A knowledge-based, structural-aided discovery of a novel class of 2-phenylimidazo[1,2-a]pyridine-6-carboxamide H-PGDS inhibitors

Through an internal virtual screen at GlaxoSmithKline a distinct class of 2-phenylimidazo[1,2-a]pyridine-6-carboxamide H-PGDS inhibitors were discovered. Careful evaluation of crystal structures and SAR led to a novel, potent, and orally active imidazopyridine inhibitor of H-PGDS, 20b. Herein, describes the identification of 2 classes of inhibitors, their syntheses, and their challenges.

The exploration of aza-quinolines as hematopoietic prostaglandin D synthase (H-PGDS) inhibitors with low brain exposure

GlaxoSmithKline and Astex Pharmaceuticals recently disclosed the discovery of the potent H-PGDS inhibitor GSK2894631A 1a (IC₅₀ = 9.9 nM) as part of a fragment-based drug discovery collaboration with Astex Pharmaceuticals. This molecule exhibited good murine pharmacokinetics, allowing it to be utilized to explore H-PGDS pharmacology in vivo. Yet, with prolonged dosing at higher concentrations, 1a induced CNS toxicity. Looking to attenuate brain penetration in this series, aza-quinolines, were prepared with the intent of increasing polar surface area. Nitrogen substitutions at the 6- and 8-positions of the quinoline were discovered to be tolerated by the enzyme. Subsequent structure activity studies in these aza-quinoline scaffolds led to the identification of 1,8-naphthyridine 1y (IC₅₀ = 9.4 nM) as a potent peripherally restricted H-PGDS inhibitor. Compound 1y is efficacious in four in vivo inflammatory models and exhibits no CNS toxicity.

2,4-Diamino-8-quinazoline carboxamides as novel, potent inhibitors of the NAD hydrolyzing enzyme CD38: Exploration of the 2-position structure-activity relationships

Starting from 4-amino-8-quinoline carboxamide lead 1a and scaffold hopping to the chemically more tractable quinazoline, a systematic exploration of the 2-substituents of the quinazoline ring, utilizing structure activity relationships and conformational constraint, resulted in the identification of 39 novel CD38 inhibitors. Eight of these analogs were 10-100-fold more potent human CD38 inhibitors, including the single digit nanomolar inhibitor 1am. Several of these molecules also exhibited improved therapeutic indices relative to hERG activity. A representative analog 1r exhibited suitable pharmacokinetic parameters for in vivo animal studies, including moderate clearance and good oral bioavailability. These inhibitor compounds will aid in the exploration of the enzymatic functions of CD38, as well as furthering the study of the therapeutic implications of NAD enhancement in metabolic disease models.

SIRT4 Is a Lysine Deacylase that Controls Leucine Metabolism and Insulin Secretion

Sirtuins are NAD⁺-dependent protein deacylases that regulate several aspects of metabolism and aging. In contrast to the other mammalian sirtuins, the primary enzymatic activity of mitochondrial sirtuin 4 (SIRT4) and its overall role in metabolic control have remained enigmatic. Using a combination of phylogenetics, structural biology, and enzymology, we show that SIRT4 removes three acyl moieties from lysine residues: methylglutaryl (MG)-, hydroxymethylglutaryl (HMG)-, and 3-methylglutaconyl (MGc)-lysine. The metabolites leading to these post-translational modifications are intermediates in leucine oxidation, and we show a primary role for SIRT4 in controlling this pathway in mice. Furthermore, we find that dysregulated leucine metabolism in SIRT4KO mice leads to elevated basal and stimulated insulin secretion, which progressively develops into glucose intolerance and insulin resistance. These findings identify a robust enzymatic activity for SIRT4, uncover a mechanism controlling branched-chain amino acid flux, and position SIRT4 as a crucial player maintaining insulin secretion and glucose homeostasis during aging.

Discovery of 4-Amino-8-quinoline Carboxamides as Novel, Submicromolar Inhibitors of NAD-Hydrolyzing Enzyme CD38

Starting from the micromolar 8-quinoline carboxamide high-throughput screening hit 1a, a systematic exploration of the structure-activity relationships (SAR) of the 4-, 6-, and 8-substituents of the quinoline ring resulted in the identification of approximately 10-100-fold more potent human CD38 inhibitors. Several of these molecules also exhibited pharmacokinetic parameters suitable for in vivo animal studies, including low clearances and decent oral bioavailability. Two of these CD38 inhibitors, 1ah and 1ai, were shown to elevate NAD tissue levels in liver and muscle in a diet-induced obese (DIO) C57BL/6 mouse model. These inhibitor tool compounds will enable further biological studies of the CD38 enzyme as well as the investigation of the therapeutic implications of NAD enhancement in disease models of abnormally low NAD.

Discovery, Synthesis, and Biological Evaluation of Thiazoloquin(az)olin(on)es as Potent CD38 Inhibitors

A series of thiazoloquin(az)olinones were synthesized and found to have potent inhibitory activity against CD38. Several of these compounds were also shown to have good pharmacokinetic properties and demonstrated the ability to elevate NAD levels in plasma, liver, and muscle tissue. In particular, compound 78c was given to diet induced obese (DIO) C57Bl6 mice, elevating NAD > 5-fold in liver and >1.2-fold in muscle versus control animals at a 2 h time point. The compounds described herein possess the most potent CD38 inhibitory activity of any small molecules described in the literature to date. The inhibitors should allow for a more detailed assessment of how NAD elevation via CD38 inhibition affects physiology in NAD deficient states.

Investigation into the relationship between the gravity vector and the flow vector to improve performance in two-phase continuous flow biodiesel reactor

The following study analyzes the performance of a continuous flow biodiesel reactor/separator. The reactor achieves high conversion of vegetable oil triglycerides to biodiesel while simultaneously separating co-product glycerol. The influence of the flow direction, relative to the gravity vector, on the reactor performance was measured. Reactor performance was assessed by both the conversion of vegetable oil triglycerides to biodiesel and the separation efficiency of removing the co-product glycerol. At slightly elevated temperatures of 40-50 degrees C, an overall feed of 1.2 L/min, a 6:1 M ratio of methanol to vegetable oil triglycerides, and a 1-1.3 wt.% potassium hydroxide catalyst loading, the reactor converted more than 96% of the pretreated waste vegetable oil to biodiesel. The reactor also separated 36-95% of the glycerol that was produced. Tilting the reactor away from the vertical direction produced a large increase in glycerol separation efficiency and only a small decrease in conversion.

Design and effective synthesis of novel templates, 3,7-diphenyl-4-amino-thieno and furo-[3,2-c]pyridines as protein kinase inhibitors and in vitro evaluation targeting angiogenetic kinases

A novel class of 3,7-diphenyl-4-amino-thieno and furo[3,2-c]pyridine has been designed based on pharmacophore models of ATP competitive kinase inhibitors. Versatile synthetic methods via double Suzuki coupling to explore SAR have been established and potent inhibitors against angiogenetic targets, VEGFR2, Tie-2, and EphB4, have been successfully discovered.

Comparison of the biochemical and kinetic properties of the type 1 receptor tyrosine kinase intracellular domains. Demonstration of differential sensitivity to kinase inhibitors

Epidermal growth factor receptor (EGFR), ErbB-2, and ErbB-4 are members of the type 1 receptor tyrosine kinase family. Overexpression of these receptors, especially ErbB-2 and EGFR, has been implicated in multiple forms of cancer. Inhibitors of EGFR tyrosine kinase activity are being evaluated clinically for cancer therapy. The potency and selectivity of these inhibitors may affect the efficacy and toxicity of therapy. Here we describe the expression, purification, and biochemical comparison of EGFR, ErbB-2, and ErbB-4 intracellular domains. Despite their high degree of sequence homology, the three enzymes have significantly different catalytic properties and substrate kinetics. For example, the catalytic activity of ErbB-2 is less stable than that of EGFR. ErbB-2 uses ATP-Mg as a substrate inefficiently compared with EGFR and ErbB-4. The three enzymes have very similar substrate preferences for three optimized peptide substrates, but differences in substrate synergies were observed. We have used the biochemical and kinetic parameters determined from these studies to develop an assay system that accurately measures inhibitor potency and selectivity between the type 1 receptor family. We report that the selectivity profile of molecules in the 4-anilinoquinazoline series can be modified through specific aniline substitutions. Moreover, these compounds have activity in whole cells that reflect the potency and selectivity of target inhibition determined with this assay system.

Pharmacokinetic parameters and mechanisms of inhibition of rat type 1 and 2 steroid 5alpha-reductases: determinants for different in vivo activities of GI198745 and finasteride in the rat

The interaction of baculovirus expressed rat steroid 5alpha-reductase types 1 and 2 (r5AR1 and r5AR2) with 17beta-N-(2,5-bis(trifluoromethyl)phenyl)carbamoyl-4-aza-5alpha-androst-1-en-3-one (GI198745) was investigated at pH 7 and 37 degrees. This 5alpha-reductase inhibitor was found previously to be a time-dependent inhibitor of the two human 5alpha-reductase isozymes. In contrast, we demonstrate in the present study that although GI198745 is a potent time-dependent inhibitor of r5AR2, it is a classical rapid-equilibrium inhibitor of r5AR1. This type of behavior with human and rat 5alpha-reductases has been shown for the inhibitor 17beta-(N-tert-butylcarbamoyl)-4-aza-5alpha-androst-1-en-3-one (finasteride), a current therapy for benign prostatic hyperplasia. Inhibition of r5AR1 by GI198745 was competitive with testosterone and followed Michaelis-Menten kinetics with a K(i) value of 0.3 +/- 0.02 nM. Data for the inhibition of r5AR2 by GI198745 were consistent with a two-step mechanism, where K(i) is the dissociation constant for an initial enzyme-inhibitor complex and k(3) is the rate constant for the second slow step. The pseudo-bimolecular rate constant (k(3)/K(i)) for the association of GI198745 with r5AR2 was (2.0 +/- 0.4) x 10(7) M(-1) sec(-1). The high affinity of this inhibitor for r5AR2 was further demonstrated by the inability of the enzyme-inhibitor complex to dissociate after approximately 7 days of dialysis at 4 degrees. Both GI198745 and finasteride appear to inactivate r5AR2 by apparent irreversible modification, but are classical, reversible inhibitors of r5AR1. Therefore, we hypothesize that because of its pharmacokinetic parameters and increased potency against r5AR1, GI198745 is more effective than finasteride in preventing the growth of the rat prostate.

A water extraction, static headspace sampling, gas chromatographic method to determine MTBE in heating oil and diesel fuel

A method was developed to determine the fuel/water partition coefficient (KMTBE) of methyl tert-butyl ether (MTBE) and then used to determine low parts per million concentrations of MTBE in samples of heating oil and diesel fuel. A special capillary column designed for the separation of MTBE and to prevent coelution and a gas chromatograph equipped with a photoionization detector (PID) were used. MTBE was partitioned from fuel samples into water during an equilibration step. The water samples were then analyzed for MTBE using static headspace sampling followed by GC/PID. A mathematical relationship was derived that allowed a KMTBE value to be calculated by utilizing the fuel/water volume ratios and the corresponding PID signal. KMTBE values were found to range linearly from 3.8 to 10.9 over a temperature range of 5-40 degrees C. This analysis method gave a MDL of 0.7 ppm MTBE in the fuel and a relative average accuracy of +/-15% by comparison with an independent laboratory using purge and trap GC/ MS analysis. MTBE was found in home heating oil in residential tanks and in diesel fuel at service stations throughout the state of Connecticut. The levels of MTBE were found to vary significantly with time. Heating oil and diesel fuel from terminals were also found to contain MTBE. This research suggests thatthe reported widespread contamination of groundwater with MTBE may also be due to heating oil and diesel fuel releases to the environment. used extensively for the past 20 years as a gasoline additive (up to 15 wt %) to reduce automobile carbon monoxide and hydrocarbon emissions. The fact that MTBE is highly soluble in water (approximately 5 wt %) (3) and chemically inert when compared to other fuel constituents causes it to be often detected at high concentrations in groundwater in the vicinity of gasoline spills. The EPA has reported that low levels of MTBE in drinking water (above 40 microg/L) may cause unpleasant taste and odors and has designated MTBE as a possible human carcinogen (4). Past studies have concentrated on the reporting of MTBE levels in groundwater near gasoline spills. Happel et al. reported an MTBE occurrence rate of approximately 78% at locations where hydrocarbons have impacted groundwater (5). Johnson et al. estimate that 9,000 leaking underground fuel tanks have caused MTBE contamination at community water supplies in the 31 states surveyed (excluding California and Texas) (6). Robbins et al. reported finding a significant number of MTBE detections in groundwater samples taken at sites in Connecticut known to be contaminated by heating oil spills (7). Later, this same research group reported finding MTBE contamination to range from 9.7 to 906 mg/L in heating oil and from 74 to 120 mg/L in diesel fuel in samples collected from storage tanks in Connecticut (8). The method used to analyze these samples was based on fuel-water partitioning and GC analysis. This present study provides the detailed basis for that analytical method. MTBE fuel-water partition coefficients as a function of temperature, which are critical to the method, are also presented. This study also reports on variations in MTBE levels as a function of time observed at several residences and a service station. Analytical results are reported for samples taken from terminals as part of an effort to assess the sources of MTBE in heating oil and diesel fuel.

