Fiber link design for the NASA-NSF extreme precision Doppler spectrograph concept "WISDOM"

We describe the design of the fiber-optic coupling and light transfer system of the WISDOM (WIYN Spectrograph for DOppler Monitoring) instrument. As a next-generation Precision Radial Velocity (PRV) spectrometer, WISDOM incorporates lessons learned from HARPS about thermal, pressure, and gravity control, but also takes new measures to stabilize the spectrograph illumination, a subject that has been overlooked until recently. While fiber optic links provide more even illumination than a conventional slit, careful engineering of the interface is required to realize their full potential. Conventional round fiber core geometries have been used successfully in conjunction with optical double scramblers, but such systems still retain a memory of the input illumination that is visible in systems seeking sub-m/s PRV precision. Noncircular fibers, along with advanced optical scramblers, and careful optimization of the spectrograph optical system itself are therefore necessary to study Earth-sized planets. For WISDOM, we have developed such a state-of-the-art fiber link concept. Its design is driven primarily by PRV requirements, but it also manages to preserve high overall throughput. Light from the telescope is coupled into a set of six, 32 μm diameter octagonal core fibers, as high resolution is achieved via pupil slicing. The low-OH, step index, fused silica, FBPI-type fibers are custom designed for their numerical aperture that matches the convergence of the feeding beam and thus minimizes focal ratio degradation at the output. Given the demanding environment at the telescope the fiber end tips are mounted in a custom fused silica holder, providing a perfect thermal match. We used a novel process, chemically assisted photo etching, to manufacture this glass fiber holder. A single ball-lens scrambler is inserted into the 25m long fibers. Employing an anti-reflection (AR) coated, high index, cubic-zirconia ball lens the alignment of the scrambler components are straightforward, as the fiber end tips (also AR coated) by design touch the ball lens and thus eliminate spacing tolerances. A clever and simple opto-mechanical design and assembly process assures micron-level self-alignment, yielding a ~87% throughput and a scrambling gain of >20,000. To mitigate modal noise the individual fibers then subsequently combined into a pair of rectangular fibers, providing a much larger modal area thanks to the 34x106 micron diameter. To minimize slit height, and thus better utilize detector area, the octagonal cores are brought very close together in this transition. The two outer fibers are side polished at one side, into a D-shaped cladding, while the central fiber has a dual side polish. These tapered, side-flattening operations are executed with precise alignment to the octagonal core. Thus the cores of the 3 fibers are brought together and aligned within few microns of each other before spliced onto the rectangular fiber. Overall throughput kept high and FRD at bay by careful management of fiber mounting, vacuum feed-through, application of efficient AR coatings, and implementation of thermal breaks that allow for independent expansion of the fibers and the protective tubing

Role of plastid markers in environmental studies on the example of the endangered species Cistus heterophyllus

[SPA] Los marcadores moleculares son una herramienta muy poderosa en muchos campos como la filogenia, la biología evolutiva o la conservación. Sin embargo, no es una tarea fácil encontrar marcadores adecuados para especies raras. Los marcadores ideales tienen que ser de carácter informativo dependiendo de la cuestión biológica: la diferenciación entre especies estrechamente relacionadas requiere un marcador para regiones altamente diferenciados, mientras marcadores para la diferenciación entre organismos pertenecientes a familias distantes están seleccionados para la detección de regiones conservadas. Importante es también el tipo de ADN como fuente de nuestro marcador. El ADN de plástidos se prefiere en proyectos sobre filogenia, mientras que la detección de eventos de hibridación demanda el análisis del ADN nuclear. Sin embargo, en el caso de especies raras, los científicos se encuentran con una falta de información sobre secuencias de los genomas bajo estudio. En este caso la única solución es la aplicación de marcadores universales, ya descritos para otros organismos. Este proyecto tiene como objetivo analizar un conjunto de marcadores moleculares para el rastreo de eventos de hibridación en la población de una especie en peligro de extinción de la familia Cistaceae, Cistus heterophyllussubsp. carthaginensis. La distribución de esta subespecie se limita a una sola población natural en el sureste de España, donde co-ocurren individuos con fenotipo silvestre y fenotipos híbridos, lo que sugiere eventos de hibridación entre esta población en peligro de extinción y una especie localmente abundante, Cistus albidus. Estos híbridos se han descrito en África como C. ×clausonis.Se realizaron búsquedas de regiones de ADN que permiten la discriminación de entre los individuos de tipo silvestre e híbridos supuestos. Los datos generados podrían mejorar la estrategia de conservación de las especies con el fin de evitar su extinción. En el capítulo 1, se describe la posible aplicación de marcadores moleculares plastídicos, regiones de marcadores conocidas como “códigos de barras”, para su aplicación de la población mencionado anteriormente. Regiones no codificantes de ADN (rbcL, trnK-matK) no resultaron lo suficientemente variables para ser informativas en individuos estrechamente relacionados. Regiones intra-específicas (trnL-F, trnH-psbA) presentan una alta tasa de cambios evolutivos, indicado por su alto grado de variabilidad. Sin embargo, encontramos que estos marcadores no son suficientemente estables como para proporcionar información fiable para la diferenciación entre individuos silvestres e híbridos. Sorprendentemente, se observó para los genes rpoBy rpoC1 una heteroplasmia en C. heterophyllusy C. × clausonislocal, pero no en C. albidusu otra especie comun a esta región, C. monspeliensis.Encontramos dos alelos distintos de rpoB, uno presente en todas las especies y un segundo presente sólo en C. heterophyllusy C.× clausonislocal. También se detectaron dos alelos de rpoC1, uno común a todas las especies analizadas y un segundo presente sólo en C. × clausonislocal. Nuestros resultados muestran que hay un alelo rpoBdistintivo y común a C. heterophyllus y C. × clausonisde África y Europa. El alelo rpoC1 unicamente encontrado en C.× clausonislocal indíca un origen de esta pequeña población diferente que no resulta de una hibridación entre los C. albiduso C. heterophyllusactualmente presentes en esta ubicación. El capítulo 2 describe la aplicación de regiones internas inter-espaciadas (ITS, internal transcribed spacer) ribosomales. Estos marcadores altamente polimórficos permiten la construcción de árboles filogenéticos moleculares con el objetivo de analizar las relaciones entre poblaciones geograficamente aislados de Cistus heterophyllus, Cistus albidus y posibles híbridos entre estos dos especies, C. × clausonisde África y de Europa. Nuestros datos indican que, depnediendo de individuo o población, C. × clausonisfilogenéticamenteparece más a Cistus heterophylluso Cistus albidus y problamente está relacionado a la homogenización de variación por evolution concertada. En el capítulo 3, se presenta un problema que surgió durante el análisis de los datos de PCR cuantitativa de los marcadores de código de barras. Como resultaron diferencias significativas entre especies en la eficiencia de la PCR aplicando el mismo marcador molecular, decidimos investigar si el sesgo observado podría perturbar la identificación de especies durante el metabarcoding de muestras. Utilizamos seis lociuniversales y 48 especies de plantas y cuantificamos el posible sesgo en cada paso del proceso de identificación desde PCR apunto final hasta la secuenciación. La amplificación a punto final fue significativamente diferente para un solo lociy entre las especies. Análisis por PCR cuantitativa reveló que el umbral Cq para diversos loci, incluso dentro de una sola extracción de ADN, mostró una