these results suggest that dopaminergic signaling is necessary for the opponent motivational response to nicotine in dependent, but not non-dependent, rodents. Further, signaling at the DA D(2) receptor is critical in mediating withdrawal aversions in nicotine-dependent animals. We suggest that the alleviation of nicotine withdrawal primarily may be driving nicotine motivation in dependent animals.

Extending the interview to all medical school candidates--Computer-Based Multiple Sample Evaluation of Noncognitive Skills (CMSENS).

BACKGROUND: Most medical school candidates are excluded without benefit of noncognitive skills assessment. Is development of a noncognitive preinterview screening test that correlates with the well-validated Multiple Mini-Interview (MMI) possible? METHOD: Study 1: 110 medical school candidates completed MMI and Computer-based Multiple Sample Evaluation of Noncognitive Skills (CMSENS)-eight 1-minute video-based scenarios and four self-descriptive questions, with short-answer-response format. Seventy-eight responses were audiotaped, 32 typewritten; all were scored by two independent raters. Study 2: 167 candidates completed CMSENS-eight videos, six self-descriptive questions, typewritten responses only, scored by two raters; 88 of 167 underwent the MMI. RESULTS: Results for overall test generalizability, interrater reliability, and correlation with MMI, respectively, were, for Study 1, audio-responders: 0.86, 0.82, 0.15; typewritten-responders: 0.72, 0.81, 0.51; and for Study 2, 0.83, 0.95, 0.46 (correlation with disattenuation was 0.60). CONCLUSIONS: Strong psychometric properties, including MMI correlation, of CMSENS warrant investigation into future widespread implementation as a preinterview noncognitive screening test.

Overview: what's worked and what hasn't as a guide towards predictive admissions tool development.

Admissions committees and researchers around the globe have used diligence and imagination to develop and implement various screening measures with the ultimate goal of predicting future clinical and professional performance. What works for predicting future job performance in the human resources world and in most of the academic world may not, however, work for the highly competitive world of medical school applicants. For the job of differentiating within the highly range-restricted pool of medical school aspirants, only the most reliable assessment tools need apply. The tools that have generally shown predictive validity in future performance include academic scores like grade point average, aptitude tests like the Medical College Admissions Test, and non-cognitive testing like the multiple mini-interview. The list of assessment tools that have not robustly met that mark is longer, including personal interview, personal statement, letters of reference, personality testing, emotional intelligence and (so far) situational judgment tests. When seen purely from the standpoint of predictive validity, the trends over time towards success or failure of these measures provide insight into future tool development.

Interactions between age and the aversive effects of nicotine withdrawal under mecamylamine-precipitated and spontaneous conditions in male Wistar rats.

RATIONALE: Adolescent onset of smoking is associated with a rapid progression to dependence. Although adolescents may exhibit a greater susceptibility to nicotine addiction, relatively little is known about the influence of the aversive effects of nicotine withdrawal in maintaining smoking behavior. OBJECTIVES: The present study investigated age differences in the motivational effects of mecamylamine-precipitated and spontaneous nicotine withdrawal in adolescent and adult rats using the conditioned place aversion procedure (CPA). MATERIALS AND METHODS: In experiment 1, adolescent (postnatal day (PD) 28) and adult (PD60) male Wistar rats chronically treated with nicotine (3 or 6 mg/kg/day, s.c.) received mecamylamine (1 mg/kg, s.c.), a nicotinic receptor antagonist, or vehicle prior to place conditioning; physical withdrawal signs were also measured. Experiment 2 was conducted to increase nicotine levels in which adolescents were treated with 4.5 or 9 mg/kg/day nicotine. In experiment 3, age differences in spontaneous nicotine withdrawal were evaluated. RESULTS: Nicotine-treated adults developed a CPA to the mecamylamine-associated compartment and expressed significant physical withdrawal signs, whereas similarly treated adolescents did not. Increasing nicotine exposure levels did not modify the adolescent response to mecamylamine-precipitated withdrawal. Spontaneous nicotine withdrawal produced similar physical withdrawal signs in adolescents and adults, but did not elicit CPA. CONCLUSIONS: The current study indicates that adolescent rats are less responsive to the aversive effects of mecamylamine-precipitated, but not spontaneous, nicotine withdrawal compared to adult rats. These findings suggest that adolescents and adults may exhibit similar sensitivity to the affective and physical effects of withdrawal following smoking cessation.

