Ocular Fluids

Cole, David

doi:10.1016/b978-0-12-206901-7.50007-5

Cited by 22 publications

(10 citation statements)

References 289 publications

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“…Adult retinal capillary endothelium also expresses the Tf receptortcarrier system, and this could account for delivery of the Tf-iron complex to the retina and vitreous, and later to the aqueous humor (Vadot et al, 1988). Transferrin may be distributed throughout the intraocular environment of the embryonic eye by way of diffusional exchange and hydraulic conductivity between the aqueous and vitreous humors (Cole, 1980;R. Tripathi and B. Tripathi, 1982).…”

Section: Trans Ferrinmentioning

confidence: 99%

The role of growth factors in the embryogenesis and differentiation of the eye

Tripathi

Livingston

et al. 1991

Am. J. Anat.

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The vertebrate eye is composed of a variety of tissues that, embryonically, have their derivation from surface ectoderm, neural ectoderm, neural crest, and mesodermal mesenchyme. During development, these different types of cells are subjected to complex processes of induction and suppressive interactions that bring about their final differentiation and arrangement in the fully formed eye. With the changing concept of ocular development, we present a new perspective on the control of morphogenesis at the cellular and molecular levels by growth factors that include fibroblast growth factors, epidermal growth factor, nerve growth factor, platelet-derived growth factor, transforming growth factors, mesodermal growth factors, transferrin, tumor necrosis factor, neuronotrophic factors, angiogenic factors, and antiangiogenic factors. Growth factors, especially transforming growth factor-beta, have a crucial role in directing the migration and developmental patterns of the cranial neural-crest cells that contribute extensively to the structures of the eye. Some growth factors also exert an effect on the developing ocular tissues by influencing the synthesis and degradation of the extracellular matrix. The mRNAs for the growth factors that are involved in the earliest aspects of the growth and differentiation of the fertilized egg are supplied from maternal sources until embryonic tissues are able to synthesize them. Subsequently, the developing eye tissues are exposed to both endogenous and exogenous growth factors that are derived from nonocular tissues as well as from embryonic fluids and the systemic circulation. The early interaction between the surface head ectoderm and the underlying chordamesoderm confers a lens-forming bias on the ectoderm; later, the optic vesicle elicits the final phase of determination and enhances differentiation by the lens. After the blood-ocular barrier is established, the internal milieu of the eye is controlled by the interactions among the intraocular tissues; only those growth factors that selectively cross the barrier or that are synthesized by the ocular tissues can influence further development and differentiation of the cells. An understanding of the tissue interactions that are regulated by growth factors could clarify the precise mechanism of normal and abnormal ocular development.

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Section: Trans Ferrinmentioning

confidence: 99%

The role of growth factors in the embryogenesis and differentiation of the eye

Tripathi

Livingston

et al. 1991

Am. J. Anat.

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“…Cells were continuously superfused with Ringer solution (Table 1) or one of the test solutions. The composition of the Ringer solution was chosen to be similar to that of the aqueous humour of the rabbit (Cole, 1984). Tetrodotoxin 84 VOLTAGE-ACTIVATED CURRENTS IN AN EPITHELIUM (TTX, Sigma; final concentration 30 or 200 nM) and tetraethylammonium chloride (TEA-Cl, Sigma; 10 mM) were added directly to the Ringer solution before each experiment.…”

Section: Superfu8ion Sy8tem and Solutionsmentioning

confidence: 99%

“…Cells were continuously superfused with Ringer solution (Table 1) or one of the test solutions. The composition of the Ringer solution was chosen to be similar to that of the aqueous humour of the rabbit (Cole, 1984 1 1-5 mM-ATP and 0'1 mM-GTP were added to the internal solution before use. Calculated free Ca2+ concentration was 1-4 x 10-8.…”

Section: Superfu8ion Sy8tem and Solutionsmentioning

confidence: 99%

“…It consists of two cell layers: the pigmented cells, which lie directly adjacent to the stroma, and the non-pigmented cells, whose basal membranes face the posterior chamber (or lumen). These two cell layers are coupled by an extensive series of gap junctions at their apical membranes (Raviola & Raviola, 1978; Green, Bountra, Georgiou & House, 1985) and probably function together to pump ions and water from blood to the posterior chamber (Cole, 1984). The function of these cells has been difficult to study, partly because of the complicated Earlier transport studies (Chu, Candia & lizuka, 1986) and intracellular recordings on the intact ciliary body epithelial tissue (Green et al 1985), as well as recordings from confluent cell culture preparations of bovine pigmented cells (Helbig, Korbmacher & Wiederholt, 1987), have shown the presence of a K+ conductance in this epithelium, which is Ca2+-and pH-dependent and is blockable by Ba2+ (Helbig et al 1987).…”

Section: Introductionmentioning

confidence: 99%

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Voltage‐activated currents recorded from rabbit pigmented ciliary body epithelial cells in culture.

