Analysis of left ventricular function of the mouse heart during experimentally induced hyperthyroidism and recovery

Many of the clinical manifestations of hyperthyroidism are due to the ability of thyroid hormones to alter myocardial contractility and cardiovascular hemodynamics, leading to cardiovascular impairment. In contrast, recent studies highlight also the potential beneficial effects of thyroid hormone administration for clinical or preclinical treatment of different diseases such as atherosclerosis, obesity and diabetes or as a new therapeutic approach in demyelinating disorders. In these contexts and in the view of developing thyroid hormone-based therapeutic strategies, it is, however, important to analyze undesirable secondary effects on the heart. Animal models of experimentally induced hyperthyroidism therefore represent important tools for investigating and monitoring changes of cardiac function. In our present study we use high-field cardiac MRI to monitor and follow-up longitudinally the effects of prolonged thyroid hormone (triiodothyronine) administration focusing on murine left ventricular function. Using a 9.4 T small horizontal bore animal scanner, cinematographic MRI was used to analyze changes in ejection fraction, wall thickening, systolic index and fractional shortening. Cardiac MRI investigations were performed after sustained cycles of triiodothyronine administration and treatment arrest in adolescent (8 week old) and adult (24 week old) female C57Bl/6 N mice. Triiodothyronine supplementation of 3 weeks led to an impairment of cardiac performance with a decline in ejection fraction, wall thickening, systolic index and fractional shortening in both age groups but with a higher extent in the group of adolescent mice. However, after a hormonal treatment cessation of 3 weeks, only young mice are able to partly restore cardiac performance in contrast to adult mice lacking this recovery potential and therefore indicating a presence of chronically developed heart pathology.

Normal Thyroid Function and the Risk of Atrial Fibrillation: the Rotterdam Study

CONTEXT Hyperthyroidism is an established risk factor for atrial fibrillation (AF), but information concerning the association with variations within the normal range of thyroid function and subgroups at risk is lacking. OBJECTIVE This study aimed to investigate the association between normal thyroid function and AF prospectively and explore potential differential risk patterns. DESIGN, SETTING, AND PARTICIPANTS From the Rotterdam Study we included 9166 participants ≥ 45 y with TSH and/or free T4 (FT4) measurements and AF assessment (1997-2012 median followup, 6.8 y), with 399 prevalent and 403 incident AF cases. MAIN OUTCOME MEASURES Outcome measures were 3-fold: 1) hazard ratios (HRs) for the risk of incident AF by Cox proportional-hazards models, 2) 10-year absolute risks taking competing risk of death into account, and 3) discrimination ability of adding FT4 to the CHARGE-AF simple model, an established prediction model for AF. RESULTS Higher FT4 levels were associated with higher risks of AF (HR 1.63, 95% confidence interval, 1.19-2.22), when comparing those in the highest quartile to those in lowest quartile. Absolute 10-year risks increased with higher FT4 in participants ≤ 65 y from 1-9% and from 6-12% in subjects ≥ 65 y. Discrimination of the prediction model improved when adding FT4 to the simple model (c-statistic, 0.722 vs 0.729; P = .039). TSH levels were not associated with AF. CONCLUSIONS There is an increased risk of AF with higher FT4 levels within the normal range, especially in younger subjects. Adding FT4 to the simple model slightly improved discrimination of risk prediction.

Sulfur Isotopic Ratios at 67P/Churyumov-Gerasimenko and Characterization of ROSINA-DFMS FM & FS

