Histology of Nucleus Flashcards Preview

Fundamentals of Molecular Medicine > Histology of Nucleus > Flashcards

Flashcards in Histology of Nucleus Deck (31):
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On this slide, the area of interest is the liver, which is the large, dark tissue in the upper right portion of the digital slide. In this organ the predominant cell type is the liver cell (red circle). In these cells, the cytoplasm is pale pink and the nuclei are round and stained deep blue. Close examination of the cytoplasm reveals clear areas; these are locations previously occupied by glycogen, which washes away during tissue preparation. Fine dark lines separate the lightly stained areas of cytoplasm in adjacent cells (blue arrows); these represent the adjacent plasma membranes of the two cells

 

The tissue that lies between the cells is extracellular matrix. However, in this liver specimen, the large clear spaces you see are blood vessels, which, as you probably know, include endothelial cells and blood cells.

 

 

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On this slide, the area of interest is the liver, which is the large, dark tissue in the upper right portion of the digital slide. In this organ the predominant cell type is the liver cell (red circle). In these cells, the cytoplasm is pale pink and the nuclei are round and stained deep blue. Close examination of the cytoplasm reveals clear areas; these are locations previously occupied by glycogen, which washes away during tissue preparation. Fine dark lines separate the lightly stained areas of cytoplasm in adjacent cells (blue arrows); these represent the adjacent plasma membranes of the two cells

 

The tissue that lies between the cells is extracellular matrix. However, in this liver specimen, the large clear spaces you see are blood vessels, which, as you probably know, include endothelial cells and blood cells.

 

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Visualize Nuclei of ECM

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This slide (low, med) was stained with the Periodic acid Schiff (PAS) method, which specifically stains carbohydrates a bright magenta. The slide was counterstained to show nuclei in blue. As you know, the plasma membrane of cells contains glycoproteins. The carbohydrate component of these glycoproteins is referred to as the glycocalyx, which, in these cells, is thicker on the apical side of the cells (the side facing the space, which is the lumen of the intestine) (oil). This is due to the fact that this apical plasma membrane in these cells contains numerous microvilli, which we will learn about later. There are also goblet cells, which contain mucus-containing granules in their cytoplasm.

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This slide (low, med) was stained with the Periodic acid Schiff (PAS) method, which specifically stains carbohydrates a bright magenta. The slide was counterstained to show nuclei in blue. As you know, the plasma membrane of cells contains glycoproteins. The carbohydrate component of these glycoproteins is referred to as the glycocalyx, which, in these cells, is thicker on the apical side of the cells (the side facing the space, which is the lumen of the intestine) (oil). This is due to the fact that this apical plasma membrane in these cells contains numerous microvilli, which we will learn about later. There are also goblet cells, which contain mucus-containing granules in their cytoplasm.

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This slide (low, med) was stained with the Periodic acid Schiff (PAS) method, which specifically stains carbohydrates a bright magenta. The slide was counterstained to show nuclei in blue. As you know, the plasma membrane of cells contains glycoproteins. The carbohydrate component of these glycoproteins is referred to as the glycocalyx, which, in these cells, is thicker on the apical side of the cells (the side facing the space, which is the lumen of the intestine) (oil). This is due to the fact that this apical plasma membrane in these cells contains numerous microvilli, which we will learn about later. There are also goblet cells, which contain mucus-containing granules in their cytoplasm.

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(microvilli with glycocalyx, blue arrow; glycocalyx on lateral cell membranes, green arrows; goblet cell, red arrow).

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Light Microscope (J. Fig. 3-1; R. Plate 66) - SL 103 - (Liver, H&E) Return to slide 103, and observe the numerous liver cell nuclei (circular areas darkly-stained with hematoxylin) (med, oil). Most of the cells have a single nucleus. Try to find a cell with two nuclei. Identify the boundary of a nucleus (a dark line). Remember that the nucleus is bounded by a nuclear envelope consisting of two adjacent membranes that are penetrated by many nuclear pores. The irregularly shaped basophilic masses within the nuclei are heterochromatin. Unstained regions are euchromatin (J. Fig. 3-1). What is the functional difference? As you study the nuclei of several cells, you will find that many nuclei contain a small, distinct, round body in addition to the dispersed chromatin. This structure is the nucleolus, (red arrows). What is its composition?

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Observe the nucleus and nuclear envelope

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nuclear pores

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Chromatin Arrangement

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Heterochromatin vs. Euchromatin

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Euchromatin vs. Heterochromatin

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What is the significance of a cell with abundant heterochromatin in the nucleus? A cell with abundant euchromatin? What is the significance of prominent or multiple nucleoli?