Detection of chemically induced DNA damage by derivative square wave voltammetry

Damage of DNA films after reaction with styrene oxide was detected using derivative square wave voltammetry. Double-stranded (ds) DNA films with initially low backgrounds developed oxidation peaks for DNA bases during incubation with styrene oxide. Films were prepared on pyrolytic graphite (PG) electrodes by casting mixtures of DNA with the poly(ester sulfonic acid) ionomer Eastman AQ38S or by covalent binding of DNA onto oxidized PG. While both types of films gave oxidation peaks in the region 0.6-1.1 V vs SCE after incubations with styrene oxide, DNA/AQ films gave the best signal-to-background ratios. Damage of DNA by reaction with styrene oxide under the electrode incubation conditions was confirmed by capillary electrophoresis. Total integrals of oxidation peaks increased with time of incubation with styrene oxide. Relative peak heights depended on the type of DNA in the order calf thymus ds DNA > salmon sperm ds DNA > supercoiled ds DNA > highly polymerized calf thymus ds DNA.

Synthesis of 4,17-diazasteroid inhibitors of human 5 alpha-reductase

The synthesis of the 17-aza isomer of finasteride is described. With the side chain amide group of the compound existing in the Z configuration the structure is similar to one of the two favored conformations of finasteride. A series of 4,17-diazasteroids was assayed against the isoenzymes of human 5 alpha-reductase.

Field examination of ground water quality as an indicator of microbiological activity at gasoline contaminated sites

Various portable electrodes and an on-line colorimetric test kit were used in the field to examine ground water quality as an indicator of natural bioremediation across two sites in Connecticut having subsurface gasoline contamination. The parameters examined included dissolved oxygen, dissolved carbon dioxide, direct redox potential (Eh), nitrate, ammonia and pH. These parameters permitted delineating regions of aerobic and anaerobic microbiological activity. Variations in these parameters over an eighteen month period along with gas chromatographic analyses of certain gasoline components in the ground water indicated that in-situ bioremediation was effective at containing the petroleum contamination at both sites. It was found that a new on-line colorimetric test kit for the determination of oxygen was more accurate than a commonly used dissolved oxygen electrode.

Inhibition of human steroid 5alpha reductases type I and II by 6-aza-steroids: structural determinants of one-step vs two-step mechanism

We have discovered that 17beta-[N,N-(diethyl)carbamoyl]-6-azaandrost-4-en-3-one is a time-dependent inhibitor of type II 5alpha-reductase, as is the drug finasteride. Unlike finasteride, the 6-aza-steroid is not a time-dependent inhibitor of type I 5 alpha-reductase. Finasteride inhibition of type II enzyme proceeds in a two-step mechanism. At pH 6 and 37 degrees C, an initial finasteride-reductase complex is formed with a K(i)(app) of 11.9 +/- 4.1 nM. In a second step, an irreversible complex is formed with a rate constant of inactivation of 0.09 +/- 0.01 s(-1). In contrast, the 6-aza-steroid is a reversible inhibitor. From the results of a simplified mathematical analysis, based on the rapid equilibrium approximation, the inhibitor and the enzyme form an initial complex with a K(i) of 6.8 +/- 0.2 nM. The reversible formation of a final complex, with an overall K(i) of 0.07 +/- 0.02 nM, is characterized by a first-order isomerization rate constant 0.0035 +/- 0.0001 s(-1) for the forward step and 0.00025 +/- 0.00006 s(-1) for the backward step. All rate constants for the two-step mechanism were obtained by using a general numerical integration method. The best fit values for the association and dissociation rate constants were 5.0 microM(-1) s(-1) and 0.033 +/- 0.008 s(-1), respectively, and the isomerization rate constants were 0.0035 +/- 0.007 s(-1) and 0.000076 +/- 0.000019 s(-1). These values correspond to an initial K(i) of 6.5 nM and an overall dissociation constant of 0.14 nM. The data presented here show that both finasteride and the 6-aza-steroid analogs are potent against type II 5alpha-reductase, although their mechanisms of inhibition are different.