Selegiline is a mechanism-based inactivator of CYP2A6 inhibiting nicotine metabolism in humans and mice.

Selegiline (l-deprenyl) is in clinical treatment trials as a potential smoking cessation drug. We investigated the affect of selegiline and its metabolites on nicotine metabolism. In mice, selegiline was a potent inhibitor of nicotine metabolism in hepatic microsomes and cDNA-expressed CYP2A5; the selegiline metabolites desmethylselegiline, l-methamphetamine, and l-amphetamine, also inhibited nicotine metabolism. Pretreatment with selegiline and desmethylselegiline increased inhibition (IC(50)) in microsomes by 3.3- and 6.1-fold, respectively. In mice in vivo, selegiline increased AUC (90.7 +/- 5.8 versus 57.4 +/- 5.3 ng/h/ml, p < 0.05), decreased clearance (4.6 +/- 0.4 versus 7.3 +/- 0.3 ml/min, p < 0.05), and increased elimination half-life (12.5 +/- 6.3 versus 6.6 +/- 1.4 min, p < 0.05) of nicotine. In vitro, selegiline was a potent inhibitor of human nicotine metabolism in hepatic microsomes and cDNA-expressed CYP2A6; desmethylselegiline and l-amphetamine also inhibited nicotine metabolism. Selegiline preincubation increased inhibition in microsomes (3.7-fold) and CYP2A6 (14.8-fold); the K(i) for CYP2A6 was 4.2 muM. Selegiline dose- and time-dependently inhibited nicotine metabolism by CYP2A6 (K(i) = 15.6 +/- 2.7 muM; k(inact) = 0.34 +/- 0.04 min(-1)), and the inhibition was irreversible in the presence of NADPH, indicating that it is a mechanism-based inhibitor of CYP2A6. Thus, inhibition of mouse nicotine metabolism by selegiline was competitive in vitro and significantly increased plasma nicotine in vivo. In humans, where selegiline is both a competitive and mechanism-based inhibitor, it is likely to have even greater effects on in vivo nicotine metabolism. Our findings suggest that an additional potential mechanism of selegiline in smoking cessation is through inhibition of nicotine metabolism.

Non-nicotinic therapies for smoking cessation.

Cigarette smoking is the primary cause of numerous preventable diseases; as such, the goals of smoking cessation are both to reduce health risks and to improve the quality of life. Currently, the first-line smoking cessation therapies include nicotine replacement products and bupropion. The nicotinic receptor partial agonist varenicline has recently been approved by the FDA for smoking cessation. A newer product currently under development and seeking approval by the FDA are nicotine vaccines. Clonidine and nortriptyline have demonstrated some efficacy but side effects may limit their use to second-line therapeutic products. Other therapeutic drugs that are under development include rimonabant, mecamylamine, monoamine oxidase inhibitors, and dopamine receptor D3 antagonists. Inhibitors of nicotine metabolism are also promising candidates for smoking reduction and cessation. In conclusion, promising new therapeutic products are emerging and they will provide smokers additional options to assist in achieving smoking cessation.

Characterization and comparison of nicotine and cotinine metabolism in vitro and in vivo in DBA/2 and C57BL/6 mice.

DBA/2 and C57BL/6 are two commonly used mouse strains that differ in response to nicotine. Previous studies have shown that the nicotine-metabolizing enzyme CYP2A5 differs in coumarin metabolism between these two strains, suggesting differences in nicotine metabolism. Nicotine was metabolized to cotinine in vitro by two enzymatic sites. The high-affinity sites exhibited similar parameters (Km, 10.7 +/- 4.8 versus 11.4 +/- 3.6 microM; Vmax, 0.58 +/- 0.18 versus 0.50 +/- 0.07 nmol/min/mg for DBA/2 and C57BL/6, respectively). In vivo, the elimination half-lives of nicotine (1 mg/kg, s.c.) were also similar between DBA/2 and C57BL/6 mice (8.6 +/- 0.4 versus 9.2 +/- 1.6 min, respectively); however, cotinine levels were much higher in DBA/2 mice. The production and identity of the putative cotinine metabolite 3'-hydroxycotinine in mice was confirmed by liquid chromatography/mass spectrometry/mass spectrometry. The in vivo half-life of cotinine (1 mg/kg, s.c.) was significantly longer in the DBA/2 mice compared with the C57BL/6 mice (50.2 +/- 4.7 versus 37.5 +/- 9.6 min, respectively, p < 0.05). The in vitro metabolism of cotinine to 3'-hydroxycotinine was also less efficient in DBA/2 than C57BL/6 mice (Km, 51.0 +/- 15.6 versus 9.5 +/- 2.1 microM, p < 0.05; Vmax, 0.10 +/- 0.01 versus 0.04 +/- 0.01 nmol/min/mg, p < 0.05, respectively). Inhibitory antibody studies demonstrated that the metabolism of both nicotine and cotinine was mediated by CYP2A5. Genetic differences in Cyp2a5 potentially contributed to similar nicotine but different cotinine metabolism, which may confound the interpretation of nicotine pharmacological studies and studies using cotinine as a biomarker.

