Effect of amino acid enriched diets on hemolymph amino acid composition in honey bees

Amino acids (AAs) are an abundant class of nectar solutes, and they are involved in the nectar attractiveness to flower visitors. Among the various AAs, proline is the most abundant proteogenic AA, and γ-amino butyric acid (GABA) and β-alanine are the two most abundant non-proteogenic AAs. These three AAs are known to affect insect physiology, being involved in flight metabolism and neurotransmission. The aim of this study was to investigate the effects of artificial diets enriched with either β-alanine, GABA, or proline on consumption, survival, and hemolymph composition in honey bees belonging to two different ages and with different metabolism (i.e., newly emerged and foragers). Differences in feed intake among diets were not observed, while a diet enriched with β-alanine improved the survival rate of newly emerged honey bees compared to the control group. Variations in the hemolymph AA concentrations occurred only in newly emerged honey bees, according to the diet and the time of hemolymph sampling. A greater susceptibility of young honey bees to enriched diets than older honey bees was observed. The variations in the concentrations of hemolymph AAs reflect either the accumulation of dietary AAs or the existence of metabolic pathways that may lead to the conversion of dietary AAs into different ones. This investigation could be an initial contribution to studying the complex dynamics that regulate hemolymph AA composition and its effect on honey bee physiology.

The Role of Amino Acids in Neurotransmission and Fluorescent Tools for Their Detection

Neurotransmission between neurons, which can occur over the span of a few milliseconds, relies on the controlled release of small molecule neurotransmitters, many of which are amino acids. Fluorescence imaging provides the necessary speed to follow these events and has emerged as a powerful technique for investigating neurotransmission. In this review, we highlight some of the roles of the 20 canonical amino acids, GABA and β-alanine in neurotransmission. We also discuss available fluorescence-based probes for amino acids that have been shown to be compatible for live cell imaging, namely those based on synthetic dyes, nanostructures (quantum dots and nanotubes), and genetically encoded components. We aim to provide tool developers with information that may guide future engineering efforts and tool users with information regarding existing indicators to facilitate studies of amino acid dynamics.

Space Flight Diet-Induced Deficiency and Response to Gravity-Free Resistive Exercise

Immune system dysregulation is among the many adverse effects incurred by astronauts during space flights. Omega-3 fatty acids, β-alanine, and carnosine are among the many nutrients that contribute to immune system health. For space flight, crewmembers are prescribed a diet with a macronutrient composition of 55% carbohydrate, 30% fat, and 15% protein. To quantify omega-3 fatty acid, β-alanine and carnosine intakes from such a diet, and to examine each nutrient's impact on exercise performance, 21 participants adhered to the aforementioned macronutrient ratio for 14 days which was immediately followed by a workout performed on gravity-independent resistive exercise hardware. Results included daily omega-3 fatty acid intakes below the suggested dietary intake. Daily omega-3 fatty acid, β-alanine and carnosine intakes each correlated with non-significant amounts of variance from the workout's volume of work. Given the nutritional requirements to maintain immune system function and the demands of in-flight exercise countermeasures for missions of increasingly longer durations current results, in combination with previously published works, imply in-flight supplementation may be a prudent approach to help address the physiological and mental challenges incurred by astronauts on future space flights.

Determination of β-N-oxalyl-L-α,β-diaminopropionic acid and homoarginine in Lathyrus sativus and Lathyrus cicera by capillary zone electrophoresis

BACKGROUND

Lathyrus species as legumes represent an alternative protein source for human and animal nutrition. Heavy consumption of these species can lead to lathyrism, caused by the non-protein amino acid β-N-oxalyl-l-α,β-diaminopropionic acid (β-ODAP). Currently, there is no well-defined level below which β-ODAP is considered non-toxic. In this work, the β-ODAP content was determined in L. sativus and L. cicera samples to assess their potential toxicity. Homoarginine is another non-protein amino acid found in Lathyrus spp. with interesting implications for human and animal nutrition.

RESULTS

The level of β-ODAP found in these two species ranged from 0.79 to 5.05 mg g(-1). The homoarginine content of the samples ranged from 7.49 to 12.44 mg g(-1).

CONCLUSION

This paper describes an accurate, fast and sensitive method of simultaneous detection and quantification of β-ODAP and homoarginine by capillary zone electrophoresis in L. cicera and L. sativus seeds. Moreover, several methods of extraction were compared to determine the highest performance.

Investigation of biomolecules trapped in fluid inclusions inside halite crystals by Raman spectroscopy

Raman spectroscopy was tested for the identification of biomolecules (glycine, L-alanine, β-alanine, L-serine, and γ-aminobutyric acid) trapped in fluid inclusions inside halite model crystals. The investigated biomolecules represent important targets for future astrobiological missions. We know from terrestrial conditions that organic molecules and microorganisms can be sealed within fluid inclusions and can survive intact even for hundreds of millions of years. Raman spectroscopy is currently being miniaturized for future extraterrestrial planetary exploration (ExoMars 2018). Raman spectroscopy has shown the ability to detect investigated aminoacids nondestructively without any sample preparation, in short measurement times, and in relatively low concentrations. The number of registered Raman bands of investigated aminoacids and their intensity clearly correlate with the given concentration of biomolecules within fluid inclusions.

The achievement of mass balance by simultaneous quantification of floxuridine prodrug, floxuridine, 5-fluorouracil, 5-dihydrouracil, α-fluoro-β-ureidopropionate, α-fluoro-β-alanine using LC-MS

5-Fluoro-2'-deoxyuridine (floxuridine, 5-FdUrd) and 5-fluorouracil (5-FU) are widely used for the treatment of colorectal cancers. The mechanisms of action of 5-FdUrd and 5-FU, as well as the biochemical pathway responsible for their metabolism, are well understood. Identification of every metabolite and achieving mass balance by conventional UV absorption-based HPLC analysis are not feasible because the metabolites beyond 5-FU in the 5-FdUrd metabolic pathway are undetectable by UV light. We therefore established a mass spectrometry method, designed for fast and convenient analysis, for simultaneously measuring 5-FdUrd, 5-FU, and their metabolites. Linearity, precision and accuracy were validated in the concentration ranges studied for each compound. Hydrolysis studies of 5-FdUrd and amino acid mono ester prodrugs of 5-FdUrd in Capan-2 cell homogenates were carried out and the achievement of mass balance was established with this method (recovery of 5'-O-l-leucyl-FdUrd was 96.6-108.2% and that of 5-FdUrd was 79.4-117.4%). This simple LC-MS method achieves reliable quantitation and mass balance of 5-FdUrd, 5-FU, and their metabolites and can be effectively utilized for further kinetic studies.

Validation of an isocratic HPLC method to detect 2-fluoro-beta-alanine for the analysis of dihydropyrimidine dehydrogenase activity

The efficacy of the chemotherapeutic drug 5'-fluorouracil is reduced by catabolism to 2'-fluoro-beta-alanine (FBAL), a three-step reaction in which dihydropyrimidine dehydrogenase (DPD) catalyzes the rate-limiting step. To study in vitro DPD activity, we developed and validated an isocratic, reverse-phase HPLC method to detect and quantify FBAL without using multiple columns or radiolabeled substrates. Pre-column derivatization of FBAL was performed using o-phthalaldehyde in the presence of two sulfur donors, ethanthiol or beta-mercaptoethanol, and the resulting products assayed. Calibration curves were linear over a range of 10-200 microg/ml and the method was successfully applied to the examination of DPD activity in cultured cells.

Identification and monitoring of intermediates and products in the acrylamide pathway using online analysis

Acrylamide formation under controlled processing conditions was studied in a starch matrix by analyzing volatile compounds in the gas phase using online mass spectrometry. Compounds were identified using mass spectral analysis, authentic standards, and the labeling patterns from isotopically labeled asparagine and sugars. Acrylamide, 3-aminopropanamide, methylpyrazine, 3-oxopropanamide, and aminopropan-2-one were assigned to the ions at m/ z 72, 89, 95, 88, and 74, respectively. Ion m/ z 60 was proposed as the transamination product of glyoxal, but labeling experiments did not support this assignment. Temporal formation of acrylamide and related compounds was studied in 51 samples containing asparagine and selected sugars or carbonyls. Data from the experiments were analyzed to investigate correlations between the amounts of acrylamide, intermediates, and pyrazines formed. A strong correlation between 3-aminopropanamide and acrylamide was found in all samples, whereas other correlations were reactant specific. Preliminary multiway analysis of the data identified temporal similarities in the ion profiles and showed that dynamic monitoring can follow the production and utilization of intermediates leading to acrylamide.

Involvement of tyrosine residues, N-terminal amino acids, and beta-alanine in insect cuticular sclerotization

During sclerotization of insect cuticle the acyldopamines, N-acetyldopamine (NADA) and N-beta-alanyldopamine (NBAD), are oxidatively incorporated into the cuticular matrix, thereby hardening and stabilizing the material by forming crosslinks between the proteins in the cuticular matrix and by forming polymers filling the intermolecular spaces in the cuticle. Sclerotized cuticle from the locust, Schistocerca gregaria, and the beetle, Tenebrio molitor, was hydrolyzed in dilute hydrochloric acid, and from the hydrolysates some components presumably degradation products of cuticular crosslinks were isolated. In two of the components, the sidechain of 3,4-dihydroxyacetophenone was linked to the amino groups of glycine and beta-alanine, respectively, and in the third component to the phenolic group of tyrosine. These three compounds, glycino-dihydroxyacetophenone, beta-alanino-dihydroxyacetophenone, and O-tyrosino-dihydroxyacetophenone, as well as the previously reported compound, lysino-dihydroxyacetophenone [Andersen, S.O., Roepstorff, P., 2007. Aspects of cuticular sclerotization in the locust, Schistocerca gregaria, and the beetle, Tenebrio molitor. Insect Biochem. Mol. Biol. 37, 223-234], are suggested to be degradation products of cuticular crosslinks, in which amino acid residues formed linkages to both the alpha- and beta-positions of the sidechain of acyldopamines.

Influence of sulfur fertilization on the amounts of free amino acids in wheat. correlation with baking properties as well as with 3-aminopropionamide and acrylamide generation during baking

Sulfur (S) fertilization has been long-known to influence the amounts of total free amino acids in plants. To determine the impact of S deficiency in wheat on the concentration of, in particular, free asparagine, the spring wheat cultivar 'Star' was grown in a laboratory scale (5 L pot) at five different levels of S fertilization. After maturity, the kernels were milled into white flours (1-5) and analyzed for their contents of total S and total nitrogen as well as for free amino acids and glucose, fructose, maltose, and sucrose. Extremely high concentrations of free asparagine (Asn; 3.9-5.7 g/kg) were determined in flours 1 and 2 (30 and 60 mg of S), whereas much lower amounts (0.03-0.4 g/kg) were present in flours grown at higher S levels. The amounts of the reducing carbohydrates were, however, scarcely affected by S fertilization. In agreement with the high amount of Asn in flours 1 and 2, heating of both flours led to the generation of very high amounts of acrylamide (1.7-3.1 mg/kg) as well as of 3-aminopropionamide (40-76 mg/kg). Similar concentrations were measured in crispbread prepared from both flours. Application of rheological measurements on doughs prepared from each flour and a determination of the loaf volume of bread baked therefrom clearly indicated that flours 1 and 2 would be excluded from commercial bread processing due to their poor technological properties. Two commercial flours showed relatively low concentrations of acrylamide after a thermal treatment.

Carnosine, taurine and enzyme activities of human skeletal muscle fibres from elderly subjects with osteoarthritis and young moderately active subjects

Ageing is associated with a reduction in muscle carnosine (beta-alanyl-L-histidine), but there are no data on the changes specifically in type I and type II muscle fibres. Given the higher carnosine content of type II fibers, changes observed in whole muscle may be secondary to a shift in fibre composition. Carnosine, beta-alanine, histidine, taurine, and citrate synthase (CS) and glycogen phosphorylase (Phos), were measured in pools of single muscle fibres from freeze-dried muscle biopsies of vastus lateralis of nine elderly sedentary subjects (65-80 years) with osteoarthritis of the knee and undergoing total knee replacement, and nine young moderately active healthy subjects (20-35 years). Fibres were characterised as type I or II by myosin ATPase activity. Carnosine was 53.2% lower in type II fibres of older subjects resulting in an estimated 7% (and most probably still higher) decline in intracellular physico-chemical buffering capacity. Younger subjects showed higher CS activities in type I and higher Phos activities in type II fibres. These differences were less apparent in elderly subjects. Possible causes for the change in the carnosine content are reduced physical activity, reduced meat intake, or the result of progressive denervation.

Quantitation of 3-aminopropionamide in potatoes-a minor but potent precursor in acrylamide formation

3-Aminopropionamide (3-APA) has recently been suggested as a transient intermediate in acrylamide (AA) formation during thermal degradation of asparagine initiated by reducing carbohydrates or aldehydes, respectively. 3-APA may also be formed in foods by an enzymatic decarboxylation of asparagine. Using a newly developed method to quantify 3-APA based on liquid chromatography/tandem mass spectrometry, it could be shown that the biogenic amine was present in several potato cultivars in different amounts. Further experiments indicated that 3-APA is formed during storage of intact potatoes (20 or 35 degrees C) or after crushing of the cells. The heating of 3-APA under aqueous or low water conditions at temperatures between 100 and 180 degrees C in model systems always generated more AA than in the same reaction of asparagine, thereby pointing to 3-APA as a very effective precursor of AA. While the highest yields measured were about 28 mol % in the presence of carbohydrates (170 degrees C; aqueous buffer), in the absence of carbohydrates, 3-APA was even converted by about 63 mol % into AA upon heating at 170 degrees C under aqueous conditions. Propanoic acid amides bearing an amino or hydroxy group in the alpha-position, such as 2-hydroxypropionamide and l-alaninamide, were ineffective in AA generation indicating that elimination occurs only from the beta-position.

Acid-neutralizing activity during amino acid fermentation by Porphyromonas gingivalis, Prevotella intermedia and Fusobacterium nucleatum

Acid-neutralizing activity during amino acid fermentation by washed cells of Porphyromonas gingivalis, Prevotella intermedia and Fusobacterium nucleatum was studied. When the washed cells of these strains were anaerobically incubated in the presence of aspartylaspartic acid or glutamylglutamic acid for P. gingivalis, aspartic acid for P. intermedia and glutamic acid for F. nucleatum at an initial pH of 5.0 or 5.5, the pH of the incubation mixtures rose toward neutral. F. nucleatum had the highest acid-neutralizing activity, followed by P. intermedia and P. gingivalis. The P. intermedia and F. nucleatum cells were used to measure the amounts of base produced at a fixed pH of 5.0. These cells generated significant amounts of base at pH 5.0 along with the production of organic acids and ammonia from aspartic or glutamic acid. Acid-base balance theoretically calculated from the amounts of consumed substrate and end products implies that the acid-neutralizing activity was derived from the decrease in acidity during the fermentation of amino acid into organic acids and ammonia.

Beta-alanine-oxalic acid (1:1) hemihydrate crystal: structure, 13C NMR and vibrational properties, protonation character

The crystal structure of beta-alanine-oxalic acid (1:1) hemihydrate complex has been reinvestigated by X-ray diffraction method at 293 K. Formation of monoclinic crystal system belonging to C2/c space group and consisting of semi-oxalate chains, diprotonated beta-alanine dimers and water molecules bonded to both these units is confirmed. New results are obtained for distances in the carboxylic groups and hydrogen bonds. These structural observations are used for protonation degree monitoring on the carboxylic oxygen atoms. They are in accordance with our vibrational study. The 13C NMR spectra provide insights into the solid structure of this complex, character of its hydrogen bonds and the beta-alanine protonation.

Beta-alanine-hydrochloride (2:1) crystal: structure, 13C NMR and vibrational properties, protonation character

The crystal structure of beta-alanine-hydrochloride (2:1) complex (2A-HCl) has been determined by X-ray diffraction method at 298 and 100 K as monoclinic, space group C2/c, Z=4. The crystal comprises chloride anions and protonated beta-alanine dimers: two beta-alanine zwitterions are joined by strong, symmetric (Ci) hydrogen bond with the O...O distance of 2.473 A at room temperature. Powder FT-IR and FT-Raman as well as solid state 13C NMR spectra provide insights into the solid structure of this complex, character of its hydrogen bonds and the beta-alanine protonation.

Development of a Simultaneous Analysis Method for Carbofuran and Its Three Derivative Pesticides in Water by GC/MS with Temperature Programmable Inlet On-column Injection

A simultaneous analytical method was examined for carbofuran and its derivative pesticides in water. Since carbofuran derivatives are hydrolyzed to carbofuran in water, the liquid-liquid extraction method was used to obtain an accurate concentration value. Moreover, since these compounds are easily decomposed at the GC/MS injection port, temperature programmable inlet on-column injection was used. By combining the two methods, a sensitive analytical method was established without hydrolysis and thermal decomposition. As a result of recovery experiments using distilled water, river water and tap water, acceptable recovery rates and favorable reproducibility were obtained. This method was used in a field investigation to determine carbofuran and its derivative pesticides in river water taken from three points of the Y river over a period of one year. Carbofuran, benfuracarb, and carbosulfan were detected and corresponded to the period when these pesticides were used in the area. Although benfuracarb and carbosulfan using traditional methods are believed to easily hydrolyze and thermally decompose during the analytical process, by using our method they can be detected.

Simultaneous determination of F-beta-alanine and beta-alanine in plasma and urine with dual-column reversed-phase high-performance liquid chromatography

F-beta-Alanine and beta-alanine were detected in plasma and urine samples with fluorescence detection of orthophthaldialdehyde derivatives of F-beta-alanine and beta-alanine after separation with dual-column reversed-phase HPLC. The detection limits of F-beta-alanine and beta-alanine in the HPLC system were approximately 0.3 and 0.7 pmol, respectively. The procedure proved to be very reproducible with intra-assay RSDs and inter-assay RSDs being less than 8%. The usefulness of the method was demonstrated by the analysis of the F-beta-alanine and beta-alanine concentrations in plasma and urine samples from tumor patients treated with S-1 (Tegafur, 5-chloro-2,4-dihydroxypyridine and potassium oxonate in a molar ratio of 1:0.4:1).