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You will find several sections of a whitefish embryo. The individual cells are large and clearly delineated. Many of the cells are in interphase; each of these cells displays a well-defined, darkly staining nucleus. If you examine the sections carefully, you will be able to identify cells in various stages of mitotic division. These will be examined in more detail with the 40X objective and then with the 100X oil immersion objective. Many of these cells also contain some yolk material that is eosinophilic and appears as large round droplets. Switch to 40X objective and focus.

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Interphase nuclei: Note that the nuclear material (chromatin) is bounded by a nuclear membrane (envelope).

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This stage is somewhat difficult to discern. The nuclear membrane (envelope) is becoming disrupted and less distinct in late prophase and may no longer be apparent. The chromatin is undergoing reorganization and should contain multiple fibrillar strands, which will condense further to become identifiable chromosomes.

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Metaphase (Metaphase): In metaphase there is no evidence at all of a nuclear membrane. The chromosomes are condensed and centrally aligned. The mitotic spindle is clearly evident. The microtubules of the spindle converge at the pole, at a site called the centrosome, which contains a pair of centrioles. (The centrioles are not visible at this magnification). The microtubules in this region include 1) microtubules that attach to the chromosomes at kinetochores, 2) nonkinetochore microtubules that overlap with microtubules from the opposite pole and, 3) astral microtubules that radiate out from the centrosome and participate in the orientation of the mitotic spindle. Remember that you will encounter many different orientations; some metaphase cells will be viewed from above, others from the side.

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Anaphase (anaphase): At this stage the chromosomes are separating towards opposite poles. Again, there is no nuclear membrane. Mitotic spindles and asters (formed of astral microtubules) are clearly apparent.

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This is EARLY

 

Telophase (early, late, telophase): The chromosomes have now completely separated, and a new cell membrane should have appeared between the sets of chromosomes to define the limits of the two daughter cells. The chromosomes become more compact, may appear to fuse with one another, and are no longer clearly discernable from one another. Formation of a new nuclear membrane should follow shortly. Sometimes remnants of the mitotic spindle are visible at this stage.

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Late Telophase

 

Telophase (early, late, telophase): The chromosomes have now completely separated, and a new cell membrane should have appeared between the sets of chromosomes to define the limits of the two daughter cells. The chromosomes become more compact, may appear to fuse with one another, and are no longer clearly discernable from one another. Formation of a new nuclear membrane should follow shortly. Sometimes remnants of the mitotic spindle are visible at this stage.

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(Pharynx) Mitosis in tissue sections. (J. 3-16) In the previous slide, the individual stages of mitosis were readily apparent. In most H&E sections, however, we can only discriminate between cells in interphase, and cells that are in mitosis. These cells in mitosis are referred to as simply mitotic figures. It is possible to “guess” the phase of mitosis of a mitotic figure, but this is not necessary. Simply appreciate that many tissues in the body (e.g. epidermis of the skin) are undergoing constant regeneration, and, in these tissues, mitotic figures are readily observed.

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"Low"

 

In this slide from the pharynx, the surface tissue (an epithelium) contains multiple layers of cells. First, be certain that you are looking in the proper region of the slide which includes the epithelium. (low, med). Once in the proper region, note that most epithelial nuclei look similar to those from the liver cell; these cells are in interphase. Then, carefully search for cells lacking a defined nucleus, but containing condensed chromatin; these are mitotic figures. (high, red circles). The presence of an increased number of mitotic figures in tissue sections can be used as an indication that a tissue contains cancer cells.

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(Medium)

 

In this slide from the pharynx, the surface tissue (an epithelium) contains multiple layers of cells. First, be certain that you are looking in the proper region of the slide which includes the epithelium. (low, med). Once in the proper region, note that most epithelial nuclei look similar to those from the liver cell; these cells are in interphase. Then, carefully search for cells lacking a defined nucleus, but containing condensed chromatin; these are mitotic figures. (high, red circles). The presence of an increased number of mitotic figures in tissue sections can be used as an indication that a tissue contains cancer cells.

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HIGH

 

In this slide from the pharynx, the surface tissue (an epithelium) contains multiple layers of cells. First, be certain that you are looking in the proper region of the slide which includes the epithelium. (low, med). Once in the proper region, note that most epithelial nuclei look similar to those from the liver cell; these cells are in interphase. Then, carefully search for cells lacking a defined nucleus, but containing condensed chromatin; these are mitotic figures. (high, red circles). The presence of an increased number of mitotic figures in tissue sections can be used as an indication that a tissue contains cancer cells.

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In this slide from the pharynx, the surface tissue (an epithelium) contains multiple layers of cells. First, be certain that you are looking in the proper region of the slide which includes the epithelium. (low, med). Once in the proper region, note that most epithelial nuclei look similar to those from the liver cell; these cells are in interphase. Then, carefully search for cells lacking a defined nucleus, but containing condensed chromatin; these are mitotic figures. (high, red circles). The presence of an increased number of mitotic figures in tissue sections can be used as an indication that a tissue contains cancer cells.

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KARYOTYPE SL 160 - (MAY BE ABSENT FROM SOME DESKS) Human Chromosomes - (J. Fig. 3-10; R. Folder. 3.1). Karyotype preparation (high, oil). This karyotype was obtained by isolating lymphocytes from blood and stimulating them to undergo mitosis by exposure to phytohemagglutinin. Colchicine was added to the preparation to prevent formation of the mitotic spindle and arrest mitosis at metaphase. Only a few cells were in mitosis when the preparation was made, therefore you will have to look through the slide carefully to find a karyotype that is complete. Obviously, specific chromosome identification is not reasonable with our microscopes, but understand that this can be done routinely, and that more powerful techniques such as fluorescence in situ hybridization (FISH) and spectral karyotyping (SKY) are available (see text for details).

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KARYOTYPE SL 160 - (MAY BE ABSENT FROM SOME DESKS) Human Chromosomes - (J. Fig. 3-10; R. Folder. 3.1). Karyotype preparation (high, oil). This karyotype was obtained by isolating lymphocytes from blood and stimulating them to undergo mitosis by exposure to phytohemagglutinin. Colchicine was added to the preparation to prevent formation of the mitotic spindle and arrest mitosis at metaphase. Only a few cells were in mitosis when the preparation was made, therefore you will have to look through the slide carefully to find a karyotype that is complete. Obviously, specific chromosome identification is not reasonable with our microscopes, but understand that this can be done routinely, and that more powerful techniques such as fluorescence in situ hybridization (FISH) and spectral karyotyping (SKY) are available (see text for details).

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KARYOTYPE SL 160 - (MAY BE ABSENT FROM SOME DESKS) Human Chromosomes - (J. Fig. 3-10; R. Folder. 3.1). Karyotype preparation (high, OIL). This karyotype was obtained by isolating lymphocytes from blood and stimulating them to undergo mitosis by exposure to phytohemagglutinin. Colchicine was added to the preparation to prevent formation of the mitotic spindle and arrest mitosis at metaphase. Only a few cells were in mitosis when the preparation was made, therefore you will have to look through the slide carefully to find a karyotype that is complete. Obviously, specific chromosome identification is not reasonable with our microscopes, but understand that this can be done routinely, and that more powerful techniques such as fluorescence in situ hybridization (FISH) and spectral karyotyping (SKY) are available (see text for details).

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a.  What is the centromere? 

b.  What group(s) show metacentric chromosomes?, submetacentric? 

c.  Are there any acrocentric groups (centromere very near one end)?

d.  Is this karyotype from a male or female?

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a.  The centromere is the region of the chromosome where the two chromotids are held together and is the region where the kinetochore (the attachment site for microtubules during mitosis) is located.

b.  Metacentric groups: A, C E, F;  Submetacentric group: B

c.  Acrocnetric groups: D and G

d.  Male

 

 

KARTYOTYPE:   Karyotypes are prepared according to the following general procedure:  Cells, usually lymphocytes, from patients are stimulated with a mitogenic agent, cultured for 3-4 days, then exposed to colcemid, that arrests mitotic division at the metaphase stage.  The cells are then exposed to a hypotonic medium (that causes the  cells to become swollen) and the chromosomes dissociated from one another by treatment with trypsin.  Fixation follows to preserve structure integrity, and finally the chromosomes are stained.  The stain used for these preparations is the Giemsa stain, hence the term G-banding.  Other selective stains can also be used for chromosome identification.  Without this procedure, chromosome identification and subsequent pairing in karyotypes is much more difficult, if not virtually impossible, to achieve.  With this technique, obviously, clinically significant aberrations in chromosomal structures are easily identified.

  Note the banding pattern is characteristic for a given chromosome. Pairs of chromosomes may be arranged into groups, classified as to their size and position of the centromere. 

 

 

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