Bone Dictionary

Appositional growth: The process that forms new cartilage at the surface of an existing cartilage.

In appositional growth, the cells undergo a differentiation process that is guided by the expression of the transcription factor SOX-9.



Canaliculi: Small tunnels that course through the mineralized matrix of bone.

The Canaliculi allow contact between the cell processes of neighboring osteocytes because the connect adjacent lacunae


Hemichannels: The unopposed half of gap junction channels that provide communication between cells and extracellular matrix

Hemmichannels allow the release of accumulated intracellular molecules into extracellular space of the canaliculi

Encounter of tissue in wounds

Outside the classroom I currently work at Washington Vascular Specialists. This is a clinic that treats peripheral arterial disease, particularly in the legs. A person who chronically suffers from this disease experiences a lack of blood flow to the feet, causing many complications. Particularly, patients who also have diabetes are at higher risks for suffering the symptoms of this disease. This is because a diabetic patient is more susceptible to develop a wound/ulcer in the foot, which I would now consider necrosis of the tissue. This causes difficulty because the patient’s poor blood circulation impedes the wound/ulcer from healing properly. Patients with non-healing wounds in the feet come to our clinic frequently for intervention procedures. My job is to prep the patient for procedures. This includes listening to the pulses of the dorsalis pedis arteries and the posterior tibial arteries with a portable doppler machine. I have to confess, many times I have to force myself to remain composed when removing socks from patients with wounds. As I examine the foot and remove the bandage I notice the tissue necrosis of the wound/ulcer. With a foot ulcer it is very clear to see where healthy tissue is missing and whether it is infected or not. For patients with infected ulcers I usually have to put an extra linen or drape because the ulcer tends to drain. Sometimes we have patients that come with gangrenous toes where the tissue has a black/greenish color to it. This experience makes me realize how important it is to know what healthy tissue looks like in order to diagnose pathological tissues.

It is neat to make a link between the patients I encounter and my histology class.

Dictionary- Intro to Histology

 Histology is a science I am very excited to start learning about on a deeper level. Upon studying a came across a couple new words that I needed to reference to the book for in order to understand the context. Below are the new words I learned this week. 

1.      Cis-Golgi network: Cisternae closest to the rough endoplasmic reticulum

Trans-Golgi network: Cisternae away from the rough endoplasmic reticulum

Secretory vesicles from the endoplasmic reticulum fuse with the cis-golgi network in order to modify and direct the proteins out through the trans-golgi network.

“Histology@Yale.” Golgi EM, medcell.med.yale.edu/histology/cell_lab/golgi_em.php.

2.      Inclusions: Stored nutrients, secretory products, and pigment granules.

Our muscles are constantly demanding energy in the form of glucose, therefore glycogen inclusions are abundant in the cells of muscles.

“Exercise 3: Cells, Organelles, and Inclusions.” Exercise 3: Cells, Organelles, and Inclusions, www.doctorc.net/Labs/Lab3/lab3.htm. Accessed 1 Sept. 2017.

3.      Necrosis: Wholesale unregulated cell death caused by lack of nutrients or infection.

Unlike apoptosis, necrosis tends to cause inflammation because of the release of intracellular contents. In apoptosis phagocytic cells quietly rid of cells that were programmed to die without inflammation. 

“Introduction to histopathology.” OpenLearn, www.open.edu/openlearn/science-maths-technology/science/biology/introduction-histopathology/content-section-3.1. Accessed 1 Sept. 2017.

End of the Semester Reflection

As we come to the close of another semester I can’t help but to look back through the weeks of taking this course and feeling accomplished. This immunology course has broadened my horizons on a branch of biology that is key to working in the healthcare field. I believe that everything that happens under the sun, happens for a reason. My academic journey has humbled me extensively by constantly reminded me that God is ultimately in control. I am a senior who is having to do an extra semester, outside of the normal 4 year curriculum. I have wrestled with God when it comes to my academic journey and my future and there are many questions I still don’t have answers to. I never saw myself having to do an extra semester because my goal from the beginning of my college journey was to finish on time and graduate as young as possible. However, my journey is not everyone else’s and in the midst of wresting with God, He convicted me in switching my major from Health Science to Biology. This switch set me back a bit but I was determined to embark this harder road with the goal of being a better candidate in the future when applying to graduate school. However, making this decision gave me the opportunity to take this course, which caught my attention since last year when some of my colleagues were taking it. Two of the most important concepts I have learned about include the MHC complex and antigen presentation along with the functions of antibodies. Taking biochemistry simultaneously with this class has enriched my learning tremendously. In biochemistry we recently had an entire chapter that gave an overview of the immune system and the major roles of B cells, T cells and immunoglobulins. It was amazing to see how much background knowledge I obtained in the field of immunology as I explained the content to my study group colleagues who have not taken the course. Overall, I am thankful for the knowledge I have gained which has allowed me to have a new perspective when dealing with diseases, colds and allergies. I now can't help but to think about the functions of the immune system when I encounter scenarios such as someone having a cold or listening to a  conversation that ties to the immune system. I am in awe when I see how God has created an “army” within us whose sole purpose is to protect us.  

