Inductive Factors Research Articles

Exploitation of Dunaliella for β-carotene production

Halotolerant microalga Dunaliella, which is exploited for the production of dried biomass or cell extract, is used as a medicinal food. With the advancement in this field in recent years, the production of bio-organic compounds such as beta-carotene is established in many countries. Large-scale production of beta-carotene is controlled by numerous stress factors like high light intensity, high salinity, temperature and availability of nutrients. The state-of-the-art strategies in industries in closed systems under new set of inductive factors will additionally promote the ease of commercial production of beta-carotene. This review mainly focuses on the different methodologies employed recently for the optimum production of beta-carotene from Dunaliella species.

Study of the Effects of Progressive Changes in Alkoxysilane Structure on Sol−Gel Reactivity

Effects of the structure of an alkoxysilane on the early reaction kinetics of sol-gel polymerization are investigated in basic and acidic conditions. Six silanes, including tetraethoxysilane (TEOS), tetramethoxysilane (TMOS), methyltrimethoxysilane (MTMS), bis(trimethoxysilyl)ethane (BTMSE), bis(trimethoxysilyl)hexane (BTMSH), and bis(trimethoxysilylpropyl)amine (BTMSPA), are selected to examine the effects of progressive changes in the silane's structure. In basic conditions, reactivities of the silanes follow the pairwise trends TEOS << TMOS, TMOS > MTMS, MTMS < BTMSE, BTMSE >> BTMSH, and BTMSH << BTMSPA. Hydrolysis rate coefficients of BTMSE, TMOS, MTMS, and BTMSPA are similar in value and are almost one order of magnitude larger than the coefficients of BTMSH and TEOS. In acidic conditions, the pairwise reactivity trends are TEOS approximately TMOS, TMOS < MTMS, MTMS > BTMSE, BTMSE >> BTMSH, and BTMSH > BTMSPA. The condensation rate coefficients of BTMSH and BTMPA are much smaller than the others. Theses relationships can be explained mainly on the basis of the expected inductive and steric factors of the silanes. Bulky organics attached to the silane lead to low reactivity in both acidic and basic conditions. A high electron density at silicon leads to a low reactivity in basic conditions but a high reactivity in acidic conditions (pH approximately 2.3). Only BTMSPA in basic conditions defies these trends, possibly because of the effects of solvation near the reactive silicon site.

Experimental analysis of lens-forming capacity inXenopus borealis larvae

Previously, the only anuran amphibians known to have the capacity to regenerate a lens after lentectomy were Xenopus laevis and Xenopus tropicalis. This regeneration process occurs during the larval life through transdifferentiation of the outer cornea promoted by inductive factors produced by the retina and accumulated inside the vitreous chamber. However, the capacity of X. tropicalis to regenerate a lens is much lower than that of X. laevis. This study demonstrates that Xenopus borealis, a species more closely related to X. laevis than to X. tropicalis, is not able to regenerate a lens after lentectomy. Nevertheless, some morphological modifications corresponding to the first stages of lens regeneration in X. laevis were observed in the outer cornea of X. borealis. This suggested that in X borealis the regeneration process was blocked at early stages. Results from histological analysis of X. borealis and X. laevis lentectomized eyes and from implantation of outer cornea fragments into the vitreous and anterior chambers demonstrated that: (i) in X. borealis eye, the lens-forming competence in the outer cornea and inductive factors in the vitreous chamber are both present, (ii) no inhibiting factors are present in the anterior chamber, the environment where lens regeneration begins, (iii) the inability of X. borealis to regenerate a lens after lentectomy is due to an inhibiting action exerted by the inner cornea on the spreading of the retinal factor from the vitreous chamber towards the outer cornea. This mechanical inhibition is assured by two distinctive features of X. borealis eye in comparison with X. laevis eye: (i) a weaker and slower response to the retinal inducer by the outer cornea; (ii) a stronger and faster healing of the inner cornea. Unlike X. tropicalis and similar to X. laevis, in X. borealis the competence to respond to the retinal factor is not restricted to the corneal epithelium but also extends to the pericorneal epidermis.