diferencia de 2000 veces en la cantidad de ADN obtenida después de la amplificación. Experimentos de secuenciación de próxima generación (NGS) en nueve especies mostraron sesgos significativos hacia especies y lociespecíficos utilizando cebadores específicos del adaptador. El sesgo durante la secuenciación NGS se puede predecir en cierta medida por los valores Cq de amplificación en qPCR y depende de la secuencia primaria de ADN. [ENG] Molecular markers are a very powerful tool in many fields such as phylogenetics, evolutionary or conservation biology. However, it is not an easy task to find proper markers for rare species. The perfect marker depends on the biological question: for differentiation among closely related species we need a sensitive marker for highly differentiated region, whereas differentiation among organisms belonging to distant families requires markers for conserved regions. Important is also the type of the DNA as source of our marker. Plastid DNA is preferred in plant phylogenetic projects whereas the analysis of hybridization events requires markers proceeding from nuclear DNA. However, in case of rare species, scientist encounter a lack of sequence information about the genomes studied. In this case the only solution are universal markers already described for other organisms. This project aims to analyse a set of molecular markers for tracing hybridization events in the population of an endangered species from the Cistaceae family, Cistus heterophyllussubsp. carthaginensis. The distribution of this subspecies is limited to only one natural population in the south-eastern Spain where individuals with wild type and hybrid phenotypes co-occure, suggesting hybridization events between the endangered population and the locally abundant Cistus albidus. These hybrids have been described in Africa as C.× clausonis. We searched for DNA regions that allow discrimination between the wild type individuals and putative hybrids. The generated data could improve the species conservation strategy in order to avoid its extinction. In chapter 1, we describe the possible application of plastid markers, regions known as ¨DNA barcodes¨ as markers for the aforementioned population. Noncoding DNA regions (rbcL, trnK-matK) were found as not variable enough to be informative in closely related individuals. Intraspecific regions (trnL-F, trnH-psbA) presented a high rate of the evolutionary changes as indicated by their high variability. However, we found these markers as not sufficiently stable to give reliable information for the identification of wild type and hybrid individuals. Surprisingly, we observed heteroplasmy for rpoBand rpoC1genes in C. heterophyllusand the local C.× clausonis, but not in C. albidusor another species common to this region, C. monspeliensis. We found two distinct alleles of rpoB, one present in all species and a second present only in C. heterophyllusand the local C.× clausonis. We also detected two alleles ofrpoC1, one common to all species analyzed and a second present only in the local C.× clausonis. Our results show that there is a distinctive rpoBallele common to C. heterophyllusand C.× clausonisfrom Africa andEurope. The unique rpoC1allele found in the local C.× clausonis directs to a different origin of this small population, indicating that it is not a hybrid originating from C. albidusor C.heterophylluscurrently present in this location. Chapter 2 describes the application of the highly polymorphic internal transcribed spacer (ITS) region of the ribosomal DNA in the construction of a molecular tree in order to unravel the relationship among geographically isolated populations of Cistus heterophyllus, Cistus albidus and possible hybrids of these two species,C. × clausonisfrom Africa and Europe. Our data indicate that, depending on the individual and population, C. × clausonis phylogenetically resembles more either Cistus heterophyllusor Cistus albidus what might be related to the homogenization of variation between repeat types through concerted evolution. In chapter 3, we present an issue that arose during the analysis of quantitative PCR data of the barcode markers. As we realized that there were significant differences between species in PCR efficiency of the same marker, we decided to investigate if the observed bias may disturb species identification during metabarcoding of samples. We used six universal lociand 48 plant species and quantified the bias at each step of the identification process from end point PCR to next-generation sequencing. End point amplification was significantly different for single lociand between species. Quantitative PCR revealed that the Cq threshold for various loci, even within a single DNA extraction, showed 2,000-fold differences in DNA quantity after amplification. Next generation sequencing (NGS) experiments in nine species showed significant biases towards species and specific lociusing adaptor-specific primers.NGS sequencing bias may be predicted to some extent by the Cq values of qPCR amplification.