摘要:

Binocular and monocular contrast sensitivities were measured at two spatial frequencies of 1 and 6 c/deg in 8 young (mean age 22.6±3.8 years) and 18 older subjects with normal healthy eyes (mean age 58.4±7.3 years). Data were analysed as binocular summation ratios defined as binocular CS/‘best eye’CS. Binocular summation ratios were higher for the younger group (1.46 and 1.48 for 1 and 6 c/deg respectively) compared to the older group who demonstrated a spatial frequency dependence (1.31 and 1.13 at 1 c/deg and 6 c/deg respectively). The results are discussed in terms of age-related cortical cell loss and increased monocular sensitivity differences between the two eyes.

ISSN:0271-3683    

DOI:10.3109/02713689609007626

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

In the present study we have analyzed the architecture of the episcleral microvasculature in the owl and cynomolgus monkey using scanning electron microscopy of resin casts. Due to the topical pretreatment with nitroprusside the complete vasculature including segments of the aqueous humor outflow channels could be visualized.We found that 1–3 mm posterior to the limbus corneae the episcleral vessels form numerous arteriovenous anastomoses (AVA) in the size of small arterioles and venules. These AVA are also located at the collector channels near Schlemm's canal and at the episcleral venous plexus which drains the collector channels.It is assumed that the AVA might influence not only the circulation in the episcleral venous plexus but also in the aqueous humor outflow routes.

ISSN:0271-3683    

DOI:10.3109/02713689609007627

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

Objectives were to identify PKC isoforms in iris sphincter isolated from rabbit, cat, dog and bovine irides, to determine their sub-cellular distribution, and to investigate the effects of the phorbol ester, PDBu, on contraction and cAMP accumulation in this tissue. Using six isoform (α,β,γ,ϵ,δ,ζ)-specific polyclonal antibodies, PKCα,β,ϵ,δ, andζwere detected in the four species, whereas PKCγwas detected only in dog and bovine. PKCαandϵare the most abundant isoforms in this tissue. PKCαis mainly cytosolic in rabbit and bovine and membrane associated in cat and dog. PKCγis equally distributed in cytosol and membrane fractions of bovine, but mostly cytosolic in dog. PKCβ,δandϵare mainly membraneous and PKCζis mainly cytosolic in all species. PDBu (100 nM) induced a contractile response in rabbit-and cat-, but not in dog and bovine, sphincters, and increased cAMP accumulation in rabbit, cat, dog and bovine by 111, 130, 458 and 294%, respectively. Therefore, the lack of effect of PDBu on contraction in dog and bovine, as compared to rabbit and cat, may be due: (a) to the presence of PKCγisoform, and (b) to the stronger stimulatory effects of the phorbol ester on cAMP production in the non-contracting species. In addition to demonstrating the presence of various PKC isoforms in the iris sphincter and the activation of adenylyl cyclase by this protein kinase, we have shown that the distribution of the PKC isoforms in this tissue is species specific. Furthermore, our data suggest that there may be specific physiological functions associated with each of the PKC isoforms and that PKC is involved in the contractile response of some but not all smooth muscles.

ISSN:0271-3683    

DOI:10.3109/02713689609007628

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

Transforming growth factorβ(TGF-β) transduces signals through mediation of type I and type II serine/threonine kinase receptors. The expression of TGF-βtype I (TβR-I) and II (TβR-II) receptors in rat eyes was investigated immunohistochemically. TβR-I and TβR-II immunoreactivity was detected in corneal and conjunctival epithelial cells, corneal endothelial cells, ciliary epithelial cells, lens epithelial cells, retinal pigment epithelial cells, and choroidal vessels. This co-expression of TβR-I and TβR-II indicates that the above cells respond to TGF-βand, because TGF-βis reported to be produced in ocular tissues, that it may have important autocrine and/or paracrine roles in the growth and metabolism of ocular tissuesin situ.

ISSN:0271-3683    

DOI:10.3109/02713689609007629

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

Mature and total TGF-β2 levels were determined in normal human tears, from 37 volunteers, using a quantitative‘sandwich’enzyme immunoassay technique. Since this ELISA method recognizes only mature TGF-β2, total TGF-β2 levels in tears were measured after acid activation. Aqueous humor samples from 9 patients with cataract were also tested as controls. Mature and total TGF-β2 in aqueous humor (AH) averaged 182 pg/ml and 737 pg/ml, respectively. The levels of mature TGF-β2 in normal human tears ranged from 36 to 71 pg/ml (mean: 55 pg/ml). And the levels of total TGF-β2 ranged from 3446 to 14910 pg/ml (mean: 7854 pg/ml), a very high level. Percentage of mature TGF-β2 ranged 0.4 to 1.3% (mean: 0.9%). It is reported for the first time that there are very high levels of total TGF-β2 in normal human tears. Curr. Eye Res. 15: 341–343, 1996.

ISSN:0271-3683    

DOI:10.3109/02713689609007630

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

Reverse transcription-polymerase chain reaction (RT-PCR) was performed to amplify a cDNA encoding a taurine transporter in the human retinal pigment epithelium (HRPE). The coding region of a PCR product was found to be 1863 bp long, predicting a 620-amino acid protein (69,826 Da). This cDNA sequence is almost identical to those taurine transporters recently determined in the human thyroid and placenta: 12 and 1 base pair(s) different from the reported thyroid and placenta transporter clones, respectively. The injection of mRNAin vitrotranscribed from the PCR product markedly increased taurine uptake inXenopus laevisoocytes. Taurine uptake is Na+and Cl-dependent. Unlabeled taurine,β-alanine andγ-amino-n-butyric acid at 100μM inhibited the uptake of radiolabeled taurine whereas 100μMα-alanine andα-aminoisobutyric acid did not. A kinetic study showed that taurine uptake is mediated by a single carrier system with the apparent Michaelis-Menten constant of approximately 2μM. These results suggest that the PCR product encodes a functional taurine transporter whose characteristics are similar to those of taurine uptake observed in the original HRPE cells. A DNA encoding the reported placental transporter was made from the PCR product by site-directed mutagenesis but it was not functional in the oocyte expression. A similar RT-PCR was performed with poly (A)+mRNA isolated from JAR human placenta choriocarcinoma cells. This PCR product was identical to that from the HRPE. In addition, the clone of the human thyroid transporter was obtained and re-sequenced. Its translation coding region was also identical to that of the PCR product from the HRPE, showing that taurine transporters are identical in the human RPE, thyroid and placenta.

ISSN:0271-3683    

DOI:10.3109/02713689609007631

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

Detection and resolution acuity was measured at 30 degrees in the periphery for sinusoidal gratings under differing amounts of optical defocus. Within the range–2.0 to +2.5 diopters defocus, detection acuity was higher than resolution acuity. As defocus increased, detection acuity decreased continuously but resolution acuity was little affected until around 2.0 diopters defocus. The results indicate that resolution performance is sampling limited in peripheral vision, even for significant refractive error, and is more robust than detection acuity to the effects of optical defocus.

ISSN:0271-3683    

DOI:10.3109/02713689609007632

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor