Characterizing and predicting the relationship between translaminar fracture toughness and pull-out length distributions under distinct temperatures

The translaminar fracture toughness reflects the damage tolerance of a fibre-reinforced composite under longitudinal tension, which often governs the final failure of structures. One of the main energy-dissipation mechanisms that contributes to the translaminar toughness of composites is the fibre pull-out process. The present study aims to quantify and model the statistical distribution of fibre pull-out lengths formed on the translaminar fracture surface of composites, for the first time in the literature; this is done under different temperatures, so that the relationship between pull-out length distributions, micromechanical properties and the translaminar fracture toughness can be established. The fracture surfaces of cross-ply compact tension specimens tested under three different temperatures have been scanned through X-ray computed tomography to quantify the extent of fibre pull-out on the fracture surfaces; the distribution of pull-out lengths showed alarger average and larger variability with an increase in temperature, which also lead to an increase in translaminar fracture toughness. A similar trend has been captured by the proposed analytical model, which predicts the pull-out length distribution based on the analysis of quasi-fractal idealizations of the fracture surface, yielding an overall accuracy of more than 85%. This article is part of the theme issue 'Ageing and durability of composite materials'.

Correction of a urea cycle defect after ex vivo gene editing of human hepatocytes

Ornithine transcarbamylase deficiency (OTCD) is a monogenic disease of ammonia metabolism in hepatocytes. Severe disease is frequently treated by orthotopic liver transplantation. An attractive approach is the correction of a patient’s own cells to regenerate the liver with gene-repaired hepatocytes. This study investigates the efficacy and safety of ex vivo correction of primary human hepatocytes. Hepatocytes isolated from an OTCD patient were genetically corrected ex vivo, through the deletion of a mutant intronic splicing site achieving editing efficiencies >60% and the restoration of the urea cycle in vitro. The corrected hepatocytes were transplanted into the liver of FRGN mice and repopulated to high levels (>80%). Animals transplanted and liver repopulated with genetically edited patient hepatocytes displayed normal ammonia, enhanced clearance of an ammonia challenge and OTC enzyme activity, as well as lower urinary orotic acid when compared to mice repopulated with unedited patient hepatocytes. Gene expression was shown to be similar between mice transplanted with unedited or edited patient hepatocytes. Finally, a genome-wide screening by performing CIRCLE-seq and deep sequencing of >70 potential off-targets revealed no unspecific editing. Overall analysis of disease phenotype, gene expression, and possible off-target editing indicated that the gene editing of a severe genetic liver disease was safe and effective.

Split AAV-Mediated Gene Therapy Restores Ureagenesis in a Murine Model of Carbamoyl Phosphate Synthetase 1 Deficiency

The urea cycle enzyme carbamoyl phosphate synthetase 1 (CPS1) catalyzes the initial step of the urea cycle; bi-allelic mutations typically present with hyperammonemia, vomiting, ataxia, lethargy progressing into coma, and death due to brain edema if ineffectively treated. The enzyme deficiency is particularly difficult to treat; early recognition is essential to minimize injury to the brain. Even under optimal conditions, therapeutic interventions are of limited scope and efficacy, with most patients developing long-term neurologic sequelae. One significant encumberment to gene therapeutic development is the size of the CPS1 cDNA, which, at 4.5 kb, nears the packaging capacity of adeno-associated virus (AAV). Herein we developed a split AAV (sAAV)-based approach, packaging the large transgene and its regulatory cassette into two separate vectors, thereby delivering therapeutic CPS1 by a dual vector system with testing in a murine model of the disorder. Cps1-deficient mice treated with sAAVs survive long-term with markedly improved ammonia levels, diminished dysregulation of circulating amino acids, and increased hepatic CPS1 expression and activity. In response to acute ammonia challenging, sAAV-treated female mice rapidly incorporated nitrogen into urea. This study demonstrates the first proof-of-principle that sAAV-mediated therapy is a viable, potentially clinically translatable approach to CPS1 deficiency, a devastating urea cycle disorder.

Improvement of diagnostic yield in carbamoylphosphate synthetase 1 (CPS1) molecular genetic investigation by RNA sequencing

Carbamoylphosphate synthetase 1 (CPS1) deficiency is a rare inborn error of metabolism leading often to neonatal onset hyperammonemia with coma and high mortality. The biochemical features of the disease are nonspecific and cannot distinguish this condition from other defects of the urea cycle, namely N‐acetylglutamate synthase deficiency. Therefore, molecular genetic investigation is required for confirmation of the disease, and nowadays this is done with increasing frequency applying next‐generation sequencing (NGS) techniques. Our laboratory has a long‐standing interest in CPS1 molecular genetic investigation and receives samples from centers in Europe and many other countries. We perform RNA‐based CPS1 molecular genetic investigation as first line investigation and wanted in this study to evaluate our experience with this approach as compared to NGS. In the past 15 years, 297 samples were analyzed, which were referred from 37 countries. CPS1 deficiency could be confirmed in 155 patients carrying 136 different genotypes with only a single mutation recurring more than two times. About 10% of the total 172 variants comprised complex changes (eg, intronic changes possibly affecting splicing, deletions, insertions, or deletions_insertions), which would have been partly missed if only NGS was done. Likewise, RNA analysis was crucial for correct interpretation of at least half of the complex mutations. This study gives highest sensitivity to RNA‐based CPS1 molecular genetic investigation and underlines that NGS should be done together with copy number variation analysis. We propose that unclear cases should be investigated by RNA sequencing in addition, if this method is not used as the initial diagnostic procedure.