Comets are thought to be the most pristine bodies present in the Solar System. In consequence of spending the majority of their existence beyond 30 AU, their composition can give insights on the physical and chemical conditions during their formation. Since August 2014 the European Space Agency spacecraft Rosetta accompanies the Jupiter family comet 67P/Churyumov-Gerasimenko on its way to perihelion and beyond. In this study the isotope fractionation of 34S are reported in H2S, OCS, SO2, S2, and CS2 at 67P. In addition for the first time the isotope fractionation for 33S is presented for cometary volatiles. The ratio 32S/33S is given for H2S, SO2 and a tentative value is given for CS2. With a mean value of -50 ± 22‰ and -306 ± 31‰ for δ34S and δ33S respectively, H2S shows a significant depletion in both 34S and 33S. For SO2 the depletion is less distinct with δ34S and δ33S being -67 ± 40‰ and -130 ± 53‰, respectively. The strongest depletion is present for CS2 with -114 ± 21‰and -276 ± 55‰, respectively. For OCS and S2 only δ34S could be determined which is -252 ± 77‰ and -357 ± 145‰, respectively. A comparison with sulfur isotopic ratios measured in SiC grains revealed that both SiC grains and the five volatile species have similar sulfur isotopic ratios. However, it is beyond the scope of this work to investigate the possibility of a link between SiC grains and cometary ices. Nevertheless, mass-dependent or mass-independent fractionation due to photo dissociation can be ruled out as sole cause of the seen depletion of 33S and 34S. Furthermore, an upper limit of (9.64 ± 0.19)·10.4 for D/H in HDS has been determined. This value is about a factor two higher than D/H in H2O for the same comet reported by (Altwegg et al., 2015). Besides the investigation concerning isotopic ratios of sulfur bearing species in this work the calibration and characterization of ROSINA/DFMS has been continued. Here it is reported about the deviation of the mass scale for MCP/LEDA low resolution spectra and the calibration measurements performed in the laboratory. Furthermore the outcome of the attempt to describe the sensitivity of DFMS with an empirical function will be discussed. The last part of the characterization of DFMS is dedicated to determine the so-called individual pixel gain for the laboratory and the flight model. Moreover, correlation between the depletion’s manifestation of the MCP with respect to the applied voltages has been investigated for both models. It has been found that further measurements are needed to understand the manifestation of depletion at the laboratory model. For the model on board of Rosetta it could be shown that most of the present feature are due to the usage of the MCP and suggestions have been made in order to answer the remaining question considering the depletion of the MCP.

Function of histaminergic retinopetal axons in rat and primate retinas

Mammalian retinas receive input from histaminergic neurons in the posterior hypothalamus. These neurons are most active during the waking state of the animal, but their role in retinal information processing is not known. To determine the function of these retinopetal axons, their targets in the rat and monkey retina were identified. Using antibodies to three histamine receptors, HR1, HR2, and HR3, the immunolabeling was analyzed by confocal and electron microscopy. These experiments showed that mammalian retinas possess histamine receptors. In macaques and baboons, diurnal species, HR3 receptors were found at the apex of ON-bipolar cell dendrites in cone pedicles and rod spherules, sclerad to the other neurotransmitter receptors that have been localized there. In addition, HR1 histamine receptors were localized to large puncta in the inner plexiform layer, a subset of ganglion cells and retinal blood vessels. In rats, a nocturnal species, the localization of histamine receptors in the retina was markedly different. Most HR1 receptors were localized to dopaminergic amacrine cells and on elements in the rod spherule. To determine how histaminergic retinopetal axons contribute to retinal information processing, responses of retinal ganglion cells to histamine were analyzed. The effects of histamine on the maintained and light-evoked activity of retinal ganglion cells were analyzed. In monkeys, histamine and the HR3 agonist, methylhistamine, increased or decreased the maintained activity of most ganglion cells, but a few did not respond. The responses of a subset of ganglion cells to light stimuli were decreased by histamine, a finding suggesting that histaminergic retinopetal axons contribute to light adaptation during the day. In rats, histamine nearly always increased the maintained activity and produced both increases and decreases in the light responses. The effects of histamine on maintained activity of ganglion cells in the rat can be partially attributed to HR1-mediated changes in the activity of dopaminergic amacrine cells, at night. Together, these experiments provide the first indication of the function of retinopetal axons in mammalian retinas. ^

