The physiologic basis of aqueous humor formation. Formation of the Aqueous Humor 35 Civan, M. Aqueous Humor Outflow ResistanceThomas F. Early studies by Ba´ra´ny 1953, 1956 showed that testicular hyaluronidase dramatically decreased outflow resistance in enucleated bovine eyes. Melatonin has been demonstrated to be circadian in the tissues where it is synthesized including the pineal gland and retina.
Deamer, Arnost Kleinzeller, and Douglas M. Overview Introduction The Aqueous Humor Regions of Low Outflow Resistance Regions of Potential Significant Outflow Resistance A. . It is determined by the use of standardized tables, by fluorophotometry, by measuring a dilution rate of tracer infused into the anterior chamber, or by measuring the rate of appearance of tracer in blood after intracameral administration. Aqueous Humor Dynamics I: Measurement methods and animal studies Carol B.
The noninvasive methods are indirect, highly variable, and fraught with many limitations and assumptions. Somatostatin regulates brain amyloid beta peptide Abeta42 through modulation of proteolytic degradation. Functional mapping of Somatostatin receptors in the retina. Neurotransmitters in the vertebrate retina. But the adherens junction itself does not represent the occluding element of the junctional complex. Summary 207 References 207 Chapter 7: Aqueous Humor Dynamics I 214 I. The full gap junction is formed by the linking of connexons of adjoining cells.
It has been suggested that cortisol may impose diurnal variation on immune responsiveness, similar to melatonin. Cats Cats have relatively large eyes with correspondingly large anterior chambers, and they produce aqueous humor at higher rates than other research animals. This is followed by active secretion of fluid from the ciliary process core across the ciliary epithelial layers and into the posterior chamber. The eye rivals the kidney in terms of the number of aquaporin homologues that are expressed, and surpasses the kidney in terms of the number of diVerent cell types that express aquaporin channels. Articles in this volume discuss ion transport, ocular aquaporins and aqueous humor dynamics, the role of Ggap junction channels in the ciliary body secretory epithelium, regional dependence of inflow, functional modulators linking Iinflow with outflow of aqueous humor, aqueous humor outflow resistance, aqueous humor dynamics, the effects of circulatory events on aqueous humor inflow and intraocular pressure, retinal ganglion cells and glaucoma, what functional genomics is teaching us about intraocular pressure regulation and glaucoma, molecular approaches to glaucoma, outflow signaling mechanisms and new therapeutic strategies for the control of intraocular pressure.
Formation of the Aqueous Humor 39 Kishida, K. There is evidence that ambient light is an important factor in inducing the ocular immune privilege in the anterior chamber Ferguson et al. This method requires a cooperative subject and a clear conjunctiva to allow an unobstructed view of an appropriate vessel. The fact that the number of giant vacuoles increases with increasing pressure suggests a relationship between their formation and outflow. Aqueous Humor Outflow 191 Raviola, G.
Tonography in the normal and glaucomatous beagle. Summary of Current Views, Recent Advances, and Future Directions 51 References 54 Chapter 2: Ocular Aquaporins and Aqueous Humor Dynamics 68 I. This is similar to patients with ocular hypertension Toris et al. Summary of Current Views, Recent Advances, and Future Directions A. One eVective mechanism to regulate communication between cells and tissues is by regulating the level of extracellular peptide. Molecular structure and physiological function of chloride channels. Effects of Circulatory Events on Aqueous Humor Inflow and Intraocular Pressure Herbert A.
Synthesis and secretion of transferrin by isolated ciliary epithelium of rabbit. In view of these observed diVerences, further study of species variance would be welcome. Aqueous humor that is secreted into the posterior chamber 1 flows across the vitreous cavity 2 or through the pupil into the anterior chamber 3. Third, we will discuss the specific role of aquaporin channels in aqueous humor dynamics. Changes have been found in glaucomatous eyes in the cells of their inner wall endothelium as compared to normal eyes. The physiological significance of this finding warrants further investigation.
The action of different kinds of hyaluronidase on the resistance to flow through the anterior chamber. Transport Components Underlying Transcellular Secretion The ciliary epithelium expresses a wide range of ion channels and transporters responsible for facilitated diVusion, cotransport, and countertransport Jacob and Civan, 1996; Krupin and Civan, 1996. Mechanisms of sodium pump regulation. In humans, who generally are more active during the day than at night, the diurnal rate of aqueous flow is about twice the nocturnal rate Reiss et al. Aqueous humor dynamics in rats. Relaxation of trabecular meshwork and ciliary muscle by release of nitric oxide.
While the flow resistance of these breaks have not been explicitly calculated, these breaks are ubiquitous and typically are a fraction of a micrometer or larger in size. The book is concerned both with basic physiology and with its implications in addressing glaucoma. This consent does not extend to other kinds of copying, such as copying for general distribution, for advertising or promotional purposes, for creating new collective works, or for resale. Since the original equation was written, the importance of 7. Aqueous humor dynamics and trabecular meshwork and anterior ciliary muscle morphologic changes with age in rhesus monkeys. A pilot study on the eVect of atrial natriuretic peptide on intraocular pressure in the human. Gap Junctions in Ciliary Epithelium 79 secretory epithelia.
Expression and cellular distribution of the alpha 1 gap junction gene product in the ocular pigmented ciliary epithelium. It seems reasonable to presume that this secretion is conducted by much the same transporters in diVerent mammalian species. There is supporting evidence that factors found in AqH follow a circadian rhythm Nii et al. Ocular Distribution of Aquaporins -- V. The diversity of volume regulatory mechanisms. Changes in aqueous humor dynamics with age and glaucoma.