Stromal layer

Cremophore EL Cremophore EL, a polyethoxylated castor oil used as a vehicle in various intravenous injections, has also been found to enhance the intraocular penetration of the drugs. Bijl et al. [83] reported that for Cremophore EL (10% and 20%), flux values of cyclosporine A across the fresh cornea were significantly higher than for corneal tissue without the enhancer for the first 16 h of the experiment. Steady-state flux rates were reached for cyclosporine A across the corneal tissue after approximately 2 h in the presence of 10% and 20% Cremophore EL. This observation can probably be explained on the basis of increased aqueous solubility of cyclosporine A in the presence of this emulsifier. Cremophore EL also improved the penetration of cyclosporine A through the epithelial and stromal layers of the cornea [83],... 

The method allows visualization of the epithelial barrier and penetration of small molecules into cell layers indicating disruption of tight junctions (Saitou et al. 1998). Slides are examined under the fluorescent microscope for bound biotin and rhodamine staining in deeper epithelial and stromal layers. Staining indicates penetration of biotin molecules into the tissue through disrupted tight junction barriers (Xu et al. 2004). Recovery from disruption is tracked on day 0,1,2,3, and 4. 

FIGURE 39.1. The three cell layers of the cornea. Shown on the left is a frozen section of an adult rabbit cornea stained with hematoxylin and eosin. On the right is a frozen section of a 6 week old mouse cornea. The mouse cornea is not fully mature until 8 weeks after birth. The left half visualizes the cornea by phase contrast microscopy. The right half shows the nuclei by DAPI staining. The density of the cells in the epithelial layer, and the paucity of keratocytes in the stromal layer are clearly seen with the nuclear stain. 

The proteins most obviously adversely affected are, indeed, those involved in the strong adhesion at the border between the epithelial and stromal layers, i.e. the basement membrane zone (Smith etal, 1998), and it is unknown why this is so. The loss of the epithelial-stromal adhesion is dramatic, initiating bhs-tering of the skin. The cornea does not bhster. Although the microbuUae that form between the comeal epithelium and stroma in response to SM exposure seem less dramatic, they clearly impair corneal integrity. Figure 39.4 shows some of the... 

The explosion of science in the latter half of the 20th century, elueidating eomponents of the adhesion complex between the epithelial and stromal layers of the cornea, suggest the basement membrane zone may become a target area for therapy in the future. Indeed, protease inhibitors of enzymes that remodel the basement membrane show promise as eountermeasures. Using rabbits for an ocular SM vapor challenge, the matrix metalloprotease inhibitors... 

The stroma constitutes approximately 90% of the total corneal thickness and is primarily composed of collagen fibers, keratocytes, and glycosaminoglycans. The imiform arrangement of the collagen fibers is the major determinant of corneal transparency, in contrast to the opaque and less regularly arranged fibers of the sclera. Disruption of the stromal layer regularity results in loss of corneal transparency and potential scar formation. 

The amnion is the innermost placental layer consisting of the inner epithelial layer, basement membrane, and stromal layer, which are located adjacent to the chorion. The stromal layer is more finely made up of a compact layer, fibroblast layer, and spongy layer. This amnion construct compiles five distinct layers and has a width ranging of 0.02-0.5mm in thickness. ... 

The chorion is a bilaminar membrane comprised of an outer reticular layer which is similar to the amnion s stromal layer and an inner, trophoblast layer. Even though the chorion layer demonstrates a greater thickness than the amnion, it demonstrates less tensile strength than the amnion layer. The chorion contains vilh that function as the barrier between maternal and fetal blood vessels. ... 

All these anti-inflammatory proteins and growth factors contained in AM may still need to have contact with the stromal layer of the amnion. Direct contact with the stroma by polymorphonuclear and mononuclear cells results in premature death. This rapid clearance of the granulocytes is an effective anti-inflammatory effect. This process is demonstrated most effectively in corneal surgery. ... 

The low-signal-intensity middle layer corresponds to the cervical stroma and mostly consists of connective tissue. The outer layer has a signal intensity that is comparable to that of the myometrium and is characterized by a more loose tissue structure [20] and may not always be distinguishable from the parametria even on T2-weighted images. The mucosa in the cervical canal shows the strongest enhancement and is thus clearly distinct from the less enhancing stromal layer. The outer stromal layer of the cervix and the portio also show contrast enhancement. 

Wilson, S., Wimpenny, I., Aheame, M., Rauz, S., El Haj, A., Yang, Y., 2012. Chemical and topographical effects on cell differentiation and matrix elasticity in a comeal stromal layer model. Advanced Functional Materials 22 (17), 3641—3649. 

The cornea serves as a protective layer of the eye and is comprised of several layers. The epithelium is the initial layer (0.1 mm). The multicellular epithelium consists of 56 layers of cells, and these layers pose a barrier to drug penetration. The tight jimctions prevent movement of drugs from the lacrimal fluid into the eye, while the stromal layer, because of its hydrated nature, hinders the movement of lipophilic drugs. These defense mechanisms of the eye protect it against foreign bodies, and consequently they affect drug... 

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