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The work presents results on the effect of prior martensite formation on bainite transformation kinetics in a 3% medium-Mn multiphase steel. The material was subjected to two isothermal holding temperatures: 400 °C (without martensite) and 350 °C (with prior martensite). According to obtained dilatometric results, the formation of prior martensite leads to the acceleration of bainite transformation kinetics. The bainite formation starts and finishes much faster, when the prior martensite was present before the isothermal holding. The microstructural investigation of the steel after heat treatment was carried out using light and scanning electron microscopy. The microstructures were composed of fine bainitic laths with retained austenite and small amount of martensitic-austenitic islands at 400 °C. At 350 °C the presence of large tempered martensite laths was detected. The bainite is composed of a mixture of fine and coarse laths. The increase of the bainitic lath thickness is attributed to the coalescence process occurring at the lower holding temperature. The differences in the steel hardness after the two heat treatments were relatively small (~ 13 HV10). [ABSTRACT FROM AUTHOR]

This work presents insights into the manganese influence on the driving force and bainite transformation kinetics. Three different medium-Mn steels were subjected to theoretical calculations and dilatometric study in order to determine the Mn impact on bainite formation. The theoretical approach shows that the increase of manganese leads to a lower bainite fraction formed during the isothermal stage. This implicates the carbon enrichment of the austenite during thermal treatment. The less bainite is formed, the higher is the fraction of residual austenite which enrichment of carbon is globally low. Meanwhile, the manganese influences the incubation and transformation time. As the manganese content increases, the incubation period and formation time of bainite are longer because the chemical driving force essential to start and complete austenite into bainite transformation decreases. This was proved by theoretical calculations and dilatometric analysis, which show that even a small increase in manganese content leads to a longer time necessary to occur the bainitic transformation. For the steel containing 5% manganese, the driving force was too small that the transformation could occur even after 3 h. Additionally, the XRD analysis was conducted to determine the retained austenite fraction and its carbon enrichment. These results were compared with the theoretical values to determine the accuracy of the applied model. [ABSTRACT FROM AUTHOR]

Isothermal bainitic transformation of a lean medium-Mn steel containing (in mass%) 0.18C–3.6Mn–1.7Al–0.23Si–0.2Mo–0.04–Nb after full austenitization at 1100 ºC was studied by means of high resolution dilatometry. The effects of isothermal holding temperatures ranging from 450 to 350 °C on the bainitic transformation kinetics was studied experimentally characterizing the microstructure present after a holding time ranging from 15 min to 2 h. The obtained results showed that the bainitic transformation is uncompleted at temperatures above 425 °C. The carbon enrichment of the austenite during isothermal treatment at 450 °C and 425 °C is not enough to avoid martensitic transformation of the austenite during cooling to room temperature. Thus, it is obtained a mixed structure including bainitic ferrite and martensite. Decreasing the austempering temperature resulted in a more pronounced bainite formation. The kinetics of the transformation during austempering at 350ºC is quite similar to that observed at 400 °C, so that 60 min are needed in both cases to complete the reaction. However, local variations in chemical composition associated to segregation of Mn and Al during casting solidification results in differences in the transformation rate of bainitic reaction between different areas in the material. A balance difference between the dendritic and interdendritic areas is responsible for the differences observed among test samples in the kinetics of the isothermal bainitic transformation and the final microstructure. [ABSTRACT FROM AUTHOR]

