RSS

Mast Cells and the Timing of Wounds

11 Sep

An interesting article will appear in the October issue of the journal of Forensic Science International. It is titled: Mast cell reactivity at the margin of human skin wounds: An early cell marker of wound survival?

What?

Let me explain.

First of all, this article deals with very sophisticated biochemistry in that they measured the activity of certain esterase enzymes in relation to time after injury. I won’t attempt to explain it, but simply point out that research is ongoing in this distinctly forensic arena. But it does bring up the question of how the ME can judge whether a wound occurred pre-mortem or post-mortem.

This is sometimes one of the most difficult determinations the ME must make and his opinion impacts many things. For example, let’s say two assailants attack a victim. One shoots him three times in the abdomen, the other stabs him in the chest after he falls to the ground. Which injury killed him?

Sometimes it’s obvious from the nature of the wounds and the organs and blood vessels injured by each wound. At other times it’s not so clear. One key determination is whether the victim was dead before the stab wound occurred or not. If so, the second assailant might dodge a murder charge; if not, then the stab would could be the proximate cause of death or could at least be a contributing factor, in which case he could face serious charges.

The ME would analyze the stab wound. If it is clean and without irregular edges he can state that the victim was not wiggling or struggling at the time of the injury and just might have been dead beforehand. Living folks tend to fight back and try to avoid stab wounds and this struggle is often reflected in the character of the wound. Dead people tend to lie still so that the wounds are clean, in and out.

If there is no bruising or bleeding into or from the wound, the ME would know that the heart had stopped and there was no blood flow before the wound occurred. If bleeding occurred, the heart must have been beating and the blood flowing at the time of the injury.

Sometimes this is all he needs, but sometimes this type of evidence isn’t clear.

So, what are mast cells and what do they have to do with this?

Whenever an injury occurs, several types of cells rush the area to begin the healing process. Platelets in the blood arrive and begin to clump together and plug any breech in the blood vessels. This action is the first step in what we call the Clotting Cascade, and without it blood clotting would not occur and even minor injuries could cause lethal bleeding. White blood cells, lymphocytes, and mast cells also appear.

Mast cells contain little packets of chemicals–histamine and certain enzymes–in their cytoplasm–the liquid part of the cell. When an injury occurs the mast cells move in and release these chemicals. When properly stained and viewed under a microscope the cytoplasm of a mast cell is filled with tiny blue granules. These are the chemical packets. As the chemicals are released, the granules disappear, a process known as degranulation. This only happens while we are alive. After death the mast cells do not degranulate.

Mast Cells

Mast Cells: The large blue blobs are the nuclei and the tiny blue dots in the cytoplasm of these cells are the granules.

To determine if a wound was pre- or post-mortem, the ME can excise some tissue from near the wound edges, stain it, and look at it under the microscope. If the mast cells have degranulated he will know that the victim was alive at the time of the injury; if not, he will know just the opposite.

This type of examination is rarely needed, rarely done, and can offer confusing results in some cases, but it is an interesting technique for determining the timing of a victim’s wounds.

 
7 Comments

Posted by on September 11, 2009 in Blood Analysis, Time of Death, Trauma

 

7 responses to “Mast Cells and the Timing of Wounds

  1. Ashley McConnell

    September 11, 2009 at 7:21 pm

    After death the mast cells do not degranulate

    How do you define “death”? Is it brain death, and if so, would mast cells continue to degranulate while the heart is still beating? Can the brain continue function after the heart ceases to beat, and if so for how long? Is the person dead if his heart is destroyed and he’s still alive for a second or two? (I guess this is sort of related to the story of the head that tried to talk after the owner was guillotined!)

    Like

     
    • D.P. Lyle, MD

      September 12, 2009 at 8:49 am

      The definition of death has been and still is controversial. Most often in a hospital setting someone isn’t pronounced dead until the heart stops. Of course there are those situations of brain death where the heart and lungs are fine. This is often the situation with organ donors but these people are not deemed to have died until the heart stops—or is removed for transplant.

      As long as the heart is beating, the blood will flow, and mast cells can arrive on the scene of an injury and then go through their degranulation process.

      The heart can carry on without the brain but the brain can’t without the heart. When the heart stops, the body’s cells no longer receive oxygen and glucose (sugar) and will begin to die almost immediately. Some tissues take longer—like muscles including the heart muscle–while other don’t tolerate a lack of blood flow very well–like the brain. The dogma is that the brain can survive for up to 4 or 5 minutes after the heart stops but this is not an all or nothing deal. Brain damage begins immediately but brain death can take several minutes. Loss of consciousness happens in seconds. again the general dogma is that loss of consciousness after the heart stops takes 4 seconds if the person is standing, 8 if sitting, and 12 if laying down. This is general but more or less accurate. These variable times are simply due to the effects of gravity, which holds more blood in the brain if laying down than if the victim is standing.

      Like

       
  2. Louise Ure

    September 12, 2009 at 9:44 am

    Thanks, Doug. This helps me understand mast cell cancer, too.

    Like

     
  3. Robert S Kish

    June 24, 2010 at 11:08 pm

    What is it considered when the heart stops during an operation?
    12 seconds goes by quickly. How long can it take to start the heart going again?
    How can the brain be tested for harm, because of the heart stopping?
    My wife had 2 operations, at 2 different hospitals, with a total of 3 stoppages.
    She went through a total of 3 seperate operations in a little over 2 and 1/2 yrs.
    At the age of 77 years, she seems to be somewhat of a different person, and did not
    have any blood transfusions, as we are Jehovahs Witnesses. She is home now and
    recouperating. Are the times of the heart stoppage recorded? Please advise asap, also
    can manslauter be condsider in this kind of situation, because of the heart stopping?
    respectfully Bob

    Like

     
    • D.P. Lyle, MD

      June 25, 2010 at 12:49 pm

      Sorry Bob, but for Medico-Legal reasons I never comment on real life situations.

      Like

       
  4. Curious

    October 14, 2010 at 5:51 am

    So there was a case just decided in NC and the irrefutable evidence according to the jury was the timing of a gun shot wound and a shroud that the body forms to protect itself. The doctor’s saw the victim 2 hours after the 911 call and say the would occurred between 4 to 12 hours previously. The doctor’s qualifications were called into question by the defense based on lack of experience and expertise in this particular case but as it turned out the timing was the damming evidence to the defendant who got life without parole. He plans to appeal.

    What type of qualifications do you need to stand up in court? Also how accurate can a Medical Examiner be in their analysis? In this case it was claimed by the defense the wound was self inflicted and the defendant called 911 immediately. The prosecution said it was premeditated and the defendant shot his pregnant wife earlier. The baby died due to premature birth.

    Sad and messy case.

    Like

     
    • D.P. Lyle, MD

      October 14, 2010 at 9:33 am

      Anyone can present to the court. It’s up to the judge. The ME always makes a best guess particularly when estimating the time of death. There is an article on this on my website under the ARTICLES tab.

      Like

       

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

 
%d bloggers like this: