The use of chimeric musculocutaneous posterior interosseous artery flaps for treatment of osteomyelitis and soft tissue defect in hand.

INTRODUCTION: There is growing evidence of the superior ability of muscular tissue to clear bacterial bone infection. Unfortunately, in the hand, there are almost no small local muscular flaps, and muscular transfers to the hand are mainly microsurgical free transfers. In this report, we present the results of the use of a chimeric posterior interosseous flap including part(s) of the forearm muscles to treat osteomyelitis and soft tissue defect of hand from a series of patients. PATIENTS AND METHODS: Four male patients with an average age of 32 years (range 20-46 years), were affected by acute osteomyelitis in hand. Previous fracture fixation with percutaneous K-wires was the cause of bone infection in three case. In one case, the osteomyelitis was a consequence of an open fracture. The bones affected were four metacarpals and one proximal phalanx, all with a minimal cortical defect (from the K-wire) obscuring a larger medullary infection, which required extensive bone and overlying soft tissue debridement, leaving a soft tissue defect to be reconstructed of size ranging from 2 x 4 cm to 5 x 7 cm. The soft tissue defects were due to concomitant superficial infection and consequent debridement. All patients were treated with bone debridement and a chimeric posterior interosseous flap, which included part of the extensor digiti minimi and/or extensor carpi ulnaris to fill the intramedullary canal of the bones. No fixation of bone was necessary. RESULTS: The skin paddle of the flaps ranged from 2 x 5 cm to 5 x 6 cm, replicating the defect area, plus a teardrop tail of skin circa 1.5 cm wide and as long as the pedicle of the flap. The muscular components of the flaps used to fill the intramedullary canals ranged from 1 x 1 x 1.5 cm to 1.5 x 1.5 x 4 cm. All flaps survived and osteomyelitis resolved in all cases without major complications. At the final follow-up at 16 months (range 12-26 months), assessment of the hands using TAM, Power Grip and Key Pinch Strength measurements and, where appropriate, Kapandji scores, demonstrated satisfactory hand function. CONCLUSION: The chimeric posterior interosseous flap including part of the muscles of the forearm may be a robust solution for augmenting the flap bulk and may be used in cases of severe osteomyelitis of the hand.

A pilot study of the comparative efficacy of 100 Hz magnetic seizure therapy and electroconvulsive therapy in persistent depression.

BACKGROUND: Magnetic seizure therapy (MST) is a novel brain stimulation technique that uses a high-powered transcranial magnetic stimulation device to produce therapeutic seizures. Preliminary MST studies have found antidepressant effects in the absence of cognitive side effects but its efficacy compared to electroconvulsive therapy (ECT) remains unclear. The aim of this study was to investigate the therapeutic efficacy and cognitive profile of MST compared to standard right unilateral ECT treatment. METHODS: Thirty-seven patients completed a course of at least nine ECT or MST treatments in a randomized double-blind protocol. Assessments of depression severity and cognition were performed before and after treatment. RESULTS: No difference in the antidepressant effectiveness between the treatments was seen across any of the clinical outcome measures, although the overall response rates in both groups were quite low. In regards to cognition, following MST there were significant improvements in tests of psychomotor speed, verbal memory, and cognitive inhibition, with no reductions in cognitive performance. Following ECT there was significant improvement in only one of the cognitive inhibition tasks. With respect to the between-group comparisons, the MST group showed a significantly greater improvement on psychomotor speed than ECT. CONCLUSIONS: MST showed similar efficacy to right unilateral ECT in patients with treatment-resistant depression without cognitive side effects but in a sample that was only of sufficient size to demonstrate relatively large differences in response between the two groups. Future research should aim to optimize the methods of MST administration and compare its efficacy to ECT in large randomized controlled trials.

Development of an LC⁻Tandem Mass Spectrometry Method for the Quantitative Analysis of Hercynine in Human Whole Blood.

