Association of proton density fat fraction in adipose tissue with imaging-based and anthropometric obesity markers in adults.

BACKGROUND/OBJECTIVES: The purpose of this study was to examine the relationship of the proton density fat fraction (PDFF), measured by magnetic resonance imaging (MRI), of supraclavicular and gluteal adipose tissue with subcutaneous and visceral adipose tissue (SAT and VAT) volumes, liver fat fraction and anthropometric obesity markers. The supraclavicular fossa was selected as a typical location where brown adipocytes may be present in humans and the gluteal region was selected as a typical location enclosing primarily white adipocytes. SUBJECTS/METHODS: In this cross-sectional study, 61 adults (44 women, median age 29.3 years, range 21-68 years) underwent an MRI examination of the neck and the abdomen/pelvis (3T, Ingenia, Philips Healthcare). PDFF maps of the supraclavicular and gluteal adipose tissue and the liver were generated. Volumes of SAT and VAT were calculated and supraclavicular and subcutaneous fat were segmented using custom-built post-processing algorithms. Body mass index (BMI), waist circumference and waist-to-height ratio were recorded. Statistical analysis was conducted using the Student's t-test and Pearson correlation analysis. RESULTS: Mean supraclavicular PDFF was 75.3±4.7% (range 65.4-83.8%) and mean gluteal PDFF was 89.7±2.9% (range 82.2-94%), resulting in a significant difference (P<0.0001). Supraclavicular PDFF was positively correlated with VAT (r=0.76, P<0.0001), SAT (r=0.73, P<0.0001), liver PDFF (r=0.42, P=0.0008) and all measured anthropometric obesity markers. Gluteal subcutaneous PDFF also correlated with VAT (r=0.59, P<0.0001), SAT (r=0.63, P<0.0001), liver PDFF (r=0.3, P=0.02) and anthropometric obesity markers. CONCLUSIONS: The positive correlations between adipose tissue PDFF and imaging, as well as anthropometric obesity markers suggest that adipose tissue PDFF may be useful as a biomarker for improving the characterization of the obese phenotype, for risk stratification and for selection of appropriate treatment strategies.

Evidence-based guideline update: pharmacologic treatment for episodic migraine prevention in adults: report of the Quality Standards Subcommittee of the American Academy of Neurology and the American Headache Society.

OBJECTIVE: To provide updated evidence-based recommendations for the preventive treatment of migraine headache. The clinical question addressed was: What pharmacologic therapies are proven effective for migraine prevention? METHODS: The authors analyzed published studies from June 1999 to May 2009 using a structured review process to classify the evidence relative to the efficacy of various medications available in the United States for migraine prevention. RESULTS AND RECOMMENDATIONS: The author panel reviewed 284 abstracts, which ultimately yielded 29 Class I or Class II articles that are reviewed herein. Divalproex sodium, sodium valproate, topiramate, metoprolol, propranolol, and timolol are effective for migraine prevention and should be offered to patients with migraine to reduce migraine attack frequency and severity (Level A). Frovatriptan is effective for prevention of menstrual migraine (Level A). Lamotrigine is ineffective for migraine prevention (Level A).

Evidence-based guideline update: NSAIDs and other complementary treatments for episodic migraine prevention in adults: report of the Quality Standards Subcommittee of the American Academy of Neurology and the American Headache Society.

OBJECTIVE: To provide updated evidence-based recommendations for the preventive treatment of migraine headache. The clinical question addressed was: Are nonsteroidal anti-inflammatory drugs (NSAIDs) or other complementary treatments effective for migraine prevention? METHODS: The authors analyzed published studies from June 1999 to May 2009 using a structured review process to classify the evidence relative to the efficacy of various medications for migraine prevention. RESULTS: The author panel reviewed 284 abstracts, which ultimately yielded 49 Class I or Class II articles on migraine prevention; of these 49, 15 were classified as involving nontraditional therapies, NSAIDs, and other complementary therapies that are reviewed herein. RECOMMENDATIONS: Petasites (butterbur) is effective for migraine prevention and should be offered to patients with migraine to reduce the frequency and severity of migraine attacks (Level A). Fenoprofen, ibuprofen, ketoprofen, naproxen, naproxen sodium, MIG-99 (feverfew), magnesium, riboflavin, and subcutaneous histamine are probably effective for migraine prevention (Level B). Treatments considered possibly effective are cyproheptadine, Co-Q10, estrogen, mefenamic acid, and flurbiprofen (Level C). Data are conflicting or inadequate to support or refute use of aspirin, indomethacin, omega-3, or hyperbaric oxygen for migraine prevention. Montelukast is established as probably ineffective for migraine prevention (Level B).

