[Neisseria gonorrhoeae: a wayward pathogen. Microbiological concepts, antimicrobial resistance and its epidemiological surveillance in Chile]. / Neisseria gonorrhoeae: un patógeno díscolo. Conceptos microbiológicos, resistencia a antimicrobianos y su vigilancia epidemiológica en Chile.

Neisseria gonorrhoeae is a nonmotile, sporulated, aerobic or facultative anaerobic gram-negative diplococcus, catalase and oxidase positive. Sexually transmitted infections caused by this microorganism were established as public health problem since the 19th century, representing a great threat to human health due to its high prevalence and multi-resistance to antimicrobials. In recent decades, reports of strains resistant to penicillin, fluoroquinolones, sulfonamides, tetracycline, macrolides, and more recently to cephalosporins and azithromycin have increased. Such a panorama has generated concern worldwide, due to the increase in cases of gonorrhea associated with multi-resistant strains. In Chile, from 2010 to 2018, the National Surveillance Program for N. gonorrhoeae was developed in order to characterize this infection in the regions and record antimicrobial resistance. This review presents an updated, systematic bibliographic analysis of the main aspects of this microorganism, its response to antimicrobials, and provides diagnostic and treatment guidelines, while waiting to advance in the understanding of the molecular mechanism and the metabolic and immunological interactions that determine infection, with a view to designing an effective vaccine.

Neisseria gonorrhoeae: un patógeno díscolo: conceptos microbiológicos, resistencia a antimicrobianos y su vigilancia epidemiológica en Chile / Neisseria gonorrhoeae: a wayward pathogen: microbiological concepts, antimicrobial resistance and its epidemiological surveillance in Chile

Resumen Neisseria gonorrhoeae es un diplococo gramnegativo, no móvil, esporulado, aerobio o anaerobio facultativo, catalasa y oxidasa positivas. Las infecciones de transmisión sexual causadas por este microorganismo son un problema de salud pública definido como tal desde el siglo XIX, representando una gran amenaza para la salud humana debido a la su alta prevalencia y multirresistencia a antimicrobianos. En las últimas décadas han aumentado los reportes de cepas resistentes a penicilina, fluoroquinolonas, sulfonamidas, tetraciclina, macrólidos, y más recientemente a cefalosporinas y azitromicina. Tal panorama ha generado preocupación a nivel mundial, debido al aumento de casos de gonorrea asociados a cepas multirresistentes. En Chile se desarrolló desde el 2010 hasta el 2018 el Programa de Vigilancia de N. gonorrhoeae a nivel nacional con el objeto de caracterizar esta infección en las regiones y registrar la resistencia a los antimicrobianos. Esta revisión presenta un análisis sistemático bibliográfico, actualizado, de los principales aspectos de este microorganismo, su respuesta a antimicrobianos, y entrega pautas de diagnóstico y tratamiento, a la espera de avanzar en la comprensión del mecanismo molecular y las interacciones metabólicas e inmunológicas que determinan la infección, con miras a diseñar una vacuna efectiva.

Abstract Neisseria gonorrhoeae is a nonmotile, sporulated, aerobic or facultative anaerobic gram-negative diplococcus, catalase and oxidase positive. Sexually transmitted infections caused by this microorganism were established as public health problem since the 19th century, representing a great threat to human health due to its high prevalence and multi-resistance to antimicrobials. In recent decades, reports of strains resistant to penicillin, fluoroquinolones, sulfonamides, tetracycline, macrolides, and more recently to cephalosporins and azithromycin have increased. Such a panorama has generated concern worldwide, due to the increase in cases of gonorrhea associated with multi-resistant strains. In Chile, from 2010 to 2018, the National Surveillance Program for N. gonorrhoeae was developed in order to characterize this infection in the regions and record antimicrobial resistance. This review presents an updated, systematic bibliographic analysis of the main aspects of this microorganism, its response to antimicrobials, and provides diagnostic and treatment guidelines, while waiting to advance in the understanding of the molecular mechanism and the metabolic and immunological interactions that determine infection, with a view to designing an effective vaccine.

A new approach in three dimensions to define pre- and intraoperative condyle-fossa relationships in orthognathic surgery - is there an effect of general anaesthesia on condylar position?

Incorrect registration of the condylar position in orthognathic surgery is supposed to cause postoperative relapse, condylar resorption and temporomandibular disorders. The aim of this prospective study was to evaluate the influence of general anaesthesia on centric relation (CR). Therefore, CR registered preoperatively in the awake patient and CR registered intraoperatively under general anaesthesia were recorded in 30 patients (14 men, 16 women) undergoing orthognathic surgery (skeletal class I: n=3, II: n=13, III: n=14; symmetric: n=20; asymmetric: n=10). CR records were digitized and, through superimposition on the preoperative cone beam computed tomography of the patient's skull, the superior, anterior and posterior joint space and the volumetric congruence of 120 condyles were analysed. The linear measurements of joint spaces did not demonstrate any clinically relevant discrepancy between the CR measured in the awake and anaesthetized patient. In contrast, volumetric analysis revealed statistically significant differences between both states, with an intraoperative condylar sag predominantly in the posterior-inferior direction. The patient's skeletal class or symmetry had no significant influence on the intraoperative condylar displacement. Thus, the risk of fixing the condyle in an unphysiological position supports the idea of using intraoperative condylar positioning devices to achieve predictable and stable outcomes.

Three-dimensional head shape acquisition in preterm infants - Translating an orthodontic imaging procedure into neonatal care.

BACKGROUND: Head shape and head volume of preterm infants give important information on short- and long-term development. Three-dimensional (3D) assessment of a preterm infant's head would therefore provide more information than currently used two-dimensional methods. AIMS: To evaluate a contactless 3D imaging system to assess head shape and volume in preterm infants. METHODS: A protocol for 3D imaging and reconstruction of an infant's head with a portable stereophotogrammetric camera system was developed. It was validated on a manikin by comparison to an established stationary stereophotogrammetric device. Feasibility for clinical routine and 3D data analysis were assessed in six preterm infants. RESULTS: Ten 3D reconstructions from a manikin were done with ten images each taken from different angles. The accuracy of the 3D reconstruction was measured at the overlapping areas between two images. Comparing the portable to the stationary system, a high concordance was found for the 3D manikin head-reconstructions (mean difference 0.21 ±â€¯0.03 mm). In preterm infants, digital evaluation of the head was proven to be feasible for head circumference (HC), cranial index and asymmetry indices. There was good concordance between manual and digital measurement of the HC (95% CI -0.85 to 0.38 mm). CONCLUSIONS: The portable camera system allowed fast and contactless 3D image capture of a preterm infant's head without any risk or interference with neonatal care. Together with a new software, this technique would allow more precise evaluation of head growth even in very preterm infants and thereby may improve their care and long-term outcome.

Traditional face-bow transfer versus three-dimensional virtual reconstruction in orthognathic surgery.

Face-bow transfer is an essential step in articulator-based orthognathic surgery planning. However, it can be a source of inaccuracy. Virtual computer-based planning avoids this error through the use of direct patient-related three-dimensional imaging data. The aim of this prospective observational study was to determine the error of face-bow transfer three-dimensionally and correlate it to the different types of malocclusion. Orthognathic surgery performed on 38 patients (10 male, 28 female; mean (standard deviation) age 24.7 (6.9) years) was planned twice: first articulator-based with plaster models and second computer-based with surgery planning software. Both models were digitized and compared regarding the angle between the Frankfort horizontal plane and the occlusal plane. In most cases, the angle in the sagittal dimension was higher in the articulator-based model than in the computer-based model. The angle in the transverse dimension was as often under- as over-represented. The type of malocclusion, i.e. skeletal class, vertical relationship, and degree of asymmetry, had no significant impact on the amount of error. In conclusion, this study indicates that computer-based planning should be considered as an advantageous alternative in orthognathic surgery planning.