Comprehensive characterization of ureagenesis in the spfash mouse, a model of human ornithine transcarbamylase deficiency, reveals age-dependency of ammonia detoxification

The most common ureagenesis defect is X-linked ornithine transcarbamylase (OTC) deficiency which is a main target for novel therapeutic interventions. The spf ^ash mouse model carries a variant (c.386G>A, p.Arg129His) that is also found in patients. Male spf ^ash mice have a mild biochemical phenotype with low OTC activity (5%-10% of wild-type), resulting in elevated urinary orotic acid but no hyperammonemia. We recently established a dried blood spot method for in vivo quantification of ureagenesis by Gas chromatography-mass spectrometry (GC-MS) using stable isotopes. Here, we applied this assay to wild-type and spf ^ash mice to assess ureagenesis at different ages. Unexpectedly, we found an age-dependency with a higher capacity for ammonia detoxification in young mice after weaning. A parallel pattern was observed for carbamoylphosphate synthetase 1 and OTC enzyme expression and activities, which may act as pacemaker of this ammonia detoxification pathway. Moreover, high ureagenesis in younger mice was accompanied by elevated periportal expression of hepatic glutamine synthetase, another main enzyme required for ammonia detoxification. These observations led us to perform a more extensive analysis of the spf ^ash mouse in comparison to the wild-type, including characterization of the corresponding metabolites, enzyme activities in the liver and plasma and the gut microbiota. In conclusion, the comprehensive enzymatic and metabolic analysis of ureagenesis performed in the presented depth was only possible in animals. Our findings suggest such analyses being essential when using the mouse as a model and revealed age-dependent activity of ammonia detoxification.

A constitutive knockout of murine carbamoyl phosphate synthetase 1 results in death with marked hyperglutaminemia and hyperammonemia

The enzyme carbamoyl phosphate synthetase 1 (CPS1; EC 6.3.4.16) forms carbamoyl phosphate from bicarbonate, ammonia, and adenosine triphosphate (ATP) and is activated allosterically by N-acetylglutamate. The neonatal presentation of bi-allelic mutations of CPS1 results in hyperammonemia with reduced citrulline and is reported as the most challenging nitrogen metabolism disorder to treat. As therapeutic interventions are limited, patients often develop neurological injury or die from hyperammonemia. Survivors remain vulnerable to nitrogen overload, being at risk for repetitive neurological injury. With transgenic technology, our lab developed a constitutive Cps1 mutant mouse and reports its characterization herein. Within 24 hours of birth, all Cps1 ^-/- mice developed hyperammonemia and expired. No CPS1 protein by Western blot or immunostaining was detected in livers nor was Cps1 mRNA present. CPS1 enzymatic activity was markedly decreased in knockout livers and reduced in Cps1^+/- mice. Plasma analysis found markedly reduced citrulline and arginine and markedly increased glutamine and alanine, both intermolecular carriers of nitrogen, along with elevated ammonia, taurine, and lysine. Derangements in multiple other amino acids were also detected. While hepatic amino acids also demonstrated markedly reduced citrulline, arginine, while decreased, was not statistically significant; alanine and lysine were markedly increased while glutamine was trending towards significance. In conclusion we have determined that this constitutive neonatal mouse model of CPS1 deficiency replicates the neonatal human phenotype and demonstrates the key biochemical features of the disorder. These mice will be integral for addressing the challenges of developing new therapeutic approaches for this, at present, poorly treated disorder.

A liver-humanized mouse model of carbamoyl phosphate synthetase 1-deficiency

A liver-humanized mouse model for CPS1-deficiency was generated by the high-level repopulation of the mouse liver with CPS1-deficient human hepatocytes. When compared with mice that are highly repopulated with CPS1-proficient human hepatocytes, mice that are repopulated with CPS1-deficient human hepatocytes exhibited characteristic symptoms of human CPS1 deficiency including an 80% reduction in CPS1 metabolic activity, delayed clearance of an ammonium chloride infusion, elevated glutamine and glutamate levels, and impaired metabolism of [¹⁵ N]ammonium chloride into urea, with no other obvious phenotypic differences. Because most metabolic liver diseases result from mutations that alter critical pathways in hepatocytes, a model that incorporates actual disease-affected, mutant human hepatocytes is useful for the investigation of the molecular, biochemical, and phenotypic differences induced by that mutation. The model is also expected to be useful for investigations of modified RNA, gene, and cellular and small molecule therapies for CPS1-deficiency. Liver-humanized models for this and other monogenic liver diseases afford the ability to assess the therapy on actual disease-affected human hepatocytes, in vivo, for long periods of time and will provide data that are highly relevant for investigations of the safety and efficacy of gene-editing technologies directed to human hepatocytes and the translation of gene-editing technology to the clinic.