[ENG] Molecular markers are a very powerful tool in many fields such as phylogenetics, evolutionary or conservation biology. However, it is not an easy task to find proper markers for rare species. The perfect marker depends on the biological question: for differentiation among closely related species we need a sensitive marker for highly differentiated region, whereas differentiation among organisms belonging to distant families requires markers for conserved regions. Important is also the type of the DNA as source of our marker. Plastid DNA is preferred in plant phylogenetic projects whereas the analysis of hybridization events requires markers proceeding from nuclear DNA. However, in case of rare species, scientist encounter a lack of sequence information about the genomes studied. In this case the only solution are universal markers already described for other organisms. This project aims to analyse a set of molecular markers for tracing hybridization events in the population of an endangered species from the Cistaceae family, Cistus heterophyllussubsp. carthaginensis. The distribution of this subspecies is limited to only one natural population in the south-eastern Spain where individuals with wild type and hybrid phenotypes co-occure, suggesting hybridization events between the endangered population and the locally abundant Cistus albidus. These hybrids have been described in Africa as C.× clausonis. We searched for DNA regions that allow discrimination between the wild type individuals and putative hybrids. The generated data could improve the species conservation strategy in order to avoid its extinction. In chapter 1, we describe the possible application of plastid markers, regions known as ¨DNA barcodes¨ as markers for the aforementioned population. Noncoding DNA regions (rbcL, trnK-matK) were found as not variable enough to be informative in closely related individuals. Intraspecific regions (trnL-F, trnH-psbA) presented a high rate of the evolutionary changes as indicated by their high variability. However, we found these markers as not sufficiently stable to give reliable information for the identification of wild type and hybrid individuals. Surprisingly, we observed heteroplasmy for rpoBand rpoC1genes in C. heterophyllusand the local C.× clausonis, but not in C. albidusor another species common to this region, C. monspeliensis. We found two distinct alleles of rpoB, one present in all species and a second present only in C. heterophyllusand the local C.× clausonis. We also detected two alleles ofrpoC1, one common to all species analyzed and a second present only in the local C.× clausonis. Our results show that there is a distinctive rpoBallele common to C. heterophyllusand C.× clausonisfrom Africa andEurope. The unique rpoC1allele found in the local C.× clausonis directs to a different origin of this small population, indicating that it is not a hybrid originating from C. albidusor C.heterophylluscurrently present in this location. Chapter 2 describes the application of the highly polymorphic internal transcribed spacer (ITS) region of the ribosomal DNA in the construction of a molecular tree in order to unravel the relationship among geographically isolated populations of Cistus heterophyllus, Cistus albidus and possible hybrids of these two species,C. × clausonisfrom Africa and Europe. Our data indicate that, depending on the individual and population, C. × clausonis phylogenetically resembles more either Cistus heterophyllusor Cistus albidus what might be related to the homogenization of variation between repeat types through concerted evolution. In chapter 3, we present an issue that arose during the analysis of quantitative PCR data of the barcode markers. As we realized that there were significant differences between species in PCR efficiency of the same marker, we decided to investigate if the observed bias may disturb species identification during metabarcoding of samples. We used six universal lociand 48 plant species and quantified the bias at each step of the identification process from end point PCR to next-generation sequencing. End point amplification was significantly different for single lociand between species. Quantitative PCR revealed that the Cq threshold for various loci, even within a single DNA extraction, showed 2,000-fold differences in DNA quantity after amplification. Next generation sequencing (NGS) experiments in nine species showed significant biases towards species and specific lociusing adaptor-specific primers.NGS sequencing bias may be predicted to some extent by the Cq values of qPCR amplification.Escuela Internacional de Doctorado de la Universidad Politécnica de CartagenaUniversidad Politécnica de CartagenaPrograma de Doctorado Técnicas Avanzadas en Investigación y Desarrollo Agrario y Alimentari

