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.
Current Concepts of Implantation and Decidualization
Gabor Huszar in The Physiology and Biochemistry of the Uterus in Pregnancy and Labor, 2020
Do the proteins that appear in decidual cells represent expressed information that directs morphological transformation or are they signal proteins such as hormones, etc.? The nature of the relationship between the synthesis and secretion of hormones and endoreduplication would also be of great interest to resolve. Replication of DNA, in the absence of cytokinesis and karyokinesis, is peculiar to the mammalian female reproductive tract during development.128 It occurs during decidualization and during differentiation of the trophoblast giant cell in which the haploid amount of DNA (£#) may increase from 2 to as much as 1024.129 During this differentiation the trophoblast giant cell expresses an intricate program of steroid and peptide hormone production.94 Is this program related to endoreduplication? Is its expression related to the replication of the whole or only a part of the genome? If hormone production proves to be a decidual cell function, is synthesis related to endoreduplication (more limited) in that cell? Why do these singular events in DNA replication occur only during development in the mammal; are they important clues to its regulation?
Basic Cell Biology
Kedar N. Prasad in Handbook of RADIOBIOLOGY, 2020
In mitosis, each chromosome duplicates itself. The duplicated strands separate as the nucleus divides, so that the daughter nuclei have the same set of chromosomes as their parent cell. Figure 2.2 shows a diagrammatic representation of the process of mitosis in a cell. During mitosis, a cell passes through four stages: prophase, metaphase, anaphase, and telophase. During prophase, each chromosome doubles itself, and the nuclear membrane and nucleus disappear. During metaphase, spindles form and chromosomes lie on the equatorial plate. During anaphase, chromosomes separate, and each half moves toward a pole. During telophase, the nucleus appears, and the cell divides into two daughter cells — each having an identical set of diploid chromosomes. The process of mitosis is so precise that any change in the chromosomes or DNA would definitely reflect in daughter cells after completion of cell division.
Neferine inhibits epidermal growth factor-induced proliferation and migration of retinal pigment epithelial cells through downregulating p38 MAPK and PI3K/AKT signalling
Published in Cutaneous and Ocular Toxicology, 2020
Sadik Altan Ozal, Vuslat Gurlu, Kader Turkekul, Hande Guclu, Suat Erdogan
The cell cycle, required for cell proliferation, comprises four phases. The first is gap phase (G1) in which the cells grow, the synthesis phase (S) in which the DNA is replicated, the second gap phase (G2) of further growth, and the mitotic (M) phase in which the cells divide35. Neferine has previously been reported to inhibit the cell cycle in various cancer cells. In the present study, it was found that neferine treatment inhibited RPE cell proliferation by arresting the cell cycle at the G1 phase. Cell division is based on the activation of cyclins that bind to cyclin-dependent kinases (CDK) inducing cells to progress into S phase and then initiate mitosis. Expression of the CDK proteins is regulated by p21 and p27 tumour suppression genes36, with increases in CDK expression levels being associated with cancer development, our studies show that neferine treatment induces cell-cycle arrest by upregulating the expression of p21 and p27 and downregulating CDK2 expression.
Pro-Apoptotic and Anti-Angiogenesis Effects of Olive Leaf Extract on Spontaneous Mouse Mammary Tumor Model by Balancing Vascular Endothelial Growth Factor and Endostatin Levels
Published in Nutrition and Cancer, 2019
Sara Milanizadeh, Mohammad Reza Bigdeli
Four stages, including: deparaffinization, hydration, staining, and dehydration have been done, [hydrate in descending alcohol solutions (100% ×2, 95% ×2, 80%, 70%, 50%)/immerse sections in the filtered Harris Hematoxylin for a minute/rinse with water/immerse in Eosin stain for 1 to 2 min/rinse with water/dehydrate in ascending alcohol solutions (50%, 70%, 80%, 95% ×2, 100% ×2)/clear with xylem (×2)]. Morphological structures of the tumor tissues were carefully studied. Apoptotic cells were distinct by following properties under microscope. Condense chromatin near the nuclear membrane, cells with huge condense nucleus. In addition, tumor cells that exhibited the morphological features characteristic for prophase, metaphase, anaphase, or telophase stages of mitosis (30,31) were identified and counted.
Expanding roles of cell cycle checkpoint inhibitors in radiation oncology
Published in International Journal of Radiation Biology, 2023
Sissel Hauge, Adrian Eek Mariampillai, Gro Elise Rødland, Lilli T. E. Bay, Helga B. Landsverk, Randi G. Syljuåsen
The transition from one cell cycle phase to the next is driven by the activation of Cyclin-dependent kinases (CDKs). According to the classical view, progression through G1 phase is controlled by Cyclin D–CDK4 and Cyclin D–CDK6 activities, and entry into S phase is driven by Cyclin E–CDK2 activity. Cyclin A–CDK2 and Cyclin A–CDK1 are then responsible for further progression through S phase and toward mitosis, and Cyclin B–CDK1 pushes the cell into mitosis (Hochegger et al. 2008). The WEE1, CHK1 and ATR kinases act as negative regulators of CDK1 and CDK2 activity (Figure 1). WEE1 is active in interphase and is inhibited when cells enter mitosis, and it works by directly mediating the inhibitory phosphorylation on tyrosine 15 (Y15) of CDK1 and CDK2 (Parker and Piwnica-Worms 1992; Watanabe et al. 1995, 2004; Katayama et al. 2005). CHK1 suppresses CDK1 and CDK2 activity by promoting degradation of the CDC25A phosphatase that removes the Y15 inhibitory phosphorylation (Zhao et al. 2002; Sørensen et al. 2003). As CHK1 is activated by ATR, ATR thus suppresses CDK1 and CDK2 activity through CHK1-mediated degradation of CDC25A (Sørensen et al. 2004).
Related Knowledge Centers
- Cell Division
- Cytoplasm
- DNA Replication
- Interphase
- S Phase
- Telophase
- Cell Nucleus
- Cytokinesis
- Cell Cycle
- Chromosome