Given that the peculiar redox behavior of ergothioneine involves a rapid regeneration process, the measurement of its precursor and redox metabolite hercynine could be particularly useful in assessing its role in oxidative stress or other biological processes. Thus, a LC-MS/MS method for the determination of hercynine concentrations in whole blood was developed. After lysis of red blood cells by cold water, samples were filtered on micro concentrators at a controlled temperature of 4 °C. The clear filtered fluid was then treated with diethylpyrocarbonate to derivatize hercynine for the analysis by LC-MS/MS. The derivatized analyte was isocratically separated as a carbethoxy derivative on a C18 column with a mobile phase of an aqueous 0.1% v/v formic acid and acetonitrile (95:5). Effluents were monitored by MRM transitions at m/z 270.28→95 and 273.21→95 for hercynine and its deuterated counterpart, respectively. No cross-talk between MRM transitions was observed and a good linearity was found within a range of 35⁻1120 nmol/L. The LOD and LOQ were, respectively, 10.30 and 31.21 nmol/L with an intraday and intermediate precision below 7%. The average hercynine concentration in whole blood from 30 healthy male volunteers (aged 77 ± 12 years) was 178.5 ± 118.1 nmol/L. Overall, the method is easy to perform, allowing a rapid and accurate assessment of whole blood concentrations of hercynine.

In vitro metabolism of the anti-inflammatory clerodane diterpenoid polyandric acid A and its hydrolysis product by human liver microsomes and recombinant cytochrome P450 and UDP-glucuronosyltransferase enzymes.

1. The metabolism of the anti-inflammatory diterpenoid polyandric acid A (PAA), a constituent of the Australian Aboriginal medicinal plant Dodonaea polyandra, and its de-esterified alcohol metabolite, hydrolysed polyandric acid A (PAAH) was studied in vitro using human liver microsomes (HLM) and recombinant UDP-glucuronosyltransferase (UGT) and cytochrome P450 (CYP) enzymes. 2. Hydrolysis of PAA to yield PAAH occurred upon incubation with HLM. Further incubations of PAAH with HLM in the presence of UGT and CYP cofactors resulted in significant depletion, with UGT-mediated depletion as the major pathway. 3. Reaction phenotyping utilising selective enzyme inhibitors and recombinant human UGT and CYP enzymes revealed UGT2B7 and UGT1A1, and CYP2C9 and CYP3A4 as the major enzymes involved in the metabolism of PAAH. 4. Analysis of incubations of PAAH with UDP-glucuronic acid-supplemented HLM and recombinant enzymes by UPLC/MS/MS identified three glucuronide metabolites. The metabolites were further characterised by ß-glucuronidase and mild alkaline hydrolysis. The acyl glucuronide of PAAH was shown to be the major metabolite. 5. This study demonstrates the in vitro metabolism of PAA and PAAH and represents the first systematic study of the metabolism of an active constituent of an Australian Aboriginal medicinal plant.

Chemotherapy-related cardiotoxicity: are Australian practitioners missing the point?

BACKGROUND: It has long been established that cardiotoxicity occurs as a result of exposure to certain chemotherapeutics, particularly anthracyclines. Historically, clinicians equate cardiotoxicity with a poor prognosis, in a small percentage of patients and deem long-term surveillance as optional. Emerging evidence suggests that anthracycline cardiotoxicity (ACT) is a life-long risk with an incidence approaching 20%. AIMS: To elucidate the incidence of anthracycline cardiotoxicity within a current paediatric oncology survivor cohort. METHODS: Participants were identified through the Haematology-Oncology database at the Royal Children's Hospital, Melbourne. Patients were identified from a retrospective audit of outpatient attendances between January 2008 and December 2015. Patients with a cancer diagnosis exposed to anthracyclines were eligible for the study. Patient demographics and echocardiogram findings were recorded with patients subcategorised according to degree of ACT. More significant ACT defined as fractional shortening (FS) <24% and less significant if FS 24-28% or a decline in baseline ejection fraction of >10%. RESULTS: Two hundred and eighty-six of a total 481 identified patients were eligible for study inclusion. Twenty patients displayed significant ACT with FS <24%. Ten patients had a FS 24-28% and 25 patients with a decline in ejection fraction from baseline of >10%. Overall, 6.6% demonstrated significant cardiac complications, whilst 19.6 % demonstrated some degree of ACT and decline in myocardial function. When stratified for cumulative anthracycline dose, the incidence of severe cardiac dysfunction was 5.1% (<250 mg/m2 ) and 25% (>250 mg/m2 ) CONCLUSION: This study demonstrates, in keeping with modern literature, the higher incidence of anthracycline associated cardiac toxicity and a need for better surveillance and follow up.