The Maunakea Spectroscopic Explorer Book 2018

(Abridged) This is the Maunakea Spectroscopic Explorer 2018 book. It is intended as a concise reference guide to all aspects of the scientific and technical design of MSE, for the international astronomy and engineering communities, and related agencies. The current version is a status report of MSE's science goals and their practical implementation, following the System Conceptual Design Review, held in January 2018. MSE is a planned 10-m class, wide-field, optical and near-infrared facility, designed to enable transformative science, while filling a critical missing gap in the emerging international network of large-scale astronomical facilities. MSE is completely dedicated to multi-object spectroscopy of samples of between thousands and millions of astrophysical objects. It will lead the world in this arena, due to its unique design capabilities: it will boast a large (11.25 m) aperture and wide (1.52 sq. degree) field of view; it will have the capabilities to observe at a wide range of spectral resolutions, from R2500 to R40,000, with massive multiplexing (4332 spectra per exposure, with all spectral resolutions available at all times), and an on-target observing efficiency of more than 80%. MSE will unveil the composition and dynamics of the faint Universe and is designed to excel at precision studies of faint astrophysical phenomena. It will also provide critical follow-up for multi-wavelength imaging surveys, such as those of the Large Synoptic Survey Telescope, Gaia, Euclid, the Wide Field Infrared Survey Telescope, the Square Kilometre Array, and the Next Generation Very Large Array.Comment: 5 chapters, 160 pages, 107 figure

Role of molecular markers in environmental studies on the example of the endangered species Cistus heterophyllus

[SPA] Este estudio tiene como objetivo analizar un conjunto de marcadores moleculares para el rastreo de eventos de hibridación en la población de una especie en peligro de extinción de la familia Cistaceae, Cistus heterophyllus subsp. carthaginensis limitada a una sola población natural en el noreste de España. En esta población coocurren individuos con fenotipo silvestre y fenotipos híbridos, descritos antes en Africa como C. × clausonis, lo que sugiere eventos de hibridación entre esta población en peligro de extinción y una especie localmente abundante, Cistus albidus. Hemos aplicado marcadores plastídicos y la region internos inter-espaciados (ITS) de la ADN ribosómico como marcadores para su aplicación en la población mencionada. Observamos heteroplasmia en C. heterophyllus y C. × clausonis local, pero no en C. albidus. La región de ITS fue analizada en poblaciones geograficamente aisladas de Cistus heterophyllus, Cistus albidus y posibles híbridos entre estos dos especies. Depnediendo de individuo o población, C. × clausonis filogenéticamente parece más a Cistus heterophyllus o Cistus albidus y problamente está relacionado a la homogenización de variación por evolution concertada. [ENG] This study aims to analyse a set of molecular markers for tracing hybridization events in the population of an endangered species from the Cistaceae family, Cistus heterophyllus subsp. carthaginensis limited to only one natural population in the north-eastern Spain. In this population individuals with wild type and hybrid phenotypes, described before in Africa as C. × clausonis, co-occure, suggesting hybridization events between the endangered population and the locally abundant Cistus albidus. We applied plastid DNA and internal transcribed spacer (ITS) region of the ribosomal DNA as markers in the aforementioned population. We observed heteroplasmy for rpoB and rpoC1 plastid genes in C. heterophyllus and the local C. × clausonis, but not in C. albidus. The ITS region was analysed in geographically isolated populations of Cistus heterophyllus, Cistus albidus and possible hybrids of these two species. Depending on the individual and population, C. × clausonis phylogenetically resembles more either Cistus heterophyllus or Cistus albidus and it might be related to the homogenization of variation between repeat types through concerted evolution.This work was funded by the Comunidad Autónoma de la Región de Murcia Project “Molecular markers in conservation and management of the flora of Murcia Region”

Quantitative evaluation of bias in PCR amplification and Next Generation Sequencing derived from metabarcoding samples

Unbiased identification of organisms by PCR reactions using universal primers followed by DNA sequencing assumes positive amplification. We used six universal loci spanning 48 plant species and quantified the bias at each step of the identification process from end point PCR to Next-Generation Sequencing. End-point amplification was significantly different for single loci and between species. Quantitative PCR revealed that Cq threshold for various loci, even within a single DNA extraction, showed 2000-fold differences in DNA quantity after amplification. Next Generation Sequencing (NGS) experiments in nine species showed significant biases towards species and specific loci using adaptor-specific primers. NGS sequencing bias may be predicted to some extent by the Cq values of Q-PCR amplification.This work was funded by the Comunidad Autónoma de la Región de Murcia Project “Molecular markers in conservation and management of the flora of Murcia Region”. This work was published in Analytical and Bioanalytical Chemistry (407(7): 1841-8

Quantitative evaluation of bias in barcode markers derived from complex samples

PCR products have become a major commodity used to identify organisms based on polymorphism at the DNA level. One problem arising is that unbiased identification of organisms takes as working hypothesis that when DNA is extracted from a sample, a positive signal will be obtained if universal primers are used and DNA quality is suitable for PCR. As this assumption is not always correct we used a system where large differences in PCR success have been described to identify where biases appear and maybe identify solutions. Plants can be identified with at least seven independent plastid‐located loci. These differ in their degree of PCR success and how informative they are in terms of taxonomically useful sequence polymorphisms. Here we used six common plastid loci spanning 48 plant species and performed a quantitative analysis of bias at each step of the identification process. As expected we found important differences in PCR efficiency within a single species, depending on the barcoding sequence being amplified. Quantitative PCR revealed that the Ct threshold for various plastid loci, even within a single species, could exhibit greater than 2000‐fold differences in DNA quantity after amplification. We then performed Next Generation Sequencing experiments in nine species using equal quantities of three plastid‐based primers and equally‐mixed quantities of DNA from multiple species. The result was significantly biased towards species and specific loci even when using adaptor‐specific primers. Our results caution that Next‐Generation Sequencing projects may suffer dramatic bias, arising largely during DNA amplification steps. Moreover, that amplification‐based Next Generation Sequencing technologies exhibit additional bias despite using adaptor‐specific primers, indicating that amplification success depends on the DNA fragment. As such, while qualitative analysis of unknown samples are prone to false negative results if a combination of widely‐successful amplicons are not used, quantitative results should be considered highly suspect, even if all species in the starting sample are known.This work was funded by the Comunidad Autónoma de la Región de Murcia Project “Molecular markers in coservation and management of the flora of Murcia Region”

Flozins - modern treatment for patients with type 2 diabetes

Introduction: Type 2 diabetes is a metabolic disease characterized by elevated blood glucose levels. Uncontrolled disease leads to many complications that significantly affect quality of life and life expectancy. Flozins – sodium-glucose cotransporter 2 (SGLT2) inhibitors are a new group of drugs used in the treatment of DM 2, which, in addition to their hypoglycemic effect in the form of increased glucose excretion in urine, also have a beneficial effect on the cardiovascular system. Objective: The aim of the study was to present the benefits of using SGLT2 inhibitors in patients with type 2 diabetes. Materials and methods: We reviewed the literature in PubMed using the keywords: “Diabetes type 2”, “Flozins”, “SGLT2 inhibitors”, “Cardiovascular disease”, and “Renal disease”. Results: It has been proven that SGLT2 inhibitors, in addition to their hypoglycemic effect, also have a beneficial effect on other systems. The studies discussed show that SGLT2 drugs reduce cardiovascular risk and have a protective effect on the kidneys. Summary: The efficacy of SGLT2 inhibitors therapy has been confirmed in clinical trials. Future studies should aim to determine at what stage treatment should be initiated in order to maximize the benefits for the patient

The importance of biochemical and ultrasound markers in prenatal diagnosis: current methods and development perspectives