Multiple, Multiloculated, and Recurrent Keratocysts of the Mandible and Maxilla in Association with Gorlin-Goltz (Nevoid Basal-Cell Carcinoma) Syndrome: A Pediatric Case Report and Follow-up over 5 Years.

BACKGROUND: We report a case of multiple keratocysts first diagnosed in an 8-year-old boy. CASE REPORT: The incidental radiographic finding of a cystic lesion in an 8-year-old boy led to the surgical enucleation and further diagnosis of a keratocyst associated with a tooth crown. In the course of dental maturation from deciduous to permanent teeth, the boy presented new lesions, always associated with the crowns of teeth. Gorlin-Goltz (nevoid basal-cell carcinoma) syndrome was suspected, and the genetic analysis detected a previously undescribed germline variant in the PTCH1 gene. TREATMENT: This included a surgical removal of the cystic lesions, as well as the affected teeth. FOLLOW-UP: Due to the high recurrence rate of the keratocysts, frequent radiological checks were performed over a 5-year period.

Muerte fetal: caracterización epidemiológica / Stillbirth: epidemiological characterization

La muerte fetal es la defunción del feto antes de su expulsión o separación completa del cuerpo de la madre, independientemente de la duración del embarazo. En un alto porcentaje se desconocen sus causas, aunque la literatura ha establecido como factores de riesgo la hipoxia intrauterina y las malformaciones congénitas. Se realizó un estudio retrospectivo, descriptivo, con el objetivo de determinar, a través de revisión de las historias clínicas, las características epidemiológicas de las muertes fetales en la Maternidad Dr. José Luis Facchin de Boni, en el período enero 2007 marzo 2013. La población fue 1236 gestantes con diagnóstico de muerte fetal, determinando una tasa de 56,28 muertes fetales por cada 1000 nacimientos y abortos. La mayoría de dichas muertes fetales (85,03%) ocurrieron por debajo de las 37 semanas, con predominio del sexo masculino. Además los factores médicos como el síndrome anémico, los obstétricos como las malformaciones fetales y las complicaciones hemorrágicas fueron los más frecuentemente encontrados en los casos de muerte fetal. Otro hallazgo importante de la investigación, fue que el peso de los fetos muertos fue menor que el peso de los nacidos vivos de la misma edad gestacional.

Stillbirth is the death of the fetus before their expulsion or complete separation of the body of the mother, regardless of the length of pregnancy. A high percentage of its causes are unknown, although the literature has established as risk factors intrauterine hypoxia and birth defects. A retrospective, descriptive study was conducted in order to determine, through review of medical records, the epidemiological characteristics of stillbirths in the Maternidad Dr. José Luis Facchin Boni, between January 2007 and March 2013. The population was 1236 pregnant women diagnosed with stillbirth, determining a rate of 56.28 stillbirths per 1000 births and abortions. Most of these stillbirths (85.03%) were below 37 weeks, with predominance of males. Medical factors such as anemic syndrome, the obstetric factors such as fetal malformations and hemorrhagic complications were most frequently found in cases of stillbirth. Another important finding of the research was that the weight of dead fetuses was less than the weight of live births of the same gestational age.

Displacement of oropharyngeal structures during suction-swallowing cycles.

