Effects of dexmedetomidine on kidney and brain tissue microcirculation and histology in ovine cardiopulmonary bypass: a randomised controlled trial.

Cardiac surgery requiring cardiopulmonary bypass is associated with postoperative acute kidney injury and neurocognitive disorders, including delirium. Intra-operative inflammation and/or impaired tissue perfusion/oxygenation are thought to be contributors to these outcomes. It has been hypothesised that these problems may be ameliorated by the highly selective α2 -agonist, dexmedetomidine. We tested the effects of dexmedetomidine on renal and cerebral microcirculatory tissue perfusion, oxygenation and histology in a clinically relevant ovine model. Sixteen sheep were studied while conscious, after induction of anaesthesia and during 2 h of cardiopulmonary bypass. Eight sheep were allocated randomly to receive an intravenous infusion of dexmedetomidine (0.4-0.8 µg.kg-1 .h-1 ) from induction of anaesthesia to the end of cardiopulmonary bypass, and eight to receive an equivalent volume of matched placebo (0.9% sodium chloride). Commencement of cardiopulmonary bypass decreased renal medullary tissue oxygenation in the placebo group (mean (95%CI) 5.96 (4.24-7.23) to 1.56 (0.84-2.09) kPa, p = 0.001), with similar hypoxic levels observed in the dexmedetomidine group (6.33 (5.33-7.07) to 1.51 (0.33-2.39) kPa, p = 0.002). While no differences in kidney function (i.e. reduced creatinine clearance) were evident, a greater incidence of histological renal tubular injury was observed in sheep receiving dexmedetomidine (7/8 sheep) compared with placebo (2/8 sheep), p = 0.041. Graded on a semi-quantitative scale (0-3), median (IQR [range]) severity of histological renal tubular injury was higher in the dexmedetomidine group compared with placebo (1.5 (1-2 [0-3]) vs. 0 (0-0.3 [0-1]) respectively, p = 0.013). There was no difference in cerebral tissue microglial activation (neuroinflammation) between the groups. Dexmedetomidine did not reduce renal medullary hypoxia or cerebral neuroinflammation in sheep undergoing cardiopulmonary bypass.

The right tool for the right question: contrasting biogeographic patterns in the notothenioid fish Harpagifer spp. along the Magellan Province.

Molecular-based analysis has become a fundamental tool to understand the role of Quaternary glacial episodes. In the Magellan Province in southern South America, ice covering during the last glacial maximum (20 ka) radically altered the landscape/seascape, speciation rates and distribution of species. For the notothenioid fishes of the genus Harpagifer, in the area are described two nominal species. Nevertheless, this genus recently colonized South America from Antarctica, providing a short time for speciation processes. Combining DNA sequences and genotyping-by-sequencing SNPs, we evaluated the role of Quaternary glaciations over the patterns of genetic structure in Harpagifer across its distribution in the Magellan Province. DNA sequences showed low phylogeographic structure, with shared and dominant haplotypes between nominal species, suggesting a single evolutionary unit. SNPs identified contrastingly two groups in Patagonia and a third well-differentiated group in the Falkland/Malvinas Islands with limited and asymmetric gene flow. Linking the information of different markers allowed us to infer the relevance of postglacial colonization mediated by the general oceanographic circulation patterns. Contrasting rough- and fine-scale genetic patterns highlights the relevance of combined methodologies for species delimitation, which, depending on the question to be addressed, allows discrimination among phylogeographic structure, discarding incipient speciation, and contemporary spatial differentiation processes.

Spatial regression techniques for inter-population data: studying the relationships between morphological and environmental variation.

Understanding the importance of environmental dimensions behind the morphological variation among populations has long been a central goal of evolutionary biology. The main objective of this study was to review the spatial regression techniques employed to test the association between morphological and environmental variables. In addition, we show empirically how spatial regression techniques can be used to test the association of cranial form variation among worldwide human populations with a set of ecological variables, taking into account the spatial autocorrelation in data. We suggest that spatial autocorrelation must be studied to explore the spatial structure underlying morphological variation and incorporated in regression models to provide more accurate statistical estimates of the relationships between morphological and ecological variables. Finally, we discuss the statistical properties of these techniques and the underlying reasons for using the spatial approach in population studies.

Cardiac hemodynamic profiles and pro-B-type natriuretic Peptide in cirrhotic patients undergoing liver transplantation.

BACKGROUND: The aim of our study was to determine concentrations of amino-terminal pro-B-type natriuretic peptide (NT-proBNP) in patients with cirrhosis, thereby describing the hemodynamic and cardiac profiles to verify the existence of cirrhotic cardiomyopathy. METHODS: Clinical data, NT-proBNP levels, echocardiography, and right heart hemodynamic measurements were performed on all patients undergoing liver transplantation for cirrhosis. RESULTS: Our patients showed a hyperdynamic circulation with elevated left-sided pressures despite high cardiac outputs. This observation suggested abnormalities in left ventricular diastolic compliance. We verified these results, because our cohort showed a significant left ventricular mass index and, consequently, diastolic dysfunction. Mean NT-proBNP levels were high. The great expansion of central volume may explain these results and the later development of left ventricular hypertrophy. CONCLUSION: We concluded that elevated concentrations of NT-proBNP indicated the presence of hyperdynamic syndrome and cardiac dysfunction.

N-terminal brain natriuretic peptide as a diagnostic test in cirrhotic patients with pulmonary arterial hypertension.

BACKGROUND: The aim of this study was to assessed the correlation of N-terminal natriuretic peptide type B (NT-proBNP) with echocardiographic and hemodynamic indexes of right ventricular (RV) function and to evaluate the sensitivity and specificity of Doppler echocardiography in the diagnosis of portopulmonary hypertension. METHODS: All patients underwent liver transplantation for cirrhosis. We obtained clinical data, NT-proBNP levels, echocardiography, and right heart hemodynamic measurements before transplantation. RESULTS: Patients with pulmonary hypertension displayed significantly higher levels of NT-proBNP. They also showed higher model for End-stage Liver Disease scores and higher indices of RV overload on cardiac hemodynamics. The negative predictive value of echocardiography to identify pulmonary hypertension was 83%. A correlation was not observed between systolic pulmonary artery pressures measured by the two methods; however, NTproBNP showed a trend toward a significant correlation with mean pulmonary pressure as determined by hemodynamics (r = .3; P < .01). CONCLUSION: We concluded that NT-proBNP values showed significant correlations with pulmonary hypertension that could assist in a noninvasive diagnoseis for this group of patients.

Role of betaine:CoA ligase (CaiC) in the activation of betaines and the transfer of coenzyme A in Escherichia coli.

AIMS: Characterization of the role of CaiC in the biotransformation of trimethylammonium compounds into l(-)-carnitine in Escherichia coli. METHODS AND RESULTS: The caiC gene was cloned and overexpressed in E. coli and its effect on the production of l(-)-carnitine was analysed. Betaine:CoA ligase and CoA transferase activities were analysed in cell free extracts and products were studied by electrospray mass spectrometry (ESI-MS). Substrate specificity of the caiC gene product was high, reflecting the high specialization of the carnitine pathway. Although CoA-transferase activity was also detected in vitro, the main in vivo role of CaiC was found to be the synthesis of betainyl-CoAs. Overexpression of CaiC allowed the biotransformation of crotonobetaine to l(-)-carnitine to be enhanced nearly 20-fold, the yield reaching up to 30% (with growing cells). Higher yields were obtained using resting cells (up to 60%), even when d(+)-carnitine was used as substrate. CONCLUSIONS: The expression of CaiC is a control step in the biotransformation of trimethylammonium compounds in E. coli. SIGNIFICANCE AND IMPACT OF THE STUDY: A bacterial betaine:CoA ligase has been characterized for the first time, underlining its important role for the production of l-carnitine with Escherichia coli.

[Assessment of behavioral dependence with the Glover-Nilsson test in smoking cessation treatment]. / Evaluación de la dependencia psicológica mediante el test de Glover-Nilsson en el tratamiento del tabaquismo.

