Qualitative and quantitative morphologic changes in the vasculature and extracellular matrix of the prelaminar optic nerve head in eyes with POAG.

PURPOSE: To analyze the vasculature and extracellular matrix changes in the prelaminar region (PreLR) of the optic nerve head (ONH) and in the peripapillary sclera of eyes with primary open-angle glaucoma (POAG) and age-matched control eyes. METHODS: In histologic sagittal sections of 46 eyes with POAG and 45 control eyes (donor ages, 20-96 years), the peripapillary sclera and penetrating vessels were investigated ultrastructurally and with antibodies against elastin, podocalyxin, and α-actin. Within the PreLR, the number and density of capillaries and the thickness of their connective tissue sheaths (CTSs) were quantified. The composition of the CTS was analyzed by using antibodies against collagen types I, III, IV, and VI, and elastin. Areas within the PreLR containing capillaries with thick or thin CTSs were determined. RESULTS: There were no glaucomatous changes in the peripapillary elastic fibers and in the arterial capillaries in the periphery of the PreLR. In the center of the PreLR, the capillaries gained a CTS that was significantly thicker in POAG eyes than in control eyes, and the area containing capillaries with thick CTSs was significantly larger. These data did not correlate with axon counts. CONCLUSIONS: Lack of glaucomatous changes in elastic fibers of the scleral suspension of the ONH seems to prevent occlusion of penetrating vessels. In the PreLR, thickening of the capillary CTS and enlargement of the area containing capillaries with thickened CTS could increase diffusion time and may impair nutrition of the neuronal tissue.

Morphology and histological annual changes of the oviduct of chaetophractus villosus (Mammalia, Xenarthra, Dasypodidae) / Morfología y cambios histológicos anuales del oviducto de Chaetophractus villosus (Mammalia, Xenarthra, Dasypodidae)

The morphological features of the oviduct in the armadillo Chaetophractus villosus (Desmarest, 1804) were studied. In the simple columnar epithelium, ciliated cells, secretory cells, and cells of the bottom of the folds are described. The most remarkable findings are the increase in number of ciliated cells, when present, from the fimbriae to the uterus, being the isthmus practically lined by ciliated cells, and that secretory cells are more abundant in the apical zone of the ampulla and fimbriae, than in the isthmus. Morphological changes along the year in the different portions are described.

Se estudiaron las características morfológicas del oviducto del armadillo Chaetophractus villosus (Desmarest, 1804). En el epitelio, columnar simple, se describen células ciliadas, secretoras y células del fondo de los pliegues. Las células ciliadas, cuando están presentes, aumentan en número desde las fimbrias hacia el útero, estando el istmo prácticamente tapizado por células ciliadas, las células secretoras son más abundantes en la zona apical de la ampolla y en las fimbrias, que en el istmo. Se describen los cambios morfológicos en las diferentes porciones a lo largo del año.

Pharmacological vascular reactivity in isolated diabetic rabbit ciliary artery.