Determination of five pesticide residues in oranges by matrix solid-phase dispersion and liquid chromatography to estimate daily intake of consumers

Residues of benzoylphenylurea insecticides (diflubenzuron, hexaflumuron, and flufenuxuron), carboxamide acaricides (hexythiazox), and carbamate insecticides (benfuracarb) were determined in 150 orange fruit samples from September 1998 to June 1999, to estimate exposure of the Valencian population to oranges contaminated with these newly developed pesticides. The method for monitoring these residues is based on matrix solid-phase dispersion and liquid chromatography with UV or atmospheric pressure chemical ionization/mass spectrometry (APCI/MS) detection. Orange samples representing 11 varieties were collected from an agricultural cooperative and examined for the 5 pesticides. In 74.6% of all analyzed samples, the pesticide residues were below detection limits, which ranged from 0.002 to 0.05 mg/kg. Residues were detected in 25.4% of the samples, with higher incidences of diflubenzuron, flufenuxuron, hexythiazox, and benfuracarb; hexaflumuron residues were detected only occasionally. Two different pesticides exceeded maximum residue limits (MRLs) in 4 (2.7%) of the orange samples. Diflubenzuron surpassed 1 mg/kg MRL in 3 samples and flufenuxuron exceeded the 0.3 mg/kg MRL in 3 samples. The estimated daily intake of the 5 pesticide residues during the period was 0.077 microg/kg body weight per day. This value is much lower than the total admissible daily intake proposed by the Food and Agricultural Organization and the World Health Organization.

Blood carbofuran concentrations in suicidal ingestion cases

We describe four fatal cases due to ingestion of carbofuran, a carbamate insecticide. Carbofuran was detected in the gastric contents using thin layer chromatography (TLC) and gas chromatography/mass spectrophotometry (GC/MS), and quantified in the blood using a gas chromatograph equipped with nitrogen-phosphorus detector (NPD). Fatal concentrations of carbofuran in blood ranged from 0.32 to 11.6 microg/ml.

Quantification of free and bound pantothenic acid in foods and blood plasma by a stable isotope dilution assay

A stable isotope dilution assay for quantification of pantothenic acid in food and blood plasma uses a 4-fold labeled isotopomer of the vitamin as an internal standard. Pantothenic acid and its labeled analogue were detected as trimethylsilyl derivatives by gas chromatography-mass spectrometry, showing a minimized spectral overlap. In starch a detection limit of 44 microg/kg, an intrasample relative standard deviation of 6.7%, and recovery values ranging between 97.5 and 99.4% were determined. Total pantothenic acid content was determined in rice, milk powder, apple juice, and blood plasma after enzymatic hydrolysis of the vitamin's conjugates; free pantothenic acid was quantified prior to enzyme treatment. Almost all results were found to be in good agreement with literature data.

Forensic toxicological implication of acute fatal poisoning cases due to benfuracarb ingestion

We describe here three cases involving acute fatalities due to benfuracarb ingestion and the forensic toxicological implications. Benfuracarb, a carbamate insecticide and its main metabolite carbofuran, were detected using thin layer chromatography (TLC) and gas chromatography/mass spectrophotometry (GC/MS) after extraction with ethyl acetate and then quantified using gas chromatography (GC) equipped with NPD. The blood levels of benfuracarb and carbofuran were in the range of 0.30-2.32 microg/ml and 1.45-1.47 microg/ml, respectively. Benfuracarb was not detected in urine, but carbofuran was detected in the range of 0.53-2.66 microg/ml.

Amino acids in the Martian meteorite Nakhla

A suite of protein and nonprotein amino acids were detected with high-performance liquid chromatography in the water- and acid-soluble components of an interior fragment of the Martian meteorite Nakhla, which fell in Egypt in 1911. Aspartic and glutamic acids, glycine, alanine, beta-alanine, and gamma-amino-n-butyric acid (gamma-ABA) were the most abundant amino acids detected and were found primarily in the 6 M HCl-hydrolyzed, hot water extract. The concentrations ranged from 20 to 330 parts per billion of bulk meteorite. The amino acid distribution in Nakhla, including the D/L ratios (values range from <0.1 to 0.5), is similar to what is found in bacterially degraded organic matter. The amino acids in Nakhla appear to be derived from terrestrial organic matter that infiltrated the meteorite soon after its fall to Earth, although it is possible that some of the amino acids are endogenous to the meteorite. The rapid amino acid contamination of Martian meteorites after direct exposure to the terrestrial environment has important implications for Mars sample-return missions and the curation of the samples from the time of their delivery to Earth.

Alterations of intratumoral pharmacokinetics of 5-fluorouracil in head and neck carcinoma during simultaneous radiochemotherapy

The kinetics of local drug uptake and metabolism of the anticancer drug 5-fluorouracil (5-FU) has been monitored by means of 19F nuclear magnetic resonance spectroscopy in 17 patients with neck tumors during concurrent radiochemotherapy. All of the patients underwent an accelerated hyperfractionated, concomitant-boost radiochemotherapy with 5-FU [600 or 1000 mg/m2 of body surface (b.s.)] and carboplatin (70 mg/m2 of b.s.). Serial 19F nuclear magnetic resonance spectra were obtained during and after the administration of 5-FU in a 15-T scanner with the use of a 5-cm diameter surface coil positioned on a cervical lymph node metastasis. Examinations were performed at day 1 of therapy and, in 13 patients, also after 43.5 Gy of irradiation at day 1 of the second chemotherapy cycle. Resonances of 5-FU and the catabolites 5,6-dihydro-5-fluorouracil (DHFU) and alpha-fluoro-beta-alanine (FBAL) were resolved in the tumor spectra. The median of the 5-FU and FBAL levels was significantly higher (more than 2-fold) at the second compared with the first examination, whereas the level of DHFU did not change. This effect could indicate an increased delivery of 5-FU into the interstitial space of the tumor in the course of the combined treatment, which would result in an enhanced exposure of the tumor cells to the drug. A potential mechanism for synergy between radio- and chemotherapy is discussed, but alternative mechanisms are also being considered. The findings indicate that a method is available to rationally address the design of dosing schedules in concurrent therapy regimens.

Matrix solid-phase dispersion microextraction and determination by high-performance liquid chromatography with UV detection of pesticide residues in citrus fruit

A multiresidue method based on matrix solid-phase dispersion (MSPD) microextraction was studied to determine the carbamate, benfuracarb, and urea insecticides, diflubenzuron, flufenoxuron hexaflumuron and hexythiazox, used in control of citrus pests. Optimisation of different parameters, such as the type of solid support for matrix dispersion, elution solvents and the clean-up step were carried out. The method used 0.5 g of orange sample, C8 bonded silica as MSPD sorbent and dichloromethane as eluting solvent. Recoveries, at spiked concentrations below the maximum residue levels established by Spanish Government, were between 74 and 84% with relative standard deviations ranging from 2 to 4%. The limits of quantification were from 0.15 to 0.25 microgram/g using high-performance liquid chromatography with UV detection at 200 nm. The method may be useful as a screening protocol for the determination of these newly developed pesticides in citrus samples.

Identification of low-molecular-weight compounds in goat epididymis using multinuclear nuclear magnetic resonance

Multinuclear nuclear magnetic resonance (NMR) (1H, 13C, and 31P) studies have been performed on aqueous solutions of lyophilysates of cell-free extract, epididymal fluid, and intact cells from caput and cauda regions of epididymis of sacrificed goats. Identification of low-molecular-weight compounds present in different maturation phases of spermatozoa has been carried out. Several low-molecular-weight compounds have been identified by assigning 600 MHz 1H NMR spectra with the help of two-dimensional homonuclear and heteronuclear correlation spectroscopy such as double quantum filtered correlation spectroscopy and heteronuclear single quantum correlation spectroscopy. Homonuclear coupling constants have also been used to get unambiguous assignments of resonances. NMR data were compared with those of standard samples measured at same pH and with those reported in the literature. Identification of several amino acids, carbohydrates, and lipids have been made and their presence has been discussed in relation to their relevance to sperm functions. The presence of beta-alanine and hypotaurine has been reported for the first time in goat epididymis.

Superiority of hepatic arterial infusion in preventing catabolism of 5-FU compared with portal vein infusion revealed by an in vivo 19F NMR study

PURPOSE

The aim of this study was to identify the route of administration of 5-FU with the greatest pharmacological advantage in a rat model using non-invasive in vivo 19F nuclear magnetic resonance (NMR) spectroscopy.

METHODS

5-FU (50 mg/kg) was administered to anesthetized Wistar rats cannulated into the hepatic artery, portal vein or tail vein and 11 NMR spectra were acquired from the liver region to 60.5 min every 5.5 min.

RESULTS

With systemic i.v. (tail vein) infusion, the 19F-NMR signal for 5-FU from the liver region peaked in the first spectrum (0-5.5 min), and then gradually decreased. The signal for the 5-FU catabolite alpha-fluoro-beta-alanine (FBAL) gradually increased to the sixth spectrum (0-33.0 min) and then plateaued. Following portal vein infusion the intensity of the first 5-FU spectrum was twice as high as that following i.v. infusion, but the intensity decreased and the FBAL signal increased gradually in the sixth spectrum as systemic i.v. infusion. In contrast, the intensity of the 5-FU signal following hepatic artery infusion was the same as that following portal vein infusion in the first spectrum, and maintained a strong intensity to the final spectrum (60.5 min). The FBAL signal was detected from the second spectrum following hepatic artery infusion, but its intensity was significantly weaker than that following i.v. or portal vein infusion.

CONCLUSIONS

Hepatic arterial infusion resulted in the active form of 5-FU being present for a longer time and its degradation in the liver being suppressed compared with the results following portal vein infusion. This catabolic advantage of hepatic arterial infusion could lead to a more potent anti-tumor activity against liver metastases, but could also lead to significant host toxicity including biliary toxicity. We recommend that the dose/schedule of 5-FU administered via the hepatic artery should be adjusted carefully.

High-performance liquid chromatographic determination of beta-alanine, beta-aminoisobutyric acid and gamma-aminobutyric acid in tissue extracts and urine of normal and (aminooxy)acetate-treated rats

A method is described for the simultaneous determination of beta-alanine, beta-aminoisobutyric acid and gamma-aminobutyric acid in biological materials. Amino acids including these beta- and gamma-amino acids were derivatized with 4-dimethylaminoazobenzene-4'-sulfonyl (dabsyl) chloride and dabsyl amino acids formed were separated by reversed-phase high-performance liquid chromatography. Dabsyl derivatives of these beta- and gamma-amino acids were well separated from other dabsyl-amino acids. The method was applied to the determination of these beta- and gamma-amino acids in trichloroacetic acid extracts of various tissues and to the urine of normal rats and those injected with (aminooxy)acetate (AOA). AOA injection (15 mg per kg of body mass) produced remarkable increase in beta-alanine contents in liver, kidney and urine (10.2, 4.6 and 25.7 times, respectively).

Identification of nonprotein amino acids from cycad seeds as N-ethoxycarbonyl ethyl ester derivatives by positive chemical-ionization gas chromatography-mass spectrometry

Nonprotein amino acids from nine species of cycad seeds were analyzed as N-ethoxycarbonyl ethyl ester (ECEE) derivatives by positive chemical-ionization gas chromatography-mass spectrometry. Based on the retention times and mass spectrometry analyses, 12 nonprotein amino acids were identified in these seeds. In addition to the excitatory and putative neurotoxin beta-N-methylamino-L-alanine (BMAA), the known neurotoxin beta-N-oxalylamino-L-alanine (BOAA) was detected from the seeds of Macrozamia moorei and M. communis, and delta-N-oxalyl-ornithine was obtained from the Cycas revoluta seeds. A novel nonprotein amino acid named cycasindene, previously reported from C. revoluta, was also found in the seeds of members of the C. angulata and C. rumphii complex. Eight additional known nonprotein amino acids were also identified. This is the first report of the neurotoxin BOAA from cycad seeds.

Solvent-mediated conformational transition in beta-alanine containing cyclic peptides. VIII

In the present paper we describe the solution nmr structural analysis and restrained molecular dynamic simulation of the cyclic pentapeptide cyclo-(Pro-Phe-Phe-beta-Ala-beta-Ala). The conformational analysis carried out in CD3CN and dimethylsulfoxide (DMSO) solutions by nmr spectroscopy was based on interproton distances derived from rotating frame nuclear Overhauser effect spectroscopy spectra and homonuclear coupling constants. A restrained molecular dynamic simulation in vacuo was also performed to build refined molecular models. The molecule is present in both solvent systems as two slowly interconverting conformers, characterized by a cis-trans isomerism around the beta-Ala5-Pro1 peptide bond. In CD3CN solution, the conformer with a ci5 peptide bond is quite similar to that observed in the solid state, while the conformer containing all trans peptide bonds is characterized by an intramolecular hydrogen bond stabilizing a C10- and a C13-ring structure. In DMSO solution, the trans isomer is partly similar to that observed in CD3CN solution while the cis isomer is different from that observed in the solid state. The effect of the solvent in stabilizing different conformations was also investigated in DMSO-CD3CN solvent mixtures.

