Endocrine Cell Signaling

This part of the blogging experience will delve into the topic of endocrine cell signaling in Xenopus Laevis, which is also known as long-distance cell signaling.

Endocrine cell signaling is seen in complex, multicellular organisms where long-distance communication is completely necessary in order to control the organisms’ behaviour. This type of cell signaling is dependent on blood flow and diffusion. The cells involved in this type of signaling secrete signaling molecules which are hormones that are responsible for taking the signal to target cells which are distributed throughout the organisms’ body. These target cells have receptors on them that allow for the hormones to bind on them. Along with nerve cells, endocrine cells work to facilitate the activities of the many cells of the organism.

A “hit” will be performed with mesenchymal stem cells from cardiomyocyte cells that were previously discussed. The communication between these is also an example of endocrine cell signaling. The interaction between these cells occurs during the occurrence of cardiac diseases for the restoration of cardiomyocyte cells that were lost (regeneration of cardiac tissue). It is important here to note that the Xenopus Laevis is an excellent model organism for the study of cardiac diseases. Communication is facilitated by nanotubules or filipodium of cardiomyocyte origin. The nanotubles posess actin and microtubules that allow for cellular components such as hormones to be transmitted.

The second “hit” will be with myoblasts, skeletal myoblasts specifically. Myoblasts secrete relaxins which are protein hormones. These protein hormones allow for immature cardiac cells to be regenerated in order for cardiac tissue to be repaired. It was found that myoblasts lead to the acceleration and enhancement of the formation of cardiac cells. These myoblasts are also essential in the restoration of cardiac tissue when there are cardiac diseases (end result of myoblast and cardiomyocyte communication). Myoblasts also guide the elongation of nanotubules, allowing for greater communication.

References:

http://cat.inist.fr/?aModele=afficheN&cpsidt=21729560

http://cardiovascres.oxfordjournals.org/content/92/1/39.full

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0056554

Cell to Cell Communication in the Xenopus Laevis :)

Cardiomyocytes are Y-shaped cells found in tissues of cardiac muscle in the heart of Xenopus Laevis, specifically by the atria and ventricle. There, they are found in interlacing bundles. They are relatively smooth and rectangular, being approximately 0.1 mm long and 0.02 mm wide.  Cardiomyocytes are known to consist of microfibrils, many mitochondria but only one nucleus. These components assist in the ability of the cells to be resistant to fatigue. The mitochondria provide the energy needed for muscle contraction to occur.

Cardiomyocytes interact with each other via autocrine cell to cell communication.

In autocrine cell signaling, the cardiomyocyte cell communicates with other cells of the same type by the secretion of signaling molecules, which have the ability to bind to the receptors on that same cardiomyocyte cell. As a result of this, autocrine cell signaling is considered the best at allowing for signaling between cells of the same type.

Some of the signaling molecules utilized in autocrine cell signaling are eicosanoids which are derivatives of fatty acids. They play a major role in muscle contraction of smooth muscle. Gap junctions also assist in the facilitation of cell signals between the cardiomyocyte cells. They allow for the formation of thin channels that are filled with water, which would connect the cytoplasms of the neighbouring cardiomyocytes. Thus, there can be the free flow of small signaling molecules in that region. Proteins at the gap junction, called Connexins play an ever crucial role, as the channels they form possess conductance properties.

These factors come together to impact impulse conduction and the morphogenesis (shaping) of the heart.

The Cardiomyocytes undergo critical interactions with Fibroblasts. These interactions prove necessary for the survival of the tissue in response to external stimuli. This is necessary for the maintenance of the heart and survival of Xenopus Laevis.

It can be said that Fibroblasts mediate Cardiomyocytes’ phenotypes by paracrine hormonal pathways due to particular proteins binding to surface receptors, located on the cell membrane, which produce a cascade reaction. The signaling molecules secreted by the cell function as local mediators and only cells in the immediate environment are affected.

Fibroblasts release various proteins, known as inhibitory or growth factors, which aid in the cardiomyocytes’ development.  The table below indicates a few of the factors and their role with respect to cardiomyoytes.

Factor	Purpose
TGFβ	Facilitates ventricular response to pressure overload
FGF2	Promote differentiation of embryonic stem cells to cardiomyocytes
IL-33	Promotes reduction of hypertrophy and cardiac fibrosis

Therefore, one may deduce that Cardiomyocytes are dependent on Fibroblast, in order to help them perform efficiently and maintain their longevity.

Xenopus laevis (African clawed frog)

…And the blogging begins again!!…This time it is for Cell and Developmental Biology, a lovely course I am doing in my second year, first semester….Enjoy!!!

This is your life! I am a radial glial cell!

We begin by looking at what is called a model organism. Model organisms are species that are not human and have been studied extensively so that biological processes can be understood. It is expected from the study of the species, that more knowledge will be gained as to how other organisms carry out their functions.

Model organisms are useful in scientific research and teaching because they are simplified systems, that can be easily worked with. Thus, characteristics such as small adult sizes and how readily available the species is, are very common characteristics that are looked for.

Throughout the study of model organisms, the student can efficiently learn new theories from a variety of subject disciplines. While working in the laboratory, it is possible to see how the organism behaves in a particular environment. Additionally,hands-on learning allows for an explanation of scientific methods.

This is your life! I am a radial glial cell!

I am a  radial glial cell, found in the ectodermal tissue of the brain of Xenopus Laevis, specifically in its right tectal lobe. 🙂

I originate from neuroepithelial cells that line the ventricles around the time of the formation of neurons. Through a series of functional and structural changes, which included the formation of “glial” features, I was able to transition into a radial glial cell.

My purpose in the Xenopus Laevis is one of great importance. I serve as a neural progenitor in the developing optic tectum. Being a neural progenitor simply means that I differentiate later into an even more special type of cell than I already am in the nervous system of the Xenopus laevis. Also, I am known to be able to enclose synaptic terminals in the cerebellum and hippocampus, where I take part in several different functions such as spine maturation and synapse plasticity and formation.

When I get older, I am going to become a neurone. That is my fate! This means that I am going to become a cell that can be excited electrically and transmit nerve impulses.

I am made up of radial glial fibres that end with pial endfeet ( large nerve fibres that are in contact with cell bodies of other nerve cells or dentrites). Since I am an animal cell, I do not have a cell wall. However, I do have a nucleus as one one of my organelles that undergoes a special process called interkinetic nuclear migration. This is where my nucleus simply moves from one position to the next. Though this process cannot be fully explained as yet, the main theory behind this phenomenon is that cell proliferation is improved and that it results in the pseudostatified look of the epithelium of the brain.