Lipid-dependent topogenesis and function of membrane proteins

Membranes are essential for the integrity and function of the cell. The collective property of the lipid bilayer is critical in providing an optimal functioning environment for membrane proteins. The simple yet well-characterized bacterium Escherichia coli serves an ideal model system to study the function of specific lipids since its lipid content can be easily manipulated. The most abundant lipid in E. coli membrane is phosphatidylethanolamine (PE, 70-80%). A PE-lacking E. coli mutant displays a complex mixture of deficient phenotypes, suggesting a profound role for PE in different aspects of cell function. A novel role of PE as a topological and functional determinant for membrane proteins has been established using lactose permease (LacY) as a model protein. PE is found to be required for energy-dependent uphill transport process of LacY. In PE-lacking membranes, LacY undergoes a dramatic conformational change, and the first half of the protein adopts an inverted topology with respect to the bilayer plane. ^ The work reported here was initiated to understand the molecular properties of lipids that enable their function as topological and functional determinants for membrane proteins. A glycolipid, monoglucosyldiacylglycerol (MGlcDAG) which shares physicochemical similarities with PE, was introduced to PE-lacking E. coli membranes. The introduction of MGlcDAG suppresses many of the PE-deficient phenotypes, and in particular supports the function and native topology of LacY. ^ The lipid-sensitive topogenic signals encoded in the amino acid sequence of LacY were also identified. Native LacY adopts an inverted topology when synthesized without PE, but mutation of specific acidic residues in the cytoplasmic extra-membrane domains can prevent this inversion and supports a native topological organization of LacY in PE-lacking membranes. These results suggest that it is the interplay between the collective charge properties of the lipid bilayer and extra-membrane loops of protein that determines the final orientation of transmembrane domains. By comparing the similarities as well as differences between these two lipids, we established how specific physical and chemical properties of lipids influence various cell functions and elucidated the molecular basis for the novel role of lipids in determining membrane protein topology. ^

Optimization of a label-free biosensor vertically characterized based on a periodic lattice of high aspect ratio SU-8 nano-pillars with a simplified 2D theoretical model

We have recently demonstrated a biosensor based on a lattice of SU8 pillars on a 1 μm SiO2/Si wafer by measuring vertically reflectivity as a function of wavelength. The biodetection has been proven with the combination of Bovine Serum Albumin (BSA) protein and its antibody (antiBSA). A BSA layer is attached to the pillars; the biorecognition of antiBSA involves a shift in the reflectivity curve, related with the concentration of antiBSA. A detection limit in the order of 2 ng/ml is achieved for a rhombic lattice of pillars with a lattice parameter (a) of 800 nm, a height (h) of 420 nm and a diameter(d) of 200 nm. These results correlate with calculations using 3D-finite difference time domain method. A 2D simplified model is proposed, consisting of a multilayer model where the pillars are turned into a 420 nm layer with an effective refractive index obtained by using Beam Propagation Method (BPM) algorithm. Results provided by this model are in good correlation with experimental data, reaching a reduction in time from one day to 15 minutes, giving a fast but accurate tool to optimize the design and maximizing sensitivity, and allows analyzing the influence of different variables (diameter, height and lattice parameter). Sensitivity is obtained for a variety of configurations, reaching a limit of detection under 1 ng/ml. Optimum design is not only chosen because of its sensitivity but also its feasibility, both from fabrication (limited by aspect ratio and proximity of the pillars) and fluidic point of view. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A function using cubic splines for the analysis of alpha--particles spectra from silicon detectors

A function based on the characteristics of the alpha-particle lines obtained with silicon semiconductor detectors and modi"ed by using cubic splines is proposed to parametrize the shape of the peaks. A reduction in the number of parameters initially considered in other proposals was carried out in order to improve the stability of the optimization process. It was imposed by the boundary conditions for the cubic splines term. This function was then able to describe peaks with highly anomalous shapes with respect to those expected from this type of detector. Some criteria were implemented to correctly determine the area of the peaks and their errors. Comparisons with other well-established functions revealed excellent agreement in the "nal values obtained from both "ts. Detailed studies on reliability of the "tting results were carried out and the application of the function is proposed. Although the aim was to correct anomalies in peak shapes, the peaks showing the expected shapes were also well "tted. Accordingly, the validity of the proposal is quite general in the analysis of alpha-particle spectrometry with semiconductor detectors.

