Severe Weakness of Hip Flexor after Iliopsoas Tenotomy: Two Case Reports.

Hip arthroscopies are becoming a standard surgical technique, with psoas tenotomy being a relatively common procedure during this operation. A 37-year-old male and a 42-year-old female with internal hip snapping came to our department. Arthroscopic partial psoas tenotomy of the iliopsoas portion of the conjoint tendon was performed, but its results were bad. Patients reported preoperative unilateral low-back pain and weakness when flexing the hip. Unilateral atrophy of the lumbar psoas and fatty multifidus were detected in both cases. Patients at risk of unsatisfactory outcomes after psoas tenotomy should be ideally identified prior to surgery. Warning symptoms, physical examination, and imaging studies should be considered to avoid unsatisfactory results.

Micellar electrokinetic chromatography with laser induced fluorescence detection shows increase of putrescine in erythrocytes of Parkinson's disease patients.

A highly sensitive method was developed to measure putrescine by micellar electrokinetic chromatography with laser induced fluorescence detection with excellent linearity in the 1 nM to 3 µM range. The technique was tested on a drop of blood from Parkinson's disease patients obtained by finger prick. The results showed a statistically significant increase of putrescine in the erythrocytes compared to controls and a non-significant increase in plasma. This high level of putrescine does not constitute by itself proof that putrescine and polyamines are directly related to Parkinson's disease. However, the present results and several others addressed in the discussion suggest that these compounds might be causally involved in the pathophysiology of Parkinson's disease. In addition, the analytical method reported here may help to find new biomarkers for many diseases including Parkinson's disease.

Effects of circuit resistance training and timely protein supplementation on exercise-induced fat oxidation in tetraplegic adults.

BACKGROUND: Substrate utilization during exercise in persons with spinal cord injury (SCI) remains poorly defined. PURPOSE: To investigate effects of circuit resistance training (CRT) and timing of protein supplementation (PS) on fuel utilization in persons with tetraplegia. METHODS: Eleven individuals with chronic tetraplegia underwent 6 months of CRT 3 times weekly. Five randomly assigned participants received immediate PS (iPS) administered in split doses prior to and following all exercise sessions. Other participants consumed a matched dose of PS that was delayed until 24 hours post-exercise (dPS). Participants underwent a maximal graded exercise test (GXT) to volitional exhaustion at 4 conditioning time points: 3 months before (-3mo), at the beginning of (0mo), 3 months into (3mo), and 6 months following (6mo) the CRT conditioning program. Respiratory measures were continuously obtained throughout the GXT via open-circuit spirometry. Fuel utilization and energy expenditure were computed from the respiratory data. RESULTS: The differences in changes in substrate utilization between the PS groups were not significant as determined by the interaction of PS group and conditioning time point, F (3, 27) = 2.32, P = .098, η(2) P = .205. Maximal absolute fat oxidation did not change significantly from 0 to 6mo (mean difference, 0.014 ± 0.031 g/min; P = .170), and fat oxidation remained low never exceeding an average of 0.10 ± 0.09 g/min for any given exercise intensity. CONCLUSION: Maximum fat utilization during exercise and fat utilization at matched exercise intensities were not increased in persons with tetraplegia, independent of PS, and levels of fat oxidation remained low after training.

Efecto de diferentes niveles de aceites esenciales de Lippia origanoides kunth en pollos de engorde / Effect of different levels of essential oils of Lippia origanoides kunth in broiler chicken