Treatment of a metabolic liver disease by in vivo genome base editing in adult mice

CRISPR-Cas-based genome editing holds great promise for targeting genetic disorders, including inborn errors of hepatocyte metabolism. Precise correction of disease-causing mutations in adult tissues in vivo, however, is challenging. It requires repair of Cas9-induced double-stranded DNA (dsDNA) breaks by homology-directed mechanisms, which are highly inefficient in nondividing cells. Here we corrected the disease phenotype of adult phenylalanine hydroxylase (Pah)^enu2 mice, a model for the human autosomal recessive liver disease phenylketonuria (PKU)¹, using recently developed CRISPR-Cas-associated base editors^2-4. These systems enable conversion of C∙G to T∙A base pairs and vice versa, independent of dsDNA break formation and homology-directed repair (HDR). We engineered and validated an intein-split base editor, which allows splitting of the fusion protein into two parts, thereby circumventing the limited cargo capacity of adeno-associated virus (AAV) vectors. Intravenous injection of AAV-base editor systems resulted in Pah^enu2 gene correction rates that restored physiological blood phenylalanine (L-Phe) levels below 120 µmol/l [5]. We observed mRNA correction rates up to 63%, restoration of phenylalanine hydroxylase (PAH) enzyme activity, and reversion of the light fur phenotype in Pah^enu2 mice. Our findings suggest that targeting genetic diseases in vivo using AAV-mediated delivery of base-editing agents is feasible, demonstrating potential for therapeutic application.

Tetrahydrobiopterin treatment reduces brain L-Phe but only partially improves serotonin in hyperphenylalaninemic ENU1/2 mice

Hyperphenylalaninemia (HPA) caused by hepatic phenylalanine hydroxylase (PAH) deficiency has severe consequences on brain monoamine neurotransmitter metabolism. We have studied monoamine neurotransmitter status and the effect of tetrahydrobiopterin (BH4) treatment in Pahenu1/enu2 (ENU1/2) mice, a model of partial PAH deficiency. These mice exhibit elevated blood L-phenylalanine (L-Phe) concentrations similar to that of mild hyperphenylalaninemia (HPA), but brain levels of L-Phe are still ~5-fold elevated compared to wild-type. We found that brain L-tyrosine, L-tryptophan, BH4 cofactor and catecholamine concentrations, and brain tyrosine hydroxylase (TH) activity were normal in these mice but that brain serotonin, 5-hydroxyindolacetic acid (5HIAA) and 3-methoxy-4-hydroxyphenylglycol (MHPG) content, and brain TH protein, as well as tryptophan hydroxylase type 2 (TPH2) protein levels and activity were reduced in comparison to wild-type mice. Parenteral L-Phe loading conditions did not lead to significant changes in brain neurometabolite concentrations. Remarkably, enteral BH4 treatment, which normalized brain L-Phe levels in ENU1/2 mice, lead to only partial recovery of brain serotonin and 5HIAA concentrations. Furthermore, indirect evidence indicated that the GTP cyclohydrolase I (GTPCH) feedback regulatory protein (GFRP) complex may be a sensor for brain L-Phe elevation to ameliorate the toxic effects of HPA. We conclude that BH4 treatment of HPA toward systemic L-Phe lowering reverses elevated brain L-Phe content but the recovery of TPH2 protein and activity as well as serotonin levels is suboptimal, indicating that patients with mild HPA and mood problems (depression or anxiety) treated with the current diet may benefit from supplementation with BH4 and 5-OH-tryptophan.

A simple dried blood spot-method for in vivo measurement of ureagenesis by gas chromatography-mass spectrometry using stable isotopes

BACKGROUND

Clinical management of inherited or acquired hyperammonemia depends mainly on the plasma ammonia level which is not a reliable indicator of urea cycle function as its concentrations largely fluctuate. The gold standard to assess ureagenesis in vivo is the use of stable isotopes.

METHODS

Here we developed and validated a simplified in vivo method with [¹⁵N]ammonium chloride ([¹⁵N]H₄Cl) as a tracer. Non-labeled and [¹⁵N]urea were quantified by GC-MS after extraction and silylation.

RESULTS

Different matrices were evaluated for suitability of analysis. Ureagenesis was assessed in ornithine transcarbamylase (OTC)-deficient spf^ash mice with compromised urea cycle function during fasted and non-fasted feeding states, and after rAAV2/8-vector delivery expressing the murine OTC-cDNA in liver. Blood (5μL) was collected through tail vein puncture before and after [¹⁵N]H₄Cl intraperitoneal injections over a two hour period. The tested matrices, blood, plasma and dried blood spots, can be used to quantify ureagenesis. Upon [¹⁵N]H₄Cl challenge, urea production in spf^ash mice was reduced compared to wild-type and normalized following rAAV2/8-mediated gene therapeutic correction. The most significant difference in ureagenesis was at 30min after injection in untreated spf^ash mice under fasting conditions (19% of wild-type). Five consecutive injections over a period of five weeks had no effect on body weight or ureagenesis.

CONCLUSION

This method is simple, robust and with no apparent risk, offering a sensitive, minimal-invasive, and fast measurement of ureagenesis capacity using dried blood spots. The stable isotope-based quantification of ureagenesis can be applied for the efficacy-testing of novel molecular therapies.

Brain catecholamine depletion and motor impairment in a Th knock-in mouse with type B tyrosine hydroxylase deficiency

Tyrosine hydroxylase catalyses the hydroxylation of L-tyrosine to l-DOPA, the rate-limiting step in the synthesis of catecholamines. Mutations in the TH gene encoding tyrosine hydroxylase are associated with the autosomal recessive disorder tyrosine hydroxylase deficiency, which manifests phenotypes varying from infantile parkinsonism and DOPA-responsive dystonia, also termed type A, to complex encephalopathy with perinatal onset, termed type B. We generated homozygous Th knock-in mice with the mutation Th-p.R203H, equivalent to the most recurrent human mutation associated with type B tyrosine hydroxylase deficiency (TH-p.R233H), often unresponsive to l-DOPA treatment. The Th knock-in mice showed normal survival and food intake, but hypotension, hypokinesia, reduced motor coordination, wide-based gate and catalepsy. This phenotype was associated with a gradual loss of central catecholamines and the serious manifestations of motor impairment presented diurnal fluctuation but did not improve with standard l-DOPA treatment. The mutant tyrosine hydroxylase enzyme was unstable and exhibited deficient stabilization by catecholamines, leading to decline of brain tyrosine hydroxylase-immunoreactivity in the Th knock-in mice. In fact the substantia nigra presented an almost normal level of mutant tyrosine hydroxylase protein but distinct absence of the enzyme was observed in the striatum, indicating a mutation-associated mislocalization of tyrosine hydroxylase in the nigrostriatal pathway. This hypomorphic mouse model thus provides understanding on pathomechanisms in type B tyrosine hydroxylase deficiency and a platform for the evaluation of novel therapeutics for movement disorders with loss of dopaminergic input to the striatum.

Determination of six pterins in urine by LC-MS/MS

BACKGROUND

The present work describes an analytical method for urinary pterins by LC-MS/MS, with emphasis on the separation of 6- and 7-positional isomers of bio- and neopterins.

RESULTS

Urine sample preparation consisted of oxidation by MnO(2), filtration and direct dilution in the mobile phase. The method was validated in urine spiked at five concentration levels with true triplicates of each level. Separation of the pterins, including the positional isomers, was achieved by employing a LUNA amino column. Six pterins were quantified (pterin, isoxanthopterin, 6-biopterin, 7-biopterin, 6-neopterin, 7-neopterin) and a linear behavior was observed; LOD varied from 7 to 360 pg/ml and correlation coefficients above 0.98 were obtained for all pterins. In addition, pterin levels were evaluated in 41 urine samples of healthy subjects, in ten urine samples of patients with classical phenylketonuria (PKU) and in one with atypical PKU.

CONCLUSION

The proposed method allowed to identify, separate and quantify six pterins in urine, using a simple and rapid sample preparation. The atypical PKU was unequivocally differentiated from the classical form, demonstrating that this method could be very useful for characterization and follow-up of diseases.

Fumaric aciduria: an overview and the first Brazilian case report

Fumaric aciduria is a rare metabolic disease, with 40 cases reported so far. Fumarase deficiency leads mainly to brain abnormalities, developmental delay, and great accumulation of fumaric acid in urine. This work presents the first case of fumaric aciduria described in Brazil, which presented with some interesting clinical and biochemical findings such as colpocephaly, hepatic alterations, and marked metabolic acidosis since birth. Common findings were ventriculomegaly, hypotonia, and microcephaly. Biochemically, besides the high urinary fumaric acid excretion, atypical elevation of plasma citrulline, tyrosine and methionine levels were also observed. In order to show all features and variants of fumaric aciduria, literature data of 40 patients was reviewed and compared with the case reported here. Findings in all these patients demonstrate that this disorder does not yet have its phenotype completely defined; it is important that more patients be described.

Serum fluctuations of total and free tryptophan levels during the menstrual cycle are related to gonadotrophins and reflect brain serotonin utilization

BACKGROUND

Serotoninergic (5-HT) neurons are suggested to regulate estrous cycle in animal models. In the present study we evaluated whether a relationship exists between the serotoninergic precursors in the central nervous system and the gonadotrophin-ovarian cyclic function.

METHODS

We measured 5-HT precursors [free (FT) and total (TT) tryptophan] and LH, FSH and 17beta-estradiol (E2) levels in the serum of 15 fertile women with normal menstrual cycles during the follicular (cycle days 1-5, 7-11), mid-cycle (cycle days 14-16) and luteal (cycle days 17-19, 22-24) phases.

RESULTS

TT and FT were significantly increased in the 7-11 and 17-19 cycle days and were decreased at mid-cycle (P < 0.01), with a cyclic and opposite behaviour when compared to that of FSH and LH. Indeed, correlation analysis through the matrix of mean values showed that LH was negatively correlated to TT (r = -0.636) and FT (r = -0.574), as well as FSH (TT, r = -0.655; FT, r = -0.663), and that TT and FT were positively correlated to each other (r = 0.801; P < 0.001). Furthermore, whilst the two FT peaks reached approximately the same levels in the follicular and luteal phase, TT levels were approximately 30% higher in the luteal than in the follicular phase of the cycle: thus in the first (follicular) phase FT peak was relatively higher than that of TT, whereas the contrary occurred in the second (luteal) phase of the cycle.

CONCLUSIONS

Both TT and FT levels have cyclic variations throughout the menstrual cycle, being lowest at mid-cycle (14-16 cycle days), concomitant with the highest LH and FSH concentrations, and higher before and after mid-cycle phase, coinciding with the lowest circulating LH/FSH levels. Since TT and FT levels in the plasma have cyclic changes, our study: (i) suggests that a consumption of serum serotonin precursors takes place concomitant with gonadotrophin release during menstrual cycle; (ii) may represent an in vivo model to investigate this relationship in women in different physiopathological conditions.