PTESFinder: a computational method to identify post-transcriptional exon shuffling (PTES) events.

BACKGROUND: Transcripts, which have been subject to Post-transcriptional exon shuffling (PTES), have an exon order inconsistent with the underlying genomic sequence. These have been identified in a wide variety of tissues and cell types from many eukaryotes, and are now known to be mostly circular, cytoplasmic, and non-coding. Although there is no uniformly ascribed function, several have been shown to be involved in gene regulation. Accurate identification of these transcripts can, however, be difficult due to artefacts from a wide variety of sources. RESULTS: Here, we present a computational method, PTESFinder, to identify these transcripts from high throughput RNAseq data. Uniquely, it systematically excludes potential artefacts emanating from pseudogenes, segmental duplications, and template switching, and outputs both PTES and canonical exon junction counts to facilitate comparative analyses. In comparison with four existing methods, PTESFinder achieves highest specificity and comparable sensitivity at a variety of read depths. PTESFinder also identifies between 13 % and 41.6 % more structures, compared to publicly available methods recently used to identify human circular RNAs. CONCLUSIONS: With high sensitivity and specificity, user-adjustable filters that target known sources of false positives, and tailored output to facilitate comparison of transcript levels, PTESFinder will facilitate the discovery and analysis of these poorly understood transcripts.

Factors to consider when applying transcranial magnetic stimulation of dorsolateral prefrontal cortex when resting motor threshold is asymmetric: A case study.

Transcranial magnetic stimulation (TMS) is an increasingly popular tool in treating psychiatric conditions. The dorsal lateral prefrontal cortex (DLPFC) is typically targeted for stimulation, with magnetic field intensity being calibrated by establishing resting motor threshold (RMT) at hand region of primary motor cortex (M1 hand). This presumes that scalp-to-cortex distance (SCD) and cortical thickness is similar at both sites. We present data from a patient who had very asymmetrical RMTs (47 and 78). We investigated SCDs in this patient at the M1 hand and DLPFC, and the M1 hand cortical thickness. We also investigated TMS electric field distribution. The M1 hand SCD and cortical thickness of the M1 hand was larger on the side with higher RMT. Electric field finite element modelling demonstrated the focal point did not effectively reach the M1 hand with higher RMT as the postcentral gyrus was shunting it. Hence, successful DLPFC treatment was based upon the side with lower RMT. This study highlights the importance of tailoring DLPFC treatment intensity not only based on RMT at the M1 hand, and upon the degree to which SCD distance differs between sites, but also based upon size, shape, and density of M1 hand, as well as electric field distribution.

Correction of Clinodactyly by Early Physiolysis: 6-Year Results.

PURPOSE: To review results at least 6 years after physiolysis for treatment of the delta phalanx associated with clinodactyly. METHODS: We present 22 cases of clinodactyly treated with physiolysis in which we removed the central part of the epiphysis, which is the portion restricting longitudinal growth unilaterally and inducing progressive finger deviation, and placed a fat graft in the resultant defect. RESULTS: This retrospective study reports the results of early physiolysis in 27 fingers with radial clinodactyly, including 17 fingers from 17 patients previously reported and 10 little fingers from 5 additional patients. All patients had a minimum follow-up of 6 years. Mean preoperative angle was 38° (range, 25° to 47°). At final follow-up, mean angle was 8° (range, 0° to 24°), a mean correction of 79%. Twelve fingers in 9 patients had more than 10° of deformity at final follow-up, whereas 15 fingers in 13 patients had a residual deformity of less than 10°, which is effectively full correction of a clinodactyly. No patient required a closing wedge osteotomy later for insufficient correction. CONCLUSIONS: These accumulative findings confirm our previous preliminary report. Early physiolysis is a quick and simple procedure that allows for growth and partial but often adequate correction of the clinodactyly. The correction occurs slowly over a period of years, which can be seen as a disadvantage, and requires careful counseling of the parents. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.

