PNH arises as a consequence of somatic mutation of a gene (PIGA) whose protein product is a glycosyl transferase that is an essential component of the biosynthetic pathway that generates glycosyl phosphatidylinositol (GPI) (Figure 1).1 This moiety serves as the anchoring mechanism for a functionally diverse group of membrane-bound proteins, more than 20 of which are expressed on hematopoietic lineage cells in humans. The PIGA mutations that give rise to PNH cause loss of enzyme function (partial or total), the end result of which is near-complete or complete absence of expression of all proteins that are GPI-anchored (Figure 1). Among the cellular membrane constituents that are GPI-anchored are the complement inhibitory proteins, CD55 (decay accelerating factor [DAF]) and CD59 (membrane inhibitor of reactive lysis [MIRL]). It is the deficiency of these 2 proteins that underlies the complement-mediated intravascular hemolysis characteristic of PNH (Figure 2).2 Despite the loss of all GPI-anchored proteins (GPI-APs) from all hematopoietic lineage cells (erythrocytes, granulocytes, monocytes, lymphocytes, and platelets) derived from the PIGA mutant stem cell, there is no compelling evidence that deficiency of GPI-APs other than CD55 and CD59 contribute clinically to the pathophysiology of PNH. In addition to complement-mediated intravascular hemolysis, the other major clinical manifestations of PNH are bone marrow failure and thrombophilia.3 Although the relationship between somatic mutation of PIGA and the hemolysis of PNH is understood in detail, the relationship between somatic mutation of PIGA (and the consequent deficiency of GPI-APs) and the bone marrow failure and thrombophilia of PNH remain largely speculative.
Lineage 2 Classic For Mac
Complement and PNH. The hemolysis of PNH is due to aberrant regulation of the APC. The APC is a component of the innate immune system. Unlike the classical pathway of complement that requires a recognition factor such as antibody to activate the pathway, the APC is continuously active. Therefore safeguards have evolved to protect host cells against APC-mediated injury. In the case of erythrocytes, 2 GPI-APs, CD55 and CD59, serve this function. Two enzymatic convertases amplify the activity of the APC (top). The C3 convertase consists of activated C3 (C3b), activated factor B (Bb, the enzymatic subunit of the complexes that is proteolytically activated by factor D, a trace plasma protein that may be activated by 1 of the mannose-binding lectin-associated serine proteases), and factor P (formerly called properdin). Factor P stabilizes the C3 convertase, allowing each convertase to activate many molecules of C3, and in the process, generate the weak anaphylatoxin, C3a. The C5 convertase is similar in structure to the C3 convertase except that 2 molecules of C3b are required to position C5 for cleavage by activated factor B (Bb). Many molecules of C5 are cleaved by the C5 convertase, and this process generates many molecules of the potent anaphylatoxin and neutrophil chemo-attractant, C5a. Activated C5 (C5b) is the nidus for formation of the MAC of complement consisting of C5b, C6, C7, C8, and multiple molecules of C9. The MAC inserts into the lipid bilayer of the cell, forming a transmembrane torus that results in osmotic lysis. CD55 (DAF) blocks the formation and stability of both the C3 and C5 convertases, whereas CD59 (MIRL) blocks formation of the cytolytic MAC, primarily by inhibiting binding and multiplicity of C9. Eculizumab is a humanized monoclonal anti-C5 antibody that prevents activation of C5 by the C5 convertase. Consequently, the MAC cannot form (and C5a is not generated), accounting for the inhibition of the intravascular hemolysis of PNH. However, eculizumab does not inhibit formation of the C3 convertase, accounting for the opsonization by activation and degradation products of C3 observed in patients with PNH treated with eculizumab. Normal RBCs are protected against APC-mediated injury (black crosses represent APC C3 and C5 convertase formation; yellow stars represent MAC formation) by CD55 (blue ovals) and CD59 (green ovals) (bottom). PNH cells lacking the complement inhibitory proteins CD55 and CD59 undergo complement-mediated lysis, releasing cellular contends including hemoglobin (red circles) and LDH into the plasma.
In patients with classic PNH (Table 2), the leukocyte and platelet counts are usually normal or nearly normal, whereas leukopenia, thrombocytopenia, or both invariably accompany PNH in the setting of another bone marrow failure syndrome (Table 2). The reticulocyte count is needed to assess the ongoing capacity of the bone marrow to respond to the anemia. Although the reticulocyte count is elevated in patients with classic PNH, it is consistently inappropriately low for the degree of anemia, reflecting underlying relative insufficiency of hematopoiesis that is characteristic of the disease. Serum LDH is always markedly elevated in classic PNH. Patients with classic PNH may be iron-deficient because of chronic hemoglobinuria and hemosiderinuria. Nonrandom cytogenetic abnormalities are uncommon in PNH.4
Management of PNH. A management scheme based on classification of PNH into 3 subcategories (subclinical, PNH in the setting of another bone marrow failure syndrome [PNH/BMF], and classic PNH. See Table 2 for characteristics of each category.
Key results: We identified populations of all seven recognized diploids plus one new lineage. Phylogenetic analysis of plastid DNA variation in diploids revealed a well-resolved, but moderately supported phylogeny, with evidence for monophyly of the North America Crepis agamic complex and no evidence of widespread homoploid hybridization. Polyploids showed evidence of multiple origins and a pattern of frequent local co-occurrence consistent with repeated colonization of suitable sites.
Conclusions: Our findings agree broadly with the distribution and variation of ploidy within and among species described by Babcock and Stebbins. One key difference is finding support for monophyly of North American species, and refuting their hypothesis of polyphyly. Our results provide an explicit phylogenetic framework for further study of this classic agamic complex.
The "Mid-2012" Mac Pro shares the same large case design as earlier Mac Pro models -- with a removable panel on the side and an assortment of hard drive bays and optical drive bays as well as expansion slots for significant and easy internal expansion. Likewise, this Mac Pro can directly trace its lineage back to the externally similar Power Mac G5, and then to the "fold down door on the side" Power Mac G3 and Power Mac G4 models all the way back to the Quadra 900, the first Mac with a tower case design.
Convert biom format to classic format, including the taxonomy observation metadata as the last column of the classic format table. Because the BIOM format can support an arbitrary number of observation (or sample) metadata entries, and the classic format can support only a single observation metadata entry, you must specify which of the observation metadata entries you want to include in the output table:
Convert biom format to classic format, including the taxonomy observation metadata as the last column of the classic format table, but renaming that column as ConsensusLineage. This is useful when using legacy tools that require a specific name for the observation metadata column.:
Mechanics Tool and Forge decided to open an associate company rather than expanding the existing product line, so on October 30, 1944, the Clinton Tool Company was born. With Clem Poole as president, Clinton operated in the same building as Mechanics Tool and Forge and is the lineage from which the present-day line of sockets and accessories hail. In 1945, Russ Darrah, an industry veteran, presented Mechanics Tool and Forge with a program to buy an allied line of tools. This resulted in the formation of Mac Allied Tools and the collective product of all three companies was referred to as "Mac Tools." 2ff7e9595c
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