Endoscopic Selective Sampling of Human Ventricular CSF: A New Perspective

Neuroendoscopy has achieved extensive acceptance among neurosurgeons as a minimally invasive technique for the treatment of patients affected by blocked hydrocephalus. During endoscopic procedures minimal CSF amounts from selected anatomic sites of the ventricles can be withdrawn. Steerable endoscopes are used and their flexibility facilitates the aspiration of CSF during the preliminary inspection through the ventricular cavities, without any interference with the surgical actions or additional risks for the patients. In this preliminary study the concentrations of melatonin and other related metabolites in the lateral ventricles, third ventricle, pineal recess and infundibular recess were examined. The data obtained from a patient affected by blocked hydrocephalus confirmed a constant and significant difference of concentration of these substances, for instance, melatonin levels were found to be much higher in the third ventricle (542 pg/mL in its centre) than in the lateral ventricle (172 pg/mL in the right ventricle). Nevertheless, instead of what we would expect, the highest melatonin concentrations were not found in the pineal recess (438 pg/mL). In the future, neuroendoscopy, beside its evident therapeutic efficacy, could open new perspectives in the study of both CSF biochemistry and physiology, allowing a highly selective approach to the various substances which are released and float in it.

Enzyme activities involved in tryptophan metabolism along the kynurenine pathway in rabbits

The following enzyme activities of the tryptophan-nicotinic acid pathway were studied in male New Zealand rabbits: liver tryptophan 2,3-dioxygenase, intestine indole 2,3-dioxygenase, liver and kidney kynurenine 3-monooxygenase, kynureninase, kynurenine-oxoglutarate transaminase, 3-hydroxyanthranilate 3,4-dioxygenase, and aminocarboxymuconate-semialdehyde decarboxylase. Intestine superoxide dismutase and serum tryptophan were also determined. Liver tryptophan 2,3-dioxygenase exists only as holoenzyme, but intestine indole 2,3-dioxygenase is very active and can be considered the key enzyme which determines how much tryptophan enters the kynurenine pathway also under physiological conditions. The elevated activity of indole 2,3-dioxygenase in the rabbit intestine could be related to the low activity of superoxide dismutase found in intestine. Kynurenine 3-monooxygenase appeared more active than kynurenine-oxoglutarate transaminase and kynureninase, suggesting that perhaps a major portion of kynurenine available from tryptophan may be metabolized to give 3-hydroxyanthranilic acid, the precursor of nicotinic acid. In fact, 3-hydroxyanthranilate 3,4-dioxygenase is much more active than the other previous enzymes of the kynurenine pathway. In the rabbit liver 3-hydroxyanthranilate 3,4-dioxygenase and aminocarboxymuconate-semialdehyde decarboxylase show similar activities, but in the kidney 3-hydroxyanthranilate 3,4-dioxygenase activity is almost double. These data suggest that in rabbit tryptophan is mainly metabolized along the kynurenine pathway. Therefore, the rabbit can also be a suitable model for studying tryptophan metabolism in pathological conditions.

Melanogenesis by tyrosinase action on 3,4-dihydroxyphenylalanine (DOPA) in the presence of polyethylene glycol: a matrix-assisted laser desorption/ionization mass spectrometric investigation

The enzymatic reaction between DOPA and tyrosinase, the enzyme considered to be responsible for melanogenesis, was carried out in the presence of polyethylene glycol (PEG). This choice was made in order to increase the solubility of melanins, since these polymers are highly insoluble. The reaction mixtures were sampled at different times, immediately ultrafiltered to remove the enzyme, lyophilized, and analyzed by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. The results were very different from those obtained in the absence of PEG. Only a few oligomers of dihydroxyindole (DHI) and dihydroxyindole-2-carboxylic acid (DHICA) were detected in low abundances, whereas new species originating from reaction of PEG with species belonging to the Raper-Mason pattern appeared. The results show that, in the presence of PEG, tyrosinase-catalyzed oligomerization of DOPA exhibits kinetics slower than those observed in the absence of the polymer. However, melanogenesis still takes place in the presence of PEG, as indicated by the formation of black pigments and by the detection of DHI and DHICA oligomers, considered to be the first intermediates in melanin formation.

Tryptophan in human hair: correlation with pigmentation

The distribution of tryptophan content in human hair of various colours was evaluated, in order to study the accumulation of this amino acid, precursor of serotonin, melatonin and niacin, in hair and the influence on hair pigmentation. Pigmentation is an important factor in determining drug incorporation into hair. Results from 1211 samples of hair from healthy subjects (577 men and 634 women) show that tryptophan levels are significantly higher in males (37.83 +/- 3.45 microg/g dry hair) than in females (26.62 +/- 2.40 microg/g hair). Besides sex, age also influences the distribution of tryptophan in human hair, the highest levels being found in both sexes in the first few years of life, probably due to the influence of milk, and in aging subjects in the groups of 61-80 and > 80 years. In order to investigate the influence of hair colour, hair samples were subdivided according to colour into blond, dark blond, red, light brown, brown, black, grey and white. The hair contents of tryptophan in both sexes was higher in brown and black hair than in blond hair, but in grey and white hair concentrations were the highest, demonstrating that tryptophan accumulates among hair fibres with age. Grouping subjects by age in relation to hair colour, we observed that at ages 1-5 and 6-12 years, colour did not influence tryptophan contents, but at ages 13-19 and 20-40 years tryptophan content increased significantly from blond to brown at 13-19 years and from blond to black at 20-40 years in both sexes. Therefore, variations in tryptophan levels of human hair appear to be correlated with differences in hair colour in both sexes. Tryptophan also accumulates in hair during keratinization, as shown by the presence of high levels of this amino acid in grey and white hair.