Identification of the Main Intermediate Precursor of l-Ergothioneine Biosynthesis in Human Biological Specimens.

A capillary electrophoresis coupled to tandem mass spectrometry (CE-MS/MS) has been used to make a qualitative determination of hercynine-the main precursor of l-ergothioneine biosynthesis-in some key human biological specimens, such as urine, whole blood, plasma, and saliva. From semiquantitative analysis results, the highest concentrations of hercynine were detected in saliva and whole blood, whereas much lower concentrations were measured in urine and plasma. Whole blood was the biological matrix with the highest concentration of l-ergothioneine followed by plasma, saliva, and urine. The antioxidant effects attributed to l-ergothioneine, along with its peculiar antioxidant mechanism, offer a possible explanation for the presence of the hercynine, as well as its concentration, in the considered biological matrices.

Morphine glucuronidation and glucosidation represent complementary metabolic pathways that are both catalyzed by UDP-glucuronosyltransferase 2B7: kinetic, inhibition, and molecular modeling studies.

Morphine 3-ß-D-glucuronide (M3G) and morphine 6-ß-D-glucuronide (M6G) are the major metabolites of morphine in humans. More recently, morphine-3-ß-d-glucoside (M-3-glucoside) was identified in the urine of patients treated with morphine. Kinetic and inhibition studies using human liver microsomes (HLM) and recombinant UGTs as enzyme sources along with molecular modeling were used here to characterize the relationship between morphine glucuronidation and glucosidation. The M3G to M6G intrinsic clearance (C(Lint)) ratio (∼5.5) from HLM supplemented with UDP-glucuronic acid (UDP-GlcUA) alone was consistent with the relative formation of these metabolites in humans. The mean C(Lint) values observed for M-3-glucoside by incubations of HLM with UDP-glucose (UDP-Glc) as cofactor were approximately twice those for M6G formation. However, although the M3G-to-M6G C(Lint) ratio remained close to 5.5 when human liver microsomal kinetic studies were performed in the presence of a 1:1 mixture of cofactors, the mean C(Lint) value for M-3-glucoside formation was less than that of M6G. Studies with UGT enzyme-selective inhibitors and recombinant UGT enzymes, along with effects of BSA on morphine glycosidation kinetics, were consistent with a major role of UGT2B7 in both morphine glucuronidation and glucosidation. Molecular modeling identified key amino acids involved in the binding of UDP-GlcUA and UDP-Glc to UGT2B7. Mutagenesis of these residues abolished morphine glucuronidation and glucosidation. Overall, the data indicate that morphine glucuronidation and glucosidation occur as complementary metabolic pathways catalyzed by a common enzyme (UGT2B7). Glucuronidation is the dominant metabolic pathway because the binding affinity of UDP-GlcUA to UGT2B7 is higher than that of UDP-Glc.

Treatment of unfavourable results of flexor tendon surgery: Ruptured repairs, tethered repairs and pulley incompetence.

As primary repair of divided flexor tendons becomes more common, secondary tendon surgery becomes largely that of the complications of primary repair, namely ruptured and adherent repairs. These occur with an incidence of each in most reported series world-wide of around 5%, with these problems having changed little in the last two decades, despite strengthening our suture repairs. Where the primary referral service is less well-developed, and as a more occasional occurrence where primary treatment is the routine, the surgeon faces different problems. Patients arrive at a hand unit variable, but longer, times after the primary insult, having had no, or bad, previous treatment. Sometimes the situation is the same, viz. an extended finger with no active flexion, but now no longer amenable to primary repair. Frequently, it is much more complex as a result of injuries to the other tissues of the digit and, also, as a result of the unaided healing process within the digit in the presence of an inactive flexor system. We present our experience in dealing with ruptured repairs, tethered repairs and pulley incompetence.

