Myocardial Communication at its Best!

Myocardial cells communicate using autocrine factors, cell to cell propagation of depolarization fronts, gap junctions and adhesion complexes. The autocrine communications involved an abundant array of secretions from leptin, FGF and TGFβ family members, midkine, hepatocyte growth factor, endothelin-1, and stromal cell–derived factor 1α, which causes the myocardial cell communications.

Adhesion complexes engage in cell to cell communication with intracellular signaling that are activated by cell to cell or cell to matrix action of specific protein in the complexes. This signal results in in the myocardial reactions to growth being changed to control cardiac development and hypertrophy.

Capture

Intercalated discs are made up of two types of cell junctions: desmosomes and gap junctions. Desmosomes comprises of strong protein fibers that are very tough and securely connects the myocardial cells together. This is a significant characteristic because of the continuous pumping of the heart results in an immense amount of pressure for the networks between the cells. Myocardial cells are stimulated to create electric current that can instigate and transmit action potentials. The transmission of action potential from one myocardial cell to another myocardial cell follows the transfer of sodium ions across the gap junction or can be referred to as an electric synapse.  Gap junctions connect the cytoplasm of a cell to bordering cells by small linking tubes called connexins, which allows miniature molecules and ions to easily move from one myocardial cell to another. Myocardial cells are branched and joined with other myocardial cells hence together with the gap junctions at the intercalated discs, an high intensity of correlations between the myocardial cells are produced. The myocardial cells linked to the gap junctions are all together known as a myocardium which functions as one. The entire myocardium contracts together when it is stimulated.

myocardial cell

“Cell Communications in the Heart .” Circulation . Accessed October 18, 2013.http://circ.ahajournals.org/content/122/9/928.full#sec-1

A myocardium is made up of two ventricles and another myocardium is from by two atria. The ventricles and the atria are dived by non-conducting fibrous skeleton. The simultaneous contraction of the myocardial cells which comprises the myocardium is essential to generate the force vital to allow pumping of blood.

References:

“Cell Communications in the Heart .” Circulation . Accessed October 18, 2013.http://circ.ahajournals.org/content/122/9/928.full#sec-1

Poon, Kar Lai , and Thomas Brand. “The zebrafish model system in cardiovascular research: A tiny fish with mighty prospects.” Global Cardiology Science & Practice 4 (2013).Accessed October 14, 2013 http://dx.doi.org/ 10.5339/gcsp.2013.4 .

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Affairs of the Heart

I have chosen to reside in the heart of the zebrafish as a myocardial cell. I was born from a stem cell which added a special touch (specialization of cells). Stem cells are non-specialized cell that undergo complex processes, both during embryonic and adult life. Mitosis causes the segregation of cells followed by the specialization of the cells, i.e. the cells get assigned functional roles in the zebrafish.  

The heart is a vital organ in any organism as it works in a transport system, where blood is carried throughout the body providing oxygen and sustenance to other cells of the body as well as ridding the body of waste products such as carbon dioxide. The heart is the first organ to function during the embryo development.

Heart muscle cells (shown in green), regress to a more youthful state after injury, start dividing again (indicated by a red marker) to replenish lost cells and then mature a second time into cardiomyocytes.

Structure of myocardial cell in the zebrafish

I have one oval/circular shaped nucleus which is responsible for the controlling my every action, such as reproduction, metabolism and growth. Therefore you can say the nucleus is like my brain. I also have DNA which allows my offspring to function exactly like me. My nucleus is well protected as it is membrane bound, just as the brain is protected by the skull.

I also have lots of energy to perform all my duties, the contracting and relaxing is quite exhausting you know. And I would like to thank the mitochondria in me that provide me with lots of ATP that get me through this active life. This to, is well protected as it is membrane bound.

I have myofibrils which is just contractile protein fibers that are elongated and in abundance. Honestly I just think they are to make me look buffJ. Unlike my other organelles the myofibrils are not membrane bound.

I don’t have much organelles, you know, because of my duty, which just requires lots of energy. But a very cool thing is I can aid in the regeneration of the heart organ (I would tell u more about this a next time).

My main purpose in life is to work alongside my brothers and sisters (other myocardial cells) that make up the cardiac muscle. Together we are responsible for the heartbeat of the zebrafish and the functioning of the cardiovascular system.

Reference:

http://cardiovascres.oxfordjournals.org/content/early/2011/05/19/cvr.cvr098.full.pdf

http://www.alnmag.com/news/2013/07/atrium-cells-regenerate-ventricle-zebrafish-hearts

http://www.salk.edu/news/pressrelease_details.php?press_id=412

http://www.salk.edu/news/pressrelease_details.php?press_id=412

Zebrafish heart

 

I choose you!

An Adult Zebrafish

Danio rerio is a petite, fresh water fish commonly known as the zebrafish. The zebrafish gets its name from the stripes that run along the length of its body and fins and the adult fish is usually no more than 5cm long. This fish lives in rivers of northern India, Pakistan, northern Pakistan, Nepal, and Bhutan in South Asia.

The zebrafish is an idyllic model organism because of:

  • The petite size.

  • The short period of time required for reproduction.

  • The large number of offsprings.

  • Easy sustenance under laboratory conditions.

  • The translucence nature of the embryos.

 

The mutations that hamper the development of the embryo have been sequestered in the fish and will assist in interpreting the genetic control system in humans.

Reference:

The Zebrafish Model Organism Database.” ZFIN. Accessed September 25, 2013zfin.org/.