Al-, Ga-, and In-doped ZnO thin films via aerosol assisted CVD for use as transparent conducting oxides

Al-, Ga-, and In-doped ZnO thin films were deposited on glass substrates by aerosol assisted chemical vapour deposition (AACVD) at a deposition temperature of 450 °C. The air-stable compound zinc acetylacetonate [Zn(acac)2] was used as a Zn source, whilst for the dopants of Al, Ga and In, the corresponding trichloride was used. Methanol solutions of the metal salts were used as precursor solutions and N2 carrier gas was used for the aerosol. Films were grown in approximately 30 min and were synthesised using dopant values of 5, 10, 15 and 20 mol.% (with respect to the Zn) in the precursor solution. XRD analysis showed that the films were wurtzite ZnO. XPS analysis confirmed the presence of the dopants in the films. Several of the films showed high transparency (>80%) in the visible range, and low resistivity (∼10−3 Ω cm)

Scaling aerosol assisted chemical vapour deposition: Exploring the relationship between growth rate and film properties

Thin films of fluorine doped tin oxide were deposited, by an aerosol assisted chemical vapour deposition route, to study the effect of scaling the growth rate. The effect of precursor concentration on the growth rate of the films and the properties of deposited films were compared. The films were characterised by X-ray diffraction, scanning electron microscopy, UV/vis spectroscopy, X-ray photoelectron spectroscopy and Hall effect measurements. A maximum film growth rate of ca. 100 nm min− 1 was observed, which is significantly faster than previously reported aerosol assisted studies. This method shows the ability of aerosol assisted methods to deliver high growth rates whilst maintaining the ease of doping and control over stoichiometry

Transparent conducting oxide thin films of Si-doped ZnO prepared by aerosol assisted CVD

For the first time, aerosol assisted chemical vapour deposition (AACVD) was used to deposit Si-doped ZnO thin films on glass. Depositions were done at a temperature of 450 °C. The precursor solution was made by dissolving the air-stable compounds zinc acetylacetonate and tetraethyl orthosilicate in methanol with a small addition of acetic acid to aid solubility. The dopant concentration in the precursor solution was optimised to find the best optoelectronic properties. The incorporation of Si into the ZnO lattice was confirmed by unit cell volumes calculated from X-ray diffraction (XRD) data and by X-ray photoelectron spectroscopy (XPS). The films consisted of pure phase wurtzite ZnO, with preferred orientation in the (002) plane. Scanning electron microscopy (SEM) was used to examine the surface morphology of the films. The optical properties of the films were analysed using UV/vis spectroscopy and indicated that the average transmittance in the visible part of the spectrum (400-700 nm) varied between 72% and 80%. The electrical properties of the films were obtained from Hall effect measurements using the van der Pauw method. The incorporation of Si into the films resulted in a decrease in resistivity down to a minimum value of 2.0 × 10−2 Ω cm for the film deposited from a 4 mol% Si : Zn ratio in the precursor solution. This conductive film was a significant improvement over the non-conductive undoped ZnO film

Nocodazole Treatment Decreases Expression of Pluripotency Markers Nanog and Oct4 in Human Embryonic Stem Cells

Nocodazole is a known destabiliser of microtubule dynamics and arrests cell-cycle at the G2/M phase. In the context of the human embryonic stem cell (hESC) it is important to understand how this arrest influences the pluripotency of cells. Here we report for the first time the changes in the expression of transcription markers Nanog and Oct4 as well as SSEA-3 and SSEA-4 in human embryonic cells after their treatment with nocodazole. Multivariate permeabilised-cell flow cytometry was applied for characterising the expression of Nanog and Oct4 during different cell cycle phases. Among untreated hESC we detected Nanog-expressing cells, which also expressed Oct4, SSEA-3 and SSEA-4. We also found another population expressing SSEA-4, but without Nanog, Oct4 and SSEA-3 expression. Nocodazole treatment resulted in a decrease of cell population positive for all four markers Nanog, Oct4, SSEA-3, SSEA-4. Nocodazole-mediated cell-cycle arrest was accompanied by higher rate of apoptosis and upregulation of p53. Twenty-four hours after the release from nocodazole block, the cell cycle of hESC normalised, but no increase in the expression of transcription markers Nanog and Oct4 was detected. In addition, the presence of ROCK-2 inhibitor Y-27632 in the medium had no effect on increasing the expression of pluripotency markers Nanog and Oct4 or decreasing apoptosis or the level of p53. The expression of SSEA-3 and SSEA-4 increased in Nanog-positive cells after wash-out of nocodazole in the presence and in the absence of Y-27632. Our data show that in hESC nocodazole reversible blocks cell cycle, which is accompanied by irreversible loss of expression of pluripotency markers Nanog and Oct4

