VOA慢速英语2021--科学家对人类早期发育进行了罕见的研究

Scientists Do Rare Study on Early Human Development

Scientists have been able to do a rare study into an important, early stage of human development. They studied an embryo¹ in its third week after fertilization — a moment in time that has previously² been difficult to study.

European researchers looked at one embryo that was 16 to 19 days old. It was donated by a woman who ended her pregnancy³.

Until now, experts said, researchers have not had a full understanding of this stage of development because human embryos⁴ at this level of development are difficult to get. Most women do not yet know they are pregnant at that time. And global rules have until recently forbidden growing human embryos in a lab beyond 14 days.

The study appeared recently online in Nature, a scientific publication. The study looked at "gastrulation," which begins about 14 days after fertilization and lasts a little more than a week. This is when the embryo is still about the size of a small seed.

Shankar Srinivas of the University of Oxford⁵ was the lead researcher on the project.

Srinivas described gastrulation as "a process by which you have this kind of explosion of cell diversity."

Srinivas, who worked with other researchers in the United Kingdom and Germany on the project, added that during gastrulation different cells are formed. These cells, he explained, start to be positioned in different places to form the body and its organs.

For many years, the so-called "14-day rule" on growing embryos in the lab has guided researchers, with some places, including the United Kingdom, writing it into law.

Earlier this year, the International Society for Stem Cell Research recommended easing the rule and allowing researchers to grow embryos past two weeks in some situations and after a tough review process. But the rule remains⁶ law in the UK.

This research was not subject to the law because the embryo was not grown in a lab. But it is an example of the types of things scientists expect to learn more about if rules are eased.

Researchers found different kinds of cells, including red blood cells and other cells that give rise to egg or sperm⁷ cells.

But the researchers did not see neurons, Srinivas said, meaning embryos are not able at this stage to sense their environment.

Oxford University officials said this stage of development has never been fully⁸ mapped out in humans before.

The authors said they hope their work not only gives information about this stage of development, but also helps scientists learn about how to make stem cells into particular types of cells that can be used to help heal damage or disease.

Robin⁹ Lovell-Badge, a stem cell expert at London's Francis Crick Institute who chaired the group behind the guidelines, said being able to culture human embryos beyond 14 days "would be incredibly important to understand not just how we develop normally but how things go wrong."

Dr. Daniel Sulmasy, director of the Kennedy Institute of Ethics¹⁰ at Georgetown University, said "those of us who are morally conservative" always thought the 14-day rule was somewhat arbitrary. Arbitrary is a term that means not planned or chosen for any particular reason. But, Sulmasy added, at least the rule "was some recognition of the humanness of the embryo."

There will be more research on older embryos, he said. "Part of what science does is to always try to go forward and learn things that are new. And that continues to be a pressure. But the mere¹¹ fact that we can do something is not sufficient to say that we ought to do it."

Words in This Story

fertilization – n. the action or process of fertilizing¹² an egg

diversity -- n. the quality or state of having many different forms, types, ideas, etc.

neuron – n. medical: a cell that carries messages between the brain and other parts of the body and that is the basic unit of the nervous system

sufficient – adj. having or providing as much as is needed

ought – modal verb — used to say or suggest what should be done

1 embryo   

n.胚胎，萌芽的事物

参考例句：

• They are engaging in an embryo research.他们正在进行一项胚胎研究。
• The project was barely in embryo.该计划只是个雏形。

2 previously   

adv.以前，先前（地）

参考例句：

• The bicycle tyre blew out at a previously damaged point.自行车胎在以前损坏过的地方又爆开了。
• Let me digress for a moment and explain what had happened previously.让我岔开一会儿，解释原先发生了什么。

3 pregnancy   

n.怀孕，怀孕期

参考例句：

• Early pregnancy is often accompanied by nausea.怀孕早期常有恶心的现象。
• Smoking during pregnancy increases the risk of miscarriage.怀孕期吸烟会增加流产的危险。

4 embryos   

n.晶胚；胚，胚胎( embryo的名词复数 )

参考例句：

• Somatic cells of angiosperms enter a regenerative phase and behave like embryos. 被子植物体细胞进入一个生殖阶段，而且其行为象胚。 来自辞典例句
• Evolution can explain why human embryos look like gilled fishes. 进化论能够解释为什么人类的胚胎看起来象除去了内脏的鱼一样。 来自辞典例句

5 Oxford   

n.牛津（英国城市）

参考例句：

• At present he has become a Professor of Chemistry at Oxford.他现在已是牛津大学的化学教授了。
• This is where the road to Oxford joins the road to London.这是去牛津的路与去伦敦的路的汇合处。

6 remains   

n.剩余物，残留物；遗体，遗迹

参考例句：

• He ate the remains of food hungrily.他狼吞虎咽地吃剩余的食物。
• The remains of the meal were fed to the dog.残羹剩饭喂狗了。

7 sperm   

n.精子，精液

参考例句：

• Only one sperm fertilises an egg.只有一个精子使卵子受精。
• In human reproduction,one female egg is usually fertilized by one sperm.在人体生殖过程中，一个精子使一个卵子受精。

8 fully   

adv.完全地，全部地，彻底地；充分地

参考例句：

• The doctor asked me to breathe in,then to breathe out fully.医生让我先吸气，然后全部呼出。
• They soon became fully integrated into the local community.他们很快就完全融入了当地人的圈子。

9 robin   

n.知更鸟，红襟鸟

参考例句：

• The robin is the messenger of spring.知更鸟是报春的使者。
• We knew spring was coming as we had seen a robin.我们看见了一只知更鸟，知道春天要到了。

10 ethics   

n.伦理学；伦理观，道德标准

参考例句：

• The ethics of his profession don't permit him to do that.他的职业道德不允许他那样做。
• Personal ethics and professional ethics sometimes conflict.个人道德和职业道德有时会相互抵触。

11 mere   

adj.纯粹的；仅仅，只不过

参考例句：

• That is a mere repetition of what you said before.那不过是重复了你以前讲的话。
• It's a mere waste of time waiting any longer.再等下去纯粹是浪费时间。

12 fertilizing   

v.施肥( fertilize的现在分词 )

参考例句：

• Sometimes the preliminary step must be taken of reducing weed population before fertilizing. 有时候，在施肥之前，必须采取减少杂草密度的预备性步骤。 来自辞典例句
• The self fertilizing garden can also be planted in raised beds. 自我施肥的菜园也可以在苗圃床中种植。 来自互联网