An Introduction to Parasitism
Eric S. Loker, Bruce V. Hofkin in Parasitology, 2023
Different biological disciplines answer this question in different ways. For example, among microbiologists and infectious disease specialists, the term parasite is often used to refer to those organisms with the properties of parasites that are eukaryotes. Eukaryotes are organisms with a defined nucleus and membrane-bound organelles, such as mitochondria. Eukaryotes include unicellular protists (or protozoa), fungi, plants and animals (this diversity is discussed in more detail in Chapter 2). Bear in mind that many eukaryotes are free-living and so are not parasites. From this vantage point, suborganismal entities, such as prions or viruses, and prokaryotes (bacteria) that infect hosts and cause them damage are not parasites. Parasites (in the restricted eukaryotic sense), viruses and some bacteria are all considered infectious agents or pathogens by this reckoning (Figure 1.4).
Introduction to Cells, DNA, and Viruses
Patricia G. Melloy in Viruses and Society, 2023
Cellular macromolecules are organized into compartments called organelles (like little organs) that have an organization allowing for the work of the cell to happen. So, like organs such as the heart and lungs that have a special role in the body, organelles have a special role inside the cell. Some examples of key cellular organelles include the nucleus (where DNA is housed), mitochondria (energy generation), and ribosomes (protein production). Except for the nucleolus residing in the nucleus, organelles are found in what is known as the cytoplasm or cytosol of the eukaryotic cell. The nucleus is an important organelle because it acts as the central control point for all the activities of the cell. The nucleus houses most of the cell’s DNA in the form of protein/DNA structures known as chromosomes that allow for condensation of the large amount of genetic material in each cell (Alberts et al. 2019). Cell division occurs in a process known as mitosis, in which the chromosomes are copied and separated equally between the two daughter cells. Later, we will talk about organelles that help move or traffic things around the cell, as well as into and out of the cell. Trafficking-related organelles include the endoplasmic reticulum, Golgi apparatus, and vesicles. Viruses can exploit the cellular trafficking network to move into and out of the cell.
Fungi and Water
Chuong Pham-Huy, Bruno Pham Huy in Food and Lifestyle in Health and Disease, 2022
Fungi including mushrooms, molds, and yeasts are eukaryotic organisms as vegetable or animal species, but are classified as a separate kingdom because fungal cell walls contain rigid chitin and glucans that are not found in animal, vegetal, or bacterial species (1–8). Eukaryotic cells are cells that contain a nucleus and other organelles enclosed within membranes. In other words, the fungal kingdom comprises a hyper diverse clade of heterotrophic eukaryotes characterized by the presence of a chitinous cell wall, the loss of phagotrophic capabilities, and cell organizations that range from completely unicellular monopolar organisms to highly complex syncytial filaments (containing several nuclei) that may form macroscopic structures (8). Mushrooms like morels, button mushroom, and puffballs are macroscopic multicellular fungi, while molds are a large group of microscopic multicellular fungi. Molds are characterized by filamentous forms named hyphae. Many fungi occur not as hyphae but as unicellular forms called yeasts, which are invisible to the naked eye and reproduce by budding (2–4).
Protective role of PERK-eIF2α-ATF4 pathway in chronic renal failure induced injury of rat hippocampal neurons
Published in International Journal of Neuroscience, 2023
Qi Chen, Jingjing Min, Ming Zhu, Zhanqin Shi, Pingping Chen, Lingyan Ren, Xiaoyi Wang
The endoplasmic reticulum is one of the most important organelles in eukaryotic cells. It is not only the site for protein translation and synthesis as well as calcium ion storage, but also a participant in the transmission and processing of various cell signals. In addition, one of the major functions of the endoplasmic reticulum is to serve as a site for synthesizing secretory and integral membrane proteins.5,6 When cells are stimulated by hypoxia, an imbalance of calcium ions or a change in their concentration occurs in the internal environment, accompanied with the accumulation of some unfolded proteins in the endoplasmic reticulum, resulting in an imbalance between the structure and function of the endoplasmic reticulum. At this time, the corresponding signal pathway is activated to further trigger the endoplasmic reticulum stress (ERS) response.7 Unfolded protein response activation can be triggered in the following three ways: (1) inhibition of protein translation to prevent the production of more folded proteins; (2) induction of the folding of unfolded proteins by the endoplasmic reticulum chaperone; (3) activation of endoplasmic reticulum associated degradation pathways to remove unfolded proteins accumulated in the endoplasmic reticulum.8 However, under prolonged or severe stress, the unfolded protein response initiates programmed cell death.
Ribosomopathies and cancer: pharmacological implications
Published in Expert Review of Clinical Pharmacology, 2022
Gazmend Temaj, Sarmistha Saha, Shpend Dragusha, Valon Ejupi, Brigitta Buttari, Elisabetta Profumo, Lule Beqa, Luciano Saso
Ribosomes are ribonucleoprotein complexes discovered by Palade and Porter in 1954 as small round bodies associated with the endoplasmic reticulum (ER), as observed using an electronic microscope [1]. It is well known that genetic information is stored in deoxyribonucleic acid (DNA) molecules, and by the highly regulated mechanism of transcription, genes, as particular segments of DNA, are copied into mRNA (ribonucleic acid) by the RNA polymerase enzyme. Ribosome macromolecules catalyze the translation of information from mRNAs into functional polypeptide chains. Ribosomes consist of large and small subunits. Eukaryotic ribosome consists of a smaller 40S subunit and a large 60S subunit. The smaller 40S subunit consists of 18S ribosomal RNA (rRNA) and 33 ribosomal protein small (RPS) subunits, whereas the 60S subunit contains 28S, 5S, and 5.8S rRNA and 47 ribosomal protein large (RPL) [2,3].
Mitochondria’s role in sleep: Novel insights from sleep deprivation and restriction studies
Published in The World Journal of Biological Psychiatry, 2022
Lindsay M. Melhuish Beaupre, Gregory M. Brown, Nicole A. Braganza, James L. Kennedy, Vanessa F. Gonçalves
Mitochondria are dynamic organelles found in the cytoplasm of all eukaryote cells. They are commonly referred to as ‘the cell’s powerhouse’ because of their unique role in energy metabolism. Mitochondria are the main site of synthesis of adenosine triphosphate (ATP), energy for the cell, via oxidative phosphorylation (OXPHOS) (Senior 1988; Griffiths and Rutter 2009). These organelles are known to continuously undergo a balance between fission (when one mitochondrion splits into two) and fusion (when two mitochondria connect, resulting in a mixing of the two membranes and contents of the mitochondrial matrix), to maintain a certain shape, size, and number (Chan 2012). Complications with these dynamics can have deleterious effects, including membrane instability, and apoptosis (Sugioka et al. 2004; Chan 2006, 2012). Proper mitochondrial dynamics also play an important role in electron transport chain (ETC) assembly. Alterations in the ETC assembly leads to impairments in OXPHOS (Liu et al. 2011; Yao et al. 2019).
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