The work addresses physical simulation and dilatometric study of one-step and double-step heat treatments of medium-Mn steel designed for automotive sheets. The conventional one-step isothermal bainitic transformation was applied as the reference heat treatment. The newly implemented heat treatment consisted of isothermal holding in a bainitic region followed by additional holding of the material at reduced temperature also in the bainitic range. This step was added to refine the microstructure, which led to the stabilization of the retained austenite. Calculations of equilibrium state and non-equilibrium cooling and simulations of the developed thermal cycles were performed using the thermodynamic JMatPro software. The physical simulations of the heat treatment were performed in the dilatometer. The obtained samples were subjected to microscopic observations using light and SEM microscopy. One- and two-step heat treatments allowed to obtain bainitic structures with high contents of retained austenite. Lowering the temperature of one-step isothermal holding resulted in the bainite refinement and adjacent retained austenite. The increased Mn content in steel increased its susceptibility to form coalesced bainite resulting in the partial formation of thicker plates despite a decrease in a process temperature. [ABSTRACT FROM AUTHOR]

The work presents the results of thermodynamic analysis of two medium manganese steels with different Mn contents. The steels containing 3.1 and 3.6% of manganese were subjected to theoretical thermodynamic calculations using MUCG83 software and dilatometric experiments. The steels were heat-treated in two different isothermal holding temperatures of 400 and 350 °C for 15 min. The bainite transformation kinetics at different temperatures for different manganese contents was investigated. In the steel including 3.1% Mn, a complete transformation was obtained. The results indicated a strong influence of the holding temperature on the kinetics of bainitic transformation. It was related to the driving force of this process. When the manganese content was increased by 0.5%, an incomplete bainite transformation occurred. The microstructure investigations after heat treatment were performed using light and scanning electron microscopy. The XRD analysis to determine retained austenite amount and its carbon enrichment was performed. The microstructure of 3MnNb steel consisted of bainite and retained austenite with filmlike and blocky morphologies. The steel with the higher Mn content contained also fresh martensite for both isothermal holding temperatures. [ABSTRACT FROM AUTHOR]

The effects of rare earth elements (RE) addition on the pearlite microstructure in low-carbon microalloyed steels have been investigated under two heat treatment conditions: (1) a normalizing treatment (as a conventional heat treatment used industrially to obtain the final mechanical properties of such steels), and (2) an isothermal treatment at 650 °C. This research reports the following effects due to the addition of RE: (i) refinement of the nodule and colony size of pearlite along with the ferrite grain size in the normalized condition, without a significant change in the volume fraction of pearlite. This microstructural refinement observed at room temperature is a consequence of the refinement of cast and austenitic microstructures formed during cooling in the presence of RE; (ii) the interlamellar spacing of pearlite isothermally transformed at 650 °C, as observed by SEM and TEM, is effectively reduced in the RE-added steel. This is likely due to two different effects combined: (i) direct influence of RE on atom carbon diffusion; and (ii) pearlite growth being boundary diffusion controlled by RE partitioning. [ABSTRACT FROM AUTHOR]

We address the prediction of low-visibility events at airports using machine-learning regression. The proposed model successfully forecasts low-visibility events in terms of the runway visual range at the airport, with the use of support-vector regression, neural networks (multi-layer perceptrons and extreme-learning machines) and Gaussian-process algorithms. We assess the performance of these algorithms based on real data collected at the Valladolid airport, Spain. We also propose a study of the atmospheric variables measured at a nearby tower related to low-visibility atmospheric conditions, since they are considered as the inputs of the different regressors. A pre-processing procedure of these input variables with wavelet transforms is also described. The results show that the proposed machine-learning algorithms are able to predict low-visibility events well. The Gaussian process is the best algorithm among those analyzed, obtaining over 98% of the correct classification rate in low-visibility events when the runway visual range is $${>}$$ 1000 m, and about 80% under this threshold. The performance of all the machine-learning algorithms tested is clearly affected in extreme low-visibility conditions ( $${<}$$ 500 m). However, we show improved results of all the methods when data from a neighbouring meteorological tower are included, and also with a pre-processing scheme using a wavelet transform. Also presented are results of the algorithm performance in daytime and nighttime conditions, and for different prediction time horizons. [ABSTRACT FROM AUTHOR]