Melanogenesis from 5-hydroxytryptamine, 5,6- and 5,7-dihydroxytryptamines. An in vitro study using MALDI-TOF

The role of tyrosinase and peroxidase in melanogenesis of 5-hydroxytryptamine, 5,6- and 5,7-dihydroxytryptamines was investigated by matrix-assisted laser desorption/ionization mass spectrometry. Each enzyme was incubated with the tryptamine derivatives and samples were drawn at various times, ultrafiltered and immediately lyophilized. The results indicated that peroxidase promotes oligomerization of 5-HT with fast kinetics but with yields lower than those achieved by tyrosinase. 5,6- and 5,7-DHT formed low molecular mass oligomers in the presence of peroxidase alone. The addition of hydrogen peroxide evidences different reactivity of the two isomers: 5,6-DHT formed immediately a black precipitate while oligomers of the molecule itself and of its oxidation products were detectable for 5,7-DHT.

Importance of L-tryptophan metabolism in trypanosomiasis

African trypanosomiasis or sleeping sickness is caused by extracellular trypanosomes. The presence of seric antibodies directed to a tryptophan-like epitope in trypanosome infected patients and animals led us to investigate the roles of tryptophan in trypanosomiasis. These antibodies are directed against a tryptophan-rich conserved sequence inside the major parasite surface glycoprotein. In vitro, a rapid uptake of tryptophan by trypanosomes is measured. Seric tryptophan levels are decreased during trypanosomiasis. This decrease may be linked with an increase in indoleamine 2,3-dioxygenase (IDO) induced by Interferon-gamma. In vivo inhibition of IDO by norharman provokes a dramatic increase in circulating parasite number. All these data show the essential role of tryptophan in parasite growth. Moreover, antibodies against tryptophan, the decreased concentration of the neurotransmitter serotonin in the brain following infection and the tryptophan metabolites (tryptophol) produced by trypanosomes may participate to the pathophysiological mechanisms provoking sleeping sickness.

Tryptophan catabolism in synovial fluid of various arthropathies and its relationship with inflammatory cytokines

Synovial fluids (SF) from patients with rheumatoid arthritis (RA), psoriatic arthritis (PsA), gout, and osteoarthritis (OA) were investigated for the levels of interleukin (IL)-1 beta, IL-6 and IL-8, tryptophan (Trp) and indoleamine 2,3-dioxygenase (IDO) activity. Significant differences exist in the levels of IL-1 beta between inflammatory arthritides RA, PsA and gout and non inflammatory arthritis, such as OA. The highest concentration of IL-1 beta was found in RA, that showed high levels also of IL-6 and IL-8. In the same disease we also found the highest IDO activity and the lowest Trp concentration. In addition, IDO activity seems to be related with the decrease in Trp, as demonstrated by the inverse correlation found between these two substances in the SF of all patients.

Liver and kidney kynurenine aminotransferase activity in different strains of rats

Variations in liver and kidney kynurenine aminotransferase (KAT) activity in Pittsburg-Yoshida, Brown-Norway, albino Wistar, Sprague-Dawley, Long Evans and heterozygous Gunn rats were studied. In liver, values of KAT specific activity, expressed as mumoles of kynurenic acid formed per hour per mg of protein, were different in the groups of Brown-Norway and Pittsburg-Yoshida rats versus Long Evans and Sprague-Dawley rats. The activity expressed as mumoles of kynurenic acid per g of fresh liver showed other differences, being significantly higher in Gunn with respect to other strains of rats and lower in Pittsburg-Yoshida and Brown-Norway rats. In addition, KAT activity was significantly lower in Pittsburg-Yoshida than in Brown-Norway rats. In kidney, the specific activity of kynurenine aminotransferase showed significant differences in the values of Sprague-Dawley and Long Evans rats versus the other strains. The activity expressed per g of fresh tissue was significantly higher in Wistar, Sprague-Dawley, Long Evans and Gunn than in Pittsburg-Yoshida and Brown-Norway rats. No significant differences were found in values between hyperlipidemic Pittsburg-Yoshida and their control Brown-Norway rats. These results high-light the importance of considering various rat strains when inbred animal experimental models are used.

Correlation between tryptophan and hair pigmentation in human hair

The concentration of tryptophan in human hair of various colours is determined in order to study their correlation with hair pigmentation. The mean levels of this amino acid in hair samples are higher in men than in women. Therefore, sex influences the content of tryptophan in human hair. In addition, age influences the distribution, the highest levels are observed in the 1-5 year age-group and in ageing subjects in the groups up to 61-80 years in both sexes. The hair samples subdivided, according the colour, into blond, dark blond, red, light brown, brown, black, grey, and white demonstrate that in both sexes the concentrations of tryptophan are higher in brown and black hair than in blond hair. However, the tryptophan levels are highest in grey and white hair, showing that tryptophan accumulates among hair fibres with age. Therefore, there is a correlation between tryptophan content and hair pigmentation.