OBJECTIVE: To assess behavioral dependence using the Glover-Nilsson test and determine its association with successful smoking cessation. MATERIAL AND METHODS: An analytical longitudinal study was carried out, the target population of which consisted of smokers who enrolled in a smoking cessation clinic for treatment. The following variables were examined: age, sex, nicotine dependence (Fagerström test), psychoactive drug use, prior attempts at quitting, and behavioral dependence measured with the Glover-Nilsson test. The most recent version of this test is an 11-item questionnaire which classifies behavioral dependence according to the scores obtained: mild (<12), moderate (12-22), severe (23-33), and very severe (>33). Successful cessation was defined as self-reported abstinence confirmed by measurement of expired CO level (< or =10 ppm). Results were expressed as means (SD) for quantitative variables and percentages and absolute frequencies for qualitative variables. RESULTS: The study population consisted of 167 smokers--89 men (53.3%) and 78 women (46.7%)--with a mean age of 43.5 (9.9) years, a nicotine dependence score (Fagerström test) of 6.5 (2.2) points, and a Glover-Nilsson score of 23.3 (6.6). Of the study population, 65.9% (n=110) had made previous attempts at quitting. Abstinence at 3 months was 55.1% (n=92). Differences between the sexes were found for age and previous attempts at quitting. Younger patients had higher scores on the Glover-Nilsson test and the Fagerström test and lower abstinence rates. CONCLUSIONS: Severe behavioral dependence can result in less successful cessation outcome. All aspects related to dependence must be assessed to help select the most adequate pharmacological and psychological treatment for results to be optimized.

[7 cases of Staphylococcus lugdunensis infection]. / Estudio de siete casos de infección por Staphylococcus lugdunensis.

Staphylococci are frequently isolated from human, animal and environmental samples. The genus Staphylococcus comprises 27 species, of which 23 are coagulase-negative. The pathogenic role of the coagulase-negative species remains to be fully established. Staphylococcus lugdunensis is a recently described coagulase-negative species. Its Latin name reflects the city (Lyon, France) where the bacteria was first described. The present study reports 7 cases of human infection caused by S. lugdunensis. Case 1: a 64 y/o diabetic woman in whom S. lugdunensis was isolated in the conjunctival exudate. Case 2: a 51 y/o male diagnosed of a bladder tumor, with S. lugdunensis detected in the purulent exudate of a transurethral resection. Case 3: an 81 y/o woman with cerebrovascular stroke, in whom S. lugdunensis was isolated from urine. Case 4: a 65 y/o male with bacterial endocarditis and S. lugdunensis isolation in blood culture. Case 5: a 79 y/o male with liver cirrhosis and S. lugdunensis in blood culture. Case 6: a 75 y/o female with cerebrovascular stroke, in whom S. lugdunensis was isolated from urine. Case 7: a 77 y/o male diagnosed of femoral osteosarcoma and isolation of S. lugdunensis in the purulent exudate of the wound. The present communication broadens the range of clinical syndromes in which coagulase-negative S. lugdunensis appears as pathogen.

[Lumbago radiating to the right leg as a form of onset of multiple myeloma in a 33-year-old patient]. / Lumbalgia irradiada a pierna derecha como forma de debut de mieloma múltiple en un paciente de 33 años.

We present the case of a 33 year old man who consulted because a lumbago; a bone lesion was detected on a lumbosacral radiography, and finally was diagnosed of Multiple Myeloma. The illness, diagnosis and epidemiology are briefly analyzed, rebounding the rarity of its presentation in a young man.

[Non-A non-B hepatitis associated with cytomegalovirus infection]. / Hepatitis no-A no-B asociada con infección por citomegalovirus.

A clinical case of a 58 year old male suffering from hepatitis non A, non B, and terminal chronic renal insufficiency under periodic dialysis, is presented. Following a 600 cc of packed red blood cells transfusion, there was an increase of antibodies IgG against cytomegalovirus (from 1/160 to 1/1560), detected by ELISA. At the same time, there were an increase of transaminases up to 404 UI/ml of GPT. Total bilirubin persisted normal. The possible etiology of the hepatitis non A, non B caused by cytomegalovirus is discussed and the results compared to those observed by other authors in immunosuppressed renal transplant patients.