Spontaneously gapped ground state in suspended bilayer graphene.

Bilayer graphene bears an eightfold degeneracy due to spin, valley, and layer symmetry, allowing for a wealth of broken symmetry states induced by magnetic or electric fields, by strain, or even spontaneously by interaction. We study the electrical transport in clean current annealed suspended bilayer graphene. We find two kinds of devices. In bilayers of type B1 the eightfold zero-energy Landau level is partially lifted above a threshold field revealing an insulating ν=0 quantum-Hall state at the charge neutrality point. In bilayers of type B2 the Landau level lifting is full and a gap appears in the differential conductance even at zero magnetic field, suggesting an insulating spontaneously broken symmetry state. Unlike B1, the minimum conductance in B2 is not exponentially suppressed, but remains finite with a value G is < or approximately equall to e(2)/h even in a large magnetic field. We suggest that this phase of B2 is insulating in the bulk and bound by compressible edge states.

OnabotulinumtoxinA improves quality of life and reduces impact of chronic migraine.

OBJECTIVE: To assess the effects of treatment with onabotulinumtoxinA (Botox, Allergan, Inc., Irvine, CA) on health-related quality of life (HRQoL) and headache impact in adults with chronic migraine (CM). METHODS: The Phase III Research Evaluating Migraine Prophylaxis Therapy (PREEMPT) clinical program (PREEMPT 1 and 2) included a 24-week, double-blind phase (2 12-week cycles) followed by a 32-week, open-label phase (3 cycles). Thirty-one injections of 5U each (155 U of onabotulinumtoxinA or placebo) were administered to fixed sites. An additional 40 U could be administered "following the pain." Prespecified analysis of headache impact (Headache Impact Test [HIT]-6) and HRQoL (Migraine-Specific Quality of Life Questionnaire v2.1 [MSQ]) assessments were performed. Because the studies were similar in design and did not notably differ in outcome, pooled results are presented here. RESULTS: A total of 1,384 subjects were included in the pooled analyses (onabotulinumtoxinA, n = 688; placebo, n = 696). Baseline mean total HIT-6 and MSQ v2.1 scores were comparable between groups; 93.1% were severely impacted based on HIT-6 scores ≥60. At 24 weeks, in comparison with placebo, onabotulinumtoxinA treatment significantly reduced HIT-6 scores and the proportion of patients with HIT-6 scores in the severe range at all timepoints including week 24 (p < 0.001). OnabotulinumtoxinA treatment significantly improved all domains of the MSQ v2.1 at 24 weeks (p < 0.001). CONCLUSIONS: Treatment of CM with onabotulinumtoxinA is associated with significant and clinically meaningful reductions in headache impact and improvements in HRQoL. CLASSIFICATION OF EVIDENCE: This study provides Class 1A evidence that onabotulinumtoxinA treatment reduces headache impact and improves HRQoL.

Superconductivity-enhanced conductance fluctuations in few-layer graphene.

We investigate the mesoscopic disorder induced rms conductance variance delta G in short few-layer graphene (FLG) flakes contacted by two superconducting (S) Ti/Al contacts. By sweeping the back-gate voltage, we observe pronounced conductance fluctuations superimposed on a linear background of the two-terminal conductance G. The linear gate voltage induced response can be modelled by a set of interlayer and intralayer capacitances. delta G depends on temperature T and source-drain voltage V(sd). delta G increases with decreasing T and |V(sd)|. When lowering |V(sd)|, a pronounced cross-over at a voltage corresponding to the superconducting energy gap Delta is observed. For [Formula: see text] the fluctuations are markedly enhanced. Expressed in the conductance variance G(GS) of one graphene-superconductor (G-S) interface, values of 0.58 e(2)/h are obtained at the base temperature of 230 mK. The conductance variance in the sub-gap region is larger by up to a factor of 1.4-1.8 compared to the normal state. The observed strong enhancement is due to phase coherent charge transfer caused by Andreev reflection at the G-S interface.

Giant fluctuations and gate control of the g-factor in InAs nanowire quantum dots.

We study the g-factor of discrete electron states in InAs nanowire based quantum dots. The g values are determined from the magnetic field splitting of the zero bias anomaly due to the spin 1/2 Kondo effect. Unlike to previous studies based on 2DEG quantum dots, the g-factors of neighboring electron states show a surprisingly large fluctuation: g can scatter between 2 and 18. Furthermore electric gate tunability of the g-factor is demonstrated.

Effect of melasma on quality of life in a sample of women living in southern Brazil.

BACKGROUND: Melasma can cause a significant effect on individual emotional well-being. Melasma Quality of Life Scale (MELASQoL) is a specific questionnaire elaborated to assess the burden of melasma on patient's quality of life. OBJECTIVE: To evaluate the clinical aspects, severity and the influence of melasma on daily living of a sample of Brazilian women. METHODS: Cross-sectional study that enrolled 85 women with melasma older than 15 years of age. Trained investigators asked 55 questions to collect epidemiological and clinical data. The disease severity was clinically assessed using Melasma Area and Severity Index (MASI). Patients answered the Portuguese version of 10-item MELASQoL scale without coaching. RESULTS: The mean +/- SD age was 41.1 +/- 6.8 years, and the mean +/- SD of MELASQoL score was 37.5 +/- 15.2 (median, 35). Patients with previous psychiatric diagnosis had significantly higher MELASQoL scores (mean, 42.8; SD, 13.6) than patients without this antecedent (mean, 35.4; SD, 15.4; P < 0.05). Patients with less than 8 years of school attendance also had significantly higher MELASQoL score (mean, 44; SD, 16.9) than more graduated ones (mean, 34.4; SD, 13.5; P < 0.05). The mean +/- SD MASI was 10.6 +/- 6.6 (median, 10.2). There was no correlation between MASI and MELASQoL. CONCLUSIONS: This study confirms that MELASQoL-BP is easy to administer, adds important information about the impact of melasma on South American women's life and, finally, contributes to building evidence on the validity, reliability and cultural adaptation of the Portuguese language MELASQoL version.

Time course of adverse events most commonly associated with topiramate for migraine prevention.

The efficacy, safety and tolerability of topiramate has been demonstrated in three large multicenter, randomized, double-blind, placebo-controlled trials. To characterize the time course of adverse events (AEs) that led to treatment discontinuation in >/=2% of patients who received topiramate 100 mg/day during three pivotal, multicenter, randomized, double-blind, placebo-controlled, and 26-week trials. The pooled population comprised all randomized patients who reported safety data during the double-blind phase (topiramate 100 mg/day, n = 386; placebo n = 372), which consisted of a 4-week titration period and a 22-week maintenance period. Incidence, time to onset, and cumulative mean rate of AEs were assessed. Overall, AEs led to treatment discontinuation in 24.9% of patients receiving topiramate 100 mg/day and 11.0% receiving placebo (P < 0.001). AEs leading to discontinuation during the double-blind phase in > or =2% of patients included paresthesia (8.0% discontinued), any cognitive symptoms (7.3% discontinued), fatigue (4.7% discontinued), insomnia (3.4% discontinued), nausea (2.3% discontinued), loss of appetite, anxiety, and dizziness (2.1% discontinued because each AE). Most AEs began during the titration period. Paresthesia, any cognitive symptoms, nausea, and loss of appetite occurred at a higher rate in the topiramate group than in the placebo group (P < 0.01). AEs leading to discontinuation of topiramate are probably to occur during dose titration. If a patient has not experienced one of these AEs within the first 6 weeks of initiating topiramate 100 mg/day, these AEs are unlikely to occur.

Migraine prevalence, disease burden, and the need for preventive therapy.

OBJECTIVES: 1) To reassess the prevalence of migraine in the United States; 2) to assess patterns of migraine treatment in the population; and 3) to contrast current patterns of preventive treatment use with recommendations for use from an expert headache panel. METHODS: A validated self-administered headache questionnaire was mailed to 120,000 US households, representative of the US population. Migraineurs were identified according to the criteria of the second edition of the International Classification of Headache Disorders. Guidelines for preventive medication use were developed by a panel of headache experts. Criteria for consider or offer prevention were based on headache frequency and impairment. RESULTS: We assessed 162,576 individuals aged 12 years or older. The 1-year period prevalence for migraine was 11.7% (17.1% in women and 5.6% in men). Prevalence peaked in middle life and was lower in adolescents and those older than age 60 years. Of all migraineurs, 31.3% had an attack frequency of three or more per month, and 53.7% reported severe impairment or the need for bed rest. In total, 25.7% met criteria for "offer prevention," and in an additional 13.1%, prevention should be considered. Just 13.0% reported current use of daily preventive migraine medication. CONCLUSIONS: Compared with previous studies, the epidemiologic profile of migraine has remained stable in the United States during the past 15 years. More than one in four migraineurs are candidates for preventive therapy, and a substantial proportion of those who might benefit from prevention do not receive it.

LY293558, a novel AMPA/GluR5 antagonist, is efficacious and well-tolerated in acute migraine.

Glutamatergic hyperactivity is implicated migraine pathogenesis. Also, LY293558, an alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate (KA) receptor antagonist, is effective in preclinical models of migraine. We therefore tested LY293558 in acute migraine. We conducted a randomized, triple-blind, parallel-group, double-dummy, multicentre trial of 1.2 mg/kg intravenous (IV) LY293558, 6 mg subcutaneous (SC) sumatriptan, or placebo in the treatment of acute migraine. The primary efficacy variable was the headache response rate, i.e. headache score improvement from moderate/severe at baseline to mild/none at 2 h. Of 45 enrolled patients, 44 patients (20M:24F; mean age +/- SD = 40 +/- 9 years) completed the study. Response rates were 69% for LY293558 (P = 0.017 vs. placebo), 86% for sumatriptan (P < 0.01 vs. placebo) and 25% for placebo. LY293558 and sumatriptan were superior to placebo (P < 0.01 for all comparisons) on all other measures of improvement in pain and migraine associated symptoms. Fifteen percent of patients who took LY293558 reported adverse events (AEs) (n = 2; one mild, one severe). Fifty-three percent of patients who took sumatriptan (n = 8; seven mild, one moderate) and 31% of those who received placebo reported AEs (n = 5; four mild, one severe). The efficacy and safety results of LY293558 in this small migraine proof of concept trial, together with supportive preclinical data, provide evidence for a potential role of nonvasoactive AMPA/KA antagonists in treating migraine. Larger trials are needed to further test the hypothesis.

The use of ibuprofen plus caffeine to treat tension-type headache.

Simple analgesics such as ibuprofen, aspirin, and acetaminophen have long been used in the treatment of tension-type headache. Studies of combination agents of aspirin with caffeine or acetaminophen with caffeine have also demonstrated efficacy as analgesic agents. Other evidence also suggests that caffeine may have an analgesic effect unto itself in the relief of pain. We undertook the direction of a multicenter, double-blind, placebo-controlled, parallel trial to assess the efficacy and safety of ibuprofen combined with caffeine in the treatment of tension-type headache. The study was designed to also verify the analgesic efficacy of caffeine and further assess the role of tension-type headache as a model for the study of pain.

Comparative study of a combination of isometheptene mucate, dichloralphenazone with acetaminophen and sumatriptan succinate in the treatment of migraine.

