MSGID: 1:317/3 649e5a6c   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    How the cat nose knows what it's smelling    
    Study reveals function behind complex nasal structure    
      
     Date:   
         June 29, 2023   
     Source:   
         Ohio State University   
     Summary:   
         Scientists have found the secret to felines' finesse at sniffing   
         out food, friends and foes. A complex collection of tightly coiled   
         bony airway structures gets the credit, according to the first   
         detailed analysis of the domestic cat's nasal airway.   
      
      
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   Scientists have found the secret to felines' finesse at sniffing out food,   
   friends and foes.   
      
   A complex collection of tightly coiled bony airway structures gets the   
   credit, according to the first detailed analysis of the domestic cat's   
   nasal airway.   
      
   The researchers created a 3D computer model of the cat nose and simulated   
   how an inhalation of air containing common cat food odors would flow   
   through the coiled structures. They found that the air separates into two   
   flow streams, one that is cleansed and humidified and another delivering   
   the odorant quickly and efficiently to the system responsible for smelling   
   - the olfactory region.   
      
   In essence, the researchers suggest, the cat nose functions as a highly   
   efficient and dual-purposed gas chromatograph - a tool that, in the   
   laboratory, detects and separates chemicals in vaporized form. In fact,   
   the cat nose is so efficient at this that its structure could inspire   
   improvements to the gas chromatographs in use today.   
      
   While the long alligator nose has also been found to mimic gas   
   chromatography, researchers theorize that the compact cat head drove an   
   evolutionary change that resulted in the labyrinthine airway structure   
   that not only fits, but helps cats adapt to diverse environments.   
      
   "It's a good design if you think about it," said Kai Zhao, associate   
   professor of otolaryngology in Ohio State's College of Medicine and   
   senior author of the study.   
      
   "For mammals, olfaction is very important in finding prey, identifying   
   danger, finding food sources and tracking the environment. In fact, a   
   dog can take a sniff and know what has passed through - was it a friend   
   or not?" he said.   
      
   "That's an amazing olfactory system - and I think potentially there have   
   been different ways to evolve to enhance that.   
      
   "By observing these flow patterns and analyzing details of these flows,   
   we think they could be two different flow zones that serve two different   
   purposes."  The research is published today (June 29, 2023) in PLOS   
   Computational Biology.   
      
   Zhao's lab has previously created models of the rat and human nose to   
   study air flow patterns, but the high-resolution cat model and simulation   
   experiments are his most complicated to date, based on micro-CT scans   
   of a cat's head and microscopic-level identification of tissue types   
   throughout the nasal cavity.   
      
   "We spent a lot of time developing the model and more sophisticated   
   analysis to understand the functional benefit that this structure serves,"   
   he said. "The cat nose probably has a similar complexity level as the   
   dog's, and it's more complex than a rodent's - and it begs the question   
   - why was the nose evolved to be so complex?"  Computer simulations   
   of breathing revealed the answer: During a simulated inhalation,   
   researchers observed two distinct regions of air flow - respiratory   
   air that gets filtered and spreads slowly above the roof of the mouth   
   on its way to the lungs, and a separate stream containing odorant that   
   moves rapidly through a central passage directly to the olfactory region   
   toward the back of the nasal cavity. The analysis took into account both   
   the location of flow and the speed of its movement through turbinates,   
   the bony structures inside the nose.   
      
   "We measured how much flow goes through specific ducts - one duct that   
   delivers most odorant chemicals into the olfactory region, versus   
   the rest, and analyzed the two patterns," Zhao said. "For respirant   
   breathing, turbinates branch to divert flow into separate channels, sort   
   of like a radiator grid in a car, which would be better for cleansing   
   and humidifying.   
      
   "But you want odor detection to be very fast, so there is one branch that   
   delivers odor at high speed, potentially allowing for quick detection   
   rather than waiting for air to filter through the respiratory zone -   
   you could lose most of the odor if air has been cleansed and the process   
   is slowed down."  The simulation also showed that the air shuttled to   
   the olfactory region is then recirculated in parallel channels when   
   it gets there. "That was actually a surprise," Zhao said. "It's like   
   you take a sniff, the air is shooting back there and then is being   
   processed for a much longer time."  This study is the first to quantify   
   the difference in gas chromatography between mammals and other species -   
   Zhao and colleagues estimate the cat's nose is more than 100 times more   
   efficient at odor detection than an amphibian-like straight nose in a   
   similarly sized skull - and to come up with a parallel gas chromatography   
   theory: parallel olfactory coils feeding from the high-speed stream to   
   increase the effective length of the flow path while slowing down the   
   local airflow speed, potentially for better odor processing.   
      
   "We know so much about vision and hearing, but not so much about the   
   nose. This work could lead to more understanding of the evolutionary   
   pathways behind different nose structures, and the functional purpose   
   they serve," Zhao said.   
      
   Zhenxing Wu, a postdoctoral scholar in Zhao's lab, is first author of the   
   study. Additional co-authors include Jianbo Jiang and Fritz Lischka of   
   Monell Chemical Senses Center in Philadelphia; Scott McGrane of Waltham   
   Petcare Science Institute in the United Kingdom; and Yael Porat-Mesenco   
   of the University of Pennsylvania.   
      
   This work was partly funded by the National Institutes of Health and   
   Mars Petcare UK.   
      
       * RELATED_TOPICS   
             o Plants_&_Animals   
                   # Cats # Veterinary_Medicine # Animals #   
                   Endangered_Animals   
             o Earth_&_Climate   
                   # Air_Quality # Air_Pollution # Environmental_Science   
                   # Pollution   
       * RELATED_TERMS   
             o Cat o Wild_Cat o Cat_flea o Adenoid o Puma o Cat_intelligence   
             o Trachea o Plant_sexuality   
      
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   Story Source: Materials provided by Ohio_State_University. Original   
   written by Emily Caldwell. Note: Content may be edited for style and   
   length.   
      
      
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   Journal Reference:   
      1. Zhenxing Wu, Jianbo Jiang, Fritz W. Lischka, Scott J. McGrane, Yael   
         Porat-Mesenco, Kai Zhao. Domestic cat nose functions as a highly   
         efficient coiled parallel gas chromatograph. PLOS Computational   
         Biology, 2023; 19 (6): e1011119 DOI: 10.1371/journal.pcbi.1011119   
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   Link to news story:   
   https://www.sciencedaily.com/releases/2023/06/230629193238.htm   
      
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