Inventario de sistema de creencias (SBI-15R) en Colombia: estructura factorial y confiabilidad en población universitaria y pacientes crónicos / System of belief inventory (SBI -15R) in Colombia: Factorial structure and reliability in university population and chronic patients / Inventário do sistema de crenças (SBI-15R) na Colômbia: estrutura dos fatores e confiabilidade na população universitária e pacientes crônicos

Estudio de corte psicométrico. Objetivo: analizar la estructura factorial y la consistencia interna del Inventario de sistema\r\nde creencias (SBI-15R) en universitarios y enfermos crónicos colombianos. Método: se aplicó el cuestionario SBI-15R a 265\r\nestudiantes universitarios adultos y 52 enfermos crónicos. Resultados: el análisis factorial muestra dos factores: Convicción religiosa y Soporte social religioso, sin hallar diferencias en la estructura para cada muestra, y un alfa de Cronbach total de 0,926.\r\nDespués de la eliminación de un ítem, se halló una alta confiabilidad y concordancia en la estructura factorial del inventario con\r\nla versión original mexicana. Conclusión: el Inventario de sistema de creencias (SBI-15R) presenta adecuada validez y confiabilidad\r\nen población colombiana.

Psychometric study. Objective: To analyze the factorial\r\nstructure and internal consistency of the System of Belief\r\nInventory (SBI-15R) in university students and chronic Colombian\r\npatients. Method: The SBI-15R questionnaire was given to\r\n265 adult university students and 52 chronic patients. Results:\r\nThe factorial analysis shows two factors: Religious Conviction\r\nand Religious social support, without finding differences in\r\nthe structure for each sample, and a total Cronbach's alpha\r\nof 0.926. After the elimination of an item, it was found that a\r\nhigh reliability and concordance in the factorial structure of\r\nthe inventory with the original Mexican version. Conclusion:\r\nThe System of Belief Inventory (SBI-15R) presents an adequate\r\nvalidity and reliability in the Colombian population.

Estudo de corte psicométrico. Objetivo: analisar a estrutura\r\ndos fatores e a consistência interna do Inventário do Sistema\r\nde Crenças (SBI-15R) em estudantes universitários e pacientes\r\ncolombianos crônicos. Método: o questionário SBI-15R foi\r\naplicado a 265 estudantes universitários adultos e 52 pacientes\r\ncrônicos. Resultados: a análise fatorial mostra dois fatores:\r\nConvicção religiosa e Suporte social religioso, sem encontrar\r\ndiferenças na estrutura para cada amostra e um alfa\r\ntotal de Cronbach de 0,926. Os resultados encontrados após\r\na eliminação de um item mostram uma alta confiabilidade e\r\nconcordância na estrutura fatorial do inventário com a versão\r\nmexicana original. Conclusão: os resultados encontrados\r\nimplicam validade e confiabilidade adequadas do teste na\r\npopulação colombiana.

[Efficacy and safety of a single intra-articular injection of 2% hyaluronic acid plus mannitol in knee osteoarthritis over a 6-month period]. / Eficacia y seguridad de una única inyección intraarticular de ácido hialurónico al 2% más manitol en artrosis de rodilla durante un periodo de 6 meses.

OBJECTIVE: To evaluate the safety and efficacy of a single intra-articular injection of 2% hyaluronic acid (HA)+mannitol in symptomatic knee osteoarthritis (KOA). MATERIAL AND METHODS: Pilot, multicentre, open, non-comparative study performed in eighty patients with painful KOA, of whom 79 completed the study. They received one injection of 2ml of 2% HA+0.5% mannitol (Day 0) and were followed-up for 6 months. On Days 0, 15, 30, 60, 90, 120, 150 and 180, pain and joint function were assessed using a visual analogue scale (VAS) and WOMAC index. Efficacy and safety by investigator and patient, and rescue medication, as an indirect measure of pain, were also recorded. RESULTS: A significant reduction in joint pain, stiffness and functional disability compared with baseline was observed at every follow-up visit (P<.001). Joint function improved by 38.7% on Day 30, reaching 47.5% on Day 180. Rescue medication use decreased from 58.2% at baseline to 2.5% on Day 90, increasing in the last visits. Efficacy and safety were positively evaluated by investigators and patients. No serious adverse events were observed. Mild side effects were reported in 4 patients (local pain and swelling in the infiltration area). DISCUSSION: There is evidence that repeated intra-articular injections of HA improve symptoms in KOA. However, studies with a single injection of HA have shown mixed results. This study demonstrates that one single intra-articular injection of non-cross-linked HA reduces joint pain and increases function in patients with KOA over a period of at least 6 months.