Effect of Sb incorporation on the electronic structure of InAs quantum dots

On the basis of optical characterization experiments and an eight band kp model, we have studied the effect of Sb incorporation on the electronic structure of InAs quantum dots (QDs). We have found that Sb incorporation in InAs QDs shifts the hole wave function to the center of the QD from the edges of the QD where it is otherwise pinned down by the effects of shear stress. The observed changes in the ground-state energy cannot merely be explained by a composition change upon Sb exposure but can be accounted for when the change in lateral size is taken into consideration. The Sb distribution inside the QDs produces distinctive changes in the density of states, particularly, in the separation between excitation shells. We find a 50% increase in the thermal escape activation energy compared with reference InAs quantum dots as well as an increment of the fundamental transition decay time with Sb incorporation. Furthermore, we find that Sb incorporation into quantum dots is strongly nonlinear with coverage, saturating at low doses. This suggests the existence of a solubility limit of the Sb incorporation into the quantum dots during growth.

Dynamic analysis of payloads and structures with intermediate modal density

La necesidad de desarrollar técnicas para predecir la respuesta vibroacústica de estructuras espaciales lia ido ganando importancia en los últimos años. Las técnicas numéricas existentes en la actualidad son capaces de predecir de forma fiable el comportamiento vibroacústico de sistemas con altas o bajas densidades modales. Sin embargo, ambos rangos no siempre solapan lo que hace que sea necesario el desarrollo de métodos específicos para este rango, conocido como densidad modal media. Es en este rango, conocido también como media frecuencia, donde se centra la presente Tesis doctoral, debido a la carencia de métodos específicos para el cálculo de la respuesta vibroacústica. Para las estructuras estudiadas en este trabajo, los mencionados rangos de baja y alta densidad modal se corresponden, en general, con los rangos de baja y alta frecuencia, respectivamente. Los métodos numéricos que permiten obtener la respuesta vibroacústica para estos rangos de frecuencia están bien especificados. Para el rango de baja frecuencia se emplean técnicas deterministas, como el método de los Elementos Finitos, mientras que, para el rango de alta frecuencia las técnicas estadísticas son más utilizadas, como el Análisis Estadístico de la Energía. En el rango de medias frecuencias ninguno de estos métodos numéricos puede ser usado con suficiente precisión y, como consecuencia -a falta de propuestas más específicas- se han desarrollado métodos híbridos que combinan el uso de métodos de baja y alta frecuencia, intentando que cada uno supla las deficiencias del otro en este rango medio. Este trabajo propone dos soluciones diferentes para resolver el problema de la media frecuencia. El primero de ellos, denominado SHFL (del inglés Subsystem based High Frequency Limit procedure), propone un procedimiento multihíbrido en el cuál cada subestructura del sistema completo se modela empleando una técnica numérica diferente, dependiendo del rango de frecuencias de estudio. Con este propósito se introduce el concepto de límite de alta frecuencia de una subestructura, que marca el límite a partir del cual dicha subestructura tiene una densidad modal lo suficientemente alta como para ser modelada utilizando Análisis Estadístico de la Energía. Si la frecuencia de análisis es menor que el límite de alta frecuencia de la subestructura, ésta se modela utilizando Elementos Finitos. Mediante este método, el rango de media frecuencia se puede definir de una forma precisa, estando comprendido entre el menor y el mayor de los límites de alta frecuencia de las subestructuras que componen el sistema completo. Los resultados obtenidos mediante la aplicación de este método evidencian una mejora en la continuidad de la respuesta vibroacústica, mostrando una transición suave entre los rangos de baja y alta frecuencia. El segundo método propuesto se denomina HS-CMS (del inglés Hybrid Substructuring method based on Component Mode Synthesis). Este método se basa en la clasificación de la base modal de las subestructuras en conjuntos de modos globales (que afectan a todo o a varias partes del sistema) o locales (que afectan a una única subestructura), utilizando un método de Síntesis Modal de Componentes. De este modo es posible situar espacialmente los modos del sistema completo y estudiar el comportamiento del mismo desde el punto de vista de las subestructuras. De nuevo se emplea el concepto de límite de alta frecuencia de una subestructura para realizar la clasificación global/local de los modos en la misma. Mediante dicha clasificación se derivan las ecuaciones globales del movimiento, gobernadas por los modos globales, y en las que la influencia del conjunto de modos locales se introduce mediante modificaciones en las mismas (en su matriz dinámica de rigidez y en el vector de fuerzas). Las ecuaciones locales se resuelven empleando Análisis Estadístico de Energías. Sin embargo, este último será un modelo híbrido, en el cual se introduce la potencia adicional aportada por