Theoretical Biochemical Mechanisms for Drug Dependence
S.J. Mulé, Henry Brill in Chemical and Biological Aspects of Drug Dependence, 2019
The transmission of the message may be examined experimentally at many levels of integration. Subcellular levels are the cytological and biochemical aspects of the generation of the impulse and its transmission. Cellular levels are the location of the cell structures where transmission of the message from cell to cell occurs. Electrochemical levels include physicochemical aspects of the movement of the electrical impulse through fibers and its dimension. Specific control systems include mechanisms and pathways, such as the autonomic nervous system, which function below the level of consciousness in the regulation of respiration, circulation, digestion, body temperature, etc. Higher levels of integration are the mechanisms and pathways of conscious behavior such as cognition, problem solving, or the use of language. Some behavioral responses are automatic, either genetically endowed or learned responses. Other behavioral responses are not automatic, but are generated through a complex system of reward, punishment mechanisms, etc.
Stem cell biology
Christine Hauskeller, Arne Manzeschke, Anja Pichl in The Matrix of Stem Cell Research, 2019
The concept of differentiation brings further complexities to the notion of a stem cell. The ability to differentiate is not necessarily realized by cell division: an individual cell may differentiate by transforming directly from one ‘cell state’ to another. A cell state, in current parlance, is a pattern of gene expression and molecular interactions that determines a cell’s structural and functional characteristics. So the idea of a cell state is a multi-level concept, linking cell and molecular levels of biological organization (see below). Self-renewal is cell division without a change in cell state. Differentiation is change in cell state, which may or may not be coordinated with cell division. In the former case, one or more offspring cells exhibit a cell state different from that of the parent. Accordingly, scientists often propose the following as a minimal or basic definition of a stem cell: A stem cell is a cell that can divide asymmetrically, so one offspring is a stem cell and the other is a more specialized cell (Figure 8.2).
Bioengineering Aids to Reproductive Medicine
Sujoy K. Guba in Bioengineering in Reproductive Medicine, 2020
Interactions are at all levels of organization of the body. Cellular level interactions are particularly important. The cell membrane has been suggested as a likely site for the radiations to act. Many investigators have looked in to the transport across the erythrocyte membrane. Ion transfer rates are affected. Exposure to 2.45-GHz continuous wave microwave at 6 W/kg (approximate field strength 87 V/m) produces inhibition of sodium/potassium ATPase activity at 25 C. It is hypothesized that the structural elements of the enzyme undergo modification. In vitro studies have also shown effects on other cell functions. Cell type specific inhibitory effects on proliferation of cultured cells exposed to 2.45-GHz microwaves has been seen. The growth of synchronized L60T cells was altered by microwave exposure only during the mitotic (M) and intermitotic (Gl) phases of the cell cycle. Whether these actions have significance relating to the response of gametes of reproduction exposed to microwaves is not clear. But a more chronic irradiation of male germ cells of the mouse does in some cases produce chromosomal aberrations although results from different studies are quite variable.64,65 Comparable well controlled studies for the ovum are not reported.
A simple geometric method for 3D morphology reconstruction of a cell based on two orthogonal phase images
Published in Computer Assisted Surgery, 2019
Yawei Wang, Hao Han, Lei Wang, Jingrong Liao, Bing Xie, Ying Ji, Yuanyuan Xu
A cell is the basic unit of an organism structure. As for individual cell, the morphological characteristic as well as the internal composition, plays a crucial role in its health status, function and activity. Most of cells are colorless and transparent, the traditional optical microscope fails to image them because of the inadequate contrast. Quantitative phase microscopy (QPM) is a solution to this engineering roadblock. Since it used the cellular refractive index (RI) as an endogenous contrast, it is a noninvasive and nondestructive imaging tool. In recent years, various QPM [1–6] techniques have been proposed with high accuracy and high speed. These techniques are mainly applied to the homogeneous cell, since there is a linear relationship between its phase and the axial thickness. However, for a heterogeneous cell, we cannot obtain its morphological information from the phase. Although we combine other technique, such as the confocal one, only the average RI or the physical thickness along the light transmission direction is obtained. Unfortunately, the axis physical thickness distribution of phase object cannot reveal the 3D structure information correctly.
How can we turn the PI3K/AKT/mTOR pathway down? Insights into inhibition and treatment of cancer
Published in Expert Review of Anticancer Therapy, 2021
Said M. Afify, Aung Ko Ko Oo, Ghmkin Hassan, Akimasa Seno, Masaharu Seno
The PI3K/AKT/mTOR signaling pathway is described as abnormally activated and plays a critical role in many types of cancers, such as cervical cancer, breast cancer, glioblastoma, gastric and pancreatic cancer, non-small cell lung cancer (NSCLC), leukemogenesis, and prostate cancer [80–86]. Although numerous studies have clearly indicated the role of this pathway in cancer, its role in CSCs is still unclear. As stem cells participate in constructing normal organs, CSCs organize the tumor tissue. In a normal organ, the apex of cellular hierarchy is the stem cell, which differentiates into progeny cells composing the bulk of an organ. In tumor tissues, the CSC is the master cell that differentiates into different phenotypes exerting heterogeneity in the tumor tissue. CSCs are generally defined as oncogenic cells having self-renewing and differentiation ability [87,88].
SAMHD1: Recurring roles in cell cycle, viral restriction, cancer, and innate immunity
Published in Autoimmunity, 2018
Christopher H. Mauney, Thomas Hollis
Substrate cycling, DNA synthesis and repair, and nucleoside import and export form a dynamic regulatory system that maintains homeostatic dNTP concentrations within the cell. The levels are finely tuned according to the cell type and stage in the cell cycle. Each canonical dNTP is not equally abundant within the cell, however. dGTP is consistently observed to be least prevalent in eukaryotic cells [2,4]. While dNTP concentrations are asymmetric, the proper balance of the dNTP pool is crucial to cell survival and genomic integrity [25]. Imbalanced dNTP pools, resulting from DNA damage, metabolic dysregulation, or mutations to the enzymes involved in maintaining dNTP equilibrium, can result in harmful consequences including: increased mutation rates and the induction of a mutator phenotype; increased DNA damage and activation of the DNA damage response; altered DNA polymerase kinetics, replication stress, and collapsed or stalled replication forks; altered replication origin spacing and usage; modified epigenetic profiles and gene expression; and restricted cell cycle progression [26–39]. These molecular perturbations of genomic fidelity manifest themselves as severe pathologies including mitochondrial depletion syndromes, severe immunodeficiency disorders, induced-cellular senescence, and cancer [40–47]. Imbalanced dNTP pools may also impact apoptosis and inflammation, as dNTPs have been implicated in the activation of both pathways [47–50].