OBJECTIVE: To compare the safety and efficacy of isometheptene mucate, dichloralphenazone with acetaminophen to sumatriptan succinate for the treatment of mild-to-moderate migraine, with or without aura, when taken at the first sign of an attack. BACKGROUND: The Food and Drug Administration approved sumatriptan succinate and the combination of isometheptene mucate, dichloralphenazone with acetaminophen for the treatment of migraine. As part of the stratified treatment of migraine, those patients whose headaches are mild or moderate may benefit from nontriptan medications. Additionally, early treatment of acute migraine before the headache has become moderate or severe may improve response to treatment. METHODS: This was a multicenter, double-blind, randomized, parallel-group study to assess the safety and efficacy of the combination of isometheptene mucate, dichloralphenazone with acetaminophen and sumatriptan succinate in the early stages of a single migraine attack. Patients diagnosed with migraine, with or without aura, as defined by the International Headache Society diagnostic criteria were enrolled. RESULTS: One hundred thirty-seven patients were enrolled in the study. Data for efficacy were available for 126 patients; safety data were available for 128 patients. No statistically significant difference between the two active agents in the patient's response to treatment was demonstrated. Headache recurrence was not significantly different over the 24-hour evaluation period for those patients responding in the first 4 hours. In those with headache recurrence, it was statistically significantly more severe in those patients treated with sumatriptan succinate. Improvement in functional disability was, in general, better among those treated with isometheptene mucate, dichloralphenazone with acetaminophen. Global analysis of efficacy was similar in the two active groups. Patients treated with sumatriptan succinate were somewhat more likely to have adverse effects than the isometheptene mucate, dichloralphenazone with acetaminophen group. CONCLUSIONS: Both isometheptene mucate, dichloralphenazone with acetaminophen and sumatriptan succinate are safe and effective when used early in the treatment of an acute migraine. Several parameters suggest that isometheptene mucate, dichloralphenazone with acetaminophen may have a slight advantage compared with sumatriptan succinate in the early treatment of mild-to-moderate migraine.

Potential of the Migraine Disability Assessment (MIDAS) Questionnaire as a public health initiative and in clinical practice.

Migraine is not always well managed in clinical practice, often being under-diagnosed and under-treated. As a result, many sufferers never consult a physician or lapse from care after physician contact. Although most migraine care is provided by general practitioners, others, including specialists, emergency room physicians, pharmacists, and alternative practitioners, may also be involved. A method of standardizing clinical information about migraine is essential for coordinated, logical, and systematic care. The impact of migraine on the patient is an important clinical parameter but one that is seldom inquired about, perhaps because it exhibits such marked variability among and within individuals. Headache-related disability can be an objective and measurable index of this impact. The Migraine Disability Assessment (MIDAS) Questionnaire is a simple and validated instrument with potential for use in clinical practice, research, and public health. It can improve communication between patients and health-care professionals regarding the impact of migraine which, in turn, allows tailoring of the intensity of treatment to the severity of the illness. Changes in the MIDAS score may serve as an end point in assessing treatment efficacy. In populations, MIDAS scores may indicate the burden of migraine in the community and spark public health initiatives to improve management.

Divalproex in the long-term treatment of chronic daily headache.

