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RATIONALE AND OBJECTIVES: The objective of this study was to analyze the role of dynamic magnetic resonance imaging (MRI) in patients who suffered from groin pain and whose physical examination and ultrasound returned inconclusive/indefinite results, as well as in patients receiving an ongoing assessment for a previous herniotomy. MATERIAL AND METHODS: For this study, 25 patients 14 women and 11 men were selected with a mean age of 41.6 years, including clinical complaints, such as groin pain and or a previous herniotomies. These patients underwent dynamic MRI. Reports were created by a radiology resident and a radiology consultant. Clinical and ultrasound documentation were compared to with imaging results from the MRI. RESULTS: The results of the dynamic MRI were negative for 23 patients (92%) and positive for two patients (8%). One patient suffered from an indirect hernia and one from a femoral hernia. A repeated hernia was an excluding for the preoperated patients with pain and ongoing assessment. CONCLUSIONS: Dynamic MRI shows substantially higher diagnostic performance in exclusion of inguinal hernia, when compared to a physical examination and ultrasound. The examination can also be used in assessments to analyze the operation's results.
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Hernia Inguinal , Masculino , Humanos , Femenino , Adulto , Hernia Inguinal/complicaciones , Hernia Inguinal/diagnóstico por imagen , Hernia Inguinal/cirugía , Ingle/cirugía , Herniorrafia/métodos , Dolor Pélvico/cirugía , Imagen por Resonancia MagnéticaRESUMEN
BACKGROUND AND PURPOSE: Prognosis after chemoradiotherapy (CRT) for anal squamous cell carcinoma (ASCC) shows marked differences among patients according to TNM subgroups, however individualized risk assessment tools to better stratify patients for treatment (de-) escalation or intensified follow-up are lacking in ASCC. MATERIALS AND METHODS: Patients' data from eight sites of the German Cancer Consortium - Radiation Oncology Group (DKTK-ROG), comprising a total of 605 patients with ASCC, treated with standard definitive CRT with 5-FU/Mitomycin C or Capecitabine/Mitomycin C between 2004-2018, were used to evaluate prognostic factors based on Cox regression models for disease-free survival (DFS). Evaluated variables included age, gender, Karnofsky performance score (KPS), HIV-status, T-category, lymph node status and laboratory parameters. Multivariate cox models were separately constructed for the whole cohort and the subset of patients with early-stage (cT1-2 N0M0) tumors. RESULTS: After a median follow-up of 46 months, 3-year DFS for patients with early-stage ASCC was 84.9%, and 67.1% for patients with locally-advanced disease (HR 2.4, p < 0.001). T-category (HR vs. T1: T2 2.02; T3 2.11; T4 3.03), N-category (HR versus N0: 1.8 for N1-3), age (HR 1.02 per year), and KPS (HR 0.8 per step) were significant predictors for DFS in multivariate analysis in the entire cohort. The model performed with a C-index of 0.68. In cT1-2N0 patients, T-category (HR 2.14), HIV status (HR 2.57), age (1.026 per year), KPS (HR 0.7 per step) and elevated platelets (HR 1.3 per 100/nl) were associated with worse DFS (C-index of 0.7). CONCLUSION: Classical clinicopathologic parameters like T-category, N-category, age and KPS remain to be significant prognostic factors for DFS in patients treated with contemporary CRT for ASCC. HIV and platelets were significantly associated with worse DFS in patients with early stage ASCC.
