Evolutionary Biology of Parasitism
Eric S. Loker, Bruce V. Hofkin in Parasitology, 2015
Another possible parasite-facilitated mechanism of host speciation also deserves mention, one that also involves hybridization but in a different way from that suggested in Figure 7.32. Hybridization can contribute to the formation of new host species by allopolyploidy, when chromosomes are contributed by different parental species to form a new species. Allopolyploidy has been postulated to account for the origin of most species in the anuran genus Xenopus. Hybrids in this case often have increased resistance for parasites as compared to either parental species, potentially providing a selective advantage to favor the persistence of new species of recent hybrid origin.
Chromosome Pairing and Fertility in Plant Hybrids
Christopher B. Gillies in Fertility and Chromosome Pairing: Recent Studies in Plants and Animals, 2020
In many instances, the infertility of a hybrid can be traced directly to the failure of chromosomes to pair during meiotic prophase. It is the nature of chromosome pairing during these prophase stages and its bearing on the fertility of the hybrid which are the subjects of this chapter. The information presented deals with “synthetic” hybrids. Natural allopolyploid hybrids are the subject of another chapter in this monograph.
Effects of resistance training on liver structure and function of aged rats
Published in The Aging Male, 2018
Ricardo Aparecido Baptista Nucci, Ana Caroline de Souza Teodoro, Walter Krause Neto, Wellington de Assis Silva, Romeu Rodrigues de Souza, Carlos Alberto Anaruma, Eliane Florencio Gama
Exercise increases oxygen consumption and reactive oxygen species (ROS) generation and, therefore, can enhance oxidative damage to nucleic acids in cells [25–28]. On the other hand, it has been well recognized that regular physical activity has health benefits such as reducing risk and progression of cardiovascular diseases, type 2 diabetes mellitus, cancer and neurodegenerative diseases [25,29–31]. Paradoxically, these diseases are suggested to be induced and exacerbated by ROS [25]. Additionally, Oliveira et al. [32] showed that animals submitted to aerobic exercise had the lower percentage of polyploids nuclei. Polyploidy results from incomplete mitotic cycles, which is tightly related to the aging process [32–34]. Our results in Figure 3 showed that the number of hepatocytes nuclei per field (NNH per field) were higher in animals submitted to RT, suggesting that exercise increase hepatocytes mitotic cycles increasing its numerical density and maintaining its area across age. These results may be related to the protective effect of regular exercise even on hepatic cells.
Noninvasive amino acid turnover predicts human embryo aneuploidy
Published in Gynecological Endocrinology, 2022
I. Orcun Olcay, Berkay Akcay, Mustafa Bahceci, Aydin Arici, Kubra Boynukalin, Cengiz Yakicier, Aysel Ozpinar, Murat Basar
Assisted reproduction technologies (ART) have two significant problems: (i) low success rates and (ii) multiple pregnancies [1,2]. Because of these problems in ART, the priority in medically assisted conception clinics is to develop a trustworthy diagnostic test that can be used to select the embryos with the ultimate developmental competence. More sophisticated methods must be employed to improve the IVF success rate by 40%, even with a limited number of embryo transfers [3–7]. Meiotic and mitotic errors in the oocyte and pre-implantation embryo can lead to different patterns of aneuploidy involving polyploidy and chaotic mosaics. Indeed, the latter account for ∼30% of aneuploidies in which multiple chromosomes are affected in each cell [8]. Unfortunately, it is impossible to distinguish morphologically between euploid embryos and those with aneuploids. Thus, many of these embryos are graded as suitable for transfer [9–11]. Overall, it is well known that subjective scoring systems based on embryo morphology are an ineffective means of selecting developmentally competent embryos. Therefore, developing an alternative approach that can be used to determine the best embryos for transfer and cryopreservation is crucial.
Gamma irradiation to induce beneficial mutants in proso millet (Panicum miliaceum L.): an underutilized food crop
Published in International Journal of Radiation Biology, 2022
Neethu Francis, Ravikesavan Rajasekaran, Iyanar Krishnamoorthy, Raveendran Muthurajan, Chitdeshwari Thiyagarajan, Senthil Alagarswamy
The advanced mutant population, i.e. M2 generation was further studied to document the new genetic variations induced at different treatments and also to identify high yielding mutants. Chlorophyll and viable MF are important in determining the effectiveness and efficiency of a mutagen in plants. In this study, the number and types of chlorophyll mutants expressed were relatively low. It can be due to the duplication of genes or chromosomes in polyploids or because of the higher stability of genes producing chlorophyll. In a study to elaborate the relationship between radiation response and polyploidy in crop plants, autotetraploid barley in comparison to the diploid species, produced no chlorophyll mutants in M2. Similarly, no chlorophyll mutants were isolated from wheat and tobacco and only two chlorophyll mutants from cotton were isolated in M2 generation (Krishnaswami 1968). Viable MF obtained from this study was 10.96% and it quantifies the beneficial variations induced by gamma. Mutation frequency, effectiveness, and efficiency were highest at 400 Gy dose followed by 500 Gy and declined at higher doses. Hence, it can be concluded that to isolate maximum beneficial mutations in proso millet, the optimum dose is 400 Gy. In a similar study in rice, 300 Gy recorded highest mutagenic effectiveness based on viable MF (Gowthami et al. 2021). In little millet, mutation rate has been reported to be highest at 500 Gy dose and mutagenic effectiveness was found to decrease with increase in dose of mutagen (Ganapathy et al. 2008).
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