Gene/Protein Disease Symptom Drug Enzyme Compound
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This review of retinal pigment epithelial (RPE) physiology pays tribute to Anthony L. F. Gorman, who introduced the author to the giant neuron of Anisodoris nobilis (the sea lemon) and cellular neurobiology. The RPE is an epithelial monolayer with tight junctions, which controls the environment of the photoreceptor outer segments. The apical and basal membranes have different electrical properties and generate a standing potential across the eye. The RPE helps maintain adhesion between the retina and the wall of the eye. Adhesion is weakened by cyanide, low pH or low calcium, but enhanced by ouabain or acetazolamide. The RPE transports water from the subretinal space toward the choroid. This water movement is inhibited by hypoxia or cyanide but enhanced by ouabain or acetazolamide. The c-wave of the electroretinogram is a composite of a cornea-positive wave produced by hyperpolarization of the apical RPE membrane and a cornea-negative wave produced by the Muller cells, both in response to the fall in extracellular potassium that follows illumination of the photoreceptors. The "light response" of the standing potential is produced by depolarization of the basal membrane of the RPE. These examples illustrate how principles of cellular neurophysiology can be applied to questions of clinical relevance.
Cell Mol Neurobiol 1983 Dec
PMID:From sea lemons to c-waves. 632 7

Rat IsK protein is a 130-amino acid membrane protein and subserves generation of K+ outward current. The expression of this putative K+ ion channel mRNA was explored in the eye with in situ hybridization. The ganglion cell layer of the retina expressed IsK mRNA in a subpopulation of ganglion cells composed of large cell bodies. The hybridization-positive cells were scattered throughout the retina. The hybridization signal was also localized to the epithelial cells throughout the cornea. The results provided evidence for IsK message in neuronal cells. Expression of IsK message in the eye was thus shown to be restricted to particular cell types.
Brain Res Mol Brain Res 1995 Apr
PMID:A subpopulation of large ganglion neurons express IsK protein mRNA: an in situ hybridization analysis in the rat eye. 760 26

Flestolol, N(1,1-dimethyl-2-ureidocthyl)-2-hydroxy-3-(o-fluorobenzoyloxy++ +) propylamine, (F), is an ester containing an ultra short-acting beta blocker intended for the treatment of myocardial dysfunctions. In vitro incubation of F, procaine, chloroprocaine, and atropine with blood from different New Zealand White (NZW) rabbits resulted in a bimodal distribution (70% fast, 30% slow) of ester hydrolysis rates. Using F as a model substrate, bimodal hydrolysis rates were also observed in NZW rabbit cornea but not aqueous humor, iris-ciliary body complex and ocular tissues of pigmented rabbits. In addition, the bimodal distribution of esterase activity was not observed in blood from rats, dogs, and humans. Incubation of esters at various positions of the phenoxypropanolamine nucleus of beta blockers with NZW rabbit blood indicated structural specificity of the carboxylesterase in terms of unimodal or biomodal distribution of activity. These results strongly suggest that the carboxylesterase in NZW rabbit blood that hydrolyzes F and similar compounds is atropine esterase as described in the literature.
Res Commun Mol Pathol Pharmacol 1995 Apr
PMID:Polymorphic metabolism of flestolol and other ester containing compounds by a carboxylesterase in New Zealand white rabbit blood and cornea. 762 Aug 41

Chronic exposure of the gray, short-tailed opossum, Monodelphis domestica, to ultraviolet radiation (UVR) induces highly vascularized mesenchymal tumors of the cornea. Cell lines derived from these UVR-induced corneal tumors and the corneal tumors themselves were examined for the presence of mRNA coding for basic and acidic fibroblast growth factors (FGF), transforming growth factors-beta and -alpha (TGF-beta and TGF-alpha), epidermal growth factor (EGF), and tumor necrosis factor-alpha (TNF-alpha). Basic FGF was expressed in the cell lines derived from corneal tumors and in the corneal tumors. Expression of basic FGF was high in one corneal tumor. Transcripts for acidic FGF were detected only in the corneal tumor cell lines, not in primary tumors. TGF-beta expression was detected in the corneal tumors and tumor-derived cell lines. TGF-alpha, EGF, and TNF-alpha transcripts were not detectable in any opossum material; however, homologous gene sequences for TGF-alpha and EGF were detected on Southern blots of opossum genomic DNA. Southern blot analysis revealed no evidence of amplification or rearrangement of the genes for basic FGF or acidic FGF in the UVR-induced corneal tumor that expressed high levels of basic FGF. Opossum basic FGF, which stimulated the proliferation of fetal bovine heart endothelial cells, was purified by heparin affinity chromatography from a UVR-induced corneal tumor and a corneal tumor cell line. Immunoblotting of opossum basic FGF from a corneal tumor cell line using antiserum to bovine basic FGF showed two prominent immunoreactive bands of 17.5 and 18.5 kDa. Expression of basic FGF and acidic FGF may play a role in the development and progression of UVR-induced corneal tumors in M. domestica.
Mol Carcinog 1993
PMID:Expression of fibroblast growth factors in ultraviolet radiation-induced corneal tumors and corneal tumor cell lines from Monodelphis domestica. 768 86

Posterior polymorphous dystrophy (PPMD) is an autosomal dominant disorder of the cornea that is clinically recognized by the presence of vesicles on the endothelial surface of the cornea. The corneal endothelium is normally a single layer of cells that lose their mitotic potential after development is complete. In PPMD, the endothelium is often multi-layered and has several other characteristics of an epithelium including the presence of desmosomes, tonofilaments, and microvilli. These abnormal cells retain their ability to divide and extend onto the trabecular meshwork to cause glaucoma in up to 40% of cases. A large family with 21 members affected with PPMD was genotyped with short tandem repeat polymorphisms distributed across the autosomal genome. Linkage was established with markers on the long arm of chromosome 20. The highest observed LOD score was 5.54 (theta = 0) with marker D20S45. Analysis of recombination events in four affected individuals revealed that the disease gene lies within a 30cM interval between markers D20S98 and D20S108.
Hum Mol Genet 1995 Mar
PMID:Linkage of posterior polymorphous corneal dystrophy to 20q11. 779 7

Wilson disease is an autosomal recessive disorder of copper transport. Disease symptoms develop from the toxic build-up of copper primarily in the liver, and subsequently in the brain, kidney, cornea and other tissues. A candidate gene for WD (ATP7B) has recently been identified based upon apparent disease-specific mutations and a striking amino acid homology to the gene (ATP7A) responsible for another human copper transport disorder, X-linked Menkes disease (MNK). The cloning of WD and MNK genes provides the first opportunity to study copper homeostasis in humans. A preliminary analysis of the WD gene is presented which includes: isolation and characterization of the 5'-end of the gene; construction of a genomic restriction map; identification of all 21 exon/intron boundaries; characterization of extensive alternative splicing in brain; prediction of structure/function features of the WD and MNK proteins which are unique to the subset of heavy metal-transporting P-type ATPases; and comparative analysis of the six metal-binding domains. The analysis indicates that WD and MNK proteins belong to a subset of transporting ATPases with several unique features presumably reflecting their specific regulation and function. It appears that the mechanism of alternative splicing serves to regulate the amount of functional WD protein produced in brain, kidney, placenta, and possibly in liver.
Hum Mol Genet 1994 Sep
PMID:Characterization of the Wilson disease gene encoding a P-type copper transporting ATPase: genomic organization, alternative splicing, and structure/function predictions. 783 24

Pili of Neisseria gonorrhoeae are correlated with increased bacterial attachment to epithelial cells and undergo both phase and antigenic variation. Phase variation of gonococcal pili can be brought about by recombination events in the pilin structural gene, pilE, or by the on/off switch in expression of PilC, a pilus biogenesis protein for which two loci exist. We have studied the binding to epithelial cell lines and to fixed tissue sections of N. gonorrhoeae MS11 derivatives and mutants carrying structurally defined PilE and PilC proteins. In situ binding studies of N. gonorrhoeae to formalin-fixed tissue sections resulted in a binding pattern similar to that obtained using viable epithelial cell lines of different origin. Piliated gonococcal clones, containing different pilE sequences, varied dramatically from one another in their efficiencies at binding to corneal and conjunctival tissue, but bound equally well to cervical and endometrial tissues. Further, the binding data suggested that PilC expression by itself, i.e. without pili, cannot confer bacterial binding and that expression of either PilC1 or PilC2 does not confer different binding properties to the bacterial cells. Possible receptors for piliated gonococci were expressed in human tissues, such as cervix, endometrium, cornea, intestine, stomach, mid-brain and meninges, but not in human kidney. Pretreatment of the target tissues with Proteinase K decreased the gonococcal binding dramatically, whereas pretreatment with neuraminidase and meta-periodate, which cleave carbon-carbon linkages between vicinal hydroxyl groups in carbohydrates, did not affect attachment of gonococci. These data argue that pilus-dependent attachment of N. gonorrhoeae to human tissue may be mediated by a eukaryotic receptor having protein characteristics, and that the pilus subunit sequence may play an important role in the interaction with human cornea.
Mol Microbiol 1994 Aug
PMID:Sequence changes in the pilus subunit lead to tropism variation of Neisseria gonorrhoeae to human tissue. 799 58

Moraxella bovis, the causative agent of infectious bovine keratoconjunctivitis, exhibits several virulence factors, including pili, haemolysin, leukotoxin, and proteases. The pili are filamentous appendages which mediate bacterial adherence. Prior studies have shown that Q-piliated M. bovis Epp63 are more infectious and more pathogenic than I-piliated and non-piliated isogenic variants, suggesting that Q pili per se, or traits associated with Q-pilin expression, promote the early association of Q-piliated bacteria with bovine corneal tissue. In order to better evaluate the role of Q pili in M. bovis attachment, several M. bovis strains and a recombinant P. aeruginosa strain which elaborates M. bovis Q pili but not P. aeruginosa PAK pili, were evaluated using an in vitro corneal attachment assay. For each strain tested, piliated organisms attached better than non-piliated bacteria. M. bovis Epp63 Q-piliated bacteria adhered better than either the I-piliated or non-piliated isogenic variants. Finally, recombinant P. aeruginosa organisms elaborating M. bovis Q pili adhered better than the parent P. aeruginosa strain which did not produce M. bovis pili. These results indicate that the presence of pili, especially Q pili, enhances the attachment of bacteria to bovine cornea in vitro.
Mol Microbiol 1993 Jan
PMID:Q pili enhance the attachment of Moraxella bovis to bovine corneas in vitro. 809 18

Synchrotron X-ray diffraction was used to monitor the changes occurring in the extracellular matrix of the corneal stroma as a result of freezing and thawing. The parameters monitored were the lateral centre-to-centre spacing between the collagen molecules within the fibrils (intermolecular spacing) and the centre-to-centre spacing between the collagen fibrils (interfibrillar spacing). Our findings suggest that, while frozen, the fibrils are reduced in diameter and are forced into close association with each other. The data also suggest that the extrafibrillar components of the cornea may become concentrated around the fibrils during freezing. However, X-ray patterns of thawed corneas show normal interfibrillar and intermolecular spacings. Time-resolved data show that, as thawing takes place, the fibrils gradually separate and regain their normal spacing while at the same time regaining their normal diameter. It seems probable that the mechanism which allows the fibrils to regain their normal arrangement after thawing involves charge interactions between the proteoglycans associated with the fibrils. However, unlike corneas at physiological hydration, certain regions of the stroma of swollen corneas do suffer irreversible damage as a result of freezing. It is possible that this ice damage may occur in regions of abnormal fibril arrangement called "lakes", which are reported to occur in swollen cornea.
J Mol Biol 1994 Feb 25
PMID:An ultrastructural, time-resolved study of freezing in the corneal stroma. 811 92

Angiotensin converting enzyme (ACE) was measured in 15 sheep tissues by spectrophotometric assay with hippuryl-L-histidyl-L-leucine as substrate. Captopril inhibited the ACE activities of all the tissues. The ACE activity was highest in caput epididymidis, corpus epididymidis, cauda epididymidis, kidney and testis. The ACE activity was moderate in retina, little in cornea and lowest in lens. The greater increase in epididymal ACE activity than that of testicular ACE activity on maturation indicates that epididymal ACE may be highly sensitive to hormones. Chloride functioned as non-essential activator of corneal and retinal ACE. The ACE activities of sheep tissues are compared with those found in other species and probable role of ACE in different tissues is discussed.
Biochem Mol Biol Int 1993 Dec
PMID:Distribution and some properties of sheep (Ovis aries) angiotension converting enzyme. 813 3


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