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Methods of Study and Characterization of Surface-Modifed Substrates
Published in Simona Badilescu, Muthukumaran Packirisamy, BioMEMS, 2016
Simona Badilescu, Muthukumaran Packirisamy
Polysomes (or polyribosomes) are complexes of mRNA and ribosomes on which polypeptides are synthesized by transcription and translation.10 For the visualization of polysomal fractions, mica is used as a substrate because when it is freshly cleaved, it has an atomically flat surface. In order to anchor biomolecules to the mica surface, divalent cations (Ni2+ as NiCl2) are used. To study the native three-dimensional form, the translation was temporarily stopped. This substrate is submerged under the buffer solution, and the imaging conditions have to be optimized before the measurement.
Variation: Boolean Representations
Published in Markus W. Covert, Fundamentals of Systems Biology, 2017
Protein production turns out to occur on a similar timescale. Ribosomes attach to free mRNAs one after the other in “polysomes” that look like pearls on a string. In this way ~10 proteins can be made simultaneously from a single transcript. The ribosome also travels at ~50 nucleotides (or ~16–17 amino acids produced) per second, which gives us ~20 s for elongation of a 333-amino-acid peptide from the 1,000-nucleotide-long gene. Again, when initiation and termination are taken into account, we can say it takes 1–2 min from mRNA existence to protein creation.
Maternal bisphenol A exposure disrupts spermatogenesis in adult rat offspring
Published in Journal of Toxicology and Environmental Health, Part A, 2019
Patricia De Campos, Isabela M. Oliveira, Janaina Sena de Souza, Rodrigo Rodrigues Da Conceição, Gisele Giannocco, Maria I Chiamolera, Magnus R.Dias-Da Silva, Marco A. Romano, Renata Marino Romano
The expression of genes is an important step to cellular function. All types of information are necessary in order for each cell type to develop its function which is stored in DNA in the form of genes. To be functional, DNA is converted into RNA during transcription, which is regulated by stimulation and repression factors, according to cellular function status. In the cytoplasm, the mRNA is recruited by polysomes to be translated into proteins. The proteins develop their functions including binding receptors, acting as enzymes, or constituents of the cell structure. In this manner, the cell regulates its biological function stimulating or repressing genes through transcription and translation processes (Alberts et al. 2002). As mRNA is critical for protein production, the up- or down-regulation of genes by chemicals may markedly affect cellular function. The results of the present study also demonstrated that perinatal exposure to BPA led to a significant reduction in Ar mRNA expression. Androgen receptor is highly expressed in the testes, especially in Sertoli cells; and plays a key role in the maintenance of spermatogenesis, as evidenced by diminished spermatogenesis and lowered response of Leydig cells to testosterone that occurs as a result of a reduction in expression of Ar (Qiu et al. 2013). The action of androgens in spermatogenesis occurs via Sertoli cells, as germinative cells do not possess receptors for androgens and are required for maintenance of blood-testis barrier, adhesion, and release of sperm from Sertoli cells (Smith and Walker 2014). In ArKO mice, a reduction in the number of spermatids was observed, possibly due to a severe disruption of germ cell development and decreased adhesion of spermatids by Sertoli cells (De Gendt et al. 2004; Wang et al. 2006). Interestingly, it is well-established that testosterone stimulates synthesis of AR and stabilizes mRNA (Mora, Prins, and Mahesh 1996), which accumulates in the polysomes (Mora and Mahesh 1999). However, in the present study, the elevation in testosterone levels was accompanied by inhibition in Ar expression, indicating possible multiple effects of BPA on endocrine regulation. The reduction in Ar expression might also be involved in the decreased caput and corpus epididymis weight. In contrast, the seminal vesicle fluid was increased in the higher BPA-treated group, indicating that androgen-sensitivity of this tissue is maintained.