This paper explores the role of biochemical and ultrasound markers in prenatal diagnosis, emphasizing their importance in early detection of chromosomal and structural abnormalities in the fetus. It aims to characterize the most relevant diagnostic markers, evaluate the sensitivity and specificity of current methods, and discuss modern advancements such as non-invasive prenatal testing (NIPT). Biochemical and ultrasound markers remain fundamental tools in prenatal screening, providing crucial information for risk stratification and early intervention. The integration of traditional methods with advanced technologies such as NIPT offers a comprehensive approach to fetal health assessment. Continuous refinement of diagnostic algorithms and broader access to non-invasive testing are key directions for future development, aiming to improve both prenatal care quality and patient safety

The impact of intensive sports training on the development of young girls

Introduction: Adolescence is a critical period for physical and mental development, during which physical activity can improve bone mineral density (BMD), reduce obesity, and enhance self-esteem. However, intense sports participation increases energy demands, potentially leading to energy deficits, particularly in female athletes. This energy imbalance can negatively impact the health of adolescent athletes. The purpose of research: This paper explores the effect of intensive training on the health of young female athletes. Material and methods: PubMed and Medline databases were searched. Relevant literature was selected. Results: A persistent state of low energy availability (LEA) has been demonstrated to lead to a variety of disorders, including menstrual irregularities, impaired bone microarchitecture, and depressive and anxiety symptoms. These abnormalities pose a particularly elevated risk to young female athletes, as they can result in severe lifelong complications. Conclusions: Every young female athlete should be screened for the symptoms of the syndrome of relative energy deficiency in sport (RED-S). Examination should be repeated at least annually. In the treatment of disorders arising from LEA, the primary objective is to enhance energy levels. In cases of low BMD, it is imperative to ensure an adequate supply of vitamin D and calcium in order to prevent fractures

Hepatic cysteine sulphinic acid decarboxylase depletion and defective taurine metabolism in a rat partial nephrectomy model of chronic kidney disease

© 2021, The Author(s). This article is licensed under a Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.Background: Taurine depletion occurs in patients with end-stage chronic kidney disease (CKD). In contrast, in the absence of CKD, plasma taurine is reported to increase following dietary L-glutamine supplementation. This study tested the hypothesis that taurine biosynthesis decreases in a rat CKD model, but is rectified by L-glutamine supplementation. Methods: CKD was induced by partial nephrectomy in male Sprague-Dawley rats, followed 2 weeks later by 2 weeks of 12% w/w L-glutamine supplemented diet (designated NxT) or control diet (NxC). Sham-operated control rats (S) received control diet. Results: Taurine concentration in plasma, liver and skeletal muscle was not depleted, but steady-state urinary taurine excretion (a measure of whole-body taurine biosynthesis) was strongly suppressed (28.3 ± 8.7 in NxC rats versus 78.5 ± 7.6 μmol/24 h in S, P < 0.05), accompanied by reduced taurine clearance (NxC 0.14 ± 0.05 versus 0.70 ± 0.11 ml/min/Kg body weight in S, P < 0.05). Hepatic expression of mRNAs encoding key enzymes of taurine biosynthesis (cysteine sulphinic acid decarboxylase (CSAD) and cysteine dioxygenase (CDO)) showed no statistically significant response to CKD (mean relative expression of CSAD and CDO in NxC versus S was 0.91 ± 0.18 and 0.87 ± 0.14 respectively). Expression of CDO protein was also unaffected. However, CSAD protein decreased strongly in NxC livers (45.0 ± 16.8% of that in S livers, P < 0.005). L-glutamine supplementation failed to rectify taurine biosynthesis or CSAD protein expression, but worsened CKD (proteinuria in NxT 12.5 ± 1.2 versus 6.7 ± 1.5 mg/24 h in NxC, P < 0.05). Conclusion: In CKD, hepatic CSAD is depleted and taurine biosynthesis impaired. This is important in view of taurine’s reported protective effect against cardio-vascular disease - the leading cause of death in human CKD.Peer reviewe