Treatment of unfavourable results of flexor tendon surgery: Skin deficiencies.

We recently reported a small study at the Federation of European Societies for Surgery of the hand, which was entitled 'What is secondary flexor tendon surgery'? This study concluded that 'secondary flexor tendon surgery' was a generic name encompassing a multitude of pathologies. Between 10% and 15% of cases exhibited pathology of the skin and subcutaneous fat and required flap reconstruction of these tissues. Skin replacement may be used prophylactically at primary surgery or become necessary at secondary surgery after release of scar contractures, to achieve cover of vital structures. The long-term problem of skin deficiency relating to flexor tendon function is one of loss of extension from longitudinal scar shortening of the integument, even if the flexor tendons are primarily concerned with bending the digits, not straightening them. This loss of extension can only be tolerated in a hand to a certain degree without significant loss of function. This paper is largely an analysis of the flaps available and suitable for different degrees of skin deficiency and at different places along the course of the flexor system. It attempts to dispel the idea that 'any flap will do' provided the flexors are adequately covered.

Infant Exposure to Armodafinil Through Human Milk Following Maternal Use of Modafinil.

INTRODUCTION: Narcolepsy, a condition adversely affecting psychological, social, and cognitive function, is more prevalent in females of childbearing age than the general population. Modafinil and armodafinil are central nervous system stimulants approved for treatment of narcolepsy. Infant exposure to these agents through human milk has not been investigated. Poor quality medication safety information during lactation is associated with early cessation of breastfeeding and suboptimal healthcare for the breastfeeding family. MAIN ISSUE: In this case study, we measured the concentration of armodafinil (the most active form of modafinil) in human milk and infant plasma to quantify infant exposure. MANAGEMENT: The participant was a 30-year-old primipara with narcolepsy, taking modafinil (300 mg morning, 100 mg noon) while breastfeeding her 6-week-old infant despite the paucity of safety information. Armodafinil concentrations were measured in eight serial human milk samples collected over a 26-hr period and in single maternal and infant plasma samples using ultra performance liquid chromatography - tandem mass spectrometry. The average concentration of armodafinil in human milk was 1.96 mg/L; the relative infant dose was 4.85%; the theoretical infant dose was 0.294 mg/kg/day. Maternal and infant plasma concentrations of armodafinil were 12.02 mg/L and 0.19 mg/L, respectively. The participant continued to exclusively breastfeed the infant, who had normal growth and development. CONCLUSION: Based on these findings, relatively small amounts of armodafinil pass into human milk, with consequent limited infant exposure. Consideration can be given to the use of modafinil or armodafinil during breastfeeding, provided the infant is monitored. Further studies are needed to confirm these findings.

A continent-wide detailed geological map dataset of Antarctica.

A dataset to describe exposed bedrock and surficial geology of Antarctica has been constructed by the GeoMAP Action Group of the Scientific Committee on Antarctic Research (SCAR) and GNS Science. Our group captured existing geological map data into a geographic information system (GIS), refined its spatial reliability, harmonised classification, and improved representation of glacial sequences and geomorphology, thereby creating a comprehensive and coherent representation of Antarctic geology. A total of 99,080 polygons were unified for depicting geology at 1:250,000 scale, but locally there are some areas with higher spatial resolution. Geological unit definition is based on a mixed chronostratigraphic- and lithostratigraphic-based classification. Description of rock and moraine polygons employs the international Geoscience Markup Language (GeoSciML) data protocols to provide attribute-rich and queryable information, including bibliographic links to 589 source maps and scientific literature. GeoMAP is the first detailed geological map dataset covering all of Antarctica. It depicts 'known geology' of rock exposures rather than 'interpreted' sub-ice features and is suitable for continent-wide perspectives and cross-discipline interrogation.

Effect of albumin on human liver microsomal and recombinant CYP1A2 activities: impact on in vitro-in vivo extrapolation of drug clearance.

Long-chain unsaturated fatty acids inhibit several cytochrome P450 and UDP-glucuronosyltransferase (UGT) enzymes involved in drug metabolism, including CYP2C8, CYP2C9, UGT1A9, UGT2B4, and UGT2B7. Bovine serum albumin (BSA) enhances these cytochrome P450 and UGT activities by sequestering fatty acids that are released from membranes, especially with human liver microsomes (HLM) as the enzyme source. Here, we report the effects of BSA on CYP1A2-catalyzed phenacetin (PHEN) O-deethylation and lidocaine (LID) N-deethylation using HLM and Escherichia coli-expressed recombinant human CYP1A2 (rCYP1A2) as the enzyme sources. BSA (2% w/v) reduced (p < 0.05) the K(m) values of the high-affinity components of human liver microsomal PHEN and LID deethylation by approximately 70%, without affecting V(max). The K(m) (or S(50)) values for PHEN and LID deethylation by rCYP1A2 were reduced to a similar extent. A fatty acid mixture, comprising 3 µM concentrations each of oleic acid and linoleic acid plus 1.5 µM arachidonic acid, doubled the K(m) value for PHEN O-deethylation by rCYP1A2. Inhibition was reversed by the addition of BSA. K(i) values for the individual fatty acids ranged from 4.7 to 16.7 µM. Single-point in vitro-in vivo extrapolation (IV-IVE) based on the human liver microsomal kinetic parameters obtained in the presence, but not absence, of BSA predicted in vivo hepatic clearances of PHEN O-deethylation and LID N-deethylation that were comparable to values reported in humans, although in vivo intrinsic clearances were underpredicted. Prediction of the in vivo clearances of the CYP1A2 substrates observed here represents an improvement on other experimental systems used for IV-IVE.

Soft and tissue repair of the hand and digital reconstruction.

This article summarizes the current views and proposed approaches to treating soft tissue defects of the hand. The article also outlines some key considerations of digital reconstruction. There are many options in treating soft tissue defects. For defects of the hand, local flaps are primarily considered if the defects are small or moderate in size. A vascularized free flap is only considered for a defect of large size (3 cm long or larger). Thumb reconstruction is of primary importance, while reconstruction of two fingers is necessary when all fingers are lost. Reconstructions of a missing distal part of a finger or reconstruction of an entire finger if only one finger is lost are cosmetic restorations; functionally these defects do not need reconstruction. Sensation is of great importance in repair or reconstruction of the tip of the thumb or finger. Therefore, sensory evaluation is a key factor in assessing and selecting the best options of surgery.

The novel UDP glycosyltransferase 3A2: cloning, catalytic properties, and tissue distribution.

The human UDP glycosyltransferase (UGT) 3A family is one of three families involved in the metabolism of small lipophilic compounds. Members of these families catalyze the addition of sugar residues to chemicals, which enhances their excretion from the body. The UGT1 and UGT2 family members primarily use UDP glucuronic acid to glucuronidate numerous compounds, such as steroids, bile acids, and therapeutic drugs. We showed recently that UGT3A1, the first member of the UGT3 family to be characterized, is unusual in using UDP N-acetylglucosamine as sugar donor, rather than UDP glucuronic acid or other UDP sugar nucleotides (J Biol Chem 283:36205-36210, 2008). Here, we report the cloning, expression, and characterization of UGT3A2, the second member of the UGT3 family. Like UGT3A1, UGT3A2 is inactive with UDP glucuronic acid as sugar donor. However, in contrast to UGT3A1, UGT3A2 uses both UDP glucose and UDP xylose but not UDP N-acetylglucosamine to glycosidate a broad range of substrates including 4-methylumbelliferone, 1-hydroxypyrene, bioflavones, and estrogens. It has low activity toward bile acids and androgens. UGT3A2 transcripts are found in the thymus, testis, and kidney but are barely detectable in the liver and gastrointestinal tract. The low expression of UGT3A2 in the latter, which are the main organs of drug metabolism, suggests that UGT3A2 has a more selective role in protecting the organs in which it is expressed against toxic insult rather than a more generalized role in drug metabolism. The broad substrate and novel UDP sugar specificity of UGT3A2 would be advantageous for such a function.