FGF10 is required for cell proliferation and gland formation in the stomach epithelium of the chicken embryo

The development of digestive organs in vertebrates involves active epithelial–mesenchymal interactions. In the chicken proventriculus (glandular stomach), the morphogenesis and cytodifferentiation of the epithelium are controlled by the inductive signaling factors that are secreted from the underlying mesenchyme. Previous studies have shown that Fgf10 is expressed in the developing chicken proventricular mesenchyme, whereas its receptors are present in the epithelium. In our present study, we show that FGF10 is an early mesenchymal signal that is critically associated with the developmental processes in the proventricular epithelium. Furthermore, virus-mediated Fgf10 overexpression in ovo results in a hypermorphic epithelial structure and an increase in epithelial cell number. In contrast, the overexpression of a secreted FGFR2b (sFGFR2b), an FGF10 antagonist, blocks cell proliferation and gland formation in the proventricular epithelium in ovo. This downregulation of proliferative activity was subsequently found to retard gland formation and also to delay differentiation of the epithelium. These results demonstrate that FGF10 signaling, mediated by FGFR1b and/or FGFR2b, is required for proliferation and gland formation in the epithelium in the developing chick embryo.

Coating of VEGF-releasing scaffolds with bioactive glass for angiogenesis and bone regeneration

Bioactive glasses are potentially useful as bone defect fillers, and vascular endothelial growth factor (VEGF) has demonstrated benefit in bone regeneration as well. We hypothesized that the specific combination of prolonged localized VEGF presentation from a matrix coated with a bioactive glass may enhance bone regeneration. To test this hypothesis, the capacity of VEGF-releasing polymeric scaffolds with a bioactive glass coating was examined in vitro and in vivo using a rat critical-sized defect model. In the presence of a bioactive glass coating, we did not detect pronounced differences in the differentiation of human mesenchymal stem cells in vitro. However, we observed significantly enhanced mitogenic stimulation of endothelial cells in the presence of the bioactive glass coating, with an additive effect with VEGF release. This trend was maintained in vivo, where coated VEGF-releasing scaffolds demonstrated significant improvements in blood vessel density at 2 weeks versus coated control scaffolds. At 12 weeks, bone mineral density was significantly increased in coated VEGF-releasing scaffolds versus coated controls, while only a slight increase in bone volume fraction was observed. The results of this study suggest that a bioactive glass coating on a polymeric substrate participates in bone healing through indirect processes which enhance angiogenesis and bone maturation and not directly on osteoprogenitor differentiation and bone formation. The mass of bioactive glass used in this study provides a comparable and potentially additive, response to localized VEGF delivery over early time points. These studies demonstrate a materials approach to achieve an angiogenic response formerly limited to the delivery of inductive growth factors.

Isolation and in vitro characterization of pancreatic progenitor cells from the islets of diabetic monkey models

Recent studies on the identification of stem/progenitor cells within adult mouse and human pancreatic islets have raised the possibility that autologous transplantation might be used in treating type 1 diabetes. However, it is not yet known whether such stem/progenitor cells are impaired in type 1 diabetic patients or diabetic animal models. The latter would also allow us to test the efficacy of autologous transplantation in large animal models prior to clinical applications. The present study aims to determine the existence of stem/progenitor cells in the islets of diabetic monkey models and to assess the proliferation and differentiation potential of such cells in vitro. Our results indicate that there are pancreatic progenitor cells in the adult pancreatic islets in both normal and type 1 diabetic monkeys. The isolated pancreatic progenitor cells can be greatly expanded in culture. Upon the removal of growth medium, these cells spontaneously form islet-like cell clusters, which could be further induced to secrete insulin by inductive factors. Furthermore, the secretion of insulin and C-peptide from the islet-like cell clusters responds to glucose and other stimuli, indicating that the differentiated cells not only resemble β-cells but also possess the unique biological function of β-cells. This study provides a foundation for further characterization of adult pancreatic progenitor cells and autologous transplantation using pancreatic progenitor cells in treating diabetic monkeys.

Kinetic Study of Hydrolysis of Benzoates. Part XXV. Ortho Substituent Effect in Alkaline Hydrolysis of Phenyl Esters of Substituted Benzoic Acids in Water

The second-order rate constants k2 for alkaline hydrolysis of phenyl esters of meta-, para- and ortho-substituted benzoic acids, X-C6H4CO2C6H5 (X = H, 3-Cl, 3-NO2, 3-CH3, 4-NO2, 4-Cl, 4-F, 4-CH3, 4-OCH3, 4-NH2, 2-NO2, 2-CN, 2-F, 2-Cl, 2-Br, 2-I, 2-CH3, 2-OCH3, 2-CF3, 2-NH2), and of substituted phenyl esters of benzoic acid, C6H5CO2C6H4-X (X = 2-I, 2-CF3, 2-C(CH3)3, 4-Cl, 4-CH3, 4-OCH3, 4-NH2), have been measured spectrophotometrically in water at 25 °C. The substituent effect in alkaline hydrolysis of phenyl esters of para-substituted benzoic acids, similar to that for ethyl esters of para-substituted benzoic acids, was found to be precisely described by the Hammett relationship (ρ = 1.7 in water). The log k value for alkaline hydrolysis of phenyl and ethyl esters of meta-, para- and ortho-substituted benzoic acids, X-C6H4CO2R, was nicely correlated with log km,p,ortho = log ko + (ρ)m,pσ + (ρI)orthoσI + (ρ°R)orthoσ°R + δorthoEsB where σ, σI, σ°R are the Hammett polar, Taft inductive and Taft resonance (σ°R = σ° - σI) substituent constants, respectively. EsB is the steric scale for ortho substituents calculated on the basis of the log k values for the acid hydrolysis of ortho- substituted phenyl benzoates in water owing to the ortho substituent in the phenyl of phenyl benzoates. In water, the main factors responsible for changes in the ortho substituent effect in alkaline hydrolysis of phenyl and ethyl esters of ortho-substituted benzoic acids, X-C6H4CO2R, were found to be the inductive and steric factors while the role of the resonance term was negligible ((ρ°R)ortho ca. 0.3). In alkaline hydrolysis of substituted benzoates in neat water, the ortho inductive effect appeared to be 1.5 times and steric influence 2.7 times higher than the corresponding influences from the ortho position in the phenyl of phenyl benzoates. The contributions of the steric effects in alkaline hydrolysis of esters of ortho-substituted benzoic acids was found to be approximately the same as in acid hydrolysis of esters of ortho-substituted benzoic and acid esterification of ortho-substituted benzoic acids.

Can 5-azacytidine convert the adult stem cells into cardiomyocytes? A brief overview

From the first report that bone marrow cells (BMC) have stem cells characteristics, several studies have debated the possibility of intervening in myocardial remodeling after injury, for example myocardial infarction, by using BMC. The goal of this paper is to review the concept of whether the demethylating agent 5-azacytidine influences the myogenic differentiation of bone marrow-derived cells. The existing data seem to indicate that in vitro treatment with 5-azacytidine, even if not enough to generate mature CMC, promotes the in vivo and in vitro commitment of BMC into cells that express muscle-specific proteins and genes and, at a very low rate, show spontaneous contractions. It is probable this treatment makes the cells less responsive to other inductive factors secreted by the microenvironment that might modulate the differentiation. These data suggest that this approach may be used to prime cells prior to their transplantation in an injury area in the heart.

Inductive tissue engineering with protein and DNA-releasing scaffolds

Cellular differentiation, organization, proliferation and apoptosis are determined by a combination of an intrinsic genetic program, matrix/substrate interactions, and extracellular cues received from the local microenvironment. These molecular cues come in the form of soluble (e.g. cytokines) and insoluble (e.g. ECM proteins) factors, as well as signals from surrounding cells that can promote specific cellular processes leading to tissue formation or regeneration. Recent developments in the field of tissue engineering have employed biomaterials to present these cues, providing powerful tools to investigate the cellular processes involved in tissue development, or to devise therapeutic strategies based on cell replacement or tissue regeneration. These inductive scaffolds utilize natural and/or synthetic biomaterials fabricated into three-dimensional structures. This review summarizes the use of scaffolds in the dual role of structural support for cell growth and vehicle for controlled release of tissue inductive factors, or DNA encoding for these factors. The confluence of molecular and cell biology, materials science and engineering provides the tools to create controllable microenvironments that mimic natural developmental processes and direct tissue formation for experimental and therapeutic applications.