Suction ability plays an important role in supporting oral nutrition and needs special care following neurological disorders and tumor-associated defects. However, the details of suction are still poorly understood. The present study evaluates displacement of orofacial structures during suction and deglutition based on manometric controlled MRI. Nine healthy subjects were scanned wearing an intraoral mouthpiece for water intake by suction and subsequent swallowing. Suction-swallowing cycles were identified by intraoral negative pressure. Midsagittal MRI slices (3 T; temporal resolution 0.53 s) were analyzed at rest, suction and pharyngeal swallowing. The mandibular displacement was measured as the distance between the anterior nasal spine and the inferior point of the mandible. Following areas were defined: subpalatal compartment (SCA), retrolingual (RLA), epipharyngeal (EPA) and mouth floor area (MFA). During rest, an average distance of 7 cm was observed between the mandibular measurement points. The measured SCA was 3.67 cm(2), the RLA 6.98 cm(2), the EPA 9.00 cm(2) and the MFA 15.21 cm(2) (average values). At the end of suction, the mandibular distance reduces (to 6.88 cm), the SCA increases significantly (to 5.96 cm(2); p = 0.0002), the RLA decreases (to 6.45 cm(2)), the EPA increases (to 10.59 cm(2)) and the MFA decreases (to 15.02 cm(2)). During deglutition, the mandible lifted significantly (to 6.81 cm; p = 0.0276), the SCA reduced to zero, the RLA was not measurable, the EPA reduces significantly (to 3.01 cm(2); p < 0.0001) and the MFA increases (to 16.36 cm(2)). According to these observations, a combined displacement of the tongue in an anteroposterior direction with active tongue dorsum-velum contact appears to be the predominant activity during suction and responsible for the expansion of the subpalatal area.

[Integrons and their relationship with resistance phenotype in Gram negative bacilli isolated in the Hospital Torres Galdames, Iquique, Chile]. / Integrones y su relación con el fenotipo de resistencia en bacilos gramnegativos aislados en el Hospital Torres Galdames de Iquique, Chile.

UNLABELLED: The antimicrobial resistance is coded in genetic elements which generate a horizontal flow of information, particularly in conditions that are under strong selective pressure like the nosocomial environment. In that sense, in the last decades, gram negative bacilli have become important agents of nosocomial infection. In order to investigate the presence of integrons among clinical isolates of gram negative bacilli and their relationship with their resistance profile, we studied 88 strains isolated from clinical specimens of different wards of the Hospital Torres Galdames, during the June-December period, 2004. They were identified according to biochemical tests. The antimicrobial susceptibility was evaluated by agar diffusion method. The integron presence was investigated by polymerase chain reaction (PCR). A cluster analysis was carried out to study the relationship between the presence of integrons and the resistance profile. The genotyping of the isolates was carried out by ERIC-PCR technique. RESULTS: Of the isolated strains, 18% corresponded to Proteus mirabilis, 17% to Escherichia coli, and 32% to Non Fermentative Gram Negative bacilli. Most isolates presented high resistance to the antibiotics studied: 83% to ampicillin, 85% to cephalotin, 82% to ceftriaxone, 82% to ciprofloxacin, 81% to gentamycin and 82% to cotrimoxazole. Seventy-five % of the 88 strains presented integrons. Class 2 integrons were found to be the most common. The results of the cluster analysis did not show a clear relationship among the presence of the integrons and the resistance profile. With the available information it is not possible to relate the integron presence with a certain resistance pattern. The patterns of bands obtained with the technique ERIC-PCR revealed a great genetic variety among the analyzed isolations, defining diverse genotypes, distributed in the different services of the hospital where they were isolated.

Integrones y su relación con el fenotipo de resistencia en bacilos gramnegativos aislados en el Hospital Torres Galdames de Iquique, Chile / Integrons and their relationship with resistance phenotype in Gram negative bacilli isolated in the Hospital Torres Galdames, Iquique, Chile

La resistencia antimicrobiana es codificada por algunos elementos genéticos que generan un flujo horizontal, particularmente, en ambientes que están sometidos a una fuerte presión selectiva, como ocurre en el ambiente hospitalario. En tal sentido, los bacilos gramnegativos, en el último tiempo, han cobrado importancia como agentes de infección nosocomial. Objetivo. Investigar la presencia de integrones en aislados clínicos de bacilos gramnegativos y su relación con el fenotipo de resistencia, Material y Métodos. Se analizaron 88 aislados clínicos de distintos servicios del Hospital Torres Galdames, durante el período: junio a diciembre de 2004. Fueron identificadas de acuerdo con su perfil bioquímico y se determinó la susceptibilidad a antimicrobianos mediante el método de difusión en agar. La presencia de integrones se detectó mediante RPC. Se realizó un análisis de cluster para estudiar la relación entre el fenotipo de resistencia y la presencia de integrones. Las cepas fueron genotipificadas mediante ERIC-PCR. Resultados. Dieciocho por ciento de las cepas aisladas correspondió a Proteus mirabilis, 17 por ciento a Escherichia coli y 32 por ciento a bacilos gramnegativos no fermentadores. La mayoría de los aislados presentó una elevada resistencia a los antimicrobianos evaluados: ampicilina 83 por ciento, cefalotina 82 por ciento, ceftriaxona 82 por ciento, ciprofloxacina 81 por ciento, gentamicina 81 por ciento y cotrimoxazol 82 por ciento. De las 88 cepas, 75 por ciento presentó integrones, siendo más común la clase 2. Los resultados del análisis de cluster no revelaron una clara relación entre la presencia de éstos y el perfil de resistencia para los antimicrobianos ensayados. Con la información disponible no fue posible relacionar la presencia de integrones con un determinado patrón de resistencia. Los patrones de bandas obtenidos con la técnica de ERIC-PCR revelaron una gran variedad genética entre las cepas analizadas, definiendo...

The antimicrobial resistance is coded in genetic elements which generate a horizontal flow of information, particularly in conditions that are under strong selective pressure like the nosocomial environment. In that sense, in the last decades, gram negative bacilli have become important agents of nosocomial infection. In order to investigate the presence of integrons among clinical isolates of gram negative bacilli and their relationship with their resistance profile, we studied 88 strains isolated from clinical specimens of different wards of the Hospital Torres Galdames, during the June-December period, 2004. They were identified according to biochemical tests. The antimicrobial susceptibility was evaluated by agar diffusion method. The integron presence was investigated by polymerase chain reaction (PCR). A cluster analysis was carried out to study the relationship between the presence of integrons and the resistance profile. The genotyping of the isolates was carried out by ERIC-PCR technique. Results: Of the isolated strains, 18 percent corresponded to Proteus mirabilis, 17 percent to Escherichia coli, and 32 percent to Non Fermentative Gram Negative bacilli. Most isolates presented high resistance to the antibiotics studied: 83 percent to ampicillin, 85 percent to cephalotin, 82 percent to ceftriaxone, 82 percent to ciprofloxacin, 81 percent to gentamycin and 82 percent to cotrimoxazole. Seventy-five percent of the 88 strains presented integrons. Class 2 integrons were found to be the most common. The results of the cluster analysis did not show a clear relationship among the presence of the integrons and the resistance profile. With the available information it is not possible to relate the integron presence with a certain resistance pattern. The patterns of bands obtained with the technique ERIC-PCR revealed a great genetic variety among the analyzed isolations, defining diverse genotypes, distributed in the different services...

1,4-dihydropyridines: reactivity of nitrosoaryl and nitroaryl derivatives with alkylperoxyl radicals and ABTS radical cation.

In the present paper, a direct quenching of radical species by a number of synthesized nitrosoaryl 1,4-dihydropyridines and their parent nitroaryl 1,4-dihydropyridines was determined in aqueous media at pH 7.4. These two series of compounds were compared with the C-4 unsubstituted 1,4-dihydropyridines derivatives and the corresponding C-4 aryl substituted 1,4-dihydropyridines derivatives. Kinetic rate constants were assessed by UV-Vis spectroscopy. Nitrosoaryl derivatives were more reactive than the parent nitroaryl 1,4-dihydropyridines. Our results strongly support the assumption that the reactivity between the synthesized 1,4-dihydropyridines derivatives with alkylperoxyl radicals involves electron transfer reactions, which is documented by the presence of pyridine as final product of reaction and the complete oxidation of the nitroso group to give rise the nitro group in the case of the nitrosoaryl 1,4-dihydropyridines derivatives.

Multiple biosynthetic pathways for vitamin B12: variations on a central theme.

The manner in which vitamin B12 is synthesized is detailed with emphasis on the different mechanisms for ring contraction encountered in aerobic and anaerobic organisms. The aerobic process utilizes two enzymes and is dependent on molecular oxygen, in stark contrast to the anaerobic mechanism which is controlled by cobalt and requires only one enzyme.