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Neoplasias del Ano , Carcinoma de Células Escamosas , Quimioradioterapia , Neoplasias del Ano/terapia , Carcinoma de Células Escamosas/terapia , Infecciones por VIH/tratamiento farmacológico , Infecciones por VIH/etiología , Humanos , Mitomicina , Pronóstico , Estudios RetrospectivosRESUMEN
BACKGROUND: Thus medical students must be inspired to undertake this specialty. Students complain that the teaching is subordinate to patient care and limited by a lack of time and medical personnel. Although there are many studies assessing student perceptions, few exist that focus on the issues that teachers face. OBJECTIVE: To analyse student teaching in the daily routine and its potential' problems from the surgeon's perspectives. MATERIAL AND METHODS: In this prospective study guidelines for semistructured interviews with formulated, open questions were created, which were specified with further questions. All interviews were conducted using these guidelines and recorded. The number of interviews were a function of the concept of content saturation. RESULTS: All 22 participants perceived that the teaching in clinical practice is of paramount importance. Nevertheless, respondents described that learning goals in the clinical routine are not always achieved. The main reason is a lack of time; however, as clinical experience increases other factors will similarly become more important: Consultants and heads of departments complain about deficiencies in students' previous knowledge, including insufficient motivation. Most respondents described that they do not feel appreciated for teaching. Overall, student teaching was perceived as an additional burden but all respondents found the task to be extremely worthwhile. CONCLUSION: In addition to the lack of personnel, a lack of appreciation is the most significant obstacle towards effective teaching. It is therefore important to increase the value of teaching by rewarding good achievements and the creation of effective transparency.
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Estudiantes de Medicina , Cirujanos , Actitud del Personal de Salud , Humanos , Motivación , Estudios Prospectivos , EnseñanzaRESUMEN
BACKGROUND: Feedback is an essential element of learning. Despite this, students complain about receiving too little feedback in medical examinations, e.g., in an objective structured clinical examination (OSCE). This study aims to implement a written structured feedback tool for use in OSCEs and to analyse the attitudes of students and examiners towards this kind of feedback. METHODS: The participants were OSCE examiners and third-year medical students. This prospective study was conducted using a multistage design. In the first step, an unstructured interrogation of the examiners formed the basis for developing a feedback tool, which was evaluated and then adopted in the next steps. RESULTS: In total, 351 students and 51 examiners participated in this study. A baseline was created for each category of OSCE station and was supplemented with station-specific items. Each of these items was rated on a three-point scale. In addition to the preformulated answer options, each domain had space for individual comments. A total of 87.5% of the students and 91.6% of the examiners agreed or rather agreed that written feedback should continue to be used in upcoming OSCEs. CONCLUSION: The implementation of structured, written feedback in a curricular, summative examination is possible, and examiners and students would like the feedback to be constant.
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Competencia Clínica , Evaluación Educacional , Retroalimentación , Humanos , Examen Físico , Estudios ProspectivosRESUMEN
BACKGROUND: Currently, no data are available, which reflect the situation of medical doctors specializing in neurology in German hospitals. In order to secure the high standard of neurological patient care it is essential to evaluate the working conditions and the specialty training in neurology. OBJECTIVE: This nationwide survey was conducted throughout Germany with the aim to address problems and to give suggestions for improvements in neurological training curricula. MATERIAL AND METHODS: The survey was online from February to May 2017 and 953 neurologists undergoing further training participated. RESULTS: More than half of the young neurologists were satisfied with their medical training. One of the main problems that complicates clinical training is the workload. In addition, organizational obstacles within the clinic, such as poor structure of education or a lack of mentors, lead to dissatisfaction among participants. The size or type of the department, as well as the prevailing service system, exert only a minor influence on the quality of specialist training, although there were differences especially in the self-assessment of the participants in connection with the type of department (university hospital versus public or private hospital). CONCLUSION: Specialist training in neurology can be improved by simple arrangements, e.â¯g., the introduction of a binding rotation scheme, internal mentoring and structured feedback. In addition, it will be necessary to relieve medical staff of administrative duties in order to create time for training and the learning of competencies.