OBJECTIVE: The purpose of this study was to assess the safety and efficacy of divalproex sodium in the long-term treatment of chronic daily headache. Correlations between treatment variables were assessed. BACKGROUND: Controlled and open-label trials of divalproex sodium have previously demonstrated its efficacy and safety in the treatment of migraine and chronic daily headaches. These data were primarily short-term and did not examine interaction between treatment variables. METHODS: Retrospective chart review with data extraction was conducted from headache diaries of 642 current patients under treatment with divalproex sodium for chronic daily headaches. One hundred thirty-eight of the patients were treated with only divalproex sodium. Demographic variables including age, sex, initial and final body weights, adverse events, dose of divalproex sodium, duration of treatment, and the ability to differentiate their chronic daily headache into its migraine and tension-type headache components were analyzed. Baseline and end of study headache frequency indices were obtained. RESULTS: The mean improvement was 47%, with an improvement in migraine of about 65%. At least a 50% reduction in headache frequency was reported by 93 of the 138 patients receiving treatment with only divalproex sodium. No correlation between response and age, sex, duration of treatment, and the prescribed dose of divalproex sodium was demonstrated. Adverse events occurred in approximately 35% of the patients. None were severe. Women were more likely to experience adverse effects than men. Weight gain, however, occurred less commonly in women (mean, 1.9 lbs) than in men (mean, 7 lbs). Initial body weight and age did not correlate with the weight change. CONCLUSIONS: Divalproex sodium can be used for a prolonged period as a sole agent for the successful treatment of chronic daily headache. Nearly 75% of the patients had at least a 50% reduction in headache frequency, and adverse effects occurred in approximately one third. Weight gain was negligible and hepatotoxicity did not occur during treatment periods of up to 6 years.

Acute treatment of migraine and the role of triptans.

The use of triptans has improved the ability to treat migraine successfully compared with older treatments. Speed of relief, consistency of effect, and good tolerability have been the hallmarks of these agents. All of the currently available triptans have comparable efficacy and tolerability. Variables between the agents may lead to one agent or dose form being preferred over another in various clinical scenarios. The triptans that are forthcoming may improve on these options through enhanced efficacy rates, tolerability, and headache recurrence rates. There exist increasing options for migraine treatment that may further improve the clinical effects of the older and newer triptans through early treatment of migraine at the stages of mild migraine pain, or even during the prodromal phase of the attack. Additionally, recent work suggests that mini-prophylaxis of migraine at the menses is a highly successful treatment option with the triptans. In this age of managed care, providing cost-effective treatment of headache will take on increasing importance. Techniques such as stratification of acute treatments may enhance cost-effective care, whereas ready availability of the triptans may lead to significant improvements in utilization of parameters such as office visits, emergency room treatment, and even hospitalization.

Intranasal civamide for the acute treatment of migraine headache.

The objective of this study was to investigate the safety and efficacy of intranasal civamide for the acute treatment of migraine headache with or without aura. Civamide is a vanilloid receptor agonist and neuronal calcium channel blocker that inhibits the neuronal release of excitatory neurotransmitters (e.g. calcitonin gene-related peptide (CGRP) and substance P (SP)) and depletes the neurones of the trigeminal plexus of their neurotransmitter content. Applied intranasally, the release of neurotransmitters to meningeal and dural blood vessels should be decreased, along with the resultant vasodilatation, plasma extravasation, and histamine/serotonin release. Subsequent migraine headache pain may also be diminished. Thirty-four patients were enrolled into a double-blind study of intranasal civamide, and randomized to receive a single dose of either 20 microg or 150 microg of civamide, for the treatment of a single migraine headache, with or without aura, of moderate to severe pain. At 2 h post-dose, 55.6% of patients treated with either dose had a decrease in pain severity, with 22.2% of patients being pain-free. At 4 h post-dose, 72.7% of patients treated with either dose had a decrease in pain severity, with 33.0% of patients being pain-free. Adverse events were similar for both dosages, with 91.2% of patients experiencing nasal burning and 44.1% of patients experiencing lacrimation. No systemic side-effects were observed. Based upon the results of this study, intranasal civamide may be effective in the acute treatment of migraine headache. Given civamide's proposed mechanism of action, intranasal civamide should be substantially more effective for prophylaxis than acute treatment of migraine. A study evaluating its efficacy in prophylaxis of migraine is currently planned.

Ibuprofen plus caffeine in the treatment of tension-type headache.

