May 16

By using frogs as a pregnancy test, humans may have indirectly destroyed nearly a hundred species of amphibians

0  comments

Beginning in 1993, strange amphibian deaths began to occur across the globe. In fact, since humanity became the “lord” of the Earth, there have been many species facing the risk of extinction, but this amphibian crisis is very strange. A large number of amphibian deaths mainly occur in primary forests or nature reserves far from humans.

Biologists collected dead amphibians from various places and conducted tests for parasites, bacteria, and viruses, but could not find any obvious pathogens from them. Instead, a fungus called chytrid spores was found in the sample’s skin and epidermal tissue. It is this chytrid fungus that has caused a purge in the amphibian world of the uninhabited rainforest of Queensland, Australia – 14 species of rainforest frogs have been severely damaged and some have been destroyed. completely extinct. Worldwide, more than 40% of amphibians are at risk of extinction due to chytrid infection.

Just as we are obsessed with finding the number of patients with infectious diseases today, so are biologists, and they have finally found the clue after years of hard work. This mysterious extinction of amphibians has something to do with human pregnancy trials. But today’s most popular pregnancy test is using a pregnancy test, what does this have to do with amphibians?

Maybe few people pay attention to the development of pregnancy testing methods. For the Chinese, the ancient technique of pregnancy testing described in many literary and cinematic works is that judging whether a person is pregnant or not is taking a pulse. However, the rest of the world is different, since ancient times people have speculated whether a person is pregnant or not by urinalysis, perhaps because the ancients believed that urine and infants seem to Both come from the same place, so during pregnancy, changes from the inside will also change the characteristics of the urine.

The ancient Egyptians 3,500 years ago were the first to discover a urine pregnancy test. Women who could become pregnant were asked to urinate into a bag of wheat and a bag of barley. A few days later, if the wheat sprouts, the woman is said to be carrying a girl and if the barley sprouts, it is said to be pregnant with a boy, and if the barley and wheat do not sprout then The woman is not pregnant. But in fact, there was still no scientific evidence that could prove this at that time.

Common sense, many people think that this metaphysical method has no effect other than spoiling food, however, it is not only passed down from generation to generation, but also spread to Europe, typically countries like Ancient Greece and Rome, in addition to this method is also recorded in a German folk book in 1699.

Ancient Egyptian papyrus documents documenting how to test for pregnancy with urine and eye diseases.

In 1963, a study revived this method and found that the urine of non-pregnant men or women could inhibit the germination of grains, and that of pregnant women did not. vice versa, and the successful germination rate of wheat can reach 70%. And using barley and wheat to judge the sex of a fetus is completely meaningless because it is not accurate.

The ancient Egyptians may have developed this method by accident, but the early European pregnancy test technology was not. In the Middle Ages, Europe also developed a profession that is observing urine, they were called “urine prophets” because they would judge a person’s pregnancy based on the color of urine. Of the woman.

There is also another method with a stronger smell, which is to soak the cloth in the urine of a suspected pregnancy, then dry it and then burn it. that person is pregnant.

In the 1920s, it was discovered that human chorionic gonadotropin (hCG), is a hormone produced by the placenta after the egg has fertilized and implanted. It is present in the blood and urine of pregnant women in high concentrations, so urine and blood hCG levels can be used as a reliable indicator of pregnancy.

Scientists Bernhard Zondek and Selma Aschheim led the way in injecting pregnant women’s urine into animals to test for pregnancy. In mice, it was found that the ovaries of rats changed under the influence of hCG just a few days after being injected with urine, so a new method of animal pregnancy testing was born. historically “AZ test”.

The “A-Z test” completely beat the previous pregnancy test methods with an accuracy rate of up to 98%, but sometimes the accuracy rate also varies due to the use of different animals. Initially to test for pregnancy they will use 5 silk female mice but gradually these mice are replaced by adult female rabbits and the number is also increasing. On average, a normal antenatal clinic can kill 6,000 rabbits per year for this test.

This pregnancy test dominated the market at the time with an outstanding accuracy rate, and women often used the word “dead rabbit” as a slang term to refer to pregnancy. In fact, the rabbit used for the pregnancy test will have to die whether the woman is pregnant or not, because they have to be dissected to see their ovaries and then evaluate. It is this drawback that has made this method gradually turned away.

British zoologist Hogben had his eye on the African clawed frog, Xenopus laevis. In 1930, Hogben experimented with injecting this frog with an extract from the pituitary gland of cows, and suddenly discovered that the frog would ovulate abnormally.

Although the method is similar to previous pregnancy tests on mice and rabbits, Hogben’s discovery demonstrates that mammalian hormones can also work in amphibians and respond ovulation will occur after they are exposed to hCG which is quicker, easier to observe, and more importantly, without having to kill them.

So Hogben briefly mentioned this idea in his study report, and brought a group of Xenopus frogs to the UK to study actual pregnancy testing methods. After many experiments, Hogben discovered that when in the wild, Xenopus frogs only lay eggs after mating and there are no spontaneous eggs. But the urine of pregnant women injected under the skin of the frog Xenopus after 6-12 hours will stimulate it to reproduce, so this method has a very high accuracy rate and a shorter waiting time than the previous method. there.

In addition to this method is reusable, a Xenopus frog can live up to 10 years in captivity so it has quickly become a new generation of pregnancy testing tools.

From the late 1930s to the 1960s, thousands of Xenopus laevis frogs were immersed in an infinite cycle of ovulation to devote themselves to the problem of human family planning. But over time, a more advanced method of chemical detection of hCG was born and saved the frog. The method uses specific binding of hCG antibodies.

First attach hCG to the surface of sheep blood cells, then use animals to generate hCG antibodies. These two substances are mixed with urine and wait for change. If the urine contains a large amount of hCG, the hCG antibody will preferentially bind to it and the sheep blood does not change, whereas if the urine hCG content is very low, the antibody will bind to hCG on the cell surface. sheep blood and induce coagulation.

The method is really complicated, has 10 steps, and the test tube needs to be isolated from vibration for 2 hours. Over time, pregnancy tests were also born and this method is still used today.

In fact, modern pregnancy testing technology has given humans more options in reproduction, but it has made the reproduction process of amphibians difficult. This new technology doesn’t really save the Xenopus frogs. Due to their widespread use in pregnancy tests, large numbers of wild Xenopus frogs are captured and sold from southern Africa to all over the world.

Scientists tracked down the chytrid fungus that has caused a large number of deaths in amphibians. The earliest specimens come from the species Xenopus laevis captured and traded in the 1930s. In other words, it was the global human trade with the Xenopus frog that caused the spread of the chytrid fungus. So why did the chytrid fungus carried by Xenopus laevis in the 1930s wait half a century to be discovered?

In fact, this is a similar story to smallpox and the Indians. Frog Xenopus laevis is a natural host of chytrid fungi, due to its long life with chytrid fungi, it has certain resistance. The chytrid fungus can only attach to the outermost layer of the epidermis in Xenopus frogs and can complete its entire reproduction process without harm.

But for amphibians outside the African continent, they are not naturally resistant to chytrid fungi, so the potential for chytrid mortality to these species is great. It not only adheres to the outermost layer of the epidermis, but also spreads to deeper skin tissues. The sporangia of this fungus rapidly grow and migrate to the surface as the host epithelial cells differentiate and shed to release new free spores.

Current research suggests that chytrid infection disrupts the ability of amphibians to regulate electrolyte balance, leading to a significant decrease in potassium and sodium levels in the body, which in turn affects the blood supply system. and eventually lead to cardiac arrest. Studies have shown that chytrid fungi can infect at least 695 species of amphibians, including frogs, toads and newts.

Although he was aware of the seriousness of the problem, at this point it was too late. Between 2004 and 2008, a field observation site in Panama estimated that 41% of local amphibians had disappeared because of chytrid fungi. Between 2009 and 2012, chytrid fungi killed 99% of Dutch fire salamanders.

What’s more cruel is that we currently have no choice but to strictly control the cross-border amphibian trade, as research on the chytrid fungus is still so scant, and there is no viable treatment. for wild species.


Tags

pregnancy test


You may also like

What if we spread solar cells to fill the Sahara?

Get in touch

Name*
Email*
Message
0 of 350