The influence of vanadium additions on transformation kinetics has been investigated in a medium carbon forging steel. Using dilatometry to track transformation during continuous cooling or isothermal transformation, the impact of vanadium on both ferrite-pearlite and bainite has been quantified. Transmission electron microscopy and atom probe tomography have been used to establish whether vanadium was present in solid solution, or as clusters and precipitates. The results show that vanadium in solid solution has a pronounced retarding influence on ferrite-pearlite formation and that, unlike in the case of niobium, this effect can be exploited even during relatively slow cooling. The influence on bainite transformation was found to depend on temperature; an explanation in terms of the effect of vanadium on heterogeneous nucleation is tentatively proposed. [ABSTRACT FROM AUTHOR]

During grasping and intelligent robotic manipulation tasks, the camera position relative to the scene changes dramatically because the robot is moving to adapt its path and correctly grasp objects. This is because the camera is mounted at the robot effector. For this reason, in this type of environment, a visual recognition system must be implemented to recognize and 'automatically and autonomously' obtain the positions of objects in the scene. Furthermore, in industrial environments, all objects that are manipulated by robots are made of the same material and cannot be differentiated by features such as texture or color. In this work, first, a study and analysis of 3D recognition descriptors has been completed for application in these environments. Second, a visual recognition system designed from specific distributed client-server architecture has been proposed to be applied in the recognition process of industrial objects without these appearance features. Our system has been implemented to overcome problems of recognition when the objects can only be recognized by geometric shape and the simplicity of shapes could create ambiguity. Finally, some real tests are performed and illustrated to verify the satisfactory performance of the proposed system. [ABSTRACT FROM AUTHOR]

An alternative procedure for indirect and automatic measurement of the prior austenite grain size (PAGS) in bainite/martensite is proposed in this work. It consists in the determination of an effective grain size by means of statistical post-processing of electron backscatter diffraction (EBSD) data. The algorithm developed for that purpose, which is available on-line, has been applied to simulated EBSD maps as well as to both nanocrystalline bainitic steel and commercial hot-rolled air-cooled steel with a granular bainitic microstructure. The new proposed method has been proven to be robust, and results are in good agreement with conventional PAGS measurements. The added value of the procedure comes from its simplicity, as no parent reconstruction is involved during the process, and its suitability for low-magnification EBSD maps, thus allowing a large step size and coverage of a substantially broader area of the sample than the previous methods reported. [ABSTRACT FROM AUTHOR]

The concepts of phase transformation theory can be exploited to design nanostructured steels that transform to bainite at temperatures as low as 150°C. The microstructure obtained is so refined that it is possible to achieve strength in excess of 2.5 GPa in a material that has considerable toughness (40 MPam). Such a combination of properties has never been achieved before with bainite. A description of the characteristics and significance of this remarkable microstructure in the context of the mechanism of transformation is provided. [ABSTRACT FROM AUTHOR]

This work reports production of nanofibers of cellulose acetate (CA) via electrospinning (ES) technology. Optimal operating conditions to produce nanofibers have been found to involve CA solutions at 20 wt% concentration, flow rate 1.0 mL h, a distance between needle tip-collector target of 15 cm and an applied voltage at 20 kV. Under these experimental conditions, nanofibers were produced by ES a solution containing a low concentration of a luminescent fluorene-based cationic conjugated polyelectrolyte. Electronic and optical microscopies were used to characterize their morphology and the diameter of fibers (over 260 nm). Composite fibers with excellent luminescence properties have been obtained and studied in the solid state. Potential applications in a sensing device for nitrobenzene have been tested. [ABSTRACT FROM AUTHOR]