Impairment of the ocular circulation induced by diabetes mellitus has not been fully defined, but is thought to be related to hemodynamic changes in the ocular circulation. The purpose of the present study is to investigate the functional and morphological changes occurring in the ciliary artery wall of rabbits with alloxan-induced diabetes mellitus. A single intravenous bolus injection of alloxan (100 mg/kg) was given to each of 26 10-week-old rabbits and 16 sham-injected control rabbits. Twenty weeks later, control rabbits and diabetic rabbits were sacrificed, and their ciliary arteries were mounted in a myograph system. The responses of these arteries to high K+ solution (K-Krebs solution), phenylephrine and carbachol were investigated using isometric tension recording. L-NAME (NG-nitro-l-arginine methyl ester; 100 microM) and indomethacin (1 microM) were also used to test the mechanism causing the carbachol induced relaxation. The arteries were also examined morphologically. The maximum tensions induced by K-Krebs solution in this tissue were not significantly different: 17.2+/-0.8 mN (n=16) in the control rabbits and 17.6+/-0.8 mN (n=23) in the diabetic rabbits (P=0.36). Phenylephrine caused dose-dependent contraction with EC50 values of 1.3+/-0.4 microM (n=6) in the control and 5.1+/-2.3 microM (n=6) in the diabetic rabbits, but there was no significant difference between the two (P=0.36). Carbachol induced dose-dependent relaxations in segments precontracted with K-Krebs solution. These relaxations were significantly reduced in the diabetic rabbits. The maximum relaxation induced by carbachol was 77.0+/-2.4% (10 microM) and 66.4+/-2.5% (100 microM) in the control and diabetic rabbits, respectively. These values were significantly different (P=0.0076). The IC(50) value for carbachol was 396.3+/-58.4 nM (n=16) in the control, and 443.6+/-141.1 nM (n=23) in the diabetic rabbit (P=0.87). Application of a 100 microM nitric oxide synthase inhibitor, L-NAME, significantly inhibited the amplitude of relaxations evoked by carbachol (P=0.0066). However, these relaxations were not inhibited by pretreatment with 1 microM indomethacin (P=0.60). Histologically, the frequency of invaginations was less in the diabetic arterioles with a flattening of the lamina in the diabetic rabbits than in the controls. The cytoplasm of endothelial cells contained large vacuoles, indicating weak adhesion to the lamina. Some endothelial cells even showed vacuolar degeneration due to breakdown of the cell membranes. However, the smooth muscle cells were well preserved in the diabetic rabbit. These results suggest that the mechanism of impairment of ocular circulation induced by diabetes mellitus is mainly the reduction of NO synthase due to endothelial cell dysfunction. Furthermore, the characteristics of rabbits with alloxan-induced diabetes mellitus probably make them a useful model for investigating ocular complications induced by diabetic mellitus.

Ocular blood flow evaluation in injured and healthy fellow eyes.

PURPOSE: To assess if injured eyes develop ocular blood flow disturbances that may contribute to development of traumatic glaucoma. METHODS: Twenty-five eyes of 25 patients hospitalized from January 1997 to July 1999 for blunt (15) or penetrating (10) eye injury and elevated intraocular pressure (IOP) (>23 mm Hg) were controlled at least 24 months after the trauma and underwent visual field examination, pulsatile ocular blood flow (pOBF), and color Doppler imaging (CDI) analysis of ophthalmic artery, central retinal artery, nasal and temporal short posterior ciliary arteries. Uninjured healthy eye was used as control. RESULTS: IOP was significantly higher in injured eyes (15.1+/-3.3 vs 13.0+/-2.7 mmHg; p<0.01), but only 2 eyes (8%) were under medical treatment. pOBF values were significantly lower in injured eyes: 11.25+/-6.56 microL/sec in the trauma eyes and 15.40+/-7.29 in fellow eyes (p=0.002). Resistivity index of all investigated retrobulbar vessels was very significantly higher in injured eyes than in fellow eyes (p<0.0001). There is no significant correlation between IOP and ocular blood flow disturbance. CONCLUSIONS: Long-term follow-up (mean 39+/-12 months) of injured eyes shows, besides a slight but significant increase of IOP, a very significant impairment of ocular blood supply to injured eyes compared to healthy fellow eyes with reduction of pulsatile ocular blood flow and marked increase of resistance to flow in all retrobulbar vessels. These anomalies may be considered an independent risk factor to develop traumatic glaucoma.

Pharmacological vascular reactivity in isolated hypercholesterolemic rabbit ciliary artery.

We have investigated functional and morphological changes occurring in the wall of the hypercholesterolemic rabbit ciliary artery. A mutant rabbit with hypercholesterolemia and atherosclerosis was created by serial breeding. Ciliary arteries from hypercholesterolemic, age-matched control and young control rabbits' eyes were mounted in a myograph system. The effects of phenylephrine (PE), carbachol and electrical field stimulation on this artery were investigated using isometric tension recording methods. The arteries were also examined morphologically. PE caused dose-dependent contraction in young control, age-matched control and hypercholesterolemic rabbits. The EC(50) values were 1.0 microm (0.2-2.1, n = 6), 1.4 microm (0.4-2.4, n = 6) and 4.7 microm (1.8-7.7, n = 8) in the young, age-matched controls and in the Kurosawa and Kusanagi-hypercholesterolemic (KHC) rabbits, respectively. The EC(50) values of the KHC rabbit were significantly different from those of control. Electrical field stimulation evoked contraction only in the control rabbits. On the other hand, electrical field stimulation evoked relaxation when the ciliary artery was pre-contracted by 10 microm histamine in each type of rabbit equally. Carbachol also induced approximately equal dose-dependent relaxation after pre-contraction. The morphological findings of KHC rabbit ciliary artery revealed irregular contours on the internal elastic lamina and deformation of the shape of the medial smooth muscle cells with irregularity in size and widening of the intercellular spaces. However, the endothelial cells were well preserved. Compared with the ciliary artery, typical atherosclerotic changes existed in the intima, not the media, in the KHC rabbit aorta. In the hypercholesterolemic rabbit ciliary artery, the vasoconstricting function was reduced but vasodilatation was well preserved. Morphological findings supported this. The pharmacological vascular reactivity in the hypercholesterolemic rabbit ciliary artery is quite different from that of the large arteries.