Expression and localisation of αv integrins in human odontoblasts

Integrin alphabeta heterodimers mediate adhesion to the extracellular matrix and at cell-cell contacts and initiate intracellular signalling cascades in response to a variety of inductive factors. Apart from the expression of alphavbeta3 that we have previously reported, little is known about the expression of integrins in odontoblasts. Here, we investigated the expression of alphav-binding beta integrin subunits in healthy human dental pulp in vivo and in odontoblasts differentiated in vitro. Reverse transcription/polymerase chain reaction analysis revealed the expression of alphav, beta1, beta5 and beta8 integrin mRNA, but not beta6, in whole pulp cells. Flow cytometry showed that the alphav and beta1 subunits were the most intensely expressed. Immunohistochemistry demonstrated that the beta1 subunit was localised in newly differentiated odontoblasts in the root and in mature odontoblasts in the crown, including their intradentinal cell processes. The alphav chain was predominantly expressed by mature odontoblasts and alphavbeta5 was only observed in mature odontoblasts. In vitro differentiated odontoblasts expressed genes for alphav, beta1 and beta5, but not for beta6 and beta8. A comparison of integrin profiles between cultured pulp cells and in vitro differentiated odontoblasts revealed that odontoblast maturation was characterised by a significant increase in the expression of alphav and beta1 subunits and alphavbeta5 integrin. The beta8 subunit was detected in nerve cells only. Histological analysis of teeth from alphav knockout mice showed no obvious structural modification in the odontoblast layer. Thus, human mature odontoblasts express alphavbeta3, alphavbeta5 and perhaps alphavbeta1 integrins, with the possible presence of alpha-beta1 pairs. The roles that these molecules play in the exchange of information throughout the odontoblast layer remain to be determined.

Delayed autocatalytic behavior of Mn(II) ions at a critical ratio: The effect of structural isomerism on permanganic oxidation of L‐norleucine

AbstractThe kinetics of the permanganic oxidation process of L‐norleucine, L‐leucine, L‐iso‐leucine, and L‐tert‐leucine in strong acid medium has been investigated using a spectrophotometric technique. Conclusive evidences have proven autocatalytic activity of Mn(II) for these reactions in strong acid medium analogous to weak acid medium, but in the former, ratio of Mn(II) to amino acid concentration must reach a certain amount for autocatalytic phenomenon to emerge, which we call “critical ratio.” This critical ratio depends on the nature of the amino acid employed. Thus considering “delayed autocatalytic behavior” of Mn(II) ions, rate equations satisfying observations for both catalytic and noncatalytic routes have been presented. Kinetic data in a noncatalytic pathway have been fitted to a biparametric equation including inductive, steric, and hyperconjugation correction effects, and it is determined that by shifting the side branch on a carbon chain toward an α‐carbon atom (adjacent to amino acid's functional group) and also adding branches to the α‐carbon atom, the reaction rate in the noncatalytic pathway decreases. Inductive and steric hindrance factors in amino acid's carbon chain are effective on processes' rate both in catalytic and noncatalytic pathways. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 38: 1–11, 2006

Pigmented epithelium to retinal transdifferentiation and Pax6 expression in larval Xenopus laevis