Structure-activity relationships for inhibition of type 1 and 2 human 5 alpha-reductase and human adrenal 3 beta-hydroxy-delta 5-steroid dehydrogenase/3-keto-delta 5-steroid isomerase by 6-azaandrost-4-en-3-ones: optimization of the C17 substituent

A variety of C17 amide-substituted 6-azaandrost-4-en-3-ones were prepared and tested versus human type 1 and 2 steroid 5 alpha-reductase (5AR) and human adrenal 3 beta-hydroxy-delta 5-steroid dehydrogenase/3-keto-delta 5-steroid isomerase (3BHSD) in order to optimize potency versus both isozymes of 5AR and selectivity versus 3BHSD. Two series of potent and selective C17 amides were discovered, 2,5-disubstituted anilides and (arylcycloalkyl)amides. Compounds from each series with picomolar IC50's versus human type 2 5AR and low nanomolar to picomolar IC50's versus human type 1 5AR possessing 100-500-fold selectivity versus 3BHSD were identified. A conformational model to predict 3BHSD potency was developed which could rationalize 3BHSD potency within three different series of compounds. Evaluation of some optimal compounds from this series in a chronic castrated rat model of 5AR inhibitor induced prostate involution, and pharmacokinetic measurements identified compounds (9, 12, 16, and 29) with good in vivo efficacy and half-life in the dog. An intact rat model of in vivo selectivity for 5AR versus 3BHSD inhibition was also developed. Dual inhibitors of both human 5AR's may show advantages over type 2 selective 5AR inhibitors, such as finasteride (1), in the treatment of disease states which depend upon dihydrotestosterone.

Effect of the plant compound indole-3-carbinol on hepatic cholesterol homoeostasis

The aim of this study was to elucidate the effects of the compound indole-3-carbinol (I3C), which is found in cruciferous vegetables, on hepatic cholesterol homoeostasis and metabolism in male CD-1 mice. Oral administration of 500 and 750 mg I3C/kg/day to mice for 1 wk resulted in increased liver mass and microsomal protein content. Hepatic microsomal cholesterol levels were not significantly altered following treatment with 100 and 250 mg I3C/kg/day, but were significantly decreased following treatment with 500 and 750 mg/kg/day. Conversely, the lower doses of I3C administered decreased serum cholesterol levels whereas the higher doses of I3C had no effect on this parameter. Alterations in cholesterol homoeostasis by I3C were not related to liver hypertrophy, since administration of phenobarbital to mice increased liver size, but had no significant effect on hepatic microsomal or serum cholesterol levels. Activities of the hepatic enzymes cholesterol ester hydrolase and cholesterol 7 alpha-hydroxylase were not altered by I3C. However, 500 and 750 mg I3C/kg/day elevated the activity of hepatic acyl-CoA:cholesterol acyltransferase (ACAT), the enzyme responsible for the formation of hepatic cholesteryl esters. These results demonstrate that (a) I3C lowers serum cholesterol levels at concentrations that have no discernible effect on hepatic cholesterol homoeostasis, and (b) at higher doses of I3C, hepatic microsomal cholesterol levels are significantly lowered and ACAT activity is significantly elevated. These latter effects are not accompanied by changes in serum cholesterol levels and may represent compensatory mechanisms to restore cholesterol homoeostasis in the body. Mechanisms responsible for the effects of I3C on cholesterol homoeostasis are proposed.

17 beta-(N-tert-butylcarbamoyl)-4-aza-5 alpha-androstan-1-en-3-one is an active site-directed slow time-dependent inhibitor of human steroid 5 alpha-reductase 1

17 beta-(N-tert-butylcarbamoyl)-4-aza-5 alpha-androstan-1-en-3-one (finasteride), which has been approved for treatment of benign prostatic hyperplasia, is shown here to be a slow time-dependent inhibitor of human steroid 5 alpha-reductase isozyme 1. This inhibition is characterized by an initial, fast step where the inhibitor binds to the enzyme followed by a slow step that leads to a final enzyme-inhibitor complex (EI*). No recovery of activity from this EI* complex was observed after dialysis for 3 days. The formation of EI* is diminished in the presence of a competitive, reversible inhibitor, indicating that the inhibition is active site-directed. At 37 degrees C and pH 7.0, the rate constant for the second, slow inhibition step, k3, is (1.40 +/- 0.04) x 10(-3) s-1 and the pseudo-bimolecular rate constant, k3/Ki, is (4.0 +/- 0.3) x 10(3) M-1 s-1. This latter rate constant is less than the value of 2.7 x 10(5) M-1 s-1 determined for the inhibition of 5 alpha-reductase 2 by finasteride [Faller, B., Farley, D., & Nick, H. (1993) Biochemistry 32, 5705-5710].(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of neural transplantation on seizures in the immature genetically epilepsy-prone rat

To study the hypothesis that neural transplantations can alter seizure susceptibility in a genetic animal model of epilepsy, 93 pubescent genetically epilepsy-prone rats with stage 9 seizures received either bilateral inferior colliculi (N = 21) or lateral ventricle (N = 42) transplants or sham transplants (N = 30). The grafts consisted of embryonic locus ceruleus, neocortical, or cerebellar tissue. Starting 2 days after the transplantation the rats were subjected to audiogenic stimulations every other day for 61 days. Latency to the running and tonic phase, seizure severity score, and duration of the tonic and clonic phase were compared in the neural transplant and sham-operated controls. Rats that received transplants had a longer latency to the tonic phase and a shorter duration of the clonic phase than the controls. At age 110 days the rats had electrodes implanted bilaterally into the angular bundle and were kindled. No difference in kindling rate was found between the rats that received neural grafts and the sham-operated controls. Cerebrospinal fluid concentration of norepinephrine was not altered by the transplants. This study demonstrates that the anticonvulsant effects of neural transplants, using the genetically epilepsy-prone model of epilepsy, are mild.

Single-donor fibrin glue for hand burns

Early tangential excision sometimes results in considerable blood loss, prolonged operative time, and partial loss of the graft secondary to hematoma formation. Previous reports document positive hemostatic effects and improved skin fixation with fibrin "glue." The commercial preparation used in Europe, however, has not been approved by the United States Food and Drug Administration because of the high risk of hepatitis and human immunodeficiency virus transmission. Using a method developed at the University of Virginia, we applied single-donor fibrin glue as an adjunct in early excision and grafting in 16 patients (26 hands). The overall graft take was 99%. In all patients, better adherence of the split-thickness graft to the recipient bed, during and immediately after application, was noted. We have observed no negative effects with regard to infection or healing. We recommend the use of single-donor fibrin glue to reduce operative blood loss, improve survival and ease of graft application, and possibly to accelerate healing.

Nerve compression syndromes of the lower extremity

Nerve compression syndromes of the lower extremity present a challenge in differential diagnosis. Compression of the common peroneal nerve occurs relatively frequently; compression of the sciatic nerve occurs infrequently. The pattern of weakness helps distinguish lumbar root entrapment from peripheral compression syndromes. Compression syndromes must also be differentiated from diabetic, alcoholic or vasculitic neuropathy. Recovery correlates with the degree and duration of nerve injury. Thus, early diagnosis and treatment are important.