T cell Development Defintions

Anergy: Unresponsiveness to antigenic stimulus

 The CD4+ T cell received only the TCR engagement signal and none other, therefore anergy  was experienced.  

 

Notch: A surface receptor that when bound is cleaved to release a transcriptional regulator that regulates cell fate decisions. Notch activation is required for T cell development and determines whether a lymphocyte precursor becomes a B vs. T cell.

 When Notch 1+ is added to stromal cells in an assay system, this induces the development of T cells rather than B cells.

 

Death by Neglect: Apoptosis of developing T cells (Typically CD4+ & CD8+ T cells) that results when they do not receive TCR signals of adequate affinity.

 

Most T cells (about 90%) undergo death by neglect in the Thymus because their receptors do not specifically recognize self MHC molecules.

Rheumatoid Arthritis Investigation

Autoimmune diseases are very interesting to study because of the mechanisms that underlie their existence and how the body mistakenly begins to fight itself. I chose to investigate the autoimmune disease Rheumatoid arthritis because my father has been diagnosed with Arthritis and I was interested in becoming knowledgeable of what could possibly be going on the inside of my father’s body.

            Rheumatoid Arthritis (RA) is an autoimmune disease in which our immune system attacks its own joints, resulting in inflammation on the inside (synovium) and bone deterioration. As the synovium thickens this tends to cause swelling and pain which usually leads to a loss of mobility. The joints at risk for RA include the hands, feet, wrists, elbows, knees and ankles. Interestingly this disease usually affects joints symmetrically, meaning that if one elbow becomes impaired it is very likely that the other elbow will be affected as well. The etiology of RA is currently uncertain but research has been able to detect many of the important immune components that trigger the inflammation and bone resorption.

            Some of the chemical mediators that trigger inflammation in RA include kinins and vasoactive amines. Kinins are a group of polypeptides that have the ability to stimulate smooth muscle, increase vascular permeability, induce pain and possibly promote leukotaxis. Histamine, a vasoactive amine is believed to have a major role in the initiation of the inflammatory response in RA. It also encourages vasodilation and vascular permeability. Lysosomes which are involved in the digestive and lytic process of cells have been suggested to release their enzymes directly into cell cytoplasm or surrounding tissue in RA, which injures the tissue and triggers the inflammation response. If this action is prolonged it results in the continuous production of autoantibodies because of the antigenic stimulation by degraded host tissues.

            Patients with RA have an increased number of T cells, which is explained by the role they play in triggering osteoclastogenesis. Osteoclstogenesis is the development of osteoclasts, which are bone cells that are specialized to reabsorb calcified tissue. This is the reason why patients with rheumatoid arthritis experience the pain they do, because with time their bones start to become fragile due to the action of these overstimulated osteoclasts. T cells express RANKL which is a member of the TNF family of cytokines. RANKL induces osteocalstogensis from monocytes or macrophages.  

 

Wilder, Ronald L. "Immunopathogenesis of Rheumatoid Arthritis." Clinical Immunology Newsletter 6.1 (1985): 1-5. Web

Panayi, G. S. "Developments in the Immunology of Rheumatoid Arthritis, a Personal Perspective." Rheumatology 50.5 (2011): 815-17. Web.

MHC & Ag presentation Encounter:

In class we have been studying the major histocompatibility complex along with antigen presentation. There are two pathways in which antigen is processed and presented to T cells depending on whether the peptide is associated with MHC class- I or MHC class-II. The Endogenous pathway is the pathway taken by peptides generated within the cell (MHC I). The Exogenous pathway is the pathway taken by peptides taken up from the extracellular environment by endocytosis (MHC II).

This past weekend our acrobatic team was away at Andrews University in Michigan for our annual Acrofest. During our nine hour bus ride there one of my teammates threw up in the bus on his way to the trashcan. Our coach made a stop to attempt to clean the area since we still had a couple hours till arriving at our destination. However, germs are hard to kill especially in an enclosed environment filled with people such as our bus. When we arrived at acrofest three other teammates progressively got sick and started to throw up as well. In the midst of this happening I couldn’t help but think about immunology and what was happening on the inside of my teammates as they were trying to fight off this virus or stomach flu. To this day we aren’t sure what exactly plagued our team.

What I am sure about is that these antigen peptides from the throw up were spreading and as they started to inhabit my teammates their immune systems were at work. These peptides were coming from the outside, therefore their system was fighting through the exogenous pathway. In the exogenous pathway the antigen is engulfed into endocytic compartments where they are degraded by acidic pH-dependent endosomal and lysosomal enzymes. These throw up peptides were then able to associate with MHC class –II and the MHC-peptide complexes were then transported to the cell membrane in preparation for antigen presentation to CD4+ T helper cells. Thankfully these teammates were able to recuperate before our performance Saturday night, meaning that their antigen presentation was successful and their immune system was actively at work in fighting off this stomach illness.