Objetivo. Determinar el nivel de inclusión de aceite esencial de Lippia origanoides Kunth (AEO) que maximice el peso corporal y la eficiencia económica. Materiales y métodos. Los AEO se obtuvieron por hidrodestilación y se analizaron por GC/MS. Se evaluaron cuatro niveles, 0, 100, 200 y 300 ppm de AEO en dos grupos de pollos; un grupo retado con ooquistes atenuados de coccidia y otro no retado. El nivel óptimo de inclusión fue estimado mediante una función sinusoidal. Resultados. La suplementación con 100 ppm de AEO redujo el impacto negativo del reto con ooquistes atenuados de coccidia sobre el peso corporal, 1.799, 1.889 y 1.995 g en los grupos retado sin AEO, retado + AEO y control, respectivamente (p<0.001). Se encontró una interacción significativa entre la suplementación con AEO y reto sobre el peso corporal y la conversión de alimento (p<0.05). El nivel de AEO que maximiza el peso corporal en los grupos de pollos no retados fue 65 ppm; mientras que para los grupos retados fue 147 ppm. Conclusiones. Se demostró que los AEO ricos en timol pueden ser un aditivo natural viable para la producción de carne de pollo.

Objective. Determine the level of inclusion of essential oil of Lippia origanoides Kunth (AEO) to maximize body weight and economic efficiency. Materials and methods. The AEO was obtained by hydrodistillation and analyzed by GC / MS. Four levels, 0, 100, 200 and 300 ppm of AEO were evaluated in two groups of chickens, a group challenged with attenuated oocysts of coccidia and another unchallenged group. Results. Supplementation with 100 ppm of AEO reduced the negative impact of the challenge with attenuated oocysts of coccidia with body weight, 1,799, 1,889 and 1,995 g in the groups challenged without AEO, challenged + AEO and control, respectively (p<0.001). A significant interaction was identified between supplementation with AEO and challenge on body weight and feed conversion (p<0.05). The AEO level that maximizes the level of body weight in non-challenged chickens groups was 65 ppm; it was 147 ppm for the challenged group. Conclusions. It was shown that AEO, rich in thymol, can be a viable natural additive for the production of chicken meat.

COMPOSITION AND BACTERICIDAL ACTIVITY AGAINST BENEFICIAL AND PATHOGENIC BACTERIA OF OREGANO ESSENTIAL OILS FROM FOUR CHEMOTYPES OF Origanum AND Lippia GENUS / COMPOSICIÓN Y ACTIVIDAD BACTERICIDA CONTRA BACTERIAS BENÉFICAS Y PATÓGENAS DE ACEITES ESENCIALES DE CUATRO QUIMIOTIPOS DE LOS GÉNEROS Origanum Y Lippia

Several studies have showed the antibacterial activity of oregano essential oils (OEO) chemotypes, carvarol and thymol against Gram positive and Gram negative pathogenic bacteria, but lack information on OEO antibacterial activity against beneficial bacteria. The object of this study was to compare the composition and minimum bactericidal concentration (MBC) of Origanum gender chemotypes: O. vulgare L. ssp. hirtum (OH), O. majorana (OM) y O. vulgare L. (OL) harvested in Colombia, against Lippia origanoides Kunth (LO) from Alto Patía in Colombia, and O. vulgare L. ssp. hirtum (OG) from Greece. The OEO composition was analyzed by gas chromatography coupled to mass spectrometer and its antibacterial activity by broth dilution and agar culture method. Three chemotypes were evaluated, OH and OG were carvacrol-type, LO and OL were thymol-tipe and OM was rich in sabinyl compound. The highest precursors content was showed to OEO from oregano varieties produced under greenhouse conditions at high altitude. The same bactericidal activity against Salmonella enteritidis (0.098 mg/mL) for OH and LO was founded. The lowest bactericidal activity against beneficial bacteria Lactobacillus acidophilus and Bifidobacterium breve was observed for OM (6.25 mg/mL) and LO (50 mg/mL), respectively. These results showed that LO native to Colombia had a comparable effect to OH and carvacrol against pathogenic enterobacteria and the lowest bactericidal activity against beneficial bacteria. These results showed a selective bactericidal effect against pathogenic beneficial bacteria of Origanum ssp. and L. origanoides chemotypes. A good potential to use L. origanoides as antimicrobial additive for animal and human health was found.

