The production of melanin pigment in mammals requires tyrosinase, an enzyme which hydroxylates the amino acid tyrosine to DOPA (3,4-dihydroxyphenylalanine), thus allowing the cascade of reactions necessary to synthesize that biopolymer. However, there are other regulatory steps that follow the action of tyrosinase and modulate the quantity and quality of the melanin produced. DOPAchrome tautome...

Background: Parthenogenetic activation of mammalian oocytes using artificial stimuli is commonly used in various reproductive bio-techniques. Calcium ionophore is known to elevate intracellular calcium levels in the cytoplasm of oocytes through the influx of calcium from extracellular spaces. Ethanol promotes a single intracellular Ca2+ increase of greater and longer amplitude than the initial ...

Slow strain rate tests on hydrogen-containing specimens of PH13–8Mo maraging stainless steel showed H-assisted subcritical quasi-cleavage cracking, accelerating material failure. Fractographic analysis revealed that is composed flat brittle areas and rougher areas. Electron backscatter diffraction (EBSD) was performed a secondary subcritically grown crack. High resolution EBSD significant cryst...

this study considers political culture (which is one of the most important issues in social and political sciences of students) in tehran university and effective factors on it. to analyze political culture, we used some theories of amond, verba, pay, rash, leibet and dal. in this study, the research method is the technique of collecting data and information through standard questionnaire. and ...

this study was undertaken to compare the efficiency of fresh and frozen-thawed buck semen on in vitro fertilization (ivf) of goat oocytes. cumulus oocytes complexes (cocs) were collected by aspiration of 2-6 mm diameter follicles, which were obtained from slaughterhouse. upon grading, only normal quality cocs were maturated in tcm-199 for 48 hours. the percentage of cocs reached to the m-ii sta...

Recently, we demonstrated chromosome instability (CIN) in human cleavage stage embryogenesis following in vitro fertilization (IVF). CIN not necessarily undermines normal human development (i.e. when remaining normal diploid blastomeres develop the embryo proper), however it can spark a spectrum of conditions, including loss of conception, genetic disease and genetic variation development. To s...

Background: Cigarette smoke contains many oxidants and may alter the human reproduction by inducing oxidative stress (OS) in both active and passive smokers. This study was designed to evaluation the effect of environment tobacco smoke (ETS) exposure on oxidative stress in follicular follicle and assisted reproduction outcomes. Materials and Methods: A prospective study was carried out on 236 i...

bacillus sp. sbs25, a gram positive bacteria isolated from soil was found to be effectivein the biodegradation of natural rubber latex. the products of latex biodegradation were separated from the ether extract by thin layer chromatography. gas chromatography and mass spectrometry showed the biodegradation of the major compound into three simpler fractions with low molecular weights. this was f...

We report a simple fluorometric method for detection of single-nucleotide changes in RNA using graphene oxide (GO) and RNA-cleaving DNAzyme. The fluorescent DNA probe (F-DNA) was annealed to RNA fragments generated by RNA cleavage with DNAzyme specific to mutant RNA. The F-DNA-RNA duplex attenuated the quenching of F-DNA fluorescence by GO.

Black adults have higher bone mass than whites in the United States, but it is not clear when black children gain bone mineral faster than white children. We performed a cohort study to compare the growth velocity of total-body bone mineral content (TBMC) between black and white children of the same sex at different ages and stages of sexual maturity. TBMC and total-body area were measured in a...