The development of dental research in Argentinean biological anthropology: current state and future perspectives.

The aim of this paper is to conduct a historical analysis of the research-oriented studies related to dental anthropology in Argentina, evaluate its current state and discuss future expectations and perspectives. In this country, anthropological studies based on analysis of dentition have been scarce and even temporarily discontinued, since they began in the late nineteenth century, simply following the course of the predominant theoretical and methodological approaches over time. Early papers, guided mainly by evolutionary ideas, were oriented towards establishing the taxonomic position of humans through the description and comparison of morphological and morphometric aspects of the dental crown and root. Later studies mainly described types of intentional modifications (i.e. dental mutilations) and tooth wear in the context of Historic-Cultural School. However, they failed to constitute valid lines of research over time. In recent years, there has been a significant change in dental studies, mainly as a result of the interest in evaluating the adaptive aspects of human populations within biocultural settings. One of the most relevant lines of studies has been the bioarchaeological analysis of health and stress indicators, such as enamel hypoplasia, caries and tooth wear in hunter-gatherer and farmer societies. More recently, the study of discrete and metric dental traits began, with a goal to contribute to the study of evolution and inter-populational biological relations among South American groups. Since teeth contain valuable information not only about the environment in which the individual lived, but also about the action of neutral and non-neutral factors on human groups, the consolidation of ongoing studies will contribute to knowledge of various aspects of the adaptation and evolution of native American populations.

Cystatin C level as a predictor of death and cardiovascular events after liver transplantation.

BACKGROUND: The diagnosis of renal failure is important in cirrhosis. Cystatin C (Cys) has been suggested not only to be a sensitive marker of renal function, but also a stronger predictor of the risk of death and cardiovascular events in heart failure. Our aims were to investigate plasma Cys concentrations for the detection of moderately impaired renal function and its association with mortality and cardiovascular events among cirrhotic patients after liver transplantation (OLT). METHODS: Clinical and biochemical data, including Cys levels, were analyzed in 99 cirrhotic candidates for OLT. We recorded cardiovascular events. RESULTS: Receiver-operator characteristics curves showed a similar efficiency to detect a creatinine clearance <60 mL/min per 1.73m(2) (Cys = 0.753; creatinine [Cr] = 0.799; glomerular filtration rate [GFR, Cockcroft-Gault formula] = 0.842; urea = 0.823; P = .001). However, at cutoff concentrations of 1.3 mg/dL, Cr showed great specificity (96%) but poor sensitivity (13%), while the sensitivity of Cys was superior (83%) with moderate specificity (55%) at a cutoff of 1400 ng/mL. Over a median follow-up of 2.7 years, 14 patients developed a cardiovascular event, including, 11 who displayed Cys levels >1400 ng/mL before OLT, showing a significant difference (P < .05) compared to patients who showed no cardiovascular event. Kaplan-Meier analysis Cys discriminated significantly better than the Model for End-Stage Liver Disease score between survivors and nonsurvivors (P < .05). CONCLUSION: Cys determinations could be a valuable tool for early diagnosis of renal dysfunction among cirrhotic patients. Furthermore, it may predict the risk of death and cardiovascular events after OLT.

