He said animals show some signs of distress, such as a hunched posture, inactivity and holding out injured limbs.
"If it's considered painful in a person, you extrapolate that it's as painful -- well, maybe not as painful, but painful for an animal," Bellinger said.
When investigators apply to conduct research on animal subjects, they must detail the amount of pain that will be caused and why it is necessary.
"Ultimately, if there's going to be pain, there has to be a mechanism to alleviate that pain," said Tony Waldrop, vice chancellor for research and graduate studies. "If the pain is not alleviated, there has to be a strong scientific justification."
Kwock said the IACUC is charged with examining the risks to an individual animal versus the benefit of the study.
"We're always faced with the dilemma of deciding whether we would give a little more pain or distress to one animal versus sacrificing another animal," Kwock said. "It's a gray area that we look at, and, in some cases, we have allowed more pain and distress than the guide recommends."
Kwock stressed that it takes the viewpoint of both medical and non-medical observers to accurately assess the ethics of any situation. The IACUC includes University faculty and staff, local scientists not associated with the University and non-scientist community members.
For example, Kwock said that although every incident in the PETA video might seem alarming and inhumane to viewers off the street, it includes examples of both justifiable and excessive behavior.
He said the scene in the video that shows a researcher cutting off a mouse's head slowly with scissors is inhumane, as is a scene in which a researcher describes euthanizing baby mice without following protocol.
In contrast, however, he said the scene that shows a researcher inducing a seizure in a rat is unpleasant to watch but was medically necessary for the purposes of a study on temporal-lobe epilepsy.
"In order to see if it works, you have to induce seizures," Kwock said. "When you see it, it's horrible, but if you look at it relative to human disease, you've got to mimic the human disease, or it's no good."
But some groups have advocated the total elimination of animal testing.
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John McArdle, executive director of the Alternatives Research and Development Foundation, said those who object to animal testing argue that the research is immoral or a poor model.
He said the most persuasive arguments are usually based on anatomical and physical differences between animals and humans. "As time accumulated, we found out animals are not such good models -- they are not mini-humans."
He cited studies done with four-footed animals -- like pigs and baboons -- that could not accurately predict the response of a human bipedal body as examples of how animal research could not be generalized to humans.
But Kwock said there are certain benefits that can be gained from research on living subjects that non-living alternatives cannot provide.
"I agree with the PETA folks that what works in an animal doesn't always work in a human, but we need to understand why," Kwock said. "It is different in a tube than being in an animal with all the metabolic controls."
Although ethical issues are different with human subjects, the same types of judgment calls must be made.
Daniel Nelson, director of UNC's Office of Human Research Studies, said institutional review boards on campus, which are responsible for evaluating and monitoring the legitimacy of a given protocol with human subjects, constantly weigh the risks and benefits to a subject.
"We try to ensure the risk is very low," Nelson said. "If someone is sick with a deadly disease, we would be willing to risk more than (with) healthy undergraduates."
Nelson said ethical conflicts also arise based on the amount of the drug administered in pharmaceutical trials. Although lower levels of a drug given to a patient with a certain disease might put the patient at lower risk of an adverse reaction, he said low doses also have less chance of curing that patient.
"No drug comes without some risk -- even aspirin can make you sick or kill you," Nelson said.
He said it is crucial to make sure subjects understand that although the research might serve a greater good, it likely will not help the subject himself.
"It becomes a difficult thing for the (institutional review boards) and investigators to lay things out in such a way that the patient understands it's not just for their benefit," Nelson said. "You don't want to hurt the person right in front of you, but the goal is to help people into the future."
Stephen Bernard, chairman of the Committee on the Protection of Rights of Human Subjects, said IRBs on campus also are concerned with the way subjects are chosen for an experiment.
He said debate often arises over the use of potentially sensitive research subjects such as pregnant women, children or prisoners. "We look at studies that involve those vulnerable populations even more critically than those with the average man on the street," Bernard said.
Additionally, Bernard said the IRB is interested in ensuring that subjects are not coerced into participation. He said that when doctors recruit patients for a study, the line is easily blurred between giving patients an option and making them feel obligated to participate.
Nelson said the IRB uses three criteria to determine whether the treatment and recruitment of human subjects is fair: respect for persons, which he described as "the notion we treat each individual as an autonomous decision-making individual and respect their choices;" beneficence, or the ability to help rather than harm a subject; and justice, or fair distribution of the gains and prices of research.
The first criterion also applies to the issue of confidentiality, which Bernard said has become increasingly important.
Bernard said that with the advent of genetic testing, it has become harder to protect the identity of patients as researchers attempt to study hereditary genetic diseases and similar topics that require knowledge of a subject's lineage.
He also said tests involving sensitive lines of questioning, such as those about a subject's drug or alcohol practices, might raise issues of confidentiality.
Although a number of federal guidelines are present to help the IACUC and IRBs resolve these issues, the decision must be made on a case-by-case basis.
Despite the difficulties of resolving ethical issues and the mistakes that Kwock and Nelson said have been made occasionally because of the subjective process, officials said ethics are always on the mind of research review boards on campus.
"Where it crosses over into unethical is not an area we want to go into," Waldrop said. "There are a number of groups that set the standards -- we feel we have to live up to those standards, and my position is that we should go beyond them."
The University Editor can be reached at udesk@unc.edu.