This study examines the retinal transdifferentiation (TD) of retinal pigmented epithelium (RPE) fragments dissected from Xenopus laevis larvae and implanted into the vitreous chamber of non-lentectomized host eyes. In these experimental conditions, most RPE implants transformed into polarized vesicles in which the side adjacent to the lens maintained the RPE phenotype, while the side adjacent to the host retina transformed into a laminar retina with the photoreceptor layer facing the cavity of the vesicle and with the ganglionar cell layer facing the host retina. The formation of a new retina with a laminar organization is the result of depigmentation, proliferation and differentiation of progenitor cells under the influence of inductive factors from the host retina. The phases of the TD process were followed using BrdU labelling as a marker of the proliferation phase and using a monoclonal antibody (mAbHP1) as a definitive indicator of retina formation. Pigmented RPE cells do not express Pax6. In the early phase of RPE to retinal TD, all depigmented and proliferating progenitor cells expressed Pax6. Changes in the Pax6 expression pattern became apparent in the early phase of differentiation, when Pax6 expression decreased in the presumptive outer nuclear layer (ONL) of the new-forming retina. Finally, during the late differentiation phase, the ONL, which contains photoreceptors, no longer expressed Pax6, Pax6 expression being confined to the ganglion cell layer and the inner nuclear layer. These results indicate that Pax6 may have different roles during the different phases of RPE to retinal TD, acting as an early retinal determinant and later directing progenitor cell fate.

Review:Mesenchymal Stem Cells: Cell–Based Reconstructive Therapy in Orthopedics

Adult stem cells provide replacement and repair descendants for normal turnover or injured tissues. These cells have been isolated and expanded in culture, and their use for therapeutic strategies requires technologies not yet perfected. In the 1970s, the embryonic chick limb bud mesenchymal cell culture system provided data on the differentiation of cartilage, bone, and muscle. In the 1980s, we used this limb bud cell system as an assay for the purification of inductive factors in bone. In the 1990s, we used the expertise gained with embryonic mesenchymal progenitor cells in culture to develop the technology for isolating, expanding, and preserving the stem cell capacity of adult bone marrow-derived mesenchymal stem cells (MSCs). The 1990s brought us into the new field of tissue engineering, where we used MSCs with site-specific delivery vehicles to repair cartilage, bone, tendon, marrow stroma, muscle, and other connective tissues. In the beginning of the 21st century, we have made substantial advances: the most important is the development of a cell-coating technology, called painting, that allows us to introduce informational proteins to the outer surface of cells. These paints can serve as targeting addresses to specifically dock MSCs or other reparative cells to unique tissue addresses. The scientific and clinical challenge remains: to perfect cell-based tissue-engineering protocols to utilize the body's own rejuvenation capabilities by managing surgical implantations of scaffolds, bioactive factors, and reparative cells to regenerate damaged or diseased skeletal tissues.

769. Tissue Engineering Scaffolds with Non-Viral Vectors: Sustained and Substrate-Mediated Delivery

The combination of gene therapy, biomaterials, and tissue engineering has the potential to direct progenitor cell development into functional tissues. A central component to many tissue engineering approaches is a polymer scaffold, which provides physical support for cell adhesion and migration, and organizes tissue formation. Gene delivery from the scaffold can localize expression of tissue inductive factors to promote the development of functional tissue. We present two mechanisms for scaffold-mediated gene transfer, which are categorized as: i) sustained release and ii) substrate-mediated delivery. Sustained release can protect DNA from clearance or degradation, and maintain elevated concentrations locally, which may extend transgene expression. Substrate-mediated delivery involves the immobilization of DNA complexes to a biomaterial and can lead to high levels of transfection because the surface-bound DNA can be delivered directly to cells that attach to the scaffold.

Reversibility of experimental cholesteatoma epithelium using Mongolian gerbils

ConclusionThe results of this study encourage our belief that some cholesteatomas can be managed using only conservative treatments.ObjectiveWe hypothesized that once cholesteatoma is in a normal environment, its cellular or molecular pathology can revert to those characteristic of normal epidermis. The aim of this study was to determine whether or not common molecular characteristics of cholesteatoma were reversible after removal of inductive factors in experimental cholesteatoma induced in gerbils.Material and methodsWe induced cholesteatoma using ear canal ligation in Mongolian gerbils. After ligation, the animals in the treated group were managed for 2 weeks. We examined differences between treated and untreated cholesteatomas using terminal deoxynucleotide transferase-mediated dUTP nick-end labeling (TUNEL) staining and an immunohistochemical technique using the proliferation markers proliferating cell nuclear antigen (PCNA) and cytokeratin (CK).ResultsWith PCNA and CK 13/16, the untreated group showed positive staining in the suprabasal and basal cells, but the treated group showed weakly positive staining only in the basal cell layer. With TUNEL staining, there were more positive cells in the untreated than the treated group.