Nicotine self-administration in mice is associated with rates of nicotine inactivation by CYP2A5.

RATIONALE: Cyp2a5, the mouse homologue of human CYP2A6, encodes for the enzyme responsible for the primary metabolism of nicotine. Variation in human CYP2A6 activity can alter the amount smoked such as number of cigarettes smoked per day and smoking intensity. Different mouse strains self-administer different amounts of oral nicotine and quantitative trait loci analyses in mice suggested that Cyp2a5 may be involved in differential nicotine consumption behaviors. OBJECTIVES: The goal of this study was to examine whether in vivo nicotine consumption levels were associated with CYP2A5 protein levels and in vitro nicotine metabolism in mice. METHODS: F2 mice propagated from high (C57Bl/6) and low (St/bJ) nicotine consuming mice were analyzed for CYP2A5 hepatic protein levels and in vitro nicotine metabolizing activity. RESULTS: We found that F2 male high-nicotine (n=8; 25.1+/-1.2 microg nicotine/day) consumers had more CYP2A5 protein, compared to low (n=11; 3.8+/-1.4 microg nicotine/day) consumers (10.2+/-1.0 vs 6.5+/-1.3 CYP2A5 units). High consumers also metabolized nicotine faster than the low consumers (6 microM: 0.18+/-0.04 vs 0.14+/-0.07; 30 microM: 0.36+/- 0.06 vs 0.26+/-0.13; 60 microM: 0.49+/-0.05 vs 0.32+/-0.17 nmol/min/mg). In contrast, female high- (25.1+/-2.1 microg nicotine/day) and low-nicotine (4.7+/-1.4 microg nicotine/day) consumers did not show pronounced differences in nicotine metabolism or CYP2A4/5 protein levels; this is consistent with other studies of sex differences in response to nicotine. CONCLUSIONS: These data suggested that among male F2 mice, increased nicotine self-administration is associated with increased rates of nicotine metabolism, most likely, as a result of greater CYP2A5 protein levels.

TCR subunit specificity of CTLA-4-mediated signaling.

Cytotoxic T-lymphocyte-associated antigen (CTLA)-4 is an activation-induced receptor that down-regulates T cell responses by antagonizing B7-dependent costimulation and/or by transducing a negative signal. The mechanism of CTLA-4-mediated negative signaling is unknown. Recently, it has been postulated that CTLA-4 inhibits T cell activation by causing specific dephosphorylation of the T cell receptor (TCR)-zeta chain of the antigen-receptor complex through an lck-dependent recruitment of the Src homology-2-containing tyrosine phosphatase-2. To test this hypothesis, we generated stably transfected T cell clones expressing doxycycline-inducible CTLA-4 with CD25:TCR-zeta (CD25-zeta) or CD25:CD3-epsilon (CD25-epsilon) fusion proteins. In these clones, ligation of CD25-zeta or of CD25-epsilon with antibodies against CD25 induced full T cell activation, as illustrated by extracellular signal-regulated kinase (ERK) activation and interleukin (IL)-2 production. More importantly, coligation of CTLA-4 with CD25-zeta or of CTLA-4 with CD25-epsilon in the respectively transfected clones inhibited ERK activation and IL-2 production, demonstrating that CTLA-4 does not specifically inhibit signals from TCR-zeta but can also inhibit signals from CD3-epsilon. Our results suggest that the target specificity of CTLA-4 is determined by its coligation with any given transmembrane receptor rather than by its intracellular mediators.