Protein profiles in sera of patients with malignant cutaneous melanoma

Seventeen samples of sera from patients with malignant cutaneous melanoma at various stages and 14 samples from healthy subjects were analysed by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. Results highlighted the presence of several protein species at molecular weights lower than 30000 Da, presumably originating from proteolysis, in the sera of the patients with melanoma. These species were completely absent in healthy subjects. In particular, the presence and abundance of species with molecular weights in the range 2500-3500 Da exhibit significant variations related to the different clinical stages of the disease.

Effects of ultraviolet irradiation on melanogenesis from tyrosine, Dopa and dopamine: a matrix-assisted laser desorption/ionization mass spectrometric study

Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry experiments were applied to study the influence of ultraviolet (UV) irradiation in melanogenesis. Samples were prepared starting from three different precursors, tyrosine, Dopa and dopamine, in the presence or absence of tyrosinase, the enzyme responsible for the synthesis of melanin. Enzymatic reactions were carried out for 10, 30, 60 and 120 min under UV irradiation at 365 nm, and aliquots were then immediately ultrafiltered and lyophilized. Samples obtained by irradiation of tyrosine solution revealed the formation of 5,6-dihydroxyindole (DHI) oligomers up to pentamers at 120 min; the reaction kinetics were markedly enhanced in the presence of tyrosinase. In the case of Dopa, UV irradiation favored melanogenesis only in the presence of the enzyme; in this case, many reaction pathways were activated, originating various oligomeric species of Dopa, DHI and 5,6-dihydroxyindole-2-carboxylic acid (DHICA). Conversely, when dopamine was used as tyrosinase substrate under UV light, mechanisms of melanogenesis different from those generated by simple enzymatic reaction without irradiation were not activated, as the same oligomeric species were present.

Application of matrix-assisted laser desorption/ionization mass spectrometry to the detection of melanins formed from Dopa and dopamine

Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry was used to study melanogenesis starting from Dopa and dopamine, the latter considered one of the precursors of neuromelanins. These substrates were left to react with the peroxidase - H(2)O(2) system, which is postulated to play an important role in melanin biosynthesis. Samples were prepared by ultrafiltering the substrate - enzyme solution after 30, 60, 120, 240 and 360 min of reaction and aliquots were immediately lyophilized. The reaction of dopamine with peroxidase - H(2)O(2) favoured the formation of dopamine oligomers up to octamers. In contrast, the action of either peroxidase or H(2)O(2) alone, studied for comparison, did not lead to melanin production and only dimeric and trimeric species were observed. Also for Dopa, analogous results were obtained in the presence of either peroxidase or H(2)O(2) alone, without melanin formation. Conversely, Dopa with the peroxidase - H(2)O(2) system led to the formation of a black precipitate after 120 min of reaction, and oligomers of 5,6-dihydroxyindole (DHI), an intermediate of melanogenesis, were detected, together with products of further oxidation. Faster kinetics were observed when Dopa was treated with tyrosinase, the enzyme catalysing the oligomerization of tyrosine to melanins, leading to the formation mainly of DHI oligomers.

Matrix-assisted laser desorption/ionization mass spectrometry in evaluation of protein profiles of infant formulae

Breast-feeding is the nutritional model in humans, and is continued after birth for variable periods. Milk represents an essential source of growth from both nutritional and functional points of view. When nursing is not possible, indicated or sufficient, artificial feeding becomes essential. Substitutes for mother's milk are usually obtained by modifying the composition of cow's milk either qualitatively or quantitatively. The changes usually involve enzymatic and/or thermal treatment, and for this reason a description of the protein profiles of milk formulae is of great interest. After examination of the results obtained by matrix-assisted laser desorption/ionization (MALDI) in the characterization of protein profiles of cow's milk after different thermal treatments, the application of this analytical technique in the above context appeared interesting. MALDI data for eleven milk formulae, directly acquired from the market, are described and discussed. Results indicate that MALDI mass spectrometry is a particularly powerful method which may be employed either during the production stages of milk formulae or to study the relationships between milk protein content and clinical formula evaluation.

Seroprevalence to bovine immunodeficiency virus and lack of association with leukocyte counts in Italian dairy cattle

We report herein on the first serological detection of antibodies to bovine immunodeficiency virus (BIV) in Italy. According to criteria of a stratified-random sampling of dairy cattle reared in the Parma area (a province in the Po Valley, Northern Italy), sera from 3166 cows belonging to 272 herds were collected. In addition, sera of 138 bulls from eight artificial-insemination (AI) centres were sampled. Seventy-eight cows (2.5%) from 16 herds (5.8%) and seven bulls (5.1%) from two AI centres were positive for BIV-R29 antibodies in the IFA-test. IFA-positive sera assayed by Western blot had reaction to different viral proteins: 81 out of 85 sera showed antibody to p26 (considered the BIV major internal core protein); four sera reacted to other viral proteins but not to p26. Peripheral blood leukocytes of 60 seropositive and 60 seronegative animals, belonging to eight BIV-infected herds, were enumerated to assess any effect of BIV infection on white-blood cells. No significant differences were detected between the two groups. These data indicate that BIV infection is present in Italian dairy cattle--but the role of BIV in inducing disease remains unclear.

