Paracortex

The arrangement of ortho- and paracortical cells differs among wool types. For example, in lincoln wool an annular (orthocortical core surrounded by paracortex) cellular arrangement is present. Merino fibers possess a characteristic crimp and in these fibers the orthocortex is located on the outer side of the crimp curvature. 

Parachlorobenzotrifluoride, 6 1341 Paracortex, in wool fibers, 22 173 Para-crystalline lattice model, 24 464 Paracyclophane synthesis, 24 38 PARAFAC (PARAllel FACtor analysis),... 

Fig. 1. Photomicrographs of a reactive lymph node follicle with germinal center (G), mantle (M), and surrounding paracortex (P) immunostained using the avi-din-biotin complex technique. (Top) Follicle stained with an antibody specific to B-cells, B1 (CD20) (Coulter Immunology, Hialeah, FL), counterstained with Methyl Green. (Bottom) Parallel section of the same follicle stained with an antibody specific to T-cells, Leu 4 (CDS) (Becton-Dickinson, Mountain View, CA). Scale bar = 100 p.

We now turn to an anatomical description of lymph nodes. The lymph node is surrounded by a thick, fibrous capsule and is subdivided into compartments by trabeculae. Inside the capsule is the subcapsular or marginal sinus, which forms the entry point of lymphatic fluid into the node, via the afferent vessel. The lymph node cortex, which lies beneath the subcapsular sinus, is the location of the primary and secondary lymphoid follicles. The primary follicles are comprised of B-lymphocytes. An immune response stimulates B-cells to replicate and differentiate, converting the primary follicle into a secondary follicle or germinal center, surrounded by a zone of small lymphocytes. The paracortex surrounds the germinal centers and primary follicles and contains mostly T-lymphocytes. The medulla is composed of medullary cords, consisting of macrophages and plasma cells, and medullary sinuses. The medullary vessels include the arteries and veins, and the afferent and efferent lymphatic vessels, respectively, deliver the lymphatic fluid into and out of the lymph node. 

Amino add Epicuticlo Paracortex + Epiouticle Heavy cortical cells Light cortical cells Cuticle Original Merino Merino 64 s 64 s wool wool ... 

The internal lymph node tissue is separated into lobes. The lobe end at the center of the node is called the medulla, whereas the wider lobe end toward the perimeter of the node is called the cortex. The lobe area just next to the cortex is called the paracortex. Surrounding the lobes is an area called the medullary sinus. T cells are concentrated in the paracortex, whereas B cells primarily are concentrated in the cortex in structures called primary follicles. Lymphocytes first travel to the medullary sinus before migrating to the cortical and paracortical regions. 

The cortical cells are not all alike in chemical reactivity nor in response to microscopical stains. The more reactive component is known as the orthocortex and the other as the paracortex. It appears that distribution of the two varieties is such as to divide the cortex longitudinally into two hemicyfinders. The relative proportions of the two phases has a bearing on the crimp of the fibre. 

Fig. 7.7 Two-dimensional color Doppler ultrasound images show a dog lymph node treated with administered L-selectin ligand-specific USCA. (A) Four selected images from the first scan. (B) Image from the second scan of the same lymph node, which was performed immediately after the first scan. The images in (A) show typical micro-bubble-based SAE signals in the paracortex,...

Atypical lymphocytes are found in the peripheral blood and T-cell areas of lymph nodes (paracortex) and may cause misdiagnosis as Hodgkin s disease histologically (therefore, don t biopsy a lymph node ). 

Figure 2.2-15 Nonspecific reactive lymphoid hyperplasia of a tracheobronchial lymph node in a cynomolgus monkey. Note the numerous reactive large germinal centers scattered deep in the paracortex.

The perinatal nodes from cynomolgus macaques contain primary follicles. T cells are centro-foUicularly positioned whereas the B cell population is located toward the periphery. Macrophages are present in the medulla and dendritic cells are present in the paracortex (Makori et al., 2003). 

Kaufman You have shown us that the B cells go to the B cell follicles because they follow some chemokines, and T cells go to the paracortex because they follow others. Who sets down the chemokines ... 

Most wool fibers contain two or even three types of cortical cells that are sometimes segregated into two distinct regions (Figure 1-29) that can be readily observed in cross section [82]. These cell types are called orthocortex, paracortex, and mesocortex. Orthocortical cells contain less matrix between the intermediate filaments and a lower sulfur content ( 3%) para-cortical cells are smaller in diameter, and they have smooth and rounded borders and a high sulfur content (-5%) [83]. 

Figure 1-29. Schematic of a wool fiber, illustrating orthocortex and paracortex regions of the cortex in relation to crimp.

The wood fiber has a scaly structure (Figures 30-4 and 38-11). It consists of two parts of differing chemical composition and different properties—the paracortex and the orthocortex. Consequently, the wool fiber is, technologically, a bicomponent fiber (see Chapter 38). The cortices are, in turn, made up of bundles of cortex cells which have a cell nucleus at the center. Each cortex cell consists of microfibrils which are arranged about a core in what is known as a matrix of very sulfur-rich proteins. Each microfibril has 11 of what are called protofibrils, nine of which surround a central pair. Each protofibril consists of two to three a helices. 

Figure 30-4. Schematic representation of the structure of wool fibers W (left) which consist of cortex cells C (center), which, in turn, consist of microfibrils M (right). The microfibrils each contain 11 protofibrils P, each of which is made up of 3 or helices, para, paracortex ortho, ortho cortex.

Except for a small amount of the amino acid methionine, the sulfur in wool occurs in the form of the amino acid cystine. Only approximately 82% of clean wool consists of keratinous proteins, which are characterized by a high concentration of cystine. Approximately 17% of the fiber is protein material of relatively low cystine content (<3%) this has been termed nonkeratinous. As a result of the lower cystine content, the nonkeratinous proteins have a lower concentration of disulfide cross-links compared with the keratinous proteins in the fiber. The nonkeratinous material is, therefore, more labile and less resistant to chemical attack than the keratinous proteins. The nonkeratinous proteins are located primarily in the cell membrane complex between the cortical cells and in the endocuticle (Fig. 3). Approximately 13% of the total nonkeratinous material is also located within the cortical cells, where its distribution differs between the cells of the ortho- and paracortex. 

Fine-granular orthocortical macrofibrils and coarser paracortical cells are distinguishable. Exocuticle, endocuticle and cell membrane in the cuticle keratin becomes also distinguishable. Cytoplasmic nuclear remnant regions in the paracortex are densely stained. 

Merino wool fiber, showing the cuticle, macrofibril (M) in the orthocortex (0) and densely stained nuclear remnant (nr) regions in the paracortex (P). Exocuticle (Ex), endocuticle (En) and cell membrane complex (cm) are clearly differentiated. 

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