Cell fate specification along the anterior–posterior axis of the intermediate mesoderm

The vertebrate intermediate mesoderm (IM) is highly patterned along the anterior-posterior (A-P) axis. In the chick embryo, the kidney tissue, which is a derivative of the IM, is generated only from IM located posterior to the sixth somite axial level, which also marks the border between cranial and trunk segments. The cellular and molecular mechanisms that govern the formation of the anterior border of the kidney morphogenetic field are currently unknown. In this study, we asked whether specific A-P patterning information is conveyed by the movement of cells through the primitive streak (PS) at different time points that consequently affects the expression of kidney genes, or by the environment that these cells encounter during their migration to the IM. In this study, we show that kidney-inductive signals are present along the whole axis, including anterior non-kidney-generating regions. These inductive signals are generated by tissues that are located medial to the anterior IM. We also demonstrate that cells that migrate through the PS of early embryonic stages (Hamburger and Hamilton stage 3-4 and earlier), which will give rise to anterior nonkidney IM, are competent to respond to these inductive factors. This prospective anterior IM tissue loses its competence to respond to kidney inducing signals during its migration from the PS to its final location in the anterior IM. We present here a model in which changes in cell competence determine the formation of the anterior border of kidney gene expression and discuss the possible evolutionary implications of this developmental mechanism.

Effects of organic acids on sol?gel transition of silicic acid?Arheological study

The sol–gel transition in the silica system is dependent upon the degree of hydrolysis and polymerization reaction in the system [1]. The polymerization reaction for the formation of the gel network occurs in different stages, i.e. polymerization of monomer to form particles, growth of particles and finally linking of particles into chains and the formation of the network which extends throughout the liquid medium. The structural evolution through the growth of silicate polymers from the genesis to the gel point has been well established by various in-situ methods such as NMR, vibrational spectroscopy and small-angle scattering. However, a rheological study can be an important tool to characterize sols and sol–gel transition and can give a qualitative information on the structure at the time of gelation. Many processing parameters, such as the presence of a catalyst, H2O:Si ratio, type of solvent, pH, temperature, steric and inductive factors, etc. effect the mechanisms of hydrolysis and condensation of silicon alkoxide [1, 2]. For the hydrolysis and condensation rate of silicon alkoxide, the effect of a catalyst was investigated by Pope and Mackenzie [3], and the dependence of gel time on H2O:Si ratio was observed by Klein [4]. Artaki et al. [5] showed the effect of different solvents on the condensation rate of silicon alkoxide. Colby et al. [6] reported the effects of temperatures on the gelation of silicon alkoxide and the pH dependence on the hydrolysis and condensation of the same system is also well known [1, 2]. Voronkov et al. [7] pointed out that steric and inductive factors influenced the condensation rate of silicon alkoxides. In the present work, a rheological study, i.e. the determination of gelling time tg, the dynamic flow behaviour, the viscoelastic property of the sols and gels and its relation to relaxation exponent n and fractal dimension df in a three-dimensional space during hydrolysis and condensation of tetraethyl orthosilicate (TEOS), in the presence of different organic acids, i.e. oxalic acid, citric acid and succinic acid was carried out at the same pH, temperature and H2O:Si ratio in the system. Silicic acid sols were prepared by using (initially) alcohol-free TEOS (Fluka Chemica, Purum grade), deionized water and different organic acids, i.e. oxalic acid, citric acid and succinic acid (AR grade, S. D. Fine Chem. Pvt. Ltd.) in the molar ratio of 14:1:0.2 respectively at 32 ± 1 ◦C. The system was stirred magnetically and the temperature was increased to 70–80 ◦C. After stirring for about 15 min, a clear sol was obtained [8]. The pH of each sol was adjusted to 3.5 by addition of dilute NH3 (25 wt%, G. R. grade, E. Merck, India). The rheological measurements of the sols were carried out by using a Haake rheometer (Rotovisco, model: RT20) at 30 ◦C. The instrument was connected to a computer, loaded with Haake software (Version V3). A cone and plate sensor (c60/1◦) was used for all measurements. Steady shear flow measurements of the samples in controlled rate (CR) mode were carried out by increasing the shear rate from 0 to 200 s−1 over 30 s followed by an immediate decrease in the shear rate from 200 s−1 back to zero in another 30 s. The dynamic flow behavior, i.e. loss modulus (G ′′) and storage modulus (G ′) of the sols and gels was determined using oscillatory flow with varying radial frequency (ω) i.e., 0.924, 1.985, 4.279 and 19.855 rad s−1. Loss tangent (tan δ) can be obtained as,

Directed differentiation of embryonic stem cells into dorsal interneurons

During neural development caudalization and dorsoventral patterning of the neural tube is directed by several inductive factors including retinoic acid, sonic hedgehog (Shh), bone morphogenetic proteins (BMPs), and Wnt signaling. The purpose of the current study was to investigate whether dorsal interneurons specific for the spinal cord can be generated from mouse embryonic stem (ES) cells using known inductive signals. Here we show that specific combination of developmental signaling molecules including all trans-retinoic acid, Shh, bone morphogenetic protein 2 (BMP2), and Wnt3A can direct differentiation of ES cells into dorsal interneurons possessing appropriate neuronal markers, synaptic proteins and functional neurotransmitter machineries. We introduce a concept that Wnt3A morphogenic action relies on crosstalk with both Shh and BMP2 signaling pathways.

Induction of proliferation and differentiation of cultured urothelial cells on acellular biomaterials.

To determine the optimum conditions for the proliferation of urothelial cells, leading to the confluent coverage of large surfaces of biocompatible membranes, and for their terminal differentiation. Porcine and human urothelial cells were cultured on different matrices under different growth conditions. Proliferative activity and the viability of cells were evaluated using fluorescent markers for nuclei and cytoplasm. Growth and differentiation were assessed by histological, histochemical and immunohistochemical methods. Under fibroblastic induction and supplementation of 5% fetal calf serum (FCS), urothelial cells showed more proliferation than in other conditions tested. Terminal differentiation of superficial cells was achieved by lowering the concentration of FCS to 1% at the air-liquid interface. The mitogenic effects of the extracellular matrix content of biological membranes and fibroblastic inductive factors are synergistic with each other, and can compensate for a low FCS concentration and the absence of other additives. Lowering the FCS concentration to 1% inhibits the proliferation of urothelial cells and permits their terminal differentiation.

Comparative study on the hydrolysis kinetics of substituted ethoxysilanes by liquid-state 29Si NMR

Liquid-state 29Si NMR was used to investigate the ammonia-catalyzed initial hydrolysis of different substituted ethoxysilanes dissolved in methanol. The following ethoxysilanes were used: tetraethoxysilane (TEOS), methyltriethoxysilane (MTES) and dimethyldiethoxysilane (DBS). Their reaction expresses were obtained by assuming first-order in the reactant ethoxysilanes and varying other reactant ammonia and water concentrations. Individual kinetic rate constants for the initial hydrolysis of each ethoxysilanes, the rate-limiting step for total reactions, were calculated, which were independent of any reactant concentration. The results indicated that the steric factors have more important effect on the reactive reactivity than inductive factors, so that the initial hydrolysis rate constants for the studied ethoxysilanes decreased in an unusual order DDS > TEOS > MTES. For these three ethoxysilanes, a common conclusion was drawn that the substitution of the hydroxyl group for the ethoxyl group resulted in a downfield shift. In the case of DDS, however, the trend was opposite to the previous studies in which the hydrolyzed resultants had upfield shift compared with DDS monomer.