Glomerular tufts

The macula densa is a dense aggregation of cells in the distal tubule of nephrons facing the glomerular tuft of capillaries. These cells sense the salt content of the distal tubular fluid and adjust glomerular perfusion and renin secretion accordingly. 

F (shrunken glomerular tufts necrosis of tubular epithelial cells)... 

The glomerular basement membrane (GBM) forms the backbone of the glomerular tuft. It is composed of three layers lamina rara interna, lamina densa, and lamina rara externa. The glomerular basement membrane is composed of a network of collagen type IV molecules (H5) intertwined with nidogen to another network composed of molecules of laminin. Type IV collagen and laminin are responsible for the firmness of the glomerular basement membrane and enable adhesion of endothelial cells and podocytes as well. 

Acute CSA-induced nephrotoxicity is a functional abnormality caused by a disproportion of the balance of vasoconstrictor and vasodilator mediators. The main characteristic of this form of nephrotoxicity is an intense intra-renal vasoconstriction, causing RBF decrease and RVR increase, accompanied by variable degree of GFR impairment. The main site for this vasoconstriction is the afferent arteriole but it also occurs in adjacent small arteries, including the glomerular tuft [13,15,16]. 

Whether LCAT deficiency leads to an increased content of UC in all cell plasma membranes is not yet clear, but analyses of tissues obtained from the patients have revealed increased contents of UC in the liver, kidneys, spleen, and arteries [67], Meanwhile, there are granular deposits in the cornea that seem to consist of lipid, and foam cells that seem to contain CE are seen in the bone marrow, spleen, and glomerular tufts of the kidney. The kidney abnormalities may be of special significance because renal dysfunction can be a life-threatening feature of the disease. Proteinuria is detectable in childhood, and sometimes progresses to renal failure later on in life. 

Focal only some of the glomeruli are affected Segmental only a portion of the glomerular tuft exhibits sclerosis... 

These membranes are distinguished from Type 1 by the presence of pores, the size of which can be gauged from the size of the largest molecule which can penetrate them. As a homologous series is ascended, substances are obtained which penetrate Type 4 membranes less (and Type 1 membranes more) readily. One of the best-known examples of a Type 4 membrane is the glomerular tuft in Bowman s capsule of the kidney (see later). This tuft is permeable to all molecules smaller than albumin (mol. wt. 70000). The pore size is estimated as 3 nm, and inulin (mol. wt. 5000) passes through easily. Mammalian capillaries and liver parenchyma, too, have Type 4 membranes, which are not often met apart from these important examples. 

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