Application of single-donor fibrin glue to burns

Early tangential excision and immediate grafting of the burn-injured patient has been shown to be effective. Along with the use of this technique, however, comes the potential for significant blood loss, prolonged operative time, and partial loss of graft due to underlying hematoma formation. Based on experience using a pooled fibrinogen preparation, European and Japanese surgeons have provided evidence for the positive hemostatic and skin transplant fixation effects of fibrin glue. This commercial preparation, however, has not been approved by the U.S. Food and Drug Administration for use in the United States because of high risk of hepatitis and HIV transmission. Using a method of preparing highly concentrated fibrinogen utilizing standard blood bank techniques developed at the University of Virginia, we have applied single-donor fibrin glue as an adjunct in the early excision and grafting of 26 patients. Since we have been using fibrin glue, we have noted a marked reduction in operative blood loss and time involved in obtaining hemostasis. Additionally, we have found the application of the grafts to be facilitated by the "stickiness" of the recipient bed. In follow-up, grafts applied utilizing the fibrin glue technique have proceeded to uncomplicated wound healing with an overall 98% graft take.

Improvement in the resolution of o-phthalaldehyde derivatized amino acids by applying gradient steepness optimization to five reversed-phase columns of different lengths and particle sizes

Twenty-two o-phthalaldehyde (OPA) derivatized amino acids were separated on five different reversed-phase, octadecyl columns. Each column was packed with the same type of spherical silica on which matched bonding chemistry had been performed. Columns of 250, 150 or 50 mm x 4.5 mm I.D. were packed with 5 microns particles, and columns of 100 or 50 mm x 4.5 mm I.D. were packed with 3 microns particles. Snyder's linear solvent strength gradient optimization method was used to determine the optimum gradient steepness by maximizing the resolution of four pairs of adjacent OPA-derivatized amino acids. An asymptotic dependence of improvement in resolution with increase in gradient time was obtained for each pair of compounds on each column. For short (50 mm) columns, resolution of very closely eluting compounds required the use of gradient steepness parameters as low as 0.05 and 0.02, due to the low efficiencies intrinsic to these short column lengths.

Pediatric burns

Burns are the second most common cause of death in childhood. More than half of pediatric burns are partial-thickness scald burns; the majority occur in the kitchen. Generally, minor burns may be treated on an outpatient basis, while moderate burns are treated in a community hospital. Children with major burns should be transferred to a regional burn unit as soon as possible after stabilization, provision of fluids and, if necessary, intubation.

High-performance liquid chromatography of substituted p-benzoquinones and p-hydroquinones. II. Retention behavior, quantitative structure-retention relationships and octanol-water partition coefficients

The retention behavior of methoxy-substituted p-benzoquinones and the corresponding hydroquinones in reversed-phase chromatography was examined on octylsilica and two octadecylsilica stationary phases and with five hydroorganic mobile phases containing acetonitrile, methanol or tetrahydrofuran and additionally in most cases (NH3OH)3PO4 used as a reducing and buffering agent. The retention order of benzoquinones and hydroquinones was the same on each stationary phase with either methanol or acetonitrile as the organic modifier. On the other hand, minor differences in the retention order were observed with the various stationary phases. In all cases, satisfactory quantitative structure-retention relationships (QSRRs) were found and the data suggest that the differences in the retention behaviour of octadecylsilicas used in this study are silanophilic interactions which, together with solvophobic interaction contribute to the retention of these eluites. Further analysis showed that QSRRs of sterically crowded molecules must take into account reduced surface area available for binding. The retention data obtained with use of aqueous tetrahydrofuran as mobile phase failed to give rise to satisfactory QSRRs. This was attributed to selective solvation of eluite by tetrahydrofuran and/or nearly equipotent binding of eluite and tetrahydrofuran to stationary phase.

High-performance liquid chromatography of substituted p-benzoquinones and p-hydroquinones. I. Interplay of on-column redox reaction and the chromatographic retention process