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Neurólogos , Neurología , Curriculum/normas , Alemania , Humanos , Neurólogos/educación , Neurólogos/estadística & datos numéricos , Neurología/educación , Neurología/estadística & datos numéricos , Encuestas y CuestionariosRESUMEN
INTRODUCTION: In current literature, the participation of residents in surgical procedures is discussed as a negative outcome factor, particularly due to an increase of postoperative complications. This study investigated whether minor proctologic surgery with resident participation has a higher rate of postoperative complications. PATIENTS AND METHODS: All patients who underwent an elective Milligan-Morgan hemorrhoidectomy or a resection of pilonidal sinus with rotational flap closure between January 2007 and December 2013 where included in a retrospective database. Primary outcome measure was postoperative complications rate with and without resident participation. RESULTS: Forty-two (6 females: 36 males) patients underwent resection of pilonidal sinus and 61 (17 females: 44 males) patients received a hemorrhoidectomy. Twenty-two patients with pilonidal sinus and 26 patients with hemorrhoids were operated by residents. There were no differences in patient demographics. Residents need significantly more time to perform a pilonidal sinus resection (54min vs. 34.5min; P = 0.004). For hemorrhoidectomy, there were no significant differences in operative time (24min vs. 23.5min; P = 0.656). There were no significant differences in the resident and the consultant group, neither in hemorrhoidectomy nor in pilonidal sinus resection regarding readmission or outpatient visits. In the group of patients with pilonidal sinus resections, 3 patients developed a recurrence, leading to a recurrence rate of 7.1% without significant differences between the two groups (0 vs. 3; P = 0.09). CONCLUSION: The participation of residents in proctologic procedures is not associated with higher postoperative complication rates. Residents should be exposed to proctology procedures on a regular basis, even though the operative time will be prolonged.
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Competencia Clínica , Cirugía Colorrectal/educación , Hemorreoidectomía/educación , Internado y Residencia , Seno Pilonidal/cirugía , Complicaciones Posoperatorias/etiología , Adolescente , Adulto , Anciano , Femenino , Estudios de Seguimiento , Alemania , Humanos , Estimación de Kaplan-Meier , Modelos Logísticos , Masculino , Persona de Mediana Edad , Complicaciones Posoperatorias/epidemiología , Estudios Retrospectivos , Colgajos Quirúrgicos , Resultado del Tratamiento , Adulto JovenRESUMEN
Cap myopathy is a rare congenital myopathy characterized by the presence of caps within muscle fibres and caused by mutations in ACTA1, TPM2 or TPM3. Thus far, only three cases with TPM3-related cap myopathy have been described. Here, we report on the first autosomal dominant family with cap myopathy in three-generations, caused by a novel heterozygous mutation in the alpha-tropomyosin-slow-encoding gene (TPM3; exon 4; c.445C>A; p.Leu149Ile). The three patients experienced first symptoms of muscle weakness in childhood and followed a slowly progressive course. They presented generalized hypotrophy and mild muscle weakness, elongated face, high arched palate, micrognathia, scoliosis and respiratory involvement. Intrafamilial variability of skeletal deformities, respiratory involvement and mild cardiac abnormalities was noted. Muscle MRI revealed a recognizable pattern of fatty muscle infiltration and masseter muscle hypertrophy. Subsarcolemmal caps were present in 6-10% of the fibres and immunoreactive with anti-tropomyosin antibodies. We conclude that the MRI-pattern of muscle involvement and the presence of masseter muscle hypertrophy in cap myopathy may guide molecular genetic diagnosis towards a mutation in TPM3. Regular respiratory examinations are important, even if patients have no anamnestic clues. We compare our findings to all cases of cap myopathy with identified mutations (n=11), thus far reported in the literature.
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Músculo Esquelético/patología , Mutación , Tropomiosina/genética , Adulto , Anciano , Diagnóstico Diferencial , Progresión de la Enfermedad , Familia , Femenino , Heterocigoto , Humanos , Hipertrofia/diagnóstico , Hipertrofia/etiología , Hipertrofia/genética , Hipertrofia/patología , Imagen por Resonancia Magnética , Masculino , Músculo Masetero/anomalías , Músculo Masetero/patología , Miopatías Estructurales Congénitas/complicaciones , Miopatías Estructurales Congénitas/diagnóstico , Miopatías Estructurales Congénitas/genética , Miopatías Estructurales Congénitas/patología , Adulto JovenRESUMEN
A rare cause of acute liver failure is adult onset Still's disease (AOSD), a systemic inflammatory disorder. We present the case of a 24-year-old woman who presented with acute liver failure necessitating high urgency liver transplantation. The diagnosis of AOSD was established in accordance with the Yamaguchi classification criteria, including arthralgia, fever, sore throat, rash and hepatosplenomegaly. The early detection and therapy of AOSD can possibly avoid the development of liver failure with a poor prognosis.
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Urgencias Médicas , Fallo Hepático Agudo/etiología , Fallo Hepático Agudo/cirugía , Trasplante de Hígado , Enfermedad de Still del Adulto/complicaciones , Enfermedad de Still del Adulto/cirugía , Adulto , Conducta Cooperativa , Diagnóstico Diferencial , Femenino , Ferritinas/sangre , Fiebre de Origen Desconocido/etiología , Estudios de Seguimiento , Humanos , Mediadores de Inflamación/sangre , Comunicación Interdisciplinaria , Relación Normalizada Internacional , Recuento de Leucocitos , Fallo Hepático Agudo/diagnóstico , Pruebas de Función Hepática , Complicaciones Posoperatorias/diagnóstico , Enfermedad de Still del Adulto/diagnóstico , Tomografía Computarizada por Rayos XRESUMEN
Photo-induced fruiting-body formation of the slime mold Physarum polycephalum can be divided into two stages. The first stage (I) starts with the beginning of illumination (0 h) and ends with the formation of nodules (12 h). The second stage (II) is characterized by culmination, sporangiophore formation and melanization of sporangiophore heads (13-17 h). We investigated the expression of actin, alpha- and beta-tubulin during this differentiation process using Northern blot analysis and run-off transcription in isolated nuclei. Whereas actin mRNA is irreversibly lost during stage I, we observed two peaks in mRNA concentration for alpha-tubulin and one peak for that of beta-tubulin during stage I and a coordinated alpha/beta-tubulin mRNA induction during stage II. Stage II induction appears to be related to a presporangial mitosis. Transcriptional activity of the three genes studied shows two maxima, namely one in the middle of stage I and the other at the end of stage II. Our data suggest that the expression of the three cytoskeletal proteins investigated follows a distinct temporal pattern comprising changes in both mRNA synthesis and decay. We also propose a novel function of tubulin in Physarum which is not related to mitosis.
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Actinas/genética , Physarum/genética , ARN Mensajero/análisis , Tubulina (Proteína)/genética , Actinas/biosíntesis , Northern Blotting , Diferenciación Celular , Núcleo Celular/metabolismo , Cromatografía de Afinidad , ADN/aislamiento & purificación , ADN/metabolismo , Sondas de ADN , Electroforesis en Gel de Poliacrilamida , Histonas/genética , Luz , Morfogénesis/efectos de la radiación , Hibridación de Ácido Nucleico , Physarum/efectos de la radiación , ARN/aislamiento & purificación , ARN/metabolismo , Esporas/genética , Transcripción Genética , Tubulina (Proteína)/biosíntesisRESUMEN
In growing plasmodia of the myxomycete Physarum polycephalum (G2-phase), three distinct classes of nuclei with a relative DNA content of 1x, 2x, and 4x are observed in the presumed haploid strain CL. The 2x and 4x species comprise up to 35% and 5% of the nuclei. Quantitative cytofluorometric studies of nuclei isolated in either G2- or S-phase or after FUDR treatment (G1 arrest) show that the three nuclear populations undergo a synchronous mitotic cycle and that the relative DNA content of the nuclear fractions in G-2 phase reflects the 2c, 4c, and 8c state. The heterogeneity of the nuclear population does, however, seem to be restricted to the growth phase. During a starvation period of 4 days that always preceeds sporulation (and also meiosis), the 4c nuclear population is reduced to 7%, 8c nuclei are no longer detected. These results suggest that a mechanism exists in Physarum for the selective detection and elimination of polyploid nuclei.
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Núcleo Celular/ultraestructura , Physarum/ultraestructura , Núcleo Celular/análisis , Replicación del ADN/efectos de los fármacos , ADN de Hongos/análisis , Citometría de Flujo , Floxuridina/farmacología , Interfase , Mitosis , Physarum/efectos de los fármacos , Physarum/crecimiento & desarrollo , PoliploidíaRESUMEN
Sporangiophore formation in Physarum plasmodia starts about 10 hr after photoinduction. It is characterized by the induction of two tubulins and of at least 15 major sporangiophore morphogenetic proteins. In vitro translation of extracted mRNA revealed that differential gene expression is based on a highly synchronous temporal program of loss of plasmodial and induction of sporulation-specific mRNA species. Using a cloned cDNA encoding part of a sporangiophore morphogenetic protein from Physarum as a probe it was found that the induction of the complementary mRNA activity is due to the induction of the mRNA itself. The results suggest that light induces, with a lag phase of about 10 hr, the transient activation of sporulation-specific genes.
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Regulación de la Expresión Génica , Physarum/fisiología , Esporas Fúngicas , Tubulina (Proteína)/genética , Proteínas Fúngicas/genética , Regulación de la Expresión Génica/efectos de la radiación , Punto Isoeléctrico , Luz , Peso Molecular , Morfogénesis , Physarum/genética , ARN Mensajero/genéticaRESUMEN
When crude extracts of the slime mold Physarum polycephalum were incubated with ATP and Mg2+ at 35 degrees C, a peptide of approximately 42,000 Da was predominantly phosphorylated. The kinase, separated from the phosphorylatable peptide, phosphorylated neither actin nor fragmin, both proteins of 42,000 Da, the latter known to cap and shorten actin filaments in a Ca2+-dependent manner. The phosphorylatable peptide was phosphorylated only at threonine residue(s), and its phosphorylation was almost completely inhibited by micromolar concentrations of Ca2+ in the extracts. The Ca2+-dependent inhibition of the phosphorylation was reversed by the subsequent addition of ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid but not by trifluoperazine. The Ca2+-dependent inhibition of the phosphorylation required either actin or another, so far unidentified, protein(s) which is distinct from calmodulin. Fragmin reversed the Ca2+/actin-dependent inhibition of the phosphorylation. The Ca2+-dependent actin-binding phosphorylatable protein named Cap 42 (a + b), consisting of two distinct 42,000-Da peptides a and b, was purified to near homogeneity. Peptide b was identified as the phosphorylatable subunit. Substoichiometric amounts of Cap 42 (a + b) reduced the low shear viscosity of F-actin solutions.
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Actinas/metabolismo , Calcio/metabolismo , Proteínas Portadoras/metabolismo , Proteínas del Citoesqueleto , Proteínas Protozoarias , Animales , Peso Molecular , Proteínas Musculares/farmacología , Faloidina/farmacología , Fosforilación , PhysarumRESUMEN
The influence of blue light on protein synthesis in spherulating Physarum polycephalum microplasmodia was studied using two-dimensional protein separation techniques. The starvation-induced plasmodium-spherule transition proceeds in the dark and is accompanied by the synthesis of 20 major differentiation-specific proteins as revealed by in vivo labelling with [35S]methionine. Three of these proteins are identical with cell wall components with respect to their mol. wts. (35 K, 34 K and 14 K) and isoelectric points. Spherulation is also accompanied by the appearance of 26 prominent differentiation-specific mRNA species translatable in the rabbit reticulocyte cell-free system. Six of the proteins synthesized in vitro co-migrate on two-dimensional gels with proteins labelled in vivo, two of them being cell wall components. Blue light, which inhibits spherulation completely, inhibits also the synthesis of spherule proteins and of spherule-specific mRNA activity. Only three protein components are induced by blue light, indicating that illumination does not induce a novel differentiated plasmodial state.
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Physarum/metabolismo , ARN Mensajero/metabolismo , ARN Protozoario/metabolismo , Animales , Luz , Proteínas Protozoarias/biosíntesis , ConejosRESUMEN
The differentiation of starving Physarum polycephalum microplasmodia into resting structures (spherules) was studied. Early events in this differentiation pathway include decreases in both plasmodial motility and protein synthesis. The starving plasmodia show a blue light avoidance response. Blue light (lambda max 450 nm, irradiance 16 W/m2) acts antagonistically to the starvation stimulus so that spherule formation is inhibited [16]. Light affects each of the above mentioned events of the differentiation pathway: the migration rate of illuminated plasmodia is stimulated, the light avoidance response is irreversibly lost. The rate of incorporation of radioactive leucine into plasmodial protein remains at a higher level in illuminated plasmodia as compared to the decreasing rate during spherule formation in the dark. Protein degradation, uptake of external leucine, and the size of the internal leucine pool are not affected by light. Analysis by SDS-polyacrylamide gel electrophoresis of pulse-labelled plasmodial proteins reveals that blue light inhibits the synthesis of distinct starvation-induced proteins and allows continued synthesis of all major plasmodial proteins. Some of the blue light responses described are mimicked by alpha-amanitin suggesting that light might influence gene expression at the level of transcription.
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Proteínas Fúngicas/biosíntesis , Regulación de la Expresión Génica/efectos de la radiación , Luz , Physarum/efectos de la radiación , Amanitinas/farmacología , Movimiento , Physarum/genética , Physarum/fisiologíaRESUMEN
Blue light induces sporulation of Physarum polycephalum macroplasmodia and reversibly inhibits spherulation (sclerotization) of microplasmodia. Illuminated microplasmodia have an abnormal appearance. The photobiological responses of the plasmodia appear to be unaffected by the absence of yellow pigment in the white mutant strain used. Illumination of microplasmodial suspensions with blue light (lambda max approximately 465 nm) results also in an early effect on glucose metabolism: glucose consumption is reversibly inhibited. By using radioactive glucose it was shown that the main products formed are a water-insoluble glucan and the disaccharide trehalose. Inhibition of glucose consumption in the light results in decreased production of these two compounds. Illumination of microplasmodial suspensions also causes a reversible effect on the pH of the medium which is interpreted as a decreased production of a yet unidentified acid from glucose. The action spectrum of the light-induced pH response shows maxima near 390, 465, and 485 nm. It resembles the absorption spectrum of a flavoprotein and confirms the existence of a blue-light receptor in P. polycephalum microplasmodia.
