Anatomy, Biochemistry and Physiology
Massimo Maffei in Vetiveria, 2002
Light microscopical observations of V. zizanioides leaves revealed the presence of Kranz BS cells common to the majority of C4 species (Laetsch, 1974). In V. zizanioides cross sections of minor veins the vascular BS appears surrounded by one layer of sheath cells, with chloroplasts in a centrifugal position (Figure 2.2a). No mestome sheath (MS) appears to be present between metaxylem vessel elements and laterally adjacent Kranz cells as in other grasses, e.g. Pooideae (Esau, 1977). According to ultrastructural studies V. zizanioides possesses a Kranz anatomy with dimorphic chloroplasts. The bundle sheath chloroplasts form larger and more numerous starch grains than the mesophyll chloroplasts and in contrast to the latter, they show a reduced grana development or none at all. In the BS, ultrastructural observations show a cell wall suberized lamella (Figure 2.2b) along with the presence of agranal chloroplasts. Sometimes these chloroplasts show an apparent distortion of the thylakoid system somewhere in the central part of the stroma (Figure 2.2b–c). Chloroplasts were observed to contain numerous starch grains (Figure 2.2b) and/or a developed peripheral reticulum, a system of anastomosing tubules contiguous with the inner membrane of the chloroplast envelope (Figure 2.2c). A few, small, and heavily cristated mitochondria were also observed. The mesophyll chloroplasts show most of the thylakoids staked in grana, the complete absence of starch grains, and the presence of several plastoglobules (Figure 2.2d–e) (Bertea et al., 2001).
Vitamin E, α-Tocopherol
Ruth G. Alscher, John L. Hess in Antioxidants in Higher Plants, 2017
Although two molecules of monodehydroascorbate dismutate to form ascorbate and dehydroascorbate, the occurrence of monodehydroascorbate reductase in plant chloroplasts provides a potentially important catalytic link between vitamin E, vitamin C, and available reducing equivalents in the cell (NADPH or NADH).46 This enzyme usually occurs in low concentration in plant extracts,46-48 and is typically considered to function in the H2O2 scavenging system of the plant. The enzyme occurs in the chloroplast stroma and contains a flavin, FAD. It differs from the Neurospora enzyme, which contains no prosthetic group, and is specific for NADH. In mammalian cells, a similar enzyme occurs in microsomal and mitochondrial membrane preparations that reacts with NADH, contains FAD, but is not soluble as is the stromal enzyme of the chloroplast. The ping-pong mechanism allows for a two-electron transfer from NAD(P)H to FAD, and for sequential reduction of two molecules of monodehydroascorbate radicals.49 Since the reaction between the tocopheroxyl radical and vitamin C will result in a one-electron transfer from the ascorbate. the monodehydroascorbate product will be an effective substrate for this enzyme. This catalysis (Figure 4A) should improve the ability of the chloroplast to regenerate vitamin Ε at the expense of NAD(P)H, and at the same time, minimize the pool sizes of either the tocopheroxyl or monodehydro-ascorbate radicals.
Dissemination and adhesion of peritoneal cancer cells to the peritoneal wall
Wim P. Ceelen, Edward A. Levine in Intraperitoneal Cancer Therapy, 2015
The tumor stroma differs from the normal stroma at several aspects. A fibronectin isoform, called oncofetal fibronectin (onfFN), is upregulated in tumor stroma, and the expression of this molecule correlates with metastatic implants in ovarian and colon cancers. The onfFN isoform may aid adhesion of the disseminated cancer cell to ECM [36,37]. There is a crosstalk between the peritoneal stroma and disseminated adhered cancer cells in the abdominal cavity. Cytokines and chemokines secreted by the cancer cell will change the local ecosystem to its own benefit. Matrix metalloprotease (MMP)-2 produced by ovarian cancer cells cleaves ECM proteins (fibronectin, vitronectin) into smaller fragments. The cancer cells adhere much stronger to smaller fragments using their fibronectin (α5β1-integrin) and vitronectin (αvβ3-integrin) receptors [3]. Furthermore, TGF-β, secreted by cancer cells, will lead to retraction of the mesothelial cells and activate tissue-resident fibroblasts (Figure 6.1) [38].
Reexamining the role of tissue inflammation in radiation carcinogenesis: a hypothesis to explain an earlier onset of cancer
Published in International Journal of Radiation Biology, 2021
The stroma is a tissue which supports the normal functions of epithelial cells. However, cancers (malignancies derived from epithelial tissue) often accompany the overgrowth of fibroblasts (CAFs) (Shimoda et al. 2010), especially in cancers of the breast, colon, stomach, and pancreas, and the stroma may comprise over 90% of the tumor mass (Dvorak 1986). Interestingly, normal fibroblasts are activated when incubated in the presence of culture supernatants from cancer cells and become myofibroblasts (i.e., they undergo epigenetic changes). Similar changes are also observed following the incubation of fibroblasts with TGF-β, PDGF, FGF2 etc. (Shimoda et al. 2010; Kalluri 2016). Furthermore, not only CAFs but also senescent appearing flat fibroblasts (stellate fibroblasts which may contain unrepaired DNA damage) can support the growth of pre-malignant or malignant, but not normal epithelial cells when these cells are co-cultured in vitro, or co-transplanted into host animals (Krtolica et al. 2001; Orimo et al. 2005; Kojima et al. 2010; Yoshida et al. 2019). The growth stimulation effect in vitro was attributed at least partly to soluble and insoluble factors derived from senescent cells (Krtolica et al. 2001). In this context, it is noted that TGF-β is released not only from myofibroblasts to support their own growth in an autocrine fashion, but also by cancer cells to support the growth of CAFs (Kojima et al. 2010). Cancer cells and CAFs exist in a mutually beneficial relationship.
The ultrastructural effects of surgical treatment of hydrosalpinx on the human endometrium: a light and electron microscopic study
Published in Ultrastructural Pathology, 2019
Tuğçe Sapmaz, Leman Sencar Gündoğdu, Mehmet Turan Çetin, Ibrahim Ferhat Ürünsak, Sait Polat
Ultrastructural examination of the endometrial tissue samples obtained from the patients with hydrosalpinx after surgical treatment, it was observed that the surface epithelium consisted of microvilli and ciliated columnar cells. It was interesting that the surface epithelium showed slight structural changes in some areas, but in most areas, its structure was more similar to control endometrium. It was determined that epithelial, glandular and stromal structures of endometrial tissues obtained after surgical treatment were similar to normal endometrium in general. Furthermore, the presence of pinopod structures formed by the apical cytoplasm of the endometrial columnar epithelial cell extending towards the lumen was observed. The nuclei of the epithelial cells had a thin, long, oval shape, and the nucleus usually were located at the base of the cell. It was observed that the cell nuclei had usually euchromatic appearance and contained one or more nucleoli in the nucleus. Normal, thin and long mitochondria, GER cisternae and Golgi complex, lipid droplets, vacuoles and glycogen particles in the cytoplasm were also observed in the cytoplasm of the cells. A thin basal lamina was noted at the lower part of the epithelium. Stromal cells in the endometrial stroma were usually round or oval in shape, with cytoplasmic organelles in normal structure and lipid droplets in some cells (Figures 13–15). Blood vessels and connective tissue fibers were also found in the stroma.
Bilateral juvenile nasopharyngeal angiofibroma: A rare case report
Published in Acta Oto-Laryngologica Case Reports, 2021
Marlinda Adham, Kartika Hajarani, Lisnawati Rachmadi, Indrati Suroyo
The triad clinical presentation of JNA are unilateral nasal obstruction, recurrent epistaxis and nasal discharge. In this case, patient experienced all the symptoms and also felt a mass on his left cheek. MRI dan CT imaging shows both were hypervascular mass suggesting an angiofibroma, in which right mass is more contrast-enhanced than the left one. Histologically, angiofibroma is composed of fibrocollagenous stromal proliferation with an admixture of variably vascular space. Vascular component is comprised of thin-walled, small to large vessels varying on appearance from stellate to staghorn to barely conspicuous, owing to mark compression by stromal fibrous tissue. Stroma is composed of fibrous tissue with fine or coarse collagen fibers whereas its cells are spindle shaped and stellate with plump nuclei, and tend to radiate around vessels [11]. In this case, histologic examination also showed us that both masses showed similar picture: vascular channels lack the surrounding smooth muscle, innervation of normal blood vessels, and stromal fibrous from spindle to stellate shaped which was concluded to be angiofibroma. However, the mass on the left side shows more fibrous stoma tissue and less vascular component rather that the right one and vice versa.
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