Fain¹,

Farahbakhsh²

1989

The Journal of Physiology

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1. The whole‐cell recording mode of the patch‐clamp technique was used to investigate the presence of voltage‐activated currents in the isolated pigmented cells from the rabbit ciliary body epithelium grown in culture. 2. In Ringer solution with composition similar to that of the rabbit aqueous humour, depolarizing voltage steps activated a transient inward current and a delayed outward current, while hyperpolarization elicited an inwardly rectified current. 3. The depolarization‐activated inward current was mainly carried by Na+ and was blocked by submicromolar concentrations of tetrodotoxin. This current in many cells was sufficiently large to produce a regenerative Na+ spike. 4. The depolarization‐activated outward current was carried by K+ and blocked by external TEA and Ba2+. Its activation appeared to be Ca2(+)‐independent. 5. The hyperpolarization‐activated inward current was almost exclusively carried by K+ and was blocked by Ba2+ and Cs+. For large hyperpolarizations below ‐120 mV, this current exhibited a biphasic activation with a fast transient peak followed by a slower sag, that appeared to be due to K+ depletion. 6. The voltage‐dependent K+ conductances probably act to stabilize the cell membrane resting potential and may also play a role in ion transport. The function of the Na(+)‐dependent inward current is unclear, but it may permit the electrically coupled epithelial cells of the ciliary body to conduct propagated action potentials.

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“…The aqueous humor is the major source of glucose supply for many avascular ocular tissues such as the cornea and crystalline lens (10,16,59). Its glucose concentration is known to be comparable and related to that of the blood plasma (5,13). The CBE is an epithelial bilayer that consists of the pigmented epithelium (PE) and the nonpigmented epithelium (NPE).…”

mentioning

confidence: 99%

Is active glucose transport present in bovine ciliary body epithelium?

Chan

Guggenheim

2007

American Journal of Physiology-Cell Physiology

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Hyperglycemia is a major risk factor for diabetic cataract formation. Effective regulation of glucose transport by the ciliary body epithelium (CBE) is pivotal to normal glycemic control in the anterior eye, which in turn affects the glucose level of the crystalline lens. The present study aimed to characterize the glucose transport mechanisms across the bovine blood-aqueous barrier (BAB) represented by the CBE. With an Ussing-type chamber, the glucose transport kinetics were measured and characterized in the presence and absence of various glucose transporter inhibitors. The saturation characteristics of the CBE to glucose were estimated from an Eadie-Hofstee plot. The mRNA expression of glucose transporters in specific regions of the bovine CBE was assessed using RT-PCR. The trans-CBE glucose flux was found to be sensitive to the glucose transporter inhibitors cytochalasin B, phloretin, and phlorizin. The transport system had a kinetic constant of 5.3 mM and a maximum velocity of 349.5 nmol.h(-1).cm(-2). Gene expression for GLUT1, GLUT3, GLUT4, GLUT5, and SGLT2 was observed in both the pars plana and pars plicata regions of the bovine CBE. This study demonstrates that glucose transport across the bovine CBE is primarily passive in nature. However, the novel findings of 1) the presence of a phlorizin-sensitive glucose flux and 2) gene expression for SGLT2 mean that a potential role for active glucose transport cannot be ruled out. The elucidation of the exact function of SGLT2 in the bovine CBE may shed important light on the glucose transport and physiology of the BAB and inform future studies of glycemic control in relation to diabetic cataract formation.

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Ocular Fluids

Cited by 22 publications

References 289 publications

The role of growth factors in the embryogenesis and differentiation of the eye

The role of growth factors in the embryogenesis and differentiation of the eye

Voltage‐activated currents recorded from rabbit pigmented ciliary body epithelial cells in culture.

Is active glucose transport present in bovine ciliary body epithelium?

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