Tissue surface structure

Once the skeleton is formed, continual remodelling of bone tissue maintains structural integrity and creates more orderly tissue structures. Remodelling involves coupled resorption and formation on all bone surfaces in a well-defined sequence of events. The remodelling sequence has been described as activation of the surface, resorption by osteoclasts, reversal, formation by osteoblasts, and return to quiescence of the surface. In... 

An old hypothesis is based on the observations of Dahlen et al. (D3), who demonstrated that above a certain concentration in plasma, Lp(a) could bind to glycosaminoglycans in the arterial wall (B12). Colocalization of Lp(a) and fibrin on the arterial wall can lead to oxidative changes in the lipid moiety of Lp(a) and induce the formation of oxidatively modified cholesterol esters, which in turn can influence the interaction of Lp(a) and its receptors on macrophages. This process is promoted by the presence of calcium ions. Cushing (C14), Loscalzo (L22), and Rath (R3) reported a colocalization of undegraded Lp(a) and apo-Bl00 in the extracellular space of the arterial wall. In contrast to LDL, Lp(a) is a substrate for tissue transglutaminase and Factor XUIa and can be altered to products that readily interact with cell surface structures (B21). 

Diethylcarbamazine immobilizes microfilariae and alters their surface structure, displacing them from tissues and making them more susceptible to destruction by host defense mechanisms. The mode of action against adult worms is unknown. 

We stress these assays because, while leading to the discovery of IAA, they imposed structure-activity requirements precluding study of the IAA conjugates--and possibly the discovery of other auxins. For a substance to be active in the assays required that they 1) permeate membranes in a cut tissue surface, 2) be transported to the growing zone, and 3) promote growth in that zone. Hopefully these three requirements may someday be studied independently. 

Identification of macroscopic metastases is easier if coloration is different from parenchyma. This was a major advantage when studying melanoma however, this characteristic was not available for other tumor types. It is possible to identify metastases in most tissues. They appear as clear or white raised gelatinous surface structures. Examination is facilitated by the use of a dissecting or stereomicroscope. However, if there are imperfections in the tissue or if the tumor is small, errors can occur. Therefore, different approaches have been employed to enhance visual contrast between tumor and parenchyma. 

The complete DNA sequence has meanwhile been clarified. HCV binds to the cell surface structure CD 81 via its envelope protein E2 for this reason, HCV can also infect other cell types (apart from hepatocytes). (318) Virus replication can be detected very early (within the first week after exposure). The viral particle load is < 10 /ml serum, which is less than half of an HBV infection. The highest antibody titres are found in the preacute and early acute stages. HCV can replicate extra-hepatically, e. g. in leucocytes and B or T lymphocytes as well as, occasionally, in oral lichen tissue. (284) The spleen serves as a large extrahepatic reservoir for HCV. (280, 288, 313, 318, 334, 342, 355, 358, 377, 383, 404) (s. p. 115)... 

The most metabolic activity of plants is carried out in the tissue called parenchyma, which generally makes up the bulk of the volume of all soft edible plant structures. The epidermis, which sometimes is replaced by a layer of corky tissue, is structurally modified to protect the surface of the organ. The highly specialized tissues collenchyma and sclerenchyma provide mechanical support for the plant. Water, minerals, and products of metabolism are transported from one part to another of the plant through the vascular tissues, xylem and phloem, which are the most characteristic anatomical features of plants on the cross section. 

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