Characterization of niflumic acid as a selective inhibitor of human liver microsomal UDP-glucuronosyltransferase 1A9: application to the reaction phenotyping of acetaminophen glucuronidation.

Enzyme selective inhibitors represent the most valuable experimental tool for reaction phenotyping. However, only a limited number of UDP-glucuronosyltransferase (UGT) enzyme-selective inhibitors have been identified to date. This study characterized the UGT enzyme selectivity of niflumic acid (NFA). It was demonstrated that 2.5 µM NFA is a highly selective inhibitor of recombinant and human liver microsomal UGT1A9 activity. Higher NFA concentrations (50-100 µM) inhibited UGT1A1 and UGT2B15 but had little effect on the activities of UGT1A3, UGT1A4, UGT1A6, UGT2B4, UGT2B7, and UGT2B17. NFA inhibited 4-methylumbelliferone and propofol (PRO) glucuronidation by recombinant UGT1A9 and PRO glucuronidation by human liver microsomes (HLM) according to a mixed (competitive-noncompetitive) mechanism, with K(i) values ranging from 0.10 to 0.40 µM. Likewise, NFA was a mixed or noncompetitive inhibitor of recombinant and human liver microsomal UGT1A1 (K(i) range 14-18 µM), whereas competitive inhibition (K(i) 62 µM) was observed with UGT2B15. NFA was subsequently applied to the reaction phenotyping of human liver microsomal acetaminophen (APAP) glucuronidation. Consistent with previous reports, APAP was glucuronidated by recombinant UGT1A1, UGT1A6, UGT1A9, and UGT2B15. NFA concentrations in the range of 2.5 to 100 µM inhibited APAP glucuronidation by UGT1A1, UGT1A9, and UGT2B15 but not by UGT1A6. The mean V(max) for APAP glucuronidation by HLM was reduced by 20, 35, and 40%, respectively, in the presence of 2.5, 50, and 100 µM NFA. Mean K(m) values decreased in parallel with V(max), although the magnitude of the decrease was smaller. Taken together, the NFA inhibition data suggest that UGT1A6 is the major enzyme involved in APAP glucuronidation.

Application of the fluorescent probe 1-anilinonaphthalene-8-sulfonate to the measurement of the nonspecific binding of drugs to human liver microsomes.

The fluorescence of 1-anilinonaphthalene-8-sulfonate (ANS) in the presence of human liver microsomes (HLMs) is altered by drugs that bind nonspecifically to the lipid bilayer. The present study characterized the relationship between the nonspecific binding (NSB) of drugs to HLMs as measured by equilibrium dialysis and the magnitude of the change in baseline ANS fluorescence. Fraction unbound in incubations of HLMs (f(u(mic))) was determined for 16 drugs (12 bases, 3 acids, and 1 neutral) with log P values in the range 0.1 to 6.7 at three concentrations (100, 200, and 500 µM). Changes in ANS fluorescence induced by each of the drugs in the presence of HLMs were measured by spectrofluorometry. Values of f(u(mic)) determined by equilibrium dialysis ranged from 0.08 to 1.0. Although NSB of the basic drugs tended to increase with increasing log P, exceptions occurred. Basic drugs generally caused an increase in ANS fluorescence, whereas the acidic and neutral drugs resulted in a decrease in ANS fluorescence. There were highly significant (p < 0.001) linear relationships between the modulus (absolute value) of the increment/decrement in ANS fluorescence and both f(u(mic)) (r = 0.90 to 0.96) and log(1 - f(u(mic))/f(u(mic))) (r = 0.85 to 0.92) at the three drug concentrations. Agreement between measured f(u(mic)) and that predicted by ANS fluorescence was very good (<10% variance) for a validation set of six compounds. The ANS fluorescence method provides an accurate measure of the NSB of drugs to HLMs. Physicochemical determinants other than log P and charge type influence the NSB of drugs to HLMs.