Electrical Stimulation Influences Satellite Cell Proliferation and Apoptosis in Unloading-Induced Muscle Atrophy in Mice

Muscle atrophy caused by disuse is accompanied by adverse physiological and functional consequences. Satellite cells are the primary source of skeletal muscle regeneration. Satellite cell dysfunction, as a result of impaired proliferative potential and/or increased apoptosis, is thought to be one of the causes contributing to the decreased muscle regeneration capacity in atrophy. We have previously shown that electrical stimulation improved satellite cell dysfunction. Here we test whether electrical stimulation can also enhance satellite cell proliferative potential as well as suppress apoptotic cell death in disuse-induced muscle atrophy. Eight-week-old male BALB/c mice were subjected to a 14-day hindlimb unloading procedure. During that period, one limb (HU-ES) received electrical stimulation (frequency: 20 Hz; duration: 3 h, twice daily) while the contralateral limb served as control (HU). Immunohistochemistry and western blotting techniques were used to characterize specific proteins in cell proliferation and apoptosis. The HU-ES soleus muscles showed significant improvement in muscle mass, cross-sectional area, and peak tetanic force relative to the HU limb (p<0.05). The satellite cell proliferative activity as detected within the BrdU+/Pax7+ population was significantly higher (p<0.05). The apoptotic myonuclei (detected by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling) and the apoptotic satellite cells (detected by cleaved Poly [ADP-ribose] polymerase co-labeled with Pax7) were reduced (p<0.05) in the HU-ES limb. Furthermore the apoptosis-inducing factor and cleaved caspase-3 were down-regulated while the anti-apoptotic Bcl-2 protein was up-regulated (p<0.05), in the HU-ES limb. These findings suggest that the electrical stimulation paradigm provides an effective stimulus to rescue the loss of myonuclei and satellite cells in disuse muscle atrophy, thus maintaining a viable satellite cell pool for subsequent muscle regeneration. Optimization of stimulation parameters may enhance the outcome of the intervention

Chlorophyll a/b binding (CAB) polypeptides of CP29, the internal chlorophyll a/b complex of PSII: characterization of the tomato gene encoding the 26 kDa (type 1) polypeptide, and evidence for a second CP29 polypeptide

CP29, the core chlorophyll a/b (CAB) antenna complex of Photosystem II (PSII), has two nuclearencoded polypeptides of approximately 26 and 28 kDa in tomato ( Lycopersicon esculentum ). Cab9, the gene for the Type 1 (26 kDa) CP29 polypeptide was cloned by immunoscreening a tomato leaf cDNA library. Its identity was confirmed by sequencing tryptic peptides from the mature protein. Cab9 is a single-copy gene with five introns, the highest number found in a CAB protein. In vitro transcription-translation gave a 31 kDa precursor which was cleaved to about 26 kDa after import into isolated tomato chloroplasts. The Cab9 polypeptide has the two highly conserved regions common to all CAB polypeptides, which define the members of this extended gene family. Outside of the conserved regions, it is only slightly more closely related to other PSII CABs than to PSI CABs. Sequence analysis of tryptic peptides from the Type II (28 kDa) CP29 polypeptide showed that it is also a member of the CAB family and is very similar or identical to the CP29 polypeptide previously isolated from spinach. All members of the CAB family have absolutely conserved His, Gln and Asn residues which could ligate the Mg atoms of the chlorophylls, and a number of conserved Asp, Glu, Lys and Arg residues which could form H-bonds to the polar groups on the porphyrin rings. The two conserved regions comprise the first and third predicted trans-membrane helices and the stroma-exposed segments preceding them.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47577/1/438_2004_Article_BF00259681.pd

A new member of the CAB gene family: structure, expression and chromosomal location of Cab -8, the tomato gene encoding the Type III chlorophyll a/b-binding polypeptide of photosystem I

We have previously reported the isolation and characterization of tomato nuclear genes encoding two types of chlorophyll a/b-binding (CAB) polypeptides localized in photosystem (PS) I and two types of CAB polypeptides localized in PSII. Sequence comparisons shows that all these genes are related to each other and thus belong to a single gene family. Here we report the isolation and characterization of an additional member of the tomato CAB gene family, the single tomato nuclear gene, designated Cab -8, which encodes a third type of CAB polypeptide localized in PSI. The protein encoded by Cab -8 is 65% and 60% divergent from the PSI Type I and Type II CAB polypeptides, respectively. The latter two are 65% divergent from each other. Only some short regions of the polypeptides are strongly conserved. The Cab -8 locus maps to chromosome 10, 9 map units from Cab -7, the gene encoding the Type II PSI CAB polypeptide. The Cab -8 gene contains two introns; the first intron matches in position the single intron in the Type II PSII CAB genes and the second intron matches in position the second intron in the Type II PSI CAB gene. Like other CAB genes, Cab -8 is light-regulated and is highly expressed in the leaf and to a lesser extent in other green organs.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43422/1/11103_2004_Article_BF00043203.pd

Systems biology discoveries using non-human primate pluripotent stem and germ cells: novel gene and genomic imprinting interactions as well as unique expression patterns

The study of pluripotent stem cells has generated much interest in both biology and medicine. Understanding the fundamentals of biological decisions, including what permits a cell to maintain pluripotency, that is, its ability to self-renew and thereby remain immortal, or to differentiate into multiple types of cells, is of profound importance. For clinical applications, pluripotent cells, including both embryonic stem cells and adult stem cells, have been proposed for cell replacement therapy for a number of human diseases and disorders, including Alzheimer's, Parkinson's, spinal cord injury and diabetes. One challenge in their usage for such therapies is understanding the mechanisms that allow the maintenance of pluripotency and controlling the specific differentiation into required functional target cells. Because of regulatory restrictions and biological feasibilities, there are many crucial investigations that are just impossible to perform using pluripotent stem cells (PSCs) from humans (for example, direct comparisons among panels of inbred embryonic stem cells from prime embryos obtained from pedigreed and fertile donors; genomic analysis of parent versus progeny PSCs and their identical differentiated tissues; intraspecific chimera analyses for pluripotency testing; and so on). However, PSCs from nonhuman primates are being investigated to bridge these knowledge gaps between discoveries in mice and vital information necessary for appropriate clinical evaluations. In this review, we consider the mRNAs and novel genes with unique expression and imprinting patterns that were discovered using systems biology approaches with primate pluripotent stem and germ cells

Deciphering the stem cell machinery as a basis for understanding the molecular mechanism underlying reprogramming

Stem cells provide fascinating prospects for biomedical applications by combining the ability to renew themselves and to differentiate into specialized cell types. Since the first isolation of embryonic stem (ES) cells about 30 years ago, there has been a series of groundbreaking discoveries that have the potential to revolutionize modern life science. For a long time, embryos or germ cell-derived cells were thought to be the only source of pluripotency—a dogma that has been challenged during the last decade. Several findings revealed that cell differentiation from (stem) cells to mature cells is not in fact an irreversible process. The molecular mechanism underlying cellular reprogramming is poorly understood thus far. Identifying how pluripotency maintenance takes place in ES cells can help us to understand how pluripotency induction is regulated. Here, we review recent advances in the field of stem cell regulation focusing on key transcription factors and their functional interplay with non-coding RNAs