「我們認為這項工作意義重大，是幹細胞研究領域的一個里程碑，」論文第一作者、美國沙克生物研究中心（Salk Institute for Biological Studies）研究員吳軍說，「這是史無前例的，是實現跨物種囊胚互補潛力的重要第一步，從而幫助研究人類發育、改善研究模型以及生產供移植的人類組織。」
負責這項研究的沙克生物研究中心教授伊斯皮蘇亞（Juan Carlos Izpisua Belmonte）強調，這項工作是「重要第一步」，但距培育可供移植器官的最終目標還有相當遙遠的距離。「現在我們想知道的是『是與否』的問題，即人類細胞能否（對人豬嵌合體）作出貢獻。既然我們得到了『是』的答案，下一個挑戰就是提高效率，引導人類細胞在豬體內形成特定器官。」
1月26日刊發於學術期刊《細胞》（Cell）的論文顯示，美國索爾克生物研究所（Salk Institute for Biological Studies，下稱 SIBS）結合基因編輯技術，將人類幹細胞（Stem Cell）注入體外培育的豬早期胚胎，再將混合胚胎植入代孕母豬子宮內，其後部分胚胎存活時間達3週以上，並成功生成含有人類細胞的器官與組織——心臟、肝臟、神經元（Neuron）等之前體。
而 SIBS 基因表達實驗室研究員、論文第一作者 Jun Wu 指出，此次實驗培育的混合胚胎中，不包含會發育成腦部的細胞，只存有可發育成肌肉與其他器官的細胞。並且聲稱，他們下一步努力的方向，是找到引導人類細胞在豬體內形成特定「人體器官」的方法，進而未來可以嘗試將有需求患者的幹細胞注入豬胚胎，培育出排斥性最低的可移植器官。
雖然皮尤研究中心（Pew Research Center）調查顯示，美國民眾對生物醫學技術持警惕態度，但2016年夏天美國國立衛生研究院（NIH）曾表示，它計劃解除「暫停用聯邦政府撥款資助嵌合體研究」的限制，只要它們通過額外的倫理審查即可。支持者認為，除了可用於器官移植以外，人與動物的嵌合體能以更好的方式推動對人類早期胚胎發育的研究，並能成為新研發藥物的毒性測試平台，將有助於各類疾病的預防與治療。
幹細胞是原始且未特化的細胞，它是未充分分化、具有再生各種組織器官潛在功能的一類細胞。幹細胞存在於所有多細胞組織裏，能經由有絲分裂與分化來分裂成多種的特化細胞，而且可以利用自我更新來提供更多幹細胞。（資料來自維基百科，百科內容以 CC BY-SA 3.0 授權）
妊娠期
妊娠期是指雌性哺乳動物從受精至分娩的這段時間，不同動物的妊娠期存在很大差異。大多數物種妊娠期的長短取決於胎兒出生時的體型，小型動物的妊娠期通常比大型動物短。例如，貓的妊娠期約為58至65天，而大象的妊娠期約為21個月；可是，並非所有物種的妊娠期都取決於胎兒的體型，尤其是那些只在每年食物充足的繁殖期才生產的物種。各種其他因素也可以影響妊娠期的持續時間。對人類而言，男嬰通常比女嬰和多胎妊娠需要更長的妊娠期。種族不同也可能改變妊娠期長短。狗的妊娠期愈長而產仔數愈少。（資料來自維基百科，百科內容以 CC BY-SA 3.0 授權）
People who love their jobs are positively committed to their organizations.
Have you ever thought about why people might become emotionally committed to your organization?
Some people are committed to their jobs because they love what they do, or because their goals align with those of the company. Others might stay because they fear what they could lose if they leave. Still others might stay because they feel obligated to the company, or to their manager.
Clearly, some of these types of commitment can have a negative effect on a person's well-being, self-respect, and job satisfaction. So, how can you avoid this, but still help team members feel committed to your team, or organization, in a positive way?
In this article we'll explore three common types of commitment, and we'll look at how you can make changes to improve team member engagement and loyalty in an effective and positive way.
About the Model
John Meyer and Natalie Allen developed their Three Component Model of Commitment and published it in the 1991 "Human Resource Management Review." The model explains that commitment to an organization is a psychological state, and that it has three distinct components that affect how employees feel about the organization that they work for.
