摘要:

The present study demonstrates, for the first time, that the excised pigmented rabbit conjunctiva is a tight barrier capable of active Cl-transport. The transepithelial potential difference was 17.7±0.8 mV (tear-side negative), the short-circuit current was 14.5±0.7μA/cm2, and the transconjunctival resistance was 1.3±0.1 k$OM.cm2for n = 45 tissues. Various inhibitors including ouabain (a Na+/K+-ATPase inhibitor), amiloride (a Na+transport blocker), N-phenylanthranilic acid (a chloride transport inhibitor), bumetanide (an inhibitor of Na+-(K+)-Cl-cotransport process), and BaCl2(a K+channel blocker) were used on the mucosal and serosal sides of the tissue mounted in Ussing chambers to determine the involvement of the respective ion transport processes in the observed short-circuit current across the conjunctiva. The results suggest that a Cl-conductive pathway is present on the mucosal side of the conjunctiva, whereas Na+/K+-ATPase, Na+-(K+)-Cl-cotransport process, and K+conductive pathways are present on its serosal side. Amiloride-sensitive Na+-conductive pathways do not appear to be present on either side of the pigmented rabbit conjunctiva.

ISSN:0271-3683    

DOI:10.3109/02713689309033501

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

The contractile activity of endothelins (ETs) and their effect on twitch contraction evoked by electrical field stimulation were studied in the isolated rabbit iris sphincter and dilator muscles using the isometric tension recording method. ET-1, ET-2 and ET-3 caused slow contractile response of the sphincter as well as the dilator muscles, with sphincter muscle EC50values of 37.3, 58.0 and 84.3 nM, and dilator muscle values of 31.7, 69.0 and 224.4 nM, respectively. These contractile responses were not affected by atropine (1μM), prazosin (1μM) or indomethacin (1μM).ET-1 and ET-3 slightly but significantly inhibited the fast cholinergic component of twitch contraction of the sphincter muscle evoked by field stimulation, without affecting the response to carbachol. However, ET-1 did not affect the slow substance P-ergic component of twitch contraction of this preparation. In the dilator muscle, ET-1 and ET-3 had little effect on the contraction induced by phenylephrine but reduced the amplitude of the twitch contraction evoked by the field stimulation. The inhibitory effect of ETs on the dilator muscle was antagonized by pretreatment with BQ-123 (100 nM), which is a selective ETA receptor antagonist. Pretreatment with indomethacin (1μM) also attenuated the inhibitory effect of ETs on the twitch contraction.These results suggest that ETs may have two sites of action, pre- and post-synaptic effects, on the rabbit iris sphincter muscle as well as the dilator muscle. All three ET isopeptides may have direct contractile activity on the smooth muscles of the sphincter as well as the dilator without mediation by prostaglandins or neuronal mechanisms. Furthermore, ETs may act on nerve endings to inhibit adrenergic and cholinergic neurotransmission in the iris dilator and sphincter, respectively.

ISSN:0271-3683    

DOI:10.3109/02713689309033502

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

DNA sequence analysis of overlapping shotgun and restriction fragments have revealed the entire sequence of the human lens fiber cell intrinsic membrane protein MP19 gene (also termed MP17, MP18, and MP20). The 8,056 bp MP19 gene contains 5 exons encoding a mature protein of 173 amino acids, which displayed a very high degree of identity (91%) with that of bovine MP19, deduced from a bovine cDNA sequence. The exons range in size from 52 bases (exon 1) to about 340 bases (exon 5). The introns consist of two large segments (introns B and C) of about 4,700 bases and 1,800 bases, respectively, and two small segments (intron A and D) of about 450 and 250 bases each. SevenAlufamily DNA repeats are found within the human MP19 gene. The sequenced gene includes 100 bases of 5′flanking sequence.

ISSN:0271-3683    

DOI:10.3109/02713689309033503

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

Contamination of contact lenses is thought to increase the risk of infectious keratins, yet factors promoting attachment of bacteria to contact lenses are not fully understood. It has been suggested that strains ofPseudomonas aeruginosaattach to mucosal surfaces via pili which are appendages found on some strains. This study investigated the role of pili and the effect of incubation time on the attachment ofP. aeruginosato 20 unworn hydrogel lenses representative of each of the four FDA categories. Ten lenses were incubated for 15 minutes and another ten for 180 minutes. Lenses were incubated with either PAK+P. aeruginosawhich possessed pili or its isogenic mutant pair, PAK-, which was genetically similar except for the absence of pili. Bacteria were quantified, following homogenization of the contact lens, by viable counts. Non-piliated bacteria were significantly more likely to adhere to the lenses (p<0.001). A significant interaction between lens type and incubation time was observed (p<0.05); thus it is difficult to generalize about either of these effects in isolation. These results show that surface characteristics may confer an attachment advantage to bacteria.

