Micrographs & Diagrams, FinEx (2) PDF

Final Exam By TEM peroxisomes (P) generally show a matrix of moderate electron density. Aggregated electron-dense particles represent glycogen (G). X30,000. Illustration of the cross section of a mitochondrion observed under different metabolic conditions. The condensed morphology appears in the pre...

Final Exam By TEM peroxisomes (P) generally show a matrix of moderate electron density. Aggregated electron-dense particles represent glycogen (G). X30,000. Illustration of the cross section of a mitochondrion observed under different metabolic conditions. The condensed morphology appears in the presence of high ADP concentrations, when mitochondria are producing ATP (state III), while the orthodox configuration occurs at low ADP concentrations, with no production of ATP (state IV). https://doi.org/10.3390/membranes11070465 Micrograph showing microtubules (arrows) of the mitotic spindle in a dividing cell. On the right- microtubules are attached to the chromosomesx 30,000. Ross,Pawlina 2016. The apical part of an epithelial cell demonstrating intermediate filaments obtained using the quick-freeze deep-etch technique; TW - The terminal web of an epithelial cell IF – The intermediate filaments; R - The long, straight actin filament cores or rootlets, extending from the microvilli, cross-linked by a dense network of actin filaments containing numerous actin-binding proteins. The network of intermediate filaments can be seen beneath the terminal web anchoring the actin filaments of the microvilli. x47,000. Specializations of the Apical Cell Surface (c) TEM of microvilli sectioned longitudinally and transversely (inset) reveals the microfilament arrays that form the core of these projections. The terminal web (TW) of the cytoskeleton is also seen. G - The glycocalyx extending from glycoproteins and glycolipids of the microvilli plasmalemma contains certain enzymes for late stages of macromolecule digestion. X15,000. TEM of cilia (C) sectioned longitudinally reveals the central and peripheral microtubules of the axonemes. Cross sections (inset) clearly shows the 9 + 2 array of the microtubule doublets. At the base of each cilium is a basal body (B) anchoring the axoneme to the apical cytoplasm. Much shorter microvilli (MV) can be seen between the cilia. X59,000. Inset: X80,000. At the apical ends of the tall epithelial cells) are numerous very long stereocilia, which increase the surface area available for absorption. This micrograph is taken from nerve tissue; Neurons contain both intermediate filaments and microtubules. Micrograph (a) shows an axon in transverse section wrapped in the cytoplasm of a Schwann cell. Intermediate filaments (known as neurofilaments in this case) are a prominent feature of nerve cells, providing internal support for the cell by cross-linkage with microtubules and other organelles. The neurofilaments NF are dispersed among and in parallel with the microtubules, but are much smaller in diameter. Micrograph (b) shows part of an axon in longitudinal section. The axonal microtubules provide structural support and transport along the axon. A dorsal root ganglion. Satellite cells are very closely associated with cell bodies of sensory nerves and support these cells in various ways. X560. H&E These long-lived neurons commonly accumulate brown lipofuscin (L). ❖ Melanin is mainly responsible for skin color; is brown pigment; is also present in nerve cells in certain brain regions such as the substantia nigra, shown in micrograph (b), where the cell cytoplasm is largely obscured by its content of brown melanin pigment. ▪ This specimen has been stained by the Azan method to pick out the nuclei N which are stained pale blue with prominent magenta nucleoli. (b) X30,000.Numerous individual or clustered electron-dense particles – glycogen granules in the liver cell cytoplasm, which lack membrane; form characteristic aggregates such as those shown; is a ready source of energy; are often abundant in cells with high metabolic activity. S - satellite cells (S) surrounding N - the perikarya of neurons (a) ✔ ✔ ✔ L - Lipid droplets in the cells of the adrenal cortex, have small spherical structures with homogenous matrices. Are aggregates of hydrophobic lipid molecules Are enclosed by a single monolayer of phospholipids with various peripheral proteins, including enzymes for lipid metabolism. White adipose tissue, human, H&E, x363; inset x700. The adipocytes (A) have a spherical profile in which they exhibit a very thin rim of cytoplasm surrounding a single, large fat-containing vacuole. Because the fat is lost during tissue preparation, one only sees the rim of cytoplasm and an almost clear space. Between the cells - delicate connective tissue stroma holding the adipocytes together, and within this stroma are small blood vessels (BV), mostly capillaries and venulesThe inset shows an adipocyte whose nucleus (N) is relatively easy to identify. It appears to reside within the rim of cytoplasm (Cy), giving the adipocyte the classic “ signet ring” appearance. A second nucleus (N’), partially out of the plane of section, appears to reside between the cytoplasmic rims of two adjacent cells. Th is is probably the nucleus of a fibroblast. Because of the relatively large size of the adipocyte, it is very infrequent that the nucleus of the cell is included in the plane of section of a given cell. Other cells that may be seen within the delicate connective tissue stroma are mast cells (MC). Pituitary neurosecretory axons of rats in PEG-TEM (Figure 2a) and conventional epoxy TEM (Figure 2b). Distinct strands with lower electron density form microtrabecular lattices (MTL) of strands (arrows) occupying the cytoplasmic matrix between membranous organe including neurosecretory granules (g) and neurotubules and neurofilaments in PEG-TEM, while flocculent or fuzzy and ill-defined strands (arrows) are present in the cytoplasmic matrix in epoxy sections. Note well correspondence of strands between the two micrographs. Bar:0.1um. FIGURE 1. TEM of a necrotic cell: the disruption of plasma membrane and organelles is observable. A relative preservation of nuclear morphology appears. (original magnification: x 10,000) FIGURE 2 TEM of an apoptotic (A) and a normal (N) cell. The characteristic chromatin rearrangement appears in A, strongly different from its normal organization (N). The good preservation of membrane and organelles is also evident. (original magnification: x 8,000) FIGURE 3. SEM of a necrotic cell. Numerous lesions appear on the cell surface. (original magnification: x 5,000) FIGURE 4. SEM of an apoptotic cell. Surface blebbing is evident. (original magnification: x 5,000) FIGURE 5. FF freeze-fracture),of normal cell, nuclear envelope. The regular distribution of nuclear pores is visible. (original magnification: x 30,000) FIGURE 6. FF of apoptotic cell. The nuclear envelope shows a characteristic clustering (asterisc) of nuclear pores. (original magnification: x 35,000) The End. APOPTOSIS vs. NECROSIS, M.Vitale, G.Zauli and E.Falcieri http://www.cyto.purdue.edu/cdroms/cyto4/15_apop/data/chap10.htm