BACKGROUND: The effectiveness of caffeine as an adjuvant to ibuprofen has been documented in investigations of acute pain. Our objectives were to assess this agent in the treatment of tension-type headache and to establish clinical trial methods capable of assessing this agent in comparison with various tension headache treatments. Stopwatch technology was used for measurement techniques. METHODS: A randomized, double-blind, parallel, multicenter, single-dose, placebo- and active-controlled study included 301 subjects diagnosed with tension-type headache. Treatment groups included ibuprofen and caffeine, ibuprofen alone, caffeine alone, or placebo. Subjects measured onset of relief (both time to first perceptible relief and time to meaningful relief) after taking a single oral dose of their assigned medication. Pain intensity and pain relief were rated over a 6-hour study period. Overall evaluation was made on completion of all other ratings. RESULTS: Ibuprofen and caffeine administered together provided significantly greater analgesic activity than ibuprofen alone, caffeine alone, and placebo. Ibuprofen and caffeine administered together demonstrated significantly shorter times to meaningful improvement in headache relief than ibuprofen or placebo; significantly greater total analgesia than ibuprofen alone, caffeine alone, or placebo; and significantly greater peak relief than ibuprofen alone, caffeine alone, or placebo. Significantly more subjects obtained meaningful headache relief with ibuprofen and caffeine administered together than with ibuprofen alone or placebo. More patients reported complete headache relief with ibuprofen and caffeine administered together than with ibuprofen alone, caffeine alone, or placebo. Ibuprofen and caffeine administered together was rated significantly better by patients than either ibuprofen alone, caffeine alone, or placebo. No subjects ended participation in the study early because of adverse events. CONCLUSIONS: Sensitive methods have been introduced to assess differences in analgesia among over-the-counter analgesic agents in relieving tension-type headache pain. A double-blind study with this method suggests that ibuprofen and caffeine administered together provides greater analgesic effectiveness than either component alone.

Degradation kinetics of leucine5-enkephalin by plasma samples from healthy controls and various patient populations: in vitro drug effects.

Incubation of [3H]tyrosine leucine5-enkephalin with platelet-poor human plasma (final concentration 1 x 10(-8) M; 1:9 ratio to Trizma base buffer, pH 7.4) resulted in rapid and complete peptide degradation in each of the subjects studied, with more than 95% of the initial labeled tyrosine consistently recovered as the free amino acid (< or =30 minutes). Essentially, and irrespective of the incubation time (1-180 minutes), tyrosine was the only Leu metabolite formed; we were unable to identify significant amounts (> or =3%) of any other possible labeled or nonlabeled Leu degradation fragments. Neither gender (64 men and 20 women; samples tested individually), age (men, 23-70; women, 25-65 years), nor the subjects' medical condition appeared to make a significant difference in either the t1/2 of Leu elimination, the initial velocity of this reaction (x +/- SD, median, minimum and maximum of 12.0 +/- 0.9, 12.0, and 10.6-13.7 minutes; 1.2 +/- 0.3, 1.1, and 0.6-2.0 pg/min, respectively), or in the Km and Vmax values for aminopeptidase Leu degradation (x +/- SD; 0.81 +/- 0.01 mM and 14.30 +/- 1.17 micromol/L/min, respectively). Subjects were diagnosed as chronic schizophrenics (n = 15), polydrug abusers including alcohol (n = 9) and polydrug abusers excluding alcohol (n = 8), chronic alcoholics (n = 12), and migraineurs (n = 10) during or outside an acute migraine episode; for comparison we used a group of gender-matched (20 men and 10 women), age-comparable, drug-free, healthy volunteers. Differences in plasma storage time or repeated sample freezing and thawing failed to alter significantly any of these kinetic parameters of Leu metabolism or to change the identity and/or relative ratio of the products formed. The Leu degradation rate was pH and temperature dependent (optimum, 7.4 and 37 degrees C, respectively). Leu degradation was strongly and similarly inhibited by puromycin, bacitracin, and bestatin (IC50 [+/- SD] of 1.4 +/- 0.2 micromol/L) and to a lesser extent by various L-tyrosine-containing Leu fragments. The kinetics of this reaction was not significantly affected by either thiorphan, N-carboxyphenylmethyl leucine, or any other of a number of monoamine neurotransmitters, substances of abuse, nonsteroidal anti-inflammatory agents, and miscellaneous compounds tested (concentration up to 10(-4) mol/L).