Solubilisation and stabilization of conjugated polymers, CPs, in aqueous media remains a challenge for many researches trying to extend the biological and environmental applications of this kind of polymers. A number of different alternatives have been considered to address this problem, which are mostly based on the enhancement of the macromolecule polarity, by appending hydrophilic side chains on the polymer backbone. In this work we have investigated a new strategy in which water solubilization is reached by external addition of classical cyclodextrins (α-, β- and γ-CDs) to a solution of non-polar CPs. This strategy allows working with such polymers eliminating the need to synthesize new water-soluble species. The polymer selected for the study was poly-[9,9-bis(6′-bromohexyl-2,7-fluoren-dyil)-co-alt-(benzene-1,4-diy)], PFPBr, a polyfluorene previously synthesized in our laboratory. Results show that PFPBr forms fluorescent complexes in aqueous media with β-CD and γ-CD, and much less efficiently with α-CD, probably due to the small size of its cavity. The new PFPBr/CD complexes are stable in time and in a large range of pH, however, at high concentration and temperature, they tend to aggregate and precipitate. In order to increase stabilization and minimize polymer aggregation, complexes were encapsulated inside the pores of silica glasses fabricated using the sol-gel process, obtaining transparent and fluorescent hybrid matrices which were stable in time and temperature. In addition, immobilization of the complexes allows an easy manipulation of the material, thus offering promising applications in the development of biological and chemical sensors. [ABSTRACT FROM AUTHOR]

In this study, the carbon content of retained austenite in a nanostructured bainitic steel was measured by atom probe tomography and compared with data derived from the austenite lattice parameter determined by X-ray diffraction. The results provide new evidence about the heterogeneous distribution of carbon in austenite, a fundamental issue controlling ductility in this type of microstructure. [ABSTRACT FROM AUTHOR]

Carbon distribution during tempering of a nanostructured bainitic steel was analyzed by atom probe tomography (APT). Three different types of particles are detected on samples tempered at 673 K (400 °C) for 30 minutes: lower bainite cementite with a carbon content of ~25 at. pct, ε-carbides with a carbon content close to 30 at. pct, and carbon clusters, small features with a carbon content of ~14 at. pct indicative of a stage of tempering prior to precipitation of ε-carbide. After tempering at 773 K (500 °C) for 30 minutes, the ε-carbide-to-cementite transition was observed. Solute concentration profiles across carbide/ferrite interfaces showed the distribution of substitutional elements in ε-carbide and cementite for all the tempering conditions. [ABSTRACT FROM AUTHOR]

The acicular ferrite formation as decomposition product of S-lean V-alloyed austenite with high N content is studied in this article. A combination of thermodynamic models as well as some physical metallurgical principles was used to analyze the intragranular nucleation potency of V(C,N) precipitates. The designed thermomechanical and heat treatments ensure an almost homogeneous microstructure consisting of acicular ferrite for this N-rich laboratory cast steel. The results presented in this work demonstrate that, in the absence of sulfide inclusions, acicular ferrite is nucleated on V(C,N) precipitates. [ABSTRACT FROM AUTHOR]

This investigation focuses on the austenite formation process during continuous heating, over a wide range of heating rates (0.05 to 20 K/s), in three low carbon-manganese steels alloyed with different levels of aluminum (0.02, 0.48, and 0.94, wt pct Al). High resolution dilatometry, combined with metallographic observations, was used to determine the starting ( Ac) and finishing ( Ac) temperatures of this transformation. It is shown that both the aluminum content and the applied heating rate have a strong influence on this process. During fast heating (>1 K/s), the pearlite phase present in the initial microstructure remains almost unaffected up to temperature Ac. On the contrary, during slow heating, cementite lamellas inside pearlite partially dissolve, this dissolution effect being more pronounced for the lower carbon and higher aluminum content steels. The changes in the initial microstructure during slow heating affect the austenite nucleation and growth processes. Furthermore, in the aluminum alloyed steels, slow heating conditions shift the Ac temperature to higher values. This shift is suggested to be due to aluminum partitioning from austenite to ferrite, which stabilizes ferrite and delays its transformation to higher temperatures. Thermodynamic calculations carried out with MTDATA software seem to support some of the experimental observations carried out under very low heating conditions close to equilibrium (0.05 K/s). [ABSTRACT FROM AUTHOR]