Experimental study on the prevention of anterior segment ischemia by preservation of anterior ciliary vessels.

PURPOSE: To observe the effect of preserving anterior ciliary vessels (ACVs) on anterior segments of rabbit eyes undergoing tenotomy of extraocular muscles. METHODS: Thirty-two adult New Zealand white rabbits were divided into four groups. Same procedures were done in both eyes in each group except that left eyes underwent preservation of ACVs. In the first group medial and lateral recti, in the second group, superior and inferior recti, in the third group, medial, lateral and superior or inferior recti and in the fourth group, all four recti, underwent tenotomy. Slit-lamp examination, intraocular pressure (IOP) measurement, total protein and lactic acid quantification in aqueous humor were done in all eyes pre- and post-operatively. By four weeks after operation, the eyes were enucleated for histological examination and electron microscopy. All data were analyzed using SPSS version 10. RESULTS: In the left eyes of both group 1 and group 2, no inflammatory response was observed. In the left eyes of group 3 and 4, we observed mild inflammatory response with slit-lamp examination, which disappeared in one wk. However, we did not find significant changes in IOP, total protein and lactic acid of aqueous humor, histology and electron microscopic examination in these groups. In the right eyes in group 2, 3 and 4, we observed moderate to severe inflammatory changes, a few even developed anterior segment ischemia, appeared as decreased IOP, increased total protein and lactic acid in aqueous humor, along with pathological and electron-microscopic changes. CONCLUSION: Simultaneous tenotomy of three or four recti or two vertical recti on one eye may decrease anterior segment blood flow even lead to ischemia. ACVs preservation may protect the blood circulation in anterior segment. Our study suggests that ACVs preservation in strabismus surgeries especially those involving multi-recti tenotomies may prevent potential anterior segment ischemia.

Specialised sympathetic neuroeffector associations in immature rat iris arterioles.

Sympathetic nerve-mediated vasoconstriction in iris arterioles of mature rats occurs via the activation of alpha(1B)-adrenoceptors alone, while in immature rat iris arterioles, vasoconstriction occurs via activation of both alpha1- and alpha2-adrenoceptors. In mature rats the vast majority of sympathetic varicosities form close neuroeffector junctions. Serial section electron microscopy of 14 d iris arterioles has been used to determine whether restriction in physiological receptor types with age may result from the establishment of these close neuroeffector junctions. Ninety varicosities which lay within 4 microm of arteriolar smooth muscle were followed for their entire length. Varicosities rarely contained dense cored vesicles even after treatment with 5-hydroxydopamine. 47 % of varicosities formed close associations with muscle cells and 88 % formed close associations with muscle cells or melanocytes. Varicosities in bundles were as likely as single varicosities to form close associations with vascular smooth muscle cells, although the distribution of synaptic vesicles in single varicosities did not show the asymmetric accumulation towards the smooth muscle cells seen in the varicosities in bundles which were frequently clustered together. We conclude that restriction of physiological receptor types during development does not appear to correlate with the establishment of close neuroeffector junctions, although changes in presynaptic structures may contribute to the refinement of postsynaptic responses.

Microvasculature of the rat optic nerve head.

PURPOSE: To describe the arterial blood supply, capillary bed, and venous drainage of the rat optic nerve head. METHODS: Ocular microvascular castings from 6 Wistar rats were prepared by injection of epoxy resin through the common carotid arteries. After polymerization, tissues were digested with 6 M KOH, and the castings washed, dried, and coated for scanning electron microscopy. RESULTS: Immediately posterior to the globe, the ophthalmic artery trifurcates into the central retinal artery and two posterior ciliary arteries. The central retinal artery directly provides capillaries to the nerve fiber layer and only contributes to capillary beds in the neck of the nerve head. The remainder is supplied by branches of the posterior ciliary arteries that are analogous to the primate circle of Zinn-Haller. Arterioles arising from these branches supply the capillaries of the transitional, or laminar, region of the optic nerve head. These capillaries are continuous with those of the neck and retrobulbar optic nerve head. All optic nerve head capillaries drain into the central retinal vein and veins of the optic nerve sheath. A flat choroidal sinus communicates with the central retinal vein, the choriocapillaris, and with large veins of the optic nerve sheath. CONCLUSIONS: The microvasculature of the rat optic nerve head bears several similarities to that of the primate, with a centripetal blood supply from posterior ciliary arteries and drainage into the central retinal and optic nerve sheath veins. Association of nerve sheath veins with the choroid represents an important difference from the primate.

Wall cytoarchitecture of the rat ciliary process microvasculature revealed with scanning electron microscopy.

Ciliary process vasculature has an important role in aqueous humor production. There have been, however, few reports describing the overall cytoarchitecture of ciliary process vasculature. The wall cytoarchitecture of microvessels in the rat ciliary process was elucidated by scanning electron microscopy after removal of ciliary epithelia and connective tissue components with HCl hydrolysis. Utilizing characteristics of cellular morphology and vessel diameters, several vascular components were identified along the vascular tree: 1) arterial iridociliary circles (30-60 microm in outer diameter), containing a compact layer of circularly oriented spindle-shaped smooth muscle cells; 2) the proximal part of the radial ciliary arteriole (10-25 microm), containing a less compact layer of circularly oriented branched-smooth muscle cells and spindle-shaped smooth muscle cells; 3) a middle part of the radial ciliary arteriole (20-35 pm), with circularly oriented branched-smooth muscle cells and irregularly oriented stellate cells with ramifying projections; 4) a distal part of the radial ciliary arteriole (10-20 microm), possessing irregularly oriented stellate cells with ramifying projections; 5) marginal venules (15-20 microm), with spidery pericytes possessing highly ramifying and overlapped projections; 6) capillaries in the ciliary process (4-7 microm), with widely scattered pericytes having longitudinal and several circular projections; 7) venules in the posterior basal region of the ciliary process (greater than 5 microm), with widely scattered pericytes having a few thin projections. From arterial iridociliary circles to venules in the basal region of ciliary process, seven parts could be recognized by wall cytoarchitecture, which was discussed in relation with the function.

Lack of bradykinin-induced smooth muscle cell hyperpolarization despite heterocellular dye coupling and endothelial cell hyperpolarization in porcine ciliary artery.

In porcine coronary artery, bradykinin-induced endothelium-dependent vasodilatations are associated with simultaneous endothelium as well as endothelium-dependent smooth muscle cell (SMC) hyperpolarizations. In contrast, in porcine ciliary artery bradykinin evokes endothelium-dependent relaxations, but no change in SMC membrane potential. This study addresses the question of whether the lack of bradykinin-induced SMC hyperpolarization is also associated with an absence of endothelial hyperpolarization in porcine ciliary artery. With a microelectrode to impale cells in arterial strips, a 12-mV transient bradykinin-induced hyperpolarization was measured in endothelial cells. Bradykinin evoked no SMC hyperpolarization deep in the media. Only occasionally, a slight 4-mV hyperpolarization could be recorded in some SMC next to the endothelium. The endothelial intracellular injection (through the recording electrode) of the fluorescent tracers, lucifer yellow or ethidium bromide, showed the existence of a heterocellular dye coupling between endothelial cells and SMC. These observations in porcine ciliary artery demonstrate that the lack of bradykinin-induced endothelium-dependent SMC hyperpolarization is not due to an absence of endothelial cell hyperpolarization, but most likely to an insufficient electrotonic propagation space constant from endothelial cells to SMC, despite the presence of a dye coupling between these cells.