ISSN:0271-3683    

DOI:10.3109/02713689309033504

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

Cytochrome c oxidase (CO) is a mitochondrial enzyme complex that was used in this study as a marker enzyme of aerobic metabolism. The activity of the enzyme was measured in the RPE of posterior and peripheral regions of bovine and human eyes. The posterior regions included the bovine area centralis or human macula. To determine if aging affected CO activity, activity was compared in RPE cells from human donors of varying age. Anin vitroaging model was also used in which CO activity was measured in bovine and human RPE cells that were aged by repeated culture passage. CO activity was found to be significantly lower in posterior RPE cells from both bovine and human eyes suggesting that aerobic metabolism in RPE cells differs regionally. For human RPE samples, CO activity was lower in posterior cells at all donor ages and no significant age-related changes in CO activity were observed except that the highest activity samples were from older donors. Similarly, RPE cells that were aged in culture showed no significant changes in CO activity per cell although there were some high activity samples among the aged cultures. With aging, RPE cell density at confluency declined resulting in lower total CO activity in the aged epithelial monolayer. The data suggest that the ability of individual RPE cells to generate energy via respiration is maintained in the aged eye, but because RPE cell number declines with age and the activity of remaining RPE cells does not increase commensurately, there may declines in the ability of the aged pigment epithelium to perform tissue-level functions (e.g., transepithelial transport). Further, the aging macula may be preferentially at risk for falling below energy thresholds to sustain high energy-requiring cellular functions since macular RPE cells appear to have a reduced respiratory capacity relative to peripheral cells.

ISSN:0271-3683    

DOI:10.3109/02713689309033505

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

Restriction of dietary calorie intake is associated with life extension and with the delay of age-related disorders. Preliminary studies demonstrated that by feeding the Emory mouse a diet restricted by 21% in calories cataract and insolubilization of protein could also be delayed. To observe the effects of calorie restriction over prolonged portions of adulthood, Emory mice were fed the control diet (C) or a diet restricted by 40% in calories (R). Feeding the R diet was associated with delayed formation or progress of cataract over virtually the entire second half of life. At 11 months of age, bilateral grade 5 cataracts were present in 17% and 2% of C and R lenses, respectively. At 22 months of age, bilateral grade 5 cataracts were present in 90% and 18% of C and R lenses, respectively. The distribution of $aL,β-, andγ-crystallins in the water-soluble, urea-soluble, and SDS-soluble fractions indicates more similarities than differences between C and R lenses with a specific grade of cataract or of a given age. However, there were significant and abrupt (after grade 4 cataract) losses of particularγ-crystallins;γ-crystallins which were not prominent at earlier stages became the majorγ-crystallin moieties. Losses of $aL-crystallins were also noted upon cataract formation or aging in most of the fractions. Aggregates includingγ-and $aL-crystallins also accumulate faster in the C group.

ISSN:0271-3683    

DOI:10.3109/02713689309033506

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

The corneal destruction associated with herpes simplex keratitis (HSK) is primarily the result of the host's immune response to herpes simplex virus type-1 (HSV-1) infection. We examined the role of T cells and T cell subsets in the pathogenesis of HSK. Naive and immune T cells and HSV-1 immune CD4+ and CD8+ subsets from Igh-1 disparate BALB/c congenic mice were adoptively transferred into athymic BALB/c nude mice, which normally do not develop HSK. The results demonstrated that while the transfer of naive T cells from either HSK-susceptible C.AL-20 (Igh-1d) or HSK-resistant C.B-17 (Igh-1b) mice had little influence on HSK development, transfer of either CD3+ or CD4+ HSV-1 immune T cells from C.AL-20 mice resulted in the development of severe HSK in all of the recipients. Transfer of the same cell populations from C.B-17 mice resulted in the development of only a mild keratitis in 50% of the recipients. Transfer of CD8+ cells from either donor strain did not result in stromal disease in any recipient mouse. These results clearly demonstrate the pivotal role of CD4+ T cells in the development of necrotizing herpes stromal keratitis, and further demonstrate that CD8+ T cells are not essential in HSK development in the BALB/c system.