Plane strain compression tests of two V microalloyed steels and one plain C-Mn steel have been done to analyse the influence of the deformation temperature, in the warm working range, on the final microstructure and subsequent mechanical behaviour. In the case of V microalloyed steels, the reheating temperature has an effect on the amount of vanadium in solution prior to deformation. This factor influences the austenite evolution during warm deformation and the transformation during cooling. As a consequence, in the microalloyed steels complex multiphase microstructures are obtained that lead to a wide range of strength-toughness combinations. In contrast, in the case of the plain C-Mn steel minor effects are observed in the deformation range from 800 to 870 °C. [ABSTRACT FROM AUTHOR]

New carbide free bainitic microstructures are gaining an increasing interest on behalf the scientific and industrial community. The excellent combination of mechanical properties achieved in those microstructures with no need of complex heat treatments or thermomechanical processes represents their main advantage. The strength is mainly achieved by means of the very fine bainitic ferrite plates, consequence of the transformation mechanism, but the parameters contributing to the ductility of those microstructures are still unclear in this type of microstructures, where a soft phase, retained austenite, is imbibed in a very strong matrix of bainitic ferrite. A priori is reasonable to assume that retained austenite will control the levels of ductility achieved. Further enhancement of ductility can be achieved by the transformation of retained austenite into martensite (strain or stress assisted), thus its mechanical stability plays an important role in the final ductility. In this study, by means of X-ray analysis of interrupted compression tests, it is studied the influence that different microstructural aspects of retained austenite may have on its mechanical stability. [ABSTRACT FROM AUTHOR]

This article deals with the mechanical properties achieved in two S-lean laboratory-cast V steels with two different N content levels, as compared with commercial acicular ferrite steel. The designed heat treatments ensure an almost homogeneous microstructure consisting of acicular ferrite for N-rich and commercial steels and consisting of bainite for the N-lean steel. The results presented in this work demonstrate that, in the absence of sulfide inclusions, acicular ferrite is nucleated on V(C,N) precipitates. The mechanical tests indicate that N-rich acicular ferrite steel achieves the same toughness values as N-lean bainitic steel but with a substantial improvement in strength properties. The S-lean steels present better toughness properties than commercial acicular ferrite steel, which is consistent with the detrimental effect of inclusions on toughness. [ABSTRACT FROM AUTHOR]

An innovative design procedure based on phase transformation theory alone has been successfully applied to design steels with a microstructure consisting of a mixture of bainitic ferrite, retained austenite, and some martensite. An increase in the amount of bainitic ferrite is needed in order to avoid the presence of large regions of untransformed austenite, which under stress decompose to brittle martensite. The design procedure addresses this diffi culty by adjusting the T′o curve to greater carbon concentrations with the use of substitutional solutes such as manganese and chromium. The concepts of bainite transformation theory can be exploited even further to design steels with strength in excess of 2.5 GPa and considerable toughness. [ABSTRACT FROM AUTHOR]

Model organisms have emerged as suitable and reliable biological tools to study the properties of proteins whose function is altered in human disease. In the case of the PI3K and PTEN human cancer-related proteins, several vertebrate and invertebrate models, including mouse, fly, worm and amoeba, have been exploited to obtain relevant functional information that has been conserved from these organisms to humans along evolution. The yeast Saccharomyces cerevisiae is an eukaryotic unicellular organism that lacks a canonical mammalian-like PI3K/PTEN pathway and PIP3 as a physiological second messenger, PIP2 being essential for its life. The mammalian PI3K/PTEN pathway can be reconstituted in S. cerevisiae, generating growth alteration phenotypes that can be easily monitored to perform in vivo functional analysis of the molecular constituents of this pathway. Here, we review the current nonmammalian model systems to study PTEN function, summarize our knowledge of PTEN orthologs in yeast species and propose the yeast S. cerevisiae as a sensitive biological sensor of PI3K oncogenicity and PTEN tumor suppressor activity.Oncogene (2008) 27, 5431–5442; doi:10.1038/onc.2008.240 [ABSTRACT FROM AUTHOR]

A local electrode atom probe has been used to analyze the solute partitioning during bainite transformation in a novel, nanocrystalline bainitic steel. Atom probe results show the absence of any partitioning of substitutional elements between the phases involved. The results are fully consistent with the diffusionless transformation of austenite to bainite. However, substitutional elements are expected to redistribute approaching an equilibrium phase boundary as the mixture of bainitic ferrite and retained austenite is tempered. The compositional analysis of the austenite/ferrite interface by atom probe tomography indicates that retained austenite decomposes during tempering before equilibrium is reached at the interface. [ABSTRACT FROM AUTHOR]

Sol-gel matrices have been shown to be relatively inert while preserving the spectroscopic properties and biological activity of the encapsulated proteins. Horseradish peroxidase (HRP) is a hemeprotein widely used in the field of biosensors because of its high specificity for hydrogen peroxide. However, partial inactivation of the protein has been reported when incorporated in aged gels. Whether that inactivation comes from the unfolding of some of the encapsulated proteins or from the leaching of the heme non-covalent active site of HRP is evaluated by absorption and fluorescence spectroscopy. This study shows that the single Trytophan (Trp) fluorescence of HRP may be used to distinguish denaturation processes from leaching of the heme group, as well as to estimate the extent of the denaturation. [ABSTRACT FROM AUTHOR]

We have investigated the complex behaviour of the time resolved fluorescence intensity and anisotropy of trans-parinaric acid, incorporated into fragments of the plasma membrane of human platelets and in multibilayers of lipids extracted from that membrane. It is shown that the observation of anisotropies that increase at long times can be satisfactorily interpreted by assuming two populations of the fluorescence probe with distinct lifetimes, rotational relaxation times and order parameters. The heterogeneous probe distribution was correlated with a similar heterogeneity in the lipid composition of the bilayer, modulated by temperature. Below 35°C an important fraction of the lipids of the plasma membrane are apparently in the form of solid-like domains (20% at 20°C). However, in the physiological temperature range that solid/fluid heterogeneity is almost negligible. Since these effects were also observed in multibilayers of lipids from the platelet membrane, the formation of solid-like clusters appears to arise from lipid-lipid interactions only, and most probably involving cholesterol. These results support the previous finding of a lateral phase separation for temperatures less than 37°C described by Gordon et al. (1983) in a spin-probe study of the platelet plasma membrane. [ABSTRACT FROM AUTHOR]

The ability of seven fluorescence polarization probes (1,6-diphenyl-1,3,5-hexatriene, 1-[(4-trimethylamino)phenyl]-6-phenyl-1,3,5-hexatriene, (2-carboxyethyl)-1,6-diphenyl-1,3,5-hexatriene, 16(9-anthroyloxy)palmitic acid, CIS-parinaric acid, trans-parinaric acid and perylene) to report changes induced by temperature and Ca in the plasma membrane of human platelets has been examined. The steady-state fluorescence anisotropy of the probes was compared after being incorporated into whole resting platelets, fragments of platelet plasma membrane and multilayers of lipids extracted from these membranes. In addition, we have investigated the molecular order and dynamics of the three preparations by time-resolved fluorescence depolarization of DPH and CE-DPH as a function of temperature and Ca concentration. The high values of the order parameters found in intact platelets (S=0.70) were almost identical to those in membrane fragments and lipid vesicles, suggesting that lipid-lipid interactions and, therefore, the lipid composition are the main factors influencing the probe order parameter. Other lipid interactions such as those with membrane proteins and intracellular components have little effect on the SDP, in platelets. These measurements also showed that the stationary fluorescence anisotropy of DPH and CE-DPH in platelets is largely determined (80%) by the structural order of the lipid bilayer. Therefore, the previous 'microviscosity' values based on stationary anisotropy data reflect the alignment and packing rather than the mobility of the bilayer components. The dynamic component of the anisotropy decay of these probes was analyzed in terms of the wobbling-in-cone model, allowing an estimation of the apparent viscosity of platelet plasma membrane (ν DPH, 36°C =−0-5 P) that is similar to that of the erythrocyte membrane. This value decreased substantially in multilayers of native lipids, indicating a large effect of the lipidprotein interactions on the probe dynamics within the bilayer. When the temperature was raised from 25° to 36°C a pronounced decrease was observed in the order parameter and apparent viscosity, followed by a tendency to level-off in the 36°-40°C interval. This may be related to the end-point of the lipid phase separation reported by Gordon et al. (1983). Finally, the rigidifying (lipid ordering) effect of Ca on the platelet plasma membrane could also be observed by the fluorescence anisotropy measurements, in the form of an increase (∼2%) of the order parameter of CE-DPH for Ca concentrations in the millimolar range. [ABSTRACT FROM AUTHOR]

Vascular endothelial growth factor (VEGF) plays a major role in the development of neovascularization in proliferative diabetic retinopathy (PDR). The source of intravitreous VEGF is presumably ischaemic retina, but increased levels derived from serum cannot be excluded. The aim of the study is to determine the intravitreous concentrations of VEGF in diabetic patients with PDR and to investigate whether serum VEGF could contribute to the intravitreous concentration. For this purpose, we studied 20 diabetic patients (5 IDDM and 15 NIDDM) with PDR in whom a vitrectomy was performed (group A). Non-diabetic patients ( n = 13) with other conditions requiring vitrectomy served as a control group (group B). In both groups, VEGF was determined in serum and undiluted vitreous samples obtained simultaneously. Furthermore, serum VEGF was determined in 69 healthy control subjects (group C) and 39 diabetic patients without microvascular complications (group D). Vitreous and serum VEGF was determined by ELISA (R & D Systems, Abingdon, UK); intra-assay CV 3.8 %, interassay CV 5.1 %. Intravitreous concentrations of VEGF were strikingly higher in group A (median 1.75 ng/ml, range 0.33–6.66) in comparison with group B (median 0.009 ng/ml, range 0.009–0.038); p < 0.0001. This difference remained significant after adjusting for intravitreous protein concentration ( p < 0.05). Differences in serum VEGF among the groups included in the study were not found. We conclude that the high vitreous levels of VEGF observed in diabetic patients with PDR cannot be attributed to serum diffusion across the blood-retinal barrier. Therefore, intraocular synthesis is the main contributing factor for the high vitreous VEGF concentrations observed in PDR. [Diabetologia (1997) 40: 1107–1109] [ABSTRACT FROM AUTHOR]

Aging impairs tissue repair. This is pronounced in skeletal muscle, whose regeneration by muscle stem cells (MuSCs) is robust in young adult animals but inefficient in older organisms. Despite this functional decline, old MuSCs are amenable to rejuvenation through strategies that improve the systemic milieu, such as heterochronic parabiosis. One such strategy, exercise, has long been appreciated for its benefits on healthspan, but its effects on aged stem cell function in the context of tissue regeneration are incompletely understood. Here we show that exercise in the form of voluntary wheel running accelerates muscle repair in old animals and improves old MuSC function. Through transcriptional profiling and genetic studies, we discovered that the restoration of old MuSC activation ability hinges on restoration of Cyclin D1, whose expression declines with age in MuSCs. Pharmacologic studies revealed that Cyclin D1 maintains MuSC activation capacity by repressing TGFβ signaling. Taken together, these studies demonstrate that voluntary exercise is a practicable intervention for old MuSC rejuvenation. Furthermore, this work highlights the distinct role of Cyclin D1 in stem cell quiescence.