摘要:

The expression of four different gap junction (GJ) transcripts, corresponding to theα1,α3,β1 andβ2 gene products, has been examined in the ciliary epithelium of human and bovine eyes, and in cultures of ciliary epithelial cells. Northern blot analysis revealed that oq mRNA, 3.6-kb in size, was the predominant transcript expressed in intact tissue and in cultures of pigmented ciliary epithelial cells (PE). No transcripts from theα3,β1 orβ2 gap junction genes were detected in intact tissue or ciliary epithelial cells as demonstrated by Northern blotting. When the levels ofαgap junction mRNA were compared between PE and NPE in primary cultures, a striking difference was observed in the level of ai transcripts: there was about a 6 to 8-fold increase inα1 levels in PE cells, relative to the NPE cells. To verify the differential level of expression of ai GJ mRNA in the two cell types, indirect immunofluorescence localization studies were performed on semithin cryostat sections of ciliary processes. These studies revealed that al gap junctions are present at the apical and lateral borders of PE cells, i.e. at the apical plasma membranes domains of PE-NPE cells, and at the lateral plasma membrane regions of PE-PE cells borders. Further analysis by immunoblotting confirmed that the 43 kD ai gap junction protein was the major gap junction gene product in the ciliary eoithelium.

ISSN:0271-3683    

DOI:10.3109/02713689209000061

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

Decreased humoral defense mechanisms may be involved in the occurrence of keratic ulcerations after contact lens wear.To investigate the effect of contact lens wear on tear protein composition a prospective study was performed whereby tears were collected with Schirmer papers from 42 healthy individuals, before and at varying times after contact lens wear. Tear proteins were quantitated using HPLC analysis. Analysis of tear fluid by HPLC is a rapid and simple technique to detect the major tear proteins. Four separate peaks containing respectively IgA, lactoferrin, TSPA and lysozyme can easily be identified.The results show that the mean relative level of secretory IgA in the collected tear samples decreased significantly after the first months of contact lens wear but was not significantly altered after one year. The decrease in IgA was accompanied by a significant increase in the relative amount of lysozyme, whereas the levels of lactoferrin and TSPA remained the same.Certain individuals showed a marked decrease in their tear secretory IgA levels after wearing the lenses for more than one year. Future studies will clarify whether such individuals are at higher risk to develop corneal complications.

ISSN:0271-3683    

DOI:10.3109/02713689209000062

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

The perforated patch technique was utilized to obtain whole-cell currents from freshly dissociated rabbit corneal keratocytes. We describe and provide the initial characterization of two distinct whole cell currents in rabbit keratocytes: a K+-selective delayed rectifier and a voltage-sensitive, tetrodotoxin blockable Na+current. The voltage-sensitive Na+current is of sufficient magnitude to allow us to initiate action potentials when current-clamping the cells. This is the first detailed electrophysiological study of corneal keratocytes.

ISSN:0271-3683    

DOI:10.3109/02713689209000063

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

The effects of phorbol esters on phospholipase C (PLC) activity towards phosphoinositides and phosphatidylcholine (PC) in bovine corneal epithelial cells were examined. The cells were labeled with32Pi, myo[H]inositol or methyl[14C]choline, and PLC stimulated by incubation of the cells with Ca2+ionophore, ionomycin. The PLC activity was assessed by monitoring the loss of radioactivity from the labeled phospholipids or the accumulation of their radioactive metabolites. The data from this study can be summarized as follows: Addition of 20 /+M ionomycin to the prelabeled cells resulted in a rapid hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2) and somewhat slower hydrolysis of phosphatidylinositol (PI) and phosphatidylcholine (PC) with concomitant several-fold increase in phosphatide acid (PA). The effects of the ionophore were time- and dose-dependent. Incubation of the cells with phorbol 12,13-dibutyrate (PDBu) or phorbol 12-myristate 13-acetate (PMA) caused increased radioactivity in PC and PA, whereas the radioactivity in PI and PIP2remained unchanged. The effects of PDBu were inhibited by staurosporine and H-7, and inactive derivatives of phorbol esters failed to exert any effect on phospholipid metabolism. Pretreatment of the corneal epithelial cells with PDBu or PMA abolished the ionomycin-induced hydrolysis of phosphoinositides and PC. The data suggest that activation of protein kinase C by phorbol esters in corneal epithelial cells results in inhibition of PLC activity towards phosphoinositides and PC through a mechanism probably involving phosphorylation of the enzyme.

ISSN:0271-3683    

DOI:10.3109/02713689209000064

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

Previous investigations have reported a correlation between outer segment disk phagocytosis by the retinal pigment epithelium (RPE), and the formation of myeloid bodies, which are lamellar specializations of the smooth endoplasmic reticulum of the RPE. To further test the hypotheses that MBs are directly related to the process of outer segment shedding, we have undertaken to study the development of the retinal pigment epithelium in the chick utilizing a morphometric ultrastructural approach with specific attention to the timing of outer segment disk shedding and the formation of myeloid bodies.This study has demonstrated a temporal relationship between the initiation of photoreceptor outer segment disk shedding in the chick embryo and the occurrence of myeloid bodies. We have shown that photoreceptor outer segment disk shedding and phagocytosis by the RPE has been initiated in a substantial proportion of the retina by day 18 of development. Myeloid body formation does not begin until two days later at embryonic day 20, and is preceded by the development within the RPE of flattened areas of the normally tubular SER (templates), which we believe represent the precursors of myeloid body formation. Temporal development of outer segment phagocytosis, lamellar SER (template) occurrence and myeloid body formation are all statistically significant at the 95% level.

ISSN:0271-3683    

DOI:10.3109/02713689209000065

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

PCR and Southern blot analyses demonstrate that mRNA for heme oxygenase (HO), a well known“stress protein”in a number of tissues, is present in human retina. Western and northern blots show that the protein and mRNA are also expressed in human Y-79 retinoblastoma cells in culture and that the HO enzyme is rapidly induced by its substrate, heme. Moreover, HO is also induced by two chemicals, sodium arsenite and menadione, that act as agents of oxidative stress. HO is the regulatory enzyme in the heme degradative pathway and an increase in its activity could lead to the accumulation of bilirubin, an antioxidant, in the cell at the expense of heme, a prooxidant. The HO pathway may thus be of importance in protecting the retina against oxidative stress in vivo. Moreover, the Y-79 culture system should provide an excellent model for use in examining stress mechanisms in retinal cells at a molecular level.

ISSN:0271-3683    

DOI:10.3109/02713689209000066

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

The effect of epinephrine on Intraocular pressure (IOP) and the hemodynamics of the ciliary process vasculature in albino rabbits was studied by intraocular microendoscopy. Intraarterial application of epinephrine (15, 50, 250ng/kg bw) lead to an immediate vasoconstriction and a reduction 1n blood flow velocity (BFV) 1n the iridial and major ciliary processes lasting from 30 to 120 sec. This anemic phase was followed by a hyperemic phase of about 60 to 240 sec. showing a vasodilation up to 150% of the Initial diameters and an increase in BFV. The hyperemic phase can be prevented by pretreatment with indomethadn. Simultaneously measured IOP decreases 1n the anemic and increases 1n the hyperemic phase parallel with the changes 1n vascular diameter.After topical administration of epinephrine (25–50ug/kg bw) a marked vasoconstriction followed by a vasodilatory phase was similarly found. However, the reactive changes of the ciliary process vasculature lasted considerably longer. The anemic phase lasted 15 minutes, the hyperemic phase 40 to 60 min. Again, this hyperemia can be prevented by Indomethadn-pretreatment. In the iridial processes the anemic phase persisted till 70 minutes. No hyperemia and no substantial Influence of indomethadn-pretreatment was found in this territory. In the anemic phase the IOP decreased in average from 20 mmHg to 15 mmHg. However, 1n contrast to the reactive changes of the IOP after intraarterial epinephrine application, the IOP did not Increase again 1n the hyperemic phase, but decreased further to about 12 mmHg. After pretreatment with Indomethadn the IOP remained at the level of 15 mmHg. The short-term IOP-changes after 1.a. application of epinephrine, mirror the vasoconstrictory and vasodilatory reactions 1n the ciliary processes and might be due to volume changes in the eye (plethysmographic effect). However, the long lasting IOP reduction after topical epinephrine in the hyperemic phase can not be due to vascular reactions in the ciliary processes. There must be other factors responsible for the long lasting pressure reducing effect of epinephrine.

ISSN:0271-3683    

DOI:10.3109/02713689209000067

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

The status of major histocompatibility complex (MHC) class I and II gene expression in the normal mouse lens was examined. No mRNA for either class I or II genes was detectable in mouse lens, while the expression of MHC genes in other tissues generally matched immunohistochemical data from human tissues. However it was observed that MHC class I mRNA is present in the mouse lens-derived cell line aTN4-l. From a new-born mouse lens cDNA library a clone was obtained for the murine homologue of the DNA-binding protein dbpB/YB-1, a protein originally identified in human lymphocytes and proposed to be a negative regulator of MHC class II gene expression. Northern blots detect dbpB/YB-1 mRNA in all mouse tissues and cells examined, including both mouse lens and QTN4-1 cells, suggesting that dbpB/YB-1 has a general and widespread role.

ISSN:0271-3683    

DOI:10.3109/02713689209000068

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

The retinal pigment epithelium (RPE) plays several important roles in the continual support and renewal of photoreceptor outer segments. In the present study, we have demonstrated that RPE cells contain a low molecular weight protein with a high capacity for zinc binding that is dependent on available sulfhydryl groups. This protein is inducible by a 24 hour incubation of cultured RPE in medium supplemented with zinc, cadmium, or dexamethasone. The induction of this protein is correlated with an increased capacity for zinc-65 uptake into cultured RPE. Analysis with a cDNA probe specific for the human metallothionein II gene corroborated the existence and induction of metallothionein gene products in RPE cells. Based on these properties, we have identified this protein as metallothionein. The induction of metallothionein likely has a critical influence on the zinc economy of the RPE.

ISSN:0271-3683    

DOI:10.3109/02713689209000069

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor

摘要:

An initial characterization of the lenticular ionic permeabilities of the isolated Sprague-Dawley rat lens utilizing short-circuiting techniques was carried out to provide the basis for further studies of mechanisms underlying cataractogenesis associated with salt-sensitive genetic hypertension in the rat. Both active and passive Na+and Kftransport were evaluated by varying ionic concentrations in the bathing solutions facing the anterior and posterior sides of the lens, as well as by the addition of BaCb and ouabain. In general, the ionic permeabilities and transport properties of the rat lens are qualitatively similar to those previously described in other species. Ionic replacement studies showed the presence of Nafand K+channels at both surfaces of the lens, with the anterior side K+conductance being larger than the posterior. In contrast, Na+conductance was similar at both lens surfaces. The effects of ouabain confirmed the presence of the Na+ -K+ -ATPase at the lens epithelium, while the effects of serial addition of BaCh and ouabain suggested that the contribution of Kfdiffusion to the short-circuit current may be considerably greater than the electrogenic component of the Na+-K+pump.

ISSN:0271-3683    

DOI:10.3109/02713689209000070

出版商:Taylor&Francis    

年代:1992

数据来源: Taylor