Chromatograms exhibiting unusual elution profiles were obtained in the reversed-phase chromatography of methoxy-substituted hydroquinones with hydro-organic mobile phases. The dependence of the elution profiles on the flow-rate and the mass of injected sample indicated that peaks were caused by the interplay of the chromatographic retention process and the concomitant oxidation of hydroquinones in the chromatographic column. The reaction was first investigated in free solution and the first-order rate constants and equilibrium constants were estimated for the oxidation of 2-methoxy-, 2,5-dimethoxy-, 2,6-dimethoxy-, 2,3,5-trimethoxy- and 2,3,5,6-tetramethoxyhydroquinones. The effect of Fe3+ and Cu2+ on the oxidation of 2,6-dimethoxyhydroquinone was also examined and it was found that Fe3+ caused a ten-fold increase in the reaction rate. The oxidation of 2-methoxy- and 2,6-dimethoxyhydroquinones in the chromatographic column showed first-order and zerothorder kinetic behavior at low and high sample loads, respectively. Such change in reaction order is typical for heterogeneous reactions that follow Langmuir-Hinshelwood kinetics and suggests the existence of catalytically active sites on the silica. Upon purging the columns with EDTA, on-column oxidation of the hydroquinones was attenuated so that no reaction zones appeared on the chromatogram. Subsequent loading of the column with Fe3+, however, gave rise to broad reaction zones and possibly to total conversion of the hydroquinones to benzoquinones in the column. In all cases investigated the rate of oxidation was much higher in the column than in free solution. On the basis of the results obtained here, heavy mental-catalyzed reaction at the stationary phase surface is proposed to be the dominant mechanism for the oxidation reaction examined here.

HPLC analysis of underivatized fatty acids in margarines

The composition of the underivatized fatty acids in margarines was determined by high performance liquid chromatography (HPLC). A 50-min analysis gave not only the distribution of the cis- and trans-isomers of the 18 carbon-length, but also a quantitative measure of seven of the underivatized fatty acids studied. High concentrations of the essential fatty acid, linoleic acid, were found in the four margarine samples. Results of the quantitation, reproducability of the HPLC analysis, and stability of the standards are discussed. It was found that the developed HPLC analysis was able to adequately separate the geometric isomers, linoleic acid (18:2 delta 9c, 12c) from linolelaidic acid (18:2 delta 9t, 12t). However, a mixture of the other two isomers, 18:2 delta 9c, 12t and 18:2 delta 9c, 12c coeluted together between the peaks due to the 18:2 delta 9c, 12c and 18:2 delta 9t, 12t isomers. This study did not attempt to separate the various positional isomers of underivatized fatty acids.

Fluorescent assay of total serum cholesterol, with use of gas-liquid chromatography to study saponification efficiency

We describe a fluorescent determination of total cholesterol in serum for which the accuracy and precision are comparable to that for the method of Abell-Kendall, a method of generally accepted accuracy. By the use of quality reagents and the rigorous exclusion of water, the strong fluorophor that develops on reacting concentrated sulfuric acid with cholesterol can be used to quantitatively determine the total cholesterol in serum. We used gas-liquid chromatography to monitor the extent of saponification of the cholesterol esters, because we found them to have fluorescent efficiencies that differed from that of free cholesterol. Sodium methoxide in methanol/methylene chloride (1/3 by vol) was shown by gas-liquid chromatography to very effectively saponify the cholesterol esters in serum.

Fluorescent assay of total serum cholesterol, with use of gas-liquid chromatography to study saponification efficiency

We describe a fluorescent determination of total cholesterol in serum for which the accuracy and precision are comparable to that for the method of Abell-Kendall, a method of generally accepted accuracy. By the use of quality reagents and the rigorous exclusion of water, the strong fluorophor that develops on reacting concentrated sulfuric acid with cholesterol can be used to quantitatively determine the total cholesterol in serum. We used gas-liquid chromatography to monitor the extent of saponification of the cholesterol esters, because we found them to have fluorescent efficiencies that differed from that of free cholesterol. Sodium methoxide in methanol/methylene chloride (1/3 by vol) was shown by gas-liquid chromatography to very effectively saponify the cholesterol esters in serum.

Effect of antacids on absorption of clorazepate

The effect of a magnesia and alumina antacid suspension on the absorption of clorazepate dipotassium was studied in 15 normal healthy adult subjects who ingested a 15-mg dose of clorazepate alone or with single or multiple doses of antacid. The results of this three-period randomized complete crossover study showed a trend of initially slower absorption and lower peak nordiazepam plasma levels when administered with the antacid suspension. However, there were no significant differences among treatments in the extent of absorption as measured by the area under the plasma level-time curves. Clorazepate plasma levels were of relatively short duration and similar for all treatments. The urinary excretion pattern was likewise comparable with conjugated oxazepam, the major species measured. Plasma elimination half-lives of nordiazepam and clorazepate were not affected by the antacid treatments.