Lab Chronicles: My Experience in the Histology Lab – Week 4, 5 and 6

Throughout my final weeks in the Histology lab, I performed a variety of special stains in order to detect connective tissues, carbohydrates, microorganisms, and pigments in the diagnosis of certain diseases. I also performed immunohistochemistry in the detection of cancer markers. In a routine hematoxylin and eosin stain, many of these components are not visible and therefore special stains are needed in order for them to be seen.

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Lab Chronicles: My Experience in the Histology Lab – Week 3

Throughout this week in the Histology lab, I was operating the automated hematoxylin and eosin stainer, while also submitting stained slides to the pathologists to be reviewed.

Hematoxylin and eosin is a stain used in routine Histology slides. The hematoxylin stains nuclei in the tissue blue, whereas eosin stains the cytoplasm and other structures varying shades of pink. Hematoxylin is a natural dye originating from the logwood tree, Haematoxylum campechianum. However, it is not hematoxylin that is truly staining the nuclei, but rather its oxidized state of hematein. Oxidation of hematoxylin to hematein can occur using two different methods. One is a natural oxidation process that uses air or light. This process takes a significant amount of time to oxidize the dye, however, it produces a very stable stain. The other method uses chemical oxidation that requires either sodium iodate or potassium iodate. While this process occurs much quicker than the natural method, these stains may deteriorate and require filtering before use. However, this oxidized state of hematoxylin is still not sufficient to stain tissues. Hematoxylin must also be combined with a ‘mordant’, which gives the dye affinity to the tissue. Typical mordants that are added to hematoxylin are aluminum, iron, lead, tungsten, and molybdenum. Continue reading

The Lab Chronicles: My Experience in the Histology Lab – Week 2

For my second week in the Histology lab, I will describe the processes of tissue processing, embedding and microtomy. During this week, I processed, embedded and cut over 100 tissues.

In my previous blog, the gross description of tissues was explained. After grossing, tissues are put into tissue processor machines. Tissue processing consists of different chemicals entering the tissue for preservation. Tissues are then embedded into paraffin wax using the appropriate orientation. After tissues are embedded in wax and cooled, they can be cut using a microtome to create thin ribbons of tissues. These thin ribbons are then put onto slides. Continue reading

The Lab Chronicles: My Experience in the Histology Lab – Week 1

For this blog, I will be describing my exciting first week in the Histology lab! For those of you who are not familiar with this department of the lab, it is where tissues are sent in order to identify diseases. The pathologist is responsible for reading tissue slides microscopically to diagnose disease. These slides are made by technologists, and there are several steps involved in the production of the final slide.

First, when tissue is received in the lab, it is accessioned and given a specimen number. It is then sent to be ‘grossed’, which means it is given a macroscopic description. Next, it is cut into small pieces that are put into cassettes. These cassettes contain either a single piece or several pieces of tissue that will be made into a slide. The cassettes are then processed in machines that make them easier to cut while maintaining the microscopic characteristics of tissues. Once they are processed, tissues are then embedded into paraffin blocks, cut into thin slices using a microtome, stained and sent to the pathologist to read.

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The Lab Chronicles: My Experience in the Clinical Microbiology Lab – Weeks 5, 6 and 7

In this blog, I have combined my final three weeks in Microbiology. These last weeks mostly consisted of myself working on practice exams, as well as my final practical and theory exam. Additionally, I began working on my Clinical Project and started the testing process. However, I will highlight a few items performed over these last few weeks that have not been previously mentioned. Continue reading

The Lab Chronicles: My Experience in the Microbiology Laboratory – Week 3

During my third week in Microbiology, I again alternated between the primary and secondary benches. One of the main tests I performed throughout the week was the β-lactamase test for Staphylococcus aureus. S. aureus is a common bacteria found in many types of infections. Unfortunately, it is also known to be resistant to a multitude of antibiotics. The β-lactamase test is performed to see if the bacteria contains the enzyme, β-lactamase. This enzyme breaks down the β-lactam ring that certain antibiotics (such as penicillin) contain. This test is performed using a small disk that is placed on a slide, which is wetted with sterile water, and inoculated with the bacteria. The testing for the specimen is performed alongside quality control specimens that are known to be positive and negative. If the control organisms do not give the expected results, the test is invalid. A positive result appears as a pink color on the disk, whereas a negative result displays no color change. Continue reading