The three components are:
Affection for your job ("affective commitment").
Fear of loss ("continuance commitment").
Sense of obligation to stay ("normative commitment").
You can use this model to increase commitment and engagement in your team, while also helping people to experience a greater feeling of well-being and job satisfaction.
Let's look at each of Meyer and Allen's three types of commitment in greater detail.
Affection for Your Job (Affective Commitment)
Affection for your job occurs when you feel a strong emotional attachment to your organization, and to the work that you do. You'll most likely identify with the organization's goals and values, and you genuinely want to be there.
If you're enjoying your work, you're likely to feel good, and be satisfied with your job. In turn, this increased job satisfaction is likely to add to your feeling of affective commitment.
Fear of Loss (Continuance Commitment)
This type of commitment occurs when you weigh up the pros and cons of leaving your organization. You may feel that you need to stay at your company, because the loss you'd experience by leaving it is greater than the benefit you think you might gain in a new role.
These perceived losses, or "side bets," can be monetary (you'd lose salary and benefits); professional (you might lose seniority or role-related skills that you've spent years acquiring); or social (you'd lose friendships or allies).
The severity of these "losses" often increases with age and experience. You're more likely to experience continuance commitment if you're in an established, successful role, or if you've had several promotions within one organization.
Sense of Obligation to Stay (Normative Commitment)
This type of commitment occurs when you feel a sense of obligation to your organization, even if you're unhappy in your role, or even if you want to pursue better opportunities. You feel that you should stay with your organization, because it's the right thing to do.
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This sense of obligation can stem from several factors. You might feel that you should remain with your organization because it hasinvested money or time in your training. Or perhaps it provided a reward in advance, such as paying for your college tuition.
This obligation can also result from your upbringing. For instance, your family might have stressed that you should stay loyal to your organization.
Note:
These three types of commitment are not mutually exclusive. You can experience all three, or two of the three, in varying degrees.
Applying the Model
By applying the Three Component Model, you can help your team develop greater positive, affective commitment. By doing this, your people are likely to feel an increased commitment to the team and organization, and they'll probably feel more positive and more motivated; and experience greater job satisfaction.
It'simportant to do your best to grow affective commitment, and reduce your team's reliance on continuance and normative commitment, so that you're leading a team of people who feel passionate for their roles.
Team members with only continuance and normative commitment may feel bored and unmotivated, and no leader wants a team with those attitudes! These team members might also block enthusiastic employees, or even lower the morale of the group.
To encourage positive changes, make sure that you're linking people's goals with those of the team or organization, using an approach like Management by Objectives. If appropriate, see whether you can better align your team's roles with their skills and interests, with techniques such as Job Crafting. It'simportant to help people find purpose in their work.
Remember that people are more likely to develop affective commitment if they experience positive emotions at work. Doing what you can to help people flourish is a great way to encourage people to thrive, and to enjoy the work that they're doing. Make sure that you give praise regularly, and create a healthy workplace, so that people are happy and productive.
Managing Continuance and Normative Commitment
In addition to helping people experience greater affective commitment, you can also use the model to carefully manage the amount of continuance and normative commitment that people may feel.
You can reduce the dependency on continuance and normative commitments by being a better leader, by working on your general team management skills, and by thinking carefully about how your actions might influence your team members.
Clearly, it doesn't make sense to try to reduce continuance or normative commitment, however you should try not to rely on it, even if you're unable to achieve affective commitment at first. You should work on ways to ensure that team members become happy and enjoy their work, without making them feel uncomfortable during the process.
Bear in mind, however, that people will likely experience continuance commitment at some point in their careers, because they'll feel that they need to stay in their job to receive pay and benefits. And some people will likely feel a sense of normative commitment if their organization has invested a lot in their training and development, for example. It's nice to have these types of commitment, however, they're a bonus, not something you should seek to create!
Key Points
John Meyer and Natalie Allen developed the Three Component Model of Commitment, and published it in the 1991 "Human Resource Management Review." The model defines the three types of commitment as follows:
Affection for your job (affective commitment).
Fear of loss (continuance commitment).
Sense of obligation to stay (normative commitment).
You can use the model to help your people experience greater affective commitment, while making sure that you don't misuse continuance and normative commitment to keep people tied to your team or organization. Your team will function best, and thrive, if you use your energy to grow affective commitment.