Diversos estudios demuestran la actividad antibacterial de distintos quimiotipos de aceites esenciales de orégano (OEO), carvacrol y timol, contra bacterias patógenas Gram positivas y Gram negativas, pero muy poca información está disponible sobre el efecto de los OEO en bacterias benéficas. El objetivo de este estudio fue comparar la composición y concentración mínima bactericida (CMB) de OEO de quimiotipos del género Origanum: O. vulgare L. ssp. hirtum (OH), O. majorana (OM) y O. vulgare L. (OL) cultivados en Colombia, frente Lippia origanoides Kunth (LO) nativo del Alto Patía en Colombia y O. vulgare L. ssp. hirtum cultivado en Grecia (OG). Los OEO se obtuvieron por arrastre de vapor, la composición se determinó por cromatografía de gases acoplada a espectrometría de masas y la actividad antibacteriana mediante el método de dilución en caldo y cultivo en agar. Se evaluaron tres quimiotipos de OEO: OH y OG tipo-carvacrol, LO y OL tipo-timol y OM rico en compuestos sabinilo. Las variedades de orégano producidas bajo condiciones de invernadero a alta altitud mostraron un alto contenido de precursores. Un valor similar de concentración mínima bactericida contra Salmonella enteritidis (0.098 mg/mL) fue observada para carvacrol, OH y LO. La más baja actividad bactericida contra las bacterias benéficas Lactobacillus acidophilus y Bifidobacterium breve fue observada para OM (6.25 mg/mL) y LO (50 mg/mL), respectivamente. Estos resultados mostraron que LO, nativo de Colombia presentó un efecto antibacteriano comparable a OH y carvacrol contra enterobacterias patógenas y una baja actividad bactericida contra las bacterias benéficas. Estos resultados mostraron un efecto bactericida selectivo contra bacterias benéficas y patógenas de los quimiotipos Origanum ssp. y L. origanoides. Se comprobó un buen potencial de L. origanoides para uso como aditivo antimicrobiano para la salud humana y animal.

Clinical usefulness of lanthanum carbonate for serum phosphate control in difficult patients.

BACKGROUND: The adequate control of phosphataemia is of major importance in end-stage renal disease patients on maintenance dialysis. Recently, lanthanum carbonate (LC) has been added to the phosphate binder armamentarium. To our knowledge, no studies have yet evaluated the usefulness of this drug in uncontrolled hyperphosphataemic patients. METHODS: This was a 6-month prospective observational study. Patients on chronic hemodialysis who had previously failed to achieve serum phosphate control were enrolled. Thirty-four patients (i.e. 11% out of 305 from three dialysis units) met the inclusion criteria. Lanthanum carbonate was introduced and titrated to achieve serum phosphate control, according to the KDOQI guidelines. Clinical targets, gastrointestinal symptoms, and patients' satisfaction with therapy were assessed at baseline and after 6 months. RESULTS: Eight patients (23.5%) were withdrawn from the study due to side effects. In the remaining patients, serum phosphate level significantly decreased from 5.8 to 4.4 mg/dl and calcium-phosphate product also decreased significantly from 55.6 to 41.8 mg(2)/dl(2). The average number of all phosphate binder tablets taken per day was reduced from 6.7 to 4.7. Evaluation scores of dyspeptic symptoms and of patient's satisfaction with therapy also improved: from 7.5 to 5.3 and from 6.6 to 8.1, respectively. CONCLUSIONS: The introduction of LC improved serum phosphate control in over 70% of these "difficult patients". A lower pill burden was also obtained, which might help to simplify treatment and increase patients' compliance. Dyspeptic symptoms and overall satisfaction with treatment also improved.

Enhanced GABAergic tone in the ventral pallidum: memory of unpleasant experiences?

The nucleus accumbens (NAc) has emerged as an important part of the neural circuitry regulating depressive-like behaviors. Given that the NAc GABAergic medium spiny neurons project to the ventral pallidum (VP), it is reasonable to suggest that the VP may also be involved in these behaviors. Consequently, we explored the role of the VP GABAergic terminals during depressive-like behaviors in rats using the forced swim test (FST) and the sucrose preference test (SPT). Microdialysis coupled with micellar electrokinetic chromatography was used to monitor in vivo changes of GABA in the VP during the FST. GABA levels significantly increased during day-1 and day-2 during swimming, returning to the pre-swimming levels after the test. Basal concentrations of GABA on day-2 of the FST significantly increased with respect to day-1. In another set of experiments, intra-VP injections of vigabatrin (a GABA transaminase inhibitor) increased extracellular GABA and immobility behaviors in the FST while the direct GABAA receptor antagonist bicuculline reduced immobility behaviors. In the SPT, intra-VP vigabatrin injection significantly reduced preference for sucrose while bicuculline did not produce any change. At the postsynaptic side, we used semiquantitative RT-PCR to measure mRNA expression of 17 GABAA receptor subunits (α1-α6, ß1-ß3, γ2, δ, ε, θ, π, and ρ1-ρ3) in rats subjected to the FST. We found a significant reduction of α3 and γ2 subunit expression and an increase of δ subunit expression after day-2 in rats subject to the FST which might enhance tonic inhibition of the VP. Furthermore, immunoblot experiments revealed that protein expression of γ2 and δ subunits changed 6 days after FST in a way similar to mRNA expression. These results suggest that the enhanced VP-GABAergic tone might trigger a low motivational state, anhedonia and a possible memory mechanism for unpleasant experiences.

[Manual single infusion of combined remifentanil and propofol for anesthesia during laparoscopic gynecology procedures: a case series]. / Infusión manual única de remifentanil y propofol para anestesia en cirugía laparoscópica ginecológica: serie de casos.

OBJECTIVE: To describe a single manual infusion technique for total intravenous anesthesia with remifentanil and propofol. MATERIAL AND METHODS: Descriptive study of a series of 30 women classified as ASA 1 or 2 who received total intravenous anesthesia by means of a single manual infusion of a combination of remifentanil and propofol for laparoscopic gynecology procedures. The patients received 5 microg of remifentanil plus 2 mg of propofol per milliliter of normal saline solution. The rate of infusion was established according to remifentanil requirements and modified in accordance with the bispectral (BIS) index. RESULTS: Sufficient hemodynamic stability was maintained in all patients, with BIS values between 40 and 60. The average time until awakening was 5.2 minutes after the anesthetic infusion had been halted. CONCLUSIONS: Total intravenous anesthesia by means of a single manual infusion of remifentanil and propofol provided appropriate anesthetic and surgical conditions, with rapid, predictable awakening.

Determinación y cuantificación de bacterias acidolácticas por PCR en tiempo real / Identification and quantification of lactic acid bacteria by real-time PCR

Objetivo. Establecer un ensayo de PCR-TR para determinar el tamaño poblacional y la composición de bacterias totales y de ácido lácticas, en particular las pertenecientes a los géneros Lactobacillus y Bifidobacterium. Materiales y métodos. La especificidad de los iniciadores fue verificada utilizando la técnica de PCR convencional. Diluciones de 101 a 10- 4 ng/μl de ADN fueron preparadas a partir de cada cultivo microbiano y utilizadas en las curvas de calibración. La temperatura de disociación y la eficiencia de cada reacción de PCR-TR se determinaron con el software del iQCycler (Bio Rad®), versión 3.1. Resultados. Los juegos de iniciadores utilizados resultaron específicos para cada grupo microbiano, sin detectar reacción cruzada. Las eficiencias de las reacciones de la PCR-TR para bacterias totales, acidolácticas, Lactobacillus y Bifidobacterium fueron 104.4%, 98.1%, 113.3% y 103.3%, respectivamente. Conclusiones. Al obtener reacciones específicas y eficiencias cercanas al 100%, es posible cuantificar las poblaciones bacterianas totales, acidolácticas, Lactobacillus y Bifidobacterium con una alta especificidad. Por lo tanto, la técnica de PCRTR puede utilizarse para monitorear cambios poblacionales bacterianos en ambientes como el tracto gastrointestinal de pollos de engorde, donde las bacterias acidolácticas, Lactobacillus y Bifidobacterium son habitantes comunes.

Proteomic study via a non-gel based approach of meningococcal outer membrane vesicle vaccine obtained from strain CU385: a road map for discovering new antigens.

This work presents the results from a study of the protein composition of outer membrane vesicles from VA-MENGOC-BC (Finlay Institute, Cuba), an available vaccine against serogroup B Neisseria meningitidis. Proteins were identified by means of SCAPE, a 2DE-free method for proteome studies. More than one hundred proteins were detected by tandem liquid chromatographymass spectrometry analysis of fractions enriched in peptides devoid of histidine or arginine residues, providing a detailed description of the vaccine. A bioinformatic analysis of the identified components resulted in the identification of 31 outer membrane proteins and three conserved hypothetical proteins, allowing the cloning, expression, purification and immunological study of two of them (NMB0088 and NMB1796) as new antigens.

[Chiari I malformation: postsurgical evolution after 2 years. Report of ten cases]. / Malformación de Chiari tipo 1: evolución postoperatoria a dos años. Análisis de 10 casos.

UNLABELLED: OBJECTIVE To describe the clinical and radiological evolution of ten patients with Chiari I malformation (CIM), treated surgically. METHOD: Ten patients with Chiari I malformation underwent suboccipital craniectomy, laminectomy of C1 and dural patch grafting. All of them were followed for at least two years. A magnetic resonance imaging was performed 6 months after surgery. Clinical preoperative evolution and time of installation, results of MRI and clinical postoperative evolution were correlated. RESULTS: In postoperative clinical evolution, we noted an important improvement in sensitive function, decrease of the syringohydromielia and partial improvement of cerebellar functions. Improvement of the motor alteration was less marked. During the two years after treatment the muscular atrophy did not change. CONCLUSIONS: Chiari I malformation is a congenital disease with many clinical manifestations which usually increase with time. A suitable diagnostic studies as well as an appropriate treatment are needed to improve the neurological results.

Malformación de Chiari tipo I: evolución postoperatoria a dos años. Análisis de 10 casos / Chiari I malformation: postsurgical evolution after 2 years. Report of ten cases

Objetivo. Describir la evolución de 10 pacientes con Malformación de Chiari tipo I (MCI), desde el punto de vista clínico y de imagen mediante resonancia magnética (RM). Método. A 10 pacientes con Malformación de Chiari se les realizó craniectomía suboccipital media, resección de arco posterior de C1 y plastia dural. A todos se les hizo un seguimiento clínico de dos años, y se hizo evaluación mediante RM a los seis meses del postoperatorio. Se correlaciona el tiempo de evolución preoperatoria, hallazgos de imagen mediante RM y la evolución clínica postoperatoria. Resultados. La evolución clínica postoperatoria mostró una mejoría importante en cuanto a función sensitiva, correlacionándose con la involución de la siringohidromielia que acompañaba a esos casos, mejoría parcial de sus funciones cerebelosas y, en menor grado, mejoría de la alteración motora. Las manifestaciones de atrofia muscular no tuvieron modificaciones en el seguimiento a dos años. Conclusiones. La MCI es una enfermedad congénita con múltiples manifestaciones clínicas que se van agravando conforme pasa el tiempo. Un diagnóstico oportuno y un tratamiento adecuado son indispensables para obtener los mejores resultado posibles desde el punto de vista neurológico

Objective To describe the clinical and radiological evolution of ten patients with Chiari I malformation (CIM), treated surgically. Method. Ten patients with Chiari I malformation underwent suboccipital craniectomy, laminectomy of C1 and dural patch grafting. All of them were followed for at least two years. A magnetic resonance imaging was performed 6 months after surgery. Clinical preoperative evolution and time of installation, results of MRI and clinical postoperative evolution were correlated. Results. In postoperative clinical evolution, we noted an important improvement in sensitive function, decrease of the syringohydromielia and partial improvement of cerebellar functions. Improvement of the motor alteration was less marked. During the two years after treatment the muscular atrophy did not change. Conclusions. Chiari I malformation is a congenital disease with many clinical manifestations which usually increase with time. A suitable diagnostic studies as well as an appropriate treatment are needed to improve the neurological results

[Association of carpal tunnel syndrome and tuberculosis]. / Asociación de síndrome del túnel del carpo y tuberculosis.

Extrapulmonary tuberculosis, and especially articular, is less frequent than their pulmonary form. We report a 59 year-old men that requests medical attention for suggestive symptoms of carpal tunnel syndrome, of which is operated, being demonstrated in the carpo a granulomatous tissue including the median nerve suggestive of sarcoidosis or tuberculosis. In sputum the presence of Micobacterium tuberculosis was demonstrated. The respiratory symptoms of pulmonary tuberculosis were for the patient less excellent symptoms in relation to those produced by compression of the median nerve. The relationship between the tuberculosis and the carpal tunnel syndrome is demonstrated.

Asociación de síndrome del túnel del carpo y tuberculosis / Association of carpal tunnel syndrome and tuberculosis

La tuberculosis de localización extrapulmonar, y especialmente articular, es menos frecuente que su forma pulmonar. Reportamos un paciente varón de 59 años que solicita atención médica por síntomas sugestivos de síndrome del tunel del carpo, del cual es operado demostrándose en el carpo un tejido granulomatoso englobando el nervio mediano sugestivo de sarcoidosis o tuberculosis. Mediante estudio del esputo se demuestra la presencia de Micobacterium tuberculosis. Se destaca que los síntomas respiratorios sugestivos de tuberculosis pulmonar fueron para el paciente síntomas menos relevantes en relación a aquellos producidos por compresión del nervio mediano. Se demuestra la relación entre la tuberculosis y el síndrome del tunel del carpo (AU)

Selective isolation and identification of N-terminal blocked peptides from tryptic protein digests.

A method for the easy isolation and direct sequencing of N-terminally blocked peptide in proteins refractory to N-terminal sequencing was developed. It is based essentially on tandem enzymatic treatments of the protein with trypsin and carboxypeptidase B, and selective isolation of the Nalpha-blocked peptide using ion-exchange chromatography. The chromatographic step was optimized for picomole amounts of sample and very short elution times by placing a thin layer of the resin over the membrane of an ultrafiltration tube. The isolated fraction can be analyzed directly using MALDI or ESI mass spectrometry. The method was applied to several recombinant and natural N-terminal acetylated proteins. A critical discussion on the intrinsic limitations of the method is also given.

Primary structure of two cytolysin isoforms from Stichodactyla helianthus differing in their hemolytic activity.

Sticholysin I (St-I) and sticholysin II (St-II) are cytolysins purified from the sea anemone Stichodactyla helianthus with a high degree of sequence identity (93%) but clearly differenced in their hemolytic activity. In order to go further into the structural determinants for the different behavior of St-I and St-II, we report here the complete amino acid sequences and the consensus secondary structure prediction of both proteins. The complete determination of St-II primary structure confirms the partial revision of cytolysin III amino acid sequence. All nonconservative changes between St-I and St-II are located at the N-terminal. According to our prediction these changes could be located at the same face of an alpha-helix during pore formation events and could account for the observed differences in hemolytic activity between St-I and St-II.

A prospective comparison of developmental outcome of children with in utero cocaine exposure and controls using the Battelle Developmental Inventory.

Children with in utero cocaine exposure may be at risk for adverse neurodevelopmental outcome. To evaluate such outcome in young children, we administered the Battelle Developmental Inventory (BDI) to a group of inner-city children with (COC) and without (CON) in utero cocaine exposure at ages 3 and 5 years. Sixty-five COC and 68 CON, similar at age of testing, were evaluated at both time points by examiners masked to child group status. Both groups scored poorly and worsened over time. Although Total BDI raw scores were lower in the COC group than in the CON group at 3 years, this difference was related to postnatal environmental factors, caregiver (p = .022), and home environment (p = .010), not to in utero cocaine exposure (p = .88). At 5 years, the Total BDI score was related to the home environment (p < .001) but not to the caregiver (p = .36) or in utero cocaine exposure (p = .83). We conclude that inner-city children are at risk for adverse developmental outcome regardless of in utero cocaine exposure.

Dextranase (alpha-1,6 glucan-6-glucanohydrolase) from Penicillium minioluteum expressed in Pichia pastoris: two host cells with minor differences in N-glycosylation.

Differences in glycosylation between the natural alpha-1,6 glucan-6-glucanohydrolase from Penicillium minioluteum and the heterologous protein expressed in the yeast Pichia pastoris were analyzed. Glycosylation profiling was carried out using fluorophore-assisted carbohydrate electrophoresis and amine absorption high-performance liquid chromatography (NH(2)-HPLC) in combination with matrix-assisted laser desorption-time of flight-mass spectrometry. Both microorganisms produce only oligomannosidic type structures, but the oligosaccharide population differs in both enzymes. The native enzyme has mainly short oligosaccharide chains ranging from Man(5)GlcNAc(2) to Man(9)GlcNAc(2), of which Man(8)GlcNAc(2) was the most represented oligosaccharide. The oligosaccharides linked to the protein produced in P. pastoris range from Man(7)GlcNAc(2) up to Man(14)GlcNAc(2), with Man(8)GlcNAc(2) and Man(9)GlcNAc(2) being the most abundant structures. In both enzymes the first glycosylation site (Asn(5)) is always glycosylated. However, Asn(537) and Asn(540) are only partially glycosylated in an alternate manner.

Differentiating alpha- and beta-aspartic acids by electrospray ionization and low-energy tandem mass spectrometry.

Spectra obtained by low-energy electrospray ionization tandem mass spectrometry (ESI-MS/MS) of 34 peptides containing aspartic acids at position n were studied and unambiguously differentiated. beta-Aspartic acid yields an internal rearrangement similar to that of the C-terminal rearrangements of protonated and cationized peptides. As a result of this rearrangement, two different ions containing the N- and the C-terminal ends of the original peptide are formed, namely, the bn-1 + H2O and y"l - n + 1 - 46 ions, respectively, where e is the number of amino acid residues in the peptide. The structure suggested for the y"l - n + 1 - 46 ion is identical to that proposed for the vn ions observed upon high-energy collision-induced dissociation (CID) experiments. The intensity of these ions in the low-energy MS/MS spectra is greatly influenced by the presence and position of basic amino acids within the sequences. Peptides with a basic amino acid residue at position n - 1 with respect to the beta-aspartic acid yield very intense bn-1 + H2O ions, while the y"l - n + 1 - 46 ion was observed mostly in tryptic peptides. Comparison between the high- and low-energy MS/MS spectra of several isopeptides suggests that a metastable fragmentation process is the main contributor to this rearrangement, whereas for long peptides (40 AA) CID plays a more important role. We also found that alpha-aspartic acid containing peptides yield the normal immonium ion at 88 Da, while peptides containing beta-aspartic acid yield an ion at m/z 70, and a mechanism to explain this phenomenon is proposed. Derivatizing isopeptides to form quaternary amines, and performing MS/MS on the sodium adducts of isopeptides, both improve the relative intensity of the bn + 1 + H2O ions. Based on the above findings, it was possible to determine the isomerization sites of two aged recombinant growth proteins.