Iranian Journal of Biotechnology
Year:2007 | Volume:5 | Issue:2|Papers Count:9

Preimplantation development of the mammalian embryo consists of stages that include formation of the zygote, blastocyst formation and implantation of the embryo into the uterus. Depending on the animal, first few cleavages of the early embryo is fully supported by translation of maternal transcripts and use of maternal proteins. After this period, the preimplantation embryo starts to transcribe from its own genome and produce products, which are necessary for further development. Eventually, differential gene expression results in production of three cell types in the preimplantation embryo; an outer transporting polarized epithelium (trophoblast) and two cell types of primitive endoderm (hypoblast), and epiblast in the inner cell mass. After implantation, the trophoblast and hypoblast give rise to extra-embryonic tissues and epiblast cells form primarily the embryo proper. Expression of maternal and embryonic transcripts and proteins, and differential expression of these products that lead to differentiation of embryonic cells are all highly coordinated events, which need to be temporally and spatially regulated during this period of development. In this review article mechanisms and paradigms that may define and regulate these cellular activities leading to the first cellular differentiation of life are presented. Considering the abundance of research data on the preimplantation development of rodents, in this review we will mainly focus on the mouse model.

Experimental and clinical studies have shown that intracoronary transplantation of autologous bone marrow mesenchymal stem cells (BMSCs) has resulted in regenerated infracted myocardium and improved left ventricular (LV) function. The aim of this pilot study was to assess the benefical effects of intracoronary transplantation of BMSC in patients with old myocardial infarction (OMI). Autologous BMSCs were transplanted by the intracoronary method via percutaneous transluminal coronary balloon angioplasty (PTCA) in five patients with old myocardial infarction. Time from myocardial infarction (MI) to cell therapy was 5.2±3.11 months (mean±SD). All patients were <70 years old (32-61 years) and had significant LV dysfunction (LV ejection fraction, mean±SD, 34%±10.83%), and severe wall motion abnormality (akinesia and / dyskinesia) at the location of infarcted area. Follow up angiography was performed 6-9 months (mean±SD,7±1.4 months) after BMSC transplantation, which revealed an increased trend in the LV ejection fraction (LVEF) of patients after treatment (LVEF: Mean±SD from 34%±10.83% to 46.25%±9.46%, P= 0.051 and median from 35% to 42.5%). Clinical follow up (for 12-18 months) also revealed appreciable improvement in their symptoms or functional class [dyspnea from New York Heart Association(NYHA)-Class Ш-IV to I–II and Chest discomfort from Canadian Cardiovascular Society (CCS) Class II-IV to I-II]. Intracoronary transplantation of autologous BMSC in patients with old myocardial infarction appears to be feasible, safe and effective .The therapeutic effect could be attributed to BMSCs ability to regenerate myocardium.

In this work, mathematical modeling of microbial (Trichosporon sp.) biomass production in a stirred tank bioreactor din an external airlift bioreactor has been investigated. A model based on a tanks-in-series model without back-flow has been used to simulate the production of single cell protein in the external airlift bioreactor under an unsteady condition and without oxygen limitation, utilizing cheese whey as a substrate.

The automatic assignment of protein secondary structure from three dimensional coordinates is an essential step in the characterization of protein structure. Although, the recognition of secondary structures such as alpha-helices and beta-sheets seem straightforward, but there are many different definitions, each regarding different criteria. We have developed a new algorithm for protein helix assignment, by using fuzzy logic based on backbone torsion angles. In this method, each residue takes a number from 0 to 100 that indicates the helical membership degree of that residue. This method can be converted to a classical method whenever we assume that any residue with a membership degree greater than 83 is a helix. Comparison of the results with structures reported in protein data bank (PDB), dictionary of secondary structure of proteins (DSSP) and structure identification (STRIDE) for 324 proteins indicate that our algorithm works as well as DSSP showing 93% agreement. We believe that the fuzzy secondary structure assignment has more advantages than the other classical approaches used for protein structure comparisons and alignments.

Interactive effect of plant growth regulators 6-Benzylaminopurine (BAP) (0, 2, 4 and 8 mM) and 1-Naphtalene acetic acid (NAA) (0, 0.05, 0.25 and 0.5 mM) in Van der Salm (VS) medium was used to optimize in vitro propagation of Rosa hybrida cv. Iceberg. Shoot proliferation and number of new leaves were measured as growth indicators. As the concentration of BAP was raised, growth rate increased with all of the above NAA concentrations. However, the highest number of axillary shoots and new leaves were produced with 4 mM BAP, which was considered the optimal level. A multiplication rate of 10 folds with a maximum number of axillary shoots (10.1) and new leaves per explant (25) were obtained in the medium containing 4 mM BAP plus 0.5 mM NAA. In vitro-derived shoots were used to investigate root initiation and growth by lowering the concentration of VS mineral salts and vitamins. Three strengths of VS (full, 1/2 and 1/4) were compared in semi-solid and liquid medium. The average number of roots (4.35) and root length (0.82 cm) were significantly higher in 1/4 strength VS. The highest percentage of rooting (93.33%) and number of roots (4.45) were significantly higher in semi-solid than liquid medium. The regenerated plantlets were successfully transferred to soil and the survival rates of the rooted plantlets transferred to soil were 70% and 90% in plants treated with semi-sold and liquid media, respectively.

A new system is presented for the generation of recombinant Bacillus subtilis strains without antibiotic markers. This system is based on two plasmids constructed in Escherichia coli. The first plasmid pHM30 contains an incomplete hisI gene, the last gene in the histidine biosynthesis operon of B. subtilis and part of the genes yvcA and yvcB of unkown function flanking hisI at the 3´-end. The spectinomycin resistance gene is inserted between hisI and the downstream yvcAB region. Transformation of B. subtilis with this plasmid pHM30 led to spectinomycin resistant, histidine auxotrophic strains. The integrated parts of pHM30 act like a docking station for the second plasmid pHM31. The plasmid pHM31 contains the same yvcAB region but a complete copy of the hisI gene and no antibiotic resistance marker. Heterologous genes to be expressed in B. subtilis were inserted into a multiple cloning site between hisI and the downstream region. Transformants of B.subtilis/pHM30 with pHM31 derivatives were selected on minimal medium without histidine. By double crossovers during homologous recombination the heterologous genes were integrated, replacing the defect copy of hisI and the spectinomycin resistance gene. The plasmids were also successfully applied in the chromosomal integration of the lipase gene of Bacillus thermocatenulatus under a B. subtilis glucose regulated promotor/antiterminator system.

This research has focused on isolation and characterization of a strain of Bacillus sp. from alkaline soil, which was able to produce extracellular alkaline protease at pHs ranging from 8 to 11 and temperatures of 20 to 50°C. Also the impact of different carbon and nitrogen sources were investigated. The yield and fold of enzyme purification was 24% and 50 times, respectively. Molecular weight of purified enzyme was measured by SDS-PAGE as 24.7 kDa. The alkaline protease produced by Bacillus sp. 2 - 5 showed the most caseinolytic activity (without any gelatinolytic activity) at pH>10.

The rate and efficiency of decolorization of dyes like Blue CA, Black B133, and Corazol Violet SR were tested to evaluate white rot fungal strains. Trametes hirsute and Pleurotus florida showed the greatest extent of decolorization on nutrient salt media. Maximum decolorization of 200 mg/l of Blue 133 was obtained by 4 days old incubated Pleurotus florida followed by Trametes hirsuta after 6 days. An attempt was made to improve the decolorization activity of both organisms with different concentrations of glucose 1 and 2% (w/v). The decolorization activity may be due to the laccase enzyme of white rot fungi. The production of this enzyme was estimated using solid state fermentation with rice bran as a substrate. It was found that P. florida exhibited 0.175 U/ml of laccase activity followed 0.126U/ml by T. hirsute, respectively. Decolourization was found to be more effective with P. florida in the presence of 2% (w/v) glucose. Crude extract containing the laccase enzyme was isolated and confirmed by SDS PAGE.