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Glucosa/metabolismo , Mutación , Células Fotorreceptoras/fisiología , Physarum/fisiología , Concentración de Iones de Hidrógeno , Cinética , Luz , Esporas Fúngicas/fisiologíaRESUMEN
The complexes formed from bacteriopsin and various retinyl compounds were analyzed by fluorescence and absorption spectroscopy. The binding of retinol occurs in two steps. In the first reaction the molecule is fixed in the retinal binding site of the protein. In this state, energy transfer from aromatic amino acid residues to the retinyl moiety is observed. all-trans-Retinal and the 13-, 11-, and 9-cis-retinols are bound in the chromophoric site. In the second reaction the cyclohexene ring and the side chain of the retinyl moiety are forced into a planar conformation. This reaction is mediated by a base (B1) with a pK of 3.8 and requires the oxygen atom but not the free hydroxyl group of retinol, indicating interaction with a group AH (pK greater than or equal to 10.5). The ring-chain planarization reaction is blocked for the 9-cis isomer of retinol. Binding studies with bacterioopsin and retinal isomers reveal that, as in the case of the corresponding retinols, B1 mediates ring-chain planarization in the case of the all-trans, 13-cis, and 11-cis isomers but not with the 9-cis isomer. Reconstitution of the purple complex from the intermediate 430-460-nm chromophore requires the presence of a second base (B2) with a pK of 4.6. This reaction is exclusive for all-trans- and 13-cis-retinal
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Bacteriorodopsinas , Carotenoides , Retinaldehído , Vitamina A , Sitios de Unión , Conformación Molecular , Unión Proteica , Conformación Proteica , Espectrometría de Fluorescencia , Espectrofotometría , Relación Estructura-Actividad , Vitamina A/análogos & derivadosRESUMEN
Fatty acid synthetase was covalently labelled with [14C]palmitic acid from [14C]palmityl-CoA. Tryptic and peptic digestion of the [14C]palmityl enzyme resulted in the formation of radioactive palmityl peptides carrying the long-chain acyl residue both in oxygen-ester and thio-ester linkage. The lipophilic palmityl peptides were purified by column and thin-layer chromatography using organic lolvent systems. Peptides arising from the acyl carrier protein, the condensing enzyme and the palmityl transferase were identified and characterized. The amino acid sequence of a 4'-phosphopant-etheine-containing peptide was established. It comprises 13 residues and shows a high degree of homology with the acyl carrier protein from Escherichia coli. A heptapeptide and an octapeptide from the palmityl transferase active site were partially sequenced. The identical amino acid composition of palmityl transferase and malonyl transferase core peptides is briefly discussed.
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Ácido Graso Sintasas/metabolismo , Ácidos Palmíticos/metabolismo , Saccharomyces cerevisiae/enzimología , Secuencia de Aminoácidos , Aminoácidos/análisis , Sitios de Unión , Cromatografía por Intercambio Iónico , Cromatografía en Capa Delgada , Electroforesis en Papel , Ácido Graso Sintasas/aislamiento & purificación , Oxidación-Reducción , Palmitoil Coenzima A/metabolismo , Fragmentos de Péptidos/análisisAsunto(s)
Bacteriorodopsinas , Carotenoides , Retinaldehído , Vitamina A , Bacteriorodopsinas/efectos de la radiación , Sitios de Unión , Carotenoides/efectos de la radiación , Concentración de Iones de Hidrógeno , Luz , Espectrometría de Masas , Unión Proteica , Espectrofotometría , Espectrofotometría Ultravioleta , Estereoisomerismo , Relación Estructura-Actividad , Rayos Ultravioleta , Vitamina A/análogos & derivadosRESUMEN
The chromophore (purple complex) of bacteriorhodopsin is reduced by sodium borohydride upon illumination to RPhv with a three-peaked absorption band at 360 nm. Treatment of this reduction product with ultraviolet light or acid yields a modified product from which retro-retinyllysine can be obtained by alkaline hydrolysis. No reduction of the 412 nm complex was found. Under specific conditions the purple complex equilibrates with a photochemically active 460 nm form that can be reduced by borohydride in the dark. This reduction product RP460 behaves idential to RPHV. Reconstitution of the purple complex from chromophore-free membrane (apomembrane) and retinal occurs via intermediates. The first (lambdamax 400nm) shows a three-peaked absorption band and is reduced to RP400 without a change of the three-peaked absorption (lambdamax 360 nm). The same product is obtained from apomembrane and retinol. Detergents shift the absorption band to 330 nm in all cases. From the experiments described no participation of retro-retinal structures during the photochemical cycle can be concluded but stereospecific interaction of the retinal moiety with the protein resulting in a specific retinal conformation os omdocated by the spectral changes observed.