Unusual conformational preferences of beta-alanine containing cyclic peptides. VII

In the present paper we describe the synthesis, purification, and single crystal x-ray analysis of the cyclic pentapeptide cyclo-(Pro-Phe-Phe-beta-Ala-beta-Ala). This compound crystallizes in the orthorhombic space group P2I2I2I from methanol and adopts in the solid state an unusual conformation characterized by a cis beta-Ala5-Pro1 peptide bond and by an intramolecular hydrogen bond stabilizing a C11-and a C12-ring structure. The C11 structure contains the Phe3 and the beta-Ala4 at the corner position of the turn; it is the first observation of a type II beta-turn enlargement due to the insertion of an extra methylene group of the beta-alanine residue. The rest of the molecule participates in a newly characterized C12-ring structure, which incorporates a beta-Ala residue at position i of the turn.

Stable isotope analysis at the molecular level: a new approach for determining the origins of amino acids in the Murchison meteorite

A combined gas chromatography/isotope ratio mass spectrometry (GC/IRMS) method has been developed that permits the direct stable carbon isotope analysis of N(O)-trifluoroacetyl-isopropyl esters of individual amino acids and their respective enantiomers at nanomole abundances. Calculation of the original delta 13C values of the amino acids is accomplished via a correction for the carbon introduced during the derivatization process. Previous GC/IRMS analyses of individual amino acids in the non-hydrolyzed water extract of an interior sample of a Murchison meteorite stone revealed an enrichment in 13C relative to terrestrial organic matter, in agreement with previous findings for bulk extracts. The range of amino acid delta 13C values (+5 to +30%, PDB) suggests possible kinetic effects during synthesis. In this study, an apparent kinetic isotope effect was also observed for the amino acid products of a spark discharge experiment. These preliminary results are supportive of a similar mechanism for the abiotic synthesis of amino acids in the Murchison meteorite.

5-Ethynyluracil (776C85): protection from 5-fluorouracil-induced neurotoxicity in dogs

5-Ethynyluracil (776C85) is a potent mechanism-based inactivator of dihydropyrimidine dehydrogenase (DPD), the enzyme that catalyzes the rapid catabolism of 5-fluorouracil (5-FU). Because catabolism is the major route for 5-FU clearance, we studied the effect of 5-ethynyluracil on the pharmacokinetics and toxicity of continuous i.v. 5-FU infusion in the dog. 5-FU at 40 mg/kg/24 hr resulted in a steady-state plasma 5-FU concentration of 1.3 microM and was fatal with dogs dying from apparent neurotoxicity. 5-Ethynyluracil lowered the total clearance of 5-FU from 9.9 to 0.2 L/hr/kg and enabled 1.6 mg/kg/24 hr 5-FU to achieve a steady-state plasma 5-FU concentration of 2.4 microM with no apparent toxicity. 5-FU at 4 mg/kg/24 hr achieved a steady-state plasma 5-FU concentration of 5.3 microM and produced only mild gastrointestinal disturbances in 5-ethynyluracil-treated dogs. Thus, a catabolite of 5-FU appears to be responsible for the 5-FU-induced neurotoxicity in dogs.

Some chemical properties of the HCl-methanol extract from the puparial cuticle of Drosophila melanogaster

1. The HCl-methanol (HCl-MeOH) soluble fraction from the puparial cuticle of yellow, black and ebony of D. melanogaster was hydrolyzed in hydrochloric acid and examined for beta-alanine, ketocatechol, and acetic acid. 2. Between beta-alanine and ketocatechol and between beta-alanine and acetic acid, a quantitatively inverse relationship was found, respectively. The former relationship was further confirmed by the feeding experiment of beta-alanine to black. 3. Of total beta-alanine in the HCl-MeOH extract, the proportion of those having free amino group was 74.8 per cent. 4. All these results indicate that the HCl-MeOH soluble fraction of the puparial cuticle may be useful for investigating the cross-link structure of the cuticle.

Simultaneous multiple synthesis of peptide-carrier conjugates

Recently, the multipin approach for simultaneous multiple peptide synthesis was applied to the analysis of T cell determinants by using a novel cleavage method (Maeji et al., 1990). A diketopiperazine forming linker allowed cleavage of peptides into aqueous buffer which, without further purification, could be used immediately in cell culture assays. Another potential application of the technique is the simultaneous cleavage and coupling of peptides to immunogenic carriers. Without further purification the resulting conjugates can be used for the production of antipeptide antisera. The choice of carrier and conjugation chemistry is not restricted as peptide/pin cleavage occurs in aqueous solution over a range of pH and ionic strength. The method was assessed using the 2,4-dinitrophenyl group as a model hapten, diphtheria toxoid as the carrier, and N-(epsilon-maleimidocaproyloxy)succinimide as the cross-linking reagent. The resulting DNP-DT conjugate was used to prepare high titered specific anti-DNP antisera in mice.

2-Fluoro-beta-alanine, a previously unrecognized substrate for bile acid coenzyme A:amino acid:N-acyltransferase from human liver

Our laboratory has demonstrated recently that conjugates of 2-fluoro-beta-alanine (FBAL) and bile acids are the major biliary metabolites of 5-fluorouracil (FUra) in cancer patients. Bile acids are normally conjugated with glycine or taurine, and therefore the identification of the FBAL-bile acid conjugates suggested that FBAL may also be a substrate for the bile acid conjugating enzyme, bile acid CoA:amino acid:N-acyltransferase. Enzyme activity detected using glycine and taurine as substrates was purified 8-fold from human liver cytosol using a DEAE-cellulose column. This preparation when tested for its activity towards beta-alanine and FBAL using cholyl CoA as the bile acid substrate only catalyzed the formation of FBAL-cholate. beta-Alanine was not a substrate. Confirmation of FBAL-cholate as the enzymatic product was demonstrated by (1) coelution of the product of this reaction on HPLC with authentic FBAL-cholate, (2) specific hydrolysis of this product by cholylglycine hydrolase, and (3) molecular weight of the product (497) being identical to that of the authentic FBAL-cholate. Kinetic experiments demonstrated that the enzyme had an affinity for FBAL (Km 1.45 mM) comparable to taurine (Km 1.32 mM), but greater than glycine (Km 6.45 mM). Formation of FBAL-cholate was inhibited competitively by taurine (Ki 1.27 mM) and glycine (Ki 4.47 mM), suggesting that a single enzyme is responsible for conjugation of glycine, taurine and FBAL with bile acids. These data indicate that the formation of the FBAL-bile acid conjugates in patients receiving FUra results from high affinity of the bile acid conjugating enzyme for FBAL.