la presencia de los modos globales. El método ha sido probado para el cálculo de la respuesta de estructuras sometidas tanto a cargas estructurales como acústicas. Ambos métodos han sido probados inicialmente en estructuras sencillas para establecer las bases e hipótesis de aplicación. Posteriormente, se han aplicado a estructuras espaciales, como satélites y reflectores de antenas, mostrando buenos resultados, como se concluye de la comparación de las simulaciones y los datos experimentales medidos en ensayos, tanto estructurales como acústicos. Este trabajo abre un amplio campo de investigación a partir del cual es posible obtener metodologías precisas y eficientes para reproducir el comportamiento vibroacústico de sistemas en el rango de la media frecuencia. ABSTRACT Over the last years an increasing need of novel prediction techniques for vibroacoustic analysis of space structures has arisen. Current numerical techniques arc able to predict with enough accuracy the vibro-acoustic behaviour of systems with low and high modal densities. However, space structures are, in general, very complex and they present a range of frequencies in which a mixed behaviour exist. In such cases, the full system is composed of some sub-structures which has low modal density, while others present high modal density. This frequency range is known as the mid-frequency range and to develop methods for accurately describe the vibro-acoustic response in this frequency range is the scope of this dissertation. For the structures under study, the aforementioned low and high modal densities correspond with the low and high frequency ranges, respectively. For the low frequency range, deterministic techniques as the Finite Element Method (FEM) are used while, for the high frequency range statistical techniques, as the Statistical Energy Analysis (SEA), arc considered as more appropriate. In the mid-frequency range, where a mixed vibro-acoustic behaviour is expected, any of these numerical method can not be used with enough confidence level. As a consequence, it is usual to obtain an undetermined gap between low and high frequencies in the vibro-acoustic response function. This dissertation proposes two different solutions to the mid-frequency range problem. The first one, named as The Subsystem based High Frequency Limit (SHFL) procedure, proposes a multi-hybrid procedure in which each sub-structure of the full system is modelled with the appropriate modelling technique, depending on the frequency of study. With this purpose, the concept of high frequency limit of a sub-structure is introduced, marking out the limit above which a substructure has enough modal density to be modelled by SEA. For a certain analysis frequency, if it is lower than the high frequency limit of the sub-structure, the sub-structure is modelled through FEM and, if the frequency of analysis is higher than the high frequency limit, the sub-structure is modelled by SEA. The procedure leads to a number of hybrid models required to cover the medium frequency range, which is defined as the frequency range between the lowest substructure high frequency limit and the highest one. Using this procedure, the mid-frequency range can be define specifically so that, as a consequence, an improvement in the continuity of the vibro-acoustic response function is achieved, closing the undetermined gap between the low and high frequency ranges. The second proposed mid-frequency solution is the Hybrid Sub-structuring method based on Component Mode Synthesis (HS-CMS). The method adopts a partition scheme based on classifying the system modal basis into global and local sets of modes. This classification is performed by using a Component Mode Synthesis, in particular a Craig-Bampton transformation, in order to express the system modal base into the modal bases associated with each sub-structure. Then, each sub-structure modal base is classified into global and local set, fist ones associated with the long wavelength motion and second ones with the short wavelength motion. The high frequency limit of each sub-structure is used as frequency frontier between both sets of modes. From this classification, the equations of motion associated with global modes are derived, which include the interaction of local modes by means of corrections in the dynamic stiffness matrix and the force vector of the global problem. The local equations of motion are solved through SEA, where again interactions with global modes arc included through the inclusion of an additional input power into the SEA model. The method has been tested for the calculation of the response function of structures subjected to structural and acoustic loads. Both methods have been firstly tested in simple structures to establish their basis and main characteristics. Methods are also verified in space structures, as satellites and antenna reflectors, providing good results as it is concluded from the comparison with experimental results obtained in both, acoustic and structural load tests. This dissertation opens a wide field of research through which further studies could be performed to obtain efficient and accurate methodologies to appropriately reproduce the vibro-acoustic behaviour of complex systems in the mid-frequency range.