Síndrome neurológico transitorio por anestésicos locales: un caso clínico con bupivacaína / Transient neurological syndrome with local anesthetics: A clinic case with bupivacaine / Síndrome neurológico transitório por anestésicos locais: um caso clínico com bupivacaína

Se presenta la historia de un paciente que después de realizarle anestesia espinal con bupivacaína hiperbárica 15 mg (0.5%), más fentanil 25 mcg, para prostatectomía abierta, presentó dolor en periné, lumbar y en miembros inferiores, 24 horas después de la aplicación del anestésico local. Se descarta compromiso mecánico y electromiográfico con tomografía, resonancia y electromiografía. Teniendo como diagnóstico definitivo el síndrome neurológico transitorio. En este caso la bupivacaína fue el agente causal. La duración de los síntomas por cerca de tres meses es un hallazgo novedoso en cuanto al tiempo de resolución del cuadro, Independiente de su asociación con infección del sitio operatorio.

This report describes the medical record of a patient whom after undergoing spinal anesthesia with hyperbaric bupivacaine 15 mg (0.5%), plus fentanyl 25mcg for an open prostatectomy presented perineal, lumbar, and lower member pain 24 hours following local anesthesia administration. Mechanical and electromyographic compromise were discarded by tomography, resonance, and electromyography. Final diagnosis was transient neurological syndrome. In this case, bupivacaine was the causative agent. Duration of symptoms for nearly three months is a novel finding with respect to the time of recovery, regardless of its association with surgical site infection.

Se apresenta a história de um paciente que depois de realizar anestesia espinal com bupivacaína hiperbárica 15 mg (0.5%), mais fentanil 25 mcg, para prostatectomia aberta, apresentou dor em períneo, lombar e em membros inferiores, 24 horas depois da aplicação do anestésico local. Se descarta compromisso mecânico e eletromiográfico com tomografia, ressonância e eletromiografia. Tendo como diagnóstico definitivo a síndrome neurológico transitório. Neste caso a bupivacaína foi o agente causal. A duração dos sintomas por ao redor de três meses é um descoberta inovador em quanto ao tempo de resolução do quadro, Independente de sua associação com infecção do lugar operatório.

Achieving sub-nanometre particle mapping with energy-filtered TEM.

A combination of state-of-the-art instrumentation and optimized data processing has enabled for the first time the chemical mapping of sub-nanometre particles using energy-filtered transmission electron microscopy (EFTEM). Multivariate statistical analysis (MSA) generated reconstructed datasets where the signal from particles smaller than 1 nm in diameter was successfully isolated from the original noisy background. The technique has been applied to the characterization of oxide dispersion strengthened (ODS) reduced activation FeCr alloys, due to their relevance as structural materials for future fusion reactors. Results revealed that most nanometer-sized particles had a core-shell structure, with an Yttrium-Chromium-Oxygen-rich core and a nano-scaled Chromium-Oxygen-rich shell. This segregation to the nanoparticles caused a decrease of the Chromium dissolved in the matrix, compromising the corrosion resistance of the alloy.

Biomechanical approach to human bitemark reconstruction.

UNLABELLED: This paper investigates the changes in upper and lower dental bite records that occur when the anterior teeth occlude into a three-dimensional rather than a flat object. METHODS: anterior bite registrations were obtained from 20 volunteers with full and unrestored dentitions. As a three- dimensional, life-like bite target we cast a silicone replica from the impression of an actual arm, fitted with a rigid bony interior. Each participant was asked to bite into a single layer of softened bite registration wax wrapped around the same location on the fake arm, as well as into a flat wafer of the same material. Upper and lower bite registrations were then scanned in the same location on a flat bed scanner. We analysed the sizes of the different bite marks by means of landmark- and semi-landmark analysis to calculate Procrustes distances between tooth outlines. In order to analyse shape variation between the two types of bite registration we carried out principal components analyses on the partial warp scores. These were derived from partial Procrustes coordinates aligned by means of thin-plate spline decomposition based on a bending energy matrix. Our results show that there are significant differences in the shape of the upper or lower teeth when they occlude into a flat or three- dimensional target. We conclude that the use of a traditional flat bite registration in human bitemark reconstruction and analysis has to be seriously questioned.

Salt stress effects on the central and carnitine metabolisms of Escherichia coli.