Nonlinear elimination kinetics of 5-fluoro-2'-deoxyuridine in isolated perfused rat liver and isolated hepatocytes

The kinetic parameters of the cytostatic agent 5-fluoro-2'-deoxyluridine (FUDR) were studied in isolated rat hepatocytes and in the isolated perfused rat liver. In both experimental setups a dose dependency of the elimination parameters, half-life and clearance, was observed with a calculated turning point around 250 microM. In the medium of rat hepatocytes incubated at low (0.1 microM) to high (2000 microM) FUDR, the majority of the metabolites consisted of the catabolite alpha-fluoro-beta-alanine. The nucleobase metabolites, 5-fluorouracil and its primary product 5,6-dihydro-5-fluorouracil, approached apparent steady-state levels comprising 10 to 15% of the initial concentration. In the intracellular phase of hepatocytes incubated at 300 microM FUDR almost 90% of the FUDR-derived material was alpha-fluoro-beta-alanine, whereas essentially no unchanged FUDR could be detected. Similar results were obtained at extracellular FUDR concentrations exceeding 300 microM. In the isolated perfused rat liver, the clearance decreased to 15 to 20% of the corresponding values when the initial concentration was raised from 24 to 2400 microM. At the end of perfusion alpha-fluoro-beta-alanine comprised 90 to 95% of FUDR-derived total radioactivity in the tissue even at initially 2400 microM FUDR, although at this FUDR dosage 20% of the substrate remained unmetabolized in the medium. These results suggest that the limitation of hepatic FUDR elimination is not due to saturable hepatic metabolism but must be due to saturable uptake of these pyrimidine derivatives across the cellular membrane of parenchymal liver cells.

Assay for beta-ureidopropionase by high-performance liquid chromatography

A sensitive assay for beta-ureidopropionase based on derivatization of the reaction product beta-alanine with phenylisothiocyanate has been developed. Purification of the resulting phenylthiocarbamoyl-beta-alanine is achieved on a LiChrospher 100 C18 reversed-phase high-performance liquid chromatography column using an isocratic elution system. Phenylthiocarbamoyl-beta-alanine is detected by its absorbance at 245 nm and quantitated by automatic peak integration referring to a calibration curve. This technique offers a high degree of sensitivity as beta-alanine quantities in the picomole range can be identified. N-Carbamoyl-beta-alanine, the natural substrate of beta-ureidopropionase, does not interfere with the described assay system. The enzymatic reaction is linear for an incubation time of 45 min with enzyme concentrations of 3.2 micrograms/ml.

Glucosamine-6-phosphate synthase from Escherichia coli: determination of the mechanism of inactivation by N3-fumaroyl-L-2,3-diaminopropionic derivatives

A mechanistic investigation of the inactivation of Escherichia coli glucosamine-6-phosphate synthase by N3-(4-methoxyfumaroyl)-L-2,3-diaminopropionate (FMDP) was undertaken. On the basis of the known participation of the N-terminal cysteine residue in this process [Chmara et al. (1986) Biochim. Biophys. Acta 870, 357; Badet et al. (1988) Biochemistry 27, 2282], the model reactions between FMDP and L-cysteine and between FMDP and the synthetic decapeptide Cys-Gly-Ile-Val-Gly-Ala-Ile-Ala-Gln-Arg, corresponding to the amino-terminal protein sequence, were studied. The results allowed us to propose a pathway that is in perfect agreement with the biochemical results: enzyme inactivation arose from Michael addition of glutamine binding site cysteine-1 on the fumaroyl double bond at the beta-position of the ester group. Upon denaturation under slightly alkaline conditions, this adduct underwent cyclization to a transient succinimide adduct, which rearranged into the stable 2-substituted 1,4-thiazin-3-one-5-carboxylate involving participation of the cysteine amino group. The tryptic radiolabeled peptides purified from [3H]FMDP-treated enzyme and resistant to Edman degradation coeluted with the products resulting from the model reaction between the synthetic decapeptide and the inhibitor.

In vivo 19F NMR spectroscopy of the antimetabolite 5-fluorouracil and its analogues. An assessment of drug metabolism

The metabolism of 5-fluorouracil (5FU) and its analogues 2'-deoxy-5-fluorouridine (2'FdURD), 5'-deoxy-5-fluorouridine (5'FdURD) and R,S-1-(tetrahydro-2-furyl)-5-fluorouracil (Ftorafur) has been studied by 19F NMR in rat liver and the rat S. G. Prolactinoma. In experiments using i.v. bolus injections of 0.46 mmol/kg 5FU was cleared more rapidly from the liver than 5'FdURD (t1/2 of 4.7 +/- 0.6 vs 15.8 +/- 0.8 min, P less than 0.001). Alphafluoro-beta-alanine (FBALA) production was almost identical after 5FU or 2'FdURD but slower and more sustained after 5'FdURD and still slower after Ftorafur. Both 5FU and 2'FdURD caused formation of toxic fluoronucleotides in S.G. Prolactinomas when administered i.v. (0.92 mmol/kg bolus). After i.v. infusion (0.23 mmol/kg/hr for 4 hr) 5FU produced fluoronucleotides whereas 2'FdURD did not; however, both 5FU and 2'FdURD (0.19 mmol/kg daily i.p. for 7 days) suppressed tumour growth. FBALA was observed in tumors following 5FU and 2'FdURD. Infusion of FBALA itself (0.17 mmol/kg/hr for 4 hr i.v.) led to signal in the tumour, so this compound could have been formed in the liver. These data demonstrate that 19F NMR can monitor drug metabolism in vivo.