Chemoenzymatic synthesis of an unnatural tetramethyl cobalt corphinoid.

The chemoenzymatic synthesis and structural characterization by 13C NMR of a tetramethyl cobalt-corphinoid produced by methylation of cobalt-precorrin-3 using CbiF are described.

Antioxidant activity of gallates: an electrochemical study in aqueous media.

The electron-donating ability of gallates, which are food and pharmaceutical antioxidants, is quantitatively assessed on the basis of their electrochemical characteristics. Gallic acid and the propyl, i-propyl, butyl, i-butyl, pentyl and i-pentyl gallate derivatives were electrochemically oxidized on the glassy carbon electrode by using differential pulse voltammetry, cyclic voltammetry and hydrodynamic voltammetry on the rotating disk electrode. All the compounds under study were easily oxidized in acidic and neutral solutions. Electrochemical oxidation occurs via two electron-transfer steps; however good resolution for the second wave was obtained only by using hydrodynamic conditions. The oxidation process results to be irreversible, diffusion controlled and pH-dependent. The introduction of the alkyl groups seems to affect the intensities of the semiquinone gallate radicals as can be ascribed from the observed differences in i(II)d/i(I)d ratio obtained from hydrodynamic voltammetric experiments for the different derivatives. We have found that the intensity of the gallate radicals follows the sequence GA > or = i-PG > PG > i-BG > BG > i-PeG > PeG. From the pH-dependence of the peak current it is possible to affirm that pH 2 is the better condition for the oxidative activity showing that the antioxidant behaviour of these compounds are important in the stomach acid.

Estudio descriptivo de brote de hepatitis viral aguda A, en comuna de Empedrado, VII región, enero-junio 1997 / Descriptive study of acute viral hepatitis A, at Empedrado, VII region, january-june 1997

Con el objetivo de conocer la realidad ocurrida en el brote de Hepatitis presentado en Empedrado, se llevó a cabo un estudio descriptivo con un universo de los casos. Se encontraron 64 casos mediante el diagnóstico clínico y de laboratorio en el consultorio de Empedrado; Se analizaron las variables edad, sexo, ruralidad, higiene ambiental (eliminación de excretas, presencia de agua potable e higiene personal), número de casos que presentan Hepatitis Aguda Fulminante, recaída de la enfermedad y los que desarrollan enfermedad a pesar de haber sido inmunizados. Se encontró un predominio de casos femeninos, entre 0 a 9 años, de procedencia urbana, que contaban con agua potable, con un deficiente higiene personal y eliminación de excretas en pozo negro. De los Contactos vacunados, la enfermedad se desarrolló e un bajo porcentaje. Del total de los casos hubo uno que evolucinó a Hepatitis Aguda Fulminante y otro que presentó recaída de la enfermedad

How corrinoids are synthesized without oxygen: nature's first pathway to vitamin B12.

BACKGROUND: During the biosynthesis of vitamin B12, the aerobic bacterium Pseudomonas denitrificans uses two enzymes, CobG and CobJ, to convert precorrin-3 to the ring-contracted intermediate, precorrin-4. CobG is a monooxygenase that adds a hydroxyl group, derived from molecular oxygen, to C-20, whereas CobJ is bifunctional, inserting a methyl group at C-17 of the macrocycle and catalyzing ring contraction. Molecular oxygen is not available to vitamin B12-producing anaerobic bacteria and members of the ancient Archaea, so the question arises of how these microbes accomplish the key ring-contraction process. RESULTS: Cloning and overexpression of Salmonella typhimurium genes has led to the discovery that a single enzyme, CbiH, is responsible for ring contraction during anaerobic biosynthesis of vitamin B12. The process occurs when CbiH is incubated with precorrin-3, but only in the presence of cobalt. CbiH functions as a C-17 methyltransferase and mediates ring contraction and lactonization to yield the intermediate, cobalt-precorrin-4, isolated as cobalt-factor IV. 13C labeling studies have proved that cobalt-precorrin-4 is incorporated into cobyrinic acid, thereby confirming that cobalt-precorrin-4 is an intermediate in vitamin B12 biosynthesis. CONCLUSIONS: Two distinct mechanisms exist in nature for the ring contraction of porphyrinoids to corrinoids-an ancient anaerobic pathway that requires cobalt complexation prior to nonoxidative rearrangement, and a more recent aerobic route in which molecular oxygen serves as the cofactor. The present results offer a rationale for the main differences between aerobic and anaerobic biosynthesis of vitamin B12. Thus, in anaerobes there is exchange of oxygen at the C-27 acetate site, extrusion of acetaldehyde and early insertion of cobalt, whereas the aerobes show no exchange of oxygen at C-27, extrude acetic acid and insert cobalt very late in the biosynthetic pathway, after ring contraction has occurred. These parallel routes to vitamin B12 have now been clearly distinguished by their differing mechanisms for ring contraction.

Biosynthesis of vitamin B12: concerning the identity of the two-carbon fragment eliminated during anaerobic formation of cobyrinic acid.

It has been proved that, during anaerobic biosynthesis of the corrin macrocycle, the two-carbon fragment excised from the precursor, precorrin-3, is acetaldehyde, which originates from C-20 and its attached methyl group. This apparently contradictory finding is rationalized in terms of the subsequent enzymatic oxidation of acetaldehyde to acetic acid, which was previously regarded as the volatile fragment released by the action of the biosynthetic enzymes of Propionibacterium shermanii. The observation that acetaldehyde (rather than acetic acid) is extruded during anaerobic B12 synthesis is in full accord with the structure of factor IV, a new intermediate on the pathway.

Genetically engineered synthesis of precorrin-6x and the complete corrinoid, hydrogenobyrinic acid, an advanced precursor of vitamin B12.

BACKGROUND: Genetically engineered synthesis, in which the gene products, cofactors, and substrates of a complete pathway are combined in vitro in a single flask to give the target, can be a viable alternative to conventional chemical construction of molecules of complex structure and stereochemistry. We chose to attempt to synthesize the metal-free corrinoid hydrogenobyrinic acid, an advanced precursor of vitamin B12. RESULTS: Cloning and overexpression of the genes necessary for the S-adenosyl methionine dependent conversion of 5-aminolevulinic acid (ALA) to precorrin-3 and those required for the synthesis of hydrogenobyrinic acid from precorrin-3 completed the repertoire of the 12 biosynthetic enzymes involved in corrin synthesis. Using these enzymes and the necessary cofactors, the multi-enzyme synthesis of hydrogenobyrinic acid from ALA can be achieved in 20% overall yield in a single reaction vessel, corresponding to an average of at least 90% conversion for each of the 17 steps involved. CONCLUSIONS: By replacing the cell wall with glass, and by mixing the soluble biosynthetic enzymes and necessary cofactors, the major segment of the physiological synthesis of vitamin B12 has been accomplished. Since only those enzymes necessary for the synthesis of hydrogenobyrinic acid from ALA are supplied, none of the intermediates is deflected from the direct pathway. This results in an efficiency which in fact surpasses that of nature.

[Changes in ethical attitudes during medical studies]. / Cambios de actitudes éticas a lo largo de los estudios de medicina.

The aim of this work was to explore the attitude changes towards ethico-medical issues in medical students as they went through medical school. A personal standardized questionnaire containing 14 closed and direct questions was applied to 27 freshmen, 38 interns and 14 post graduates. The most outstanding differences in ethical attitudes occurred between first year students and the older groups. The younger students adhered to ethical principles, valued justice towards patients and moral integrity in physicians. The older students and post graduates emphasized the professional role of physicians and preferred institutional ethical regulations over public control. They also considered more valuable therapeutic efficiency and paternal attitudes towards patients as well as social prestige and economical rewards. We conclude that there is a progressive erosion of humanistic principles along the medical studies, that are substituted by a model of professional competence, social recognition and internal ethical control.