Merit function for the evaluation of color uniformity in the far field of LED spot lights

The scope of the present paper is the derivation of a merit function which predicts the visual perception of LED spot lights. The color uniformity level Usl is described by a linear regression function of the spatial color distribution in the far field. Hereby, the function is derived from four basic functions. They describe the color uniformity of spot lights through different features. The result is a reliable prediction for the perceived color uniformity in spot lights. A human factor experiment was performed to evaluate the visual preferences for colors and patterns. A perceived rank order was derived from the subjects’ answers and compared with the four basic functions. The correlation between the perceived rank order and the basic functions was calculated resulting in the definition of the merit function Usl. The application of this function is shown by a comparison of visual evaluations and measurements of LED retrofit spot lamps. The results enable a prediction of color uniformity levels of simulations and measurements concerning the visual perception. The function provides a possibility to evaluate the far field of spot lights without individual subjective judgment. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

Suppression of protein synthesis in brain during hibernation involves inhibition of protein initiation and elongation

Protein synthesis (PS) has been considered essential to sustain mammalian life, yet was found to be virtually arrested for weeks in brain and other organs of the hibernating ground squirrel, Spermophilus tridecemlineatus. PS, in vivo, was below the limit of autoradiographic detection in brain sections and, in brain extracts, was determined to be 0.04% of the average rate from active squirrels. Further, it was reduced 3-fold in cell-free extracts from hibernating brain at 37°C, eliminating hypothermia as the only cause for protein synthesis inhibition (active, 0.47 ± 0.08 pmol/mg protein per min; hibernator, 0.16 ± 0.05 pmol/mg protein per min, P < 0.001). PS suppression involved blocks of initiation and elongation, and its onset coincided with the early transition phase into hibernation. An increased monosome peak with moderate ribosomal disaggregation in polysome profiles and the greatly increased phosphorylation of eIF2α are both consistent with an initiation block in hibernators. The elongation block was demonstrated by a 3-fold increase in ribosomal mean transit times in cell-free extracts from hibernators (active, 2.4 ± 0.7 min; hibernator, 7.1 ± 1.4 min, P < 0.001). No abnormalities of ribosomal function or mRNA levels were detected. These findings implicate suppression of PS as a component of the regulated shutdown of cellular function that permits hibernating ground squirrels to tolerate “trickle” blood flow and reduced substrate and oxygen availability. Further study of the factors that control these phenomena may lead to identification of the molecular mechanisms that regulate this state.

A homeobox gene with potential developmental control function in the meristem of the conifer Picea abies

Many homeobox genes control essential developmental processes in animals and plants. In this report, we describe the first cDNA corresponding to a homeobox gene isolated from a gymnosperm, the HBK1 gene from the conifer Picea abies (L.) Karst (Norway spruce). The sequence shows distinct similarities specifically to the KNOX (knotted-like homeobox) class of homeobox genes known from different angiosperm plants. The deduced amino acid sequence of HBK1 is strikingly similar within the homeodomain (84% identical) to the maize gene Knotted1 (Kn1), which acts to regulate cell differentiation in the shoot meristem. This similarity suggested that the phylogenetic association of HBK1 with the KNOX genes might be coupled to a conservation of gene function. In support of this suggestion, we have found HBK1 to be expressed in the apical meristem in the central population of nondifferentiated stem cells, but not in organ primordia developing at the flanks of the meristem. This pattern of expression is similar to that of Kn1 in the maize meristem. We show further that HBK1, when expressed ectopically in transgenic Arabidopsis plants, causes aberrations in leaf development that are similar to the effects of ectopic expression of angiosperm KNOX genes on Arabidopsis development. Taken together, these data suggest that HBK1 has a role, similar to the KNOX genes in angiosperms, in the control of cellular differentiation in the apical meristem of spruce. The data also indicate that KNOX-gene regulation of vegetative development is an ancient feature of seed plants that was present in the last common ancestor of conifers and angiosperms.

Activation of Androgen Receptor Function by a Novel Nuclear Protein Kinase

Androgen receptor (AR) belongs to the nuclear receptor superfamily and mediates the biological actions of male sex steroids. In this work, we have characterized a novel 130-kDa Ser/Thr protein kinase ANPK that interacts with the zinc finger region of AR in vivo and in vitro. The catalytic kinase domain of ANPK shares considerable sequence similarity with the minibrain gene product, a protein kinase suggested to contribute to learning defects associated with Down syndrome. However, the rest of ANPK sequence, including the AR-interacting interface, exhibits no apparent homology with other proteins. ANPK is a nuclear protein that is widely expressed in mammalian tissues. Its overexpression enhances AR-dependent transcription in various cell lines. In addition to the zinc finger region, ligand-binding domain and activation function AF1 of AR are needed, as the activity of AR mutants devoid of these domains was not influenced by ANPK. The receptor protein does not appear to be a substrate for ANPK in vitro, and overexpression of ANPK does not increase the extent of AR phosphorylation in vivo. In view of this, it is likely that ANPK-mediated activation of AR function is exerted through modification of AR-associated proteins, such as coregulatory factors, and/or through stabilization of the receptor protein against degradation.

Structure-based assignment of the biochemical function of a hypothetical protein: A test case of structural genomics

Many small bacterial, archaebacterial, and eukaryotic genomes have been sequenced, and the larger eukaryotic genomes are predicted to be completely sequenced within the next decade. In all genomes sequenced to date, a large portion of these organisms’ predicted protein coding regions encode polypeptides of unknown biochemical, biophysical, and/or cellular functions. Three-dimensional structures of these proteins may suggest biochemical or biophysical functions. Here we report the crystal structure of one such protein, MJ0577, from a hyperthermophile, Methanococcus jannaschii, at 1.7-Å resolution. The structure contains a bound ATP, suggesting MJ0577 is an ATPase or an ATP-mediated molecular switch, which we confirm by biochemical experiments. Furthermore, the structure reveals different ATP binding motifs that are shared among many homologous hypothetical proteins in this family. This result indicates that structure-based assignment of molecular function is a viable approach for the large-scale biochemical assignment of proteins and for discovering new motifs, a basic premise of structural genomics.

Viral mediated expression of insulin-like growth factor I blocks the aging-related loss of skeletal muscle function

During the aging process, mammals lose up to a third of their skeletal muscle mass and strength. Although the mechanisms underlying this loss are not entirely understood, we attempted to moderate the loss by increasing the regenerative capacity of muscle. This involved the injection of a recombinant adeno-associated virus directing overexpression of insulin-like growth factor I (IGF-I) in differentiated muscle fibers. We demonstrate that the IGF-I expression promotes an average increase of 15% in muscle mass and a 14% increase in strength in young adult mice, and remarkably, prevents aging-related muscle changes in old adult mice, resulting in a 27% increase in strength as compared with uninjected old muscles. Muscle mass and fiber type distributions were maintained at levels similar to those in young adults. We propose that these effects are primarily due to stimulation of muscle regeneration via the activation of satellite cells by IGF-I. This supports the hypothesis that the primary cause of aging-related impairment of muscle function is a cumulative failure to repair damage sustained during muscle utilization. Our results suggest that gene transfer of IGF-I into muscle could form the basis of a human gene therapy for preventing the loss of muscle function associated with aging and may be of benefit in diseases where the rate of damage to skeletal muscle is accelerated.