ISSN:0271-3683    

DOI:10.3109/02713689309033507

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

10 retinal vessel patterns with neovascularisation at or near the optic disk (NVD) from eyes of patients with diabetic retinopathy were compared with vascular patterns from 14 normal eyes. The vascular patterns were taken from low angle fundus photographs. After digitizing, the fractal dimensions were calculated by means of the density-density correlation function method. The fractal dimension was found to be significantly higher for vessel patterns with NVD [D = 1.845±0.056 (m±sd)] as compared with the normal control group (D = 1.708±0.073) (p<0.001). The fractal dimension of 1.8 appears to be a cutoff value. Higher values may indicate proliferative changes. Under these conditions the sensitivity of the method for the detection of NVD±Grade 3 in the Early Treatment Diabetic Retinopathy Study (ETDRS) grading system is 90%. The presence of such NVD in an eye is a“high risk characteristic”for severe visual loss, which requires panretinal laser treatment. Fractal analysis is therefore a possible new strategy for computer assisted“automated”detection and quantification of proliferative diabetic retinopathy. The fractal dimension of the new vessels suggests possible mechanisms involved in retinal vasculogenesis.

ISSN:0271-3683    

DOI:10.3109/02713689309033508

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

The temporal pattern of changes in the specific activities of retinal Na+, K+-ATPase (Na, K-ATPase) and Mg2+-ATPase (Mg-ATPase) were determined at several time intervals following the onset of diabetes in streptozotocin-induced diabetic (STZ: at 1,2, 4 and 6 months) Long-Evans hooded rats, spontaneously diabetic Zucker diabetic fatty (ZDF: at 1,2 and 4 months) rats and their age-matched controls. These animals were utilized as models for insulin-dependent diabetes mellitus (IDDM) and non-insulin-dependent diabetes mellitus (NIDDM), respectively. Na, K-ATPase specific activity, using 103M ouabain, was decreased (-6% to -14%) at all time points after the appearance of hyperglycemia in the ZDF rat, but was reduced only after 4 and 6 months in the STZ rat (-8% and -14%, respectively). In contrast, Mg-ATPase activity was significantly increased (13%) after 4 months in the ZDF rat and after 6 months in the STZ rat (8%). The concentration-dependent inhibitory effects of ouabain (10-9to 10-3M) on the activity of Na, K-ATPase in diabetic rats and age-matched controls was used to assess the time-dependent effects of diabetes on the $aL3-high ouabain affinity or the $aL1-low ouabain affinity retinal Na, K-ATPase isozymes. The retinal Na, K-ATPase activity for the $aL3 isozyme was significantly lower at all times examined for the ZDF (-5% to -26%) and STZ-induced diabetic rats (-8% to -14%). This was reflected in the markedly decreased half-maximal inhibitory concentrations (IC50) of ouabain for the $aL3 isozyme. For example, after four months of diabetes, the mean±SEMIC50values were 12±3 nM in the STZ rats and 48±6 nM in the age-matched controls and 19±3 nM in the ZDF rats and 30±4 nM in the age-matched controls. In contrast, the activity of the $aL1 isozyme was slightly, but significantly, decreased at 2 and 4 months in the ZDF rats (-4% to -7%) and after 4 and 6 months in the STZ-induced diabetic rats (-3% to -9%) while the IC50values were unchanged. Moreover, the Hill coefficient for the $aL3 isozyme was decreased in both diabetic groups while it was unchanged for the $aL1 isozyme. Our findings suggest that diabetes-induced changes in specific activity and ouabain sensitivity of Na, K-ATPase isozymes result mainly from alterations in the $aL3 isozyme which is located primarily in the outer or distal retina. The exact cellular mechanisms accounting for these changes and their significance in the pathogenesis of diabetic retinopathy remain to be clarified.

ISSN:0271-3683    

DOI:10.3109/02713689309033509

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

TGF$aL, a member of the epidermal growth factor family stimulates proliferation of various cells. In the search for molecules that regulate cell division in the lens epithelium, the effect of numerous growth factors including EGF and FGF has been determined. In this study, the effect of TGF$aL on lens epithelial cells (LEC) from rabbit and monkey was investigated and compared to FGF and EGF. Since TGF$aL is suggested to be a factor that is regulated by auto and/or paracrine mechanisms, an immunohistochemical visualisation of the factor in the rabbit lensin situwas performed.TGF$aL stimulates LEC in a dose-dependent manner with a maximal threefold increase in cellular proliferation at 100 ng/ml. At a concentration above 10 ng/ml the cells lost their epithelial morphology and became irregular and star-shaped. Since TGF$aL is a potent LEC mitogen and has shown to increase in aqueous humour after trauma to the eye, this factor might be one of the molecules that regulate normal cell division in the ocular lens as well as LEC growth after cataract surgery.

ISSN:0271-3683    

DOI:10.3109/02713689309033510

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor