Introduction to Cells, DNA, and Viruses
Patricia G. Melloy in Viruses and Society, 2023
Before learning about viruses, it is useful to understand what they infect: our cells. It has been known for quite some time that our bodies are made of cells. Going back to the early 1800s, Matthias Schleiden and Theodor Schwann determined that all animals and plants are made of cells. Cells are defined philosophically as being the fundamental units of life and are distinctive for being able to reproduce themselves to make other cells. All these ideas (animals and plants are made of cells, cells are the fundamental units of life, cells give rise to other cells) put together became what is now called the cell theory (Alberts et al. 2019). From the point of view of chemical content, one can also define cells as containing many macromolecules needed for the processes of life, protected by the cell membrane. Although our cells are mostly made of water, the key macromolecules present are critical for cellular function, including nucleic acids, carbohydrates, proteins, and lipids. DNA and ribonucleic acids (RNA) are nucleic acids, made of building blocks called nucleotides. Proteins are made of amino acids. Carbohydrates are made of sugar subunits. Lipids, also known as fats, are made of fatty acids and glycerol. See Table 1.1 for key definitions.
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Anton Sebastian in A Dictionary of the History of Medicine, 2018
Schwann, Theodor (1810–1882) German physiologist who is famous for his classic cell theory (1839). He was born in Neuss and graduated in medicine from Berlin in 1834. He described the neurilemma (sheath of Schwann) in 1839. The striped muscle in the upper part of the esophagus is named after him. He moved to Belgium and was professor of anatomy and physiology at Louvrain in 1838 and Liège in 1848. He showed that air is necessary for development of the embryo, that putrefaction is produced by living bodies and cannot occur in sterile broth, and discovered the organic nature of fermentation in yeast. He isolated pepsin during his work with Johannes Müller (1801–1858) in 1835, and demonstrated that bile is essential to digestion. He proved that the tension of muscle contraction varies with its length.
The Nature and Cause of Cancer: Historical Overview
Jeremy R. Jass in Understanding Pathology, 2020
Theodor Schwann (1810–1882) established the universal cell theory in 1839: the cell unit comprised a nucleus and surrounding cell sap enclosed by a wall. The cell sap was found to be contractile and glutinous, and was described as protoplasm (now known as cytoplasm) by Jan Purkinje (1787–1869). It was originally held that cells formed like crystals but in a biological medium called ‘cytoblastema’. Microscopic techniques aided the recognition of replication of cells by division into two identical ‘daughter’ cells a number of years later. Walther Flemming (1843–1905) recognised the separation of chromosomes during cell division, introducing the term ‘mitosis’ to describe this process. Rudolf Virchow (1821–1902) was the first to appreciate that cancer was a disease of cells that grew through the process of cell division, but believed that cancers arose from ‘embryonic’ or primitive cells scattered throughout the connective tissue of the body. It was Wilhelm Waldeyer (1837–1921) who argued for the origin of cancers from the tissues with which they were associated, cancers of skin arising from the epithelium of the skin itself and cancers of the epithelium lining hollow organs arising from the same.
Microscopic anatomy of sensory receptors
Published in Journal of the History of the Neurosciences, 2019
The microscopic world was transformed by the introduction of powerful achromatic instruments in the 1830s, and rapid advances were made thereafter (Finger, 1994; Harris, 1999; Schickore, 2001, 2007). Among those who combined the achromatic microscope with remarkable observational skills was Jan Purkinje (or Purkyně; 1787–1869; 1837; see Figure 1). In 1832, Purkinje obtained an achromatic microscope manufactured by Simon Plössl (1794–1868) in Vienna (Chvátal, 2017) and directed it at the large cells in the cerebellum, thereby identifying the cells that bear his name. His microscopic observations were made before any adequate staining methods had been developed. Purkinje used alcohol to fix his preparations, and he made thin sections so they could be examined microscopically. Purkinje’s laboratory at Breslau (present-day Wroclaw) has been described as the cradle of histology, and it was matched only by that in Berlin (Otis, 2007), established by Johannes Müller (1801–1858). Cell theory was most clearly articulated by Matthias Schleiden (1804–1881; 1838) for plants and Theodor Schwann (1810–1882; 1839) for animals, and it is associated with their names. At the end of the century, Wilhelm von Waldeyer (1836–1921; 1891) extended the doctrine to nerves. He named the nerve cell body, its fibers, and arborizations as a “neurone” and supported the doctrine that neurons were the fundamental structural and functional units of the nervous system (see Shepherd, 1991).
Neuroanniversary 2021
Published in Journal of the History of the Neurosciences, 2021
Rudolf Ludwig Carl Virchow (1821–1902; see Figure 2) was a German physician, anthropologist, pathologist, prehistorian, biologist, writer, editor, and politician. Known as the father of modern pathology, he studied medicine at the Friedrich-Wilhelms Institute under Johannes Peter Müller (1801–1858) and worked at the Charité hospital under Robert Froriep (1804–1861), whom he succeeded as prosector. A prolific writer, his scientific writings alone exceeded 2000 publications. Cellular Pathology (1858), regarded as the root of modern pathology, introduced the third dictum in cell theory: Omnis cellula e cellula [All cells come from cells]. Virchow was the first to describe and name diseases such as leukemia, chordoma, ochronosis, embolism, and thrombosis. He coined biological terms such as chromatin, neuroglia, agenesis, parenchyma, osteoid, amyloid degeneration, and spina bifida; terms such as Virchow’s node, Virchow–Robin spaces, Virchow–Seckel syndrome, and Virchow’s triad are named after him.
Female infertility caused by organophosphates: an insight into the latest biochemical and histomorphological findings
Published in Toxin Reviews, 2023
Mohammad Samare-Najaf, Ali Samareh, Bahia Namavar Jahromi, Navid Jamali, Sina Vakili, Majid Mohsenizadeh, Cain C. T. Clark, Ali Abbasi, Nastaran Khajehyar
According to the two-cell theory, the biosynthesis of ovarian E2 requires both theca and granulosa cells (Voutilainen et al.1986). In this regard, it has been documented that theca cells are responsible for the biosynthesis of androstenedione from cholesterol which is stimulated by LH. The produced androstenedione, in the next step, will be transported to granulosa cells, converted to estrone, and under the stimulation of FSH, will be converted to E2 (Doshi and Agarwal 2013). Therefore, any dysfunction of these two cells, or irregular secretion of regulatory hormones, will be accompanied by a lack of E2 production and expectable consequences. Importantly, previous studies have revealed that OPs can cause an oxidative imbalance in both cells, as well as impair the secretion of LH and FSH, hence disrupting the biosynthesis of sex steroids, which, in turn, results in fertility disorders.
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