Determination of copper and zinc levels in human hair: influence of sex, age, and hair pigmentation

The Cu and Zn levels of both 607 men (1-85 y old) and 649 women (1-92 y old) were determined by atomic absorption spectrometry. Sex does not influence Cu (14.89 + or - 0.89 mu g/g and 15.26 + or - 0.79 mu g/g hair for males and females, respectively) and Zn contents (200.97 + or - 9.68 mu g/g for men and 209.81 + or - 9.49 mu g/g hair for women). Age influences Cu and Zn concentrations, but only significantly in females: Cu levels decrease over 60 y of age; whereas Zn levels increase significantly from age groups 2-5 to 20-40 years. Hair color influences Cu concentrations in both males and females. In males, white hair contains less Cu than black hair; in females, white hair's Cu levels are significantly lower than those of dark blond, red, light brown, and brown hair. There are no significant differences in Zn concentrations with respect to different hair colors, in either males or females.

Biosynthesis of melanin from dopamine. An investigation of early oligomerization products

Matrix-assisted laser desorption/ionization (MALDI) and fast-atom bombardment (FAB) mass spectrometry experiments were applied to the study of the early stages of the oligomerization reaction of dopamine with mushroom tyrosinase. Ultrafiltration was employed to remove the enzyme at various reaction times, to prevent possible attachment of the protein to the highly reactive intermediates. Two sets of five samples each, obtained at different reaction times, in one case immediately lyophilized and in the other left to react under an oxygen stream for 24 h before lyophilization, were compared. FAB showed the presence of various species and of these, that at m/z 305 increased in abundance with reaction time in immediately lyophilized set of samples only. Accurate mass measurements and tandem mass spectrometric experiments indicated the structure of a dopamine protonated dimer for this ion. MALDI measurements showed that all samples were composed of clusters of oligomers differing in degree of oligomerization. Oligomerization increases with reaction time, resulting in the formation of species at 2643-2911 Da. These clusters in turn were formed of species with a different degree of oxidation, detected in both sets of samples.

Laser desorption ionization mass spectrometry in the study of natural and synthetic melanins. II--Serotonin melanins

Various biosynthetic melanins obtained by enzymic oxidation of serotonin with polyphenol oxidase from Psalliota campestris mushroom or potato, and with tyrosinase from Sepia officinalis or from Sigma were studied by means of laser desorption ionization mass spectrometry. Various oligomeric clusters were evidenced, proving that the examined melanins are composed of sets of different oligomers, the production of which strongly depends on the enzyme reaction. While serotonin melanins obtained with polyphenol oxidase from potato showed wide species distribution with molecular weights ranging from 2008 to 13,000 Da, the same melanins obtained from mushroom showed oligomer distributions from 1505 to 9000 Da. Serotonin melanins prepared with tyrosinase from Sepia showed oligomers from 1636 to 18,000 Da. A dopa-melanin obtained with mushroom polyphenol oxidase showed oligomer species from 1709 to 17,874 Da. Comparison of molecular weight distributions of the various oligomer sets in serotonin melanins with those in tyrosine melanins revealed clear differences, which are investigated and discussed.

The influence of color, age, and sex on the content of zinc, copper, nickel, manganese, and lead in human hair

The hair of 132 healthy subjects between 6 and 40 yr old living in the Veneto region in Italy was analyzed by means of HPLC method in order to determine the presence of zinc, copper, nickel, manganese, and lead. The collected samples were subdivided on the basis of age (6-11 and 19-40 yr), and sex and color (black, red, brown, and blond). From the data some evident differences were emphasized. In female hair the content of metals was higher than in male hair independently of color. Blond hair gave the lowest concentration values of the elements studied independently of sex. The maximum amount of the metals was found generally in black hair, followed by red and brown hair. Age seems to have a different influence, with the copper element decreasing appreciably in brown and blond female hair as the age of the subjects increased.

Laser desorption ionization mass spectrometry in the study of natural and synthetic melanins. I--Tyrosine melanins

Nine synthetic, biosynthetic and natural tyrosine melanins, together with dopa and catechol melanins, have been studied by means of laser desorption ionization mass spectrometry. The results obtained have shown that all the melanins under study consist of homogeneous sets of oligomers and have led to definitive information on their molecular weight distribution (from 500 to 30,000 Da). A deeper analysis of the spectra, in terms of mass differences among the various oligomers, allowed the identification of some monomeric units, identical or analogous to those already proposed in the literature.

Melanin biosynthesis from dopamine. II. A mass spectrometric and collisional spectroscopic investigation

Electron impact (EI) and fast atom bombardment (FAB) mass spectrometry together with collisional activation (CA) experiments were applied to the study of the oxidation pathway of dopamine by tyrosinase. In order to prevent attachment of the protein to the highly reactive intermediates, ultrafiltration was employed to remove the enzyme at different reaction times. FAB, privileging molecular species formation, was successfully used for identification of transient intermediates and their relative concentrations with respect to time, directly in the reaction mixture. The presence of isobaric molecular species made chromatographic separation necessary. Further EI mass spectrometry and collision spectroscopy led to structural identification of pure components. Of these, dopamine-o-quinone, leucoaminochrome, and aminochrome semiquinone were characterized for the first time as real intermediates in dopamine melanogenesis, in agreement with previous hypotheses. This approach elucidated the pathway of dopamine melanogenesis.

Fast atom bombardment mass spectrometry in the study of dopamine melanogenesis intermediates

Fast atom bombardment was applied to the study of the intermediates of the reaction dopamine-tyrosinase after treatment with diazomethane. The identification of trimethoxyindoline, dopamine-o-quinone and dimethoxyindole was easily achieved by this ionization method, together with accurate mass measurements and collision experiments. The structures of these compounds are in agreement with those already hypothesized in studies on melanogenesis.