The limbal vascular response to corneal injury. An autoradiographic study.

Thermal cautery of the peripheral cornea in rats caused proliferation of the limbal vasculature and invasion of the cornea. Tritiated-thymidine was used to identify premitotic activity in a total of 53,192 limbal vascular cells in five categories, viz., arteriolar endothelial cells, venular endothelial cells, arteriolar perivascular cells, venular perivascular cells, and capillary cells. From normal values in the range of 0.29 to 1.37%, the 2 h labeling indices reached a maximum of 13 to 14% in both endothelial and perivascular cells of venules and capillaries. Of particular interest was the finding of 18% labeling in arteriolar perivascular cells, and 7% in arteriolar endothelial cells. The categories showed a staggered onset of DNA synthesis, ranging from 17 h postcautery for capillary cells to 36 h for arteriolar endothelium and both arteriolar and venular perivascular cells. The duration of increased DNA synthesis also varied. Endothelial cells of both arterioles and venules showed narrow labeling peaks (12 to 24 h), while the adjacent perivascular cells and cells of the small vessels labeled for some 60 to 70 h. These results suggest that more than one stimulus to angiogenesis may be involved, or that the various cell types respond differently to the same stimulus.

Limbal lymphangiogenesis after corneal injury: an autoradiographic study.

Blood and lymphatic vessel proliferation into the cornea occurs after severe trauma. Whilst the events early in blood vessel growth are reasonably understood, little is known of the early events in lymphangiogenesis. In this study, a model for proliferating lymphatic vessels using tritiated-thymidine autoradiography and light microscopy is described. A two-hour labeling index of 0.59% occurred in the lymphatic endothelium of the normal unstimulated limbus. After thermal cautery of the peripheral cornea, labeling of the limbal lymphatic vessels increased significantly at 36 hours, rose to a maximum of 6.8% four days after injury and thereafter returned to normal levels. Blood capillaries with a background level of 0.83% showed an increase in labeling at 17 hours, with high levels occurring at 36 hours (13.6%) and again from 61 to 84 hours (12.6%). Venular cells increased labeling at 25 hours from a control level of 0.58%, with a sharp peak of activity around 36 hours (13.2%). Synthesis of DNA similarly returned to normal levels in the blood vessels after four days. The staggered onset and differing durations of significantly increased labeling suggest either that various stimuli or arrays of stimuli are involved, or each cell type responds differently to the same stimulus for proliferation.

Change in the fatty acid pattern of erythrocyte membrane phospholipids after oral supplementation of specific fatty acids in patients with gastrointestinal diseases.

BACKGROUND/OBJECTIVES: The fatty acid pattern of membrane phospholipids is suggested to affect membrane fluidity and epithelial barrier function as a result of membrane fatty acid unsaturation. The incorporation of n-3 polyunsaturated fatty acids (PUFAs) into membrane phospholipids may diminish inflammatory potential in patients with gastrointestinal diseases. The aim of this study was to improve the fatty acid profile of erythrocyte membrane phospholipids after oral supplementation of specific fatty acids in patients with maldigestion and/or malabsorption. SUBJECTS/METHODS: We conducted a randomized, double-blind, controlled trial. A total of 48 patients with gastrointestinal diseases received either fat-soluble vitamins A,D,E,K (ADEK) or ADEK plus fatty acids alpha-linolenic acid (ALA), docosahexaenoic acid (DHA) and medium-chain triglycerides (FA-ADEK) for 12 weeks. The fatty acid profile of erythrocyte membrane phospholipids, dietary intake, plasma antioxidant vitamins and serum gamma-glutamyl transferase (GGT) were evaluated at baseline, 8 and 12 weeks after supplementation. RESULTS: Supplementation with FA-ADEK increased ALA, DHA and eicosapentaenoic acid (EPA) concentrations of erythrocyte membrane phospholipids by 0.040, 1.419 and 0.159%, respectively, compared with ADEK supplementation (-0.007, 0.151 and 0.002%, respectively) after 12 weeks (all P

Lymphatic sinusoids exist in chick but not in rabbit choroid.

PURPOSE: Although it is generally thought that lymphatics do not exist in the choroid, there is mounting evidence that lymphatic-like structures do exist in primates and fowl. METHODS/RESULTS: Our comparison of the ultrastructure of chick and rabbit outer choroid indicates that major differences exist in the non-vascular areas of the choroid: notably, the chick has large lymphatic sinusoids, whereas the rabbit only has a system of large vacuoles contained within the processes of individual fibroblasts. CONCLUSIONS: These results raise questions regarding the similarities or otherwise between species of the management of retinal metabolites, excess tissue fluid and choroidal homeostasis, especially during conditions of overload.

X-ray elemental analysis differentiates blood vessels and lymphatic vessels in the chick choroid.

PURPOSE: Chick choroidal lymphatics swell rapidly during recovery from form-deprivation occlusion, leading to the question of functional significance. To date, analysis of lymph in initial lymphatics has been problematic because of the difficulties of access. However, elemental composition can be determined using scanning electron microscope (SEM) X-ray microanalysis. This study investigated whether cryo-fixation would permit vascular fluids to be analysed in situ. METHODS: Two chicks were raised normally and seven were raised with monocular occlusion for 12 days before varying periods of normal visual experience. The eyes were rapidly frozen, fractured and X-ray spectra obtained from the lumina of lymphatic and blood vessels in a Cambridge S360 SEM. RESULTS: The elemental signatures of Na/Cl/K/P/S distinguished the two vessel types. CONCLUSIONS: These results suggest this bulk-frozen tissue technique can quantify relative changes in elemental species present in various ocular compartments in response to light-induced changes in the retina.

A role for choroidal lymphatics during recovery from form deprivation myopia?

BACKGROUND: The choroid of the chick swells markedly during recovery from experimentally induced myopia. It has been demonstrated previously that the lymphatic sinusoids of the choroid contribute most to the expansion. This raises important questions about the particular ultrastructural changes occurring in choroidal lymphatics as a means of understanding the role these vessels might play in emmetropization. METHODS: Thirteen hatchling chicks were monocularly occluded for 2 weeks to induce myopia and then allowed normal visual experiences during recovery for periods of 0 to 72 h before sacrifice. RESULTS: Electron microscopic analysis detailed the temporal progression of vascular changes and provides qualitative evidence for edema in the extravascular space. Quantitative analysis showed that the frequency of open junctions between lymphatic endothelial cells (an indicator of passive fluid transfer) increased over the 3 days of recovery. Lymphatic fenestrations (an indicator of active fluid transfer) were rare in both nondeprived eyes and in form-deprived eyes at the time of occluder removal, but increased in density significantly over the first 24 h of recovery before returning to control levels by 72 h. The number of lymphatic endothelial caveolae did not change significantly during recovery, nor did the number of fenestrations along the walls of choriocapillaris vessels. CONCLUSIONS: The walls of the lymphatics of the chick choroid open to allow greater fluid transfer during re-emmetropization than normal; the lymphatics may play an important role in the maintenance of chorioretinal fluid balance and homeostasis.