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Light blue flag: Why can the flagellum of Sauron cells affect the water balance of organisms?
In biology, Sauron cells are elongated flagellated cells that are common in some low-life organisms, such as flatworms (Phylum Coelozoa) and Toxoheads. These cells play an important role in the excretory system of the host organism. Taking the round-lipped fish (genus name: Branchiostoma) as an example, they use the protonephric ducts of Solon cells for excretion. In addition to their excretory functions, these cells contribute to ion regulation and stabilization of water balance. This makes Sauron cells a subtype of protonephric ducts, often compared to flame cells, another specialized excretory cell. Sauron cells have flagella, whereas flame cells are usually ciliated.
Cell structure and configuration
Solon cells originate from the mesoderm and have various shapes. They contain a cell body and a nucleus, and are connected to the cell body by a long tube. There can be one or two long flagella in the lumen inside the cell. These constantly moving flagella extend from a protein structure called the basal body, which is located at the base of the flagellum structure. The walls are composed of thin, columnar rod-like structures, and these openings may be where interstitial fluid is filtered. Approximately 500 Solon cells can be found in a single renal tubule, each cell is approximately 50 microns in length (including cell body and duct). The excretory organs of the round-lipped fish contain clusters of Sauron cells whose distribution creates a structure similar to the mesothelial cells surrounding human internal organs.
Function and operation mechanism
Functionally, flagella play an important role in the excretory properties of Solon cells. These mobile appendages extend from the Sauron cell membrane and rely on an axoneme, or axon, for support, a basal body, and numerous microtubules. The stability of the flagellum is important for its movement. The basal body consists of nine sets of triple-connected microtubules that functionally anchor the flagella (as altered centrioles). At the center of each flagellum is a highly conserved axon, which contains nine pairs of double sets of microtubules surrounding a pair of single sets of microtubules (forming a 9+2 pattern). Thousands of motility dynamins are anchored to the double set of microtubules in the axon, causing the hydrolysis of adenosine ribonucleic acid (ATP), which supplies flagellum movement.
More specifically, these dynamins attach to a set of pairs within the outer microtubule ring, and as they "walk" to adjacent pairs, the entire flagellar structure is allowed to bend and flap. Collectively, the movement of flagella enables Solon cells to push excretory materials and luminal fluid into the lumen inside the cell. In a variety of lower invertebrates, populations of Sauron cells project directly into the lumen, where they are soaked in luminal fluid. This fluid contains a variety of substances, including salts, proteins, and blood cells. Therefore, Solon cells play an important role in water regulation, ion regulation, and homeostasis. The protonephric ducts of Cynodon also possess small blood vessels that function to absorb the diffusion of nitrogen waste from the luminal fluid and blood.
The significance of the research
In addition to improving our understanding of the excretory organs of other invertebrates, further study of the composition and function of Sauron cells could advance our current knowledge of kidney function, human health, and even certain genetic diseases. The cephalochordate Cynodontidae became an important subject of this study because of its close relationship with vertebrates.
Hacek kidney
In contrast to the paired protonephric ducts, Hatschek's nephridium is a large unpaired excretory structure in Branchiostoma virginiae. The kidney and its collecting duct are located to the left of the notochord, next to the left anterior artery. Hacek's kidney is similar to the protonephric duct, with a curved branch and a large number of Sauron cells. The anterior end of this structure is located just anterior to the Haczek's pit, while the posterior end opens into the endodermal pharynx. Filter cells called arcuate cells occupy the entire length of the collecting duct and are similar in structure and function to Sauron cells.
Kidney function
Research suggests that luminal myoepithelial cells in the round-lipped toothfish may be important for kidney function. These cells are distributed along the cavity and possess thick (18-25 nm in diameter) and thin (5-7 nm in diameter) microfilaments. Microfilaments appear to be more abundant in myoepithelial cells close to Søren cells attached to the luminal surface. The flagella of Solon cells beat in the process of expelling luminal fluid. It is believed that myoepithelial cells close to Solon cells can affect renal function by regulating the flow of fluid.
Human health and genetic diseases
In the evolution of vertebrates, significant genome duplication occurred after the divergence from the cynodont fish. Therefore, the cynodont fish has become an important model for in-depth exploration of the biological mechanisms of vertebrates. The round-lipped toothfish is very useful for research investigating human health and genetic diseases. In addition to signaling pathways, homologs of many vertebrate organs share cellular, developmental, and physiological similarities with their vertebrate counterparts. Based on this, the role of Sauron cells in round-lipped toothfish may provide insights into metabolic diseases such as renal cell carcinoma (RCC).
These biological studies have promoted a deeper understanding of life, making us wonder how much impact these tiny cells can have on the water balance of organisms?
