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An Overview of Parasite Diversity
Published in Eric S. Loker, Bruce V. Hofkin, Parasitology, 2023
Eric S. Loker, Bruce V. Hofkin
No species consists of individuals that are completely uniform genetically. Even in species that routinely engage in self-fertilization or asexual reproduction, genetic variants nonetheless occur thanks to the ongoing process of mutation or other genetic modifications that might arise. It is this intraspecific genetic variation that forms the substrate upon which natural selection acts, favoring some variants over others. For example, individual parasites with a variant gene that confers resistance to a particular drug might be favored during a control program testing the use of that drug. In Chapter 7, we revisit the importance of genetic variation and population structure within parasite species when we discuss the evolution of parasites. For now, the mission is to show that diversity exists within parasite species and that this variation is consequential and needs to be considered.
The Zigzag Trail of Symbiosis among Chepang, Bat, and Butter Tree
Published in Mahendra Rai, Shandesh Bhattarai, Chistiane M. Feitosa, Wild Plants, 2020
Tirth Raj Ghimire, Roshan Babu Adhikari, Ganga Ram Regmi
Secondly, it is interesting to know that frugivore bats do not eat the fruits hanging on the parent plant, but pick the fruit and carry them to near or far distances, hang on to another plant, and consume them. They suck up all the inner fleshy materials and let the seeds and peel drop down to the ground, ensuring the continuous propagation of the BT. Eonycteris spelaea, a cave-dweller and long distance-traveler for foraging activities, seems to be a critical mammal in pollinating and dispersing seeds of the BT in the current study area (SMCRF 2010, Acharya et al. 2015, Sharma et al. 2018). Long-distance pollination by bats is crucial in the conservation of the species. It is because human disturbance fragments plant populations and increases geographic isolation. In the absence of long-distance pollination, plants within habitat fragments experience self-fertilization compared to those in continuous forests (Fleming et al. 2009). Although frugivores such as Eonycteris spelaea, Cynopterus sphinx, and Rousettus leschanaultii take part in the pollination and seed dispersal of many plants, such as banana, jackfruit, litchi, mango, papaya, palm, sacred fig, East Indian shade tree, Eucalyptus, Indian lilac, they may assist in the livelihood of the Chepang alternatively.
Programmed Cell Death: The Biology of Cell Death in the Nematode Caenorhabditis elegans and Implications for the Understanding and Treatment of Human Brain Injury after Cardiac Surgery
Published in Richard A. Jonas, Jane W. Newburger, Joseph J. Volpe, John W. Kirklin, Brain Injury and Pediatric Cardiac Surgery, 2019
C. elegans is a free-living nonparasitic nematode.4 There are two sexes: male and hermaphrodite, the latter of which makes both sperm and eggs and is capable of reproducing either by self-fertilization or by mating with males. These animals are cellularly very simple. For example, the adult hermaphrodite contains a total of 959 cells, 302 of which are neurons. The complete connectivity of the nervous system has been determined by the analysis of serial-section electron micrographs. The neurotransmitters in this nervous system have also been characterized, and about 40% of the 302 neurons now have defined neural transmitters associated with them. These neurotransmitters are familiar and include acetylcholine, serotonin, octopamine, dopamine, and GABA. The cell lineage of C. elegans, which describes the pattern of cell divisions and cell fates that occur as the single-celled egg generates the 959-celled adult, has also been determined in its entirety.
Toxicity of nanoplastics during the embryogenesis of the ascidian Ciona robusta (Phylum Chordata)
Published in Nanotoxicology, 2020
Maria Concetta Eliso, Elisa Bergami, Loredana Manfra, Antonietta Spagnuolo, Ilaria Corsi
Gametes were obtained from each individual by dissecting the gonoducts with a scalpel. To avoid the self-fertilization, oocytes and sperms were collected by distinct individuals. The oocytes were rinsed twice in 0.22 µm filtered NSW while dry sperm was pooled and stored on ice until fertilization. Fertilization was performed by adding diluted sperm (1:100 in NSW) to the eggs suspension. After 10 min of incubation on a rotating shaker, the fertilized eggs were transferred to tissue culture plates and further rinsed in 0.22 µm filtered NSW.
High genetic complexity but low relatedness in Plasmodium falciparum infections from Western Savannah Highlands and coastal equatorial Lowlands of Cameroon
Published in Pathogens and Global Health, 2022
Ngoh Ines Atuh, Damian Nota Anong, Fru-Cho Jerome, Eniyou Oriero, Nuredin Ibrahim Mohammed, Umberto D’Alessandro, Alfred Amambua-Ngwa
We combined several indices (MOI, sMLH and Fws) to evaluate the level of complexity within infections. These indices were highly correlated, with the most significant correlation being between sMLH and Fws. The variant of the inbreeding coefficient (Fws) used here was based on the frequency of alleles per individual compared to that within the source population, therefore allowing for comparison between populations [42]. In line with previous data, relatively more complex infections were observed from the higher transmission LHD sites, though polyclonal infections were common in all sites. Heterogeneity in infection complexity seen for sites within each health district could be due to discontinuity in spatial malaria transmission especially in NHD, where sites were on average separated by ~10 km. This could also be driven by low transmission in the NHD. The highest number of monoclonal infections were detected in the cosmopolitan semi-urban sites of Bamunka in NHD. With better infrastructure, transmission is low in the town and most infections may have resulted from local outbreaks from small reservoir. This is contrary to importation due to urban migration which results in diverse parasites [43]. The differences in diversity between the health districts was also observed from linkage disequilibrium. The index of association between loci was low as expected for most malaria endemic population in Africa, but it significantly deviated from random allelic association. This significant LD suggest some level of inbreeding arising from self-fertilization or because of high genetic relatedness among isolates, especially in the low transmission sites in NHD (IBS = 0.086, mean ISA = 0.376). LD has been inversely associated with intensity of malaria transmission [23,25]. In areas of high transmission, LD is rapidly broken down due to increased proportion of mixed genotypes, leading to cross-fertilization and meiotic recombination. On the other hand, where transmission is low, the frequency of mixed genotypes decreases, leading to self-fertilization and increased LD and genetic relatedness. Relatedness between pairs of isolates from different health districts was weak, an indication that there is break in connectivity and mixing. There were also lower levels of pairwise relatedness between the LHD coastal cosmopolitan sites, probably a reflection of high rates of transmission and recombination or importation of diverse parasites from neighboring rural areas. The sites in LHD were within 7 km from each other, within the town of Limbe, a popular local tourism destination that could fuel diversity of infection due to importation.
Caenorhabditis elegans as a tool for environmental risk assessment: emerging and promising applications for a “nobelized worm”
Published in Critical Reviews in Toxicology, 2019
L. Queirós, J. L. Pereira, F. J. M. Gonçalves, M. Pacheco, M. Aschner, P. Pereira
Table 1 depicts a summary with the strengths and limitations of C. elegans as an experimental model organism in biomedical research, as well as an appraisal of the features that can concomitantly be valuable for understanding the worm as a model in ERA. The promotion of this nematode species as a laboratory model in medical fields stems from several internal and external attributes that have been making the research with this species particularly fruitful. The knowledge of its complete genome sequence bearing conserved gene sequences, and the peculiar sharing of signaling pathways and cellular machinery for DNA replication and repair between C. elegans and humans (Table 1) are worth noting in this context. These are key attributes for the investigation of the modes of toxic action and disease pathways, which are frequently similar between humans and this invertebrate model (Cole et al. 2004; Kaletta and Hengartner 2006; Leung et al. 2008; Destefani et al. 2017). The available mutant and transgenic C. elegans strains (Table 1) are also very useful to mechanistically clarify modes of action, oxidative stress pathways, DNA damage patterns, and neurodegeneration (Corsi et al. 2015; Hunt 2016). As an organism with metabolically active digestive, reproductive, endocrine, sensory, and neuromuscular systems (Table 1), C. elegans responds as a functional multicellular and multisystems unit in the toxicity assays. Furthermore, the logistics involved in culturing and testing with C. elegans is relatively easy to handle, which mostly derives from the species biological and physiological characteristics (Table 1). The nematode has a life cycle that extends only for 3.5 days when incubated at 20 °C (Figure S1). The organisms of this species are mostly self-fertilizing hermaphrodites, meaning that only one animal is needed to populate an entire plate. Only 0.1–0.2 % of the population produced by self-fertilization are males as consequence of the rare meiotic non-disjunction of the X chromosome, with most of the tests being carried out with hermaphrodites even though tests with males can also be done depending on the research hypothesis. As integrated in ERA, tests with hermaphrodites would, thus, be the most straightforward option following, with the advantage of supporting comparison to previous data, but sex-specific effects can also be tested particularly at higher ERA tiers where population and community studies are typically considered for a better and more direct insight on ecological responses (see Figure 1). C. elegans can be cultured within a large interval of temperature, ranging from 12 to 25 °C, meaning that its growth rate can be controlled by manipulating the temperature within this range. In vivo toxicity assays with the organism can be performed within a short time period and using simple equipment. Moreover, they are cheaper and faster than the tests available with rodent models (Hunt 2016). All mentioned features are also valuable in the environmental sciences field, specifically regarding integration in ERA approaches.