biology zoology blog benno meyer rochow sneeze

The Science behind Sneezing

Have your handkerchief handy

Have you noticed that most of the words related to the “nose” start with the letters ‘n’ and ‘sn’? Apart from nose, nares, nostril, and nasal you’d find snot, snort, sniff, snuff, snore, snooze, snub-nosed and, of course, sneeze. The most common reason advanced for why people (and other animals) sneeze is that the act of sneezing removes an irritant or obstruction in the nasal passage. Suffering from hayfever (my children used to have fun chasing me around in the garden with flowers in their hands) I once counted that I was sneezing forty times in a row  – and that was not at all because of an obstruction in my nasal passages (or looking into the sun, which is said to trigger sneezing in some people). So, what goes on?

The allergic reaction to pollen like the one that made me sneeze is probably one of the commonest reasons of sneezing in humans. But it’s complicated, for it involves an oversensitivity reaction in which substance P (cf., my earlier blog) is increased in the nasal epithelium together with other neuropeptides like, for example, calcitonin (cf. also old blog). These and the release of antibodies and histamine by the body’s immune system to the perceived threat posed by the inhaled pollen, lead to the hypersensitivity reactions (e.g. nose and eye itch). All these in conjunction with neurotrophic factors stemming from the allergy, target neuronal fibres like chemo- and pain receptors and those sensing itch, which then send the information to the trigeminal ganglion. The trigeminal nerve that serves also the cheek and orbital region of the face then instructs the sneezing centre in the brain’s medulla to take action.

Action means that effector neurons should become active. Those involved with breathing make sure that deep inspirations occur prior to the sneeze and that the eyes and the glottis close, before through an increase of the pressure in the lungs the glottis suddenly opens and releases in an explosive action air and fluid droplets through mouth and nose. The pressures involved in a sneeze can be 176 mm Hg, which would be one tenth of the pressure of a tyre of a small car or one third of the pressure penguins generate to poop. During a sneeze thousands of tiny droplets of liquid are released up to a metre and sounds accompanying a sneeze can vary from faint to deafening.

People who own a dog or a cat know that their pets may occasionally sneeze spontaneously or when you tickle their nose or when they smell irritating chemicals. The same holds true for humans and I for one avoid the perfume sections of the department store because the odours there could make me sneeze. The sneezing that accompanies a cold is usually related to a mucus build-up in the nasal passages that the sneeze tries to remove. The Galapagos iguana and some marine birds sneeze to remove salt crystals that have accumulated in the nasal passage and need to be flushed out.  All vertebrate animals with lungs and a connection between the nose and the pharynx (that excludes the fish) are said to have ‘choanae’ (= internal nares) and can sneeze. The nose of a fish consists of two nasal openings for the inflow and two for the outflow of the water. Located between in and outflow nares is the olfactory epithelium with its odour sensitive cells. Thus, looking at the head of a fish you will see 4 nasal openings and not just two as in all terrestrial vertebrates. Sneezing in fish is therefore not possible.

Antarctica is a good place for people with pollen allergies. Although you can get cold there, you are not likely to ‘catch a cold’ there, but on one of my trips to the icy continent my friend and colleague Taka Hariyama sneezed (dust does exist in some areas of Antarctica). He sneezed once and seemed happy, exclaiming joyfully “only once!”. I was puzzled why he stressed “only once”, until I learned that ‘sneezing once’ suggests to a Japanese that someone is saying good things about the ‘sneezer’, but that sneezing twice means the opposite. Yet, what it means to sneeze 40 times in a row I don’t want to know.

© Dr V.B. Meyer-Rochow and, 2021.
Unauthorized use and/or duplication of this material without express and written permission from this site’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to V.B Meyer-Rochow and with appropriate and specific direction to the original content. 

Take some Bile once in a While

It’s versatile, but will it make you smile?

One of my ethnobiological research projects deals with traditional uses of zootherapies. In many parts of the world animals, their tissues or their products are used as medicines in the form of solids, potions, powders and soups to be ingested, as lotions and creams to be applied and even as steams and fumes. One of the most widely used animal-derived treatments involve bile, i.e. the green fluid in the gall bladder of vertebrate animals produced by the liver. Bear bile has been used for perhaps thousands of years by the Chinese as a remedy for a wide range of ailments and bear farms exist in China, where bile is collected from live bears without killing them. Elsewhere, wild animals and not just bears are used.

What makes bile so special? The bioactive compound in bear bile has been identified as ursodeoxycholic acid. But as with biles from other vertebrates such as humans and fish, the fluid consists of mostly water (ca. 98%) plus a variety of bile salts, the pigment bilirubin, small amounts of cholesterol, fatty acids and lecithin. Bile is released from the gall bladder into the small intestine (the duodenum) in humans, where it acts as an emulsifier and surfactant upon the fatty components of the food. Without the bile most of the ingested fats would be wasted and not available to the body for growth and maintenance; the bile therefore has a very important function. Whether it is that understanding or the observation that bile medicines can apparently exert a positive effect on a sufferer from an illness, injury and allergy that have made bile therapies so popular, is difficult to know, but fact is millions believe in bile remedies.

It has been reported that tribal people in Burkina Faso treat earaches with the bile of a hedgehog, but from Brazil it is known that some people purchase the vulture bile, dry it and then turn it into a powder, which is put it into the drink of an alcohol addict to cure his addiction. According to E. Costa-Neto there are reports that this works. Wild cat bile apparently acts upon the liver and helps in cases of cirrhosis, as has also been reported for bear bile. The latter is used for so many different maladies and afflictions that it is difficult to list them all, but just like the bile of many other animals it is supposed to help against malaria, stomach ache, dysentery and even rheumatism. Most commonly bile is mixed with boiling water and drunk, but carp bile may be swallowed raw to lower a fever and porcupine bile soaked in rice to fight dysentery is used by North-East Indian tribals. Naga people use the bile of the mithun ox mixed with rice and eaten twice a day for a week to treat asthma. Cat bile and that of the flying squirrel are also said to have anti-asthma properties and that of a large monitor lizard (taken orally and raw) is meant to work as an antidote to spider bites. Porcupine bile helps in cases of impotence, but enlarged spleens are said to need pangolin bile treatment (but sadly it won’t help this globally most trafficked of all wild animals).

The big question is how one bodily secretion (the bile) can have so many different therapeutic functions and effects.  It is of course possible that pre-treatments like drying, smoking, mixing with rice, herbs or minerals and different kinds of uses like external application or ingestion with or without water at specific day times may liberate and/or activate separate bioactive chemicals in the bile. They could then possibly act directly or indirectly by activating the recipient’s defence systems.  As sad and awful these traditional bile uses are, they seem to have stood the test of time and we must find the reason for that. Once we have the answer, we may be able to save the animals that supply the bile  -and let them live and smile.  

© Dr V.B. Meyer-Rochow and, 2021.
Unauthorized use and/or duplication of this material without express and written permission from this site’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to V.B Meyer-Rochow and with appropriate and specific direction to the original content. 

Blind as a Bat: Certainly Not

And also not bad or beastly   

In the early 1980s in Finland I met a bat researcher who explained to me a device called the bat detector which works by changing the high frequencies of a bat’s cry, inaudible to humans, into audible lower frequencies. That device allows the researcher to look for the bats that s/he then knows are around. Sadly, that very bat researcher died in 1985 after being bitten by a bat that had transmitted the rabies virus to him. This was such a rare and isolated case in Finland that it made headlines and led to a hiatus in Finnish bat research. Despite the fact that bats can indeed harbour loads of viruses and other pathogens (but don’t get sick themselves) and may be pestered by parasitic flies of the families Nycteribiidae and Streblidae (because of the bats’ habit to be colonial, which involves close contact between individuals), they are, generally, of absolutely no danger to humans. Their life is an alien life that can last 40 years, a life in the dark, a quiet and secret life (except that of the thousands of fruit bats in Australia roosting in trees of parks and gardens). However, bats are absolutely fascinating mammals and earlier I already pointed out some of their remarkable reproductive adaptations with suspended pregnancies and (in some species) milk-producing “father bats” helping “mother bats” in parenting.

There are at least 1200 species of bats, which means 20% of all mammals can fly. Their sizes range from that of a bumblebee to that of a small dog but none of them is blind; a fossil Burrowing Bat from New Zealand is estimated to have weighed 40 kg. Their food habits are amazingly varied: some tropical species are important pollinators and visit flowers, others munch leaves or attack fruits; many species feast on insect pests like moths and beetles that fly around at night and some (the fish-eating bats) have even become accomplished piscivores. The notorious vampire bat of Central and South America is the only mammal that depends on blood for its diet, but although that may not be very nice, their habit of sharing a blood meal through a kiss with a colony member that hadn’t been able to find a food source shows an altruistic side. It is well known that bats form friendships with other bats and that bat orphans will be adopted by not even genetically closely related individuals of a colony. Bats are not blind but locate obstacles and food in the dark by echolocation (which I mentioned in an earlier blog).

Scientifically referred to as Chiroptera (from Greek “cheir” = hand and “pteron” = wing), bat wings are the result of a thin membrane between four of their fingers and are thus analogous to bird wings. Being able to fly, bats colonized far away islands like New Zealand, Hawaii and Galapagos, but being nocturnal only a handful species could survive in northern Finland despite the abundance of mosquitoes and other insects in the summer (only daylight in summer nights). The cold and long winters are no problem: many species enter into a state of torpor and hibernate in caves or other sheltered places. To rest and roost, most bats hang upside down, which required special adaptations with regard to their hind extremities, joints, muscles, tendons and circulatory system (a human would die if in an upside-down position for too long). An exception, as Daniel Riskin & Paul Racey could show in 2010, are sucker-foot bats like the Madagascar Myzopoda aurita: it clings head-up to leaves using specialized pads on its wrists and ankles.

I’m not aware of bats other than the large fruit-eating species being consumed as food by humans, but falsely accused of being a symbol of evil in many western societies, people should focus on the charming side of bats and revere them as harbingers of Good Luck and Prosperity as in some parts of China where bats often adorn wedding cards. Actually, in Europe killing a bat can result in hefty fines – that’s a start.

© Dr V.B. Meyer-Rochow and, 2021.
Unauthorized use and/or duplication of this material without express and written permission from this site’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to V.B Meyer-Rochow and with appropriate and specific direction to the original content.