摘要:

The relationship between the suppression-recovery phenomenon and sensitivity changes during light adaptation was investigated in the cone photoreceptors of the isolated, superfused bullfrog retina using barium as a tool. Barium reduced the shift of the stimulus-response function that occurs during light adaptation. Barium also reduced the maximum response amplitude seen after recovery from suppression induced by a flickering light stimulus. The effect of barium on the recovered response amplitude could not be explained by barium's known ability to attenuate the dark adapted cone response, since the magnitude of the depression of the recovered response amplitude was significantly greater at all concentrations than was the magnitude of the depression of the response of the dark adapted cones. Moreover, the thresholds for barium's effect, as well as the shapes of the dose-response curves, were quite different for the two types of responses. The results are consistent with the idea that the recovery from suppression induced by flicker is due to the same change in receptor sensitivity that manifests itself as a shift of the stimulus-response curve during light adaptation.

ISSN:0271-3683    

DOI:10.3109/02713688709025212

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

The activity of lactate dehydrogenase (LDH) and its isoenzyme pattern were studied in four concentric layers of adult bovine and calf lenses. In both groups the specific activity of the total LDH diminished progressively toward the internal nuclear layer; the decrease was greater in the adult lenses. The enzyme activities in the cortical layers of the calf lens were lower than in the adult lens, but in the inner nuclear layers, the opposite was found. All of the 5 LDH isoenzymes were found in each layer. In both groups of animals the LDH1 isoenzyme prevailed, followed by LDH2. No differences were found in the percentage of each isoenzyme in the different lens layers. The differences in the activitie (s) of LDH found may be due to post-translational or post-synthetic modifications which may occur during the aging process.

ISSN:0271-3683    

DOI:10.3109/02713688709025213

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

The naturally occurring humoral immune response of Campbell and Hunter strains of Royal College of Surgeons (RCS) rat to bovine retinal S-antigen and bovine rod outer segments was tested by a sensitive ELISA (enzyme linked immunosorbent assay) in animals up to the age of 9 weeks. Controls of piebald Virol Glaxo, Wistar and DA rats were also employed. The ELISA results indicate that rats of all strains had a response to both antigens. The magnitude of the response in any particular strain varied with the age of the animal and the antigen and serum dilution employed in the assay, considerable variation in response was observed among animals of the same strain at any one particular age. Immunoblot analysis of the strongest ELISA positive sera detected S-antigen and other autoantigenic proteins in both RCS and Wistar rats. The data suggest that the antibody response observed may have little significance to the retinal degeneration observed with RCS rats.

ISSN:0271-3683    

DOI:10.3109/02713688709025214

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

There have been consideraole difficulties in developing a satisfactory method for the Cryopreservation of corneas. In this paper we describe the effect of two variables that appear to influence the effectiveness of preservation, the concentration of cryoprotectant and the medium that surrounds the cornea during freezing. Rabbit corneas were exposed to the cryoprotectant dimethyl sulphoxide (Me2SO) in concentrations of 1 or 2 mo1/1 in a high-potassium well-buffered solution, and then cooled to—196°C either in air or surrounded by 5 ml of the Me2SO solution. After storage at-196°C, thawing and removal of the Me2SO, survival was assessed by electron microscopy and measurement of stromai thickness during perfusion on the specular microscope.The least degree of damage was observed when corneas were equilibrated with 1M Me2SO and frozen in air. The evidence suggests that 2M may be an excessive concentration of Me2SO in this system and that damage to the stroma may be reduced by freezing the cornea in air rather than surrounded by the Me2SO solution.

ISSN:0271-3683    

DOI:10.3109/02713688709025215

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

Trifluridine (TFT) and a structurally related analogue, 5-fluoro-2′-deoxyuridine (FDU), were investigated for their efficacy in the topical treatment of experimental keratitis caused by thymidine kinase-positive (TK+) and thymidine kinase-deficient (TK−) herpes simplex virus type 1 (HSV-1) strains. Bromovinyldeoxyuridine (BVDU) was used as a reference compound. Both 0.2 % BVDU and 0.2 % TFT eyedrops produced a highly significant healing of TK+HSV-1 keratitis as compared to the placebo and 0.2 % FDU eyedrops (P≪0.005), whereas the latter compound did not differ from placebo eyedrops. In the treatment of TKHSV-1 keratitis, none of the drugs exhibited a beneficial healing effect, although the virus strain used was inhibitedinvitroby TFT and FDU at a very low concentration (0.02–0.04μg/mL).

ISSN:0271-3683    

DOI:10.3109/02713688709025216

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

Human tear fluid collected in glass capillaries was absorbed in cellulose sponges. After various time intervals the recovery was measured for total protein, amylase (AMY), lysozyme (LZM), immunoglobulin A (IgA) and lactoferrin (LF). After one day storage at 4°C of moistened sponges of at least 92% recovery was observed. Storage for longer periods at 4°C up to seven days showed a decreasing recovery for total protein, AMY and IgA. Tear collection with sponges and storage of wet sponges for maximally one day at 4°C followed by centrifugation or storage of the fluid at-20°C are reliable ways of sample treatment.

ISSN:0271-3683    

DOI:10.3109/02713688709025217

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

Previous freeze-fracture results from our laboratory have shown a reduction in a population of intramembrane particles in the lateral endothellal membranes from dysfunctional human corneas. The size range of these intramembrane particles corresponds to that which has previously been reported for the glycoprotein enzyme Na, K-ATPase in enzyme enriched freezefractured membranes. In order to investigate glycoconjugate changes potential ly related to the particle reduction, wheat germ agglutinin (WGA), which has been shown to bind to the sugar residues In the ATPase subunlt, was used to label three types of corneas with dysfunctional endothelial cells (Fuchs' endothelial dystrophy, aphakic and pseudophakic bullous keratopathy) and two types of corneas (eye bank and keratoconus) with functional endothelium using the technique of thin section freeze-fracture label. Apical WGA labelling on all types of dysfunctional cells was shown to be drastically reduced in comparison to both types of functional corneal endothelial cells. Lateral membranes of dysfunctional cells, exposed by freeze-fracturing, also showed a great reduction in WGA labelling as compared to the fractured lateral membranes of functional cells. The differences observed in lectin labelling of lateral membranes may be related in part to the decreased intramembrane particle density observed in dysfunctional human corneal endothelial cells.

ISSN:0271-3683    

DOI:10.3109/02713688709025218

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

Successive fiber fractions isolated from individual bovine lenses were fractionated to examine changes in lens proteins and membrane lipids as a function of age. In calf lens of about 1.2 gm wet weight, cholesterol (C) is maintained at a level of 3.3 ug/mg dry weight in the outer cortical 30% of the lens. In the inner cortex, a C content of 2.4 ug/mg was found that decreased somewhat to 2.1 ug/mg in the inner nuclear 20% of the lens. The almost linear decrease in phospholipid (p) content from 11.6 in the cortex to 1.7 ug/mg in the nucleus resulted in a cortex to nucleus increase in C/P ratio from 0.5 to about 2.0 (mol/mol). Compared to calf lenses, a low C level of 2.4 ug/mg was observed in the outer cortex of cow lenses (approximately 3.0 gm wet weight). No significant difference in C level was found between the calf and cow lenses either in the inner cortical or nuclear regions. The P level was reduced to 6 and 1.2 ug/mg in the outer cortex and nucleus of the cow lens, respectively. The low nuclear P content is responsible for the observed high C/P value of 3.6. The lower lipid content found in the cortex of older lens suggests an age dependent decrease in the amount of available membrane lipid to envelope the newly formed fibers. A cortex to nucleus increase in the amount of urea-soluble (US) protein fraction from about 6 to 14% of total fiber mass was observed with the calf lens. In the cow lenses, the nuclear US fraction accounts for almost 30% of the fiber. These results and data from lipid composition are discussed with the age-related changes in lipid observed with human lenses.

ISSN:0271-3683    

DOI:10.3109/02713688709025219

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

During the process of light-adaptation, a part of retinal S-antigen (“48-kDa protein”) is bound to the photoreceptor cell membranes. This fraction can be isolated by first extracting the soluble S-antigen with isotonic buffer and subsequently extracting the bound S-antigen with detergent. In this way we found that light-adaptation to 250 1x or more induces a maximum binding of 62% of total S-antigen within 2 minutes in rat retina in vivo. At low light intensity (50 1x) this process lasts 15 minutes, while at 5 1x only 30% of S-antigen is bound. Presumably the number of available phosphorylated (bleached) rhodopsin molecules is the limiting factor in time and quantity. Dark-adaptation causes an initial rapid release of S-antigen during the first 5 minutes, but it takes more than 2 hours to reach the minimum level of about 10% bound S-antigen. The rates of binding of S-antigen in the light and of release of S-antigen in the dark are compared to other phenomena of light and dark adaptation.

ISSN:0271-3683    

DOI:10.3109/02713688709025220

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

The present study used the rabbit iontophoresis model to examine the thymidine kinase (TK) requirement for HSV-1 latency, and test the round trip theory of latency with emergent phenotypic mutations of the HSV-1 TK negative (TK−) inoculating strain. The results demonstrated repeated induced ocular shedding of latent HSV-1 in 14–100% of rabbits. The TK phenotype of recovered tear film following spontaneous shedding and repeated iontophoresis induction wasthymidine Kinase negativein 90% of eyes. Sequential shedding of TK−virus from the same eye over time was demonstrated in 21% of eyes in 33% of rabbits. We conclude that TK isnotan absolute requirement for the establishment or reactivation of latent HSV-1 in the rabbit model. The round trip theory of latency wasnotsupported as TK+isolates and syncytial variants of the TK−inoculating strain which were recovered at the ocular surface after the initial iontophoresis couldnotbe demonstrated following subsequent trials of iontophoresis.

ISSN:0271-3683    

DOI:10.3109/02713688709025221

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor