麥千葉

Nearly one in five people who have had COVID-19 in the United States continue to suffer from symptoms of long COVID. But why some people recover completely while others remain sick has been a mystery. Now research has provided some interesting clues.

A new study shows that bits of virus that survive in the gut（腸道） cause chronic inflammation， which reduces production of serotonin — a molecule critical for communication between nerve cells in the gut and brain. The authors of the new article suggest that waste of serotonin disrupts gut-to-brain communication， which can cause long-term neurological（神經(jīng)系統(tǒng)的） symptoms such as “brain fog” and impaired memory.

The brain and the gut talk to each other. In fact， the gastrointestinal（胃腸的） nervous system with its own 500 million neurons is so large， it is sometimes called the “second brain.”

About 95 percent of the serotonin is produced in the gut， although the brain makes its own supply. Microbes that live in our gut also produce chemical neurotransmitters， including serotonin. While serotonin produced in the gut does not directly reach the brain， it can influence the brain via neuronal circuits through vagus nerve.

“Thats why when youre feeling stressed， you can get abdominal pain or diarrhea，” says Kenji Hashimoto， a neuroscientist at Chiba University in Japan.

This may explain how “l(fā)ong COVID might be linked through a pathway that originates in the gut and leads to serotonin reduction，” says Christoph Thaiss， a microbiologist at the University of Pennsylvania， who led the study.

“These are very important findings that help explain why serotonin levels remain low in certain long COVID patients following SARS-CoV-2 infection，” says Liam OMahony， an immunologist at APC Microbiome Ireland， University College Cork， who was not involved in Thaiss work.

（材料來(lái)自National Geographic網(wǎng)站，有刪改）

1. According to the text， what makes some people suffer from long COVID？

A. The production of serotonin in the gut.

B. The production of serotonin in the brain.

C. The reduction of serotonin in the gut.

D. The reduction of serotonin in the brain.

2. What does the underlined word “impaired” in Paragraph 2 refer to？

A. Self-healed. B. Damaged.

C. Renewed.D. Strengthened.

3. According to Hashimoto， you can suffer from? under pressure.

A. abnormal painB. cell loss

C. toothacheD. diarrhea

4. Whats the attitude of experts mentioned in the text toward the new study？

A. Supportive. B. Disapproved.

C. Indifferent. D. Neutral.

1. C。解析：細(xì)節(jié)理解題。材料第二段中提到“在腸道中存活的少量病毒會(huì)導(dǎo)致慢性炎癥，從而減少血清素的產(chǎn)生——血清素是一種對(duì)腸道和大腦神經(jīng)細(xì)胞之間的交流至關(guān)重要的分子，血清素的消耗會(huì)破壞腸道與大腦的交流，從而導(dǎo)致長(zhǎng)期的神經(jīng)系統(tǒng)癥狀”。C項(xiàng)“腸道中血清素的減少”與原文相符，故選C。

2. B。解析：詞義猜測(cè)題。材料第二段的第二句提到“血清素的消耗會(huì)破壞腸道與大腦的交流，從而導(dǎo)致長(zhǎng)期的神經(jīng)系統(tǒng)癥狀，如‘腦霧和記憶受損”。B項(xiàng)“被損壞的”與文意更為契合，故選B。

3. D。解析：細(xì)節(jié)理解題。材料第五段提到“這就是為什么當(dāng)你感覺(jué)到壓力時(shí)，你可能會(huì)腹痛或腹瀉”，A項(xiàng)“反常的疼痛”與原文中的“腹痛”不符，B項(xiàng)“細(xì)胞消亡”和C項(xiàng)“牙痛”在原文中未有提及。D項(xiàng)“腹瀉”與原文相符，故選D。

4. A。解析：推理判斷題。綜合材料最后三段的內(nèi)容——“這就是為什么當(dāng)你感覺(jué)到壓力時(shí)，你可能會(huì)腹痛或腹瀉”“這也許解釋了為什么‘長(zhǎng)新冠可能與一種通過(guò)起源于腸道并導(dǎo)致血清素減少的途徑相關(guān)聯(lián)”“這些非常重要的發(fā)現(xiàn)有助于解釋為什么某些長(zhǎng)期感染新型冠狀病毒的患者血清素水平仍然很低”，我們可知三個(gè)專家對(duì)這項(xiàng)新研究都持贊同的態(tài)度。故選A。