The aim was to understand how interaction of the central carbon and the secondary carnitine metabolisms is affected under salt stress and its effect on the production of L-carnitine by Escherichia coli. The biotransformation of crotonobetaine into L-carnitine by resting cells of E. coli O44 K74 was improved by salt stress, a yield of nearly twofold that for the control being obtained with 0.5 M NaCl. Crotonobetaine and the L-carnitine formed acted as an osmoprotectant during cell growth and biotransformation in the presence of NaCl. The enzyme activities involved in the biotransformation process (crotonobetaine hydration reaction and crotonobetaine reduction reaction), in the synthesis of acetyl-CoA/acetate (pyruvate dehydrogenase, acetyl-CoA synthetase [ACS] and ATP/acetate phosphotransferase) and in the distribution of metabolites for the tricarboxylic acid cycle (isocitrate dehydrogenase [ICDH]) and glyoxylate shunt (isocitrate lyase [ICL]) were followed in batch with resting cells both in the presence and absence of NaCl and in perturbation experiments performed on growing cells in a high density cell recycle membrane reactor. Further, the levels of carnitine, crotonobetaine, gamma-butyrobetaine and ATP and the NADH/NAD(+) ratio were measured in order to know how the metabolic state was modified and coenzyme pools redistributed as a result of NaCl's effect on the energy content of the cell. The results provided the first experimental evidence of the important role played by salt stress during resting and growing cell biotransformation (0.5 M NaCl increased the L-carnitine production in nearly 85%), and the need for high levels of ATP to maintain metabolite transport and biotransformation. Moreover, the main metabolic pathways and carbon flow operating during cell biotransformation was that controlled by the ICDH/ICL ratio, which decreased from 8.0 to 2.5, and the phosphotransferase/ACS ratio, which increased from 2.1 to 5.2, after a NaCl pulse fivefold the steady-state level. Resting E. coli cells were seen to be made up of heterogeneous populations consisting of several types of subpopulation (intact, depolarized, and permeabilized cells) differing in viability and metabolic activity as biotransformation run-time and the NaCl concentration increased. The results are discussed in relation with the general stress response of E. coli, which alters the NADH/NAD(+) ratio, ATP content, and central carbon enzyme activities.

Role of energetic coenzyme pools in the production of L-carnitine by Escherichia coli.

The aim of this work was to understand the steps controlling the biotransformation of trimethylammonium compounds into L(-)-carnitine by Escherichia coli. The high-cell density reactor steady-state levels of carbon source (glycerol), biotransformation substrate (crotonobetaine), acetate (anaerobiosis product) and fumarate (as an electron acceptor) were pulsed by increasing them fivefold. Following the pulse, the evolution of the enzyme activities involved in the biotransformation process of crotonobetaine into L(-)-carnitine (crotonobetaine hydration), in the synthesis of acetyl-CoA (ACS: acetyl-CoA synthetase and PTA: ATP: acetate phosphotransferase) and in the distribution of metabolites for the tricarboxylic acid (ICDH: isocitrate dehydrogenase) and glyoxylate (ICL: isocitrate lyase) cycles was monitored. In addition, the levels of carnitine, the cell ATP content and the NADH/NAD(+) ratio were measured in order to assess the importance and participation of these energetic coenzymes in the catabolic system. The results provided an experimental demonstration of the important role of the glyoxylate shunt during biotransformation and the need for high levels of ATP to maintain metabolite transport and biotransformation. Moreover, the results obtained for the NADH/NAD(+) pool indicated that it is correlated with the biotransformation process at the NAD(+) regeneration and ATP production level in anaerobiosis. More importantly, a linear correlation between the NADH/NAD(+) ratio and the levels of the ICDH and ICL (carbon and electron flows) and the PTA and ACS (acetate and ATP production and acetyl-CoA synthesis) activity levels was assessed. The main metabolic pathway operating during cell metabolic perturbation with a pulse of glycerol and acetate in the high-cell density membrane reactor was that related to ICDH and ICL, both regulating the carbon metabolism, together with PTA and ACS enzymes (regulating ATP production).