Enkephalin analogues containing beta-naphthylalanine at the fourth position

To examine the importance of the aromatic side chains of enkephalin on opiate activity, we report the synthesis and conformational analysis of a series of analogues related to enkephalin with beta-naphthylalanine in place of phenylalanine at the fourth position. Three linear analogues (Tyr-D-Ala-Gly-(L and D)-beta Nal(1)-Leu-NH2 and Tyr-D-Ala-Gly-beta Nal(2)-Leu-NH2) were initially synthesized to examine the effect of the substitution on biological activity. The increased activity of these peptides at the mu-opiate receptor, compared to native Leu-enkephalin, prompted us to examine the more conformational constrained analogues, Tyr-c[D-A2bu-Gly-(L and D)-beta Nal(1)-Leu], incorporating a alpha, gamma-diaminobutyric acid at the second position and cyclization to the carboxylic end of the leucine. These two cyclic analogues provide insight into the necessity for the L chirality of the aromatic residue at position 4. The Tyr-c[D-A2bu-Gly-L-beta Nal(1)-Leu] analogue is highly potent and displays a slight preference for the mu receptor. The conformational analysis indicates that despite the high flexibility of the tyrosine side chain, the aromatic rings of the tyrosine and naphthylalanine are relatively distant from each other. The presence of two intramolecular hydrogen bonds help maintain the conformation of the 14-membered backbone ring that keeps the side chains directed away from each other. These findings are in agreement with our model of an extended structure required for mu selectivity and a folded form with close aromatic ring placement for delta selectivity.

Altered amino acid levels in brainstem regions of spontaneously hypertensive rats

The contents of glutamate, gamma-aminobutyric acid (GABA), glycine, beta-alanine and taurine in brainstem regions responsible for blood pressure regulation, the rostral ventrolateral medulla (RVL), the nucleus tractus solitarii (NTS) and the caudal ventrolateral medulla (CVL) regions, were determined in spontaneously hypertensive rats (SHR) as compared with Wistar Kyoto rats. In SHR, the content of glutamate was increased in the RVL, NTS and CVL regions whereas GABA and beta-alanine contents were decreased in the RVL and all the regions studied, respectively. There was no difference between WKY and SHR in glycine and taurine contents in all the regions studied. These results provide evidence suggesting alterations of brainstem amino acid metabolism in SHR.

Modified methods for measuring citrulline and carbamoyl-beta-alanine with reduced light sensitivity and sucrose interference

Two modified procedures for the colorimetric quantitation of citrulline aimed primarily at the assay of ornithine transcarbamylase were developed. Both methods give highly reproducible results in a short period of time since color is developed in 25 min at 100 degrees C. One method is more sensitive than previous methods and the other is as sensitive but requires less than one-fifth as much acid for color development. The reduction in acid concentration results in the stability of the colored complex for at least 50 min under the laboratory lighting conditions and allows for the presence of 5 mumol sucrose and 0.03 mumol mercaptoethanol in the assay. A low-acid modification for quantitating carbamoyl-beta-alanine is described also and may be applicable to the assay of dihydropyrimidinase.

[Release of beta-alanine from the frog skeletal muscle determined by thin-layer chromatography]

The release of beta-alanine from the resting and contracting frog sartorius muscles was demonstrated by the two-dimensional thin-layer chromatography. The release of beta-alanine from indirectly stimulated muscles of frogs in winter was about 230% higher than at rest. When synaptic transmission was blocked by d-tubocurarine the release of beta-alanine from directly stimulated muscles did not exceed the release at rest. Thus, activation of neuromuscular synapse leads to increased beta-alanine release from contracting muscle.

Isolation and characterization of bulgecins, new bacterial metabolites with bulge-inducing activity

Bulgecins A, B and C, new bacterial metabolites which induce the formation of bulges by cooperation with beta-lactam antibiotics, were isolated from the culture broth of Pseudomonas mesoacidophila. The three components, separated by column chromatography on QAE-Sephadex A-25, are water-soluble acidic compounds containing a sulfate group in the molecule. Acid hydrolysis showed that D-glucosamine and a new proline derivative are common constituents of the three components. In addition, taurine and beta-alanine are constituents of bulgecins A and B, respectively.

The chemical conditions on the parent body of the Murchison meteorite: some conclusions based on amino, hydroxy and dicarboxylic acids

Amino and hydroxy acids have been identified in the Murchison meteorite. Their presence is consistent with a synthetic pathway involving aldehydes, hydrogen cyanide and ammonia in an aqueous environment (Strecker-cyanohydrin synthesis). From the various equilibrium and rate constants involved in this synthesis, four independent estimates of the ammonium ion concentrations on the parent body at the time of compound synthesis are obtained; all values are about 2 x 10(-3) M. Succinic acid and beta-alanine have also been detected in the Murchison meteorite. Their presence is consistent with a synthesis from acrylonitrile, hydrogen cyanide and ammonia. Using the equilibrium and rate constants for this synthetic pathway, and the succinic acid/beta-alanine ratio measured in the Murchison meteorite, an estimate of the hydrogen cyanide concentration of 10(-3) to 10(-2) M is obtained. Since hydrogen cyanide hydrolyzes relatively rapidly in an aqueous environment (t1/2 < 10(4) yrs) this high concentration implies a period of synthesis of organic compounds as short as 10(4) years on the Murchison meteorite parent body.

Beta-alanine and tanning polymorphisms

1. Beta-alanine is found in mycelial walls of mature tan, but not immature white, stage of Morchella esulenta, nor in any stage of a permanently white mutant. 2. Beta-alanine is also found in hydrolysed water-extracts of human hair, the concentration being higher in blond than in dark brown, and in pigmented than in unpigmented hair. 3. Beta-alanine, added to tyrosinase-oxidized tyrosine, dopa, or dopamine has only a slight yellowing influence on the final black pigment; but when the amino group of tyrosine is combined with leucine, added beta-alanine produces stable tan pigments. 4. With L-alanine substituted for beta-alanine in this reaction, green pigment results. 5. Gelatin filters stained with the tan pigment allow solar heating of underlaying water more quickly than do those stained with the black pigment. Unstained filters allow such heating even more quickly. 6. Beta-alanine enhances production of tan pigment when heated with the phospholipid, lecithin. Implications for pigmentary adaptation, and formation of lipofuscin-like age pigments are discussed.